Lubricant composition for preventing or reducing friction in a mechanical system

Abstract

The present application relates to a lubricant composition, in particular for preventing and / or reducing friction in a mechanical system lubricated with the lubricant composition, which comprises: i. at least one base oil; ii. at least one spiro compound having the following formula (I) wherein: M is an atom selected from boron and aluminium; n1 and n2, independently of one another, have a value of 0, 1, 2, 3 or 4, and R represent, independently of one another, a hydrocarbon group comprising from 1 to 50 carbon atoms; iii. at least one molybdenum complex comprising ligands free of sulphur and phosphorus; and iv. at least one non-metal phosphorus-sulphur additive.

Description

[0001] Description Title: Lubricating composition for preventing or reducing friction in a mechanical system Technical field The present invention relates to the field of lubricating compositions, in particular usable in mechanical systems, such as engines, in particular internal combustion engines, and mechanical transmission components. More particularly, the present invention provides new lubricating compositions which, when used, make it possible to prevent or reduce friction present in a mechanical system. Prior art Lubricating compositions, also called "lubricants", are commonly used in mechanical systems, to reduce friction between parts and thus protect the parts against wear.In addition to wear phenomena, friction can oppose the relative movement of the parts in contact and induce energy losses that are detrimental to optimal operation of the mechanical system. Lubricants are used for multiple applications, for example for metalworking, in particular for metal deformation operations, for gas or steam turbines in the fields of aeronautics, naval, rail transport and electricity production, for propulsion systems of motor vehicles, for example for the lubrication of bearings, gears, an engine, etc.For example, in the field of lubricants for motor vehicle engines or transmissions, the formulation of lubricants represents an important issue insofar as they make it possible to act on fuel consumption, and consequently on carbon dioxide emissions, via their impact on the friction forces generated between the various components of motor vehicles. In addition, engines using so-called decarbonized fuel, in particular hydrogen or ammonia fuel, do not generate carbon dioxide but consume an expensive fuel whose production is particularly energy-intensive. Reducing the consumption of fossil or decarbonized fuels through the use of lubricants that reduce friction between parts is therefore both an environmental and economic issue. Whatever the intended application, the most widespread lubricants are hydrocarbon-based lubricants.These hydrocarbon lubricants are conventionally composed of one or more base oils, to which are generally associated additives dedicated to boosting the lubricating performance of the base oils, such as for example friction modifier additives. Lubricants comprising a combination of friction modifier additives in base oils are notably proposed. For example, the document Bec S. et al., “Synergistic effect of MoDTC and ZDTP on frictional behavior of tribofilms at the nanometer scale”, Tribology Letters, 2004, 4, pp. 797-809, proposes the combination of a molybdenum dithiocarbamate compound (MoDTC) and a zinc dialkyldithiophosphate compound (DTPZn or ZnDTP), i.e. two modifier additives, in a base oil in order to improve the tribological properties, in particular friction reduction, compared to a base oil without these additives.In particular, such lubricants promote the formation of molybdenum disulfide films, with the chemical formula MoS2. In particular, the tribological properties of MoS2 films to reduce friction have been known for a long time. Nevertheless, despite the synergistic effect of the combination of the two friction modifiers MoDTC and DTPZn in a lubricating composition, friction within mechanical systems lubricated by compositions comprising such a combination, in particular in mixed or limit lubrication regimes, remains high, leading in particular to a significant source of inefficiency and overconsumption of energy in the system.Furthermore, the presence of MoDTC in a lubricating composition increases the risks of premature wear of DLC ("Diamond-Like Carbon") coatings, in particular those used in mechanical systems including transmission components and an internal combustion engine, as described in the document by De Feo M. et al., "MoDTC lubrication of DLC-involving contacts. Impact of MoDTC degradation", Wear, 2016, vol. 348-349, p. 116-125. Finally, the presence of DTPZn in a lubricating composition increases the ash content, in particular sulfated ash, during use of the lubricant, in particular in mechanical systems including, for example, transmission components and an internal combustion engine. Such an increase in ash, in particular sulfated ash, promotes, in particular: - the fouling of post-treatment systems such as particulate filters in gasoline or heavy-duty engines, as described in the document Bernardoff R.et al., “A Study of Ash Accumulation in the After-treatment System of a Gasoline Direct Injection Engine Equipped with a Gasoline Particulate Filter”, SAE Technical Paper 2017-01-0879, 2017; and Obiols J. et al., “An Innovative On-Line Measurement Method for Studying the Impact of Lubricant Formulations on Poisoning and Clogging of After-Treatment Devices”, SAE Technical Paper 2005-01-2178, 2005; - the risk of pre-ignition in spark-ignition engines, particularly in hydrogen engines, as described in Obrecht, N., “Hydrogen internal combustion engine lubrication challenges and engine oil requirements”, SIA Powertrain & Energy - Rouen 2022; and / or - particle emission, as described in Tabata K., “Studies on Characteristics of Nanoparticles Generated in a Gasoline Direct-Injection Engine,” JSAE 20199132, SAE Technical paper 2019-01-2328, 2019.Thus, there remains a need to be able to develop new lubricating compositions making it possible to improve the tribological properties, in particular in terms of friction reduction, in particular in mixed or limit lubrication regimes, of existing lubricating compositions, in particular lubricating compositions comprising one or more base oils. There also remains a need to propose new lubricating compositions limiting the degradation of coatings commonly used in mechanical systems, in particular in transmission components and an internal combustion engine, such as DLC coatings.There also remains a need to provide new lubricating compositions for reducing the formation of ash, for example sulfated ash, during use, in particular, in mechanical systems comprising transmission components and an internal combustion engine, in order to reduce or avoid in particular fouling of the mechanical system and / or the post-treatment system, the risk of pre-ignition in spark-ignition engines, for example in hydrogen engines, and / or the emission of particles. The present invention aims precisely to meet these needs. Disclosure of the invention According to a first aspect, the present invention relates to a lubricating composition comprising: i. at least one base oil; ii. at least one spiro compound of the following formula (I) [Chem 1]. in which: M is an atom chosen from boron and aluminum; n1 and n2 are, independently of each other, 0, 1, 2, 3 or 4, and R represent, independently of each other, a hydrocarbon group comprising from 1 to 50 carbon atoms; iii. at least one molybdenum complex comprising ligands free of sulfur and phosphorus; and iv. at least one non-metallic phosphosulfur additive. In the remainder of the text, the term "lubricating composition" or "lubricant" according to the invention will be used to refer to a lubricating composition as defined above. In the remainder of the text, the term "spiro compound" according to the invention will also be used to refer to a spiro compound of formula (I) as defined above. Examples of spiro compounds considered according to the invention are described in more detail in the remainder of the text.The spiro compounds of formula (I) as defined above have already been described for their use as detergent and / or antioxidant additives, in particular for controlling deposit or oxidation in a mechanical system. However, the detergent and / or antioxidant properties of the spiro compounds of formula (I) could in no way suggest an improvement in the tribological properties of a lubricant, when such a spiro compound is used in association with a molybdenum complex comprising ligands free of sulfur and phosphorus and a non-metallic phosphosulfur additive.Surprisingly, as illustrated in the examples which follow, the inventors have discovered that the implementation of the association of a spiro compound of formula (I), a molybdenum complex comprising ligands free of sulfur and phosphorus and a non-metallic phosphosulfur additive, in a lubricating composition, synergistically allows a reduction in friction, in particular in mixed or limit lubrication regimes, in a mechanical system. Thus, the tribological properties of a lubricating composition as defined above are improved. The lubrication conditions in "limit regime" (conditions of high temperature and / or pressure, severe mechanical contacts, high shear, etc.), are known to the person skilled in the art and are defined for example in the Manuel des Techniques de l'ingénieur, Introduction à la tribologie, Partie 2.1, Jean Frêne and Hamid Zaïdi, publication date September 10, 2011.The good tribological properties of the lubricating compositions according to the invention, in particular in mixed or limit lubrication regimes, allow their widespread use. These tribological properties, in particular in terms of friction reduction, can be evaluated by implementing conditions such as those defined in the test detailed in the section “Evaluation of tribological properties”, carried out on a so-called Anton Paar MCR302 rheometer with a T-PTD-200 tribological assembly (“ball on three planes”), also called a tribometer with a rotating three-plane ball contact, as described in the publication by Yu Min Kiw et al., “Molecular evidence for improved tribological performances of MoDTC induced by methylene-bis(dithiocarbamates) in engine lubricants”, RSC Adv., 2022, 12, pp. 23083–23090.Such conditions require more particularly to carry out lubrication for a contact present between the ball and the three rotating planes, under conditions of temperature greater than or equal to 80°C; pressure greater than or equal to 700 MPa; and rotation speeds greater than or equal to 0.01 m / s. Furthermore, the lubricating compositions according to the invention allow prevention or reduction of sulfated ash formed, for example, during the use of an internal combustion engine lubricated by lubricating compositions comprising the combination of molybdenum dithiocarbamate or MoDTC and metallic phosphosulfur additive such as DTPZn. Thus, fouling of the post-treatment systems of internal combustion engines, such as particulate filters, is reduced, or even avoided.Finally, the lubricating compositions according to the invention make it possible, in particular, to reduce the premature degradation and / or chemical alteration of DLC ("Diamond-Like Carbon") coatings in a mechanical system, present in particular when using lubricating compositions comprising molybdenum dithiocarbamate or MoDTC. More particularly, the present invention relates to a lubricating composition comprising: i. at least one base oil chosen from group I to V base oils and mixtures thereof, for example a group IV base oil; ii. at least one spiro compound of formula (I) in which M is a boron atom, n1 and n2 are 1, each R represents a C alkyl chain. 10 to C 20 , or even in C 10 to C 18, or C10 to C16, and for example C16 or C18; iii. at least one molybdenum complex comprising ligands free of sulfur and phosphorus such as those described below; and iv. at least one non-metallic phospho-sulfur additive such as those described below. According to another aspect, the present invention relates to the use in a lubricating composition of at least one spiro compound of formula (I), a molybdenum complex comprising ligands free of sulfur and phosphorus and a non-metallic phospho-sulfur additive for preventing and / or reducing friction in a mechanical system lubricated by means of said lubricating composition, said system comprising in particular an engine, for example an internal combustion engine, and / or a mechanical transmission member.According to another aspect, the present invention relates to the use of the lubricating composition as defined above, for preventing and / or reducing friction in a mechanical system lubricated by means of said lubricating composition, said system comprising in particular an engine, for example an internal combustion engine, and / or a mechanical transmission member, more particularly an internal combustion engine. According to another aspect, the present invention also relates to the use of at least one spiro compound of formula (I) as an additive for improving the tribological properties, in particular in terms of reducing friction and optionally in terms of reducing wear, of a composition comprising at least one base oil, a molybdenum complex comprising ligands free of sulfur and phosphorus and a non-metallic phosphosulfur additive.The invention also relates to a method or process for preventing and / or reducing friction in a mechanical system comprising the lubrication of said mechanical system with a lubricating composition according to the invention as defined above. Such a system comprises, in particular, an engine, for example an internal combustion engine and / or a mechanical transmission member. Said method or process more particularly comprises a step of bringing at least one mechanical part of said mechanical system, for example a mechanical part of an engine, into contact with a lubricating composition according to the invention as defined above. Other characteristics, variants and advantages of a lubricating composition according to the invention will become more apparent upon reading the description and examples which follow, given by way of illustration and not limitation of the invention.The expressions “between … and …”, “ranging from … to …”, “formed from … to …”, and “varying from … to …”, must be understood inclusively, unless otherwise stated. In the description and examples, unless otherwise stated, the percentages are percentages by weight. The percentages are therefore expressed by mass relative to the total mass of the composition. The temperature is expressed in degrees Celsius unless otherwise stated, and the pressure is atmospheric pressure, unless otherwise stated. Detailed description Definitions By alkyl group, we mean a hydrocarbon group, in particular an aliphatic hydrocarbon, linear or branched, comprising from 1 to 24 carbon atoms, in other words C1 to C24, for example from 4 to 18 carbon atoms, in other words C4 to C. 18. In particular, the alkyl group is selected from the group consisting of methyl, ethyl, propyl, isopropyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, isotridecyl, tetradecyl, hexadecyl, stearyl, icosyl, docosyl, tetracosyl, triacontyl, 2-ethylhexyl, 2-butyloctyl, 2-butyldecyl, 2-hexyloctyl, 2-hexyldecyl, 2-octyldecyl, 2-hexyldodecyl, 2-octyldodecyl, 2-decyltetradecyl, 2-dodecylhexadecyl, 2-hexadecyloctadecyl, 2-tetradecyloctadecyl, myristyl, palmityl and stearyl. By alkenyl group is meant a linear or branched hydrocarbon group comprising at least one double bond and comprising from 2 to 24 carbon atoms, in other words C2 to C 24The alkenyl group may be chosen from vinyl, allyl, propenyl, butenyl, isobutenyl, pentenyl, isopentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tetradecenyl and oleic. Aryl group means a polycyclic aromatic hydrocarbon group or an aromatic group, substituted or not. The aryl group may comprise from 6 to 24 carbon atoms, in other words C6 to C24. In particular, the aryl group may be selected from the group consisting of phenyl, toluyl, xylyl, cumenyl, mesityl, benzyl, phenethyl, styryl, cinnamyl, benzhydryl, trityl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, dodecylphenyl, phenylphenyl, benzylphenyl, phenyl-styrene, p-cumylphenyl and naphthyl.By cycloalkyl group is meant a polycyclic or cyclic hydrocarbon, substituted or not by an alkyl group. By cycloalkenyl group is meant a polycyclic or cyclic hydrocarbon, substituted or not by an alkyl group, and comprising at least one unsaturation. The cycloalkyl groups and the cycloalkenyl groups may comprise from 3 to 24 carbon atoms, in other words from C3 to C24. In particular, the cycloalkyl groups and the cycloalkenyl groups may be chosen, in a non-limiting manner, from the group consisting of cyclopentyl, cyclohexyl, cycloheptyl, methylcyclopentyl, methylcyclohexyl, methylcycloheptyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, methylcyclopentenyl and methylcyclohexenyl. Base oil As mentioned previously, a lubricating composition according to the invention comprises at least one base oil.These base oils may be chosen from base oils conventionally used in the field of engine lubricating oils, in particular for internal combustion engines, such as mineral, synthetic or natural, animal or vegetable oils. It may be a base oil alone or a mixture of several base oils, for example a mixture of two, three or four base oils. The base oils of the lubricating compositions considered according to the invention may be in particular oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and presented in Table 1 below or their mixtures. [Table 1].

[0002] Mineral base oils include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, dealphating, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing. Synthetic base oils may be esters of carboxylic acids and alcohols, polyalphaolefins or polyalkylene glycols (PAGs) obtained by polymerization or copolymerization of alkylene oxides comprising 2 to 8 carbon atoms, in particular 2 to 4 carbon atoms. Polyalphaolefins used as base oils are for example obtained from monomers comprising 4 to 32 carbon atoms, for example from decene, octene or dodecene, and whose viscosity at 100°C is between 1.5 and 15 mm².s -1according to ASTM D445. Their average molecular weight is generally between 250 and 3000 according to ASTM D5296. Mixtures of synthetic and mineral oils, which may be bio-sourced, may also be used. There is generally no limitation on the use of different base oils in the lubricating composition, except that they must have properties, in particular viscosity, viscosity index, sulfur content or oxidation resistance, suitable for use in internal combustion engines, in particular vehicle engines, for example light vehicles, heavy goods vehicles, off-road vehicles, engines used in marine, trains, and aviation. Preferably, a lubricating composition considered according to the invention comprises at least one base oil chosen from group I to V base oils and mixtures thereof, for example a group IV base oil.In particular, such a lubricating composition may comprise at least one mixture of at least two group I to V base oils, for example a mixture of group IV base oil and a group V base oil. The base oils suitable for the invention may have a kinematic viscosity measured at 40°C according to the ASTM D445 (KV40) standard ranging from 10 to 550 mm² / s. They may have a kinematic viscosity measured at 100°C according to the ASTM D445 (KV100) standard ranging from 1 to 35 mm² / s. In a particular embodiment, the base oils suitable for the invention may have a kinematic viscosity measured at 40°C according to the ASTM D445 (KV40) standard ranging from 10 to 150 mm² / s, in particular from 12 to 50 mm² / s, more particularly from 15 to 40 mm² / s.The base oils suitable for the invention may have a kinematic viscosity measured at 100°C according to the ASTM D445 (KV100) standard ranging from 1 to 15 mm² / s, in particular from 2 to 10 mm² / s, more particularly from 3 to 8 mm² / s. Other base oils of a more viscous grade may be used, in particular in combination with more fluid base oils as described above, for example group I base oils of the BBS (distillation residue) type, with a kinematic viscosity measured at 40°C according to the ASTM D445 (KV40) standard of the order of 450 to 550 mm² / s and / or a kinematic viscosity measured at 100°C according to the ASTM D445 (KV100) standard of the order of 30 to 35 mm² / s. These base oils are traditionally used for cylinder lubricants for marine engines.The base oil(s) may be present in a lubricating composition according to the invention in a content of at least 50% by mass relative to the total mass of the lubricating composition, in particular at least 60% by mass relative to the total mass of the lubricating composition, more particularly ranging from 60 to 99% by mass relative to the total mass of the lubricating composition, even more particularly ranging from 70 to 99% by mass relative to the total mass of the lubricating composition and preferably ranging from 80 to 99% by mass relative to the total mass of the lubricating composition.Preferably, the group IV oil or oils represent(s) at least 50% by mass of the total mass of the base oils of the lubricating composition, in particular at least 60% by mass of the total mass of the base oils of the lubricating composition, more particularly between 70 and 100% by mass of the total mass of the base oils of the lubricating composition, for example between 80 and 100% by mass of the total mass of the base oils of the lubricating composition. Spiro compound As indicated above, a lubricating composition according to the invention comprises at least one spiro compound of formula (I) as defined above. As mentioned above, the spiro compound considered according to the invention is of the following formula (I) [Chem 2]. in which: M is an atom chosen from boron and aluminum, in particular is a boron atom; n1 and n2 are, independently of one another, 0, 1, 2, 3 or 4; and R represent, independently of one another, a hydrocarbon group comprising from 1 to 50 carbon atoms, in particular from 3 to 30 carbon atoms, in particular from 5 to 25 carbon atoms, more particularly from 10 to 20 carbon atoms or from 10 to 18 carbon atoms, or from 10 to 16 carbon atoms, and for example in C16 or in C 18. The hydrocarbon groups considered according to the invention may optionally be interrupted by one or more heteroatoms, for example -O-, -NH-, -N= or -S-, in particular -O- or -NH-; and / or optionally substituted by one or more -OH, -NH2 and -SH groups, in particular -OH or -NH2. According to a particular embodiment, the R groups are composed solely of carbon and hydrogen atoms. The hydrocarbon groups may in particular be alkyl, alkenyl, aryl or aralkyl groups.According to a particular embodiment, the substituents R represent, independently of one another, a hydrocarbon group, preferably a linear or branched aliphatic chain, comprising from 3 to 50 carbon atoms, in particular from 3 to 30 carbon atoms, in particular from 5 to 25 carbon atoms and more particularly from 10 to 20 carbon atoms, or else 10 to 18 carbon atoms or else 10 to 16 carbon atoms, and for example 16 or 18 carbon atoms. In particular, the substituents R may represent, independently of one another, a linear or branched aliphatic chain, in particular an alkyl chain, preferably linear, C1 to C50, in particular C3 to C30, in particular C5 to C25, more particularly C. 10 to C 20 or even in C 10 to C 18 , or even in C 10 to C 16 , and for example in C 16 or in C 18. According to a particular embodiment, n1 and n2 are 0. According to another particular embodiment, n1 and n2 are 1 or 2. When n1 is 2 or n2 is 2, the R groups, carried by the same cycle, may be identical or different. According to a particular embodiment, the spiro compound may be of formula (I) above, in which n1 and n2 are 1; the R substituents may be identical or different, preferably identical. According to a particular embodiment, the spiro compound is of formula (I) above, in which: n1 and n2 are 1; and the R groups, which are identical, represent alkyl groups, preferably linear, C1 to C 50 , especially in C3 to C 30 , especially in C5 to C 25 and more particularly in C 10to C20, or C10 to C18, or C10 to C16, and for example C16 or C18. According to a particular embodiment, the spiro compound is of formula (I) in which M is a boron atom. In other words, according to this particular embodiment, the spiro compound may be a so-called spiroboronate compound, of the following formula (I'): [Chem 3] in which n1 and n2 and R are as defined above. According to another particular embodiment, the spiro compound is of formula (I) in which M is an aluminum atom. In other words, according to this particular embodiment, the spiro compound may be a so-called spiroaluminate compound, of the following formula (I''): [Chem 4] in which n1, n2 and R are as defined above. The invention thus relates, according to another of its aspects, to a spiro compound of formula (I) above, in which: - M is an aluminum atom; - n1 and n2 are, independently of each other, 0, 1 or 2, at least one of n1 and n2 being 1 or 2; preferably n1 and n2 are 1; - the R groups represent, independently of each other, a linear or branched aliphatic chain, in particular an alkyl chain, preferably linear, in C1 to C50, in particular in C3 to C30, in particular in C5 to C25, more particularly in C10 to C20, or even in C 10 to C 18 , or even in C 10 to C 16 , and for example in C 16 or in C 18. In other words, the invention relates to a spiroaluminate type compound of formula (I'') above, in which: - n1 and n2 are, independently of each other, 0, 1 or 2, at least one of n1 and n2 being 1 or 2; preferably n1 and n2 are 1; and - the R groups represent, independently of each other, a linear or branched aliphatic chain, in particular an alkyl chain, preferably linear, in C1 to C 50 , especially in C3 to C 30 , especially in C5 to C 25 , more particularly in C 10 to C 20 , or in C10 to C18, or in C10 to C16, and for example in C16 or in C18. According to a particular embodiment, the spiroaluminate type compound according to the invention is of formula (I'') in which: - n1 and n2 are 1; and - the R groups, identical or different, preferably identical, represent alkyl chains, preferably linear, in C1 to C 50 , especially in C3 to C30 , notably in C5 to C25, more particularly in C10 to C20, or even in C10 to C18, or even in C10 to C 16 , and for example in C 16 or in C 18 . The spiro compound used according to the invention can be prepared from at least salicylic acid or a salicylic acid derivative and a boron compound or an aluminum compound. More particularly, it can be obtained by reaction: - of at least one compound chosen from salicylic acid and its derivatives, of the following formula (Ia): [Chem 5] in which R is as defined above and n3 is as defined above for n1 and n2; and - at least one boron or aluminum compound, in particular boric acid or aluminum hydroxide. The preparation of the spiro compound used in the lubricating composition according to the invention does not involve any step, subsequent to the reaction of salicylic acid or one of its derivatives with said boron or aluminum compound, of reaction with an amine compound, as is the case for example in the context of the preparation of the compounds proposed in applications WO2018 / 220007 and WO2018 / 220009. Salicylic acid and its derivatives of formula (Ia) above can be synthesized according to synthesis methods known to those skilled in the art or be commercially available.The boron compound (in other words, boron-based) may be chosen in particular from boric acid (B(OH)3), boronic acids, boric and boronic esters, boron oxide and boric acid complexes. In particular, the boron compound may be chosen from boric acid; boron oxide; boric acid complexes; trialkyl borates, in particular in which the alkyl groups comprise, independently of one another, from 1 to 4 carbon atoms; boronic acids having a C1-C12 alkyl group; boric acids substituted by two alkyl groups, in particular C1 to C. 12; boric acids substituted by two aryl groups, in particular C6 to C12; boric acids substituted by one or two aralkyl groups, in particular C7 to C12, and derivatives of these compounds obtained by substitution of at least one alkyl group by one or more alkoxy groups. Boric acid complexes are in particular complexes of boron with one or more molecules comprising one or more alcohol functions. According to a particular embodiment, the boron compound is boric acid. The aluminum compound (in other words, aluminum-based) may be chosen, for example, from aluminum hydroxide (Al(OH)3), aluminum oxide, aluminum sulfate (Al2SO4)3. It is up to a person skilled in the art to adjust the reaction conditions between said compound(s) (Ia) and the boron or aluminum compound to obtain the desired spiro compound.In particular, the reaction may be carried out in a solvent medium consisting of one or more apolar solvents and / or protic polar solvents. The solvent medium may consist of one or more solvents chosen from naphtha, protic polar solvents, such as water and alcohols, for example methanol, ethanol, propanol, butanol; and mixtures thereof. According to one embodiment, one or more spiro compounds of formula (I) are used in a content of between 0.1 and 5.0% by mass relative to the total mass of the lubricating composition. In particular, one or more spiro compounds of formula (I) are used in a content of between 0.5 and 4.0% by mass relative to the total mass of the lubricating composition. More particularly, one or more spiro compounds of formula (I) are used in a content of between 1 and 3.0% by mass relative to the total mass of the lubricating composition.Molybdenum complex comprising ligands free of sulfur and phosphorus As indicated above, a lubricating composition according to the invention comprises at least one molybdenum complex comprising ligands free of sulfur and phosphorus as mentioned above. The molybdenum complex according to the present invention may be chosen from organic molybdenum complexes comprising at least one molybdenum (Mo) atom and at least one ligand such as a carboxylate ligand, an ester ligand, an amide ligand. For example, organic molybdenum complexes with carboxylates, esters, amides may be obtained by reaction of molybdenum oxide or ammonium molybdates with fatty substances, glycerides, fatty acids or fatty acid derivatives (esters, amines, amides, etc.). For the purposes of the invention, the carboxylate ligands, the ester ligands and the amide ligands are free of sulfur and phosphorus.According to a particular embodiment, the molybdenum complex is chosen from molybdenum complexes with amide ligands, in particular prepared by reaction of a source of molybdenum, which may be for example molybdenum trioxide, and an amine derivative, and fatty acids comprising for example from 4 to 36 carbon atoms such as for example the fatty acids contained in vegetable or animal oils. The synthesis of such compounds is for example described in patent US4889647.According to a particular embodiment, the molybdenum complex is chosen from organic molybdenum complexes and their mixtures, in particular with amide ligands, obtained by reaction: (a) of a fatty substance of mono, di or tri glyceride type, or fatty acid, comprising in particular from 4 to 36 carbon atoms, particularly from 4 to 20 carbon atoms, more particularly from 6 to 18 carbon atoms; (b) of an amine source of formula (A), in particular diethanolamine: [Chem 6]. in which: - X 1 represents an oxygen atom or a nitrogen atom, - X 2 represents an oxygen atom or a nitrogen atom, - n or m represents 1 when respectively X 1 or X 2 represents an oxygen atom, - n or m represents 2 when respectively X 1 or X 2represents a nitrogen atom; and (c) a source of molybdenum chosen from molybdenum trioxide or molybdates, in particular ammonium molybdate. In particular, the molybdenum complex is chosen from organic molybdenum complexes: (a) of formula (II) below: [Chem 7] in which R1 represents a linear or branched, saturated or unsaturated alkyl group comprising from 4 to 36 carbon atoms, in particular from 4 to 20 carbon atoms, particularly from 6 to 18 carbon atoms; (b) of the following formula (III): [Chem 8] in which: X 1 represents an oxygen atom or a nitrogen atom, X 2 represents an oxygen atom or a nitrogen atom, n represents 1 when X 1 represents an oxygen atom and m represents 1 when X 2 represents an oxygen atom, n represents 2 when X 1 represents a nitrogen atom and m represents 2 when X 2represents a nitrogen atom, and R1 represents a linear or branched, saturated or unsaturated alkyl group comprising from 4 to 36 carbon atoms, in particular from 4 to 20 carbon atoms, particularly from 6 to 18 carbon atoms; (c) of formula (IIIbis) following: [Chem 9] in which: X 1 represents an oxygen atom or a nitrogen atom, X 2 represents an oxygen atom or a nitrogen atom, n represents 1 when X 1 represents an oxygen atom and m represents 1 when X 2 represents an oxygen atom, n represents 2 when X 1 represents a nitrogen atom and m represents 2 when X 2represents a nitrogen atom, R1 represents a linear or branched, saturated or unsaturated alkyl group comprising from 4 to 36 carbon atoms, in particular from 4 to 20 carbon atoms, particularly from 6 to 18 carbon atoms, and R2 represents a linear or branched, saturated or unsaturated alkyl group comprising from 4 to 36 carbon atoms, in particular from 4 to 20 carbon atoms, particularly from 6 to 18 carbon atoms; and (d) mixtures thereof. According to a particular embodiment, the molybdenum complex of formula (II), (III) or (IIIbis) is prepared by reaction: (a) of a fatty substance of mono, di or tri glyceride type, or fatty acid, (b) of diethanolamine or 2-(2-aminoethyl) aminoethanol, (c) and of a source of molybdenum chosen from molybdenum trioxide or molybdates, preferably ammonium molybdate.In particular, the molybdenum complex of formula (III) may be chosen from a molybdenum complex: (a) of formula (IIIa): [Chem 10]. R1 represents a linear or branched, saturated or unsaturated alkyl group comprising from 4 to 36 carbon atoms, in particular from 4 to 20 carbon atoms, particularly from 6 to 18 carbon atoms; (b) of formula (IIIb): [Chem 11] R1 represents a linear or branched, saturated or unsaturated alkyl group comprising from 4 to 36 carbon atoms, in particular from 4 to 20 carbon atoms, particularly from 6 to 18 carbon atoms; and (d) mixtures thereof. According to a particular embodiment, the molybdenum complex comprising ligands free of sulfur and phosphorus is derived from the reaction between a fatty substance of mono, di or tri glyceride type, or fatty acid as defined above, an amine source of formula (A) defined above, in particular diethanolamine, and a source of molybdenum, the molybdenum complex being chosen from the compounds of the following formulas (II) or (IIIa), or their mixture [Chem 12] , in which R1 represents a residue of the fatty body of mono, di or tri glyceride type, or of fatty acid, comprising from 4 to 36 carbon atoms, in particular from 4 to 20 carbon atoms, particularly from 6 to 18 carbon atoms. According to one embodiment, one or more molybdenum complexes comprising ligands free of sulfur and phosphorus mentioned above provide a quantity of molybdenum atoms of between 10 and 2000 ppm by mass relative to the total mass of the lubricating composition. Particularly, one or more molybdenum complexes comprising ligands free of sulfur and phosphorus provide a quantity of molybdenum atoms of between 100 and 1000 ppm by mass relative to the total mass of the lubricating composition.More particularly, one or more molybdenum complexes comprising ligands free of sulfur and phosphorus provide a quantity of molybdenum atoms of between 200 and 800 ppm by mass relative to the total mass of the lubricating composition. Phosphosulfur additive As indicated previously, a lubricating composition according to the invention comprises at least one non-metallic phosphosulfur additive as mentioned previously. According to one embodiment, the non-metallic phosphosulfur additive is chosen from non-metallic dithiophosphates, non-metallic thiophosphates, and mixtures thereof. According to one embodiment, the non-metallic phosphosulfur additive is chosen from non-metallic dithiophosphates and non-metallic thiophosphates, or mixtures thereof, for example as defined in document US8404624.According to a particular embodiment, the non-metallic dithiophosphates are chosen from compounds derived from 3-dithiophosphorylpropionic acid of the following formula (IV) [Chem 14]. in which R7 and R8, identical or different, independently represent a C3 to C alkyl group 18 , a C5-C cycloalkyl group 12 , in particular a C9-C10 cycloalkyl group, a C9-C10 bicycloalkylmethyl group, a C9-C10 tricycloalkylmethyl group, a phenyl group or a C7-C alkylphenyl group 24 , or R7 and R8 together form a group: [Chem 15] R9 represents a hydrogen atom or a methyl group. According to a particular embodiment, R7 and R8 independently represent a C3 to C18 alkyl group, more particularly an isopropyl, isobutyl or 2-ethylhexyl group.R7 and R8 may also represent other groups including an n-propyl group, an n-butyl group, a tert-butyl group, an n-pentyl group, an isoamyl group, a neopentyl group, a 2-ethylbutyl group, an n-hexyl group, a 1-methylpentyl group, a 1,3-dimethylbutyl group, an n-heptyl group, an isoheptyl group, an n-octyl group, a 1,4,4-trimethyl-2-pentyl group, a 3,4-dimethyl-1-hexyl group, a 3,5-dimethyl-1-hexyl group, a 4,5-dimethyl-1-hexyl group, a 3-methyl-heptyl group, a 5-methyl-heptyl group, a 1,1,3,3- tetramethylbutyl, a branched octyl group as obtained from an isobutylene dimer, an n-nonyl group, a 1,1,3-trimethylhexyl group, a branched nonyl group as obtained from a tripropylene trimer.More particularly, non-metallic dithiophosphates correspond to compounds derived from 3-dithiophosphorylpropionic acid of formula (IV) as defined above, in which R7 and R8 represent a C3 to C alkyl group. 18 , for example a 2-methylpropyl group, and R9 represents a methyl group. For example, a non-metallic dithiophosphate corresponds to a derivative of 3-dithiophosphorylpropionic acid corresponding to 3-[[bis(2-methylpropoxy)phosphinothioyl]thio]-2-methylpropanoic acid. According to another particular embodiment, the phosphosulfur additive is chosen from non-metallic thiophosphates, in particular the thiophosphoric acid esters of the following formula (V) [Chem 16] in which R10, R11 and R12, which may be identical or different, represent hydrocarbon groups comprising from 3 to 20 carbon atoms. In particular, R10, R11 and R12 independently represent a C3 to C3 aliphatic or aromatic group. 20 , in particular a phenyl group optionally substituted by a linear or branched C7 to C24 alkyl chain. According to a particular embodiment, R 10 , R 11 and R 12 independently represent a phenyl group or a (C7-C20)alkylphenyl group. According to a particular embodiment, R10, R11 and R12 independently represent a phenyl group or a (C1-C9alkyl) group 1-3 phenyl. According to a particular embodiment, R10, R11 and R12 represent a phenyl group; or one of R10, R11 and R12 represents a phenyl group and two of R10, R 11 and R 12 represent a (C1-C9alkyl) group 1-3 phenyl; or two of R10 , R 11 and R 12 represent a phenyl group and one of R 10 , R 11 and R 12 represents a (C1-C9alkyl)1-3phenyl group; or R10, R11 and R12 represent a (C1-C9alkyl) group 1-3 phenyl. According to a particular embodiment, R10, R11 and R12, identical or different, represent a C3 to C alkyl group 20 , a grouping (C5-C 12 )cycloalkyl, a phenyl group, a (C7-C 20 )alkylphenyl, a group (C7-C 20)alkoxyphenyl, naphthyl and (C7-C9)phenylalkyl. In particular, a C3 to C20 alkyl group is, for example, an isopropyl group, n-nonyl group, a 1,1,3-trimethylhexyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, a 1-methylundecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-neptadecyl group or an n-octadecyl group. In particular, a (C5-C 12 )cycloalkyl is for example a cyclopentyl group or a cyclohexyl group. In particular, a (C5-C 12)cycloalkyl-(C1-C4)alkyl is, for example, a cyclopentylmethyl group, a 2-cyclopentylethyl group, a cyclohexylmethyl group or a 2-cyclohexylethyl group. In particular, a (C7-C20)alkylphenyl group is a phenyl group which is substituted, for example, by one, two or three C1-C4 alkyl groups, or by one, two or three C1-C6 alkyl groups, or one, two or three C1-C12 alkyl groups. In particular, a (C7-C2)alkoxyphenyl group is a phenyl group which is substituted, for example, by one, two or three C1-C4 alkoxy groups, in particular a methoxy or ethoxy group, or by one, two or three C1-C6 alkoxy groups, or by one, two or three C1-C12 alkoxy groups, these groups being analogous to the aforementioned alkyl groups. In particular, a (C7-C9)phenylalkyl group is, for example, a benzyl group, a 1-phenyl-1-ethyl group or a 2-phenyl-1-ethyl group.According to a particular embodiment, the non-metallic phosphosulfur additive is a mixture of thiophosphoric acid esters of the following formula (Va) [Chem 17]. in which x is between 0 and 2.5, y is equal to 3−(x+z), z is between 0 and 3−(x+y), and x+y+z=3, and Ar represents a phenyl group, a (C7-C 18 )alkylphenyl, a group (C7-C 18)alkoxyphenyl, a naphthyl group or a (C7-C9)phenylalkyl group mentioned above. The preparation of thiophosphoric acid esters of formula (Va) is for example described in document EP368803. According to one embodiment, the thiophosphoric acid esters of formula (Va) are mixtures of triarylthiophosphate, such as mixtures of n-decylphenyl-n-nonylphenyl-phenylthiophosphate, o-tert-butylphenyl-o-isopropylphenyl-phenylthiophosphate, and / or n-hexylphenyl-phenylthiophosphate. According to another embodiment, the non-metallic phosphosulfur additive is a thiophosphoric acid ester of the triphenylthiophosphate type, such as O,O,O-tris(2(or4)-C9-10-isoalkylphenyl)phosphorothioate. According to a particular embodiment, the non-metallic dithiophosphates correspond to ammonium salts of dithiophosphoric acid of formula (VI): [Chem 18] in which R7 and R8 are as defined previously, R a , R b , Rc and R d , identical or different, represent a hydrogen atom or a C6 to C20 hydrocarbon group. According to a particular embodiment, R7 and R8 of formula (VI) independently represent a phenyl group or a (C3-C8)alkyl group, and in particular an isopropyl group. According to a particular embodiment, Ra, Rb, Rc and Rd, independently represent a hydrogen atom or a (C 12 -C 20)alkyl. According to another embodiment, the non-metallic phosphosulfur additive is chosen from compounds derived from 3-dithiophosphorylpropionic acid of formula (IV) as described above, thiophosphoric acid esters of formula (V) as described above, ammonium salts of dithiophosphoric acid of formula (VI) as described above, and mixtures thereof. According to one embodiment, one or more non-metallic phosphosulfur additives provide a quantity of phosphorus atoms of between 50 and 2000 ppm by mass relative to the total mass of the lubricating composition. In particular, one or more non-metallic phosphosulfur additives provide a quantity of phosphorus atoms of between 100 and 1000 ppm by mass relative to the total mass of the lubricating composition.More particularly, one or more non-metallic phosphosulfur additives provide a quantity of phosphorus atoms of between 200 and 800 ppm by mass relative to the total mass of the lubricating composition. Other additives According to a particular embodiment, the composition further comprises one or more additional additives, distinct from the aforementioned spiro compound(s) of formula (I), from the aforementioned molybdenum complex(es) and from the aforementioned non-metallic phosphosulfur additive(s). In particular, such additional additives are chosen from antioxidants, anti-wear additives, dispersants, detergents, anti-corrosion additives, anti-foaming agents, pour point lowering additives, seal swelling additives and viscosity index improvers.It is understood that said additional additive(s) are compatible with their implementation in a lubricating composition as considered above. Said additive(s) are of course chosen with regard to the intended application for the lubricant. Of course, those skilled in the art will take care to choose the possible additives and / or their quantity in such a way that the advantageous properties of the lubricating composition according to the invention, in particular the tribological properties, in particular friction reduction and possibly protection against wear, are not impaired by the envisaged addition. A lubricating composition considered according to the invention may comprise at least one antioxidant additive. The antioxidant additives are essentially dedicated to delaying the degradation of the lubricating composition in service.This degradation can notably result in the formation of deposits, the presence of sludge or an increase in the viscosity of the lubricating composition. They act in particular as radical inhibitors or hydroperoxide destroyers. Among the antioxidant additives commonly used, mention may be made of phenolic type antioxidant additives and amine type antioxidant additives. Phenolic antioxidant additives may be ash-free or in the form of neutral or basic metal salts. The antioxidant additives may notably be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted by at least one C1-C12 alkyl group, N,N'-dialkyl-aryl-diamines and mixtures thereof.Preferably, the sterically hindered phenols are chosen from compounds comprising a phenol group of which at least one vicinal carbon of the carbon carrying the alcohol function is substituted by at least one C1-C alkyl group. 10 , preferably a C1-C6 alkyl group, preferably a C4 alkyl group, preferably by the tert-butyl group. Sulphurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives. Amino compounds are another class of antioxidant additives that can be used, optionally in combination with the phenolic antioxidant additives. Examples of amine compounds are aromatic amines, for example aromatic amines of formula NR ’ R ’’ R ’’’ in which R ’ represents an aliphatic group or an aromatic group, optionally substituted, R ’’represents an aromatic group, optionally substituted, R ’’’ represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R e S(O) z R f in which R e represents an alkylene group or an alkenylene group, R frepresents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2. In particular, an antioxidant amine compound is chosen from alkylated diphenylamines or ADPA. According to one embodiment, a lubricating composition considered according to the invention may comprise from 0.1% to 5% by mass, relative to the total mass of the lubricating composition, of at least one antioxidant additive. In particular, a lubricating composition considered according to the invention may comprise from 0.2% to 3% by mass, relative to the total mass of the lubricating composition, of at least one antioxidant additive.More particularly, a lubricating composition considered according to the invention may comprise from 0.3% to 2% by mass, relative to the total mass of the lubricating composition, of at least one antioxidant additive. A lubricating composition considered according to the invention may also comprise at least one pour point depressant additive (also called “PPD” agents for “Pour Point Depressant” in English). By slowing down the formation of paraffin crystals, pour point depressant additives generally improve the cold behavior of the lubricating composition. Examples of pour point reducing agents include polyalkyl methacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes and alkylated polystyrenes. A lubricating composition considered according to the invention may also comprise at least one viscosity index (VI) improver.Viscosity index (VI) improvers, in particular viscosity index improving polymers, ensure good cold resistance and minimal viscosity at high temperatures. Examples of viscosity index improving polymers include polymer esters, homopolymers or copolymers, hydrogenated or non-hydrogenated, of styrene, butadiene and isoprene, homopolymers or copolymers of olefin, such as ethylene or propylene, polyacrylates and polymethacrylates (PMA). Advantageously, a lubricating composition according to the invention comprises at least one viscosity index improver chosen from polymethacrylates (PMA) and hydrogenated polyisoprene-styrene (PISH), linear, grafted, comb or star, preferably star.In particular, the viscosity index improving additive(s) may be present in a lubricating composition used according to the invention in a content ranging from 1 to 15% by mass, in particular from 2 to 10% by mass, relative to the total mass of the lubricating composition. According to one embodiment, a lubricating composition according to the invention is free of viscosity index improving additive. A lubricating composition considered according to the invention may also comprise at least one dispersing agent. The dispersing agents ensure the maintenance in suspension and the removal of insoluble solid contaminants consisting of the secondary oxidation products which form when the lubricating composition is in service. They may be chosen from Mannich bases, succinimides and their derivatives.In particular, a lubricating composition considered according to the invention may comprise from 0.2 to 10% by mass of dispersing agent(s), relative to the total mass of the lubricating composition. A lubricating composition considered according to the invention may also comprise at least one anti-foam additive. The anti-foam additives may be chosen from polar polymers such as polymethylsiloxanes or polyacrylates. In particular, a lubricating composition considered according to the invention may comprise from 0.01 to 3% by mass of anti-foam additive(s), relative to the total mass of the lubricating composition. According to a particular embodiment, the composition further comprises at least one detergent additive distinct from the spiro compound of formula (I).Such detergent additives are generally anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head, the associated cation being able to be a metal cation of an alkali or alkaline-earth metal. They are generally chosen from alkali metal or alkaline-earth metal salts of carboxylic or sulfonic acids, in particular sulfonates, salicylates, naphthenates, phenates, carboxylates and mixtures thereof. The alkali and alkaline-earth metals are preferably calcium, magnesium, sodium or barium. These metal salts generally comprise the metal in a stoichiometric quantity or in excess, therefore in a quantity greater than the stoichiometric quantity.These are then overbased detergent additives; the excess metal providing the overbased character to the detergent additive is then generally in the form of a metal salt insoluble in the base oil, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate. According to a particular embodiment, a lubricating composition according to the invention comprises at least one metallic detergent additive, distinct from the spiro compounds of formula (I) according to the invention, in particular chosen from salts of alkali metals or alkaline-earth metals, overbased or not, in particular from calcium salts, magnesium salts and their mixtures. The invention will now be described by means of the following examples, given as an illustration and not as a limitation of the invention. Application As indicated previously, a lubricating composition according to the invention is intended for the lubrication of a mechanical system.A mechanical system comprises, for example, an engine and / or one or more transmission components. The lubricating compositions according to the invention are advantageously used for any type of engine, for mobile or stationary applications, which may be subject, during their operation, to friction phenomena. These are more particularly internal combustion engines of vehicles, such as gasoline engines, Diesel engines, gas-powered engines, engines powered by alternative fuels such as oxygenated biofuels, hydrogen, ammonia, methanol or synthetic fuel. A “Diesel engine” within the meaning of the invention is a combustion engine whose fuel is diesel. Gas-powered engines designate internal combustion engines whose fuel comprises at least one gas, including biogas.They include engines running exclusively on gas, known as gas engines, for example engines running on natural gas (liquefied natural gas (LNG) or compressed natural gas (CNG)) or liquefied petroleum gas (LPG), and hydrogen or ammonia engines, but also engines running on gas and gasoline (gas / gasoline “dual fuel” engines), engines running on gas and diesel (“dual fuel” gas / diesel engines). Engines for mobile applications are more specifically engines used in vehicles, including heavy-duty vehicles, so-called “off-road” mobile machines, light vehicles, electric vehicles or even marine vehicles, trains or aircraft. Engines for stationary applications, or stationary engines, can find applications, for example, in devices for producing electrical energy. This may be, for example, a stationary gas engine.The term "transmission members" means, for example, elements corresponding to the bearings, gears and bearings known to those skilled in the art. The lubricating compositions according to the invention are advantageously used for any type of mechanical vehicle transmissions defined above, in particular synchronized or not. The lubricating compositions according to the invention are advantageously used for any type of industrial gear reducers, in particular such a reducer is intended to modify the speed ratio and / or the torque between the input shaft and the output shaft of a mechanism such as a gear. The invention will now be described by means of the following examples, given as an illustration and not as a limitation of the invention.Examples Evaluation of tribological properties Tribological properties can be evaluated by measuring the coefficients of friction by a test on a tribometer with a rotating three-plane ball contact, for example a so-called Anton Paar MCR302 rheometer with a T-PTD-200 tribological assembly (“ball on three planes”) described in the publication by Yu Min Kiw et al. mentioned above, having the following characteristics: - ball diameter: 12.7 mm, - Ball material: 100C6, - Plane material: AISI5200, - temperature: 80°C, - Normal load: 12 N, and - Rotation speed: increase from 0 to 210 rpm in 850 s – hold at 210 rpm for 400 s – decrease from 210 to 0 rpm in 850 s. Note that the previous conditions correspond to limit regime lubrication conditions. The coefficient of friction is measured throughout the test procedure described above.The measurement of the area under the friction curve over the test time reflects the friction quality of the lubricant composition being tested and is called the friction score. The lower the friction score, the better the friction loss reduction performance of a lubricant composition. During the test protocol, four separate reference lubricant compositions were each repeated twice to establish a friction score measurement uncertainty within a 95% confidence interval. The lubricant compositions tested in the examples below were tested only once.Example 1 Preparation of the lubricating compositions Three lubricating compositions were formulated: - a reference lubricant, not in accordance with the invention, noted CC1, free from non-metallic phosphosulfur additive and comprising a metallic phosphosulfur additive, in particular DTPZn (C4 / C6); - a reference lubricant, not in accordance with the invention, noted CC2, free from non-metallic phosphosulfur additive and comprising a phosphite compound, in particular dibutyl hydrogen phosphite; and - a lubricant, in accordance with the invention, noted I1, corresponding to the formulation CC1 in which the metallic phosphosulfur additive DTPZn (C4 / C6) has been replaced by a non-metallic phosphosulfur additive at 0.54% by mass relative to the total mass of the lubricating composition, in particular a non-metallic dithiophosphate. The components and quantities (expressed as a mass percentage) for the three lubricants are indicated in the following table.Lubricants are formulated by simple mixing and stirring at 60°C of the different components. [Table 2].

[0003] (1) Molybdenum complex resulting from the reaction between coconut oil glycerides, diethanolamine and molybdenum oxide. (2) Metallic phosphosulfur additive DTPZn of formula Zn((SP(S)(OR5)(OR6))2obtained from secondary alcohols of formula R5OH and R6OH. R5 representing a C4 alkyl group and R6 representing a C6 alkyl group, (3) Non-metallic dithiophosphate, corresponding to 3-[[bis(2-methylpropoxy)phosphinothioyl]thio]-2-methylpropanoic acid. (4) Dibutyl hydrogen phosphite of general formula P(OH)(OR) c )(GOLD d ), with R c and R d representing a butyl group. (5) Spiro compound of formula (I), in which M is a boron atom, R each represents an octadecyl group (C18), n1 and n2 are 1. (6)ADPA or alkylated diphenylamine (butyl / octyl) corresponding to an antioxidant. (7)Group IV base oil (KV100 = 3.8 – 4.6; KV40 = 17.0 – 22.0; VI (Viscosity Index) 120-126). Example 2 Lubricant Evaluation The tribological performances, particularly in terms of friction reduction, of the different lubricants prepared in Example 1 were evaluated according to the Tribological Properties Evaluation protocol described above. It is noted that the compositions contain identical amounts of molybdenum and phosphorus, respectively; in other words, the compositions have an isotenor in molybdenum and phosphorus, potentially allowing a tribofilm, such as a molybdenum disulfide (MoS2) film, to be enriched in a similar manner during the tests. Such tests are therefore directly comparable with respect to their performance potential. The friction score results are presented in the table below.[Table 3] Conclusion: These results show that the use of a spiro compound of formula (I), a molybdenum complex comprising ligands free of sulfur and phosphorus and a non-metallic phosphosulfur additive, in lubricating compositions according to the invention, makes it possible to improve the tribological properties, in particular by reducing friction. In particular, the tribological properties of the lubricating composition according to the invention I1 are improved in comparison with those of the comparative compositions CC1 and CC2 which do not comprise a non-metallic phosphosulfur additive. The standard deviation of each value of the friction scores shows a repeatability of the results and the presence of a significant difference between the value of the results obtained for the comparative compositions CC1 and CC2, and the value of the results obtained for the composition according to the invention I1, since no overlap of the deviation values ​​is present.

Claims

Claims 1. Lubricating composition, comprising: i. at least one base oil; ii. at least one spiro compound of the following formula (I): wherein: M is an atom selected from boron and aluminum; n1 and n2 are, independently of each other, 0, 1, 2, 3 or 4, and R represent, independently of each other, a hydrocarbon group comprising from 1 to 50 carbon atoms; iii. at least one molybdenum complex comprising ligands free of sulfur and phosphorus; and iv. at least one non-metallic phosphosulfur additive.

2. A lubricating composition according to claim 1, wherein said base oil is selected from group I to V base oils and mixtures thereof, for example a group IV base oil. 3.Lubricating composition according to any one of claims 1 or 2, in which said spiro compound is of formula (I) in which: - M is a boron atom; and / or - the substituents R represent, independently of one another, an aliphatic chain, linear or branched, in particular an alkyl chain, preferably linear, C1 to C50, in particular C3 to C30, in particular C5 to C25, more particularly C10 to C20, or even C. 10 to C 18 , or even in C 10 to C 16 , and for example in C 16 or in C 18 ; and / or - n1 and n2 are 1, the substituents R being identical.

4. Lubricating composition according to any one of the preceding claims, in which said molybdenum complex is chosen from organic molybdenum complexes and their mixtures, obtained by reaction: (a) of a fatty substance of mono, di or tri glyceride type, or fatty acid, comprising in particular from 4 to 36 carbon atoms, particularly from 4 to 20 carbon atoms, more particularly from 6 to 18 carbon atoms; (b) of an amine source of formula (A), in particular diethanolamine: in which: X 1 represents an oxygen atom or a nitrogen atom, X 2 represents an oxygen atom or a nitrogen atom, n or m represents 1 when respectively X 1 or X 2 represents an oxygen atom, n or m represents 2 when respectively X 1 or X 2represents a nitrogen atom; and (c) a source of molybdenum, in particular chosen from molybdenum trioxide or molybdates, particularly ammonium molybdate.

5. Lubricating composition according to the preceding claim, in which said molybdenum complex comprises at least one compound of the following formulas (II) or (IIIa), or their mixture in which R1 represents a residue of the fatty body of mono, di or tri glyceride type, or of fatty acid, comprising from 4 to 36 carbon atoms, in particular from 4 to 20 carbon atoms, particularly from 6 to 18 carbon atoms.

6. Lubricating composition according to any one of the preceding claims, in which said non-metallic phosphosulfur additive is chosen from non-metallic dithiophosphates, non-metallic thiophosphates, and mixtures thereof, in particular from: - compounds derived from 3-dithiophosphorylpropionic acid of the following formula (IV): in which R7 and R8, identical or different, independently represent a C3 to C alkyl group 18 , a C5 to C cycloalkyl group 12 , a C9 to C10 bicycloalkylmethyl group, a C9 to C10 tricycloalkylmethyl group, a phenyl group or a C7 to C24 alkylphenyl group, or R7 and R8 together form a group: , and R9 represents a hydrogen atom or a methyl group; - the thiophosphoric acid esters of the following formula (V) - in which R10, R11 and R12, identical or different, independently represent a C3 to C3 aliphatic or aromatic group 20 , in particular a phenyl group optionally substituted by a C7 to C alkyl chain 24 linear or branched; - the ammonium salts of dithiophosphoric acid of the following formula (VI) in which R7 and R8, identical or different, are as defined for formula (IV), and in particular independently represent a phenyl group or a (C3-C8)alkyl group, and Ra, Rb, Rc and Rd, identical or different, represent a hydrogen atom or a C6 to C20 hydrocarbon group, and independently represent a hydrogen atom or a (C 12 -C 20)alkyl; and - mixtures thereof.

7. Lubricating composition according to any one of the preceding claims, in which the said spiro compound(s) are used in a content of between 0.1 and 5.0% by mass relative to the total mass of the lubricating composition, in particular of between 0.5 and 4.0% by mass relative to the total mass of the lubricating composition, more particularly of between 1 and 3.0% by mass relative to the total mass of the lubricating composition; and / or the said molybdenum complex(es) provide a quantity of molybdenum atoms of between 10 and 2000 ppm by mass relative to the total mass of the lubricating composition, particularly of between 100 and 1000 ppm by mass relative to the total mass of the lubricating composition,more particularly between 200 and 800 ppm by mass relative to the total mass of the lubricating composition; and / or and / or said non-metallic phosphosulfur additive(s) provide a quantity of phosphorus atoms between 50 and 2000 ppm by mass relative to the total mass of the lubricating composition, particularly between 100 and 1000 ppm by mass relative to the total mass of the lubricating composition, more particularly between 200 and 800 ppm by mass relative to the total mass of the lubricating composition.

8. Lubricating composition according to any one of the preceding claims, comprising one or more additional additives, distinct from said base oil(s), said spiro compound(s) of formula (I), said molybdenum complex(es) and said non-metallic phosphosulfur additive(s), chosen from antioxidants, anti-wear additives, dispersants, detergents,anti-corrosion additives, anti-foaming agents, pour point depressants, seal swelling additives, viscosity index improvers., 9. Use in a lubricating composition of at least one spiro compound of formula (I), a molybdenum complex and a non-metallic phosphosulfur additive, as defined according to any one of claims 1 to 6, for preventing and / or reducing friction in a mechanical system lubricated by means of said lubricating composition, said system comprising in particular an engine, for example an internal combustion engine, and / or a mechanical transmission member.

10. Use of the lubricating composition defined according to one of claims 1 to 8, for preventing and / or reducing friction in a mechanical system lubricated by means of said lubricating composition, said system comprising in particular an engine, for example an internal combustion engine, and / or a mechanical transmission member, more particularly an internal combustion engine.

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