Polynuclear metal compounds

Abstract

To provide a novel polynuclear metal compound having great potential as a catalyst, a magnetic material or the like.SOLUTION: The present invention discloses a polynuclear metal compound having 10 or more metal atoms different from a poly atom introduced to a deficient structure site of a cyclic polyoxomethalate compound. The cyclic polyoxomethalate compound includes a ring composed of a poly atom-oxygen atom bond having a polyoxomethalate compound-derived structural site as a constitutional unit, the constitutional unit directly bonding to other two constitutional units, and the other two constitutional units further bonding directly or via another constitutional unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a polynuclear metal compound, more specifically to a polynuclear metal compound that may be suitably used as a functional material such as a catalyst, a medicine, or a magnetic material, and a method for producing the same. [Background technology]

[0002] Polyoxometalates are attractive materials in various fields such as catalysis, medicine, and functional materials due to their high stability and easily tunable chemical and physical properties. For this reason, there is a demand for the development of polyoxometalates with new structures.

[0003] Up until now, cluster synthesis based on polyoxometalates has had drawbacks such as the instability of the resulting structures (polyoxometalates with clusters) in solution and the difficulty of synthesizing multinuclear clusters. For example, until recently, the limit for Ag clusters was four nuclei (see Non-Patent Document 1) or six nuclei (see Non-Patent Document 2).

[0004] Recently, defect-type tungstosilicic acid SiW9O 34 It has been reported that a polyoxometalate having an Ag27 core with precisely controlled structure can be obtained by self-assembly synthesis with Ag using Ag as a template (see Non-Patent Document 3). Also, defective phosphotungstic acid P2W 12 O 48 Ring-shaped polyoxometalate P8W self-assembled 48 O 184 It has also been reported that the following compound was successfully synthesized (see Non-Patent Document 4). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Kikukawa et al., and 3 others, Angewandte Chemie International Edition (Germany), 2012, Vol. 51, pp. 2434-2437 [Non-Patent Document 2] Kikukawa et al., et al., Chemical Communications (UK), 2013, Vol. 49, pp. 376-378 [Non-Patent Document 3] Yonezato et al., and seven others, Journal of the American Chemical Society (USA), 2019, Vol. 141, pp. 19550-19554 [Non-Patent Document 4] Sasaki et al., and 4 others, "Inorganic Chemistry" (USA), 2019, Vol. 58, pp. 7722-7729 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, there is a need for further development of polyoxometalates with new structures, and it has been desirable to make better use of the diverse properties that are exhibited depending on the type and coordination state of the metal atoms. The present invention has been made in view of the above-mentioned circumstances, and has an object to provide a novel metal compound which is promising as a catalyst, a magnetic material, etc. [Means for solving the problem]

[0007] The present inventors have investigated novel metal compounds that are promising as catalysts, magnetic materials, etc., and have focused on the synthesis of novel polynuclear clusters. They have found that, while large compounds formed by self-assembly of defective polyoxometalates are generally unstable, when these are made into a ring-like (annular) shape, they become stable, and that by synthesizing clusters using this as a base, it is possible to suitably obtain polynuclear metal compounds having a structure in which 10 or more metal atoms different from polyatoms are introduced into the defective structural sites of a cyclic polyoxometalate compound, thereby arriving at the present invention.

[0008] That is, the present invention is a polynuclear metal compound having a structure in which 10 or more metal atoms other than polyatoms are introduced into defective structural sites of a cyclic polyoxometalate compound, the cyclic polyoxometalate compound being a structural unit derived from a polyoxometalate compound, the structural unit being directly bonded to two other structural units, and the other two structural units being further bonded directly or via other structural units to form a ring formed of a bond between a polyatom and an oxygen atom. This is also referred to as the first present invention in this specification.

[0009] The present invention also relates to a polynuclear metal compound having a structure in which 10 or more metal atoms other than polyatoms are introduced into the defective structural sites of a cyclic polyoxometalate compound, the cyclic polyoxometalate compound also being a polynuclear metal compound containing a ring formed by a polyatom-oxygen atom bond and having an inner diameter of 0.4 nm or more, which is also referred to as the second present invention in this specification. The present invention will be described in detail below. In addition, a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

[0010] <Polynuclear metal compound of the present invention> (Polynuclear metal compound according to the first aspect of the present invention) The first polynuclear metal compound of the present invention is a polynuclear metal compound having a structure in which 10 or more metal atoms other than polyatoms are introduced into the missing structural sites of a cyclic polyoxometalate compound, and the cyclic polyoxometalate compound has a structural site derived from a polyoxometalate compound as a structural unit, and the structural unit is directly bonded to two other structural units, and the other two structural units are further bonded directly or via other structural units to form a ring consisting of a polyatom-oxygen atom bond.

[0011] In the first polynuclear metal compound of the present invention, the other two structural units are further bonded directly or via "other structural units" so that the structural units as a whole are bonded to form a ring; when bonded via "other structural units", the "other structural units" may be one or more. As described below, it is particularly preferable that the number of "other structural units" is one.

[0012] The cyclic polyoxometalate compound in the first polynuclear metal compound of the present invention has a structural unit derived from the above polyoxometalate compound, and contains a ring formed by a polyatom-oxygen atom bond, formed by at least three such structural units being bonded in a ring. In particular, in the structural units formed by bonding in a ring, it is preferable that adjacent structural units are directly bonded to each other. In other words, it is preferable that each structural unit is directly bonded to two other structural units. The cyclic polyoxometalate compound preferably has as its constituent unit a structural moiety derived from a polyoxometalate compound having a structure in which a polyatom is coordinated to a heteroatom via an oxygen atom.

[0013] The ring consisting of a polyatom-oxygen atom bond is formed by cyclically bonding at least three of the above-mentioned structural units in the polynuclear metal compound of the present invention, and is composed of a polyatom-oxygen atom bond contained in each of the at least three structural units. Each of the polyatoms in the ring is bonded to two oxygen atoms forming the ring, and may further be bonded to a metal atom different from the polyatom contained in the structural unit, or a heteroatom, etc., described below. Each of the oxygen atoms in the ring is bonded to two polyatoms forming the ring.

[0014] In the first polynuclear metal compound of the present invention, it is preferable that the above-mentioned structural units are bonded in a ring shape in the form of four or more units. It is also preferable that the above-mentioned structural units are bonded in a ring shape in the form of nine or less units, and more preferably, six or less units. Among these, it is particularly preferred that four of the above structural units are bonded in a ring shape. That is, it is particularly preferred that the above cyclic polyoxometalate compound has a structural unit derived from a polyoxometalate compound, and the structural unit is directly bonded to two other structural units, and each of the other two structural units is further bonded to one other structural unit (most preferably directly bonded) to form a ring consisting of a polyatom-oxygen atom bond.

[0015] In this specification, the term "cyclic polyoxometalate compound" and "cyclically bonded" refers to, for example, when the above-mentioned constituent units are four, A, B, C, and D, A is bonded to B, B is bonded to C, C is bonded to D, and D is further bonded to A.

[0016] The preferred embodiments of the polynuclear metal compound according to the first aspect of the present invention described above can be preferably applied to the polynuclear metal compound according to the second aspect of the present invention.

[0017] (Polynuclear metal compound according to the second aspect of the present invention) The second polynuclear metal compound of the present invention is a polynuclear metal compound having a structure in which 10 or more metal atoms other than polyatoms are introduced into the defective structural sites of a cyclic polyoxometalate compound, and the cyclic polyoxometalate compound includes a ring consisting of a polyatom-oxygen atom bond and having an inner diameter of 0.4 nm or more. The above inner diameter is determined by measuring the distance between oxygen atoms that are symmetrically positioned within the ring structure (facing each other about the center of the ring structure) based on the molecular structure determined by single crystal X-ray structure analysis, and the shortest distance between these is taken as the inner diameter.

[0018] The inner diameter is preferably 0.5 nm or more, more preferably 0.8 nm or more, and even more preferably 1 nm or more. The upper limit of the inner diameter is not particularly limited, but is preferably, for example, 10 nm or less, more preferably 8 nm or less, further preferably 5 nm or less, and particularly preferably 3 nm or less. In addition, when the second polynuclear metal compound of the present invention has multiple equivalent or unequivalent rings formed from the above-mentioned polyatom-oxygen atom bonds, the above-mentioned inner diameter is the inner diameter of only one of the multiple rings having the smallest inner diameter.

[0019] In the polynuclear metal compound of the second aspect of the present invention, instead of specifying the inner diameter of the cyclic polyoxometalate compound, the preferred form described above in the first aspect of the present invention, the total atomic number of polyatoms and oxygen atoms constituting the ring formed by the polyatom-oxygen atom bonds, and the sum of the distances of the polyatom-oxygen atom bonds constituting the ring may be specified. The total number of polyatoms and oxygen atoms constituting the ring formed by the above polyatom-oxygen atom bond is preferably 6 or more, more preferably 8 or more, even more preferably 10 or more, and particularly preferably 12 or more. The total number of atoms is preferably 100 or less, more preferably 75 or less, further preferably 60 or less, and particularly preferably 48 or less. In addition, when the second polynuclear metal compound of the present invention has multiple equivalent or unequivalent rings formed from the above polyatom-oxygen atom bonds, the above total number of atoms refers to the total number of atoms of only one ring among the multiple rings that has the smallest total number of atoms.

[0020] In the ring consisting of the above polyatom-oxygen atom bonds, the sum of the distances of the polyatom-oxygen atom bonds constituting the ring is preferably 1 nm or more, more preferably 2 nm or more, even more preferably 3 nm or more, and particularly preferably 5 nm or more. The sum of the bond distances of the polyatoms-oxygen atoms is preferably 100 nm or less, more preferably 50 nm or less, further preferably 20 nm or less, and particularly preferably 10 nm or less. In addition, when the second polynuclear metal compound of the present invention has multiple equivalent or unequivalent rings consisting of the above polyatom-oxygen atom bonds, the sum of the distances of the polyatom-oxygen atom bonds is the sum of the distances of the polyatom-oxygen atom bonds of only one ring among the multiple rings in which the sum of the distances of the polyatom-oxygen atom bonds is the shortest. The preferred embodiments of the polynuclear metal compound according to the second aspect of the present invention described above can be preferably applied to the polynuclear metal compound according to the first aspect of the present invention.

[0021] Hereinafter, common points between the polynuclear metal compound of the first invention and the polynuclear metal compound of the second invention will be explained. In this specification, the first invention and the second invention will be simply referred to as the present invention.

[0022] In the polynuclear metal compound of the present invention, the metal atom other than the polyatoms is preferably a metal atom other than the polyatoms and heteroatoms. For example, when the cyclic polyoxometalate compound has a structure in which a polyatom is coordinated to a heteroatom via an oxygen atom, in this specification, a metal atom different from the polyatom is also different from the heteroatom, and can be rephrased as a metal atom different from the heteroatom and the polyatom.

[0023] The polynuclear metal compound of the present invention has a structure in which 10 or more metal atoms different from polyatoms are introduced into the defective structural sites of a cyclic polyoxometalate compound. The number of metal atoms different from polyatoms introduced is preferably 12 or more, more preferably 14 or more, even more preferably 16 or more, and particularly preferably 24 or more. The upper limit of the number of metal atoms different from polyatoms introduced is not particularly limited, but is preferably 1000 or less, more preferably 100 or less, and even more preferably 50 or less. The metal atoms different from polyatoms may be of only one type, or may be of two or more types.

[0024] The polyatom in the polynuclear metal compound of the present invention is preferably at least one selected from the group consisting of Mo, W, V, Nb, and Ta. Among them, W, Mo, and V are preferable, and W is more preferable.

[0025] The heteroatom in the polynuclear metal compound of the present invention is preferably at least one selected from the group consisting of P, Si, Ge, and As. Among these, P, Si, and Ge are more preferable, and P is further preferable.

[0026] In the polynuclear metal compound of the present invention, the metal atom different from the polyatom is preferably at least one selected from the group consisting of 3d transition metal atoms, Ru, Re, Ir, Pd, Pt, Ag, and Au. In other words, the metal atom different from the polyatom is preferably at least one selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ru, Pd, Ag, Re, Ir, Pt, and Au.

[0027] Examples of the 3d transition metal atom include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu. Among them, Ti, V, Mn, Co, and Cu are preferable, and Mn is more preferable. As the other metal atoms (Ru, Pd, Ag, Re, Ir, Pt, Au), Pd, Ag, Pt, and Au are preferable, and Ag and Au are more preferable.

[0028] In addition, when it is not possible to distinguish whether the two or more types of metal atoms contained in a polynuclear metal compound are polyatoms or metal atoms different from the polyatoms introduced into the defective structure sites, one of them can be a polyatom and the others can be metal atoms different from the polyatoms.

[0029] The polynuclear metal compound of the present invention has a structure in which 10 or more metal atoms different from polyatoms are introduced into the defective structure sites of the cyclic polyoxometalate compound, and this usually means that the atom such as an oxygen atom in the defective structure site is directly or indirectly bonded to a metal atom different from a polyatom. In particular, it is preferable that the oxygen atom in the defective structure site is directly bonded to a metal atom different from a polyatom. The number of defective structure sites in the structural unit constituting the cyclic polyoxometalate compound is usually two or more, and the structural unit is preferably a two-defect type or three-defect type. For example, the structural unit may be originally a two-defect type having a structure in which a metal atom different from a polyatom is introduced into each of the two defective structure sites, or may be originally a three-defect type having a structure in which a metal atom different from a polyatom is introduced into at least two of the three defective structure sites. The structural unit is preferably a structure in which a metal atom different from a polyatom is introduced into at least two defective structure sites, and more preferably a structure in which a metal atom different from a polyatom is introduced into all defective structure sites. In particular, it is particularly preferred that each of the above structural units has a structure in which a metal atom other than a polyatom is introduced into all of the defective structural sites, in other words, that the above cyclic polyoxometalate compound has a structure in which a metal atom other than a polyatom is introduced into all of the defective structural sites.

[0030] The polynuclear metal compound of the present invention contains a polyoxometalate anion in its crystal structure. The polyatom in the polyoxometalate anion is preferably at least one selected from the group consisting of Mo, W, V, Nb, and Ta. In addition, when the polynuclear metal compound of the present invention contains a heteropolyoxometalate anion in its crystal structure, the heteroatom is preferably at least one selected from the group consisting of P, Si, Ge, and As. Such a heteropolyoxometalate anion has, for example, a crystal structure called a Keggin type in which 9 to 11 polyatoms are coordinated to the heteroatom via oxygen.

[0031] The polynuclear metal compound of the present invention generally forms a salt, and the cation (counter cation) for forming the salt may be either an inorganic cation or an organic cation. Examples of inorganic cations include alkali metal cations, alkaline earth metal cations, transition metal cations, typical metal cations, protons, ammonium, etc., and one or more of these can be used. The organic cation includes organic ammonium, organic phosphonium, etc., and one or more of these can be used. Among these, the counter cation is preferably an organic cation. The organic cation preferably has 4 to 48 carbon atoms, more preferably 4 to 40 carbon atoms, and further preferably 4 to 30 carbon atoms.

[0032] The organic ammonium is preferably a quaternary organic ammonium. Examples of the quaternary organic ammonium include tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, tributylmethylammonium, trioctylmethylammonium, trilaurylmethylammonium, benzyltrimethylammonium, benzyltriethylammonium, benzyltributylammonium, cetylpyridinium, and the like, and one or more of these can be used.

[0033] The organic phosphonium is preferably a quaternary organic phosphonium, such as tetramethylphosphonium, tetraethylphosphonium, tetrabutylphosphonium, tetraphenylphosphonium, ethyltriphenylphosphonium, and benzyltriphenylphosphonium, and one or more of these may be used.

[0034] The polynuclear metal compound of the present invention can be used as a catalyst for organic reactions such as various oxidation reactions, acid-base reactions, etc. It is also expected to be used in various fields such as medicines and functional materials such as magnetic materials.

[0035] <Method of producing the polynuclear metal compound of the present invention> The present invention is a method for producing a polynuclear metal compound having a structure in which 10 or more metal atoms other than polyatoms have been introduced into defective structural sites of a cyclic polyoxometalate compound. The method also includes a step of reacting a cyclic polyoxometalate compound (A1) containing a ring formed by a polyatom-oxygen atom bond, in which a structural site derived from a polyoxometalate compound is used as a structural unit of a cyclic polyoxometalate compound, the structural unit being directly bonded to two other structural units, and the other two structural units are further bonded directly or via other structural units, with a compound (B) containing a metal atom other than a polyatom. The cyclic polyoxometalate compound (A1) preferably has as its constituent unit a structural moiety derived from a polyoxometalate compound having a structure in which a polyatom is coordinated to a heteroatom via an oxygen atom.

[0036] The present invention is a method for producing a polynuclear metal compound having a structure in which 10 or more metal atoms other than polyatoms have been introduced into the defective structural sites of a cyclic polyoxometalate compound, and the production method also comprises a step of reacting a cyclic polyoxometalate compound (A2) containing a ring formed by a polyatom-oxygen atom bond and having an inner diameter of 0.4 nm or more with a compound (B) containing a metal atom other than a polyatom. In the production method of the present invention, a stable cyclic polyoxometalate compound (A1) or (A2) is used as a raw material, and by reacting this with the above-mentioned compound (B), it is possible to appropriately introduce metal atoms derived from compound (B) that are known as heterometals in polyoxometalates. First, the raw material compounds and preferred reaction conditions in the reaction steps will be described below.

[0037] The cyclic polyoxometalate compound (A1) or (A2) is a compound that serves as a template for forming the polynuclear metal compound of the present invention. The preferred form of the cyclic polyoxometalate compound (A1) or (A2) is the same as the preferred form of the cyclic polyoxometalate compound in the first polynuclear metal compound of the present invention and the second polynuclear metal compound of the present invention, except for the features related to the metal atoms different from the polyatoms.

[0038] The cyclic polyoxometalate compound (A1) or (A2) is, for example, a compound represented by the following general formula (1); [Q j Z k O l ] m n- (1) (wherein Q represents a heteroatom; Z represents a polyatom; j, k, l, and n are positive numbers; m is a positive number of 3 or more; and n is determined by the valences of Q and Z, j, k, l, and m). The cyclic polyoxometalate compound (A1) or (A2) has a structure represented by the general formula (1) and may further contain, as a ligand, one or more of an NO group, an OH group, a water molecule, a CHOH group, a hydrogen atom, an RCO group (R represents an organic group), and an alkali metal atom.

[0039] In the general formula (1), Z is more preferably at least one selected from the group consisting of Mo, W, V, Nb, and Ta, and further preferably Z is W. In general formula (1), Q is more preferably at least one selected from the group consisting of P, Si, Ge, and As, and further preferably, Q is P.

[0040] Examples of the cyclic polyoxometalate compound (A1) or (A2) include [P8W 48 O 184 ] 40- (The inner diameter of the present invention is 1.0 nm, see Non-Patent Document 4.) [Mo 154 (NO) 14 O 420 (OH) 28 (H2O) 70 ] (25±5)- (Muller type Mo154, inner diameter 2.0 nm according to the present invention, see Angew. Chem. Int. Ed. Engl. 1995, 34, 2122.), [(MoO3) 176 (H2O) 63 (CH3OH) 17 H n ] (32-n)- (Muller type Mo176, inner diameter 2.3 nm according to the present invention, see J. Chem. Soc., Chem. Commun. 1998, 1501.), [{Mo6O 21 (H2O)6} 12 {(Mo2O4) 30 (RCO2) 30}] 42- (Keplerate type Mo132, inner diameter 2.3 nm according to the present invention, see Angew. Chem. Int. Ed. 1998, 37, 3359.), [H 12 W 36 O 120 ] 12- (W36, inner diameter 0.6 nm according to the present invention, see Dalton Trans. 2006, 2852), [NaP5W 30 O 110 ] 14- (Preyssler type P5W30, inner diameter 0.5 nm according to the present invention, unit P2W 18 and P3W 18 For further details, see Bull. Soc. Chim. Fr. 1970, 30. P2W 18 and P3W 18Ring-shaped POM P5W 30 For the synthesis of: J. Am. Chem. Soc. 1985, 107, 2662.) or [Si3W 27 O 96 ] 18- (Si3W 27 , and those having an inner diameter of 0.4 nm according to the present invention, and one or more of these can be used.

[0041] The cyclic polyoxometalate compound (A1) or (A2) according to the present invention may form a salt. The cation (counter cation) for forming the salt is the same as that described above for the polynuclear metal compound of the present invention.

[0042] Suitable metal atoms other than the polyatoms in the compound (B) are the same as those mentioned above in relation to the polynuclear metal compound of the present invention.

[0043] The compound (B) having a metal atom different from the polyatom preferably contains at least one group selected from the group consisting of a carboxylate group, a trifluoromethanesulfonate group, an acetylacetonate group, and a methylimidazolate group, of which the acetylacetonate group and the methylimidazolate group are more preferred.

[0044] Particularly preferred examples of the compound (B) having a metal atom different from the polyatom include manganese acetylacetonate, silver acetylacetonate, and gold methylimidazolate, and one or more of these can be used. The compound (B) containing a metal atom different from a polyatom is preferably a compound (B') containing a metal atom different from a polyatom and a heteroatom. For example, when the above cyclic polyoxometalate compound (A1) or (A2) has a structure in which a polyatom is coordinated to a heteroatom via an oxygen atom, in this specification, the compound (B) containing a metal atom other than the above polyatom can be rephrased as a compound (B') containing a polyatom and a metal atom other than the heteroatom. The preferred compounds (B') containing a metal atom different from the polyatoms and heteroatoms are the same as the preferred compounds (B) containing a metal atom different from the polyatoms.

[0045] The molar ratio of the cyclic polyoxometalate compound (A1) or (A2) to the compound (B) in the above reaction step may be appropriately set depending on the number of metal atoms different from the polyatoms contained in compound (B) and the number of said metal atoms to be introduced into one cyclic polyoxometalate compound (A1) or (A2). For example, the molar ratio is preferably 1:1 to 1:100, more preferably 1:5 to 1:90, and even more preferably 1:10 to 1:80.

[0046] In the reaction step, it is also preferable to react the cyclic polyoxometalate compound (A1) or (A2) with the compound (B) so that the ratio of the number of defective structural sites in the cyclic polyoxometalate compound (A1) or (A2) to the number of metal atoms other than polyatoms in the compound (B) is, for example, 1:10 to 10:1. This ratio is more preferably 1:5 to 5:1, and even more preferably 1:2 to 2:1.

[0047] The production method of the present invention is not particularly limited as long as it includes a step of reacting the specific cyclic polyoxometalate compound (A1) or (A2) with a compound (B) containing a metal atom different from the polyatom, but a preferred production method includes reacting in the presence of a reducing agent. That is, the reaction step is preferably carried out in the presence of a reducing agent.

[0048] The reducing agent is not particularly limited, but examples thereof include amine compounds or salts thereof, such as monoethanolamine, diethanolamine, triethanolamine, hydroxylamine, hydrazine, hydroxylamine hydrochloride, and tetraalkylammonium; alkali metal sulfites, such as sodium hydrogensulfite; metadisulfite; sodium hypophosphite; organic compounds or salts thereof having a group such as an -SH group, a -SOH group, a -NHNH group, and a -COCH(OH)- group, such as sodium formaldehyde sulfoxylate and sodium hydroxymethanesulfinate dihydrate; thiourea compounds, such as thiourea and thiourea dioxide; L-ascorbic acid, sodium L-ascorbate, L-ascorbic acid esters, erythorbic acid, sodium erythorbate, and erythorbic acid esters, and one or more of these may be used. The reducing agent is preferably an amine compound or a salt thereof, more preferably a quaternary ammonium salt, such as hydroxylamine hydrochloride or a tetraalkylammonium salt, preferably a tetraalkylammonium salt, and more preferably a tetrabutylammonium salt. When the reducing agent is a salt, examples of an anion (counter anion) for forming the salt include hydroxide, halide anion, borohydride, etc., and among these, borohydride is preferred.

[0049] The amount of the reducing agent used is, for example, preferably 70 mol % or more, more preferably 100 mol % or more, and even more preferably 150 mol % or more, relative to 100 mol % of the cyclic polyoxometalate compound (A1) or (A2). The amount of the reducing agent used is preferably 1000 mol % or less, more preferably 500 mol % or less, and even more preferably 300 mol % or less.

[0050] In addition, as a preferred embodiment of the production method of the present invention, when the cyclic polyoxometalate compound (A1) or (A2) is reacted with the compound (B) containing a metal atom different from the polyatoms, the two compounds are mixed in an organic solvent or in a solvent containing an organic solvent. Here, a reducing agent is added as necessary to the liquid in which the cyclic polyoxometalate compound (A1) or (A2) is dispersed or dissolved, and then the compound (B) containing a metal atom different from the polyatoms is added as a powder or as a solution to produce the polynuclear metal compound. The cyclic polyoxometalate compound (A1) or (A2) and the compound (B) containing a metal atom different from the polyatoms may be added to the solvent at the same time. The cyclic polyoxometalate compound (A1) or (A2) may be added all at once or gradually. The polynuclear metal compound may be produced in a single step or in multiple steps. For example, the product may be removed without mixing a predetermined amount of cyclic polyoxometalate compound (A1) or (A2), or a portion of compound (B), and the product may be redissolved in a solvent and then mixed with the remaining cyclic polyoxometalate compound (A1) or (A2), or compound (B).

[0051] In the above reaction step, the mixing time of the cyclic polyoxometalate compound (A1) or (A2) with the compound (B) is preferably 1 minute or longer, from the viewpoint of sufficiently introducing the compound (B) into the defective structural sites of the cyclic polyoxometalate compound (A1) or (A2). The mixing time is more preferably 1 hour or longer, and even more preferably 4 hours or longer. The mixing time is preferably 480 hours or shorter, more preferably 360 hours or shorter, even more preferably 240 hours or shorter, and particularly preferably 180 hours or shorter. The mixing time mainly means the time during which the cyclic polyoxometalate compound (A1) or (A2) and the compound (B) coexist and are mixed in a homogeneous solution, and refers to the time from the time when the cyclic polyoxometalate compound (A1) or (A2) is added to the solution containing the compound (B) to the time when an inorganic salt, an organic salt, or a poor solvent is added to precipitate the polynuclear metal compound. The mixing can be performed using a commercially available stirrer or the like. If impurities precipitate during the mixing, they can be removed by filtration or the like as necessary. The setting of the mixing time is one of the important factors that determine the structure of the polynuclear metal compound, and may be appropriately set within the above range depending on the type of element introduced by the compound (B). The polynuclear metal compound can be purified by recrystallization or the like. It can also be prepared and stored in the system without isolation, and used as a catalyst or the like as it is.

[0052] In the above reaction step, the temperature at which the cyclic polyoxometalate compound (A1) or (A2) and the compound (B) are mixed is preferably 0° C. or higher, more preferably 15° C. or higher, and even more preferably 40° C. or higher. The temperature is preferably 150° C. or lower, more preferably 100° C. or lower, and even more preferably 70° C. or lower. The above reaction step can be carried out under increased pressure, normal pressure, or reduced pressure.

[0053] As described below, an acid may be added during or after mixing of the cyclic polyoxometalate compound (A1) or (A2) with the compound (B). Alternatively, a method can be used in which the cyclic polyoxometalate compound (A1) or (A2) is mixed with the compound (B) to introduce an element derived from the compound (B) into the cyclic polyoxometalate compound (A1) or (A2), and then the cyclic polyoxometalate compound (A1) or (A2) or the compound (B) is added to obtain a polynuclear metal compound. Alternatively, a method can be used in which a compound obtained by introducing an element derived from compound (B) into one cyclic polyoxometalate compound (A1) or (A2) is dissolved in a solvent to obtain a compound, to which a compound obtained by introducing an element derived from compound (B) into said one cyclic polyoxometalate compound (A1) or (A2) is further added, and a poor solvent is then added to obtain a polynuclear metal compound.

[0054] The solvent preferably contains an organic solvent. The solvent containing an organic solvent may contain other components as long as it contains an organic solvent, but one of the preferred forms of the solvent containing an organic solvent is a mixed solvent of an organic solvent and water. The volume ratio of the organic solvent to water in the above solvent is not particularly limited, but is preferably 100:0 to 30:70, more preferably 100:0 to 50:50, and even more preferably 100:0 to 70:30.

[0055] The organic solvent is not particularly limited, and examples thereof include one or more of acetone, acetonitrile, benzonitrile, methanol, ethanol, propanol, butanol, chloroform, dichloroethane, hexane, octane, benzene, toluene, xylene, ethyl acetate, butyl acetate, propylene carbonate, diethyl ether, dibutyl ether, diisopropyl ether, dioxane, tetrahydrofuran, cyclopentyl methyl ether, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, and nitromethane. Among these, acetone, acetonitrile, benzonitrile, methanol, ethanol, butanol, dichloroethane, hexane, octane, toluene, xylene, ethyl acetate, butyl acetate, propylene carbonate, diethyl ether, dioxane, tetrahydrofuran, cyclopentyl methyl ether, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and nitromethane are preferred, and acetone, acetonitrile, benzonitrile, methanol, ethanol, butanol, dichloroethane, toluene, xylene, ethyl acetate, butyl acetate, propylene carbonate, diethyl ether, dioxane, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethyl sulfoxide, and nitromethane are more preferred. Even more preferred are acetone, acetonitrile, benzonitrile, butanol, toluene, ethyl acetate, butyl acetate, propylene carbonate, dichloroethane, diethyl ether, methyl isobutyl ketone, dimethylformamide, dimethyl sulfoxide, and nitromethane.

[0056] As the poor solvent, one or more of hexane, octane, benzene, toluene, xylene, ethyl acetate, butyl acetate, propylene carbonate, diethyl ether, dibutyl ether, diisopropyl ether, dioxane, tetrahydrofuran, cyclopentyl methyl ether, methyl ethyl ketone, methyl isobutyl ketone, dichloroethane, chloroform, and the like can be used.

[0057] The volume of the solvent is preferably 1 mL or more per 1 mmol of the cyclic polyoxometalate compound (A1) or (A2). More preferably, it is 10 mL or more, and even more preferably, it is 20 mL or more. Also, it is preferably 5000 mL or less. More preferably, it is 2500 mL or less, and even more preferably, it is 1000 mL or less.

[0058] The above-mentioned reducing agent and acid may be further mixed when or after mixing the cyclic polyoxometalate compound (A1) or (A2) with the compound (B). It is preferable to mix the acid after mixing the cyclic polyoxometalate compound (A1) or (A2) with the compound (B). The acid that can be used includes inorganic acids such as nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and boric acid, as well as organic acids such as p-toluenesulfonic acid, acetic acid, benzoic acid, and malonic acid. The amount of the acid used is preferably 0.01 moles or more, more preferably 0.1 moles or more, and even more preferably 1 mole or more, per mole of the cyclic polyoxometalate compound (A1) or (A2). The amount used is preferably 100 moles or less, more preferably 50 moles or less, and even more preferably 10 moles or less.

[0059] The production method of the present invention may be a stepwise production method in which a polynuclear metal compound is produced by the above-mentioned method, and then another operation is performed on the polynuclear metal compound. For example, a two-step production method can be used, and a reducing agent can be added in the latter step. By such a multistep production method, it is possible to produce a polynuclear metal compound containing more metal atoms different from polyatoms, a polynuclear metal compound containing two or more types of metal atoms, or a polynuclear metal compound having a specific structure.

[0060] Also suitable is a multi-step production method in which the obtained polynuclear metal compound is dissolved in an organic solvent, a counter cation is added and the mixture is stirred, and then the solvent is removed to obtain a solid, which is then recrystallized in the presence of a specific organic solvent.

[0061] Also suitable is a multi-step production method in which a polynuclear metal compound having one type of metal atom different from polyatoms is produced, then the polynuclear metal compound is dissolved in an organic solvent, and a compound of a metal atom different from the metal atom of the polynuclear metal compound is added to the obtained solution and stirred to produce a polynuclear metal compound having two or more types of metal atoms as metal atoms different from polyatoms. By such a production method, a polynuclear metal compound having two or more types of metal atoms different from polyatoms can be produced.

[0062] The production method of the present invention may further include a step of subjecting a polyoxometalate compound to a self-assembly reaction to obtain the above-mentioned cyclic polyoxometalate compound (A1) or (A2). As the self-assembly reaction, for example, the method described in Non-Patent Document 4 can be suitably adopted. The polynuclear metal compound of the present invention can be suitably obtained by the production method of the present invention. Effect of the Invention

[0063] The method for producing a polynuclear metal compound of the present invention makes it possible to obtain a novel polynuclear metal compound which is expected to be used in various fields such as catalysts, medicines, magnetic materials, and other functional materials. [Brief description of the drawings]

[0064] [Figure 1] FIG. 1 is a schematic diagram showing an outline of the production method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by weight" and "%" means "% by mass." "TBA" is an abbreviation for tetra-n-butylammonium, "acac" is an abbreviation for acetylacetonate, and "py" is an abbreviation for pyridine.

[0066] For X-ray crystal structure analysis, diffraction data was acquired using a Rigaku MicroMax-007 Saturn724 and analyzed using SHELXL-2014. Mass spectrometry was performed using a JEOL JMS-T100CS and a Waters Xevo G2-XS QTof. Infrared spectroscopy (IR) measurements were performed using a JASCO FT / IR-460 and a JASCO FT / IR-4100.

[0067] In a similar manner to that described in Non-Patent Document 4, TBA 12 H 28 [P8W 48 O 184 ]·30H2O (compound (1) shown in Figure 1) was synthesized. According to the results of X-ray structural analysis, the inner diameter of the ring consisting of the polyatom-oxygen atom bond in compound (1) was 0.9 nm, the total number of atoms in the ring was 32 (16 W + 16 O), and the total bond distance of the polyatom-oxygen atom in the ring was 6.1 nm. In addition, compound (1) contains two equivalent rings each formed by a polyatom (W)-oxygen atom bond, and the above-mentioned inner diameter, sum of the number of atoms, and sum of the polyatom-oxygen atom bond distances are calculated for only one ring in accordance with the description in this specification.

[0068] (Example 1) Synthesis of Mn20 core structure compound (compound (2) shown in Figure 1) TBA in acetonitrile (2.5 mL) 12 H 28 [P8W 48 O 184 ]·30H2O(1) (387 mg, 0.025 mmol) was dissolved, Mn(OAc)3·2H2O (147 mg, 0.55 mmol) was added, and the mixture was stirred at 50 °C for 7 days. The reaction solution was then added to diethyl ether (300 mL), and the resulting precipitate was collected by filtration using a membrane filter. The resulting precipitate was washed with diethyl ether (200 mL) to obtain the desired product as a brown powder (200 mg, 95% yield).

[0069] The IR measurement results of the obtained powder are as follows: IR(KBr):3440,2960,2873,1628,1482,1380,1153,1092,954,891,812,735,611,528cm -1 . The powder was dissolved in a solvent (1,2-dichloroethane) and then recrystallized by adding ethyl acetate to obtain a single crystal. The results of X-ray structural analysis of the crystal are shown in Table 1.

[0070] [Table 1]

[0071] From the results of X-ray structural analysis, the inner diameter, the sum of the number of atoms, and the sum of the polyatom-oxygen atom bond distances of the ring consisting of polyatom-oxygen atom bonds in the target product were the same as the inner diameter, the sum of the number of atoms, and the sum of the polyatom-oxygen atom bond distances of the ring in compound (1), respectively.

[0072] (Example 2) Synthesis of Ag16 core structure compound (compound (3) shown in Figure 1) TBA 12 H 28 [P8W 48 O 184 ]·30H2O(1) (0.025 mmol) was dispersed in acetone (10 mL), tetrabutylammonium hydroxide (160 mg, 0.20 mmol) was added, and silver acetate (66.7 mg, 0.40 mmol) was added and stirred at room temperature for 9 hours. The reaction solution was filtered, and then ethyl acetate was added and allowed to stand to obtain the silver-16 core structure as a colorless block crystal (single crystal) (yield 60%).

[0073] The results of elemental analysis of the obtained crystals are as follows: TBA 16 H8[Ag 16 P8W 48 O 184Calculated values ​​for ]·8H2O (%): C, 17.30; H, 3.40; N, 1.26; P, 1.39; Ag, 9.71; W, 49.69. Found values: C, 17.11; H, 3.62; N, 1.24; P, 1.37; Ag, 9.79; W, 48.42. The results of X-ray structural analysis of the obtained crystals are shown in Table 2.

[0074] [Table 2]

[0075] From the results of X-ray structural analysis, the inner diameter, the sum of the number of atoms, and the sum of the polyatom-oxygen atom bond distances of the ring consisting of polyatom-oxygen atom bonds in the target product were the same as the inner diameter, the sum of the number of atoms, and the sum of the polyatom-oxygen atom bond distances of the ring in compound (1), respectively.

[0076] (Example 3) Synthesis of silver nanocluster (Ag32 core, compound "Ag nanocluster" shown in Figure 1): N,N-dimethylformamide (9.0 mL) was added to the silver 16-core structure compound (3) (0.020 mmol), and silver acetate (53 mg, 0.32 mmol) was added and stirred at room temperature for 24 hours. Tetrabutylammonium borohydride (0.040 mmol) was added and stirred for 48 hours, after which ethyl acetate was added and the mixture was allowed to stand, yielding silver nanoclusters as brown block-shaped crystals (40% yield).

[0077] The results of elemental analysis of the obtained crystals are as follows: TBA 16 [Ag 32 P8W 48 O 184 Calculated values ​​for ]·2C3H7NO·8H2O (%): C, 15.91; H, 3.17; N, 1.27; P, 1.25; Ag, 17.45; W, 44.61. Found values: C, 16.02; H, 3.11; N, 1.28; P, 1.26; Ag, 17.57; W, 44.94. The results of X-ray structural analysis of the obtained crystals are shown in Table 3.

[0078] [Table 3]

[0079] From the results of X-ray structural analysis, the inner diameter, the sum of the number of atoms, and the sum of the polyatom-oxygen atom bond distances of the ring consisting of polyatom-oxygen atom bonds in the target product were the same as the inner diameter, the sum of the number of atoms, and the sum of the polyatom-oxygen atom bond distances of the ring in compound (1), respectively.

[0080] Example 4: Synthesis of silver-gold nanocluster (compound "Ag-Au nanocluster" shown in FIG. 1): Tris[μ-1-methylimidazolato-N 3 ,C 2 ] Tri-gold (I) (4.45 mg, 0.016 mmol) was added to dried N,N-dimethylformamide (1.8 mL), and Ag16 core structure compound (3) (0.0020 mmol) was added to this solution. Tetrabutylammonium borohydride was added, and the solution was stirred. Ethyl acetate was added to the solution, and the solution was allowed to stand, yielding silver-gold nanoclusters as reddish-brown block-shaped crystals (40% yield).

[0081] The results of elemental analysis of the obtained crystals are as follows: Found values: P, 1.06; Ag, 9.86; Au, 6.49; W, 39.65. The results of X-ray structural analysis of the obtained crystals are shown in Table 4.

[0082] [Table 4]

[0083] From the results of X-ray structural analysis, the inner diameter, the sum of the number of atoms, and the sum of the polyatom-oxygen atom bond distances of the ring consisting of polyatom-oxygen atom bonds in the target product were the same as the inner diameter, the sum of the number of atoms, and the sum of the polyatom-oxygen atom bond distances of the ring in compound (1), respectively.

[0084] From the above-mentioned examples, the synthesis of a novel Mn20 core structure compound, Ag16 core structure compound, silver nanocluster, and silver-gold nanocluster was confirmed. In the above-mentioned embodiment, the polyatom (W) is coordinated to the heteroatom (P) via an oxygen atom. did A polyoxometalate compound having the structure, manganese acetate, silver acetate, or Tris[μ-1-methylimidazolato-N 3 ,C 2 ]tri-gold (I), but it is believed that a specific ring-shaped polyoxometalate (a cyclic polyoxometalate compound containing a ring consisting of a polyatom-oxygen atom bond, in which a structural portion derived from a polyoxometalate compound is used as a structural unit of a cyclic polyoxometalate compound, and this structural unit is directly bonded to two other structural units, and the other two structural units are further bonded directly or via other structural units to form a ring consisting of a polyatom-oxygen atom bond, or a cyclic polyoxometalate compound containing a ring consisting of a polyatom-oxygen atom bond and having an inner diameter of 0.4 nm or more) is sufficiently stable and capable of forming a polynuclear structure, and therefore it is certain that a wide variety of new polynuclear metal compounds can be obtained by reacting this with a compound containing a metal atom other than the polyatom.

Claims

1. A polynuclear metal compound having a structure in which 10 or more metal atoms other than polyatoms are introduced into defective structural sites of a cyclic polyoxometalate compound, The cyclic polyoxometalate compound has a structural unit derived from a polyoxometalate compound having a structure in which a polyatom is coordinated to a heteroatom via an oxygen atom, and the structural unit is directly bonded to two other structural units, and the other two structural units are further bonded directly or via other structural units to form a ring consisting of a polyatom-oxygen atom bond; the heteroatom is at least one selected from the group consisting of P, Si, Ge, and As; The polyatom is at least one selected from the group consisting of Mo, W, V, Nb, and Ta; The metal atom different from the polyatom is at least one selected from the group consisting of 3d transition metal atoms, Ru, Re, Ir, Pd, Pt, Ag, and Au; Polyatoms and metal atoms bonded together A polynuclear metal compound comprising:

2. A polynuclear metal compound having a structure in which 10 or more metal atoms other than polyatoms are introduced into defective structural sites of a cyclic polyoxometalate compound, The cyclic polyoxometalate compound has a structural unit derived from a polyoxometalate compound having a structure in which a polyatom is coordinated to a heteroatom via an oxygen atom, and contains a ring having an inner diameter of 0.4 nm or more and formed by a polyatom-oxygen atom bond; the heteroatom is at least one selected from the group consisting of P, Si, Ge, and As; The polyatom is at least one selected from the group consisting of Mo, W, V, Nb, and Ta; The metal atom different from the polyatom is at least one selected from the group consisting of 3d transition metal atoms, Ru, Re, Ir, Pd, Pt, Ag, and Au; Polyatoms and metal atoms bonded together A polynuclear metal compound comprising:

3. A method for producing a polynuclear metal compound having a structure in which 10 or more metal atoms other than polyatoms are introduced into defective structural sites of a cyclic polyoxometalate compound, comprising the steps of: The production method includes a step of reacting a cyclic polyoxometalate compound (A1) containing a ring formed by a bond between a polyatom and an oxygen atom, the ring being formed by a polyatom-oxygen atom bond, the ring being formed by a polyatom-oxygen atom bond, the polyatom being directly bonded to two other structural units, the other two structural units being further bonded directly or via other structural units, with a compound (B) containing a metal atom different from the polyatom, the heteroatom is at least one selected from the group consisting of P, Si, Ge, and As; The polyatom is at least one selected from the group consisting of Mo, W, V, Nb, and Ta; The metal atom different from the polyatom is at least one selected from the group consisting of 3d transition metal atoms, Ru, Re, Ir, Pd, Pt, Ag, and Au; The production method further includes a step of reacting the polynuclear metal compound obtained in the reacting step with a reducing agent, or the reacting step is carried out in the presence of a reducing agent.

2. A method for producing a polynuclear metal compound comprising the steps of:

4. A method for producing a polynuclear metal compound having a structure in which 10 or more metal atoms other than polyatoms are introduced into defective structural sites of a cyclic polyoxometalate compound, comprising the steps of: The production method includes a step of reacting a cyclic polyoxometalate compound (A2) having an inner diameter of 0.4 nm or more and a ring formed by a polyatom-oxygen atom bond, the cyclic polyoxometalate compound having a structural unit derived from a polyoxometalate compound having a structure in which a polyatom is coordinated to a heteroatom via an oxygen atom, with a compound (B) containing a metal atom different from the polyatom, the heteroatom is at least one selected from the group consisting of P, Si, Ge, and As; The polyatom is at least one selected from the group consisting of Mo, W, V, Nb, and Ta; The metal atom different from the polyatom is at least one selected from the group consisting of 3d transition metal atoms, Ru, Re, Ir, Pd, Pt, Ag, and Au; The production method further includes a step of reacting the polynuclear metal compound obtained in the reacting step with a reducing agent, or the reacting step is carried out in the presence of a reducing agent.

2. A method for producing a polynuclear metal compound comprising the steps of:

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