Methods for manufacturing alkylated metallocenes having one or more tetrahydropentalenyl groups

Abstract

The realizations of the present disclosure are directed to methods for making an alkylated metallocene having one or more tetrahydropentalenyl groups, the method comprising: reacting a chloride compound with a lithium compound to make a reaction mixture comprising an intermediate dichloride compound; and reacting the intermediate dichloride compound with an alkylating agent to make the alkylated metallocene having one or more tetrahydropentalenyl groups, wherein the dichloride compound is not isolated from the reaction mixture, wherein the lithium compound is represented by: where R1, R2, R3, R4 and R5 are each independently H or an alkyl (C1-C4).

Description

Methods for manufacturing alkylated metallocenes having one or more tetrahydropentalenyl groups Field of invention The methods described herein are directed to methods for manufacturing metallocenes, more specifically, for manufacturing alkylated metallocenes having one or more tetrahydropentalenyl groups. Background Metallocenes can be used in a variety of applications, including the following: as polymerization catalysts, as antiknock additives in gasoline and as lubricants, as well as potential use in medical applications such as treatments for cancer, malaria and bacterial infections. Summary The present description provides various embodiments, including the following: a method for preparing an alkylated metallocene having one or more tetrahydropentalenyl groups, the method comprising: reacting a chloride compound with a lithium compound to prepare a reaction mixture comprising a dichloride intermediate; and reacting the dichloride intermediate with an alkylating agent to prepare the alkylated metallocene having one or more tetrahydropentalenyl groups, wherein the dichloride compound is not isolated from the reaction mixture, and wherein the lithium compound is represented by: where R1, R2, R3, R4 and R5 are, each independently, H or an alkyl (C1-C4), and where the reactions take place in the same reaction vessel. Detailed description Previously, alkylated metallocenes were prepared by reacting a chloride compound, containing a metal atom, with a lithium compound to form an intermediate compound containing the metal atom and several chlorine atoms. The reaction that forms the intermediate compound can be called a metalation reaction. After the metalation reaction, the intermediate compound is usually isolated from a reaction mixture containing unused reactants, byproducts, and / or secondary products. The isolated intermediate compound is then reacted with an alkylating agent to produce the alkylated metallocene. Without wishing to limit the theory, it is believed that in the above methods for preparing alkylated metallocenes, one or more intermediate compounds have been isolated to separate the intermediate compounds from the byproducts, to switch to different solvents for different reaction steps, to separate the intermediate compounds from the side products, and / or to reduce the likelihood of low product yields, for example, due to competing reactions. Byproducts are produced as a result of a desired reaction. Side products are produced from side reactions. The preparation of cyclic organic compounds and substituted metallocenes is described in WO 2019 / 067272 A1. Surprisingly, it has been discovered that alkylated metallocenes containing one or more tetrahydropentalenyl groups can be prepared without isolating the intermediate compound from the reaction mixture. In other words, alkylated metallocenes containing one or more tetrahydropentalenyl groups can be prepared without isolating the intermediate compound from the reaction mixture before reacting the intermediate compound with the alkylating agent. Furthermore, it has been found that methods for preparing alkylated metallocenes containing one or more tetrahydropentalenyl groups, as described herein, can yield an improved, i.e., higher, percentage of product compared to alkylated metallocenes prepared by other methods.Furthermore, it has been found that methods for manufacturing alkylated metallocenes having one or more tetrahydropentalenyl groups, as described herein, can provide an improved, i.e., reduced, amount of by-products and / or secondary products, compared to other methods for manufacturing alkylated metallocenes having one or more tetrahydropentalenyl groups. As used herein, all reference to the periodic table of elements and groups therein is the NEW NOTATION published in HAWLEY'S CONDENSED CHEMICAL DICTIONARY, thirteenth edition, John Wiley & Sons, Inc., (1997) (reproduced therein with permission of the IUPAC), unless reference is made to the earlier IUPAC form denoted by Roman numerals (which also appear herein), or unless otherwise indicated. The embodiments provide alkylated metallocenes having one or more tetrahydropentalenyl groups that can be prepared by reacting a chloride compound with a lithium compound to produce a reaction mixture comprising a dichloride intermediate compound; and by reacting the dichloride intermediate compound with an alkylating agent to produce the alkylated metallocene having one or more tetrahydropentalenyl groups. The embodiments state that the chloride compound can be represented as MCln, where M is a metal, Cl are chlorine atoms, and n is an integer from 3 to 4. The embodiments state that M can be zirconium, hafnium, or titanium. The embodiments state that the chloride compound includes a plurality of chlorine atoms. For example, one or more embodiments state that the chloride compound includes 3 or 4 chlorine atoms. One or more embodiments state that the chloride compound is selected from zirconium(IV) chloride and n-(propylcyclopentadienyl)hafnium(dimethoxyethane) trichloride. The embodiments state that the lithium compound can be represented by the following formula: wherein R1, R2, R3, R4, and R5 are each independently H or a (C1-C4) alkyl, and wherein the reactions take place in the same reaction vessel. One or more embodiments specify that at least one of R1, R2, R3, R4, and R5 is a (C1-C4) alkyl. One or more embodiments specify that at least two of R1, R2, R3, R4, and R5 are a (C1-C4) alkyl. One or more embodiments specify that R1, R2, and R3 are each H, and R4 and R5 are a (C1-C4) alkyl. One or more embodiments specify that R1, R2, and R3 are each H, and R4 and R5 are a (C1) alkyl. As mentioned, the chloride compound and the lithium compound are reacted to produce a reaction mixture comprising a dichloride intermediate. One or more embodiments state that the dichloride intermediate can be represented by the following formula, which includes one or more, namely two, tetrahydropentalenyl groups: where R4 and R5 are as defined above. One or more embodiments state that the intermediate dichloride compound can be represented by the following formula, which includes a tetrahydropentalenyl group: As shown in the formulas above, the dichloride intermediate includes two chlorine atoms. Furthermore, as shown in the formulas above, the dichloride intermediate includes one or more tetrahydropentalenyl groups. The embodiments stipulate that the reaction mixture prepared by reacting the chloride compound and the lithium compound may include the dichloride intermediate, unreacted chloride compound, unreacted lithium compound, one or more by-products, one or more secondary products, and / or one or more known reaction components, e.g., a solvent. As mentioned, it has been advantageously found that methods for manufacturing alkylated metallocenes having one or more tetrahydropentalenyl groups, as described herein, can provide an improved, i.e., reduced, amount of by-products and / or secondary products compared to other methods for manufacturing alkylated metallocenes having one or more tetrahydropentalenyl groups. The embodiments further stipulate that the reaction mixture does not include an alkylating agent. In other words, the reaction of the chloride compound with the lithium compound to prepare the reaction mixture comprising the dichloride intermediate takes place in the absence of an alkylating agent. The embodiments stipulate that the dichloride intermediate is not isolated from the reaction mixture prior to a subsequent chemical reaction, namely an alkylation reaction. In other words, as described herein, the manufacture of alkylated metallocenes having one or more tetrahydropentalenyl groups by reacting the chloride compound with the lithium compound to prepare the reaction mixture comprising the dichloride intermediate and reacting the dichloride intermediate with an alkylating agent to prepare the alkylated metallocene having one or more tetrahydropentalenyl groups may be referred to as a one-pot reaction. Examples of isolation procedures include distillation, extraction, filtration, and decantation. As such, "not isolated" indicates that the dichloride intermediate remains with other reagents used and / or generated in the reaction that produces the dichloride intermediate before a subsequent chemical reaction for the synthesis of alkylated metallocenes having one or more tetrahydropentalenyl groups. In other words, the purity of the dichloride intermediate is not increased before a subsequent chemical reaction for the synthesis of alkylated metallocenes having one or more tetrahydropentalenyl groups. The embodiments stipulate that the intermediate dichloride compound is reacted with an alkylating agent to produce the alkylated metallocene having one or more tetrahydropentalenyl groups. In other words, the intermediate dichloride compound is not isolated from the reaction mixture; rather, the alkylating agent is added to the reaction mixture that includes the intermediate dichloride compound. Alkylating agents are known in the art and can be obtained commercially. The alkylating agent can be synthesized by a known process, for example, using known components and under known conditions. One or more embodiments specify that the alkylating agent is a Grignard reagent, for example, an alkyl Grignard reagent, which may be referred to as an alkylmagnesium halide. Examples of alkylating agents include methylmagnesium bromide, methylmagnesium chloride, methyllithium, phenylmagnesium bromide, benzylmagnesium bromide, trimethylsilylmethyllithium, trimethylsilylmethylmagnesium bromide, and combinations of these compounds. The alkylating agent can be used with a known component, such as a solvent, for example, diethyl ether. The reaction of the intermediate compound dichloride with the alkylating agent produces the alkylated metallocene having one or more tetrahydropentalenyl groups. One or more embodiments, for example, when the chloride compound includes zirconium, establish that the alkylated metallocene having one or more tetrahydropentalenyl groups can be represented by the following formula: This alkylated metallocene includes two tetrahydropentalenyl groups. One or more embodiments, for example, when the chloride compound includes hafnium, establish that the alkylated metallocene having one or more tetrahydropentalenyl groups can be represented by the following formula: This alkylated metallocene includes a tetrahydropentalenyl group. As mentioned, alkylated metallocenes having one or more tetrahydropentalenyl groups can be prepared without isolating the intermediate compound from the reaction mixture. In other words, alkylated metallocenes having one or more tetrahydropentalenyl groups can be prepared without isolating the intermediate compound from the reaction mixture before reacting the intermediate compound and the alkylating agent. The reaction of the chloride compound with the lithium compound to prepare a reaction mixture comprising the dichloride intermediate, and the reaction of the dichloride intermediate with an alkylating agent to produce the alkylated metallocene having one or more tetrahydropentalenyl groups, take place in the same reaction vessel.Using a single reaction vessel can advantageously avoid several purification procedures, minimize chemical waste, and / or reduce the synthesis time of a target molecule, such as the alkylated metallocenes with one or more tetrahydropentalenyl groups described herein. Without wishing to limit the theory, it is believed that methods previously employed multiple reaction vessels and isolated intermediate compounds were limited by the generation of byproducts, secondary products, the desire to use different solvents for different reaction steps, and / or impractically low product yields. Alkylated metallocenes containing one or more tetrahydropentalenyl groups can be used for a variety of applications. For example, alkylated metallocenes containing one or more tetrahydropentalenyl groups can be used to manufacture polymerization catalysts, which can be called metallocene catalysts. Metallocene catalysts are well known in the art. For instance, alkylated metallocenes containing one or more tetrahydropentalenyl groups can be contacted, under activation conditions, with an activator to activate the metallocene, thereby producing the polymerization catalyst. The activation conditions are well known in the art. The polymerization catalyst, which is manufactured from an alkylated metallocene containing one or more tetrahydropentalenyl groups, can be used to produce a polymer. For example, the polymerization catalyst and an olefin can be brought into contact under polymerization conditions to form a polymer, such as a polyolefin polymer. The polymerization process can be a suspension polymerization process, a coarse suspension polymerization process, and / or a gas-phase polymerization process. The polymerization process can utilize known equipment and reaction conditions, such as known polymerization conditions. The polymerization process is not limited to any specific type of polymerization system. The polymer can be used for a variety of articles, such as films, fibers, nonwoven and / or woven textile materials, extruded articles, and / or molded articles. The embodiments state that the chloride compound and the lithium compound can be reacted at a ratio of 1.0 to 2.7 molar equivalents of lithium compound per 1 molar equivalent of chloride compound. One or more embodiments state that the chloride compound and the lithium compound are reacted at a ratio of 1.1 to 2.0 molar equivalents of lithium compound per 1 molar equivalent of chloride compound. The embodiments state that the chloride compound and the lithium compound can be reacted at a temperature of -50 °C to 75 °C. NMR (nuclear magnetic resonance spectroscopy) analysis can be used to monitor the formation of the dichloride intermediate compound. Other known reaction components and / or reaction conditions can be used. The embodiments state that the dichloride intermediate and the alkylating agent can be reacted at a ratio of 2.0 to 3.0 molar equivalents of alkylating agent per 1 molar equivalent of dichloride intermediate. One or more embodiments state that the dichloride intermediate and the alkylating agent can be reacted at a ratio of 2.2 to 2.6 molar equivalents of alkylating agent per 1 molar equivalent of dichloride intermediate. The embodiments state that the dichloride intermediate and the alkylating agent can be reacted at a temperature of -50 °C to 75 °C. Other known reaction components and / or reaction conditions may be used. The embodiments state that the lithium compound can be prepared by reacting butyllithium with a bicyclic alkene compound. Butyllithium is known in the art and can be obtained commercially. The bicyclic alkene compound can be represented by the following formula: where R1, R2, R3, R4 and R5 are as described above, i.e., each is independently H or an alkyl (C1-C4). The embodiments state that butyllithium and the bicyclic alkene compound can be reacted at a ratio of 1.0 to 2.5 molar equivalents of butyllithium per 1 molar equivalent of bicyclic alkene compound. One or more embodiments state that butyllithium and the bicyclic alkene compound are reacted at a ratio of 1.1 to 1.6 molar equivalents of butyllithium per 1 molar equivalent of bicyclic alkene compound. The embodiments state that butyllithium and the bicyclic alkene compound can be reacted at a temperature of -0 °C to 50 °C. Other known reaction components and / or reaction conditions may be used. The embodiments state that the bicyclic alkene compound can be prepared by reacting a bicyclic ketone compound with an alkylating agent and diethyl ether to form a bicyclic alcohol compound, and then dehydrating the bicyclic alcohol compound to prepare the bicyclic alkene compound. The bicyclic ketone compound can be represented by the following formula: where R1, R2, R3 and R4 are as described above, i.e., each is independently H or a (C1-C4) alkyl. The alkylating agent can be as described above. The embodiments state that the bicyclic ketone compound and the alkylating agent can be reacted at a ratio of 1.0 to 2.0 molar equivalents of alkylating agent per 1 molar equivalent of bicyclic ketone compound. One or more embodiments state that the bicyclic ketone compound and the alkylating agent can be reacted at a ratio of 1.1 to 1.6 molar equivalents of alkylating agent per 1 molar equivalent of bicyclic ketone compound. The embodiments state that the bicyclic ketone compound and the alkylating agent can be reacted at a temperature of 10 °C to 50 °C. Other known reaction components and / or reaction conditions may be used. The bicyclic alcohol compound can be represented by the following formula: where R1, R2, R3, R4 and R5 are as described above, i.e., each is independently H or an alkyl (C1-C4). As mentioned, the bicyclic alcohol compound can be dehydrated to produce the bicyclic alkene compound. The bicyclic alcohol compound can be dehydrated by a known process, for example, using known components and under known conditions. For instance, the bicyclic alcohol compound can be dehydrated by reacting it with HCl, among other known dehydrating reagents. For example, anhydrous HCl or hydrochloric acid (aqueous HCl) of 0.6 molar (M) or higher molarity in an organic solvent such as ethanol, tetrahydrofuran, or toluene can be used. The hydrochloric acid can be from 0.2 M to 12 M, or alternatively, from 0.6 M to 6 M. One or more embodiments state that the bicyclic alcohol compound can be dehydrated using p-toluenesulfonic acid. For example, one can use from 0.1 mol% to 20 mol% (based on 1 equivalent of bicyclic alcohol compound) of p-toluenesulfonic acid.One or more embodiments specify that from 2 mol% to 10 mol% (based on 1 equivalent of bicyclic alcohol compound) of p-toluenesulfonic acid is used; one or more embodiments specify that 5 mol% (based on 1 equivalent of bicyclic alcohol compound) of p-toluenesulfonic acid is used. The embodiments state that the bicyclic ketone compound can be prepared by reacting a cyclic alkene compound with an acid compound in the presence of an aprotic solvent and an effective amount of phosphoric and / or sulfonic acid reagent. The cyclic alkene compound can be represented by the following formula: where R1, R2, and R3 are as described above, i.e., each is independently H or a (C1-C4) alkyl group. The cyclic alkene compound can be obtained commercially. The cyclic alkene compound can be synthesized by a known process, for example, using known components and under known conditions. The acidic compound can be represented by the following formula: where R4 is as described above, i.e., R4 is H or a (C1-C4) alkyl group. The acid compound can be obtained commercially. The acid compound can be synthesized by a known process, for example, using known components and under known conditions. One or more embodiments establish that the acid compound is (E)-2-butenoic acid, which may be called crotonic acid. The embodiments specify that the cyclic alkene and the acid compound can be reacted in a molar ratio of 1:1 to 1.5:1 moles of cyclic alkene to moles of acid. The embodiments also specify that the cyclic alkene and the acid compound can be reacted at a temperature of -10 °C to 75 °C. Other known reaction components and / or reaction conditions may be used. As mentioned, the bicyclic ketone compound can be prepared by reacting a cyclic alkene compound with an acid compound in the presence of an aprotic solvent. The aprotic solvent can be either polar or dipolar. It can be selected from sulfolane, dipropylsulfone, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dichloromethane, diethyl ether, and mixtures of two or more of these compounds. Sulfolane is a dipolar aprotic solvent, while dipropylsulfone, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dichloromethane, and diethyl ether are polar aprotic solvents. One or more embodiments state that the aprotic solvent may be a sulfone, an ether (including glycol ethers), an organochloride, or a combination of these compounds. The embodiments stipulate that the bicyclic ketone compound and the cyclic alkene compound are reacted in the absence of a cyclic ether. In other words, the aprotic solvent excludes, i.e., does not contain, cyclic ethers. Examples of cyclic ethers include tetrahydrofuran and dioxane. The aprotic solvent (polar and / or dipolar) can have a relative polarity greater than 0.099 and less than 0.444. All individual values ​​and subintervals from greater than 0.099 to less than 0.444 are included; for example, the aprotic solvent can have a relative polarity from 0.117 to 0.410, from 0.231 to 0.309. The relative polarity of solvents is readily available in published materials, such as Christian Reichardt, Solvents and Solvent Effects in Organic Chemistry, Wiley-VCH Publishers, 3rd ed., 2003, which is referenced for the relative polarity mentioned herein. The use of the aprotic solvent, as described herein, when reacting the cyclic alkene compound with the acid compound to prepare the bicyclic ketone compound, can advantageously provide a homogeneous reaction mixture. A homogeneous reaction mixture can indicate solvent stability, which is desirable for this reaction. The use of the aprotic solvent, as described herein, when reacting the cyclic alkene compound with the acid compound to prepare the bicyclic ketone compound, can advantageously yield a product area count, determined by GC / MS (gas chromatography / mass spectrometry), greater than 1,000,000. For example, the product area count determined by GC / MS may range from 1,000,000 to 10,000,000, or from 1,500,000 to 6,000,000. A product area count determined by GC / MS greater than 1,000,000 may indicate desirable product formation. The GC / MS analysis can be performed as follows.The concentration of the desired product can be determined using a gas chromatography system comprising an Agilent Technologies 7890A GC system equipped with an analytical column (Agilent 19091S-433 HP-5ms 0 °C - 325 °C: 15 m x 250 µm x 0.25 µm) using helium / hydrogen as the carrier gas, along with a mass spectrometer comprising an Agilent Technologies 5977B MSD analyzer operating in electron impact (EI) mode. The raw data can be analyzed by performing an ion extraction of the desired product's molecular weight, for example, 136 g / mol, and the resulting spectra can be integrated to obtain area counts. As mentioned, the bicyclic ketone compound can be prepared by reacting a cyclic alkene compound with an acid compound in the presence of an effective amount of a phosphoric and / or sulfonic acid reagent. In some embodiments, the sulfonic acid reagent is, or essentially consists of, a mixture of P₂O₅ / H₃CSO₃H, or a reaction product thereof. Alternatively, the sulfonic acid reagent may essentially consist of an alkylsulfonic acid such as a C1-C6 alkylsulfonic acid, such as methanesulfonic acid. The expression "essentially consists of a mixture of P₂O₅ / H₃CSO₃H" means that the sulfonic acid reagent is free of polyphosphoric acid (PPA). In some respects, the P₂O₅ / H₃CSO₃H mixture is a 0.1 / 1 (w / w) P₂O₅ / H₃CSO₃H mixture, known as Eaton's reagent. Methanesulfonic acid is a compound with the formula H3CSO3H and has the CAS number 75-75-2 and is widely available from commercial suppliers. The mixture of phosphorus pentoxide and methanesulfonic acid, or P₂O₅ / H₃CSO₃H mixture, is a mixture or reaction product of phosphorus pentoxide and methanesulfonic acid. The weight / weight ratio of P₂O₅ / H₃CSO₃H in the mixture may be 0.05:1, alternatively 0.075:1, alternatively 0.077:1, alternatively 0.1:1, and alternatively 0.2:1. The 0.075 / 1 (weight / weight) P₂O₅ / H₃CSO₃H mixture is commercially available and may again be referred to as Eaton's reagent. The P₂O₅ / H₃CSO₃H mixture may be formed in situ, for example, in the presence of one or more reagents, such as before or during a reaction described herein. Alternatively, the P₂O₅ and CH₃SO₃H mixture can be prepared before carrying out the reaction. It may be convenient to prepare the P₂O₅ / CH₃SO₃H mixture before carrying out other reactions and to store the resulting mixture for later use in embodiments of the present description. A sulfonic acid reagent is an acidic material having OP(O)-OH and / or CS(O)2-OH acidic groups, or an acidic reaction product of these compounds. The sulfonic acid reagent may be, or may consist essentially of, a mixture of phosphorus pentoxide and methanesulfonic acid ("P2O5 / H3CSO3H mixture"), or a reaction product of these compounds. In some embodiments, the sulfonic acid reagent consists essentially of the P2O5 / H3CSO3H mixture. Alternatively, the sulfonic acid reagent may consist essentially of an alkylsulfonic acid such as a C1-C6 alkylsulfonic acid, such as methanesulfonic acid. The expression "consists essentially of" means that the phosphoric and / or sulfonic acid reagent, as well as the reaction in which it is used, is exempt from PPA. Polyphosphoric acid or PPA has the CAS number 8017-16-1 and is a compound generally of the formula HO-[P (=O) (OH) ]nH, where the subscript n indicates the degree of polymerization. Phosphorus pentoxide is a compound with the formula P2O5 and has the CAS number 1314-56-3 and is widely available from commercial suppliers. In some respects, each reactant, reagent, solvent, or other material used in the embodiments described herein, and each of their products, is free of Pt, Ni, Pd, Rh, and Ru. An effective quantity is an amount sufficient to enable the manufacture of a detectable quantity of the desired product. An effective quantity of phosphoric and / or sulfonic acid reagent is an amount sufficient to enable the preparation of a detectable quantity of the bicyclic ketone compound. Detectable quantities can be detected, and optionally characterized, by any suitable analytical method, such as 1H nuclear magnetic resonance (1H-NMR), high-performance liquid chromatography (HPLC, against a known standard), gas chromatography (GC, against a known standard), or mass spectrometry; typically, by 1H-NMR. The effective quantity of phosphoric and / or sulfonic acid reagent used in the preparation of the bicyclic ketone compound may vary depending on its composition, reaction conditions, and cost.An experienced person can easily determine an effective amount by starting with an initial reaction mixture of reactants and 90 wt% of the phosphoric and / or sulfonic acid reagent, and then systematically testing reaction mixtures containing less than 90 wt% of the phosphoric and / or sulfonic acid reagent until an optimum result is found under the reaction conditions. When the phosphoric and / or sulfonic acid reagent is polyphosphoric acid (PPA), the P₂O₅ / H₃CSO₃H mixture, or the combination of PPA and the P₂O₅ / H₃CSO₃H mixture, the effective amount can be 55 to 90 wt%, or alternatively 60 to 85 wt%, based on the total weight of the reactants and the phosphoric and / or sulfonic acid reagent.Alternatively, the effective amount of the P₂O₅ / H₃CSO₃H mixture can be 1 to 10 molar equivalents, alternatively 1 to 5 molar equivalents, or alternatively 1 to 3 molar equivalents, relative to the number of moles of cyclic alkene compound. For example, if 1.0 mol of cyclic alkene compound is used, then the effective amount of the P₂O₅ / H₃CSO₃H mixture can be 1 to 10 molar equivalents, alternatively 1 to 5 molar equivalents, or alternatively 1 to 3 molar equivalents. As used in this dissertation, an "alkyl" includes linear, branched, and cyclic paraffinic radicals deficient in one hydrogen. Therefore, for example, a CH3 group ("methyl") and a CH2CH3 group ("ethyl") are examples of alkyls. As used in this document, an "alkylene" includes linear, branched, and cyclic hydrocarbon radicals deficient in two hydrogens. Therefore, CH2 ("methylene") and CH2CH2 ("ethylene") are examples of alkylene groups. Other groups deficient in two hydrogen radicals include "arylene" and "alkenylene". The following provides a series of aspects of this description. Aspect 1 provides a method for preparing an alkylated metallocene having one or more tetrahydropentalenyl groups, the method comprising: reacting a chloride compound with a lithium compound to prepare a reaction mixture comprising a dichloride intermediate; and reacting the dichloride intermediate with an alkylating agent to prepare the alkylated metallocene having one or more tetrahydropentalenyl groups, wherein the dichloride compound is not isolated from the reaction mixture, and wherein the lithium compound is represented by: where R1, R2, R3, R4 and R5 are, each independently, H or an alkyl (C1-C4). Aspect 2 provides the method of Aspect 1, wherein the reaction of the chloride compound with the lithium compound to prepare the reaction mixture comprising the intermediate dichloride compound takes place in the absence of the alkylating agent. Aspect 3 provides the method of any of aspects 1-2, where the chloride compound includes 3 or 4 chlorine atoms. Aspect 4 provides the method of any of Aspects 1-3, wherein the chloride compound is selected from zirconium(IV) chloride and n-(propylcyclopentadienyl)hafnium(dimethoxyethane) trichloride. Aspect 5 provides the method of any of Aspects 1-4, wherein the intermediate dichloride compound includes one or more tetrahydropentalenyl groups. Aspect 6 provides the method of any of Aspects 1-5, wherein the alkylating agent is an alkylmagnesium halide. Aspect 7 provides the method of any of Aspects 1-6, wherein the lithium compound is prepared by reacting butyllithium with a bicyclic alkene compound represented by: Aspect 8 provides the method of Aspect 7, wherein the bicyclic alkene compound is prepared by reacting a bicyclic ketone compound with an alkylating agent and diethyl ether to form a bicyclic alcohol compound and dehydrating the bicyclic alcohol compound to prepare the bicyclic alkene compound, wherein the bicyclic ketone compound is represented by: Aspect 9 provides the method of Aspect 8, wherein the bicyclic ketone compound is prepared by reacting a cyclic alkene compound represented by: with an acidic compound represented by: in the presence of an aprotic solvent and an effective amount of phosphoric and / or sulfonic acid reagent and under reaction conditions sufficient to prepare the bicyclic ketone compound. Aspect 10 provides the method of aspect 9, wherein the aprotic solvent has a relative polarity greater than 0.099 and less than 0.444. Aspect 11 provides the method of any of aspects 9-10, wherein the phosphoric and / or sulfonic acid reagent is a mixture of P2O5 / H3CSO3H. Examples Unless otherwise indicated herein, use the following preparations for characterizations. Perform syntheses in a dry nitrogen atmosphere in a glove box when indicated. Carry out reactions requiring anhydrous conditions in a dry nitrogen atmosphere in oven-dried glassware cooled in a stream of dry nitrogen. Anhydrous toluene, hexanes, tetrahydrofuran, diethyl ether, and 1,2-dimethoxyethane are from Sigma-Aldrich. Sulfolane, dipropylsulfone, DMSO, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dichloromethane, ethanol, tert-butanol, tetrahydrofuran, 1,4-dioxane, and diethyl ether were purchased from Sigma-Aldrich or Fisher.The solvents used for experiments conducted in a nitrogen-filled glove box (inert atmosphere) are further dried by storage on activated 4-Angstrom molecular sieves. Zirconium(IV) chloride (ZrCl4) and hafnium(IV) were purchased from Boulder Scientific and STREM and are used as received. All other reagents are purchased from Sigma-Aldrich and used as received. For example, the P2O5 / CH3SO3H mixture (7.7 wt. P2O5) can be purchased from Sigma-Aldrich, CAS No. 39394-84-8, and the P2O5 / CH3SO3H mixture (7.5 wt. P2O5) from Frontier Scientific can be purchased from Fisher Scientific, CAS No. 39394-84-8. 1H-NMR (proton nuclear magnetic resonance spectroscopy) chemical shift data are presented in low-field parts per million (ppm) relative to tetramethylsilane (TMS), using residual protons in a deuterated solvent as a reference. 1H-NMR chemical shift data measured in CDCl3 are referenced to 7.26 ppm, data measured in benzene-d6 (C6D6) to 7.16 ppm, and data measured in tetrahydrofuran-d8 (THF-d8) to 3.58 ppm. 1H-NMR chemical shift data are presented in the format: chemical shift in ppm (multiplicity, coupling constant(s) in hertz (Hz) , and integration value. Multiplicities are abbreviated as s (singlet), d (doblet), t (triplet), q (quartet), pent (pentet), m (multiplet) and br (width). GC / MS (EI) refers to gas chromatography-mass spectrometry (electron ionization). GC-MS analysis: The concentration of the desired product in the crude organic product is measured using a gas chromatography system comprising an Agilent Technologies 7890A GC system with an analytical column (Agilent 19091S-433 HP-5ms 0 °C - 325 °C: 15 m x 250 µm x 0.25 µm) using helium / hydrogen as the carrier gas, along with a mass spectrometer comprising an Agilent Technologies 5977B MSD analyzer operating in electron impact (EI) mode. The raw data are analyzed by performing an ion extraction of the desired product (136 g / mol), the resulting spectra are integrated, and the area counts are reported below. In the following examples, 1 oz = 28.3495 g and 1 torr = 133.322 Pa. Example 1. The synthesis of a metallocene having a tetrahydropentalenyl group was carried out as follows: The synthesis of a bicyclic ketone compound was carried out as follows. The bicyclic ketone compound can be represented by the following formula: where R1, R2, R3 and R4 are, each independently, H or an alkyl (C1-C4). A cyclic alkene compound was used which can be represented by the following formula (cyclopentene; R1, R2 and R3 were each H): and an acidic compound that can be represented by the following formula: acid (E)-2-butenoic acid; R4 was CH3). In a fume hood under a nitrogen atmosphere, an acid compound ((E)-2-butenoic acid; 40.0 g; 464.63 mmol) and a cyclic alkene compound (cyclopentene; 41.05 mL, 464.63 mmol) were added to a container (1-liter round-bottom flask fitted with a stirring rod). A polar aprotic solvent (sulfolane; 150 m; relative polarity: 0.41) was then added to the contents of the container. The contents of the container were cooled to 0 °C. The P2O5 / H3CSO3H mixture (7.5 wt% P2O5) (221.2 mL, 1393.9 mmol) was then added dropwise at 0 °C to the container. While stirring, the contents of the container were heated to approximately 20 °C and then stirred for 72 hours. The resulting crude product was diluted with water (40 mL). The contents of the container were then diluted with diethyl ether (200 mL).The reaction was slowly stopped with sodium hydroxide (680 mL) at the following concentrations and in the following order of addition: 1N NaOH (50 mL), 2N NaOH (50 mL), 2.5N NaOH (270 mL), and 3N NaOH (310 mL). The contents of the container were tasted until a pH of 8–9 was reached after the addition of NaOH. The aqueous and organic layers were separated in a separatory funnel. The aqueous layer was extracted three times with diethyl ether (3 x 160 mL). The organic layers were combined and washed with 0.5N NaOH (300 mL). A final wash with brine (60 mL) was then performed, followed by drying over anhydrous magnesium sulfate and filtration. The solvent was removed under vacuum, yielding the bicyclic ketone compound (53, 76; observed as a dark brown liquid product; 85% yield). The bicyclic ketone compound (where R1, R2, and R3 were each H, and R4 was CH3) was characterized by 1H NMR and GC / MS. 1H NMR (400 MHz, chloroform-d) 3, 0.- 2, 88 (m, 1H) , 2, 8.- 2, 71 (m, 1H) , 2, 6.- 2, 46 (m, 1H) , 2, 4.- 2, 28 (m, 3H) , 2, 2.- 2, 15 (m, 1H) , 2, 1.- 1, 98 (m, 1H) , 1, 9.- 1, 43 (m, 2H) , 1, 2.- 1, 13 (m, 3H) . The first synthesis of a bicyclic alkene compound, which can be represented by the following formula, was carried out as follows: Methylmagnesium bromide solution (3M in diethyl ether; 76.36 mL; 229.1 mmol) was added to a first container (1-liter, two-necked, round-bottom reaction flask) under a dry nitrogen atmosphere, followed by diethyl ether (80 mL). The contents of the first container were cooled to 0 °C and then stirred for 15 minutes. The bicyclic ketone compound (24 g; 176.22 mmol) was dissolved in anhydrous diethyl ether (190 mL) in a second container (250 mL round-bottom flask). The contents of the second container were then added to the contents of the first container over a period of 30 minutes, while maintaining the temperature below 10 °C. The contents of the first container were then stirred for 20 hours at approximately 20 °C, resulting in a mixture containing a bicyclic alcohol compound that can be represented as follows: where R1, R2 and R3 were each H, and R4 and R5 were each CH3. The bicyclic alcohol compound was not isolated or characterized by 1H NMR. The bicyclic alcohol compound was then dehydrated by adding aqueous HCl (0.6 M; 300 mL) at approximately -10 °C to the contents of the first container, followed by the addition of aqueous HCl (6 M; 50 mL), also at approximately -10 °C, to the contents of the first container; the total HCl addition lasted approximately 1.5 hours. The contents of the container were then vigorously stirred for 5 hours at approximately 20 °C. The organic phase was separated, and the aqueous layer was extracted with diethyl ether (2 × 25 mL). The combined organic layers were washed with saturated NaHCO3 (150 mL) and brine (150 mL). The organic layers were dried on magnesium sulfate and filtered, and the solvent was removed under vacuum.The product was passed through a silica gel plug and eluted with diethyl ether / hexane, yielding the bicyclic alkene compound (20.2 g; 85%; where R1, R2 and R3 were each H, and R4 and R5 were each CH3). The bicyclic alkene compound was obtained as a mixture of double bond regioisomers.1H-NMR (400 MHz, chloroform-d) 3, 07 (d, J = 2, 7 Hz, 2H) , 2, 8.- 2, 69 (m, 3H) , 2, 62 (q, J = 8, 1, 7, 2 Hz, 1H) , 2, 3.- 2, 17 (m, 7H) , 2, 1.- 2, 02 (m, 3H) , 1, 9.- 1, 83 (m, 8H) , 1, 8.- 1, 63 (m, 12H) , 1, 58 (s, 5H) . The second synthesis of a bicyclic alkene compound, which can be represented by the following formula, was carried out as follows: A 100 mL three-necked flask was fitted with a rubber septum and a nitrogen inlet; a stir bar was added under N2. The flask was evacuated under vacuum and filled three times with N2. The flask was charged with MeMgBr in diethyl ether (3.0 M; 9.5 mmol; 3.2 mL). The flask was then immersed in an ice bath before distilled enone (1.0 g; 7.3 mmol) in diethyl ether (19 mL) was added dropwise using a syringe (addition rate was 20 mL / h). An aliquot of the reaction mixture was then stopped with a few drops of methanol, diluted with ethyl acetate, and analyzed by gas chromatography and monitored for the presence of enone. Once the enone was consumed, the reaction was maintained at 0 °C and stopped with NH4Cl (10% wt / v; 1.3 equiv.; 5.1 ml), which was added for 20 minutes (addition rate was 20 ml / h).The bath was kept at 0 °C during the addition; the reaction was stirred for 1 h, yielding a bicyclic alcohol compound that can be represented as follows:. where R1, R2 and R3 were each H, and R4 and R5 were each CH3. Next, p-toluenesulfonic acid (70 mg, 0.4 mmol, 5 mol%, based on 1 equivalent of the bicyclic alcohol compound) was added, and the reaction was monitored by thin-layer chromatography (TLC). When the allyl alcohol had been completely consumed, the organic layer was washed with saturated aqueous NaHCO3 (2 x 10 mL). The organic layer was then dried over MgSO4 and a rotary evaporator, yielding the bicyclic alkene compound (0.79 g, 80% yield) where R1, R2, and R3 were each H, and R4 and R5 were each CH3. The synthesis of a lithium compound, which can be represented as follows, was carried out as follows: In a glove box, the bicyclic alkene compound, as prepared in Synthesis Number One (20.2 g; 150.5 mmol), was dissolved in hexanes (350 mL) while stirring. A solution of n-butyllithium in hexanes (2.5 M; 78.26 mL; 195.65 mmol) was added dropwise to the container, and the contents were stirred for 20 hours at approximately 20 °C. The contents of the container were then collected by vacuum filtration, washed with hexanes, and dried under vacuum conditions, yielding the lithium compound (6.89 g; 33% yield; where R1, R2, and R3 were each H, and R4 and R5 were each CH3) .1H-NMR (400 MHz, THF-d8) 5.13 (s, 1H) , 2.43 (t, J = 6.8 Hz, 4H) , 2.2.- 2.08 (m, 2H) , 1.95 (s, 6H) . This metallocene, which has the tetrahydropentalenyl group, can be represented as follows: In a dry box, a chloride compound (zirconium(IV) chloride; 3.32 g; 14.27 mmol) and toluene (330 mL) were added to a container (32-oz glass jar), stirred, and cooled to -33 °C for 45 minutes. Lithium compound (5.0 g; 35.67 mmol) was added to the contents of the container in several portions. The contents of the container were then stirred for 24 hours at approximately 20 °C to prepare a reaction mixture. NMR analysis was used to monitor the formation of an intermediate compound, namely bis(4,6-dimethyl-1,2,3,4-tetrahydropentalenyl) zirconium dichloride, in the reaction mixture by removing an aliquot from the container. 1H-NMR (400 MHz, benzene-d6) 5.39 (d, J = 8.4 Hz, 2H) , 3.09 (ddd, J = 14.6, 8, 6, 1.6 Hz, 4H) , 2.6.- 2.43 (m, 2H) , 2.38 (dt, J= 14, 6, 8, 6 Hz, 4H), 2, 0.- 2, 00 (m, 2H), 1, 75 (s, 12H) .Next, without isolating the intermediate compound, a solution of methylmagnesium bromide in diethyl ether (3.0 M; 9.51 mL; 228.54 mmol) was added dropwise to the contents of the container, which was stirred for 24 hours at approximately 20 °C. The contents of the container were filtered, and the solvent was removed under vacuum. The resulting solid product was then dissolved in hexanes (500 mL) and stirred for 3 hours. Subsequently, the resulting solid product was filtered again, and the solvent was removed under vacuum, yielding the metallocene having a tetrahydropentalenyl group, as previously indicated (3.54 g; 64% yield; which may be designated bis(4,6-dimethyl-1,2,3,4-tetrahydropentalenyl) zirconium dimethyl). 1H-NMR (400 MHz, benzene-d6) 4, 83 (s, 2H), 2, 71 (ddd, J = 14, 5, 8, 0, 3, 3 Hz, 4H), 2, 57 (dt, J = 14, 7, 8, 7 Hz, 4H), 2, 2.- 2, 08 (m, 4H) , 1.72 (s, 12H) , -0.39 (s, 6H) .The performance is presented in Table 1. Comparative Example A was carried out as follows. In a dry box, zirconium(IV) chloride (0.125 g; 0.54 mmol) and toluene (8 mL) were added to a first container (2-oz glass jar), stirred, and cooled to -33 °C for 30 minutes. A solution of methylmagnesium bromide in diethyl ether (3.0 M; 0.358 mL; 1.073 mmol) was cooled to -33 °C for 30 minutes in a second container (20 mL vial). The contents of the first container were then added to the contents of the second container, which had been maintained at -33 °C for 30 minutes. The lithium compound (0.150 g; 1.073 mmol) was then added to the contents of the second container in several portions while stirring. Stirring was continued for 24 hours at approximately 20 °C. The solvent was then removed under vacuum conditions. The resulting solid product was then dissolved in 30 mL of hexane and filtered.The solvent was removed under vacuum conditions, yielding bis(4,6-dimethyl-1,2,3,4-tetrahydropentalenyl)zirconium dimethyl (0.052 g; 25% yield). 1H-NMR 4.83 (s, 2H) , 2.72 (ddd, J = 14, 4, 7, 9, 3, 4 Hz, 4H) , 2.57 (dt, J = 14, 7, 8, 7 Hz, 4H) , 2.2.- 2.08 (m, 4H) , 1.72 (s, 12H) , -0.39 (s, 6H) . In addition to bis(4,6-dimethyl-1,2,3,4-tetrahydropentalenyl)zirconium dimethyl, the presence of additional byproducts was observed by NMR analysis. The yield is presented in Table 1. Comparative Example B was carried out as follows. In a dry box, zirconium(IV) chloride (0.125 g, 0.54 mmol) and toluene (10 mL) were added to a first container (2-oz glass jar) and stirred and cooled to -33 °C for 30 minutes. A solution of methylmagnesium bromide in diethyl ether (3.0 M; 0.358 mL; 1.073 mmol) was cooled to -33 °C for 30 minutes in a second container (20 mL vial). The contents of the first container were then added to the contents of the second container, and the combined contents were heated very rapidly to approximately 20 °C and stirred for 15 minutes at that temperature. Next, the lithium compound (0.150 g; 1.073 mmol) was added to the contents of the second container in several portions while stirring; stirring was continued for 24 hours at approximately 20 °C. Then, the solvent was removed under vacuum conditions.The resulting solid product was then dissolved in hexanes (30 ml) and filtered. The solvent was removed under vacuum conditions, yielding bis(4,6-dimethyl-1,2,3,4-tetrahydropentalenyl)zirconium dimethyl (0.055 g; 26% yield). 1H-NMR (400 MHz, benzene-d6) 4.83 (s, 2H) , 2.72 (ddd, J = 14, 4, 7, 9, 3, 4 Hz, 4H) , 2.57 (dt, J = 14, 7, 8, 7 Hz, 4H) , 2.2.- 2.08 (m, 4H) , 1.72 (s, 12H) , -0.39 (s, 6H) . The yield is presented in Table 1. In addition to bis(4,6-dimethyl-1,2,3,4-tetrahydropentalenyl)zirconium dimethyl, the presence of additional byproducts was observed by NMR analysis, for example, byproducts A and B shown below. 1H NMR (400 MHz, benzene-d6) 5, 60 (s, 1H) , 5, 50 (s, 0, 26H) , 2, 4.- 2, 32 (m, 4H) , 2, 03 (s, 1H) , 2, 0.- 1, 94 (m, 2H) , 1, 80 (br s, 6H) , 0, 49 (s, 2H) , 0, 37 (s, 9H) . byproduct A, byproduct B. Comparative Example C was carried out as follows. In a dry box, zirconium(IV) chloride (0.113 g; 0.485 mmol) and toluene (7 mL) were added to a container (2-oz glass jar) and stirred. Then, lithium compound (0.150 g; 1.067 mmol) was added to the contents of the container in several portions while stirring. Next, a solution of methylmagnesium bromide in diethyl ether (3.0 M; 0.356 mL; 1.067 mmol) was added dropwise to the contents of the container, which was stirred for 24 hours at approximately 20 °C. The solvent was then removed under vacuum. The resulting solid product was then dissolved in hexanes (15 mL) and filtered. The solvent was removed under vacuum conditions, yielding bis(4,6-dimethyl-1,2,3,4-tetrahydropentalenyl) zirconium dimethyl (0.058 g; 30% yield).1H-NMR (400 MHz, benzene-d6) 4, 83 (s, 2H) , 2, 72 (ddd, J = 14, 4, 7, 9, 3, 4 Hz, 4H) , 2, 57 (dt, J = 14, 7, 8, 7 Hz, 4H) , 2, 2.- 2, 08 (m, 4H) , 1, 72 (s, 12H) , -0, 39 (s, 6H) . In addition to bis(4,6-dimethyl-1,2,3,4-tetrahydropentalenyl) zirconium dimethyl, the presence of additional byproducts was observed by NMR analysis. The yield is presented in Table 1. Table 1 The data in Table 1 illustrate that Example 1 has improved, i.e., higher, performance compared to the AC comparative Examples. The data in Table 1 illustrate that Example 1 has an improved, i.e., reduced, by-product generation, as demonstrated by the improved performance, compared to the AC comparative Examples. Bis(n-propylcyclopentadienyl)hafnium dichloride (25.0 g, 53.91 mmol) was melted at 140 °C and HfCl₄ (17.27 g, 53.91 mmol) was added. After stirring for approximately 30 minutes, a bulb-to-bulb distillation apparatus was connected, and the vessel was heated to approximately 135 °C. (PrCp)HfCl₃ was distilled in approximately 1 hour at approximately 110 °C and 0.4 torr as a whitish solid with traces of a tan contaminant. After cooling to room temperature, the distillate was dissolved in toluene (50 mL) and DME (45 mL) at 80 °C to form a clear solution. This product was cooled to room temperature and then placed in a freezer. The product was collected by filtration, washed with hexane (3 x 20 ml) and then dried under vacuum conditions. (N-Propylcyclopentadienyl)hafnium trichloride (dimethoxyethane) was obtained as a white crystalline solid (39.79 g), with a yield of 76.5%.1H-NMR (400 MHz, benzene-d6) 6.22 (t, J = 2.8 Hz, 2H) , 6.15 (t, J = 2.7 Hz, 2H) , 3.5.- 3.06 (m, 4H) , 3.0.- 2.98 (m, 2H) , 1, 58 (dq, J = 14, 9, 7, 4 Hz, 2H), 0. 86 (t, J = 7, 4 Hz, 3H). (N-propylcyclopentadienyl) hafnium trichloride (dimethoxyethane) can be represented by the following formula: Example 2. The synthesis of a metallocene having a tetrahydropentalenyl group was carried out as follows. This metallocene having the tetrahydropentalenyl group can be represented by the following formula: In a dry box, a compound of (n-propylcyclopentadienyl)hafnium(dimethoxyethane) trichloride (5.50 g; 11.41 mmol) and toluene (130 mL) were added to a 16-oz glass jar and stirred. Lithium (2.0 g; 14.27 mmol) was added to the contents of the jar in several portions, and the mixture was stirred for 24 hours at approximately 20 °C to prepare a reaction mixture. NMR analysis was used to monitor the formation of an intermediate compound, namely n-PrCp(4,6-dimethyl-1,2,3,4-tetrahydropentalenyl)hafnium dichloride, in the reaction mixture by removing an aliquot from the jar. 1H-NMR (400 MHz, benzene-d6) 5.86 (t, J = 2.7 Hz, 2H), 5.71 (t, J = 2.7 Hz, 2H), 5.30 (s, 1H), 3.03 (ddd, J = 13.7, 8.4, 1.3 Hz, 2H) , 2, 7.- 2, 67 (m, 2H) , 2, 44 (ddd, J = 14, 3, 10, 2, 8, 0 Hz, 2H) , 2, 3.- 2, 21 (m, 1H) , 2, 0.- 1, 95 (m, 1H) , 1, 76 (s, 6H) , 1, 5.- 1.44 (m, 2H) , 0.84 (td, J = 7, 4, 5, 5 Hz, 3H) . Next, without isolating the intermediate compound, a solution of methyl-magnesium bromide in diethyl ether (3.0 M; 7.61 ml; 22.83 mmol) was added dropwise to the contents of the container, which was stirred for 24 hours at approximately 20 °C. The solvent was then removed by vacuum and the resulting solid product was dissolved in hexanes (250 ml). The hexanes were vacuum removed, yielding the metallocene having a tetrahydropentalenyl group, as indicated above (4.79 g; 93% yield; which may be called n-PrCp(4,6-dimethyl-1,2,3,4-tetrahydropentalenyl) hafnium dimethyl). 1H-NMR (400 MHz, benzene-d6) 5, 69 (t, J = 2, 7 Hz, 2H) , 5, 44 (t, J = 2, 6 Hz, 2H) , 5, 07 (s, 1H) , 2, 5.- 2, 43 (m, 6H) , 2, 0.- 1, 96 (m, 1H) , 1, 8.- 1, 80 (m, 1H) , 1, 78 (s, 6H) , 1, 59 (dq, J = 14, 7, 7, 4 Hz, 2H) , 0, 9.- 0, 84 (m, 3H) , -0, 39 (s, 6H) . The performance is presented in Table 2. Comparative Example D was carried out as follows. In a dry box, (n-propylcyclopentadienyl)hafnium(dimethoxyethane) trichloride (0.344 g; 0.713 mmol) and toluene (4 mL) were added to a container (40 mL glass vial) and shaken. The lithium compound (0.10 g; 0.713 mmol) was added to the contents of the container in several portions, and the contents were shaken for 24 hours at approximately 20 °C. The contents of the container were filtered, and the solvent was removed under vacuum to obtain n-PrCp((4,6-dimethyl-1,2,3,4-tetrahydropentalenyl)hafnium) chloride (30% yield). The presence of additional byproducts was observed by NMR analysis. 1H-NMR (400 MHz, benzene-d6) 5.86 (t, J = 2.7 Hz, 2H), 5.71 (t, J = 2.7 Hz, 2H), 5.30 (s, 1H), 3.03 (ddd, J = 13.7, 8.4, 1.3 Hz, 2H) , 2, 7.- 2, 67 (m, 2H) , 2, 44 (ddd, J = 14, 3, 10, 2, 8, 0 Hz, 2H) , 2, 3.- 2, 21 (m, 1H) , 2, 0.- 1, 95 (m, 1H) , 1, 76 (s, 6H) , 1, 5.- 1.44 (m, 2H) , 0.84 (td, J = 7, 4, 5, 5 Hz, 3H) . The performance is presented in Table 2. Comparative Example E was carried out as follows. In a dry box, (n-propylcyclopentadienyl)hafnium(dimethoxyethane) trichloride (0.275 g; 0.571 mmol) and toluene (5 mL) were added to a container (40 mL glass vial) and shaken. A solution of methylmagnesium bromide in diethyl ether (3.0 M; 0.50 mL; 1.49 mmol) was then added dropwise to the contents of the container. The lithium compound (0.10 g; 0.713 mmol) was then added to the contents of the container in several portions, and the contents were shaken for 24 hours at approximately 20 °C. The solvent was removed under vacuum, and the resulting solid product was dissolved in hexanes (40 mL), stirred for 10 minutes, and filtered. The hexanes were removed under vacuum, yielding n-PrCp(4,6-dimethyl-1,2,3,4-tetrahydropentalenyl) hafnium dimethyl (40% yield). The presence of additional byproducts was detected by NMR analysis.1H-NMR (400 MHz, benzene-d6) 5.69 (t, J = 2.7 Hz, 2H) , 5.44 (t, J = 2.6 Hz, 2H) , 5.07 (s, 1H) , 2.5.- 2.43 (m, 6H) , 2.0.- 1, 96 (m, 1H), 1, 8.- 1, 80 (m, 1H), 1, 78 (s, 6H), 1, 59 (dq, J = 14, 7, 7, 4 Hz, 2H), 0, 9.- 0, 84 (m, 3H), -0, 39 (s, 6H). The presence of byproduct D was identified by NMR analysis: 1H-NMR (400 MHz, benzene-d6) 5, 73 (s, 4H) , 2, 2.- 2, 15 (m, 2H) , 1, 40 (dq, J = 14, 8, 7, 4 Hz, 2H) , 0, 79 (t, J = 7, 3 Hz, 3H) , 0, 20 (s, 9H) . The yield is presented in Table 2. Table 2 The data in Table 2 illustrate that Example 2 has improved, i.e., higher, performance compared to the comparative Examples DE. The data in Table 2 illustrate that Example 2 has an improved, i.e., reduced, by-product generation, as demonstrated by the improved performance, compared to the comparative Examples DE. Example 3, a synthesis of a bicyclic ketone compound, was carried out as follows. The bicyclic ketone compound is as described above and is prepared by reacting the cyclic alkene compound (as described above; cyclopentene; R1, R2 and R3 were, each, H) with the acid compound (as described above; (E)-2-butenoic acid). In a fume hood under a nitrogen atmosphere, the acid compound (E)-2-butenoic acid; 1.0 g; 11.61 mmol) was added to a 40 mL vial fitted with a stirring rod, followed by a cyclic alkene compound (cyclopentene; 1.03 mL; 11.61 mmol). An aprotic solvent (sulfolane, 3 mL) was then added, and the contents of the vial were cooled to 0 °C. Next, the P₂O₅ / H₃CSO₃H (0.1 / 1) mixture (55.3 mL; 34.85 mmol) was added dropwise at 0 °C. The contents of the vial were then heated to room temperature while stirring. Visual inspection was used to determine if the contents of the vial were homogeneous. The contents of the vial were then shaken at room temperature for 24 hours. After 24 hours, the contents of the vial were slowly deactivated with NaOH (3 N; 20 ml). The aqueous layer was extracted with diethyl ether (6 ml).An aliquot of the organic layer (0.25 ml) was withdrawn with a syringe and placed in a GC / MS vial, and then diluted with diethyl ether (1.25 ml). The organic layer was characterized by GC / MS to determine product formation. The GC-MS analysis was performed as follows. The concentration of the desired product in the crude organic product was measured using a gas chromatography system comprising an Agilent Technologies 7890A GC system with an analytical column (Agilent 19091S-433 HP-5ms 0 °C - 325 °C: 15 m x 250 µm x 0.25 µm) using helium / hydrogen as the carrier gas, along with a mass spectrometer comprising an Agilent Technologies 5977B MSD analyzer operating in electron impact (EI) mode. The raw data were analyzed by performing an ion extraction of the desired product (136 g / mol). The resulting spectra were integrated, and the area counts are presented in Table 4. The relative polarity values ​​were normalized from measurements of the solvent absorption spectra shifts and were extracted from Christian Reichardt, Solvents and Solvent Effects in Organic Chemistry, Wiley-VCH Publishers, 3rd ed., 2003. Examples 4-9 and the Comparative Examples FK were carried out as in Example 3, with the change that different solvents were used, as indicated in Table 3. Table 3 Table 3 Homogeneous1. In the case of Comparative Example I, it is noted that, although homogeneous, when the reaction was stopped there was precipitation and an emulsion was produced after extraction with ether. This indicated an undesirable lack of solvent stability. The data in Table 4 show that, advantageously, each of Examples 3-9, unlike each of the comparative Examples FK, provided homogeneity in synthesizing the bicyclic ketone compound, and each provided a product area count, by GC / MS, greater than 1,000,000.

Claims

1. A method for manufacturing an alkylated metallocene having one or more tetrahydropentalenyl groups, the method comprising: reacting a chloride compound with a lithium compound to prepare a reaction mixture comprising a dichloride intermediate; and reacting the dichloride intermediate with an alkylating agent to prepare the alkylated metallocene having one or more tetrahydropentalenyl groups, wherein the dichloride compound is not isolated from the reaction mixture, wherein the lithium compound is represented by: wherein R1, R2, R3, R4, and R5 are each independently H or a (C1-C4) alkyl, and wherein the reactions take place in the same reaction vessel.

2. The method of claim 1, wherein the reaction of the chloride compound with the lithium compound to prepare the reaction mixture comprising the dichloride intermediate takes place in the absence of the alkylating agent. 3.The method of any one of claims 1-2, wherein the chloride compound includes 3 or 4 carbon atoms.

4. The method of any one of claims 1-3, wherein the chloride compound is selected from zirconium(IV) chloride and n-(propylcyclopentadienyl)hafnium(dimethoxyethane) trichloride.

5. The method of any one of claims 1-4, wherein the dichloride intermediate includes one or more tetrahydropentalenyl groups.

6. The method of any one of claims 1-5, wherein the alkylating agent is an alkylmagnesium halide.

7. The method of any one of claims 1-6, wherein the lithium compound is prepared by reacting butyllithium with a bicyclic alkene compound represented by: 8.The method of claim 7, wherein the bicyclic alkene compound is prepared by reacting a bicyclic ketone compound with an alkylating agent and diethyl ether to form a bicyclic alcohol compound and dehydrating the bicyclic alcohol compound to prepare the bicyclic alkene compound, wherein the bicyclic ketone compound is represented by:

9. The method of claim 8, wherein the bicyclic ketone compound is prepared by reacting a cyclic alkene compound represented by: with an acid compound represented by: in the presence of a polar aprotic solvent or a dipolar aprotic solvent and an effective amount of a phosphoric and / or sulfonic acid reagent and under reaction conditions sufficient to prepare the bicyclic ketone compound. 10.The method of claim 9, wherein the solvent has a relative polarity greater than 0.099 and less than 0.444, provided that the solvent is not a cyclic ether.

11. The method of any of claims 9-10, wherein the phosphoric and / or sulfonic acid reagent is a mixture of P2O5 / H3CSO3H.