Zirconium complex zirconocene dichloride

The only other zirconium bis(iminophosphorano)methandiide was reported by Roesky. Complex 150 was prepared from zirconocene dichloride and 7 with concomitant elimination of KC1 and C5H6.68 Complex 150 is similar to 132 except, for the obvious dilference that one chloride is replaced by a cyclopentadienyl group, the CP2N2Zr ring is not planar. 

The results of 1H- and 13C-NMR analysis of the complexes 11-13 are given in Table 8. For comparison, the NMR resonances of the corresponding fragments of the zirconocene dichloride and free diamine used in the synthesis of amido zirconium complexes are also shown. 

Zirconocene dichloride reacts with dibromomethane in the presence of Zn to yield a methylene-zirconium complex 4.105, which is used for the methylenation of carbon compounds to produce the terminal alkenes h... 

Zrrconocene, ZrCp2, generated in situ from zirconocene derivatives, mediates diverse ring-closures. Thus treatment of 2,4,4-trimethyl-l,6-heptadiene with butyllithium and Bu2ZrCp2 yields the zirconium complex 218, which gives 1,1,3,3,5-pentamethylcyclopentane on aqueous work-up (equation 111). The reaction of 1,7-octadiene with butyknagnesium chloride and a catalytic amount of zirconocene dichloride, followed by water, gives frons-l,2-dimethylcyclohexane (219) in excellent yield (equation 113) similarly, the diene ether 220 affords the cyclopentane derivative 221 (equation 113). ... 

Treatment of zirconocene dichloride, 50, with 2 equiv. of an appropriate alkyllithium or Grignard reagent generates transient zirconocene olefin complexes that upon loss of alkene provide access to zirconocene, 109, and the powerful reduction chemistry of divalent zirconium.48 Owing to the utility of this reagent in organic synthesis and organometallic reactions, the low-temperature alkylation of zirconocene dichloride, 50, with BunLi has been... 

Heterobimetallic /x-oxo complexes 854 are formed via halide displacement reactions between trioxo anions such as [Cp M(0)3] (M = Mo, W) and Cp2ZrCl2655 (Scheme 214). The corresponding heterotrinuclear complexes 855 are obtained by addition of 2 equiv. of trioxoanion complexes to zirconocene dichloride. Other heterobimetallic complexes such as //-773-C02-bridged ruthenium-zirconium and rhenium-zirconium complexes have also been prepared.656... 

Insertion reaction of alkyne and zirconium-silene complexes 883, which are generated from disilylzirconocenes 882 prepared from the reaction of zirconocene dichloride with 2equiv. of Me2PhSiLi, affords... 

Titanium(IV) and zirconium(IV) complexes of the types Cp2MCl(HPO), Cp2M(HPO)2, Cp2M(0-N-0), and Cp2M(0-N-S) have been prepared by reaction of titanocene dichloride or zirconocene dichloride with the appropriate ligand using THF as the solvent (Scheme 7.18). The reactions are complete in 4-7 min as opposed to 14-18 h conventionally. Yields were always higher for the microwave approach (YIF = 1.1-1.2). 

A variety of chiral, non-racemic zirconium complexes were explored in attempts to develop an enantioselective variant of this reaction (Scheme 3) [7-9]. Eor example, when allyUc amines lla,b were treated with EtMgCl and 10% of C2-symmetric BINOL-zirconium bis(tetrahydroindenyl)ethane (12, Brintzinger s catalyst [10], BINOL is l,l -binaphthalene 2,2 -dioate), chiral ethylated products 13a,b were obtained in 34-39% yield with enantiomeric excesses (ee) of ca. 26% [8]. Use of a (neomenthylindene)ZrCpCl2 catalyst 14, designed to improve the steric differentiation of the diastereomeric transition states, improved the chemical yields of amines at lower catalyst loadings (2-4%) and increased the ees of the reactions by a factor of three in the case of 11a [8,9]. Similar reactivity is observed in zirconocene dichloride-catalyzed cyclization of 1,6- and 1,7-enynes with 12.5% Cp2ZrCl2 using EtsAl as the stoichiometric reductant. For these substrates, the alkyne coordinates... 

Coupling Reactions.—Acetylenes react with organoalanes, e.g. MesAl, and zirconocene dichloride to form the alkenyl metal complexes (38) in high yield. The exact structure of these complexes is not known but both aluminium and zirconium are essential. The stereoselectivity of the reaction is shown to be 98% c/s-addition, and once formed the complexes (38) undergo a variety of useful... 

Four new asymmetric ansa-zirconocene dichlorides, rac-[l-(9-ri -fluorenyl)-2-(2-phenyl-l-ri -indenyl)ethane]zirconium dichloride, rac-[(9-ri -fluorenyl)(5,6-cyclopenta-2-methyl-l-ri -indenyl)dimethylsilane]zirconium dichloride, rac-[(9-ri -fluorenyl)(2-methyl-l-ri -indenyl)dimethylsilane]zirconium dichloride and rac-[(9-r -fluorenyl)(2-phenyl-l-ri -indenyl)dimethylsilane]zirconium dichloride, have been prepared and evaluated as propene polymerisation catalysts. The synthesis of the [2,5-diisopropylcyclohexane-l,4-bis(indenyl)]titanium dichloride and [2,5-diisopropylcyclohexane-l,4-bis(tetrahydroindenyl)]titanium dichloride complexes, shown as 20, and their use as catalysts for the enantioselective pinacol coupling of benzaldehyde have been described. ... 

The metallocene dichloride of zirconium and hafnium 20b and 20c were also prepared and underwent reduction with potassium to give monomeric metallocene monochloride complexes 21b and 21c (Eq. 8) [39b]. The structure of the zirconocene complex 21 b in the crystal showed a conformation which suggests a less steric strain as compared to 21a due to zirconium s larger atomic size. As a consequence of the coordinative unsaturation an unusually short Zr —Cl bond length was found. 

The isotacticities and activities achieved with nonbridged metallocene catalyst precursors were low. Partially isotactic polypropylene has been obtained by using a catalyst system of unbridged (non-ansa type) metallocenes at low temperatures [65]. A chiral zirconocene complex such as rac-ZrCl2(C5H4 CHMePh)2 (125) is the catalyst component for the isospecific polymerization of propylene (mmmm 0.60, 35% of type 1 and 65% of type 2 in Scheme Y) [161]. More bulky metallocene such as bis(l-methylfluorenyl)zirconium dichloride (126) together with MAO polymerized propylene to isotactic polypropylene in a temperature range between 40 and 70°C [162]. 

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