Zirconocene dichlorides, preparation

Bis[iV,iV -di(2-pyridyl)-imidazol-2-ylidene]aurate(I) tetrafluoroborates, preparation, 2, 292-293 Bis[iV,iV -di(2-pyridyl-methyl)-imidazol-2-ylidene]aurate(I) tetrafluoroborates, preparation, 2, 292-293 Bis(diselenolate) complexes, dinuclear iron compounds, 6, 242 Bis(dithiolene) compounds, in tungsten carbonyl and isocyanide complexes, 5, 644 Bis(enolato) complexes, with bis-Cp Ti(IV), 4, 589 Bis(enones), in reductive cyclizations, 10, 502 Bis(ethanethiolato) complexes, with bis-Cp Ti(IV), 4, 601 Bis(ethene)iridium complexes, preparation, 7, 328-329 -Bis(fluorenyl)zirconocene dichlorides, preparation,... 

Cyclopentadienylstannanes, preparation, 3, 840 z/ .tz/-(Cyclopcritadienyl-substituted-indenyl)zirconocene dichlorides, preparation, 4, 958 Cyclopentadienyl-substituted phosphaferrocenes, preparation, 6, 210-211... 

The bis-zirconocene complex CpjClZrCHjCHjZrCpjCl has been isolated upon double hydrozirconation of acetylene with 1 [102]. Recently, the preparation of a heterogeneous bis-zirconocene catalyst was succesfully achieved from zirconocene dichloride complexes containing alkenyl or alkynyl substituents [224]. 

Schwartz s Reagent3 is available commercially (from the Aldrich Chemical Company, Inc.) although it is quite expensive. Two literature preparations of this important reagent are available. The first utilizes LiAI(OtBu)3H to reduce zirconocene dichloride.4 The second method utilizes sodium bis(2-methoxyethoxy) aluminum hydride (RED-AL) as the reducing agent.2a The disadvantages of these procedures have been discussed.3... 

Alternately, CpjZr can also be prepared by the reaction of Cp2ZrCl2with two equivalents of n-BuLi at —78°C E.-I Negishi, F. K. Cederbaum and T. Takahashi, Reaction of zirconocene dichloride with alkyl lithiums or alkyl Grignard reagents as a convenient method for generating a zirconocene equivalent and its use in zirconium promoted cyclization of alkenes, alkynes dienes, eneynes and diynes, Tetrahedron Lett. 27 2829 (1986). 

Instead of titanocene dichloride, zirconocene dichloride can be used for the preparation of the carbene complex 219. The Lewis acidity of Zr is lower than that of Ti, and the Zr reagent 219 reacts smoothly with aldehydes and ketones, but not with esters [69]. 

Preparation (14, 81). Full details are available for the preparation by reduction of zirconocene dichloride with LiAlH4 followed by a methylene chloride wash to convert the unwanted Cp2ZrH2 to 1. Overall yield is 77-92%. 

Arylated cyclopentadienes, especially pentaarylcyclopentadienes 6, have interesting properties as ligands for transition metals [1] or as electroluminescent materials [2], The classical methods for their preparation are multistep procedures [3], which are somewhat tedious and usually less suitable for sterically demanding aryl groups. In contrast, the palladium-catalyzed arylation of either metallocenes such as zirconocene dichloride (1) or simply cyclopentadiene (3) with aryl halides leads to the target compounds 4—6 in a single preparative step (Scheme 1) [4—6]. 

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. 

Recently, a novel C[-symmetric zirconocene dichloride CpCp ZrCla (Cp = C5H5, Cp = 1-neomenthyl-4,5,6,7-tetrahydroindenyl) was prepared, in which the alkene can only approach from one side. With this chiral ligand, the ethylmagnesiation of unsubstituted allylic amines or alcohols leads to good enantioselectivities [125]. 

Dialkyl and diaryl Ti and Zr derivatives (18) are somewhat less stable than their monosubstituted analogs. They are generally prepared by alkylation of the corresponding dichloro compounds (17 equation 1 1).i3,29,30 jjjg dichloro derivatives themselves can be prepared in turn by reaction of tetrachlorides with the required amount of organometallic species. For example, zirconocene dichloride is prepared by treating zirconium(IV) chloride with cyclopentadienylsodium. ... 

Zirconocene dichlorides having the ether functionality at the Cp substituents with variable spacing between the oxygen donor and metal center, such as complexes 603 (n = 2, 4, 6, 8) shown in Scheme 136,435 were prepared to elucidate how that spacing affects their catalytic behavior. The presence of the oxygen atom close to the metal center severely reduced the olefin polymerization activity, whereas such activity increased as the distance between... 

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... 

Insertion of PhNCS and CS2 into the Zr-P bond of the chlorozirconocene primary phosphido complex 923, which is prepared by the reaction of the zirconocene dichloride with LiPhCy, yields the corresponding insertion products 924 and 925, respectively (Scheme 232).701 The molecular structure of the complex 924 confirms the -bonding mode of the iV-ligation. 

---