tert-Butylsilylcyclopentadienyl Group 4 metal complexes
摘要:
New Group 4 metal t-butyldimethylsilyleyclopentadienyl complexes [MCpCp'Cl-2] (Cp = eta(5)-C5H5 : Cp' = eta(5)'-C5H4SiMe2',Bu; M = Ti 4, Zr 5, Hf 6) were prepared by reaction of 1 equiv. of the lithium (2) and thallium (3) salts of t-butyldimethylsilylcyclopentadiene I with the monocyclopentadienyl complexes [MCpCl3. DME] (M = Zr, Hf) and [TiCpCl3], respectively, A similar reaction using ZrCl4(THF)2 and HfCl4 with 2 equiv. of the lithium salt 2 gave the symmetric [MCp2Cl2] (M = Zr 7, Hf8) rnetallocenes. Alkylation of these compounds with 2 equiv. of MgRCl (R = Me. CH2Ph) and Li(CH2CMe2Ph) afforded the dialkyl complexes [MCpCp'R-2] (R = Me, M = Zr 9, Hf 10: R = CH2Ph. M = Ti 11. Zr 12. Hf 13). [ZrCp2(CH2Ph):] 14 and [ZrCpCp'(CH2CMe2Ph)(2)] 17, A Similar reaction of 5 with 1 equiv. of Mg(CH2Ph)Cl gave the monobenzyl compound [ZrCpCp'Cl(CH2Ph)] (15), Hydrolysis of 15 with a stoichiometric amount of water afforded the dinuclear mu-oxo compound [(ZrCpCp'Cl)(2)(mu-O)] (16). All of the new complexes reported were characterized by elemental analysis and H-1 and C-13 NMR spectroscopy and the molecular structures of 4 and 16 were determined by X-ray diffraction methods. Ethylene polymerization activities were measured for compounds 4-7. (C) 2002 Elsevier Science B.V. All rights reserved.
Influence of the Departing Group on the Electrophilic Cleavage of Silicon−Carbon Bonds Adjacent to Zirconocene Dichloride. Preparation of Electrophile-Functionalized Zirconocene Dibromides
摘要:
(EtMe2SiC5H4)CpZrCl2 (5) reacts with BBr3 in 1,2-dichloroethane (reflux, 24 h) to afford a 4:1 mixture of (EtMeBrSiC5H4)CpZrBr2 (10) and (BrMe2SiC5H4)CpZrBr2 (11) in a nearly quantitative conversion. Similarly, ((BuMe2SiC5H4)-Bu-t)CpZrCl2 (6) reacts with BBr3 to afford a 15:1 mixture of ((BuMeBrSiC5H4)-Bu-t)CpZrBr2 (13) and 11. The product 11 is obtained independently by treating (Me3SiC5H4)CpZrCl2 (12) with BBr3. In contrast, Si-Ph bonds are cleaved with complete selectivity in the presence of Si-Me groups. (PhMe2SiC5H4)(2)-ZrCl2 (8) reacts with excess BCl3 in dichloromethane (reflux, 15 h) to afford (ClMe2SiC5H4)(2)-ZrCl2 (14) in 72% yield. (Ph2MeSiC5H4)(2)ZrCl2 (9) reacts with excess BBr3 in 1,2-dichloroethane (reflux, 15 h) to afford (Br2MeSiC5H4)(2)ZrBr2 (15) in 79% yield. Complexes 9 and 15 were analyzed by single-crystal X-ray diffraction. Crystalline 9 adopts a pseudo-C-2 conformation in which the face of the Ph group of one ligand shows a weak interaction with a C-H bond of the other ligand. Crystalline 15 also adopts a pseudo-C-2 conformation, in which the SiBr2 groups are directed away from the ZrBr2 group.