Methyl-substituted zirconocene-bis(trimethylsilyl)acetylene complexes (C(5)H(5-n)Me(n))(2)Zr(eta(2)-Me(3)SiC CSiMe(3)) (n=2-5)

The (C(5)H(5-n)Me(n))(2)Zr[eta(2)-C-2(SiMe(3))(2)] (n = 2-5; 1,3-dimethyl, 1,2,3-trimethyl) (2C-F) complexes were prepared by the reduction of corresponding zirconocene dichlorides with magnesium in THF in the presence of bis(trimethylsilyl)acetylene (BTMSA). All of them are stable in the absence of THF. Crystal structures of (C(5)HMe(4))(2)Zr[eta(2)-C-2(SiMe(3))(2)] (2E) and (C(5)Me(5))(2)Zr[eta(2)-C-2(SiMe(3))(2)] (2F) and ofthe analogous titanium complexes are isomorphous. The red shift of the nu(C=C) vibration and the downfield shift of C-13 delta(C=C) indicate that BTMSA in 2C-F is more strongly coordinated than in analogous titanocene complexes. The nonisolated complex (C(5)H(4)Me)(2)Zr[eta(2)-C-2(SiMe(3))(2)](THF) (2B . THF) rearranges after the loss of THF to give the dimer [(eta(5)-C(5)H(4)Me)(eta(1)-C(SiMe(3))=CH(SiMe(3))Zr(mu-eta(1):eta(5)-C(5)H(3)Me)](2) (3B).