Neutral and Cationic [Bis(η~1-amidosilyl)-η~5-cyclopentadienyl]titanium and -zirconium Complexes: Synthesis, X-ray Molecular Structures and DFT Calculations

摘要

Treatment of LiNHtBu with THF solutions of C_5H_4(SiMe_2Cl)_2 gave C_5H_4(SiMe_2NHtBu)_2 (1). Deprotonation of 1 with M(NMe_2)_4 (M = Ti, Zr) under different conditions provided the monocyclopentadienyl complexes [M(η~5-C_5H_3-[SiMe_2(NHtBu)_2}(NMe_2)_3] [M = Ti (2), Zr(3)] and the single (η-amidosilyl)cyclopentadienyl compounds [M(η~5-C_5H_3[Si-Me_2(NHtBu)][SiMe_2(η~1-NtBu)]}(NMe_2)_2] [M = Ti (4), Zr (5)]. The related dibenzyl compounds [M{η~5-C_5H_3[SiMe_2-(NHtBu)][SiMe_2(η~1-NtBu)]}(CH_2Ph)_2] [M = Ti (6), Zr (7)] resulted from treatment of 1 with M(CH_2C_6H_5)_4 (M = ti, Zr). Further deprotonation of the amido complexes 4 and 5 and the benzyl complexes 6 and 7 by heating in toluene solution gave the bis(η-amidosilyl)cyclopentadienyl complexes [M(η~5-C_5H_3[SiMe_2(η~1-NtBu)]_2(NMe_2)] [M = Ti (8), Zr (9)] and [M{η~5-C_5H_3[SiMe_2(η~1-NtBu)]_2}(CH_2Ph)] [M = Ti (10), Zr (11)], respectively. Treatment of the monobenzyl complexes 10 and 11 with B(C_6F_5)_3 yielded the cationic compounds [M{η~5-C_5H_3[SiMe_2(η~1-NtBu)]_2}]~+ as [(CH_2Ph)B(C_6F_5)_3]~- [M = Ti (12), Zr(13)] salts. All new compounds were characterized by NMR spectroscopy, and the crystal structures of 10 and 13 were studied by diffraction methods. DFT calculations for the neutral and cationic species are described and provide an explanation for the unusual η~1 coordination of a phenyl ring to a group-4 metal cation.