Mono- and di-cyclopentadienyl zirconium derivatives containing the dimethylsilylcyclopentadienyl ligand. Agostic linear Si–H–Zr interaction in the molecular structure of [Zr{η5-C5H4(SiMe2H)}Cl3]2

Abstract

Dimethylsilyl substituted mono- and di-cyclopentadienyl zirconium chlorides have been prepared and their reactions with amido and alkyl reagents studied. The silylcyclopentadienes C₅H₅(SiMe₂H) 1, C₅H₄(SiMe₂H)₂2 and C₅H₄(SiMe₃)(SiMe₂H) 3 can be prepared by reaction of Na(C₅H₅) with the appropriate chlorosilane reagent. The lithium salt Li[C₅H₄(SiMe₂H)] reacts with ZrCl₄ or [Zr(C₅H₅)Cl₃] to give the metallocene complexes [Zr(C₅H₄R){C₅H₄(SiMe₂H)}Cl₂] (R = SiMe₂H 4 or H 5) whereas the reaction of the disilylcyclopentadiene C₅H₄(SiMe₂H)₂ with ZrCl₄ afforded the monocyclopentadienyl complex [Zr{C₅H₄(SiMe₂H)}Cl₃] 6, which exchanges the Si–H and Zr–Cl bonds. The reaction of 6 with lithium amides produces different products depending on the basicity of the nitrogen atom and the steric demands of its amido substituents. The reaction with LiN(SiMe₃)₂ and LiNH(2,6-Me₂C₆H₃) afforded the corresponding amido zirconium complexes [Zr{C₅H₄(SiMe₂H)}(NRR′)Cl₂] (R = R′ = SiMe₃7; R = H, R′ = 2,6-Me₂C₆H₃8), but in the case of the reaction with LiNH^tBu the known cyclopentadienylsilylamido derivative [Zr(η⁵,η¹-C₅H₄SiMe₂N^tBu)Cl₂] was formed. The monoamido, diamido and dialkyl dicyclopentadienyl complexes [Zr(C₅H₄R){C₅H₄(SiMe₂H)}X(Y)] (R = SiMe₂H 9 or H 10, X = Cl, Y = NH^tBu; R = SiMe₂H 11 or H 12, X = Y = NH^tBu; R = SiMe₂H 13 or H 14, X = Y = Me) have been synthesized by reaction of 4 and 5 with the appropriate amido or methyl reagent. Compound 9 reacts with a stoichiometric amount of water with selective hydrolysis of the Zr–amido bond to give the corresponding μ-oxo dinuclear complex [{Zr[C₅H₄(SiMe₂H)]₂Cl}₂(μ-O)] 15. The molecular structure of [Zr{C₅H₄(SiMe₂H)}Cl₃] 6 was established by X-ray crystallography. Compound 6 is a dimer, in the solid state, in which dimerization occurs through Zr–H–Si agostic interactions and two chloride bridges.