Dinuclear zirconium complexes with Me2Si(C5H4)2 as bridging ligand. Molecular structure of [{Zr(η5-C5H3-But2)Me}2(µ-O){µ-Me2Si(C5H4)2}]

Abstract

The reaction of Li₂[Me₂Si(C₅H₄)₂] with 2 equivalents of [ZrLCl₃](L = C₅Me₅ or C₅H₃Bu^t₂) in toluene under reflux gave the known [{Zr(C₅Me₅)Cl₂}₂{µ-Me₂Si(C₅H₄)₂}]1 and the new chloro derivative [{Zr(C₅H₃Bu^t₂)Cl₂}₂{µ-Me₂Si(C₅H₄)₂}]2 in good yields. Addition of 4 equivalents of LiMe (or MgMeCl) to a pentane solution of 1 or 2 afforded the tetramethyl derivatives [{Zr(C₅Me₅)Me₂}₂{µ-Me₂Si(C₅H₄)₂}]3 and [{Zr(C₅H₃Bu^t₂)Me₂}₂{µ-Me₂Si(C₅H₄)₂}]4. Compound 3 is extremely moisture sensitive leading to the µ-oxo dinuclear complex [{Zr(C₅Me₅)Me}₂(µ-O){µ-Me₂Si(C₅H₄)₂}]5, as demonstrated by ¹H NMR spectroscopy. Compound 4 reacted with water, in pentane or toluene, to give the µ-oxo dimethyl complex [{Zr(C₅H₃Bu^t₂)Me}₂(µ-O){µ-Me₂Si(C₅H₄)₂}]6. Further reaction of 6 with water in toluene gave an unidentified insoluble yellow powder through the intermediate formation of a µ-dioxo methyl complex 7, identified by ¹H NMR spectroscopy. The crystal structure of 6 has been determined by X-ray diffraction methods: monoclinic, space group P2₁/n, a= 15.494(4), b= 13.338(3), c= 19.933(4)Å, β= 107.19(1)° and Z= 4. Complex 6 is a dimer produced by the interaction of two Zr(η⁵-C₅H₃Bu^t₂) Me units bridged by one oxygen atom and the Me₂Si(C₅H₄)₂ group.