Synthesis, crystal structure and reactions of zerovalent 16-electron bis(η-cycloheptatriene)zirconium

Abstract

Reduction of ZrCl₄ with sodium amalgam in the presence of cycloheptatriene gives the crystallographically identified [Zr(η⁶-C₇H₈)₂]1 which exhibits a non-parallel arrangement of the cycloheptatrienyl ligands. This reacts with PMe₃ or 1,2-bis(dimethylphosphino)ethane (dmpe) to yield [Zr(η⁷-C₇H₇)(η⁵-C₇H₉)(PMe₃)]2 and [{Zr(η⁷-C₇H₇)(η⁵-C₇H₉)}₂(dmpe)]3 respectively. Treatment of compound 1 with (AlEt₂Cl)₂ in tetrahydrofuran (thf) yields [{Zr(η⁷-C₇H₇)(thf)(µ-Cl)}₂]4 which reacts with N,N,N′,N′-tetramethylethylenediamine, PMe₃, dmpe and 1,2-dimethoxyethane to produce [Zr(η⁷-C₇H₇)(Me₂NCH₂CH₂NMe₂)Cl]5, [Zr(η⁷-C₇H₇)(PMe₃)₂Cl]6, [Zr(η⁷-C₇H₇)(dmpe)Cl]7 and [Zr(η⁷-C₇H₇)(MeOCH₂CH₂OMe)Cl]8, respectively. The electronic structures of 1 and [Zr(η⁷-C₇H₇)(η⁵-C₇H₉)]11 have been investigated by photoelectron spectroscopy and extended-Hückel molecular-orbital calculations.