Studies of the Formation and Decomposition Pathways for Cationic Zirconocene Hydrido Silyl Complexes

Abstract

Reactions and intermediates leading to zirconocene complexes [Cp‘2Zr(μ-H)(SiHR)]22+[BR‘n(C6F5)4-n]22- (Cp‘ = Cp, MeCp, Me5Cp; R = Ph, PhCH2; R‘ = Bu or H; 1a−e) were investigated in situ by NMR and EPR studies and by trapping unstable intermediates with PMe3. Two novel ZrIII complexes, [Cp2ZrIII]+[BBun(C6F5)4-n]- (5) and [Cp2ZrIII(PMe3)2]+[BBun(C6F5)4-n]- (8) were identified by EPR spectroscopy. Redistribution of borate butyl and pentafluorophenyl ligands was found to occur by a direct boron to boron migration and not by a metal-assisted mechanism. The latter was ruled out by an independent synthesis of expected reaction intermediates for both reaction pathways ([Ph3C][BBu(C6F5)3], [Cp2Zr(C6F5)]+[BBun(C6F5)4-n]-, and [Cp2Zr(C6F5)(μ3-HB(C6F5)3)]2) and an investigation of their model redistribution reactions by NMR spectroscopy.