Studies of the formation and decomposition pathways for cationic zirconocene hydride silyl complexes

Reactions and intermediates leading to zirconocene complexes [Cp-2'Zr(mu-H)(SiHR)](2)(2+)[BRn'- (C6F5)(4-n)](2)(2-) (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 Zr-III complexes, [Cp2ZrIII](+)[BBun(C6F5)(4-n)](-) (5) and [Cp2ZrIII(PMe3)(2)](+)[BBun(C6F5)(4-n)](-) (8) were identified by EPR spectroscopy. Redistribution of berate 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)(mu(3)-HB(C6F5)(3))](2)) and an investigation of their model redistribution reactions by NMR spectroscopy.