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

Reactions and intermediates leading to zirconocene complexes [Cp‘ 2 Zr(μ-H)(SiHR)] 2 2+ [BR‘ n (C 6 F 5 ) 4 - n ] 2 2 - (Cp‘ = Cp, MeCp, Me 5 Cp; R = Ph, PhCH 2; R‘ = Bu or H; 1a − e ) were investigated in situ by NMR and EPR studies and by trapping unstable intermediates with PMe 3 . Two novel Zr III complexes, [Cp 2 Zr III ] + [BBu n (C 6 F 5 ) 4 - n ] - ( 5 ) and [Cp 2 Zr III (PMe 3 ) 2 ] + [BBu n (C 6 F 5 ) 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 ([Ph 3 C][BBu(C 6 F 5 ) 3 ], [Cp 2 Zr(C 6 F 5 )] + [BBu n (C 6 F 5 ) 4 - n ] -, and [Cp 2 Zr(C 6 F 5 )(μ 3 -HB(C 6 F 5 ) 3 )] 2 ) and an investigation of their model redistribution reactions by NMR spectroscopy.