Insertion of Isonitriles into the Zr–CH3 Bond of Cp*2Zr(CH3)2 and Electrophilic Cleavage of the Remaining Methyl Group

Abstract

The insertion of tert-butyl isonitrile (tBuNC) into the M–C bond of Cp*2Zr(CH3)2 (1) leads to the formation of a monoiminoacyl product Cp*2Zr(iminoacyl)CH3 (2). SC-XRD analysis has revealed that the η2 coordinated iminoacyl ligand has an “N-outside” orientation. Compound 2 undergoes rapid Zr–C bond cleavage with the Bronsted acid CpCr(CO)3H or the Lewis acid B(C6F5)3, yielding Zr cation 4 or 5 with the corresponding anion [MeB(C6F5)3]− or [CpCo(CO)3]−. In the solid-state structure of 4, the Zr cation features an η2 “N-inside” geometry for the iminoacyl group and interacts with the [CpCo(CO)3]− via the oxygen atom of one of the CO ligands. Cleavage of the methyl ligand from the Zr of 1 with CpCr(CO)3H proceeds with a second-order rate constant k1 of 2.11(4) × 10–3 M–1 s–1, whereas cleavage of the methyl ligand from the Zr of 2 is significantly faster, with an estimated k2 greater than 104 M–1 s–1. In light of the observed “N-outside” to “N-inside” change from 2 to 4, we propose that the enhanced rate with ...