Synthesis of Molybdenum and Tungsten Alkylidene Complexes That Contain the 2,6-Bis(2,4,6-triisopropylphenyl)phenylimido (NHIPT) Ligand

Abstract

Molybdenum and tungsten alkylidene complexes that contain the sterically demanding hexaisopropylterphenylimido ligand, N-2,6-(2,4,6-i-Pr[subscript 3]C[subscript 6]H[subscript 2])[subscript 2]C[subscript 6]H[subscript 3] (NHIPT), have been prepared from Mo(N-t-Bu)[subscript 2]Cl[subscript 2](1,2-dimethoxyethane) or W(N-t-Bu)[subscript 2]Cl[subscript 2](pyridine)[subscript 2], employing tert-butylimido ligands as sacrificial proton acceptors. These complexes include M(NHIPT)(CH-t-Bu)Cl[subscrip 2] (M = Mo, W), Mo(NHIPT)(CH-t-Bu)(pyrrolide)[subscript 2], and Mo(NHIPT)(CH-t-Bu)(pyrrolide)(OC[subscript 6]F[subscript 5])(CH[subscript 3]CN). In all cases only anti alkylidene isomers are observed in solution, as a consequence of the steric demands of the NHIPT ligand. An X-ray structure of W(NHIPT)(CH-t-Bu)Cl[subscript 2] showed it to be a monomer with a disordered alkylidene that is 86% in the anti configuration and 14% in the syn configuration.