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

Molybdenum and tungsten alkylidene complexes that contain the sterically demanding hexaisopropylterphenylimido ligand, N-2,6-(2,4,6-i-Pr3C6H2)2C6H3 (NHIPT), have been prepared from Mo­(N-t-Bu)2Cl2(1,2-dimethoxyethane) or W­(N-t-Bu)2Cl2(pyridine)2, employing tert-butylimido ligands as sacrificial proton acceptors. These complexes include M­(NHIPT)­(CH-t-Bu)­Cl2 (M = Mo, W), Mo­(NHIPT)­(CH-t-Bu)­(pyrrolide)2, and Mo­(NHIPT)­(CH-t-Bu)­(pyrrolide)­(OC6F5)­(CH3CN). 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)­Cl2 showed it to be a monomer with a disordered alkylidene that is 86% in the anti configuration and 14% in the syn configuration.