Bis(tert-butylimido)bis(N,O-chelate)tungsten(VI) Complexes: Probing Amidate and Pyridonate Hemilability.

Four new bis(tert-butylimido)bis(N,O-chelate)tungsten(VI) complexes (3-6), in which the N,O-chelate is an amidate or pyridonate ligand, have been synthesized and characterized. Computational analysis has been used to calculate the relative energies of different stereoisomers and shown how the steric demand of each ligand influences coordination and bonding modes. The electronically saturated complexes have been employed to evaluate 1,3-N,O-chelated metal-ligand interactions. Complexes 3-6 were treated with electrophilic reagents, which resulted in strikingly different reactivity patterns between the amidate and the pyridonate ligated complexes. The observed reactivity differences are accompanied by direct observation of different trends in the hemilability of these two different classes of 1,3-N,O-chelates.