Adduct formation of [(η7-C7H7)Hf(η5-C5H5)] with isocyanides, phosphines and N-heterocyclic carbenes: An experimental and theoretical study

The reactions of [(η7-C7H7)Hf(η5-C5H5)] (1b) with the two-electron donor ligands tert-butyl isocyanide (tBuNC), 2,6-dimethylphenyl isocyanide (XyNC), 1,3,4,5-tetramethylimidazolin-2-ylidene (IMe) and trimethylphosphine (PMe3) are reported. The 1:1 complexes [(η7-C7H7)Hf(η5-C5H5)L] (2b, L = tBuNC; 3b, L = XyNC; 4b, L = IMe, 5b, L = PMe3) have been isolated in crystalline form, and their molecular structures have been determined by X-ray diffraction analyses. The stabilities of these hafnium complexes were probed via spectroscopic and theoretical methods, and the results were compared to those previously reported for the corresponding zirconium complexes derived from [(η7-C7H7)Zr(η5-C5H5)] (1a). The X-ray crystal structure of the PMe3 adduct [(η7-C7H7)Zr(η5-C5H5)(PMe3)] (5a) was also established.