UNEXPECTED CARBON-CARBON COUPLING BETWEEN ORGANIC CYANIDES AND AN ISOPROPYL BETA-CARBON IN A HAFNIUM ENE DIAMIDE COMPLEX

A reaction sequence involving two hydrogen transfers and a C-C coupling on the beta-carbon of an isopropyl group leads to formation of a new dianionic tridentate ligand in the reaction of the ene diamide complex Cp*Hf(sigma-2, pi-iPr-DAB)Cl (1; Cp* = eta-5-C5Me5, iPr-DAB = 1,4-dilsopropyl-1,4-diaza-1,3-butadiene) with organic cyanides. The product Cp*Hf [iPrNCH=CHNC(Me)= CHC(tBu)=NH]Cl was structurally characterized (Pbca, a = 13.454 (1) angstrom, b = 11.470 (1) angstrom, c = 31.297 (2) angstrom, 100 K). The reaction sequence is probably initiated by the transfer of the iPr alpha-H atom to a coordinated cyanide. Such a hydrogen transfer was observed in the reaction of 1 with ketones, producing the ene imine alkoxide complexes Cp*Hf[iPrNCH=CHN=CMe2](OCHR2)Cl, which were identified by NMR spectroscopy.