2,2,6,6-Tetramethylpiperidinogallium as a Terminal and Bridging Ligand in Homo- and Heteroleptic Chromium, Nickel, and Cobalt Complexes

By reaction of the gallium(I) derivative Ga4tmp4 (tmp = 2,2,6,6-tetramethylpiperidino) with Cr(CO)5(cyclo-octene), Co2(CO)8, and Ni(cyclooctadiene)2, respectively, the Gatmp complexes [Cr(CO)5Gatmp], (CO)3Cr(μ2-Gatmp)3Cr(CO)3, (CO)3Co(μ2-Gatmp)2Co(CO)3, and (tmpGa)2Ni(μ2-Gatmp)3Ni(Gatmp)2 were obtained. The latter are described as derivatives of the binuclear metal carbonyls Cr2(CO)9, Co2(CO)8, and Ni2(CO)7, where some or all carbonyls are replaced by the amino gallylene group. All compounds are characterized by spectroscopy and crystal structure analysis. The change of the bonding situation from localized two-center gallium metal bonds in the chromium derivative to three-center bonds in the cobalt complex is discussed by means of density functional theory calculations.