Reaction of Ni(CO)4 in toluene at room temperature with one equivalent of GaAr′ (Ar′ = C6H3-2,6-(C6H3-2,6-iPr2)2) and GaL (L = HC[C(Me)N(C6H3-2,6-iPr2)]2) formed the mono-substituted Ni(CO)3(GaAr′) (1) and Ni(CO)3(GaL) (3), respectively. Compound 1 decomposed under reduced pressure or upon heating in toluene to give the new cluster species Ni4(CO)7(GaAr′)3 (2). Reaction of 3 with a second equivalent of GaL in toluene at 95 °C afforded the disubstituted complex Ni(CO)2(GaL)2 (4). All the compounds were characterized by IR, 1H and 13C{1H} NMR spectroscopy and X-ray crystallographic studies were undertaken to elucidate the structures of the complexes 2, 3 and 4. The reaction of Ni(CO)4 with GaAr′ affords [Ni(CO)3(GaAr′)] (Ar′ = C6H3-2,6-(C6H3-2,6-iPr2)2) which readily decomposes to the new nickel carbonyl cluster [Ni4(CO)7(GaAr′)3].