Reaction of Ni₂Cp₂(μ-CO)₂ with the Alkylgallium(I) and Alkylindium(I) compounds E₄[C(SiMe₃)₃]₄ (E = Ga, In). Insertion of E-R groups into the Ni-Ni bond versus replacement of CO by the Isolobal E-R Ligands

The monomeric fragment In-C(SiMe₃)₃ was inserted into the Ni-Ni bond of Ni₂Cp₂(μCO)₂ upon treatment of the carbonyl complex with the tetraindium(I) compound In₄[C(SiMe₃)₃]₄, 1, in a molar ratio of 4 to 1. The product (3) contains an indium atom coordinated to one alkyl substituent and two Ni(Cp)CO groups in a planar coordination sphere. Reaction of the starting compounds in a molar ratio of 2 to 1 led to the replacement of both CO ligands by two InR groups. A compound (4) was formed that is isostructural to the carbonyl nickel complex and has a Ni₂ couple bridged by two InR ligands and two terminally coordinated cyclopentadienyl groups. The insertion product was not observed with the gallium derivative Ga₄[C(SiMe₃)₃]₄ (2); instead, a nickel gallium complex (5) analogous to 4 containing two bridging GaR ligands was isolated as the only product regardless of the ratio of the starting compounds. On the basis of quantum chemical calculations, we conclude that there is no evidence for an In-In or Ga-Ga bond in complexes 4 or 5, respectively. This, however, supports a butterfly geometry, which is isostructural to the starting carbonyl complex Ni₂Cp₂(μ-CO)₂.