Reaction of Ni2Cp2(mu-CO)(2) with the alkylgallium(I) and alkylindium(I) compounds E-4[C(SiMe3)(3)](4) (E = Ga, In). Insertion of E-R groups into theNi-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 N i2Cp2(mu -CO)(2) upon treatment of the carbonyl complex with the tetraindiu m(I) compound In-4[C(SiMe3)(3)](4), 1, in a molar ratio of 4 to 1. The prod uct (3) contains an indium atom coordinated to one aikyr substituent and tw o 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 lig ands by two InR groups. A compound (3) was formed that is isostructural to the carbonyl nickel complex and has a Nit couple bridged by two InR ligands and two terminally coordinated cyclopentadienyl groups. The insertion prod uct was not observed with the gallium derivative Ga-4[C(SiMe3)(3)](4) (2); instead, a nickel gallium complex (5) analogous to 4 containing two bridgin g GaR ligands was isolated as the only product regardless of the ratio of t he starting compounds. On the basis of quantum chemical calculations, we co nclude 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(mu -CO)(2).