A facile high-yield synthesis of the tetrahedral gallium(I) compounds Ga4[C(SiMe2R)3]4 -: crystal structure of Ga4[C(SiMe2Et)3]4

Alkyl gallium(I) derivatives with gallium in an unusual low oxidation state of +I are important starting materials for the synthesis of novel organo gallium compounds of main group or transition metal elements. Up to now, they were synthesized by a disproportionation reaction with yields below 15% with respect to the alkyl substituents. We succeeded now in synthesizing these compounds on a very simple route by the reduction of the chloro complexes Li[Cl3Ga-C(SiMe2R)(3)] (R = Me: 1; R = Et: 2) in toluene at 70-80 degrees C by the two-electron donor Rieke magnesium in a yield of more than 70%. While the crystal structure of [GaC(SiMe3)(3)](4) 3 showed a severe disorder of the whole molecule, [GaC(SiMe2Et)(3)](4) 4 gives a clearly resolved crystal structure with an almost undistorted Ga-4 tetrahedron in the molecular center and a Ga-Ga distance of 271.0 pm on average. 4 gradually monomerizes in benzene with increasing dilution of the solutions to give the monomeric fragment Ga-C(SiMe2Et)(3). (C) 1998 Elsevier Science S.A. All rights reserved.