PRIMARY AMIDO AND AMINE ADDUCT COMPLEXES OF GALLIUM - SYNTHESIS AND STRUCTURES OF [TERT-BU2GA(MU-NHPH)]2 AND TERT-BU3GA.NH2PH

Reaction of t-Bu2GaCl with LiNHPh in toluene/diethylether (4:1) at - 78-degrees-C gives the dimeric primary amido complex [t-Bu2Ga(mu-NHPh)]2 (1) in 60% yield. The reaction of t-Bu3Ga with NH2Ph at - 78-degrees-C in toluene gives the adduct t-Bu3Ga.NH2Ph (2) in 75% yield. The structures of both compounds have been determined by X-ray crystallography. The molecular geometry of 1 consists of a dinuclear unit with two bridging -NHPh groups and two terminal t-Bu groups bound to each gallium atom. The coordination geometry of both the gallium and nitrogen atoms is distorted tetrahedral. The molecular geometry of 2 involves a fairly long dative N --> Ga donor bond [2.246(9) angstrom] and the configuration of the amine is distorted from an idealized tetrahedral geometry due to steric repulsions. Crystallographic data for both 1 and 2 suggest the presence of close interactions between the N-H hydrogen atoms and the gallium atoms (N-H...Ga).