Synthesis and Molecular Structure of an Orthometalated Aminogallane, [MeGaN(CH2C6H4)(CH2Ph)]2

Abstract

Monitoring the thermolysis reaction of Me3Ga with HN(CH2Ph)2 in toluene with multinuclear NMR spectroscopy indicates the initial formation of [Me2GaN(CH2Ph)2]2 via 1,2-elimination of CH4 followed by additional 1,2-elimination steps that give the orthometalated gallium dimer [MeGaN(CH2C6H4)(CH2Ph)]2 in 65% yield. This is the first reported example of orthometalation of an aromatic ring carbon by gallium. Because [MeGaN(CH2C6H4)(CH2Ph)]2 forms prior to the complete conversion of (PhCH2)2NH·GaMe3 to [Me2GaN(CH2Ph)2]2, thermolysis of a Me3Ga/HN(CH2Ph)2 mixture is not a viable route to [Me2GaN(CH2Ph)2]2. Instead it was prepared by a salt elimination reaction. The single-crystal X-ray diffraction analysis establishes the dimeric nature of the orthometalated compound and indicates a structure that is consistent with the NMR chemical shift assignements obtained using both 1-D and 2-D NMR techniques.