Photochemical cleavage of pentamethylcyclopentadienyl-gallium bonds: An alternative approach to the formation of digallanes

The novel digallanes [GaN(Dipp)CH=CHN-(Dipp)](2) (3) (Dipp = 2,6-diisopropy lphenyl) and [GaN-(Dep)CH=CHN(Dep)](2) (4) (Dep = 2,6-diethylphenyl) were o btained in quantitative yield by photolysis of the 1-galla-2,5-diazoles [(e ta (1)-Cp*)GaN(Dipp)CH=CHN(Dipp)] (1) and [(eta (1)-Cp*)GaN(Dep)CH=CHN(Dep) ] (2), respectively. This alternative approach to the synthesis of digallan es demonstrates the efficiency of the Cp* moiety as the leaving group in th e formation of metal-metal bonds. Compounds 3 and 4 were characterized ky s pectroscopic and analytical data. Compound 3 could further be characterized by X-ray crystallography; its molecular structure is compared with the str uctures of some other digallanes. Density functional calculations for diffe rently substituted digallanes are presented.