Reactions of a gallium(II)-diazabutadiene dimer, [{{[(H)C(But)N]2}GaI}2], with [ME(SiMe3)2] (M = Li or Na; E = N, P or As): Structural, EPR and ENDOR characterization of paramagnetic gallium(III) pnictide complexes

The reactions of the paramagnetic gallium(II) complex [{(But-DAB)GaI}2] (But-DAB = {(But)NC(H)}2) with the alkali metal pnictides [ME(SiMe3)2] (M = Li or Na; E = N, P, or As) have been carried out under a range of stoichiometries. The 1:2 reactions have led to a series of paramagnetic gallium(III)−pnictide complexes, [(But-DAB)Ga{E(SiMe3)2}I] (E = N, P, or As), while two of the 1:4 reactions afforded [(But-DAB)Ga{E(SiMe3)2}2] (E = P or As). In contrast, treatment of [{(But-DAB)GaI}2] with 4 equiv of [NaN(SiMe3)2] resulted in a novel gallium heterocycle coupling reaction and the formation of the diradical species [(But-DAB)Ga{N(SiMe3)2}{[CC(H)N2(But)2]Ga[N(SiMe3)2]CH3}]. The mechanism of this unusual reaction has been explored, and evidence suggests it involves an intramolecular transmethylation reaction. The X-ray crystal structures of all prepared complexes are reported, and all have been characterized by EPR and ENDOR spectroscopies. The observed spin Hamiltonian parameters provide a detailed picture of the distribution of the unpaired spin density over the molecular frameworks of the complexes