Group 2 and 12 Metal Gallyl Complexes Containing Unsupported Ga-M Covalent Bonds (M = Mg, Ca, Sr, Ba, Zn, Cd)

Reactions of the anionic gallium(I) heterocycle [:Ga(DAB)](-) (DAB = {N(Dip)C(H)}(2) Dip = C6H3-Pr-2(i),-2,6) with several group 2 and 12 metal halide complexes are reported. Treatment of in situ generated [MI2(tmeda)(n)] (M = Ca, Sr, Ba; tmeda = N,N,N',N'-tetramethylethylenediamine) with 2 equiv of [K(tmeda)][:Ga(DAB)] leads to salt elimination and formation of the neutral metal gallyl complexes trans-[M{Ga(DAB)}(2)(tmeda)(2)]. Reaction of [(Nacnac)MgI(OEt2)] (Nanac = {N(Dip)C(Me)}(2)CH) with [K(tmeda)][:Ga(DAB)] gives [(Nacnac)(kappa(1)-tmeda)Mg{Ga(DAB)}]. All complexes we re crystallographically characterized and display isomerism in solution, which for the latter compound has been investigated by variable-temperature NMR spectroscopy. The 1:1 reactions of [K(tmeda)][:Ga(DAB)] with [MX2(tmeda)] (M = Zn, X = Br; M = Cd, X = 1) yield [(tmeda)MX{Ga(DAB)}], the cadmium example of which is the first molecular complex bearing a Ga-Cd bond. Attempts to reduce these compounds to low-valent species, e.g. [{(DAB)Ga}MM{Ga(DAB)}], were unsuccessful. Treating [(Nacnac)Zn(mu-Br)(2)Li(OEt2)(2)] with [K(tmeda)][:Ga(DAB)] gave [(Nacnac)Zn{Ga(DAB)}], the X-ray crystal structure of which is reported.