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 = C₆H₃Prⁱ₂-2,6) 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)}₂CH) with [K(tmeda)][:Ga(DAB)] gives [(Nacnac)(κ¹-tmeda)Mg{Ga(DAB)}]. All complexes were 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 = I) 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(μ-Br)₂Li(OEt₂)₂] with [K(tmeda)][:Ga(DAB)] gave [(Nacnac)Zn{Ga(DAB)}], the X-ray crystal structure of which is reported.