Structural diversity in bishydroxylamine complexes of gallium.

Reactions of bishydroxylamines of the type HON(R)CH2CH2N(R)OH (R = Me, tBu) with trimethyl- and triisopropylgallium gave bicyclic metalla cages of the formula R′2GaO(R)NCH2CH2N(R)OGaR′2 [R′ = Me, R = Me (3a), tBu (3b); R′ = iPr, R = Me (4a), tBu (4b)] with six-membered Ga2O2N2-rings. While the complexes show the same core constitution in the solid state, NMR spectra reveal the steric influence of the isopropyl substituent of the compounds 4a/4b on its behaviour in solution. The reaction of the sterically more demanding substituted tri-tert-butylgallium with HON(Me)CH2CH2N(Me)OH yielded a heterodimeric complex O′-[HON(Me)CH2CH2NH(Me)O(tBu2Ga)]-cyclo-(tBu2Ga)-O,N′-[ON(Me)CH2CH2N(Me)O] (5) with two gallium atoms of different surrounding and two different bishydroxylamine ligands, one doubly deprotonated and one protonated, but at one end in its tautomeric aminoxide form. Further condensation of 5 was observed to give a tricyclic compound cyclo-[(tBuGa)ON(Me)CH2CH2N(Me)O]2 (6) with a central Ga2O2N2 ring resulting from two Ga–N donor–acceptor bonds. [ABSTRACT FROM AUTHOR]