Structural diversity in bishydroxylamine complexes of gallium

摘要

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(tBu(2)Ga)]-cyclo-(tBu(2)Ga)-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)CH2H2N(Me)O](2) (6) with a central Ga2O2N2 ring resulting from two Ga-N donor-acceptor bonds.