Group 13 metal complexes containing the bis-(4-methylbenzoxazol-2-yl)-methanide ligand

Abstract

To focus on the high importance of low-valent main group metal complexes, which can be applied to catalytic transformations, this article deals with the promising new ligand system (4-MeNCOC6H3)2CH2 (1). It is patterned on the well known nacnac ligand and further development of the parent bisheterocyclo methanes. In comparison with the results of previous studies based on the bisheterocyclo methanes (NCOC6H4)2CH2 and (NCOC6H4)2CH2 derivative 1 was modified by adding a methyl group to the annulated benzene perimeters to enhance the steric protection of a potentially coordinated main group metal cation. On reaction of 1 with group 13 trimethyl reagents and dialkyl aluminium halides the ligand backbone gets deprotonated and the two endocyclic nitrogen donor atoms coordinate with the remaining organometallic fragment to form a six-membered metalla heterocycle. The synthesis of [Me2Al{(4-MeNCOC6H3)2CH}] (2), [Me2Ga{(4-MeNCOC6H3)2CH}] (3), [Me2In{(4-MeNCOC6H3)2CH}] (4), [ClMeAl{(4-MeNCOC6H3)2CH}] (5), [IMeAl{(4-MeNCOC6H3)2CH}] (6) and [IEtAl{(4-MeNCOC6H3)2CH}] (7) could be accomplished. A structural comparison of those metallated species based on single crystal X-ray analyses identifies them as ideal precursors generating new low-valent main group complexes.