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.