Synthesis and structure of organoaluminum O,C,O pincer compounds

Abstract

The set of four organoaluminum compounds containing O,C,O chelating ligands [2, 6 - (ROCH 2) 2C 6H 3]AlCl 2; (R = Me (1); R = Et (2); R = i-Pr (3); R = t-Bu (4)), so called pincer ligands, have been prepared by the metathetical reaction of corresponding organolithium compounds with AlCl 3·Et 3N adduct, in moderate yields. Prepared compounds have been characterized by elemental analysis, multinuclear ( 1H, 13C and 27Al) NMR spectroscopy and cryoscopy measurements. The monomeric structure of studied compounds 1-4, containing a five-coordinated central aluminum atom, was obtained in diluted solutions of non-polar solvents (benzene, toluene), while the concentration of the samples resulted in monomer - dimer equilibrium based on 1H, 27Al NMR spectroscopy and cryoscopy. The XRD study of 4 revealed a monomeric structure, contanining five-coordinated aluminum located in the centre of a trans-trigonal bipyramid.