Vanadate complexes bearing an imidazolidine-bridged bis(aryloxido) ligand: synthesis and solid state and solution structure

A new imidazolidine-bridged bis(aryloxido) ligand precursor (H2L) [H2L = 2,2'-(imidazolidine-1,3-diylbis(methylene)) bis(4-(1,1,3,3-tetramethylbutyl-2-yl)phenol)] was prepared in a relatively high yield (similar to 60%) via a single-step Mannich condensation of 4-(1,1,3,3-tetramethylbutyl)phenol, ethylenediamine and paraformaldehyde at 2 : 1 : 3 molar ratio and characterized by chemical and physical techniques including X-ray crystallography. Reactions of H2L with [VO(OEt)(3)] at 1 : 1 and 1 : 2 molar ratios in toluene afforded [V(L-kappa O-3,N,N,O)(O)(OEt)] (1) and [V-2(mu-L-kappa O-4,N,N,O)(mu-OEt)(2)(O)(2)(OEt)(2)] (2), respectively. Alcoholysis of 1 with EtOH enables elimination of one molecule of H2L and the formation of 2. Compounds 1 and 2 were characterized by IR and NMR spectroscopy as well as ES-MS experiments. The definitive molecular structure of 2 was provided by a single-crystal analysis and revealed its dinuclear nature, featuring two octahedral vanadium centres bridged by both OEt groups and the L ligand. The V-51, H-1 and C-13 NMR spectra as well as ES-MS showed that 2 does not stay intact in solution and undergoes dissociation to give 1 and [VO(OEt)(3)].