Hydroxylation of a methyl group:: synthesis of [Cu2(btmmO)2I]+ and of [Cu2(btmmO)2]2+ containing the novel ligand {bis(trimethylmethoxy)guanidino} propane (btmmO) by copper-assisted oxygen activation

The reaction of the bisguanidine copper(I) compounds [Cu(btmgp)I] and [Cu-2(btmgp)(2)][PF6](2) with molecular oxygen afforded at low temperatures complexes containing the bis-mu-oxo dicopper(III) core, which is capable to hydroxylate one of the N-CH3-groups of the {bis(tetramethyl)guanidino} propane ligands. The formation of the novel ligand {bis(trimethylmethoxy)guanidino} propane (btmmO) is reported as it represents the first hydroxylation of a N-methyl group. The products of this reaction are novel alkoxo-bridged binuclear copper complexes, namely [Cu-2(btmmO)(2)I](+) containing an iodide ion in a novel bridging situation, as well as [Cu-2(btmmO)(2)](2+) which have been identified in their complex salts [Cu-2(btmmO)(2)I]I(.)1/2 C2H5OH and [Cu-2(btmmO)(2)][PF6](2)(.)2-MeCN, respectively. Concomitantly, the hydroxo-bridged binuclear copper compounds [Cu-2(btmgp)(2)(mu-OH)(2)]I-2 and [Cu-2(btmgp)(2)(mu-OH)(2)][PF6](2) are formed as couple products. The formation of the bis-mu-oxodicopper(III) complexes was monitored by UV/Vis-spectroscopy, and the reaction products were characterised by X-ray diffraction, vibrational spectroscopy and elemental analysis. (c) 2004 Elsevier B.V. All rights reserved.