The binuclear trimethyl/triethylantimony(V) bis-catecholate derivatives of four-electron reduced 4,4′-di-(3-methyl-6-tert-butyl-o-benzoquinone)

The reaction of 4,4`-di-(3-methyl-6-tert-butyl-o-benzoquinone) (Q-Q) with trimethyl- or triethylstibine proceeds as a two-electron oxidative addition of each quinone moiety and allows to prepare binuclear bis-catecholates R(3)Sb(Cat-Cat)SbR(3) with a nearly quantitative yield (R = Me, 1; R = Et, 2). The products 1 and 2 were characterized by IR-, (1)H and (13)C NMR spectroscopy. Molecular structure of triethylantimony (V) bis-catecholate 2 was confirmed by single-crystal X-ray analysis. Each Sb(V) atom adopts square pyramidal geometry with Cat moiety in basal positions, dihedral angle between Cat fragments is 74.27 (5)degrees. The oxidation of bis-catecholates by ferrocenium tetrafluoroborate or tetrabromo-p-benzoquinone leads to loss of one trialkylantimony(V) moiety forming paramagnetic salts containing one-side decoordinated mononuclear semiquinone-catecholato [R(3)Sb(Cat-SQ)](-) anion detected by EPR. The oxidation of 1 by air oxygen allows to prepare mononuclear quinone-catecholate Me(3)Sb(Cat-Q) (3). (c) 2010 Elsevier B.V. All rights reserved.