An acetate-bridged dicopper(II) complex of a binucleating Schiff-base chelate

#-Acetato-( O,O')-#-( 5,11-diethyl-6,10-diaza3,5,10,12-pentadecatetraene-3,8,13-triolato-O,N,#-O', N',O")-dicopper(II), [Cu2(C2H302)(C17H27N203)], M r = 493.54, monoclinic, C2/c, a = 16.034 (5), b = 17.481 (3), c = 9 . 2 0 5 (4)A, f l= 123.76 (3) ° , V= 2144.9/~3, Z = 4 , D x = l . 5 2 9 g c m -3, 2 ( M o K a ) = 0.71069 A, # = 19.4 cm -~, F(000) = 1024, T = 297 K, R = 0.031 for 1521 independent observed reflections. The molecule crystallizes as discrete neutral binuclear Cu" units, with crystallographically imposed twofold symmetry. The Cu atoms are bridged endogenously by the alkoxide O of the pentafunctional chelate ligand and exogenously by an acetato ligand. The coordination sphere is four-coordinate, planar with an NO 3 donor set. Introduction. Binuclear transition-metal centers in biological systems displaying unusual physical properties have been at the center of attention of many chemists and biologists for the last decade. Investigations into the native molecules and model systems have led to a variety of interesting results on both the biological and fundamental physical levels. An example of the latter can be found in the discussions of the structures of two isomeric forms of an asymmetrically bridged dicopper(II) complex, [Cu 2(Me2H2Me2htn)(OAc)] (Nishida, Takeuchi, Takahashi & Kida, 1983; Fallon, Murray, Mazurek & O'Connor, 1985)ff These complexes differ primarily in their degree of hydration and magnetic properties, although no direct interrelationship has been established. Here we wish to report the structure of a structurally similar molecule, [Cu2(Et2H2Et2malhtn)(OAc)]. * To whom correspondence should be addressed. f The notation used to describe the complexes is as follows: