THE REACTIONS OF CU2(O2CME)4(H2O)2 WITH 2,2'-BIPYRIDINE (BPY) - INFLUENCE OF THE CU-BPY RATIO, AND THE STRUCTURE OF A LINEAR POLYMER COMPRISING 2 ALTERNATING TYPES OF CU2 UNITS

Further investigation of the Cu2(O2CMe)4(H2O)2/bpy reaction system is described, including the determination of the influence of the Cu(II): bpy ratio (x) on the identity of the reaction products. Values of x in the 1-2 range have been employed. Reaction of Cu2(O2CMe)4(H2O)2 with two equivalents of bpy (x = 1) in MeCN yields [Cu2(O2CMe)4(bpy)2]. 2H2O (1) in 79% yield. Treatment of Cu2(O2CMe)4(H2O)2 with 1.33 equivalent of bpy (x = 1.5) in MeCN leads to precipitation of the polymeric compound [-Cu2(O2CMe)2(bpy)2-O2CMe-Cu2(O2CMe)4-O2CMe-]n (2); from the filtrate 1 slowly crystallizes in 15% yield. A high yield (89%) of pure 2 can be obtained by increasing x from 1.5 to 2. Treatment of 1 with Cu2(O2CMe)4(H2O)2 in MeCN provides an additional route to 2. Compound 2 reacts with equimolar bpy in EtOH to yield complex 1. Complex 1 undergoes facile carboxylate substitution in MeCN with an excess of PhCOOH, leading to reasonable yields (40 65%) of [Cu2(O2CPh)4(bpy)2].MeCN (3a) or [Cu2(O2 CPh)4(bpy)2].2H2O (3b), depending on the rate of crystallization. Complex 2 is converted to the known compound Cu2(O2CPh)4(EtOH)2 (4) or 3b by treatment with excess PhCOOH in EtOH or MeCN, respectively. Complexes 1 and 2 undergo a variety of additional reactions that lead to the dinuclear complexes [Cu2(O2CMe)3(bpy)2](ClO4) (5), [Cu2(OH)(H2O)(O2CMe)(bpy)2](ClO4)2 (6), Cu2(OH)2(bpy)2(ClO4)2 (7), [Cu2(O2CMe)2 (H2O)2(bpy)2](ClO4)2.H2O (8) and Cu2(O2CMe)2(ClO4)2(bpy)2 (9). Complex 1 crystallizes in the triclinic space group P1BAR with (at -143-degrees-C) a = 8.842(2). b = 12.266(2), c = 7.708(1) angstrom, alpha = 98.72(1), beta = 106.35, gamma = 109.68(1)-degrees, Z = 1 and V = 726.68 angstrom3. A total of 2318 unique reflections with F > 3.00-sigma(F) were refined to values of R and R(w) of 2.67 and 2.87%, respectively. Compound 2 crystallizes in the triclinic space group P1BAR with (at - 155-degrees-C) a = 9.272(2), b = 14.718(3), c = 8.023(1) angstrom, alpha = 102.66(1), beta = 103.89(1), gamma = 94.00(1)-degrees, Z = 1 and V = 1028.21 angstrom3. A total of 2319 unique reflections with F > 3.00-sigma(F) were refined to values of R and R(w) of 3.68 and 3.96%. respectively. The structure of 1 consists of a [Cu2(O2CMe)4(bpy)2] molecule located at a centre of symmetry with two syn,anti acetate bridges. The molecules of 1 form infinite ladder-like chains as a result of hydrogen-bonding interactions with the water molecules. The structure of 2 is composed of one-dimensional, well-separated polymeric chains and contains two different types of copper((II) dinuclear units, each at a crystallographic centre ot' symmetry. The chains are formed by alternating Cu2(O2CMe)4 and [Cu2(O2CMe)2(bpy)2]2+ units which are linked by syn,anti bridging acetates. The Cu2(O2CMe)4 unit has a tetra-bridged structure with four syn,syn bridging acetates and two oxygens from the two syn,anti acetates occupying the axial positions. The other dinuclear unit has a structure with two acetate groups forming mono-atomic bridges. From the IR and UV-vis solution spectra, it is concluded that the polymeric structure of 2 is not retained in MeCN. A cyclic voltammetric study of 1 in MeCN reveals a quasi-reversible reduction at -0.82 V vs ferrocene, and an irreversible reduction at -1.82 V yielding copper metal which deposits on the electrode. Complex 3b displays almost identical processes. Compound 2 displays two reduction processes at -0.84 and -1.82 V.