Pseudo-oxocarbons complexes - complexation of 2,4-bis(dicyanomethylene)-cyclobutane-1,3-dione dianion with copper. X-ray identification and electrochemical properties of the dianion and copper(I) and (II) complexes

The compound (Ph4P)(2)(trans-cdcb). 2H(2)O (trans-cdcb(2-) = 2,4-bis(dicyan omethylene)-cyclobutane-1,3-dione dianion) has been synthesized and charact erized by X-ray crystallography. Crystal data: triclinic, space group <P(1) over bar>, a = 10.829(2) Angstrom, b = 11.297(2) Angstrom, c = 11.515(2) An gstrom, alpha = 79.61(1)c, beta = 68.54(1)c, gamma = 63.49(1)c, V = 1172.9( 4) Angstrom(3), Z = 1, R = 0.036, Rw = 0.047. With the dianion as a ligand, two complexes have been obtained and characterized by X-ray crystallograph y, UV-visible spectroscopy, and electrochemistry. The copper(II) complex [C u(trans-cdcb)(H2O)(4). 2H(2)O](n) consists of polymeric chains with copper atoms bonded to two of the nitrile groups of the ligand. Crystal data: mono clinic, space group P2(1)/c, a = 9.6366(6) Angstrom, b = 7.1292(3) Angstrom , c = 10.7018(6) Angstrom, beta = 99.603(4)c, V = 724.92(7) Angstrom(3), Z = 2, R = 0.026, Rw = 0.041. The copper(I) complex[Cu-2(trans-cdcb)(CH3CN)(4 ). 2CH(3)CN](n) consists of polymeric chains with copper atoms bonded by al l the four nitrile groups of the ligand. Crystal data: monoclinic, space gr oup P2(1)/n, a = 10.654(2) Angstrom, b = 8.736(1) Angstrom, c = 14.654(3) A ngstrom, beta = 109.01(2)c, V = 1291.3(9) Angstrom(3), Z = 2, R = 0.037, Rw = 0.041. In CH3CN solution, the copper complexes are dissociated. Moreover , copper(II) is reduced into copper(I) by the dianion. Electrochemistry in the solid state (polymer coated electrode) showed the redox transitions of the different compounds.