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

Abstract

The compound (Ph4P)2(trans-cdcb)·2H2O (trans-cdcb2- = 2,4-bis(dicyanomethylene)-cyclobutane-1,3-dione dianion) has been synthesized and characterized by X-ray crystallography. Crystal data: triclinic, space group P1, a = 10.829(2) Å, b = 11.297(2) Å, c = 11.515(2) Å, α = 79.61(1)°, β = 68.54(1)°, γ = 63.49(1)°, V = 1172.9(4) Å3, Z = 1, R = 0.036, Rw = 0.047. With the dianion as a ligand, two complexes have been obtained and characterized by X-ray crystallography, UV-visible spectroscopy, and electrochemistry. The copper(II) complex [Cu(trans-cdcb)(H2O)4·2H2O]n consists of polymeric chains with copper atoms bonded to two of the nitrile groups of the ligand. Crystal data: monoclinic, space group P21/c, a = 9.6366(6) Å, b = 7.1292(3) Å, c = 10.7018(6) Å, β = 99.603(4)°, V = 724.92(7) Å3, Z = 2, R = 0.026, Rw = 0.041. The copper(I) complex[Cu2(trans-cdcb)(CH3CN)4·2CH3CN]n consists of polymeric chains with copper atoms bonded by all the four nitrile groups of the ligand. Crystal data: monoclinic, space group P21/n, a = 10.654(2) Å, b = 8.736(1) Å, c = 14.654(3) Å, β = 109.01(2)°, V = 1291.3(9) Å3, 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.Key words: pseudo-oxocarbons, X-ray diffraction, copper(II) complex, copper(I) complex, electrochemical behaviour.