RATIONAL SYNTHESIS OF DINUCLEAR MIXED-VALENCE CU(I) CU(II) CARBOXYLATE DERIVATIVES - STERIC INFLUENCE OF PHOSPHINE-LIGANDS ON THE STRUCTURES OF THE COMPLEXES/

The mixed-valence Cu(I)/Cu(II) complexes (Ph3P)4CuI2CuII(O2CCH2CO2)2 ( 1) and (Cy3P)4CuI2CuII(O2CCH2-CO2)2 (2), have been prepared from the a cid-base reaction of Cu(II)(acac)2 or Cu(II)(butyrate)2 with the respe ctive copper(I) hydrogen dicarboxylate derivative and their solid-stat e structures determined crystallographically. The Cu(II) center in bot h derivatives is chelated by two malonate dianions in a square-planar geometry. In complex 1 the two bis(triphenylphosphine)copper(I) moieti es are coordinated to the internal oxygen atoms of the Cu(II) malonate core at an average distance of 2.177 [4] angstrom, resulting in a Cu( I)...Cu(II) separation of 3.132(1) angstrom. On the other hand in comp lex 2 the two bis(tricyclohexylphosphine)copper(I) groups are appended asymmetrically to opposite ketonic oxygens of the malonate ligands, h ence affording a larger Cu(I)...Cu(II) separation of 4.600(1) angstrom . That is, the Cu(I) center in complex 1 is four-coordinate and a dist orted tetrahedron, whereas in complex 2 the Cu(I) center is three-coor dinate and trigonal planar. These structural differences, which persis t in dichloromethane solution, are ascribed to the steric requirements of the phosphine ligands. Crystal data for 1: space group P2(1)/n, a = 9.978(2) angstrom, b = 23.365(5) angstrom, c= 16.703(10) angstrom, b eta = 103.840(0)degrees, Z = 2, R = 6.04%. Crystal data for 2: space g roup P1BAR, a = 9.7280(10) angstrom, b = 15.084(2) A, c = 17.198(2) an gstrom, alpha = 103.910(10)degrees, beta = 98.680(10)degrees, gamma = 102.890(10)degrees, Z = 1, R = 5.89%.