Rational Synthesis of Dinuclear Mixed-Valence Cu(I)/Cu(II)Carboxylate Derivatives. Steric Influence of Phosphine Ligands on the Structures of the Complexes
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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 acid-base reaction of CuII(acac)2 or CuII(butyrate)2 with the respective copper(I) hydrogen dicarboxylate derivative and their solid-state structures determined crystallographically. The Cu(II) center in both derivatives is chelated by two malonate dianions in a square-planar geometry. In complex 1 the two bis(triphenylphosphine)copper(I) moieties are coordinated to the internal oxygen atoms of the Cu(II) malonate core at an average distance of 2.177 Å, resulting in a Cu(I)…Cu(II) separation of 3.132(1) Å. On the other hand in complex 2 the two bis(tricyclohexylphosphine)copper(I) groups are appended asymmetrically to opposite ketonic oxygens of the malonate ligands, hence affording a larger Cu(I)—Cu(II) separation of 4.600(1) Å. That is, the Cu(I) center in complex 1 is four-coordinate and a distorted tetrahedron, whereas in complex 2 the Cu(I) center is three-coordinate and trigonal planar. These structural differences, which persist in dichloromethane solution, are ascribed to the steric requirements of the phosphine ligands. Crystal data for 1: space group P21/n, a = 9.978(2) A, b = 23.365(5) Å, c = 16.703(10) Å, β = 103.840(0)°, Z = 2, R = 6.04%. Crystal data for 2: space group P[formula omitted], a = 9.7280(10) Å, b = 15.084(2) Å, c = 17.198(2) Å, α = 103.910(10)°, β = 98.680(10)°, γ = 102.890(10)°, Z = 1, R = 5.89%. © 1994, American Chemical Society. All rights reserved.
author list (cited authors)
Darensbourg, D. J., Holtcamp, M. W., Khandelwal, B., Klausmeyer, K. K., & Reibenspies, J. H.