ELECTRONIC-SPECTRA AND BONDING OF THE PLANAR COMPLEXES [CU(H2O)2CL2].4(C6H5)3PO AND CU(4-METHYLPYRIDINE N-OXIDE)2CL2

The vibrational and single-crystal “d-d” electronic spectra of the compounds [CuCl2(H2O)2]·4(C6H5)3PO and Cu(4-methylpyridine N-oxide)2Cl2 are reported. The temperature dependence of the band intensities of the former complex are interpreted in terms of vibronic coupling, and the energies of the ungerade vibrations inducing intensity are consistent with those derived from the infrared spectrum. Vibrational fine structure observed in the electronic spectra at low temperature is apparently due to progressions in the two totally symmetric a, vibrations expected for each complex, and for the planar CuCl2(H2O)2 group present in the former compound an estimate of the changes in the Cu-Cl and Cu-O bond lengths accompanying the electronic excitations has been made. A weak band observed at high energy in the spectrum of [CuC12(H2O)2]·4(C6H5)3PO has been assigned to coupling of the 2Ag(z2) ← 2Ag(x2 - y2) transition with O-H stretching vibrations of the water ligands, though the precise mechanism by which the band gains intensity is uncertain. The transition energies of the complexes have been interpreted in terms of angular overlap metal-ligand bonding parameters, and these have been compared with those of other planar complexes. © 1990, American Chemical Society. All rights reserved.