Metal-metal interactions in heterobimetallic d8-d10 complexes.: Structures and spectroscopic investigation of [M′M(μ-dcpm)2(CN)2]+ (M′ = Pt, Pd;: M = Cu, Ag, Au) and related complexes by UV-vis absorption and resonance Raman spectroscopy and ab initio calculations

X-ray structural and spectroscopic properties of a series of heterodinuclear d(8)-d(10) metal complexes [M'M(mu-dcpM)(2)(CN)(2)](+) containing d(8) Pt(II), Pd(II), or Ni(II) and d(10) Au(I), Ag(I), or Cu(I) ions with a dcpm bridging ligand have been studied (dcpm = bis(dicyclohexylphosphino)methane; M' = Pt, M = Au 4, Ag 5, Cu, 6; M = Au, M' = Pd 7, Ni 8). X-ray crystal analyses showed that the metal(...)metal distances in these heteronuclear metal complexes are shorter than the sum of van der Waals radii of the M' and M atoms. The UV-vis absorption spectra of 4-6 display red-shifted intense absorption bands from the absorption spectra of the mononuclear trans-[Pt(phosphine)(2)(CN)(2)] and [M(phosphine)(2)] counterparts, attributable to metal-metal interactions. The resonance Raman spectra confirmed assignments of (1)[nd(sigma)*-->(n + 1)p(sigma)] electronic transitions to the absorption bands at 317 and 331 nm in 4 and 6, respectively. The results of theoretical calculations at the MP2 level reveal an attractive interaction energy curve for the skewed [trans- Pt(PH3)(2)(CN)(2)-Au(PH3)(2)(+)] dimer. The interaction energy of Pt(II)-Au(I) was calculated to be ca. 0.45 ev.