Metal−Metal Interactions in Heterobimetallic d8−d10Complexes. 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(PH(3))(2)(CN)(2)-Au(PH(3))(2)(+) dimer. The interaction energy of Pt(II)-Au(I) was calculated to be ca. 0.45 ev.