The pressure tunning Raman and IR spectral studies on the multinuclear metal carbyne complexes

The Raman and infrared (IR) spectra of four tungsten metal carbyne complexes I, II, IV and V [Cl(CO)(2)(L)WdropCC(6)H(4)drop (CdropCC(6)H(4))ndropNdropCdrop](2)M (L = TMEDA, n = 0, M = PdI2 or ReCl(CO)(3); L = DPPE, n = 1, M = PdI2 or ReCl(CO)(3)) were studied at high external pressure. Their pressure-induced phase transitions were observed near 20 kbar (complexes I), 15 kbar (complexes II), 25 kbar (complex IV) and 30 kbar (complex V). The pressure-induced phase transition likely is first order in complex I and the pressure-induced phase transitions of complexes II, IV and V are mostly second order. The pressure sensitivities dnu/dp of nu(WdropC) are high in the low-pressure phase area and very low in the high-pressure phase area due to the pressure strengthening pi back-bonding from metal W to pi* orbital of CdropO in fragment Cl(CO)(2)(L)WdropC. The pressure strengthening metal pi back-bonding from metal Re or Pd to pi* orbital of CdropO or CdropN also happened to both of central metal centers of NCPd(I-2)CN in complex I and NCReCl(CO)(3)CN in complex II. (C) 2004 Elsevier B.V. All rights reserved.SpectroscopySCI(E)EIPubMed5ARTICLE5995-10006