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)Wtriple bond]CC6H4triple bond](Ctriple bond]CC6H4)ntriple bond]Ntriple bond]Ctriple bond]]2M (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 20kbar (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 d nu/dp of nu(Wtriple bond]C) 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 Ctriple bond]O in fragment Cl(CO)2(L)Wtriple bond]C. The pressure strengthening metal pi back-bonding from metal Re or Pd to pi* orbital of Ctriple bond]O or Ctriple bond]N also happened to both of central metal centers of NCPd(I2)CN in complex I and NCReCl(CO)3CN in complex II.