Pressure-tuning infrared spectroscopic study of trans-di-N-thiocyanato-bis(tribenzylphosphine)nickel(II), trans-Ni[(PhCH2)3P]2(NCS)2

Infrared spectra of trans-di-N-thiocyanato-bis(tribenzylphosphine)nickel(II), trans-Ni[(PhCH2)3P]2(NCS)2, have been recorded at high external pressures up to ∼50 kbar using a commercial diamond-anvil cell. Two pressure-induced phase transitions were detected at ∼16 and ∼32 kbar. The number of IR bands neither increases nor decreases with increasing pressure and the changes in the pressure sensitivities (dν/dP) of the bands are not particularly abrupt during the phase transition suggesting that the two phase transitions are most probably second-order. The results of two pressure-induced phase transitions and the behavior of the CN stretching modes at ambient pressure suggest that there may be two different forms of the Ni(II) complexes in the solid state, as is the case for several other Ni(II) complexes.