Effect of high external pressures on the vibrational spectra of crystalline dichloro(1,5-cycloctadiene)platinum(II), Pt(η4-C8H12)Cl2

The effects of high external pressures on the principal IR and Raman bands of crystalline dichloro(1,5-cycloctadiene)platinum(II), Pt(COD)Cl2 (COD = η4-C8H12), have been investigated for pressures up to ∼30 kbar by diamond-anvil cell microspectroscopy. This square-planar Pt(II) complex does not undergo any pressure-induced structural change throughout the pressure range investigated and the pressure dependences (dν/dP) for the vibrational modes range from −0.18 to 0.79 cm−1 kbar−1. The negative dν/dP value observed for the IR band at 1426 cm−1 (−0.18 cm−1 kbar−1) suggests that this band is chiefly associated with a Cdouble bond; length as m-dashC stretching mode of the Pt–COD group. This observation provides yet another indication that high-pressure vibrational spectroscopy may indeed be a general method for establishing the presence of π-backbonding in organometallic complexes, such as metal carbonyls and alkenes.