Pressure tuning IR and micro-raman spectra of solid zeiseߣs salt, kp[pt(η-C2H4)Cl4], and the related dimer, [Pt(η-C2H4)Cl2]2

Abstract

Pressure-tuning vibrational spectroscopy using diamond-anvil cells is now well established as a useful technique for investigating the phase-transition behavior of inorganic and organic solids. Much of our recent research has been focused on organotransition metal compounds, especially metal carbonyls. The pressure dependences (dv/dP) of the v(CO) modes provide important information on the extent of #- backbonding between the metals and the carbonyl groups. We have now extended these high-presure studies to other #-acceptor ligands, including olefins. We report here the results of a high-pressure IR and micro-Raman spectroscopic investigation of the ethylene complexes, K[Pt(η-C2H4)C13] (Zeise's salt) and the related dimeric species, [Pt(η-C2H4)C12]2- We were interested in examining the effect of high pressures on the Dewar-Chatt-Ducanson σ-/π-bonding description of the platinum-ethylene bonding. There is still considerable controversy over the relative σ- and π-contributions to the overall bonding in such metal-olefin complexes.Micro-Raman spectra of solid K[Pt(η-C2H4)C13] were obtained at room temperature for the low-energy region (500-180 cm-1) at varying pressures up to 33 kbar with the aid of a diamond-anvil cell. Similarly, pressure-tuning IR spectra were measured for Zeise's salt (3080-480 cm-1; 32 kbar) and Zeise's dimer (4000-480 cm-1; 28 kbar) up to the pressures indicated.