Phase transition in metal–organic complex trans-PtCl2(PEt3)2 under pressure: insights into the molecular and crystal structure

Abstract

Structural studies on Pt(II) complexes which have direct correlation with their stereochemistry and microscopic interactions are of immense technological, catalytic and pharmacological importance. Here, we present high-pressure studies on trans-PtCl₂(PEt₃)₂ (Et = C₂H₅) using infrared (IR) and Raman spectroscopy combined with powder X-ray diffraction (XRD) studies. The ambient structure was solved using single-crystal XRD studies and was further optimized using density functional theory (DFT) simulations. It has been shown that subtle molecular reorientations result in structural phase transition at pressures as low as ∼0.8 GPa. The emergence of Raman active modes in the IR spectra and vice versa indicates the loss of inversion symmetry across the phase transition. The crystal structure of the high-pressure phase has been found to be non-centrosymmetric using XRD studies, which suggest a change in space group from P2₁/n to P2₁ across 0.8 GPa. The spectroscopy results also indicate strengthening of inter- and intramolecular C–H⋯Cl hydrogen bonds resulting in a hydrogen bonded supramolecular network. On further compression up to 4.7 GPa, another phase transformation has been detected. The structure was completely retrieved on release of pressure. Thus, the present findings provide sound evidence of intramolecular rearrangements playing a decisive role in tuning bonding and structural characteristics and hence the physicochemical properties of Pt(II) complexes under varying environments.