The vibrational spectra of several platinum-ethylene complexes: K[PtCl3(C2H4)]·H2O (Zeise's salt), K[PtCl3(C2D4)] · H2O and [PtCl2(C2H4)]2

A Combined Gas‐Phase Photoelectron Spectroscopic and Theoretical Study of Zeise’s Anion and Its Bromine and Iodine Analogues

“…[6] The C À C stretching frequency is also red-shifted. [7][8][9] These findings can be qualitatively explained by the DCD bonding model, [3,4] and have been essentially confirmed by earlier molecular orbital calculations [13,14] and related theoretical studies. [15][16][17][18][19][20] Besides being a historically key species in the field of organometallic chemistry in defining new chemical concepts (such as hapticity) and modes of chemical bonding, Zeises salt and its dimer have also been found to be effective in many important catalytic processes, [21][22][23] as well as being used as versatile chiral derivatizing agents in asymmetric synthesis.…”

“…However, no similar structure was observed for the Br and I analogues. According to the reported vibrational frequencies obtained from the solid-state and solution-phase studies, [7] both the PtÀC 2 and the PtÀCl symmetric stretching of the anion have frequencies in that range. The observation that only the spectrum of the Cl analogue exhibits this vibrational fine structure suggests that the observed vibrational excitation is due to the symmetric PtÀCl stretching in the neutral potential energy surface and, in turn, implies that the highest occupied molecular orbital (HOMO) of [PtCl 3 (C 2 H 4 )] À mainly consists of the PtCl 3 Calc.…”

“…This structural arrangement was confirmed by X-ray and neutron diffraction studies in the 1970s, [5,6] 150 years after the original discovery of the platinum-ethylene complex. Many experimental studies have been conducted to probe the structure and bonding of Zeises salt, including X-ray and neutron diffraction, [5,6] vibrational spectroscopy, [4,[7][8][9] and ultraviolet solution absorption spectroscopy. [10][11][12] The ethylene ligand symmetrically interacts with the Pt atom, with the C À C axis being perpendicular to the PtCl 3 plane.…”

Effect of high external pressures on the vibrational spectra of Zeise’s complexes, K[Pt(η2-C2H4)Cl3] and [Pt(η2-C2H4)Cl2]2

“…An intense, polarized peak at 1243 cm À1 in the solution Raman spectrum of ZeiseÕs salt was assigned by Hiraishi [7] to the m(C@C) mode coupled to the CH 2 scissoring mode. In the solid, under pressure, the Raman intensity of this peak decreased dramatically at around 16 kbar and was overlapped by the diamond band at 1353 cm À1 .…”

“…Moreover, despite extensive vibrational studies of ZeiseÕs salt [3,[7][8][9][10][11][12][13][14][15][16], there is still considerable disagreement over the correct assignment of the C@C stretching mode. There is a related platinum-ethylene complex, known as ZeiseÕs dimer [Pt(g 2 -C 2 H 4 )Cl 2 ] 2 , which is chlorine-bridged; however, this complex has been less well characterized structurally and spectroscopically [7,9]. The application of high external pressures to ZeiseÕs salt and the related dimer should lead to reductions in the Pt-C 2 H 4 distances in the complexes, thereby increasing the p-backbonding and further weakening the C@C bonds and affording lower m(C@C) frequencies.…”