Ligand fields in planar platinum(II) complexes

Abstract

The ‘d–d’ transition energies in seven platinum(II) chromophores have been carefully analysed within the cellular ligand-field model. Earlier analyses are shown to be incorrect. The study distinguishes [PtCl₃(NH₃)]^– and [PtCl₃(NMe₃)]^– systems from [PtCl₃(PEt₃)]^–, [PtCl₃(PPh₃)]^– and [PtCl₃(AsPh₃)]^– complexes, and from cis-[PtCl₂(NH₃)₂] and [PtCl₂(en)](en = ethane-1,2-diamine). Parameter values are unavoidably correlated in these high-symmetry species. The nitrogen, phosphorus and arsenic ligands are all stronger σ bases than is chloride. The halides act as π bases while the phosphines and arsine act as π acids. The trans influence of amine, phosphine and arsine is evident in the spectra of the these compounds. The continued applicability of the ligand-field method in these third-row d-block species is further attested by a successful reproduction and analysis of the intensity distribution in the spectra of [PtCl₃(NH₃)]^–; the intensity arises from both statically and vibronically sourced parity-mixing processes.