LIGAND-FIELDS IN PLANAR PLATINUM(II) COMPLEXES

The 'd-d' transition energies in seven platinum(II) chromophores have been carefully analysed within the cellular ligand-fie[d model. Earlier analyses are shown to be incorrect. The study distinguishes [PtCl3(NH3)](-) and [PtCl3(NMe(3)](-) systems from [PtCl3(PEt(3)](-), [PtCl3(PPh(3))](-) and [PtCl3(AsPh(3))](-) complexes, and from cis- [PtCl3(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 sigma bases than is chloride. The halides act as pi bases while the phosphines and arsine act as pi acids. The trans influence of amine, phosphine and arsine is evident in the spectra of 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.