Gold(I) complexation with trialkyl/triaryl phosphine selenide ligands

A number of phosphine selenide ligands and their gold(I) complexes of general formula R₃P=Se-Au-X (where X is Cl^-, Br^- and CN^- and R = phenyl, cyclohexyl and tolyl) were prepared. The complexes were characterized by elemental analysis, IR and ³¹NMR spectroscopic methods. In the IR spectra of all complexes a decrease in frequency of P=Se bond upon coordination was observed, indicating a decrease in P=Se bond order. ³¹NMR showed that the electronegativity of the substituents is the most important factor determining the ³¹P NMR chemical shift. It was observed that phosphorus resonance is more downfield in alkyl substituted phosphine selenides, as compared to the aryl substituted ones. Ligand disproportionation in the complex Cy₃P=SeAuCN in solution to form [Au(CN)₂]^- and [(Cy₃P=Se)₂Au]⁺ was investigated by ¹³C and ¹⁵N NMR spectroscopy.