Synthesis, spectroscopy, electrochemistry, and coordination chemistry of substituted phosphine sulfides and selenides

Abstract

Phosphines and phosphine chalcogenides are important ligands for various metal systems, especially catalysts. Based on previously synthesized phosphine oxide ligands, we describe here the synthesis and characterization of a series of compounds having the general formula, EPPh2Ar, E=S, Se; Ar=1-naphthyl, 9-phenanthryl, 9-anthracenyl, 1-pyrenyl. Reaction of EPPh2(9-phenanthryl), E=S, Se, with HAuCl4 yields ArPh2PEAuCl. Similar to the phosphine oxide derivative, the anthracenyl compounds, EPPh2(9-anthracenyl), showed a nonplanar conformation within the anthracene ring as observed using X-ray crystallography. The difference in fluorescence spectrum relative to the parent aryl species is attributed to this deformation. The deviation is probably due to steric strain within the phosphine ligand due to its position on the anthracenyl ring since DFT calculations suggest that the 1-anthracenyl ligand should be planar. Each compound has been characterized using 1H, 13C, 31P, and (where applicable) 77Se NMR, and IR spectroscopy, with structure determination by X-ray crystallography. Finally, the electrochemistry of the unoxidized phosphines is reported, showing one-electron reductions in the polycyclic aromatic hydrocarbons.