A PH-functionalized dicationic bis(imidazolio)diphosphine.

ABSTRACT

Reaction of the iodide salt of a secondary imidazolio-iodophosphine [(L)PHI]I (L+ = 1,3-diarylimidazolium-yl) with an imidazolio-phosphide (L)PH in the presence of GaI3 afforded the isolable salt of a dicationic, bis(imidazolio)-substituted dihydro-diphosphine [(L)2P2H2][GaI4]2. Non-preparative formation of the cationic diphosphines was also observed upon spontaneous "dehalo-coupling" of [(L)PHI]+, or in reactions of [(L)PHI]I and (L)PH in the absence of GaI3. Further reaction of [(L)2P2H2]2+ with (L)PH produced an iodide salt of a known (bis)imidazolio-diphosphide monocation [(L)2P2H]+. The identity of cationic diphosphines and diphosphides was established by single-crystal X-ray diffraction studies. NMR spectroscopy revealed that dications [(L)2P2H2]2+ exist as a mixture of meso- and rac-diastereomers in solution. Computational studies confirmed the stereochemical assignment of the isomers observed, and gave insight into the bonding situation of the diphosphine dications.