A PH-functionalized dicationic bis(imidazolio)diphosphine.

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 GaI 3 afforded the isolable salt of a dicationic, bis(imidazolio)-substituted dihydro-diphosphine [(L) 2 P 2 H 2 ][GaI 4 ] 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 GaI 3 . Further reaction of [(L) 2 P 2 H 2 ] 2+ with (L)PH produced an iodide salt of a known (bis)imidazolio-diphosphide monocation [(L) 2 P 2 H] + . The identity of cationic diphosphines and diphosphides was established by single-crystal X-ray diffraction studies. NMR spectroscopy revealed that dications [(L) 2 P 2 H 2 ] 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.