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 GaI3 afforded the isolable salt of a dicationic, bis(imidazolio)-substituted dihydro-diphosphine [(L)(2)P2H2][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)(2)P2H2](2+) with (L)PH produced an iodide salt of a known (bis)imidazolio-diphosphide monocation [(L)(2)P2H](+). The identity of cationic diphosphines and diphosphides was established by single-crystal X-ray diffraction studies. NMR spectroscopy revealed that dications [(L)(2)P2H2](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.

Automated summary

The reaction between the iodide salt of a secondary imidazolio-iodophosphine and an imidazolio-phosphide in the presence of GaI3 results in the isolable salt of a dicationic, bis(imidazolio)-substituted dihydro-diphosphine. Further reactions and computational studies have provided insights into the structure, stereochemistry, and bonding situation of the diphosphine dications. NMR spectroscopy showed that the dications exist as a mixture of meso- and rac-diastereomers in solution.