A neutral analogue of a phosphamethine cyanine.

Reaction of an imidazolio-phosphide with an N-heterocyclic bromo-borane and NaH afforded a neutral analogue of a phosphamethine cyanine cation. DFT studies were used to analyse the dative bonding across P-C/B bonds and the conformational preferences and imply that the observed conformation is imposed by sterics.

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 afforded the isolable salt of a dicationic, bis(imidazolio)-substituted dihydro-diphosphine [(L)PH][GaI]. 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. Further reaction of [(L)PH] with (L)PH produced an iodide salt of a known (bis)imidazolio-diphosphide monocation [(L)PH].

Proton transfer vs. oligophosphine formation by P-C/P-H σ-bond metathesis: decoding the competing Brønsted and Lewis type reactivities of imidazolio-phosphines.

Studies of the protonation and alkylation of imidazolio-phosphides and deprotonation of imidazolio-phosphines reveal a complex behaviour that can be traced back to an interplay of Brønsted-type proton transfers and Lewis-type P-P bond formation reactions. As a consequence, the expected (de)protonation and (de)alkylation processes compete with reactions producing cyclic or linear oligophosphines. A careful adjustment of the conditions allows us to selectively address each reaction channel and devise specific synthesis methods for primary, secondary and tertiary imidazolio-phosphines, imidazolio-alkylphosphides, and cyclic oligophosphines, respectively.