Phosphorus-containing multiple-bond systems have received great interest in various applications but often require elaborate syntheses and special precursors. In this paper, we describe simple methods for the synthesis of imidazoyl phosphinidenes and bis(imidazolyl)-P(I) halides from elemental phosphorus or the heptaphosphides Na 3 P 7 and (Me 3 Si) 3 P 7 . The reactions of imidazolium salts with KOtBu and P 4 afford mixtures of imidazoyl phosphinidenes and P n compounds and, for N-methylated imidazolium salts, also bis(imidazolyl)-P(I) hal- [a] Scheme 8. Transient intermediates E/Z-10 (R = mesityl) and 11 [40] observed during the reactions of imidazolium salt and /KOtBu with P 4 .

Cationic imidazolio-phosphines show two-sided reactivity towards bases, undergoing either Brønsted-type proton transfer to imidazolio-phosphides or autocatalytic Lewis acid/base reaction cascades to yield P-free imidazolium ions and oligophosphines.

Reactions of PH-substituted phosphinidene-imidazolylidenes with I afford isolable NHC-adducts of the transient diiodophosphine PHI. The products, which show a surprising structural diversity, are according to DFT studies best formulated as charge-transfer complexes of onio-substituted cationic phosphines with I and are capable of reaction under formal transfer of an NHC-P unit.

Reaction of methylene‐ and ethylene‐bridged bis‐imidazolium salts with white phosphorus in the presence of KOtBu furnished moderate yields of tricyclic bis‐imidazolio‐phosphanide halides. Further oxidation of the products with one equivalent of I2 gave bis‐imidazolio‐diiodophosphoranide iodides. All newly prepared compounds were characterized by analytical and spectroscopic data and single‐crystal XRD studies. DFT calculations provide evidence for substantial stabilization of cyclic bis‐imidazolio‐phosphanide cations by π‐conjugation effects and suggest describing the bis‐imidazolio‐diiodophosphoranide cations as charge‐transfer complexes of dicationic iodophosphines with iodide.

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(imdiazolio)-substituted...