In 2019,Chemistry – A European Journal included an article by Rottschaefer, Dennis; Sharma, Mahendra K.; Neumann, Beate; Stammler, Hans-Georg; Andrada, Diego M.; Ghadwal, Rajendra S.. Quality Control of 1,3-Bis(2,6-diisopropylphenyl)-4,5-dihydro-1H-imidazol-3-ium chloride. The article was titled 《A Modular Access to Divinyldiphosphenes with a Strikingly Small HOMO-LUMO Energy Gap》. The information in the text is summarized as follows:
The olefinic C-H bond functionalization of (NHC)CHPh (NHC = IPr =C{(NAr)CH}2 1; SIPr = C{(NAr)CH2}2 2; Ar = 2,6-iPr2C6H3), derived from classical N-heterocyclic carbenes (NHCs), with PCl3 affords the dichlorovinylphosphines {(NHC)C(Ph)}PCl2 (NHC = IPr 3, SIPr 4). Two-electron reduction of 3 and 4 with magnesium leads to the formation of the divinyldiphosphenes [{(NHC)C(Ph)}P]2 (NHC = IPr 5, SIPr 6) as crystalline solids. Unlike literature-known diphosphenes, which are mostly yellow or orange, 5 is a green whereas 6 is a purple solid. Although the P:P bond lengths of 5 (2.062(1)) and 6 (2.055(1) Å) are comparable to those of the known diphosphenes (2.02-2.08 Å), the C-P bond lengths of 5 (1.785(1)) and 6 (1.797(1) Å) are, however, considerably shorter than a Csp2-P single bond length (1.85 Å), indicating a considerable π-conjugation between C:C and P:P moieties. The HOMO-LUMO energy gap for 5 (4.15) and 6 (4.52 eV) is strikingly small and thus the narrowest among the diphosphenes (>4.93 eV) reported as yet. Consequently, 5 readily undergoes P:P bond cleavage at room temperature on treatment with sulfur to form the unique dithiophosphorane {(IPr)C(Ph)}P(S)2 7. Interestingly, reaction of 5 with selenium gives the selenadiphosphirane [{(IPr)C(Ph)}P]2Se 8 with an intact P-P bond. In the experimental materials used by the author, we found 1,3-Bis(2,6-diisopropylphenyl)-4,5-dihydro-1H-imidazol-3-ium chloride(cas: 258278-25-0Quality Control of 1,3-Bis(2,6-diisopropylphenyl)-4,5-dihydro-1H-imidazol-3-ium chloride)
1,3-Bis(2,6-diisopropylphenyl)-4,5-dihydro-1H-imidazol-3-ium chloride(cas: 258278-25-0) has been employed in an efficient, one-pot synthesis of N-heterocyclic carbene-allylpalladium complexes.Quality Control of 1,3-Bis(2,6-diisopropylphenyl)-4,5-dihydro-1H-imidazol-3-ium chlorideIn addition, it can efficiently catalyze the Suzuki-Miyaura coupling of aryl chlorides with aryl boronic acids.
Referemce:
Imidazole – Wikipedia,
Imidazole | C3H4N2 – PubChem