The reaction of 1,3-diisopropyl-4,5-dimethylimidazol-2-yli-give the Im . S(Me)OC12 cation (15). Surprisingly, reduction dene (4, Im) with sulfur halides and sulfur oxygen halides of the sulfur centre (2) occurs on treatment of 4 with SF4 to may be described as a coordination (1) or reduction (2) pro-form the ImF+SF, salt 18 containing the new SF3 anion. As cess in respect to the sulfur centre. With SC12 and SOClz the expected, the same type of reaction occurs with the sulfuryl hypervalent sulfur compounds Im . SClz (5) and Im . S(0)Cl2 halides S0,ClF and S02F, to give the fluorosulfites ImCl+- Chern.

2,3‐Dihydro‐1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐yliden (7, Carb) reagiert mit Chlordiphenylphosphan zum kationischen Phosphan [Ph2(Carb)P]Cl (10), das mit AlCl3 in das stabilere Salz [Ph2(Carb)P]AlCl4 (13) überführt wird. Das kationische Phosphanselenid [Ph2(Carb)PSe]AlCl4 (14) wird aus 13 und Selen erhalten. Spektroskopische und strukturelle Daten weisen [Ph2(Carb)P]+ als kationisches Analogon von Ph3P aus. Die Kristallstruktur von 13 wird berichtet.

The carbene adducts 3a-c (R 1 = Me, Et, iso-Pr; R2 = Me) are formed from the 2,3-dihydroimidazol-2-ylidenes la-c and 1,2-dichloroethane as air-sensitive solids in good yields. The compounds exhibit a reactive Cl-Cl bond. Benzene is chlorinated by 3a,b to give chlorobenzene and the imidazolium salts 10a,b under mild conditions. 3c acts as a chloride donor to give with AICI3 and S 0 2 the 2-chloroimidazolium salts 12c andl3c (X = A1C14, S 0 2C1). On hydrolysis, the less reactive hydrate salt 14c is formed from 3c. The X-ray structures of 10a and 14c are reported.

The 2,3-dihydro-l,3,4,5-tetraalkylimidazol-2-ylidenes 3 (R = Me, i'so-Pr) react immediately with pentafluoropyridine to form the 2-tetrafluoropyridylimidazolium salts 4 in good yields. In contrast with the tetramethyl derivative 4a, alkyl fluoride is eliminated from the isopropyl salt 4b to give 1 -isopropyl-4,5-dimethyl-2-tetrafluoropyridylimidazole, which dimerises via hydrogen bridges in the solid state (7). The X-ray structures of l,3-diisopropyl-4,5-dimethyl-2-tetrafluoropyridylimidazolium chloride (5) and 7 are reported.

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