No abstract

2,

Deprotonation of the 2-amino- 1,3-dimethylimidazolium salt 5 (obtained through methylation of 2-amino-l-methylimidazole (4)) by KH gives 2-imino-1,3-dimethylimidazoline 6. The trimethylsilylimino compound 14 is formed on the reaction of 6 with chlorotrimethylsilane in the ratio 2:1. Further reaction with chlorotrimethylsilane gives the silylated aminoimidazolium salt 15. The X-ray structures of 5 and 6 are reported.

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 imidazolium-2-amidinate 6 is obtained from the reaction of 2,3-dihydro-1,3-diisopropyl- 4,5-dimethylimidazol-2-ylidene (4) with diisopropylcarbodiimide (5) as stable solid. Overcrowding causes a lowered symmetry of the amidinate fragment indicated both by structural and NMR data. The strongly basic properties of 6 allow facile protonation with HCl to the cationic amidine derivatives 7 and 8. The ketoamidine 10 is formed by a ring opening reaction of 6 with water. The X-ray structures of 6 and 10 are reported.