The ylidic properties of 1,3,4,5-tetramethyl-2-methyleneimidazoline 4, obtained by deprotonation of the pentamethylimidazolium ion 3, are revealed both by its physical and chemical properties; the X-ray structure of 4 is reported.

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.

The carbene adducts 3 are obtained as stable solids from the im idazol-2-ylidenes 1 and CS2. 3 c reacts with bromine to give the cationic bromosulfane 4, whereas iodine forms the charge-transfer adduct 5. Oxidative coupling to the dicationic disulfane 6 is observed with excess of iodine. The X-ray structure analyses of 3b, 4, 5 and 6 are reported.

-(CBH14NZ)M(C0)5 (M = Mo, W) -Terminal Coordination of an Olefin in PentacarbonylMetal Complexes* The 2-methylenimidazoline complexes (C8H14N2)M(C0)5 veal the strong donor character of the ylidic ligand in 6. The (M = Mo, W; 6) are obtained from M(C0)6 and 1,3,4,5-tetra-end-on coordination mode of the olefin is demonstrated by methyl-2-methyleneimidazoline (5). Spectroscopic data re-an X-ray structure analysis of 6a.Olefine sind an Ubergangsmetall-Zentren im Regelfall uber beide olefinischen Kohlenstoff-Atome koordiniert (1; ,,side-on") [ Ein Vergleich der I3C-NMR-Daten von 6 mit denen des nichtkoordinierten Liganden 5 [6 = 153.65 (C-2), 40.22 (CH2)][9] zeigt fur das Methylen-Kohlenstoff-Atom rnit 6 = -6.74 (6a) bzw. -2.87 (6b) die erwartete Hochfeldverschiebung sowie fur C-2 (6a: 6 = 163.77; 6b: 6 = 163.42) eine deutliche Koordinationsentschirmung. Im 'H-NMR-Spektrum zeigt sich ein drastischer Koordinationseffekt beziiglich der chemischen Verschiebung der MethylenChem.