CYCLOADDITION REACTIONS OF ORGANOMETALLIC COMPOUNDS .15. SYNTHESIS AND STRUCTURE OF A NOVEL BICYCLIC COBALT DITHIOLENE - FORMATION OF A 5-MEMBERED COS2C2 RING FROM A COSCNC PRECURSOR AND ELEMENTAL SULFUR AS A SUBSTRATE

The cobalt isocyanide complex C5H5Co(PMe2Ph)(CNMe) (3), prepared from C5H5Co(PMe2Ph)2 (2) and CNMe by ligand exchange, reacts with methyl iodide to form the imidoylcobalt compound [C5H5Co(PMe2Ph)(CH3CNMe)]I (4), which on further treatment with CS2 in the presence of sodium methoxide gives the metallaheterocycle C5H5(PMe2Ph) activated CoC(= CH2)N(CH3)C(= S)S (5). The X-ray crystal structure of 5 has been determined: monoclinic, space group P2(1)/n (No. 14), a = 8.461 (1) angstrom, b = 13.885 (3) angstrom, c = 15.187 (1) angstrom, beta = 93.57 (1)-degrees, Z = 4. The reaction of 5 with S8 leads to the elimination of the phosphine ligand and affords the novel bicyclic cobalt dithiolene complex C5H5Co[eta(2)S2C2(SC(= S)NCH3)] (6) in 50% yield. The X-ray structure analysis of 6 (monoclinic, space group P2(1)/n (No. 14), with a = 13.757 (4) angstrom, b = 12.614 (2) angstrom, c = 14.555 (4) angstrom, beta = 112.69 (1)-degrees, and Z = 8) reveals an almost exactly planar bicyclic system in which partial electron delocalization is to be expected. From labeling studies with (CH3I)-C-12 it is found that the second carbon atom of the C = C bond in 6 stems from the exocyclic CH2 group of the heterocyclic ring system in 5.