Sulfur-containing carbene-metal compounds: General route from carbon disulfide manganese complexes; X-ray structure of 1,3-dithiol-2-ylidenemanganese(I) derivative

Chiral carbene-manganese(I) complexes have been synthesized by the cyclo-addition of dimethyl acetylenedicarboxylate to the coordinated CS₂ ligand in Mn(η²-CS₂)(CO)(L)C₅H₄R (L = P(OMe)₃; PMe₂Ph; PMe₃). Irrespective of the nature of the ligand L, these 1,3-dithiol-2-ylidenemanganese(I) complexes are stable towards isomerisation into heterometallocycles and exhibit low frequency carbonyl absorption bands in the infrared consistent with a strong electron releasing effect of the carbene ligand. The structure of Mn(CS₂C₂(CO₂Me)₂)(CO)(P(OMe)₃)(C₅H₅) has been determined by X-ray analysis of a suitable crystal. The molecule shows a carbene carbonmanganese bond C(7)Mn of length 1.876 Å and a planar carbene which does not adopt the 1,3-dithiolium aromatic-ring geometry but contains a carboncarbon double bond, C(8)C(9), of length of 1.341 Å. The CO₂Me groups are out of the plane of the carbene ligand and two positions with equal occupancy are found for each oxygen atom O(3) and O(5) belonging to the CO groups.