Organic syntheses via transition metal complexes. 104. Cyclopentadienyl thiolacylates from (1-alkynyl)carbene complexes (M = Cr, W): Sulfur-centered fragmentation of ligand side chains

Cyclopentadienes containing sulfur substituents were generated by addition of sulfur nucleophiles to [1-alkynyl-2-(cycloaIk-1-enyl)]carbene complexes 1a-f (M = W, Cr). Cyclopentadienyl thiol(NH-imino)acylate-N complexes 12b-d ,f,g were obtained in 82-95% yields by addition of thioamides RC(=S)NH2 (10 ; R = Ph, Me) to (1-alkynyl)carbene complexes 1 at 20 degrees C (20 min). C ompounds 12 on thermolysis at 50 degrees C gave cyclopentene-1-thione compl exes 9 and nitriles 13 by a sulfur-centered fragmentation of the ligand sid e chain. Addition of thioamide MeC(=S)NHPh (16) to (l-alkynyl)carbene compl exes 1 afforded thermally stable cyclopentadienyl thiol(NPh-imino)acylate-N complexes 17b,c in 94-96% yield. Valence isomers 18a-c of the latter compo unds were generated in 83-89% yields, if the reaction was performed in the presence of a base, e.g. triethylamine. Addition of thiocarboxylic acids 6a ,b to tungsten (1-alkynyl)carbene complexes 1a,b at 20 degrees C produced c yclopentene-1-thione complexes 9a,b. Addition of thiocarboxylic acids 6a,b to the tungsten (1-alkynyl)carbene complex 19 at 20 degrees C afforded 4-(S -thioacyl)-1-tungsta-1,3-butadienes 20.