Mono- and bicyclic organometallic ring systems with exocyclic C=C and C=S bonds

Article abstract of DOI:10.1002/cber.19971300710

The cobaltaheterocycles [C₅H₅Co{κ₂(C,S)-C(=CH ₂)-N(R)C(=S)S)(PMe₂Ph)] (5-7), which contain both an exocyclic C=C and C=S bond, were prepared from the iminoacylcobalt compounds [C₅H₅Co|C(CH₃)=NCH₃)(PMe ₂Ph)]I (2-4) on treatment with either CS₂/NaOCH₃ or K[S₂CNMe₂], respectively. While protonation of 5 (R = CH₃) and 7 (R = CH₂Ph) with HBF₄ occurs at the exocyclic C=CH₂ bond to give cations containing a CoC(CH₃)N(R)C(=S)S ring, the methylation of 5 and 7 with [OMe₃]BF₄ takes place at the exocyclic C=S bond and generates five-membered heterocycles with an SCH₃ substituent. The reaction of 5-7 with S₈ leads to the elimination of the phosphane ligand and affords the bicyclic dithiolenecobalt complexes 14 -16 in moderate to good yields. On treatment of 5-7 with C₂(CO₂R′)₂ (R′ = Me, Et), an insertion of the alkyne into the C=CH₂ bond occurs and five-membered ring systems 19-22 with an unsaturated exocyclic =C(CO₂R′)-C(CO₂R′)=CH₂ group are formed. As in the case of 5 and 7, protonation and methylation reactions of 19 also take place at different sites leading to cations with either a delocalized CoCN or NCS unit. Keywords: Cobalt / Cyclopentadienyl complexes / Heterocycles / Electrophilic addition / Insertion reaction VCH Verlagsgescllschaft mbH.