Synthesis and spectroscopic characterisation of compounds with formula [{Fe2S2(CO)5}Ph2P(CH2)nPPh2{Fe(CO)4}] and [{Fe2S2(CO)5}2Ph2P(CH2)nPPh2] (n=3, 4 and 6)

The work described herein concerns the synthesis and characterisation of compounds with formula [{Fe2S2(CO)5}Ph2P(CH2)nPPh2{Fe(CO)4}] and [{Fe2S2(CO)5}2Ph2P(CH2)nPPh2] (n=3, 4, 6). The iron bis-phosphine cluster compounds with formula [{Fe3(CO)11}2Ph2P(CH2)nPPh2] and [{Fe3(CO)11}Ph2P(CH2)nPPh2{Fe(CO)4}] (n=3, 4, 6)] were reacted with stoichiometric amounts of cyclohexene episulfide [SC6H10] in toluene at 70°C for 30–60 min. Optimum yields of 42.1–78.2%, were obtained for {Fe2S2Fe} type species when a 1:4 cluster–ligand mole ratio was used, while the {Fe2S2}2 type species were prepared in yields of 30–38% when a 1:8 cluster–ligand mole ratio was used. The volume of reaction solvent was kept to a minimum. For the latter cluster compounds, three isomeric products were isolated from each reaction; a justification for their presence is offered. All of these reactions afford clusters with fewer iron atoms but with S atoms incorporated. In these reactions the Fe3-unit is ‘degraded’ but at the same time the cluster is expanded from three atoms {Fe3} to four {Fe2S2}.