The synthesis, fluxionality and reactivity of the heterobimetallic complex [FeRu(CO)2(μ-CO)2(η-C5H5)(η-C5Me5)] (5) are described. Complex 5 exhibits enhanced photolytic reactivity towards alkynes compared to its homometallic analogues, forming the dimetallacyclopentenone complexes [FeRu(CO)(μ-CO){μ-η1:η3-C(O)CR″CR′}(η-C5H5)(η-C5Me5)] (9, R′ = R″ = H; 10, R′ = R″ = CO2Me; 11, R′ = H, R″ = CMe2OH). Prolonged photolysis with diphenylethyne gives the dimetallatetrahedrane complex [FeRu(μ-CO)(μ-η2:η2-CPhCPh)(η-C5H5)(η-C5Me5)] (17), which contains the first iron–ruthenium double bond. Complexes containing a number of organic fragments can be synthesised using 9, 10 and 11. Heating a solution of 10 gave the alkenylidene complex [FeRu(CO)2(μ-CO){μ-η1:η1-C![[double bond, length as m-dash]](http://www.rsc.org/images/entities/char_e001.gif)
C(CO2Me)2}(η-C5H5)(η-C5Me5)] (23) through an unusual methylcarboxylate migration. Protonation and then addition of hydride to 9 gives the ethylidene complex [FeRu(CO)2(μ-CO)(μ-CHCH3)(η-C5H5)(η-C5Me5)] (27) via the ionic vinyl species [FeRu(CO)2(μ-CO)(μ-η1:η2-CHCH2)(η-C5H5)(η-C5Me5)][BF4] (25). Compound 25 exhibits cis/trans isomerisation at room temperature. Protonation of 11 gives the allenyl species [FeRu(CO)2(μ-CO)(μ-η1:η2-CHCCMe2)(η-C5H5)(η-C5Me5)][BF4] (30). Compound 30 exist as three isomers, two cis and one trans. The two cis isomers are shown to be interconverting by σ–π isomerisation. The solid state structures of 5, 11, 12, 17, 23, 25 and 30 were established by X-ray crystallography and are discussed.
![Graphical abstract: The synthesis of [FeRu(CO)2(μ-CO)2(η-C5H5)(η-C5Me5)] and convenient entries to its organometallic chemistry](http://hg.y866.cn/compound/lib/scimg/usr/1/B414412K.jpg)
