Synthesis of tetracobalt clusters from dicobalt alkyne complexes

Abstract

The room-temperature reactions of [Co2(µ-PhCCH)(CO)6] or [Co2(µ-MeCCMe)(CO)6] with Ph2PCCPh (L) afford [Co2(µ-PhCCH)(CO)5(η1-L)] or [Co2(µ-MeCCMe)(CO)5(η1-L)] and [Co2(µ-MeCCMe)(CO)4(η1-L)2], respectively, in which L is bound via the phosphine functionality. The structure of [Co2(µ-MeCCMe)(CO)4(η1-L)2] has been established by X-ray crystallography and comprises two Co(CO)2(η1-L) units bridged by a MeCCMe ligand. Reactions of [Co2(µ-R1CCR2)(CO)5(η1-L)] with [Co2(CO)8] afford [Co2(µ-R1CCR2)(CO)5(µ-η1:η2-L)Co2(CO)6](R1= Ph, R2= H; R1= R2= Me), in which L is bound to the Co2(CO)6 unit via the alkyne functionality. Pyrolysis of [Co2(µ-MeCCMe)(CO)5(µ-η1:η2-L)Co2(CO)6] results in phosphorus–carbon bond cleavage and cobalt–cobalt and carbon–carbon bond formation to afford a butterfly cluster [Co4{µ4-η3-PhCCC(Me)C(Me)C(O)}(µ-PPh2)(µ-CO)6], whose structure has been established by X-ray diffraction.