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.