A comparison between the reaction of P2Ph4 with [{Co2(CO)6}2(μ-η2:μ-η2-HOCH2CCCCCH2OH)] and the reaction of [Co2(μ-PPh2)2(CO)6] with HOCH2CCCCCH2OH

Reaction of P2Ph4 with the diyne–diol complex [{Co2(CO)6}2(μ-η2:μ-η2-HOCH2CCCCCH2OH)] in toluene at 65 °C gives [{Co2(μ-P2Ph4)(CO)4}{Co2(CO)6}(μ-η2:μ-η2-HOCH2CCCCCH2OH)] (1). Thermolysis of 1 at 95 °C leads to [{Co2(CO)5}2(μ-P2Ph4)(μ-η2:μ-η2-HOCH2CCCCCH2OH)](2) and (μ2-PPh2)(μ2-CO)(CO)7] (3). The structures of 1–3 have been established by X-ray crystallography. In 1, a pseudoequatorial P2Ph4 ligand bridges the cobalt–cobalt bond of a Co2(CC)(CO)4 unit. By contrast, in isomeric 2, a pseudoaxial P2Ph4 ligand spans two Co2(CC)(CO)5 units, a new coordination mode for [{Co2(CO)5L}2(μ-η2:μ-η2-diyne)] complexes. Complex 3 arises from dehydration–cyclocarbonylation of the diyne–diol in 1 to give a 2(5H)-furanone, a process that has not been previously reported. Reaction of HOCH2CCCCCH2OH with [Co2(μ-PPh2)2(CO)6] at 80 °C in toluene gave [Co3(μ-PPh2)3(CO)6], [Co2(CO)6(μ-η2-HOCH2CCCCCH2OH)] and [Co2{μ-η4-PPh2C(CCCH2OH)C(CH2OH)CO}(μ-PPh2)(CO)4] (4). The regiochemistry of 4 was confirmed by X-ray crystallography.

Graphical abstractReaction of P2Ph4 with the diyne–diol complex [{Co2(CO)6}2(μ-η2:μ-η2-HOCH2CCCCCH2OH)] gives [{Co2(μ-P2Ph4)(CO)4}{Co2(CO)6}(μ-η2:μ-η2-HOCH2CCCCCH2OH)] (1). Thermolysis of 1 leads to isomeric [{Co2(CO)5}2(μ-P2Ph4)(μ-η2:μ-η2-HOCH2CCCCCH2OH)] in which the P2Ph4 ligand adopts a new pseudoaxially-spanning bonding mode, and (μ2-PPh2)(μ2-CO)(CO)7] which arises from 2,4-hexadiyne-1,6-diol dehydration-cyclocarbonylation. Reaction of HOCH2CCCCCH2OH with [Co2(μ-PPH2)2(CO)6] follows a different course giving 3 products including [Co{μ-PPh2C(CCCH2OH)C(CH2OH)CO}(μ-PPh2)(CO)4].Figure optionsDownload full-size imageDownload as PowerPoint slideFigure optionsDownload full-size imageDownload as PowerPoint slide