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 P 2 Ph 4 with the diyne–diol complex [{Co 2 (CO) 6 } 2 (μ-η 2 :μ-η 2 -HOCH 2 C C C CCH 2 OH)] in toluene at 65 °C gives [{Co 2 (μ-P 2 Ph 4 )(CO) 4 }{Co 2 (CO) 6 }(μ-η 2 :μ-η 2 -HOCH 2 C C C CCH 2 OH)] ( 1 ). Thermolysis of 1 at 95 °C leads to [{Co 2 (CO) 5 } 2 (μ-P 2 Ph 4 )(μ-η 2 :μ-η 2 -HOCH 2 C C C CCH 2 OH)]( 2 ) and (μ 2 -PPh 2 )(μ 2 -CO)(CO) 7 ] ( 3 ). The structures of 1 – 3 have been established by X-ray crystallography. In 1 , a pseudoequatorial P 2 Ph 4 ligand bridges the cobalt–cobalt bond of a Co 2 ( C C )(CO) 4 unit. By contrast, in isomeric 2 , a pseudoaxial P 2 Ph 4 ligand spans two Co 2 ( C C )(CO) 5 units, a new coordination mode for [{Co 2 (CO) 5 L} 2 (μ-η 2 :μ-η 2 -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 HOCH 2 C C C CCH 2 OH with [Co 2 (μ-PPh 2 ) 2 (CO) 6 ] at 80 °C in toluene gave [Co 3 (μ-PPh 2 ) 3 (CO) 6 ], [Co 2 (CO) 6 (μ-η 2 -HOCH 2 C C CCCH 2 OH)] and [Co 2 {μ-η 4 -PPh 2 C(CCCH 2 OH)C(CH 2 OH)CO}(μ-PPh 2 )(CO) 4 ] ( 4 ). The regiochemistry of 4 was confirmed by X-ray crystallography.