The reactions of tricobalt alkylidyne complexes [Co3(μ3−CR)(CO)9](R = Me, CO2Me) with the vinyl phosphine ligands PPh2CHCH2 and cis-Ph2PCHCHPPh2; crystal structure of [Co3(μ3−CCO2Me)(μ-Ph2PCHCHPPh2)(CO)7]

Abstract The alkylidyne-capped complexes [ Co 3 (μ 3 − CR )( CO ) 9 ] ( R = Me 1a , CO 2 Me 1b ) react with PPh 2 CHCH 2 in heptane at 308 K to give the phosphine-substituted complexes [Co 3 ( μ 3 −CR)(CO) 8 (PPh 2 CHCH 2 )] ( R = Me 2a , CO 2 Me 2b ) , [Co 3 ( μ 3 −CR)−(CO) 7 (PPh 2 CHCH 2 ) 2 ] ( R = Me 3a , CO 2 Me 3b ) and, in the case of R = CO 2 Me, the tris -substituted complex [CO 3 ( μ 3 −CCO 2 Me)(CO) 6 (PPh 2 CHCH 2 ) 3 ] 4 . Heating of complexes 2a and 2b at 343 K results in loss of a CO group and coordination of the vinyl moiety of the PPh 2 CHCH 2 ligand to afford [Co 3 ( μ 3 −CR)( μ −PPh 2 CHCH 2 )(CO) 7 ] ( R = Me 5a , CO 2 Me 5b ) . In contrast, reaction of [Co 3 ( μ 3 −CR)(CO) 9 ](R = Me 1 a , CO 2 Me 1 b ) with cis -Ph 2 PCHCHPPh 2 (dppee) gives [Co 3 ( μ 3 −CR)( μ −Ph 2 PCHCHPPh 2 )(CO) 7 ] (R = Me 6 a , CO 2 Me 6 b ) in which the dppee ligand bridges two adjacent cobalt atoms via both phosphino moieties. Nuclear magnetic resonance studies on 5a and 5b indicate that two isomeric structures in a ratio of 7:3 are present in solution at 293 K. Conversion of [Co 3 ( μ 3 −CR)( μ −PPh 2 CHCH 2 )(CO) 7 ] 5a and 5b back to [Co 3 ( μ 3 −CR)(CO) 8 (PPh 2 CHCH 2 )] 2a and 2b can be achieved by purging with CO at 293 K while further purging at 343 K results in conversion to [Co 3 ( μ 3 −CR)(CO) 9 ] 1a and 1b . The structure of [Co 3 ( μ 3 −CCO 2 Me)( μ −Ph 2 PCHCHPPh 2 )(CO) 7 ] 6b was determined by single-crystal X-ray diffraction. All the complexes have been characterized spectroscopically and by elemental analysis.