The reactions of tricobalt alkylidyne complexes [Co-3(mu(3)-CR)(CO)(9)] (R=Me, CO(2)Me) with the vinyl phosphine ligands PPh(2)CH=CH2 and cis-Ph(2)PCH=CHPPh(2); Crystal structure of [Co-3(mu(3)-CCO(2)Me)(mu-Ph(2)PCH=CHPPh(2))(CO)(7)]

The alkylidyne-capped complexes [Co-3(mu(3)-CR)(CO)(9)] (R = Me 1a, CO(2)Me 1b) react with PPh(2)CH=CH2 in heptane at 308 K to give the phosphine-substituted complexes [Co-3(mu(3)-CR)(CO)(8)(PPh(2)CH=CH2)] (R = Me 2a, CO(2)Me2b), [Co-3(mu(3)-CR)-(CO)(7)(PPh(2)CH=CH2)(2)] (R = Me 3a, CO(2)Me 3b) and,in the case of R = CO(2)Me, the tris-substituted complex [Co-3(mu(3)-CCO(2)Me)(CO)(6)(PPh(2)CH=CH2)(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=CH2 ligand to afford [Co-3(mu(3)-CR)(mu(3)-PPh(2)CH=CH2)(CO)(7)] (R = Me 5a, CO(2)Me 5b). In contrast, reaction of [Co-3(mu(3)-CR)(CO)(9)] (R = Me 1a, CO(2)Me 1b) with cis-Ph(2)PCH=CHPPh(2) (dppee) gives [Co-3(mu(3)-CR)(mu-Ph(2)PCH=CHPPh(2))(CO)(7)] (R = Me 6a, CO(2)Me 6b) 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(mu(3)-CR)(mu-PPh(2)CH-CH2)(CO)(7)] 5a and 5b back to [Co-3(mu(3)-CR)(CO)(8)(PPh(2)CH=CH2)] 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(mu(3)-CR)(CO)(9)] 1a and 1b. The structure of [Co-3(mu(3)-CCO(2)Me)(mu-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.