Phosphorus-oxygen bond formation on organo-capped tricobalt centres via phosphorus-hydrogen or phosphorus-phosphorus bond scission

Chromatographic work-up of the initial products of the reaction of the secondary phosphine PPh2H with [Co-3(mu(3)-CR)(CO)(9)] (R = Me 1a or CO2Me 1b) at 308 K in heptane gave the mono-and bis-substituted complexes [Co-3(mu(3)-CR)(Co)(8)(PPh2H)] (R = Me 2a or CO2Me 2b) and [Co-3(mu(3)-CR)(CO)(7)(PPh2H)(2)] (R = Me 3a or CO2Me 3b) and, in addition, when R = Me, the complex [Co-2(mu(3)-CMe)(mu-Ph2PoPPh2)(CO)(6)(PPh2H)] 4a, in which phosphorus-oxygen bond formation has occurred. Thermolysis of complex 2a at 343 K in heptane gave 1a and [Co-3(mu(3)-CMe)(mu-H)(mu-PPh2)(CO)(7)] 5a, while thermolysis of 3a under the same conditions afforded 4a, a trace of 5a and [Co-3(mu(3)-CMe)(mu-H)(mu-PPh2)(CO)(6)(PPh2H)] 6a. Similar reactions with the mu(3)-CCO2Me capped species 2b and 3b resulted in unstable non-isolable species. Treatment of complexes 3a, 3b with CO at 343 K causes the replacement of first one and then the other PPh2H ligand by CO to give 2a, 2b and then la, Ib respectively, while reformation of a phosphorus-hydrogen bond to give initially 2a or 3a can be achieved on carbonylation of either complex 5a or 6a. Substitution of a PPh2H group in 4a can be achieved by purging with CO to give [Co-3(mu(3)-CMe)(mu-Ph2POPPh2)(CO)(7)] 7a. Complex 7a can also be prepared directly by the reaction of 1a with the diphosphane P2Ph4 as can the analogue [Co-3(mu(3)-CCO2Me)(mu-Ph2POPPh2)(CO)(7)] 7b on reaction of 1b. The intermediates [Co-3(mu(3)-CR)(CO)(8)(P2Ph4)] (R = Me 8a or CO2Me 8b) and [Co-3(mu(3)-CR)(mu-P2Ph4)(CO)(7)] (R = Me 9a or CO2Me 9b) isolated in the reactions can be converted under the same reaction conditions into 7a and 7b respectively, Complex [Co-3(mu(3)CMe)(mu-Ph2POPPh2)(CO)(6)(PPhMe2)] 4a', the tertiary phosphine analogue of 4a, has been prepared from the reaction of 7a with PPhMe2. The structures of complexes 4a' and 5a have been determined by single crystal X-ray diffraction studies.