REACTIONS OF THE HETERONUCLEAR ALKYNE-BRIDGED COBALT-MOLYBDENUM COMPLEX [(OC)3CO(MU-C2(CO2ME)2)MO-(CO)2(ETA-5-C5H5)] WITH PPH2H, P2PH4 AND PPH2(SPH)

The complex [(OC)3Co{mu-C2(CO2Me)2}Mo(CO)2(eta5-C5H5)] 1 reacts preferentially at the Co atom with PPh2H, P2Ph4 and PPh2(SPh) to give initially the mono-substituted products [L(OC)2Co{mu-C2(CO2Me)2}-Mo(CO2(eta5-C5H5)] [L = PPh2H 2, P2Ph4 3 or PPh2(SPh) 41. In the case of PPh2H further reaction takes place at the Mo atom to give the bis-substituted product [(HPh2P)(OC)2Co{mu-C2(CO2Me)2}-Mo(CO)(eta5-C5H5)(PPh2H)] 5. Thermolysis of the substituted derivatives 2-5 results in either P-H, P-P or P-S bond cleavage. Thus for 2, the isomeric species [(eta5-C5H5)(OC)Mo{mu-C(CO2Me)=CH-(CO2Me)}(mu-PPh2)Co(CO)2] 6 and [(OC)2Co{mu-C(CO2Me)=CH(CO2Me))(mu-PPh2)Mo(CO)(eta5-C5H5)] 7 are obtained, whereas 3 gives [(OC)2Co{mu-PPh2C(CO2Me)=C(CO2Me)}(mu-PPh2)Mo(CO)(eta5-C5H5)] 8, in which the Co atom is incorporated into a four-membered metallacycle. Thermolysis of 4 gives [(eta5-C5H5)(OC)Mo{mu-PPh2C(CO2Me)=C(CO2Me)}(mu-SPh)Co(CO)2] 9 (in which the Mo atom is incorporated into a four-membered metallacycle) and thermolysis of 5 gives [(eta5-C5H5)(OC)Mo-{mu-C(CO2Me)=CH(CO2Me)}(mu-PPh2)Co(CO)(PPh2H)] 10. Complex 6 can be converted to 10 by reaction with PPh2H. The crystal structures of compounds 6 and 8 have been determined.