1,2,3-Triphenylphosphirene derivatives of the iridium carbonyl clusters [HIr4(CO)(9)L(mu-PPh2)] (L = CO, PPh3) resulting from substitution, insertionand hydrometallation processes

1,2,3-Triphenylphosphirene reacts with [HIr4(CO)(10)(mu-PPh2)] 1, at room t emperature, to afford [Ir-4(CO)(8)(mu(3)-eta(2)-PhPCPh=CPh)(mu-PhPCPh=CHPh) (mu-PPh2)] 2 which contains the phosphametallacycle (mu(3)-eta(2)-PhPCPh=CP h) and the phosphidoalkenyl (mu-PhPCPh=CHPh) ligands arising from insertion and hydrometallation processes respectively. In contrast, the PPh3 derivat ive of 1, [HIr4(CO)(9)(PPh3)(mu-PPh2)] 3, reacts selectively at room temper ature with the phosphirene to give only CO substitution products, [HIr4(CO) (9-n)(PPh3)(eta(1)-PhPCPh=CPh)(n)(mu-PPh2)] (n=1, 4 and 2, 5) which are the first carbonyl cluster compounds containing intact eta(1)-ligated phosphir ene rings. High yield conversion of compound 4 into the phosphametallacycle species [HIr4(CO)(7)(PPh3)(mu(3)-eta(2)-PhPCPh=CPh)(mu-PPh2)] 6 is achieve d under mild thermolytic conditions. An insight into the mechanism of forma tion of 2 was given by the reaction of the phosphirene ring with the anion [Ir-4(CO)(10)(mu-PPh2)](-) 1a derived from 1, followed by protonation, whic h gave [HIr4(CO)(8)(mu(3)-eta(2)-PhPCPh=CPh)(mu-PPh2)] 7, which is analogou s to 6 with a CO ligand replacing PPh3. Quantitative conversion of the hydr ide phosphametallacycle 7 into the labile phosphidoalkenyl cluster [Ir-4(CO )(11)(mu-PhPCPh=CHPh)(mu-PPh2)] 8 is easily achieved in the presence of CO (1 atm, RT, 2 h), as a result of the reductive elimination of a C-H group. Compound 8 undergoes facile CO dissociation and co-ordination of the phosph idoalkenyl C=C bond to the metal centre to produce [Ir-4(CO)(9)(mu(3)-eta(3 )-PhPCPh=CHPh)(mu-PPh2)] 9. The molecular structures of compounds 2, 4, 6 a nd 9 were established by X-ray diffraction studies and the structures of al l compounds in solution were investigated by a combination of H-1 and P-31{ H-1} NMR studies.