Reactions of the cyclometallated triosmium cluster [Os3H2(CO)9{P(C6H4)Ph}] with brøsnsted acids and dihydrogen: synthesis and X-ray crystal structure of [Os3H2(CF3CO2)(CO)9(µ-PPh2)]
Abstract
The cyclometallated cluster [Os3H2(CO)9{P(C6H4) Ph}](1) reacts with Brøsnsted acids HX via a protonation then anion co-ordination sequence to give the addition products [Os3H2(X)(CO)9-(PPh2)][X = Cl (2), Br (3), CF3CO2(4), or MeCO2(6)]. An X-ray analysis of (4) shows that the triangular metal framework of (1) is retained, and the oxygen-bound CF3CO2 ligand occupies a terminal axial site on the Os atom which is not bridged by the µ-PPh2 group. With HBF4·Et2O the cationic cluster [Os3H3(CO)9{P(C6H4)Ph}]+(5) is obtained, and this reaction may be thought of as involving the isolation of an intermediate in the above reactions. With HBr, addition of excess of acid to (1) leads to metal bond cleavage and cluster fragmentation, providing a novel route to new dimeric phosphido-bridged complexes [Os2H3(CO)6(PPh2)](7), [Os2H2(Br)(CO)6(PPh2)](8), and [Os2H(Br)2(CO)6(PPh2)](9). In contrast, reaction of (1) with H2 leads to carbon-phosphorus bond cleavage to give the phosphinidene-capped cluster [Os3H2(CO)9(µ3-PPh)](10).