During the action of triphenylphosphine on Os3(Μ-H)(vt-O2CCF3)(CO)10 the substitution of the trifluoroacetate ligand and the substitution of one CO group take place in parallel with the formation of the clusters Os3(Μ-H)(O2CCF3)(CO)10(PPh3) and Os3(Μ-H)(Μ-O2CCF3)(CO)9 (PPh3). In the reaction of the cluster Os3(Μ-H)(Μ-O2CCH3)(CO)10 with triphenylphosphine only Os3(Μ-H)(Μ-O2CCH3)(CO)9(PPh3) is formed with a quantitative yield.

The protonation of trinuclear osmium clusters of the type Os3(μ-H) (μ-L) (CO)10 in CF3COOH-CH2Cl2 mixtures was studied by PMR and EAS spectroscopy. Equilibrium constants for these protonation reactions were determined and revealed that, relative to its dependence on the nature of the ligand L, the basicity of the clusters increases in the order: OPh< SPh=NHPh << 2-NC5H4.

The acidic properties of cyclo-Os3(μ-H)(μ-OH)(CO)9L clusters [L=CO (I), Ph3P (II)] were studied.

PMR and IR spectroscopy has been used to show that in the reactions of the cluster Os3(μ-H)2(CO)10 with CFgCOOH in CH2C12, addition of a molecule of acid to the Os=Os double bond takes place to give, in the first step of the reaction, the stereochemically flexible cluster [{Os3(H)(μ-H)2(CO)10}+(CF3CO2−)] which contains one terminal and two bridge hydride ligands, and is of a zwitterionic structure.

HOs3(OH)(CO)10 reacts with RCO2H (R=CF3, CH3, CD3, and H) with replacement of the bridging OH group by the RCO2 group.

The following occurs when HOs3(OH)(CO)10 is reacted with pyridine or deuteropyridine: replacement of both bridge ligands in the osmium cluster, cleavage of the C-H or C-D bond, and migration of the H or D atom into the metal ring.