Hydrido-clusters derived by protonation, hydrogenation, or photolytic decarbonylation of the chelating diphosphine compounds 1,1-[Os3(CO)10(diphosphine)] where diphosphine is Ph2PCH2CH2PPh2 or Ph2PCH2CH2CH2PPh2, and crystal structure of [OsH2{Ph2P(CH2)3PC6H4}(CO)8]·0.5CH2Cl2

Abstract

The hydrides 1,1-[Os₃H(CO)₁₀(diphosphine)]⁺ were formed by the addition of trifluoroacetic acid to the chelating diphosphine compounds 1,1-[Os₃(CO)₁₀(diphosphine)], where diphosphine = Ph₂PCH₂CH₂PPh₂(dppe) or Ph₂PCH₂CH₂CH₂PPh₂(dppp) and were isolated as hexafluorophosphate salts. Reactions of the parent diphosphine compounds with H₂ at atmospheric pressure in refluxing toluene do not lead to the simple dihydrides [Os₃H₂(CO)₈(diphosphine)] as found for the corresponding 1,2 isomers. Instead the clusters [Os₃H₂{Ph₂P(CH₂)_nPC₆H₄}(CO)₈](n= 2 or 3) are obtained by loss of C₆H₆ and orthometallation. The X-ray structure when n= 3 establishes the presence of the six-electron donating ligand µ₃-Ph₂PCH₂CH₂CH₂PC₆H₄. Orthometallation of the clusters 1,1-[Os₃(CO)₁₀(diphosphine)] occurs on u.v. photolysis to give [Os₃H{Ph₂P(CH₂)_nPPhC₆H₄}(CO)₉](n= 2 or 3) which can be hydrogenated to give the clusters [Os₃H₂{Ph₂P(CH₂)_nPC₆H₄}(CO)₈]. This is evidence that decarbonylation and orthometallation could occur before hydrogenation in the initial thermal reaction of the diphosphine compounds with H₂.