Three isomeric hydride compounds formed by protonation of decacarbonyl-bis(dimethylphenylphosphine)triosmium and the X-ray structures of two of these: 1,1- and 1,2-[Os3H(CO)10(PMe2Ph)2][PF6]

Abstract

The compounds 1,1- and 1,2-[Os₃(CO)₁₀(PMe₂Ph)₂] react with trifluoroacetic acid in chloroform to give the singly protonated cations 1,1- and 1,2-[OS₃(µ-H)(CO)₁₀(PMe₂Ph)₂]⁺, isolated in high yields as the hexafluorophosphate salts. The 1,2-isomer exists in solution as two isomers, the major one having equivalent phosphines in adjacent equatorial sites and the minor one having non-equivalent phosphines, which is quite a different isomer distribution from that of the neutral precursor. X-Ray crystal structures are reported for 1,1- and 1,2-[Os₃(µ-H)(CO)₁₀(PMe₂Ph)₂][PF₆]. The structure of the 1,2-compound corresponds with that of the major isomer in solution. The bridged Os–Os distances are the longest, 3.064(4) and 3.062(4)Å for the two independent cations in the 1,1-isomer and 3.059(4)Å for the 1,2-isomer, and large OsOsC and OsOsP angles are found adjacent to the µ-hydride. Protonation of 1,2-[Os₃(CO)₁₀L₂], where L = PPh₃ or P(OMe)₃ and of the 1,2,3- and 1,1,2-isomers of [Os₃(CO)₉(PMe₂Ph)₃] have also been examined. There is a general marked preference for isomers with phosphines cis to the bridging hydride.