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]

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)A for the two independent cations in the 1,1-isomer and 3.059(4)A 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.