New triosmium complexes containing a partially hydrogenated bis(ferrocenyl)butadiyne ligand. Their structures and electrochemical responses

The reaction of Os-3(CO)(10)(mu(3)-FcC(4)Fc) (3) (Fe = C5H5FeC5H4) with water in thf solvent at reflux yielded three new cluster complexes: Os-3(CO)(9)(mu(3)-eta(3)-E-FcC(3)CHFc)(mu-OH) (4) (54%), Os-3-(CO)(9)(mu(3)-eta(3)-Z-FcC(3)CHFc)(mu-OH) (5) (11%), and Os-3(CO)(9)(mu(3)-eta(3)-E-FcC(3)CHFc)(mu-OH) (6) (16% yield) in 40 h. The same products were obtained from the reaction of 3 with Me3NO . 2H(2)O in 35 min at 25 degrees C, but the yield of 4 was lower (13%), the yield of 5 was higher (34%), and the yield of 6 was about the same (12%). Compounds 4-6 were characterized by single-crystal X-ray diffraction analyses. All three compounds contain a triply bridging eta(3)-bis(ferrocenyl)ynenyl, FcCCC=C(H)Fc, ligand formed by the addition of one hydrogen atom to the FcC(4)Fe ligand in 3. Compound 4 contains a closed triangular triosmium cluster with one bridging hydride ligand. Compounds 5 and 6 are isomers. Both contain an open triosmium cluster with a bridging hydroxo ligand. The isomers differ by E- and Z-configurations of the enyl group of the FcCCC=C(H)Fc Ligand. All three compounds show two resolved one-electron oxidations for the ferrocenyl groups: for 4 at E degrees = +0.43 and +0.56 V vs Ag/AgCl, Delta E degrees = 0.13 V; for 5 at E degrees = +0.38 and +0.46 V, Delta E degrees = 0.08 V; for 6 at E degrees = +0.39 and +0.49 V, Delta E degrees = 0.10 V. The potential differences Delta E are all larger than that in 3. This may be due in part to increased bonding between the carbon atoms in the C-C triple bond and C-C double bond in the bis(ferrocenyl)ynenyl ligand caused by the coordination to the metal atoms.