ISOLATION, CHARACTERIZATION, AND SUBSTITUTION-REACTIONS OF THE TRINUCLEAR TRIFLATE COMPLEX H2OS3(CO)9(O3SCF3)2 - X-RAY CRYSTAL-STRUCTURE OF THE MIXED OXY LIGAND CLUSTER (MU-H)2OS3(CO)9(MU,ETA-2-O2CCH3)(ETA-1-O3SCF3)

The complex H2Os3(CO)9(O3SCF3)2 (1) has been prepared from the reaction of (mu-H)3Os3(CO)9(mu-3-CH) with neat trifluoromethanesulfonic acid. The reaction of 1 with various protonic acids has been studied, and two kinds of product have been obtained. These were (i) replacement of both triflate ligands and isolation of the previously reported cluster (mu-H)2Os3(CO)9(mu-3,eta-3-O3SO) (2) or the new oxy ligand clusters (mu-H)2Os3(CO)9(mu,eta-2-O2CR)(eta-1-O2CR) [R = H (6), CF3 (7)] and (ii) replacement of just one triflate ligand and isolation of mixed oxy ligand clusters (mu-H)2Os3(CO)9(mu,eta-2-O2CR)(eta-1-O3SCF3) [R = H (3), CH3 (4), CF3 (5)]. Reaction of 1 with MeCN also lead to displacement of both triflate ligands to give ](mu-H)2Os3(CO)9(MeCN)3[]O3SCF3[2 (8). The new compounds were isolated as crystalline solids and were characterized analytically and spectroscopically; in the case of compound 4, a single-crystal X-ray diffraction study was conducted. (mu-H)2Os3(CO)9(mu,eta-2-O2CCH3)(eta-1-O3SCF3) (4) crystallizes in the monoclinic space group P2(1)/n with a = 8.469 (3) angstrom, b = 20.840 (9) angstrom, c = 12.562 (4) angstrom, beta = 95.49 (3)-degrees, V = 2207 (2) angstrom-3, and Z = 4. The structure was solved by conventional methods and refined to final agreement factors of R = 0.033 and R(w) = 0.043 for the 3079 unique reflections. The molecule contains a triangular triosmium core in which each osmium atom is linked to three terminal carbonyl ligands. Acetate bridges diaxially the Os(2)-Os(3) edge, and the Os(1)-Os(2) and Os(1)-Os(3) edges are apparently each bridged by a hydride ligand (which was not located directly). The triflate ligands is axially bound to Os(1), on the opposite side of the trimetal plane from the bridging acetate ligand, and displays unusual distances to the coordinated oxygen atom [Os-O = 2.146 (10) angstrom; S-O = 1.50 (1) angstrom] suggestive of strong binding. Compound 4 did not react with a variety of possible donor ligands (CO, MeCN, PhCN, THF, and H-2) at 72-degrees-C in 1,2-dichloroethane over 2 h. Under similar conditions, reactions with Cl-, I-, and S2O3(2-) gave the known clusters (mu-H)Os3(CO)10(mu-X) [X = Cl, I] and (mu-H)2Os3(CO)9(mu-3-S), respectively. In neat acetic acid at 60-degrees-C, compound 4 formed Os2(CO)6(mu-O2CCH3)2, apparently via H2Os3(CO)9(O2CCH3)2.