The complex (µ-H)(µ-Cl)OS3(CO)10 has been studied via a single-crystal X-ray structural analysis. The complex crystallizes in the centrosymmetric triclinic space group P1 with a = 7.8230 (14) Å, b = 8.8678 (23) Å, c =13.6583 (26) Å, α = 94.829 (18)°, β = 103.028 (15)°, γ = 110.677 (18)°, and V = 849.6 (3) Å3. The calculated density is 3.467 g cm-3 for Z = 2 and mol wt 887.17. Diffraction data were collected on a Syntex P21 automated four-circle diffractometer by using Mo Ka radiation (20max = 45.0°). The structure was solved by a combination of Patterson, Fourier, and least-squares refinement techniques. Final discrepancy indices are RF =3.1% and RWF = 2.9% for those 2143 data with F0 < σ7(F0) and RF = 3.4% and RWF = 2.9% for all 2243 independent data. All nonhydrogen atoms were located, and the hydride ligand was included in its idealized position. The molecule contains a triangular arrangement of osmium atoms. Os(1) and Os(3) are each associated with three carbonyl ligands, while Os(2) is linked to four such ligands. In addition, Os(1) and Os(3) arc mutually bridged both by a hydride ligand and by a chloride ligand. Osmium-osmium bond lengths are Os(1)-Os(2) = 2.829 (1) Å and Os(2)-Os(3) = 2.836 (1) Å, while the dibridged osmium-osmium distance is Os(1)-Os(3) = 2.846 (1) Å. A single unsupported bridging hydride ligand normally causes a significant expansion in a metal-metal bond (relative to its value in an analogous nonbridged system). However, in the present case this effect appears to be almost counterbalanced by the presence of the bridging chloride ligand. Osmium-chlorine distances are symmetrical, with Os(1)-Cl = 2.454 (3) Å and Os(3)-Cl = 2.458 (3) Å; the angle Os(3)-Cl-Os(3) is quite acute, with a value of 70.83 (9)°. © 1979, American Chemical Society. All rights reserved.