Structural and Bonding Studies of the Hexachlorobis(μ-chloro)(μ-hydrido)dimolybdenum(III) Ion, [Mo₂Cl₈H]³⁻

The preparations and structures of two compounds containing the [Mo₂Cl₈H]³⁻ ion are reported. The pyridinium salt, (C₅NH₆)₃[Mo₂Cl₈H] (1), crystallizes in space group [formula omitted] with a = 10.550 (1) Å, b = 15.162 (2) Å, c = 8.392 (1) Å, α = 99.14 (1)°, β = 111.68 (1)°, γ = 81.22 (1)°, V = 1225.1 (5) ų, and Z = 2. Using 2786 reflections and 257 variables, refinement led to R₁ = 0.026 and R₂ = 0.040. The mean values of important dimensions of the [Mo₂Cl₈H]³⁻ ion are Mo-Mo = 2.371 (1) Å, Mo-Cl_b = 2.492 (4) Å, Mo-Cl_t(trans to Cl) = 2.389 (11) Å, Mo-Cl_t(trans to H) = 2.489 (15) Å, Mo-H = 1.68 (6) Å, and ∠Mo-H-Mo = 89.6 (3)°. The second compound, [N(C₂H₅)4]₂[H₅O₂][Mo₂Cl₈H] (2), crystallizes in space group Pnma with a = 15.436 (3) Å, b = 10.578 (2) Å, c = 19.233 (2) Å, V = 3140 (2) ų, and Z = 4. For the [Mo₂Cl₈H]³⁻ ion, the principal dimensions are Mo-Mo = 2.384 (1) Å, Mo-Cl_b = 2.474 (1) Å, Mo-Cl, (trans to Cl) = 2.398 (4) Å, Mc-Cl, (trans to H) = 2.517 (1) Å, Mo-H = 1.793 (4) Å, and ∠Mo-H-Mo = 83.3 (2)°. Using the average dimensions of the [Mo₂Cl₈H]³⁻ ion calculated from those reported here for structure 2, an SCF-Xα-SW calculation has been carried out to learn more about the electronic structure of this ion and to make comparisons with the earlier results of Ginsberg on the [Mo₂Cl₉]³⁻ ion.