It has been found that when Re2(piv)4Cl2 (piv = the pivalato group, (CH3)3CCO2) is heated at temperatures of 220 ΔC or above, decomposition occurs, and the two chief products, which may be isolated in crystalline form by fractional sublimation, are Re2(piv)2Cl4 (lb) and Re2(piv)3Cl3 (2). Both of these compounds have been characterized thoroughly, including X-ray crystallographic structure determination. Compound 1 crystallizes in space group Cmcm with a = 14.062 (3) Å, b = 11.935 (8) Å, c = 11.147 (5) Å, F = 1870 (2) Å3 and Z = 4. The molecule has rigorous mm (C2v) symmetry with Re2Cl4 lying in one of the mirror planes and the Re-Re bond being bisected by the other. The full symmetry is close to D2h neglecting the orientations of the methyl groups. Important distances are Re-Re = 2.209 (2) Å, Re-Cl = 2.23 (1), 2.34 (1) Å, and Re-O = 2.02 (1) Å. The molecules are linked into chains by coordination of Cl atoms of one molecule to axial positions on neighboring molecules with Re⋯Cl = 2.90 (1) ⋯. The longer intramolecular Re-Cl distances are to the Cl atoms that form these bridges. Compound 2 crystallizes in space group Cc with a = 13.877 (4) ⋯, b = 13.445 (5) ⋯, c = 13.497 (3) ⋯, β = 106.56 (2)Δ, V = 2414 (1) Å3 and Z = 4. The structure consists of infinite chains of Re2(piv)3Cl2 units linked by bridging Cl atoms coordinated in axial positions of adjacent Re2(piv)3Cl2 units, at Re⋯Cl distances of 2.63 and 2.68 Å. Some important distances are Re-Re = 2.229 (2) Å, Re-Cl = 2.28 (1) Å, and Re-O = 2.03 (3) Å. © 1979, American Chemical Society. All rights reserved.
