PREPARATION AND STRUCTURE OF DICHLOROTETRAKIS(ORTHO-OXYPYRIDINE)DIRHENIUM(III)

The reaction of (N-n-Bu4)2Re2Cl8 with 2-hydroxypyridine (Hhp) gives Re2(hp)4Cl2, a red-brown solid, insoluble in most common solvents but slightly volatile. By use of a crystal grown by sublimation, the structure has been determined. The crystal contains Re2(hp)4Cl2 molecules, each with a rigorous crystallographic inversion center and virtual C2h symmetry, packed with normal van der Waals contacts in a unit cell belonging to space group C2/c with the dimensions a = 17.309 (5) Å,b = 9.345 (3) Å, c = 17.203 (5) Å, β = 128.85 (2)°, and V= 2167 (1) β3. There are four molecules per unit cell. A total of 841 reflections with I > 2σ(I) were used to refine 111 parameters to final discrepancy indices of R1 = 0.051 and R2 = 0.059 in a model that omits hydrogen atoms and allows for random twofold disorder in the orientation of one of the two crystallographically independent hp ligands. The distances and angles in the molecule are all approximately those expected by comparison to the Re2(O2CR)4Cl2 species (R = Ph, t-Bu) previously studied except for the Re-Re distance, 2.206 (2) Å, which is about 0.03 Å shorter than those in the carboxylates. This is a shortening effect quite comparable to that previously seen among Mo24+ compounds of analogous types. © 1979, American Chemical Society. All rights reserved.