THE MULTIPLY BONDED OCTAHALODIOSMATE(III) ANIONS .2. STRUCTURE AND BONDING
Academic Article
Overview
Identity
Additional Document Info
Other
View All
Overview
abstract
The green crystalline compounds [(n-Bu)4N]2[Os2X8] (X = Cl (1), Br (2)) have been prepared, and their crystal and electronic structures have been studied. The two compounds form isotypic crystals in space group PI, with the following unit cell dimensions, given first for 1 and then for 2: = 11.797 (2), 12.143 (3) ; b = 18.650 (4), 18.687 (6) ; c = 11.506 (2), 11.764 (3) ; a = 104.73 (1), 103.58 (2); = 103.06 (1), 105.06 (2); = 100.00 (1), 99.81 (2); V = 2312 (2), 2428 (1) 3. With Z = 2, the molecular formula defines the asymmetric unit and no crystallographic symmetry is imposed on the Os2X82- ions. In fact, they come very close to having D4dsymmetry, with the following dimensions for 1 and 2: OsOs, 2.182 (1), 2.196 (1) ; OsX(av), 2.322 [6], 2.444 [4] ; zOsOsX, 104.2 (3), 104.3 (4); mean torsion angle, 49.0 [3], 46.7 [1]. The electronic structure of the Os2Cl82 ion in its eclisped (D4h) conformation has been calculated by the SCFXSW method, including relativistic corrections. The results support the shorthand description of the metal-metal bond as a d5d5, 242*2, triple bond. The HOMO is the 2blu(*) orbital, followed closely (~0.3 eV) by the 2b2g() orbital. The OsOs bonding is concentrated mainly in the 2euorbital and the bonding almost entirely in the 2a1gorbital. Both of these are very stable, thus accounting for the shortness of the OsOs bond. 1986, American Chemical Society. All rights reserved.
