INFLUENCE OF S-ARYL GROUPS IN THE COORDINATION AND REACTIVITY OF (NIDO-THIOCARBORANE)RUTHENIUM COMPLEXES

The reaction of [RuCl2(PPh3)(3)] and [NMe4][7,8-(SPh)(2)-7,8-C2B9H10] in ethanol yields [RuCl(7,8-(SPh)(2)-7,8-C2B9H10)(PPh3)(2)]. CH2Cl2 (1 ). The structure of 1 has been determined by crystallographic studies. The crystal contains the two isomers 1a and 1b in a ratio of ca. 3:1. In both isomers the metal has an octahedral geometry and the carboran e ligand tricoordinates the Ru(II) center by means of S-Ru, B(11)-H-Ru , and B(2)-H-Ru bonds. Two PPh3 groups and a chloride ligand fulfill t he coordination sphere of the metal. The two isomers arise from two di fferent dispositions of the [RuCl(PPh3)(2)](+) fragment with regard to the carborane cluster. The preference for two agostic B-H-Ru bonds ra ther than a second S-Ru bond appears to be due to steric factors. The reaction of [RuCl2(PPh3)(3)] and the cesium or tetramethylammonium sal ts of [7-(SPh)-8-R-7,8-C2B9H10](-) (R = Me, Ph) yields [RuCl(7-SPh-8-R -7,8-C2B9H10)(PPh3)(2)] (2, R = Me; 3, R = Ph). NMR spectroscopic anal yses of 2 and 3 also indicate the presence of isomers analogous to tho se observed for 1. Unlike the S-alkyl-substituted (monothiocarborane)r uthenium complexes reported earlier, complexes 1-3 do not undergo B(5) elimination to form an arachno cluster. Complex 2 catalyzes the hydro genation of 1-hexene, exhibiting a TON of 115 ([1-hexene] = 3.9 M, [2] = 5.21 x 10(-4) M, 66 degrees C, P = 45 bar, 1 h).