Facile Preparation of Chloro-Cage-Substituted 11-Vertex 1-(η6-Arene)-isonido-1,2,4-ruthenacarboranes from [RuCl2(PPh3)3] and nido-5,6-C2B8H12 in Arene Solvents

A series of arene-ruthenium 11-vertex complexes 3-Cl-1-(η6-arene)-isonido-1,2,4-RuC2B8H9 (4a-4h) and 6-Cl-1-(η6-arene)-isonido-1,2,4-RuC2B8H9 (5a, 5b, 5f, 5g) (arene = p-xylene (a), mesitylene (b), p-cymene (c), benzene (d), toluene (e), hexamethylbenzene (f), 1,2,4,5-tetramethylbenzene (g), 1,2,4-trimethylbenzene (h)) have been obtained as isomeric mixtures 4a, 4b, 4f, 4g and 5a, 5b, 5f, 5g or, predominantly, as single isomers 4c-4e, 4h by the treatment of nido-5,6-C2B8H12 (1) with [RuCl2(PPh3)3] (2), either in the corresponding arene solvents at 80-85 °C (in the case of 4a-4e and 5a, 5b) or in the arene/1,2-dichloroethane solution under reflux (in the case of 4f-4h and 5f, 5g) in the presence of N,N,N',N'-tetramethylnaphthalene-1,8-diamine. The compounds prepared were characterized by combination of analytical, IR and multinuclear NMR data, including a crystallographic study of 4b. A possible pathway for the formation of isomeric complexes 4 and 5 is discussed.