Catalytic hydrogenation of aromatics under biphasic conditions:: isolation and structural characterisation of the cluster intermediate [(η6-C6Me6)2(η6-C6H6)Ru3(μ2-H)2(μ2-OH)(μ3-O)]+

The water-soluble cluster cation [(eta (6)-C6Me6)(2)(eta (6)-C6H6)Ru-3(mu (2)-H)(3)(mu (3)-O)](+) (2) catalyses the hydrogenation of benzene and benzene derivatives to give the corresponding cyclohexanes under biphasic conditions. The catalytic activity of 2 depends markedly on the substrate, an extremely high activity being observed for ethylbenzene. The cationic species present in the catalytic mixture of the ethylbenzene hydrogenation could be isolated as the tetrafluoroborate salt and characterised as the cation [(eta (6)-C6Me6)(2)(eta (6)-C6H6)Ru-3(mu (2)-H)(2)(mu (2)-OH)(mu (3)-O)](+) (3). With 3 as the catalyst, the catalytic activity is also much higher for other benzene derivatives. (C) 2001 Elsevier Science B.V. All rights reserved.