Direct preparation of [Ru(η2-O2CO)(η6-arene)(L)] carbonate complexes (L = phosphane, carbene) and their use as precursors of [RuH2(p-cymene)(PCy3)] and [Ru(η6-arene)(L)(MeCN)2][BF4]2:: X-ray crystal structure determination of [Ru(η2-O2CO)(p-cymene)(PCy3)]•1/2CH2Cl2 and [Ru(η2-O2CO)(η6-C6Me6)-(PMe3)]•H2O

[RuCL2(eta(6)-arene)(PR3)] complexes react with K2CO3 in the presence of water to afford the carbonatoruthenium(ii) derivatives [Ru(eta(2)-O2CO)(eta(6)-arene)(PR3)] (2; arene = p-cymene, R = Cy, Ph, or Me; arene = hexamethylbenzene, R = Me) involving a planar Ru(eta(2)-O2CO) moiety as shown by X-ray crystal structure determination of 2a (p-cymene, PCy3) and 2d (hexamethylbenzene, PMe3). The complex [Ru(eta(2)-O2CO)(p-cymene)(PCy3)] is cleanly converted in hot methanol into the dihydride [RuH2(p-cymene)(PCy3)]. The related complexes [Ru(eta(2)-O2CO)(eta(6)-arene)(IMes)] [arene = p-cymene or hexamethylbenzene, IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene] are straightforwardly prepared by treating [RuCl2(eta(6)-arene)](2) precursors with 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride and K2CO3 in THF at reflux. The removal of the carbonato ligand from complexes 2 with HBF4 in the presence of acetonitrile leads to the dicationic derivatives [Ru(eta(6)-arene)(L)(MeCN)(2)][BF4](2) (L = PR3 or IMes). ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)