Surface-assisted synthesis and behavior of dimetallic mixed-metal complexes [M2Cl2(μ-Cl)4(CO)6M′(L)2] (M = Ru, Os; M′ = Fe, Co; L = CH3CH2OH, H2O)

The reductive carbonylation of ruthenium and osmium halides in the presence of cobalt and iron surfaces was studied. In these surface-assisted reactions the metal surface plays an active role in releasing metal ions, which can be used for the in situ synthesis of mixed-metal compounds. A linear, dimetallic, chlorido-bridged, trinuclear complex [Ru2Cl2(mu-Cl)(4)(Co)(6)Co(CH3CH2OH)(2)] was obtained by the interaction between reducing RuCl3 and the cobalt surface. In the reaction the RuCl3 is reduced with carbon monoxide in the presence of a solid cobalt surface in ethanol solution. During the reduction of the RuCl3 the cobalt surface was simultaneously corroded, releasing cobalt cations. In addition to [Ru2Cl2(mu-Cl)4(CO)(6)Co(CH3CH2OH)(2)], the reaction also produced other trinuclear complexes and mononuclear products, such as a bent and linear dimetallic, chlorido-bridged complex with the aqua ligand [Ru2Cl2(mu-Cl)(4)(CO)(6))(6)Co(H2O)(2)] and ionic [RuCl3(CO)(3))(2))[Co(H2O)(6)]. The carbon monoxide reduction of RuI3 produced the ionic complex [RuI3(CO)(3)](2)[M'(H2O)(6)] (M' = Fe, Co) in the presence of iron, stainless steel or cobalt. Iodido-bridged trinuclear mixed-metal complexes were not observed. The surf ace-assisted process proved to be useful with other metal combinations as well. When RuCl3 was replaced with OsCl3, a variety of trinuclear mixed-metal complexes, such as [Os2Cl2(mu-Cl)(4)(CO)(6)CO(CH3CH2OH)(2)] and ionic [OsCl3(CO)(3)](2)[M(H2O)(6)] (M = Fe, Co), were obtained, depending on the metal surface used. Due the lability of the chlorido-bridged trinuclear complexes, the possible decomposition steps of [M2Cl2(mu-Cl)(4))(4)(CO)(6)M'(CH3CH2OH)2] (M = Ru, Os; M' = CO, Fe) were studied computationally, using DFT methods. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).