Synthesis, properties and crystal structures of [RuIII2(tacn)2(µ-OH)2(µ-CO3)]Br2·3.75H2O and [Ru3.52(dtne)(µ-O)2(µ-CO3)]PF6·5H2O [tacn = 1,4,7-triazacyclononane, dtne = 1,2-bis(1,4,7-triazacyclononan-1-yl)ethane]

The mono- and di-nuclear complexes [RuIII(tacn)Cl3]1, [RuIII2(dtne)Cl6]2, and [RuIII2(dtne)Br6]3 have been synthesised from [RuII(dmso)4Cl2](dmso = dimethyl sulfoxide), the respective amine and concentrated HCl or HBr in the presence of air where tacn and dtne represent 1,4,7-triazacyclononane and 1,2-bis(1,4,7-triazacyclononan-1-yl)ethane. The compounds proved to be useful starting materials for the hydrolytic generation of hydroxo/oxo-bridged dinuclear RuIII2 and RuIIIRuIV species in aqueous solution containing sodium carboxylates or sodium carbonate. The diamagnetic red-purple species [RuIII2(dtne)(µ-OH)2(µ-PhCO2)][PF6]34 and its green µ-carbonato analogue [Ru2III(tacn)2(µ-OH)2(µ-CO3)]Br2·3.75H2O 5 were prepared. Replacement of the µ-carboxylato bridge in 4 by a µ-CO32– bridge in the presence of air gave green crystals of the mixed-valent species [Ru3.52(dtne)(µ-O)2(µ-CO3)]PF6·5H2O 6. Complexes 5 and 6 have been structurally characterized by X-ray crystallography; both contain a bioctahedral edge-sharing unit of RuIII2(µ-OH)2(µ-CO3)2+ and Ru3.5(µ-O)2(µ-CO3)+, respectively, with Ru–Ru metal–metal bonds [2.560(1) in 5, 2.469(1) in 6]. The RuIV2 analogues of 5 and 6 have been generated chemically and electrochemically in solution. The UV/VIS spectra, magnetic properties and the electrochemistry of 4–6 are reported.