Ru(IV)-Ru(IV) complexes having the doubly oxido-bridged core with a bridging carbonato or hydrogencarbonato ligand

Ru(IV)-Ru(IV), Ru(III)-Ru(IV), and Ru(III)-Ru(III) complexes having a sulfato bridging ligand on the doubly oxido-/hydroxido-bridged core, and their crystallographic and electronic structures

The Ru2(IV,IV), Ru2(III,IV), and Ru2(III,III) complexes with the doubly oxido- and/or hydroxido-bridged diamond core {Ru2(μ-O(H))2}, bridged by an η1:η1:μ2-type bidentate sulfato ligand, [{Ru(L)}2(μ-O)2(μ-O2SO2)]m+ (m = 1: [III,IV]+; m = 2: [IV,IV]2+), [{RuIII,IV(L)}2(μ-O)(μ-OH)(μ-O2SO2)]2+ ([III,IV_1H]2+), and [{RuIII,III(L)}2(μ-OH)2(μ-O2SO2)]2+ ([III,III_2H]2+) (L = ethylbis(2-pyridylmethyl)amine), were synthesised as ClO4--salts, and their crystal and electronic structures investigated. The corresponding hydrogencarbonato-bridged Ru2(III,III) complex, [{RuIII,III(L)}2(μ-OH)2(μ-O2COH)]3+ ([III,III(HCO3)_2H]3+), was also prepared and its crystallographic and electronic structures compared to those of the sulfato-bridged system, [III,III_2H]2+. All the sulfato-bridged complexes isolated were confirmed in the Pourbaix diagram, wherein the redox potential was plotted as a function of pH. The pKas were determined using UV-vis-NIR spectroscopic measurements and incorporated into the Pourbaix diagram. This is the first sequential study, both experimentally and theoretically, on the various oxidation states of Ru centres and the number of protons on the {Ru2(μ-O(H))2} core in the same tridentate ligand system for complexes with the {Ru2(μ-O(H))2(μ-O2XY)}-type dinuclear framework, which are analogous to the intermediate structures of the diiron-containing soluble methane monooxygenase.

Edge-sharing bi-octahedral diruthenium(IV,IV) compounds containing Ru-Ru bonds chelated and bridged by two carbonate and two oxo groups

From paddle-wheel starting material Na3Ru2(CO3)4·6H2O, a family of edge-sharing bi-octahedral (ESBO) diruthenium(IV,IV) compounds formulated as Ru2O2(CO3)2(H2O)2L2·nH2O [L = piperazine (1) or 2-methylpiperazine (2), n = 4, and L = 2,2-dimethylpiperazine (3), n = 12] and Ru2O2(CO3)2(OH)4{M(H2O)4}2·nH2O [M = Mg (4), n = 4, and Ni (5), n = 2] were prepared and structurally characterized. The Ru28+ dimer is chelated and bridged by two CO32- and two μ-O in a trans manner, and the Ru-Ru distances fall in the range 2.3808(6)-2.4001(4) Å. Compound 2 shows the shortest Ru-Ru distance for all known ESBO Ru2 compounds reported thus far. Increasing -CH3 groups of terminal piperazine ligands coordinated to the Ru(μ-O)2(μ-O3C)2Ru core, and according to Raman spectra experiments combined with theoretical calculations, the intense bands of compounds 1-3 appearing at ∼360 cm-1 can be assigned to the stretching of Ru-Ru bonds.