Two new oxo-centred trinuclear ruthenium clusters supported by six dichloroacetate ligands, [Ru3(μ3-O)(μ-CHCl 2COO)6(CH3OH)3]CHCl2COO (1) and [Ru3(μ3-O)(μ-CHCl2COO)6(pyridine) 3] (2), have been synthesised and characterised by spectroscopic methods, electrospray ionisation mass spectrometry, single-crystal X-ray diffraction, and cyclic voltammetry. Due to the strong inductive effect of the dichloroacetate ligands, the redox potential of 2 was shifted to the positive side (∼1.0V or more) relative to the acetate analogue [Ru3(μ3-O) (μ-CH3COO)6(pyridine)3], and also the rate of pyridine/pyridine-d5 exchange reaction of 2 in CD3CN was retarded with the rate constant of kex298K=1. 9×10-8s-1 which is 105-fold smaller than the value for [Ru3(μ3-O)(μ-CH3COO) 6(pyridine)3]. Highly positive activation parameters obtained for 2, ΔH‡=138±7kJmol-1 and ΔS‡=71±20JK-1mol-1, illustrate a dissociative activation pathway in which rupture of the Ru-N(pyridine) bond is involved in the rate-determining step.
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