Syntheses, characterization and redox properties of di- and poly-phosphine linked oligomeric complexes of oxo-centered triruthenium clusters

Synthesis and properties of the cyano complex of oxo-centered triruthenium core [Ru3(μ3-O)(μ-CH3COO)6(pyridine)2(CN)]

The preparation and properties of a new cyano complex containing the Ru3(μ3-O) core, [Ru3(μ3-O)(μ-CH3COO)6(py)2(CN)] (1; py = pyridine), are reported. Complex 1 in CH2Cl2 showed intense absorption bands at 244, 334, and 662 nm, corresponding to a π-π* transition of the ligand, cluster-to-ligand charge transfer, and intracluster transitions, respectively. The cyclic voltammogram of 1 in 0.1 M (n-Bu)4NPF6-CH2Cl2 showed redox waves for the processes Ru3(II,II,III)/Ru3(II,III,III), Ru3(II,III,III)/Ru3(III,III,III), and Ru3(III,III,III)/Ru3(III,III,IV) at E1/2 = -1.49, -0.26, and +1.03 V vs Ag/AgCl, respectively. The first two redox potentials are more negative by ca. 0.2 V in comparison with the corresponding potentials of [Ru3(μ3-O)(μ-CH3COO)6(py)3](+). This is in sharp contrast to the positive shifts of the corresponding waves of [Ru3(II,III,III)(μ3-O)(μ-CH3COO)6(py)2(CO)]. Density functional theory (DFT) calculations of [Ru3(II,III,III)(μ3-O)(μ-CH3COO)6(py)3], [Ru3(II,III,III)(μ3-O)(μ-CH3COO)6(py)2(CN)](-), and [Ru3(II,III,III)(μ3-O)(μ-CH3COO)6(py)2(CO)] showed that the positive charge of the ruthenium is delocalized over the triruthenium cores of the first two and is localized as Ru(II)(CO){Ru(III)(py)}2 in the CO complex. The calculations explain the difference in the π interactions of the two ligands with the triruthenium cores.

Preparation and characterization of novel oxo-centered basic p-chlorobenzoic bridging trinuclear complexes

Three new oxo-centered trinuclear complexes, one of them a mixed-valence complex [Mn3O(C7H4O2Cl)6(Py)3]Py (1) and the others, mixed-metal complexes of [Fe2MnO(C7H4O2Cl)6(Py)3]NO3 (2) and [Fe2CoO(C7H4O2Cl)6(Py)3] (3) were synthesized by the direct reaction between metal nitrates and p-chlorobenzoic acid. These complexes were characterized by elemental analyses (CHN), atomic absorption spectroscopy and spectral (IR, electronic) studies. These are new type of oxo-bridged mixed-metal complexes in which the carboxylate ligand is pchlorobenzoic acid. The UV spectra of the complexes exhibited a strong band in the region 42,500 cm-1 which is related to the (? ? ?*) transitions of the pyridine ligand. The IR spectra of these compounds showed two strong stretching vibrations bands, indicating a bridging coordination mode of the carboxylic group of the ligand in the complexes.