The hydrated cobalt ions, Co + (H 2 O) n (n = 4-6), are studied with the infrared (IR) photodissociation spectroscopy in the OH-stretch region and density functional theory calculations. The calculations predict a T-shaped coordination structure for Co + (H 2 O) 3 , which exposes empty coordination sites for additional H 2 O ligands. Nevertheless, the IR spectrum of Co + (H 2 O) 4 indicates that the fourth H 2 O prefers to occupy the second shell through H-bonding rather than coordinate directly to Co +. A comparison between the experimental and theoretical IR spectra suggests that the T-shaped coordination remains intact in the n = 4-6 ions, leaving the direct coordination sites unoccupied.

Both the fac- and mer-isomers of tricyano[bis(2-pyridylmethyl)amine = 2-DPA]ferrate(II) were isolated and their spectroscopic properties compared. The fac-isomer was converted to the corresponding iron(III) complex under acidic conditions. Oxidation of the ferrate(II) complexes with ammonium peroxodisulfate yielded the mer-isomer of the dehydrogenated ferrate(II) compound, but only the metal-oxidized iron(III) complex for the fac-isomer was produced under neutral or basic conditions. Electrochemical measurements confirmed this difference in the oxidation behavior, in which the nature of the coordination governs the ease of oxidative dehydrogenation.

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