A study of the oxygenation of some manganese (II) tetradentate schiff base complexes

Manganese(II) complexes formed by the reaction of either salicylaldehyde or 5-chlorosalicylaldehyde and 1,4-diaminobutane (SALBTDA), 1,6-diaminohexane (SALHXDA), 1,8- diaminooctane (SALOTDA), and 1,10- diaminodecane (SALDCDA) have been isolated. The complexes Mn(SALHXDA), Mn(SALOTDA), and Mn(SALDCDA) rapidly darken upon exposure to air. Mn(SALBTDA), Mn(5C1SALHXDA), Mn(5C1SALHTDA), and Mn(5C1SALOTDA) are stable in air when dry. When suspended in DMSO all complexes, with the exception of Mn(SALBTDA), react with oxygen to form Mn(IV) complexes. All of the complexes react with oxygen when in solution.

The rates of oxygenation of the complexes were studied in the solid state, as DMSO suspensions, and in pyridine solution. A two step oxygenation with a proposed manganese(III) intermediate was observed for all complexes in all systems. These results have been correllated with oxygenations of Mn(SALEN), Mn(SALTM), Mn(SALPTDA), and Mn(SALHTDA) from the reaction of salicylaldehyde with ethylenediamine, 1,3-diaminopropane, 1,5-diaminopentane, and l,7-diaminoheptane, respectively. The structure of the oxygenated complexes are prpposed to be polymeric with μ dioxo bridges between manganese atoms.