REACTION OF THE SCHIFF-BASE COMPLEXES (X-SALPRN)MN(II) [X = H, 5-CL, 5-CH3O SALPRN = 1,3-BIS(SALICYLIDENEAMINO)PROPANE] WITH DIOXYGEN AND REACTIVITY OF THE OXYGENATED PRODUCTS

The Schiff-base complexes (X-SALPRN)Mn(II) [X = H, 5-Cl, 5-CH3O; SALPRN = 1,3-bis(salicylidencamino)propane] were reacted with dioxygen in CH3CN and CH2Cl2. Mn(IV), Mn(IV) bis(mu-oxo) dimers [(X-SALPRN)Mn(IV)(mu-O)]2 [X - H (1), 5-Cl (2), 5-CH3O (3)] were isolated in high yields and as the sole products from oxygenation in CH3CN, but two products were isolated when the oxygenation was performed in CH2Cl2. One product was the bis(mu-oxo) dimer, while the second was a green compound formulated as {[(X-SALPRN)Mn(III)]2O}x, where x = 1 or 2 [X - H (4), 5-Cl (5), 5-CH3O (6)]. These green compounds formed by reaction of 1-3 with its appropriate Mn(II) complex in a 1:2 ratio. The bis(mu-oxo) dimers each exhibited a single, reversible one-electron couple E-degrees-1 = -480 mV, E-degrees-2 = -340 mV, and E-degrees-3 = -590 mV all vs SSCE. All of the green compounds exhibited two redox processes, both of which were multielectron transfer reactions. The ESR spectrum of a frozen solution of the mixed-valence form of 1 observed at 6 K showed the presence of an antiferromagnetically coupled S = 1/2 system with the following best fit parameters: g(x) = 2.0092, g(y) = 2.006 1, g(z) = 1.9925; A1x = 492 MHz, A1y = 448 MHz, A1z - 385 MHz, A2x = 231 MHz, A2y = 227 MHz, A2z = 209 MHz. A complete intermetal oxygen atom transfer reaction for compound 4 was observed to occur with (SALEN)Fe(II) [SALEN = 1,2-bis(salicylideneamino)ethane] resulting in formation of the (SALPRN)Mn(II) and [(SALEN)Fe(III)]2(mu-O) (7), both in quantitative yield.