PRODUCTS FROM REACTIONS OF [MN2O2(O2CCH3)(TPEN)]2+ IN ACIDIC AND NEUTRAL AQUEOUS-MEDIA - [MN2(MU-O)2(MU-O2CCH3)(TPEN)]3+ AND [(MN3(MU-O)4(OH)(TPEN))2(MU-TPEN)]6+

The mixed-valence compound [Mn2(mu-O)2(mu-O2CCH3)(tpen)](ClO4)2-3H2O (2.3H2O) reacts to form [Mn2(mu-O)2(mu-O2CCH3)(tpen)](ClO4)3 (3) is acidic aqueous solution and in contrast is converted to [{Mn3(mu-O)4(OH)-(tpen)12(mu-tpen)](ClO4)6-4H2O (4-4H2O) in distilled water (tpen is N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethanediamine). Both reactions were carried out in the presence of a large excess of perchlorate counterion. Syntheses, structures, and selected properties of 3 and 4 are reported. Compound 3 crystallizes as 3.CH3CN from a solution of CH3CN and C6H5CH3 (2:1) in the space group P1BAR with a = 14.733 (3) angstrom, b = 14.815 (2) angstrom, c = 18.157 (2) angstrom, alpha = 85.392 (11)-degrees, beta = 80.014 (15)-degrees, gamma = 75.572 (14)-degrees, V = 3777.2 (1) angstrom3, and Z = 4. Structural parameters for 3 are consistent with both manganese ions being in the 4+ oxidation state. The cyclic voltammogram of 3 in CH3CN exhibits IV,IV/IV,III and IV,III/III,III reductions at +0.90 and -0.13 V, respectively, vsSSCE. Compound 4 crystallizes as 4.8CH3CN from CH3CN-C6H5CH3 (1: 1) in the space group P1BAR with a = 15.298 (8) angstrom, b = 15.391 (4) angstrom, c = 15.382 (4) angstrom, alpha = 114.80 (2)-degrees, beta = 115.09 (3)-degrees, gamma = 93.98 (3)-degrees, V = 2839.6 (6) angstrom3, Z = 1. The cation in 4 resides on an inversion center. Bond distances and angles in 4 confirm that all Mn atoms are in the +4 oxidation state. The structure of 4 consists of two {Mn3O4}4+ units linked by one tpen moiety. The {Mn3O4}4+ cores in 4 are distorted in a manner that is reminiscent of [Mn3O4(OH)(bpea)3]3+ (J. Am. Chem. Soc. 1992, 114, 6398-6406). The cyclic voltammogram of 4 in CH3CN displays two irreversible reduction responses at +0.10 and -0.27 V vs SSCE. The EPR spectrum of 4.4H2O in frozen CH3CN-C6H5CH3 is consistent with an S = 3/2 ground-state origin. Both 3 and 4.4H2O were also characterized by infrared and electronic spectral measurements.