Products from Reactions of [Mn < inf > 2 < /inf > O < inf > 2 < /inf > (O < inf > 2 < /inf > CCH < inf > 3 < /inf > )(tpen)] < sup > 2+ < /sup > in Acidic and Neutral Aqueous Media: [Mn < inf > 2 < /inf > (µ-O) < inf > 2 < /inf > (µ-O < inf > 2 < /inf > CCH < inf > 3 < /inf > )(tpen)] < sup > 3+ < /sup > and [{Mn < inf > 3 < /inf > (µ-O)4(OH)(tpen)} < inf > 2 < /inf > (µ-tpen)] < sup > 6+ < /sup >

Abstract

The mixed-valence compound [Mn2(µ-O)2(µ-O2CCH3)(tpen)](ClO4)2∙3H2O (2∙3H2O) reacts to form [Mn2(µ-O)2(µ-O2CCH3)(tpen)](ClO4)3(3) is acidic aqueous solution and in contrast is converted to [{Mn3(µ-O)4(OH)-(tpen)}2(µ-tpen)](ClO4)6∙4H2O (4∙4H20) in distilled water (tpen is N, N, Nʹ,Nʹ-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 P1 with a = 14.733 (3) Å, b = 14.815 (2) Å, c = 18.157 (2) Å, α = 85.392 (11)°, β = 80.014 (15)°, γ = 75.572 (14)°, V = 3777.2 (1) Å3, 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, vs SSCE. Compound 4 crystallizes as 4.8CH3CN from CH3CN-C6H5CH3(1:1) in the space group P1 with a = 15.298 (8) Å,b = 15.391 (4) Å, c = 15.382 (4) Å, α = 114.80 (2)°, α = 115.09 (3)°, α = 93.98 (3)°, V= 2839.6 (6) Å3, 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 44H2O in frozen CH3CN-C6H5CH3is consistent with an S = 3/2ground-state origin. Both 3 and 4∙4H2O were also characterized by infrared and electronic spectral measurements. © 1992, American Chemical Society. All rights reserved.