STRUCTURALLY DIVERSE MANGANESE(III) SCHIFF-BASE COMPLEXES - CHAINS, DIMERS, AND CAGES

Abstract

Manganese(III) forms a rich variety of complexes with the dianion of the Schiff base ligand N,N′-disalicylidene-2-hydroxypropylenediamine (2-OH-SALPN) and its ring-substituted derivatives. Single crystals of [Mn(2-OH-SALPN)OAc] n (1) are isolated when manganese(III) acetate is reacted with 2-OH-SALPN, in DMF. This infinite chain shows an anti-anti configuration for the bridging acetates. When 1 is dissolved in methanol and 1 equiv of NaOH is added, a dinuclear [Mn III 2(2-OH-SALPN) 2(CH 3OH)]·CH 3OH complex, 3, is isolated. X-ray analysis of crystals of the 5-chloro-2-OH-SALPN derivative 4 show this compound to be a monoalkoxy-bridged species with the longest Mn(III)-Mn(III) separation (3.808 A) yet observed for a discrete single-atom-bridged dimer. If NaOMe is used as a base rather than NaOH, the first example of a totally encapsulated tetrakis(phenolato)-bis(acetato)-caged sodium cation, 5, is isolated. Two Mn III(2-OH-SALPN) units are linked by this sodium ion, forming a bimetallic, trinuclear cluster. The variable-temperature magnetic behavior of these materials shows that spin exchange between the manganese ions is weak or nonexistent [1, J = -1.72 cm -1 and g = 1.97; 4, J = -3.55 cm -1 and g = 1.95; 5, follows Curie-Weiss law behavior with no evident spin exchange between Mn(III) ions (g ∥ = 2.00, g ⊥ = 2.05, D = -6.13 cm -1)]. X-ray crystallographic parameters: 1, C 19H 19N 2O 5Mn, mol wt 410.3, orthorhombic crystal system (Pnma), a = 6.528 (4) A, b = 16.827 (6) A, c= 16.754 (6) A, V = 1840 (1) A 3, Z = 4, 2054 data collected with 0° < 2θ < 50°, 1180 data with I > 3σ(I), R = 0.057, R w = 0.057; 4, C 36H 34N 4O 8Mn 2Cl 4, mol wt 900, monoclinic crystal system (P2 1/c), a = 10.944 (2) A, b = 23.275 (5) A, c = 16.047 (2) A, β = 99.29 (1)°, V = 4034 (1) A 3, Z = 4, 5315 data collected with 0° < 2θ < 45°, 3247 data with I > 2σ(I), R = 0.057, R w = 0.045; 5, C 44H 55N 4O 18Mn 2Na, mol wt 1060, triclinic crystal system (P1), a = 9.434 (5) A, b = 10.436 (4) A, c = 12.758 (8) A, α = 94.42 (4)°, β = 105.50 (4)°, γ = 91.50 (4)°, V = 1205 (1) A 3, Z = 1, 3174 data collected with 0° < 2θ < 45°, 2445 data with I > 3σ(I), R = 0.068, R w = 0.068.