From monomeric to polymeric manganese complexes bearing bis(imino)pyridine and related ligands

Reactions of MnX2 with the tridentate nitrogen donor ligands [2,6-{(2,4,6-Me3C6H2)N=CMe}(2)C5H3N], [2,6-{( Me) (Ph)NN=CMe}(2)C5H3N] and [2-{(2,6-(Pr2C6H3)-C-i)N=CH}-6-{(2,6-(Pr2C6H3)-C-i)NHCH(Me)}C5H3N] in refluxing acetonitrile yield the high spin divalent monometallic manganese complexes, [2,6-{(2,4,6-Me3C6H2)NN=Me}(2)C5H3N] MnX2 (X = Br 1), [2,6-{(Me)(Ph)NN=CMe}(2) C5H3N]MnX2 (X = Cl-2) and [2-{(2,6-(Pr2C6H3)-C-i)N=CH}-6-{(2,6-(Pr2C6H3)-C-i)NHCH(Me)}C5H3N]MnX2 (X = Cl-3), respectively, in good yield. Crystallographic studies on 1-3 reveal all three complexes to be pentacoordinate with geometries that can be best described as distorted trigonal bipyramidal (1, 2) or square pyramidal (3). Conversely, treatment of MnCl2 with [2-{(2"-H2NC6H4-C2H4-2"-C6H4)N=CMe}-6-{O=CMe}C5H3N] (prepared from the incomplete condensation reaction of the diamine [{2,2"-(NH2)C6H4}(2)(CH2CH2)] with 2,6- diacetylpyridine) under similar reaction conditions results in self-assembly to afford the antiferromagnetically coupled polymetallic salt[{2,6-{(2',2"-C6H4-CH2)(2)(N=CMe)(2)}(2)(C5H3N)(2)}Mn2Cl3 (NCMe)(2)][{2,6-{(2', 2"-C6H4-CH2)(2)(N=CMe)(2)}(2) (C5H3N)(2)}Mn2Cl3(MnCl4)](n) (4). The molecular structure of 4 shows a discrete dimanganese cation and polymeric manganese anion with each ionic unit supported by a 26-membered macrocyclic hexadentate nitrogen donor ligand.