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

Abstract

Reactions of MnX2 with the tridentate nitrogen donor ligands [2,6-{(2,4,6-Me3C6H2)NCMe}2C5H3N], [2,6-{(Me)(Ph)NNCMe}2C5H3N] and [2-{(2,6-Pri2C6H3)NCH}-6-{(2,6-Pri2C6H3)NHCH(Me)}C5H3N] in refluxing acetonitrile yield the high spin divalent monometallic manganese complexes, [2,6-{(2,4,6-Me3C6H2)NCMe}2C5H3N]MnX2 (X = Br 1), [2,6-{(Me)(Ph)NNCMe}2C5H3N]MnX2 (X = Cl 2) and [2-{(2,6-Pri2C6H3)NCH}-6-{(2,6-Pri2C6H3)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)NCMe}-6-{OCMe}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(NCMe)2}2(C5H3N)2}Mn2Cl3(NCMe)2][{2,6-{(2′,2″-C6H4–CH2)2(NCMe)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.