A series of heteroleptic complexes of the type fac-[Mn^IIIL₂]^- [H₂L=derivatives of N-(2-hydroxybenzyl)glycine or N-(5-nitro-2-hydroxybenzyl)sarcosine] possessing unusual Mn(III) co-ordination spheres

The mononuclear manganese(III) complexes [C₅H₁₀NH₂][MnL₂] [L^2-=a substituted N-(2-hydroxybenzyl)glycinate (hbg^2-) viz. 3,5-dibromo- (3,5-Br-hbg^2-), 3,5-dichloro- (3,5-Cl-hbg^2-), 3-methyl-5-chloro- (3,5-Me,Cl-hbg^2-), 5-bromo- (5-Br-hbg^2-), 5-chloro- (5-Cl-hbg^2-), 5-nitro- (5-NO₂-hbg^2-) or N-(5-nitro-2-hydroxybenzyl)sarcosine (5-NO₂-hbs^2-)] have been synthesised by reaction of the appropriate ligand with manganese(II) perchlorate under ambient conditions in a 2:1 molar ratio using piperidine as base. The structures of three of these complexes, [C₅H₁₀NH₂][Mn(3,5-Cl-hbg)₂] (2), [C₅H₁₀NH₂][Mn(5-NO₂-hbg) ₂] (6) and [C₅H₁₀NH₂][Mn(5-NO₂-hbs) ₂] (7) have been elucidated by single-crystal X-ray crystallography and each displays two similar, independent [MnL₂]^- ions in the asymmetric unit linked via piperidinium cations through hydrogen bonding. The ligands co-ordinate in a facial tridentate fashion with the three donor atoms being the phenolate and carboxylate oxygens and the amine nitrogen. The geometry at the Mn centres is compressed rhombic octahedral consistent with a pseudo-Jahn-Teller compression along the Mn-O(phenolate) axis. Mean bond lengths are in the ranges 1.886-1.889 Å for the Mn-O(phenolate), 2.062-2.125 Å for the Mn-O(carboxylate) and 2.091-2.184 Å for the Mn-N(amine) distances. The magnetic susceptibility and electronic and IR spectroscopic data are discussed with reference to the crystal structures.