Crystal structure of a seven-coordinate manganese(II) complex with tris-(pyridin-2-ylmeth-yl)amine (TMPA)

Structural analysis of (acetato-κ²O,O')(methanol-κO)[tris-(pyridin-2-ylmeth-yl)amine-κ⁴N,N',N'',N''']manganese(II) tetraphenyl-borate, [Mn(C₂H₃O₂)(C₁₈H₁₈N₄)(CH₃OH)](C₂₄H₂₀B) or [Mn(TMPA)(Ac)(CH₃OH)]BPh₄ [TMPA = tris-(pyridin-2-ylmeth-yl)amine, Ac = acetate, BPh₄ = tetra-phenyl-borate] by single-crystal X-ray diffraction reveals a complex cation with tetra-dentate coordination of the tripodal TMPA ligand, bidentate coordination of the Ac ligand and monodentate coordination of the methanol ligand to a single Mn^II center, balanced in charge by the presence of a tetra-phenyl-borate anion. The Mn^II complex has a distorted penta-gonal-bipyramidal geometry, in which the central amine nitro-gen and two pyridyl N atoms of the TMPA ligand, and two oxygen atoms of the acetate ligand occupy positions in the penta-gonal plane, while the third pyridyl nitro-gen of TMPA and the oxygen from the methanol ligand occupy the axial positions. Within the complex, the acetate O atoms participate in weak C-H⋯O hydrogen-bonding inter-actions with neighboring pyridyl moieties. In the crystal, complexes form dimers by pairs of O-H⋯O hydrogen bonds between the coordinated methanol of one complex and an acetate oxygen of the other, and weak π-stacking inter-actions between pyridine rings. Separate dimers then undergo additional π-stacking inter-actions between the pyridine rings of one moiety and either the pyridine or phenyl rings of another moiety that further stabilize the crystal.