Geometrical variations of two manganese(II) complexes with closely related quinoline-based tripodal ligands.

Structural analyses of the compounds di-μ-acetato-κ ⁴ O : O '-bis-{[2-meth-oxy- N , N -bis-(quinolin-2-ylmeth-yl)ethanamine-κ ⁴ N , N ', N '', O ]manganese(II)} bis-(tetra-phen-yl-borate) di-chloro-methane 1.45-solvate, [Mn ₂ (C ₂₃ O ₂ ) ₂ (C ₂₃ H ₂₃ N ₃ O) ₂ ](C ₂₄ H ₂₀ B)·1.45CH ₂ Cl ₂ or [Mn(DQMEA)(μ-OAc) ₂ Mn(DQMEA)](BPh ₄ ) ₂ ·1.45CH ₂ Cl ₂ or [1] (BPh ₄ ) ₂ ·1.45CH ₂ Cl ₂ , and (acetato-κ O )[2-hy-droxy- N , N -bis(quinolin-2-ylmeth-yl)ethanamine-κ ⁴ N , N ', N '', O ](methanol-κ O )manganese(II) tetra-phenyl-borate methanol monosolvate, [Mn(CH ₃ COO)(C ₂₂ H ₂₁ N ₃ O)(CH ₃ OH)](C ₂₄ H ₂₀ B)·CH ₃ OH or [Mn(DQEA)(OAc)(CH ₃ OH)]BPh ₄ ·CH ₃ OH or [2] BPh ₄ ·CH ₃ OH, by single-crystal X-ray diffraction reveal distinct differences in the geometry of coordination of the tripodal DQEA and DQMEA ligands to Mn ^II ions. In the asymmetric unit, compound [1] (BPh ₄ ) ₂ ·(CH ₂ Cl ₂ ) _1.45 crystallizes as a dimer in which each manganese(II) center is coordinated by the central amine nitro-gen, the nitro-gen atom of each quinoline group, and the meth-oxy-oxygen of the tetra-dentate DQMEA ligand, and two bridging-acetate oxygen atoms. The symmetric Mn ^II centers have a distorted, octa-hedral geometry in which the quinoline nitro-gen atoms are trans to each other resulting in co-planarity of the quinoline rings. For each Mn ^II center, a coordinated acetate oxygen participates in C-H⋯O hydrogen-bonding inter-actions with the two quinolyl moieties, further stabilizing the trans structure. Within the crystal, weak π - π stacking inter-actions and inter-molecular cation-anion inter-actions stabilize the crystal packing. In the asymmetric unit, compound [2] BPh ₄ ·CH ₃ OH crystallizes as a monomer in which the manganese(II) ion is coordinated to the central nitro-gen, the nitro-gen atom of each quinoline group, and the alcohol oxygen of the tetra-dentate DQEA ligand, an oxygen atom of OAc, and the oxygen atom of a methanol ligand. The geometry of the Mn ^II center in [2] BPh ₄ ·CH ₃ OH is also a distorted octa-hedron, but the quinoline nitro-gen atoms are cis to each other in this structure. Hydrogen bonding between the acetate oxygen atoms and hydroxyl (O-H⋯O) and quinolyl (C-H⋯O and N-H⋯O) moieties of the DQEA ligand stabilize the complex in this cis configuration. Within the crystal, dimerization of complexes occurs by the formation of a pair of inter-molecular O3-H3⋯O2 hydrogen bonds between the coordinated hydroxyl oxygen of the DQEA ligand of one complex and an acetate oxygen of another. Additional hydrogen-bonding and inter-molecular cation-anion inter-actions contribute to the crystal packing.
(© Frey et al. 2021.)