Manganese(II) chloride complexes with pyridine N-oxide (PNO) derivatives and their solid-state structures

Three manganese(II) N-oxide complexes have been synthesized from the reaction of manganese(II) chloride with either pyridine N-oxide (PNO), 2-methyl-pyridine N-oxide (2MePNO) or 3-methyl-pyridine N-oxide (3MePNO). The compounds were synthesized from methano-lic solutions of MnCl₂·4H₂O and the respective N-oxide, and subsequently characterized structurally by single-crystal X-ray diffraction. The compounds are catena-poly[[aqua-chlorido-manganese(II)]-di-μ-chlorido-[aqua-chlorido-manganese(II)]-bis-(μ-pyridine N-oxide)], [MnCl₂(C₅H₅NO)(H₂O)] or [MnCl₂(PNO)(H₂O)] (I), catena-poly[[aqua-chlorido-man-gan-ese(II)]-di-μ-chlorido-[aqua-chlorido-manganese(II)]-bis-(μ-2-methyl-pyridine N-oxide)], [MnCl₂(C₆H₇NO)(H₂O)] or [MnCl₂(2MePNO)(H₂O)] (II), and bis-(μ-3-methyl-pyridine N-oxide)bis-[di-aqua-dichlorido-manganese(II)], [Mn₂Cl₄(C₆H₇NO)₂(H₂O)₄] or [MnCl₂(3MePNO)(H₂O)₂]₂ (III). The Mn^II atoms are found in pseudo-octa-hedral environments for each of the three complexes. Compound I forms a coordination polymer with alternating pairs of bridging N-oxide and chloride ligands. The coordination environment is defined by two PNO bridging O atoms, two chloride bridging atoms, a terminal chloride, and a terminal water. Compound II also forms a coordination polymer with a similar metal cation; however, the coordination polymer is bridged between Mn^II atoms by both a single chloride and 2MePNO. The distorted octahedrally coordinated metal cation is defined by two bridging 2MePNO trans to each other, two chlorides, also trans to one another in the equatorial (polymeric) plane, and a terminal chloride and terminal water. Finally, complex III forms a dimer with two bridging 3MePNOs, two terminal chlorides and two terminal waters forming the six-coordinate metal environment. All three compounds exhibit hydrogen bonding between the coordinating water(s) and terminal chlorides.