Synthesis of the Mn(II) hexafluoroacetylacetonate adduct with 4-cyanopyridine N-oxide: Crystal structure of the complex [Mn 2(Hfa)4(μ-Cpo)(H2O)2]

The synthesis of the mixed-ligand complex [Mn(Hfa)2(Cpo)] (Hfa is hexafluoroacetylacetonate anion, Cpo is 4-cyanopyridine N-oxide) is described. The crystal structure of the complex [Mn2(Hfa) 4(μ-Cpo)(H2O)2] (I) prepared by slow crystallization of a solution of [Mn(Hfa)2(Cpo)] in chloroform is determined by X-ray diffraction. Crystals of I are monoclinic: a = 21.88(2) Å, b = 8.012(9) Å, c = 22.74(2) Å, β = 92.18(7)°, V = 3983(6) Å3, Z = 4, space group C2/c, R = 0.094 for 1448 reflections. A molecule of I has a dimeric structure; two Mn atoms are linked by the bridging Cpo ligand. The coordination polyhedra of both metal atoms are distorted octahedra; their conventional equatorial planes are formed by four oxygen atoms of two bidentate hexafluoroacetylacetonate ligands (average Mn-O 2.142(7) Å). The axial positions of one Mn atom are occupied by the oxygen atoms of the water molecule and Cpo ligand, and the axial positions of the second Mn atom are occupied by the oxygen atom of the water molecule and the nitrogen atom of the cyano group of the Cpo ligand; Mn-O(H2O) 2.158(9) Å, Mn-O,N(Cpo) 2.23(1) Å. The structure contains two disordered molecules of I with opposite orientations of the Cpo ligand; their superposition results in the appearance of the statistical inversion center and, hence, in the central symmetry of the dimer.