Redetermination of bis(acetylacetonato-κ2 O,O′)(1,10-phenanthroline-κ2 N,N′)manganese(II)

In the crystal structure of the title compound, [Mn(C5H7O2)2(C12H8N2)], the Mn2+ cation is coordinated by one bidentate 1,10-phenanthroline ligand and two acetylacetonate anions within a slightly distorted N2O4 octahedron. The asymmetric unit consists of one Mn2+ cation situated on a twofold rotation axis, one half of a 1,10-phenanthroline ligand and one acetylacetonate anion. In comparison with the previous determination based on visually estimated intensities recorded on precession photographs, the current redetermination with image-plate data reveals bond lengths and angles with much higher precision.

In the crystal structure of the title compound, [Mn(C 5 H 7 O 2 ) 2 -(C 12 H 8 N 2 )], the Mn 2+ cation is coordinated by one bidentate 1,10-phenanthroline ligand and two acetylacetonate anions within a slightly distorted N 2 O 4 octahedron. The asymmetric unit consists of one Mn 2+ cation situated on a twofold rotation axis, one half of a 1,10-phenanthroline ligand and one acetylacetonate anion. In comparison with the previous determination based on visually estimated intensities recorded on precession photographs, the current redetermination with image-plate data reveals bond lengths and angles with much higher precision.

Related literature
For the previous determination of the crystal structure, see: Stephens (1977).

Comment
The title compound was serendipitously obtained within a project on the synthesis of manganese(III) coordination polymers containing cyanate anions and neutral N-donor co-ligands. Within this project manganese(III) acetylacetonate was reacted with 1,10-phenanthroline and potassium cyanate in acetonitrile leading to the formation of crystals of the title compound, the composition of which was determined by X-ray structure analysis. The crystal structure of this compound has already been reported by Stephens (1977) from visually estimated intensity data recorded on precession photographs.
We decided to redetermine the structure on basis of image plate intensity data to achieve higher precision with respect to lattice parameters, atomic coordinates and resulting bond lengths and angles.
The manganese(II) cation is coordinated by two nitrogen atoms of the 1,10-phenanthroline ligand and four oxygen atoms of two symmetry-related acetylacetonate anions into discrete complexes that are located on twofold rotation axes ( Fig. 1). The coordination polyhedron of the manganese(II) cation can be described as a slightly distorted MnN 4 O 2 octahedron. Bond lengths and angles are comparable to those of the previous determination (Stephens, 1977), however with much higher precision, e.g. 2.2962 (18) Å for the Mn-N, and 2.1139 (16) and 2.1543 (16) Å for the two Mn-O bond lengths determined during the present redetermination versus 2.307 (5), 2.116 (5) and 2.152 (5) Å, respectively, of the previous determination.
Individual complex molecules are mainly held together by van der Waals forces. In the crystal structure, the discrete complexes are arranged in columns extending parallel to [001] (Fig. 2). Within these columns neighbouring complexes are related by centers of inversion.

Experimental
Manganese(III) 2,4-pentadionate and 1,10-phenanthroline were purchased from Alfa Aesar. Potassium cyanate was purchased from Fluka. The title compound was obtained by the reaction of 70.5 mg Mn(III) 2,4-pentadionate (0.20 mmol), 48.7 mg potassium cyanate (0.6 mmol) and 144.32 mg 1,10-phenanthroline (0.8 mmol) in 1.5 ml acetonitrile at RT in a closed 3 ml snap cap vial. After three days brown crystals of the title compound, mostly in the form of needles, were obtained by slow evaporation of the solvent.

Figure 1
The molecular structure of the title compound with labelling and displacement ellipsoids drawn at the 50% probability  The crystal structure of the title compound in a projection along [001]. -κ 2 O,O′)(1,10-phenanthroline-κ 2 N,N′)

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.