Crystal structure of a third polymorph of tris(acetylacetonato-κ 2 O , O ′)iron(III)

In the structure of the title complex, [Fe(C 5 H 7 O 2 ) 3 ] or Fe(acac) 3 , the asymmetric unit contains one molecule in a general position. The coordination sphere of the Fe III atom is that of a slightly distorted octahedron. The crystal under investigation was a two-component pseudo-merohedral twin in the monoclinic system with a β angle close to 90°. Twin law [100/0-10/00-1] reduced the R 1 residual [ I > 2 σ ( I )] from 0.0769 to 0.0312, and the mass ratio of twin components refined to 0.8913 (5):0.1087 (5). In the crystal, molecules are arranged in sheets normal to [001] via non-classical C—H...O hydrogen bonding. No other significant intermolecular interactions are observed. The structure is a new polymorph of Fe(acac) 3 and is isotypic with one polymorph of its gallium analog.