DISTORTIONS OF THE COORDINATION POLYHEDRON IN HIGH-SPIN MANGANESE(III) COMPLEXES .2. CRYSTAL-STRUCTURE OF THIOCYANATOBIS(ACETYLACETONATO)MANGANESE(III)

The crystal structure of thiocyanatobis(acetylacetonato)manganese(III), Mn(O2C5H7)2(NCS), has been determined by single-crystal X-ray diffraction techniques and refined anisotropically for all nonhydrogen atoms by full-matrix least-squares techniques to R1 = 0.057 and R2 = 0.061 by using 1917 independent diffractometer-recorded reflections (Nb-filtered Mo Kα radiation and θ-2θ scans) having 2θMOKα < 55° and I > 2σ(I), The compound crystallizes in the uniquely determined centrosymmetric orthorhombic space group Pbca with eight molecules in a unit cell of dimensions a = 13.422 (2) Å, b - 14.519 (3) Å, and c = 13.763 (3) Å (ρcalcd = 1.541 g/cm3, ρobsd = 1.540 g/cm3). Each thiocyanato ligand bridges two adjacent quasi-planar Mn(acac)2+ groups in the three-dimensional lattice by using the glide operator perpendicular to the c axis of the unit cell to generate infinite chains of octahedral Mn(III) subunits along the a axis. The octahedral coordination polyhedron is tetragonally elongated and approximates idealized C4υ, symmetry with the trans-coordinated thiocyanato nitrogen and sulfur atoms on the pseudo-fourfold axis. The four “short” Mn-0 bonds have average lengths of 1.912 (4) Å while the two long trans Mn-N and Mn-S´ bonds to the ends of bridging thiocyanato ligands have lengths of 2.189 (5) and 2.880 (2) Å, respectively. The dissimilarity of the two ends of the thiocyanato ligand has a pronounced effect on the Mn coordination geometry in this complex. The Mn atom is displaced by 0.12 A from the mean plane of the quasi-square of four coordinated oxygen atoms toward the coordinated thiocyanato nitrogen atom. © 1979, American Chemical Society. All rights reserved.