Crystal Structure of (CH3CH2CH2NH3)2MnCl4

The crystal structure of (CH₃CH₂CH₂NH₃)₂MnCl₄ has been determined by Weissenberg single crystal diffraction techniques. The crystals are orthorhombic, space group Cmca, with $\text{a=7.29\hspace{0.17em} Å, b=25.94\hspace{0.17em}Å}$ , and $\text{c=7.51\hspace{0.17em}Å}$ . Least squares refinement with anisotropic temperature factors yielded a final R value of 0.116. The outstanding feature of the structure is the existence of a two‐dimensional metal—halogen framework formed by MnCl₆ octahedra sharing corners. Each metal—halogen sheet is ``sandwiched'' between layers of propylammonium ions, thus effectively isolating it from adjacent sheets. This provides an exciting new class of compounds for studying two‐dimensional magnetic interactions. The coordination sphere around the Mn(II) ion has approximately D<sub>4h</sub> symmetry with two $\mathrm{Mn}–\mathrm{Cl}$ bond lengths of 2.475 Å and four bond lengths of 2.629 Å. Existence of $\mathrm{N}–\mathrm{H}\mathrm{···}\mathrm{Cl}$ hydrogen bonds cause the four‐fold axis of the distorted octahedra to be tipped 8.0° away from the crystallographic b axis. This produces a ``washboard'' effect when each metal—halogen sheet is viewed from the $\text{〈 100 〉}$ direction and leads to nonlinear $\mathrm{Mn}–\mathrm{Cl}–\mathrm{Mn}$ bridges. A comparison with the structure of the corresponding copper(II) salts is made.