INFEBR3 AND INMNBR3 - SYNTHESIS, CRYSTAL-STRUCTURE, MAGNETIC-PROPERTIES, AND ELECTRONIC STRUCTURE

Yellow and pink crystals of InFeBr3 and InMnBr3, the first structurall y characterized transition metal bromides containing univalent indium, are synthesized from elemental Fe/Mn and molten InBr3. The orthorhomb ic crystal structures (InFeBr3: a = 934.81(9) pm, b = 394.35(4) pm, c = 1514.1(2) pm; InMnBr3: a = 943.1(1) pm, b = 398.95(4) pm, c = 1535.3 (2) pm; Pnma, Z = 4) are isotypic with NH4CdCl3. While the transition metals cations are octahedrally coordinated by Br- anions, monovalent indium cations are found in strongly distorted trigonal Br- prisms whi ch are tricapped by additional Br- anions. InFeBr3 and InMnBr3 show Cu rie-Weiss paramagnetism whereas only InFeBr3 exhibits antiferromagneti c ordering below 15 K. Semiempirical band structure calculations (CSC- EH-TB) reflect strongly covalent contributions to In+-Br- bonding, exc eeding those interactions found in the binary In/Br crystal chemical s ystem. Moreover, there is weak In+-In+ bonding between neighboring uni t cells. Valence charge density plots based on ab initio band structur e computations (TB-LMTO-ASA) disprove the existence of a directional e lectron ''lone-pair'' centered on monovalent In.