IN3TI2BR9 - JAHN-TELLER UNSTABLE INDIUM(I) AND ANTIFERROMAGNETICALLY COUPLED TITANIUM(III) ATOMS

Dark green crystals of In3Ti2Br9 have been synthesized from elemental Ti and molten InBr3 at 450 degrees C, The X-ray diffractional characte rization by means of single-crystal and powder Rietveld refinement rev eals a hexagonal crystal structure (a = 738.2(2), c = 1813.9(3) pm; P6 (3)/mmc, Z = 2) of Cs3Cr2Cl9 type, containing Ti2Br93- dimers and univ alent indium cations. Self-consistent, semiempirical band structure ca lculations show the structural distortions of the two monovalent indiu m cations to arise from a second-order Jahn-Teller instability. The ne w compound's magnetic susceptibility and microscopic antiferromagnetic exchange are analyzed by using a Bleaney-Bowers ansatz.