  A previously unreported layered spin 1/2 triangular lattice polymorph of TiI3
is described, synthesized under 6 GPa of applied pressure at 900 C, but stable
at atmospheric pressure. This air-sensitive material has a CdI2-type layered
structure (P-3m1 (#164), a = 4.012 A and c = 6.641 A at 120 K, Z = 1 of
Ti0.667I2) with an in-plane triangular lattice, related to that of TiI4
(Ti0.5I2). Although the TiI3 formula is consistent with expectations for a
layered honeycomb lattice of spin 1/2 Ti(III), there appears to be disorder in
the crystal structure. Magnetic susceptibility and heat capacity measurements
suggest that the material undergoes several low temperature phase transitions.
