A diamagnetic dititanium(III) paddlewheel complex with no direct metal-metal bond

Reaction of Ti[N(But)Ar]3 (Ar = 3,5-C6H3Me2 or Ar' = C6H5) with CO2 at -40 degrees C produces diamagmetic Ti(III) paddlewheel complexes with long Ti-Ti separations (>3.4 Angstrom), thus excluding direct Ti-Ti bonding. 1H NMR spectroscopy shows that the compounds are diamagnetic in solution in the temperature range of -65 to +70 degrees C. In the solid state, the diamagnetism was found to persist between 2 and 300 K. Calculations at the density functional theory level suggest that the diamagnetism results from antiferromagnetic coupling by superexchange through the ligand pi system.