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

Reaction of Ti[N(Bu-t) 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. H-1 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.