Bisaryl Diruthenium(III) Paddlewheel Complexes: Synthesis and Characterization

Aryls represent a class of both sigma- and pi-donating electron-rich axial ligands that is underexplored in the field of metal-metal multiply bonded paddlewheel species. By a decrease in the steric bulk around the diruthenium axial sites and an increase in the basicity of the bridging ligands, the first examples of bisaryl diruthenium(III) paddlewheel complexes have been isolated. Compounds of the form Ru-2(DMBA)(4)Ar-2 (DMBA = N,N'-dimethylbenzamidinate, Ar = C6H4-4-Bu-t (1), C6H5 (2), C6H3-3,5-(OCH3)(2) (3)) were synthesized via a lithium-halogen exchange reaction between Ru-2(DMBA)(4)Cl-2 and excess LiAr and characterized using mass spectrometry, electronic absorption spectroscopy, cyclic and differential pulse voltammetry, and H-1 NMR spectroscopy. The molecular structures of compounds 1-3 were established using single-crystal X-ray diffraction analysis and their electronic structures (both ground and excited state) analyzed using density functional theory calculations.