Electronic Structures of [Ru-II(cyclam)(Et(2)dtc)](+), [Ru(cyclam)(tdt)](+), and [Ru(cyclam)(tdt)](2+) : An X-ray Absorption Spectroscopic and Computational Study (tdt = toluene-3,4-dithiolate; Et(2)dtc = N,N-diethyldithiocarbamate(1-))

摘要

The reaction of [Ru-III(cyclam)Cl-2]Cl with 2 equiv of sodium N,N-diethyldithiocarbamate in methanol afforded [Ru-II(cyclam)(Et(2)dtc)](BPh4) (1(BPh4)). The same reaction with only 1 equiv of toluene-3,4-dithiol and a base yielded [Ru(cyclam)(tdt)](PF6) (2(PF6)) which was oxidized by 1 equiv of ferrocenium hexafluorophosphate generating [Ru(cyclam)(tdt)](PF6)(2) (2(ox)(PF6)(2)). The crystal structures of 1 and 2 have been determined by X-ray crystallography at 100 K. The electronic structures of diamagnetic 1 (PhO, paramagnetic 2(PF6) (S=1/2), and diamagnetic 2(ox)(PF6)(2) have been studied by magnetochemistry, spectroelectrochemistry, electron paramagnetic resonance spectroscopy, and H-1 NMR spectroscopy. X-ray absorption spectroscopy on Ru K- and L-edges as well as S K-edges has been employed. Finally, the molecular and electronic structures of all three species have been calculated by using density functional theory (B3LYP). It is shown that 2(ox) comprises an electronic structure which is best described by three resonance structures {[Ru-II}(cyclam)(tdt(0))](2+) <-> [Ru-III(cyclam)(tdt center dot)](2+) <-> [Ru-IV(cyclam)(tdt(2-))](2+)} with a closed-shell singlet ground state. This is in stark contrast to the iSOEflectronic iron species, namely, [Fe-III(cyclam)(tdt center dot)](2+) which is a singlet diradical with a low-spin ferric ion coupled intramolecularly antiferromagnetically to a ligand pi radical monoanion (tdt center dot)(-).