Ruthenium(II) complexes containing 2-pyridineformamide- and 2-benzoylpyridine-derived thiosemicarbazones and PPh3: NMR and electrochemical studies of cis–trans-isomerization

[RuCl(L)(PPh3)2] complexes with 2-benzoylpyridine- and 2-pyridineformamide-derived thiosemicarbazones (HL) were obtained and fully characterized. The complexes form cis–trans isomers. The cis isomer is disfavored by the sterical effect of two bulky groups close to each other whereas the trans isomer is disfavored by the electronic effect of competition of two phosphorous for π-bonding d orbitals of the metal. Our results suggest that, although both factors may be operating simultaneously, in CH2Cl2 solution the balance of these counterpoising effects favors the formation of the trans isomer.