The first examples of nitrobenzoate coordinated ruthenium(II) organometallics: reaction conditions driven product formation

The homogeneous phase reaction of [Ru(η²-RL)(PPh₃)₂(CO)(Cl)] (1) [η²-RL is C₆H₂O-2-CHNHC₆H₄R(p)-3-Me-5 and R is OMe, Cl] with the sodium salts of p-nitrobenzoic acid [NaPNB] and m-nitrobenzoic acid [NaMNB] afforded the complexes of the type [Ru(η¹-RL)(PPh₃)₂(CO)(PNB)] (2(R)) and [Ru(η¹-RL)(PPh₃)₂(CO)(MNB)] (3(R)) respectively in excellent yield [η¹-RL is C₆H₂OH-2-CHNC₆H₄R(p)-3-Me-5]. When 1 was reacted with the nitrobenzoic acid instead of their sodium salt, the Ru─C(aryl) bond cleavage products [Ru(PPh₃)₂(CO)(Cl)(PNB)] (4) and [Ru(PPh₃)₂(CO)(Cl)(MNB)] (5) were obtained. The spectral (UV–vis, IR, NMR) and electrochemical data of the complexes are reported. In dichloromethane solution the type 2(R) and 3(R) complexes display two successive quasi-reversible one electron oxidation processes whereas the complexes 4 and 5 display only one oxidation process. The crystal structures of [Ru(η¹-ClL)(PPh₃)₂(CO)(MNB)] (3(Cl)) and [Ru(PPh₃)₂(CO)(Cl)(MNB)] (5) are reported, which revealed a distorted octahedral RuP₂C₂O₂ coordination sphere for 3(Cl) and RuP₂CO₂Cl coordination sphere for 5. The electronic structure and absorption spectra of the complexes are scrutinized by DFT and TD-DFT analyses. The complex 3(Cl) was tested for its ability to exhibit DNA-binding activity.