fac-/mer-[RuCl3(NO)(P–N)] (P–N = [o-(N,N-dimethylamino)phenyl]diphenylphosphine): Synthesis, characterization and DFT calculations

Complex fac-[RuCl3(NO)(P–N)] (1) was synthesized from the reaction of [RuCl3(H2O)2(NO)] and the P–N ligand, o-[(N,N-dimethylamino)phenyl]diphenylphosphine) in refluxing methanol solution, while complex mer,trans-[RuCl3(NO)(P–N)] (2) was obtained by photochemical isomerization of (1) in dichloromethane solution. The third possible isomer mer,cis-[RuCl3(NO)(P–N)] (3) was never observed in direct synthesis as well as in photo- or thermal-isomerization reactions. When refluxing a methanol solution of complex (2) a thermally induced isomerization occurs and complex (1) is regenerated.The complexes were characterized by NMR (31P{1H}, 15N{1H} and 1H), cyclic voltammetry, FTIR, UV–Vis, elemental analysis and X-ray diffraction structure determination. The 31P{1H} NMR revealed the presence of singlet at 35.6 for (1) and 28.3 ppm for (2). The 1H NMR spectrum for (1) presented two singlets for the methyl hydrogens at 3.81 and 3.13 ppm, while for (2) was observed only one singlet at 3.29 ppm. FTIR Ru–NO stretching in KBr pellets or CH2Cl2 solution presented 1866 and 1872 cm−1 for (1) and 1841 and 1860 cm−1 for (2). Electrochemical analysis revealed a irreversible reduction attributed to RuII–NO+ → RuII–NO0 at −0.81 V and −0.62 V, for (1) and (2), respectively; the process RuII → RuIII, as expected, is only observed around 2.0 V, for both complexes.Studies were conducted using 15NO and both complexes were isolated with 15N-enriched NO. Upon irradiation, the complex fac-[RuCl3(NO)(P–N)] (1) does not exchange 14NO by 15NO, while complex mer,trans-[RuCl3(NO)(P–N)] (2) does. Complex mer,trans-[RuCl3(15NO)(P–N)] (2′) was obtained by direct reaction of mer,trans-[RuCl3(NO)(P–N)] (2) with 15NO and the complex fac-[RuCl3(15NO)(P–N)] (1′) was obtained by thermal-isomerization of mer,trans-[RuCl3(15NO)(P–N)] (2′).DFT calculation on isomer energies, electronic spectra and electronic configuration were done. For complex (1) the HOMO orbital is essentially Ru (46.6%) and Cl (42.5%), for (2) Ru (57.4%) and Cl (39.0%) while LUMO orbital for (1) is based on NO (52.9%) and is less extent on Ru (38.4%), for (2) NO (58.2%) and Ru (31.5%).

Graphical abstractThe fac-[RuCl3(NO)(P–N)] (1) complex was synthesized from reaction of [RuCl3(H2O)2(NO)] and o-[(N,N-dimethylamino)phenyl]diphenylphosphine) (P–N); the mer, trans-[RuCl3(NO)(P–N)] (2) complex was obtained from isomerization reaction of (1). DFT calculations on isomer energies, electronic spectra and electronic configurations were done.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Two isomers of [RuCl3(NO)(P–N)] were synthesized. ► 15N-enriched nitrosyl complexes were synthesized. ► DFT calculations were carried out to understand the electronic properties. ► The complexes were fully characterized by 31P{1H}, 15N and 1H NMR.