Fac-/mer-[RuCl_3(NO)(P-N)] (P-N = [o-(N,N-dimethylamino)phenyl] diphenylphosphine): Synthesis, characterization and DFT calculations

摘要

Complex fac-[RuCl_3(NO)(P-N)] (1) was synthesized from the reaction of [RuCl_3(H_2O)_2(NO)] and the P-N ligand, o-[(N,N-dimethylamino)phenyl]diphenylphosphine) in refluxing methanol solution, while complex mer,trans-[RuCl_3(NO)(P-N)] (2) was obtained by photochemical isomerization of (1) in dichloromethane solution. The third possible isomer mer,cis-[RuCl_3(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 (~(31)P{~1H}, ~(15)N{~1H} and ~1H), cyclic voltammetry, FTIR, UV-Vis, elemental analysis and X-ray diffraction structure determination. The ~(31)P{~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 CH_2Cl_2 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 Ru~(II)-NO~+ → Ru ~(II)-NO~0 at -0.81 V and -0.62 V, for (1) and (2), respectively; the process Ru~(II) → Ru~(III), as expected, is only observed around 2.0 V, for both complexes. Studies were conducted using ~(15)NO and both complexes were isolated with ~(15)N-enriched NO. Upon irradiation, the complex fac-[RuCl_3(NO)(P-N)] (1) does not exchange ~(14)NO by ~(15)NO, while complex mer,trans-[RuCl _3(NO)(P-N)] (2) does. Complex mer,trans-[RuCl_3(~(15)NO)(P-N)] (2′) was obtained by direct reaction of mer,trans-[RuCl_3(NO)(P-N)] (2) with ~(15)NO and the complex fac-[RuCl_3(~(15)NO)(P-N)] (1′) was obtained by thermal-isomerization of mer,trans-[RuCl_3(~(15)NO)(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%).