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Reaction of fac- [RuCl 3 (NO)(P–N)] (1) with the triarylphosphines PR 3 in MeOH allows for isolation of the monocationic Ru(II) complexes [RuCl 2 (NO)(P–N)(PR 3 )]PF 6 ; P–N = o -diphenylphosphino- N , N -dimethylaniline, and R = p -MeO-C 6 H 4 (complex 2 ), p -Me-C 6 H 4 ( 3 ), Ph ( 4 ), and p -F-C 6 H 4 ( 5 ). The complexes were characterized by elemental analysis, 31 P{ 1 H}, 1 H NMR and IR spectroscopies, ESI-MS, CV, and X-ray structural data for complexes 3 – 5 . The 31 P{ 1 H} spectra display two doublets with 2 J pp values consistent with cis P-atoms. The ESI-MS spectra reveal the molecular ion [RuCl 2 (NO)(P–N)(PR 3 )] + and the fragmentation ions [M−PR 3 ] + , [M−PR 3 −Cl] + , and [M−PR 3 −2Cl] + . CV data show a one-electron, quasi-reversible reduction process centred at the Ru–NO unit that depends on the p K a of the PR 3 . The IR spectra reveal ν NO bands for coordinated NO + . A known, empirical inverse correlation between the δ P value and the Ru–P bond length of the P–N ligand that exists for a series of cis - and trans -RuX 2 (L)(P–N)(PR 3 ) complexes (X = Cl or Br), where L is a range of small molecules, is extended with L = NO + and now covers the respective ranges of about 30–80 ppm and 2.39–2.17 Å. [ABSTRACT FROM AUTHOR]

Abstract: 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 28.3ppm for (2). The 1H NMR spectrum for (1) presented two singlets for the methyl hydrogens at 3.81 and 3.13ppm, while for (2) was observed only one singlet at 3.29ppm. FTIR Ru–NO stretching in KBr pellets or CH2Cl2 solution presented 1866 and 1872cm−1 for (1) and 1841 and 1860cm−1 for (2). Electrochemical analysis revealed a irreversible reduction attributed to RuII–NO+ →RuII–NO0 at −0.81V and −0.62V, for (1) and (2), respectively; the process RuII →RuIII, as expected, is only observed around 2.0V, 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%). [Copyright &y& Elsevier]