Comparison of the reactivity, electrochemical behaviour, and structure of the trans-bis(acido)tetra(pyridine)nitrosylruthenium cations (acido = hydroxo or chloro)

An Electron‐Rich {RuNO}6 Complex: trans‐[Ru(DMAP)4(NO)(OH)]2+ – Structure and Reactivity

“…The +2 cation was precipitated by adding a slight excess of PF 6 -or BF 4 -. [15] Finally, the N-O distance and Ru-N-O angle are 1.245(8) Å and 169.3(6)°, compared with 1.145(4) Å and 172.8(3)°for the analogous [Ru(py) 4 (NO)(OH)] 2+ . Compound 1(PF 6 ) 2 crystallizes in the tetragonal P4/mnc space group.…”

“…Recrystallization from CH 3 CN/Et 2 O yielded crystalline materials suitable for X-ray diffraction analysis. [15] All these values, but particularly the last ones, point to a {RuNO} 6 moiety with a high degree of metal-to-ligand backbonding. The unit cell comprises 4 units of the compound and no solvent molecules.…”

“…All attempts to modify the reaction conditions (T in the range 4-65°C; pH = 5-10) yielded the same results. [14,15] In the pseudo-C 4 axis the Ru-O(H) and Ru-N(O) bond lengths are 1.919(5) and 1.748(8) Å, respectively; both values are shorter than the ones in [Ru(py) 4 -(NO)(OH)] 2+ [1.910(2) and 1.756(3) Å]. Recrystallization from CH 3 CN/Et 2 O yielded crystalline materials suitable for X-ray diffraction analysis.…”

Synthesis and characterization of trans-[Ru(NO)Cl(L)4](PF6)2 (L = isonicotinamide; 4-acetylpyridine) and related species

“…It should be noted that tetrakispyridine and bisbipyridine nitrosyl complexes were isolated as hydroxo species even at H + concentrations as high as 6 mol L À1 [12,19]. With regard to the presence of the nitrosyl ligand in the metal coordination sphere, the trans ligand to NO is more acidic than in the complexes without the coordinated NO.…”

“…It was suggested that rapid cogwheel rotation of the pyridine rings about the Ru-N(py) axis is occurring in solution, which would explain the three aromatic ring H's NMR signals instead of five for trans-[Ru(NO)Cl(py) 4 ](PF 6 ) 2 Á ½H 2 O [11]. Since, trans-[Ru(NO)(OH)(py) 4 ] 2+ has the same trans configuration [12], it is reasonable to expect the same NMR pattern. The spectrum obtained in D 2 O presents three signals at 7.66 (8H, t, H 2,4 Â 4), 8.24 (4H, t, H 3 Â 4), 8.41 (8H, d, H 1,5 Â 4) but does not show the singlet signal due to H exchange with D. In summary, the 1 H NMR spectrum informs that the hydroxo complex is formed instead of an aquo complex, despite being synthesized at pH $ 1.…”