A proton NMR study of reduced paramagnetic tris(2,2'-bipyridine) complexes of iron(II), ruthenium(II) and osmium(II)

1H NMR assignment corrections and 1H, 13C, 15N NMR coordination shifts structural correlations in Fe(II), Ru(II) and Os(II) cationic complexes with 2,2′‐bipyridine and 1,10‐phenanthroline

“…Our attributions are consistent with the following reports for salts with other than chloride counterions: [Fe(bpy) 3 ](ClO 4 ) 2 ,2 [Fe(bpy) 3 ](PF 6 ) 2 ,3 [Ru(bpy) 3 ](SCN) 2 ,8 [Ru(bpy) 3 ](ClO 4 ) 2 ,2, 9 [Ru(bpy) 3 ](PF 6 ) 2 ,10–13, 15–18 [Ru(bpy) 3 ](BF 4 ) 2 ,19, 20 [Os(bpy) 3 ] (ClO 4 ) 2 ,2, 21 [Os(bpy) 3 ](PF 6 ) 2 ,22 [Fe(phen) 3 ](ClO 4 ) 2 ,24 [Ru (phen) 3 ](ClO 4 ) 2 ,9, 24, 28 [Ru(phen) 3 ]SO 4 30. On the contrary, the assignments proposed by some other authors for [Ru(bpy) 3 ] (PF 6 ) 2 ,14 [Fe(phen) 3 ](ClO 4 ) 2 ,23 [Ru(phen) 3 ](ClO 4 ) 2 ,14 [Ru (phen) 3 ](PF 6 ) 2 ,29 [Ru(phen) 3 ](BF 4 ) 2 19 and [Os(phen) 3 ](CF 3 SO 3 ) 2 32 were probably wrong.…”

“…The increase of the 1 H shielding effect for H(6) in bpy and H(2) in phen following the Ru(II) → Fe(II) and Ru(II) → Os(II) transitions can also be deduced from the literature data. Particularly, the δ 1H values for the respective salts containing various central atoms but identical counterions, measured in the same solvents, decrease as follows: δ H(6) = 8.07 ppm for [Ru(bpy) 3 ](PF 6 ) 2 13 →δ H(6) = 7.72 ppm for [Fe(bpy) 3 ](PF 6 ) 2 3 (both in acetone‐ d 6 ); δ H(6) = 7.72 ppm for [Ru(bpy) 3 ](ClO 4 ) 2 2 →δ H(6) = ca 7.4 ppm for [Os(bpy) 3 ](ClO 4 ) 2 21 (both in DMSO‐ d 6 ); δ H(2) = 8.13 ppm for [Ru(phen) 3 ](ClO 4 ) 2 24, 28 →δ H(2) = 7.78 ppm for [Fe(phen) 3 ](ClO 4 ) 2 24 (both in D 2 O).…”

“…The respective 1 H peaks were shifted to lower frequency by ca 0.6–1.3 ppm (LL bpy ) or ca 0.9–1.55 ppm (LL phen ), either in cases when exact Δ 1H coord coordination shifts could be determined (i.e. when the δ 1H chemical shifts for the complex and the ligand concerned the same solvent: [Fe(4,4 ′ ‐dimethoxy‐bpy) 3 ] 2+ ,48 [Fe(5,5 ′ ‐diamino‐bpy) 3 ] 2+ ,49, 50 [Ru(4,4 ′ ‐dimethyl‐bpy) 3 ] 2+ ,2 [Ru(5,5 ′ ‐dimethyl‐bpy) 3 ] 2+ ,2 [Ru(bpy‐4,4′‐dicarboxylate) 3 ] 4− ,51, 52 [Ru(bpy‐5,5 ′ ‐dicarboxylate) 3 ] 4− ,53 [Ru(bpy‐4,4 ′ ‐disulfonate) 3 ] 4− ,54 [Os(bpy‐4,4 ′ ‐dicarboxylate) 3 ] 4− 52 and [Fe(4,7‐diphenyl‐phen) 3 ] 2+ ,55 [Ru(4,7‐diphenyl‐phen) 3 ] 2+ 56) or when they were evaluated only approximately (due to the change of solvent: [Fe(4,4 ′ ‐dimethyl‐bpy) 3 ] 2+ ,57 [Ru(4,4 ′ ‐di‐ tert ‐butyl‐bpy) 3 ] 2+ ,29, 58 [Ru(4,4 ′ ‐dichloro‐bpy) 3 ] 2+ ,29 [Ru(4,7‐dichloro‐phen) 3 ] 2+ ,59 [Os(4,7‐dimethyl‐phen) 3 ] 2+ ,31 [Os(5,6‐dimethyl‐phen) 3 ] 2+ 31).…”

“…It is really surprising, however, that their assignments were inconsistent, although the spectral patterns of such highly symmetric [M(LL) 3 ] 2+ cations were relatively simple, containing two doublets [H(3)/H(6)] and two triplets [H(4)/H(5)] for LL = bpy, or two doublets [H(2)/H(4)], a doublet of doublets [H(3)] and a singlet [H(5)] for LL = phen. Particularly, the predominantly suggested orders of the 1 H resonances, H(3) > H(4) > H(5)/H(6) for [M(bpy) 3 ] 2+ 2, 3, 8–13, 15–17, 19–22 and H(4) > H(5) > H(2) > H(3) for [M(phen) 3 ] 2+ ,7, 9, 24, 26–28, 30, 31 contrasted to those proposed by some other authors: H(6) > H(3) > H(4) > H(5),1 H(6) > H(4) > H(3) > H(5),4 H(6) > H(5) > H(3) > H(4),5–7 H(3) > H(6) > H(5) > H(4)14 (all for [M(bpy) 3 ] 2+ ) and H(4) > H(2) > H(5) > H(3),29 H(2) > H(4) > H(3) > H(5),14 H(2) > H(3) > H(4) > H(5),19 H(2) > H(5) > H(4) > H(3),23, 32 H(2) > H(4) > H(5) > H(3)25 (all for [M(phen) 3 ] 2+ ). In our opinion, very large variations cannot be caused by the change of solvent and/or counterions, but they reflect erroneous attributions in some articles (the largest differences concerned peaks with the same multiplicity: H(3)/H(6) and H(4)/H(5) in bpy; H(2)/H(4) in phen).…”

“…The 1 H NMR data for their salts were assigned in case of [Fe(bpy) 3 ]Cl 2 ,1 [Fe(bpy) 3 ](ClO 4 ) 2 ,2 [Fe(bpy) 3 ](PF 6 ) 2 ,3 [Ru(bpy) 3 ] Cl 2 ,4–7 [Ru(bpy) 3 ](SCN) 2 ,8 [Ru(bpy) 3 ](ClO 4 ) 2 ,2, 9 [Ru(bpy) 3 ] (PF 6 ) 2 ,10–18 [Ru(bpy) 3 ](BF 4 ) 2 ,19, 20 [Os(bpy) 3 ]Cl 2 ,5 [Os(bpy) 3 ] (ClO 4 ) 2 ,2, 21 [Os(bpy) 3 ](PF 6 ) 2 22 and [Fe(phen) 3 ](ClO 4 ) 2 ,23, 24 [Ru(phen) 3 ]Cl 2 ,7, 25–27 [Ru(phen) 3 ](ClO 4 ) 2 ,9, 14, 24, 28 [Ru(phen) 3 ] (PF 6 ) 2 ,29 [Ru(phen) 3 ](BF 4 ) 2 ,19 [Ru(phen) 3 ]SO 4 ,30 [Os(phen) 3 ] Cl 2 ,31 [Os(phen) 3 ](CF 3 SO 3 ) 2 32. It is really surprising, however, that their assignments were inconsistent, although the spectral patterns of such highly symmetric [M(LL) 3 ] 2+ cations were relatively simple, containing two doublets [H(3)/H(6)] and two triplets [H(4)/H(5)] for LL = bpy, or two doublets [H(2)/H(4)], a doublet of doublets [H(3)] and a singlet [H(5)] for LL = phen.…”