15N and 31P NMR Coordination Shifts in Transition Metal Complexes with Nitrogen- and Phosphorus-Containing Heterocycles

Synthesis and NMR Analysis of 1,4‐Disubstituted 1,2,3‐Triazoles Tethered to Pyridine, Pyrimidine, and Pyrazine Rings

“…These values are in good agreement with literature reports for 2-methylpyridine (δ = 309 ppm) [32,40] or 2-benzylpyridine (δ = 316 ppm), [32,34,40] for example. In a π-conjugated framework where the triazole N-1 atom is attached directly to the pyridine C-2Ј atom, i.e., in the 1-(2-pyridyl)triazole series 3 (δ = 283-286 ppm, Table 5, entries 1-8), a large shielding effect of ca.…”

“…[34] Although the low natural abundance of 15 N and its low gyromagnetic ratio make direct observation of the 15 N nuclide difficult, this has been largely circumvented by the advent of the inverse-detected long-range heteronuclear shift correlation techniques, introduced by Bax and Summers. [32,35,36] For the assignments of the proton and carbon resonances in compounds 3-6, we carried out 1D NMR ( 1 H and Figure 3 by curved arrows. The atom-numbering scheme and selected data are presented in Figure 3 and Table 5.…”

Solvent Effects on Nitrogen Chemical Shifts

“…N-M replacement, as it rather reflects the N-H ! N-M substitution, and thus provides smaller jΔ 15N coord j than would be expected [82]. This is true also for azoloazine complexes possessing nonsubstituted nitrogens (Scheme 1B).…”

“…Proposed reaction pathways with dimethyl sulfoxide-d 6 or dimethylformamide-d 7 as solvents and PMePh 2 as the P ligands are depicted in Scheme 3 and the chemical shifts are given in Table 15 [111,113,114,116] [113] recalculated in respect to neat CH 3 NO 2 by subtracting 1.9 ppm relative originally reported chemical shift. [82] The δ 15N lig for 9-MeAd for DMSO-d 6 is given in [111]. When several conformers are present in solution, the data of the major one is shown.…”

“…In order to compensate the effect of such weak hydrogen bonds, the δ 15N determined in water-d 2 are often compared with chemical shifts measured in polar, aprotic dimethylsulfoxide-d 6 or apolar, aprotic chloroform-d [82]. It should be noted that weak hydrogen bonds between free ligands and water (N⋯H 2 O), non-neglectably affecting δ 15N , may also occur to some extent in hygroscopic solvents such as dimethylsulfoxide-d 6 , dimethylformamide-d 7 or acetonitrile-d 3 , which often contain some residual water [59,65].…”