Synthesis and characterization of tetracarbonyl complexes of molybdenum and tungsten with functionalized imines. Crystal structure of cis-Mo(CO)4[CH3)(C6H5) C=N (CH)2)]2

NMR study of the coordinating behavior of 2,6-bis(benzimidazol-2?-yl)pyridine

“…We decided to begin by an evaluation of the actual structure of the free ligand 1 in THF-d 8 or DMSO-d 6 solution, through the analysis of the 1 H and 13 C NMR spectra at different temperatures and by comparison with benzimidazole 2, as shown in Tables 1 and 2. In order to have a reference for the structural analyses, we decided to study the 1 H and 13 C NMR spectra of the protonated 3-5 ( Figure 3) and the dianionic species of 6-9 ( Figure 4) of compounds 1 and 2, respectively. We have also prepared the Co(III) compound 10 derived from ligand 1 (Figure 5), which is a stable and diamagnetic complex, in order to analyze the effect of the metallic coordination to 1.…”

“…All new compounds were characterized by 1 H and 13 C NMR spectroscopy and by heteronuclear correlation experiments. The anions of benzimidazole and 2,6-bis(2-benzimidazol-2Ј-yl)pyridine were handled under an N 2 atmosphere using carefully dried glassware and dried solvents.…”

“…Therefore we have used a stronger acid such as fuming H 2 SO 4 (4) and recorded the corresponding NMR spectra in DMSO-d 6 , and all the three basic nitrogen atoms were found to be completely protonated. The 13 C chemical shift of C-4 at 142.9 clearly indicates protonation at the pyridinic nitrogen atom. The same reaction was performed with 2 to give compound 5.…”

“…We have collected 1 H, 13 C, HETCOR, and NOESY spectra in order to make unequivocal assignments. The 13 C spectrum of 10 shows 10 signals for two magnetically equivalent ligands bonded to Co(III).…”

“…This study is part of our continuing interest in the coordinating ability of aromatic nitrogenated molecules bearing sp 2 nitrogen atoms as present in pyrrole, pyridine, imines, anilines, or imidazole, especially because they can be part of strongly basic polydentate ligands [10][11][12][13][14][15][16][17][18][19][20][21][22]. Aromatic polydentate compounds show different behavior compared to their aliphatic analogs as a consequence of their planar conformation, which allows in some cases increased stability and better crystallizing ability.…”