Comparison of Heteronuclear Coupling Constants for Isostructural Nitrogen Coordination Compounds of ^111/113Cd and ¹⁹⁹Hg

Abstract

The complexation of Cd(II) by the tripodal ligand tris[(2-pyridyl)methyl]amine and dipodal ligand bis[(2-pyridyl)methyl]amine was investigated by solution-state NMR and X-ray crystallography. Cadmium coordination compounds exhibiting rarely observed solution-state NMR (1)H-(111/113)Cd satellites were characterized. The eight-coordinate complex [Cd(TMPA)(2)](ClO(4))(2).toluene (1) crystallizes in the triclinic space group P1 with a = 9.629(2) Å, b = 11.020(2) Å, c = 11.641(2) Å, alpha = 114.069(13) degrees, beta = 97.492(13) degrees, gamma = 91.034(14) degrees, and Z = 1. The average Cd-N(amine) distance is 2.53(4) Å and the average Cd-N(pyridyl) distance is 2.54(6) Å. The complex [Cd(BMPA)(NCCH(3))(OH(2))(OClO(3))][Cd(BMPA)(2)](ClO(4))(3).(CH(3)CN) (2) crystallizes in the triclinic space group P&onemacr; with a = 10.446(2) Å, b = 16.653(3) Å, c = 17.736(3) Å, alpha = 62.479(9) degrees, beta = 80.606(14) degrees, gamma = 84.66(2) degrees, and Z = 2. In the pseudo-octahedral monocation, the nitrogen-containing ligands occupy equatorial positions with Cd-N distances of 2.321(8), 2.283(7), and 2.263(8) Å for the amine, pyridyl (average) and acetonitrile nitrogens, respectively. Significant axial interactions occur with Cd-O bond distances of 2.313(7) Å (water) and 2.478(7) Å (perchlorate). In the pseudo-trigonal prismatic dication, the average Cd-N(amine) distances is 2.395(5) Å and the average Cd-N(pyridyl) distance is 2.362(8) Å. The solid-state structures and solution-state NMR trends were very similar to recently reported isovalent complexes of Hg(II), providing an exceptional opportunity to compare coupling constants of coordination compounds. Implications for the use of (111/113)Cd and (199)Hg NMR as metallobioprobes are discussed.

Synthesis and Characterisation of the Cd(II) Complex of a Hexadentate(N4O2) Schiff Base Ligand; IR, NMR and Theoretical Studies

“…The very similar magnetogyric ratio of 113 Cd and 111 Cd, -5.93303 and -5.6720 × 10 -7 rad/Ts, respectively, lead to satellite overlap at the resolution available. It should be noted that there are several reports of 111/113 Cd-1 H heteronuclear coupling, [10][11][12][13][14][15] and we very recently published a clear picture of these satellites very similar to that shown in Fig. 1.…”

“…9 Obviously the observation of such coupling suggests that the Cd-N im bond remains intact in solution. Although there are several reports of 111/113 Cd-1 H heteronuclear coupling, [10][11][12][13][14][15] we could not find any clear pictures of the satellites similar to that reported in our research. Therefore we were interested to synthesise new Schiff base Cd complexes to study the latter interesting heteronuclear couplings.…”

Zinc triad metal ion complexes ofNN′S ligandN-(2-pyridylmethyl)-N-(2-(methylthio)ethyl)amine

“…Although the N 2 N' ligand bis(2-methylpyridyl)amine has been used to prepare 1:1 metal to ligand complexes of zinc triad perchlorates [12,13], various attempts to obtain related complexes with tridentate thioether ligands as single crystals have not yet been successful [7,8]. In contrast, a variety of tridentate N,SR 2 ligands have formed isolable Zinc triad metal ion complexes of NN 0 S ligand zinc triad chlorides [7,8].…”

“…Between sheets, there are interstrand hydrogen bonding interactions between S and H c . [7,8,12,13].…”

KvAP-Based Model of the Pore Region of Shaker Potassium Channel Is Consistent with Cadmium- and Ligand-Binding Experiments

“…In the nonconstrained trajectories, the strong electrostatic attraction of the divalent cation to electronegative atoms influenced the formation of coordinating bonds. Too-close coordination of the divalent cation with the electronegative atoms was precluded by flat-bottom penalty functions with no upper-distance limit and lower-distance limits of 2.65, 2.3, and 2.47 Å , which are seen in the x-ray structures of Cd 21 coordinated to sulfur (29), nitrogen (30), and oxygen (29), respectively. Subsequent removal of the flat-bottom penalty functions and additional energy minimizations did not noticeably change the complexes found.…”