Investigation of the mercury(ii) coordination chemistry of tris[(1-methylimidazol-2-yl)methyl]amine by X-ray crystallography and NMR

Abstract

The coordination chemistry of Hg() with tris[(1-methylimidazol-2-yl)methyl]amine (TMIMA) was investigated. The structures of [Hg(TMIMA) 2 ](ClO 4 ) 2 (1), [Hg(TMIMA)(NCCH 3 )](ClO 4 ) 2 (2) and [Hg(TMIMA)Cl] 2 (HgCl 4 ) (3) were characterized by X-ray crystallography. Complex 1 has six strong Hg-N imidazoyl bonds ranging from 2.257(5) to 2.631(6) Å. Ligand geometry suggests the Hg-N (NR 3 ) distances of 2.959(6) Å in 1 reflects weak bonding interactions. This complex has a 199 Hg chemical shift of Ϫ1496 ppm, significantly upfield from nitrogen coordination complexes with lower coordination numbers. The five-coordinate complex 2 has Hg-N (NR 3 ) , Hg-N imidazoyl and Hg-N acetonitrile bond lengths of 2.642(8), 2.198(5) and 2.264(11) Å, respectively. Complex 3 is also five coordinate, with Hg-N (NR 3 ) , Hg-Cl and average Hg-N imidazoyl distances in the cations of 2.758(7), 2.424(2) and 2.29(4) Å, respectively. Conditions for slow exchange on the J(HgH) coupling time-scale were found for both 1 : 1 metal-to-ligand complexes in acetonitrile-d 3 . Observed heteronuclear coupling constants were similar to those associated with Hg() substituted proteins with histidine-metal bonds. Solution and solid-state comparisons to the Hg() coordination chemistry of tetradenate pyridyl ligands are made. Relevance to development of 199 Hg NMR as a metallobioprobe is discussed.

Theoretical study of the experimental coordination behavior of N-(2-aminophenyl)-d-glycero-d-gulo-heptonamide to Hg(II) ion

“…The Hg-N distance found for this structure is in good agreement with the bond length values reported for other imidazole mercury complexes, where this bond ranges from 2.20 to 2.29 Å. [16][17][18] The conformation of the hydroxylic chain favors the formation of two symmetric intramolecular hydrogen bonds between the proton attached to O3 and O2. Those bonds rigidify the structure because they link the two ligand units thus stabilizing the arrangement around Hg 2+ .…”

Structural, Spectroscopic, and Reactivity Properties of N2S2(thioether)‐O(amide)‐Ligated HgII Complexes: The First Examples of HgII‐Mediated Amide Cleavage

“…[1][2]1 H NMR studies of Hg II complexes of tripodal ligands have contributed to our understanding of the interplay of Hg II coordination and spectroscopic properties by providing information regarding the magnitude of J199 Hg 1 H and J199 Hg 13 C coupling constants as a function of the nature of the Hg II ligand environment. [3][4][5][6][7] Herein we outline the synthesis, structural and spectroscopic characterization, and amide cleavage properties of two Hg II 3 interactions. Second, we have commenced investigations into biologically-relevant reactions as a function of the group 12 metal ion present.…”

Phenylselenolate mercury alkyl compounds, PhSeHgMe and PhSeHgEt: Molecular structures, protolytic Hg–C bond cleavage and phenylselenolate exchange

“…For example, the fact that the exchange averaged alkyl signals in the mixture of PhSeHgR and RHgCl retain 199 Hg coupling (albeit a weighted average of the exchanging species) indicates that Hg–C bond cleavage does not occur on the timescale associated with the observed exchange process. 48,49 …”