H(C)Ag: a triple resonance NMR experiment for ¹⁰⁹Ag detection in labile silver‐carbene complexes

Abstract

In silver complexes, indirect detection of (109) Ag resonances via (1) H,(109) Ag-HMQC frequently suffers from small or absent JHAg couplings or rapid ligand dissociation. In these cases, it would be favourable to employ H(X)Ag triple resonance spectroscopy that uses the large one-bond JXAg coupling (where the donor atom of the ligand X is the relay nucleus). We have applied an HMQC-based version of the H(C)Ag experiment to a labile silver-NHC complex (NHC=N-heterocyclic carbene) at natural (13) C isotopic abundance and variable temperature. In agreement with simulations, H(C)Ag detection became superior to (1) H,(109) Ag-HMQC detection above -20 °C.

Chirality influence on the cytotoxic properties of anionic chiral bis(N-heterocyclic carbene)silver complexes

“…This signal appeared at around 180 ppm, but only for complexes 2c and 2e is well resolved showing the well-known pattern of two doublets due to coupling constants of 1 J CAg = 185 and 213 Hz. These values of 1 J CAg are in agreement with an homoleptic binding mode of NHC ligands, C-Ag-C, in agreement with the proposed formulation, because larger coupling constants are often observed for heteroleptic binding modes, C-Ag-X or C-Ag-N [40,41]. Additionally, enantiomeric complexes Na 3 [Ag{(S,S)-NHC R } 2 ] (R = Me, 2b; i Pr, 2c) and Na 3 [Ag{(R,R)-NHC R } 2 ] (R = Me, 2b'; i Pr, 2c') were spectroscopically characterized by circular dichroism (CD).…”

Triple Resonance Experiments for the Rapid Detection of 103Rh NMR Shifts: A Combined Experimental and Theoretical Study into Dirhodium and Bismuth–Rhodium Paddlewheel Complexes

“… After extensive testing, a pulse sequence introduced by Mobley and co-workers was found to give the best results (Figure ). − In the essence, intensive nuclei enhancement by polarization transfer (INEPT) is used for a first magnetization transfer from 1 H to 13 C as the relay atom, followed by a heteronuclear multiple quantum correlation (HMQC) transfer from 13 C to 103 Rh…”

Synthesis, Structure and Catalytic Activity of NHC–AgI Carboxylate Complexes

“…Next, the solution state structures were examined by analysing the 13 C NMR resonance signal corresponding to the coordinated C 2 carbenic carbon, which is easily identifiable as two doublets due to the coupling to magnetically active 107 Ag and 109 Ag isotopes. The observed 1 J ( 107/109 Ag− 13 C) values mirror the gyromagnetic ratio of the two silver isotopes, which suggests slow or no ligand exchange on the NMR timescale . This also applies to the relatively unstable I Ad complexes 3 a and 3 b , which slowly decomposed during the acquisition of their NMR spectra.…”

“…The observed 1 J( 107/109 AgÀ 13 C) values mirror the gyromagnetic ratio of the two silver isotopes, which suggestss low or no ligand exchange on the NMR timescale. [8,42] This also appliest ot he relatively unstable IAd complexes 3a and 3b,w hich slowly decomposed during the acquisitionoft heir NMR spectra.…”