An experimental and computational NMR study of organometallic nine‐membered rings: Trinuclear silver(I) complexes of pyrazolate ligands

Abstract

This work reports the calculation of the nuclear magnetic resonance (NMR) chemical shifts of eight trinuclear Ag(I) complexes of pyrazolate ligands using the relativistic program ZORA. The data from the literature concern exclusively 1H, 13C, and 19F nuclei. For this reason, one of the complexes that is derived from 3,5‐bis‐trifluoromethyl‐1H‐pyrazole has been studied anew, and the 15N and 109Ag chemical shifts determined for the first time in solution. Solid‐state NMR data of this compound have been obtained for some nuclei (1H, 13C, and 19F) but not for others (14N, 15N, and 109Ag).

Regium Bonds between Silver(I) Pyrazolates Dinuclear Complexes and Lewis Bases (N2, OH2, NCH, SH2, NH3, PH3, CO and CNH)

“…Furthermore, a good relationship between the chemical shielding and the intramolecular Ag-Ag distance (only for complexes with two ligands) was found ( Figure S3). Unfortunatelly, there are no experimental data on (PzAg) 2 compounds but a recent report on (PzAg) 3 derivatives show that the methodology used here provides δ 109 Ag values within 10 ppm of the experimental ones [46]. In order to explore the potential aromaticity of the six membered ring formed by the nitrogen atoms of the pyrazoles and the two silver atoms, the NICS(0) and NICS(1) have been calculated (Table 5).…”

“…In this article, the dinuclear silver(I) pyrazolates (Scheme 1) have been considered following a previous paper on trinuclear silver(I) pyrazolates [46]. The effect of the ligands on the silver atom and the substituents on the pyrazole rings on the structure, energetic, electronic and magnetic properties have been analyzed.…”

Rivalry between Regium and Hydrogen Bonds Established within Diatomic Coinage Molecules and Lewis Acids/Bases

“…[24] The NMR shifts of ninemembered rings formed by trinuclear silver pyrazolate com-plexes were measured and computed using ZORA relativistic method. [25] DFT studies were carried out on copper (I) complexes in the carboxylation of arylboronated esters. [26] Complexes of Cu(I) with O-, S-, and N-containing ligands were compared with the SIBFA molecular mechanism versus ab initio methods.…”

A Computational Study of Metallacycles Formed by Pyrazolate Ligands and the Coinage Metals M = Cu(I), Ag(I) and Au(I): (pzM)n for n = 2, 3, 4, 5 and 6. Comparison with Structures Reported in the Cambridge Crystallographic Data Center (CCDC)

“…The main conclusions were that the pz-M bond has an elevated covalent character, especially when M = Au(I), and that the pyrazole ligands are strongly aromatic, although they are insulated because there is no through-bond metal-ligand conjugation. Our group published a paper, in collaboration with Rasika Dias and another with Kiyoshi Fujisawa, on the NMR study of the organometallic nine-membered rings corresponding to trinuclear silver(I) complexes of pyrazolate ligands [14,15], and another on regium bonds between dinuclear silver(I) pyrazolates complexes and Lewis bases [16], two on regium bonds formed by Au2 [17] and Ag2, Cu2 and mixed binary regium molecules [18], and finally, one on the comparison of acidity of Au(I) and Au(III) [19].…”