13C Chemical Shift of N-Heterocyclic Carbenes in Coinage Metal(I) Complexes and Clusters: trans-Influence and Spin–Orbit Coupling

• DOI: 10.1021/jacs.5c03929
• Publication Date: 2025-05-16T17:01:36Z
• Authors: Shahar Dery; Christian Ehinger; Jeremy Roudin; Yuya Kakiuchi; Domenico Gioffrè; Christophe Copéret
• Keywords: Chemical shift; Spin–orbit interaction

N-Heterocyclic carbenes (NHCs) are versatile ligands in organometallic chemistry, prized for their strong σ-donating and tunable electronic properties. They used to stabilize a wide range of motifs, including clusters nanoparticles, based particular on coinage metals─Cu, Ag, Au. Notably, the carbene 13C NMR isotropic chemical shift (δiso) NHC-coinage metal complexes varies significantly across these elements, reflecting nuanced interplay structural factors. Here, we study carbon NHC-Au(I)-X (X = H, OH, halides, CN, N3, neutral such as pyridine NHC) compared Cu Ag congeners. Density functional theory calculations analyze shielding tensor components, revealing that stronger σ-donor X-ligands lead greater deshielding δiso through enhanced paramagnetic contributions and, Au, spin-orbit comparable magnitude. Moreover, correlation between contribution (σso) Au-carbene bond distance highlights critical role trans-influence modulating coupling overall shift. Analysis σso shows ligands, associated with elongated bond, higher-lying NHC-Au σ-bond lower-lying π*-orbital, ultimately yielding higher This work provides insight into how factors govern shifts NHC-based Au clusters, establishing direct link spectroscopic descriptors structure, thus opening avenues developing structure-activity relationships catalysis materials science.