13C NMR Spectroscopy of N‐Heterocyclic Carbenes Can Selectively Probe σ Donation in Gold(I) Complexes. Issue 11 (23rd January 2017)

• Record Type: Journal Article
• Authors: Marchione, Demian; Izquierdo, Maria A.; Bistoni, Giovanni; Havenith, Remco W. A.; Macchioni, Alceo; Zuccaccia, Daniele; Tarantelli, Francesco; Belpassi, Leonardo
• Is Part Of: Chemistry. Volume 23:Issue 11(2017)
• Page Start: 2722
• Page End: 2728
• Publication Date: 2017-01-23
• Subjects: bond theory -- gold -- N-heterocyclic carbenes -- NMR spectroscopy; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201605502
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The Dewar–Chatt–Duncanson (DCD) model provides a successful theoretical framework to describe the nature of the chemical bond in transition‐metal compounds and is especially useful in structural chemistry and catalysis. However, how to actually measure its constituents (substrate‐to‐metal donation and metal‐to‐substrate back‐donation) is yet uncertain. Recently, we demonstrated that the DCD components can be neatly disentangled and the π back‐donation component put in strict correlation with some experimental observables. In the present work we make a further crucial step forward, showing that, in a large set of charged and neutral N‐heterocyclic carbene complexes of gold(I), a specific component of the NMR chemical shift tensor of the carbenic carbon provides a selective measure of the σ donation. This work opens the possibility of 1) to characterize unambiguously the electronic structure of a metal fragment (LAu(I) n +/0 in this case) by actually measuring its σ‐withdrawing ability, 2) to quickly establish a comparative trend for the ligand trans effect, and 3) to achieve a more rigorous control of the ligand electronic effect, which is a key aspect for the design of new catalysts and metal complexes. Abstract : A call for solid‐state NMR experiments : In a large set of charged and neutral N‐heterocyclic carbene complexes of gold(I), it has been demonstrated that a specific component of the NMR chemical shift tensor of the carbenic carbon provides a selective measure of the σ donation of the Dewar–Chatt–Duncanson bonding model.