Cationic Gold(I) Diarylallenylidene Complexes: Bonding Features and Ligand Effects

Abstract

Using computational approaches, we qualitatively and quantitatively assess the bonding components of a series of experimentally characterized Au(I) diarylallenylidene complexes (N.Kim, R.A.Widenhoefer, Angew. Chem. Int. Ed . 2018 , 57 , 4722–4726). Our results clearly demonstrate that Au(I) engages only weakly in π‐backbonding, which is, however, a tunable bonding component. Computationally identified trends in bonding are clearly correlated with the substitution patterns of the aryl substituents in the Au(I) diarylallenylidene complexes and good agreement is found with the previously reported experimental data, such as IR spectra, 13 C NMR chemical shifts and rates of decomposition together with their corresponding barrier heights, further substantiating the computational findings. The description of the bonding patterns in these complexes allow predictions of their spectroscopic features, their reactivity and stability.

Tuning the Gold(I)‐Carbon σ Bond in Gold‐Alkynyl Complexes through Structural Modifications of the NHC Ancillary Ligand: Effect on Spectroscopic Observables and Reactivity

“…It has been also suggested that the electronic properties (and in particular the π‐accepting power) of NHC‐metal compounds could be efficiently probed via NMR spectroscopy [103] . Moreover, we have recently demonstrated that the extent of the π communication in gold(I) diarylallenylidene compounds tightly correlates with the experimental 13 C NMR chemical shifts [58] . In the present case, NMR 13 C chemical shifts of the two carbon atoms of the alkynyl may be in principle shielded and deshielded by different bonding mechanisms and in particular by the π communication between the alkynyl ligand and the metal fragment.…”

“…[103] Moreover, we have recently demonstrated that the extent of the π communication in gold(I) diarylallenylidene compounds tightly correlates with the experimental 13 C NMR chemical shifts. [58] In the present case, NMR 13 C chemical shifts of the two carbon atoms of the alkynyl may be in principle shielded and deshielded by different bonding mechanisms and in particular by the π communication between the alkynyl ligand and the metal fragment. The π donation component possesses two essential features: i) an increase of π communication extent causes, in principle, the two carbon atoms to be deshielded and ii) π communication shows a variability along the series, suggesting that for the complexes with larger π donation an appreciable deshielding on the two carbon atoms should be observed.…”

“…The CD-NOCV scheme has been applied with success in very different contexts to characterize the chemical interactions throughout the whole periodic table, from weak chemical bond involving helium [55] to the coordination bond in gold complexes. [56][57][58] The method has been found to be particularly useful to single out specific correlations between coordination bonding features and experimental observables. [56,[58][59][60][61][62] Using its 4-component relativistic formulation, [63] the coordination and halogen bonds involving heavy elements was studied.…”

“…[56][57][58] The method has been found to be particularly useful to single out specific correlations between coordination bonding features and experimental observables. [56,[58][59][60][61][62] Using its 4-component relativistic formulation, [63] the coordination and halogen bonds involving heavy elements was studied. [64][65][66] In this work we also used the Energy Decomposition Analysis (EDA) [67] to get further and complementary insights into the gold-alkynyl bond.…”

Sesquicarbene Complexes: Bonding at the Interface Between M–C Single Bonds and M═C Double Bonds

“…We chose to employ intrinsic bond orbitals (IBOs) to generate localized bond orbitals. − They are physically equivalent to the canonical molecular orbitals but give an intuitively understandable picture of bonding situations that has been shown to describe both the Lewis contributions and the relevant delocalization contributions well. − …”