Deciphering the Primary Role of Au⋠⋠⋠H-X Hydrogen Bonding in Gold Catalysis.

Au⋅⋅⋅H-X (X=N or C) hydrogen bonding is gaining increasing interest, both in the study of its intrinsic nature and in their operability in different fields. While the role of these interactions has been studied in the stabilization of gold(I) complexes, their role during the minimum free energy reaction pathway of a given catalytic process remains unexplored. We report herein that complex [Au(C≡CPh)(pip)] (pip=piperidine) catalyses the A3 -coupling reaction for the synthesis of propargylamines, thanks to the ability of Au(I) to promote weak hydrogen bonding interactions with the reactants along the free energy profile. Density Functional Theory (DFT) calculations show that these Au⋅⋅⋅H-X interactions play a directing role in the catalysed A3 -coupling. Topological non-covalent interactions (NCI), interaction region indicator (IRI) and quantum theory of atoms in molecules (QTAIM) analysis in real space of the electron density provide a description of these interactions accurately.

Double Photoinduced Jahn-Teller Distortion of Tetrahedral AuI SnII Complexes.

Tetrahedral AuI complexes [L3 Au(SnCl3 )] (L=PMe3 (1), PMe2 Ph (2), PMePh2 (3), and PPh3 (4)) were prepared by treatment of the [(tht)Au(SnCl3 )] (tht=tetrahydrothiophene) complex with three equivalents of the corresponding tertiary phosphine. The crystal structures of complexes 1-4 have been determined through X-ray diffraction studies showing, in all cases, [SnCl3 ]- fragments covalently bonded to the corresponding [Au(PR3 )3 ]+ units, which leads to a tetrahedral coordination environment for gold. Complexes 3 and 4 show phosphorescence in the solid state at room temperature and 77 K that is largely redshifted relative to the free [Au(PR3 )3 ]+ and [SnCl3 ]- counterparts. Correlated MP2, SCS-MP2, and ONIOM MP2/UFF calculations suggest a largely distorted lower triplet excited state (T1 ) for each model system. The AuP3 + moiety is distorted leading to a T-shape, whereas the SnCl3 - unit is left almost unaltered. Molecular orbital and population analysis suggest that the emission of these tetrahedral AuI complexes arises from a 3 MC transition slightly perturbed by the SnCl3 - fragment.