Au⋅⋅⋅H−C Hydrogen Bonds as Design Principle in Gold(I) Catalysis

Abstract

Secondary ligand–metal interactions are decisive in many catalytic transformations. While arene–gold interactions have repeatedly been reported as critical structural feature in many high‐performance gold catalysts, we herein report that these interactions can also be replaced by Au⋅⋅⋅H−C hydrogen bonds without suffering any reduction in catalytic performance. Systematic experimental and computational studies on a series of ylide‐substituted phosphines featuring either a PPh3 (PhYPhos) or PCy3 (CyYPhos) moiety showed that the arene‐gold interaction in the aryl‐substituted compounds is efficiently compensated by the formation of Au⋅⋅⋅H−C hydrogen bonds. The strongest interaction is found with the C−H moiety next to the onium center, which due to the polarization results in remarkably strong interactions with the shortest Au⋅⋅⋅H−C hydrogen bonds reported to date. Calorimetric studies on the formation of the gold complexes further confirmed that the PhYPhos and CyYPhos ligands form similarly stable complexes. Consequently, both ligands showed the same catalytic performance in the hydroamination, hydrophenoxylation and hydrocarboxylation of alkynes, thus demonstrating that Au⋅⋅⋅H−C hydrogen bonds are equally suited for the generation of highly effective gold catalysts than gold‐arene interactions. The generality of this observation was confirmed by a comparative study between a biaryl phosphine ligand and its cyclohexyl‐substituted derivative, which again showed identical catalytic performance. These observations clearly support Au⋅⋅⋅H−C hydrogen bonds as fundamental secondary interactions in gold catalysts, thus further increasing the number of design elements that can be used for future catalyst construction.

Enantioselective C−H Functionalization Reactions under Gold Catalysis

“…The agostic interaction between gold center and CÀ H bonds, which is a necessary step for oxidative insertion pathway, has been recently observed. [157,158] However, the exploitation of this reactivity for accessing effective CÀ H activation processes is yet to be realized.…”

“…As far as inner sphere pathway is concerned, only electrophilic auration is operational for the gold‐catalyzed C−H functionalization reactions. The agostic interaction between gold center and C−H bonds, which is a necessary step for oxidative insertion pathway, has been recently observed [157,158] . However, the exploitation of this reactivity for accessing effective C−H activation processes is yet to be realized.…”

Au⋅⋅⋅H−C Interactions Support a Robust Thermally Activated Delayed Fluorescence (TADF) Gold(I) Complex for OLEDs with Little Efficiency Roll‐Off and Good Stability

“…The crystallographic data is summarized in Table S1 and key structural parameters in Table S2. [13] As depicted in Figures 2a, b [11,14] The CÀ HÀ Au angles of 141.32°and 138.72°also favor this type of interactions. Therefore, the tDIDCz ligand chelates the Au atom in a pincer mode, albeit with weaker strength than that of terdentate ligands.…”

“…0.020 and 0.053 manifest the attractive Au•••HÀ C interactions. [11] The noncovalent interactions can also be visualized by reduced density gradient (RDG) isosurfaces (Figures 2g and S5). To understand the role of these secondary interactions on stabilizing of the Au-aryl coordination, detachment energies for the aryl ligands were computed (Figure S6, Supporting Information).…”

“…In the past few years, the anagostic Au⋅⋅⋅H−X hydrogen bond has been experimentally and theoretically validated after a long‐standing debate [10] . Of note, the secondary interaction has been recognized as useful for design of stable Au I catalysts [11] . Whereas, its impact on the stability of luminescent mononuclear Au I complexes as optoelectronic materials has yet to be explored.…”