We report the synthesis and crystallographic characterization of a novel Au(III)À OH complex featuring a N^N^N-pincer ligand. Reactivity studies towards oxygen atom transfer (OAT), a type of reactivity previously reported for a Au(III)À OH complex, indicate that this complex provides both a sterically encumbered Au atom and a sterically poorly accessible OH group leading to no reactivity with a series of phosphines. The steric encumbrance sets this example apart from the known examples of Au(III)À OH (pincer) complexes, which commonly feature planar ligands that provide little control over steric accessibility of the Au and O atoms in these complexes. Implications for the mechanism of OAT from AuÀ OH complexes are briefly discussed.Only few examples of structurally defined Au(III) hydroxide complexes have been reported featuring pincer-type ligands, [1] and for most, little is known regarding their reactivity (Figure 1). [2] A notable feature of all reported complexes thus far is that the ligands are planar and therefore provide comparable steric environments. AuÀ OH complexes in general, both Au(I) and Au(III), can be used as synthons to introduce for example anionic ligands, such as a hydride, aryls, and N-heterocycles by ligand exchange. [2c,3] Among the Au(III)À OH complexes an exceptionally wellstudied example is the (C^N^C)AuÀ OH complex from the Bochmann group, which not only serves as a synthon, but also undergoes oxygen atom transfer (OAT) with various phosphines to form the corresponding phosphine oxides and Au(III)À H (Figure 2). [4] Based on a series of experiments, the Bochmann group proposed a concerted mechanism for OAT in which there is planar attack of the phosphine directly onto the oxygen leading to both P=O bond formation and proton reduction giving a AuÀ H (Figure 2). The possibility of an initial AuÀ P interaction was judged unlikely based on DFT calculations [4] and further corroborated by a computational study on the corre-[a

We studied the influence of changing the degree of fluorination in eight new gold(i) derivatives containing both JohnPhos phosphine and polyfluorinated thiolates: [Au(SR)(JPhos)], JPhos = P(CH-CH)(t-But) and R = CF (1), CHF (2), CHF-3,5 (3), CHF-2,4 (4), CHF-2 (5), CHF-3 (6), CHF-4 (7) and CF (8). We determined the molecular and crystal structures of all new compounds by single crystal X-ray diffraction. Later, we characterised the chemical bonding scenario with quantum chemical topology tools, specifically the Quantum Theory of Atoms in Molecules (QTAIM) and the analysis of the NCI-index. Our QTAIM results indicate that while the linear S-Au-P moiety is unaffected by the variation of the fluorine content on the thiolates and that Au-S and Au-P bond strengths are mostly constant for all compounds in the series, the π character of gold bonds seems to be modified by the fluorination of the substituents at the thiolate ligand. Besides, the examination of the NCI-index reveals the presence of weak Au-π non-covalent interactions in all compounds. Overall, this study shows the relevance of (i) the π-backbonding properties of the metal centre and (ii) different non-covalent interactions in the stability of JohnPhos gold(i) compounds.

Crystallographic distances and the electron density of bi- and tri-nuclear gold(I) compounds reveal that the existence of multiple Au···Au interactions increases their individual strength in the order of 0.9-2.9 kcal·mol-1....

Spatial control of reactivity is intrinsically difficult in gold catalysis due to the linear coordination mode of Au(I) and the commonly flat ligands employed for Au(III) complexes. Our recent report of a novel and sterically encumbered (NNN)diiPrAu−OH complex (Eur. J. Inorg. Chem. 2021, 3561–3564.) suggested that the (NNN) ligand framework is capable of sterically interacting with substrates through its conveniently oriented aryl groups. We have now examined these steric properties in more detail by varying the ortho‐substituent of the aryl group in (NNN)xAu−Cl complexes. With just small modifications we were able to vary the buried volume around the Cl atom and correlate this to yields obtained in a Au‐catalyzed Overman rearrangement. Computationally we further elucidate that the stark difference in yields obtained originates from a shift in binding mode of the substrate to the Au catalyst in the rate limiting step of the reaction. We thus conclude that delicate spatial control can be exercised in gold catalysis and propose the (NNN) ligand framework to be an attractive platform for the efficient design of Au(III) complexes for stereoselective catalysis.