A series of catecholato phosphonium ions, including the first stable bis­(catecholato)-substituted derivatives, are isolated and fully characterized. The cations rank among the most potent literature-known Lewis acids on the Gutmann–Beckett and ion affinity scales. In contrast to halogenated or multiply charged phosphorus cations, Lewis superacidity is imparted by structural constraints, as disclosed by energy decomposition analysis. The modular access provides a tunable scaffold while maintaining extreme affinity, demonstrated by the synthesis of a chiral Lewis superacid. The combination of electrophilic phosphorus and basic oxygen substituents leverages new reactivity modes by phosphorus–ligand cooperativity. With this, a phosphorus-mediated C–H bond activation is accomplished.

An extensive kinetic study of selected key reactions of (oxidative) gold catalysis concentrates on the decrease of the catalytic activity due to inhibition of the gold(I) catalyst caused by pyridine derivatives that are obtained as by-products if N-oxides are applied as oxygen donors. The choice of the examined pyridine derivatives and their corresponding N-oxides has been made regardless of their commercial availability; particular attention has been paid to the practical benefit which up to now has been neglected in most of the reaction screenings. The test reactions were monitored by GC and 1 H NMR spectroscopy. The received reaction constants provide information concerning a correlation between the electronic structure of the heterocycle and the catalytic activity. Based on the collected kinetic data, it was possible to develop a basic set of three N-oxides which have to be taken into account in further oxidative gold(I)-catalyzed reactions.

The front cover picture, provided by Stephen Hashmi and co‐workers, represents the result of their work on establishing a fundamental set of N‐oxides in homogeneous oxidative gold catalysis. This basic set of N‐oxides should be an integral component in each reaction optimization which allows identification of the best N‐oxide in less steps. This is illustrated in the cover picture by the chemist who is pondering which N‐oxide of the wide selection might be the best. The artist is Jasmin Schießl. Details of this work can be found in the full paper on pages 725–738 (J. Schießl, P. M. Stein, J. Stirn, K. Emler, M. Rudolph, F. Rominger, A. S. K. Hashmi, Adv. Synth. Catal. 2019, 361, 725–738; DOI: 10.1002/adsc.201801007).