Nitrogen Lewis acids (NLAs) are emerging as a powerful tool in strong bond activation and catalysis. Till now, N,N-dialkyl-nitrenium salts were known and utilized in chemical transformations. In this article, we report on the synthesis and characterization of the next generation of nitrenium-based Lewis acidsN,N-diaryl-substituted naphthotriazinium salts,which opens the door to libraries of stereoelectronically modifiable catalysts. We exemplify the potency of these Lewis acidic catalysts in a gram-scale hydrosilylation of various ketimines and aldimines in yields up to 99% and a catalyst loading as low as 0.1 mol %. Notably, dialkyl-nitrenium salts proved inefficient in this reaction. Based on our experimental and theoretical studies, we elucidated the mechanistic action of nitrenium Lewis acids in such reductiontype reactions, demonstrating a unique hydridic behavior of N−H bonds in triazanes.

We describe a new type of nitrenium-based Lewis acids: tetraaryl-1,2,3-triazolium salts. These were fully characterized by NMR and X-ray crystallography. The Gutmann–Beckett acidity numbers were determined to be up to 35.6, which is high compared to those of previously studied nitrenium salts. These salts catalyze the facile hydrosilylation-deoxygenation of ketones, aldehydes, acetals, alcohols, ethers, and silyl ethers under mild conditions in excellent yields. To our knowledge, this represents a first example of triazolium ions used as Lewis acid catalysts.

Nitrogen Lewis acids (NLAs) are emerging as a powerful tool in strong bond activation and catalysis. Till now, N,N-dialkyl-nitrenium salts were known and utilized in chemical transformations. In this article, we report on the synthesis and characterization of a new generation of nitrenium-based Lewis acids – N,N-diaryl-substituted naphthotriazinium salts, which open a door to libraries of stereoelectronically modifiable catalysts. We exemplify the potency of these new Lewis acidic catalysts in a gram-scale hydrosilylation of various ketimines and aldimines in yields up to 99% and a catalyst loading as low as 0.1mol%. Notably, dialkyl-nitrenium salts proved inefficient in this reaction. Based on our experimental and theoretical studies, we elucidated, for the first time, the mechanistic action of nitrenium Lewis acids in such reduction-type reactions, demonstrating a unique hydridic behavior of N-H bonds in triazanes.

Herein we present the synthesis, full characterization and systematic investigation of intramolecular Lewis pairs incorporating Lewis acidic N‐heterocyclic nitrenium salts linked to phosphine Lewis bases. Intramolecular Lewis adducts and frustrated Lewis pairs (FLPs) were obtained, depending on different modification to the molecular structure. Several different aryl and alkyl groups were utilized as substituents on the core naphthotriazinium and phosphine components, which were linked by an alkyl chain of variable length. Whereas an intermolecular Lewis adduct of nitrenium with a relatively weak phosphine donor (Ph2PMe) was not observed, the corresponding intramolecular version (Ph2PR) was detected both in a dissociated Lewis pair form and as a coordinated Lewis adduct simultaneously. Additionally, one set of modifications led to a unique rearrangement of the nitrenium core, resulting in a fused heterocycle. The mechanism of this rearrangement was analyzed computationally.

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