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. [ABSTRACT FROM AUTHOR]