AbstractMany observations prove that a number of silylation reactions of a trialkylsilyl halide‐uncharged base system occur with the transient formation of a 1:1 tetrahedral silicon ionic complex of the silyl halide with the base. Some catalytic processes of phosphorylation of protonic substrates with tricoordinate phosphorus halides in mixture with an uncharged base show similar features to these silylation reactions, implying that a similar mechanism may operate. It was demonstrated that Ph2PCl phosphorylates t‐BuOH faster under catalysis with 4‐N,N‐dimethylamino pyridine orN‐methylimidazole than in the presence of Et3N by a factor of 400 and 33, respectively. The catalytic phosphorylation process exhibits a very low activation energy and a high negative value of entropy of activation. The interaction of the uncharged bases with model tricoordinate phosphorus halides was demonstrated to lead to the formation of ionic 1:1 complexes without changing the coordination number of phosphorus, in full analogy to the silyl halide complex formation. Finally, the interaction of phosphorous tris(dimethylamide) with a silyl iodide and a phosphorous iodide results in both cases in the formation of the ionic 1:1 complex, which also leads to analogous reactions of exchange of the amide group with iodide. These close similarities imply that some phosphorylation reactions with tricoordinate phosphorus halides catalyzed with uncharged bases occur via a tricoordinate phosphorus cation int