Reaction of Ruthenium Complexes Having both a Phosphite and a Group 14 Element Ligand with a Lewis Acid

Reactions of having an alkyl group (ER₃ = Me (1a), CH₂SiMe₃ (2a)), a silyl group (ER₃ = SiMe₃ (3a), SiMe₂SiMe₃ (4a)), a germyl group (ER₃ = GeMe₃ (5a)), or a stannyl group (ER₃ = SnMe₃ (6a), SnⁿBu₃ (7a), SnPh₃ (8a)) with a Lewis acid (BF₃·OEt₂ or Me₃SiOSO₂CF₃ (TMSOTf)) have been examined. In the reactions with BF₃·OEt₂, in any case except for 8a, an OMe abstraction as an anion uniformly takes place at the first stage to give the corresponding cationic phosphenium complex (1b−7b). The successive reaction depends on the type of ER₃ group. Alkyl complexes (1b and 2b) immediately undergo migratory insertion of the phosphenium ligand into the Ru−C bond, and a subsequent reaction with PPh₃ gives the cationic complex (ER₃ = Me (1c), CH₂SiMe₃ (2c)). Silyl and germyl complexes (3b−5b) are stable with the Ru−Si and Ru−Ge bonds intact. In contrast, stannyl complexes (6b and 7b) undergo migration of one of the R groups on Sn to give the stannylene complex (R = Me (6e), ⁿBu (7e)). The reactions with another Lewis acid, TMSOTf, exhibit reactivities similar to those with BF₃·OEt₂, except when ER₃ is a stannyl group. In the reaction of 6a, 7a, or 8a with TMSOTf, one of the R groups on Sn is directly abstracted to give the corresponding stannylene complex (R = Me (6f), ⁿBu (7f), Ph (8f)). 8f has been determined to be a doubly base stabilized stannylene complex by single-crystal X-ray diffraction.