Studies on the reactivity of isocyanates and isothiocyanates with palladium-imidoyl complexes

The reactions of palladium-iminoacyl complexes with isocyanates (RNCO) and isothiocyanates (RNCS) have been investigated. The reaction of Pd{C(Me)=NXy}(Cl)(P-P) (P-P = dppe, 1; dppp, 2) with RNCE (E = O, S) in the presence of AgBF₄ yields the novel compounds {Pd{C(=CH₂)N(Xy)C(=E)NHR}(dppe)][BF₄] (E = O and R = Et, 3; Ph; 4; E = S and R = Me, 5; Ph, 6); the formation of these complexes results from an addition reaction followed by the migration of a proton from the methyl group in the imidoyl fragment to the nitrogen in the RNCE moiety. In contrast, the reaction between Pd{C(Ph)=NXy}(I)(dppe) and RNCO in the presence of AgBF₄ yields the addition product [Pd{C(Ph)=N(Xy)C(=O)(= NPh)}(dppe)]-[BF₄] (10). Protonation of the imidoyl group in Pd{C(Me)=NXy}(Cl)(dppe) suppresses the addition reaction when the protonated complex is reacted with RNCS; the products obtained in this case are [Pd{C(Me)=NHXy}(dppe)(S=C=NR)][BF₄]₂ (R = Me, 15; Ph, 16).