Cycloruthenated Complexes from Iminophosphoranes: Synthesis, Structure, and Reactivity with Internal Alkynes

Cycloruthenated complexes [(η6-arene)Ru(C6H4-2-PPh2NR)Cl] (arene = benzene, p-cymene; R = Ph, H) containing orthometalated iminophosphoranes have been obtained by transmetalation reactions from Hg(C6H4-2-PPh2NR)2 derivatives to [(η6-arene)Ru(μ-Cl)Cl]2. These complexes react cleanly with internal alkynes R1CCR2 (R1, R2 = Ph, Et, CO2Me), KPF6, and CuBr2, yielding the 1,1,2-triphenyl-3,4-di(alkyl/aryl)-2,1λ5-benzazaphosphinin-2-ium heterocycles [C6H4-PPh2-NPh-C(R1)C(R2)-3,4]+ as PF6 salts. In all studied cases only the monoinsertion products have been observed. In the case of the asymmetric alkyne MeCCPh the insertion is regioselective, and the [C6H4-PPh2-NPh-C(Me)C(Ph)-3,4]PF6 salt is obtained.