Ruthenaphosphaalkenyls: Synthesis, Structures, and Their Conversion to η2‑Phosphaalkene Complexes

The ruthena­phospha­alkenyls [Ru­{PCH­(SiMe2R)}­Cl­(CO)­(PPh3)2] (R = Me, Ph, Tol) have been prepared in good yield by the facile hydroruthenation of the respective phospha­alkynes, RMe2SiCP, with [RuHCl­(CO)­(PPh3)3]; all three compounds have been structurally characterized in the solid state. Complemented by DFT studies of these, and the precedent [Ru­{PCH­(tBu)}­Cl­(CO)­(PPh3)2], the phospha­alkenyl moieties have been established unequivocally to behave as one-electron donors to the coordinately unsaturated, 15-electron “RuCl­(CO)­(PPh3)2” fragment, corroborating an earlier demonstration of nucleophilic character at phosphorus within the tert-butyl system. Notwithstanding, the ruthena­phospha­alkenyls are shown to react with the nucelophiles Lipz′ (pz′ = pz, pz*, pzH,CF3, pzMe,CF3) to afford the η12-chelated pyrazolyl­phospha­alkene complexes [Ru­{η1-N2-P,C-P­(pz′)CH­(R)}­(CO)­(PPh3)2], which feature a three-membered metallacyclic (Ru–C–P) core. The nature of these novel compounds is discussed, alongside preliminary insight into the process by which they are formed.