Transition-metal derivatives of arenediazonium ions. Part VI. Ligand-substitution reactions of some iron(I) arenediazo- and nitrosyl cations

Abstract

The benzenediazo-cations [(PhN₂) Fe(CO)₂L₂]⁺(L = PPh₃, PMePh₂, or PMe₂Ph), unlike their nitrosyl analogues, are almost inert to substitution of a carbonyl group by excess of ligand L. Only where L = P{(OCH₂)₃ CMe} has formation of a trisubstituted cation been detected. Both the ions [(p-MeC₆H₄N₂)Fe(CO)₂(PPh₃)₂]⁺ and [(NO)Fe(CO)₂(PPh₃)₂]⁺ react smoothly with (Ph₃PNPPh₃)⁺X^–(X = Cl or Br) to give new complexes [(p-MeC₆H₄N₂)Fe(CO)(PPh₃)₂X] and [(NO)Fe(CO)(PPh₃)₂X] respectively. The corresponding azide salt reacts with the p-toluenediazo-cation to yield only [(p- MeC₆H₄N₂) Fe(CO)(PPh₃)₂N₃]. With the nitrosyl analogue, this reaction gives both [(NO)Fe(CO)(PPh₃)₂N₃] and [(NO)Fe(CO)(PPh₃)₂NCO]. These results are interpreted in terms of the ArN₂⁺ ligand being a poorer π-acceptor than the NO⁺ group.