The mechanisms of the reactions between hydrido-complexes and diazonium salts. Part 2. The reactions of cis,mer-[RhHCl2(PEtPh2)3]

Abstract

The mechanisms of the reactions between cis,mer-[RhHCl₂(PEtPh₂)₃] and (p-R′C₆H₄N₂)BF₄(R′= Cl, Me, or MeO) have been investigated in both methanol and acetonitrile. The influence of acid, chloride, and the para substituent on the aryl group defines a mechanism common to both solvents. Upon dissolution of cis,mer-[RhHCl₂(PEtPh₂)₃], the solvento-species [RhHCl₂(PEtPh₂)₂(solvent)] is formed rapidly. Subsequent substitution of the solvent molecule for the diazonium cation gives the intermediate [RhH(N₂C₆H₄R′-p)Cl₂(PEtPh₂)₂]⁺, in which the hydrido-group has been rendered sufficiently acidic that it is subsequently lost from the metal. Attack of chloride at the metal increases the basicity of the aryldiazenido-ligand sufficiently for it to be protonated and yield the aryldiazene product trans,mer-[Rh(NHNC₆H₄R′-p)Cl₃(PEtPh₂)₂]. The various influences of isotopic substitution of the hydrido-group in cis,mer-[RhHCl₂(PEtPh₂)₃] and in the acid have been explored for the reactions in acetonitrile.