Rh(III) and Ir(III) complexes of bis(pyrazolyl)diphenylborate ligand: hydrolysis of the B-N bond and benzene C-H activation

Pentamethylcyclopentadienyl complexes of Rhodium and Iridium have been massively used as a starting materials for a wide number of organometallic complexes that found applications in several fields. Cp*M fragments (M = Rh or Ir) complexes containing scorpionates ligands have recently attracted considerable attention because of their ability to activate the aliphatic and aromatic C-H bonds of hydrocarbons and other substrates. As an extension of ours previous works we have undertaken a systematic study of the reactions between [MCp*Cl2]2 dimers (M = Rh, Ir) and the bis(pyrazolyl)diphenylborate ligand K(pz)2B(Ph)2. The Cp*M[2-(pz)2B(Ph)2]Cl compounds (M=Rh and Ir) (fig. 1a) are prepared under anhydrous conditions and new Cp*Rh(Ph)[2-(pz)(OH)B(Ph)2] (fig. 1b) and Cp*Ir(pzH)[2-(pz)(OH)B(Ph)2]Cl (fig. 1c) derivatives containing the in situ-formed ligand Ph2B(pz)OH have additionally been obtained when the reactions are carried out in incompletely anhydrous acetonitrile solvent. Reaction between Cp*Rh[2-(N-pz)2B(Ph)2]Cl and AgClO4 in acetonitrile affords the ionic Cp*Rh(Ph)[2-(N-pz)(OH)B(OH)]ClO4 complex. Their structure has been confirmed by analytical and spectral (IR, 1H NMR, 13C NMR, ESI-MS, X-ray). X-ray diffraction studies have been performed, together with theoretical modelling, and hydrolysis mechanism of bis(pyrazolyl)diphenyl borate ligand has been proposed.