Rearrangements of phosphinoimines to phosphine–imines in ruthenium chelate complexes

Abstract

Thermal reaction of 1 : 1 mixtures of the RuCl₂(PPh₃)₃ and phosphinoimine R₂PNCPh₂ (R = Ph, iPr, Me) at 140 °C results in isolation of the dimeric species [RuCl(μ-Cl)(PPh₃)(C₆H₄(PPh₂)C(Ph)NH)]₂ (R = Ph 1, iPr 2, Me 3) containing phosphine–imine chelating ligands. Subsequent reaction of 1 and 3 with one equivalent of pyridine at room temperature give RuCl₂(PPh₃)(py)(C₆H₄(PR₂)C(Ph)NH) (R = Ph 4, Me 5). Excess pyridine reacts with 2 to give a mixture of the cis and trans-isomers of RuCl₂(py)₂(C₆H₄(PiPr₂)C(Ph)NH) 6 and 7 respectively. Treatment of 5 with excess PPh₃ affords RuCl₂(PPh₃)₂(C₆H₄(PMe₂)C(Ph)NH) 8. Aspects of the mechanism of the thermal rearrangements of the phosphinoimine to the phosphine–imine ligands are considered and the isolation of RuCl₂(Ph₂PNCPh₂)(SIMes)(CHPh) 9 and RuCl₂(PPh₃)₂(HNC(Ph)C₆H₄) 10 provide support for a proposed mechanism involving a intermediate containing a Ru-bound metallated aryl-imine fragment.