A Cationic Terminal Methylene Complex of Ir(I) Supported by a Pincer Ligand

A rare example of a cationic methylene complex of Ir­(I), [(PONOP)­Ir­(CH₂)]⁺, 2 (PONOP = 2,6-bis­(di-tert-butylphosphinito)­pyridine), has been prepared by α-hydride abstraction from the previously described neutral methyl complex [(PONOP)­Ir­(CH₃)]. The intrinsic high reactivity of the compound prevented both the isolation of a pure solid and its full characterization in the solid state. Nevertheless, the proposed molecular structure finds unequivocal support in multinuclear NMR spectroscopy and in reactivity studies that include reactions with Lewis bases, dihydrogen, and ethyl diazoacetate. An ylide compound, 3, resulted from the reaction between [(PONOP)­Ir­(CH₂)]⁺ and PMe₃, while the η²-alkene complex 5 formed in a CC coupling reaction involving the methylene ligand of 2 and ethyl diazoacetate. Hydrogenolysis of the IrCH₂ linkage of 2 led to several, previously known, hydride and dihydrogen iridium complexes.