Synthesis and characterization of new (pyrazolyl)aryl phosphinite PCN pincer palladium(II) complexes

Two unsymmetrical PCN pincer Pd(II) complexes 3a–3b which are based on (pyrazolyl)aryl phosphinite ligands and contain two fused six-membered palladacycles have been synthesized from 3-(3,5-dimethylpyrazol-1-ylmethyl)benzyl alcohol (2) by one-pot phosphorylation/palladation reaction via C–H bond activation of the related ligands. The pyrazole-coordinated phosphine-free Pd(II) complex (4) was also isolated in the preparation of pincer complex 3a. The new complexes were characterized by elemental analysis, 1H NMR, 13C NMR, 31P {1H} NMR (for pincer complexes) and IR spectra. And the molecular structures of 3b and 4 have been further determined by X-ray single-crystal diffraction. The pincer Pd complexes 3a and 3b exhibited rather low activity in the allylation of benzaldehyde.

Two new unsymmetrical PCN pincer Pd(II) complexes 3a-3b with (pyrazolyl)aryl phosphinite ligands have been conveniently prepared. These new pincers contain two fused six-membered palladacycles and an X-ray single-crystal structure of 3b has been obtained. The two complexes exhibited rather low activity in the allylation of benzaldehyde.Figure optionsDownload as PowerPoint slideHighlights
► Two new (pyrazolyl)aryl phosphinite PCN pincer Pd(II) complexes were prepared.
► They are unsymmetrical pincers and contain two fused six-membered palladacycles.
► An X-ray single-crystal structure of the new pincer complex has been obtained.