Electronic Effects in Phosphino‐Iminophosphorane Pd II Complexes upon Varying the N Substituent
Résumé
Abstract Three series of palladium(II) complexes supported by a phosphine‐iminophosphorane ligand built upon an ortho‐phenylene core were investigated to study the influence of the iminophosphorane N substituent. Cis ‐dichloride palladium(II) complexes 1 in which the N atom bears an isopropyl (iPr, 1 a ), a phenyl (Ph, 1 b ), a trimethylsilyl (TMS, 1 c ) group or an H atom ( 1 d ) were synthesized in high yield. They were characterized by NMR, IR spectroscopy, HR‐mass spectrometry, elemental analysis, and X‐ray diffraction. A substantial bond length difference between the Pd−Cl bonds was observed in 1 . Complexes 1 a – d were converted into [Pd(L R )Cl(CN t Bu)](OTf)] 2 a – d whose isocyanide is located trans to the iminophosphorane. The corresponding dicationic complexes [Pd(L R )(CN t Bu) 2 ](OTf) 2 3 a – d were also synthesized, however they exhibited lower stability in solution than 2 , the isopropyl derivative 3 a being the most stable of the series. Molecular modeling was performed to rationalize the regioselectivity of the substitution of the single chloride by isocyanide (from 1 to 2 ) and to study the electronic distribution in the complexes. In particular differences between the TMS and H containing complexes vs. the iPr and Ph ones were found. This suggests that the nature of the N substituent is far from innocent and can help tune the reactivity of iminophosphorane complexes.
Domaines
ChimieOrigine | Fichiers produits par l'(les) auteur(s) |
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