Τίτλος:
Effects of the halogenido ligands on the Kumada-coupling catalytic activity of [NitBuN(PPh2)2-κ2PX2], X = Cl, Br, I, complexes
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
Novel nickel(ii) complexes bearing (tbutyl)bis(diphenylphosphanyl)amine and different halogenido ligands, [Ni(P,P)X2] = [Ni{tBuN(PPh2)2-κ2P}X2], (X = Cl, Br, I) are prepared, characterized by IR and NMR spectroscopy, mass spectrometry and X-ray crystallography, and tested as catalysts in the Kumada cross-coupling reaction of model substituted iodobenzenes and p-tolylmagnesium bromide. The data obtained together with DFT calculations indicate that these new catalysts operate in the Ni(i)–Ni(iii) mode. The highest catalytic activity and selectivity are exhibited by [Ni(P,P)Cl2], which is most easily reduced by the used Grignard reagent to the Ni(i) state. This process is much more energy demanding in the case of the bromido and iodido complexes, causing the appearance of the induction period. [Ni(P,P)Cl2] is also very active in the cross-couplings of substrates with iodine atoms sterically shielded by ortho substituents. The data obtained are in good accordance with the described positive effect of the increased electron-releasing power of N-substituents R′ on the overall catalytic performance of [Ni{R′N(PPh2)2-κ2P}X2] complexes. This journal is © The Royal Society of Chemistry
Συγγραφείς:
Ioannou, P.-C.
Coufal, R.
Kakridi, K.
Raptopoulou, C.P.
Trhlíková, O.
Psycharis, V.
Zedník, J.
Kyritsis, P.
Vohlídal, J.
Εκδότης:
Royal Society of Chemistry
Λέξεις-κλειδιά:
Ligands; Mass spectrometry; Nickel compounds; Nuclear magnetic resonance spectroscopy; X ray crystallography, Cross coupling reactions; DFT calculation; Energy; Grignard reagent; Induction periods; Iodobenzene; IR and NMR spectroscopy; Kumada cross-coupling; Nickel complex; ]+ catalyst, Catalyst activity
