Faculté des sciences

Palladium complexes containing potentially chelating pyridylidene-type carbene ligands

Poulain, Aurélie ; Neels, Antonia ; Albrecht, Martin

In: European Journal of Inorganic Chemistry, 2009, no. 13, p. 1871 - 1881

Oxidative addition of 2-bromopyridine derivatives containing a potentially chelating donor group E (E = NMe₂, SMe, SPh) to palladium(0) gives C,E-bound pyridylpalladium(II) complexes. Mono-, di-, and polymeric palladium complexes are obtained depending on the type of functionalization at the pyridyl nitrogen. With a lone pair at nitrogen, dimetallic products are isolated, while... Plus

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    Summary
    Oxidative addition of 2-bromopyridine derivatives containing a potentially chelating donor group E (E = NMe₂, SMe, SPh) to palladium(0) gives C,E-bound pyridylpalladium(II) complexes. Mono-, di-, and polymeric palladium complexes are obtained depending on the type of functionalization at the pyridyl nitrogen. With a lone pair at nitrogen, dimetallic products are isolated, while protonation gives monometallic pyridylidene-type complexes. Remarkably, N-methylation inhibits chelating ligand coordination and a one-dimensional polymer is formed instead. Heck-type arylation of styrene is used as a probe for the catalytic activity of the palladium pyridylidene complexes and reveals moderate activities. Mechanistic studies support a heterogeneous mode of action, including loss of the pyridylidene-type ligand from the metal coordination sphere.