1 research outputs found
Silver and Palladium Complexes Containing Ditopic N‑Heterocyclic Carbene–Thione Ligands
The mixed donor N-heterocyclic carbene (NHC)/thione ligand
precursors [1-(3-R-2<i>H</i>-imidazol-1-yl-2-thione)methyl-3-R-2<i>H</i>-imidazol-2-ium]X, [H<b>CS</b><sup><b>R</b></sup>]X (R = methyl, benzyl; X = Br, I), have been utilized to prepare
a range of silver and palladium complexes. The coordination of <b>CS</b><sup><b>R</b></sup> to silver(I) salts has been explored,
providing dimeric complexes of the type [AgX(<b>CS</b><sup><b>R</b></sup>)]<sub>2</sub> (where R = methyl, benzyl; X = Br, I).
Structural characterization of [AgX(<b>CS</b><sup><b>Bn</b></sup>)]<sub>2</sub> revealed a bidentate coordination mode for the
mixed donor ligand and dinuclear structures where the silver centers
are bridged by two bromido centers. Palladium complexes bearing one
or two <b>CS</b><sup><b>R</b></sup> ligands have additionally
been prepared either directly, utilizing [Pd(OAc)<sub>2</sub>] as
precursor, or via transmetalation strategies. The dicationic complexes
[Pd(<b>CS</b><sup><b>R</b></sup>)<sub>2</sub>][X]<sub>2</sub> and neutral complexes [PdX<sub>2</sub>(<b>CS</b><sup><b>R</b></sup>)] (where R = methyl, benzyl; X = Br, I, PF<sub>6</sub>) have been synthesized and fully characterized. The <b>CS</b><sup><b>R</b></sup> ligand in the aforementioned complexes
does not undergo transformation of the NHC unit to a urea function,
which had been found to occur in the previously reported copper complexes.
Palladium complexes containing both NHC/thione and bis-phosphine ligands
were also prepared. Complexes of the type [Pd(<b>CS</b><sup><b>Me</b></sup>)(L<sub>2</sub>)][X]<sub>2</sub> and [PdX(<b>CS</b><sup><b>Me</b></sup>)(L<sub>2</sub>)][X] (where L<sub>2</sub> = dppe, dppp; X = Br, OAc, I, PF<sub>6</sub>) were obtained.
The presence of the bis-phosphine appears to destabilize the coordination
of the NHC/thione ligand and as a consequence leads to its elimination
from the complex