Hemilabile bonding of 1-oxa-4,7-dithiacyclononane in cyclometallated palladium(ii) complexes

Abstract

The synthesis and characterization of a series of cyclometallated complexes of Pd(ii) incorporating the mixed donor ligand 1-oxa-4,7-dithiacyclononane ([9]aneS2O) are presented in this study.

Synthesis of mononuclear and dinuclear palladium (II) complexes containing oxadithioether ligands and their catalytic activities in norbornene polymerization

“…Two signals from ‐CH 2 O‐, ‐CH 2 S‐, and acac groups are apparent in the 13 C NMR spectrum of 2b at 25°C, with coalescence occurring at ≈70°C in CD 3 CN. The free energy of activation estimated according to the equation Δ G # = R T c [22.96 + ln ( T c /δ ν )] [ 10,75 ] for the dynamic fluxional behavior of 2b from NMR at coalescence temperatures suggests a barrier of approximately 16 kcal/mol. An activation energy Δ G # of 16.9 kcal/mol was determined for the process of pyramidal inversion of sulfur atoms occurring at the chelate complex cis ‐[PdCl 2 (MeSCH 2 CH 2 SMe)].…”

“…To further investigate the dynamic behavior of the oxadithioether ligands, we performed variable temperature 1 H NMR experiments with cationic complex 2b. [10,75] for the dynamic fluxional behavior of 2b from NMR at coalescence temperatures suggests a barrier of approximately 16 kcal/mol. An activation energy ΔG # of 16.9 kcal/mol was determined for the process of pyramidal inversion of sulfur atoms occurring at the chelate ].…”

“…[1][2][3] Among these complexes, particular attention has recently been given to palladium (II) complexes with sulfur-containing compounds, especially thiacrown ligands. [4][5][6][7][8][9][10][11][12][13][14] These compounds have interesting properties, including the stabilization of rare mononuclear trivalent oxidation states, C-H bond activation, anion recognition, photophysical properties, intermolecular π-π stacking motifs, and axial ligand-metal interactions in square planar complexes. [8,9,[15][16][17][18][19][20][21][22][23][24][25] The last structural property for Pd (II) complexes are of theoretical interest, as these complexes may contain a weak bonding component and serve as important models in associative mechanisms for ligand substitution reactions in d 8 square planar complexes.…”

“…[ 8,9,15–25 ] The last structural property for Pd (II) complexes are of theoretical interest, as these complexes may contain a weak bonding component and serve as important models in associative mechanisms for ligand substitution reactions in d 8 square planar complexes. [ 8,10 ]…”

“…[8,9,[15][16][17][18][19][20][21][22][23][24][25] The last structural property for Pd (II) complexes are of theoretical interest, as these complexes may contain a weak bonding component and serve as important models in associative mechanisms for ligand substitution reactions in d 8 square planar complexes. [8,10] Sulfur species are poisons for many catalytic processes; therefore, sulfur-containing compounds are not usually employed as ligands in transition metal-catalyzed reactions. In contrast to phosphorus, sulfur atoms in thioether ligands have only two substituents, which can create a less hindered environment.…”