Trithiacrown palladium(II) complexes with cyclometallating ligands: Isomer effects, intramolecular palladium–sulfur interactions, and reversible PdII/III and PdIII/IV oxidations

Synthetic and structural studies of heteroleptic platinum(II) and palladium(II) complexes containing thiacrown and monodentate phosphane ligands

“…Nevertheless, it is not the only contributor. We would note that all [9]aneS 3 complexes of Pt(II), Pd(II), and Au(III) with cyclometallating nitrogen-containing ligands, such as phenylpyridine, also contain a "unsymmetrical" [S 2 + NC] coordination environment, but in contrast display a AA'BB' proton pattern [7,33,34], the same as the bis phosphane complexes reported here. We suggest that coupling involving the 31 P nucleus is playing a role.…”

“…Our group and others have previously reported on Pt(II) and Pd(II) complexes with the thiacrown ligand, 1,4,7-trithiacyclononane ( [9]aneS 3 ) and related macrocyclic ligands [1][2][3]. The complexes show an interesting array of unusual properties including the stabilization of rare mononuclear trivalent oxidation states [4][5][6][7][8][9][10], C-H bond activation [12], anion recognition [13], photophysical properties [14,15], antimony-carbon bond activation [16], geometric distortions in five coordination [17], different intermolecular π-π stacking motifs [18], and uncommon metal-metal bond formation [19]. Heteroleptic Pt(II) and Pd(II) complexes with trithiacrowns form geometries best described as elongated square pyramids, with two of the three sulfur donors lying in the square plane while the third forms a long distance axial interaction.…”

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

“…More recently, cyclometallated palladium systems have shown evidence suggesting the Pd(III) oxidation state can play an important role in catalysis. [4][5][6][7] Our previous studies of cyclometallated Pd(II) complexes with [9]aneS 3 (1,4,7-trithiacyclononane) have shown unusual well-defined sequential 1-e-reversible Pd II/III and Pd III/IV electrochemistry, suggesting some stability of a potentially five-coordinate Pd(III) species 8,9 Solid-state structural evidence also suggests axial Pd⋯S interactions of [9] aneS 3 play a key role in this behavior. The vast majority of structures of d 8 metal complexes with [9]aneS 3 demonstrate that the ligand forms two M-S bonds with a third M⋯S interaction longer than a bond but significantly shorter than the sum of van der Waals radii.…”

“…The vast majority of structures of d 8 metal complexes with [9]aneS 3 demonstrate that the ligand forms two M-S bonds with a third M⋯S interaction longer than a bond but significantly shorter than the sum of van der Waals radii. The disparity between the electronic preferences of square planar d 8 ions and the endodentate geometric preference of the [9]aneS 3 ligand permits stabilization of related complexes in unusual oxidation states such as Pd(III), 10 Pt(III), 11 and Au(II). 12 While the coordination chemistry of [9]aneS 3 has been studied widely, reports of metal complexes of related mixed donor tridentate macrocyclic ligands such as [9]aneS 2 N ( [9]aneS 2 N = 1-aza-4,7-dithiacyclonone) 13 and [9]aneS 2 O ( [9]aneS 2 O = 1-oxa-4,7-dithiacyclononane) are sparse.…”

“…Unlike complexes of [9]aneS 3 which almost exclusively display endodentate ligand conformations, [9]aneS 2 O can bind in both exodentate and endodentate fashion. While the endo/exo preference of bonding [9]aneS 2 O to transition metals likely involves the coordination number and stereochemical preferences of the metal and hard/soft compatibility, d 8 metal complexes present additional complexity with the possibility of axial interactions. Of particular interest are the complexes Pt( [9] aneS 2 O)Cl 2 and Pd( [9]aneS 2 O)Cl 2 .…”