Ni(II), Pd(II) and Pt(II) complexes with SacNac tridentate ligand

Helical dinuclear 3d metal complexes with bis(bidentate) [S,N] ligands: synthesis, structural and computational studies

A diprotic bis(β-thioketoimine) ligand precursor featuring a flexible 4,4'-methylbis(aniline) linker, H22, was synthesised via treatment of the corresponding bis(β-ketoimine) with Lawesson's reagent. Lithiation of H22 and coordination with one equivalent of d-block metal(II) chlorides MCl2(THF)x (M = Fe, Co and Zn) yielded a corresponding series of homoleptic dinuclear complexes, [M2(μ-2)2]. X-ray diffraction analysis reveals a tetrahedral geometry for the two metals and a double-stranded helicate structure arising from inter-strand face-face π-stacking. These interactions create a helical 'twist' of ca. 70°. Utilising a bulky mononucleating β-thioketoiminate ligand, [3]-, the analogous series of homoleptic monometallic complexes, [M(3)2] (M = Fe, Co and Zn), were prepared and characterised by spectroscopic and analytical techniques. A comprehensive DFT study of all complexes reveals a stronger M-S bonding compared to M-N due to a higher degree of covalency. Solution magnetic studies and natural bonding orbital calculations on the mono- and dinuclear iron and cobalt complexes are consistent with high-spin tetrahedral Fe(II) and Co(II) centres, and cyclic voltammetry reveals both oxidation and reduction processes are accessible.

Steric and electronic influence on Cu-Cu short contacts in β-thioketiminato tricopper(I) clusters

A series of β-thioketiminate copper(I) complex trimers [LCuI]3 were synthesized by modifying the ligand framework with electron-withdrawing groups (F and Cl) or electron-donating groups (iPr and Me) at the N-aryl ring as well as with CF3 groups on the chelating backbone. This ligand modification significantly impacts the enhancement of Cu⋯Cu short contacts, which can be rationalized by using steric and electronic factors of the chelated ligand. We observed that this intramolecular cuprophilicity among [LCuI]3 complexes is primarily governed by the size of N-aryl ortho-substituents. These findings were well supported by X-ray crystallography, Raman spectroscopy, and Mayer bond order analysis. The electronic effects induced by the ligand modification on the LCuI fragment were investigated using CO and 2,4,6-CNC6H2Me3 as probe molecules. Corroborated by the FTIR and CV measurements, our results reveal that the β-thioketiminate SN chelators induce more pronounced changes in the electronic character of the LCuI fragment due to the presence of CF3 groups on the chelating backbone in comparison with the F or Cl substituents on the N-aryl ring.

Effect of chalcogen bonding interactions on molecular structures; theoretical and crystallographic studies on two palladium(ii) acetate complexes

New palladium complexes, [Pd(L)(OAc))], have been synthesized. The complexes and their ligand have been characterized by X-ray crystal structure analysis. Interestingly, the molecular structures of the two complexes are stabilized by S⋯O chalcogen bonds.