Synthesis and Characterization of Methyl-Palladium and -Platinum Complexes Supported by N,O- and N,S-Donor Ligands

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.

Controlled Access to Four- and Six-Membered Palladacycles via Modifying Donor Abilities of β-Ketiminato Ligands ("NacAcs")

The synthesis of Pd complexes of the type [PdBr(ⁱPr₂-bimy)(NacAc)] (NacAc = β-ketiminate, ⁱPr₂-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene) was attempted, in a continuing effort to quantify donor abilities of chelating β-ketiminate ligands using the Huynh electronic parameter for bidentate donors (HEP2). Subtle variation of N-substituents on the NacAc backbone was discovered to induce a drastic change in the preferred chelating mode, in that the commonly encountered κ²-N,O-six-membered palladacycles were observed with R = Me and Et, while the unusual κ²-C,N-four-membered palladacycles were isolated with R = ⁱPr, Cy, and ^tBu. Computational studies subsequently corroborated these findings, in the form of an overall exergonic six-to-four-membered ring contraction process and a lower associated activation energy for the three more electron-donating alkyl moieties. This trend in the established energy profiles can be attributed to a reduced HOMO-LUMO gap in the corresponding optimized structures of the six-membered ring complexes.

Bis(dimethylsulfoxide)carbonateplatinum(ii), a new synthon for a low-impact, versatile synthetic route to anticancer Pt carboxylates

The work describes a new low-impact synthetic route to Pt(ii)-carboxylate complexes, a class of compounds provided with established anticancer activity. The process is based on the ligand substitution on [PtCO3(Me2SO-S)2] (), a new synthon that can be easily prepared in water with high yield, is stable as a solid, and is reactive in solution where all its ligands can be easily replaced. It reacts with acidic O-donors releasing CO2 as the only side-product, whose development also supplies a driving force toward the products. The substitution of carbonate led to new Pt-DMSO carboxylate complexes , while the total substitution of the ligands of complex gave new Pt-phosphino carboxylates in high yields. The X-ray crystal structures of complexes [Pt(d(-)-quinate-O,O')(Me2SO-S)2] (), [Pt(salicylate)(Me2SO-S)2] () and [Pt(salicylate)(PPh3)2] () were determined. The tests of the antiproliferative activity of complexes on two human tumoral cell lines, A2780 (cisplatin-sensitive) and SKOV-3 (cisplatin-resistant), showed that the PTA (PTA = 1,3,5-triaza-7-phosphaadamantane) complexes were the most active on both cell lines.

Diverse modes of functionalisation of ruthenium coordinated β-ketoiminate analogues

Varying chelation assisted as well as solvent dependent reactivity profiles of isostructural β-ketoiminate analogues explicate their non-spectator behaviour and fractional redox non-innocence.