Cobaltoceniumselenolate Gold(I) Complexes: Synthesis, Spectroscopic, Structural and Anticancer Properties

Curious Case of Cobaltocenium Carbaldehyde

Cobaltocenium carbaldehyde (formylcobaltocenium) hexafluoridophosphate, a long sought-after functionalized cobaltocenium salt, is accessible from cobaltocenium carboxylic acid by a three-step synthetic sequence involving (i) chlorination to the acid chloride, (ii) copper-borohydride reduction to the hydroxymethyl derivative, and (iii) Dess-Martin oxidation to the title compound. Due to the strongly electron-withdrawing cationic cobaltocenium moiety, no standard aldehyde reactivity is observed. Instead, nucleophilic addition followed by haloform-type cleavage prevails, thereby ruling out common useful aldehyde derivatization. One-electron reduction of cobaltocenium carbaldehyde hexafluoridophosphate affords the deep-blue, isolable cobaltocene carbaldehyde 19-valence-electron radical whose spin density is located fully at cobalt and not at the formyl carbon atom. ¹H/¹³C NMR, IR, EPR spectroscopy, high-resolution mass spectrometry, cyclic voltammetry, single crystal structure analysis (XRD), and density functional theory are applied to characterize these unusual formyl-cobaltocenium/cobaltocene compounds.

Recent development of gold(I) and gold(III) complexes as therapeutic agents for cancer diseases

Metal complexes have demonstrated significant antitumor activities and platinum complexes are well established in the clinical application of cancer chemotherapy. However, the platinum-based treatment of different types of cancers is massively hampered by severe side effects and resistance development. Consequently, the development of novel metal-based drugs with different mechanism of action and pharmaceutical profile attracts modern medicinal chemists to design and synthesize novel metal-based agents. Among non-platinum anticancer drugs, gold complexes have gained considerable attention due to their significant antiproliferative potency and efficacy. In most situations, the gold complexes exhibit anticancer activities by targeting thioredoxin reductase (TrxR) or other thiol-rich proteins and enzymes and trigger cell death via reactive oxygen species (ROS). Interestingly, gold complexes were recently reported to elicit biochemical hallmarks of immunogenic cell death (ICD) as an ICD inducer. In this review, the recent progress of gold(I) and gold(III) complexes is comprehensively summarized, and their activities and mechanism of action are documented.

Bis(μ-cobaltoceniumselenolate-1:2κ2 Se:Se)bis[bis(cobaltoceniumselenolate-κSe)mercury(II)] tetrakis(hexafluoridophosphate) acetonitrile disolvate

The cation in the title salt has a bi­tetra­hedral {Hg₂Se₆} core.

The title compound, [Co₆Hg₂(C₅H₅)₆(C₅H₄Se)₆](PF₆)₄·2CH₃CN or [Hg₂(CcSe)₆][PF₆]₄·2CH₃CN (Cc = C₁₀H₉Co), was obtained as bright-orange needle-shaped crystals. It is a salt containing a tetra­cationic dimercury species with six cobaltoceniumseleno­late ligands, four hexa­fluorido­phosphate counter-ions and two aceto­nitrile solvent mol­ecules. The cation (point group ) has a bi­tetra­hedral {Hg₂Se₆} core with two bridging Se atoms and four terminal Se atoms.