Antimony(V) Chloride, SbCl5 as a Labile Reagent in Organic Transformations

Oxidation Pathways Involving a Sulfide-Endcapped Donor-Acceptor-Donor π-Conjugated Molecule and Antimony(V) Chloride

The oxidation pathways and products of a discrete, sulfide-endcapped donor-acceptor-donor (D/A/D) molecule, namely, propylenedioxythiophene-benzothiadiazole-propylenedioxythiophene, are investigated. The electrochemical and chemical oxidations proceed by two distinct routes. Specifically, electrochemical oxidation undergoes a sequential two-step, one-electron (1e^-) oxidation route with a 117 mV difference between consecutive half-wave potentials. In contrast, chemical oxidation by antimony(V) chloride (SbCl₅) causes the generation of four different oxidized species: (a) the 1e^- oxidation state, (b) a decomposition product, (c) the 2e^- oxidation state, and (d) a chloride adduct of the 2e^- oxidation state. The decomposition product is generated by the reaction of the 1e^- oxidation state with residual water, resulting in nucleophilic aromatic substitution at the sulfide group terminal positions. This reaction leads to the formation of a 2e^- oxidized, oxygen atom (ketone) terminated decomposed molecule. The chloride adduct is determined to be produced by electrophilic chloronium ion (2e^-) oxidation by the SbCl₄⁺ complex, which is a product of SbCl₅ ligand disproportionation. The formation of the 2e^- oxidized chlorine adduct shows to be linearly dependent on the molarity of SbCl₅ in dichloromethane, giving new insight into the concentration dependent reactivity of SbCl₅ as a 2e^- oxidant. The electronic, optical, and magnetic properties and geometric structures of the 1e^- and 2e^- oxidized hexachloroantimonate salts are fully characterized by a combination of electrochemistry, X-ray crystallography, UV-vis-NIR, electron paramagnetic resonance, NMR spectroscopies, and density functional theory calculations. The aim of this study is to provide a thorough understanding of the redox pathways of a D/A/D π-conjugated organic molecule for potential application in organic electrochromic devices.

Establishing the correlation between catalytic performance and N→Sb donor–acceptor interaction: systematic assessment of azastibocine halide derivatives as water tolerant Lewis acids

A series of organoantimony(iii) halide complexes with a tetrahydrodibenzo[c,f][1,5]azastibocine framework were synthesized and employed as water tolerant Lewis acid catalysts.