The unique liquid chromatographic properties of Group 11 transition metals for the separation of unsaturated organic compounds

Abstract

Silver(I) and copper(I) are known to form reversible complexes with π bonds, which have been exploited in LC for separating unsaturated organic compounds. Prominent examples include the use of AgNO3-impregnated silica gel in LC, and the use of copper(I) salts for selective extraction of alkenes from hydrocarbon mixtures. The Dewar-Chatt-Duncanson model is often invoked to explain the interaction between Ag(I) and Cu(I) and π bonds. However, it is unclear if such a reversible interaction is directly related to their d(10) outer electronic configurations. Particularly, Au(I) has not been reported to separate olefins with different numbers of double bonds in LC. Also, there has not been a systematic comparison of the liquid chromatographic properties of other d(10) transition metal salts (e.g., Zn(II), Cd(II)), making it difficult to fully understand the observed reversible interactions of Ag(I) and Cu(I) with π bonds. We demonstrate for the first time that silica gel impregnated with all three Group 11 transition metals with 1+ oxidation state strongly and similarly retain olefin compounds in LC, while transition metals from Groups 10 and 12 do not. We also tested a range of functionalized silica gels to improve the stability of Cu(I) and Au(I) ions on the surface of the silica.

Chromatography with silver nitrate: part 2

“…Figure 14 Aponte and Huang et al [113][114][115][116] have spent considerable effort developing solid supported silverthiolate and related chromatography materials (e.g. 252-257) (Figure 15), which have been observed to be highly efficient in the separation of alkane/alkene mixtures differing by a single double bond.…”

Abrupt Freshening Since the Early Little Ice Age in Lake Sayram of Arid Central Asia Inferred From an Alkenone Isomer Proxy

“…The extracts were purified by column chromatography with silica gel using n ‐hexane and DCM, respectively. The DCM fractions were further purified by column chromatography with silver thiolate silica (Aponte et al, 2013; L. Wang, Longo, et al, 2019). An increasing polarity sequence of solvents (hexane: DCM [2 ml, 2:1, v:v], DCM [1 ml], and acetone [2 ml]) was used to separate compounds.…”

Rapid sequential separation of sedimentary lipid biomarkers via selective accelerated solvent extraction

“…Polyunsaturated hydrocarbons with non-conjugated double bonds (e.g. squalene) form stable charge transfer complexes with Ag + Si-gel (Guha and Janak, 1972;Cagniant, 1991;Nocun and Andersson, 2012), which can severely decrease recovery, even though such strong retention can aid in the separation of aromatic from saturated compounds (Cagniant, 1991;Hollender et al, 2003;Aponte et al, 2013;Dillon et al, 2012;Nocun and Anderson, 2012). To minimize π electron complexation with Ag + (Cagniant, 1991), this ASE method incorporated four precautionary measures: (i) inserting the filter above the Ag + Si-gel to prevent intermixing with activated Si-gel during cell construction or handling, (ii) adjusting the amount of activated Si-gel to prevent PAHs from reaching the Ag + Si-gel during the initial hexane elution, (iii) loading the TLE between layers of activated Si-gel and (iv) inverting the columns to reverse flow direction after the initial hexane elution.…”