Structure and bonding analysis in dihalobismuth complexes of iron, ruthenium and osmium [(η5-C5H5)(CO)2M(BiX2)]: A theoretical study

Pandey, Krishna K.; Patidar, Pankaj; Tiwari, Pradeep

doi:10.1016/j.poly.2011.12.028

Cited by 4 publications

(1 citation statement)

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“…To gain a deeper understanding of how bismuth promoter 1 interacts with the thioglycosides in solution and to construct a model that incorporates the experimental findings reported above, we carried out a series of quantum chemical calculations using density functional theory (DFT). Although theoretical studies of bismuth-containing systems are less common than studies on completely organic or transition metal-containing systems, a significant amount of work has shown that DFT can be effective for modeling Bi(III) chemistry, − although dispersion corrections are often needed. Fewer studies have been performed on Bi(V) systems; however, there are some notable examples. , Assuming that the Bi(V) species acts as a Lewis acid, one plausible mode of interaction may be its coordination to the glycosyl donor by binding to the thiopropyl arm.…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Studies of Bismuth(V)-Mediated Thioglycoside Activation Reveal Differential Reactivity of Anomers

et al. 2016

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The mechanism of bismuth(V)-mediated thioglycoside activation was examined using reaction kinetics and quantum chemical reaction models. NMR experiments show an unusual nonlinear growth/decay curve for the glycosylation reaction. Further studies suggest an anomeric inversion of the β-glycoside donor to the α-donor during its activation, even in the presence of a neighboring 2-position acetate. Interestingly, in situ anomerization was not observed in the activation of an α-glycoside donor, and this anomer also showed faster reaction times and higher product diastereoselectivites. Density functional theory calculations identify the structure of the promoter triphenyl bismuth ditriflate, [Ph3Bi(OTf)2, 1], in solution and map out the energetics of its interactions with the two thioglycoside anomers. These calculations suggest that 1 must bind the thiopropyl arm to induce triflate loss. The computational analyses also show that, unlike most O-glycosides, the β- and α-donor S-glycosides are similar in energy. One energetically reasonable anomerization pathway of the donors is an SN1-like mechanism promoted by forming a bismuth-sulfonium adduct with the Lewis acidic Bi(V) for the formation of an oxacarbenium intermediate. Finally, the computed energy compensations needed to form these α vs β Bi adducts is a possible explanation for the differential reactivity of these donors.

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