530403-13-5Relevant articles and documents
The role of ate complexes in the lithium-sulfur, lithium-selenium and lithium-tellurium exchange reactions
Reich, Hans J.,Gudmundsson, Birgir Oe.,Green, D. Patrick,Bevan, Martin J.,Reich, Ieva L.
, p. 3748 - 3772 (2007/10/03)
Hypervalent ate complexes are presumptive intermediates in the metal-halogen, metal-tellurium, and related exchange reactions. The effect of o,o′-biphenyldiyl vs. diphenyl substitution on formation of tellurium ate complexes was studied by a kinetic technique and by NMR spectroscopy. Only a modest increase in the association constant (Kate) was measured. When Li/M exchanges of o,o′-biphenyldiyl sulfides and selenides were made intramolecular by means of a m-terphenyl framework (12-S, 12-Se, 21), enormous increases (> 109) in the rate of Li/S and Li/Se exchange were observed compared to acyclic models. Apparently, these systems are ideally preorganized to favor the T-shaped geometry of the hypervalent intermediates. For the selenium systems, ate complex intermediates (20-Se, 26) were detected spectroscopically in THF- or THF/HMPA-containing solutions. A DNMR study showed that Li/Se exchange was substantially faster than exchange of the lithium reagents with the ate complex. Therefore, these ate complexes are not on the actual Li/Se exchange pathway.
