Synthesis and reactivity of subvalent compounds

C4-bound imidazolylidenes: from curiosities to high-impact carbene ligands

“…Deuterium incorporation has been accomplished within few minutes by exposure of the carbene to dmso-d 6 or to CD 3 OD. 14 Exchange under such mild conditions is remarkable and indicates a considerable lability of these protons. Notably, the corresponding imidazolium salt is resistant towards such isotope exchange reactions.…”

NHC adducts of tantalum amidohalides: the first example of NHC abnormally coordinated to an early transition metal

“…The activation of THF-d 8 with an aNHC complex was reported recently by Goicoechea et al 24 In addition, the HCvCH backbone of imidazoline-base NHC is known to be liable for the H/D exchange. 25 In CD 2 Cl 2 3 behaves similarly. Immediately after preparation, its 1 H NMR spectrum features characteristic C 2 H and C 5 H doublets at 7.90 and 7.74 ppm, respectively, along with minor signals belonging to another aNHC complex yet to be identified, and at least one additional Mes-containing species.…”

Abnormal Reactivity of an N‐Heterocyclic Carbene (NHC) with a Phosphaalkene: A Route to a 4‐Phosphino‐Substituted NHC

“…This electrophilic aromatic substitution-type mechanism appears to be involved in the reported deuteration of ItBu at the 4-and 5-positions by [D 6 ]DMSO. [10] Preliminary calculations using IMes (1) and phosphaalkene 2 showed that the initial addition to the P=C bond at the 4-position of IMes did not lead to a stable geometry for such an intermediate. Therefore, this mechanism was not considered further.…”

“…[7,8] In contrast, the abnormal behavior of an NHC in p-block chemistry is rarely observed, especially when the 2-position is not blocked or bound to a metal. [9][10][11][12] The prospect of directly functionalizing a free NHC at the 4-and 5-positions with p-block moieties is exciting as it could enable the synthesis of ligands with unique electronic and coordination properties.…”