The first bismuth–NHC complexes

Abstract

The synthesis, isolation and crystallographic characterization of the first N-heterocyclic carbene adducts of bismuth is reported, by direct reaction of the Dipp2NHC (Dipp = 2,6-diisopropylphenyl) or (i)Pr2(Me2)NHC with BiCl3. This represents the last non-radioactive element from groups 13-17 for which an NHC-element fragment remained unreported.

Isolation of Cyclic(Alkyl)(Amino) Carbene–Bismuthinidene Mediated by a Beryllium(0) Complex

“…This is in part due to metallic nature of bismuth, which results in significant differences in stability and reactivity compared to light Pn elements. Dutton and co‐workers reported the first examples of N‐heterocyclic carbene–bismuth complexes; however, attempts to reduce the bismuth(III) chloride adducts to subvalent species were unsuccessful . Goicoechea and co‐workers synthesized NHC–bismuth(III) tribromides, but the reactivity with reducing agents was not reported.…”

“…There is no example of a carbene‐bismuthinidene compound that can be used to compare to compound 3 . The Bi−C carbene bond in 3 [Bi1−C1: 2.199(2) Å] is the shortest bond in all reported C carbene −Bi bonds (2.35–2.4566 Å) and significantly shorter than that in the Bi III compound Et2 CAAC‐Bi(Ph)Cl 2 [2.4566(15) Å] . Notably, the Bi1−C1 bond [2.199(2) Å] is shorter than the covalent Bi− C Ph bond [Bi1‐C23: 2.278(2) Å] in compound 3 , which is indicative of partial double bond character of between CAAC and bismuth metal center.…”

“…Dutton and co-workers reported the first examples of N-heterocyclic carbene-bismuth complexes;h owever,a ttempts to reduce the bismuth(III) chloride adductst os ubvalent species were unsuccessful. [11] Goicoechea and co-workerss ynthesized NHC-bismuth(III) tribromides, [12] but the reactivity with reducing agents was not reported. Ar ecent comprehensive review of the fieldh ighlighted the difficulty in synthesizingN HC adducts of heavierP ne lements, whichw as partly attributed to the destabilizationo ft he 2p p -np p interaction as you descend the group.…”

“…2.199(2) ]ist he shortest bond in all reportedC carbene ÀBi bonds (2.35-2.4566 )a nd significantly shortert han that in the Bi III compound Et2 CAAC-Bi(Ph)Cl 2 [2.4566 (15) ]. [11][12]15] Notably,t he Bi1ÀC1 bond [2.199(2) ]i ss horter than the covalentB i ÀC Ph bond [Bi1-C23:2 .278(2) ]i nc ompound 3,w hich is indicative of partial double bond character of between CAAC and bismuth metal center. There is no significant differencei nt he BiÀ C Ph bond in compound 3 [2.278(2) ]a nd Et2 CAACÀBi(Ph)Cl 2 [2.2732 (16) ].…”

London Dispersion Interactions in Pnictogen Cations [ECl2]+ and [E=E]2+ (E=P, As, Sb) Supported by Anionic N‐Heterocyclic Carbenes

“…Although NHC‐stabilized diantimony and dibismuth were also calculated to be stable entities, the isolation of (IDipp) 2 E 2 (E=Sb, Bi) by reduction of the carbene adducts (IDipp)ECl 3 failed, suggesting “that the ′carbene‐stabilization′ strategy may be less effective with the heavier pnictogens.” Likewise, the attempted reduction of a series of six‐membered tetrahydropyrimidin‐2‐ylidene adducts of group 15 element trichlorides only returned a mixture of products, including significant amounts of the free carbene . Cyclic (alkyl)(amino)carbenes (CAACs), however, which were also employed for the preparation of the (CAAC) 2 E 2 species X (E=P) and XI (E=As), allowed the preparation of (CAAC) 2 Sb 2 ( XI ) by three‐electron reduction of (CAAC)SbCl 3 with KC 8 (Figure ) .…”