Electronic Structure Trends in N-Heterocyclic Carbenes (NHCs) with Varying Number of Nitrogen Atoms and NHCTransition-Metal Bond Properties

Theoretical strategies toward stabilization of singlet remote N-heterocyclic carbenes

Theoretical investigations predict that the singlet states of ylide-substituted remote carbenes are significantly stable and comparable to those of experimentally known NHCs. They are also found to be strongly σ-donating in nature as evident from an evaluation of the carbonyl stretching frequencies (νCO ) of their complexes with the [Rh(CO)2 Cl] fragment. NICS and QTAIM based bond magnetizability calculations indicate the presence of cyclic electron delocalization in majority of the molecules. © 2016 Wiley Periodicals, Inc.

Bimetallic Cu(i) complex with a pyridine-bridged bis(1,2,3-triazole-5-ylidene) ligand

Expanded π-conjugated system catalyst for hydroboration of alkenes.

Nucleophilicity of normal and abnormal N-heterocyclic carbenes at DFT: steric effects on tetrazole-5-ylidenes

Nucleophilicity of both normal (1R) and abnormal (2R) N-heterocyclic carbene (NHC); every 2R showing a higher nucleophilicity than its corresponding 1R isomer (R = H, methyl, ethyl, i-propyl, and t-butyl).

Direct estimate of the internal π-donation to the carbene centre within N-heterocyclic carbenes and related molecules

Fifteen cyclic and acylic carbenes have been calculated with density functional theory at the BP86/def2-TZVPP level. The strength of the internal X→p(π) π-donation of heteroatoms and carbon which are bonded to the C(II) atom is estimated with the help of NBO calculations and with an energy decomposition analysis. The investigated molecules include N-heterocyclic carbenes (NHCs), the cyclic alkyl(amino)carbene (cAAC), mesoionic carbenes and ylide-stabilized carbenes. The bonding analysis suggests that the carbene centre in cAAC and in diamidocarbene have the weakest X→p(π) π-donation while mesoionic carbenes possess the strongest π-donation.

Quantifying N-heterocyclic carbenes as umpolung catalysts in the benzoin reaction: balance between nucleophilicity and electrophilicity

Different types of N-heterocyclic carbenes, i.e. normal, reduced heteroatom stabilized, remote and abnormal carbenes, are computationally assessed (THF-CPCM-B3LYP/6-311+G(d,p)//B3LYP/6-31G(d)) in the benzoin reaction to study their characteristics as umpolung catalysts.

Structure and bonding of [(SIPr)AgX] (X = Cl, Br, I and OTf)

A series of iso-structural complexes [(SIPr)AgX] (X = Cl, Br, I, OTf; SIPr = 1,3-bis(2,6-diisopropylphenyl)imidazolidene) were synthesised, including the first example of a N-heterocyclic carbene silver(i) complex containing an O-bound triflate.

Activation of boryl-, borylene and metalloborylene complexes by isonitriles

One or several isonitriles can insert into metalloboryl and metalloborylene complexes to afford cyclic or spiro compounds with bonding controlled by the electron count at the metal and in the ring.

Chelation assistance as a tool for the selective preparation of an imidazole-based mesoionic palladium carbene complex

A C(4)-bound palladium-N-heterocyclic carbene (4) was selectively obtained from the C(2)-unsubstituted imidazolium salt 3. The higher stability of the C(4) versus the C(2)-bound carbene complex due to pyridine chelation assistance allowed this mesoionic compound to be obtained.

Pincer versus pseudopincer: isomerism in palladium(ii) complexes bearing κ3C,S,C ligands

In NHC pincer complexes incorporating a hemilabile donor site, there exists an equilibrium between the true pincer form and a pseudopincer coordination isomer.

‘Janus-type’ organopotassium chemistry observed in deprotonation of mesoionic imidazolium aminides and amino N-heterocyclic carbenes: coordination and organometallic polymers

Deprotonation of the observable tautomeric equilibrium mixture of mesoionic 4-aminide imidazoliums and the corresponding 4-amino NHCs allows isolation of a monomeric potassium (imidazol-2-ylidenyl)(anilide), a ‘free’ anionic carbene, or polymeric organometallics with ‘Janus-type’ anionic NHC repeat units.