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

Abstract

The first abnormally coordinated NHC complex of an early transition metal, [(aIMes)TaCl2(NMe2)3], is prepared.

Imidazolinium N-Heterocyclic Carbene Ligands for Enhanced Stability on Gold Surfaces

“…We postulated that the imidazolinium NHC ligand, 2 , would exhibit enhanced stability in acid due to increased σ-donation and because it would not be prone to the electrophilic attack at the 4 and 5 positions on the ring in the same manner as imidazole NHC, 1 . Indeed, a few unsaturated imidazoliums have been converted to saturated imidazoliniums by the addition of a strong acid. , Upon submerging the respective NHC-coated AuFONs in hydrochloric acid (1 M) for 24 h, we observed a complete degradation of the imidazolium NHC signal (Figure , right), whereas the imidazolinium variant is unchanged (Figure , left). These results demonstrate a limitation for one of the two most commonly used NHC ligands on gold surfaces: stability toward strong acids.…”

“…66 Indeed, a few unsaturated imidazoliums have been converted to saturated imidazoliniums by the addition of a strong acid. 67,68 Upon submerging the respective NHC-coated AuFONs in hydrochloric acid (1 M) for 24 h, we observed a complete degradation of the imidazolium NHC signal (Figure 5, right), whereas the imidazolinium variant is unchanged (Figure 5, left). These results demonstrate a limitation for one of the two most commonly used NHC ligands on gold surfaces: stability toward strong acids.…”

Mesoionic and Related Less Heteroatom-Stabilized N-Heterocyclic Carbene Complexes: Synthesis, Catalysis, and Other Applications

“…For example, [Co{N(SiMe 3 ) 2 } 2 ] induces C−H bond activation in the imidazolium salt 245 and affords the bis(carbene) cobalt(II) complex 366 with two mesoionic 4-imidazolylidene ligands (Scheme 143). 246 Likewise, [Ta(NMe 2 ) 5 ] activates the imidazolium C4−H bond even in C2-protonated imidazolium salts such as 272c•HCl to produce complex 367 (Scheme 144), 309 presumably as a result of the large steric demand of the NMe 2 ligands around tantalum.…”

Structural Characterization of a Fluorido‐Amide of Niobium, and Facile CO2 Incorporation Affording a Fluorido‐Carbamate

“…To date, this flourishing investigation has not led to the synthesis of ternary fluorido‐amides of niobium or tantalum, which remain a substantially unknown family of inorganic compounds , . Few relevant, well‐characterized species comprise the amido unit as part of a pincer multidentate framework and/or additional ligands …”