Nickel‐Catalyzed Intramolecular 1,2‐Aryl Migration of Mesoionic Carbenes (iMICs)

Abstract

Intramolecular 1,2‐Dipp migration of seven mesoionic carbenes (iMICAr) 2 a–g (iMICAr=ArC{N(Dipp)}2CHC; Ar=aryl; Dipp=2,6‐iPr2C6H3) under nickel catalysis to give 1,3‐imidazoles (IMDAr) 3 a–g (IMDAr=ArC{N(Dipp)CHC(Dipp)N}) has been reported. The formation of 3 indicates the cleavage of an N−CDipp bond and the subsequent formation of a C−CDipp bond in 2, which is unprecedented in NHC chemistry. The use of 3 in accessing super‐iMICs (5) (S‐iMIC=ArC{N(Dipp)N(Me)C(Dipp)}C) has been shown with selenium (6), gold (7), and palladium (8) compounds. The quantification of the stereoelectronic properties reveals the superior σ‐donor strength of 5 compared to that of classical NHCs. Remarkably, the percentage buried volume of 5 (%Vbur=45) is the largest known amongst thus far reported iMICs. Catalytic studies show a remarkable activity of 5, which is consistent with their auspicious stereoelectronic features.

Tuning the π‐Accepting Properties of Mesoionic Carbenes: A Combined Computational and Experimental Study

“…This NMR‐based methodology was introduced by the group of Ganter in 2013 [42] . Since then, and it has become a popular method for evaluating the π‐accepting properties of singlet carbenes [21,42,47,61,62] . The broad spectral range of 77 Se NMR allows for a good discrimination of closely related carbenes.…”

“…Previous investigations have shown that the substituent at C4 position of a mesoionic imidazolylidene ligand has a strong influence on the stability and the stereoelectronic properties of the MIC. [ 22 , 23 , 47 , 48 ] The remote substituent at C2 position was thought to be less important. [23] We have recently studied MIC ligands featuring unusual diazoaryl substituents at C2.…”

“… [42] Since then, and it has become a popular method for evaluating the π‐accepting properties of singlet carbenes. [ 21 , 42 , 47 , 61 , 62 ] The broad spectral range of 77 Se NMR allows for a good discrimination of closely related carbenes. Furthermore, Se adducts of carbenes are easily accessible by the addition of elemental selenium to an in situ generated carbene.…”

Isolation of 1,4‐Diarsinine‐1,4‐diide and 1,4‐Diarsinine Derivatives

“…[15] The As À C bond lengths (Table 1) of 4 (1.947(3)-1.957(3) ) are smaller than that of (IPr)AsCl 3 (2.018(3) ), [15] which is consistent with the stronger sdonor property of C4 carbenes. [18] The CÀC bond lengths (1.361(4), 1.364( 4) ) and the N-C'-N bond angles (106.4(2), 107.5(2)8) of the C 3 N 2 ring of 4 are comparable with those of 1 (1.353(2) and 106.4(2)8). [19] The six-membered C 4 As 2 ring of 5 and 6 (Figure 2) is almost planar.…”

Trendbericht Anorganik 2022 Teil 2: Nebengruppen und Koordinationschemie, Bioanorganik und mehr

“…Die Methylierung des Imidazols und anschließende Deprotonierung erzeugt eine neue Ligandenklasse, die sonst möglicherweise nicht zugänglich ist. 40) Goicoechea und Weller haben einen Zintl-Cluster als Homogenkatalysator genutzt. Kombination der Cluster K[Ge 9 (Si(SiMe 3 ) 3 ) 3 ] und RhCl(COD) liefert einen definierten Rhodiumkatalysator.…”