Transfer of heterocyclic carbene ligands from chromium to gold, palladium and platinum

Kessler, Florian; Szesni, Normen; Maaß, Chaya; Hohberger, Christiane; Weibert, Bernhard; Fischer, Helmut

doi:10.1016/j.jorganchem.2007.03.022

Cited by 54 publications

(45 citation statements)

References 65 publications

(43 reference statements)

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“…The Au-Cl bonds in 6 and 8 [2.304 (2) [28] but roughly comparable to the same separation in chloro(pyrazolin-3-ylidene)-gold complexes [2.307(2) and 2.299(2) Å]. [29] It came as somewhat of a surprise that the crystal structure of 8, shown in Figure 5, consists of discrete molecules, devoid of any close sub-van der Waals interactions. Given the low steric demand of the 1-methylpyridin-4(1H)-ylidene ligand, this complex seemed a natural candidate for Au···Au interactions.…”

Section: Nmr Spectroscopymentioning

confidence: 82%

Preparation of Remote NHC Complexes of Rhodium(I) and Gold(I) by Ligand Transfer

et al. 2009

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The rNHC complexes (5-butyl-1,2-dimethylpyridin-4(1H)-ylidene)Cr(CO) 5 (1), as well as the novel compounds (1,2-dimethyl-5-phenylpyridin-4(1H)-ylidene)M(CO) 5 (2, M = Cr; 3, M = W) and (1-methylpyridin-4(1H)-ylidene)Cr(CO) 5 (7) were prepared from Fischer carbene complexes. Reaction of 1 with [Rh 2 (µ-Cl) 2 (CO) 4 ] then afforded the first rNHC Rh I complex, 4. Transfer of the ligand in 2 to Ph 3 PAu + afforded the cationic rNHC gold complex, 5 and reaction of 3 and 7

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Section: Nmr Spectroscopymentioning

confidence: 82%

Preparation of Remote NHC Complexes of Rhodium(I) and Gold(I) by Ligand Transfer

et al. 2009

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“…Whereas complex 10 draws its stability mainly from charge delocalization over the (aromatic) organic ligand framework, [25] complex 11 features an unusual trigonal coordination geometry about the Au I center, [26] while the carbene unit in complex 12 is massively shielded. [24,27] Together with other relevant data, [28][29][30] these species greatly help in putting the mechanistic discussions on af irmer basis,b ut do not allow certain subtle but important aspects of gold catalysis to be rationalized. It is well known, for example,that the reactivity of gold carbenes is tunable by proper choice of the ancillary ligand.…”

Section: Methodsmentioning

confidence: 99%

The First Crystal Structure of a Reactive Dirhodium Carbene Complex and a Versatile Method for the Preparation of Gold Carbenes by Rhodium‐to‐Gold Transmetalation

2015

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The dirhodium carbene derived from bis(4‐methoxyphenyl)diazomethane and [Rh(tpa)4]⋅CH2Cl2 (tpa=triphenylacetate) was characterized by UV, IR, and NMR spectroscopy, HRMS, as well as by X‐ray diffraction. The isolated complex exhibits prototypical rhodium carbene reactivity in that it cyclopropanates 4‐methoxystyrene at low temperature. Experimental structural information on this important type of reactive intermediate is extremely scarce and thus serves as a reference point for mechanistic discussions of rhodium catalysis in general. Moreover, dirhodium carbenes are shown to undergo remarkably facile carbene transfer on treatment with [LAuNTf2] (L=phosphine). This formal transmetalation opens a valuable new entry into gold carbene complexes that cannot easily be made otherwise; three fully characterized representatives illustrate this aspect.

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“…[16][17][18] Indeed, reaction of 7 with [(Cy 3 P)Au]NTf 2 furnished 8 in good yield (Scheme 2). [16][17][18] Indeed, reaction of 7 with [(Cy 3 P)Au]NTf 2 furnished 8 in good yield (Scheme 2).…”

Section: Methodsmentioning

confidence: 99%

“…Zuschriften work exceedingly well for the preparation of stabilized Fischer-type carbene complexes of gold. [16][17][18] Indeed, reaction of 7 with [(Cy 3 P)Au]NTf 2 furnished 8 in good yield (Scheme 2). Although the preparative experiments were carried out at ambient temperature, NMR spectroscopy revealed that this formal transmetalation proceeds even at À50 8C.…”

Section: Methodsmentioning

confidence: 99%

Gold Carbenoids: Lessons Learnt from a Transmetalation Approach

et al. 2013

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Carbophilic catalysts that are based on Au I allow a host of different nucleophiles to be added across various p systems. [1][2][3] Although many of these reactions are thought to proceed via gold carbenoids, the challenge to observe and characterize these putative intermediates has basically been unmet. [4] The current mechanistic interpretation therefore largely relies on indirect evidence and computational data, some of which are subject to debate. [5] In an attempt to fill this gap, we pursued a potential route to gold carbenoids by formal transmetalation of chromium or tungsten Fischer carbene complexes with [LAu] + . Whereas this transformation proceeds with exceptional ease as long as a stabilizing heteroelement is present on the carbene center, it stops half-way in its absence. Rather unusual bimetallic arrays are formed, which allow the charge density to delocalize over several positions. The obvious difficulty of releasing an "unstabilized" gold carbenoid has potential mechanistic implications for the understanding of p-acid catalysis in general.

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Transfer of heterocyclic carbene ligands from chromium to gold, palladium and platinum

Cited by 54 publications

References 65 publications

Preparation of Remote NHC Complexes of Rhodium(I) and Gold(I) by Ligand Transfer

Preparation of Remote NHC Complexes of Rhodium(I) and Gold(I) by Ligand Transfer

The First Crystal Structure of a Reactive Dirhodium Carbene Complex and a Versatile Method for the Preparation of Gold Carbenes by Rhodium‐to‐Gold Transmetalation

Gold Carbenoids: Lessons Learnt from a Transmetalation Approach

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