Synthesis of dinuclear N-heterocyclic dicarbene Au(III)/Au(III) and Au(II)/Au(II) complexes via oxidative addition of chlorine or bromine to Au(I)/Au(I) species

Baron, Marco; Tubaro, Cristina; Basato, Marino; Biffis, Andrea; Graiff, Claudia

doi:10.1016/j.jorganchem.2012.02.020

Cited by 25 publications

(16 citation statements)

References 36 publications

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“…Comparison of complexes 2 c I and 4 c I with the chlorine and bromine analogues, shows a halogen‐related trend in the chemical shifts of the 1 H and 13 C{ 1 H} NMR signals (Table ). In the 1 H NMR spectra this is particularly noticeable for the singlet associated with the methyl groups, whose chemical shift decreases in the order Cl>Br>I.…”

Section: Resultsmentioning

confidence: 99%

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Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes

Baron

Tubaro

Basato

et al. 2016

Chemistry A European J

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Gold(I) dicarbene complexes [Au2 (MeIm-Y-ImMe)2 ](PF6 )2 (Y=CH2 (1), (CH2 )2 (2), (CH2 )4 (4), MeIm=1-methylimidazol-2-ylidene) react with iodine to give the mixed-valence complex [Au(MeIm-CH2 -ImMe)2 AuI2 ](PF6 )2 (1 a(I) ) and the gold(III) complexes [Au2 I4 (MeIm-Y-ImMe)2 ](PF6 )2 (2 c(I) and 4 c(I) ). Reaction of complexes 1 and 2 with an excess of ICl allows the isolation of the tetrachloro gold(III) complexes [Au2 Cl4 (MeIm-CH2 -ImMe)2 ](PF6 )2 (1 c(Cl) ) and [Au2 Cl4 (MeIm-(CH2 )2 -ImMe)2 ](Cl)2 (2 c(Cl) -Cl) (as main product); remarkably in the case of complex 2, the X-ray molecular structure of the crystals also shows the presence of I-Au-Cl mixed-sphere coordination. The same type of coordination has been observed in the main product of the reaction of complexes 3 or 4 with ICl. The study of the reactivity towards the oxidative addition of halogens to a large series of dinuclear bis(dicarbene) gold(I) complexes has been extended and reviewed. The complexes react with Cl2 , Br2 and I2 to give the successive formation of the mixed-valence gold(I)/gold(III) n a(X) and gold(III) n c(X) (excluding compound 1 c(I) ) complexes. However, complex 3 affords with Cl2 and Br2 the gold(II) complex 3 b(X) [Au2 X2 (MeIm-(CH2 )3 -ImMe)2 ](PF6 )2 (X=Cl, Br), which is the predominant species over compound 3 c(X) even in the presence of free halogen. The observed different relative stabilities of the oxidised complexes of compounds 1 and 3 have also been confirmed by DFT calculations.

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Section: Resultsmentioning

confidence: 99%

“…However, the reaction output depends on the nature of the bridge Y and of the halogen X 2 , so that, for example, with Y=propylene and X 2 =Cl 2 or Br 2 , the gold(II)/gold(II) complexes n b X become predominant. In these last cases the unusual +II oxidation state is stabilised by a direct bond between the two gold centres …”

Section: Introductionmentioning

confidence: 99%

Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes

Baron

Tubaro

Basato

et al. 2016

Chemistry A European J

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“…The slightly lower stability of [Au(L 2 ) 2 Cl 2 ] + may be a consequence of slightly higher strain in the chelate rings (e.g., in the ethylene link joining the NHC units in [Au(L 2 ) 2 Cl 2 ] + , N-C-C angles are 113.4(3), 113.8(4), 115.7(4) and 116.4(4)°; in the methylene linker in [Au(L 1 ) 2 Cl 2 ] + , N-C-N angles are 108.5 (7) and 109.1 (7)°, closer to the ideal tetrahedral angle, 109.5°). For comparison, salts of the dinuclear Au III complex [Au 2 (L 1 ) 2 Cl 4 ] 2+ and its bromido counterpart, 8,47 which contain Au III (NHC) 2 X 2 moieties rather than Au III (NHC) 4 (Fig. S21 †).…”

Section: H-d Exchange Reactionsmentioning

confidence: 99%

“…The imidazolium salts L 1 ·2HCl, L 2 ·2HCl, 55,56 and L 3 ·4HCl 57 were prepared according to literature procedures, and the Au III complexes [Au 2 (L 1 ) 2 X 4 ]X 2 (X = Cl, Br) and [Au 2 (L 2 ) 2 Br 4 ]Br 2 were prepared in the same way as the corresponding hexafluorophosphate salts. 8,47 Synthesis of Au III -NHC complexes Complex 2, [Au(L 1 ) 2 Cl 2 ]Cl. A solution of LiOAc (80 mg, 1.21 mmol) in DMF (5 mL) was added to a solution of the bis (imidazolium) salt L 1 ·2HCl (99 mg, 0.40 mmol) and KAuCl 4 (75 mg, 0.20 mmol) in DMF (10 mL) at 80°C.…”

Section: General Proceduresmentioning

confidence: 99%

Stable Au^III complexes with four N-heterocyclic carbene groups can be prepared in high yield directly from KAuCl₄

2017

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Gold(iii) N-heterocyclic carbene (NHC) complexes of form [Au(NHC)Cl]Cl were synthesized by reaction of KAuCl with bis- and tetrakis(imidazolium) salts in the presence of a mild base. Treatment of these complexes with KPF afforded four-coordinate Au complexes of form [Au(NHC)](PF). X-Ray crystallography showed the [Au(NHC)] cations in the hexafluorophosphate salts to have a square planar Au(NHC) moiety [AuC 2.024(4)-2.082(7) Å]. In the [Au(NHC)Cl] cations in the chloride salts, coordination about Au was tetragonally-distorted octahedral, the axial Au-Cl bonds being substantially longer [AuCl 3.148(2)-3.693(1) Å] than the equatorial Au-C bonds [AuC 2.024(4)-2.082(7) Å]. NMR and conductance studies suggested that the structures of the complexes seen in the solid state persisted in DMSO solution, except in one case where a chlorido ligand dissociated from [Au(NHC)Cl] to form [Au(NHC)Cl]. The Au(NHC) unit was surprisingly robust. An Au complex was found to undergo H/D exchange reactions in DO solution at 100 °C with no signs of decomposition detectable by H NMR spectroscopy.H NMR studies showed that various complexes containing Au(NHC) moieties underwent little or no decomposition when heated at 120 °C in DMSO-d for extended periods.

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“…Recently, we have extended our interest in the organometallic chemistry of such ligands to group 11 metals, in particular gold(I) and gold(III) centers [54–56]. In the present contribution we would like to assess the catalytic efficiency of such gold complexes with NHC ligands for the hydroarylation of alkynes.…”

Section: Introductionmentioning

confidence: 99%

Alkyne hydroarylation with Au N-heterocyclic carbene catalysts

Tubaro¹,

Baron²,

Biffis³

et al. 2013

Beilstein J. Org. Chem.

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SummaryMono- and dinuclear gold complexes with N-heterocyclic carbene (NHC) ligands have been employed as catalysts in the intermolecular hydroarylation of alkynes with simple unfunctionalised arenes. Both mono- and dinuclear gold(III) complexes were able to catalyze the reaction; however, the best results were obtained with the mononuclear gold(I) complex IPrAuCl. This complex, activated with one equivalent of silver tetrafluoroborate, exhibited under acidic conditions at room temperature much higher catalytic activity and selectivity compared to more commonly employed palladium(II) catalysts. Moreover, the complex was active, albeit to a minor extent, even under neutral conditions, and exhibited lower activity but higher selectivity compared to the previously published complex AuCl(PPh3). Preliminary results on intramolecular hydroarylations using this catalytic system indicate, however, that alkyne hydration by traces of water may become a serious competing reaction.

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Synthesis of dinuclear N-heterocyclic dicarbene Au(III)/Au(III) and Au(II)/Au(II) complexes via oxidative addition of chlorine or bromine to Au(I)/Au(I) species

Cited by 25 publications

References 36 publications

Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes

Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes

Stable Au^III complexes with four N-heterocyclic carbene groups can be prepared in high yield directly from KAuCl₄

Alkyne hydroarylation with Au N-heterocyclic carbene catalysts

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Synthesis of dinuclear N-heterocyclic dicarbene Au(III)/Au(III) and Au(II)/Au(II) complexes via oxidative addition of chlorine or bromine to Au(I)/Au(I) species

Cited by 25 publications

References 36 publications

Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes

Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes

Stable AuIII complexes with four N-heterocyclic carbene groups can be prepared in high yield directly from KAuCl4

Alkyne hydroarylation with Au N-heterocyclic carbene catalysts

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Stable Au^III complexes with four N-heterocyclic carbene groups can be prepared in high yield directly from KAuCl₄