An efficient and sustainable synthesis of NHC gold complexes

Johnson, Alice; Gimeno, M. Concepción

doi:10.1039/c6cc05190a

Cited by 42 publications

(29 citation statements)

References 42 publications

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“…The formation of gold(I) complexes 3 was easily accomplished by the reaction of AuCl•SMe2 with chloride salts of N-heterocyclic carbene precursors 1 in the presence of K2CO3 in DCM or acetone. Recently, the application of NBu4(acac) as a base has been reported for the efficient preparation of sterically unhindered complexes [59]. In addition, stronger bases are occasionally used, such as KHMDS [potassium bis(trimethylsilyl)amide] [60] or the mixture of NaH/KOtBu [61] (NaH is used as the stoichiometric base, whereas KOtBu acts Considering all the above aspects, N-heterocyclic carbene gold complexes offer an excellent opportunity for the development of efficient enantioselective processes.…”

Section: Mono-n-heterocyclic Gold(i) Complexesmentioning

confidence: 99%

Chiral N-heterocyclic Carbene Gold Complexes: Synthesis and Applications in Catalysis

Michalak

Kośnik

2019

Catalysts

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N-Heterocyclic carbenes have found many applications in modern metal catalysis, due to the formation of stable metal complexes, and organocatalysis. Among a myriad of N-heterocyclic carbene metal complexes, gold complexes have gained a lot of attention due to their unique propensity for the activation of carbon-carbon multiple bonds, allowing many useful transformations of alkynes, allenes, and alkenes, inaccessible by other metal complexes. The present review summarizes synthetic efforts towards the preparation of chiral N-heterocyclic gold(I) complexes exhibiting C 2 and C 1 symmetry, as well as their applications in enantioselective catalysis. Finally, the emerging area of rare gold(III) complexes and their preliminary usage in asymmetric catalysis is also presented. Scheme 3. The synthesis of a gold(I) complex from (R)-1-aminotetralin.An elegant approach to C2-symmetric gold(I) complexes was described by Czekelius et al. [72] (Scheme 4), inspired by previous Herrmann's work [73]. The synthetic approach involves chiral amines 24, readily available from the corresponding phenylacetic acid 22 via the Friedel-Crafts reaction of bromobenzene and fractional crystallization of the corresponding tartaric acid amine salt upon reductive amination. The resulting amine 24 was further formylated and subjected to Bischler-Napieralski cyclization to give 3-aryl-substituted dihydroisoquinoline 25. Subsequent reductive coupling afforded the basic diamine skeleton 26 into a single diastereomer, which appeared a perfect platform for structural ligand diversification via Suzuki coupling. The functionalized diamines 26 were then cyclized into imidazolium salts 27 with triethyl orthoformate to give the products with yields in the range of 49-94% (for selected examples, see Scheme 4). The formation of gold(I) complexes 28 was accomplished under rather unusual conditions, by the reaction of gold(I) chloride with a carbene generated by the action of KOtBu. Scheme 4. The synthesis of C2-symmetric gold(I) complexes accessible via a reductive coupling. The application of other chiral building blocks has recently been reported by the Toste group (Scheme 5) [74]. Besides chiral amines, amino alcohols 29 were also utilized in the synthesis of C2-Scheme 3. The synthesis of a gold(I) complex from (R)-1-aminotetralin.An elegant approach to C 2 -symmetric gold(I) complexes was described by Czekelius et al. [72] (Scheme 4), inspired by previous Herrmann's work [73]. The synthetic approach involves chiral amines 24, readily available from the corresponding phenylacetic acid 22 via the Friedel-Crafts reaction of bromobenzene and fractional crystallization of the corresponding tartaric acid amine salt upon reductive amination. The resulting amine 24 was further formylated and subjected to Bischler-Napieralski cyclization to give 3-aryl-substituted dihydroisoquinoline 25. Subsequent reductive coupling afforded the basic diamine skeleton 26 into a single diastereomer, which appeared a perfect platform for structural ligand diversification via Suzuki...

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Section: Mono-n-heterocyclic Gold(i) Complexesmentioning

confidence: 99%

Chiral N-heterocyclic Carbene Gold Complexes: Synthesis and Applications in Catalysis

Michalak

Kośnik

2019

Catalysts

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“…The carbene resonances in the 13 C{ 1 H} spectra are found at δ =172.8 ppm ( 4 ), 190 ppm ( 5 ) and 185.4 ppm ( 6 ). These are typical values for NHC gold complexes bearing chlorido, or pentafluorophenyl substituents or (bis)NHC complexes . In the solid‐state, compounds 4 and 5 show the common coordination number of two around the gold atoms with only small deviations from linearity (177.4(2)° ( 4 ) and 176.7(2)° ( 5 )).…”

Section: Resultsmentioning

confidence: 85%

Bimetallic d¹⁰‐Metal Complexes of a Bipyridine Substituted N‐Heterocyclic Carbene

Kaub

Lebedkin

et al. 2018

Chemistry A European J

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The hybrid ligand 3-(2,2'-bipyridine-6-ylmethyl)-1-mesityl-1H-imidazolylidene (NHC ) featuring both carbene and N-donor sites, was selectively complexed with various d metal cations in order to examine its coordination behavior with regard to homo and heterometallic structures. Respective silver complexes can be obtained by the silver oxide route and are suitable transmetallation reagents for the synthesis of gold(I) compounds. Starting from the mononuclear complexes [(NHC )AuCl], [(NHC )Au(C F )] and [(NHC ) Au][ClO ], open-chain as well as cyclic heterobimetallic complexes containing Cu , Ag , Zn , Cd , and Hg were synthesized. Furthermore, the homobimetallic species [(NHC ) M ][ClO ] (M=Cu, Ag) were obtained. All bimetallic compounds were fully characterized including single-crystal X-ray analysis. Their photoluminescence (PL) properties were investigated in the solid state at temperatures between 15 and 295 K and compared with those of the mononuclear species. There is a clear difference in PL properties between the open chain and the cyclic heterobimetallic complexes. The latter species show different PL properties, depending on the metals involved. In addition, collision-induced dissociation (CID) experiments were performed on electrosprayed cations of the cyclic heterobimetallic compounds, to compare the metal binding at the carbene and N-donor sites.

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“…The use of NBu 4 (acac) as ab ase in the synthesis of gold complexes under mild conditions has previously been shown to be highlys uccessfulw ith NHC gold complexes. [41] Here the NBu 4 (acac) deprotonates the ylide to form the yldiide which will readily displace the labile tht from the gold precursor.I nt he absence of the gold precursor this deprotonation does not occur,c onfirmed by NMR studies (see Supporting Information), suggesting coordination to the first gold centre musto ccur before the deprotonation step. Anionic trinucleard erivatives 3 and 4 were synthesised by initial preparation of the previously reported bis-ylide complex [39] II ands ubsequentd eprotonation with two equivalents of NBu 4 (acac) in the presence of two equivalents of [AuX(tht)] (X = Cl, C 6 F 5 ).…”

Section: Resultsmentioning

confidence: 99%

Yldiide Ligands as Building Blocks for Polynuclear Coinage Metal Complexes: Metal Squares, Triangles and Chains

Johnson

Gimeno

2020

Chemistry A European J

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Yldiides have unique electronic properties and donor abilities, but as ligands in transition metal complexes they are scarcely represented in the literature. Here, the controlled synthesis of a series of polynuclear gold yldiide complexes derived from triphenyl(cyanomethyl)phosphonium bromide, [Ph3PCH2CN]Br, under mild conditions is described. Anionic dinuclear NBu4[(AuX)2{C(CN)PPh3}] (X=Cl, C6F5) or trinuclear derivatives NBu4[Au3X2{C(CN)PPh3}] bearing terminal chloride or pentafluorophenyl groups and bridging yldiide ligands have been prepared. These compounds evolve in solution giving rise to the formation of an unprecedented tetrameric gold cluster, [Au4{C(CN)PPh3}4], by the loss of the gold complex NBu4[AuX2]. This gold cluster can also be prepared in high yield by a transmetalation reaction from the analogous tetrameric silver cluster, and two geometric isomers have been characterised, their formation dependent on the synthetic route. The triphenylphosphonium cyanomethyldiide ligand has also been used to build different dinuclear and trinuclear cationic complexes bearing phosphine or diphosphine ancillary ligands and bridging yldiide moieties. Further coordination through the cyano group of the yldiide ligand gives heterometallic trinuclear or pentanuclear derivatives. Structural characterisation of many of these compounds reveals the presence of complex molecular systems stabilised by gold⋅⋅⋅gold interactions and bridging yldiide ligands.

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An efficient and sustainable synthesis of NHC gold complexes

Abstract: A simple, efficient and sustainable method for the general synthesis of NHC gold(i) complexes is described.

Cited by 42 publications

References 42 publications

Chiral N-heterocyclic Carbene Gold Complexes: Synthesis and Applications in Catalysis

Chiral N-heterocyclic Carbene Gold Complexes: Synthesis and Applications in Catalysis

Bimetallic d¹⁰‐Metal Complexes of a Bipyridine Substituted N‐Heterocyclic Carbene

Yldiide Ligands as Building Blocks for Polynuclear Coinage Metal Complexes: Metal Squares, Triangles and Chains

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An efficient and sustainable synthesis of NHC gold complexes

Abstract: A simple, efficient and sustainable method for the general synthesis of NHC gold(i) complexes is described.

Cited by 42 publications

References 42 publications

Chiral N-heterocyclic Carbene Gold Complexes: Synthesis and Applications in Catalysis

Chiral N-heterocyclic Carbene Gold Complexes: Synthesis and Applications in Catalysis

Bimetallic d10‐Metal Complexes of a Bipyridine Substituted N‐Heterocyclic Carbene

Yldiide Ligands as Building Blocks for Polynuclear Coinage Metal Complexes: Metal Squares, Triangles and Chains

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Bimetallic d¹⁰‐Metal Complexes of a Bipyridine Substituted N‐Heterocyclic Carbene