The rational design of binuclear Au(I)–Au(I), Au(II)–Au(II), and Au(I)–Au(III) complexes requires an understanding of how the redox states interconvert. Herein, the electrochemical ...interconversion of the three oxidation states I, II, and III is reported on the voltammetric (cyclic and rotating disk electrode) time scales for binuclear gold complexes containing C6F4PPh2 as a ligand, to demonstrate for the first time formation of a binuclear Au(II)–Au(II) from a Au(I)–Au(III) complex. Results are supported by bulk electrolysis and coulometry with reaction products being identified by 31P NMR and UV–vis spectroscopy. All electrochemical processes involve an overall two-electron charge-transfer process with no one-electron intermediate being detected. Importantly, the kinetically rather than thermodynamically favored isomer Au2 IIX2(μ-2-C6F4PPh2)2 is formed on redox cycling of XAuI(μ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuIIIX (X = Cl, ONO2). Finally, a mechanism is proposed to explain the simultaneous change of coordination of the chelating carbanionic ligand to bridging mode and interconversion of oxidation states in binuclear gold complexes.
Monometallic (Ag, Au, Pd), bimetallic (AgAu, AuPd) and trimetallic (Ag-Au-Pd) nanostructures, were generated using dextran as a natural polymer. The simultaneous co-reduction of multiple metal ...precursors with dextran gave a fine control to produce spherical shape Ag-Au-Pd trimetallic nanostructures. Small-sized Ag monometallic nanostructures of 8.7 nm were enlarged to 15.7 nm for AgAu bimetallic nanostructures. While, trimetallic nanostructures from Ag-Au-Pd was produced with much smaller size of 3.8 nm and quite narrower size distribution of 2–7 nm. The spectral analysis confirmed that the alcoholic groups of dextran were responsible for the reduction of metal ions to produce nanostructures and consequently oxidized to aldehydic/ketonic groups. The catalytic performance of the synthesized nanostructures was evaluated for the reduction of p-nitroaniline and the results demonstrated that there was a strong correlation between catalytic activity and composition of nanostructures. Half time of the reduction was diminished from 3.93 to 0.90 min. for Pd monometallic and Ag-Au-Pd trimetallic nanostructures, respectively. Using of the trimetallic nanostructure as a catalyst results in acceleration the reduction reaction 151 times. The results showed a promising approach to boost catalytic activities of the trimetallic nanostructures which were prepared via quite simple green method at ambient conditions.
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•Fabrication of monometallic, bimetallic, and trimetallic nanostructures by using dextran was presented.•AgNPs, Ag-AuNPs and Ag-Au-PdNPs were produced with 8.7, 15.7, and 3.8 nm, respectively.•Dextran alcoholic groups reduced metal ions to metallic nanostructures.•Trimetallic nanostructure as a catalyst accelerated the reduction of p-nitroaniline by 151 times.•The half time of reduction reaction was diminished from 3.93 min. for PdNPs to 0.90 min. for Ag-Au-PdNPs.
The X-ray structure of the {Cu(NH
3
)
4
Au(CN)
2
}
+
Au(CN)
2
−
salt is reported showing an unprecedented d
9
Cu d
10
Au coinage bond. The physical nature of the interaction has been studied using ...DFT calculations, including the quantum theory of atoms-in-molecules, the noncovalent interaction plot and the natural bond orbital analysis, revealing the nucleophilic role of the d
10
Au metal and the electrophilic role of d
9
Cu metal.
The X-ray structure of the {Cu(NH
3
)
4
Au(CN)
2
}
+
Au(CN)
2
−
salt is reported showing an unprecedented d
9
Cu d
10
Au coinage bond.
In this paper, Au@Ag nanopencil is designed as a multimodality plasmonic nanoprobe based on asymmetric etching for the detection of SCN
and ClO
. Au@Ag nanopencil with Au tip and Au@Ag rod is ...prepared by asymmetric tailoring of uniformly grown silver-covered gold nanopyramids under the combined effect of partial galvanic replacement and redox reaction. By asymmetric etching in different systems, Au@Ag nanopencil exhibits diversified changes in the plasmonic absorption band: O
facilitated by SCN
etches Au@Ag rod from the end to the tip, causing a blue shift of the localized surface plasmon resonance (LSPR) peak as the aspect ratio decreases; while the ClO
can retain Au@Ag shell and etch Ag within rod from the tip to the end, causing a redshift of the LSPR peak as the coupling resonance weakens. Based on peak shifts in different directions, a multimodality detection of SCN
and ClO
has been established. The results demonstrate the detection limits of SCN
and ClO
are 160 and 6.7 nm, and the linear ranges are 1-600 µm and 0.05-13 µm, respectively. The finely designed Au@Ag nanopencil not only broadens the horizon of designing heterogeneous structures, but also enriches the strategy of constructing multimodality sensing platform.
Metal-metal bonding interactions have been used to generate a number of unique supramolecular assemblies with fascinating functions. We presented here a new class of gold(I)-containing ...metallosupramolecular cages and cage-built two-dimensional (2-D) arrays of {Au8L2}n (n = 1 or ∞, L = tetrakis-dithiocarbamato-calix4arene, TDCC), 1-3, which are constructed from the self-assembly of deep-cavitand calix4arene-based supramolecular cages consisting of octanuclear Au(I) motifs. Synchrotron radiation X-ray diffraction structural analyses of 1-3 revealed their quadruple-stranded helicate dimeric cage structure and the presence of 2-D arrays of cages linked together by inter- and intramolecular Au(I)···Au(I) interactions. Electronic absorption and emission studies of complexes 1-3 indicated the occurrence of a programmable self-assembly process in a concentration-dependent stepwise manner with the links built via aurophilic interactions. These novel gold(I) supramolecular cages exhibited green phosphorescence and have been shown to serve as highly selective proof-of-concept luminescent sensors toward Ag(I) cation among various competitive transition-metal ions.
Cycling between Au(
i
) and Au(
iii
) is challenging, so gold-catalyzed cross-couplings are rare. The (MeDalphos)AuCl complex, which we showed was prone to undergo oxidative addition, is reported ...here to efficiently catalyze the C-N coupling of aryl iodides and amines. The transformation does not require an external oxidant or a directing group. It is robust and works with a wide scope of aryl iodides and
N
-nucleophiles under mild conditions. Mechanistic studies, including the NMR and MS characterization of a key aryl amido Au(
iii
) complex, strongly support a 2e redox cycle in which oxidative addition precedes transmetalation and reductive elimination is the rate-determining step.
Gold-catalyzed coupling of aryl iodides and amines
via
a ligand-enabled 2e redox cycle.
Gold complexes have emerged as the catalysts of choice for various functionalization reactions of C-C multiple bonds due to their inherent carbophilic nature. In a parallel space, efforts to realize ...less accessible cross-coupling reactivity have led to the development of various strategies that facilitate the arduous Au(
i
)/Au(
iii
) redox cycle. The interplay of the two important reactivity modes encountered in gold catalysis, namely carbophilic activation and Au(
i
)/Au(
iii
) catalysis, has allowed the development of a novel mechanistic paradigm that sponsors 1,2-difunctionalization reactions of various C-C multiple bonds. Interestingly, the reactivity as well as selectivity obtained through this interplay could be complementary to that obtained by the use of various other transition metals that mainly involved the classical oxidative addition/migratory insertion pathways. The present review shall comprehensively cover all the 1,2-difunctionalization reactions of C-C multiple bonds that have been realized by the interplay of the two important reactivity modes and categorized on the basis of the method that has been employed to foster the Au(
i
)/Au(
iii
) redox cycle.
This review highlights a decade-long journey of Au-catalyzed 1,2-difunctionalization reactions of C-C multiple bonds that have been realized due to the productive integration of Au(
i
)/Au(
iii
)catalysis with unique π-activation mode of gold complexes.
New dinuclear Au(I), Au(II) and Au(III) complexes containing (CF2)n bridging chains were obtained. Metallomacrocycles Au2{μ‐(CF2)4}{μ‐diphosphine} show an uncommon figure‐eight structure, the ...helicity inversion barrier of which is influenced by aurophilic interactions and steric constraints imposed by the diphosphine. Halogenation of LAu(CF2)4AuL (L=PPh3, PMe3, (dppf)1/2, (binap)1/2) gave Au(II)2 species, some of which display unprecedented folded structures with Au−Au bonds. Aurophilic interactions facilitate this oxidation process by preorganizing the starting Au(I)2 complexes and lowering its redox potential. The obtained Au(II)2 complexes undergo thermal or photochemical elimination of R3PAuX to give Au(III) perfluorinated auracycles. Evidence of a radical mechanism for these decomposition reactions was obtained.
Aurophilic interactions promote the oxidation of AuI2 compounds to give complexes containing a AuII‐AuII bond instead of AuIII2 or mixed‐valent species. The obtained AuII complexes undergo thermal or photochemical elimination of R3PAuX to give AuIII perfluorinated auracyclic complexes through radical intermediates.
Although N-heterocyclic carbenes (NHCs) have been demonstrated as suitable ligands for the stabilisation of gold nanoparticles (AuNPs) through a variety of methods, the manner in which such AuNPs ...form is yet to be fully elucidated. We report a simple and fast one-step synthesis of uniform chiral (
l
/
d
)-histidin-2-ylidene stabilised gold nanoparticles using the organometallic Au(
i
) complex as a well defined starting material. The resulting nanoparticles have an average size of 2.35 ± 0.43 nm for the L analog whereas an average size of 2.25 ± 0.39 nm was found for the D analog. X-ray photoelectron spectroscopy analyses reveal the presence of Au(
i
) and Au(0) in all NHC stabilised AuNPs. In contrast, measured X-ray photoelectron spectra of dodecanethiol protected gold nanoparticles showed only the presence of a Au(0) species. This observation leads us to postulate that AuNPs synthesised from organometallic NHC-Au(
i
) complexes exhibit a monolayer of Au(
i
) surrounding a Au(0) core. This work highlights the importance of synthetic method choice for NHC-stabilized AuNPs, as this could determine Au oxidation states and resulting AuNP properties such as catalytic activities and stabilities.
NHC-AuNPs prepared
via
chlorido(1,3-dimethyl-
N
-Boc-
O
-methylhistidin-2-ylidene)gold(
i
), an NHC-Au(
i
) complex, affords AuNPs containing not just Au(0), but also Au(
i
).
A (MeDalphos)AuCl complex was found to efficiently catalyze the cross-coupling of indoles and allyl acetates/alcohols. The reaction tolerates many functional groups and selectively affords the ...branched C3-allylated products from both α- and γ-substituted allyl substrates. It takes the advantage of the hemilabile character of the P∧N ligand. The C(sp2)–C(sp3) coupling operates via a Au(I)/Au(III) redox cycle and involves a dicationic π-allyl Au(III) complex as a key intermediate. In this case, the allyl moiety adopts an asymmetric σ + π-coordination mode, as substantiated by NMR spectroscopy and density functional theory (DFT) calculations.
![Unprecedented [d]Cu [d]Au c...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1359-7345/small "Unprecedented [d]Cu [d]Au coinage bonding interactions in {Cu(NH)[Au(CN)]}[Au(CN)] salt")
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