Direct Evidence for Intermolecular Oxidative Addition of σ(SiSi) Bonds to Gold

Transition-metal-catalyzed cross-couplingr eactions are central to many organic synthesis methodologies. Traditionally,P d, Ni, Cu, and Fe catalysts are used to promote these reactions. Recently,m any studies have showedt hat both homogeneous and heterogeneous Au catalysts can be used for activating selective cross-coupling reactions.H ere, an overview of the past studies, current trends, andf uture directions in the field of gold-catalyzed coupling reactions is presented.D esign strategiest oa ccomplish selective homocoupling and cross-coupling reactions under both homogeneous and heterogeneous conditions, computational and ex-perimental mechanistic studies, and their applicationsi nd iverse fields are critically reviewed. Specific topics covered are:o xidant-assisted and oxidant-free reactions;s train-assisted reactions;d ual Au and photoredoxc atalysis;b imetallic synergistic reactions;m echanismso fr eductivee limination processes;e nzyme-mimicking Au chemistry;c lustera nd surface reactions;a nd plasmonic catalysis. In the relevant sections, theoretical and computational studies of Au I /Au III chemistry are discussed and the predictionsf rom the calculationsa re compared with the experimental observations to derive useful design strategies.A. Nijamudheen earnedh is PhD from IACS, Kolkata,i n2 015. Currently,h ei sapostdoctoral researcher atF loridaS tate University.H is researchi nterests are in computational catalysis, solar energym aterials, and beyond Li-ion battery technologies.Ayan Dattai sc urrently aP rofessor at IACS, Kolkata.H is research interests include theoretical and computational studieso ft ransitionmetal-catalyzed reactions,o pto-electronic properties of organic and solid-statem aterials, and the design of renewableenergymaterials. He has won several awards including the DST-SERB Distinguished Investigator Award (DIA) in 2019.

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“… (a) Low‐temperature oxidative addition of diphosphine‐disilane to Au I . (b) Oxidation of disilane–Au III forming the disiloxane–Au III complex …”

Section: Oxidant‐free Approaches For Homogeneous Au‐catalyzed Cross‐c...mentioning

confidence: 99%

Gold‐Catalyzed Cross‐Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications

Nijamudheen

Datta

2019

Chemistry A European J

153

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“…Such a contact may be understood as a σ-complex and strongly suggests that we are observing a direct Si to Au contact in single molecule circuits, similar to what has been observed in Au-mediated organosilane reaction chemistry. 60…”

Section: High Conductance Pathways In Ring-strained Disilanesmentioning

confidence: 99%

Silane and Germane Molecular Electronics

Klausen

et al. 2017

Acc. Chem. Res.

118

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This Account provides an overview of our recent efforts to uncover the fundamental charge transport properties of Si-Si and Ge-Ge single bonds and introduce useful functions into group 14 molecular wires. We utilize the tools of chemical synthesis and a scanning tunneling microscopy-based break-junction technique to study the mechanism of charge transport in these molecular systems. We evaluated the fundamental ability of silicon, germanium, and carbon molecular wires to transport charge by comparing conductances within families of well-defined structures, the members of which differ only in the number of Si (or Ge or C) atoms in the wire. For each family, this procedure yielded a length-dependent conductance decay parameter, β. Comparison of the different β values demonstrates that Si-Si and Ge-Ge σ bonds are more conductive than the analogous C-C σ bonds. These molecular trends mirror what is seen in the bulk. The conductance decay of Si and Ge-based wires is similar in magnitude to those from π-based molecular wires such as paraphenylenes However, the chemistry of the linkers that attach the molecular wires to the electrodes has a large influence on the resulting β value. For example, Si- and Ge-based wires of many different lengths connected with a methyl-thiomethyl linker give β values of 0.36-0.39 Å, whereas Si- and Ge-based wires connected with aryl-thiomethyl groups give drastically different β values for short and long wires. This observation inspired us to study molecular wires that are composed of both π- and σ-orbitals. The sequence and composition of group 14 atoms in the σ chain modulates the electronic coupling between the π end-groups and dictates the molecular conductance. The conductance behavior originates from the coupling between the subunits, which can be understood by considering periodic trends such as bond length, polarizability, and bond polarity. We found that the same periodic trends determine the electric field-induced breakdown properties of individual Si-Si, Ge-Ge, Si-O, Si-C, and C-C bonds. Building from these studies, we have prepared a system that has two different, alternative conductance pathways. In this wire, we can intentionally break a labile, strained silicon-silicon bond and thereby shunt the current through the secondary conduction pathway. This type of in situ bond-rupture provides a new tool to study single molecule reactions that are induced by electric fields. Moreover, these studies provide guidance for designing dielectric materials as well as molecular devices that require stability under high voltage bias. The fundamental studies on the structure/function relationships of the molecular wires have guided the design of new functional systems based on the Si- and Ge-based wires. For example, we exploited the principle of strain-induced Lewis acidity from reaction chemistry to design a single molecule switch that can be controllably switched between two conductive states by varying the distance between the tip and substrate electrodes. We found that the strain intrin...

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“…In most cases, Au···Au dinuclear structures are obtained instead 41 . Au(I) cationic complexes featuring monodentate ligands (L=R 3 P or N-heterocyclic carbenes) have also been shown to undergo oxidative addition 35 , 42 , 43 , but the generated three-coordinate Au(III) species are highly unstable and difficult to exploit in further reactivity. In contrast, four-coordinate Au(III) complexes are quite stable 44 .…”

Section: Introductionmentioning

confidence: 99%

Rational development of catalytic Au(I)/Au(III) arylation involving mild oxidative addition of aryl halides

Zeineddine¹,

Estévez²,

et al. 2017

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The reluctance of gold to achieve oxidative addition reaction is considered as an intrinsic limitation for the development of gold-catalyzed cross-coupling reactions with simple and ubiquitous aryl halide electrophiles. Here, we report the rational construction of a Au(I)/Au(III) catalytic cycle involving a sequence of Csp2–X oxidative addition, Csp2–H auration and reductive elimination, allowing a gold-catalyzed direct arylation of arenes with aryl halides. Key to this discovery is the use of Me-Dalphos, a simple ancillary (P,N) ligand, that allows the bottleneck oxidative addition of aryl iodides and bromides to readily proceed under mild conditions. The hemilabile character of the amino group plays a crucial role in this transformation, as substantiated by density functional theory calculations.

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Direct Evidence for Intermolecular Oxidative Addition of σ(SiSi) Bonds to Gold

Cited by 27 publications

References 65 publications

Gold‐Catalyzed Cross‐Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications

Gold‐Catalyzed Cross‐Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications

Silane and Germane Molecular Electronics

Rational development of catalytic Au(I)/Au(III) arylation involving mild oxidative addition of aryl halides

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