Dithiophosphonate-Protected Eight-Electron Superatomic Ag21 Nanocluster: Synthesis, Isomerism, Luminescence, and Catalytic Activity.

The structure-property relationship considering isomerism-tuned photoluminescence and efficient catalytic activity of silver nanoclusters (NCs) is exclusive. Asymmetrical dithiophosphonate NH4[S2P(OR)(p-C6H4OCH3)] ligated first atomically precise silver NCs [Ag21{S2P(OR)(p-C6H4OCH3)}12]PF6 {where, R = nPr (1), Et (2)} were established by single-crystal X-ray diffraction and characterized by electrospray ionization mass spectrometry, NMR (31P, 1H, 2H), X-ray photoelectron spectroscopy, UV-visible, energy-dispersive X-ray spectroscopy, Fourier transforms infrared, thermogravimetric analysis, etc. NCs 1 and 2 consist of eight silver atoms in a cubic framework and enclose an Ag@Ag12-centered icosahedron to constitute an Ag21 core of Th symmetry, which is concentrically inscribed within the S24 snub-cube, P12 cuboctahedron, and the O12 truncated tetrahedron formed by 12 dithiophosphonate ligands. These NCs facilitate to be an eight-electron superatom (1S21P6), in which eight capping Ag atoms exhibit structural isomerism with documented isoelectronic [Ag21{S2P(OiPr)2}12]PF6, 3. In contrast to 3, the stapling of dithiophosphonates in 1 and 2 triggered bluish emission within the 400 to 500 nm region at room temperature. The density functional theory study rationalized isomerization and optical properties of 1, 2, and 3. Both (1, and 2) clusters catalyzed a decarboxylative acylarylation reaction for rapid oxindole synthesis in 99% yield under ambient conditions and proposed a multistep reaction pathway. Ultimately, this study links nanostructures to their physical and catalytic properties.

A Simple Nickel Metal-Organic Framework-Catalyzed Borylation of Aryl Chlorides and Bromides.

We report a recyclable and efficient catalyst system based on a nickel-benzene tricarboxylic acid metal-organic framework (Ni-BTC MOF) for the borylation of aryl halides, including aryl chlorides, with bis(pinacolato)diboron, affording aryl boronate esters in high yields (up to >99% yield) with high selectivity. This protocol demonstrates broad functional group tolerance. Catalyst can be recyclable up to four times, and gram-scale reactions further highlights the usefulness of this method. In situ EPR experiments confirmed the formation of catalytically active Ni(I) species.

Synthesis of Alkyl and Aryl Boronate Esters via CeO2-Catalyzed Borylation of Alkyl and Aryl Electrophiles Including Alkyl Chlorides.

A recyclable protocol using a CeO2-nanorod catalyst for borylation of alkyl halides with B2pin2 (pin = OCMe2CMe2O) is reported. A wide range of synthetically useful alkyl boronate esters are readily obtained from primary and secondary alkyl electrophiles, including unactivated alkyl chlorides, demonstrating broad utility and functional group tolerance. Preliminary investigation revealed an involvement of in situ formed catalytically active boryl species. The catalyst can be reused for up to six runs without appreciable loss in activity. In addition, we have demonstrated the use of this recyclable catalyst for the borylation of aryl halides with B2pin2, providing valuable aryl boronate esters under neat conditions.

Transition metal- and solvent-free anti-Markovnikov selective protoboration of alkenes with bis(pinacolato)diboron.

An efficient anti-Markovnikov selective transition metal- and solvent-free Lewis base-mediated protoboration of aromatic and aliphatic alkenes with bis(pinacolato)diboron (B2pin2) as the boron reagent is reported. This protocol is practical and demonstrates broad substrate scope and good functional-group tolerance on alkenes to give synthetically useful alkyl boronate esters in excellent yields under mild reaction conditions. The gram-scale reaction further highlighted the usefulness of this method.

Ag-S Type Quantum Dots versus Superatom Nanocatalyst: A Single Sulfur Atom Modulated Decarboxylative Radical Cascade Reaction.

The preparation of high-nuclearity silver nanoclusters in quantitative yield remains exclusive and their potential applications in the catalysis of organic reactions are still undeveloped. Here, we have synthesized a quantum dot (QD)-based catalyst, [Ag62S13(SBut)32](PF6)4 (denoted as Ag62S12-S) in excellent yield that enables the direct synthesis of pharmaceutically precious 3,4-dihydroquinolinone in 92% via a decarboxylative radical cascade reaction of cinnamamide with α-oxocarboxylic acid under mild reaction conditions. In comparison, a superatom [Ag62S12(SBut)32](PF6)2 (denoted as Ag62S12) with identical surface anatomy and size, but without a central S2- atom in the core, gives an improved yield (95%) in a short time and exhibits higher reactivity. Multiple characterization techniques (single-crystal X-ray diffraction, nuclear magnetic resonance (1H and 31P), electrospray ionization mass spectrometry, energy dispersive X-ray spectroscopy, Brunauer-Emmett-Teller (BET), Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis) confirm the formation of Ag62S12-S. The BET results expose the total active surface area in supporting a single e- transfer reaction mechanism. Density functional theory reveals that leaving the central S atom of Ag62S12-S leads to higher charge transfer from Ag62S12 to the reactant, accelerates the decarboxylation process, and correlates the catalytic properties with the structure of the nanocatalyst.

Recent advances in the chemistry of the phosphaethynolate and arsaethynolate anions.

Over the past decade, the reactivity of 2-phosphaethynolate (OCP-), a heavier analogue of the cyanate anion, has been the subject of momentous interest in the field of modern organometallic chemistry. It is used as a precursor to novel phosphorus-containing heterocycles and as a ligand in decarbonylative processes, serving as a synthetic equivalent of a phosphinidene derivative. This perspective aims to describe advances in the reactivities of phosphaethynolate and arsaethynolate anions (OCE-; E = P, As) with main-group element, transition metal, and f-block metal scaffolds. Further, the unique structures and bonding properties are discussed based on spectroscopic and theoretical studies.

First-Row d-Block Element-Catalyzed Carbon-Boron Bond Formation and Related Processes.

Organoboron reagents represent a unique class of compounds because of their utility in modern synthetic organic chemistry, often affording unprecedented reactivity. The transformation of the carbon-boron bond into a carbon-X (X = C, N, and O) bond in a stereocontrolled fashion has become invaluable in medicinal chemistry, agrochemistry, and natural products chemistry as well as materials science. Over the past decade, first-row d-block transition metals have become increasingly widely used as catalysts for the formation of a carbon-boron bond, a transformation traditionally catalyzed by expensive precious metals. This recent focus on alternative transition metals has enabled growth in fundamental methods in organoboron chemistry. This review surveys the current state-of-the-art in the use of first-row d-block element-based catalysts for the formation of carbon-boron bonds.

Transition metal chemistry of heavier group 14 congener triple-bonded complexes: syntheses and reactivity.

The diversification and synthetic utility of carbyne complexes in organometallic chemistry and catalysis are well recognized, but the syntheses of related heavier group 14 alkylidyne complexes are a recent advancement. A wide range of metal-ylidyne M[triple bond, length as m-dash]E (E = Si-Pb) complexes were synthesized and characterized spectroscopically. The synthetic methodology generally involves elimination or substitution chemistry between metallates and suitable group 14 precursors. The reluctance in forming triple bonded complexes makes this field quite fascinating and challenging. This article gives a brief overview of the pioneering reports followed by detailed information on the latest developments of complexes having a triple bond between a metal and heavier group 14 elements (Si, Ge, Sn, and Pb). Their synthesis and chemistry of the earlier reports followed by recent progress in this field will be discussed. Furthermore, their unique structures and bonding properties will be described based on spectroscopic and theoretical studies.

Bonding Relationship between Silicon and Germanium with Group 13 and Heavier Elements of Groups 14-16.

The topic of heavier main group compounds possessing multiple bonds is the subject of momentous interest in modern organometallic chemistry. Importantly, there is an excitement involving the discovery of unprecedented compounds with unique bonding modes. The research in this area is still expanding, particularly the reactivity aspects of these compounds. This article aims to describe the overall developments reported on the stable derivatives of silicon and germanium involved in multiple bond formation with other group 13, and heavier groups 14, 15, and 16 elements. The synthetic strategies, structural features, and their reactivity towards different nucleophiles, unsaturated organic substrates, and in small molecule activation are discussed. Further, their physical and chemical properties are described based on their spectroscopic and theoretical studies.

A nano-catalytic approach for C-B bond formation reactions.

Herein, we present a chronological survey of the metal/metal oxide nanoparticle-catalysed borylation reactions. Transition metal-catalysed borylation is considered to be one of the most efficient methods for the synthesis of organoboron derivatives. Considering chemical and pharmaceutical processes, the major drawbacks of homogeneous catalysis are metal contamination in products and inability to recover catalysts for reuse, which limit its application industrially, in biomolecules, and materials science. The use of nanoparticles as heterogeneous catalysts is a current topic of research to overcome these limitations. This review gives an overview of the metal nanoparticle-catalysed borylation reactions and also discusses the reaction mechanisms.

Acylboranes: synthetic strategies and applications.

An overview of the synthesis and chemistry of acylborane compounds is presented. Acylboranes are a rare class of boron compounds, previously proposed as intermediates in several transformations and considered to be difficult to prepare. Methodologies for the preparation of acylborane compounds are based on both electrophilic and nucleophilic sources of boron. The former methods include addition of electrophilic boron reagents to acyl-anion equivalents, while the latter methods are based on boryl anion reagents which are trapped by electrophiles, such as aldehydes, diethyl carbonate and ethyl acetate. New methods to achieve acylboron-compounds based on oxidation of MIDA α-hydroxyboronates or α-bromomethyl alcohol are discussed. A one-step catalytic C-B coupling reaction for preparing acylboranes from palladium-catalyzed borylation of acyl chlorides using nucleophilic borylzinc reagents is included. Applications of acylboranes in chemoselective amide-bond forming reactions, converting them into functionalised boron derivatives are also discussed.

Zinc-Catalyzed Dual C-X and C-H Borylation of Aryl Halides.

A zinc-catalyzed combined C-X and C-H borylation of aryl halides using B2 pin2 (pin=OCMe2 CMe2 O) to produce the corresponding 1,2-diborylarenes under mild conditions was developed. Catalytic C-H bond activation occurs ortho to the halide groups if such a site is available or meta to the halide if the ortho position is already substituted. This method thus represents a novel use of a group XII catalyst for C-H borylation. This transformation does not proceed via a free aryne intermediate, but a radical process seems to be involved.

Iridium-catalyzed borylation of pyrene: irreversibility and the influence of ligand on selectivity.

The iridium-catalyzed borylation of pyrene, using 4,4'-dimethyl-2,2'-bipyridine as the ligand, in the presence of t-BuOK, gave a mixture of 2,4,7,9-tetrakis(Bpin)pyrene (c4) and its 2,4,7,10-isomer (m4) in a 2.2:1 ratio, and the selectivity of the Ir-catalyzed borylation of pyrene is kinetically determined and can be influenced to some extent by the nature of the ligand.

Efficient synthesis of aryl boronates via zinc-catalyzed cross-coupling of alkoxy diboron reagents with aryl halides at room temperature.

A zinc(II)/NHC system catalyzes the borylation of aryl halides with diboron (4) reagents in the presence of KOMe at rt. This transformation can be applied to a broad range of substrates with high functional group compatibility. Radical scavenger experiments do not support a radical-mediated process.

Zinc-catalyzed borylation of primary, secondary and tertiary alkyl halides with alkoxy diboron reagents at room temperature.

A new catalytic system based on a Zn(II) NHC precursor has been developed for the cross-coupling reaction of alkyl halides with diboron reagents, which represents a novel use of a Group XII catalyst for CX borylation. This approach gives borylations of unactivated primary, secondary, and tertiary alkyl halides at room temperature to furnish alkyl boronates, with good functional-group compatibility, under mild conditions. Preliminary mechanistic investigations demonstrated that this borylation reaction seems to involve one-electron processes.

Syntheses and characterization of new vinyl-borylene complexes by the hydroboration of alkynes with [(µ3-BH)(Cp*RuCO)2(µ-CO)Fe(CO)3].

Room temperature photolysis of a triply-bridged borylene complex, [(µ(3)-BH)(Cp*RuCO)(2)(µ-CO)Fe(CO)(3)] (1 a; Cp* = C(5)Me(5)), in the presence of a series of alkynes, 1,2-diphenylethyne, 1-phenyl-1-propyne, and 2-butyne led to the isolation of unprecedented vinyl-borylene complexes (Z)-[(Cp*RuCO)(2)(µ-CO)B(CR)(CHR')] (2: R, R' = Ph; 3: R = Me, R' = Ph; 4: R, R' = Me). This reaction permits a hydroboration of alkyne through an anti-Markovnikov addition. In stark contrast, in the presence of phenylacetylene, a metallacarborane, closo-[1,2-(Cp*Ru)(2)(µ-CO)(2){Fe(2)(CO)(5)}-4-Ph-4,5-C(2)BH(2)] (5 a), is formed. A plausible mechanism has been proposed for the formation of vinyl-borylene complexes, which is supported by density functional theory (DFT) methods. Furthermore, the calculated (11)B NMR chemical shifts accurately reflect the experimentally measured shifts. All the new compounds have been characterized in solution by mass spectrometry and IR, (1)H, (11)B, and (13)C NMR spectroscopies and the structural types were unequivocally established by crystallographic analysis of 2, 5 a, and 5 b.

Synthesis and structure of dirhodium analogue of octaborane-12 and decaborane-14.

We present the results of our investigation of a thermally driven cluster expansion of rhodaborane systems with BH(3)·THF. Four novel rhodaborane clusters, for example, nido-[(Cp*Rh)(2)B(6)H(10)], 1; nido-[(Cp*Rh)B(9)H(13)], 2; nido-[(Cp*Rh)(2)B(8)H(12)], 3; and nido-[(Cp*Rh)(3)B(8)H(9)(OH)(3)], 4 (Cp* = η(5)-C(5)Me(5)), have been isolated from the thermolysis of [Cp*RhCl(2)](2) and borane reagents in modest yields. Rhodaborane 1 has a nido geometry and is isostructural with [B(8)H(12)]. The low temperature (11)B and (1)H NMR data demonstrate that compound 1 exists in two isomeric forms. The framework geometry of 2 and 3 is similar to that of [B(10)H(14)] with one BH group in 2 (3-position), and two BH groups in 3 (3, 4-positions) are replaced by an isolobal {Cp*Rh} fragment. The 11 vertex cluster 4 has a nido structure based on the 12 vertex icosahedron, having three rhodium and eight boron atoms. In addition, the reaction of rhodaborane 1 with [Fe(2)(CO)(9)] yielded a condensed cluster [(Cp*Rh)(2){Fe(CO)(3)}(2)B(6)H(10)], 5. The geometry of 5 consists of [Fe(2)B(2)] tetrahedron and an open structure of [(Cp*Rh)(2)B(6)], fused through two boron atoms. The accuracy of these results in each case is established experimentally by spectroscopic characterization in solution and structure determinations in the solid state.

Theoretical and experimental investigations on hypoelectronic heterodimetallaboranes of group 6 transition metals.

Density functional theory (DFT) has been used to probe the bonding and electronic properties of dimolybdaborane [(Cp*Mo)(2)B(5)H(9)], 1 (Cp* = η(5)-C(5)Me(5)), and several other heterodimolybdaborane clusters, such as [(Cp*Mo)(2)B(5)(µ(3)-OEt)H(7)] (2), [(Cp*Mo)(2)B(5)(µ(3)-OEt)(n-BuO)H(6)] (3), [(η(5)-C(5)H(5)W)(2)B(4)H(4)S(2)] (4), and [(Cp*Mo)(2)B(4)H(4)E(2)] (5-7, where, for 5, E = S, for 6, E = Se, and for 7, E = Te). The DFT results were also used to address some key points such as (i) the metal-metal bond length, (ii) the location and number of bridging and terminal hydrogen atoms, (iii) the molecular orbital analysis, and (iv) the assignment of (11)B and (1)H NMR chemical shifts. These studies further provide meticulous insight into similarities and differences between various dimetallaborane clusters 1-7. In addition, the crystal structures of 5 and 7 are reported, which come on top of the already existing literature of dimetallaboranes and support the theoretical findings.