Bismuth in Radical Chemistry and Catalysis

Whereas indications of radical reactivity in bismuth compounds can be traced back to the 19th century, the preparation and characterization of both transient and persistent bismuth-radical species has only been established in recent decades. These advancements led to the emergence of the field of bismuth radical chemistry, mirroring the progress seen for other main-group elements. The seminal and fundamental studies in this area have ultimately paved the way for the development of catalytic methodologies involving bismuth-radical intermediates, a promising approach that remains largely untapped in the broad landscape of synthetic organic chemistry. In this review, we delve into the milestones that eventually led to the present state-of-the-art in the field of radical bismuth chemistry. Our focus aims at outlining the intrinsic discoveries in fundamental inorganic/organometallic chemistry and contextualizing their practical applications in organic synthesis and catalysis.

Aryl sulfonate anion stabilized aromatic triangular cation [Pd3]+: syntheses, structures and properties

A series of sulfonate anions paired aromatic triangular palladium clusters 3-7, abbreviated as [Pd3]+[ArSO3]-, were synthesized using a simple "one pot" method, and gave excellent isolated yields (90-95%). Their structures and properties have been fully characterized and further investigated by fluorescence, single crystal X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). In varying organic solvents, they presented apparently stronger absorption and emission in MeOH, driven by the combined interactions of hydrogen bonds and polarity. The crystallographic data demonstrated that the methyl orange ion stabilized complex 7 possessed a D3h symmetric metallic core which was still coplanar and almost equilateral, jointly influenced by the giant hindrance and milder donating effect from the sulfonate. The binding energies for Pdn+ 3d5/2 and Pdn+ 3d3/2 measured by XPS presented at 336.55 and 342.00 eV, respectively. These data were much lower than that of a usual Pd2+ 3d and significantly higher than that of a Pd0 species, further proving the unified palladium valence state (+4/3) in the tri-palladium core and its aromaticity featured by the cyclic electron delocalization.

Hypervalent organobismuth complexes: pathways toward improved reactivity, catalysis, and applications

Hypervalent (three-center, four-electron) bonding in organobismuth complexes has been extensively studied due to its ability to affect molecular geometry, dynamic behavior, or to stabilize the ligand scaffold. This work addresses the effects of this bonding on reactivity, catalytic activity, redox processes, and its potential applications in biosciences, materials science, and small molecule activation.

Synthesis, structure and properties of trivalent and pentavalent tricarbabismatranes

The first trivalent and pentavalent tricarbabismatranes were synthesized by the reaction of N(CH₂{2-LiC₆H₄})₃ with BiCl₃ and subsequent reaction with XeF₂, respectively. The trivalent bismatrane was easily oxidized by air, while the pentavalent bismatrane difluoride was relatively stable to air. A similar pentavalent bismatrance dichloride was prone to C-Cl bond reductive elimination even at room temperature.

Electrochemical Studies of the Cycloaddition Activity of Bismuth(III) Acetylides Towards Organic Azides Under Copper(I)-Catalyzed Conditions

Time-dependent monitoring of the reactive intermediates provides valuable information about the mechanism of a synthetic transformation. However, the process frequently involves intermediates with short lifetimes that significantly challenge the accessibility of the desired kinetic data. We report in situ cyclic voltammetry (CV) and nuclear magnetic resonance (NMR) spectroscopy studies of the cycloaddition reaction of organobismuth(III) compounds with organic azides under the copper(I)-catalyzed conditions. A series of bismuth(III) acetylides carrying diphenyl sulfone scaffolds have been synthesized to study the underlying electronic and steric effects of the tethered moieties capable of transannular oxygen O···Bi interactions and para-functionality of the parent phenylacetylene backbones. While belonging to the family of copper-catalyzed azide-alkyne cycloaddition reactions, the reaction yielding 5-bismuth(III)-triazolide is the sole example of a complex catalytic transformation that features activity of bismuth(III) acetylides towards organic azides under copper(I)-catalyzed conditions. Stepwise continuous monitoring of the copper(I)/copper(0) redox activity of the copper(I) catalyst by cyclic voltammetry provided novel insights into the complex catalytic cycle of the bismuth(III)-triazolide formation. From CV-derived kinetic data, reaction rate parameters of the bismuth(III) acetylides coordination to the copper(I) catalyst (K_A) and equilibrium concentration of the copper species [cat]_eq. are compared with the overall 5-bismuth(III)-triazolide formation rate constant k_obs obtained by ¹H-NMR kinetic analysis.

A new C-anionic tripodal ligand 2-{bis(benzothiazolyl)(methoxy)methyl}phenyl and its bismuth complexes

A new tripodal C-anionic ligand, 2-{bis(benzothiazolyl)(methoxy)methyl}phenyl (L), was stably generated by the reaction of the ligand precursor (L'), the corresponding bromide (2-BrC6H4)(MeO)C(C7H4NS)2 (C7H4NS = 2-benzothiazolyl), with nBuLi at -104 °C in the presence of TMEDA (N,N,N',N'-tetramethylethylenediamine). The ligand lithium salt reacted with BiCl3 to give a 2 : 1 complex L2BiCl. A 1 : 1 complex LBiCl2 was obtained in good yield by the redistribution reaction between L2BiCl and BiCl3. X-ray diffraction analysis revealed that the ligand L coordinated in an expected κ3-C,N,N' coordination mode in LBiCl2, while it coordinated in κ3-C,N,O and κ2-C,O coordination modes in L2BiCl. The ligand precursor reacted with BiX3 (X = Cl, Br) to give 1 : 1 complexes L'BiX3 and was found to act as a neutral tripodal C(π),N,N-ligand.

Bismuth species in the coordination sphere of transition metals: synthesis, bonding, coordination chemistry, and reactivity of molecular complexes

This contribution is focused on bismuth species in the coordination sphere of transition metals. In molecular transition metal complexes, three types of Bi-M bonding are considered, namely dative Bi→M interactions (with Bi acting as a donor), dative Bi←M interactions (with Bi acting as an acceptor) and covalent Bi-M interactions (M = transition metal). Synthetic routes to all three classes of compounds are outlined, the Bi-M bonding situation is discussed, trends in the geometric parameters and in the coordination chemistry of the compounds are addressed, and common spectroscopic properties are summarized. As an important part of this contribution, the reactivity of bismuth species in the coordination sphere of transition metal complexes in stoichiometric and catalytic reactions is highlighted.

Molecular bismuth(iii) monocations: structure, bonding, reactivity, and catalysis

Structurally defined, molecular bismuth(iii) cations show remarkable properties in coordination chemistry, Lewis acidity, and redox chemistry, allowing for unique applications in synthetic chemistry.

Oxidative addition of Bi-C bonds to Pt(0): reaction of Pt(PEt3)3 with cyclic organobismuth compounds

The reaction of cyclic organobismuth compounds, 12-phenyl- and 12-chloro-5,6,7,12-tetrahydrodibenz[c,f][1,5]azabismocines, with Pt(PEt3)3 was examined. Oxidative addition of the exocyclic Bi-C bond to Pt(0) selectively took place in the reaction of the 12-phenyl derivative. Oxidative addition of the exocyclic Bi-Cl bond reversibly took place and was kinetically preferred, while endocyclic Bi-C bond oxidative addition products were thermodynamically favored and became the final products in the reaction of 12-chloro derivatives. These results demonstrate the oxidative addition of a Bi-C bond to a transition metal complex for the first time.

(N),C,N-Coordinated Heavier Group 13-15 Compounds: Synthesis, Structure and Applications

The aim of this review is to summarize recent achievements in the field of (N),C,N-coordinated group 13-15 compounds not only regarding their synthesis and structure, but mainly focusing on their potential applications. Relevant compounds contain various types of N-coordinating ligands built up on an ortho-(di)substituted phenyl platform. Thus, group 13 and 14 derivatives were used as single-source precursors for the deposition of semiconducting thin films, as building blocks for the preparation of high-molecular polymers with remarkable optical and chemical properties or as compounds with interesting reactivity in hydrometallation processes. Group 15 derivatives function as catalysts in the Mannich reaction, in the allylation of aldehydes or activation of CO₂ . They were used as transmetallation reagents in transition metal catalysed coupling reactions. The univalent species serve as ligands for transition metals, activate alkynes or alkenes and are utilized as catalysts in the transfer hydrogenation of azo-compounds.

Crystal structure of 6-cyclohexyl-6,7-dihydrodibenzo[c,f][1,5]azabismocin-12(5H)-yl nitrate, C20H23O3N2Bi

C20H23O3N2Bi, monoclinic, P21/n (no. 14), a = 10.6897(5) Å, b = 10.5590(5) Å, c = 17.4099(9) Å, β = 105.491(2)°, V = 1893.71(16) Å3, Z = 4, R gt(F) = 0.0253, wR(F 2) = 0.0576, T = 296(2) K.