Oxidative Addition of Diphenyldichalcogenides PhEEPh (E = S, Se, Te) to Low-Valent CN- and NCN-Chelated Organoantimony and Organobismuth Compounds

Carbodiphosphorane-Activated Distibene and Dibismuthene Dications

Low-valent antimony and bismuth have emerged as novel platforms for achieving reversible small-molecule activation at main-group metals. Although various examples of oxidative addition reactions at monomeric Sb(I) and Bi(I) have been reported, the chemistry of the heavy group 15 Sb(I)═Sb(I)/Bi(I)═Bi(I) double bonds toward small molecules remains largely unexplored. In this study, we present a straightforward synthesis of distibene and dibismuthene dications coordinated with a neutral carbodiphosphorane (CDP) ligand. The nonbonding interactions between the occupied p-orbital at the CDP ligand and the π-bonding orbital of the Sb═Sb/Bi═Bi bonds yield compounds with exceptionally small HOMO-LUMO gaps. In addition, the reduction of steric hindrance compared to known neutral derivatives stabilized with bulky aryl groups allows for better accessibility of the double bonds. This high reactivity is demonstrated in the oxidative addition of distibene to diphenyldisulfide as well as in [2+2] cycloadditions to alkynes. Additionally, the Sb═Sb bond reversibly adds to 2,3-dimethylbutadiene in a [4+2] cycloaddition reaction.

Facile synthesis and antifungal evaluation of hypervalent organoantimony(III) and organobismuth(III) thioates with tridentate C,N,C-coordinating ligands

In the present work, a series of organometallic thioates bearing a 5,6,7,12-tetrahydrodibenzo[c,f][1,5]azastibocine or -azabismocine framework were synthesized through the cross-coupling reactions of the corresponding halide precursors with thiols and disulfides at room temperature. The former transformation can be achieved under additive-free conditions, and mild dithiothreitol (DTT) is the only additive in the latter. Both methods feature simple operation, a broad substrate scope, and good reaction yields. Antifungal assays showed that the synthesized organobismuth(III) thioates possess significantly higher antibiotic activity against Candida albicans than clinical fluconazole, while the inhibitory effects of Sb-sulfenylated products are low to negligible. Furthermore, the antibiofilm potential of such Bi-S bond-containing compounds was discovered as well.

Dual Fluorescence and Phosphorescence Emissions from Dye-Modified (NCN)-Bismuth Pincer Thiolate Complexes

We report the synthesis, characterization, and photophysical properties of four new dye-modified (NCN)Bi pincer complexes with two mercaptocoumarin or mercaptopyrene ligands. Their photophysical properties were probed by UV/vis spectroscopy, photoluminescence (PL) studies, and time-dependent density functional theory (TD-DFT) calculations. Absorption spectra of the complexes are dominated by mixed pyrene or coumarin π → π*/n(pS) → pyrene or coumarin π* transitions. While unstable toward reductive elimination of the corresponding disulfide under irradiation at room temperature, the complexes provide stable emissions at 77 K. Under these conditions, coumarin complexes 2 and 4 exhibit exclusively green phosphorescence at 508 nm. In contrast, the emissive properties of pyrene complexes 1 and 3 depend on the excitation wavelength and on sample concentration. Irradiation into the lowest-energy absorption band exclusively triggers red phosphorescence from the pyrenyl residues at 640 nm. At concentrations c < 1 μM, excitation into higher excited electronic states results in blue pyrene fluorescence. With increasing c (1-100 μM), the emission profile changes to dual fluorescence and phosphorescence emission, with a steady increase of the phosphorescence intensity, until at c ≥ 1 mM only red phosphorescence ensues. Progressive red-shifts and broadening of steady-state excitation spectra with increasing sample concentration suggest the presence of static excimers, as we observe it for concentrated solutions of pyrene. Crystalline and powdered samples of 1 indeed show intermolecular association through π-stacking. TD-DFT calculations on model dimers and a tetramer of 1 support the idea of aggregation-induced intersystem crossing (AI-ISC) as the underlying reason for this behavior.

Antimony Redox Catalysis: Hydroboration of Disulfides through Unique Sb(I)/Sb(III) Redox Cycling

The stibinidene ArSbI (Ar = [2,6-(tBuN═CH)2-C6H3], 1) reacts with S2Tol2 (Tol = p-tolyl) to form ArSbIII(STol)2 (2), which upon treatment with pinacolborane, regenerates 1. These processes unveil an unprecedented antimony redox catalysis involving Sb(I)/Sb(III) cycling for the hydroboration of organic disulfides. Elementary reaction studies and density functional theory calculations support that the catalysis mimics transition metal processes, proceeding through oxidative addition, ligand metathesis, and reductive elimination. The thiophenols and sulfidoborates generated from the hydroboration of disulfides react in situ with α,β-unsaturated carbonyl compounds with the assistance of 1 as a base catalyst. These tandem reactions establish a one-pot synthetic method for β-sulfido carbonyl compounds, in which a stibinidene functions as a redox catalyst and a base catalyst successively, illustrating the versatility and efficiency of antimony catalysis in organic synthesis.

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.

Ligand-enforced geometric constraints and associated reactivity in p-block compounds

The geometry at an element centre can generally be predicted based on the number of electron pairs around it using valence shell electron pair repulsion (VSEPR) theory. Strategies to distort p-block compounds away from these predicted geometries have gained considerable interest due to the unique structural outcomes, spectroscopic properties or reactivity patterns engendered by such distortion. This review presents an up-to-date group-wise summary of this exciting and rapidly growing field with a focus on understanding how the ligand employed unlocks structural features, which in turn influences the associated reactivity. Relevant geometrically constrained compounds from groups 13-16 are discussed, along with selected stoichiometric and catalytic reactions. Several areas for advancement in this field are also discussed. Collectively, this review advances the notion of geometric tuning as an important lever, alongside electronic and steric tuning, in controlling bonding and reactivity at p-block centres.

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.

Catalytic Mechanisms of Transfer Hydrogenation of Azobenzene with Ammonia Borane by Pincer Bismuth Complex: Crucial Role of C=N Functional Group on the Pincer Ligand

Transfer hydrogenation of azobenzene with ammonia borane mediated by pincer bismuth complex 1 was systematically investigated through density functional theory calculations. An unusual metal-ligand cooperation mechanism was disclosed, in which the saturation/regeneration of the C=N functional group on the pincer ligand plays an essential role. The reaction is initiated by the hydrogenation of the C=N bond (saturation) with ammonia borane to afford 3^CN , which is the rate-determining step with Gibbs energy barrier (ΔG^≠ ) and Gibbs reaction energy (ΔG) of 25.6 and -7.3 kcal/mol, respectively. 3^CN is then converted to a Bi-H intermediate through a water-bridged pathway, which is followed up with the transfer hydrogenation of azobenzene to produce the final product N,N'-diphenylhydrazine and regenerate the catalyst. Finally, the catalyst could be improved by substituting the phenyl group for the tert-butyl group on the pincer ligand, where the ΔG^≠ value (rate-determining step) decreases to 24.0 kcal/mol.

Base-Promoted Reactions of Organostibines with Alkynes and Organic Halides to Give Chalcogenated (Z)-Olefins and Ethers

Herein, with air-stable chalcogenated stibines (Sb-ER) as organometallic chalcogenating reagents, we developed base-promoted (Z)-hydrochalcogenation of alkynes with DMSO/DMSO-d₆ as hydrogen/deuterium sources, giving chalcogenated (Z)-olefins in good yields and with excellent regioselectivity. These reagents, easily synthesized from halostibines with in situ generated [Zn(ER)₂] at room temperature within a few minutes, could be also used in the base-promoted C(sp³)-S(Se) cross-coupling with C(sp³)-X and copper-catalyzed C(sp²)-S(Se) cross-coupling with C(sp²)-X (X = F, CI, Br, I) under mild conditions. This protocol could also be simply extended to organobismuth complexes (Bi-ER) with good functional tolerance.

Organopnictogen(III) bis(arylthiolates) containing NCN-aryl pincer ligands: from synthesis and characterization to reactivity

Salt elimination reactions between organopnictogen(III) dichlorides, RPnCl₂ [R¹ = 2,6-(Me₂NCH₂)₂C₆H₃, Pn = Sb (1), Bi (2); R² = 2,6-{MeN(CH₂CH₂)₂NCH₂}₂C₆H₃, Pn = Sb (3), Bi (4); R³ = 2,6-{O(CH₂CH₂)₂NCH₂}₂C₆H₃, Pn = Sb (5), Bi (6)] and 2 equivalents of KSC₆H₃Me₂-2,6 afforded the isolation of a series of new NCN-chelated monoorganopnictogen(III) bis(arylthiolates), RPn(SC₆H₃Me₂-2,6)₂ [R¹, Pn = Sb (7), Bi (8); R², Pn = Sb (9), Bi (10); R³, Pn = Sb (11), Bi (12)]. Compounds 7 and 8 are unstable upon exposure to a dry O₂ atmosphere and their aerobic decomposition yields the monoorganopnictogen(III) oxides, cyclo-[2,6-(Me₂NCH₂)₂C₆H₃Pn(μ-O)]₂ [Pn = Sb (13), Bi (14)] with concomitant formation of the corresponding disulfide, ArS-SAr (Ar = C₆H₃Me₂-2,6). The oxidative addition of elemental sulfur or selenium to 7 undergoes a similar reaction path and gives stable heterocyclic species cyclo-[2,6-(Me₂NCH₂)₂C₆H₃Sb(μ-E)]₂ [E = S (15), Se (16)]. The reaction of 12 with I₂ (1 : 1 molar ratio) gives the diiodide [2,6-{O(CH₂CH₂)₂NCH₂}₂C₆H₃]BiI₂ (17), along with the S-S oxidative coupling by-product, ArS-SAr. The use of an excess of iodine affords the crystallization of a 2 : 1 iodine adduct of 17 (17·0.5I₂), built through halogen bonding. All new compounds were characterized by multinuclear NMR spectroscopy and ESI-MS as well as single crystal X-ray diffraction (except compounds 9 and 10).

Two Faces of the Bi-O Bond: Photochemically and Thermally Induced Dehydrocoupling for Si-O Bond Formation

The diorgano(bismuth)alcoholate [Bi((C6H4CH2)2S)OPh] (1-OPh) has been synthesized and fully characterized. Stoichiometric reactions, UV/Vis spectroscopy, and (TD-)DFT calculations suggest its susceptibility to homolytic and heterolytic Bi-O bond cleavage under given reaction conditions. Using the dehydrocoupling of silanes with either TEMPO or phenol as model reactions, the catalytic competency of 1-OPh has been investigated (TEMPO=(tetramethyl-piperidin-1-yl)-oxyl). Different reaction pathways can deliberately be addressed by applying photochemical or thermal reaction conditions and by choosing radical or closed-shell substrates (TEMPO vs. phenol). Applied analytical techniques include NMR, UV/Vis, and EPR spectroscopy, mass spectrometry, single-crystal X-ray diffraction analysis, and (TD)-DFT calculations.

Non-conventional Behavior of a 2,1-Benzazaphosphole: Heterodiene or Hidden Phosphinidene?

The titled 2,1-benzazaphosphole (1) (i. e. ArP, where Ar=2-(DippN=CH)C6 H4 , Dipp=2,6-iPr2 C6 H3 ) showed a spectacular reactivity behaving both as a reactive heterodiene in hetero-Diels-Alder (DA) reactions or as a hidden phosphinidene in the coordination toward selected transition metals (TMs). Thus, 1 reacts with electron-deficient alkynes RC≡CR (R=CO2 Me, C5 F4 N) giving 1-phospha-1,4-dihydro-iminonaphthalenes 2 and 3, that undergo hydrogen migration producing 1-phosphanaphthalenes 4 and 5. Compound 1 is also able to activate the C=C double bond in selected N-alkyl/aryl-maleimides RN(C(O)CH)2 (R=Me, tBu, Ph) resulting in the addition products 7-9 with bridged bicyclic [2.2.1] structures. The binding of the maleimides to 1 is semi-reversible upon heating. By contrast, when 1 was treated with selected TM complexes, it serves as a 4e donor bridging two TMs thus producing complexes [μ-ArP(AuCl)2 ] (10), [(μ-ArP)4 Ag4 ][X]4 (X=BF4 (11), OTf (12)) and [μ-ArP(Co2 (CO)6 )] (13). The structure and electron distribution of the starting material 1 as well as of other compounds were also studied from the theoretical point of view.

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.

Main Group Redox Catalysis of Organopnictogens: Vertical Periodic Trends and Emerging Opportunities in Group 15

A growing number of organopnictogen redox catalytic methods have emerged-especially within the past 10 years-that leverage the plentiful reversible two-electron redox chemistry within Group 15. The goal of this Perspective is to provide readers the context to understand the dramatic developments in organopnictogen catalysis over the past decade with an eye toward future development. An exposition of the fundamental differences in the atomic structure and bonding of the pnictogens, and thus the molecular electronic structure of organopnictogen compounds, is presented to establish the backdrop against which organopnictogen redox reactivity-and ultimately catalysis-is framed. A deep appreciation of these underlying periodic principles informs an understanding of the differing modes of organopnictogen redox catalysis and evokes the key challenges to the field moving forward. We close by addressing forward-looking directions likely to animate this area in the years to come. What new catalytic manifolds can be developed through creative catalyst and reaction design that take advantage of the intrinsic redox reactivity of the pnictogens to drive new discoveries in catalysis?

Trimerization and cyclization of reactive P-functionalities confined within OCO pincers

In order to stabilize a 10–P–3 species with C_2v symmetry and two lone pairs on the central phosphorus atom, a specialized ligand is required. Using an NCN pincer, previous efforts to enforce this planarized geometry at P resulted in the formation of a C_s-symmetric, 10π-electron benzazaphosphole that existed as a dynamic “bell-clapper” in solution. Here, OCO pincers 1 and 2 were synthesized, operating under the hypothesis that the more electron-withdrawing oxygen donors would better stabilize the 3-center, 4-electron O–P–O bond of the 10–P–3 target and the sp³-hybridized benzylic carbon atoms would prevent the formation of aromatic P-heterocycles. However, subjecting 1 to a metalation/phosphination/reduction sequence afforded cyclotriphosphane 3, resulting from trimerization of the P(i) center unbound by its oxygen donors. Pincer 2 featuring four benzylic CF₃ groups was expected to strengthen the O–P–O bond of the target, but after metal–halogen exchange and quenching with PCl₃, unexpected cyclization with loss of CH₃Cl was observed to give monochlorinated 5. Treatment of 5 with (p-CH₃)C₆H₄MgBr generated crystalline P-(p-Tol) derivative 6, which was characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography. The complex ¹⁹F NMR spectra of 5 and 6 observed experimentally, were reproduced by simulations with MestreNova.

Attempted synthesis of OCO-supported 10–P–3 species led to trimerization or cyclization.

Well-Defined, Molecular Bismuth Compounds: Catalysts in Photochemically Induced Radical Dehydrocoupling Reactions

A series of diorgano(bismuth)chalcogenides, [Bi(di-aryl)EPh], has been synthesised and fully characterised (E=S, Se, Te). These molecular bismuth complexes have been exploited in homogeneous photochemically-induced radical catalysis, using the coupling of silanes with TEMPO as a model reaction (TEMPO=(tetramethyl-piperidin-1-yl)-oxyl). Their catalytic properties are complementary or superior to those of known catalysts for these coupling reactions. Catalytically competent intermediates of the reaction have been identified. Applied analytical techniques include NMR, UV/Vis, and EPR spectroscopy, mass spectrometry, single-crystal X-ray diffraction analysis, and (TD)-DFT calculations.

Low-Valent, Multiply Bonded, Trigonal-Planar Sb Complex: Rational Syntheses, Dual Acidic/Basic Properties, and Unexpected Semiconducting Characteristics

A 4-center, 6π-conjugated, multiply bonded trigonal-planar complex, [Sb{Cr(CO)₅}₃]^- (1), was synthesized via the hydride abstraction of [HSb{Cr(CO)₅}₃]^2- (1-H) with HBF₄·H₂O, with the release of high yields of H₂. The oxidation state of the Sb atom in [Et₄N][1] was well-defined as 0, which was evidenced by X-ray photoelectron spectroscopy and X-ray absorption near-edge structure. The distinct color-structure relationship of this low-valent Sb complex 1 toward a wide range of organic solvents was demonstrated, as interpreted by time-dependent density functional theory calculations, allowing the trigonal-planar 1 and the tetrahedral solvent adducts to be probed, revealing the dual acid/base properties of the Sb center. In addition, 1 showed pronounced electrophilicity toward anionic and neutral nucleophiles, even with solvent molecules, to produce tetrahedral complexes [(Nu)Sb{Cr(CO)₅}₃]^n- [1-Nu; n = 2, Nu = H, F, Cl, Br, I, OH; n = 1, Nu = PEt₃, PPh₃, N,N-dimethylformamide (DMF), acetonitrile (MeCN)]. On the contrary, the Fe/Cr hydride complex [HSb{Fe(CO)₄}{Cr(CO)₅}₂]^2- (2-H) was obtained by treating 1 with [HFe(CO)₄]^-. Upon hydride abstraction of 2-H with HBF₄·H₂O or [CPh₃][BF₄], a multiply bonded Fe/Cr trigonal-planar complex, [Sb{Fe(CO)₄}{Cr(CO)₅}₂]^- (2), was produced in which the oxidation coupling Sb₂-containing complexes [Sb₂Cr₄Fe₂(CO)₂₈]^2- (3-Cr) and [HSb₂Cr₃Fe₂(CO)₂₃]^- (3-H) were yielded as final products. Complex 3-Cr exhibited dual Lewis acid/base properties via hydridation and protonation reactions, to form 2-H or 3-H, respectively. Surprisingly, [Et₄N][1] possessed a low energy gap of 1.13 eV with an electrical conductivity in the range of (1.10-2.77) × 10^-6 S·cm^-1, showing that [Et₄N][1] was a low-energy-gap semiconductor. The crystal packing, crystal indexing, and density of states results of [Et₄N][1] further confirmed the efficient through-space conduction pathway via the intermolecular Sb···O(carbonyl) and O(carbonyl)···O(carbonyl) interactions of the 1D anionic zigzag chain of 1.

Molecular Bismuth Cations: Assessment of Soft Lewis Acidity

Three-coordinate cationic bismuth compounds [Bi(diaryl)(EPMe3 )][SbF6 ] have been isolated and fully characterized (diaryl=[(C6 H4 )2 C2 H2 ]2- , E=S, Se). They represent rare examples of molecular complexes with Bi⋅⋅⋅EPR3 interactions (R=monoanionic substituent). The 31 P NMR chemical shift of EPMe3 has been found to be sensitive to the formation of LA⋅⋅⋅EPMe3 Lewis acid/base interactions (LA=Lewis acid). This corresponds to a modification of the Gutmann-Beckett method and reveals information about the hardness/softness of the Lewis acid under investigation. A series of organobismuth compounds, bismuth halides, and cationic bismuth species have been investigated with this approach and compared to traditional group 13 and cationic group 14 Lewis acids. Especially cationic bismuth species have been shown to be potent soft Lewis acids that may prefer Lewis pair formation with a soft (S/Se-based) rather than a hard (O/N-based) donor. Analytical techniques applied in this work include (heteronuclear) NMR spectroscopy, single-crystal X-ray diffraction analysis, and DFT calculations.

Methylbismuth: an organometallic bismuthinidene biradical

We report the generation, spectroscopic characterization, and computational analysis of the first free (non-stabilized) organometallic bismuthinidene, BiMe. The title compound was generated in situ from BiMe3 by controlled homolytic Bi-C bond cleavage in the gas phase. Its electronic structure was characterized by a combination of photoion mass-selected threshold photoelectron spectroscopy and DFT as well as multi-reference computations. A triplet ground state was identified and an ionization energy (IE) of 7.88 eV was experimentally determined. Methyl abstraction from BiMe3 to give [BiMe2]• is a key step in the generation of BiMe. We reaveal a bond dissociation energy of 210 ± 7 kJ mol-1, which is substantially higher than the previously accepted value. Nevertheless, the homolytic cleavage of Me-BiMe2 bonds could be achieved at moderate temperatures (60-120 °C) in the condensed phase, suggesting that [BiMe2]• and BiMe are accessible as reactive intermediates under these conditions.

A Survey of Supramolecular Aggregation Based on Main Group Element⋯Selenium Secondary Bonding Interactions—A Survey of the Crystallographic Literature

The results of a survey of the crystal structures of main group element compounds (M = tin, lead, arsenic, antimony, bismuth, and tellurium) for intermolecular M⋯Se secondary bonding interactions is presented. The identified M⋯Se interactions in 58 crystals can operate independent of conventional supramolecular synthons and can sustain zero-, one-, two, and, rarely, three-dimensional supramolecular architectures, which are shown to adopt a wide variety of topologies. The most popular architecture found in the crystals stabilized by M⋯Se interactions are one-dimensional chains, found in 50% of the structures, followed by zero-dimensional (38%). In the majority of structures, the metal center forms a single M⋯Se contact; however, examples having up to three M⋯Se contacts are evident. Up to about 25% of lead(II)-/selenium-containing crystals exhibit Pb⋯Se tetrel bonding, a percentage falling off to about 15% in bismuth analogs (that is, pnictogen bonding) and 10% or lower for the other cited elements.

Crystalline Divinyldiarsenes and Cleavage of the As=As Bond

The first divinyldiarsenes [{(NHC)C(Ph)}As]₂ (NHC=IPr 3 a, SIPr 3 b; IPr=C{(NAr)CH}₂ ; SIPr=C{(NAr)CH₂ }₂ ; Ar=2,6-iPr₂ C₆ H₃ ) are reported. Compounds 3 a and 3 b were prepared by the reduction of corresponding chlorides {(NHC)C(Ph)}AsCl₂ (NHC=IPr 2 a, SIPr 2 b) with Mg. Calculations revealed a small HOMO-LUMO energy gap of 3.86 (3 a) and 4.24 eV (3 b). Treatment of 3 a with (Me₂ S)AuCl led to the cleavage of the As=As bond to restore 2 a, which is expected to proceed via the diarsane [{(IPr)C(Ph)}AsCl]₂ (4). Remarkably, 4 as well as 2 a can be selectively accessed on treatment of 3 a with an appropriate amount of C₂ Cl₆ . Moreover, 3 a readily reacts with PhEEPh (E=Se or Te) at room temperature to give {(IPr)C(Ph)}As(EPh)₂ (E=Se 5 a; Te 5 b), revealing the cleavage of As=As and E-E bonds and the formation of As-E bonds. Such highly selective stepwise oxidation (3 a→4→2 a) and bond metathesis (3 a→5 a,b) reactions are unprecedented in main-group chemistry.

Bi(I)-Catalyzed Transfer-Hydrogenation with Ammonia-Borane

A catalytic transfer-hydrogenation utilizing a well-defined Bi(I) complex as catalyst and ammonia-borane as transfer agent has been developed. This transformation represents a unique example of low-valent pnictogen catalysis cycling between oxidation states I and III, and proved useful for the hydrogenation of azoarenes and the partial reduction of nitroarenes. Interestingly, the bismuthinidene catalyst performs well in the presence of low-valent transition-metal sensitive functional groups and presents orthogonal reactivity compared to analogous phosphorus-based catalysis. Mechanistic investigations suggest the intermediacy of an elusive bismuthine species, which is proposed to be responsible for the hydrogenation and the formation of hydrogen.

Reactivity of bis[{2,6-(dimethylamino)methyl}phenyl]telluride with Pd(ii) and Hg(ii): isolation of the first Pd(ii) complex of an organotellurenium cation as a ligand

The first complex of an organotellurenium cation as a ligand with Pd(ii) is reported.

Heterocyclic bismuth(iii) compounds with transannular N→Bi interactions as catalysts for the oxidation of thiophenol to diphenyldisulfide

Aerial oxidation of thiophenol to diphenyl disulfide proceeds with high reaction rates, total conversion and selectivity in ionic liquids by using diorganobismuth(iii) catalysts.

Synthesis of Highly Functionalized Triarylbismuthines by Functional Group Manipulation and Use in Palladium- and Copper-Catalyzed Arylation Reactions

Organobismuthines are an attractive class of organometallic reagents that can be accessed from inexpensive and nontoxic bismuth salts. Triarylbismuthines are particularly interesting due to their air and moisture stability and high functional group tolerance. We report herein a detailed study on the preparation of highly functionalized triarylbismuth reagents by triple functional group manipulation and their use in palladium- and copper-catalyzed C-, N-, and O-arylation reactions.

Insights from the computational studies on the oxidized as-isolated state of [NiFeSe] hydrogenase from D. vulgaris Hildenborough

A density functional theory study of the active site structure and features of the oxygen tolerant [NiFeSe] Hase in the oxidized as-isolated state of the enzyme D. vulgaris Hildenborough (DvH) is reported here. The three conformers reported to be present in the X-ray structure (PDB ID: ) have been studied. The novel bidentate interchalcogen ligand (S-Se) in Conf-I of the [NiFeSe] Hase reported for the first time in hydrogenases (Hase) is found to be of donor-acceptor type with an uneven η(2) L → M σ-bond. The symmetry mismatch at the sp orbital of Se and at the dz(2) orbital of Ni has been identified to be the reason for the inability of Conf-II to convert to Conf-I. NBO analysis shows that the sulfinate ligand peculiar to the state stabilizes the active site through n →π* interactions. The results reveal that the isolated oxidized state of the [NiFeSe] Hase is significantly different from the well-known [NiFe] Hase.

Antimony(III) and bismuth(III) amides containing pendant N-donor groups--a combined experimental and theoretical study

N,N- and N,N,N-chelated antimony(III) and bismuth(III) chlorides L(1-3)MCl2 1-4 [for L(1): M = Sb (1), for L(2): M = Sb (2) and for L(3): M = Sb (3) and Bi (4)], containing ligands L(1-3) derived from the pyrrole ring (where L(1) = C4H3N-2-(CH[double bond, length as m-dash]N-2',6'-iPr2C6H3), L(2) = C4H2N-2,5-(CH2NMe2)2, L(3) = C4H2N-2,5-(CH2NC4H8)2), were prepared by the treatment of lithium precursors with SbCl3 or BiCl3. Molecular structures 1-4 of were described both in solution (NMR spectroscopy) and in the solid state (single-crystal X-ray diffraction analysis). Structures of 1-4 were also subjected to a density functional theory study.