Recent developments in the ligand chemistry of tellurium

Catalytic system having an organotellurium ligand on graphene oxide: immobilization of Pd(0) nanoparticles and application in heterogeneous catalysis of cross-coupling reactions

First heterogeneous catalytic system, having a covalently linked hybrid bidentate organotellurium ligand [i.e., PhTe-CH2-CH2-NH2] on the surface of graphene oxide, has been synthesized with immobilized and stabilized Pd(0) nanoparticles. To the best of our knowledge, it is the first such catalytic system in which a heterogenized organotellurium ligand has been used. It has been well-characterized using different physicochemical characterization techniques viz. P-XRD, XPS, HR-TEM, EELS, FE-SEM, EDX, TGA, BET surface area analysis, FT-IR spectroscopy, and Raman spectroscopy. The Pd content of the final system has been quantified using ICP-OES. Its applications have been explored in Suzuki-Miyaura C-C cross coupling and C-O cross coupling reactions. Hot filtration experiments corroborate the heterogeneous nature of the catalysis. It is recyclable for up to five reaction cycles in Suzuki-Miyaura and C-O cross coupling with marginal loss in performance. It also catalyzes the reactions of chloroarenes such as chlorobenzene, 4-chloroaniline, 1-chloro-4-nitrobenzene, 4-chloroacetophenone, 4-chlorobenzophenone for Suzuki coupling, and 1-chloro-4-nitrobenzene, 4-chlorobenzonitrile, chlorobenzene, and 4-chlorotoluene for C-O coupling. P-XRD, FE-SEM, and EDX study reveals that the catalytic system retains its structural originality and functionality after recycling.

QTAIM analysis of the bonding in anionic group 6 carbonyl selenide clusters: [Se2M3(CO)10]2- (M=Cr, Mo, W)

CONTEXT

This research aims to offer a deeper understanding of the bonding interactions between M-Se and M-CO and how these interactions change across the group 6 transition metal series: [Se2M3(CO)10]2- (M = Cr, Mo, W). It also seeks to explore the impact of carbonyl groups on M-M interactions within the clusters. Seven criteria, which are based on QTAIM properties, have been considered and compared with the corresponding criteria in other transition metal clusters. The results confirm that no such bond critical points or bond baths occur between transition metals, which instead have 5c-7e bonding interactions delocalized over their five-membered M3(μ-Se)2 ring, as evidenced by the non-negligible nonbonding delocalization indices. The topological properties of three bond clusters, Cr-Se, Mo-Se, and W-Se, resemble those of "intermediate closed shell characters," which combine covalent and electrostatic properties. Source function calculations indicated that the bonded Se atom contributed the most to each Cr-Se and Mo-Se bcp. The OCO atoms and nonbonded Se atoms also contributed to some extent. However, metal atoms act as sinks rather than as sources of electron density. In contrast, the majority of the metal atoms, both bonded and nonbonded, contribute to Cr-W bcps. Analysis of the delocalization indices δ(M…O) in the three clusters indicates that CO significantly contributes to Cr π-back donation in cluster 1. In contrast, no π-back donation occurs from CO to Mo or W in clusters 2 or 3, respectively.

METHODS

The B3P86 hybrid functional was used for computations in the Gaussian 09 software. The LanL2DZ basis set was employed for Cr, Mo, and W, while the 6-31G (d, p) basis set was used for C, O, and Se atoms. We performed QTAIM analysis using the AIM2000 and Multiwfn packages, incorporating B3P86/WTBS for Cr, Mo, and W atoms. The 6-311++G(3df,3pd) basis set was used for C, O, and Se atoms. Additionally, we utilized the ELF and SF.

Formation, Characterization, and Bonding of cis- and trans-[PtCl2{Te(CH2)6}2], cis-trans-[Pt3Cl6{Te(CH2)6}4], and cis-trans-[Pt4Cl8{Te(CH2)6}4]: Experimental and DFT Study

[PtCl2{Te(CH2)6}2] (1) was synthesized from the cyclic telluroether Te(CH2)6 and cis-[PtCl2(NCPh)2] in dichloromethane at room temperature under the exclusion of light. The crystal structure determination showed that in the solid state, 1 crystallizes as yellow plate-like crystals of the cis-isomer 1cis and the orange-red interwoven needles of 1trans. The crystals could be separated under the microscope. NMR experiments showed that upon dissolution of the crystals of 1cis in CDCl3, it isomerizes and forms a dynamic equilibrium with the trans-isomer 1trans that becomes the predominant species. Small amounts of cis-trans-[Pt3Cl6{Te(CH2)6}4] (2) and cis-trans-[Pt4Cl8{Te(CH2)6}4] (3) were also formed and structurally characterized. Both compounds show rare bridging telluroether ligands and two different platinum coordination environments, one exhibiting a cis-Cl/cis-Te(CH2)6 arrangement and the other a trans-Cl/trans-Te(CH2)6 arrangement. Complex 2 has an open structure with two terminal and two bridging telluroether ligands, whereas complex 3 has a cyclic structure with four Te(CH2)6 bridging ligands. The bonding and formation of the complexes have been discussed through the use of DFT calculations combined with QTAIM analysis. The recrystallization of the mixture of the 1:1 reaction from d6-DMSO afforded [PtCl2{S(O)(CD3)2}{Te(CH2)6}] (4) that could also be characterized both structurally and spectroscopically.

A tellura-Baeyer-Villiger oxidation: one-step transformation of tellurophene into chiral tellurinate lactone

Baeyer-Villiger (BV) oxidation is a fundamental organic reaction, whereas the hetero-BV oxidation is uncharted. Herein, a tellura-BV oxidation is discovered. By oxidizing a tellurophene-embedded and electron-rich polycycle (1) with mCPBA or Oxone, an oxygen atom is inserted into the Te-C bond of the tellurophene to form tellurinate lactone mono-2. This reaction proceeds as follows: (i) 1 is oxidized to the tellurophene Te-oxide form (IM-1); (ii) IM-1 undergoes tellura-BV oxidation to give mono-2. Moreover, the hybrid trichalcogenasumanenes 7 and 8 are, respectively, converted to tellurinate lactones mono-9 and mono-10 under the same conditions, indicating that tellura-BV oxidation shows high chemoselectivity. Due to the strong secondary bonding interactions between the Te[double bond, length as m-dash]O groups on tellurinate lactones, mono-2, mono-9, and mono-10 are dimerized to form U-shaped polycycles 2, 9, and 10, respectively. Notably, mono-2, mono-9, mono-10, and their dimers show chirality. This work enables one-step transformation of tellurophene into tellurinate lactone and construction of intricate polycycles.

Chemistry inside a Porphyrin Skeleton: Platinacyclopentadiene from Tellurophene

Platinum(II) binds to 21,23-ditelluraporphyrin forming a side-on complex, which can be easily transformed into an aromatic metallaporphyrin, that is, 21-platina-23-telluraporphyrin, with a platinacyclopentadiene unit built in the porphyrin skeleton in place of one pyrrole ring. The central platinum(II) ion with a CCNTe square-planar coordination sphere can be oxidized to platinum(IV) by chlorine, bromine, methyl iodide or allyl chloride to yield octahedral complexes. All platinatelluraporphyrins show dynamic behavior involving the platinum ion coordination sphere fluxionality and the porphyrin skeleton deformation, both in-plane and out-of-plane, as demonstrated by ¹ H NMR spectroscopy.

Synthesis and crystal structures of two new (Te, N,) type hybrid organotellurium ligands

The reaction of N-(2-chloroethyl)benzamide and N-[3-bromopropyl]phthalimide with ArTe- Na+ generated in situ by borohydride reduction of Ar2Te 2, has resulted in N-[2-(4-methoxyphenyltelluro)ethyl] benzamide (L1) and N-[2-(4-methoxyphenyl telluro)propyl] phthalimide (L2) respectively, which are potentially (Te, N)-type ligands. Their NMR (1H and 13C) spectra are characteristic and single crystal structures are solved. The Te-C(alkyl) distance [2.140(8)/2.151(4) Å] is longer than Te-C(aryl) distance [2.107(8)/2.128(5) Å].

Bis(6-Diphenylphosphinoacenaphth-5-yl)Telluride as a Ligand toward Manganese and Rhenium Carbonyls

The reaction of the previously known bis(6-diphenylphosphinoacenaphthyl-5-)telluride (6-Ph₂P-Ace-5-)₂Te (IV) with (CO)₅ReCl and (CO)₅MnBr proceeded with the liberation of CO and provided fac-(6-Ph₂P-Ace-5-)₂TeM(X)(CO)₃ (fac-1: M = Re, X = Cl; fac-2: M = Mn, X = Br), in which IV acts as bidentate ligand. In solution, fac-1 and fac-2 are engaged in a reversible equilibrium with mer-(6-Ph₂P-Ace-5-)₂TeM(X)(CO)₃ (mer-1: M = Re, X = Cl; mer-2: M = Mn, X = Br). Unlike fac-1, fac-2 is prone to release another equivalent of CO to give (6-Ph₂P-Ace-5-)₂TeMn(Br)(CO)₂ (3), in which IV serves as tridentate ligand.

Emerging tellurium nanostructures: controllable synthesis and their applications

Tellurium (Te) is a rare element in trace amounts of about one part per billion, comparable to that of platinum and ranked 75th in the abundance of the elements in the earth crust. Te nanostructures, as narrow bandgap semiconductors, have numerous potential applications in the fabrication of many modern devices. The past decades have witnessed an explosion in new strategies for synthesizing diverse emerging Te nanostructures with controlled compositions, sizes, shapes, and structures. Their structure-determined nature makes functional Te nanomaterials an attractive candidate for modern applications. This review focuses on the synthesis and morphology control of emerging Te nanostructures and summarizes the latest developments in the applications of Te nanostructures, such as their use as chemical transformation templates to access a huge family of nanowires/nanotubes, batteries, photodetectors, ion detection and removal, element doping, piezoelectric energy harvesting, gas sensing, thermoelectric devices and many other device applications. Various Te nanostructures with different shapes and structures will exploit the beneficial properties associated with their assembly process and nanofabrication. Finally, the prospects for future applications of Te nanomaterials are summarized and highlighted.

Synthesis, characterization and determination of absolute structures of palladium complexes of novel chiral acyclic tellurated Schiff base ligands

Enantiomerically pure chiral hybrid organotellurium ligands and their asymmetric palladium complexes have been synthesized and characterized.

Chalcogen Bonding Macrocycles and [2]Rotaxanes for Anion Recognition

Electron-deficient heavy chalcogen atoms contain Lewis acidic σ-holes which are able to form attractive supramolecular interactions, known as chalcogen bonding (ChB), with Lewis bases. However, their potential in solution-phase anion binding applications is only just beginning to be realized in simple acyclic systems. Herein, we explore the 5-(methylchalcogeno)-1,2,3-triazole (chalcogen = Se, Te) motif as a novel ChB donor for anion binding. Other than being chemically robust enough to be incorporated into macrocyclic structures, thereby significantly expanding the scope and complexity of ChB host systems, we also demonstrate, by ¹H NMR and DFT calculations, that the chalcogen atoms oriented within the macrocycle cavity are able to chelate copper(I) endotopically. Exploiting this property, the first examples of mechanically interlocked [2]rotaxanes containing ChB-donor groups are prepared via an active metal template strategy. Solution-phase ¹H NMR and molecular modeling studies provide compelling evidence for the dominant influence of ChB in anion binding by these interlocked host systems. In addition, unprecedented charge-assisted ChB-mediated anion binding was also studied in aqueous solvent mixtures, which revealed considerable differences in anion recognition behavior in comparison with chalcogen-free host analogues. Moreover, DFT calculations and molecular dynamics simulations in aqueous solvent mixtures indicate that the selectivity is determined by the different hydrophilic characters of the anions allied to the hydration of the binding units in the presence of the anions. Exploiting the NMR-active nuclei of the ChB-donor chalcogen atoms, heteronuclear ⁷⁷Se and ¹²⁵Te NMR were used to directly study how anion recognition influences the local electronic environment of the chalcogen atoms in the mechanically bonded rotaxane binding sites in organic and aqueous solvent mixtures.

Emerging trends in organotellurolate chemistry derived from platinoids

This perspective begins with the discussion of various basic synthetic approaches applied for the synthesis of several organotellurium ligands, their chemistry derived from platinum group metals, and the reactivity difference among them.

Synthesis, characterization, and ligand behaviour of a new ditelluroether (C10H7)Te(CH2)4Te(C10H7) and the concurrently formed ionic [(C10H7)Te(CH2)4]Br

The reaction of 1-naphthyl bromide with n-butyl lithium, elemental tellurium, and 1,4-dibromobutane in THF affords both (C₁₀H₇)Te(CH₂)₄Te(C₁₀H₇) (1) and [(C₁₀H₇)Te(CH₂)₄]Br (2) in good yields. 1 is preferentially formed at low temperatures and is a rare example of a structurally characterized ditelluroether in which the tellurium atoms are bridged by a hydrocarbon chain. In the solid state, 1 shows secondary bonding TeTe interactions, which connect the molecules into layers which are further linked to 3-dimensional frameworks by TeH hydrogen bonds. [(C₁₀H₇)Te(CH₂)₄]Br (2) is formed concurrently during the synthesis of 1 and is the main product, when the reaction is carried out at room temperature. The revPBE/def2-TZVPP calculations of the reaction profiles indicate that the formation of 2 is somewhat more favourable than that of 1. Furthermore, at room temperature the activation energy for the formation of 2 is lower than that of 1. At low temperatures the activation energy of the reaction leading to 1 is lower than that to 2, which is consistent with the synthetic observations. When 1 was treated with CuBr, [Cu₂(μ-Br)₂{μ-(C₁₀H₇)Te(CH₂)₄Te(C₁₀H₇)}₂] (3) was formed. It crystallizes as two polymorphs (3a) and (3b) in which both the packing and the conformation of the ditelluroether ligands are different. The reaction of 1 with HgCl₂ produces [(C₁₀H₇)Te(CH₂)₄]₂[HgCl₄]·CH₂Cl₂ (4·CH₂Cl₂) and that of 1 with CuCl₂ affords [(C₁₀H₇)Te(CH₂)₄]Cl (5). 2 and 5 are isomorphous.

Improved selectivity for Pb(ii) by sulfur, selenium and tellurium analogues of 1,8-anthraquinone-18-crown-5: synthesis, spectroscopy, X-ray crystallography and computational studies

Selectivity for toxic Pb(ii) ion is improved by changing donor heteroatoms in the host.

Synthesis, crystal structure, and optical characteristics of [Pd2Hg4Cl6{Te(DMB)}6]·2DMF, [HgClTe(DMB)]4, and the ring-forming cluster [Pd12(TePh)24]·2DMF

Exploring the use of metal organo chalcogenolates to achieve the rational growth of cluster complexes.