An Experimental and Theoretical Insight into I2 /Br2 Oxidation of Bis(pyridin-2-yl)Diselane and Ditellane

The reactivity between bis(pyridin-2-yl)diselane o Py2 Se2 and ditellane o Py2 Te2 (L1 and L2, respectively; o Py=pyridyn-2-yl) and I2 /Br2 is discussed. Single-crystal structure analysis revealed that the reaction of L1 with I2 yielded [(HL1+ )(I- )⋅5/2I2 ]∞ (1) in which monoprotonated cations HL1+ template a self-assembled infinite pseudo-cubic polyiodide 3D-network, while the reaction with Br2 yielded the dibromide Ho PySeII Br2 (2). The oxidation of L2 with I2 and Br2 yielded the compounds Ho PyTeII I2 (3) and Ho PyTeIV Br4 (6), respectively, whose structures were elucidated by X-ray diffraction analysis. FT-Raman spectroscopy measurements are consistent with a 3c-4e description of all the X-Ch-X three-body systems (Ch=Se, Te; X=Br, I) in compounds 2, 3, Ho PyTeII Br2 (5), and 6. The structural and spectroscopic observations are supported by extensive theoretical calculations carried out at the DFT level that were employed to study the electronic structure of the investigated compounds, the thermodynamic aspects of their formation, and the role of noncovalent σ-hole halogen and chalcogen bonds in the X⋅⋅⋅X, X⋅⋅⋅Ch and Ch⋅⋅⋅Ch interactions evidenced structurally.

Ionic-liquid-based synthesis of tellurium-rhenium carbonyls with specific reaction control

The novel tellurium rhenium carbonyls [TeI2Re(CO)5][AlCl4] (1), [BMIm][Te2I4(μ-I)2Re(CO)4] (2), {Te3I2(μ-I)3(μ3-I)}Re(CO)3 (3) and [BMIm][(Te2)3{Re(CO)3}2{Re(CO)4}3] (4) were prepared by reacting TeI4 and Re2(CO)10 in ionic liquids (ILs). [TeI2Re(CO)5][AlCl4] (1) was obtained in a mixture of [BMIm]Cl (BMIm: 1-butyl-3-methylimidazolium) and AlCl3 (ratio: 1 : 1) and contains a [TeI2Re(CO)5]+ cation. Increasing the amount of AlCl3 ([BMIm]Cl : AlCl3 = 1 : 2) results in [BMIm][Te2I4(μ-I)2Re(CO)4] (2) with the anion [Te2I4(μ-I)2Re(CO)4]-. At a [BMIm]Cl to AlCl3 ratio of 1 : 3, {Te3I2(μ-I)3(μ3-I)}Re(CO)3 (3) was realized with a Te3I3 ring and μ3-coordinating iodine. Finally, [BMIm][(Te2)3{Re(CO)3}2{Re(CO)4}3] (4) was prepared in [BMIm][OTf] (OTf: triflate) and contains the ufosan-like anion [(Te2)3{Re(CO)3}2{Re(CO)4}3]- with three Te22- and two Re(CO)3+ units that establish a distorted heterocuban-like cage. The compounds were characterized by single-crystal structure analysis, energy dispersive X-ray (EDX) analysis, thermogravimetry (TG), and infrared spectroscopy (FT-IR). The course of the reaction and the formation of the four novel tellurium-rhenium carbonyls can be directly correlated to the reaction conditions and especially to the acidity of the IL.

Selone-stabilized aryltellurenyl cations

Controlled bromination of a diarylditelluride, R2Te2 (R = 2,6-dimethylphenyl) (6) in dichloromethane led to the formation of a Te(II)-Te(IV) mixed-valent tellurenyl bromide, RBr2TeTeR (7). A further reaction of 7 with 1,3-dibutylbenzimidazolin-2-selone, C15H22N2Se (L) (9), produced the first selone adduct of the 2,6-dimethylphenyltellurenyl cation with the 2,6-dimethylphenyltellurium dibromide anion, [(2,6-Me2C6H3)Te(L)](+)[(2,6-Me2C6H3)TeBr2](-) (10). The red colored cationic adduct 10 is not stable in acetonitrile and disproportionated to give the selone adduct of 2,6-dimethylphenyltellurenyl bromide, [(2,6-Me2C6H3)Te(L)Br] (11b) and bis(2,6-dimethylphenyl)tellurium dibromide, [(2,6-Me2C6H3)2TeBr2], (13). The metathesis reaction of 11b with AgBF4 produced a stable dark red colored selone adduct of the 2,6-dimethylphenyltellurenyl cation with the BF4(-) anion, [(2,6-Me2C6H3)Te(L)](+)BF4(-) (15). The selone adducts of aryltellurenyl halides, i.e. [(2,6-Me2C6H3)Te(L)X] (X = Cl, Br, I) (11a-11c), have been synthesized by a one-pot reaction of 6 with an equimolar mixture of 9 and 1,3-dibutylbenzimidazolin-2-dihaloselones, C15H22N2SeX2 (14a-14c). Triphenylphosphine (PPh3), when treated with [(2,6-Me2C6H3)Te(L)X] (11a-11c), substitutes selone from the adduct to afford the triphenylphosphine adducts of aryltellurenyl halides, [(2,6-Me2C6H3)Te(PPh3)X] (16a-16c).

Synthesis of organochalcogen propargyl aryl ethers and their application in the electrophilic cyclization reaction: an efficient preparation of 3-halo-4-chalcogen-2H-benzopyrans

We herein described the synthesis of various organochalcogen propargyl aryl ethers via reaction of lithium acetylide intermediate with electrophilic chalcogen (sulfur, selenium, tellurium) species. Various aryl and alkyl groups directly bonded to the chalcogen atom were used as electrophile. The results revealed that the reaction does not significantly depend on the electronic effects of substituents in the aromatic ring bonded to the chalcogen atom of the electrophilic chalcogen species. Additional versatility in this process was demonstrated with respect to a diverse array of functionality in the aromatic ring at propargyl aryl ethers. These propargyl aryl ethers, bearing the chalcogen group, underwent highly selective intramolecular cyclizations when treated with I(2) or ICl affording 3-iodo-4-chalcogen-2H-benzopyrans. The results demonstrated that the cyclization efficiency was significantly influenced by the steric effects of aromatic ring, since the cyclization reaction gave low yields with aromatic rings having a substituent at orto position than those having no substituent. The reactivity of 3-iodo-4-chalcogen-2H-benzopyrans was also studied. 4-Selenobutyl benzopyrans were treated under Neghishi cross-coupling conditions providing the corresponding 3-aryl benzopyran derivatives in good yields. In addition, using the copper catalyzed cross-coupling reactions with thiols, in the absence of any cocatalyst, we were able to introduce a thiol function in 3-iodo-benzopyran derivatives.

Four Distinctively Different Decomposition Pathways of Metastable Supermesityltellurium(IV) Trichloride

Chlorination of bis(supermesityl)ditelluride RTeTeR (R = 2,4,6-t-Bu3C6H2) with 3 equiv of sulfuryl chloride SO2Cl2 provided the intrinsically unstable supermesityltellurium(IV) trichloride RTeCl3 (1) as bright yellow crystals. Severe repulsion between the equatorial Cl atom and one tert-butyl group in an ortho position in the supermesityl ligand is the reason for the extreme reactivity of 1, which is in contrast to that of all previously known monoorganotellurium trihalides. In the solid state at room temperature, (the triclinic modification of) 1 reacts slowly under HCl elimination and intramolecular Te-C bond formation to give the bicyclic 5,7-di-tert-butyl-2-hydro-3,3-dimethylbenzo[b]tellurophene-1,1-dichloride (2), which was originally obtained as a colorless amorphous solid. On one occasion, when the solid-state reaction was allowed to occur under air conditions, compound 2 and a colorless crystalline byproduct, namely, trans-supermesityltellurium hydroxide dichloride (3), had formed, from which a few crystals were hand-selected. The formation of 3 has been tentatively rationalized by a solid-state hydrolysis of a second (monoclinic?) modification present in the bulk material of 1. In diethyl ether, THF, or carbon disulfide, a redox equilibrium exists between yellow supermesityltellurium(IV) trichloride RTeCl3 (1), deep blue supermesityltellurenyl(II) chloride RTeCl (4), and chlorine gas, which can be shifted to 4 when the reaction vessel is purged with argon to remove the chlorine gas. Compound 4 was also obtained by the reaction of RTeTeR (R = 2,4,6-t-Bu3C6H2) with 1 equiv of SO2Cl2. When a solution of 1 was stored with an excess of SO2Cl2 for a prolonged amount of time, Te-C bond cleavage occurred and [(Et2OH)2Te2Cl10].2Et2O (5) was formed. Compounds 1-5 have been characterized by X-ray crystallography.