Rafael C. Guadagnin

Copper Catalyzed Cross-Coupling Reactions of Diaryl Ditellurides with Potassium Aryltrifluoroborate Salts

Apresentamos aqui resultados das reacoes de acoplamento de diteluretos de diarila com sais de ariltrifluoroborato de potassio, usando quantidades cataliticas de Cu(OAc) 2 e bipiridina, em uma mistura de DMSO/H 2 O, sob ar atmosferico. Estas reacoes de acoplamento sao gerais e sao realizadas com diteluretos de diarila e sais de ariltrifluoroborato de potassio contendo substituintes neutros, retiradores e doadores de eletrons, fornecendo os correspondentes teluretos de diarila nao simetricos em rendimentos de bons a excelentes. We present here results of the cross-coupling reaction of diaryl ditellurides with potassium aryltrifluoroborate salts using a catalytic amount of Cu(OAc) 2 and bypiridine in DMSO/H 2 O under air atmosphere. This cross-coupling reaction is general and was performed with diaryl ditellurides and potassium aryltrifluoroborate salts bearing electron-withdrawing, electron-donating and neutral substituents, affording the corresponding unsymmetrical diaryl tellurides in good to excellent yields.

Crystal and molecular structures of dichloro((Z)-2-chloro-2-phenylvinyl)(organo)tellurium(IV) for organo = n-butyl and phenyl

Abstract In each of the title compounds, R[Ph(Cl)C=(H)C]TeCl2, R = nBu (1) and Ph (2), the primary geometry about the TeIV atom is a pseudo-trigonal-bipyramidal arrangement, with two Cl atoms in apical positions, and the lone pair of electrons and C atoms in the equatorial plane. As the TeIV is involved in two, an intra- and an inter-molecular, Te···Cl interactions the coordination geometry might be considered as a ψ-pentagonal bipyramid in each case. In addition, in (2) there is a hint of a Te···π interaction (Te···C = 3.911(3) Å). The key feature in the crystal structure of both compounds is the formation of supramolecular chains mediated by Te···Cl contacts.(1): C12H15Cl3Te, triclinic, P-1, a = 5.9471(11), b = 10.7826(22), c = 11.7983(19) Å, α = 75.416(12), β = 78.868(13), γ = 80.902(14)°, V = 713.6(2) Å3, Z = 2, R1 = 0.021; (2): C14H11Cl3Te, orthorhombic, Pcab, a = 7.7189(10), b = 17.415(2), c = 21.568(3) Å, V = 2899.3(6) Å3, Z = 8, R1 = 0.027.

Potassium trifluoro­[(Z)-3-methoxy­prop-1-en­yl]borate

In the title salt, K+·C4H7BF3O−, the K atom is surrounded by six anions making close contacts through seven F [K⋯F = 2.779 (1)–3.048 (1) Å] and two O [K⋯O = 2.953 (2) and 3.127 (2) Å] atoms in a trivacant fac-vIC-9 icosahedral coordination geometry.

Crystallographic, DFT and docking (cathepsin B) studies on an organotellurium(IV) compound

Abstract Some biologically active organotellurium compounds exhibit inhibitory potency against cathepsin B. In this study, an alkyl derivative, viz. [CH3(CH2)2C(I)=C(H)](nBu)TeI2, 1, has been structurally characterised by X-ray crystallography and shown to be coordinated within a C2I2 donor set. When the stereochemically active lone pair of electrons is taken into account, a distorted trigonal bipyramidal geometry results with the iodide atoms in axial positions. Both intra- and inter-molecular Te···I interactions are also noted. If all interactions are considered, the coordination geometry is based on a Ψ-pentagonal bipyramidal geometry. An unusual feature of the structure is the curving of the functionalised C5 chain. This feature has been explored by DFT methods and shown to arise as a result of close C–H···I interactions. A docking study (cathepsin B) was performed to understand the inhibition mechanism and to compare the new results with previous observations. Notably, 1 has the same pose exhibited by analogous biologically active compounds with aryl groups. Thus, the present study suggests that (alkyl)2TeX2 compounds should also be evaluated for biological activity.

Dichloro(cyclohexilidene-1-methylene)(phenyl)Te(IV). Looking for the theoretical treatment

Abstract C13H16Cl2Te, Mr = 370.76, P21/a, a = 8.1833(8), b = 8.4163(8), c = 20.787(2) Å, β = 99.52(1)°, Z = 4, R1 = 0,0275. The primary coordination around the TeIV atom is consistent with a pseudo-trigonal bipyramidal bond configuration with two Cl atoms occupying axial positions while the C atoms and the lone pair of electrons occupy the equatorial positions. The TeIV atom is involved in an intermolecular secondary interaction resulting in the self assembly of zigzag-chains supramolecular array. In order to determine the theoretical basis set for the Te atom which leads to the best agreement with the experimental data, a large series of geometry optimizations were performed on dichloro dimethyl Te(IV), as a model compound, and the results compared with the mean distances and angles obtained from 45 X-ray structures. The Ahlrichs basis set plus the Hay & Wadt ECP was selected and used for a series of calculations performed on the title compound.

Potassium trifluoro­[(Z)-3-(oxan-2-yl­oxy)prop-1-en-1-yl]borate monohydrate

The title compound, K+·C8H13BF3O2 −·H2O, which was obtained from the reaction of a modified form of Z-vinylic telluride via a transmetalation reaction with n-BuLi, crystallizes as K+ and C8H13BF3O2 − ions along with a water molecule. The K+ cation is surrounded by four anions, making close contacts with six F atoms at 2.659 (3)–2.906 (3) Å and with two O atoms at 2.806 (3) and 2.921 (3) Å in a distorted bicapped trigonal-prismatic geometry.

Mechanistic aspects of the isomerization of Z-vinylic tellurides double bonds in the synthesis of potassium Z-vinyltrifluoroborate salts

Through direct transmetalation reaction of Z-vinylic tellurides with nBuLi was observed the unexpected isomerization of double bonds leading to potassium E-vinyltrifluoroborates salts in low to moderate yields. Using EPR spin trapping experiments the radical species that promoted the stereoinversion of Z-vinylic organometallic species during the preparation of potassium vinyltrifluoroborate salts was identified. The experiments support the proposed mechanism, which is based on the homolytic cleavage of the TenBu bond.

1-[(Z)-1-Bromo-2-(butyl-dichloro-λ-tellan-yl)ethen-yl]cyclo-hex-1-ene.

The TeIV atom in the title compound, [Te(C4H9)(C8H10Br)Cl2] or C12H19BrCl2Te, is in a distorted ψ-trigonal–bipyramidal geometry, with the lone pair of electrons projected to occupy a position in the equatorial plane, and with the Cl atoms being mutually trans [172.48 (4)°]. Close intramolecular [Te⋯Br = 3.3444 (18) Å] and intermolecular [Te⋯Cl = 3.675 (3) Å] interactions are observed. The latter lead to centrosymmetric dimers which assemble into layers in the bc plane. The primary connections between layers are of the type C—H⋯Cl.