Syntheses and Reactions of Hexavalent Organotellurium Compounds Bearing Five or Six TelluriumCarbon Bonds

Abstract

A variety of hexaorganotellurium compounds, Ar(6-n)(CH3)nTe [Ar=4-CF3C6H4, n=0 (1a), n=1 (3a), n=2 (trans-4a and cis-4a), n=3 (mer-5a), n=4 (trans-6a); Ph, n=0 (1b), n=1 (3b), n=2 (trans-4b); 4-CH3C6H4, n=0 (1c), n=1 (3c), n=2 (trans-4c), n=4 (trans-6c); 4-BrC6H4, n=0 (1d)] and Ar5(R)Te [Ar=4-CF3C6H4, R=4-CH3OC6H4 (8); Ar=4-CF3C6H4, R=vinyl (9), Ar=Ph, R=vinyl (10), Ar=4-CF3C6H4, R=PhSCH2 (11), Ar=Ph, R=PhSCH2 (12), Ar=4-CF3C6H4, R=nBu (13)] and pentaorganotellurium halides, Ar5TeX [Ar=4-CF3C6H4, X=Cl (2a-Cl), X=Br (2a-Br); Ar=Ph, X=Cl (2b-Cl), X=Br (2b-Br); Ar=4-CH3C6H4, X=Cl (2c-Cl), X=Br (2c-Br); Ar=4-BrC6H4, X=Br (2d-Br)] and (4-CF3C6H4)4(CH3)TeX [X=Cl (trans-7a-Cl) and X=Br (trans-7a-Br)] were synthesized by the following methods: 1) one-pot synthesis of 1 a, 2) the reaction of SO2Cl2 or Br2 with Ar5Te(-)Li+ generated from TeCl4 or TeBr4 with five equivalents of ArLi, 3) reductive cleavage of Ar(6-m)(CH3)(m)Te (m=0 or 2) with KC8 followed by treatment with CH3I, 4) valence expansion reaction from low-valent tellurium compounds by treatment with KC8 followed by reaction with CH3I, 5) nucleophilic substitution of Ar(6-y-z)(CH3)zTeX(y-z) (X=Cl, Br, OTf; z=0, 1; y=1, 2) with organolithium reagents. The scope and limitations and some details for each method are discussed and electrophilic halogenation of the hexaorganotellurium compounds is also described.

Studies on hypervalent compounds and synthetic work using heteroaromatic cations

“…Lithium pentaaryltelluranide 181 (Ar = p ‐trifluoromethylphenyl) is the predominant species in equilibrium with its starting material ( 183 + ArLi) and their reactions with electrophiles are reported (Scheme ). There is considerable difference in stability and reactivity of compounds between the phenyl group and the p ‐trifluoromethylphenyl group 127,128. Syntheses of hypervalent aromatic organotellurium compounds including hexa( p ‐trifluoromethylphenyl)tellurium (Ar 6 Te) 185b and related species are summarized in Scheme 129,130.…”

“…(82‐i)). Great difference of reactivities between the two salts is due to intercalation of potassium cation in graphite to afford free, reactive anion of 187b 128. The methyl group of 186c was substituted for halogen ( 182 ) easily (Eq.…”

7 Oxygen, sulfur, selenium and tellurium

“…26 Hexavalent organotellurium compounds TeAr 6 (Ar = Ph or 4-CF 3 C 6 H 4 ) are formed in the reaction of TeCl 4 with four equivalents of ArLi in diethyl ether at 278 uC, pentaaryl halides TeAr 5 Hal (Hal = Cl or Br) were prepared by halogenating Li[TeAr 5 ] intermediates with sulfuryl chloride or dibromine respectively. 27 DFT studies of the ring currents in chalcogen-containing monocycles were used to probe their aromaticity. Diatropic p-currents reinforced by s-circulations were found in [S 3 N 3 ] 2 , [S 4 N 3 ] + , [S 4 N 4 ] 2+ and [S 5 N 5 ] + , but the currents were in opposition in the four-membered rings [S 4 ] 2+ , [Se 4 ] 2+ and S 2 N 2 , compatible with height profiles of calculated nucleus-independent chemical shifts.…”