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Syntheses and Properties of Ditelluroxanes and Oligochalcogenoxanes: Hypervalent Oligomers with Te−O Apical Linkages in the Main Chain
Author(s) -
Kobayashi Kenji,
Tanaka Kunimasa,
Izawa Hiroyuki,
Arai Yoriko,
Furukawa Naomichi
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20011001)7:19<4272::aid-chem4272>3.0.co;2-u
Subject(s) - chemistry , hypervalent molecule , reactivity (psychology) , carboxylate , cationic polymerization , nucleophile , chemical shift , equilibrium constant , medicinal chemistry , reaction rate constant , stereochemistry , crystallography , polymer chemistry , organic chemistry , kinetics , catalysis , reagent , medicine , physics , alternative medicine , pathology , quantum mechanics
The reaction of ditelluroxanes [Ar 2 Te‐O‐TeAr 2 ] 2+ [X] 2 − ( 2 ) (Ar= p ‐tolyl) with a telluroxide 1 , a selenoxide 7 , or a carboxylate 10 to produce oligochalcogenoxanes with hypervalent Te−O apical linkages in their main chain is described. The 125 Te NMR chemical shifts of 2 ( 2 a : X − =CF 3 SO 3 − , 2 b : X − =CF 3 CO 2 − , 2 c : X − =CH 3 CO 2 − , 2 d : X − =Cl − ) are shifted downfield with decreasing nucleophilicity of the counteranions. This result reflects both the cationic character and the reactivity of the Te atoms of 2 . The reaction of 2 a with one, two, three, or four equivalents of telluroxide 1 a (Ar= p ‐tolyl) selectively gave a tritelluroxane 3 a , tetratelluroxane 4 a , pentatelluroxane 5 a , and hexatelluroxane 6 a , respectively. In contrast, the reaction of 2 b with an excess of 1 a produced only tritelluroxane 3 b . An equilibrium between the oligotelluroxanes was confirmed by crossover experiments of the reactions of 2 a with 4 a and of 2 a with 1 b (Ar=Ph). The selective equilibrium formation of a selenoxaditelluroxane 8 or a bis(selenoxa)ditelluroxane 9 was achieved by the reaction of 2 a with one or two equivalents of selenoxide 7 , respectively. The association constant of 2 a with 7 to form 8 was estimated to be K a =(2.18±0.12)×10 4 M −1 in CD 3 CN at −40 °C. The reaction of 2 a with two equivalents of carboxylates 10 a – d gave a mixture of bis(carboxylate)ditelluroxanes 11 a – c and diaryldicarboxytelluranes 12 b – d , respectively, in which the product ratio of these depended upon the electron‐withdrawing ability of 10 . The reaction of 3 a with two equivalents of 10 a – d afforded 11 a – d in all cases. The present results suggest that the σ*–n orbital interaction plays an essential role in the reactivity of ditelluroxanes and in the formation of self‐assembled oligochalcogenoxanes, and that a hypervalent bond via a σ*–n orbital interaction is viable as a new supramolecular synthon for molecular assembly.