Room-Temperature Insertion of Elemental Tellurium into the C_sp^₃−Br and −I Bonds of α-Bromo- and α-Iodopinacolone

Abstract

Pinacolyltellurium(IV) dihalides, ( t -BuCOCH 2 ) 2 TeX 2 (X = Br ( 1b ), I ( 1c )) and Ar( t -BuCOCH 2 )TeCl 2 (Ar = 1-C 10 H 7 (Np) ( 2a ), 2,4,6-Me 3 C 6 H 2 (Mes) ( 3a )), are readily prepared at room temperature by the oxidative insertion of elemental tellurium into the C sp 3 −Br or −I bond of the α-halopinacolone and by the reaction of ArTeCl 3 with the pinacolone t -BuCOCH 3 . The bromides Np( t -BuCOCH 2 )TeBr 2 ( 2b ) and Mes( t -BuCOCH 2 )TeBr 2 ( 3b ) can be prepared by the addition of bromine to the telluride Ar( t -BuCOCH 2 )Te or of α-bromopinacolone to ArTeBr. Variable-temperature 1 H and 13 C NMR of the separate signals for the o -Me groups in 3a, b indicate a very high barrier to rotation about the Te−C(aryl) bond. Crystal diffraction data for 1c, 2a − c, and 3b show that intramolecular 1,4-Te···O(C) secondary bonding interactions (SBIs) are retained even in the presence of bulky aryl groups and intermolecular Te···X SBIs are subject to electronic population and steric congestion around the Te(IV) center in the solid state.