A Substrate-Dependent Redox Catalysis of Tellurenyl Species Involving Oxidation States +I, +II, and +IV

Neutral Te(II) species 2-(tBuNCH)C6H4TeCl ([I]Cl) as well as tellurenyl
Te(II)+ cations [2-(tBuNCH)C6H4Te][X] (X = OTf or SbF6), i.e., [I][OTf] and [I][SbF6],
exhibit a
wide range of reactivity toward various ortho-quinones.
While the reaction of ortho-chloranil leads to the
oxidation of Te(II) into Te(IV), 3,5-di-tert-butyl-ortho-benzoquinone leads only to partial oxidation due to
an ongoing dynamic reversible reaction, being the first example of
a chemically reversible two electron Te(II)/Te(IV) redox couple. By
contrast, 9,10-phenanthrenequinone as a very weak oxidant shows no
reaction; however, the most Lewis acidic [I][SbF6] produces a corresponding Lewis
adduct interacting by both electrostatic and weak chalcogen bond interactions.
The diverse reactivity scope is further complemented by DFT computed
thermochemistry data. Furthermore, [I][OTf] is successfully
utilized for the catalytic transfer of silanes (Et3SiH,
Ph3SiH, Ph2SiH2, and (EtO)3SiH) to ortho-quinones via redox single or double
Si–H bond activation, yielding silylated catechols, monomeric
cyclic catecholatosilanes, or bis(catecholato)silanes. Surprisingly,
in the absence of the catalyst [I][OTf], the reactivity
spans from no reaction to the formation of hexachloro-dibenzo[1,4]dioxine-2,3-dione.
The latter product is an entirely different substance class compared
to the one formed during the catalyzed reaction.