1 research outputs found
Dual Reactivity of a Stable Zwitterionic N-Heterocyclic Silylene and Its Carbene Complex Probed with Muonium
The reactivity of the multifunctional cyclic silylene <b>4</b> and its carbene complex <b>5</b> have been investigated
by
a combination of muon spin spectroscopy and computation. The free
radicals formed by muonium (Mu) addition to <b>4</b> were identified,
showing that there are two dominant sites of free radical attack:
on the Si atom and on the exocyclic methylene carbon. Reaction of
muonium with <b>5</b> also produced two radicals, but with markedly
different hyperfine constants. For both compounds avoided level-crossing
resonance spectra and calculation of hyperfine constants show that
one of the radicals results from Mu addition to the methylene group,
yielding radicals <b>4a</b> and <b>5a</b>. Each contains
a muoniated methyl group, −CH<sub>2</sub>Mu, which undergoes
restricted rotation with respect to the plane of the ring. For <b>4</b> the second product is readily assigned as the muoniated
silyl radical <b>4b</b>, on the grounds of its high muon hyperfine
constant (716 MHz). The second product from <b>5</b> shows instead
a very small coupling constant, 19 MHz, assignable to the muoniated
complex <b>5b</b>, in which the spin density has been transferred
from the silicon to the carbenic carbon