Propulse spectrometer

CAUTION: Beryllium
and its compounds are extremely toxic. Suitable precautions (e.g.,
use of protective clothing, a breathing apparatus, and a well-ventilated
fume cupboard) should be taken for all manipulations involving these
species. Our general policy when handling beryllium compounds and
reagents is to limit the potential for ambient proliferation by working
on a microscale.
All manipulations were carried out using standard
Schlenk line and glovebox techniques under an inert atmosphere of
argon. NMR experiments were conducted in J. Young tap NMR tubes prepared
in a glovebox. NMR spectra were recorded on a Bruker BioSpin GmbH
spectrometer operating at 400.13 MHz (¹H), 61.42 MHz (²H), 100.62 MHz (¹³C) and 56.2 MHz (⁹Be) or on an Agilent ProPulse spectrometer operating at 194.3 MHz
(⁷Li). Solvents were dried by passage through a commercially
available solvent purification system and stored under argon in ampules
over 4 Å molecular sieves. C₆D₆ and C₇D₈ were purchased from Merck, and dried over potassium
before distilling and storage over molecular sieves. {CH₂SiMe₂N(H)Dipp}₂ and [{CH₂SiMe₂NDipp}₂BeClLi] (IV^Li) were synthesized according to literature procedures.^{31 (link),33 (link)}

Unless stated otherwise, all
of the experiments were conducted using standard Schlenk line and/or
glovebox techniques under an inert atmosphere of argon. NMR spectra
were recorded with an Agilent ProPulse spectrometer (¹H
at 500 MHz, ¹³C at 126 MHz). The spectra are referenced
relative to residual protio solvent resonances. Elemental analyses
were performed at Elemental Microanalysis Ltd., Okehampton, Devon,
UK. Solvents were dried by passage through a commercially available
solvent purification system and stored under argon in ampules over
4 Å molecular sieves. C₆D₆ was purchased
from Sigma-Aldrich and dried over a potassium mirror before distilling
and storage over molecular sieves. {CH₂SiMe₂N(H)Dipp}₂ and [{SiN^Dipp}MgNa]₂ (4) were synthesized according to literature procedures.^{33a ,36 (link)} Benzophenone and TEMPO were purchased from Merck and purified by
sublimation prior to usage. All other chemicals were purchased from
Merck and used as received.