Stable Radicals from Commonly Used Precursors Trichlorosilane and Diphenylchlorophosphine

Intermediate species dichlorosilylene
was generated in
situ from trichlorosilane and inserted into the P-Cl bond
of diphenylchlorophosphine (Ph2P-Cl) to obtain Ph2P-SiCl3 (1). Monodechlorination of 1 by cyclic alkyl­(amino) carbenes (cAACs)/KC8 in
THF at low temperature led to the formation of stable radicals Ph2P-Si­(cAAC·)­Cl2 (2a,b). Compounds 2a,b were characterized by X-ray single
crystal diffraction, mass spectrometry and studied by cyclic voltammetry
and theoretical calculations. Radical properties of 2 are confirmed by EPR measurements that suggest the radical electron
in 2 couples with 14N (I =
1), 35/37Cl (I = 3/2), and 31P (I = 1/2) nuclei leading to multiple hyperfine
lines. Hyperfine coupling parameters computed from DFT calculations
are in good agreement with those of experimental values. Electronic
distributions obtained from the theoretical calculations suggest that
the radical electron mostly resides on the carbene C of 2.