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.