Carbene Supported Dimer of Heavier Ketenimine Analogue with P and Si Atoms

A cyclic alkyl­(amino) carbene (cAAC)
stabilized dimer [(cAAC)­Si­(P-Tip)]2 (2) (Tip
= 2,4,6-triisopropylphenyl) is reported. 2 can be considered
as a dimer of the heavier ketenimine (R2CCN–R)
analogue. The dark-red rod-shaped
crystals of 2 were synthesized by reduction of the precursor,
cAAC-dichlorosilylene-stabilized phosphinidene (cAAC)­SiCl2→P-Tip with sodium napthalenide. The crystals of 2 are storable at room temperature for several months and stable up
to 215 °C under an inert atmosphere. X-ray single-crystal diffraction
revealed that 2 contains a cyclic nonplanar four-membered
SiPSiP ring. Magnetic susceptibility measurements confirmed the singlet
spin ground state of 2. Cyclic voltammetry of 2 showed a quasi-reversible one-electron reduction indicating the
formation of the corresponding radical anion 2•–, which was further characterized by EPR measurements in solution.
The electronic structure and bonding of 2 and 2•– were studied by theoretical calculations.
The experimentally obtained data are in good agreement with the calculated
values.