Electrochemical Oxidation and Radical Cations of Structurally Non‐rigid Hypervalent Silatranes: Theoretical and Experimental Studies

Using 18 silatranes XSi(OCH 2 CH 2 ) 3 N ( 1 ) as examples, the potentials of electrochemical oxidation E 0 of the hypervalent compounds of Si were calculated for the first time at the ab initio and DFT levels. The experimental peak potentials E p (acetonitrile) show an excellent agreement (MAE=0.03) with the MP2//B3PW91 calculated E 0 (C‐PCM). Radical cations of 1 reveal a stretch isomerism of the N→Si dative bond. Localization of the spin density (SD) on the substituent X and the short ( s ) coordination contact Si⋅⋅⋅N ( d SiN <2.13 Å) along with the high five‐coordinate character of Si are typical for the first isomer 1 +.( s ) , whereas the second one, 1 +.( l ) , has a longer ( l ) Si⋅⋅⋅N distance ( d SiN >3.0 Å), the four‐coordinate Si and the SD localized on the silatrane nitrogen atom N s . The vertical model of adiabatic ionization ( 1 → 1 +.( s ) or 1 → 1 +.( l ) ) was developed. It allows, in accordance with an original experimental test (electrooxidation of 1 in the presence of ferrocene), a reliable prediction of the most probable pathways of the silatrane oxidation. The reliable relationships of E 0 ( 1 ) with the strength characteristics of the dative contact N→Si were revealed.