Silyl Group Insertion into the N−N Bond: Experimental and Quantum Chemical Results

The synthesis of the cyclodisilazane 1b in a ring-expansion reaction is the first example of a reductive
insertion into the nitrogen−nitrogen single bond accompanied by migration of a phenyl group from the silicon
to a nitrogen atom. An analogous ring expansion is observed in the synthesis of the cyclodisilazane 2b, which
is the first reaction that involves migration of a hydrogen atom from a silicon to a nitrogen atom. A crystal
structure is presented for compound 1b. Quantum chemical calculations support the experimental findings.
The reaction enthalpy ΔRH°(298 K) of the isomerization reaction converting the three-membered-ring (Me3SiN)2SiF2 (3a) into the cyclodisilazane Me2Si(NSiMe3NMe)SiF2 (3b) is calculated to be −72.1 kcal mol-1.
The transition state and the unimolecular reaction mechanism are discussed in detail.