Silyl group insertion into the N-N bond: Experimental and quantum chemicalresults

The synthesis of the cyclodisilazane Ib in a ring-expansion reaction is the first example of a reductive insertion into the nitrogen-nitrogen single b ond accompanied by migration of a phenyl group from the silicon to a nitrog en atom. An analogous ring expansion is observed in the synthesis of the cy clodisilazane 2b, which is the first reaction that involves migration of a hydrogen atom from a silicon to a nitrogen atom. A crystal structure is pre sented for compound Ib. Quantum chemical calculations support the experimen tal findings. The reaction enthalpy Delta H-R degrees (298 K) of the isomer ization reaction converting the three-membered-ring (Me3SiN)(2)SiF2 (3a) in to the cyclodisilazane Me2Si(NSiMe3NMe)SiF2 (3b) is calculated to be -72.1 kcal mol(-1) The transition state and the unimolecular reaction mechanism a re discussed in detail.