THERMAL-DECOMPOSITION OF [ME3SINCH2CH2NSIME3]CENTER-DOT-LI-2(THF)(2) TO [LIN(SIME3)(2)CENTER-DOT-THF](2) VIA A 1,4-TRIMETHYLSILYL SHIFT

The dilithium salt [Me3SiNCH2CH2NSiMe3].Li-2(THF)(2) decomposes slowly upon heating forming a metastable structure of the crystalline [LiN(S iMe3).THF](2). The crystal structure of the new form was established b y single crystal X-ray diffraction showing a decrease in the a and b p arameter values of the unit cell, and an expansion of the c value as c ompared with the structure obtained at room temperature. The major dis crepancies among the known and the metastable crystalline framework ar e the Li-O bond length and the dihedral angle disposition of the trime thylsilyl groups as regarded to the middle Li-N-Li-N heterocyclobutane ring. Attempts to trap the expected additional lithium imine product were unsuccessful although quenching experiments produced polyethylene imine. (C) 1997 Elsevier Science S.A.