AGGREGATION, REAGGREGATION AND DEGRADATION OF A TRIFUNCTIONAL THALLIUM(I) AMIDE INDUCED BY WEAK TL-I-CENTER-DOT-CENTER-DOT-CENTER-DOT-TL-I ATTRACTION

Metal exchange of the solvated tripodal lithium amide [H3CC{CH2N(Li-so lv)SiMe3}(3)] (1, solv = ether solvent) with thallium(I) chloride lead s to the previously reported pentametallated dimeric thallium amide [{ H3CC(CH2NSiMe3)(3)}(2)(H)Tl-5] (2) in high yield. That the redox-induc ed partial demetallation of the amide presumably occurs at an intermed iate stage of the metal exchange is inferred from the isolation and st ructural characterization of the mixed Tl-Li amide C{CH3N(Tl)-SiMe3}(3 )][H3CC{CH2NSiMe3}(3)(H)(Tl)(Li -thf)].(toluene) (3), which has a crys tal structure closely related to that of 2. In both cases the central structural motif, defined by weakly attractive Tl ... Tl contacts, is a tetrahedral metal array in which a triangular thallium triamide unit is capped by an exposed Tl atom of a second building block. Compound 3 may be converted to 2 by metal exchange with TlCl. The two supramole cular components of 2 reaggregate upon recrystallization in a nonpolar solvent such as pentane to yield the dimeric aggregate of the fully m etallated thallium amide [H3CC{CH2N(Tl)-SiMe3}(3)](2) (4), An X-ray cr ystallographic study of 4 established the existence of dimeric aggrega tion through Tl ... Tl interactions leading to a more open dimeric for m than 2 and 3, which is interpreted as being due to a structural mism atch of the building blocks. Compound 4 may be thermally degraded by p rolonged stirring in toluene at ambient temperature to yield the previ ously reported mixed-valence (TlTlII)-Tl-I amide [H3CC(CH2NSiMe3)(3)Tl -2] (5).