On the formation of intermetalloid clusters: Titanocene(III)diammin as a versatile reactant toward nonastannide Zintl clusters

The reactivity of TiCp₂Cl₂ (d⁰) towards Zintl clusters was studied in liquid ammonia (Cp = cyclopentadienyl). Reduction of Ti^IVCp₂Cl₂ and ligand exchange led to the formation of [Ti^IIICp₂(NH₃)₂]⁺, also obtainable by recrystallization of [CpTi^IIICl]₂. Upon reaction with [K₄Sn₉], ligand exchange leads to [TiCp₂(η¹-Sn₉)(NH₃)]^3-. A small variation of the stoichiometry led to the formation of [Ti(η⁴-Sn₈)Cp]^3-, which cocrystallizes with [TiCp₂(NH₃)₂]⁺ and [TiCp₂(η¹-Sn₉)(NH₃)]^3-. Finally, the large intermetalloid cluster anion [Ti₄Sn₁₅Cp₅]^n- (n = 4 or 5) was obtained from the reaction of K₁₂Sn₁₇ and TiCp₂Cl₂ in liquid ammonia. The isolation of three side products, [K([18]crown-6)]Cp, [K([18]crown-6)]Cp(NH₃), and [K([2.2]crypt)]Cp, suggests a stepwise elimination of the Cl^- and Cp^- ligands from TiCp₂Cl₂ and thus gives a hint to the mechanism of the product formation in which [Ti(η⁴⁺²-Sn₈)Cp]^3- has a key role.