Organotitanyl “TiCp” Fragment Capping the Bowl-Shaped Unit in the Ternary Anion [(Cp)Ti(Sn₃Bi₃)]²⁻

Unlike homoatomic nine-atom clusters of heavier tetrel elements, which retain their identity upon dissolution, intermetalloid clusters are not formed directly from ternary alkali-metal alloys in a straightforward manner. In general, the composition of the species formed in solution deviates from that of the starting alloy. Although the heteroatomic anion [Sn₂Bi₂]²⁻ serves as a precursor in numerous follow-up reactions toward intermetalloid clusters, its formation in solution from the corresponding precursor alloys remains poorly understood. We report the dissolution of the phase-pure, well-defined and readily accessible K₂SnBi, which comprises ¹_∞[SnBi]²⁻ polyanionic zigzag chains, in ethylenediamine. This process leads to the formation of [Sn₂Bi₂]²⁻ with tetrahedral shape. Subsequent reaction of the dissolved phase with [TiCp₂Cl]₂ yielded a new ternary anion [(η⁵-Cp)Ti(Sn₃Bi₃-κ³)]²⁻, which can be regarded as an adduct of the formerly reported bowl-shaped cluster anion [Sn₃Bi₃]⁵⁻ and the cationic [TiCp]³⁺ fragment. The resulting complex features the first structurally characterized TiBi bond and represents a promising entry point toward larger organotitanyl [TiCp] decorated tin bismuthides, analogous to the known organotitanyl decorated polystannides: The cluster core of [(η⁵-Cp)Ti(Sn₃Bi₃-κ³)]²⁻ corresponds to one half of previously described twelve-vertex Sn–Sb, Sn–Bi, and Pb–Bi intermetalloid clusters encapsulating two transition-metal centers, suggesting that the bowl-shaped fragment represents a genuine intermediate along the growth pathway toward higher nuclearity anions.