Step-by-step synthesis of the endohedral stannaspherene [Ir@Sn12]3- via the capped cluster anion [Sn9Ir(cod)]3-.

The endohedral stannaspherene cluster anion Ir@Sn(12) was synthesized in two steps. The reaction of K(4)Sn(9) with IrCl(cod) (cod: 1,5-cyclooctadienyl) in ethylenediamine (en) solution first yielded the K(2,2,2-crypt) salt (2,2,2-crypt: 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) of the capped cluster anion Sn(9)Ir(cod). Subsequently, crystals of this compound were dissolved in en, followed by the addition of triphenylphosphine or 1,2-bis(diphenylphosphino)ethane and treatment at elevated temperatures. Ir@Sn(12) was obtained and characterized as the K(2,2,2-crypt) salt. The isolation of Sn(9)Ir(cod) as an intermediate product establishes that the formation of the stannaspherene Ir@Sn(12) occurs through the oxidation of Sn(9)Ir(cod). Among the structurally characterized tetrel cluster anions, Ir@Sn(12) is a unique example of a stannaspherene, and one of the rare spherical clusters encapsulating a metal atom that is not a member of Group 10. Single-crystal structure determination shows that the novel Zintl ion cluster has nearly perfect icosahedral I(h) point symmetry.