A Triptycene Complex of Tin(II): [(C₂₀H₁₄)SnCI(AICI₄)]₂

Triptycene (C₂₀H₁₄) reacts with equimolar quantities of anhydrous SnCl₂ and AlC1₃ in benzene to give a crystalline complex [(C₂₀H₁₄)SnCl(AlCl₄)]₂•2C₆H₆. [Triclinic, space group P1, a = 10.404 (3) Å, b = 13.343 (3) Å, c = 11.194 (2) Å, α = 98.63 (2)°, β = 109.23 (2)°, γ = 105.77 (2)°, V = 1375.3 ų, Z = 1, R_w = 0.032 for 298 refined parameters and 3597 unique reflections with F_o ≥ 4.0σ(F_o).] According to the X-ray crystal structure analysis, the compound features discrete centrosymmetrical dinuclear complex units, with each tin atom η⁶-coordinated to two neighboring benzene rings of a triptycene ligand but at different metal-ring distances (2.90 and 3.38 Å). The angle between the two coordinated arene rings is contracted to 108.2°, as compared to 120° in the parent hydrocarbon. The ψ-octahedral coordination sphere of the Sn(II) centers is completed by two tin-bridging chlorine atoms and a chelating tetrachloroaluminate ligand. The benzene of crystallization is not engaged in metal complexation. A lead(II) complex [(C₂₀H₁₄)Pb-(AlCl₄)₂-0.5C₆H₆] has also been prepared and characterized by analytical data.