When complexed by tetrabenzo-24-crown-8, the cesium ion can accommodate unprecedented ligation. The structures of the following complexes are presented. [Cs(tetrabenzo-24-crown-8)(η1-NCMe)2(η2-NCMe)][NO3] (1): triclinic P1̄, a = 12.0119(14) Å, b = 13.3680(15) Å, c = 13.7859(12) Å, α = 89,124(8)°, β = 66.928(9)°, γ = 71.536(10)°, V= 1916.7(4) Å3, Z = 2. [Cs(tetrabenzo-24-crown-8)(η1-NCMe)2(η2-CH2Cl2)][NO3] (2): triclinic, P1̄, a = 12.295(3) Å, b = 13.295(3) Å, c = 13.782(3) Å, α = 89.105(17)°, β = 66.096(18)°, γ = 71.980(19)°, V = 1929.5(8) Å3, Z = 2. These structures are the first reported examples of linear η2-acetonitrile coordination to any metal ion and the first structures illustrating η2-acetonitrile and dichloromethane ligation to an alkali metal ion. Possible steric and electronic origins of these unusual metal - ligand interactions are discussed.
