Alkali Metal-Templated Assembly of Cyanometalate “Boxes” (NEt4)3{M[CpRh(CN)3]4[Mo(CO)3]4} (M = K, Cs). Selective Binding of Cs

• Published in: Journal of the American Chemical Society Vol. 121; no. 12; pp. 2705 - 2711
• Main Authors: Klausmeyer, Kevin K, Wilson, Scott R, Rauchfuss, Thomas B
• Format: Journal Article
• Language: English
• Published: American Chemical Society 31.03.1999
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja982347w

The box-like cages {M[Cp*Rh(CN)3]4[Mo(CO)3]4}3- form as the sole metal-containing products of the reaction of [Cp*Rh(CN)3]- and (η6-C6H3Me3)Mo(CO)3 in the presence of K+ and Cs+. Well-defined species could not be identified in solutions of Cp*Rh(CN)3 - and (η6-C6H3Me3)Mo(CO)3 in the absence of alkali metal cations. The new cages were isolated as their Et4N+ salts, M = K+ (1), Cs+ (2). Crystallographic characterization of 1 and 2 reveals box-like M8(μ-CN)12 cages containing alkali metal cations. The cages feature 12 external CO and 4 external C5Me5 ligands. In 1, the K+ is disordered over two off-center positions, whereas in the case of 2, the Cs+ is centered in the cage with a formal coordination number of 24. Otherwise, the structures of the two compounds are virtually indistinguishable. The persistence of the solid-state structures in solution was established through 13C NMR spectroscopy and electrospray mass spectrometric measurements. 133Cs NMR spectroscopy, which readily distinguishes free from included Cs+, shows that the boxes preferentially bind Cs+ relative to K+.