Alkali Metal - Templated Assembly of Cyanometalate “ Boxes ” ( NEt 4 ) 3 { M [ Cp

The box-like cages {M[Cp*Rh(CN)3]4[Mo(CO)3]4} form as the sole metal-containing products of the reaction of [Cp*Rh(CN)3] and (η-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 (η-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+.