Metal cages cubanes

In addition to analogs of known C-based structures, transition metals offer novel bonding possibilities having no known precedents in main-group chemistry. As a variation on the cubane-like cage motif of Fig. 4.26(c) built from tetravalent osmium, we can envision construction of the analogous naked metal cage compound Irg... 

When the reaction mixture, as given in Scheme 51, is heated to 100°C for an hour before workup, the metal-free cages 171-174 can be separated by medium-performance liquid chromatography (MPLC).82 (See Formula 2.) Formally, compound 171 is derived from tetraphosphacubane 156a by addition of a fifth equivalent of f-BuC=P, and 172 results from the cubane by incorporating one P2 unit. Cages 173 and 174 are constructed from five... 

The capping atoms in the hexa-, octa-, dodeca-, and octadecanuclear structures listed in Table III all have the same disposition i.e., they are attached to a /u,4-oxo group of the central cubane(s) to complete a tetrahedral coordination geometry about this site. This contrasts with the additional metal sites in the decanuclear cages, where they are attached to ixq-oxo groups which have octahedral geometries. 

Most freqnently, cubane or other alnminum-nitrogen cage snpermolecnles are formed throngh additional dative bonds (making the metal four-coordinate). ... 

Figure 6.31 The structures of (a) dodeca-, (b) pentadeca-, and (c) octadeca-nuclear clusters templated by two IX4-H ions, a X5-X (X = C1, Br) ion, and Xe p r r r r r COj , respectively. Formal assembly of a 60-metal hydroxide complex featuring 26 vertex-sharing [Ln4(ti3-OH)4] cubane units. These cubane building blocks form six dodecanuclear squares and eight octadecanuclear hexagons [102]. (Redrawn from X. Kong et al, A chiral 60-metal sodaUte cage featuring 26 vertex-sharing [Er4(p.3-OH)4] cubanes, Journal of the American Chemical Society, 131, 6918-6919, 2009.)...

The structure of complex 20, outlined in Fig. 5, consists of a cubane-like, 72-electrons M4E4 cage core, which is unprecedented for ruthenium and selenium. Also this complex should be regarded as a secondary product, probably formed by the self-assembly of two dinuclear Ru2Sc2 groups, derived from 18 (Ru3Se2) by loss of a mononuclear metal fragment. 

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