Cage structures synthesis

Li Q, Walter EC, van der Veer WE, Murray BJ, Newberg JT, Bohannan EW, Switzer JA, Hemminger JC, Penner RM (2005) Molybdenum disulfide nanowires and nanoribbons by electrochemical/chemical synthesis. J Phys Chem B 109 3169-3182 Tenne R, Homyonfer M, Feldman Y (1998) Nanoparticles of layered compounds with hollow cage structures (inorganic fuUerene-like structures). Chem Mater 10 3225-3238 Shibahara T (1993) Syntheses of sulphur-bridged molybdenum and tungsten coordination compounds. Coord Chem Rev 123 73-147... 

Two approaches have been used in the synthesis of these types of compounds. Small boron-phosphorus ring compounds can serve as building blocks, and addition and elimination reactions with other main group elements can then extend the cage structure (see Schemes 23 and 24, Section 12.12.6.4.5). Alternatively, an unsaturated carbenoid fragment can be added to the bicyclic fragment as illustrated in Scheme 31 <1998IC490>. 

This chapter is an extension of Chapter 1 and discusses the more recent research into energetic compounds which contain strained or caged alicyclic skeletons in conjunction with C-nitro functionality. This chapter complements Chapter 1 by providing case studies which show how the same methods and principles that introduce C-nitro functionality into simple aliphatic compounds can be used as part of complex synthetic routes towards caged polynitrocycloalkanes. The chemistry used for the synthesis of caged structures can be complex but the introduction of C-nitro functionality follows the same principles as discussed in Chapter 1. It is suggested that chemists who are not familiar with this field of chemistry consult Chapter 1 before reading this chapter. 

Proceeding from a precursor polyaza-caged structure, which may be different from the desired product, but includes the final structure within the cage. Although not a caged compound the synthesis of RDX from the nitrolysis of hexamine would fit this category. 

Since the pioneering work of Gilman and co-workers in the 1960s,1-3 several standard preparative methods have been developed for the synthesis of chain and branched-chain organopolysilanes. More recently, the latter have been used in the design of new dendrimeres4 or cage structures. However, only a few donor-functionalized silanes have found an application in coordination chemistry. 

In small pore zeolites with cage structure, e. g., faujasites, dye molecules encapsulated by in situ synthesis or crystallization inclusion are stable against extraction.1 2 However, these methods fail for MCM-41 due to the channel structure and the wider pore diameter (3 nm) of the host material. Covalent bonding of guests is necessary to obtain diffusion stability. Therefore, anchoring of organic molecules with catalytic functions into MCM-41 by covalent bonding was recently reported by Brunei et al.3... 

Further developments are likely as the chemistry of the compounds described above is explored. Moreover, entirely new dimensions may be added. For example, the synthesis of tungsten-alkylidyne complexes with carba-borane ligands with cage structures smaller than the icosahedral C2B9 fragment should result in the isolation of new electronically unsaturated metal cluster and electron-deficient molecules of types as yet unknown. 

The convenient synthesis of adamantane [26] led to several significant developments. 1 -Adamantyl substrates (54, Scheme 2.19) are tertiary alkyl compounds for which the caged structure prevents rear-side nucleophilic attack, and elimination does not occur because adamantene (55) is too highly strained. The following question arises when does product formation occur in the solvolytic process Product studies from competing nucleophilic substitutions in mixed alcohol-water solvent mixtures have provided an answer. To explain the background to this work, we first need to discuss product selectivities. 

The synthesis of cobalt carbonyl-boimd silanetriol, Coa(CO)9CSi(OH)a (11) was originally reported by Seyferth et al. (34) by careful hydrolysis of Si—Cl bonds present in Coa(CO)9CSiCla (Scheme 8B). The X-ray crystallographic measurement (35) reveals a cage structure for compound 11. The OH groups present in 11 can be used further for the buildup of a number of heterosiloxanes. The cobalt carbonyl-boimd silanetriol 11 exhibits very high catalytic activity in the hydroformylation of 1-hexene in a biphasic vide infra) system (35). 

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