Polyhedral compounds

S. Nagase, Polyhedral compounds of the heavier group 14 elements silicon, germanium, tin and lead. Acc. Chem. Res. 28, 469-76 (1995). 

A. Comparative Ring Strain of the Polyhedral Compounds Theoretical... 

E. Cyclic Metallanes Rings, Polycyclic and Polyhedral Compounds... 

Metallabicyclo[2.2.0]hexanes 26 are considerably less strained than 25. The strain in MgHio, calculated by the homodesmotic equation 18, decreases in the order M = C > Si > Ge > Sn > Pb from ca 54 kcalmol-1 for M = C to 19 kcalmol-1 for M = Pb, very similar to the trend in the monocyclic M4H8 series (Table 21). Nagase and Kudo observed that the strain energy in polycyclic and polyhedral compounds (see below) is additive, e.g. it is twice as large in 26 than in the monocyclic M4H8194. 

The boron hydrides are one of most beautiful classes of polyhedral compounds whose representatives range from simple to rather complicated systems. Our description here is purely phenomenological. Only in passing is reference made to the relationship of the characteristic polyhedral cage arrangements of the boron hydrides and the peculiarities of multicenter bonding that has special importance for their structures. 

M. F. Hawthorne Recent developments in the chemistry of polyhedral compounds from metals and carboranes, pp. 547-567 (32). 

The formation of these isomers can be explained in terms of different pathways during the hydrolytic polycondensation process. At present, two different hydrolysis processes are proposed in the literature. According to Sprung and Guenther [9], the polysiloxane build-up from methylalkoxysilanes CH3Si(OR)3 involves the stepwise formation of linear cyclic -> polycyclic polyhedral compounds with randomly increasing molecular size. For higher alkyltrichlorosilanes (Ce-C9) a similar mechanism is assumed [10]. 

Kingma, K., Meade, C., Hemley, R.J., Mao, H.-H., and Veblen, D.R. (1993) Mi-crostructural observations of a-quartz amorphization. Science, 259, 666-669. Chaplot, S.L., and Sikka, S.K. (1993) Molecular-dynamics simulation of pressure induced crystalline-to-amorphous transition in some corner-linked polyhedral compounds, Phys. Rev., B47, 5710-5715. 

J. Taylor, J. Caruso, A. Newlon, U. Englisch, K. Ruhlandt-Senge, J. T. Spencer, Polyhedral-based nonlinear optical materials. 3. synthetic studies of eyelopentadiene- and cycloheptatriene-substituted polyhedral compounds synthesis of l,12-[(CH)CBH(CHMe)] and related species. Inorg. Chem. 2001,40, 3381. 

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