Dodecahedryl anion (1a) was generated in a Fourier transform mass spectrometer by deprotonation of dodecahedrane (1). Examination of the acid and base behavior of 1 and 1a, respectively, enabled the acidity of 1 to be determined (∆H°a cid ) 402 ( 2 kcal/mol). Good agreement is found with the 298 K computed MP2/6-31+G(d)//HF/6-31+G(d) value of 405.1 kcal/mol. In a similar manner, the electron affinity of dodecahedryl radical was measured (EA ) 4 ( 2 kcal/mol). These results were combined in a thermodynamic cycle to afford the C-H bond dissociation energy of dodecahedrane (BDE ) 92 ( 3 kcal/mol), which is reasonably well reproduced (96.7 kcal/mol) at the MP2//HF level but leads to the suggestion that the reported heat of hydrogenation of dodecahedrene is in error. The DePuy kinetic method for measuring the acidity of 1 also was explored. It was found that this approach works well with triphenylsilyldodecahedrane but gives poor results with triethylsilyldodecahedrane. This latter failure is attributed to steric effects, and provides a rationale for several problem cases and a means to overcome these difficulties.

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As part of a study to achieve selective oligo(poly)bromination-ultimately perbromination-of the dodecahedral C(20) skeleton, the extent and direction of the ionic bromination of dodecahedrene and 1,16-dodecahedradiene were explored. Along sequences of Br(+) additions/deprotonations and allylic rearrangements, up to ten hydrogen atoms were substituted (traces of C(20)H(x)Br(10)). Tetrabromododecahedrenes obtained under defined conditions in up to 50 % total yield with three and four allylic bromine substituents protecting the extremely bent C==C bonds, proved highly unreactive even towards oxygen but reacted rapidly with CH(2)N(2). Upon electron impact ionization (MS) of the newly secured oligo(poly)bromododecahedra(e)nes, sequential loss of the substituents ended generally in polyunsaturated dodecahedranes (in the extreme C(20)H(4), "tetrahydro-C(20) fullerenes"). Only subsequently did skeletal fragmentations occur. From X-ray crystal-structure analyses, more information was obtained on the structural response of the dodecahedral skeleton to the strain induced by the voluminous substituents. As Appendix, the forcing radical bromination of 1,6-dibromododecahedrane and exploratory cis-beta-HBr/cis-beta-Br(2) eliminations in bromododecahedranes with [Fe(2)(CO)(9)], P(2)F/[FeCp(2)] and [Fe(tmeda)Cp*Cl] (in situ protection) are presented.

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