Unsaturated Dodecahedranes—In Quest of the C20H14 1,4,16-Triene and C20H12 1,4,10(14),16-Tetraene, and Their Cations and Anions

Reinbold, Jens; Sackers, Emmerich; Osswald, Thomas; Weber, Klaus; Weiler, Andreas; Voss, Torsten; Hunkler, Dieter; Wörth, Jürgen; Knothe, Lothar; Sommer, Frank; Morgner, Nina; Issendorff, Bernd von; Prinzbach, Horst

doi:10.1002/1521-3765(20020118)8:2<509::aid-chem509>3.0.co;2-d

Cited by 19 publications

(6 citation statements)

References 47 publications

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“…The simplest (and perhaps the best when the number of centers equal the number of mobile electrons) is to compare the energy of the singlet with its much less stable (84.9 kcal mol −1 ) high‐spin nonet state. As expected, 7 is much higher in energy than the classical C 20 H 12 dodecahedratetraenes (131.9 and 131.0 kcal mol −1 for the two isomers 8 ( D 2h ) and 9 ( C 2 ), respectively;12 Figure 4), as a result of the bond energy of the four CC bonds. However, taking 65–70 kcal mol −1 to be the π‐bond energy range of ethene,13 the total π‐bond energy of 7 would be in the 260–280 kcal mol −1 energy range.…”

Section: Methodssupporting

confidence: 71%

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et al. 2002

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Since aromaticity [1] is not confined only to planar rings but also exists in three-dimensional systems, [2] the same should be true of homoaromaticity. [3±5] Although the 4Nþ2 H¸ckel electron-counting rule is defined for planar systems it has been applied to rationalize the properties of three-dimensional homoaromatic systems. [5] Recently, the 2(Nþ1) 2 counterpart of the H¸ckel rule [6] has been extended successfully [2e, 7, 8] to the aromaticity of three-dimensional delocalized systems with near spherical geometries: fullerenes, hydrogen and lithium clusters, as well as some well-known closoboranes and Zintl ions. It was found that the highest degree of aromaticity can only be achieved in systems with fully filled valence shells. We now present new conceptual applications of this electron-counting rule to three-dimensional homoaromatic systems with cubane, dodecahedrane, and adamantane frameworks. Families of spherical homoaromatics with both two and eight mobile electrons (including several neutral ZUSCHRIFTEN

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Section: Methodssupporting

confidence: 71%

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et al. 2002

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“…The intention is to analogously “collect” the isomerically uniform C 20 H 12 anion D - in the vapor phase and to analyze structures and electron configurations by PE spectroscopy 37 and calculations . Preliminary MS measurements have confirmed the loss of the four protecting groups to give, though not exclusively, the m / z = 252 cation D + …”

Section: Discussionmentioning

confidence: 96%

Pentagonal Dodecahedranes: Polyfunctionalization and MS Fragmentation

et al. 2001

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With the use of four- to eight-fold functionalized dodecahedranes (1−3), opportunities to arrive at highly strained dodecahedranes with two to four pairs of vicinal, eclipsed bromine substituents through front-side substitution and addition reactions have been explored. In standard processes, the interception of β-OCH3 radical/cationic intermediates was not problematic (9−12, 37, 50). The interception of β-CO2R radicals was possible for Cl• (18) but not for Br• (17). The interception of β-chloro radicals was possible for Cl• (27) but not for Br• (26), and the interception of β-Br cations (“bromonium ions”) with Br- was modest (45) to highly inefficient (24, 26). Two X-ray structural analyses (dimethoxy dibromide 9 and tetramethoxy tetrabromide 53) indicated the structural consequences of the molecular strain introduced by the two (four) vicinal CH3O/Br pairs. A systematic analysis of the MS spectra confirms that, in virtually all cases studied, the elimination of the substituents occurs without significant carbon-cage disruption, leading ultimately to multiply unsaturated dodecahedral ions for dodecahedrahexa(C20H8)enes, -hepta(C20H6)enes, and -octa(C20H4)enes.

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Section: Generation Of C 20 -Fullerenementioning

confidence: 99%

“…Subsequently, Prinzbach et al systematically developed approaches to several highly strained oligodehydrododecahedranes by b-eliminations on the dodecahedrane skeleton [67]. According to their studies, pure dodecahedrene (68) can be isolated upon dehydrobromination of bromododecahedrane (67) [68] induced by the strongly basic naked fluoride ion provided by the iminophosphorane base ''P 2 F'' developed by Schwesinger et al [59] (Scheme 13). The fact that dodecahedrene (68), with its highly out-of-plane bent CbC double bond (c ¼ 43.5 , Figure 8), can be isolated, is quite remarkable on its own, but even more remarkable is the observation that 68 dimerizes only under forcing conditions (around 300 C) [70].…”

Section: Generation Of C 20 -Fullerenementioning

confidence: 99%

“…The calculated degree of pyramidalization of the double bonds in 70 (c ¼ 42.8 ) is slightly smaller than that in dodecahedrene 68 (Figure 8). Oligodehydrododecahedrane derivatives with an even greater degree of unsaturation have also been approached by Prinzbach et al [67,68,70,73,74]. While the monoene 68 and diene 70 can be obtained as single regioisomers, the possibility of forming double bond isomers became a serious problem for the characterization of more highly unsaturated structures generated by dehydrobromination of tri-and tetrabromododecahedrane derivatives with the Schwesinger base ''P 2 F''.…”

Section: Generation Of C 20 -Fullerenementioning

confidence: 99%

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Oligounsaturated Five‐Membered Carbocycles – Aromatic and Antiaromatic Compounds in the Same Family

Haag

Meijere

2002

Modern Arene Chemistry

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Most compounds containing oligounsaturated five-membered carbocycles ranging from cyclopentadiene to C 20 fullerene display interesting electronic and structural properties. This chapter describes recent developments in this area, starting with stabilized cyclopentadienyl cations, then discusses several fulvenes as well as spiroannelated cyclopentadiene derivatives and eventually linearly as well angularly fused oligocyclic five-membered ring systems. Among these oligounsaturated di-, tri-, and oligoquinanes, the features of the rather unstable pentalene and acepentalene are discussed with respect to their generation and electronic ground states. Structural properties, including those of the stable dilithium diides as well as several metal complexes are presented. Finally, the generation and characterization of the highly unstable C 20 fullerene, which sets a new benchmark for this class of molecules, are highlighted. 2.1

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Unsaturated Dodecahedranes—In Quest of the C20H14 1,4,16-Triene and C20H12 1,4,10(14),16-Tetraene, and Their Cations and Anions

Cited by 19 publications

References 47 publications

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Pentagonal Dodecahedranes: Polyfunctionalization and MS Fragmentation

Oligounsaturated Five‐Membered Carbocycles – Aromatic and Antiaromatic Compounds in the Same Family

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