2.6- Adamantanediyl dication

The 1,3-adamantanediyl dication (47) could not be prepared from the ionization of the 1,3-difluoroadmantane (45) in a variety of superacids. Only the monocation monodonor-acceptor complex (46) was obtained. In 47, the two positive charges are separated by just one carbon, thus precluding its formation in the absence of extra neighboring group stabilization." ... 

The dissolution of the adamanantane-2,6-dione in 1 4 SbFs FSO3H/SO2 gave the 2,6-dihydroxy-2,6-adamantanediyl dication (99). This dicarboxonium ion has more oxonium character than the carbenium character as shown by the much shielded absorption for the carbonyl carbon (8 C 247.7), relative to the monocarboxonium ion, 100(8 C 267.1). ... 

The l,3-dehydro-5,7-adamantanediyl dication, 160, was obtained through the ionization of l,3-dehydro-5,7-difluoroadamantane (159). This dication shows three-dimensional... 

There are several other carbodications that may be represented as 1,3-dicationic systems (or nonclassical, highly delocalized systems), including Schleyer s l,3-dehydro-5,7-adamantanediyl dication (28),11 Hogeveen s pyramidal dication (29),12 diallyl dications (i.e., 30),13 dicationic ethers (i.e., 31),14 diprotonated pyrones (32),15 as well as various aromatic dications. 

Schleyer, P. v. R., Bremer, M., Schotz, K., Kausch, M. Schindler, M. 1987 Four-center two-electron bonding in a tetrahedral topology. Experimental realization of three-dimensional homoaromaticity in the l,3-dehydro-5,7-adamantanediyl dication. Angew. Chem. Int. Ed. Engl. 26, 761 763. 

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