On the existence of uncharged molecules with a pyramidally coordinated carbon: the cases of pentacyclo[4.3.0.0(2,9).0(3,8).0(7,9)]non-4-ene and heptacyclo- [7.6.0.0(1,5).0(5,15).0(6,14).0(10,14).0(10,15)]pentadecane.
[reaction: see text] B3LYP/6-31G(d) and MP2 calculations predict interactions between the divalent carbon and one double bond in tricyclo[3.2.2.0(2,4)]nona-6,8-dien-3-ylidene (3). Carbene 3 easily forms the more stable 4, a species with a pyramidal geometry. Moreover, the kinetic stability of 4 has been investigated, and some of its decay products are described. Interestingly, 3,3-dibromotricyclo[3.2.2.0(2,4)]nona-6,8-diene (1), the precursor of carbenoid 3, has already been reported and shown to undergo a formal dimerization to give 2. In addition, 15, a compound structurally related to 4, is expected to have a substantially greater stability toward further rearrangement.
Mieusset
Jean-Luc
JL
Institut für Organische Chemie, Universität Wien, Währinger Strasse 38, A-1090 Wien, Austria.
Brinker
Udo H
UH