"in-Phosphaphane"
In this cyclophane, a phosphine lone pair is forced into the center of
an aromatic ring. Even though there is no bond between the phosphorus
and the basal ring carbons, these atoms show strong spin-spin coupling
in the carbon-13 NMR spectrum of the molecule. The phosphine is
completely protected from ordinary chemical reagents: it is not oxidized
by hydrogen peroxide or peracids, and it cannot even be protonated by
strong anhydrous acids. When resolved, this and related propeller-shaped
molecules display exceptionally high optical rotations. For a brief
communication describing its synthesis, X-ray crystal structure, and
properties, see
"Synthesis and Structure of an
in-Phosphaphane: Enforced Interaction of a Phosphine and an
Aromatic Ring." R. A. Pascal, Jr., A. P. West, Jr., and D. Van
Engen, J. Am. Chem. Soc. 1990, 112, 6406-6407.
