| dc.description.abstract | A brief review of the importance and variety of symmetrical
and unsymmetrical bisphosphines is given and the possible theoretical
and synthetic value of bisphosphines in which one of the phosphorus
atoms is included in a phosphole ring is outlined. This is followed
by a brief account of the electronic structure of phospholes in
the context of the possible aromaticity of such systems and the present
conflicting position is discussed. The catalytic activity of phosphole
complexes is also briefly reviewed in the context of possible extension
to catalytically active systems based upon phosphino-substituted
phospholes. Synthetic approaches to bisphosphines in general, and
the [superscript 31] P and [superscript 13] C NMR spectral properties of these and some of their metal complexes are discussed in some detail.
In the new work reported in this thesis, a number of
synthetically useful and structurally interesting five-membered
heterocyclic bisphosphines containing both ring and side-chain P atoms
have been synthesized. Their [superscript 31] P, [superscript '] H and [superscript 13] C spectral properties, particularly unusual [superscript 31] P shifts and long-range P - C couplings, have been thoroughly investigated and their structures have been unambiguously
established. It has been found that many of the reactions used
in these various syntheses are stereospecific or stereoselective.
A new and possibly general route to 4-oxo-2-phospholene oxides or sulfides from the corresponding 4-methy1ene compounds is described.
This highly unusual reaction involves free-radical catalysed
oxidative cleavage of the 4-methylene group by molecular oxygen and
the reaction was found to proceed very smoothly when AIBN is used
as the radical initiator for the oxidation. A possible mechanism
for this oxidation is proposed. | |
