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Title: Structural investigation of some molecular complexes, and their related compounds
Author: Cameron, T. S.
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 1968
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The reduction of benzotrifuroxan(I) by triethyl phosphite gives a crystalline 1:1 molecular complex of benzotrifurazan(II) with triethyl phosphate ester. The structure of the complex (at -120°C) was solved by X-ray crystallography and the molecules were found to be associated by a weak 'polar' interaction between the phosphoryl (P=0) bond of the phosphate and the molecular system of benzotrifurazan. The phosphoryl bond was almost coincident with the three-fold axis of the heterocycle. The reaction of triphenyl phosphine with benzotrifuroxan was very complex and the product contained a large number of coloured compounds but no benzotrifurazan. Five crystalline compounds were isolated in small yield: a red, a light green, a yellow, a darker green and traces of a blue compound. Analysis of the first four showed that they contained both nitrogen and phosphorus but the physical data for the compounds gave little further information. The structures of all five compounds have been solved by X-ray crystallography. The red compound is a molecular complex of an aci- nitro- benzo- difurazan, associated as an ion pair with protonated triphenyl phosphine oxide(III). There is also a close approach of the planes through two difurazan molecules and the red colour is thought to result from charge transfer between these two molecules. The light green compound is a triphenylphosphine-nitroso-benzo- difurazan and is best represented as (IV). The colour is attributed to the aromatic nitroso chromophore. The yellow compound is a sym-triphosphazine-trinitrobenzene and is represented as (V). The central C6 ring is distorted from a regular hexagon by the nitro groups bonded to it, and the planes of these nitro groups are almost perpendicular to the planes of the central ring. The blue compound is an unusual diphosphorane (VI). The central C6 rings are deformed into boat conformations without completely destroying the associated π system and the geometry of the compound is that expected for an overcrowded aromatic molecule. The structure of the dark green compound (VII) was determined by Miss J.M. Evans (Oxford University). The reaction mechanisms for the reduction of benzotrifuroxan by triphenyl phosphine and by trialkyl phosphites is discussed within the context of the general reactions of P(III) compounds, and possible methods are suggested for the formation of the red, light green and yellow compounds and for the phosphate ester complex.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available