Acta Crystallographica Section B

Structural Science

Volume 58, Part 6 (December 2002)

research papers

Acta Cryst. (2002). B58, 1067-1073 [ doi:10.1107/S0108768102018608 ]

Structural investigations of phosphorus-nitrogen compounds. 5. Relationships between molecular parameters of 2,2-diphenyl-4,6-cis-oxytetra(ethyleneoxy)-4,6-R₂-cyclotriphosphazatrienes (R = Cl, OCH₂CF₃, OPh, OMe, NHPh, NHBu^t) and substituent basicity constants

S. Besli, S. J. Coles, D. B. Davies, M. B. Hursthouse, A. Kiliç, T. A. Mayer and R. A. Shaw

Abstract: A systematic study of the products of nucleophilic substitution reactions of cis-ansa N₃P₃Ph₂[O(CH₂CH₂O)₄]Cl₂ (3) is reported. These reactions give a number of new structures with the general formula N₃P₃Ph₂[O(CH₂CH₂O)₄]R₂ [where R = OCH₂CF₃ (4), OPh (5), OMe (6), NHPh (7·H₂O), NHBu^t (8)]. A comparison has been made between the sum of the substituent basicity constants, $\textstyle\sum$ [alpha] _R, that are obtained in nitrobenzene solution and eight molecular parameters of the N₃P₃ ring [the P-N bond lengths a, b, c; the internal bond angles [alpha] , [beta] , [bold gamma] , [bold delta] ; and the difference between the bond lengths a and b, [Delta] (P-N)]. It is found that the systematic changes in the molecular parameters of (3)-(8) are in line with changes in [alpha] _R values. This result implies the similarity in relative electron-releasing capacity of substituents R in the solid state and in solution.

Keywords: phosphorus-nitrogen compounds; cyclophosphazenes; substituent basicity constants; molecular parameters.


	PDF file (17.9 kbytes) Preparation of the compounds

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