Effect of chain length on the formation of intramolecular and intermolecular products: Reaction of diols with cyclotriphosphazene Serap Bes ßli a,⇑ , Simon J. Coles b , Derya Davarcı a , David B. Davies c , Fatma Yuksel a a Department of Chemistry, Gebze Institute of Technology, Gebze, Kocaeli 41400, Turkey b Department of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK c School of Biological and Chemical Sciences, Birkbeck College (University of London), Malet Street, London WC1E 7HX, UK article info Article history: Received 29 July 2010 Accepted 28 October 2010 Available online 5 November 2010 Keywords: Cyclophosphazene derivatives Diol Single-bridged compounds Double-bridged compounds Triple-bridged compounds Crystal structure abstract The reactions of cyclotriphosphazene, N 3 P 3 Cl 6 (1), in a 1:1.2 stoichiometry with the sodium derivative of seven diols [ethane- (2a), 1,3-propane- (2b), 1,4-butane- (2c), 1,5-pentane- (2d), 1,6-hexane- (2e), 1,8- octane- (2f) and 1,10-decane- (2g) diol] in THF solution at room temperature have been used to investi- gate the effect of chain length on the formation of reaction products. Although no new products were found for the reaction of 1 with diols 2a–c compared to those in the literature using other bases and solu- tion conditions, the reactions of 1 with the diols 2d–g gave six different types of products, whose struc- tures have been characterized by elemental analysis, mass spectrometry, 1 H and 31 P NMR spectroscopy; ansa compounds N 3 P 3 Cl 4 [O(CH 2 ) n O], (5d–5g); single-bridged compounds N 3 P 3 Cl 5 [O(CH 2 ) n O]N 3 P 3 Cl 5 (6d– 6f); double-bridged compounds N 3 P 3 Cl 4 [O(CH 2 ) n O] 2 N 3 P 3 Cl 4 (7d–7g, syn and anti) and triple-bridged compounds, N 3 P 3 Cl 3 [O(CH 2 ) n O] 3 N 3 P 3 Cl 3 (8d–f). Where suitable single crystals were obtained, X-ray crys- tallographic studies confirmed the structures of two ansa compounds (5d and 5f), one single-bridged compound (6e), and five double-bridged compounds (meso-anti for 7d, 7e, 7f and meso-syn for 7d and 7f). 31 P NMR measurements of the reaction mixtures were used to quantify the formation of products for the reactions 1 with all the diols, 2a–g; it is found that, with increasing chain length of the diol, there is a decrease in the products formed by intramolecular reactions (spiro and ansa derivatives) and a con- comitant increase in the amounts of products formed by intermolecular reactions (single-, double- and triple-bridged derivatives) of cyclophosphazene. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction The nucleophilic substitution reactions of cyclophosphazenes with difunctional reagents have been intensively investigated [1–17], because difunctional reagents may lead to different types of products; open chain, bridged, spiro, ansa, oligomer or polymer and their mixtures. The formation of these products depends on many factors such as solvent, base, temperature, the dinucleophile and the size of the cyclophosphazene ring. For example, using pyridine as the base in dichloromethane or diethylether, reaction of cyclotriphosphazene, N 3 P 3 Cl 6 (1), with ethane-, 1,3-propane- and 1,4-butane-diols predominantly gave spiro derivatives [1], whereas reaction of compound 1 with sodium tetraethylene glycol in THF gave predominantly a cis-ansa macrocylic cyclophospha- zene derivative [7]. Reaction of 1 with amino-alcohols, diamines and their NMe derivatives, again showed a preference for spiro- derivatives, when the linking –(CH 2 ) n – group of the reagent consisted of n = 2, 3, 4 moieties [15]. Bridged compounds became important for reactions of 1 with diamines of increasing chain length and with chain lengths n P 5 only bridged compounds were reported [15–17]. Similarly, previous work on the reaction of 1 with the sodium derivative of the fluorinated diols (1,4-butane- [12], 1,5-pentane- [13] and 1,6-hexane-diols [14]) has shown that spiro and ansa derivatives (intramolecular reaction) are formed exclusively for diols having the linking –(CF 2 ) nÀ2 – group with n = 4, 5, whereas bridged compounds (intermolecular reaction) are also formed for the diol with n = 6. In order to assess the impor- tance of ring size on products formed by intramolecular and inter- molecular mechanisms, we have investigated quantitatively the reactions of N 3 P 3 Cl 6 (1) with the sodium derivatives of seven diols having chain lengths from 2 to 10 carbon atoms, [HO–(CH 2 ) n –OH, n = 2–6, 8, 10; 2a–2g]. The results of the reactions with ethane- (2a), 1,3-propane- (2b), 1,4-butane- (2c) were compared with pre- vious work [1] using different reaction conditions (in the presence of pyridine in dichloromethane or diethyl ether), whereas the reac- tions of compound 1 with 1,5-pentane- (2d), 1,6-hexane- (2e), 1,8- octane- (2f) and 1,10-decane- (2g) diols were investigated for the first time in this work. 0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2010.10.020 ⇑ Corresponding author. Tel.: +90 262 6053120; fax: +90 262 6053101. E-mail address: besli@gyte.edu.tr (S. Bes ßli). Polyhedron 30 (2011) 329–339 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly