Harvey, David Allan (1984) The synthesis and oxidation of some cyclophosphazanes. PhD thesis http://theses.gla.ac.uk/4036/ Copyright and moral rights for this thesis are retained by the author A copy can be downloaded for personal non-commercial research or study, without prior permission or charge This thesis cannot be reproduced or quoted extensively from without first obtaining permission in writing from the Author The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the Author When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given Glasgow Theses Service http://theses.gla.ac.uk/ [email protected] THE SYNTHESIS AND OXIDATION OF SOME CYCLOPHOSPHAZANES. A thesis submitted to the University of Glasgow in fulfilment of the requirements for the degree of DOCTOR OF PHILOSOPHY by David Allan Harvey, B. Sc. Department of Chemistry, University of Glasgow, Glasgow G12 8QQ To My Mother and Father. Acknowledgements I wish to thank my supervisor, Dr R. Keat for his support, advice and encouragement throughout the course of this work. I would also like to thank my colleagues in the Chemistry Department for their assistance. In particular, is special thanks due to Dr. D. S. Rycroft for his help with 31P n. m. r. spectroscopy. Thanks is also due to Mrs. M. Ewart, who assisted with the typing and preparation of this thesis. Finally, I would like to thank the University of Glasgow for their financial support of this research. D. A. Harvey. List of Contents. Page Abstract (i) Chapter 1 General Introduction 1.1 General 1 1.2 Nomenclature 4 1.3 Historical and Synthesis 9 1.4 Reactions of cyclophosph($)azanes 14 1.5 Bonding, Structure and Reactivity 37 Chapter 2 Reactions of nhos hazanes with "di borane B2H6 and boron trifluoride-diethyletherate BF3-Et20. 2.1 Introduction 67 2.2 Results 68 2.3 Discussion 77 2.4 Experimental 89 Chapter 3 Reaction of phosphazanes with halogens. 3.1 Introduction 98 3.2 Results and Discussion io? 3.3 Experimental z21; Chapter 4 Formation and reactions of cage and bridged vhosphazanes. 4.1 Introduction 133 4.2 Results and Discussion 134 4.3 Experimental 165 Appendix A Purification of solvents and reagents. 189 Appendix B Instrumentation. 190 References 191 Abstract The reactions of a series of cyclic and acyclic phosph(])azanes with diborane and borane adducts were investigated in an attempt to establish the most reactive nucleophilic sites in the phosph(31t)azanes and to gain information relating conformation and reactivity. (dim triethylamine Tris ethyl amino) phosphine, P(NMe2)3, reacted with -borane, Et3NBH3, to produce the monoborane adduct, (Me2[(Me2N)2P]2NMeN)3PBH3. Reaction of diborane, B2H6, with the acyclic phosph(7I[)azanes, gave a diborane adduct. In similar reactions of B2H6 with a series of phosph(I)azanes (Ph2P)2NR, (R = Me, Et and Pr' the products rapidly decomposed, but evidence was obtained for the formation of a monoborane adduct where R= Me and Et. In all cases where an acyclic phosphazane-borane adduct was obtained it was established that the BH3 group was bonded to the phosphorus atom. Analogous reactions with cyclodiphosph(=)azanes have shown that BH3 groups bond to the P2N2 ring through the phosphorus atoms. The reactions (Me2NPNBut)2 of cis and trans with 1 mole equivalent of Et3NBH3 produced only cis Me2N(BH3)PNBut. P(NMe2)NBut 2 Et3NBH3 a bis , with mole equivalents of borane adduct was obtained, the proportion of the geometrical isomers produced being dependent on the temperature of the reaction. The reaction of (Me2NPNBut)2 with excess diborane, B2H6, proceeded with Analogous (MeOPNBut) overall retention of configuration. reactions using 2 (MeOPNBut)2 gave a bis borane adduct, similar to those above but was less reactive than (Me2NPNBut)2" (C1PNBut)2 An attempted reaction between and Et3NBH3 failed to produce a borane adduct, but when the reaction was repeated using tetrabydro- NBut furan-borane, C1(BH t formed. THF. BH3, the monoborane adduct , )pNBu was Over a period of several weeks cis-Me 2N(BH3)PNButP-(NMe2)NBut disproportionated to cis-(Me 2NPNBut)2 and cis-(Me 2N(BH3)PNBut)2" Nmr data indicates that the reaction of (XPNBut)2 (X = Cl or We2) 1 and mole equivalent of chlorine gave a product which is either XPNBXNB t t the ionic XPNBuF+C1 When or salt me2NBut Cl . the reaction was repeated (C1PNBut)2 using and excess chlorine, ring cleavage occured, the only identifiable product being Cl2P(0)I PCl2N(H)But. (ClPNBut)2 and bromine resulted mainly in the formation of decomposition products. Reaction of C1PNButPC1NR (R = Me, Et) with excess of dry chlorine +t (R surprisingly gave a zwitterionic product, C12PNBuP C14NR = Me, Et). The reaction of ClPNButPClNEt with 1 mole equivalent of bromine gave either "-I C1PNButPC1Br2NEt or C1PNButP+BrXNEt Y (X and Y= Cl or Br). When the reaction was repeated with 2 mole equivalents or excess bromine, a zwitterionic product was obtained. By contrast, the reaction of (C1PNPh)2 and excess chlorine (C13PNPh)2. resulted in the simple oxidation product, Reactions of excess chlorine with a series of acyclic phosph(M)azane ) of the type (C12P)2N. R (R = Me, Et and Prn gave cyclodiphosph(Y)azanes, (Cl3PNR)2 (R = Me, Et, and Prn). These reactions have been shown to proceed via two intermediate. compounds, the first is still unidentified but the second has been identified by nmr as the hitherto unknown monomeric species Cl3P=NR (R = Me, Et, and Prn), and C13P=NBut. When the reactions were repeated with bromine the products again included (C13PNR)2, (BrCl2PNR)2, (Br2C1PNR)2 though small quantities of and (Br3PNR)2 were found in small traces along with PC13, PC12Br, and PC1Br2. -iii- The formation of phosph(IIL)azanes by the reaction of PC13 with EtNH3C1 in refluxing sym-tetrachloroethane has been reinvestigated. It found (C12P)2NEt, was that different major products (C1PNEt)3 and P4(NEt)5C12 could be obtained by suitable variation of the stoichiometry, However, when the reactions were repeated using McNH3Cl instead of (C12P)2NMe EtNH3C1, only could be obtained. When (C12P)2NR (R - Me or (C1PNR)3 Et) was heated, (R = Me or Et) and PC13 were produced along with decomposition products. The reverse reaction was also possible; refluxing a solution containing PC13 and p4(NEt)5Cl2 gave (C1PNEt)3 and3in turn, (C12P)2NEt. A series of derivatives of (C1PNEt)3 were prepared, (Me2NPNEt)3 (MeOPNEt) was obtained only as a trans isomer while 3 and (FPNEt) trans isomers. 3 were present as a mixture of cis and Conformational information for these rings was difficult to establish. The ring compound (C1PNEt)3 was also reacted with a series of monoamines H2NR (R = Et, Pri, and But) to produce a trans substituted product, (R(H)NPNEt)3 (R = Et, Pri, and But), and a fused ring compound, 2,4-ethylimino-6-ethylamino-1,3,5-triethylcyclotriphosph(I[I)azane. The ratio of the two types of products varied with the size of R, the larger R the more the fused ring compound was favoured. This proportion lH 31P of products, as detected by and nmr, was also affected by heating which favoured the fused ring compound. An adamantane like cage molecule P4(IEt)6 was also identified. Fluoro-, alkylamino- and alkoxy- derivatives of'p4(NEt)5Cl2 were prepared by reaction with SbF3, Me2NH, Et2NH, C5H10NH, NeOH and ButOH. In all cases two isomers were formed, termed 'symmetric' and 31p 'asymmetric' (these terms are based on consideration of the nmr spectra and the resulting structural assignments of the terminal phosphorus atoms. The reaction of P4(NEt)5C12 with a series of monoamines RNH2 (R = Et, But and H) led to the formation of a series of compounds P4(NR)5(NR') (R = Et, R' = But or H) with an adamantane-like cage structure. In the reaction of P4(NEt)5C12 with EtNH2 an intermediate with a direct P -P bond was tentatively identified. Oxidation So, Sen, Tea reactions using VV and BuL00H were carried out on (ClPNEt) P4(NEt)5C12 their derivatives. 3 and and The reaction (Me2NPNEt)3 (MeOPNEt) of and 3 with sulphur and selenium gave the oxidation products (Me2N(X)PNEt)3 (X =S or Se), and (Me0(Y)PNEt)3 (Y =S or Se). In all cases only a trans isomer was obtained regardless the (C1PNEt)3 of structure of the starting material. The reaction of with three moles of Me2SO gave only a small amount of the trans mono- and di-o7yr derivatives, Cl(0)PNEt. P(C1)NEt. P(Cl)NEt and Cl(0)PNEt. P(Cl)(0)NEt. P(Cl)NEt respectively. Dithio-derivatives P4(NEt)5 (NMe P4(NEt)5(NC5H10)2S2 made by reaction 2)2S2 and were also with elemental sulphur. Only one isomer was obtained in each case, possibly containing the sulphur atoms bonded to terminal phosphorus atoms. Reactions with elemental Se8 mainly produced decomposition products. The oxide, p4(NEt)5c120, as a mixture of two isomers, was produced by the reaction of Me2SO on P4(NEt)5C12 and it was also found as an impurity in a number of reactions. CHAPTER 1 GENERALINTRODUCTION. 1 1.1 General. The element phosphorus, which does not occur free in nature, was first discovered in 1667 by Hennig Brand of Hamburg, who, from his experiments with boiling down of urine, found a substance which glowed in the dark and ignited when exposed to the air. Its "glowing" properties led it to be called phosphorus from the Greek for 'light-bearing'.