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Title: The synthesis and oxidation of some cyclophosphazanes
Author: Harvey, David Allan
ISNI:       0000 0004 2752 0292
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1984
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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. Tris (dim ethyl amino) phosphine, P(NMe2)3, reacted with triethylamine -borane, Et3NBH3, to produce the monoborane adduct, (Me2N[()M3Pe2BNH)32.P ]R2eNaMcetio n 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 of cis and trans (Me2NPNBut)2 with 1 mole equivalent of Et3NBH3 produced only cis Me2N(BH3)PNBut. P(NMe2)NBut , with 2 mole equivalents of Et3NBH3 a bis 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 overall retention of configuration. Analogous reactions using (MeOPNBut) 2 gave a bis borane adduct, similar to those above but (MeOPNBut)2 was less reactive than (Me2NPNBut)2" An attempted reaction between (C1PNBut)2 and Et3NBH3 failed to produce a borane adduct, but when the reaction was repeated using tetrabydrofuran- borane, THF. BH3, the monoborane adduct , C1(BH )pNBu t NBut was formed. 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) and 1 mole equivalent of chlorine gave a product which is either XPNBXNB t or the ionic salt XPNBuF+C1 me2NBut Cl . When the reaction was repeated t using (C1PNBut)2 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 surprisingly gave a zwitterionic product, C12PNBuP C14NR (R = 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 resulted in the simple oxidation product, (C13PNPh)2. 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, though small quantities of (BrCl2PNR)2, (Br2C1PNR)2 and (Br3PNR)2 were found in small traces along with PC13, PC12Br, and PC1Br2. The formation of phosph(IIL)azanes by the reaction of PC13 with EtNH3C1 in refluxing sym-tetrachloroethane has been reinvestigated. It was found that different major products (C12P)2NEt, (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 EtNH3C1, only (C12P)2NMe could be obtained. When (C12P)2NR (R - Me or Et) was heated, (C1PNR)3 (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 was obtained only as a trans isomer while (MeOPNEt) 3 and (FPNEt) 3 were present as a mixture of cis and trans isomers. 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 of products, as detected by lH and 31P 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 'asymmetric' (these terms are based on consideration of the 31p 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 reactions using So, Sen, Tea and BuL00H were VV carried out on (ClPNEt) 3 and P4(NEt)5C12 and their derivatives. The reaction of (Me2NPNEt)3 and (MeOPNEt) 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 of the structure of the starting material. The reaction of (C1PNEt)3 with three moles of Me2SO gave only a small amount of the trans monoand 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 2)2S2 and P4(NEt)5(NC5H10)2S2 were also made by reaction 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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry