David G. Thompson

Phosphorus–nitrogen–phosphorus spin coupling in the nuclear magnetic resonance spectra of some cyclodiphosph(III)azanes

The magnitude and sign of the coupling constant 2J(PNP) has been obtained from the n.m.r. spectra of a series of cyclodiphosphazanes, [graphics omited]But(X = Y = F, Me,OMe, or NMe2; X = Cl, Y = F, OMe, or NMe2; X = F, Y = NMe), [graphics ommited] (X = OMe or NMe2), and But [graphics omited] +AIC14– by single- and double-resonance methods. More positive PNP couplings are found in those derivatives where X and Y are of relatively high electron-withdrawing power, although chlorine-containing compounds have more positive couplings than analogous fluorine-containing compounds. When X = Y = OMe or NMe2, geometrical isomers have PNP couplings of opposite sign.

Synthesis and properties of 2,4-dialkoxy-1,3-di-t-butylcyclodiphosph(III)-azanes

A series of alkoxycyclodiphosph(III)azanes, XP(NBut)2PY [X = Y = OMe (two isomers); X = Y = OEt (two isomers); X = Y = OCH2CF3(one isomer); X = Y = OBut(one isomer); X = Cl, Y = OMe (one isomer)] has been prepared from the reactions of CIP(NBut)2PCl with alcohols in the presence of triethylamine. The product of reaction with ButOH is easily converted into (ButO)P(NBut)2P(O)H. Analogous reactions with ethane-1,2- and propane-1,3-diols give the cage compounds [graphic omitted] (n= 2 or 3) and polymeric materials. Geometrical isomers of (MeO)P(NBut)2P(OMe) showed a different degree of reactivity towards methyl iodide, elemental sulphur, or selenium. Isomeric forms of the sulphides and selenides, (MeO)P(NBut)2P(X)(OMe)(X = S or Se), (MeO)(X)P(NBut)2P(X)(OMe)(X = S or Se), and of methyl iodide adducts have been obtained. Aspects of the 1H, 13C, and 31P n.m.r. and i.r. spectra of cyclodiphosph(III)azanes are discussed.

Nuclear magnetic resonance investigation of rotation about phosphorus(V)–nitrogen bonds in aminocyclodiphosph(V)azanes

Hydrogen-1 n.m.r. data on the cyclodiphosph(V)azanes R2N(X)[graphic omitted]But(R = Me, X = O, S, or Se; R = Et, X = S or Se) and Me2N(O)[graphic omitted]R (R = Ph or CH2Ph) indicate that rotation about the exo PV–N bonds is slow on the n.m.r. time scale at ambient or sub-ambient temperatures. In the former series, trans isomers have higher rotational barriers, ΔGTc‡, than analogous cis isomers and these barriers are also greater for trans oxides than analogous sulphides or selenides. The rotational barriers for PV–N and PIII–N have also been measured for the compounds Me2N[graphic omitted] But(X = S, Se, or Mel), Me2N(X)[graphic omitted]But(X = S, Y = lone pair; X = O, Y = O), and cis-Me2N(S)[graphic omitted] But. Carbon-13 n.m.r. data obtained at various temperatures on geometrical isomers of Me2N(X)[graphic omitted] But(X = O, S, or Se) indicate that J(PNC)(exo) is much more stereospecific than J(PNCH), especially when X = S or Se.

Nuclear magnetic resonance studies of rotation about phosphorus–nitrogen bonds in dialkylaminocyclodiphosphazanes

The 1H n.m.r. spectra of dimethylaminocyclodiphosphazanes, X[graphic omitted]R2[X = Cl, Y = NMe2, R1= Me, R2= But, R1= R2= But, R1= R2= Ph; X = Y = NMe2, R1= Me, R2= But, R1= R2= But, R1= R2= C6H4Z-p(Z = H, Cl, Me, and OMe)], at, or below, ambient temperatures show that in some cases the dimethylamino-protons are non-equivalent. Measurements of the free energy of activation (ΔG‡Tc) in these, in the diethylamino-derivatives, (Et2N)[graphic omitted]R (R = But and Ph), and in the di-isopropylamino-derivative, Cl[graphic omitted]But, indicate that the non-equivalence is due to restricted rotation about the exocyclic phosphorus–nitrogen bonds. Exceptionally high barriers are found for one of the two possible isomeric forms of Cl[graphic omitted]But and of (Me2N)[graphic omitted]But(16.9 and 17.6 kcal mol–1 respectively), and there are substantial differences in ΔG‡Tc(3–6 kcal mol–1) for pairs of geometrical isomers. The 31P chemical shifts of the aminocyclodiphosphazanes, measured by 1H-{3lP} double resonance, are temperature dependent, and this dependence is discussed in relation to possible conformational effects.

New aminocyclodiphosph(III)azanes and the influence of geometrical isomerism on their properties

A series of aminocyclodiphosph(III)azanes (R1R2N)[graphic ommitted]But(R1= H, alkyl, or SiMe3; R2= alkyl) have been prepared by the reactions of [graphic ommitted]But with primary or secondary amines, or with NMe(SiMe3)2. In some cases geometrical isomers have been separated by fractional crystallisation and thermal methods. Other cyclodiphosph(III)azanes, (Me2N) [graphic ommitted]R (R = Me or Et), have been synthesised by heating diphosphinoamines (Me2N)2P–NR–P(NMe2)2(R = Me or Et)in vacuo. Selected physical (1H, 13C, 31P n.m.r., i.r., dipole-moment, and mass-spectral) properties of these derivatives are reported and discussed.

Structures and properties of isomeric cyclodiphosph(III)azanes; X-ray crystal and molecular structure of 2,4-dipiperidino-1,3-di-t-butylcyclodiphosph(III)azane

Marked differences have been found in the nucleophilic reactivity, basicity, and photoelectron spectra of geometrical isomers of the cyclodiphosph(III)azanes, (XPNBut)2(X = NMe2 or OMe), whose structures were assigned by reference to the crystal structure of cis-(C5H10N·PNBut)2.

Alkylaminocyclodiphosph(III)azanes

The preparation of a series of aminocyclodiphosph(III)azanes, [graphic omitted]R2(R1= Me, R2= But; R1= R2= But; R1= R2= Ph) and (R12N)·[graphic omitted]R3[R1= Me, R2= Me, R3 But; R1= Me, R2= Et, R3= But; R1= Me, R2= R3= But; R1= Et, R2= R3= But; R1= Me, R2= R3= C6H4X-p(X = H, Me, Cl, or OMe); and R1= Et, R2= R3= Ph] by aminolysis of chlorocyclodiphosph(III)azanes is described. In many cases geometrical isomers are obtained which display exceptionally large differences (65–90 p.p.m.) in 31P chemical shift. Aspects of the 1H and 31P n.m.r., mass, and i.r. spectra of those compounds are recorded and discussed.

Some oxidation reactions of aminocyclodiphosph(III)azanes

The reactions of cis and trans isomers of the aminocyclodiphosph(III)azane, Me2[graphic omitted]But with t-butyl hydroperoxide, sulphur, selenium, tellurium, and methyl iodide give the oxidation products, Me2N(Z)-[graphic omitted]But(Z = S, Se, Te, or MeI) and Me2N(Z)[graphic omitted]But(Z = O, S, or Se), cis and trans isomers being isolated in each case (except where Z = Te). No reaction occurs with dimethyl sulphoxide. A series of sulphides and selenides of R2N[graphic omitted]R1(R2= Et2 or C5H10, R1= But; and R2= Me2, R1= Ph), Me[graphic omitted]H2)2, and Cl[graphic omitted]But have also been obtained by analogous routes. trans Isomers of Me2N[graphic omitted]But are more reactive than the analogous cis isomers, and it has been established that the oxidation of both isomers by sulphur or selenium occurs with retention of configuration at phosphorus. Exchange of selenium and of tellurium between phosphorus atoms has been observed in some derivatives, and in one case indentification of the products of exchange enabled structural assignments to be made.The chlorocyclodiphosph(V)azanes Cl(Y)[graphic omitted]R (R = But; Y = Z = O or S) react very slowly with dimethylamine even under forcing conditions. However, the latter compounds (R = Me, Y = lone pair, Z = O or S) are readily aminolysed by dimethylamine at the PIII atom. Selected 1H and 31P n.m.r. and i.r. data are reported and their relevance to structural assignments discussed.