Rodney Keat

Conformational effects on P–N–P coupling constants in diphosphinoamines and related compounds

1 H-{31P} and 31P n.m.r. measurements on the triphosphazanes (Ph2P·NR)2PPh show that J(PNP) is +280 Hz when R = Me and 25.1 Hz when R = Et. A similar marked dependence on the R groups has been found for the diphosphinoamines, Ph2P·NR·PPhCl (R = Me, Et, Prn, Pri, and But)(+334 to –35 Hz), and this may be related to the conformations about the P–N bonds, which are influenced by the stereochemical bulk of R. 1H-{31P} INDOR experiments on the symmetrical diphosphinoamines, Ph2P·NR·PPh2(R = Me, Et, and Pri), indicatethat J(PNP) is much greater when R = Me than when R = Et or Pri.

Conformations of diphosphinoamines; variable-temperature nuclear magnetic resonance and X-ray crystallographic studies

The variable-temperature 31P-{1H} n.m.r. spectra of a series of diphosphinoamines, X2PN(R)PX2(R = H, Me, Et, or Pri, X = Ph; R = Me, But, or CH2But, X = Cl; R = Me or But, X = F; R = Et, X = NMe2) have been studied. Complementary information on these compounds has been obtained from 1H, 13C, and 19F n.m.r., including double and triple resonance experiments. The coupling constant, 2J(PNP), covers the range –23.9 to 731.9 Hz, and its magnitude and sign can be related to the proportion of molecules in which the local symmetry of the P–N–P skeleton is C2v rather than CS. Diphosphinoamine conformers of the latter type have been clearly identified for the first time both in solution (for R = Et or Pri, X = Ph, and R = But or CH2But, X = Cl) and also in the solid phase. X-Ray analysis of Ph2PN(Pri)PPh2, based on 1 269 diffractometric intensities refined to R= 0.035, shows that the symmetry of the P–N–P skeleton is close to Cs in the solid, with P–N = 1.706(4) and 1.711(4)A, and PNP = 122.8(3)°.

Aminolysis reactions of 1-dichlorophosphinyl-2,2,2-trichlorophosphazene, Cl2P(O)·NPCl3

Abstract The reactions of 1-dichlorophosphinyl-2,2,2-trichlorophosphazene, Cl2P(O)·NPCl3, with methylamine and t-butylamine have been studied. The acyclic amino-derivatives, Cl2P(O)·NCl2(NHMe), Cl2P(O)·PCl(NHBut) [or its trautomer, Cl2P(O)·NH·PCl2(NBut)], Cl2P(O)·PCl(NHMe)2, and Cl(ButNH)P(O)·NPCl2(NHBut) have been isolated, the position of chlorine-atom replacement being established by 1H and 31P n.m.r. spectroscopy. No evidence for the formation of cyclic phosphazenes, ClR NP(O)·NP Cl2 (R = Me, But) has been obtained.

The Nuclear Magnetic Resonance Spectra of Geometrical Isomers of 2,4-Difluoro-l,3- di-t-butylcyclodiphosph(III)azane

A new synthetic method for the preparation of the geometrical isomers of (FPNBut)2 by amine elimination from Me2N-P(F)-NButSiMe2 is described. The 13C, 19F, and 31P NMR investigations lead to new structural assignments

PHOSPHORUS-NITROGEN COMPOUNDS. PART 471. CONFORMATIONS AND PHOSPHORUS-PHOSPHORUS SPIN–SPIN COUPLING CONSTANTS IN PHOSPHAZENYLCYCLOPHOSPHAZENES

Abstract 4 J PP Spin–spin coupling constants have been measured in a series of phosphazenylcyclophosphazenes. They can be correlated with the conformations adopted by the phosphazenyl substituents in the solid state, which are also believed to be the predominant ones in solution. The conformations are depicted by suitable orthographic projections based on published X-ray crystallographic data.

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.

Conformational effects on PNCH, PNC, and PNSi spin coupling in tervalent phosphorus–nitrogen compounds

The 1H and 13C n.m.r. spectra of a series of tervalent phosphorus-nitrogen compounds having a known conformation about the P–N bond have been obtained. These measurements confirm previous assumptions that the coupling constants J(PNCH) and J(PNC) are relatively large and positive for a methyl group having a cis relation with the lone pair of electrons on phosphorus. J(PNCH) is small, and J(PNC) small and negative when the methyl group is trans to the lone pair. The results are discussed by reference to compounds of unknown conformation. The coupling constant, J(PNSi), in a series of silylaminophosphines, Ph2P·NR·SiMe3(R = Me, Et, Pr1, or But), also appears to be related to the conformation adopted by the P–N bond.

Chlorine-35 nuclear quadrupole resonance studies of some chlorocyclotriphosphazatrienes

Abstract Chlorine-35 NQR frequencies, v (MHz), in the chlorocyclotriphosphazatrienes are related to the corresponding PC1 bond lengths, d ( A ): d = −0.012 8 v + 2.355. v is also related to θCl, the valence shell electronic population localized on the chlorine atom: θCl = −0.0345v + 8. Chlorine-35 NQR frequencies discriminate between the positional isomers of N3P3C13(NMe2)3. Chlorine-35 NQR frequencies in N1P3Cl6, N3P3Cl5NHPri, N3P3Cl5NC5H10, cis-N3P3Cl4(NMe2)2, and trans-N3P3Cl4(NMe2)2 are linear functions of the applied pressure, P, within the range 1 to 700 kg cm−2. N3P3CI5NC5H10, cis-N3P3Cl4(NMe2)2 and trans-N3P3Cl4(NMe2)2 undergo minor phase changes at about 150 K. The partial differential coefficients (ϖv ϖP) T=293 K′ (ϖv ϖT) P=1kgcm −2 , T=293 K′ and (ϖv ϖT) V,T=293K have been evaluated for each of the resonance frequencies in N3P3Cl6, N3P3Cl5NHPri, N3P3Cl5NC5H10, cis-N3P3Cl4(NMe2)2, and trans-N3P3Cl4(NMe2)2. The pressure derivatives, (ϖv ϖP) T , discriminate between geometric isomers. The temperature derivatives, (ϖv ϖT) , and the pressure derivatives together discriminate between molecular conformers and give detailed information about molecular dynamics in these solids.

A nuclear magnetic resonance study of some bis(phosphinoyl)amines and bis(phosphinothioyl)amines

1 H, 31P and 13C N.m.r. spectra have been obtained for a number of bis(phosphinoyl)amines (I) and bis(phosphinothioyl)amines (II). The spectra have been analysed to give chemical shifts and coupling constants, which are presented and discussed here. The sign of 2JPNP has been determined by heteronuclear spin tickling in several cases and found to be positive.

Formation of cyclophosph(III)azanes and their oxo- and thioxo-derivatives

The reactions of phosphorus trichloride with three molar equivalents of methylamine and ethylamine give bis-(dichlarophosphino)amines (Cl2P)2NR (R = Me and Et), and with isopropylamine and t-butylamine, cyclodi-phosph(III)azans, (ClPNR)2(R = PrI and But) are obtained as major products. There is mass spectroscopic evidence for the cyclophosph(III)azans, (ClPNEt)n(n= 2 or 3) in the products from the reaction with ethylamine, but these compounds have not been obtained pure. Several other potential routes to N-methylcydophosph(III)azanes were examined, inculding the reaction of phosphorus trichloride or of bis(dichlorophosphino)methylamine, (Cl2P)2NMe, with heptamethyldisilazane, (Me3Si)2NMe, which gave the dichiorophosphinamines, Cl2P·NMe·SiMe3(Cl2P)2NMe, and the cage compound P4(NMe)6, but no compounds of the type (ClPNMe)nwere obtained. Similarly, dichloroaiylphosphines and hepiamcthyldisilazane gave the phosphinamines ClArP·NMe·SiMe3 and (ClArP)2NMe (Ar = Ph or C6H4-p-Me). m-Chtoroaniline hydrochloride reacts with phosphorus trichloride affording (Cl2P)2NC6H4-m-Cl, which with SbF3produces (F2P)2NC6H4-m-Cl. (Cl2P)2NPh and the analogous fluoride were obtained similarly. The cyclodiphosph(III)azanes, (ClPNR)2(R = PrI or But), gave monoxides and monsulphides containing PIII and PV atoms within the ring system, on reaction with dimethyl sulphoxide and elemental sulphur respectively. Oxothioxocyclodiphosphazanes were obtained by a related route. The 1H and 31P n.m.r. spectra of these compounds are reported and discussed.