Gordon Bulloch

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.

New observations on the cyclisation of compounds containing the P–N–P skeleton by primary amines; an extension to diphosphinoyl-methanes

Dichlorophosphino(dichlorophosphinoyl)methylamine, Cl2P·NMe·P(O)Cl2, reacts with 3 mol equiv of t-butyl-amine to give the cyclodiphosphazane Cl[graphic omitted]But. By contrast, (ButHN)[graphic omitted]But is the only product isolated from the analogous reaction with Cl2P·NMe·P(S)Cl2. Similar reactions of Cl2(O)P·CH2·P(O)Cl2 with NH2But and NH2Pri give a new class of ring compound, Cl(O)[graphic omitted]R (R = Pri or But)(1,2,4-azadiphosphetans), but no cyclic products have been identified from analogous reactions with Cl2(O)P· CH2·CH2·P(O)Cl2. Attempted cyclisation of (Me2N)Cl(O)P-CH2-P(O)Cl(NMe2) by NH2But gives an acyclic product. (ButHN)(Me2N)(O)P·CH2·P(O)(NMe2)(NHBut), rather than (Me2N)(O)[graphic omitted]But. The latter cyclic derivative, obtained by heating (Me2N)2(O)P·CH2·P(O)(NMe2)(NHBut), is resistant to ring opening by NHMe2, whereas ring opening occurred in the attempted dimethylaminolysis of Cl(O)[graphic omitted]But. Attempts to prepare pure samples of Cl2P·CH2·PCl2, as a substrate for cyclisation reactions, from the reaction of PCl3 with Ph2P·CH2·PPh2, have been unsuccessful, and some of the products of these reactions are described.

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.

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.

Dimethylaminolysis of dichlorophosphinothioyl compounds

The reactions of [Cl2(S)P]2NR (I; R = Me or Ph) with dimethylamine have been investigated. When R = Me, mono-, non-geminal bis-, and tetrakis-dimethylamino-derivatives have been isolated, and the new ring compound (II), Me2N(S)[graphic omitted], obtained by reaction with 6 mol dimethylamine heated under reflux in chloroform solution. The analogous N-ethyl ring compound has been obtained from (I; R = Et). Attempts to synthesise the geminal bis(dimethylamino) derivatives, Cl2(S) P·NR·P(S)(NMe2)2, have been unsuccessful, although the reaction of Cl2(S)P·NHPh with dimethylamine gives (Me2N)2(S)P·NPh·P(S)(NMe2)(NHPh). Aminolysis of Cl2(O) P·NMe·P(S)Cl2 by dimethylamine, (dimethylamino)trimethylsilane, and (diethylamino)trimethylsilane initially occurs at the phosphinothioyl centre in non-donor solvents, but in diethyl ether solution dimethylaminolysis preferentially occurs at the phosphinoyl centre. Similar results have been obtained for Cl2(O) P·NPh·P(S) Cl2. By contrast, dimethylaminolysis of the cyclodiphosphazane Cl(O)[graphic omitted]But occurs exclusively at the phosphonoyl centre in donor and non-donor solvents. Non-geminal bis- and tetrakis-ditnethylamino-derivatives of Cl2(O)P·NMe·P(S)Cl2 have also been isolated.

Cyclisation of bis(dichlorophosphino)-, bis(dichlorophosphinoyl)-, and bis(dichlorophosphinothioyl)-amines by primary amines

The compounds [Cl2P(X)]2NR (IIIa, X = lone pair, R = Me, Et, or But; IIIb, X = O, R = Me or Et; IIIc, X = S, R = Me) react with 3 mol equiv. of t-butylamine to give cyclodiphosphazanes Cl(X)[graphic omitted]But, (V). Preparation of the long-sought cyclophosph(III)azanes (ClPNR)n(R = Me or Et) from (IIIa) has also been attempted by the same route, and new n.m.r. and mass-spectroscopic evidence has been obtained for formation of these derivatives (n= 3 and 4, R = Me; n= 2 and 3, R = Et), but no pure products have been isolated. Only when X = O and R = Me or Et could evidence for the formation of derivatives Cl2P(X)·NR·P(X)Cl·N(H)But, (II), be obtained, and possible reasons for the rapid cyclisation step involved are discussed. The known derivative Cl2P(O)·NMe·P(O)Cl·N(H)Me, (IIb), was readily cyclised by t-butylamine to give [ClP(O)·NMe]2, (Ib). Phosphoryl chloride reacts with 3 mol equiv. of primary amines to give mixtures of the derivatives Cl2P(O)·N(H)R (R = Me, Et, Pri, or But) and ClP(O)[N(H)R]2(R = Me, Et, or Pri), rather than cyclodiphosphazanes as obtained in analogous reactions with phosphorus trichloride.