Robert A. Shaw

The reactions of phosphazenes with difunctional and polyfunctional nucleophilic reagents

Abstract After a brief introduction of the reaction patterns of N3P3Cl6 and N4P4Cl8 with monofunctional nucleophilic reagents, the reactions of these two chlorocyclophosphazenes with difunctional, trifunctional and tetrafunctional nucleophilic reagents are surveyed. These reagents contain aliphatic and aromatic hydroxyl and primary and secondary amino groups. Spiro, ansa, dangling and bridging units have been observed as well as a combination of these. The stability of the various ring systems is discussed. Crystal structures and 1H, 13C and 31P n.m.r. spectroscopic studies are reported.

PHOSPHORUS-NITROGEN COMPOUNDS. PART 64.1 THE REACTIONS OF HEXACHLOROCYCLOTRIPHOSPHAZATRIENE WITH 2, 2-DIMETHYLPROPANE-1, 3-DIOL. NUCLEAR MAGNETIC RESONANCE STUDIES OF THE PRODUCTS

Abstract The reactions of hexachlorocyclotriphosphazatriene, N3 P3 CI6, with 2, 2-dimethylpropane-1, 3-diol yield monospiro-, N3 P3 Cl4 [(OCH2)2 CMe2, dispiro-, N3 P3 Cl4((OCH2)2CMe2|2, and trispiroderivatives, N3 P3 ((OCH2)2, CMe2]3. An ansa, N3 P3 CI4 [(OCH2)2 CMe2]2 and a spiro-ansa, N3 P3 Cl2- ((OCH2), CMe2,]2 and a doubly-bridged compound, (N3 P3 Cl4,)2[(OCH2)]2 were also isolated. Product types and relative yields were compared with those arising from propane-1, 3-diol. The yields of ansa products from the reactions of the dimethyl diol seem to be considerably enhanced relative to those of its unmethylated analogue. 31P and 1H n.m.r. spectra are reported.

The structural and stereogenic properties of pentaerythritoxy-bridged cyclotriphosphazene derivatives: spiro-spiro, spiro-ansa and ansa-ansa isomers.

Reactions of pentaerythritol with hexachlorocyclotriphosphazene, N3P3Cl6, and gem-disubstituted cyclotriphosphazene derivatives, N3P3Cl4R2 [R = Ph, NHBu(t) or (OCH2CF2CF2CH2O)0.5] gave a series of pentaerythritol-bridged derivatives linked spiro-spiro, spiro-ansa and ansa-ansa. The structures and stereogenic properties of the products were characterised by X-ray crystallography and 31P NMR spectroscopy on addition of the chiral solvating agent, (S)-(+)-2,2,2-trifluoro-1-(9-anthryl)ethanol. Molecules with spiro-spiro and spiro-ansa bridged gem-disubstituted cyclophosphazenes [R = Ph, NHBu(t) or (OCH2CF2CF2CH2O)0.5] are found to be chiral and exist as racemates. Molecules with ansa-ansa bridged cyclophosphazenes [R = Cl or (OCH2CF2CF2CH2O)0.5] have been characterised for the first time and are shown to have meso configurations. Analysis of crystal structure data shows that the six-membered chair form of the spiro rings and the eight-membered boat-chair form of the ansa rings in the bridged compounds are similar to analogous spiro and ansa exocyclic ring conformations of 1,3-propanedioxy-derivatives of cyclophosphazenes.

Spirocyclic phosphazenes derived from the reaction of N3P3Cl6 and N4P4Cl8 with bifunctional reagents

Four possible reaction paths may be envisaged when a chlorocyclophosphazene reacts with a bifunctional reagent (FIGURE). He have shown recently that 1,2-diaminoethane and ethanolamine react initially with N3P3CI 6 to give the spirocyclic derivatives, N3P3CI4(HNCH2CH2X) X = NH, 0 (I). Further reaction with these bifunctional reagents leads to the formation of non-crystalline resins [reaction (iii)] albeit two isomeric bls(spirocyclic)- ethanolamino derivatives were isolated in low yields (vSZ).

PHOSPHAZENES AND PHOSPHAZANES

Abstract Three types of phosphazene and four types of phosphazane structural units are classified on the basis of the coordination number of the phosphorus atoms involved. Phosphorus-nitrogen bond lengths are discussed in acyclic compounds and this information is used in analysing ring systems consisting wholly or partially of phosphorus-nitrogen skeletons. Four-, five-, six-, seven-, eight-, ten-, and twelve-membered rings are surveyed, as are polycyclic systems. Methods of synthesis for cyclophosphazanes, and mixed cyclo-phosphazene-phosphazanes are briefly considered, as are some of their reactions. The minimum ring size where stable phosphazenes have been observed is referred to. The effect of protonation, methylation, or coordination to a metal moiety on adjacent phosphorus-nitrogen bonds is discussed. The conformations of dimethylamino and phenyl substituents on phosphorus are considered, as is the conformations of the ring skeletons. The flexibility of a cyclic and cyclic phosphorus-nitrogen skelet...

Structural investigations of phosphorus–nitrogen compounds. 7. Relationships between physical properties, electron densities, reaction mechanisms and hydrogen-bonding motifs of N3P3Cl(6 − n)(NHBut)n derivatives

A series of compounds of the N3P3Cl(6 - n)(NHBu(t))n family (where n = 0, 1, 2, 4 and 6) are presented, and their molecular parameters are related to trends in physical properties, which provides insight into a potential reaction mechanism for nucleophilic substitution. The crystal structures of N3P3Cl5(NHBu(t)) and N3P3Cl2(NHBu(t))4 have been determined at 120 K, and those of N3P3Cl6 and N3P3Cl4(NHBu(t))2 have been redetermined at 120 K. These are compared with the known structure of N3P3(NHBu(t))6 studied at 150 K. Trends in molecular parameters [phosphazene ring, P-Cl and P-N(HBu(t)) distances, PCl2 angles, and endo- and exocyclic phosphazene ring parameters] across the series are observed. Hydrogen-bonding motifs are identified, characterized and compared. Both the molecular and the hydrogen-bonding parameters are related to the electron distribution in bonds and the derived basicities of the cyclophosphazene series of compounds. These findings provide evidence for a proposed mechanism for nucleophilic substitution at a phosphorus site bearing a PCl(NHBu(t)) group.

PHOSPHORUS-NITROGEN COMPOUNDS. PART 72.1 THE REACTIONS OF OCTACHLOROCYCLOTETRA-PHOSPHAZATETRAENE WITH SPERMIDINE AND SPERMINE

Abstract The reactions of octachlorocyclotetraphosphazatetraene, N4P4Cl8, with spermidine and spermine in a mixture of Et2O/MeCN (1:2) have been studied. Spermidine gave two products. Both consisted of two tetramer units: in one they were linked by one spermidine residue, in the other by two. Spermine gave one product, two tetramer units linked by a spermine residue. All three products contained six-membered spiro moieties. Their 31P and 13C n.m.r. spectra are reported and compared with the products of the same two amines with hexachlorocyclotriphosphazatriene, N3P3Cl6.

Isolation, n.m.r. spectra, and X-ray crystal structures of two isomeric N3P3Cl2[O(CH2)3O]2 derivatives. The first example of dispiro/spiro–ansa isomerism in phosphazene chemistry

From the reaction of N3P3Cl6 with 1, 3-dihydroxypropane two isomeric N3P3Cl2[O(CH2)3O]2 derivatives were isolated, whose n.m.r. spectra suggest, and crystal structures prove, that they represent an example of dispiro/spiro–ansa isomerism, the first of its kind in phosphazene chemistry.

Phosphorus–nitrogen compounds. Part 50. Further studies on the formation of bicyclic cyclotetraphosphazatetraene derivatives

The reactions of hexachloro-2,6-bis(ethylamino)cyclotetraphosphazatetraene, N4P4Cl6(NHEt)2, with pyrrolidine, piperidine, morpholine, diethylamine, or cyclopropylamine give bicyclic N4P4(NRR′)5(NHEt)(NEt), as well as monocyclic derivatives N4P4(NRR′)6(NHEt)2(NRR′= pyrrolidino, piperidino, morpholino, diethylamino, or cyclopropylamino). The reactions of N4P4Cl8 with cyclopropylamine give the bicyclic, N4P4(NHC3H5)6(NC3H5), and monocyclic, N4P4(NHC3H5)8, products, the former being the first structure of its kind with an α-branched alkyl group at the bridgehead to be isolated. Salient features of the 1H and 31P n.m.r. spectra of these bicyclic phosphazenes are discussed and related to their structures. Likely reaction mechanisms are considered.

Competitive formation of cis and trans derivatives in the nucleophilic substitution reactions of cyclophosphazenes having a mono-spiro P–NHR group

Nucleophilic substitution reactions of N(3)P(3)Cl(4)[NH(CH(2))(3)NMe] (1) and N(3)P(3)Cl(4)[NH(CH(2))(3)O] (2) with mono-functional alcohols (methanol, 2,2,2-trifluoroethanol, phenol) and a secondary amine (pyrrolidine) were used to investigate the relationship between the incoming nucleophile and the proportions of products with substituents that are cis or trans to the spiro NH moiety. The reaction products were characterized by elemental analysis, mass spectrometry, (1)H and (31)P NMR spectroscopy and the configurational isomers by X-ray crystallography. Six products have been characterised with the substituent cis to the spiro NH group for the alcohol (methanol, phenol) and pyrrolidine derivatives of both compounds 1 and 2, compared to just one derivative with the substituent trans to the spiro NH group, that for the pyrrolidine derivative of compound 2. For each reaction the relative proportions of cis and trans isomers were determined by (31)P NMR measurements of the reaction mixtures. It was found that the reactions of compound 1 with all three alcohols and of compound 2 with methanol lead to exclusive formation of isomers with the substituent cis to the NH moiety, whereas all other reactions lead to mixtures of cis and trans isomers in different ratios under standard reaction conditions. However, when crown ether is included in the reaction medium for the reactions of compound 2 with both 2,2,2-trifluoroethanol and phenol, it is found that only cis isomers are formed. All these results are rationalised in terms of the competition between at least two effects; the cis-directing effect by hydrogen bonding of the incoming nucleophile to the spiro N-H group already present on the cyclophophazene ring and the cis-directing effect of the sodium cation coordinating to the oxygen lone pairs of the P-O moiety of the spiro ring.