Ottfried Schlak

PREPARATION AND NMR STUDY OF PHOSPHORUS-FLUORINE COMPOUNDS UNDERGOING INTRAMOLECULAR EXCHANGE. PART 1.1 BENZYLMETHYLAMINOFLUORO-PHOSPHORANES

Abstract The preparation is described of a series of benzylmethylamino-substituted fluorophosphoranes of general formula PhCH2(Me)NPF4–n R n (where R = Me, Ph; n = 0, 1, 2) from the cleavage of the silicon-nitrogen bond in benzylmethylamino-trimethylsilane by fluorophosphoranes. The structures of the new compounds are deduced from 1H, 19F and 31P nmr data. Variable temperature spectra give information about intramolecular exchange processes, and a detailed study was made of benzylmethylamino-diphenyldifluorophosphorane and of the corresponding 2-methyl-piperidyl compound.

PREPARATIVE AND N.M.R. STUDIES OF PHOSPHORUS-FLUORINE COMPOUNDS UNDERGOING INTRAMOLECULAR EXCHANGE. PART 2. UNSYMMETRICAL FLUORINATED PHOSPHADIAZETIDINONES

Abstract The preparation of fluoro-phosphadiazetidinones, O[dbnd]C(NMe)(NEt)PF2R (R [dbnd] Me, Et, Ph), unsymmetrically substituted on nitrogen, from the reaction of tetrafluorophosphoranes with the silyl urea, O[dbnd]C(NMeSiMe3)-(NEtSiMe3) is described. The compounds undergo partial equilibration to the symmetric species, O[dbnd]C(NMe)2PF2R and O[dbnd]C(NEt)2PF2R. Low temperature 31P and 19F n.m.r. spectra indicate changes which are rationalized in terms of variations in the population of energetically different conformers and in the exchange rates between conformers. The conformational differences involved are those arising from pseudorotation at trigonal-bipyramidal phosphorus. Comparable n.m.r. data are also given for some related compounds.

PREPARATION AND NMR STUDY OF PHOSPHORUS-FLUORINE COMPOUNDS UNDERGOING INTRAMOLECULAR EXCHANGE. PART 3.1 SUBSTITUTED FLUORODIAZADIPHOSPHETIDINES

Abstract Proton, 19F and 31P NMR studies of a number of tetra-, tri- and di-fluorodiazadiphosphetidines have yielded information about the barriers to pseudorotation at the phosphorus atoms. The data are classified according to the process studied, and are discussed in terms of the feasible exchange mechanisms. The PFR2 group is substantially more rigid than the PF2R group.

Phosphorus–fluorine chemistry. Part XXXV. Unsymmetrical 1,3-diaza-2,4-diphosphetidines of zwitterionic structure

The reactions of 2,2,2,4,4,4-hexafluoro-1,3-dimethyl-1,3-diaza-2,4-diphosph(V)etidine with NN′-dilithio-NN′-dimethylethylenediamine, and of the 1,3-t-butyl analogue with t-butyl-lithium gave rise to zwitterionic species, involving tetra- and hexa-co-ordinate phosphorus atoms, instead of the products of normal nucleophilic substitution in which phosphorus retains co-ordination number five. The zwitterionic structure of these products has been established by 1H, 19F, and 31P n.m.r. spectroscopy. Mass spectroscopy has shown that decomposition into monomeric phosphine imides, which is characteristic of 1,3-diaza-2,4-diphosph(V)etidines, does not occur in the case of the zwitterionic compounds.

PREPARATIVE AND NMR STUDIES OF PHOSPHORUS-FLUORINE COMPOUNDS UNDERGOING INTRAMOLECULAR EXCHANGE. PART 2. UNSYMMETRICAL FLUORINATED PHOSPHADIAZETIDINONES

Fluorophosphadiazetidinones I (R = Me, Et, Ph), unsym. substituted on N were prepd. from the reaction of tetrafluorophosphoranes with the silyl urea (Me3Si)MeNCONEt(SiMe3). The compds. undergo partial equilibration to the sym. species II and III. Low temp. 31P and 19F NMR spectra indicate changes which are rationalized in terms of variations in the population of energetically different conformers and in the exchange rates between conformers. The conformational differences involved are those arising from pseudorotation at trigonalbipyramidal P. Comparable NMR data are also given for some related compds.

Preparative and structural studies of diazadiphosphetidines. Part 9. X-Ray and nuclear magnetic resonance investigations of (Ph2FPNMe)n

It has been established by X-ray and n.m.r. analyses that the compund (Ph2FPNMe)n can be prepared as a dimer with a diazadiphosphetiding ring. The 1H spectrum of the NMe group may be explained in terms of a slow pseudorotation between two conformations. The two values of 3JPH(16.78 and 6.17 Hz) are considerably different, and involve coupling paths through axial and equatorial P–N bonds. Crystals of (Ph2FPNMe)2 are triclinic, space group P, with a= 9.849(2), b= 14.858(3), c= 8.236 (1)A, α= 93.53(2), β= 94.70(2), γ= 104.04(2)°, Z= 2. There are two independent crystallographically centrosymmetric molecules within the unit cell. Distorted trigonal-bipyramidal co-ordination is observed at phosphorus with mean bond lengths; P–F 1.683(3), P–N eq 1.652(3), P–Nax 1.780(1), and P–C 1.835(4)A. The Structure was solved by direct methods and refined to R 0.063 for 3 299 diffractometer-measured unique reflections.

Preparative and nuclear magnetic resonance studies of diazadiphosphetidines. Part VIII. 2,2,2,4-Tetrafluoro-1,3-dimethyl-4-o-phenylenedioxy-1,3-diazadiphosphetidine

The preparation and mass spectrum of the title compound containing a chelating catechol substituent are described. The 31P–{1H} and 19F–{1H} n.m.r. spectra have been analyzed, and the results indicate that the single fluorine attached to the chelated phosphorus atom is basically equatorial rather than axial.

Preparative and nuclear magnetic resonance studies of diazadiphosphetidines. Part VI. 2,4-Dialkyl-2,2,4,4-tetrafluoro-,3-dimethyl-1,3,2,4-diazadiphosphetidines

Proton-decoupled 19F and 31P n.m.r. spectra of a series of dialkyltetrafluorodiazadiphosphetidines. (RF2PNMe)2(I; R = Me, Et, Pri, or But), have been recorded and analysed for temperatures high enough for gauche⇌trans exchange to be rapid on the n.m.r.timescale, and at low temperatures when the exchange is slow. Some 1H n.m.r. data are also given, including the results of a comoplete analysis of the spectrum of (I; R = Me) on an [A(X)2M3]2 basis. Many signs of coupling constants have been obtained either from the spectral analysis or from double resonance experiments. The coupling constants and chemical shifts are compared and discussed. There is a very large isomer effect on 2JPP, especially for the But compound. Isomer populations have been obtained by several methods. The preparations of the Pri and But compounds, not previously reported, are described in detail.

Preparative and nuclear magnetic resonance studies of 1,3,2,4-diazadiphosphetidines. Part IV. Methyl- and methoxy-fluorodiazadiphosphetidines

The preparation of a series of methyl- and methoxy-fluoro-1,3,2,4-diazadiphosphetidines [(I) and (II) respectively] has been accomplished, in many cases by substitution reactions on heavily fluorinated diazadiphosphetidines using organometallic reagents.The 19F{1H} and 31P{1H} n.m.r. spectra of these compounds have been analysed, using subspectral techniques and iterative computer fitting. In only two cases axial ⇌ equatorial exchange may be slowed on the n.m.r. time scale at low temperatures; the reason for this lies in the concerted pseudorotation nature of the exchange. The chemical shift and coupling constant data show the influences of substituents and geometry. It has been demonstrated that 2JPP is positive, and its values can be reproduced by a product of parameters characteristic of the environment of each phosphorus nucleus.