Mass spectra of the bromofluorocyclotriphosphazenes

.I. inorg, nucl. Chem. Vol. 43, pp. 46%475 Pergamon Press Ltd., 1981. Printed in Great Britain

0022-1902/81/0301-0467/$02.00/0

MASS SPECTRA OF THE BROMOFLUOROCYCLOTRIPHOSPHAZENES PHILIP CLARE Department of Chemistry, University of Cape Coast, Ghana and D. BRYAN SOWERBY* Department of Chemistry, University of Nottingham, University Park. Nottingham, England (Received 12 February 1980; receivedfor publication 29 May 1980)

A~tract--The mass spectra of geminal-, cis- and trans..bromofluorocyclotriphosphazenes (N3P3Br,F 6 - . , n = 2-5) have been obtained at an electron energy of 70 eV. When n = 2 or 3 there is a substantial difference between the geminal and non-geminal isomers for the process involving loss of a bromine atom from the parent ion. When n = 2-4 there is a distinction between the types of linear ions formed from geminal and non-geminal isomers. Cisand trans-isomers could not be distinguished. The relative proportions of cyclic and linear ions are discussed. Groups of partially resolved ions were observed resulting from the decomposition of isotopically related metastable ions. Several new types of metastable transition were observed. INTRODUCTION

Mass spectra have been reported for the bromophosphazenes (NPBrE)3~s[1], the chlorophosphazenes (NPCI9~[2,3], the fluorophosphazenes (NPF2)3_1614] and the isothiocyanates [NP(NCS)2]3.4[5]. Mixed nongeminal isomers of bromochloro-[6] and chlorofluorotriphosphazenes[7] have been discussed. Work on pure isomers of the chloro-[8] and fluorophenylphosphazenes[9] has indicated substantial differences in the fragmentation patterns of geminal and non-geminal isomers which has been suggested as a possible means of identifying the stereochemistry of trace products from preparative reactions[8]. In favourable cases, clear distinction can be seen between the cis and trans non-geminal isomers [9]. In general, fragmentation patterns of phosphazenes are complex, giving rise to cyclic and linear ions, both singly and doubly charged and, in the case of higher oligomers, to ring contraction rearrangements. The presence of polyatomic exocyclic substituents can further complicate the fragmentation pattern. In the present work, the relatively simple bromofluorotriphosphazenes; N3P3BrsF, geminal and non-geminal (mixture of cis- and transisomers) N3P3Br4F2, cis-, trans- and gem-N3P3Br3F3, and cis-, trans- and gem-N3P3Br2F4 have been examined specifically to investigate the effects of changes in stereochemistry on the mode of fragmentation. The stereochemistry of the three possible isomeric forms, for example, for the stoichiometry N3P3Br3F3 is shown in Fig. I. The natural isotopic abundance of bromine makes it possible to determine the empirical formulae of most ions in the spectra, without recourse to accurate mass measurement. Monoisotopic mass spectra are listed in Tables 1-4 where data are reported as a percentage of the total ionisation from the parent ion down to m/e 45 (NP+), while a summary of the data in terms of the types of ion obtained is included in Table 5. Assignment of *Author to whom correspondence should be addressed. 467

F

F~,,, BF N/F~N II

I.. F

Br -~p~N ~. p, F "Br (o)

/Br

Br" ~LN~'I ,P~IBr F 'F (b) Br~ ,,Br II

I

F-~P\N~P,"~F F ~Br (c) Fig. 1, Isomeric forms for the stoichiometry N3P3Br3F3; (a) non-geminal cis, (b) non-geminal trans, (c) geminal. ions was assisted by a simple computer program which calculated the masses of all possible fragments, N,,P. FaXb, where n>-m and a + b = O - 2 n . Similar programs have been discussed[10]. EXPERIMENTAL

The geminal-bromofluorophosphazenes were prepared by the method of Steger and Klemm[ll] and separated by preparative gas-liquid chromatography. A 5'x I" glass column containing 15% silicone gum rubber on Chromosorb W was used in temperatureprogrammed runs between 50 and 200°. The stoichiometries of the separated compounds were confirmed by IR, ~9F NMR and mass spectroscopy. A similar mixture of products was obtained by homogenous reaction of N3P3Br6 and three moles of AgF at room temperature in acetonitrile. In this reaction, the HF catalyst was not required and the silver bromide was filtered off. The non-geminal isomers were prepared by deamination of the corresponding dimethylaminofluorophosphazenes[12,13] and separated by preparative gas liquid chromatography. Separation of the cis- and trans-isomers of N3P3Br4F2was not possible. The mass spectra were obtained on an A.E.I. MS902 mass spectrometer at 70 eV, with an ion chamber temperature between 100 and 160°, depending on the volatility of the samples, which were admitted through the glass heated-inlet system.

468

PHILIP CLARE and D. BRYAN SOWERBY Table 1. Monoisotopic"mass spectrum of N3P3BrsF m/e

Assignment

Abundance

m/e

Assignment

549

N3P3Br5F+

3.1 (6.4)b

155

NP2Br+

0.5

530

N3P3Br5 +

154

N3P3 F+

3.2

470

N3P3Br4F+

149

N2P3Br2 F2+

0.6

442

NP3Br4F+

t

143

NPBrF +

0.6

391

N3P3Br3F+

1.5

129

PBrF +

2.1

377

N2P3BE3 F+

0.3

126

NP3 F+

0.7

346

N2P2BE3 F+

O.I

124

NPBr +

0.8

332

NP2Br3F+

0.5

116.5

N3P3BrF 2+

0.9

312

N3P3Br2F+

8.9

114

NP2F2 +

t

298

N2P3Br2 F+

t

110

PBr +

1.1

239

P2Br2 F+

t

109

N2P2 F+

0.8

234

NP2Br2 +

0.4

95

NP2F +

2.0

tc 48.2 (iOO)

Abundance

233

N3P3BrF+

2.9

90

N2P2 +

O.i

228.5

N2P3BE42+

0.4

80

BrH +

6.6

219

N2P3BrF+

0.4

79

Br +

3.5

214

N3P3Br +

t

76

NP2 +

1.2

205

NP3BrF+

0.2

69

PF2+

0.3

N3P3Br3 F2+

0.6

64

NPF +

0.2

189

PBr2 +

0.9

62

P2 +

0.3

188

N2P2BEF+

0.7

59

N2 P+

0.3

174

NP2BrF +

3.0

50

PF +

1.3

173

N3P3F2 +

t

45

NP +

I.O

195.5

"Based on ~Br. bFigures in parentheses are % of base peak. ~t = trace.

RF~ULTS AND DISCUSSION For the purpose of this discussion, those fragments retaining the N3P3 unit are referred to as cyclic, whilst the remainder containing nitrogen and phosphorus are described as linear. This attempts to simplify comparisons as some authors have included N2P~ and NP containing fragments with "cyclic" ions, whereas others suggest N2P2 may be isostructural with the P4 molecule [1, 3]. Furthermore, as D(PN) has been estimated to be ca. 3501drool-' (in N3P3F6) and D(PF) to be ca. • 10~mol-', N3P3 ions that have lost a fluorine atom may also be linear. Cyclic ions

Ions that retain the N3P3 unit are abundant in the spectra of all these mixed halotriphosphazenes and account for between 62.4 and 75.0% of the total ionisation. A similar situation occurs for N3P3Br6, N3P~Br, CI6-, and N3P3C1616] whereas linear ions predominate for N3P3F614]. The parent ion was observed in all cases, but its intensity was substantially lower for those molecules containing a PBr2 group, where intensities of less than 5.3% of the base peak, i.e. (parent-Br) +, were recorded. This is in good agreement with the non-geminal

bromochlorophosphazenes[6] where bromine atoms are readily lost from PBrCI and PBr2 groups and parent ions are less than 3.9% of the base peak. On the other hand, however, those parent ions containing only PBrF and PF, groups are more stable, their intensities being greater than 20% of the base peak in all cases. This reflects the greater stability of the PBr bond in a PBrF group, compared with a PBh group, and clearly differentiates between geminal and non-geminal isomers for N3P3Br3F3 and N3P3Br2F4. All spectra are dominated by ions formed by loss of a bromine atom from the parent ion and which contribute from 41.6 to 63.9% to the total ionisation of these compounds. The parent ion and the base peak are the first two members of a series in which the heavier halogens are successively lost. The interesting alternation of intensities, previously observed in the spectra of halophosphazenes is well illustrated here by N3P3BrsF, where all six ions from N3P3BrsF+ to N3P3F+ inclusive are observed and have intensities of 3.1, 48.2, 1.5, 8.9, 2.9 and 3.2%, respectively. This is correlated with the extra stability associated with ions containing an even number of electrons, i.e. an odd number of halogens in the N3P3 series. As the PF bond is almost twice as strong as the PBr

469

Mass spectra of the bromofluorocyclotriphosphazenes Table 2. Monoisotopica mass spectra of N3P3Br4F2 m/e

Assignment

Abundance non-gem b

489

N3P3Br4F2+

Assingmant

470

N~r4

410

N~r~2

331

N~r2F2+

3.0

i. 9

317

N2P ~r2F2+

i. 2

312

N~r2

287 272 252

N~rF2

gem

PBrF+

1.5

0.9

128

N2P2F2 +

O. 6

2.4

124

NPBr+

0.3

0.4

119

N2P3BrF22+

O. 7

O. 5

O. 4

ll4

NP2F2+

4.7

4.2

O. 1

t

llO

PBr+

O. 5

O. 7

PBr~ +

O. 8

O. 3

109

N ~ 2 F+

t

N~2Br2F+

0.4

O. 4

i00

P2F2 +

10.3

20.0

ta +

F+

+

245.5 N ~ r 4 F 2 2 +

55.8 (I00)

O. 1 42.7 (i00)

96.5 NP2BrF22+

t -

O. 2

O.i

0.i

t

95

NP2F+

2.5

i. 5

0.2

0.2

81

BrH+

1.6

2.1

0.2

t

79

Br +

i. 4

3.1

N2P ~ r 3F22+

O. 4

O. 3

76

NP2 +

O. 7

i. 2

NP2BrF2 +

O. 2

O. 2

73

N3P+

O. 4

0.1

h~2BrF+

1.0

i.O

69

PF2 +

2.4

4.1

238

N~rF2

233

N ~ 3BrF+

198 193 174

+

-

2.2 (5.2)

Abundance non-g~n

129

F+

1.3 (2.4)a

m/e

g~m

173

N~3F2 +

3.8

4.9

64

NPF+

O. 2

O. 1

169

0.8

0.4

62

P2 +

0.i

0.2

155

N2P~2+ + NP2Br

O.i

0.2

59

N2P+

0.2

0.3

154

N3PBF+

0.i

0.i

50

PF+

2.1

1.5

148

PBrF2+

t

O. 1

45

PN +

O. 1

O. 9

143

NPBrF+

O. 1

O. 1

aSee footnotes a--cin Table 1. bMixture of cis and trans isomers.

bond, ions formed by loss of one or more fluorine atoms are relatively weak compared with those formed by loss of one or more bromine atoms. There is an additional statistical effect for most stoichiometries, but for the non-geminal tribromotrifluorides, where loss of either halogen is statistically equally likely, N3P3Br2F3÷ is ca. 200 times more intense than N3P3Br3F2÷. Similarly, N3P3CI2F3+ predominates over N3P3CI3F2 + by a factor of 90[7] and N3P3Br2CI/over NaP3Br3CI/by a factor of 50. Those ions that result from complete bromine loss, but complete fluorine retention, i.e. N3P3F, +, n = 1-4, show two trends. As the fluorine content increases, so does the abundance of the ion: furthermore, the ion for the geminal isomer is slightly more abundant than for either non-geminal isomer. This indicates that even though there will be a reduction in ring stability caused by loss of halogens, the N3P3 unit is stabilised by fluorine substituents, just as in neutral halophosphazene, and that the presence of a PF2 unit is more stabilising than two PF units. A similar effect can be observed in the i.r. spectra of these compounds, as shown in Table 6, where the ring stretching mode, v,~[14], which is usually considered to increase with the strength of the ring bonding, is at slightly higher energy in the geminal isomers than for the corresponding cis and trans isomers which themselves absorb at almost identical positions.

Linear ions

The relative abundances of N3P3 and two classes of 'linear' fragments, i.e. those where the number of P atoms is greater than the number of nitrogen atoms and those where P-< N are compared in Table 5. Similar distributions are shown for the three hexahalocyclotriphosphazenes. In all cases ions in the P > N class are more abundant than those with P- N are slightly more abundant than for geminal isomers, whilst for the P-< N fragments the opposite holds true. This does not, however, extend to each particular example in Tables 2-4. Overall linear ion formation does not show any relationship with structure, and indeed remains almost constant at ca. 15% for the nine bromofluorophosphazenes discussed here. This is in contrast to the tetrafluorodiphenylphosphazenes where linear ion formation was favoured in the presence of at least one fluorine atom on each phosphorus[9]. Nor are the abundances of ions for the cis isomers generally higher than for the trans isomers. The even-electron ions in the N2P~ and NP2 series now contain an even number of halogens, and a similar

470

PHILIP CLARE and D. BRYAN SOWERBY Table 3. Monoisotopic mass spectra of N3P3BraF3 m/e

Assignment

Abundance ci___~s

tran_____~s

geminal

11.9 (24.7)

13.4

0.8

429

N3P3Br3F3 +

410

N3P3Br3F2 +

350

N3P3Br2F3 +

331

N3P3Br2F2+

0.i

0.i

t

271

N3P3BrF3 +

3.1

3.5

3.0

0.3 48.1 (iO0)

(28.5)

0.2 47.1 (i00)

(1.8) t

45.9

(iOO)

357

N2P3BrF3+

2.3

2.1

0.6

252

N3P3BrF2+

0.3

0.2

0.i

238

N2P3BrF2+

t

233

N3P3BrF +

t

-

N3P3Br3F32+

t

0.2

212

NP2BrF3+

0.6

0.6

0.3

192

N3P3F3 +

8.6

7.9

10.2

214.5

178

N2P3F3+

175

N3P3Br2F 3

174

-

1.2

1.3

0.5

0.2

0.2

0.6

NP2BrF +

0.3

0.2

0.2

2+

173

N3P3F2 +

0.3

0.2

0.2

168

N2P3Br2F32+

0.4

0.4

0.3

165.5

N3P3Br2F22+

0.2

0.i

O.i

159

N2P3F2+ +

t

t

t

148

FBrF 2

0.2

0.2

0.3

147

N2P2F3 +

t

t

0.3

135.5

N3P3BrF32+

t

0.5

1.2

133

NP2F3+

0.9

0.9

1.0

129

PBrF

1.2

1.0

0.6

t

t

t

128.5

N2P3BrF 3

2+

128

N2P2F2+

O. 1

O. 1

O. 2

124

NPBr +

0.I

O.i

0.i

119

N2P3BrF22+

0.i

0.i

0.5

114

NP2F2+

5.6

5.8

2.4

llO

PBr +

t

O.i

2.6

104

N3P2 +

t

t

t

i00

P2F2 +

t

t

t

95

NP2 F+

1.3

1.2

2.0

89

N2P3F32+

0.4

0.4

0.6

88

PF3+

0.i

0.i

0.6

80

BrH +

1.7

1.7

0.5

79

Br +

1.5

1.2

0.7

78

N2PF +

0.3

0.3

O.1

76

NP2 +

0.2

0.2

0.3

73

N3P+

-

0.4

3.1

69

PF2 +

3.8

3.8

3.5

NP2F32+

0.2

0.2

0.3

NPF +

0.2

0.2

0.i

66.5 64

471

Mass spectra of the bromofluorocyclotriphosphazenes Table 3 (Contd) m/e

Assignment

Abundance ci__ss

trans

geminal

62

P2 +

0.3

0.2

59

N2P+

O.i

0.2

0.6

50

PF +

2.8

2.7

15.2

45

NP +

0.6

0.5

0.6

pattern of alternating intensities is observed, e.g. in the spectrum of N3P3FBrs, N2P3Br3F+ (0.5), N2P3Br2F÷ (trace), N2P3BrF÷ (0.4), N2P3F÷ (0.0), to that for even and odd electron species in the N3P3 series.

Remaining ions Doubly charged ions are of relatively low abundance in these spectra (see Table 5) and are similar to the abundances for the hexafluoride. Surprisingly, there is no increase with increase in bromine content, even though the abundance is about four times greater for the hexabromide than for the hexafluoride. The remaining unclassified ions are mainly of low m/e values and are due to phosphorus halide fragments or to free halogens. Especially prominent are the expected fragments containing phosphorus and fluorine, as well as some formed by halogen redistribution, e.g. PF2+ from N3P3Br~F and PBr3F+ from the tetrabromo isomers. The extraordinarily high intensity of PF +, 15.2%, in the spectrum of gem-N3P3Br3F3 is quite atypical and appears to be related to the unusually low abundance of N3P3 fragments in this spectrum. This may be related to the fact that the geminal tribromide was observed to be the least stable of all these compounds, decomposing within a few days in the laboratory.

Metastable ions The decompositions of many metastable ions were observed and these are summarized in Table 7. These processes must occur in the field-free region between the electric and magnetic sectors, since decompositions occurring before the ions enter the velocity selector can only be detected for mass changes of less than 1.3%[15]. Ions discussed here were detected in the normal scanning mode of the spectrometer, and although a particular transition was not always detected for all three isomers, a special scan with a constant B/E ratio would be required to show if the transition was present or not[15]. Thus no special structural significance can be drawn from variations between isomers. The most prominent metastable ions, observed in all these compounds, result from loss of a bromine atom from the parent ion. Indeed, for N3P3BrsF the complete series of transitions due to stepwise loss of bromine atoms was observed. Since naturally occurring bromine has two isotopes of approximately equal abundance, there will be n +1 ions for a general ion containing n bromines. Most of these isotopic variants can decompose by loss of 79Br or S'Br and consequently give a group of broad lines in the spectrum separated by small m/e increments. In some cases, only the profile of a group of related ions was observed but generally at least a partial resolution was achieved. Two examples of such partially resolved groups of ions are illustrated in Fig. 2, where

t

the sharper lines represent normal ions in the mass spectrum. The weighting factors for isotopic abundances of 79Br and StBr and the statistical probability of a mode of decomposition have been included and confirm the presence of all the expected decompositions of the polyisotopic parent group. A most interesting transition in the spectrum of the pentabromide involved loss of a bromine molecule from the base peak, i.e. N3P3Br4F÷. Although this type of process has been predicted[l] this is the first reported example. (The simultaneous elimination of two NCS fragments reported in the mass spectrum of N3P3(NCS)6[5] is presumably open to interpretation as loss of a thiocyanogen molecule.) However, a similar loss of bromine was not observed in the spectrum of geminal-N3P3Br4F2 at m/z 154.9, even though the intensity of the N3P3Br3F2+ ions is about 10% lower than expected from comparison with the non-geminal isomers, and N3P3BrF+ is about 10% higher. Other than this example, only transitions due to loss of bromine atoms from the N3P3 series are observed in the spectra of N3P3BrsF and all isomers of N3P3Br4F2. The elimination of an NP unit is observed for the non-geminal tribromide and there are two examples for each dibromide isomer. These are the first reported processes of this type for cyclotriphosphazenes and are to be expected for the N2P3X.+~NP2X.+ system. In the case of higher phosphazene oligomers, loss of NP is associated with the high abundance of N3P3 fragments. Several of the NP2 series of ions were observed to carry four fluorine atoms indicating that rearrangement of the substituents had occurred before, or concurrently with, the decomposition of the parent fragment. Trans-N3P3Br2F4 shows the result of one decomposition at m/e 58.2 which corresponds to the elimination of NF4 from N2P3F4÷. A complete cross check of all ions with intensities greater than 0.1% of total ionisation confirms this as the only transition to fit the data. Loss of NF4 has not been reported before although it may be separate radicals and molecules, e.g. NF2 and F2. Further, the process may be collision induced as it was observed only at a relatively high sample pressure in the source. Similarly, the elimination of N2P during fragmentation is another previously unreported transition and was only observed at a high sample pressure. In conclusion it seems that mass spectrometry can be used to identify unambiguously the geminal or nongeminal nature of N3P3Br3F3 and N3P3Br2F4 isomers. When all isomers are present (or a mixture of nongeminal isomers and the geminal isomer) the ratio of different types of linear fragments can also distinguish geminal from non-geminal. Disappointingly, however, distinction between cis- and trans-non-geminal isomers does not appear possible for these compounds on the

472

PHILIP CLARE and D. BRYAN SOWERBY

Table 4. Monoisotopic mass spectra of N3P3Br2F4 m/e

Assignment

Abundance cis. 10.4

(22.0)

trans

geminal

10.7 (25.8)

1.8 (3.4)

369

N3P3Br2F4 +

350

N3P3Br2F3+

290

N3P3BrF4 +

47.1 (iOO)

271

N3P3BrF3 +

0.2

0.2

O.i

257

N2P3BrF3+

0.5

t

t

211

N3P3F4 +

197

N2P3F4 +

193

NP2BrF2 +

192

N3P3F3 +

178 174 173

N3P3F2 +

0.3

-

171

N3PBrF +

1.3

-

166

N2P2F4 +

i.O

1.2

4.0

152

NP2F4+

1.6

1.9

0.8

148

PBrF2+

t

O.i

0.3

147

N2P2F3 +

O.i

O.i

t

145

N3P3BrF42+

0.2

O.i

1.2

135.5

0.9

14.2

0.7 41.6

(iOO)

0.8 52.1

(iOO)

14.1

18.3

3.1

4.1

0.8

t

0.8

-

0.7

0.6

0.5

N2P3F3 +

O.i

0.i

0.i

NP2BrF +

t

t

t t

N3P3BrF32+

0.3

0.2

0.3

133

NP2F3 +

1.2

1.4

0.6

129

PBrF +

0.6

1.7

0.4

128

N2P2F2 +

t

t

0.4

114

NP2F2+

2.9

3.6

3.0

iiO

PBr +

0.i

O.i

0.3

107

NP3 +

0.7

i.O

1.5

104

N3P2 +

0.4

t

O.i

98.4

N2P3F42+

-

O.i

95

NP2 F+

i.i

0.7

0.6

83

NPF2 +

2.1

0.5

t

80

BrH +

0.4

0.6

0.3

79

Br +

0.8

0.8

0.6

78

N2PF +

0.5

0.6

0.6

69

PF2 +

4.6

6.1

7.3

64

NPF +

0.2

0.3

O.i

59

N2 P+

t

O. 2

O. 3

50

PF +

3.7

4.1

2 .O

45

NP +

0.4

0.4

0.7

473

Mass spectra of the bromofluorocyclotriphosphazenes Table 5. Types of ion in mass spectra of bromofluorotriphosphazenes (as % total ionisation) N3P 3

P > N

P .< N

N3P3Br5F

69.4

10.2

4.5

2.5

non-gem-N3P3Br4F2

74.6

13.O

2.O

1.2

gem-N3P3Br4F 2

72.0

10.5

4.4

0.9

cis-N3P3Br3F3

73.1

13.5

1.4

1.5

trans-N3P3Br3F3

73.6

13.4

1.8

2.1

gem-N3P3Br3F3

62.1

9.0

5.1

3.6

cis-N3P3Br2F 4

74.3

11.2

4.7

0.5

trans-N3P3Br2F 4

68.2

13.6

4.6

0.3

gem-N3P3Br2F4

75.1

7.5

5.9

1.6

N 3 P 3 B r 6 (6)

67.9

10.4

8.4

ii.i

N3P3CI 6 (6)

71.3

16.O

3.9

iO.O

N3P3F 6

29.4

33.8

3.6

2.4

(4)

I

I

I

I

I

I

I

I

2+

I

285

290

m/e

•

(o)

i

i

i

i

i

i

230

i

i 225

,,

m/e

Fig. 2. Examples of partially resolved metastable ions for (a) N3P3Br3F3 and (b) N3P3Br2F4. The interpretations below show the presence of all expected decompositions. Calculated

Relative

Intensity

Relativea Daughter Ion

m/e

Intensity

N3P3SIBr3F3+ (a) N3p3SIBr279BrF3+

0.125 0.375

NjPjSaBr79Br2F3+

0.375

N3P3SJBr2F3+ + SIBr NaP3StBr2F3+ + 79Br N3P381Br79BrF3+ + SlBr N3P3SIBr79BrF3 + + 79Br N3P379Br2F3~ + SiBr N3P379Br2F3+ + 79Br N3P3SIBrF4+ + SIBr N3P3SaBrF4+ + 79Br N3P379BrF4+ + S~Br N3P379BrF4+ + 79Br

288.1 289.4 286.2 287.5 284.2 285.5 228.6 229.8 226.7 227.9

0.125b 0.125 0.250~ 0.250b 0.125 0.125c 0.25d 0.25 0.25 0.25d

Parent Ion

N3p379Br3F3+ (b) N3P~81Br2F4+ N3p381Br79BrF4+

0.125 0.25 0.50

N3P379Br2F4+

0.25

a Calculated assuming 79 Br = 81 Br = 50% natural abundance. b~dpairs Of ions so designated were not resolved.

474

PHILIP CLARE and D. BRYAN SOWERBY Table 6. I.R. stretching frequencies (~,.) for bromofluorotriphosphazenes(cm-') Stoichiometry

ci___ss

trans

N3P3Br4F 2 a

geminal

1223

1237

1215

1205

(ii)

1253 N3P3Br3F3

1235

1233 1223

N3P3Br2F 4

Mixture

o f cis

1264

1262

1272

1247

1242

1238

and trans

isomers

Table 7. Summaryof metastable transitions~ m/e (calc)b

m/e (obs)

498.2

408.1

NsP379Br281Sr3F+ ÷ N3P379BrB1Br3F+ + 79Br

329.2

329.3

N~379Br281Sr2 F+ ÷ N?379BrS~r2F+

250.9

ca 250

207.1

ca 207

N~379Br28~r2F+ + N3P379Br8~rF+ + 79BrS~r

172.9

(very ~ak)

N~379Br28~rF + ÷ N3P379Br2F+ + 81Br

Assig~m-~nt N3P3_BrsF

i01.8

+ 79Br

N~379Br28~rF + + N3P379BrSiBrF+ + 79Br

N~379BrF + + N ~ 3 F+ + 79Br

i01.7

N~3Br4F 2 (non-gem)

(gem)

345.7

345.6

345.8

N3P379Br381BrF2+ ~ N3P379Br28~rF2 + + 79Br

267.2

267

266.5

N~379Br3F2 + + N~379Br2F2 + + 79Br

N3.Pgr3F3 (cls)

(trans) (gem)

286.2c 286.4

286.2

285.9

N~37%rS½r2e3+ +

211.7

211.8

211.6

N~379Br8~rF3 + ÷ N3P38~rF3 + + 79Br

211.8

201.1d ,fN2P28~rF3+ ~ ~28½~h ÷ + N

200.9 200.7

tN~38~r~3 ÷ ~ N2P28½~÷ +

176.8 ca 177 ca 177

N~381BrF3+ ÷ h~281BrF3+ + NP

-

136.1

136.1

136.2

229.8e 229.8

229.8

-

136.0

~3P37%rS½rz3 + . 8 ~ r

N~379BrF3 + ~ N ~ 3 +

+ 79Br

N~9~2~4 152.7 152.5

152.4

130.6

130.7

130.7

N~4

117.3

117.2 117.2

117.2

N{£4 ÷~{4

75.1

75.3

61.6

61.5

130.6

-

58.1

+ ~ N{2F4 + + NP

N~2+

tN£{3 +

58.2

-

79Br

N~38~rF4+ + N~3F4+ + 8~r

+

÷

~ h~2F2+ + h~N

61.6 J ~ N ~ 4 ÷ ~ ~ 2

61.4

b c d e

N3~37%ralBrF4 + . N938ISrF4 ÷ +

152.5

÷ ÷ ~2Pr2

~ 2 F÷ + = 2

N~3F4 + + ~ 3 + + ~ 4

In a l l c a s e s involving Br less a group of ions was Observed, see text. Calculated using the formula m* = ml2/mj. See Fig. 2a. Resolution insufficient to distinguish between alternatives. See Fig. 2b.

basis of their mass spectra alone, even though some success was obtained with the fluorophenylphosphazenes[9]. Several new processes have been observed in the decomposition of metastable ions to give neutral Br2, NP, N2P and NF4 fragments. Recent uses of phosphazenes as mass markers in organic mass spectrometry[16] and negative ion mass

spectrometry[17] may require a better understanding of fragmentation pathways if these uses are to be extended. REFERENCES 1. G. E. Coxon and D. B. Sowerby, J. Chem. Soc. (A) 1568 (1%7). 2. C. E. Brion and N. L. Paddock, J. Chem. Soc. (.4) 388 (1%8).

Mass spectra of the bromofluorocyclotriphosphazenes 3. C. D. Schmulbach, A. G. Cook and V. R. Miller, lnorg. Chem. 7, 2463 (1%8). 4. C. E. Brion and N. L. Paddock, J. Chem. Soc. (A) 392 (1%8). 5. T. Moeller and A. J. Wagner, J. Chem. Soc. (A) 5% (1971). 6. G. E. Coxon, T. F. Palmer and D. B. Sowerby, J. Chem. Soc. M) 358 (1%9). 7. B. Green, Ph.D. Thesis, University of Nottingham (1%9). 8. C. W. Alien, R. L. Dieck, P. Brown and T. Moeller, J. Chem. Soe. Dalton 173 (1978). 9. C. W. Allen and P. L. Toch, J. Chem. Soc. Dalton 1685 (1974). 10. G. Beech, Fortran in Chemistry. Wiley, London (1975).

475

I1. E. Steger and D. Klemm, J. lnorg. NucL Chem. 29, 1812 (1%7). 12. P. Clare, B. Green and D. B. Sowerby, J. Chem. Soc. Dalton 2374 (1972). 13. P. Clare and D. B. Sowerby, Inorganic Syntheses XVIll, 194 (1978). 14. S. Califano, J. Inorg. Nucl. Chem. 24, 483 (1%2). 15. J. Beynon and A. E. Fontaine, Z. Matur]orsch. 22A, 334 0%7). 16. K. L. Olsen, K. L. Reinhart and J. C. Cook Jr., Biomed. Mass Spectr. 4, 284 (1977). 17. Y. Hirata, K. Matsumoto and T. Takeuchi, Org. Mass Spectrom. 13, III (1978).