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Bromine AzideЧDetermination of the Molecular Structure by Electron Diffraction in the Gas Phase.

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2 a : A pale yellow solution of LiPHPh (1.260g. 10.860mmol. 2.1 equiv) in
250 mL ofether was chilled to -4O'C, and l(3.163 g, 5.172 mmol) was added
with stirring: the color changed t o deep burgundy and then t o yellow-gold over
a period of 10 min. The reaction mixture was stirred overnight at 25 'C, at
which point LiCl was removed by filtration through a bed ofcelite. The solvents
were removed in vacuo. and the yellow residue was washed with 100 mL of
pentane. collected by filtration. and dried in vacuo to yield 2 a (2.920g,
4.501 mmol. 87%) as a yellow powder. 2 a may be obtained readily in crystalline form bychillingaconcentratedethersolutiont o -4O'C. 2 b a n d 2c were
prepared similarly. except that they are more soluble than 2 a in pentane. and
therefore were crystallized from pentane at -40°C.
4b: Astirred solutionofZa(1.274 g. 1.964 mmol)in 15 mLofdichloromethane
was treated with pivalaldehyde (254 mg. 2.946 mmol). After 3 h the solvent was
removed in vacuo. the residue was extracted with lOmL of ether, and the
extract was filtered through a 1.5 cm plug of basic alumina in a 30 mL sintered
grass frif. The plug was then washed with 50 mL of additional ether. The ether
was removed from the filtrate in vacuo to give 4 b as a nonvolatile oil (291 mg,
1.633 inmol. 839'0) that was > 95% pure by N M R ('H. L3C,and "P).
Reveived: December 18. 1992 [Z 5762IEl
German version: Angetv. Clten?.1993, 105, 758
[11 R. Appel, Multiple Bonds und Low Coordination in Phosphorus Chemistry
(Eds.: M. Regitz, 0.J. Scherer), Thieme, Stuttgart, 1990, pp. 157-219.
[2] R. Appel, F. Knoll, 1. Ruppert, Angew. Chem. 1981. 93,771; A n g e x Chem.
fnt. Ed. Engl. 1981. 20, 731.
[3] G . Becker, 2. Anorg. Allg. Chem. 1976. 423, 242.
[4] T. A . van der Knaap,T. C. Klebach. F. Visser, F. Bickelhaupt. Tetrohedron
1984, 40. 765.
[5] F. Mathey, Arc. Chem. Rec.. 1992, 25, 90.
161 A. H. Cowley, A. R. Barron, Ace. Chem Res. 1988. 21, 81.
171 P. B. Hitchcock, M. E Lappert. W.-P. Leung. J. Chem. Soc. Chem. C o n mun. 1987, 1282.
181 R . Bohra. P. B. Hitchcock. M. F. Lappert, W:P. Leung, Poldiedron 1989.
[9] A. H. Cowley, B. Pellerin, J L. Atwood. S. G . Bott, J Am. Chrm. Soc.
1990. 112, 6734.
[lo] E. Niecke. J. Hein, M. Nieger, Orgunomerd1ic.s 1989,8,2290; this communication describes terminal aminophosphinidene complexes (M = Mo, W)
generated in situ.
[ l l ] F. Mathey, Angew. Chem. 1987,99,285: Angew. Chem. I n f .Ed. Engl. 1987.
26. 275.
1121 A discussion of electrophilic and nucleophilic complexes with terminal
phosphinidene ligands is given in ref. [I]. pp. 38-45.
[13] C C. Cummins, J. Lee, R. R. Schrock, W. M Davis, Angew Chem. 1992.
(04. 1510; Angcw. Chem. Inr. Ed. Engl. 1992. 31, 1501.
[14] C. C. Cummins. R. R. Schrock, W. M. Davis, Organomeiallics 1992, 11,
[15] F. A. Cotton, G . Wilkinson, AdvancedInorgunic Chemistry, 5th ed., Wiley.
New York, 1988, pp. 1318-1323.
[16] H. V. R. Dias, P. P. Power, J. Am. Chem. Sac. 1989, 111, 144.
[17] Z. Hou. D. W. Stephan, J Am. Chem. Sac. 1992, 114, 10088.
[18] A "P N M R shift of 6 =193.0 is given for a linear phosphinidene 191,
whereas bent phosphinidenes have 31P N M R signals in the range 6 =
666.1 to 799.5 [7,8].
1191 S M. Socol. S. Lacelle, J. G . Verkade, Inorg. Chem. 1987, 26, 3221.
[20] N M R und the Periodic Table (Eds.: R. K. Harris, B. E. Mann), Academic
Press. New York, 1978.
[21] Structure o f t b . Data were collected at -72 "Con an Enraf-Nonius CAD4 diffractometer with Mo,, radiation (graphite monochromator). A total
of 3900 reflections were collected to a 2 8 value of 54.9". An empirical
absorption correction was applied. The structure was solved by a combination of Patterson and difference Fourier techniques. Carbon and nitrogen
atoms were refined isotropically due to absorption problems; the heavier
atoms were refined anisotropicically. Due to disorder, the cyclohexyl moiety was modeled as a rigid group. The final cycle of full-matrix feastsquares refinement was based o n 2375 observed reflections ( I > 3.00o(l))
and 128 variable parameters and converged (largest parameter shift was
less than 0.01 times its esd) with R = 0.065 and R, = 0.064. A final difference Fourier map showed n o chemically significant features. Crystal data
are u = 19.754(2). h = 11.862(1). c = 12.993(1) A, V = 3044.4(X) A'% space
group Pnu 2 , , 2 = 4. Further details of the crystal structure investigation
may be obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technische Information mbH, D-W-7534 Eggenstein-Leopoldshafen 2 (FRG). on quoting the depository number
CSD-57068, the names of the authors, and the journal citation.
[22] L. Pauling. The Nature of the Chemical Bond, 3rd ed., Cornell University
Press. New York, 1960.
1231 A. van Asselt, B. J. Burger. V. C. Gibson, J. E. Bercaw, J Am. Chem. Sac.
1986. 108. 5347.
A I I ~ P IC'hem.
In[. Ed. Engl. 1993. 32. N o . 5
D. R. Neithamer, R. E. LaPointe. R. A. Wheeler, D S. Richeson. G. D.
Van Duyne, P. T. Wolczanski, J Am. Chem. Soc.1989. I J I , 9056.
G . Parkin. J. E. Bercaw, J; Am. Chem. SOC.1989. l J f 3 391.
R. R. Schrock, J; Am. Chem. Sue. 1976, 98. 5399.
G. C. Bazan, R R. Schrock, M. B. O'Regan. Orgunomrtullics 1991, 10.
An X-ray structural determination on [(N3N)TaCH3(q1-03SCF3)]
that the tertiary amine moiety is distant from Ta (2.536 8)compared with
the corresponding parameter for 2 b (2.36(2) A); C. C . Cummins. R R.
Schrock, W. M. Davis, unpublished results.
E. Niecke, E. Symalla. Chimia 1985, 39. 320.
R. Appel. J. Menzel, F. Knoch. P. Volz. 2. Anorg. Allg. Chrm. 1986, 534.
M. Yoshifuji, K . Toyota. N. Inamoto. Terruhedron Leu 1985, 26, 1727.
D. E. Bublitz. K.L. Rinehart, Jr., Org. React. 1969, 17, 1.
For a discussion of 1.3-diphosphetanes see ref. 111. p. 162, and references
For a discussion of [4 21 cycloadditions involving phosphaalkenes see
ref. [l], p. 163-166, and references therein
Ref. [17] gives evidence for a transient Zrl" phosphinidene complex.
L. Pauling, General Chemirfry, 3rd ed., Freeman, San Francisco. 1970,
p. 913.
M. W Schmidt, P. N. Truong, M. S. Gordon, J! Am. chem. So<. 1987. 109,
P. von R. Schleyer, D. Kost, J. Am. Chem. Sor. 1988, 110. 2105.
R . R. Schrock, Acr. Chem. Res. 1990, 23. 158.
Bromine Azide-Determination of the Molecular
Structure by Electron Diffraction
in the Gas Phase**
By Magdolna Hargittai,* Inis C. Tornieporth-Oetting.*
Thomas M . Klapotke,* Maria Kolonits, and Istvan Hargittai*
The experimental determination of the molecular structure of halogen azides XN, (X = F, CI, Br, I) is particularly
hindered, since all XN, compounds are explosive substances." -41 Nevertheless many azides have been structurally characterized: HN,[51 and FN,I6] by microwave (MW)
spectroscopy, F,CN, by a combined analysis of electron diffraction (ED) and MW spectro~copy['~
CIN, by MW spectroscopy!']
IN, by X-ray crystallography of single crystals,['] and H,CN, by ED.['*' Recently quantum mechanical
ab initio calculations have increased knowledge on the structures of halogen azides. For example ab initio calculations
were carried out at a high level for HN,,["I FN 3 , [ 7 . 1 1 1
GIN,,["] BrN,,["]
and I,N:.f121 Prior to this
work there were no reports of structural data for BrN, and
IN, determined by gas-phase experiments. Since, on the basis of available structural information for halogen azides, the
structure parameters for BrN, could be predicted with high
accuracy, the experimental determination of the molecular
structure was an interesting challenge.
['I Prof. Dr. M. Hargittai, M. Kolonits
Structural Chemistry Research Group
of the Hungarian Academy of Sciences,
Eotvos University, H-1431 Budapest, PO Box 117 (Hungary)
Priv.-Doz. Dr. T. M. Klapotke, Dr. I. C. Tornieporth-Oetting
Institut fur Anorganische und Analytische Chemie
der Technischeii Universitiit
Strasse des 17. Juni 135, D-W-1000 Berlin 12 (FRG)
Telefax: Int. code (30)314-21 106
Prof. Dr. I. Hargittai
Institute of General and Analytical Chemistry
Budapest Technical University
and Hungarian Academy of Sciences, H-1521 Budapest (Hungary)
[**I This research was supported by the Hungarian National Scientific Research Foundation (OTKA, No. 2103), the Fonds der Chemischen Industrie, the Deutsche Forschungsgemeinschaft (KL 636/2-2), the Bundesministerium fur Bildung und Wissenschaft (Graduiertenkolleg : Synthese
und Strukturaukllrung niedermolekularer Verbindungen) and the German-Hungarian (TU Berlin, T U Budapest) partnership.
(i? VCH Verlug.sgesell.schafimhH. W-6940 Weinheim. 1993
o570-0833193j0505-0759 3 10.00+ .25/0
The crucial problem was to produce the bromine azide
vapor and direct it into the electron diffraction apparatus
safely. Finally, BrN, was synthesized according to Equation (a) (see Experimental Procedure).
l h 20°C
+ NaN,
+ NaBr
The electron diffraction intensities from experiments for
the two camera distances used are shown in Figure 1. The
radial distribution obtained from the 50 cm camera distance
is shown in Figure 2.
Fig. 1. Electron diffraction intensities from the molecular beam of the gaseous
product from the reaction of bromine and sodium azide. Conditions: 60 kV
electrons, sample container at - 78 "C, nozzle at room temperature. The data,
which were determined with a camera distance of 50 cm, were best approximated by a model of 73% BrN, and 27% Br,. The data, which were determined
with a camera distance of 19 cm, could be approxlmated by bromine alone.
M(S) = molecular intensity, s = (4rr/h) sin(8/2) in A - '
Table 1. Bond lengths rg[A] and bond angles I"] of BrN, determined by electron
diffraction (ED) [a. b] and ab initio calculations for comparison [Ill.
1.180 k 0.003
0.102 [el
1.129 F 0.022
1.231 k 0.022
1.899 f 0.006
170.7 f 2.4
109.7 I 1.1
HF/6-31G(d,p) [c]
[a] The azide content of the sample was found to be 73 I 1 %, the Br-Br
distance in Br, was determined to be rs(Br-Br) = 2.284 f 0.005 A. [b] Estimated total errors [23], indicated as error limits, include
times the leastsquares standard deviation, a systematic error of 0.2%, and an uncertainty
introduced by a change of 0.044 8, (the difference between the HF and MP2 all
electron calculations, see ref. [I 11) in the assumed AN-N value. [c] All electron
H F MO calculation [ll]. [d] All electron MP2 MO calculation [ll].
[el Assumed from the MP2 calculation [l I].
configuration for which the Br-N bond lengths and the
mean N-N bond lengths, as well as the Br-N-N and the
N-N-N bond angles are determined with relatively high precision (Scheme 1). These structure parameters are consistent
with those of other halogen azides. Quite recently the structure of the isoelectronic BrNCO was determined by MW
spectroscopy.['41This contains a NCO chain, which is slightly bent away (ca. 8") from the Br atom (cf. BrN,, 9"). In
BrNCO the Br-N distance was found to be 1.862 A, just
slightly shorter than that in BrN, (1.899 A). The angle at the
bromine-carrying nitrogen atom, however, in BrNCO is significantly larger than the corresponding Br-N-N angle in
BrN, (117.99 vs. 109.7").
Scheme 1. Molecular structure of BrN,.
Fig. 2. Radial distributionfTr) obtained from the electron diffraction intensities of the data from the experiment with a camera distance of 50 cm (cf. Fig. 1).
The heights of vertical bars are roughly proportional to the relative weights of
the contributions of internuclear distances I to electron scattering.
The experiment with a camera distance of 50 cm was carried out with sufficient BrN, to elucidate its structure with
the assumption of some of the parameters. The two N-N
bond lengths could not be refined independently from one
another so their difference was constrained from the MP2
MO calculations.[' The mean amplitudes of vibration were
calculated by a normal coordinate analysis. The results of
the structural analysis are summarized in Table 1. Although
the structure parameters obtained experimentally generally
agree with those of the HF MO calculation, the distances
determined from the MP2 calculation seem to be too large.
This effect is not unexpected, because the equilibrium bond
length (the result of the computation, re) should always be
smaIler than the experimentally determined thermal average
bond length ( Y ~ ) . [ ' ~The
calculated difference of the two
N-N bond lengths is probably much better determined than
the individual bond lengths. The BrN, molecule has a trans
8 VCH Verlag.sgrselkchafimhH, W-6940 Wrinheim, 1993
Although halogen azides can be handled more readily in
solution, preparations for the pure compounds have been
described.[l5In a separate experiment we synthesized
BrN, on a preparative scale in order to grow single crystals
of BrN,.['91 However, this has so far been unsuccessful,
which is mainly due to the fact that BrN, always explodes
during the liquid/solid phase transition.
Experimental Procedure
At - 196°C bromine (0.25 g, 1.56 mmol) was placed in a glass tube (diameter
4 mm) and sodium a i d e (0.13 g, 2.00 mmol) was layered over it. The glass tube
was then warmed to 10 "C and placed into the container of the nozzle system
of the electron diffraction apparatus. A modification of a previously described
nozzle system built for very volatile substances was used 1201.The flow of vapor
was regulated by a needle valve. The sample container was first recooled to
- 196 "C and evacuated. The sample was then warmed to 0 "C and allowed to
react for 1 h at room temperature with'the needle valve closed. In the most
successful experiment (SO cm camera distance) the valve was gradually opened
during electron diffraction.
Setting the nozzle system to the 19 cm camera distance, we experienced that
only bromine escaped from the reaction mixture. In another experiment the
sample was allowed to warm to 0°C with the needle valve left open. After
20 minutes the electron diffraction patterns were recorded and they proved to
originate predominantly from bromine.
Caution: Bromine azide is explosive[21]and very sensitive to phase transitions
and pressure changes! I n one experiment the NaN, was compacted on the
S 10.00+ .2S/0
Angew. Chem. Ini. Ed. Engl. 1993, 32, No. 5
frozen Br, to make it more difficult for bromine to escape. This sample exploded and the (PTFE) container was blown apart. When the surface of the cold
trap was cleaned there was also a small explosion.
Received: December 23, 1992 [Z 5768 lE]
German version: Angew. Chem. 1993, 105, 773
[ l ] D. E. Milligan. M. E. Jacox, J. Chem. Phys. 1964, 40, 2461.
121 F Rdschig, Ber. Disrh. Chem. Ges. 1908, 41, 4194.
[3] D A. Spencer, J. Chem. Soc. 1925, 127, 217.
[4] A. Hantzsch. M. Schumann, Ber. Dlsch. Chem. Ges. 1900. 33, 522.
[5] B P. Winnewisser, J. Mol. Spec,frosc. 1980, 82, 220.
[6] D. Christen, H. G . Mack, G. Schatte, H. Willner. J. Am. Chem. Soc. 1988,
IIO. 707.
[7] K . 0. Christe. D. Christen, H. Oberhammer, C. J. Schack, Inorg. Chem.
1984. 23,4283.
[S] R . L. Cook. M. C. L. Gerry, J. Chem. Phys. 1970, 53, 2525.
[9] P. Buzek, T. M. Klapotke, P. von R. Schleyer, I. C. Tornieporth-Oetting,
P. S. White. Annex. Chem. 1993, 105. 289; Anzew. Chem. I n f . Ed. Engl.
1993, 32, 275.
D. W. W. Anderson. D. W. H. Rankin, A. Robertson, J. Mol. Strucf. 1972,
14. 385.
[ l l ] M . Otto. S. D. Lotz. G. Frenking. Inorg. Chem. 1992. 31. 3647.
I121 I . C . Tornieporth-Oettmg, P. Buzek. P. von R. Schleyer, T. M. Klapotke,
A n g w . Chem. 1992,104. 1391: Angew. Chem. Inr. Ed. Engl. 1992,31, 1338.
[13] M Hargittai. I. Hargittai, Int. J. Quant. Chem. 1992, 44, 1057.
[14] K . D. Hensel. M. E. Lam, M. C. L. Gerry, H. Willner, J Mol. Specfrosc.
1992. 151, 184.
[15] K Dehnicke. J. Inorg. Nucl. Chem. 1965, 27, 809.
[16] K . Dehnicke. Angen. Chem. 1967, 79, 253; Angew. Chem. Int. Ed. Engl.
1967. 6. 240.
[17] a j K . Dehnicke. Angeu. Chem. 1976. 88, 612; Angew. Chem. Inf. Ed. Engl.
1976. 15. 5 5 3 ; b j K. Dehnicke, Adv. Inorg. Chem. Rudiochem. 1983, 26,
I181 K. Dehnicke. Angew. Chem. 1979. 91, 527; Angen. Chem. Inf. Ed. Engl.
1979, IR. 500.
[19] IR (gas. 2 Tom, 20'C. 10 cm): 3170 w ( v , v2). 2282 m (2 v 2 ) , 2038 vs ( v , :
wN,. asym.). 1156s/1143 s ( v 2 : v-N,, sym.), 688 m/676m (v,; v-BrN),
460 wi445 w (>,+;6-N,).
[20] I. Hargittai, 1. Hemidi, J. Tremmel, Jenaer Rundschuu 1968, 13, 3. See also
J. Tremmel, I. Hargittai in SrereochemicalApplications of Gas-Phuse Election D!ffrurfion, Purr A . (Eds.: I . Hargittai, M. Hargittai), VCH, New
York. 1988. Chapter 6.
[21] AH:' (BrN,, gj = +90 k c a l m o l ~ ' ; estimated from: A@ (Br. g) =
26.8 kcalmol-I, A@ (N,, g) = f105.0 kcalmol-I 112,221 and BE (N(from:
Br) = 42 kcalmol-'
BE(N-Br) = 0.5[BE(N2)+ BE(Br,)]
2 3 . 3 ~ I~~ , ) ~BE
) . = bond energy.
[22] D. A. Johnson. Some Thermodynamic Aspects of Inorganic Chemisfry,
Cambridge University Press, Cambridge, 1982.
[23] M. Hargittai. I. Hargittai, J. Chem. Phys. 1973, 59, 2513.
Phosphane (PH,) in the Biosphere**
By Giinter Gassmunn* and Dietmar Glindemann
Synthetic phosphane (PH,) is an industrial product and
used in the form of metal phosphides as insecticides and as
dopant gas in electronic chip
Mineral phosphides are only known from meteorites in the form of
schreibersite.[21Biogenic phosphane has been detected and
described a few times since the beginning of this century.[31
These early reports of biogenic phosphane formation in Nature have been questioned until recently.141In 1988, Hungarian scientists succeeded in detecting biogenic phosphane in
[*I Dr. G. Gassmann, D. Glindemann
Biologische Anstalt Helgoland
Zentrale Hamburg
Notkestrasse 31. D-W-2000 Hamburg 52 (FRG)
[**I This work was supported in part by the Bundesministerium fur Forschung
und Technologie. -According to the IUPAC rules for nomenclature both
phosphine and phosphane is permitted for PH,; however, the second name
is recommended. See Nommclurure of Inorganic Chemistr-y (Ed.: G. J.
Leigh), Bkackwell Scientific Publ.. Oxford, 1990.
AngeM'. Chrm. Inr. Ed. Engl. 1993. 32, No. 5
sewage sludgeF5]and they predicted its ubiquitous occurrence in the hydrosphere. This prediction was confirmed
recently, when phosphane was detected in harbor sludge and
In these cases phosphane occurred together with methane, confirming reports from as early as
1929.['] This points to an obligatory correlation between
methanogenesis and the reduction of phosphate to phosphane in Nature. The global production of biogenic methane
is estimated to be 500 million metric tons per year,[*] of
which 100 million metric tons originate from bovine rumens.
If methanogenesis and the reduction of phosphate to phosphane are correlated as indicated above, measurable
amounts of phosphane must be expected in the biosphere.
To test the hypothesis that CH, and PH, production occurs together, we searched for phosphane in various sources
including the feces of cattle. In the fresh pats from grazing
cattle we detected phosphane in nanogram quantities. Phosphane was also found in the content of rumen, gut, and
manure of freshly slaughtered cattle. Interestingly, the phosphane concentration increases along the course of digestion,
with highest values in the excretion products (Table 1, entries 1-4).
Table 1. PH, in the digestive tract of cattle, and in the feces and manure of
cattle and swine.
rumen (of cattle)
gut (of cattle)
cow pat
cattle manure
colon (of swine)
manure (of swine)
2.9 i- 0.1
5.1 k1.1
9.0 f 0.1
13.9 i- 5.4
103.0 f 4.5
964.1 t 11.7
If measurable amounts of phosphane are present in the
intestinal tract of a herbivore, higher concentrations should
be expected in the gut content of an omnivore, even if less
methane will be formed. The higher phosphate contents of
the food could yield larger amounts of phosphane. Our results on the feces of pigs are listed in Table 1 (entries 5 and 6).
Humans consume phosphate-rich food like meat, sausage,
cheese spread, and soft drinks. Consequently, we expected to
find phosphane in their feces. We examined the feces of a
baby (milk diet), of an eight-month-old weaned toddler
(mixed diet), of an adult vegetarian, and of a married couple
(identical mixed diet), and found the phosphane quantities
given in Table 2.
Table 2. PH, content of the feces of man.
PH, [ w k g - ' l
baby (4.5 months old; milk diet)
toddler (8.5 months old; mixed diet)
married couple (husband: mixed diet)
married couple (wife; mixed diet)
not detectable
162.1 k11.7
12.7 k1.7
81.0 k17.3
81.2 k 16.4
Due to their phosphate-rich food omnivores are expected
to show a high phosphane production. Thus, we examined
two species of predatory fish, plaice and cod. In cod we
found an age-dependent phenomenon. While immature cod
showed no phosphane in their guts, mature cod had detecbble
phosphane concentrations in their intestinal tracts (Table 3 ;
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structure, molecular, azideчdetermination, diffraction, electro, bromine, gas, phase
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