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A reinvestigation of the structure of GeBr4 by electron diffraction
442 Jcmrnal a/ Malecular C! Elscvicr Scientific
Structure. Publishing
25 (1975) 442-444 Company. Amsterdam
- Printed
in The Ncthcrlands
Short communication
A REINVESTIGAIION
OF GeBr4 BY ELECTRON
OF THE STRUCTURE
DIFFRACTCON”
Ci. G. I3. SOUZA Instituta (Brusil)
de Quimicu.
Departauwuto
de Quinrica
I-irndrmentai,
Cidade
Unirersitariu.
.%a
Pa~tla
AND J. D. WIEXK”” Departrmwt
of Clrrr~ristr.~ Indiana
Uniccrsit_v
Blaatuirrgtot:,
Ittdiana
47401
(U.S. A.)
(Rcccivcd 31 May 1974)
The molecular
structure of germanium tetrabromide in the gas phase was first determined to be r(Ge-Br) 2.32 A and r(Br - - Br) = 3.79 A by Rouault [I ] using electron diffraction. Two years later, after reanalyzing the data using more elaborate techniques, hc reported (21 these parameters as r(Gc-Br) = 2.34&-O-04 A and r( Br - - Br) = 3.82 &0.06 A. Sh ortly thereafter, Lister and Sutton [3] also using gas electron ditTraction established the bonded distance in GcBr4 to bc 2.29+ 0.02 A. In addition to GeBr,, two other members of the germanium--bromine series have been investigated. Recently Beagley and coworkers [4] determined the Ge-Br bond length in GeH,Br, to be 2.277 f0.003 A using electron diffraction. Mays and Dailey [S, 61, using microwave substitution methods, established
r,(Ge-Br)
= 2.298~0.003
A in GeH,Br_
Thcrc is a trend in many systems for the M-X bond length to dccrcasc as additional halogen atoms are attached to the central atom [7, 81. Using the available internuclear distances, the germanium-bromine series is an apparent anomoly. However, since the most recent results for GeBr, were obtained more than thirty years ago using the visual method, it was decided to reinvestigate the molecular structure of germanium tetrabromide. In addition, because intramolecular multiple scattering effects have been shown to make significant contributions in heavy atom molecules [9], the possibility exists in GeBra that these effects, if neglected, could alter the resulting structural parameters. The sample was obtained from Alfa Inorganics with a cited purity of 99.9 “/ Since GeBr, hydrolyzes rapidly in the presence of water, cart was taken to handle __._... __ Contribution No. 2542 from the Chemical Laboratories of Indiana * To whom inquiries regarding this communication should be sent.
l l
University.
443 the sample only in a nitrogenous environment. The electron diffraction data were collected on the Indiana University apparatus at 40 kV with a sample tcmpcrature of 120°C. Three high quality plates were selected for microphotomctering for each camera length (12 and 29 cm). The data were treated using currently employed procedures [IO]. Mean amplitudes of vibration wcce calculated directly from experimentally observed frequencies using a stcpwise coupling method described by Hilderbrandt [I I]. The frequencies used came from a recent assignment by Clark and Rippon [12]. The model was constrained to tetrahedral symmetry throughout the refinement and the results are listed in Table 1. TABLE
I
LEASI’ squ~ftrs
PARA~WIEHS
FOR GcBrr
(Distances arc in r,(O) formalism .-_ --.-__
AT 120 “C
and unccrtaintics arc three times the standard deviation.) .-._ -._-. ._-. .- _ -.._.
Disfro~~cc (.f ) -.
--.
-...
.-._. -
Gc-Br Br . . Br
_ .-
--
-.
Arnplirrcde (.-I )
-...
-..
-
2.272 +0.001 3.705 5 0.002
.-
--
.-
_--.-
-_.
..-.--.
Culcrrlirred (.-I )
--..
.-
0.053 :i.O.OOI 0.131 &O.(x)3
.--
-.
__-.. ___
--. .-.
.-.
0.0528 0.1272
.._ .._.
-_
.-
-.
_-
.
When the three atom scattering terms of Wong and Bartcll [I31 were included in the analysis, the indices of resolution improved slightly and the R-factor for the intensity curve was reduced from 3.5 to 3.4 ‘% but the structural parameters did not change significantly. However, from the available data and the results of this study, it appears that the question regarding the anomalous behavior of the Ge-Br bond length in germanium tetrabromide has been eradicated.
ACKNOWI.EDGEMENT
The authors wish to thank Professor R. A. Bonham for the USCof his facilsupport from the Conselho ities. One of us (G.G.B.S.) wishes to acknowledge National dc Pesquisas, The Banco National de Pcsquisas, the Banco National para Disenvolvimcnto, the Atlantic Petroleum Company of Brazil, the Agency for the National Academy of Sciences, the National International Development, Science Foundation, the Anderson Foundation and the Atlantic Richfield Corporation of the United States for their support of this work.
REFERENCES I M. Rouault, C. R. Acad. Sci.. 206 (1938) 51. 2 M. Rouault. Ann. P/JYS. (Puris), I4 (1940) 78. 3 M. W. Listcr and L. E. Sutton, Trans. Faraday Sot.,
37 (1941)
393.
444 4 B. Beagley, D. P. Brown and J. M. Freeman, J. Mol. Sfrrrct., 18 (1973) 335. 5 A. H. Sharbaugh, B. S. Pritchard, V. G. Thomas, J. M. Mays and B. P. Dailey, PIrys. Ner.. 79 (1950) 189. 6 J. M. Mays and P. Dailey. J. Chew. Phys.. 20 (1952) 1695. 7 B. Bcaglcy, in L. E. Sutton (Ed.), Cltenc. Sot. S~~eciulisr Periudicul, Report 20 (1973). Chapters 2 and 3. 8 B. Beagley. D. P. Brown and J. M. Freeman. 1. Icfol. Sfnrcf.. 18 (1973) 337. 9 E. J. Jacob and L. S. Bartell. J. Chew. Phys., 53 (1970) 2231. IO R. L. Hildcrbrandt and J. D. Wiescr, J. C/tent. f%_vs.. 55 (1971) 4648. I I R. L. Hilderbtondt, /. 1+4o/. Strrtcr., I3 (1972) 33. 12 R. J. H. Clark and D. M. Rippon. C/tern. CoIttn!ctn., (1971) 1295. 13 T. C. Wong and L. S. Bartell, /. Clreru. Phys., 58 (1973) 5654.
Structure. Publishing
25 (1975) 442-444 Company. Amsterdam
- Printed
in The Ncthcrlands
Short communication
A REINVESTIGAIION
OF GeBr4 BY ELECTRON
OF THE STRUCTURE
DIFFRACTCON”
Ci. G. I3. SOUZA Instituta (Brusil)
de Quimicu.
Departauwuto
de Quinrica
I-irndrmentai,
Cidade
Unirersitariu.
.%a
Pa~tla
AND J. D. WIEXK”” Departrmwt
of Clrrr~ristr.~ Indiana
Uniccrsit_v
Blaatuirrgtot:,
Ittdiana
47401
(U.S. A.)
(Rcccivcd 31 May 1974)
The molecular
structure of germanium tetrabromide in the gas phase was first determined to be r(Ge-Br) 2.32 A and r(Br - - Br) = 3.79 A by Rouault [I ] using electron diffraction. Two years later, after reanalyzing the data using more elaborate techniques, hc reported (21 these parameters as r(Gc-Br) = 2.34&-O-04 A and r( Br - - Br) = 3.82 &0.06 A. Sh ortly thereafter, Lister and Sutton [3] also using gas electron ditTraction established the bonded distance in GcBr4 to bc 2.29+ 0.02 A. In addition to GeBr,, two other members of the germanium--bromine series have been investigated. Recently Beagley and coworkers [4] determined the Ge-Br bond length in GeH,Br, to be 2.277 f0.003 A using electron diffraction. Mays and Dailey [S, 61, using microwave substitution methods, established
r,(Ge-Br)
= 2.298~0.003
A in GeH,Br_
Thcrc is a trend in many systems for the M-X bond length to dccrcasc as additional halogen atoms are attached to the central atom [7, 81. Using the available internuclear distances, the germanium-bromine series is an apparent anomoly. However, since the most recent results for GeBr, were obtained more than thirty years ago using the visual method, it was decided to reinvestigate the molecular structure of germanium tetrabromide. In addition, because intramolecular multiple scattering effects have been shown to make significant contributions in heavy atom molecules [9], the possibility exists in GeBra that these effects, if neglected, could alter the resulting structural parameters. The sample was obtained from Alfa Inorganics with a cited purity of 99.9 “/ Since GeBr, hydrolyzes rapidly in the presence of water, cart was taken to handle __._... __ Contribution No. 2542 from the Chemical Laboratories of Indiana * To whom inquiries regarding this communication should be sent.
l l
University.
443 the sample only in a nitrogenous environment. The electron diffraction data were collected on the Indiana University apparatus at 40 kV with a sample tcmpcrature of 120°C. Three high quality plates were selected for microphotomctering for each camera length (12 and 29 cm). The data were treated using currently employed procedures [IO]. Mean amplitudes of vibration wcce calculated directly from experimentally observed frequencies using a stcpwise coupling method described by Hilderbrandt [I I]. The frequencies used came from a recent assignment by Clark and Rippon [12]. The model was constrained to tetrahedral symmetry throughout the refinement and the results are listed in Table 1. TABLE
I
LEASI’ squ~ftrs
PARA~WIEHS
FOR GcBrr
(Distances arc in r,(O) formalism .-_ --.-__
AT 120 “C
and unccrtaintics arc three times the standard deviation.) .-._ -._-. ._-. .- _ -.._.
Disfro~~cc (.f ) -.
--.
-...
.-._. -
Gc-Br Br . . Br
_ .-
--
-.
Arnplirrcde (.-I )
-...
-..
-
2.272 +0.001 3.705 5 0.002
.-
--
.-
_--.-
-_.
..-.--.
Culcrrlirred (.-I )
--..
.-
0.053 :i.O.OOI 0.131 &O.(x)3
.--
-.
__-.. ___
--. .-.
.-.
0.0528 0.1272
.._ .._.
-_
.-
-.
_-
.
When the three atom scattering terms of Wong and Bartcll [I31 were included in the analysis, the indices of resolution improved slightly and the R-factor for the intensity curve was reduced from 3.5 to 3.4 ‘% but the structural parameters did not change significantly. However, from the available data and the results of this study, it appears that the question regarding the anomalous behavior of the Ge-Br bond length in germanium tetrabromide has been eradicated.
ACKNOWI.EDGEMENT
The authors wish to thank Professor R. A. Bonham for the USCof his facilsupport from the Conselho ities. One of us (G.G.B.S.) wishes to acknowledge National dc Pesquisas, The Banco National de Pcsquisas, the Banco National para Disenvolvimcnto, the Atlantic Petroleum Company of Brazil, the Agency for the National Academy of Sciences, the National International Development, Science Foundation, the Anderson Foundation and the Atlantic Richfield Corporation of the United States for their support of this work.
REFERENCES I M. Rouault, C. R. Acad. Sci.. 206 (1938) 51. 2 M. Rouault. Ann. P/JYS. (Puris), I4 (1940) 78. 3 M. W. Listcr and L. E. Sutton, Trans. Faraday Sot.,
37 (1941)
393.
444 4 B. Beagley, D. P. Brown and J. M. Freeman, J. Mol. Sfrrrct., 18 (1973) 335. 5 A. H. Sharbaugh, B. S. Pritchard, V. G. Thomas, J. M. Mays and B. P. Dailey, PIrys. Ner.. 79 (1950) 189. 6 J. M. Mays and P. Dailey. J. Chew. Phys.. 20 (1952) 1695. 7 B. Bcaglcy, in L. E. Sutton (Ed.), Cltenc. Sot. S~~eciulisr Periudicul, Report 20 (1973). Chapters 2 and 3. 8 B. Beagley. D. P. Brown and J. M. Freeman. 1. Icfol. Sfnrcf.. 18 (1973) 337. 9 E. J. Jacob and L. S. Bartell. J. Chew. Phys., 53 (1970) 2231. IO R. L. Hildcrbrandt and J. D. Wiescr, J. C/tent. f%_vs.. 55 (1971) 4648. I I R. L. Hilderbtondt, /. 1+4o/. Strrtcr., I3 (1972) 33. 12 R. J. H. Clark and D. M. Rippon. C/tern. CoIttn!ctn., (1971) 1295. 13 T. C. Wong and L. S. Bartell, /. Clreru. Phys., 58 (1973) 5654.