.
37B
Contribution from the Department of Chemistry,
Rice University, Houston, Texas 77001, U.S.A.
!
i
J
!
!
rnetabor
bora te i
isos truct
sizes of
High Pressure - High Temperature Syntheses.* 1.
The Preparation of Mercury Metab<?rate, Hg 40(B0 2 )6
Tabl e 1-
C. H. Chang and J. L. Margrave
Relat ive
Intensity
Metabora
Received July 20, 1967
Ma
S
f
I
I
I
i
Mercury meta borate has been synthesized ,in a tetrahedral anvil press at pressures of 24 to 40 kllobars and
temperatures from 700 to 940·C. The new me~abora!e,
isostructural with zinc metaborate,- has a cubIc .latt!ce
with a = 7.56±O.02 A. The tetrahedral coordmatzon
around boron in this compound is established by the
infrared absorption spectrum. The borate decomposes
in a stream of H2 at 360·C and both (1.-B 20 3and ~B2C?3 .
are formed during the decomposition . . Hg 40(B02J6 IS
more stable than mercuric oxide and decomposes at
565·C under vacuum.
Introduction
Anhydrous metal borates have received considerable ,
attention from chemists and many borates have been
In most borates, the boron atoms
reported to exist.
are in the centers of triangles, surrounded by three
equivalent oxygen atoms; but boron c~n h~ve coordination numbers 3 and 4 at the same hme m some
borates. There are only a few known. borates which
contain only tetrahedrally-coordinated borons.
In Group lIb, zinc has been reported to form the
meta borate, Zn.j0(B02)6, in which all of the boron
atoms have coordination number 4.
Zn40(B0 2)6
crystallizes in a cubic structure,I.2 with a = 7.49 ±
0.06 A. and space group Td 3-143m.
It has strong
absorption bands in the region 800 to 1100 cm.- I,
characteristic of 4-fold coordination of boron.3.4
Mercuric oxide, HgO , is stable only up to 400·Cs
at atmospheric pressure and no correspondmg mercury
meta borate has .been reported.
From a thermal
decomposition study of HgO,6 it has been found
possible to retain HgO even up to -1000·C under
high pressures. Furthermore, the increase;: in pressure
favor.s higher coordination numbers.7 It IS, theref~re,
reasonable to speculate that a mercury metaborate, 1S0structural with Zn 40(130 2)6, can be synthesized under
high pressures and high temperature.
(0) Extracted. In part . from the Ph. D . tbesls of C. H . Chang, submilled to the faculty of Rice University, May (1967) .
(1) P. Smith, S. Garcia-BIanco and L. Rlvolr, Z. Krist., 115, 460
(196 1).
.
.
(2) S. T erol, M. J. Ollero de la Candard, An. Soc. Esp. Flslca y
Oulm. , 57 (3 ). 343 ( 1961 ) .
(3) I. Krogh· Moe, Z. Krist .• 117, 116 (1962).
(4) C. E. Weir and R. A. Schroeder, ,. Research NBS, 68A, 465 (1964).
(5) D. Taylor , , . Chem. Soc., 1047 (1962) .
.
(6) C. H . Chang, Ph. D. Thesis, Rice University (1967).
(7) See for example . M. L. Huggins, p . 238, «Phase Transfonnallons
In Solid. >. edited by R. Smoluchoskl and J. E. l'4aycr,.1. Wllc)" Ncw
York.
Inorganica Chimica Acta
1:3
I
S
M
Experimental Section
S
W
S
W
89
•
The tetrahedral anvil was used for this study. The
pressure scale was calibrated at the Bil-I1, Bi ll ·1II and
M
TIll-ill transitions and temperatures were measured by
W
inserting a Pt-Pt + 10% Rh thermocouple into the
W
W
sample container through edges of the tetrahedron. 6
M
Boric oxide, B20 3, was obtained from U. S. Borax
VW
and dried at 170·C for more than 24 hours before being
W
used. AI: 1 molar mixture of B20 3 and reagent grade
W
W
yellow HgO (Merck and Co., Inc.) was prepared in the
dry box and transfered into the tetrahedral high , W
M
pressure cell, with BN as the container.
Pressures
M
used for the reaction ranged from 24 to 32 kilobars and
W
temperatures from 700 to BOO·C. After the mixture
S
M
was kept under high pressure and high temperature for
W
a period of 40 hours. the heating current was shut off
W
and the whole system was cooled by a blast of cool air
VW.
S
in .a few seconds . The pressure was then released
S
in one minute_ The yellow product obtained was then
S
heated in an H2 stream at 250·C for 5 hours to give a
S
black product, mercury metaborate.
When a 2: 1 a = 7_56 ;;1
molar mixture of purified BN powder (Fisher) and HgO
was heated at 40 kilobars and 940·C in a BN-containcr
with a graphite heater for 8 hours, the black mercury
2
metaborate was obtained after quenching.
1
Excess HgO was decomposed and removed in a Hr
100
·11
stream at 250·C to prevent the decomposition of
1
mercury metaborate and unreacted B20 3 was dissolved
10
in hot water. Liquid mercury formed in the reaction
5
was "distilled" in vacuum at 160·C and condensed at
20
3
liquid Nrtemperature.
1
4
4
Results and Discussion
5
Quenched mercury metaborate is black in color. The
Debye-Scherrer powder photograph was taken al
room temperature in a Norclco 114.6-m.m . camera
with Ni-filtcrcd CuK" radi ation at 35 kV and 18 rnA
for 4 hours. The diffraction pattern could be indexed
on a cubic lattice structure with a = 7.56 ± 0.02 A.
The Miller indices and relative intensities confirm thaI
merc.ury metaborate is indeed isostructural wi.th cu?ic
zinc metaborate. Table I shows the results of mdexlng
and a comparison with the diffraction pattern of zinc
(8) H. T. Hall, Rev. Sci. Inst., 29, 267 (1958).
(9) H. T . Hall. «High Pressure-Temperature Apparatus. in .M~talluri1
at High Pressures and High Temperatures>. edited by K. A. Gsche.dne r I..
M. T. Hepworth and N . A. D. Parlee. Cordon and Breach Scleocc
Publlshcn. Ncw York (1964).
December, 1967 .
... ,.
..
i
= 7.49 ±
' 5, stron g;
Ihis line dfrom P_ Sm
Kr;sla//ogr
The inf
were reco
:cchn ique,
meter. A
borate are
• borons are
between 1
coardinati
r
emistry,
.S. A.
379
f
:;etaborate.
The cell constant of the new mercury
"rate is quite reasonable when compared with that of
.JstructuraI zinc borate if one considers the relative
!:zes of the Hgii and Znll ions.
'Ible I. . X·ray DifIraction Patterns for Mercury and Zinc
·lctaborates
I_-------~-------------------------------!;dative
d
hkl
a
' :tensity
y. The
and
ured by
nto the
dron. 6
}. Borax
re being
nt grndl!
>d in thl!
al high
ressu rl!S
ars and
mi xture
lture for
shut ofT
cool air
released
as then
o give a
1·1\[
,.
Mercury Metaborate
5.30
110
3.08
211
2.39
310
222
2.18
2.02
321
400
1.890
1.781
411
1.671
332
1.483 b
510
521
1.380
440
. 1.341
1.302
530
611
1.233
541
1.171
622
1.146
631
1.121
721
1.030
730
0.994
732
0.962
811
0.933
653
0.906
830
0.882
751
0.870
832
0.859
0.848
840
0.838
900
0:8 18
920
0.800
922
0.783
852
0.775
9.52
Figure 1.
..
7.50
7.54
7.56
7.55
7.56
7.57
7.56
7.58 .
7.56
7.56
7.58
7.59
7.60
7.59
7.60
7.60
7.57
7.57
7.57
. 7.58
7.58
7.54
7.54
7.54
7.58
7.54
7.54
7.55
7.55
7.51
'
a 2: 1
ndHgO
ontainer
mercury
in a H 2t ion of
lissolvcd
reaction
ensed at
15
" 20
j 3
l 1
4
1
4
5
Zinc Metaborate c
5.43
3.76
3.05
2.36
2.16
1.995
1.868
1.761
110
200
211
310
222
321
400
411
1.672
420
1.593
1.525
1.465
1.364
332
422
510
521
7.68
7.52
7.47
7.46
7.48
7.47
7.47
7.47
7.48
7.47
7.47
7.47
7.47
.. \
\
7.49±0.06 A
\ strong-; -M--,-m-c-d-iu-m-;--W--,-w-c-ak-;--y-,-v-e-ry-.----b-F-o-lIo-w-,-·n-g
'~ li nc d·va lucs arc calcula tcd from CuK.,.
c Data are takcn
P. Smith, S. Garcia·Blanco and L. Rivoir, Zeilschrijt juer '
isla/lograp/Zie, 115, 460 (1961) .
!=
r.
The
aken nt
camera
18 mA
indexed
. 0.02 A.
firm that
th cubic
'ndexing
of zinc
.MClnll urgy
cheldncr I .•
ch SclcOl:O
1 .
The infrared absorption spectra of various borates
':re recorded, (see Figure 1), by using the KBr-disk
,:hnique, and a Beckman IR-9 Infrared Spectrophoto. ter. All of the absorption bands for mercury metalate are below -1200 cm.- I , indicating that the
.:rons are in 4-fold coordination. The strong bands
,ween 1000-1100 cm.- I are ch.a racteristie of 4-fold
ordination.
/
Infrared Spectrum of Mercury Metaborate.
The assignments of the observed bands in Table II,
given on the basis of Weir and Schroeder's assignment
for zinc metaborate! and assuming effective C 3v symmetry for the BO.-group using the terminology of
Herzberg,Io imply '116 "'" 200 ± 50 em. -I.
Table II. Infrared Absorption Spectra of Cubic Mercury and .
Zinc Metaborates
Zn,O(BO,). a
Hg,O(BO,),
WSh"
WSh
SVB
M
S
S
S
WSh
WSh
WSh
SB
M
SB
S
1200
1160
1082
1037
927
717
470
1200
1100
1075
1025
1000
910
700
( -400)
Assignment
b
'11,+'11,
('11,+ '11,), or ('11,+'11,)
'IIs(E)
'II,(A,)
'II,(A,)
'II,(E)
'II,(A,)
a Data from C. E. Weir and R. A. Schroeder, J. Research N.B.S .•
68A, 465 (1964).
b W, weak; M, medium; S, strong; Y,
very; B, broad; and Sh, shoulder.
One should note that as the unit cell dimension
increases, the absorption frequencies shift to lower
frequencies. The behavior parallels that found previously in isostructural divalent metal orthoborates 4 and
in isostructural carbonates and nifrates ll where the
shift was attributed to the effect of less anion repulsion
in the more loosely packed structure.
A purified sample was introduceci into a res istivelyheated alumina Knudsen cell in a Bendix Model
14-206a time-of-flight mass spectrometer; at 565°C, both
Hg + and Hg2+ were observed, due to the thermal
decomposition of the borate. Under hi gh vacuum in
the mass spectrometer, pure HgO decomposes at
270°C; 12 thus, the borate is more stable thermalIy than
the oxide.
When mercury myta borate was heated at 360°C for
5 hours in a stream of H 2, decomposition occurred and
the color changed from black to white. The x-ray diffraction pattern shown in Table III indicates the formation '
of both (1.- and B-B20 3. The formation of some dense
~~B203 from the tetrahedrally,coordinated Hg 40(B0 2 )6
is consistent with the observation ·of Dachille and Roy13
who calculated from infrared data on ()-B 20 3 that B
has an average coordination number of 3 .4, while in
(I.-B 20 3 the average coordination number is 3.2.
(10) G. Herzberg. Molecular Spectra and Molecular Slructure, II.
Infrared and Raman Speclra of Polyalomlc Molecule~, D. Van Nostrand
Co., Inc .• New York (1949) .
(II) C. E. Weir and E. R. Lippincott. / . Research NBS, 64A, 103
(1960) . .
(12) M. Onchl and I. Kusunoki, Nippon Kagaku Zcsshl, 85, 617 (1964).
(13) F. Dachllle and R. Roy. /. Am. Ceram. Soc., 42. 78 (1959).
Chang, Margrave
I· Highe
Pressure ~ High Temperature SY.n theses
4 '
JIBO
Table III.
X·ray DifTraction Pattern of Decomposed Mercury Metaborate
ci:....B,O,4
Relative
Intensity
d
Product
Relative
Intensity
d
.W
M
M
W
M
S
M
S
VW
W
VW '
W
VW
W
VW
VW
,I
6.10
33.8
3.42
3.20
2.85
2.78
2.23
2.10
2.06
1.98
1.92
1.82
1.79
1.71
1.40
1.20
d
VS
3.905
VS
2.865
M
1.987
W
1.789
20
20
50
50
50
.
f
\
1\(ixed chlol
~d both by~
halides ani
chloride an
case mixtur
liquid chn
magnetic re
that the
chloride re
compounds.
13HgO + 6BN
I
. ',.
,.,
,
•
"
~
' J
t
l'
•
!.
I
<I
.. of
J
:I
I
,
I
.
.
,
1
I
'
The prer
,
bromotriph
and Rome
reported by
isolated fro
however. OJ
infrared sp
products fr
Bo th Rotzs
lhat it was J
these syste
I members 0
could be sel
now report
. bromophos
alternative
PJN3CI~Br2
j
/
)
,l
~
,
"
" :
;
\
40 Kbar )
940·C, 10 hrs
A9knowledgments. This work was supported finan.
cially by the U. S. Army Research Office, Durham,
North Carolina. The authors wish to express their
appreciation to Dr. P. Ficalora for his technical assist·
ance.'
.
:,
I
2.08
"
,,,
)
6
Introducti(
30 Kbar ) yellow
H,
)
770·C,40hrs product 250°C,5hrs
,
3.18
Data taken from Dachille and Roy.'. Am. Ceram. Soc., 42, 78 (1959).
(2)
,
100
1.710
1.403
1.197
The preparation of cubic mercury metaborate has
been accomplished as follows:
2HgO + B20 J
6.04
1.920
1.822
Conclusions
(1)
20
2.78
. 2.23
2.096
90
70
100
b
H,BO, 4
Relative
Intensity
d
b
' 3.42
50
4 Data taken from ASTM cards.
f)-B,O,
Relative
Intensity
Experime
, I
,
Reaction
IlI10nium
b
~ \
>
I'
!method was
p~ntnc hlori
bromidl.! ( I
• "tion of th
t light petrol
!
129·131·.
Ihis solid b
,
.
....
.I (
l )
"
"
,.1 1
,
'"
. !
"
r
,
I
1: J
December, 1967
,
'.
(0) Pari IV.
Soc .• A , 1568
(1) R. Sch.
"
.JJI
(2) R. G.
J.
j'
,I't
I norganica Chimica Acla
"
t' •
;
,
"
I
I', '
1'.
Inorg . Nuclear
(3) E. Siege
(4) H. Rot
18. 687 (1966).
(5) G . E.
Chem. Leiters,
,. ,
I
,
_ _ _ _ _ _ 0....,.', -
-.