ORNL-TM-1976.txt

 

 

OAK RIDGE NATIONAL LABORATORY
operated by

UNION CARBIDE CORPORATION
NUCLEAR DIVISION i
for the
U.S. ATOMIC ENERGY COMMISSION

ORNL- TM- 1976

 

A LITERATURE SURVEY OF THE FLUORIDES
AND OXYFLUORIDES OF MOLYBDENUM

C. F. Weaver
H. A. Friedman

NOTICE This document contains information of a preliminary noture
and was prepored primorily for internal use at the Oak Ridge National
Laboratory. It is subject to revision or correction and therefore does
not represent a final report.

BISTRIBUTION O Ui ~ocuME i Ul lE
 

 

 

 

LEGAL NOTICE

This report was prepared as an account of Government sponsored work. Neither the United States,

nor the Commission, nor any person acting on behalf of the Commission:

A. Mokes any worranty or representation, expressed or implied, with respect to the accuracy,
completeness, or usefuiness of the information contained in this report, or that the use of
any information, apparatus, method, or process disclosed in this report may not infringe
privately owned rights; or

B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of
any information, apparatus, method, or process disclosed in this report.

** includes any emplovea cr

As used in the above, “person acting on behalf of the Commission
contractor of the Con.mission, or employee of such contractor, tc the extent that such employee
or contractor of the Commission, or employee of such contracter prepares, disseminates, or
provides access to, ony information pursuant to his employment or contract with the Commission,

or his employment with such contractor.

 

 

 
ORNL-TM-1976

Contract No. W—-7405-eng-26

N
REACTOR CHEMISTRY DIVISIO

E SURVEY OF THE FLUORIDES

A LITERATUR NN

AND OXYFLUORIDES OF M

iedman
C. F. Weaver and H. A. Fried

LEGAL NOTICE

This report wag prepared as an acoount of Government sponsored work. Neither the United
States, nor the Commission, nor any person acting on behalf of the Commission:

A. Makes any warranty or representation, expressed or jimplied, with respect to the acey-
racy, completeness, or usefulness of the information contained in this report, or that the use
of any information, apparatus, method, or process disclosed in this report may not infringe
privately owned rights; or

B. Assumes any liabilities with respect to the use of, or for damages resulting from the
use of any information, apparatus, method, or process disclosed in this report,

As used in the above, “‘pergon acting on behalf of the Commisaion’ includes any em-
ployee or contractor of the Commission, or employee of auch contractor, to the extent that
such employee or contractor of the Commission, or employee of such contractor prepares,
disseminates, or provides access to, any information puresuant to his employment or coniract
with the Commission, or his employment with sych contractor,

OCTOBER 196/

RY
K RIDGE NATIONAL LABORATO
oA Oak Ridge, Te%nessee
operated Dby X
UNION CARBIDE CORPORATIO

for the
U.S. ATOMIC ENERGY COMMISSION
A LITERATURE SURVEY OF THE FLUORIDES
AND OXYFLUORIDES OF MOLYBDENUM
C. F. Weaver and H. A. Friedman

 

 

INTRODUCTION

Molybdenum is one of the more important fission products
with respect to the amount produced as well as its thermal
neutron absorption cross section. Consequently the chemical
behavior of molybdenum and its fluorides in molten salt reac-
tor fuels which are in contact with graphite and Hastelloy

is of interest.l’z’3

A research program to determine the
extent and rate of the pertinent reactions has recently been
initiated. The necessary literature review of the fluorides
and oxyfluorides of molybdenum is summarized in this report

for the convenience of others.

MoF,

 

Reported methods for the synthesis of MoF; are:
1. MoBr; + 3HF —MoF; + 3HBr at 600° in a Pt boat en-
closed in a Cu tube.4
2. 2Mo + 6HF §%§;gs 2MOF; + 3H,.°
MoF; + Mo — MoF; at 400°C in a Ni capsule.
4, MoF; + SbF; —MoF; + ?. The SbF; was carried in a
stream of A at 150 to 200°C.6
The product produced by method (1) has different prop-
erties than that of methods (3) and (4). The authors of ref-

erence 6 stated that products similar to that obtained by

6

method (1) were produced under hydrolyzing conditions. The
properties of both materials are described below. Although
it is possible for MoF; to exist in two crystalline forms,
it is more likely that the product described in reference 4
is an oxyfluoride.
Properties reported for "MoF;" from method (1) are:
non-hygroscopic, dark pink, shows no evidence of melting or
subliming at 800°C in the absence of air, is isostructural with
ReO; and, TaF,; (cubic, space group Pm3m, a = 3.8985 = 0.005)
at <800°, has a distorted structure at >800°7 and is reduced
by H, to Mo metal.4 The material produced by method (2) was
found to be cubic by x-~ray analysis5 and is probably the
same as the product of method (1),

Properties reported6 for MoF,; from methods (3) and (4)
are: variable color (ochre, light-green, gray, black, dark
red, yellowish tan), stable to at least 900° in Ni under its
own pressure, stable to 500° under vacuum, disproportionates
above 600° to form Mo metal and higher fluorides, density
4.64 £ 0.07 g/cm3® (measured), 4.50 g/cm® (x-ray) and VF,
type structure (space group R3c¢) determined by x-ray and
neutron diffraction. Other workers (ref. 8) have confirmed
that MoF; has a bimolecular rhombohedral unit cell with the
R3c space group. They have also shown that the compound
is antiferromaghetic below 185°K. The trace of a neutron
diffraction powder pattern taken at 4.2°K may be found in

this reference.

MoF,
Reported methods for synthesis of MoF, are:
_7E0 0
1. 2Mo(CO), + 3F, 15 2Mo,F, + 12CO; Mo, F, 170 MoF, +
MOF5 .9
2. Same as above except that the temperatures were -650

and 100°, respectively.lo

3. Mo(CO), + MoF, —MoF,; + MoF, + CO; volatile prod-
10,11
ucts removed by vacuum.
0
4. MoFy 129" woF, + MoF,.10»11

This compound has been described as light green,
9,10,11

9,11

non-volatile, and immediately hydrolyzable with H,0.°
Mo, F,

An olive green solid of this composition has been re-

ported,g’10 but the authors of reference 9 suggested that
it was a mixture rather than a single compound. It was pre-
_ _7E0
pared by the reactions: 4Mo(CO), + 9F, 83 to 7--5-*-2Mo_,‘F9 +
100-170°

24C0O and disproportionates by the reaction: Mo,F,
MoF, + MoF;.

MoFE

MoF; is a yellow hygroscopic substance which melts to

9,11 It fumes in air forming

form a yellow viscous liquid.
blue hydrolysis products, but is stable in air dried with
P,05. The viscosity and high Trouton constant of MoF; are
explained by assuming self ionization: 2MoF; —>M0F4+ + MOF;-Z

This compound has been synthesized by:

_ 0
Mo, Fy 0024707 wor, + Mor, .77 10
ZMoF, + PF, amb. ZMoFs + PF._f,.lz_14
Mo + F, —MoF, + '"residue", ''residue" distill MoF5.6’11
0 log%frtz

MO(CO)6 + MOF6 22” MOF5 + MOF4 + CO,

W(CO)6 + MOF6 —'MOFS + WF4 + CO.ll

0
Mo(CO) + F, ~&2 MoF, 1! + (2)

MOF, + Mo — MoFs . 1

WF, + 2MoF, 2"P" 2MoF, + WF,.>>
MoF; disproportionates irreversibly (>150°) below its
10,11

co ~ o Ut A W

Its vapor pressure
10

boiling point to form MoF, and MoF,.
in the range 70.0 to 160° is given by log P = 8.58 - 2772/T

Table I provides a summary of the properties of MoF;. MoF,
12

dissolves in MoF, to form a yellow solution. It is mono-
0
clinic (space group C2m) with a = 9.61 + 0.01A, b = 14.22 =
o 0
0.02A, ¢ = 5.16 + 0.01A, and B = 94°% 21' < 20'.11 An elec-

tron density projection on the 001 plane and a table of inter-

atomic distances may also be found in reference 11. MoF; will

reduce UF, to UF; in excess UF; and to UF, in excess M0F5.14
MMoFy

The compounds MM0F615 (M = Na, K, Rb, Cs) were formed

by: 2MoF, + 2MI ~60° I, + 2MMoF, and the impurities removed
by exposure to vacuum at 200°C. All of these compounds form
white crystals which are stable at 250°C, but attack glass
above 250°C and turn blue in moist air. KMoF, has a magnetic
moment of 1.24 Bohr magnetons at 25°C, the low value being
attributed to spin orbit coupling. The Na, Rb6 and Cs com-

pounds are cubic with a = 8.20, 5.11, and 5.29A, respectively.

0

The K compound is tetragonal with a = 10.17 and ¢ = 9.97A.15
0

The Mo-F distance in NaMoF, is 1.74 = 0.03A.11“'The Na com-

pound has been further studied (ref. 16) and found to be face
centered cubic, space group Fm3m (0}, No. 255). All of the

interatomic distances are listed in this report.

Kz MOOFE
The compound K,MoOF; has been reported15 to be a readily
hydrolyzed pale green solid.

MoFg

Molybdenum hexafluoride has been synthesized by:
1. F, + Mo 007200° yop, 4,10,12,17-21 4 py poat in Ni
or Cu. F, diluted with N,.

2. Mo + BrF; — MoF, + ?.22

3. Mo + CIF; — MoF, + ? in Ni boat.?’

4. MoCl, + HF — MoFg + ?.°9

The MoF, is purified by trap to trap distillation over
NaF.12:17:23 pne reactivity of MoF, with respect to fluor-
ination has been described13’14 as CrF; > UFg > MoF, > WF,.

18,24 and a colorless liquid.19’20’24’25
2427

It forms a white solid

with
13,28

The colorless gas consists of octahedral molecules

d?sp® hybrid bonds, has a bond strength of 105Kcal/mole

and has a second virial coefficient of -923 cm3/mole.21
The Mo-F bond has a reported length of 1.833.,29'311.8402\,27
1.8304,°2 and a stretching force constant of 5.00,3° 5.13,13
4.73, %23 5 087,25 5.080,%% 4.9972,3° 4.9875,3% (x 107"
dynes/cm). The physical, structural, and thermal properties
of MoF¢ are summarized in Tables II-VII. Traces of the

19,25,27 19,24,27 ultraviolet,25 and nuclear

Raman, infrared,
magnetic resonance37 spectra of MoF,; have been reported.

The values of Cp?, S°, H° - H), -(F° - HY)/T for gaseous
MoF, in the ideal state have been calculated from the funda-
mental frequencies over the temperature range 50-1600°K and
are tabulated in references 21, 24, 27, 31, and 38.

The values of Cp determined calorimetrically for solid
and liquid MoF, from 50 to 298.5%°K are tabulated in refer-
ence 39. The enthalpy and entropy of gaseous MoF; from 400
to 2000°K are tabulated40 and summarized as HT - H298.15 =
35.80T + 0.59 x 10 3T2+ 6.97 x 105T°! - 13,064 (298-2000°K,
gas)4o and Cp = 35.80 + 1.18 x 1073T - 6.97 x 105772.40
The functions Cp®, S8°, H° - H}, -(F° - H})/T are also tab-
ulated in reference 21 for solid 5-290.70°K, liquid 290.76
~ 350°K, and gas 50 - 1000°K. The values for the solid and
liquid are based on calorimetric data. Those for the gas
are based on a combination of calorimetric and spectroscopic

data.

The System MoF,-UF,

 

The system MoF,-UF, has a eutectic at 22 M/O UF; and

41

13.7°C, and incomplete solid solution. A phase diagram

of the system may be found in reference 41.

M, MoF,

The family of compounds M,MoFg (M = K, Rb, Cs) has been
reported.22 The authors of reference 22 tried but failed to

synthesize the sodium analog.

—
MoOF,
The compound M00F44’10’33’42 tends to hydrolyze in
air,33 but is stable in glass to at least 180°. 1Its vapor

pressure is given by the following relations:
log P = 8.716 - 2671/T for liquid, 95-185°C°
log P = 9.21 - 2854/T for solid 40—95°C10

Other physical and thermodynamic properties of this material

are summarized in Table VIII.

MOOZ FZ

33,42 sublimes with decomposition

33

The compound MoO,F,
at ~270°C42 and tends to hydrolyze in air.

Container Materials

 

The fluorides of molybdenum react readily with moisture.
Hence the systems in which they are handled must be scrupu-
lously dried by outgasing, flaming, or baking. The following
container materials have been used with molybdenum fluorides:

Material Reference

Cu 12,18-21

Ni 13,18-21,23,41

Pt 18,23

Monel 21,23,41

Brass 41

Glass, pyrex, quartz 12,13,17,18,20,24

Fluoethane 19

Kel-F tubes 13,14

Teflon 13,18,20,21,23,41
Fluorinated greases have been used,18 but packless all metal

values are to be preferreol.il'2 The use of NaF as an HF getter

will allow storage of MoF, in glass at room temperature for

18,20

many days without etching. In general, glass and plastic

type materials are useful to about 200°C above which the
metals are necessary.
TABLE I
Physical Properties of MoF,

M. P. 649,2P 7€
B. P. 213.69,9 211°
T. P. 67.0°, pressure very 1ow

d
Afivapadzation 12,370 cal/mole

d

Asvapaflzation 25.4 cal/mole/deg.
Vapor pressure ~2mm (at 659)€ ’
Density 3.44 (measured, solid)®
Density 3.61 (x-ray)c

ar. D. Peacock, "Two New Fluorides of
Molybdenum," Proc. Chem. Soc., 59 (1957).

by, E. Lavalle, R. M. Steele, M. K. Wilkinson

and H. L. Yakel, Jr., '"The Preparation and
Crystal Structure of Molybdenum (III) Fluoride,"
J. Am. Chem. Soc. 82, 2433~4 (1960).

 

Ca. J. Edwards, R. D. Peacock, and R. W. H. Small,
"The Preparation and Structure of Molybdenum
Pentafluoride,” J. Chem. Soc., 4486-91 (1962).

 

dGeorge H. Cady and George B. Hargreaves, "Vapor

Pressures of Some Fluorides and Oxyfluorides of
Molybdenum, Tungsten, Rhenium, and Osmium," J.
Chem. Soc., 1568-74 (1961).

 
TABLE II
Thermal and Structural Properties of MoF,
M. P. 17,2 17.4,°79 17.5,% 17.420.50¢t
B. P. 35,81C98 34 goch
T. P. 17.59C & 406.5mm, ’'%® 17.4 &
398. 1mm
. : s e,d h
Solid-Solid Transition -9.6, —8f7 & 104. 7mm,
-9,8=0.5
0 .
High Temperature Form bcec a = 6.23 1
Low Temperature Form at -20°C orthorhomicfc’,1
a = 9.65%.02A
b = 8.68+,03A
¢ = 5.05x.02A

20tto Ruff and Fritz Eisner, '"Uber die Darstellung und Eigen-
schaften von Fluoriden des Sechswertigen Molybdans," Berichte
40, 2926-35 (1907). -

bT. A. O'Donnell, "The Preparation and Manipulation of Moly-
bdenum Hexafluoride," J. Chem. Soc., 4681-2 (1956).

CN. S. Nikolaev and A. A. Opalovskii, "Solubility Isotherm
at 0° of the HF-MoF,-H,0 System,'" Russian J. Inorg. Chem. 4,
532-6 (1959).

dBernard Weinstock, ''Some Properties of the Hexafluoride Mole-
cules," Record Chem. Progress 23, 23-50 (1962).

€a. P. Brady, 0. E. Myers, and J. K. Clauss, '"Thermodynamic
Properties of High Fluorides. 1. The Heat Capacity, Entropy
and Heats of Transition of Molybdenum Hexafluoride and Niobium
Pentafluoride,” J. Phys. Chem. 64, 588-91 (1959).

L. E. Trevorrow, M. J. Steindler, D. V. Steidl, and J. T.
Savage, '"'Laboratory Investigations in Support of Fluid-Bed
Fluoride Volatility Processes. Part XIII. Condensed-Phase
Equilibria in the System Molybdenum Hexafluoride — Uranium
Hexafluoride,'" ANL-7240, August 1966.

€Von Otto Ruff and Ernst Ascher, "Einige Physikalsiche Kon-
stanten von SiF,, WF,, and MoF,," Zeitschrift fur anorgan-
ische und allgemeine Chemie. Band 196, 413-20 (1931).

hGeorge H. Cady and George B. Hargreaves, '""The Vapor Pressures
of Some Heavy Transition-metal Hexafluorides," J. Chem. Soc.,
1563-68 (1961). ““'

parrell. Osborne, Felix Schreiver, John G. Malm, Henry Selig,
and Leou Rochester, "Heat Capacity and Other Thermodynamic
Properties of MoF; Between 4° and 350°K," J. Chem. Physics
44, 2802-9 (1966). -

 

 

 

 

f

 

 

 

 
10

TABLE III

Density of MoF,

Density, High Temp. Solid 8°C 2.91 g/cc (measured)?

" " " " 0°C 2.88 " "

" " " " 10°C 2.88 " (x-ray)

" noooom " 278°K 2.88  0.04 (x-ray)?

" Low " " 237K 3.27 + 0.03 "

" Liquid 17.59¢c © 2.551 g/cm?

" " 19°C 2.543 "

" " 27°C 2.503 "

" " 34°C 2.470 "

" " 17.4°C d 2.551 "
d(Low Temp. Solid) for 77.16 to 237°K = 3,619 - 0.00 130T (g/cm’)b
d(High Temp. Solid) = 3.464 - 0.00210T (g/cm?®)
d(Liquid) for 294.33 to 344.63°K = 3,733 - 0.00404T (g/cm®) P
a

L. E. Trevorrow, M. J. Steindler, D. V. Steidl, and J. T. Savage,
"Laboratory Investigations in Support of Fluid-Bed Fluoride Volatility
Processes. Part XIII. Condensed-Phase Equilibria in the System Moly-
bdenum Hexafluoride and Uranium Hexafluoride,'" ANL-7240, August 1966.

bbarrell Osborne, Felix Schreiver, John G. Malm, Henry Selig and Leon

C

d

Rochester6 "Heat Capacity and Other Thermodynamic Properties of MoF,
Between 4° and 350°K,” J. Chem. Physics 44, 2802-9 (1966).

Yon Otto Ruff and Ernst Ascher, "Einige Physikalische Konstanten von
SiF,, WF,, and MoF,;," Zeitschrift fur anorganische und allgemeine Chemie.
Band 196, 413-20 (1931).

N. S. Nikolaev and A, A. Opalovskii, "Solubility Isotherm at 0° of the
HF-MoF;-H,0 System," Russian J. Inorg. Chem. 4, 532-6 (1959).
11

TABLE IV
Vapor Pressures of MoF,
Solid log P = :lfi%i;l + 8.880%
Liquid log P = 22229 4 7,407
Liquid log p = =2229:2 7.766"
17.4 to 34°C
Solid log P = 231%542, + 8.533P
_8.7 to 17.4°C
Solid log P = :E%EQ;E 5 10.216°
-60 to -8.7°C
. . _ C
Liquid 1og10Pmm = -2047.15/T L
-4.28004 1og10T
+ 20.19354

von Otto Ruff and Ernst Ascher, "Einige Physikalische Kon-
stanten von SiF,, WFy, and MoF,," Zeitschrift fur anorgan-
ische und allgemeine Chemie. Band 196, 413-20 (1931).

bGeorge H. Cady and George B. Hargreaves, ''The Vapor Pressures
of Some Heavy Transition-metal Hexafluorides," J. Chem. Soc.
1563-68 (1961).

CDarrell W. Osborne, Felix Schreiver, John G. Malm. Henry
Selig, and Leon Rochester, "Heat Capacity and Other Thermo-
dynamic Properties of MoF, Between 4% and 350°K," J. Chem.
Phys. 44, 2802-9 (1966). -

 

 

 

 
12

TABLE V
Thermodynamic Properties of MoF; For Change of State?

AH 8.30 K cal/mole”
AH_(>-8.7°C) 7.850 " ¢
AH_(<-8.7°C) 9.810 t ¢
(AHvap)g 11.1485 " i
AHV 6.36 "

A 6.940 . ¢
AHV(298.15°K) 6.630 = 0,025 " d
AH 1.059 + 0.010 " ©
AH, 0.920 . ¢
AH (290.7°K) 1.0342 + 0.001 " d
A 1.957 + 0.010 " ©
N 1.960 " ¢
AHt(263.489K) 1.9333 + 0.002 " d
ASV 22.5 cal/deg/moleC
aS (298.15%K) 22.24 = 0.08 " d
AS, 3.15 o :
AS 3.65 " 4
AS g 3.557 £ 0.10 "
oS 7.40 a z
A8, 7.72 "

s = sublimation v = vaporization

f = fusion t = solid state transition

bVon Otto Ruff and Ernst Ascher, "Einige Physikalische Kon-

stanten von SiF,, WF¢, and MoF,," Zeitschrift fur anorganische

 

und allgemeine Chemie. Band 196, 413-20 (1931).

cGeorge H. Cady and George B. Hargreaves, "The Vapor Pressures
of Some Heavy Transition-metal Hexafluorides," J. Chem. Soc.,
1563-68 (1961). -

dDarrell. Osborne, Felix Schreiver, John G. Malm, Henry Selig,
and Leon Rochester, "Heat Capacity and Other Themodynamic
Properties of MoF, Between 4° and 350°K," J. Chem. Phys. 44,
2802-9 (1966). T -

€a. p. Brady, 0. E. Myers and J. K. Clauss, "Thermodynamic
Properties of Higher Fluorides. 1. The Heat Capacity, Entropy,
and Heats of Transition of Molybdenum Hexafluoride, and Nio-
bium Pentafluoride,” J. Phys. Chem. 64, 588-91 (1959).

fBernard Weinstock, '"Some Properties of the Hexafluoride Mole-
cules," Record Chem. Progress 23, 23-50 (1962).

 

 

 

 

 
13

TABLE VI
Thermodynamic Properties of MoFg.

Formation Values.

AH® (25°C, gas) -372.3 % 0.2 K cal/mole?

AH  (25°C, gas™) ~382 " b

AH  (25°C, 1iq.) ~388.6 " b

AH? (25°C, gas) -370.2 % 0.23 oo ¢

AE® (25°C, gas) -371.1 + 0.2 g a

AF° (25°C, gas) -350.8 % 0.2 " a

AF  (25°C, 1liq.) -361.2 " b

AF® (25°C, gas) -351.9 + 0.23 i ¢

AS® (25°C, gas) - 72.13 cal/deg/molea

AS® (25°C, gas) - 68.41 *+ 0.19 " c

*At vapor pressure of liquid.

dJack L. Settle, Harold M. Feder and Ward N. Hubbard, "Fluorine
Bomb Calorimetry. 1I. The Heat of Formation of Molybdenum
Hexafluoride," J. Phys. Chem. 65, 1337-40 (1961).

bO. E. Myers and A. P. Brady, "ThermodYnamic Properties of

Higher Fluorides. 11. The Heats of Solution and of Formation
of Molybdenum Hexafluoride, Tungsten Hexafluoride and Niobium
Pentafluoride," J. Phys. Chem. 64, 591-4 (1960).

 

“Darrell Osborne, Felix Schreiver, John G. Malm, Henry Selig,
and Leon Rochester, '"Heat Capacity and Other Themodynamic
Properties of MoF, Between 4° and 350°K," J. Chem. Physics
44, 2802-9 (1966). -

 
Normal Frequencies of MoF,

Ref. a b

vy 741 736
Vv, 643 641
Vs 741 319
Vg 262 22 6%
Vg 312 619%
Vg 122% 328%

*Calculated
ADarrell Osborne,

and Leoun Rochester,

14

TABLE VII
(em 1)

c,d e, T
741 736
645 641
741 742
260 269"
322 319
234* 240%

g
736

641
742
269
319
240

h,J
741
643
741
264
306
190

k
738.5
643
741.5
264.5
320.5
237

*These frequencies are the most consis-
tent with calorimetric values.

Felix Schreiver,
"Heat Capacity and Other Themodynamic

John G. Malm,

Henry Selig,

Properties of MoF, Between 4° and 350°K," dJ. Chem. Physics

44, 2802-9 (1966).
K. N.Tanner and A.B.F. Duncan,

b

 

"Raman Effect and Ultraviolet

Spectra of Molybdenum and Tungsten Hexafluorides," J. Am.
Chem. Soc. 73, 1164-7 (1951). -

 

°“T. G. Burke, D. F. Smith, and A. H. Nielsen, "The Molecular

Structure of MoF,, WF.,
Spectra,” J. Chem. Phys. 20, 447-54 (1952).

d

 

 

K. Venkateswarln and S. Sundaram,
Molecules of the Type XY,," Z. Phys. Chem. (New
Series) 9, 174-9 (1956). -

€J. Gaunt, '"The Infra-red Spectra and Molecular Structure of
Some Group 6 Hexafluorides," Trans. Faraday Soc. 49, 1122-31

stants:

(1953).

and UF, from Infrared and Raman

"Evaluation of Force Con-

 

 

 

fS. Sundaram, ''Mean Amplitudes of Thermal Vibrations and
Thermodynamic Properties of Metal Hexafluorides," Z. Phys.
Chem. (New Series) 34, 225-32 (1962). -

£G. Nagarajan, '"'"Mean Amplitudes of Thermal Motion and Shrink-
ages of Chemical Bonds:

Pure Appl

. Phys. 4,

 

hHoward H.

Claasen,

237-4

Henry

 

Octahedral Hexafluorides," Indian J.
3. (1966).
Selig, and John G. Malm, "Vibrational

 

 

Spectra of MoF, and TcF,," J. Chem. Phys. 36, 2888-90 (1962).

Jg. Nagarajan, '"Potential Constants for the Hexafluorides of
Molybdenum and Rhenium," Aust. J. Chem. 16, 906-7 (1963).

kC.W.F.T. Pistorius, '"Potential Field and Force Constants of
Octahedral Molecules,” J. Chem. Phys. 29, 1328-32 (1958).

 

 

 

 
15

TABLE VIII

Physical and Thermodynamic Properties of MoOF,

M. P.

B. P.

T. P.

Color

AH fusion

AS fusion

AH vaporization
AH sublimation
AS vaporization

186.0°,% 180?04

97.2° and 28.8mm°
White®

1020 cal/mole®
2.768 cal/mole/degC
12,090 cal/molec
13,100 cal/mole®
26.3 cal/mole/degc

20tto Ruff and Fritz Eisner, ''Uber die Darstellung und
Eigenschaften von Fluoriden des Sechswertigen Molybdans,”
Berichte 40, 2926-35'(1907).

bJ. Gaunt, "The Force Constants and Bond Léngths of Some
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546-~51 (1954).

cGeorge H. Cady and George B. Hargreaves, '"Vapor Pressures
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Rhenium, and Osmium," J. Chem. Soc., 1568-74 (1961).

d

A, J. Edwards, R. D. Peacock, and R. W. H. Small, "The

Preparation and Structure of Molybdenum Pentafluoride,"

 
10.

11.

12.

16

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M. K. Wilkinson, E. O. Wollan, H. R. Child, and J. W,
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Howard H. Claassen, '"Force Constants of Metal Hexafluor-
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Otto Ruff and Fritz Eisner, '"Uber die Darstellung und
Eigenschaften von Fluoriden des sechswertigen Molybdans,"
Berichte 40, 2926-35 (1907).
e
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21

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