Molybdenum hexafluoride MoF6

NASA TECHNICAL TRANSLATION NASA TT F-12,702

CsJ

o

^ MOLYBDENUM HEXAFLUORIPE MoF

6
Maurice Carles

<

Translation of "L 'Hexaf luorure de Molybdene ^^o¥/^

Commissariat a L'Energie Ato/iique, Pierrelatte (France),
Report CEA-BIB^124, pp. 1-25, Sept, I968.

N

70-1157^

(ACCESSION NJW3ER)

45

1PASE61

-,.;ASA en OR TMX OR AJ NUMBtR) .**...«—. , ... , .^

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
Washington, D. C. 205^6 NOVEMBER, 1969

Starting with 19b8 C.E.A. repoil;^ scce classified according to the cate-
gories appearing in the classification schedule herein below; they ar0 avail-
able either as conplete sets or as partial sets on the basis of said
categories. i i

i

Those of our correspondents who systematically receive our reports by
way of exchange, and who are interested in this selective distribution, are
referred to circular letter CENS/DOC/67/4690, of December 20, 1967, mailed to
them, in which conditions of distribution were set forth.

We take this opportunity to remind you that, starting with 1968, CEA
reports are also available singly at the Direction de la Documentation
Francaise (French Bureau of Documents), 31, Quai Voltaire, Paris 7e.

Classification Schedule

1. Industrial Application of Isotopes and Radiation

2. Biology and Medicine

2.1 . General Biology

2.2. Nuclear Indicators in Biology

2.3. Industrial Medicine

2.^. Radiobiology and Radioagronomy

2.5- Use of Nuclear Techniques in Medicine

3. Chemistry

3.1. General Chemistry

3.2. Analytical Chemistry
3.3* Separation Procedures
3 . ^ . Radi ochemi s t ry

k. Studies in the Field of Space

5. Geophysics, Geolcqy, Mineralogy, and Meteorology

6. Metals, Ceramics and Other Materials

6.1. Manufacture, Properties and Structure of Materials

11

r"6.2. Effects of Radiation on Materialsj
6.3. Corrosion

7. Neutron Physics, Physics and Reaqtor Technology
^7.1. Neutron and Reactor Physics

7*2. Cooling, Protection Control and Safety

7.3. Structural Materials and Conventional Elements of Reactors

8. Physics

8. 1 . Accelerators

8.2. Electricity, Electronics, Radiation Detection

8.3. Plasma Physics

8.4. Physics of Condensed States of Matter

8.5. High-Energy Corpuscular Physics

8.6. Nuclear" Physics

8.7. Quantum Electronics, Lasers

9. Theoretical Physics and Mathematics

10. Protection and Control of Radiation, Treatment of Effluents
10,1 Health Protection

10.2. Radiation Control

10.3. Treatment of Effluents

11. Separation of Isotopes

12. Techniques

12.1. Mechanics of Fluids - Vacuum Techniques

12.2. Extreme Tenperature Techniques
12.3* Mechanics and Equipment

111

r

M3. Use and Development of Atomic Energy

[ 13*1* Centers of Nuclear Studies, Laboratories and Plants

, 13*2. Economic Studies, Program

t.J3.^» Miscellaneous (Documents, Management, Legislation, etc.)

The C.E.A. bibliographies, starting from 1968, are available at the
Documentation Francaise, Secretariat Generale du Gouvemement, Direction de
la Documentation, 31, quai Voltaire, Paris, Vlleme.

IV

NASA TT F- 12, 702
MOLYBDENUM HEXAFLUORI DE MoF^

M, Carles

ABSTRACT. MoF^ is generally prepared by direct synthesis

of its components. The molecule is entirely symmetrical in
structure; the metal atom is located in the center of an
octahedron, the apexes of which are occupied by fluorine
atoms. When cold, this compound appears as a crystallized
white solid body. It melts around 17.5*^C and boils around
35°C under air pressure. Very sensitive to hydrolysis and
reduction, molybdenum hexafluoride forms addition compounds
with sodium, potassium, rubidium, and cesium flour ides. It
also forms complex compounds with nitrile and nitrosyl
fluorides and nitrogen oxides. The reactivity of this
symmetrical molecule shows the nonsaturation properties of
molybdenum regarding coordination. Inversely, the high
inertia of sulfur and seleni-m hexafluoride molecules,
which are sirnilar, is to be noted.

1 . Introduction.

Molybdenum, of the 6a transition group, is one of the numerous metals or [V
metalloids that yield a volatile hexavalent compound with fluorine. Let us
mention among then MoF., WF , UF., PuF,, NpF., TeF^, R^F^* SF^, SeF^, OsF.,

etc.

Many of these compounds have a similar structure and very close chemical
properties. The strucutres of said formula XY^ molecules, and particularly

the structure of MoF^, have been studied by many investigators. Let us men-
tion here the remarkable synthesis of B. Weinstock [1] on the comparative prop-
erties of these different hexaf luorides .

Other studies have dealt with the complexes that said molecules are cap-
able of forming with certain fluorides, in particular MoF. , UF^, and PuF^,

these latter works being generally directed either to the sepatation of fission
products obtained by volatilization of irradiated fuels or to the purification
of UF^ by dry means.

^Numbers in the margin indicated pagination in the foreign text.

We express our appreciation to Mrs. Courtot and Mr. Simon, of the
Document Service, for their val^uable assistance in the preparation of this
paper.

2. Preparations

2.1. By Direct Action of Fluorine on the Metal

The preparation of molybdenum hexafluoride was described for the first
time by Ruff and collaborators [2, 3], who prepared it in 1907 by causing dry
fluorine at about 60° to react directly with the powdered metal placed in a
platinum tube.

Fluorine can be diluted in a nitrogen current [4].

The reaction can also be carried out at a higher temperature (31S°C) in
a nickel apparatus, where yield is then 78% [5].

Reaction can also take place in a copper tube [6]. The product obtain-
ed, collected in a dry and grease-free glass trap, is purified by vacuum dis-
tillation [6, 7]. It can be kept indefinitely in the glass vessel at room [Jl
temperature without formation of SiF - [6] .

2.2. By Action of Bromine and Chlorine Trifluoride on the Metal or the
Corresponding Oxide.

BrF reacts with the metal at 3S0°C to yield MoF [4], [8].

Nikolaev [9, 10] 'ises either gaseous chlorine trifluoride, C1F«, which

he causes to react with the metal powder in a quartz reactor or bromine tri-
fluoride, BrF^, which he causes to react with the oxide MoO-.

The use of BrF, is preferable in the latter case, because the reaction
of GIF with the oxide is more violent. The action of BrF- can be controlled
better.

2.3. MoFx is Also Obtained by the Action of Anhydrous Hydrofluoric Acid on
Molybdenum Pentachloride in the Presence of Air [?]•

l.k. By Action of Sulphur Tetraf 1 uoride on the Corresponding Acid

Excess SF. reacts with metallic oxides to yield a fluoride or an oxy-

fluoride by substitution of two atoms of fluorine for one atom of oxygen.
With temperatures ranging between 20 and 500^, depending on the case, MoF^

was obtained in this manner [11, 12].

2.5. MoF^ Has Been Prepared by Dl rect jFluorinatlon In a KF.2HF Electrolyte '
and Measured by Potentlometpy <{;l3il asi^wel 1 as According to the Reaction !

1

Mo ♦ 6NOF . 3 HF > MoF^ ♦ 6 NO ♦ 18 HP (M)

3. Methods of Analysis in the Gaseous Phase

3.1. Gas-Liquid Chromatography

This method enables us to measure gaseous MoF, in a mixture with another

o

gas. The coltuims used are polyfluoromonochlorethylene granules impregnated

with oil of the same nature. It is thus possible to measure MoF^ in UF^ [14]

or to measure MoF^ and W in CIF^ [15].

3.2. Infrared Spectrophotometry /3

As the MoF^ absorption spectrum presents very sensitive infrared absorp-
tion bands (reference given in the structure chapter) it is possible in many
cases, to measure traces of MoF^ in a gas with the aid of a spectrophotometer

covering the 2.5 - 20 micron range anH an analysis cell adapted to fluorinated
elements [16, 17].

3.3. M35S Spect rome t ry

It is possible to measure MoF^ traces in natural UF^ using a mass spect-
rometer with which the peaks corresponding to ions ^^oF^ and ^^^UFt are
compared.

An automatic apparatus based on this principle was developed by the Oak
Ridge gaseous diffusion plant [18].

3.^. Atomic Absorption

Gaseous uranium hexafluoride is sent to a premix heater and the molyb-
denum is determined from a standard curve obtained from synthetic mixtures of
uranium hexafluoride and molybdenum hexafluoride. The field of optimal con-
centration ranges between 10 and 50 ppm of molybdenum by weight in relation to
uranium. Ultimate detection is 2 ppm [94].

4. Molecular Structure

Numerous investigators have studied the structure of the regular octa-
hedral molecules of which molybdenum hexafluoride is a part. The metal atom
is situated in the center of an octahedron whose summits are occupied by
fluorine atoms. This structure is deduced from the study :)f the infrared

!

[-spectra of the Raman spectra, of electron diffraction, as well as from the
I nuclear magnetic resonance.

, '^.1. Infrared Spectrum of the Gas

Only the basic V^ and V. bands are active in the infrared. They are

observed in the following frequencies expressed in cm

-1

Bands

(1»)

.References
1 [20]

(ID

^

742

741

741

^4

U9

•

MO

ac4

^

040)

(234)

(I»0)

/4

Band V^ is inactive in the infrared. The values

given in this table were calculated. (See also
[22] and [23]).

k.2, Raman Spectra

The basic bands active in the Raman spectrum for the gas and the liquid
are:

Bands

(24) Uq.

References
(20) liq.

r

[21] gas

796 •

-I

741 liq.

741 ♦ 1

641 cm

645 Uq.

643 4^5

316 cm

-1

331 Uq.

uncertain

^.3. Absorption Spectrum in the Ultraviolet

The UV absorption spectrum were studied by Tanner and Duncan [24]; they
found the following a values for the absorption coefficient:

MoFr Pressure

6

Torr

o

en*

•

A

ssa

o.og

35 524

(2815)

7.07

6.8

41 484

a. 51

18

43 280

0.S4

57,6

48 356

0.34

61.4

48 852

O.M

68.4

48 358

0,S4

83.6

48 702

0.S4

127

50 226

0,34

176

50 761

(1870)

Jr.

Note: C(

Dmmas Indica

ite decimal points. 1

/5

The coefficient a is defined according to the following formula:

Tr. Note: Cornmas indicate decimal points •

La I / lo • a lo

where I/To is the luminous energy fraction transmitted by a cell, lo in length
expressed in cm, filled with gas at a pressure of 760 Torr measured at 0°C.

4.4. Nuclear Magnetic Resonance Speccrum

The high-resolution magnetic resonance spectra of the fluorines of the
liquid hexaf luorides , MoF^, WF^, UP., contain essentially a single line in

agreement with a regular octahedral structure. For MoF^ this is a weak and

distant field line at 56.4 MHz, with 15,910 ± 40 Hz in relation to the mono-

fluorotrichlorethane taken as reference, Rigny [25]. The relaxation time of
the molecule measured at 2.8, 16 and 56.4 MHz is equal to:

Tj • 0,85 ♦ 0,1 • kZrC (25)

Blinc and collaborators also studied the NMR spectra and the relaxation
time as a function of temperature and of the magnetic field [26J.

4.5. Atomic Distances

All of these studies agree in defining a regular octahedral structure of
Oh symmetry group--a structure common to numerous molecules of the XY^ formula.

The length of the metal-fluorine link is equal to:

Mo

r • l.MA^ (17) (18)
P • 1.840 A (84)

^.6. Force Constants Z^

The force constants calculated and expressed in millidynes/A are equal to:

k'

HM

rad

f

l» --!#••

rH

r"H

M# • - r'd#)

BM.

4.8875
4.71

O.IS38
0.844

0.1561

0.890

0.0810

-0. 104S

•0. 91118

0.4846

(89)
(90)

fd

Jr. Note: Commas indicate decimal points,
being the Mo-F fo?.'ce constant.

fdd and f'dd the adjacent and non-radjaccnt link interaction constants.

f0 the deformation constant.

The other constants being interaction link - link and link - deformation
constants.

See also [27] and [31] to [39].

For electron diffraction see [40].

For the Bastiansen-Morino effect see [41].

For the Jahn-Teller effect see [42, 73].

5. Physical Properties

When cold MoF^ is a snowy crystallized solid; it melts at 17.5** and boils
at 35'C at atmospheric pressure [43]. (Figure 1).

5.1. The physical constants are:

Units

Values

/7

References

Molecular Mass

Melting !>oint

6oi 1 ing Point at
760 mm Hg

''C
**C
"K
*C
*C

209,93

17.5
17
290,76
36,0
35"

(A6)

(^3) (^6) (47)
(23) (44) (45) (48)

(57)
(2) (44) (49) (48>

(45) (47)

Units

Values

Reference

Vapor Tension

for the sol id
For the liquid

p

in

nvn

Hg

t

•

in

»c

p

•
in

nun

Hg

T

•
in

»K

P

in

rum

Hg

T in "K

Densi ty of the sol id

Calculated by x

diffraction
Calculated by I ine

displacement

Density of the liquid
Measure by pycnotneter

Magnetic susceptibility

Solid transition
temperature

Valid from 291 to 320**K

2.88 at •t-S^'C (calculated)

3.27 at -36*C(calculated)
3.5I9 at 77. 1 6* K (measured)

3.5I9 at 77-l6°K(calculated)
3.393 at 173.83*K(measured)
3.393 ** 173.83°K(calculated)

2.5A4 at 294.33°K(measured)
2.5^^ at 29^. 33** K (calculated)

2.491 at 307.08*K(measured)

2.492 at 307.08*K(calcu>ated)

Xg - - (0,124 ± 0,005) 10-6

Xs = -26.10-6 e 25*C

263,6 (-9,6*'C)

263,48 1 0, 02

-9.8»

-8,7

Note: Commas indicate decimal points.

9^ M «0
Molar % UFg

Figure 1* MoF^ - UF^

Sol id-Liquid Equi 1 i-
brium Diagram.

^.2. Crystalline Structure

Molybdenum hexafluoride crystallizes at room temperature following the
body cente"«^ed cubic system; the lattice constant is equal to

/8

at + lO^^C
at + S'^C

a ■ 6.aS j:0«01 A (55)
a « 6.23 ^0.04 A 'SO)

Below the transition point (-9*6°) the orthorhombic structure is obtained.
The lattice constants are then

at -20°C

at -se'^c

a « 9.65 ^0,02 A
b - 6.68 ^C, 03 A
c 5.05 -«- 0,02 A

a - 9.61 ^0.02 A
b • 8.75 ♦0.02 A
c - 5.07 ^0.02 A

(55)

5.3. Thermodynanic Constants

Units

Values

Reference

Liquid formation enthalpy

at 298J6^!<, AH'f

Gas formation enthalpy,

H**f
F *ee liquid formation energy

at 298.16*'K; AGM
Standard enthropy of gas, S^

Standard enthropy of liquid, S*
Transition enthalpy o^ solid;

Triple point fusion heat
Vaporization heat, aH''293

Subl imation heat, AH'

298

Kcal/Mole

Kcal/iDole

Kcal/zDole
cal/Mole deg.

cal/Mole deg.

cal/Molft

cal/Mole

cal/MolA

cal/Mote

- 390.9

- 388.6

- 392.2

- 390.9

372.3- +0.022

- 363.1

- 361.2

83.77 + 0,1
79.76
80.60
79,7 +0.6

62.06 + 0.06
CO.! ;60.6

X933.2 + 2.0
1960

1034.2 + 1.0
1060

6000
6630 + 25

8500

Tr. Note: Cowrmas indicate decimal points.

The specific heats and thermodynamic functions of gaseous MoF^ at a

pressure of 1 atmosphere calculated at different temperatures yield the fol-
lowing values :

/9

TTC

^P' .1
cal. mole

caLmoto

IT. h:

Cld.lBOl* '^

. (c» - voir

250

26.425

76.4S4

4 201.6

59.648

273.15

27. 544

78.844

4 826.S

61.174

298.15

28.61C

81,303

5 528.8

62.760

300

28,683

81.481

5 581.8

62.875

350

30.415

86.039

7 061.1

65.864

400

31.743

90.190

11616.5

68.649

500

33.565

97.486

11 889

73.707

600

34. 700

103.714

15 307

78.202

700

35.441

109,122

18 816

82.241

800

35.948

113.890

32 387

85.905

900

36. 307

118.145

26 001

89.255

1 COO

36.571

121.985

29 646

92.340

Tr. Note: Conmds indicate decimal points.

See also [27] for temperatures comprised between 100 and 1,500°K, [51]
for temperatures comprised between 5 and 350^K as well as [60] to [63].

5.^. UF, - MoF, Liquid-Solid Equilibrium Diagram

The UF^ - MoF^ liquid-solid equilibrium diagram was studied by Trevorrow

and collaborators [55], Two solid solutions coexist at low temperatures, one
30% molar MoF^ in UF^ and the other 13% molar UF^ in MoF^, see Figure 1.

5.5. Solubility in Uranium Hexafluoride and Liquid Hydrofluoric Acid

Mears and collaborators studied the solubility of different fluorides in
liquid UF at 70**C [65] for purposes of recovering UF^ by distillation. The

solubility of MoF^ is more than 22.5% by weight at 38*^0. The only point of

liquid-vapor equilibrium established by Mears indicates that the behavior of
the solution is close to that of an ideal solution.

Trevorrow [68], on the other hand, finds a marked deviation from ideality /lO
but the four points established show a great dispersion of results.

Frlec and Hyman studied the solubility of different hexafluorides in
liquid hydrofluoric acid [68]. They obtained the following values at room
temperature

MoF^

WF,

VF^

Molea f 1 OOOgd'HF

1.50

3.14
0.49

Tr. Note: Commas
indicate decimal points

R«f.

(66)
(66)

(67)

r

MoF,

WF^

UF,

% in Weight
by HF

18,5+1
: 1 . 52 + 1.5
0,98 + 0. 5

Tr. Note: Commas
indicate decimal points

The$e authors also measured the
electric conductivity of these solutions
[66]. Nikolaev and collaborators also
studied said solubilities [97, 98] at

5.6. Recovery of \}F^ Polluted by Moly-

bdenum Hexafluoride by Distilla-
tion.

Several papers deal with the distil-
lation of UF, - MoF^ mixtures. In ad-
6 6

dition to the values of the separation
factor measured by Mears [65] and by
Trevorrow [68] we find a description of a
distilling column [70].

6.

Reference [69] also deals with the distillation of said mixtures.
Chemical Properties

As seen in the introduction, molybdenum hexafluoride presents numerous
chemical analogies with other hexafluorides, especially with those of tungsten
and uranium, which we shall examine.

6.1. Reactions by Addition of MoF,, WF^ and UF, to Certain Flourldes

The molybdenum, tupgsten and uranixim hexafluorides combine with certain
alkaline fluorides giving alkaline fluoro-molybdates, txmgstates and uranates
where the transition metal is in the oxidation six state. Said fluorine salts
yield by decomposition or reduction complexes in wliich the metal has a valence
5 or 4. The following are obtained, in particular with MoF^:

'from gaseous MoF — MoF + NaF yield Na MoF-, Na^MoFg [71, 72, 90, 91j .

M2M0F with (M = K, Rb, Cs) [8j are also obtained,
-in solution in IF^ £74]

. Rb MoF^
. CsMoF^ .

/ll

10

Several authors studied the dissociation pressure of the MoF, - NaF
complexes. They find:

at 100"

0.4 to 4.6 mm Hg

[78]

at 150"

8.4 to 27 mm Hg

[78]

at 200"

64 mm Hg

[78]

Katz obtained the following formulas:

-for the vapor tension of MoF^ of the equilibrium MoF + 2 NaF ^^ Na^MoF^

log P mm Hg = 8.27 ± 0.07 -(2.87 x 10^)/T„ I71].

-for the vapor tension of MoF, of the equilibrium Na^MoF^ + ^^^a ^'^
^"^ 2 NaMoF^ log P mm Hg = 7.29 ± 0.03 -(1,83 x lO"^) Tj^ I72j.

See also [79, 80] and [81] which deal with MoF^ - NaF complexes.

-while manganese fluoride, MnF^, reacts with UF, and WF , it does not
with MoF^ even at 330**C [75].

-a U. S. Patent [76] indicates that magnesium fluoride can selectively
absorb MoF. present in trace form in UF,, together with other volatile

fluorides. Another paper [77] indicates that said absorption is low at
250^ F.

-MoF. in solution in CIF- also forms complexes with cesium and ammonium
fluorides. Cs(MoFp and NH^(MoF^) [88] are obtained. UF^ and WF yield
analogous compounds .

-MoF., finally, forms an addition con5)ound with sulphur tetrafluoride, /12
SF . at 40®C. The solid obtained is intense yellow in color, it decomposes
at a higher temperature [89].

6.2. Reaction of MoF^, WF^ and UF^ with the Nitrile and Nitrosyl Fluorides
NO2F, NOF and Nitrogen Oxides

These three hexafluorides react with gaseous NO2F or NOF [81', 83, 85] to
yield solid addition compounds of the form

NO F • MF. where M can be Mo, W, U
x o

X can be equal to I or 2.

11

Infrared data indicates that said compounds are all in ion form.

NO + and MF -

-The gaseous nitric oxide, NO, reacts with MoF, and UF^ to yield the

o o

solid ion compounds [83, 84, 87].

NO* (MoF. ) " and NO* (UF^) ' .

O D

The same compounds are obtained by causing mitrosyl fluoride to react
with MoFg and UF^. On the other hand, no reaction is observed between WF and

NO.

-Gaseous nitrogen dioxide, NO2 reacts with UF, [82, 85] to yield the

solid confound NO-UF^, but no reaction occurs under the same conditions

with MoF, and WF,.
o o

Gaseous liquid peroxide NO reacts finally with MoF, and WF to give,

respectively, nitrosyl pentafluoromolybdate and pent afluorotungst ate, white
solid confounds [86].

2 MoFj ♦ 3 Nj O^ » 2NOM0OF5 * NOjF ♦ NOF + NjGj

Nj O^ Uqaid
2Wr,*3N,0, » '*,05W,Fjj*NO,F*Nj05

The second con^jound decomposes at between 100-200* to yield:

UFg reacts with liquid N^O^ yielding solid NOUF,

Gaseous N20^ excess reacts with MoF, and WF. to yield nitrile fluoride and the
nitrosyl salt [86] .

12

^^6 (g) * "^2^, (g, * N««^OF^ ^^, . NO^F ,^,

UF, likewiise reacts under the same conciltions to yield NOUF,.

-Nitrous oxide N^O yields no reaction with MoF^ , WF, and UF, [84, 87].

2 600

6.3. Reaction with Nitrosyl Chloride, NOCl

NOCl reacts with MoF, and UF, to yield the nitrosyl salt NOMoF or NOUF^,
on the other hand no reaction is observed with WF^ [82, 83].

NOCl , , * MF, . . » NOMF, , . * J CI

(g) 6 (g) 6 (g) 2 2 (g)

M being Mo or U.

6.4. Oxidation-Reduction Reaction

Molybdenum hexafluoride behaves like a fluorinating agent with numerous
halides. The following reactions are obtained [92, 93]

PF andiioF » MoF^andPFj

Cs^andMoFg ► M0F5. (CF,J, S^nd.s

WF^andMoFg ♦ MoF^and^Fj

It may thus be stated that molybdenum hexafluoride is an oxidizing agent
with respect to tungsten fluoride. It is known, moreover, that UF6 is in it-
self an oxidizing agent with respect to molybdenum sub -fluorides, sis we have
the reaction:

UFg tt M0F5 » MoKgandUf4 (93) (or UF- in excess of UF,)

The following classification is thus obtained:

'*" ^'^6 UF^ being the greatest oxidizing agent of the

'*■ ^°^\ three hexaf luorides .

3-. WFg

/14

13

H6.5. Exchange Reaction with Ha) ides

i-

' Molybaenum hexafluoride reacts with the following compounds to yield
either molybdenum pentafluoride or a molybdenum halogen fluoride [92],

PCI yields ^<^2^^3^6' ^^^5 ^^ ^^5 ^^^ MoCl^, PF- and PCK in excess

of MoF^)

AsCl- yields Mo.Xl^F^* and AsF.

SbCl^ yields Mo^Cl^F^, and SbCl2F^
TiCl^ yields ^'^2^^Z^6 ^^ ^^^4 ^^^ MoCl^, TiF^ and Cl^ in excess of

MoF^)

C CI4 yields Mo2Cl2F^, CCl^F, CCI2F2 and CCIF^

SiCl^ yields Mo2Cl2F^ and SiF^

BCl^ yields Mo2Cl2F^, BF^, BCIF2 and BCI2F (or MoCl^, BF^, BCIF2 and

BCl F in excess of MoF^)
PBr2 yields MoBr., PF«, PF. and Br2.

On the other hand MoF^ yields no reaction with the following compounds
[92, 95] ^

AsFg, SoF^, BiF .

6.6. Hydrolysis Reacti'^n

Pure water hydrolyzes molybdenum hexafluoride into molybdic and hydro-
fluoric acids without reduction (Ruff and Ascher) [2]. Nikolaev and collab-
orators studied this hydrolysis reaction [97, 98]

and determined the equilibrium constant at -5°C.

K • 3.10'

They get, under the same conditions, 6 x 10^ for WF^ and 9 x 10^ for UF,. IIL

Nikolaev and collaborators likewise studied the MoF^ - HF - H^O system
[100]; the following phases were brought out:

14

HjMoOjFj. 1.5 H,0
Hjf.oOjFj. H,0

"2 ^*^4

In thb MoF^ hydro fluorhydric acid sy start the following phases appear
[101]: ^

"2 ^^3^2 • ^2^

and 2 2 4

6.7- Relative Acidity of Molybdenum Hexafluoride

The relative acidity of an entire series of fluorides, wherexn MoF, and
WF^ has been detected by their solubility in HF and by the ability of their
solution to dissolve the fluorides classified in order of basicity [102].

6.8. Reduction of Molybdenum Hexafluoride

Ogle and Smith [103] studied the reduction of MoF^ at 25° by the follow-
ing gaseous con5)ounds:

HCl
HBr
HI
CO

The only solid product obtained is molybdenum pentafluoride MoF..

The reduction of MoF^ by hydrogen is used in the fabrication of metal

objects [104] and powders [115]. Deposition is effected in several stages at
temperatures ranging between 400 - 800^. A similar technique is used to
manufacture binary NK) - W alloys by reduction of a mixture of molybdenixm and
tungsten hexafluorides [105]. Metallic molybdenum can likewise be recovered
from MoF^ reduced on a heated metal plate [106], or even by electro-deposition

[107]. Corrosion of nickel and its alloys by MoF^ in a mixture with F^ has

been the object of a special study [99, 108].

MoF^ may also be reduced by carbon [109]. CF. is obtained above 1,000**, /16
as well as small amounts of heavier fluorocarbons. C^F. is obtained at the
electric arc temperature.

With CF2, MoF. is also reduced and yields CF. [110].

15

6.9. Different Uses of Molybdenum Hex^fluoride

MoF. is used as a molybdenum hallde ^in the manufacture of additives for

6 r

lubricatinig mineral oils [111> 112].

MoF^ is also used to accelerate, on the surface, the fluoridizing of
o

aluminum objects by fluorine [113].

FiMlly, MoF^ is used in the preparation of an additive to prevent pi?ra- •
site coloring of electrotypes used in lithography [114].

VII. Conclusions

Molybdenum hexafluoride is a volatile flouride with a symmetrical octa-
hedral structure like many of the XY^ formula molecules.

It crystallizes at room temperature in a body-centered cubic form. It
exhibits, moreover, a low -temperature transition point below which it crystall-
izes in the orthorhombic system.

Melting at 17.5 and boiling at 25*^0 at atmospheric pressure its vapors
hydrolize in contact with moist air. Like other hfexafluorides, it gives add-
itional compounds with sodium, potassium, rubidiim and cesium fluorides as
well as with mitrile or nitrosyl fluorides, and with nitrogen oxides. It also
gives place to different oxidation -reduction reactions with numerous halides.

The sensitivity of this symmetrical molecule to hydrolysis and to re-
duction thus reveals its non-saturated nature, from the point-of-view of the
coordination of metallic molybdenum whose greatest coordinance is S, which con-
trasts with the high inertia value of similar sulphur or selenii:an hexafluoride
molecules.

REFERENCES ZiZ.

i. Keinstock, B.: Chemiaal and Engineering NewOf Vol. 38, pp. 86-100, 1964.

2. Ruff, 0. and Eisner, Ber. . Vol. 40, p. 2926, 1907.

5. Ruff, 0. and As Cher: Z. Anox^, Chm, , Vol. 196, p. 418, 1931.

4. Emeleus, H. J. and Gutmann: J. Chem. Soo.j p. 7979, 1949.

5. Bernhardt, H. A.; H. W. Bishop and J. P. Brusie: TID Report No. 5^12,

pp. 153-154.

6. O'Donnell, T. A.: J. Chem. Soo.j pp. 4681-4682, 1956.

7. Ruff, 0. and Eisner: Z. Angew. Chem. ^ Vol. 20, p. 1217, 1307.

B. Cox, B., D. Sharpe and A. Sharpe: J. Chem. Soc, pp. 1242-1244, 1956.

9. Nikolaev, N. S.; Yu. A. Buslaev an-d A. A. Opalovskii: Zhur. Neorg. Kkim.,

Vol. 3, pp. 1731-1733, 1958.

10. Nikolaev, N. S. and V. F. Sukhoverkho v : BuL^ Inst. Politeb laei^ Vol. 3,

Nos. 1-2, pp. 61-66, 1957,

16

11. Du Pont de Nemours, (W. S. Smith): U. S, Patent No. 2.094,398^ Sept. 15, /1 8

1959.

12. Oppegard, A. L.] W. S. Smith; E. L. Muetterties and V. A. Engelhardt:

J. Amer. Chem. Soa,, Vol. 82, pp. 3835-3838, 1960.

13. Kreshkov, A. P.; V. A Drozdov; E. C. Vlasova; S. V. Vlasov and Yu. A.

Buslaev: Atom. Enex>g. (USSR) ^ Vol. 11, pp. 553-554, 1961.

14. Shinohara, H.; N. A»akura and S. Tsujimura: J. Nuol. Soi. Teahnol. Tokyo^

Vol. 3, No. 9, pp. 373-378. 1966.

15. Juvet, R. S. Jr. and R. L. Fisher: Analytical Chemistvy^ Vol. 37 (13),

pp. 1752-1755, 1965.

16. Noe, P.; D. Delafosse and J. Clement: Chimie Analytique^ Vol. 49, No. 5,

pp. 287-289, 1967.

17. Smith, D. F. : Second International Geneva Conference^ Vol. 28, pp. 130-

138, 1958.

18. Horton, S. C; S. R. Thomas and V. L. Warren: Report K 1453.

19. Gaunt, J.: Trans. Faraday Soo.^ Vol. 49, pp. 1122-1131, 1953.

20. Burke, T. G.; D. F. Smith and A. H. Nielsen: J. Chem. Phya.^ Vol. 20, No.

3, p. 447, 1952.

21. Claassen, H. H.; H. Selig and J. G. Malm: J. Chem. Phys.^ Vol. 36, No. 1,

pp. 2888-2890, 1962.

22. Hiraishi, J.; I. Nakagawa and T. Shimanouchi : Speotroohim. Acta. Vol. 20.

No. 5, pp. 819-828, 1954. i * "" ,

-23. Gaunt, J.: AERE Report C/I\.1023. j. j

24, Tanne;r, K. N. and A. B. F. t^^^ih':!'./. i4w. Chem. Sco.^ Vol. 73, pp. 1164- ;

116i7, 1951. ; I

25. Rignyi, P. and A. Demortier: .C..i?,_L4od^4.^ Sciences; ^°^* 26.^, Series B, /19

No. 25; pp. 1408-1410, 1966. andVbl. ^65, Series B, pp. 1058-J061,

1967. ;

•26. Blinc, R. ; E. Pirkmayer; J. Slivnik and I. Zupancic: J. Chem. Phys.^

Vol. 45, No. 5, pp. 1488-1495, 1966.

.27. Sundaram, S.: Z. Physik Chem. ^ Vol. 34, Nos. 1-4, pp. 225-232, 1962.

28. Gaunt, J.: Trans. Faraday Soc, Vol. 50, pp. 546-551, 1954.

29. Nagarajan, G. : Australian J. Chem.,, Vol. 16, No. 5, pp. 906-907, 1963. ;

30. Claassen, H. H.: J. Chem. Phys.j Vol. 30, No. 4, pp. 968-972, 1959.

31. Venkateswarlu, K. and S. Sundaram: Z. Physik Chem. ^ Vol. 9, pp. 174-179, i

1956.

32. Pistorij- , C.W.F.T.: J. Chem. Phys., Vol. 29, pp. 1328-1332, 1958. !

33. Califano, S.: Att. Accad Nazi. Lincei^ Rend. Classe Soi. Fis. Mat and Nat.

Vol. 25, pp. 284-291, 1958.

34. Linnett, J. W. and C.J.S.M. Siuipsoin: Tre6i.8. Faraday Soo.^ Vol. 55, pp.

857-866, 1959.
• 35. Meisingseth, E. and S. J. Cysin: Acta Chem. Scand. j Vol. 16, pp. 2452-
2453, 1962.

36. Nagarajan, G. : Bull. Soo. Chim. Beiges, Vol. 72, No. 7-8, pp. 537-559,

1963.

37. Nagarajan, G.: Bull. Soo., Chim. Beiges, Vol. 71, pp. 276-285, 1963.

ZS. Singh, 0. N. and D. K. Rai: Can. J. Phys., Vol. 43, No. 2, pp. 378-382,

1963.
39. Singh, R. B. and D. K. Rai: Can. J. Phys., Vol. 43, No. 1, pp. 167-169, /20

1965.
' 40. Brcune, H. and P. Pinnow: Z .Physik Chem., Vol. 35, p. 239, 1937.

17

4i. Nagarajaii, G.: Indian «/. Pux*e Appl. Phys.^ Vol. 4, No. 6, pp. 237-243,
1966.

42. Weinstock, B. and H. H. Claassen: J. Chem. Phys.^ Vol. 31, pp. 262-263,

1959.

43. Pascal (Mar.son Edit.); Novve^au Tv^ite ck Cliimle Mi^neralei Vol. XIV, p. 617.

44. Perry's OientiQal Engng. Handbook, pp. 3-45.

45. Simons, J. H.: Fluorine Chemistry, Vol. 1, p. 11.

46. Handbook of Chemistry and Physios, 48th Edition.

47. Vdovenko, V. M. : AEC Report 642.1 p. 648.

48. Kelly, C. S, Bur. Mines, Vol. 383, 1935.

49. Peterson, S. and R. G. Wymer: Chemistry in Nuclear Technology, p. 247.

50. Siegel, S. and D. A. Northrop: Inorganic Chemistry, Vol. 5, No. 12, pp.

2187-2188, 1966.

51. Osborne, D. W.; F. Schreiner; J. G. Malm; H. Selig and L. Rochester:

J, Chem, Phys,^ Vol. 44, No. 7, pp. 2802-2809, 1966.

52. Hankel - Klemm: Z. Anorg, Chem,, Vol. 222, p. 70, 1935.

53. Brady, A. P.; J. K. Clauss and 0. E. Myers: MdC Report TR 56.

54. Brady, A. P.; 0. E. Myers and J. K. Clauss: J. Phys. Chem., Vol. 64, /2_1_

pp. 588-594, 1960.

-55. Trevorrow, L. E.; M. J. Steindler;! D. V. Steidl and J. T. Savage': ANL j;

Report 7240, ^ ! ,. . ,

"-S6. Cady,; G. H. and G. B. Haxi-t^eiiJ^^em, Soc, pp. 1563-1574, 1961.
rS7. Brad/i, A. P.: NP Report 5809, ) ' '

1"58. flyers;, 0. E.: NP Report 5856, ..,•,, i '

'59. Settle, J. L.; H. Feder and W. N. Hubbard: J. Phys. Chem., Vol. ^5, No. 8,

^p. 1337-1340, 1961. •

60. Hargreaves, G. B. and G. h. Cady: NP Report 9270, Technical Repor^: No. 28,

And 29.

61. TID Report 14,392. .

62. Gerasimov, Ya. I.; A. N.. Krestovnikov and A. S. Shakhov: NASA TT-F 285

. Report,

63. Nagarajan, G.: Bull. Soc. Chim, Beiges, Vol. 71, No. 1, pp. 77-81, 1962.

64. Nazarian:, Ph, D, Thesis, California Institute of Technology, Pasadena,

California, 1957.

65. Mears, W. H.; R. V. Townend; R. D. Broadley; A. D. Turissini and R. F.

Stahl: Ind, Eng, Chem,, Vol. 50, pp. 1771-1773, 1958.

66. Frlec, B. and H. H. Hyman: Inorgani'j Chemistry, Vol. 6, No. 8, pp. 1596-

1598, 1967.

67. Rutledge, G. P.; R. L. Jarry and W. Davis: J, Phys. Chem,, Vol. 57,

p. 541, 1953.
6£ Trevorrow, L. : APL Report RCV SL 1094.

69. ANL, 5623 Report. fjyy

70. Mecham, W. ; R. Lumatainen; R. Kessie and L. Trevorrow: Progress in Nuolear^

Chemistry, Series III, Process Chemistry, Vol. 3, pp. 118-125. *.

71. Katz, S, -.Inorganic Chemistry, Vol. 3, No. 11, pp. 1598-1600, 1964.

72. Katz, S.: Inorganic Chemistry, Vol. 5, No. 4, pp. 666-668, 1966.

73. Weinstock, B.; H. H. Claassen and C. L. Chemick: J. Ch-im, Phys., Vol. 38,

pp. 1470-1475, 1963.

74. Hargreaves, G. B. and R. D. Peacock: J, Chem, Soc, pp. 4390-4391, 1958.

75. Reynes, J.: "Reactions of Uranium Tungsten and Molybdenum Hexafluorides

18

with Manganese Fluorides. Thesis, Lyon School of SaienoeSj No. 442,
June, 1967.

76. GoU'her, W. R. : Frenah Patent No. 1.S5S.220.

77. ORO Report 656,

78. Groves, F. R.: ORIiL EepoPt 3088,

79. Gathers, G. I.: Amer. Chem. Soq. Ahstr. of Papers :, No. 410, p. 30N, 1961.

80. Brookshank, W. A. Jr.; R. J. Carter and M. F. Osborne: CF Report 58-6-86.

81. ORNL Report 2614.

82. Geichman, J. R. ; L. R. Swaney and P. R. Ogle: GAT Report 971.

83. Geichman, J. R.; E. A. Smith and P. R. Ogle: Inorganio Chemistry ^ Vol. 2,

.No. 5, pp. 1012-1016, 1963.

84. Geichman, J. R.; E. A. Smith; S. S. Trond and P. R. Ogle: Inorganic /23

Chemistry; Vol. 1, No. 3, pp. 661-665, 1962. .

85. Geichman, J. R.; P. R. Ogle and L. R. Swaney: GAT Report 809.

86. Geichman, J. R.; E. A. Smith; L. R. Swaney and P. R. Ogle: GAT Report 970.

87. Ogle, P. R.; J. R. Geichman and S. S. Trond: GAT Report 552.

88. Nikolaev, N. S. and V. F. Siikhoverkhov: Doktady Akademii Ifauk^ SSSR,

Vol. 136, No. 3, pp. 621-623, 1961.

^9. Bartlett, N. and P. L. Robinson: J. Chem. Soa.^ pp. 3417-3425, 1961.
^90. Katz, S.: ORNL P Report 321 (CONF 653-4).
-91.. ORNL Report 3627^ p, 30. '
92.. O'Donnell, T. A. and D. F. Stewart: Inorganic Chemistry^ Vol. 5, No. 8,

pp. 1^34-1437, 1966.
"93. O'Donnell, T. A. and D. F. Stewart: Inorganio Chemistry^ Vol. S, No. 8,

pp. 1438-1441, 1966.

94. Sassoulas, R. and J. Serpinet: Spectrochimica Aota^ Vol. 23B, pp. 227-

234, 1968.

95. O'Donnell, T. A. and D. F. Stewart: J. Inorg. Nuol. Chem. , Vol. 26,

pp. 309-314, 1962.

96. Allied Chemical Corp., Neth. Appl.j No. 6,400.628, July 7, 1964.

97. Nikolaev, N. S.; S. V. Vlasov; Yu. A. Buslaev and A. A. Opalovskii: B'iz.

. Khim. Analiz. Akad. Nauk. SSSR, Sihirsk, Otd Inst. Neorgan. Khim.
Novosibirsk^ pp. 97-103, 1960.

98. Nikolaev, N. S.; S. V. Vlasov; Yu. A. Buslaev and A. A. Opalovskii: /24

Iznest. Sibir. Otdel. Akad. liauk. SSSR^ No. 10, pp. 47-56, 1960.

99. Jonke, A. A. and J.J. Barshusen: ANL Report 7125.

100. Nikolaev, N. S. and A. A. Opalovskii: Tkur. Neorg. Khim. ^ Vol. 4, pp.

1174-1183, 1959.

101. Nikolaev, N. S. and A. A. Opalovskii: Izvest. Sibir. Otdel. Akad. Nauk.

SSSR, No. 12, pp. 49-57, 1959.

102. Clifford, A. F.; H. C. Beachert and W. ii. Jack: J. Inorg. & Nuclear

Chem., Vol. 5, pp. 57-70, 1957.

103. Ogle, P. R. and E. A. Wmith: ^mr. Chem. Soo. Abstr. of Pqpers^ No. 141,

p. 20M, 1962.

104. Allied Chemical Corp.: Neth. Appl., No. 6,602.009, August 18j 1966.

105. Donaldson, J. G. and H. Kenworthy: BM-RI Report 6853,

106. Epshtein, A. L.; L. A. Izhvanov; Yu. M. Korolev; V. I. Stolyarov and

N. V. Fobedash: Russian Patent No, 180,800, March -21, 1966.

107. Ractor Mater. Fall., Vol. 9, pp. 197-202, 1966.

108. AKL Report 7122, pp. 42-49.

19

109. U. S. Patent No, 2.709.189.

110. Mall3r, W. : Inorganic Chemistry^ Vol. 2, p. 230, 1963.

HI. Fischer, K. A. and E. Brandt: German Patent^ No. 954.448^ Dec. 20, 1956.

112. Fischer, K. A.; E. Brandt and W. Hansen: German Patent No. 1.092.590,

Oct. 10, 1958.

113. Sukhoverkhov, V. F.; N. S. Nikolaev; I. F. Alenchikov and E. I. /25

Usherenko: Russian Patent No. 165.203^ 23 Sept. 1964.

114. Borchers, H. H.; E. Hausmann and D. Osswald: German Patent No. 1.165.617,

March 19, 1964.
US. Smiley, S. H.; D. C. Brater and H. L. Kaufman: KT. Report 6020.

Translated for the National Aeronautics and Space Administration under con-
tract No. NASw-1695 by Techtran Corporation, P.O. Box 729, Glen Burnie, MJ.
21061.

20