Some physical properties of d-transition metal fluorides in unusual oxidation states

Journal of Fluorine Chemistry, 25 (1984) 83-90

SOME

PHYSICAL

UNUSUAL

PROPERTIES

OXIDATION

J. GRANNEC,

Laboratoire

de

d-TRANSITION

METAL

FLUORIDES

IN

tours

la

STATES

A. TRESSAUD

and P. HAGENMULLER

Chimie

33405

Liberation,

OF

83

du

Talence

Solide Cedex

du

CNRS,

351,

de

(France).

SUMMARY

Unusual metal

oxidation

fluorides

states

high-pressure

elementary

temperature,

etc

physical

can

be obtained

by way of various fluorine,

. ..

properties

high

Relationships

are described

in d-transition

experimental

procedures:

pressure

between

in the solid

structures

in some selected

stz

and

examples.

INTRODUCTION

During important optical

recent

development

materials

of

with

synthesis

used

new

research

examples

conditions physical

and

some

organic

and

states,

applied

we have elements

phases

teams.

obtained

out the preparation

in various

fluorinating

Many

in this

fields

:

of molecules.

interest

carried

out

characterized

of this

We have

techniques,

relationships

has met with

etc. A number

of transition

states.

by various

characteristic

for

fundamental

oxidation

of fluorides

isolated

point

be

the

oxidation

chemistry

electrochemistry,

may also

Because

fluorine

due to new prospects

properties,

fluorides

unusual

years

of the by

type

have

been

selected

here

some

laboratory.

We shall

the stabilization between

structure

and

properties.

0022-l 139/84/$3.00

0 Elsevier Sequoia/Printed in The Netherlands

84 EXPERIMENTAL

PROCEDURE

preparative

Several

-

solid

palladium

-

state

sealed

-

syntheses

to 550°C

-

platinum

in a nickel

in

reactions

PROPERTIES

Ferromagnetic

Most

be

derived

often

from

required

is

point

- Ni

by

under

states

12 bar

type)

kbar

; up

fluorine

or under

300

(e.g. Rb2CuF6).

the II

neutron

to determine

cations.

ferromagnetic has a high

orbitals.

may

Ml*" This

= transition structure

distortion

diffraction

the exact

properties

additional

(with MI',

LiSbF 6 type. a rhombohedral

by

However

can

and

experiments

a are

space group [1,2 ] .

be associated In Ni1'Mn1"F6

with

ordering

for instance

-

fluoride with the highest Curie 6 2 IV configuration, whereas Mn 2geg The e orbitals are ferromagnetig superexchange involving the 2p

spin t

' configuration. a t3 2geg tally coupled thanks to fluorine

70

under

(e.g. NaPdF4)

a flow of fluorine

the

has

here

or

FLUORIDES

fluorides

the MI1 and M""

which

oxidation

in

Re03

ordering.

Ferromagnetic between

gold

behaviour

crystallize

cationic

under

(e.g. RhF5

OF M"M""F6

of M11M'1vF6

elements)

tubes

device

bombs

compounds

bar up to 500°C for high

ELECTRONIC

boat

in

;

thick-walled

for volatile

pressure

;

sealed

in a 'belt'-type

(e.g. Na2LiNiF6)

pressure

normal

(e.g. Rb2NaPdF6)

in

up to 600°C

:

have been used

at

reactions

tubes

reactions

pressure

methods

This

type

of

coupling,

which

is

enhanced

t

is -P-t*g interactions, 2g IIM'IVF responsible for the ferromagnetic behaviour of most M 6 compounds (Table I). It probably explains the existence of

R1'Ptn7F6inwhich with

a high

ferromagnetic

Pt+II

has

been

spin configuration

stabilized [4 ] .

for the

first

time

85 TABLE

I data of some M IIM,IVF 6 compounds

Magnetic Can-

NiMnF6 ZnMnF6

TC(io

Magnetization at 4.2K (ug)

39

9.5

8

6

4.5

2.9

2.3

2

2

2

Ref.

Piezoresistive

For M element

II

has

M'

IVF

Fig.

1

2

Pd2F6.

the

1.34 Such

1.4

1.0

3

3

in which

Between

type

of

gauges

STABILIZATION

be

1.5

1

3

3

4

material

copper

it appeared

25

with

kbar a strong dlog p _ dp - _. . 18

varies

from

on

the

basis

attributable

have been observed

of

to

an the

be

used

more We

for

measuring

or

systems.

IN SOME CRYOLITES

element

+I11

in

(M = Ni, Cu, Pd) compounds

STATE+111

or palladium.

and

is illustrated

2Pd'I'.

(A, B = alkali

d elements,

high pressure.

energy

largely

could

state

transition

a reversi-

down to 0.07 eV at 60 kbar

transitions

OF OXIDATION

COMPOUNDS

nickel,

1.7

interpreted

for high pressure

Altlough oxidation other

1.1

under

bar

MIIPdIVF 6 (M = Ni, Cu) or M11PtrVF6

A2BMF6

1.8

observed

pressure

can

hopping mechanism II + PdrV H+p. equilibrium : Pd t electronic

1

is

electron

This

16

the appropriate

the activation

eV at normal

calibrating

25

of the resistivity

resistivity

properties

Similar

PdPtF6 PtPtF,

8

(4d and 5d series)

is observed

dependence

Simultaneously,

kbar-'.

10

d orbitals

transition

for

of

10

6 fluorides

extended

The pressure

decrease

PdPdF6NiPtF6

behaviour

ble electronic

in

NiPdF6 CuEiF

CdMnF6

AND

; M = Ni, Cu, Pd)

can be easily difficult

succeeded

obtained

for

to stabilize

for

in preparing

phases

161.

86

300 K

P62F6 (1-M)

I

(212K)

I

I

J 1 : Piezoresistive

Fig. viour

of Pd2FS

kSSK)

/-’

H 1ooG

Fig. 2 : Variation

beha-

at 300 K.

of the

Cs2KBdFg ESR spectra with tenperature.

which

structures

are

separated

indeed

very

II

cations

palladium

of

which

there

until

Pd+III

yielding

as the MFf, octahedra

the

fluorides

crystallize

states

previously

mentioned.

elpasolites

doublet

ground

configuration.

was

recently

preferentially

oxidation

in

suitable,

Such

elpasolite-type.

are

by AFS octahedra.

some

reports

alkali

or

cryolite

involving

in one

two

structural

or the other. For

for

the

from each other

Table different type

in

crystallize

-

the at

(Table state Fig.

no

due

unequivocal

to

stable

least

a

under

has

been

II).

The

ESR

evidence

2 illustrates

dismutation mechanism 2 (t6 e ) and +IV(t2g 6, 2g g normal pressure - as

+I1

Pd+III

;

evidence

unambiguously spectra is

for

obtained

characterize

given Cs2KPdF6

of a

8

a

l 2geg transition a

87

TABLE

II

Ternary

fluorides

Ni+III,

Cu+III

of

cryolite

and

elpasolite

typescontaining

or Pd+III.

-

r-

Element

CU

Ni

Zryolite-type

Pd

INaZLiNiF6[7]

NaZLiCuF6 [7]

1Na3NiF6

Na3CuF6

[8]

K2NaNiF6[12]

[9]

Na3PdF6

[lo]

K2LiCuF6

[ll]

K2LiPdFs

K2NaCuF6

[13]

K2NaPdF6klistmcted)cl47

[lo]

Elpasolite-type Rb2XNiF6

[12]

Rb2NaCuF6[13]

Rb2NaPdF6(

’

) LlOl

Rb2KNiF6

[12]

Rb2KCuF6

[13]

Rb2KPdF6(

'

1[lo1

Cs2KNiF6

[12]

Cs2KCuF6

[15]

Cs2KPdF6(

”

,LlO]

Cs2RbCuF6 [153

Cs2RbPdF6

from

static

a

symmetry) in NaPdF4,

for

whose

A similar

t6 *gei low

variation might

of

be

2

high

t2geg

(de) presents

OF COBALT+IV state

Oxidation

the last elements with

the

Bonding that the

between

between synthesis

thanks

allows

1

high

difficult

here

The

and

the

to the strong

and the

Cs2MF6

the

phases

F2 HIGH to

range.

PRESSURE

stabilize

containing

isolated

from

the electrostatic alkali

a

for

it can be obtained

octahedra

completely

us to minimize

fluorine

of

However

;

[171 . On the

measurement

UNDER

The

transition

spin

in the whole

detected

temperature

elpasolite

in similar

is very

.

measurements.

are in progress

structure.

fluorine

[16j

increasing

OR COPPER+IV

+IV

are

element

which

with

) Do1

orthorhombic

has been

magnetic

of the 3d series.

K2PtC16-type

transition other,

by

spin

spin configuration

STABILIZATION

from KBrF4

constant low

a

an

’

has been obtained

configuration

on such behaviour

contrary,Cu+III 6

derives

low spin

Curie

to

investigations

(with Pd+III

temperature

the

due

one.

structure

Ni+III

at

effect Moreover

Jahn-Teller

to a dynamic

(

metal

the each

repulsions.

competes

with

transition

element

: therefore

is

greatly

facilitated

phases

ionic character

of the Cs-F bond.

88 Use necessary alkali

to

case

are

necessary

Co+IV

CLUSTERS

Platinum

clearly

shown

a

large

The

best

gnetic

0

and

fitting

constant

I

Fig.

share

the

range

calculated

units

is obtained

J/k = -8.3 K 1241

: Thermal

[22]

can

consist

of

. In a tetramer,

[23]

corners

in

c&-position.

susceptibility properties

124-26 ]

for

in

of 250 bar

RhF5-type

of

of a tetranuclear

data

(M =

60 bar

F2 pressures

of

two

magnetic

.

is shown

data

RuF5

cluster

Comparison in Fig.3

an intracluster

and

have OsF5

model

ove

between for RuF5.

antiferroma-

.

L

100 3

phases

under

PENTAFLUORIDES

magnetic

in terms

temperature

experimental

, but

tetrameric

and

that

can be interpreted

M2CuF6

absolutely

1211 and Rb2CuF6 [20] - Cs2CuF6 300 bar fluorine pressure.

groups

diffraction

and

is

be obtained

pentafluorides

M4F20

MF 6

M2CoF6

already

IN PLATINUM-METAL

metal

packed

octahedral Neutron

under

pressure

high

[18, 191

for K

only be isolated

closely

may

of Cs or Rb

MAGNETIC

the

synthesize

metal).

the

under

fluorine

of

variation

200 300 TIKI of the magnetic susceptibility

of

RuF5.

ACKNOWLEDGEMENT The authors J. DARRIET results.

are pleased

for their

helpful

to acknowledge contribution

Drs J.M. DANCE

and

in ESR and magnetic

89

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