Solvent electrical properties effects on oxidation potentials of [(dmit)2M] (NBu4)2; M=Ni, Pt

Synthetic Metals, 41--43 (1991) 1929-1937

1929

SOLVENT ELECTRICAL PROPERTIES EFFECTS ON OXIDATION POTENTIALS OF [(dmit)2Ml (NBu4_)2 ; M=Ni. Pt

A. SABIRI, M. EBEL, G. LE COUSTUMER and J.P. SAUVE Laboratoire des Composrs Thioorganiques -I.S.M.Ra -URA 480 -CNRS -Universit6 de CAEN 14000 Caen - (France).

ABSTRACT Electrochemical study of title compounds is achieved in various solvents. We noticed that the sequence of oxidation and reduction potential values is not the same for the nickel and platinum derivatives. This last sequence is also different from the sequence of dipole moment Ix, dielectric constant e, Kirkwood parameter [KP = (e -1)/(2e +1)] and electrostatic force (F=e*Ix) of the solvents. One other hand, there is a close correlation between the experimental and calculated oxidation potential values if we add to experimental E0 values of one solvent ( la0, ~ ) an increment relative to another studied solvent; increment values are defined by the relation: E = E 0 + a[1- (IX0/IX)a ] + b [1-(£0/e)15 ]

with ct=~=0.5

INTRODUCTION Organometallic compounds such as bis [2-thioxo-l,3 -dithiole-4,5-dithiolato] Metal(II) ammonium [[(dmit)2 M] (NBu4)2 ;M=Ni, Pt ] are precursors of materials [1] showing electrical properties, specially high conductivity and supraconductivity [2] They arise from the association of an electron donor with the electroactivated species of [(dmit)2 M] (NR4) ]2. So, their oxidation potential value is of a great importance to intend such materials. Then we can think that the solvent electrical properties in which this process occurs will have some influence about this potential. So the understanding of this influence allows to better control the parameters which govern the formation of complexes. Particularly the polar character of the solvent, precised by the dipole moment tx will induce or hinder the formation then the solvatation of the radical ion. The solvent dielectric properties, and hence the dielectric constant value e, show the ability of the solvent to separate the ions. Besides, 0379-6779/91/$3.50

@ Elsevier Sequoia/Printed in The Netherlands

1930

the electrochemical redox potential value may be used as a measure of the electron donor electronic affinity.

DISCUSSION We have noticed that the sequence of the oxidation and reduction potential values in various solvents is not the same for the Ni or Pt derivatives. So we have studied the influence of IX and e about these potentials. Recently F. Wudl and coll. [3J have tried to find a relationship between the oxidation potentials and a specific cation stabilization parameter for several electron donors within tetrathiafulvalene family:

TTF,

bis(ethylenedithio)tetrathiafulvalene

(BEDT-TTF)

and

bis(ethylenedioxy)tetrathiafulvalene (BEDO-TI'F). No simple relation between tx and £ and the oxidation potential values has been found by these authors. The same result is observed with the ET constant [3, 4a] and the Kirkwood parameter [KP = (e -1)/(2e +1)]. Nevertheless they discovered that the difference between the first and the second oxidation steps of TTF and BEDT-TTF and the difference of the two oxidation states of BEDO-TI'F was in good correlation. The ratio of these two differences remains constant for ten solvents. TABLE 1 Physical constants of solvents and variation of first oxidation (or reduction) potential values with solvent nature of [(dmit)2 M ] (NBu4)2 ; ( i M = Ni; 2 M = Pt ) complexes.

Solvent

Nature

CH3CN CH3COCH3 THF DMF C6HsCN C2HsCN

~(D)

3.44 2.86 1.75 3.86 4.05 4.02

e

37.5 20.7 7.58 3.70 25.2 27.2

KP

[(dmi02 Ni] (NBu4)2 1

[(dmit)2PI] (NBu4)2 2

ACV

ACV

CV

CV

EF

0.480 ! 1 2 9 0.465 59.2 0.407 13.27 0.480 '142.82 0.471 102.06 0.473 109.34

Ep(V)

Ea(V) Ec(V) Ep(V)

Ea(V)

-0.430 -0.460 -0.485 -0.450 -0.487 -0.477

-0.411 -0.438 -0.457 -0.427 -0.461 -0.450

-0.450 -0.459 -0.484 -0.449 -0.451 -0.448

-0.470 -0.500 -0.545 -0.490 -0.526 -0.520

-0.472 -0.485 .-0.515 -0.475 -0.480 -0.470

Ec -0.506 -0.520 -0.585 -0.510 -0.522 -0.508

The first oxidation or reduction potential values of the two complexes [[(dmit)2 Nil (NBu4)2] I and [[(dmit)2 Pt] (NBu4)2] 2 measured by ac voltammetry (ACV) or cyclic vohammetry (CV) are included in Table 1. In this last case Ea represents the first anodic oxidation potential value, Ec the corresponding reduction potential value whereas with ac voltammetry the step is noted Ep. All the potentials values were determined vs. Ag/AgNO3 (0.01 M in acetonitrile) using tetrabutylammonium tetrafluoroborate (0.1 M) as electrolyte.The sweep rate was 50 mV.s -1 (cyclic voltammetry) and 150 mV.min- 1 (ac voltammetry).

1931

Simply I..t and e variation shows a linear relation between Ep, Ea, Ec and the electrostatic force (EF) for the Pt complex, for all solvents except THF, specially for the reduction step (Figure 1). The correlation is quite correct for the high EF solvent values. E

(v)

E

-0~400

(V)

-0,400

I

2

3 4

5

r ,

-0,4.50

-o,5oo

~

'

2

i

r '

,

,

,

',

,

3

i

,

i

'

i i

~'

-0,450

4

, q q '

r

~

. ,

j j ~ ,

ir

6

!

~

i

Ii r

5

6

, ' ,

,

ii

-o,5oo

/ -0,550

-0,550

t l

P

0

l

, I p

-0,600

I

50 ELECTROSTATIC

I

I O0 FORCE

~

50

-0,60C~

I

0

(EF)

Figure 1. Plots o f Ep o , E a v , Ec u vs. electrostatic force o f Pt complex 2 in various solvents, S o l v e n t s : I,tetrahydrofurane ; 2 ,acetone ; 3,benzonitrile ; 4,propionitrile ; 5,acetonithle ; 6,dimethylformarrude

,

I'

50

'

II

I O0

ELECTROSTATIC

FORCE

J

150 (EF)

Figure 2. Plots of Ep o , Ea v , Ec o vs. electrostatic force o f Ni complex I in various solvents. Solvents." l,tetrahydrofurane ; 2 ,acetone ; 3,benzonitrile ;

4,propionitrile ; 5,acetonitrile ; 6,dimethylformamide

Figure 2 shows that the results are very different for the Ni complex. Good linear correlations exist between Ep, Ea, Ec values for the three nitrile solvents as for the three oxygenated solvents (DMF, THF, acetone) with different slope values, although the nitrile solvents show a similar behaviour. We noticed that DMF does not belong to this series despite the fact that dipole moment and dielectric constant values usually translate the main electrical properties of the solvents. Figure 3 displays a good correlation between the Ep, Ea, Ec potential values and the solvent Kirkwood parameter (KP) [4b] for the Pt complex. We noticed too that the THF figurative points are part of this relation. For the Ni complex (Figure 4), we find again two groups of three solvents. Although the THF KP value is fully different from those of the other solvents, there is a good correlation with acetone and DMF values. By means of dimensional analysis we tried to establish a relation to find a theoretical potential E for one solvent (I t and E are precised) by adding to a reference potential value E0, an increment relative to the influence of these parameters. E = E 0 + a[1-(l_t0/It) cz ] + b [ 1 - ( £ 0 / a ) [3 ]

with a=13=0.5

1932 It can be found for each of the six solvents used as reference, a couple of values (a, b) leading to correct results (Tables 2 and 3). The constant values a and b (Table 4) for each reference solvent have been obtained from a non linear regression calculation. E

(V)

E (V)

-0,a00

2 3a'56 i

I f

-0,450

I

-0,500

i

-0,40o

1

2 34 56

I I

i

I

i

i

I J

I

i

i

i

i i it

i f

i

I

.... ~!~V rlI' VI' i,

l

/ # //0

:

#

-0,450 -0,500

I

I

; /

i J

-0,550

/

I

I

I

I

t

-0,550

l ~

t,

I

I r

I,

I

-0,600

l ,400

,r 0,420

0,440

KIRKWOOD

0,460

PARAMETER

-0,600 0,480 (KP)

Figure 3. Plots ofEp o , Eav , Ec ca vs. Kirkwood parameterof Pt complex 2 in varioussolvents, Solvents: 1,tetrahydrofurane; 2 ,acetone ; 3,benzonitrile; 4,propionitrile ; 5,acetonitrile; 6,dimethylformamide

i 0,400

, 0,420

, 0,440

KIRKWOOD

0,460

PARAMETER

I I

, 0,480

(KP)"

Figure 4. Plots ofEp o , Ea v , Ec D vs. Kirkwood parameterof Ni complex 1 in varioussolvents. Solvents: l,tetrahydrofurane; 2 ,acetone ; 3,benzonilrile; 4,propionitrile ; 5,acetonitrile; 6,dimethylformamide

It clearly appears that for one reference solvent, the increment value will be much lower for platinum than for nickel compound because the constant values a and b are lower for platinum. This remark is more obvious for the oxidation (Ep, Ea) than for the reduction (Ec). Whereas the a and b values are of opposite signs for the nickel compound (a<0, b>0), a and b are positive for the platinum except for the reduction steps in acetone and benzonitrile (a<0). Tables 5,6 show the increment values. They are fully higher for nickel than platinum derivative. This large difference was not expected from the A variations between the external potentials induced by the solvent effects. So, these values A1/A2 are for I and 2 Ep : 57/45 ; Ea : 50/36 ; Ec : 75/79. Besides the increment average (Ecalc-E0) is of the same order of magnitude for the nickel (22.8 mV) and for the platinum compound (17.1mV). Although there is no positive rule for the nickel complex, generally the increments are of opposite signs, the global increment being a difference between two specific influences. The platinum increment is usually the addition of two lower increments with the same sign. So, it seems that the influence of the polarity of the solvent is more pronounced for the nickel complex 1 and the transformation possesses a higher ionic character than for platinum complex 2. The behaviour of 2 shows a covalence character in relation to the better electrical properties of this complex.

1933 TABLE 2 Oxidation potential values of [(dmit)z Ni] (NBu~)z 1 in various solvents

E calculated (V) with reference solvent :

Ei.exp(V)

CH~CN

CH3COCH ~

TIIF

DMF

CtHs CN

CzHs CN

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ECalc. ~SE ECalc.

CIIz,CN

8E

ECalc. 8E ECalc. 8E ECalc. 5E ECalc. 5E

Ep -0.430

-0.43(I

0

-0.442 12

-0.434

4

-0.433

3

-0.433

3 -0.434

4

Ea -0.411

-0.411

0

-0.423

12

-0.414

3 -0.412

1

-0.414

3 -0,414

3

Ec -0.470

-0.470

0

-0,475

5

-0.472

2 -0.474

4

-0.473

3 -0.472

2

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CH3COCH 3

Ec -0.460

-0.451

9

-0,460

0

-0.453

7

-0,453

7

-0.453

7 -0.453

7

Ha -0.438

-0.429

9

-0.438

0

-0.430

8 -0.430

8

-0.431

7 -0.431

7

Ec -0,500

-0.496

4

-0.500

0

-0.497

3 -0.498

2

-0.498

2 -0.498

2

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TIIF

Ep -0.485

-0.487

2

-0.492

7

-0.485

0

-0.487

2

-0.487

2 -0,487

2

Ea -0.457

-0.460

3

-0.465

8

-0.457

0

-0.459

2

-0.459

2 -0,459

2

Ec -0,545

-0.546

1

-0.547

2

-0.545

0

-0.545

0

-0.545

0 -0,546

0

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

DMF

Ep -0.450

-0,448

2

-0.456

6

-0.451

I

-0,450

0

-0.451

1 -0.450

0

Ha -0.427

-0.427

0

-0.434

7

-0,429

2

-0.427

0

-0.429

2 -0.428

1

Ec -0.490

-0.487

3

-(I.491

I

-0.489

1 -0.490

0

-0.489

1 -0.489

1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CtHsCN

Ep -0.487

-0.487

0

-0.486

1

-0.486

1 -0.486

1

-0.487

0 -0.484

0

Ha -0.461

-0.460

1

-0.458

3

-0,459

2 -0.458

3

-0.461

0 -0.456

5

Ec -0.526

-0.528

2

-(I.527

1

-0,527

1 -0.528

2

-0.526

0 -0.528

2

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CzHsCN

Ep -0.477

-0.479

2

-0.479

2

-0,479

2

-0.479

2

-0.480

3 -0.477

0

Ha -0.450

-0.453

3

-0.453

3

-0.453

3

-0.452

2

-0.454

4 -0,450

0

Ec -0,520

-0.519

1

-0.520

0

-0.519

1 -0.520

0

-0.518

2 -0.520

0

Deviation : 5E = I Ecalc-Ecxp I Arithmetic average of : ~Ep : 2.9 mV ~Ea : 3.3 mV t~Ec : 1.4 mV

1934 TABLE 3 Oxidation potential values of [(dmit), Pt] (NBth)2 2 in vmious solvents E calculatcd (V) with reference solvent : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Ei.exp(V)

CHjCN

C1t3COCI13

THF

DMF

C6 H5 C.N

C2H5 CN

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Ecalc. Ep CH3CN

6E

ECalc. ~SE

ECalc. 6E ECalc. /SE ECalc. 5E ECalc. 5t

-0.472

-0.472

0

-0.474

2

-0.473

1 -0.477

5

-0.473

1 -0.474

2

Ea -0.450

-0.450

0

-0.450

0

-0.451

1 -0.451

1

-0.450

0 -0.451

1

Ec -0.506

-0.506

0

-0.496

10

-0.505

1 -0.511

5

-0.503

3 -0.505

1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CH,COCH3

Ep -0.485

-0.484

1

-0.485

0

-0.485

0

-0.487

2

-0.485

0 -0.484

1

Ea -0.459

-0.459

0

-0.459

0

-0.459

0

-0.460

1

-0.459

0 -0.459

0

Ec -0.520

-0.527

7

-0.520

0

-0.527

7

-0.531 11

-0.526

6 -0.526

6

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

THF

Ep -0.515

-0.516

I

-0.515

0

-0.515

0

-0.514

1

-0.515

0 -0.515

0

Ea -0.484

-0.484

0

-0.484

0

-0.484

0

-0.483

1

-0.484

0 -0.484

0

Ec -0.585

-0.583

2

-0.577

8

-0.585

0

-0.581

4

-0.583

2 -0.583

2 5

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

DMF

Ep -0.475

-0.471

4

-0.472

3

-0.472

3

-0.475

0

-0.473

2 -0.470

Ea -0.449

-0.448

1

-0.448

1

-0.448

1 -0.449

0

-0.448

1 -0.447

2

Ec -0.510

-0.505

5

-0.500

10

-0.505

5

0

-0.505

5 -0.502

8 I0

-0.510

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C~}15 C N

Ep -0.480

-0.477

3

-0.476

4

-0.476

4

-0.478

2

-0.480

0 -0.470

Ea -0.451

-0.450

1

-0.450

1

-0.450

1 -0.450

1

-0.451

0 -0.448

3

EC -0.522

-0.517

5

-0.518

4

-0.518

4

2

-0.522

0 -0.510

12 0

-0.520

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C2HsCN

Ep -0.470

-0.476

6

-0.475

5

-0.475

5

-0.477

7

-0.478

8 -0.470

Ea -0.448

-0.450

2

-0.450

2

-0.450

2

-0.450

2

-0.450

2 -0.448

Ec -0.508

-0.515

7

-0.514

6

-0.515

7

-0.518 10

-0.518 I 0 - 0 . 5 0 8

0 0

Deviation : ~SE = [ Ecalc-Eexp [ Arithmetic average deviation : aEp : 2.4 mV ,~Ea : 0.8 mV 6Ec : 4.9 mV TABLE 4 a and b constant values of [( dmit )~ M] (NBth)2 complexes Nature

Calculated values with referencesolvent : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

of

CH3CN

CH~COCH3

THF

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

DMF

CaHsCN

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Ni

Pt

Ep Ea Ee

-309 -265 -293

148 127 158

-252 -202 -283

157 127 193

-401 -344 -389

Ep Ea

20 40

29 15

36 45

E¢

18

57

-52

31 19 110

42 59 13

.¶

CatlsCN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

302 257' 335

-270 -235 -258

139 121 149

-270 -240 -247

171 150 180

-250 -205 -261

155

54 30 139

38 43

17 11

1 32

42 20

69 51

11 11

25

49

-26

91

58

50

128 179

TABLE 5

mV

Ep -430 Ea -411 Ec -470

Solvent

CH3CN

0 0 0

0 0 0

~Sp_ ~SE

CH3CN

0 0 0

G -22 -18 -25

~Spt 40 33 50

~5~

CH3COCH3 Gp.

12 -115 12 -99 5-112

G 166 141 184

&~:

TMF

4 3 2

~ 16 14 15

~l.t

30 26 28

-51 -44 -55

9 9 4

0 0 0

0 0 0

0 0 0

-87 -75 -85

119 101 132

7 8 3

44 38 42

Ep -485 Ea -457 Ec -545

124 -181 107 -155 118 -193

2 3 1

70 -102 56 -83 79 -126

7 8 2

0 0 0

0 0 0

0 0 0

Ep -450 Ea -427 Ec -490

-17 -15 -16

-1 -1 -1

2 0 3

-35 -28 -39

40 32 49

6 -131 7 -112 1 -127

165 141 183

1 2 1

0 0 0

Ep -487 Ea -461 Ec -526

-24 -21 -23

-33 -28 -35

0 1 2

-40 -32 -45

15 12 18

1 -137 3 -118 1 -133

136 116 151

1 2 1

-6 -6 -6

C2HsCN

-23 -20 -22

-26 -22 -28

2 3 I

-39 -32 -44

20 16 25

2 -136 3 -117 0 -132

5 : Eexp - Ecalc. difference

~e : dielectric constant increment : b (1-~ v_.o/ e)

Gp_: dipole moment increment : a (1-~/ ~o/~)

Ep -477 Ea -450 Ec -520

143 121 158

2 3 1

-5 -5 -5

........................................................................................................................................................................

C6HsCN

........................................................................................................................................................................

DMF

-47 -41 -50

1 1 1

~

DMF

-23 -20 -25

-29 -26 -32

0 0 0

131 -168 114 -146 125 -180

........................................................................................................................................................................

THF

.........................................................................................................................................................................

CH3COCH3 Ep -460 Ea -438 Ec -500

........................................................................................................................................................................

Eexp.

Solvent. Ref.

2 2 0

1 3 2

0 0 0

2 2 0

7 8 2

3 1 4

5

-18 -16 -19

31 27 32

8~

1 1 1

0 0 0

7 6 6

6 6 7

0 0 0

30 26 31

141 -141 125 -123 129 -148

51 46 47

23 20 21

5p.

C6 Hs CN

3 4 2

0 0 0

1 2 1

2 2 0

7 7 2

3 3 3

5

-23 -19 -26

23 19 27

~

0 0 0

-1 -1 -1

5 4 5

0 0 0

-6 -5 -7

22 18 26

129 -139 106 -114 135 -160

46 38 48

20 17 21

iSp.

C2H5 CN

Increment values from dipole moment, 8p., and from dielectric constant, de, for [(dmit)2 Ni] (NBu4)2 1

0 0 0

0 5 2

0 1 1

2 2 0

7 7 2

4 3 2

i..a ko

E,p -515 Ea -484 Ec -585

Ep -475 Ea -449 Ec -510

Ep -480 Ea -451 Ec -522

Ep -470 Ea -448 Ec -508

DMF

CnHsCN

Call5 CN

Ep -485 Ea -459 Ec -520

CH~COCI-I3

THF

Ep -472 Ea --450 Ec -506

Eexp. mV

CH3CN

Solvent. Ref. Solvent

1 3 1

2 3 1

1 2 1

-8 -16 -7

-2 -4 -2

0 0 0

~l.t

-5 -3 -10

-6 -3 -13

0 0 0

-36 -18 -70

-10 -5 -20

0 0 0

6 2 7

3 1 5

4 1 5

I 0 2

1 0 7

0 0 0

CH3CN 8e ~

6 7 -8

6 7 -8

5 6 -7

-16 -13 14

0 0 0

3 4 -5

4 2 14

3 2 10

8 5 28

-20 -12 -72

0 0 0

5 2 6

4 1 4

3 1 10

0 0 8

0 0 0

8 2 5 0 28 10

CH~COCH3 8~t ~e 3

14 20 4

14 20 4

14 19 4

0 0 0

9 13 3

12 17 4

5~t

25 14 66

24 14 63

30 16 76

0 0 0

21 12 55

30 17 77

THF ~

5 2 7

4 1 4

3 1 5

0 0 0

0 0 7

1 1 1

~

1 1 1

1 1 1

0 0 0

-18 -21 -I2

-6 -7 -4

-2 -3 -1

~t

-3 -2 -8

-4 -2 -10

0 0 0

-21 -13 -59

-6 -4 -17

0 0 0

5 1 5 0 -6 -5

0 -3 2

7 2 10

2 1 2

0 0 0

0 0 0

0 0 0

0 -1 I

2 1 3

0 0 0

7 3 16

-35 -16 -75

-4 -2 -9

8 4 16

8 2 10

0 0 0

2 1 5

0 0 2

0 0 6

1 0 3

C~H5 CN 5~t fie fi

1 -1 1 -17 4 14

2 1 11

DMF ~ 5

0 0 0

0 0 0

-1 -1 -1

-36 -26 -30

-13 -9 -11

0 0 0

0 0 -2

2 2 7

-10 -10 -45

-2 -2 -7

2 2 7

0 0 0

10 3 12

5 2 8

0 0 2

1 0 6

2 1 1

C2H~ CN 5p. ~ 8 -6 -4 -5

TABLE 6 Increment values from dipole moment, ~ , and from dielectric constant, for [(dmit)2Pt] (NBu~)2 2

t~

1937

EXPERIMENTAL Synthesis of compounds I and 2 were achieved following the indications of G. Steimecke [6].Electrochemical studies were performed with a three electrodes apparatus with Pt counter and working electrodes. The potentials were determined vs. Ag/AgNO3 (0.01M in acetonitrile). The working electrode is a rotating disk electrode Tacussel ED1. Linear and alternative current voltamrnetries were realised with a Tacussel Tipol 2 equipped with Adapal and cyclic vohammetry with a Solartron 1286A apparatus monitored by a Micral 35 computer. All the solvents were purified and degased before recording.

REFERENCES 1 G. Le Coustumer, N. Bennasser, Y. Mollier ; Synthetic Metals, 27, (1988), B 523. 2 L. Brossard, M. Ribault, M. Bousseau, L. Valade et P. Cassoux ; C.R. Acad. Sc. Paris, t. 302, s6rie II, n° 5, (1986), 205. 3 K. Hinkelmann, K.K. Lion, F. Wudl ; J. Chem. Soc., Chem. Comm., (1989), 1744. 4 C. Reichardt, Solvent effects in organic chemistry, Verlag Chemie, Winheim, New York; 1979 4a p. 237; 4b p. 135; 4c p. 42; 4 d

p. 270.

5 K. Jeffrey Johnson, Numerical Methods in chemistry, Ed. DEKKER (1980), p. 278.