Charge-Transfer Salts of Octamethylferrocenyl Thioethers and [M(mnt)2]- Complexes (M = Ni, Co, Pt). Synthesis, Structure, and Physical Properties

Article abstract of DOI:10.1021/ic9802045

The new ferrocene derivatives Fe(η⁵-C₅Me₄SR)₂ (R = Me, 4: R = t-Bu, 5) have been prepared from the corresponding cyclopentadiene and FeCl₂. 5 may be converted to the bis(thiobenzoate) 6, a protected form of dithiol 8. From 6 the octamethyl trithiaferrocenophane 9 may be obtained in good yields. Compounds 4 and 5 are easily oxidized and form paramagnetic salts containing [M(mnt)₂]^- anions (M = Co, Ni, Pt). The derivatives [Fe(η⁵-C₅Me₄SMe)₂][Ni(mnt) ₂], 14, [Fe(η⁵-C₅Me₄SMe)₂][Pt(mnt) ₂], 15, [Fe(η⁵-C₅Me₄SMe)₂][Co(mnt) ₂], 16, [Fe- (η⁵-C₅Me₄St-Bu)₂][Ni(mnt) ₂], 17, [Fe(η⁵-C₅Me₄St-Bu) ₂][Pt(mnt)₂], 18, and [Fe(η⁵-C₅Me₄St-Bu) ₂][Co(mnt)₂], 19, have been prepared and fully characterized. X-ray crystal structural studies of 14 and 16-19 have been carried out. 14 and 16 display stacks of strongly interacting [M(mnt)₂]^- anions, whereas 19 contains discrete [Co(mnt)₂] dimers. 17 and 18 are isomorphous and display a typical D⁺A^-D⁺A^- structural motif. SQUID susceptibility measurements indicate a weak ferromagnetic ordering at low temperature for these two compounds.

Full text of DOI:10.1021/ic9802045

Inorg. Chem. 1998, 37, 4015-4021
4015
Charge-Transfer Salts of Octamethylferrocenyl Thioethers and [M(mnt)2]- Complexes (M
) Ni, Co, Pt). Synthesis, Structure, and Physical Properties
Stefan Zu1rcher, Volker Gramlich, Dieter von Arx, and Antonio Togni*
Laboratory of Inorganic Chemistry, ETH-Zentrum, Swiss Federal Institute of Technology,
CH-8092 Zu¨rich, Switzerland
ReceiVed February 24, 1998
The new ferrocene derivatives Fe(η5-C5Me4SR)2 (R ) Me, 4: R ) t-Bu, 5) have been prepared from the
corresponding cyclopentadiene and FeCl2. 5 may be converted to the bis(thiobenzoate) 6, a protected form of
dithiol 8. From 6 the octamethyl trithiaferrocenophane 9 may be obtained in good yields. Compounds 4 and 5
are easily oxidized and form paramagnetic salts containing [M(mnt)2]- anions (M ) Co, Ni, Pt). The derivatives
[Fe(η5-C5Me4SMe)2][Ni(mnt)2], 14, [Fe(η5-C5Me4SMe)2][Pt(mnt)2], 15, [Fe(η5-C5Me4SMe)2][Co(mnt)2], 16, [Fe-
(η5-C5Me4St-Bu)2][Ni(mnt)2], 17, [Fe(η5-C5Me4St-Bu)2][Pt(mnt)2], 18, and [Fe(η5-C5Me4St-Bu)2][Co(mnt)2], 19,
have been prepared and fully characterized. X-ray crystal structural studies of 14 and 16-19 have been carried
out. 14 and 16 display stacks of strongly interacting [M(mnt)2]- anions, whereas 19 contains discrete [Co(mnt)2]
dimers. 17 and 18 are isomorphous and display a typical D+A-D+A- structural motif. SQUID susceptibility
measurements indicate a weak ferromagnetic ordering at low temperature for these two compounds.
Introduction
also in the related field of organic superconductors.5 Thus, an
alternation between the acceptor and the compact, highly
symmetrical (C5V) decamethylferrocene seems to be one neces-
sary condition for magnetic cooperativity.4a With these con-
siderations in mind, we previously described studies concerning
the use of new, less symmetrical (C2, Cs) ferrocene derivatives
containing conjugated sulfur heterocycles and demonstrated their
ability to form, e.g., semiconducting CT complexes.6 In
continuation of these studies, we report herein the synthesis of
new 1,1′-bis(alkylthio)octamethylferrocenes of C2V or C2h sym-
metry. These compounds turn out to be excellent electron
donors affording highly crystalline CT complexes with M(mnt)2
acceptors, partly displaying the structural requirements for
magnetic cooperativity.
Decamethylferrocene has been used since almost two decades
as an electron donor for the formation of charge-transfer (CT)
complexes with a variety of electron acceptors.1 The radical
cation/radical anion salts thus formed display a wide range of
magnetic behaviors, from, e.g., metamagnetism for [FeCp*2]-
[TCNQ],2 to bulk ferromagnetism for the corresponding CT
complex containing tetracyanoethylene reported by Miller and
co-workers.3 Beside these systems containing organic acceptors,
analogous CT complexes formed from inorganic acceptors such
as monoanionic maleonitrilodithiolate metal complexes (M(mnt)2)
have been reported.4
We note that the tridimensional solid-state structure of such
CT complexes is both very much unpredictable and of primary
importance in determining the magnetic properties. Similarly,
the packing of anions and cations is a very significant issue
Results and Discussion
Synthesis and Properties of Sulfur Substituted Octam-
ethylferrocenes. We first attempted to prepare octamethylfer-
rocene bis(thioethers) by alkylation of the corresponding dithiol.
However, whereas ferrocene 1,1′-dithiol is accessible in two
steps from ferrocene (dilithiation followed by the reaction with
elemental sulfur and reduction), a similar procedure fails in the
octamethyl series. An alternative route was found involving
the reaction of the known 1-bromo-2,3,4,5-tetramethylcyclo-
pentadiene7 (1) with thiolates and subsequent formation of the
(1) For reviews, see: (a) Togni, A. In Ferrocenes. Homogeneous Catalysis,
Organic Synthesis, Materials Science, Togni, A., Hayashi, T., Eds.;
VCH: Weinheim, 1995; pp 433-469. (b) Epstein, A. J.; Miller, J. S.
Angew. Chem. 1994, 106, 399-432 (Angew. Chem., Int. Ed. Engl.
1994, 33, 385-416) and references therein. For selected original
papers, see: (c) Gebert, E.; Reis, A. H.; Miller, J. S.; Rommelmann,
H.; Epstein, A. J. Am. Chem. Soc. 1982, 104, 4403-4410. (d)
Broderick, W. E.; Thompson, J. A.; Godfrey, M. R.; Sabat, M.;
Hoffman, B. M. J. Am. Chem. Soc. 1989, 111, 7656-7657. (e)
Eichhorn, D. M.; Skee, D. C.; Broderick, W. E.; Hoffmann, B. M.
Inorg. Chem. 1993, 32, 491-492. (f) Broderick, W. E.; Hoffmann,
B. M. J. Am. Chem. Soc. 1991, 113, 6334-6335. (g) Broderick, W.
E.; Thompson, J. A.; Day, E. P.; Hoffmann, B. M. Science 1990, 249,
401-403.
(5) For a discussion of structural aspects in organic superconductors, see,
e.g.: Williams, J. M.; Ferraro, J. R.; Thorn, R. J.; Carlson, K. D.;
Geiser, U.; Wang, H. H.; Kini, A. M.; Whangbo, M.-H. Organic
Superconductors (Including Fullerenes). Synthesis, Structure, Proper-
ties, and Theory; Prentice Hall: Englewood Cliffs, NJ, 1992; Chapter
3, pp 65-114.
(2) Reis, A. H.; Preston, L. D.; Williams, J. M.; Peterson, S. W.; Candela,
G. A.; Swartzendruber, L. J.; Miller, J. S. J. Am. Chem. Soc. 1979,
101, 2755-2758.
(3) (a) Miller, J. S.; Calabrese, J. C.; Epstein, A. J.; Bigelow, R. W.; Zhang,
J. H.; Reiff, W. M. J. Chem. Soc., Chem. Commun. 1986, 1026-
1028. (b) Miller, J. S.; Epstein, A. J.; Reiff, W. M. Science 1988,
240, 40-47.
(4) a) Miller, J. S.; Calabrese, J. C.; Epstein, A. J. Inorg. Chem. 1989,
28, 4230-4238. (b) Fettouhi, M.; Ouahab, L.; Hagiwara, M.; Codjovi,
E.; Kahn, O.; Constant-Machado, H.; Varret, F. Inorg. Chem. 1995,
34, 4152-4159.
(6) (a) Togni, A.; Hobi, M.; Rihs, G.; Rist, G.; Albinati, A.; Zanello, P.;
Zech, D.; Keller, H. Organometallics 1994, 13, 1224-1234. (b) Hobi,
M.; Zu¨rcher, S.; Gramlich, V.; Burckhardt, U.; Mensing, C.; Spahr,
M.; Togni, A. Organometallics 1996, 15, 5342-5346. (c) Hobi, M.;
Ruppert, O.; Gramlich, V.; Togni, A. Organometallics 1997, 16,
1384-1391.
(7) Jutzi, P.; Schwartzen, K.; Mix, A. Chem. Ber. 1990, 123, 837-840.
S0020-1669(98)00204-3 CCC: $15.00 © 1998 American Chemical Society
Published on Web 07/23/1998

4016 Inorganic Chemistry, Vol. 37, No. 16, 1998
Zu¨rcher et al.
Table 1. Formal Electrode Potentials (vs Fc/Fc+) for Ferrocene
Scheme 1
and M(mnt)2 Derivatives in Dichloromethane Solutiona
compound
(reduced form)
E1°′ ∆Ep
E2°′ ∆Ep
E3°′
[V] [mV] ipc/ipa [V] [mV] ipc/ipa [V]
Fe(η5-C5Me5)2
-0.48 110
Fe(η5-C5Me4SCMe3)2 -0.29 134 1.00
Fe(η5-C5Me4SMe)2
-0.27 218 1.00
Fe(η5-C5Me4SCOPh)2 -0.09 98 0.98
Fe(η5-C5Me4S)2CO
Fe(η5-C5Me4S)2S
[Ni(mnt)2]-
+0.08 120 1.01
-0.10 272 1.00
-0.31 266 0.94 +0.69 144 0.69
-0.32 86 0.96 +0.59 103 0.84
-0.51 164 1.06 +0.34b 116 0.92 (+0.98)
[Pt(mnt)2]-
[Co(mnt)2]-
a All experiments carried out in dry dichloromethane/0.1 M [NBu4]BF4
vs 0.05 M Fc/Fc+ reference electrode with E°′ ) +0.042 V for
ferrocene, and a Pt working electrode (all values are corrected for 0
V). Values in brackets are Epa (anodic peak potential) only assigned to
b
2-
irreversible oxidation steps. Scan rate: 100mV/s. [Co(mnt)2]2
/
-
[Co(mnt)2]2 (values of ipc and ipa are exactly half compared to the
first oxidation step).
Scheme 2
ferrocenes, as shown in Scheme 1. Thus, the thermally labile
tetramethylthioalkylcyclopentadienes 2 and 3 were obtained in
good yields as mixtures of isomers, differing in the position of
the diene system with respect to the position of the sulfur
substituent (only one isomer is shown in Scheme 1). Depro-
tonation with LDA and reaction with anhydrous FeCl2 in THF
afforded the ferrocenes 4 and 5 in moderate to good yields.
The tert-butyl thioether 5 was converted in the presence of AlCl3
to the corresponding bis(thiobenzoate) 6, a protected form of
dithiol 8. The latter was prepared and isolated as a very air-
sensitive material upon methanolysis to the reactive disodium
dithiolate 7 (not isolated) and protonation in diethyl ether.
Furthermore, reaction of 7 with sulfur gave the octamethyl
trithiaferrocenophane 9 in good yield. Finally, the carbonyl
ferrocenophane 10 was obtained from the dithiol upon reaction
with triphosgene in the presence of NEt3. The preparations of
compounds 6-10 is reported here to illustrate the synthetic
utility of thioethers 4 and 5. However, their chemistry, in
particular involving CT complexes of ferrocenophane 9, shall
be described elsewhere.
Routine cyclovoltammetric measurements, carried out in
dichloromethane show a totally reversible (as indicated by the
ratio of ipc and ipa of 1.0) one electron oxidation step at -0.23
V for 4 and -0.25 V for 5, as referred to the ferrocene/
ferrocenium couple. This is ca. 0.25 V higher, as compared to
decamethylferrocene. Yet higher redox potentials are displayed
by derivatives 6, 9, and 10 in which the two sulfur substituents
fully counter balance the eight methyl groups in determining
the redox propensity. For comparison, analogous measurements
have been carried out for the [M(mnt)2] salts under identical
conditions.8 Redox potentials are reported in Table 1.
Synthesis of Charge-Transfer Complexes. For the syn-
thesis of CT complexes containing the monoanionic, formally
M(III) acceptors [M(mnt)2]- (M ) Ni, Pt, Co) and the ferrocene
donors 4 and 5, two different strategies were used. For the
nickel and platinum derivatives, the reagents [FeCp2]+[M(mnt)2]-
were the key intermediates fulfilling two functions: (1) deliver-
ing the anion [M(mnt)2]- and (2) oxidizing the desired donor,
the only byproduct being the readily soluble ferrocene. The
ferrocenium salts 11 and 12 were obtained as previously reported
from our laboratory.6b Their reaction with the donors 4 and 5,
respectively, in hot acetonitrile gave after evaporation of the
solvent the desired CT complexes that were purified by
recrystallization from ethyl acetate and obtained as shiny black
crystals in moderate to good yields, as shown in Scheme 2. For
the cobalt analogues, probably because of the different redox
behavior and the pronounced tendency to dimerize, we were
not able to prepare [FeCp2]+[Co(mnt)2]-. Therefore, the donors
(8) Redox potentials of [M(mnt)2]- derivatives in different solvents and
referred to different standard electrodes have been reported previously.
See: a) McCleverty, J. A. Prog. Inorg. Chem. 1968, 10, 50-215. (b)
Nu¨sslein, F.; Kisch, H.; Peter, R. Chem. Ber. 1989, 122, 1023-1030.
(c) Schmauch, G.; Knoch, F.; Kisch, H. Chem. Ber. 1994, 127, 287.
(d) Holm, R. H.; Davison, A. Inorg. Synth. 1967, 10, 8-26. (e) Gama,
V.; Henriques, R. T.; Bonfait, G.; Almeida, M.; Meetsma, A.; van
Smaalen, S.; de Boer, J. L. J. Am. Chem. Soc. 1992, 114, 1986-
1989. (f) Gama, V.; Henriques, R. T.; Almeida, M.; Veiros, L.;
Calhorda, M. J.; Meetsma, A.; Boer, J. L. Inorg. Chem. 1993, 32,
3705-3711. For a discussion of the redox couple Fc/Fc+, see: Conelly,
N. G.; Geiger, W. E. Chem. ReV. 1996, 96, 877-910.
were first oxidized with [FeCp2]+BF4 and then added to
-
(NEt4)+[Co(mnt)2]- 9 to obtain the desired products 16 and 19
in good yields. For all CT complexes 14-19 a clean 1:1

CT Salts of Ferrocenyl Thioethers and [M(mnt)2]- Complexes
Inorganic Chemistry, Vol. 37, No. 16, 1998 4017
Table 2. Experimental Data for the X-ray Diffraction Studies of 14, 16, 17, 18 and 19
14
16
17
18
19
empirical formula
mol wt
C28H30N4S6FeNi
729.5
C28H30CoFeN4S6
729.70
C34H42N4S6FeNi
813.6
C34H42N4S6FePt
950.0
C34H42N4S6FeCo
813.9
crystal dimens, mm
cryst syst
space group
temp
a (Å)
b (Å)
0.2 × 0.25 × 0.4
0.2 × 0.4 × 0.4
monoclinic
P2(1)/n (No. 14)
room temp
15.109(10)
8.588(6)
25.36(20)
90.00
99.12(6)
90.00
3248.9(40)
4
1.492
13.68
0.2 × 0.38 × 0.4
0.6 × 0.6 × 0.9
0.2 × 0.4 × 0.4
triclinic
triclinic
triclinic
triclinic
P1h (No. 2)
room temp
8.649(3)
14.080(4)
15.358(4)
65.27(2)
77.77(2)
80.78(2)
1654.8(9)
2
P1h (No. 2)
room temp
9.619(9)
9.622(10)
11.253(12)
79.72(9)
78.66(8)
76.62(8)
984(2)
P1h (No. 2)
room temp
9.591(4)
9.681(3)
11.252(2)
78.17(2)
78.47(3)
77.38(3)
984.6(5)
1
P1h (No. 2)
room temp
10.007(5)
14.481(7)
15.024(7)
104.79(2)
97.21(2)
107.47(2)
1959(2)
c (Å)
R_(deg)
â_(deg)
γ_(deg)
V (Å3)
Z
1
2
F (calcd) (g cm-3
)
1.464
14.11
Syntex P21
1.373
67.45
Picker-Stoe
1.602
42.63
Syntex P21
1.380
94.94
Picker-Stoe
µ (cm-1
)
diffractometer
radiation
θ range (deg)
no. of measd reflcns
Syntex P21
Mo KR, λ ) 0.710 73 Å Mo KR, λ ) 0.710 73 Å Cu KR, λ ) 1.541 78 Å Mo KR, λ ) 0.710 73 Å Cu KR, λ ) 1.541 78 Å
1.60-20.04
3362
1.63-20.04
3150
4.05-49.99
2023
1.87-20.04
1812
3.12-50.00
4013
no. of indep data collcd 3091
3053
2523
2023
1768
1812
1778
4013
3065
no. of obsd reflcns (n)a
2614
no. of params refined (p) 362
362
212
233
419
wR2 [I > 2σ(I)]b
R1 [I > 2σ(I)]c
GOFd
0.1293
0.0467
1.051
0.1245
0.0406
1.044
0.1479
0.0597
1.052
0.1006
0.0386
1.071
0.1240
0.0505
1.070
a (|Fo | > 4.0 σ(|F| )). b wR2 ) [σ[w(Fo - Fc2)2]/σ[w(Fo )2]1/2
.
c R1 ) σ||Fo| - |Fc||/σ|Fo|. d GOF ) S ) [σ (w(Fo - Fc2)2]/(n - p)]1/2
.
2
2
2
2
2
stoichiometry of donor and acceptor was observed in product
crystals, even when the precursors were mixed in different ratios.
For [M(mnt)2] derivatives the CN stretching frequency of the
mnt ligand provides a diagnostic tool correlating with the state
of charge of the whole fragment. All new [M(mnt)2] com-
pounds of this study display sharp ν(CN) bands in the narrow
range between 2205 and 2209 cm-1. This is also true for the
starting monoanionic forms [NEt4][M(mnt)2] (2205-2208 cm-1).
Solid-State Structure of Charge-Transfer Salts. For the
1:1 salts obtained above and containing charge-transfer partners
differing only in the nature of the thioalkyl substituent on the
ferrocene unit or having a different metal in the anionic
counterpart, respectively, it was of interest to observe how such
relatively small variations would influence the solid-state
structure. Crystals suitable for X-ray diffraction studies were
obtained for compounds 14 and 16-19. Table 2 gives the
relevant crystal and data collection parameters. Bond distances
and angles of each asymmetric unit were found to fall in the
expected ranges and will not be discussed here (they are
provided as Supporting Information, along with ORTEP rep-
resentations). Figures 1-4 illustrate the relative arrangement
of the molecular components of each compound in tridimen-
sional space.
In the structure of 14 pairs of ferrocenium cations (Fe-Fe
distance 9.90 Å) form columns, each of which is surrounded
by four stacks of [Ni(mnt)2] anions, as shown by the projection
along the crystallographic a axis of Figure 1. No inversion
center coincides with either the nickel or iron atom. This leads
to C1 symmetry for the ferrocenium ion. The two Cp rings are
almost ideally parallel, with an interplanar angle of 2°, and are
rotated with respect to each other by 86° along the molecular
vertical axis. The [Ni(mnt)2] units form dimers with the Ni
atom interacting with a sulfur atom of the second fragment at
a distance of 3.72 Å. This leads to a zigzag arrangement along
the Ni stacks with alternating Ni-Ni distances of 4.29 and 5.10
Å.6b,10 In the asymmetric unit the plane of the anion is very
much tilted with respect to the plane of the Cp ring close to it,
the corresponding interplanar angle being 78°.
The general qualitative structural features of the analogous
Co compound 16 (see Figure 2) are very similar to those of 14,
with the same relationships between [Co(mnt)2] stacks and
ferrocenium columns. However, the [Co(mnt)2] units form, as
expected, much tighter centrosymmetric dimers, with a pro-
nounced pyramidalization of the Co centers.4b Along the Co
stacking direction (crystallographic b axis) the difference
between the alternating long and short metal-metal distances
is also more conspicuous than in the Ni derivative (3.15 and
5.47 Å, respectively). The ferrocenium cation shows an almost
antiperiplanar conformation, with the two Cp rings being rotated
169° with respect to each other.
The two Ni and Pt compounds 17 and 18, respectively, both
containing the bulkier ferrocenium cation derived from 5, are
isomorphous. The most prominent general structural feature
of these compounds is constituted by the presence of alternating
layers of [M(mnt)2] and ferrocenium units. The Ni and Pt
atoms, respectively, occupy the corners of the unit cell, whereas
the Fe centers are located in the center of each bc plane, thus
corresponding to an inversion center. Along the crystallographic
(0 1 1) and (0 1-1) vectors a D+A-D+A- structural motif with
two different Fe-Ni distances of 6.72 and 8.03 Å is apparent
(in the Pt compound the corresponding distances are 6.63 and
8.14 Å), as shown in Figure 3. The Fe-Fe distances and M-M
distances (Ni-Ni and Pt-Pt) correspond to the unit cell
dimensions. Along the b axis, two [M(mnt)2]-units are separated
by two tert-butyl groups of two adjacent ferrocenium ions. The
angle between the Cp plane and the plane of the [M(mnt)2] anion
in the asymmetric unit is 46° in 17 and 44° in 18, respectively.
The latter planes are also tilted with respect to the bc plane,
i.e., for the anion by ca. 20°, thus recalling a scaled structure,
and by ca. 35° for the ferrocenium. Finally, the sulfur atoms
(9) (a) Edelstein, N.; Holm, R. H.; Maki, A. H.; Davison, A. Inorg. Chem.
1963, 2, 1227. (b) Holm, R. H.; Davison, A. Inorg. Synth. 1967, 10,
8-26. (c) Bray, J.; Locke, J.; McCleverty, J. A.; Coucouvanis, D.
Inorg. Synth. 1971, 13, 187-195.
(10) Weiher, J. F.; Melby, L. R.; Benson, R. E. J. Am. Chem. Soc. 1964,
86, 4329-4333.

4018 Inorganic Chemistry, Vol. 37, No. 16, 1998
Zu¨rcher et al.
Figure 2. Perspective view of [Fe(η5-C5Me4SMe)2][Co(mnt)2], 16,
down the crystallographic b axis.
For compounds 14-16 and 19 , θ values of zero (16, 19) or
slightly negative (14, 15) were found. For 14 and 15 this
observation, together with the abrupt drop of ømolT at temper-
atures below 50 K, indicates a transition most likely dominated
by intermolecular antiferromagnetic interactions. However,
alternatively to such a magnetic ordering, this behavior could
be explained by a depopulation of spin-orbit states. From the
high temperature ømolT data the effective magnetic moments
may be calculated (µeff ) (3kømolT/Nâ2)1/2). They assume values
between 1.73 µB/mol for 16 and 2.73 µB/mol for 15. Thus, the
Figure 1. Perspective view of [Fe(η5-C5Me4SMe)2][Ni(mnt)2], 14,
down the crystallographic a axis, showing the four stacks of [Ni(mnt)2]
anions surrounding a double column of ferrocenium cations.
are located at 0.08 Å (17) and at 0.10 Å (18) below the
respective Cp plane, i.e., in the region between the two Cp rings.
For the last member of the series, compound 19, differing
from its companions 17-18 only by the replacement of Ni/Pt
by Co, yet a different structure is observed. As shown in Figure
4, the presence of [Co(mnt)2]- dimers leads to a structure best
described as belonging to the D+(A2)2-D+ type. The iron atoms
of the two inequivalent ferrocenium cations in the unit cell
coincide with two symmetry centers, one in the middle of the
a axis, the other at the center of the bc plane. The [Co(mnt)2]2
dimeric unit is centrosymmetric and resides in the middle of
the c axis.
Magnetic Measurements. Magnetic susceptibility measure-
ments were carried out for the CT complexes 14-19 using a
SQUID susceptometer in the temperature range between 2 and
300 K. Plots of the reciprocal susceptibility 1/ømol and of ømolT
vs T, respectively, are shown in Figure 5. The compounds 14-
19 obey a modified Curie-Weiss expression ø ) C/(T + θ) +
q, where q is the sum of core diamagnetism and temperature
independent paramagnetism (TIP). For all compounds q is
positive, meaning that TIP is larger than the diamagnetic
component.
1
former case turns out to be a perfect S ) /2 system with non
interacting spins. This behavior may be well understood on
the basis of the solid-state structure discussed above. The
[Co(mnt)2]- units form diamagnetic stacked dimers and the
magnetic properties are conveyed by the virtually isolated
ferrocenium ions.
A significantly different magnetic behavior is shown by the
two derivatives 17 and 18. In fact, an increase of ømolT in the
low-temperature range, as well as a positive θ value of ca. 3 K
for both compounds is observed (also the effective magnetic
moment is 2.68 µB/mol for 17 and 2.94 µB/mol for 18). This
is indicative of a weak but significant ferromagnetic coupling.
This magnetic ordering becomes possible because of the
alternating D+A-D+A- structure common to these two com-
pounds (see above),4a impeding strong interactions between
[M(mnt)2]- units.
Conclusions
We have shown that new persubstituted ferrocene derivatives
suited as electron donors and containing thioethers fragments
are easily accessible from the corresponding preformed cyclo-

CT Salts of Ferrocenyl Thioethers and [M(mnt)2]- Complexes
Inorganic Chemistry, Vol. 37, No. 16, 1998 4019
Figure 4. Perspective view of [Fe(η5-C5Me4St-Bu)2][Co(mnt)2], 19,
down the crystallographic a axis, showing the [Co(mnt)2] dimers.
cooled to 0 °C. A 44 mL (70 mmol) amount of a 1.6 M n-BuLi solution
in hexane was added. The resulting mixture was stirred and allowed
to warm to room temperature overnight. A solution of 7.4 g (70 mmol)
of cyanogen bromide in 20 mL of diethyl ether was then added over a
period of 30 min at -78 °C. The mixture was stirred for 2h at -78
°C and then warmed slowly to 0 °C. The yellow solution was filtered,
and the solvents were evaporated. The resulting yellow 1-bromo-
2,3,4,5-tetramethylcyclopentadiene (1) was directly dissolved in 150
mL of MeOH and cooled to -78 °C. A 5.0 g (71 mmol) amount of
NaSMe was added, and the mixture was allowed to warm to room
temperature overnight. The solvent was removed under vacuum, and
the desired product was extracted with hexane. Yield: 10.8 g (92%)
of a yellow oil. This product proved to be a mixture of several isomers
of 1-methylthio-2,3,4,5-tetramethylcyclopentadiene (2) (by NMR) and
was used without further purification. MS: m/z 168 (M+, 100), 153,
139, 120, 105, 91, 79.
The intermediate thioether (2) thus obtained (10.8 g, 57.5 mmol)
was dissolved in 100 mL of THF, cooled to -78 °C, and mixed with
a freshly prepared solution of lithium diisopropylamide (from 9.8 mL
of diisopropylamine, 45.8 mL of 1.6 M of n-BuLi, and 50 mL of THF).
The mixture was stirred for 10 min, and then 6.1 g (48.18 mmol) of
FeCl2 was added in small portions. The mixture was allowed to warm
to room temperature overnight and was then refluxed for an additional
hour. The black reaction mixture was mixed with dichloromethane
and extracted twice with 2 N HCl and sodium dithionite and once with
water. The organic layer was evaporated and flash chromatographed
with hexane/EtOAc, v/v 20:1. Yield: 4.97 g (40% from tetramethyl-
cyclopentadiene). Mp: 152-154 °C (dec). 1H NMR (250.13 MHZ,
CDCl3): δ 1.76 (s, 12H), 1.87 (s, 12H), 1.99 (s, 6H). 13C NMR (62.895
MHZ, CDCl3): δ 9.34, 18.49, 77.99, 81.20, 83.60. MS: m/z 390 (M+,
100), 375, 344, 327, 297, 254, 223, 205, 195, 174, 151, 119, 105, 91,
56. Anal. Calcd for C20H30S2Fe: C, 61.53; H, 7.74; S, 16.43.
Found: C, 61.58; H, 7.90; S, 16.65. IR (KBr): 2967, 2914, 1448,
1419, 1372, 1360, 1332.
Figure 3. Perspective view of the two isomorphous compounds [Fe-
(η5-C5Me4St-Bu)2][M(mnt)2] (M ) Ni, 17; M ) Pt, 18) down the
crystallographic a axis, showing the typical alternating D+A-D+A-
arrangement.
pentadienes. These donors, in their oxidized form, lead to
crystalline salts with [M(mnt)2]- derivatives. Subtle and
nonpredictable changes in the solid state structure are observed
upon changing the nature of the alkyl group on sulfur. Whereas
methyl derivatives give structures containing stacked and
strongly interacting anions, their tert-butyl counterparts favor
alternating arrangements of donors and acceptors in the solid
state, with a typical D+A-D+A- structure for the isomorphous
compounds 17 and 18. The structural differences are in turn
responsible for the different magnetic behaviors observed, a
weak ferromagnetic coupling arising from the alternating
framework.
We are currently studying the properties of analogous
compounds derived from donors 4 and 5 and containing electron
acceptors derived from the TCNQ basic structure. The results
of these studies shall be reported in due course.
2,2′,3,3′,4,4′,5,5′-Octamethyl-1,1′-bis(tert-butylthio)ferrocene (5).
2,3,4,5,-Tetramethyl-1-(tert-butylthio)cyclopentadiene (3) was obtained
in an analogous manner as described above for the methylthio derivative
from 6.58 g (53.8 mmol) of tetramethylcyclopentadiene, 250 mL of
hexane, 27 mL (53.8 mmol) of 2.0 M n-BuLi in hexane, 5.69 g (53.8
mmol) of cyanogen bromide in 20 mL of diethyl ether, and 6.45 g
(57.5 mmol) of NaSt-Bu in 150 mL of MeOH, yielding 8.3 g (57.5
mmol, 73%) of the crude mixture of isomers (MS: m/z 210 (M+), 154
(100), 139, 120, 105, 91, 77, 57). After dissolution in 100 mL of THF,
Experimental Section
General experimental techniques were described earlier.6a
2,2′,3,3′,4,4′,5,5′-Octamethyl-1,1′-bis(methylthio)ferrocene (4).
2,3,4,5,-Tetramethyl-1-methylthiocyclopentadiene (2): 8.6 g (70 mmol)
of tetramethylcyclopentadiene was dissolved in 250 mL of hexane and

4020 Inorganic Chemistry, Vol. 37, No. 16, 1998
Zu¨rcher et al.
(M+, 100), 556, 490, 465, 434, 360, 329, 313, 285, 209, 174, 119,
105, 77. Anal. Calcd for C32H34O2S2Fe: C, 67.36; H, 6.01; S 11.24.
Found: C, 67.45; H 5.97; S, 11.37. IR (KBr): 2968, 2905, 1675, 1579,
1446, 1377, 1310, 1206, 1170, 1028, 1001, 902, 771, 685, 645, 616,
554, 509, 467, 445.
2,2′,3,3′,4,4′,5,5′-Octamethyl-ferrocene-1,1′-dithiol (8). A 200 mg
(0.35 mmol) amount of 6 and 123 mg (2.2 mmol) of NaOMe were
dissolved in 30 mL of THF/MeOH (1:1) and stirred overnight at room
temperature. To this solution was added 2.2 mL of 1.0 M HCl solution
(2.2 mmol) in Et2O, and the solvents were evaporated. Extraction with
Et2O (or MTBE) yielded the dithiol 8 in quantitative yield. 1H NMR
(250.13 MHz, CDCl3): δ 1.71 (s, 12H), 1.93 (s, 12H). 13C NMR
(62.895 MHz, CDCl3): δ 9.30, 9.85, 80.70, 83.13. MS: m/z 362 (M+,
100), 329, 295, 241, 209. Anal. Calcd for C18H26 S2Fe: C, 59.66; H,
7.23; S, 17.70. Found: C, 59.77; H7.02; S, 17.49. IR (KBr): 2968,
2944, 2903, 2512 (S-H st), 1637, 1461, 1374, 1028, 455.
2,2′,3,3′,4,4′,5,5′-Octamethyl-1,1′-trithia[3]ferrocenophane (9). The
disodium bisthiolate 7 was prepared in situ from 1.152 g (2 mmol) of
6 and 648 mg (12 mmol) of NaOMe as described above. A 512 mg
(16 mmol) amount of sulfur was added, and the resulting suspension
was stirred for 24 h. The solvents were evaporated, and the residue
was chromatographed over silica with hexane as eluent. Yield: 644
mg (81%). 1H NMR (250.13 MHz, CDCl3): δ 1.35 (s, 6H), 1.49 (s,
6H), 1.63 (s, 6H), 1.67 (s, 6H). 13C NMR (62.895 MHz, CDCl3): δ
8.196 (2*CH3), 8.698 (4*CH3), 9.784 (2*CH3), 78.548, 81.175, 82.994,
87.142, 89.180. MS: m/z 392 (M+, 100), 359, 325, 240, 206, 152,
119, 91, 56. Anal. Calcd for C18H24S3Fe: C, 55.09; H, 6.16; S, 24.51.
Found: C, 55.33; H, 5.97; S, 24.20. IR (KBr): 2970, 2947, 2902, 1474,
1451, 1375, 1320, 1153, 1027, 746, 616, 513, 488, 462, 389, 376.
2,2′,3,3′,4,4′,5,5′-Octamethyl-1,1′-dithiacarbonyl[3]ferroceno-
phane (10). A 317 mg (0.87 mmol) amount of 8 was dissolved in 20
mL of THF and cooled to -78 °C. Triphosgene (86.5 mg, 0.29 mmol)
was added, and 242 µL (1.74 mmol) of NEt3 was added dropwise to
the resulting solution. The reaction mixture was allowed to warm to
room temperature, and the solvent was evaporated. Chromatographic
purification of the residue over silica (hexane/toluene 5:2) yielded 236
1
mg (70%) of the product. H NMR (250.13 MHz, CDCl3): δ 1.50 (s,
12H), 1.71 (s, 12H). 13C NMR (62.895 MHz, CDCl3): δ 9.496, 9.646,
74.531, 84.529, 84.573. MS: m/z 388 (M+), 360, 327(100), 294, 205,
174, 119, 91, 56. Anal. Calcd for C19H24OS2Fe: C, 58.76; H, 6.23; S,
16.51. Found: C, 58.71; H, 6.23; S, 16.54. IR (KBr): 3199, 2906,
1612, 1458, 1378, 1030, 894, 470, 430.
[FeCp2][Pt(mnt)2] (12). A 1.00 g (0.959 mmol) amount of [NBu4]2-
[Pt(mnt)2] and 0.57 g (2.0 mmol) of [FeCp2]BF4 were separately
dissolved in 1,2-dichloroethane (50 and 100 mL, respectively). The
ferrocinium solution was filtered and slowly added dropwise to the
solution of [NBu4]2[Pt(mnt)2]. Diethyl ether (100 mL) was added, and
the green microcrystalline material which formed was filtered off.
Yield: 466 mg (73%). Mp: >260 °C (dec). Anal. Calcd for
C18H10N4S4FePt: C, 32.68; H, 1.52; N, 8.47. Found: C, 32.66; H,
1.74; N, 8.31. IR (KBr): 3106, 2207, 1442, 1414, 1162, 1108, 1057,
1006, 850, 519, 500.
Preparation of Charge-Transfer Complexes. The procedure for
the preparation of CT complexes with [M(mnt)2]- (M ) Ni, Pt, Co) is
exemplified by the synthesis of 14. 4 (100 mg, 0.256 mmol) and
[FeCp2][Ni(mnt)2] (135 mg, 0.256 mmol) were dissolved in hot
acetonitrile, filtered, and dried in vacuo. The brown-black residue was
recrystallized from EtOAc to obtain small shiny black crystals.
Yield: 96 mg (51%). Mp: 199 °C (dec). Anal. Calcd for C28H30N4S6-
FeNi: C, 46.10; H, 4.14; N, 7.68. Found: C, 46.20; H, 4.00; N, 7.73.
IR (KBr): 2980, 2926, 2207, 1450, 1378, 1307, 1159, 1026, 970, 524,
500.
Compound 15 was obtained in an analogous manner from 100 mg
(0.256 mmol) of 4 and 169 mg (0.256 mmol) of [FeCp2][Pt(mnt)2].
Yield: 180 mg (81%). Mp: 214 °C (dec). Anal. Calcd for
C28H30N4S6FePt: C, 38.84; H, 3.49; N, 6.47. Found: C, 38.81; H,
3.47; N, 6.44. IR (KBr): 2980, 2926, 2209, 1458, 1439, 1379, 1162,
1017, 698, 668, 524, 499.
Compound 16 was obtained similarly from 100 mg (0.256 mmol)
of 4, 70 mg (0.256 mmol) of [FeCp2]BF4 in acetone/CH2Cl2 (1/1), and
120 mg (0.256 mmol) of [Co(mnt)2]NEt4 in hot acetonitrile. Yield:
Figure 5. SQUID susceptibility data for compounds 14-19 measured
in an external magnetic field of 1000 G.
the ligand was treated with a freshly prepared solution of lithium
diisopropylamide (from 8.3 mL of diisopropylamine, 28.1 mL of 1.6
M n-BuLi in hexane, and 50 mL of THF) and subsequently with 3.75
g (29.6 mmol) of FeCl2, as described above. Yield: 7.29 g (57% from
tetramethylcyclopentadiene). Mp: 179 °C (dec). 1H NMR (250.13
MHZ, CDCl3): δ 1.13 (s, 18H), 1.76 (s, 12H), 1.85 (s, 12H). 13C
NMR (62.895 MHZ, CDCl3): δ 9.91, 11.16, 31.26, 46.36, 75.40, 82.01,
84.61. MS: m/z 474 (M+, 100), 418, 362, 327, 294, 206, 174, 119,
105, 57. Anal. Calcd for C26H42S2Fe: C, 65.80; H, 8.92; S, 13.51.
Found: C, 65.86; H, 8.78; S, 13.24. IR (KBr): 2960, 2898, 1472,
1457, 1375, 1360, 1323, 1170, 1025, 992, 518, 466, 451.
2,2′,3,3′,4,4′,5,5′-Octamethylferrocen-1,1′-diyl Bis(thiobenzoate)
(6). A 3 g (6.3 mmol) amount of 5 and 1.8 g (12.6 mmol) of AlCl3
were suspended in 20 mL of benzoyl chloride. The reaction mixture
was heated to 60 °C for 3 h, and then the excess of benzoyl chloride
was removed under reduced pressure. The residue was dissolved in
CH2Cl2/MTBE and extracted twice with saturated NaHCO3 solution
and once with lime. The organic phase was dried with MgSO4 and
evaporated, and the residue was chromatographed over silica (hexane/
toluene 1/5). The product was recrystallized from CH2Cl2/hexane to
yield 2.86 g (79%) of a yellow powder. Mp: 242 °C (dec). 1H
NMR: δ 1.79 (s, 12H), 1.85 (s, 12H), 7.4-7.7 (m complex, 8H), 8.0-
8.1 (m complex, 2H). 13C NMR (62.895 MHz): δ 9.74, 9.82, 69.88,
82.86, 84.41, 127.43, 128.59, 133.30, 136.84, 129.19. MS: m/z 570

CT Salts of Ferrocenyl Thioethers and [M(mnt)2]- Complexes
Inorganic Chemistry, Vol. 37, No. 16, 1998 4021
150 mg (72%). Mp: >260 °C (dec). Anal. Calcd for C28H30N4S6-
FeCo: C, 46.09; H, 4.14; N, 7.68. Found: C, 45.99; H, 4.32; N, 7.62.
IR (KBr) 2924, 2205, 1453, 1379, 1309, 1157, 1025, 968, 696, 570,
508, 467.
Compound 17 was obtained similarly from 50 mg (0.105 mmol) of
5 and 55.1 mg (0.105 mmol) of [FeCp2][Ni(mnt)2]. Yield: 61.5 mg
(72%). Mp: 210 °C (dec). Anal. Calcd for C34H42N4S6FeNi: C,
50.19; H, 5.20; N, 6.89. Found: C, 50.15; H, 5.12; N, 6.89. IR
(KBr): 2959, 2208, 1473, 1454, 1381, 1363, 1160, 1025, 570, 526,
502.
Compound 18 was obtained similarly from 93.3 mg (0.196 mmol)
of 5 and 130.2 mg (0.196 mmol) of [FeCp2][Pt(mnt)2]. Yield: 107
mg (58%). Mp: 224 °C (dec). Anal. Calcd for C34H42N4S6FePt: C,
42.98; H, 4.46; N 5.90. Found: C, 42.90; H, 4.24; N, 6.04. IR
(KBr): 2976, 2959, 2922, 2209, 1473, 1458, 1441, 1382, 1366, 1162,
1025, 668, 571, 500.
measured every 120 reflections and no significant variation was
detected. The structures were solved by Patterson Methods and refined
by full-matrix least-squares using anisotropic displacement parameters
for all non hydrogen atoms. The contribution of the hydrogen atoms
in their idealized position (Riding model with fixed isotropic U ) 0.080
Å2) was taken into account but not refined. All calculations were
carried out by using the Siemens SHELX93 (VMS) system.
Magnetic Measurements. The magnetic susceptibility ø of CT
complexes 14-19 was measured in the temperature range of 2-300
K in an external variable magnetic field, by means of a Quantum Design
superconducting quantum interference device (SQUID) magnetometer.
The polycrystalline samples were mounted in a sample holder tube
made of quartz glass in order to keep the magnetic background as low
as possible. Routine corrections for core diamagnetism, temperature
independent paramagnetism and the sample holder were applied.
Compound 19 was obtained similarly from 100 mg (0.21 mmol) of
5, 98.6 mg (0.21 mmol) of [Co(mnt)2]NEt4, and 57.2 mg (0.21 mmol)
of [FeCp2]BF4. Yield: 120 mg (70.5%). Mp: 240 °C (dec). Anal.
Calcd for C34H42N4S6FeCo: C, 50.17; H, 5.20; N, 6.88. Found: C,
50.37; H, 5.13; N, 6.91. IR (KBr): 2960, 2920, 2896, 2862, 2205,
1473, 1456, 1380, 1364, 1160, 1025, 572, 528, 508.
X-ray Crystallographic Study of 14, 16, 17, 18, and 19. Suitable
crystals for an X-ray analysis of all these compounds were obtained
by slow diffusion of hexane into a solution of the CT complex in
dichloromethane. Selected crystallographic and relevant data collection
parameters are listed in Table 2. Data were measured at room
temperature with variable scan speed to ensure constant statistical
precision on the collected intensities. One standard reflection was
Acknowledgment. S.Z. is grateful to the Swiss National
Science Fundation for financial support (Grant No. 20-
41974.94).
Supporting Information Available: Tables of atomic coordinates,
complete listing of bond distances and angles, tables of anisotropic
displacement coefficients, coordinates of hydrogen atoms, as well as
ORTEP representations and atom numbering schemes for 14 and 16-
19 (39 pages). Ordering and access information is given on any current
masthead page. Tables of calculated and observed structure factors may
be obtained from the authors upon request.
IC9802045