Synthesis, characterization, and metal complexation of unsymmetrical 1,1′-bis(organylthiolato)ferrocenes

Article abstract of DOI:10.1021/om034287v

A series of new unsymmetrical 1,1′-disubstituted ferrocenediyl ligands featuring thioether substituents (SR, SR′ where R ≠ R′: Me, Ph, ^tBu) have been conveniently synthesized via cleavage of ferrocenylsulfanes. The ligands display a range of coordination chemistry, exemplified by reaction with Pt, Pd, and W metal centers, and structural characterization indicates the bidentate, chelating nature of the ligands. Electrochemical studies show that the diferrocenyldisulfanes exhibit two separated one-electron exidations where the mixed-valent monocations belong to the partially delocalized Robin-Day Class II, while for the metallocenophanes, chemical reversibility is noted along with some decomposition over time.

Full text of DOI:10.1021/om034287v

Organometallics 2004, 23, 957-967
957
Syn th esis, Ch a r a cter iza tion , a n d Meta l Com p lexa tion of
Un sym m etr ica l 1,1′-Bis(or ga n ylth iola to)fer r ocen es
Vernon C. Gibson,† Nicholas J . Long,*,† Richard J . Long,† Andrew J . P. White,†
Charlotte K. Williams,† David J . Williams,† Emanuela Grigiotti,‡ and
Piero Zanello‡
Department of Chemistry, Imperial College London, South Kensington,
London, U.K. SW7 2AZ, and Dipartimento di Chimica, Universita` di Siena,
Via Aldo Moro, 53100 Siena, Italy
Received November 10, 2003
A series of new unsymmetrical 1,1′-disubstituted ferrocenediyl ligands featuring thioether
t
substituents (SR, SR′ where R * R′: Me, Ph, Bu) have been conveniently synthesized via
cleavage of ferrocenylsulfanes. The ligands display a range of coordination chemisty,
exemplified by reaction with Pt, Pd, and W metal centers, and structural characterization
indicates the bidentate, chelating nature of the ligands. Electrochemical studies show that
the diferrocenyldisulfanes exhibit two separated one-electron oxidations where the mixed-
valent monocations belong to the partially delocalized Robin-Day Class II, while for the
metallocenophanes, chemical reversibility is noted along with some decomposition over time.
In tr od u ction
potentially form unsymmetrical monoferrocenediyl
ligands.
We report herein the convenient syntheses of novel
The formation of unsymmetrical, multidentate ligands,
focusing on aspects of hemilability,1 continues to be of
great interest. In particular, ferrocenyl and ferrocene-
diyl ligands are sought after due to their extensive
coordination chemistry and applications within cataly-
sis.2,3 Ferrocene species with donor heteroatoms (e.g. P,
N, S, O) substituted onto the cyclopentadienyl rings are
well-known, especially those featuring homo-substitu-
tion (i.e. the same donor atom along with the same alkyl
or aryl substituents) but much less well-known are
unsymmetrical 1,1′-disubstituted ferrocenes featuring
hetero-combinations of N, P, or S atoms, or R groups.4
1-(PR2),1′-(SR)-ferrocenediyl ligands (R ) alkyl, aryl)
have been formed5 and most recently by us6 but as far
as we are aware 1-(SR),1′-(SR′)-ferrocenediyl ligands are
unknown where R * R′ (alkyl or aryl). Bis(1′-organ-
ylthiolatoferrocenyl)disulfanes (R ) n-butyl, phenyl)
were first reported by Herberhold in 19917 via cleavage
of the trisulfur bridge in 1,2,3-trithia-[3]-ferrocenophanes
by organolithium reagents, followed by air oxidation. No
further studies were reported, but we recognized that
cleavage of the S-S bond in these disulfanes could
unsymmetrical thioether-substituted ferrocenediyl ligands
(where R * R′: Me, Ph, tBu) via cleavage of the analog-
ous ferrocenyldisulfane species. Various methods have
been investigated and compared and found to be de-
pendent upon the nature of the R/R′ groups. Also includ-
ed are examples of the coordination chemistry of the
new ferrocenediyl ligands via reaction with palladium,
(4) Some examples of ferrocenes substituted with heteroatoms
directly on the cyclopentadienyl rings: (a) Butler, I. R.; Griesbach, U.;
Zanello, P.; Fontani, M.; Hibbs, D.; Hursthouse M. B.; Malik, K. L. M.
A. J . Organomet. Chem. 1998, 565, 243. (b) Butler, I. R.; Quayle, S. C.
J . Organomet. Chem. 1998, 552, 63. (c) Butler, I. R.; Drew, M. G. B.;
Greenwell, C. H.; Lewis, E.; Plath, M.; Mussig, S.; Szewezyk, J . Inorg.
Chem. Commun. 1999, 2, 576. (d) Deng, W.-P.; Hou, X.-L.; Dai, L.-X.;
Yu, Y.-H.; Xia, W. Chem. Commun. 2000, 285. (e) Deng, W.-P.; Hou,
X.-L.; Dai, L.-X.; Dong, X.-W. Chem. Commun. 2000, 1483. (f) Brous-
sier, R.; Bentabet, E.; Laly, M.; Richard, P.; Kuz’mina, L. G.; Serp, P.;
Wheatley, N.; Kalck, P.; Gautheron, B. J . Organomet. Chem. 2000,
613, 77. (g) Broussier, R.; Ninoreille, S.; Bouron, C.; Blacque, O.;
Ninoreille, C.; Kubicki, M. M.; Gautheron, B. J . Organomet. Chem.
1998, 561, 85. (h) Balavoine, G. A.; Daran, J .-C.; Iftiem, G.; Manoury,
E.; Moveau-Bossuet, C. J . Organomet. Chem. 1998, 567, 191. (i) Priego,
J .; Garcia Mancheno, O.; Cabrera, S.; Gomez Arraya, R.; Llamas, T.;
Carretero, J . C. Chem. Commun. 2002, 2512. (j) Seo, H.; Park, H.-J .;
Yun Kim, B.; Hoon Lee, J .; Ukk Son, S.; Keun Chung, Y. Organome-
tallics 2003, 22, 618. (k) Neumann, B.; Siemeling, U.; Stammler, H.
G.; Vorfeld, U.; Delis, J . G. P.; van Leeuwen, P. M. W. N.; Vrieze, K.;
Fraanje, J .; Goubitz, K.; Fabrizi de Biani, F.; Zanello, P. J . Chem. Soc.,
Dalton Trans. 1997, 4705. (l) Siemeling, U.; Vorfeld, U.; Neumann,
B.; Stammler, H. G.; Zanello, P.; Fabrizi de Biani, F. Eur. J . Inorg.
Chem. 1999, 38, 1. (m) Bradley, S.; McGowan, P. C.; Oughton, K. A.;
Thornton-Pett, M.; Walsh, M. E. Chem. Commun. 1999, 77. (n) Bradley,
S.; Camm, K. D.; Liu, X.; McGowan, P. C.; Mumtaz, R.; Oughton, K.
A.; Podesta, T. J .; Thornton-Pett, M. A. Inorg. Chem. 2002, 41, 715.
(o) Carr, J . D.; Coles, S. J .; Hursthouse, M. B.; Wright, M. E.; Munro,
E. L.; Tucker, J . H. R.; Westwood, J . Organometallics 2000, 19, 3312.
(p) Carr, J . D.; Coles, S. J .; Hursthouse, M. B.; Tucker, J . H. R. J .
Organomet. Chem. 2001, 637-639, 304. (q) Wrackmeyer, B.; Maisel,
H. E.; Herberhold, M. J . Organomet. Chem., 2001, 637-639, 727.
* Address correspondence to this author. Phone: +44 (0)20 7594
5781. Fax: +44 (0)20 7594 5804. E-mail: n.long@imperial.ac.uk.
† Imperial College London.
‡ Universita` di Siena.
(1) Bader, A.; Lindner, E. Coord. Chem. Rev. 1991, 108, 27.
(2) For a detailed literature review see: (a) Ferrocenes: Homogeneous
Catalysis-Organic Synthesis-Materials Science; Togni, A., Hayashi,
T., Eds.; VCH: Weinheim, Germany, 1995. (b) Metallocenes; Togni,
A., Halterman, R. L., Eds.; Wiley-VCH: Weinheim, Germany, 1998.
(3) For a comprehensive overview of ferrocene and other metallocene
chemistry see: Long, N. J . In Metallocenes: An Introduction to
Sandwich Complexes; Blackwell Science: Oxford, UK, 1998.
10.1021/om034287v CCC: $27.50 © 2004 American Chemical Society
Publication on Web 02/04/2004

958 Organometallics, Vol. 23, No. 5, 2004
Sch em e 1. F or m a tion of Com p ou n d s 1-8
Gibson et al.
platinum, and tungsten metal centers, with full spec-
troscopic, electrochemical, and structural characteriza-
tion.
Resu lts a n d Discu ssion
F igu r e 1. The trimeric species 4.
I. P r ep a r a tion of Bis(1′-or ga n ylth iola tofer r ocen -
yl)d isu lfa n es. The bis(1′-organylthiolatoferrocenyl)-
disulfanes, RS-Fc-SS-Fc-SR (where R ) Me (1), Ph (2),
and tBu (3)) have all been prepared in a general,
variable yielding synthesis (Scheme 1). A THF solution
of 1,2,3-trithia-[3]-ferrocenophane was cooled to -78 °C,
reacted with 2 equiv of the appropriate organolithium
reagent, and stirred for 20 h. The reaction was exposed
to the air, and water was added leading to a gradual
lightening of the dark-red solution. The THF was
removed under vacuum and the aqueous suspension
extracted with dichloromethane. Column chromatogra-
phy (neutral grade II alumina) gave a band due to
unreacted 1,2,3-trithia-[3]-ferrocenophane followed by
several other orange products, the first of which was
the major product of the reaction, the desired bis(1′-
organylthiolatoferrocenyl)disulfane. The methyl and
phenyl derivatives (1 and 2) were isolated as deep
orange oils, which solidified over time. The tert-butyl
derivative was isolated as a flaky yellow/orange solid.
All of the products are air stable and soluble in common
organic solvents, but are only sparingly soluble in
alcohols. The reaction with phenyllithium also gave
isolable quantities of a yellow trimeric ferrocenediyl
species containing two disulfide bridges (4) (Figure 1).
Very small quantities of the analogous trimer were also
found with the methyllithium and tert-butyllithium
reactions but these were not isolated.
t
Ph, and Bu, respectively) and seem to depend on the
dilution and temperature of the reaction. Addition of
water to the crude reaction mixture (to quench excess
lithiating agents) before THF removal is crucial to
obtain a pure product. Failure to do so results in a range
of other monomeric and dimeric ferrocenediyl species,
which are largely inseparable by column chromatogra-
phy. For 1-3, four pseudotriplets (an AA′BB′CC′DD′
splitting pattern) would be expected in the 1H NMR
spectra. However, as a result of closely overlapping
signals, only the methyl derivative comes close to
showing this pattern. The spectra show a highfield
triplet and a downfield multiplet. For the tert-butyl
derivative the multiplet is split into a triplet and a
singlet.
Slow evaporation of a hexane solution of 1 gave yellow
platy needles and the single-crystal X-ray analysis
confirmed the structure and showed it to have a fairly
extended geometry with approximate C2 symmetry and
a torsional twist of ca. 87° about the S-S linkage
(Figure 2). The S(1)-S(2) bond length of 2.068(4) Å is
typical of an S-S single bond. Both ferrocenediyl units
have essentially eclipsed geometries with a stagger of
the Cp rings of less than 3° for Fe(1) and ca. 5° for Fe-
(2), the C5H4 rings being inclined to each other by 3° in
each case. The nonbonded S‚‚‚S distances within each
ferrocenediyl unit are both 3.56 Å. There are no inter-
molecular packing interactions of note.
The yields of the reactions to form 1, 2, and 3 were
variable (the best being 40%, 25%, and 70% for R ) Me,
II. P r elim in a r y Stu d ies of th e Coor d in a tion
Ch em ist r y of Bis(1′-or ga n ylt h iola t ofer r ocen yl)-
d isu lfa n es. The bis(1′-organylthiolatoferrocenyl)dis-
ulfanes (1-3) synthesized have the potential to bind to
metal centers in a variety of ways. The most likely
donors are the thioether sulfur atoms. The size and
flexibility of the ligands makes chelation of the two
thioether substituents to one metal center unlikely and
therefore oligomeric products may form. If chelates form
then it will prove interesting to see the involvement (if
(5) (a) Adeleke, J . A.; Chen, Y.-W.; Liu, L.-K. Organometallics 1992,
11, 2543. (b) Adeleke, J . A.; Liu, L.-K. J . Chin. Chem. Soc. 1992, 39,
61. (c) Dong, T.-Y.; Chang, C.-K. J . Chin. Chem. Soc. 1998, 45, 577.
(d) Butler, I. R.; Mussig, S.; Plath, M. Inorg. Chem. Commun. 1999, 2,
424. (e) Alexakis, A.; Benhaim, C. Tetrahedron: Asymmetry 2001, 12,
1151.
(6) (a) Long, N. J .; Martin, J .; Opromolla, G.; White, A. J . P.;
Williams, D. J .; Zanello, P. J . Chem. Soc., Dalton Trans. 1999, 1981.
(b) Gibson, V. C.; Long, N. J .; White, A. J . P.; Williams, C. K.; Williams,
D. J .; Fontani, M.; Zanello, P. J . Chem. Soc., Dalton Trans. 2002, 3280.
(7) Herberhold, M.; Nuyken, O.; Pohlmann, T. J . Organomet. Chem.
1991, 405, 217.

Unsymmetrical 1,1′-Bis(organylthiolato)ferrocenes
Organometallics, Vol. 23, No. 5, 2004 959
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 5
mol. A
mol. B
mol. A
mol. B
Pd-Cl
Pd-S(2)
S(1)-C(1)
2.327(2)
2.304(2)
1.774(6)
2.326(2)
2.306(2)
1.752(5)
Pd-S(1)
Pd-S(2A)
S(2)-C(6)
2.3546(14)
2.3025(12)
1.771(5)
2.3595(13)
2.3106(12)
1.781(5)
Cl-Pd-S(1)
102.25(6)
88.69(6)
168.96(7)
104.8(3)
120.2(3)
104.7(2)
101.38(6)
89.52(6)
169.05(7)
104.3(3)
120.7(2)
103.0(3)
Cl-Pd-S(2)
171.99(5)
172.90(6)
Cl-Pd-S(2A)
S(1)-Pd-S(2A)
C(1)-S(1)-C(11)
C(11)-S(1)-Pd
C(6)-S(2)-Pd
S(1)-Pd-S(2)
S(2)-Pd-S(2A)
C(1)-S(1)-Pd
C(6)-S(2)-PdA
PdA-S(2)-Pd
85.68(5)
83.35(6)
105.1(2)
102.7(2)
96.65(6)
85.48(6)
83.66(6)
104.3(2)
103.3(2)
96.34(6)
tion into the S-S bond had occurred resulting in a
structure reminiscent of that of a closely related mesityl-
substituted analogue reported by us recently.8 Crystals
of 5 contain two crystallographically independent com-
plexes, each with essentially identical geometries. The
complex has crystallographic Ci symmetry and a planar
central Pd2S2 ring (Figure 3), but with the chelating
sulfur lone pairs on S(1) and S(2) both lying on the same
side of the palladium coordination plane whereas in the
related mesityl species the symmetry is C2, the central
Pd2S2 ring being folded with the chelating sulfur lone
pairs lying on opposite sides.8 The geometry at pal-
ladium is distorted square planar with cis angles in the
range 83.35(6) to 102.25(6)° [83.66(6) to 101.38(6)° in
the second independent molecule], the most acute angle
in each case being associated with the Pd2S2 ring. The
Pd-S distances in the four-membered ring are ef-
fectively the same at ca. 2.31 Å (Table 1) and the Pd-S
bond to S(2), trans to chlorine, is ca. 0.05 Å shorter than
that to S(1), trans to sulfur. The pseudo-six-membered
chelate ring formed by Pd/S(1)/C(1)/Fe/C(6)/S(2) has a
sharply folded conformation with an out-of-plane fold
angle about the S(1)‚‚‚S(2) vector of ca. 71° [73°]; the
nonbonded S(1)‚‚‚S(2) separation is 3.17 Å [3.17 Å] and
the transannular Pd‚‚‚Fe separation is 3.88 Å [3.82 Å].
The ferrocenediyl units in both independent molecules
have essentially eclipsed geometries with stagger angles
of less than 5°, the rings being nearly parallel (maxi-
mum inclination of 2°). The only intermolecular interac-
tion of note is the formation, to each independent
complex, of C-H‚‚‚Cl hydrogen bonds from the ordered
included chloroform solvent molecules; the C‚‚‚Cl and
H‚‚‚Cl distances are 3.45, 2.55 Å [3.52, 2.65 Å] with
C-H‚‚‚Cl angles of 152° [148°]. There are no intercom-
plex interactions of note.
F igu r e 2. The molecular structure of 1; the S(1)-S(2) bond
length is 2.068(4) Å and the C(1)-S(1)-S(2) and S(1)-
S(2)-C(11) angles are 103.6(4)° and 103.7(4)°, respectively.
The 1H NMR shows an extremely broad ferrocenyl
region, with a broad singlet for the tert-butyl protons.
The mass spectrum shows a very small peak for the
molecular ion, and fragment peaks for loss of chloride,
and for the loss of both chlorides and both tert-butyl
groups. A peak for the free ligand is also evident. For 5
to be formed, the disulfane, 3, must first be reduced to
the thiolate. The thiolate is unstable and spontaneously
oxidizes back to the disulfane in the presence of oxygen.
As the reaction was not done under an inert atmo-
spheres (as it was not expected to be air-sensitive) an
improved yield would be expected if the reaction were
run under nitrogen in degassed solvents. The reducing
agent has not been identified, though the square-planar
geometry of the metal center shows that the incorpo-
rated palladium remains in the +2 oxidation state.
F igu r e 3. The molecular structure of one of the crystal-
lographically independent centrosymmetric complexes in
the crystals of 5; the transannular Pd‚‚‚Pd and S‚‚‚S
distances are 3.44 Å [3.44 Å] and 3.06 Å [3.08 Å], respec-
tively, the values in square brackets relating to the second
independent dimer.
any) of the disulfide bridge in the complex. The reaction
of 3 with [Pd(PhCN)2Cl2] gave a small quantity of a
dark-red precipitate (5), which was also soluble in polar
solvents but insoluble in nonpolar solvents. Dark-brown
needles suitable for X-ray diffraction were grown by slow
evaporation of a chloroform solution and the X-ray
analysis showed that the attempt to synthesize an
extended S,S′ palladium chelate complex of 3 had
proven unsuccessful. Instead an unusual insertion reac-
(8) Gibson, V. C.; Long, N. J .; White, A. J . P.; Williams, C. K.;
Williams, D. J . Chem. Commun. 2000, 2359.

960 Organometallics, Vol. 23, No. 5, 2004
Gibson et al.
methyl iodide 6 and 7 were synthesized in near quan-
titative yield. Both of these reactions were carried
out in THF at room temperature. Attempts were made
to introduce tert-butyl groups to cleaved 2 by using tert-
butyl bromide as the alkyl halide to give FcStBuSPh (8),
but with only limited success. When THF is used as the
solvent there is no reaction even after reflux for 24 h.
This is not too surprising as nucleophilic substitutions
with tert-butyl bromide go via an SN1 mechanism. SN1
reactions require polar, protic solvents (such as water
or methanol) to proceed efficiently, but such solvents
cannot be used in the first step of the reaction as lithium
triethylborohydride will reduce with them.
Meth od C. Th e “On e-P ot” Rea ction : Elu cid a tion
of th e Mech a n ism for 1,2,3-Tr ith ia -[3]-fer r ocen o-
p h a n e Clea va ge. Unlike the other methods used for
synthesizing 1,1′-bis(organothiolato)-ferrocenes this
method did not involve the isolation of a disulfane. As
before, 2 equiv of phenyllithium were reacted with 1,2,3-
trithia-[3]-ferrocenophane. However, instead of being
exposed to the air, and undergoing oxidation, the
unstable intermediate (as proposed by Herberhold9) was
kept under an inert atmosphere and reacted with
methyl iodide. It was hoped that FcSPhSMe (6) would
then be produced, probably in a higher yield than those
recorded for the other methods. However, though large
amounts of the desired products were formed, this was
coupled with significant amounts of BMSF and BPSF
that proved to be inseparable by column chromatogra-
phy (ratio 6 (63%):MSF (33%):BPSF (4%)).
F igu r e 4. Cleavage of (a) bis(1′-organothiolatoferrocenyl)-
disulfanes with organolithiums and (b) 1,2,3-trithia-[3]-
ferrocenophane with organolithiums.
III. Clea va ge of th e Disu lfa n es To Give 1,1′-Bis-
(or ga n ylth iola to)fer r ocen es: Syn th esis. Several un-
symmetrical 1,1′-bis(organylthiolato)ferrocenes (FcS-
MeSPh, 6; FcStBuSMe, 7; FcStBuSPh, 8) have been
synthesized (Scheme 1). 6 and 7 were isolated as deep
orange oils, whereas 8 is a yellow solid. All the species
are air-stable and soluble in most common organic
solvents, though 8 is only sparingly soluble in alcohols.
Three methods (A, B, and C) were utilized and though
method C did not give pure products, it did allow
elucidation of the mechanism for 1,2,3-trithia-[3]-ferro-
cenophane cleavage, leading to an explanation of the
origin of the different products formed during the
synthesis of bis(1′-organylthiolatoferrocenyl)disulfanes.
Meth od A. Organolithium reagents can be used to
cleave the disulfide bridge of bis(1′-organothiolatofer-
rocenyl)disulfanes. This was already shown when
methyllithium was used to cleave bis(1′- mesitylthio-
latoferrocenyl)disulfide.8 This methodology has been
used to synthesize 6 and 8 by cleaving 1 and 3,
respectively, with phenyllithium. The products are
easily purified by column chromatography. 6 was iso-
lated in only a 30% yield as a deep orange oil, and 8 in
a 50% yield as a yellow solid (the maximum yield
possible as the other 50% reforms the starting material
on exposure to air) (Figure 4a).
Meth od B. Yields can be improved by cleaving the
disulfide symmetrically. This allows both of the ferro-
cenyl units to become 1,1′-disubstituted products, hence
giving a maximum yield of 100%. The only limitation
is that any aromatic substituents must be introduced
first as they cannot easily be introduced by nucleophilic
substitution reactions. Both 2 and 3 were cleaved with
lithiumtriethylborohydride to give a 1-thiolato,1′-orga-
nothiolatoferrocene. These were then used as nucleo-
philes in substitution reactions with alkyl halides to give
6-8 (Scheme 1).
Realistically, the only reaction methyl iodide can
partake in is nucleophilic substitution. Therefore, any
methylthio groups in the products must have been
produced from thiolato attack on methyl iodide. There-
fore, the intermediates shown below must all be pro-
duced from the cleavage of 1,2,3-trithia-[3]-ferroceno-
phane with phenyllithium. Now that the products of the
cleavage are known the mechanism can be postulated.
Attack on the sulfur bridge of 1,2,3-trithia-[3]-ferro-
cenophane can occur in two places, either on the first
sulfur of the bridge, route i, or on the central sulfur,
route ii (Figure 4b). The reaction uses 2 equiv of the
organolithium; therefore the intermediate produced in
the first step must also be susceptible to nucleophilic
attack. The intermediate in route (i) can only realisti-
cally (a negatively charged lithium reagent is unlikely
to attack a negatively charged atom) be attacked at the
-
first sulfur of the disulfide, eliminating S2 to give the
symmetrical 1,1′-bisorganylthiolatoferrocenyl species.
Attack by the second equivalent of the organolithium
on the intermediate produced by route ii can occur at
either sulfur atom of the disulfide, giving the 1,1′-
dithiolato or the 1-thiolato,1′-thioether ferrocenediyl
species, eliminating R2S and RS-, respectively. The
product distribution will vary with different organo-
lithium reagents, based on their reactivity and sterics.
For instance, tert-butyllithium is much more reactive
than phenyllithium and on these grounds would there-
fore show an increased preference for route i. In
contrast, however, tert-butyllithium is also more steri-
cally bulky than phenyllithium, which would favor
attack at the bridgehead sulfur (route ii).
Methyl groups were easily introduced using methyl
iodide. When 2 and 3 were cleaved and reacted with
(9) Herberhold, M.; Brendel, H. J . Organomet. Chem. 1991, 413, 65.

Unsymmetrical 1,1′-Bis(organylthiolato)ferrocenes
Organometallics, Vol. 23, No. 5, 2004 961
F igu r e 5. Possible products from the oxidation step of method 4.
F igu r e 6. Oxidation step without RS-.
Via this mechanism, the products produced from
aerial oxidation of the reaction mixture can be ex-
plained. There are three thiolato species that can oxidize
to form disulfides: RS-, RS-Fc-S-, and S--Fc-S-. As one
of them is a dithiolato species it need not be just two
species that combine. The combinations are shown in
Figure 5. Obviously the larger n the more unlikely that
combination is. When water is added to the reaction
mixture, before the THF is removed, the impurities and
the monomeric ferrocenyl species are not observed. The
amount of the three thiolato species cannot be affected
at this point, but the way in which they oxidize can. If
the RS- species is “removed” from reaction then the
range of products is reduced. Monomeric ferrocenyl
species cannot be formed as no nonferrocenyl thiolato
species are present (Figure 6). The water addition forces
RS- to oxidize with itself to give RSSR (oxidation 4,
Figure 5), leaving the ferrocenyl species free to form the
products shown above. The oxidation of thiolates by
oxygen proceeds via an electron-transfer mechanism,
initially giving a thiyl radical and a peroxide ion.
Dimerization of the thiyl radical gives the disulfide.
the alkyl- and aryl-thio substituents are slightly electron
withdrawing.
The positive ion FAB mass spectra of all three ligands
gave strong molecular ions, with the tert-butyl-substi-
tuted ligands showing a peak at [M - 56]+ indicating a
tendency to lose the tert-butyl substituent. 8 also showed
a peak for 1-(tert-butylthio),1′-(thiolato)ferrocene from
unsymmetrical cleavage of the ethyl bridge.
IV. Meta l Com p lexes of Liga n d s 6-8. Complexes
of 6-8 have been formed via reaction with palladium-
(II), platinum(II), and tungsten(0) reagents (Scheme 2).
P r ep a r a tion of P la tin u m a n d P a lla d iu m Com -
p lexes. The dichloroplatinum and -palladium complexes
of 6-8 have all been synthesized by reacting a small
excess of ligand with [M(PhCN)2Cl2] (M ) Pt, Pd) in
toluene at 60 °C for 20 h. The complexes were isolated
as deep-brown solids in yields between 64% and 75%.
All of the complexes (9-14) were insoluble in nonpolar
solvents, and most only sparingly soluble in chlorinated
1
solvents. H NMR spectra were measured for all of the
complexes except for 14, which was not sufficiently
soluble to give a signal, and significant changes occur
in the spectra when compared to those for the free
ligands. Several broad peaks are observed in the ferro-
cenyl region, all of which are significantly shifted
downfield (some by over 1 ppm). The peaks for the sulfur
substituents are also shifted downfield with slight
broadening. The downfield shift can be assigned to
magnetic anisotropy, or the inductive effect of the metal
dihalide moiety. As with other [3]-ferrocenophanes, the
broad signals can be attributed to fluxionality. There
are two fluxional modes that operate, the first being
bridge reversal, which is analogous to the chair-chair
conformational exchange observed in cyclohexane. The
rate of bridge reversal depends on the length of the
Ch a r a ct er iza t ion . As with the bis(1′-organylthio-
latoferrocenyl)disulfanes, an AA′BB′CC′DD′ splitting
1
pattern is expected in the H NMR, appearing as four
pseudotriplets. This pattern is clearly evident for 6-8,
although there is significant overlapping in some of the
spectra. Precise assignment of the triplets to specific
protons is difficult, but tentative assignments can be
made by comparison to the analogous symmetrically
substituted ferrocenes.10 All of the pseudotriplets occur
downfield of ferrocene (δ 4.04 ppm), indicating that both
(10) Orrell, K. G.; Sik, V.; Brubaker, C. H., J r.; McCulloch, B. J .
Organomet. Chem. 1984, 276, 267.

962 Organometallics, Vol. 23, No. 5, 2004
Sch em e 2. F or m a tion of Com p ou n d s 9-17
Gibson et al.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 9
Pd-S(1)
Pd-Cl(1)
S(1)-C(1)
2.3134(13)
2.294(2)
1.767(5)
Pd-S(2)
Pd-Cl(2)
S(2)-C(6)
2.3225(14)
2.299(2)
1.755(6)
Cl(1)-Pd-Cl(2)
Cl(2)-Pd-S(1)
Cl(2)-Pd-S(2)
90.45(6)
93.59(5)
175.24(5)
Cl(1)-Pd-S(1)
Cl(1)-Pd-S(2)
S(1)-Pd-S(2)
C(1)-S(1)-Pd
175.90(6)
93.40(6)
82.54(5)
103.0(2)
C(1)-S(1)-C(16) 104.5(2)
C(16)-S(1)-Pd
C(6)-S(2)-Pd
114.87(14) C(6)-S(2)-C(17) 100.3(3)
101.6(2) C(17)-S(2)-Pd 113.7(3)
the geometry at palladium are small with cis angles in
the range 82.54(5)-93.59(5)°. The only intercomplex
interaction of note is a parallel π-π stacking of Ci-
related S-phenyl rings having mean interplanar and
centroid‚‚‚centroid separations of 3.56 and 4.24 Å,
respectively.
F igu r e 7. The molecular structure of 9.
P r ep a r a tion of Tu n gsten Com p lexes. W(CO)5(thf)
is a well-known precursor for tungsten complexes and
can be made by irradiating a THF solution of tungsten
hexacarbonyl with UV radiation (from a mercury lamp,
125 W). With longer irradiation times, significant
quantities of W(CO)4(thf)2 may also be produced. When
synthesizing the tungsten complexes of the ferrocenediyl
ligands 6-8 the tungsten hexacarbonyl solution was
irradiated for 10 min, giving significant quantities of
both the penta- and tetracarbonyl precursors. The
precursor solution was then added to a solution of each
of the ligands 6-8 in THF and stirred for 20 h at room
temperature; however, only 1-(tert-butylthio),1′-(meth-
ylthio)ferrocene (7) reacted well to give 16. The other
two solutions were heated at 40 °C for a further 24 h,
which gave small quantities of 17 but no 15 (Scheme
2). It is possible that the phenylthio group is not a strong
enough donor to displace a THF ligand (remembering
that THF is present in a huge excess as it is the solvent).
bridge, and the atoms that make up the bridge. The
second fluxional mode, which only occurs in heteroatom-
substituted ferrocenophanes, is pyramidal heteroatom
inversion. In symmetrically substituted 1,1′-bis(orga-
nylthiolato)ferrocenes complexed to MX2 metal frag-
ments (M ) Pd, Pt) the rate of sulfur inversion is
dependent on the transition metal, the halogen, and the
sulfur substituent.10 Sulfur inversion tends to be slow
on the NMR time scale. These fluxional processes in
related compounds have been well-studied and we
believe similar findings would be observed here but this
has not been pursued.
A two-layer crystallization (dichloromethane:hexane
1:1) of 9 gave orange platy needles suitable for an X-ray
diffraction study. The complex has a solid-state struc-
ture in which the ferrocenediyl units have an eclipsed
geometry (stagger and inclination angles of less than
1°) and a nonbonded S‚‚‚S contact of 3.06 Å (Figure 7,
Table 2). The six-membered chelate ring (vide supra)
has a steeply folded geometry very similar to that seen
for 5 with an out-of-plane bend about the S(1)‚‚‚S(2)
vector of ca. 76°, the sulfur lone pairs both lying on the
same side of the palladium coordination plane; the
nonbonded Pd‚‚‚Fe separation is 3.76 Å. Distortions in
1
The complexes 16 and 17 were characterized by H
NMR, IR, and mass spectrometry. In contrast to the
platinum and palladium derivatives these complexes
1
show four sharp pseudotriplets in their H NMR. This
indicates that both the fluxional processes (bridge
reversal and sulfur inversion) are at their fast-exchange

Unsymmetrical 1,1′-Bis(organylthiolato)ferrocenes
Organometallics, Vol. 23, No. 5, 2004 963
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 16
W-S(1)
2.585(2)
1.964(8)
2.026(7)
1.755(7)
W-S(2)
2.565(2)
1.970(8)
2.043(7)
1.769(7)
W-C(16)
W-C(18)
S(1)-C(1)
W-C(17)
W-C(19)
S(2)-C(6)
C(16)-W-C(17)
C(17)-W-C(18)
C(17)-W-C(19)
C(16)-W-S(2)
C(18)-W-S(2)
C(16)-W-S(1)
C(18)-W-S(1)
S(2)-W-S(1)
87.9(3)
86.4(3)
86.4(3)
89.8(2)
90.5(2)
171.3(2)
88.3(2)
82.59(5)
114.7(2)
100.3(3)
109.7(2)
C(16)-W-C(18)
C(16)-W-C(19)
C(18)-W-C(19)
C(17)-W-S(2)
C(19)-W-S(2)
C(17)-W-S(1)
C(19)-W-S(1)
C(1)-S(1)-C(11)
C(11)-S(1)-W
C(6)-S(2)-W
87.7(3)
87.2(3)
171.3(3)
176.2(2)
96.4(2)
99.6(2)
97.7(2)
102.1(3)
117.0(2)
113.8(2)
C(1)-S(1)-W
C(6)-S(2)-C(15)
C(15)-S(2)-W
F igu r e 8. The molecular structure of 16.
limit. All four have significant downfield shifts from the
free ligand and as expected there are also downfield
shifts of the pendant thioether groups. The mass spectra
of 16 and 17 show the molecular ion and a sequence of
peaks from the loss of carbon monoxide and tert-butyl
(which weighs approximately the same as two carbon
monoxides). Tungsten fragments are easily identified
from their isotope pattern (180W ) 0.13%, 182W ) 26.3%,
183W ) 14.3%, 184W ) 30.6%, 186W ) 28.6%). The CO
stretches in the IR spectra for 16 and 17 match the
pattern for symmetrically substituted ferrocenediyl
tungsten complexes,11 indicating that the asymmetry of
the ligand is too far away to significantly affect the
carbonyl stretches.
F igu r e 9. Cyclic (s) and Osteryoung square wave (- - -)
voltammograms recorded at a platinum electrode in CH2-
Cl2 solutions containing (a) 3 (1.0 × 10-3 mol dm-3) and
(b) 5 (0.8 × 10-3 mol dm-3). Supporting electrolyte: [NBu4]-
[PF6] (0.2 mol dm-3) Scan rates: (s) 0.2 V s-1; (- - -) 0.1 V
Crystals of 16 suitable for X-ray structure determi-
nation were grown by cooling a dichloromethane-
hexane (1:1) solution to 0 °C. An X-ray analysis shows
16 to have a structure very similar to that of its PPh2,-
SMe analogue6b but with the sulfur lone pairs lying on
opposite sides of the equatorial tungsten coordination
plane (Figure 8), cf. the syn geometries observed in 5
and 9. This anti relationship of the lone pairs in 16 is a
consequence of an inversion of the chirality at one of
the sulfur centers. The six-membered chelate ring has
a ca. 55° fold about the S(1)‚‚‚S(2) vector and the C5H4
rings are eclipsed (stagger of 2°) and essentially parallel
(tilt of 2°). The nonbonded W‚‚‚Fe distance is 4.37 Å, cf.
4.36 Å in the PPh2,SMe analogue.6b Distortions from
octahedral geometry at tungsten are small with cis
angles ranging between 86.4(3)° and 99.6(2)°. The axial
W-CO bond lengths are both essentially the same
(Table 3) and are noticeably slightly longer (by ca. 0.07
Å) than their equatorial counterparts. There are no
noteworthy intermolecular packing interactions.
Electr och em istr y. As previously reported for un-
substituted diferrocenyldisulfane,12 complexes 1 and 3
in CH2Cl2 solution exhibit two separated one-electron
oxidations. As a typical example, Figure 9a shows the
cyclic voltammetric profile of complex 3. Also illustrated
is the voltammetric response of the dipalladium complex
5, Figure 9b, which originates from complex 3 (see
above). It is noted that, despite the features of chemical
s-1
.
reversibility of the sequence [3]/[3]+/[3]2+, step-by-step
controlled electrolysis followed by cyclic voltammetric
tests on the resulting solutions proved that the mono-
cation [3]+ is quite stable, whereas the dication [3]2+
slowly decomposes. On passing from 3 to [3]+, the
original yellow solution turns orange-brown, thus sug-
gesting that the sulfur substituents significantly con-
tribute to the HOMO level of the mixed-valent ferroce-
nium monocation (iron-centered ferrocenium species are
blue to green).
In qualitative terms, similar behavior is displayed by
complex 1. Both complexes also exhibit a further ir-
reversible oxidation at higher potential values (Ep in the
range +1.5 to +1.6 V), which is attributed to the
disulfane bridge. Complex 5 also exhibits two separated
one-electron oxidations, even if their separation (∆E° ′
) 85 mV) is significantly lower than that of complexes
3 and 1 (∆E° ′ ) 150 mV), presumably due to the
increased distance between the iron centers. The close-
ness of the two steps prevented the determination of
the stability of the monocation [5]+ by controlled po-
tential coulometry, but also in this case exhaustive two-
electron oxidation led to decomposition. Though not
shown in the figure, complex 5 also undergoes a single
irreversible reduction, (Ep ) -1.0 V), which is desig-
nated as palladium-centered.
Since the separation between the formal electrode
potentials of two redox sites present in a molecule is
routinely assumed to be representative of the degree of
their intramolecular electronic communication,13 it is
suggested that the electronic mobility in 3 (and 1) is
(11) Abel, E. W.; Long, N. J .; Orrell, K. G.; Osborne, A. G.; Sik, V.
J . Organomet. Chem. 1989, 387, 275.
(12) (a) Scholl, H.; Sochaj, K. Electrochim. Acta 1989, 34, 915. (b)
Osborne, A. G.; Hollands, R. E.; Nagy, A. G. J . Organomet. Chem. 1989,
373, 229.

964 Organometallics, Vol. 23, No. 5, 2004
Gibson et al.
Ta ble 4. F or m a l Electr od e P oten tia ls (V vs SCE)
a n d P ea k -to-P ea k Sep a r a tion s (m V) for th e
F er r ocen e-Cen ter ed P r ocesses Exh ibited by
Com p lexes 1, 3, a n d 5 in CH2Cl2 Solu tion
Ta ble 5. F or m a l Electr od e P oten tia ls (V vs SCE)
a n d P ea k -to-P ea k Sep a r a tion s (m V) for th e Red ox
P r ocesses Exh ibited by Com p lexes 9-14 in CH2Cl2
Solu tion
a
a
a
b
a
complex
E° ′0/+
∆Ep
E° ′+/2+
∆Ep
complex
E° ′(0/+)
∆Ep
i
pc/ipa
Ep(0/2-)
1
3
5
+0.50
+0.59
+0.83b
+0.39
60
62
c
+0.65
+0.74
+0.92
65
71
c
9 (Pd)
+1.08c,a
+1.04
-0.67
-0.60
-0.58
-1.43
-1.64
-1.34
10 (Pd)
11 (Pd)
12 (Pt)
13 (Pt)
14 (Pt)
60
0.3
+1.05c,a
+1.08
F cH
60
60
62
80
0.7
0.7
0.5
+1.00
+0.99
Measured at 0.1 V s-1
.
From OSWV. c Difficult to measure.
a
b
a
b
Measured at 0.1 V s-1
.
Measured at 0.2 V s-1
.
c Peak
potential value for irreversible processes.
platinum monocations tend to decompose. All the plati-
num and palladium complexes also show the irrevers-
ible reduction assigned to the M(II)/M(0) electron trans-
fer. The pertinent electrochemical data are compiled in
Table 5.
Exp er im en ta l Section
Gen er a l P r oced u r es. All preparations were carried out
with the standard Schlenk techniques.16 All solvents were
distilled over standard drying agents under nitrogen directly
before use and all reactions were carried out under an
atmosphere of nitrogen. Alumina gel (neutral, grade II) was
used for chromatographic separations. All NMR spectra were
recorded with use of a Delta upgrade on a J EOL EX270 MHz
spectrometer operating at 250.1 MHz (1H). Chemical shifts are
reported in δ with CDCl3 (1H, δ 7.25 ppm) as the reference for
the spectra. Infrared spectra were recorded with NaCl solution
cells (CH2Cl2) and a Mattson Polaris Fourier Transform IR
spectrometer. Mass spectra were recorded by using positive
FAB methods, on an Autospec Q mass spectrometer. Mi-
croanalyses were carried out in the Department of Chemistry,
University of North London.
F igu r e 10. Cyclic voltammograms recorded at a platinum
electrode in CH2Cl2 solutions containing [NBu4][PF6] (0.2
mol dm-3) and (a) 12 (0.8 × 10-3 mol dm-3) or (b) 9 (0.9 ×
10-3 mol dm-3). Scan rate: 0.2 V s-1
.
higher than that in 5. It is, however, important to
underline that in 5 the insertion of the two palladium
atoms does not compromise the mutual interaction
between the two peripheral ferrocenediyl units.
From the electrochemical viewpoint, based on the
respective comproportionation constants13 ([1]+, Kcom
)
340; [3]+, Kcom ) 340; [5]+, Kcom ) 26), the mixed-valent
monocations [1]+ and [3]+ belong to the partially delo-
calized Robin-Day Class II, whereas [5]+ belongs to the
localized Class I.14 The formal electrode potentials of
the redox processes of complexes 1, 3, and 5 are reported
in Table 4.
St a r t in g Ma t er ia ls. 1,2,3-Trithia-[3]-ferrocenophane,17
19
[Pd(PhCN)2Cl2],18 [Pt(PhCN)2Cl2],18 and [Cu(MeCN)4]PF6
were synthesized by using standard literature procedures,
except that the 1,1′-dilithioferrocene intermediate in the
synthesis of 1,2,3-trithia-[3]-ferrocenophane was used in situ.
t
All chemicals were purchased from Aldrich, except for BuLi,
MeLi, and LiEt3BH, which were purchased from Acros.
P r ep a r a tion of Bis(1′-or ga n ylth iola tofer r ocen yl)d is-
u lfa n es. Gen er a l p r oced u r e: To a solution of 1,2,3-trithia-
[3]-ferrocenophane (1 equiv) in dry deoxygenated THF cooled
to -78 °C was added an organolithium reagent (2.2 equiv).
The orange solution gradually darkened to deep red on
warming to room temperature and stirring for 20 h. The
reaction was exposed to the air and water was added (50 mL).
The THF was removed under vacuum and the aqueous layer
extracted with dichloromethane (8 × 50 mL). The combined
organic fractions were dried (MgSO4) and evaporated to
dryness. Column chromatography (7:3 hexane:dichloromethane)
allowed the separation of the products. All of the columns gave
small amounts of 1,2,3-trithia-[3]-ferrocenophane, and several
other yellow fractions. The first of which was the desired
product.
The difference in redox potentials between 1 and 3 is
obviously expected on the basis of the inductive effects
of the substituents, and as expected the complexation
of 3 with palladium makes the oxidation significantly
more difficult. Considering the metalloferrocenophanes
9-14, as a representative example, Figure 10 compares
the cyclic voltammetric profile of the platinum complex
12 with that of the corresponding palladium complex
9. As already observed for related complexes15 (and in
contrast to the platinum complexes that afford an
oxidation process with features of transient chemical
reversibility in the cyclic voltammetric time scale), the
palladium complexes give rise to an oxidation process
that is accompanied by fast release of the corresponding
free ferrocene ligands. It is, however, noted that in the
long times of macroelectrolysis, the electrogenerated
Bis(1′-m eth ylth iola tofer r ocen yl)d isu lfa n e (1): Reaction
of 1,2,3-trithia-[3]-ferrocenophane (1.40 g, 5.00 mmol) with
MeLi (1.6 M in ether, 7.0 mL, 11.2 mmol) gave an oily orange
crude product. Column chromatography (7:3 hexane:dichlo-
romethane) gave MeS-Fc-SS-Fc-SMe (0.53 g, 1.00 mmol, 40%
(13) (a) Palaniappan, V.; Singru, R. M.; Agarwala, U. C. Inorg. Chem.
1988, 27, 181. (b) Astruc, D. Electron Transfer and Radical Processes
in Transition-Metal Chemistry; Wiley-VCH: New York, 1995. (c)
Brunschwig, B. S.; Sutin, N. Coord. Chem. Rev. 1999, 187, 233. (d)
Demadis, K. D.; Hartshorn, C. M.; Meyer, T. J . Chem. Rev. 2001, 101,
2655. (e) Barriere, F.; Camire, N.; Mueller-Westerhoff, U. T.; Sanders,
R. J . Am. Chem. Soc. 2002, 124, 7262.
(14) Robin, M. B.; Day, P. Adv. Inorg. Chem. Radiochem. 1967, 10,
247.
(15) Gibson, V. C.; Long, N. J .; Williams, C. K.; Fontani, M.; Zanello,
P. J . Chem. Soc., Dalton Trans. 2003, 3599.
(16) Errington, R. J . In Advanced Practical Inorganic and Metalor-
ganic Chemistry; Blackie: London, UK, 1997.
(17) Bishop, J . J .; Davidson, A.; Katcher, M. L.; Lichtenberg, D. W.;
Merrill, R. E.; Smart, J . C. J . Organomet. Chem. 1971, 27, 41.
(18) Hartley, F. R. The Chemistry of Platinum and Palladium;
Applied Science Publishers: London, UK, 1971; p 462.
(19) Kubas, G. J . Inorg. Synth. 1990, 28, 68.

Unsymmetrical 1,1′-Bis(organylthiolato)ferrocenes
Organometallics, Vol. 23, No. 5, 2004 965
yield) as a deep-red oil. Anal. Calcd for C22H22S4Fe2: C, 50.20,
H, 4.21. Found: C, 50.26, H, 4.25. 1H NMR (CDCl3, 270 MHz,
ppm) δ 4.30-4.25 (m, 12H, C5H4), 4.15 (t, 4H, C5H4), 2.25 (s,
6H, CH3). Mass spectrum (m/z): 526 ([M]+), 263 ([M -
SfcSMe]+). Crystals suitable for X-ray analysis were grown
from slow evaporation of a hexane solution. Crystal data for
1: C22H22S4Fe2, M ) 526.3, orthorhombic, Pna21 (no. 33), a )
14.820(1) Å, b ) 6.271(1) Å, c ) 23.169(1) Å, V ) 2153.2(2) Å3,
Z ) 4, Dc ) 1.624 g cm-3, µ(Cu KR) ) 14.5 mm-1, T ) 293 K,
yellow platy needles; 1524 independent measured reflections,
F2 refinement, R1 ) 0.052, wR2 ) 0.132, 1374 independent
observed absorption corrected reflections [|Fo| > 4σ(|Fo|), 2θmax
) 120°], 255 parameters. Polarity tests gave evidence of
racemic twinning [R1+ ) 0.0573, R1- ) 0.0581, x+ ) +0.51(3),
x- ) +0.49(3)] and no absolute structure could be assigned.
CCDC 229586.
p r oced u r e: To a solution of the bis(1′-organylthiolatoferro-
cenyl)disulfane (1 equiv) in dry deoxygenated THF cooled to
-78 °C was added an organolithium reagent (2.2 equiv). The
yellow solution was allowed to warm to room temperature and
was stirred for 20 h. The reaction was exposed to the air and
the solvent removed. The residual orange oil was dissolved in
dichloromethane and extracted with water (50 mL). The
aqueous layer was further extracted with dichloromethane (5
× 50 mL) and the combined organic fractions dried (MgSO4)
and evaporated to dryness. Column chromatography (7:3
hexane:dichloromethane) allowed the separation of the prod-
ucts with the desired product comprising the first band and
the starting material the second.
1-(Meth ylth iola to),1′-(p h en ylth iola to)fer r ocen e (6): Re-
action of MeS-Fc-SS-Fc-SMe (1) (0.20 g, 0.38 mmol) with PhLi
(1.8 M in cyclohexane/ether (7:3), 0.5 mL, 0.90 mmol) gave an
oily orange crude product. Column chromatography (7:3 hex-
ane:dichloromethane) gave MeS-Fc-SS-Fc-SMe (6) (0.13 g, 0.25
mmol) and an orange oil of FcSMeSPh (0.08 g, 0.23 mmol, 30%
yield). Anal. Calcd for C17H16S2Fe: C, 60.10, H, 4.74. Found:
C, 60.14, H, 4.81. 1H NMR (CDCl3, 270 MHz, ppm) δ 7.19-
7.13 (m, 2H, C6H5), 7.06-7.02 (m, 3H, C6H5), 4.50-4.36 (m,
6H, C5H4), 4.27 (t, 2H, C5H4), 2.32 (s, 3H, CH3). Mass spectrum
(m/z): 340 ([M]+).
Bis(1′-p h en ylth iola tofer r ocen yl)d isu lfa n e (2): Reaction
of 1,2,3-trithia-[3]-ferrocenophane (2.01 g, 7.14 mmol) with
PhLi (1.8 M in cyclohexane/ether (7:3), 9.0 mL, 16.20 mmol)
gave an oily orange crude product. Column chromatography
(7:3 hexane:dichloromethane) gave PhS-Fc-SS-Fc-SPh as a
yellow powder (0.58 g, 0.90 mmol, 25% yield) and the trimeric
species PhS-Fc-SS-Fc-SS-Fc-SPh (4) (0.12 g, 0.13 mmol, 5%
yield) also as a yellow powder. PhS-Fc-SS-Fc-SPh (2): Anal.
Calcd for C32H26S4Fe2: C, 59.09, H, 4.03. Found: C, 59.14, H,
3.94. 1H NMR (CDCl3, 270 MHz, ppm) δ 7.18-7.11 (m, 2H,
C6H5), 7.07-6.99 (m, 3H, C6H5), 4.39-4.37 (m, 6H, C5H4), 4.32
(t, 2H, C5H4). Mass spectrum (m/z): 650 ([M]+), 325 ([M -
1-(ter t-Bu tylth iola to),1′-(p h en ylth iola to)fer r ocen e (8):
t
Reaction of BuS-Fc-SS-Fc-StBu (3) (0.86 g, 1.40 mmol) with
PhLi (1.8 M in cyclohexane/ether, 1.75 mL, 3.15 mmol) gave
an oily orange crude product. Column chromatography (7:3
SFcSPh]+). PhS-Fc-SS-Fc-SS-Fc-SPh (4): Anal. Calcd for
t
hexane:dichloromethane) gave BuS-Fc-SS-Fc-StBu and FcSt-
1
C
42H34S6Fe3: C, 56.14, H, 3.81. Found: C, 56.21, H, 3.75. H
BuSPh (8) (0.27 g, 0.71 mmol, 50% yield) as a yellow powder.
Anal. Calcd for C20H22S2Fe: C, 61.62, H, 5.99. Found: C, 61.72,
H, 5.85. 1H NMR (CDCl3, 270 MHz, ppm) δ 7.18-7.12 (m, 2H,
C6H5), 7.09-7.00 (m, 3H, C6H5), 4.40 (t, 2H, C5H4), 4.37 (t, 2H,
C5H4), 4.36 (t, 2H, C5H4), 4.33 (t, 2H, C5H4), 1.20 (s, 9H, CH3).
NMR (CDCl3, 270 MHz, ppm) δ 7.17-7.12 (m, 4H, C6H5),
7.06-6.98 (m, 6H, C6H5), 4.38-4.21 (m, 24H, C5H4). Mass
spectrum (m/z): 898 ([M]+), 325 ([PhSFcS]+).
Bis(1′-ter t-bu tylth iola tofer r ocen yl)d isu lfa n e (3): Reac-
tion of 1,2,3-trithia-[3]-ferrocenophane (3.06 g, 10.92 mmol)
t
Mass spectrum (m/z): 382 ([M]+), 326 ([M - Bu]+).
t
with BuLi (1.5 M in pentanes, 16.0 mL, 24.00 mmol) gave an
Meth od B. 1-(Meth ylth iola to),1′-(p h en ylth iola to)fer -
r ocen e (6): To a solution of the bis(1′-phenylthiolatoferro-
cenyl)disulfane (0.35 g, 0.54 mmol, 1 equiv) in dry deoxygen-
ated THF (40 mL) was added lithium triethylborohydride (1.0
M in THF, 1.35 mL, 1.35 mmol, 2.5 equiv). The solution was
stirred for 3 h, during which time the yellow solution turned
orange. A deoxygenated solution of methyl iodide (0.15 mL,
2.41 mmol) in THF (20 mL) was added and the reaction was
stirred for 20 h. The THF was evaporated to dryness and the
crude product redissolved in dichloromethane (50 mL) and
washed with water (50 mL) with the aqueous layer being
washed further with dichloromethane (3 × 30 mL). The
combined organic fractions were dried (MgSO4) and evaporated
to dryness. A short column (7:3 hexane:dichloromethane) was
run to remove any traces of the starting material to leave an
orange oil of FcSMeSPh (0.35 g, 1.01 mmol, 94% yield).
orange crude product. Column chromatography (7:3 hexane:
dichloromethane) gave tBuS-Fc-SS-Fc-StBu (2.33 g, 3.81 mmol,
70% yield) as a flaky, semicrystalline yellow solid. Anal. Calcd
for C28H34S4Fe2: C, 55.09, H, 5.61. Found: C, 55.48, H, 5.27.
1H NMR (CDCl3, 270 MHz, ppm) δ 4.28 (s, 8H, C5H4), 4.26 (t,
3
4H, C5H4), 4.20 (t, 4H, J ) 1.7 Hz, C5H4), 1.14 (s, 18H, CH3).
Mass spectrum (m/z): 610 ([M]+), 305 (([M - SFcStBu]+)), 249
([S - Fc - S]+).
P r ep a r a t ion of Bis(1′-ter t-b u t ylt h iola t ofer r ocen yl)-
d isu lfa n e Com p lex of P a lla d iu m (5). Gen er a l p r oced u r e:
To a solution of [M(PhCN)2Cl2] (M ) Pt, Pd) (1 equiv) in
toluene (50 mL) at 60 °C was added a toluene (10 mL) solution
of the ligand (3) (1.1 equiv). The solution immediately dark-
ened and was stirred for 20 h by which time a dark precipitate
had formed. The reaction was cooled and the precipitate
filtered, washed with hot hexane (50 mL) and diethyl ether
(50 mL), and dried in vacuo for 1 h, to give a dark-red
precipitate of [{FcStBu(µ-S)}2Pd2Cl2] (0.03 g, 0.04 mmol, 28%
yield). Anal. Calcd for C28H34S4Fe2Pd2Cl2: C, 37.61, H, 3.83.
1-(ter t-Bu tylth iola to),1′-(m eth ylth iola to)fer r ocen e (7):
To a solution of bis(1′-tert-butylthiolatoferrocenyl)disulfane
(0.61 g, 1.00 mmol, 1 equiv) in dry deoxygenated THF (50 mL)
was added lithium triethylborohydride (1.0 M in THF, 2.50
mL, 2.50 mmol, 2.5 equiv). The solution was stirred for 3 h,
during which time the yellow solution turned orange indicating
the presence of a ferrocenyl thiolate. A deoxygenated solution
of methyl iodide (0.30 mL, 4.82 mmol) in THF (20 mL) was
added and the reaction was stirred for 20 h. The THF was
evaporated to dryness and the crude product redissolved in
dichloromethane (50 mL) and washed with water (50 mL), the
aqueous layer being washed further with dichloromethane (3
× 50 mL). The combined organic fractions were dried (MgSO4)
and evaporated to dryness. A short column (7:3 hexane:
dichloromethane) was run to remove any traces of the starting
material giving an orange oil of FcStBuSMe (0.63 g, 1.98 mmol,
99% yield). Anal. Calcd for C15H20S2Fe: C, 56.25, H, 6.29.
1
Found: C, 38.07, H, 3.76. H NMR (C2D2Cl2, 270 MHz, ppm)
δ 5.10-4.00 (m, br, 16H, C5H4), 1.36 (s, 18H, CH3). Mass
spectrum (m/z): 894 ([M]+), 857 ([M - Cl]+), 709 ([M - 2Cl -
tBu]+), 305 ([FcStBuS]+). Crystals suitable for X-ray diffraction
were grown by slow evaporation of a CHCl3 solution. Crystal
data for 5: C28H34S4Cl2Fe2Pd2‚2CHCl3, M ) 1132.9, triclinic,
P1h (no. 2), a ) 11.441(1) Å, b ) 13.605(1) Å, c ) 13.961(1) Å,
R ) 89.41(1)°, â ) 72.57(1)°, γ ) 79.37(1)°, V ) 2035.4(3) Å3,
Z ) 2 (two independent Ci symmetric molecules), Dc ) 1.849
g cm-3, µ(Mo KR) ) 2.32 mm-1, T ) 293 K, very dark-brown
needles; 7167 independent measured reflections, F2 refine-
ment, R1 ) 0.046, wR2 ) 0.093, 5049 independent observed
absorption corrected reflections [|Fo| > 4σ(|Fo|), 2θmax ) 50°],
416 parameters. CCDC 229587.
1
Clea va ge of th e Disu lfid es To Give 1,1′-Bis(or ga -
n ylt h iola t o)fer r ocen es, F cSR SR′. Met h od A. Gen er a l
Found: C, 56.34, H, 6.41. H NMR (CDCl3, 270 MHz, ppm) δ
4.30-4.28 (m, 4H, C5H4), 4.25 (vt, 2H, C5H4), 4.19 (vt, 2H,

966 Organometallics, Vol. 23, No. 5, 2004
Gibson et al.
C5H4), 2.28 (s, 3H, CH3), 1.18 (s, 9H, CH3). Mass spectrum (m/
([M]+), 523 ([M - Cl]+), 488 ([M - 2Cl]+), 467 ([M - Cl -
t
t
z): 320 ([M]+), 264 ([M - Bu]+).
tBu]+), 431 ([M - 2Cl - Bu]+), 382 ([FcStBuSPh]+).
Meth od C. On e-P ot Syn th esis of 1-Meth ylth io-1′-p h en -
ylth iofer r ocen e, F c(SMe)(SP h ) (6). Excess MeI: To a
solution of 1,2,3-trithia-[3]-ferrocenophane (1.26 g, 4.50 mmol)
in dry deoxygenated THF (80 mL) at -78°C was added PhLi
(1.8 M solution in cyclohexane/ether (7:3), 6.5 mL, 11.7 mmol,
2.6 equiv). The solution was allowed to warm to room tem-
perature and was stirred for 20 h, during which time the
orange solution turned deep red. A solution of deoxygenated
MeI (3 mL, 48.20 mmol) in dry deoxygenated THF (20 mL)
was added, immediately changing to a yellow solution, which
was then stirred for 20 h, and the THF was removed in vacuo.
The crude product was redissolved in dichloromethane (50 mL)
and washed with water (50 mL), the aqueous layer being
washed further with dichloromethane (3 × 50 mL). The
combined organic fractions were dried (MgSO4) and evaporated
to dryness. Column chromatography (9:1 hexane:dichlo-
romethane) gave a deep orange oil (1.28 g) as the first product
from the column. The oil was found to contain Fc(SMe)(SPh)
(6), 1,1′-bis(methylthio)ferrocene (BMSF), and 1,1′-bis(phen-
ylthio)ferrocene (BPSF) in a ratio of approximately 63%:33%:
[1-(Meth ylth iola to),1′-(p h en ylth iola to)fer r ocen e]p la ti-
n u m d ich lor id e (12): Reaction of 6 (0.10 g, 0.29 mmol) with
bis(benzonitrile)platinum dichloride (0.12 g, 0.25 mmol) gave
a dark-brown precipitate of [Pt(FcSMeSPh)Cl2] (0.11 g, 0.19
mmol, 75% yield). Anal. Calcd for C17H16S2FePtCl2: C, 33.68,
H, 2.66. Found: C, 33.58, H, 2.63. 1H NMR (C2D2Cl2, 270 MHz,
ppm) δ 7.38-7.32 (m, 8H, C6H5), 5.54 (br, C5H4), 5.33 (br,
C5H4), 4.92 (br, C5H4), 4.71 (br, C5H4), 4.61 (br, C5H4), 4.44
(br, C5H4), 4.35 (br, C5H4), (5.54-4.35 ppm ) 8H), 2.63 (s, 3H,
3J Pt-H ) 43.3 Hz; CH3). Mass spectrum (m/z): 606 ([M]+), 571
([M - Cl]+), 340 ([FcSMeSPh]+).
[1-(ter t-Bu t ylt h iola t o),1′-(m et h ylt h iola t o)fer r ocen e]-
p la tin u m d ich lor id e (13): Reaction of 7 (0.93 g, 0.29 mmol)
with bis(benzonitrile)platinum dichloride (0.12 g, 0.25 mmol)
gave a dark-brown precipitate of [Pt(FcStBuSMe)Cl2] (0.10 g,
0.18 mmol, 70% yield). Anal. Calcd for C15H20S2FePtCl2: C,
30.73, H, 3.44. Found: C, 30.75, H, 3.18. 1H NMR (C2D2Cl2,
270 MHz, ppm) δ 4.85-435 (m, br, 8H, C5H4), 2.50 (s, 3H,
CH3), 1.48 (s, 9H, CH3). Mass spectrum (m/z): 320 (FcSt-
BuSMe).
[1-(ter t-Bu t ylt h iola t o),1′-(p h en ylt h iola t o)fer r ocen e]-
p la tin u m d ich lor id e (14): Reaction of 8 (0.05 g, 0.13 mmol)
with bis(benzonitrile)platinum dichloride (0.05 g, 0.11 mmol)
gave a dark-brown precipitate of [Pt(FcStBuSPh)Cl2] (0.06 g,
0.09 mmol, 68% yield). Anal. Calcd for C20H22S2FePtCl2: C,
37.03, H, 3.39. Found: C, 37.33, H, 3.25. 1H NMR (C2D2Cl2,
270 MHz, ppm): too insoluble to get a signal.
Tu n gsten (0) Com p lexes. P r ep a r a tion of W p r ecu r sor :
A solution of tungsten hexacarbonyl was dissolved in dry,
degassed THF (200 mL) and irradiated with a mercury UV
lamp (125 W, λ ) 354 nm, 10 min) to give a sufficiently high
concentration of W(CO)5thf/W(CO)4thf2. IR/cm-1 (THF solu-
tion): major signals 1974.1 (W(CO)6), 1927.0 (W(CO)5thf),
1891.5 (W(CO)4thf2).
1
4% by H NMR integration.
Metal Com plexes. P alladiu m (II) an d platin u m (II) Com -
p lexes. Gen er a l p r oced u r e: To a solution of [M(PhCN)2Cl2]
(M ) Pt, Pd) (1 equiv) in toluene (50 mL) at 60 °C was added
a toluene (10 mL) solution of the ligand (FcSRSR′) (1.1 equiv).
The solution immediately darkened and was stirred for 20 h
by which time a dark precipitate had formed. The reaction was
cooled and the precipitate filtered, washed with hot hexane
(50 mL) and diethyl ether (50 mL), and dried in vacuo for 1 h
to give [M(FcSRSR′)Cl2].
[1-(Met h ylt h iola t o),1′-(p h en ylt h iola t o)fer r ocen e]p a l-
la d iu m d ich lor id e (9): Reaction of 6 (0.10 g, 0.29 mmol) with
bis(benzonitrile)palladium dichloride (0.08 g, 0.25 mmol) gave
a dark-brown precipitate of [Pd(FcSMeSPh)Cl2] (9) (0.09 g, 0.18
mmol, 72% yield). Anal. Calcd for C17H16S2FePdCl2: C, 39.45,
H, 3.12. Found: C, 39.40, H, 3.02. 1H NMR (C2D2Cl2, 270 MHz,
ppm) δ 7.41-7.30 (m, 3H, C6H5), 7.27-7.24 (m, 2H, C6H5), 5.30
(br, C5H4), 4.57-4.48 (m, br, C5H4) (5.30-4.48 ppm ) 8H), 2.47
(s, 3H, CH3). Mass spectrum (m/z): 518 ([M]+), 483 ([M - Cl]+),
447 ([M - 2Cl]+), 340 ([FcSMeSPh]+). Crystals suitable for
X-ray diffraction were grown from a two-layer C2H2Cl2-hexane
(1:1) solvent system. Crystal data for 9: C17H16S2Cl2FePd, M
) 517.6, triclinic, P1h (no. 2), a ) 5.872(1) Å, b ) 8.669(1) Å, c
) 17.882(2) Å, R ) 91.82(1)°, â ) 94.21(1)°, γ ) 102.01(1)°, V
) 886.9(2) Å3, Z ) 2, Dc ) 1.938 g cm-3, µ(Cu KR) ) 19.7
mm-1, T ) 293 K, orange platy needles; 2638 independent
measured reflections, F2 refinement, R1 ) 0.036, wR2 ) 0.084,
2208 independent observed absorption corrected reflections
[|Fo| > 4σ(|Fo|), 2θmax ) 120°], 197 parameters. CCDC 229588.
[1-(ter t-Bu t ylt h iola t o),1′-(m et h ylt h iola t o)fer r ocen e]-
p a lla d iu m d ich lor id e (10): Reaction of 7 (0.06 g, 0.20 mmol)
with bis(benzonitrile)palladium dichloride (0.07 g, 0.17 mmol)
gave a dark-brown precipitate of [Pd(FcStBuSMe)Cl2] (0.05 g,
0.11 mmol, 64% yield). Anal. Calcd for C15H20S2FePdCl2: C,
36.21, H, 4.05. Found: C, 37.10, H, 4.28. 1H NMR (CDCl3, 270
MHz, ppm) δ 5.67 (br, C5H4), 4.82 (br, C5H4), 4.59 (br, C5H4),
4.33 (br, C5H4) (5.67-4.33 ppm ) 8H), 2.45 (s, 3H, CH3), 1.47
(s, 9H, CH3). Mass spectrum (m/z): 498 ([M]+), 463 ([M - Cl]+),
[1-(ter t-Bu t ylt h iola t o),1′-(m et h ylt h iola t o)fer r ocen e]-
tu n gsten tetr a ca r bon yl (16): To a solution of 7 (0.10 g, 0.30
mmol, 1 equiv) in dry deoxygenated THF (15 mL) was added
to tungsten precursor solution (30 mL, 1.5 equiv (initial
concentration: 0.015 mol dm-3 W(CO)6 in THF)). The reaction
was stirred at room temperature for 20 h and the solvent
removed in vacuo. Column chromatography (7:3 hexane:
dichloromethane) enabled separation of the product from
unreacted ligand to give [(FcStBuSMe)W(CO)4] (16) (0.07 g,
0.12 mmol, 40% yield). Anal. Calcd for C19H20S2FeW: C, 37.04,
H, 3.27. Found: C, 36.96, H, 3.18. 1H NMR (CDCl3, 270 MHz,
ppm) δ 4.64 (t, 2H, C5H4), 4.61 (t, 2H, C5H4), 4.36 (t, 2H, C5H4),
4.33 (t, 2H, C5H4), 2.83 (s, 3H, CH3), 1.34 (s, 9H, CH3). Mass
spectrum (m/z): 616 ([M]+), 589 ([M - CO]+), 560 ([M - tBu]+,
[M - 2CO]+), 532 ([M - tBu - CO]+, [M - 3CO]+), 507 ([M -
t
tBu - 2CO]+, [M - 4CO]+), 475 ([M - Bu - 3CO]+), 447 ([M
- tBu - 4CO]+), 320 ([M - W(CO)4]+, free ligand). IR/cm-1 (υ
CO) (dichloromethane solution): 2017, m; 1898, vs, br; 1849,
s. Crystals suitable for X-ray diffraction were grown by cooling
a dichloromethane:hexane (1:1) solution to 0°C. Crystal data
for 16: C19H20O4S2FeW, M ) 616.2, monoclinic, P21/n (no. 14),
a ) 15.964(4) Å, b ) 8.289(1) Å, c ) 16.714(4) Å, â ) 113.12-
(2)°, V ) 2034.1(7) Å3, Z ) 4, Dc ) 2.012 g cm-3, µ(Mo KR) )
6.59 mm-1, T ) 293 K, yellow blocks; 3572 independent
measured reflections, F2 refinement, R1 ) 0.034, wR2 ) 0.078,
3079 independent observed absorption corrected reflections
[|Fo| > 4σ(|Fo|), 2θmax ) 50°], 245 parameters. CCDC 229589.
[1-(ter t-Bu t ylt h iola t o),1′-(p h en ylt h iola t o)fer r ocen e]-
tu n gsten tetr a ca r bon yl (17): To a solution of 8 (0.05 g, 0.13
mmol, 1 equiv) in dry deoxygenated THF (15 mL) was added
tungsten precursor solution (30 mL, 2.3 equiv (initial concen-
tration: 0.01 mol dm-3 W(CO)6 in THF)). The reaction was
heated at 40 °C for 24 h, after which a small amount of product
was detectable by TLC. The solvent was removed in vacuo and
column chromatography (7:3 hexane:dichloromethane) enabled
t
428 ([M - 2Cl]+), 404 ([M - Cl - Bu]+), 371 ([M - 2Cl -
tBu]+), 320 ([FcStBuSMe]+).
[1-(ter t-Bu t ylt h iola t o),1′-(p h en ylt h iola t o)fer r ocen e]-
p a lla d iu m d ich lor id e (11): Reaction of 8 (0.06 g, 0.15 mmol)
with bis(benzonitrile)palladium dichloride (0.05 g, 0.13 mmol)
gave a dark-brown precipitate of [Pd(FcStBuSPh)Cl2] (0.05 g,
0.09 mmol, 67% yield). Anal. Calcd for C20H22S2FePdCl2: C,
42.92, H, 3.96. Found: C, 42.82, H, 3.87. 1H NMR (C2D2Cl2,
270 MHz, ppm) δ 7.40-7.32 (m, 3H, C6H5), 7.25-7.23 (m, 2H,
C6H5), 5.30 (br, C5H4), 4.60 (br, C5H4), 4.54 (br, C5H4) (5.30-
4.54 ppm ) 8H), 1.48 (s, 9H, CH3). Mass spectrum (m/z): 560

Unsymmetrical 1,1′-Bis(organylthiolato)ferrocenes
Organometallics, Vol. 23, No. 5, 2004 967
separation of the product from unreacted ligand to give [(FcSt-
BuSPh)W(CO)4] (17) (0.01 g, 0.01 mmol, 8% yield). Anal. Calcd
for C20H22S2FeW: C, 42.50, H, 3.27. Found: C, 42.69, H, 3.40.
1H NMR (CDCl3, 270 MHz, ppm) δ 7.44-7.40 (m, 2H, C6H5),
7.36-7.26 (m, 3H, C6H5), 4.78 (t, 2H, C5H4), 4.69 (t, 2H, C5H4),
4.44 (t, 2H, C5H4), 4.42 (t, 2H, C5H4), 1.38 (s, 9H, CH3). Mass
spectrum (m/z): 678 ([M]+), 649 ([M - CO]+), 617 ([M - tBu]+,
[M - 2CO]+), 596 ([M - tBu - CO]+, [M - 3CO]+), 535 ([M -
Matthey plc are thanked for the loan of precious metal
salts. P.Z. gratefully acknowledges the financial support
from the University of Siena (PAR 2003) and the
technical assistance of Dr. Marco Fontani (recently
moved to the University of Florence).
Su p p or tin g In for m a tion Ava ila ble: Details about the
X-ray crystal structures, including ORTEP diagrams for 1, 5,
9, and 16. This material is available free of charge via the
Internet at http://pubs.acs.org.
t
tBu - 3CO]+), 509 ([M - Bu - 4CO]+), 382 ([M - W(CO)4]+,
free ligand). IR/cm-1 (υ CO) (dichloromethane solution): 2018,
m; 1899, vs, br; 1853, s.
Ack n ow led gm en t. This research was supported
financially by the EPSRC and ICI (Wilton), and J ohnson
OM034287V