Heterometallic dithiolene complexes formed by stepwise displacement of cyclopentadienyl ligands from nickelocene with CpMo(S2C 2Ph2)2

Article abstract of DOI:10.1021/ic0606227

The dithiolene ligand transfer reaction between Ni(S₂C ₂Ph₂)₂ (1) and CpMo(CO)₃Cl (2; Cp = η-C₅H₅) affords the neutral paramagnetic molybdenum bis(dithiolene) complex CpM(S₂

Full text of DOI:10.1021/ic0606227

Inorg. Chem. 2006, 45, 10967−10975
Heterometallic Dithiolene Complexes Formed by Stepwise Displacement
of Cyclopentadienyl Ligands from Nickelocene with CpMo(S2C2Ph2)2
Harry Adams, Hannah C. Gardner, Richard A. McRoy, Michael J. Morris,* Jeffrey C. Motley, and
Sebastian Torker
Department of Chemistry, UniVersity of Sheffield, Sheffield S3 7HF, United Kingdom
Received April 12, 2006
The dithiolene ligand transfer reaction between Ni(S2C2Ph2)2 (1) and CpMo(CO)3Cl (2; Cp ) η-C5H5) affords the
neutral paramagnetic molybdenum bis(dithiolene) complex CpM(S2C2Ph2)2 (3), which has been structurally
characterized. As found in other d1 complexes of this type, one dithiolene ligand is planar while the other is significantly
folded toward the Cp ligand. An unexpected second product of the reaction is the unusual trinuclear species
Ni[Mo(S2C2Ph2)2Cp]2 (4), which in the solid state contains three different dithiolene bonding modes (terminal, bridging,
and semi-bridging) in the same molecule. Complex 4 can also be synthesized by displacement of the diene ligands
in Ni(cod)2 with 2 equiv of 3. In contrast, the reaction of nickelocene with 3 proceeds by displacement of the Cp
ligands in a stepwise manner to give initially the dinuclear species NiMo(µ-S2C2Ph2)2Cp2 5, which then reacts
further with 3 to produce 4.
Scheme 1. Canonical Forms of Dithiolene Ligand
Introduction
Since their rise to prominence over 40 years ago, com-
plexes of dithiolene (1,2-enedithiolate) ligands have been
recognized as displaying unusual properties.1 Foremost
among these is the existence of multiple accessible redox
states, for example, in [Ni(S2C2R2)2]n- (n ) 0-2); indeed,
one of the main achievements of the 1960s work was the
realization that apparently disparate nickel complexes pro-
duced in different research laboratories were in fact related
by simple redox processes.2 The redox activity of the
dithiolene ligand itself can be described by the existence of
three canonical forms separated by the removal or addition
of one electron (Scheme 1): a dianionic dithiolate, a radical
monoanion, and a neutral dithioglyoxal structure. In this way,
the formal oxidation state of the metal in a bis(dithiolene)
complex such as Ni(S2C2R2)2 could be formally regarded as
anywhere between +4 and zero. This ambiguity is an
archetypal example of what we now recognize as non-
innocent behavior.3 As a result of their redox and optical
properties, dithiolene complexes have been investigated for
potential applications as nonlinear optical materials, conduct-
ing and superconducting solids, and molecular magnets.4
Dithiolene complexes of molybdenum and tungsten have
received particular attention since the discovery that oxido-
reductase enzymes containing these metals involve either one
or two pterin ligands bound through a dithiolene linkage at
the active site.5 The enzyme systems are thought to cycle
between oxidation states M(IV) and M(VI), with M(V)
intermediates sometimes observable by EPR spectroscopy.
(3) Ward, M. D.; McCleverty, J. A. J. Chem. Soc., Dalton Trans. 2002,
275.
* To whom correspondence should be addressed. E-mail: M.Morris@
sheffield.ac.uk.
(4) (a) Robertson, N.; Cronin, L. Coord. Chem. ReV. 2002, 227, 93. (b)
(1) (a) McCleverty, J. A. Prog. Inorg. Chem. 1969, 10, 49. (b) Eisenberg,
R. Prog. Inorg. Chem. 1970, 12, 295. (c) Burns, R. P.; McAuliffe, C.
A. AdV. Inorg. Chem. Radiochem. 1979, 22, 303. (d) Mueller-
Westerhoff, U. T.; Vance, B. In ComprehensiVe Coordination
Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J. A., Eds.;
Pergamon: Oxford, 1987; Vol. 2, Ch. 16.5. (e) Stiefel, E. I. Dithiolene
Chemistry. Prog. Inorg. Chem. 2004, 52.
Fourmigue´, M. Acc. Chem. Res. 2004, 37, 179.
(5) (a) Hille, R. Chem. ReV. 1996, 96, 2757. (b) Johnson, M. K.; Rees,
D. C.; Adams, M. W. W. Chem. ReV. 1996, 96, 2817. (c) Enemark,
J. H.; Cooney, J. J. A.; Wang, J.-J.; Holm, R. H. Chem. ReV. 2004,
104, 1175. (d) Sugimoto, H.; Harihara, M.; Shiro, M.; Sugimoto, K.;
Tanaka, K.; Miyake, H.; Tsukube, H. Inorg. Chem. 2005, 44, 6386.
(e) Sugimoto, H.; Sakurai, T.; Miyake, H.; Tanaka, K.; Tsukube, H.
Inorg. Chem. 2005, 44, 6927. (f) Wang, J.-J.; Tessier, C.; Holm, R.
H. Inorg. Chem. 2006, 45, 2979.
(2) Davison, A.; Edelstein, N.; Holm, R. H.; Maki, A. H. J. Am. Chem.
Soc. 1963, 85, 2029.
10.1021/ic0606227 CCC: $33.50
Published on Web 12/06/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 26, 2006 10967

Adams et al.
Consequently, the redox properties and EPR parameters of
Mo and W dithiolene complexes have been closely studied,
even in cases where they do not contain biological co-ligands.
These include the bis-cyclopentadienyl compounds Cp2M-
(S2C2R2) and dinuclear species such as Mo2(µ-SCRdCRS)2-
Cp2.6,7
Fe(CO)5,18 until the synthesis of the heterodinuclear complex
(Ph2C2S2)Fe(µ-S2C2Ph2)2RuCp* (Cp* ) η-C5Me5) by the
reaction of Fe2(S2C2Ph2)4 with Ru2(CO)4Cp*2.19 Building on
the earlier work of Schrauzer and Holm, we have recently
reported that dithiolene ligands can be transferred from Ni-
(S2C2Ph2)2 to the dimolybdenum center of Mo2{µ-C2(CO2-
Me)2}(CO)4Cp2 to give the alkyne-dithiolene complex Mo2{µ-
C2(CO2Me)2}(µ-S2C2Ph2)2Cp2.20 Very recently, the mixed
ligand Ni(III) dithiolene complexes CpNi(S2C2R2) (RdPh,
Me) have been efficiently prepared by dithiolene transfer
from Ni(S2C2R2)2 to nickelocene with displacement of one
Cp ligand.21
Three general methods have been used since the 1960s to
prepare dithiolene complexes of virtually all the transition
metals:8 (i) the reaction of metal halides with salts of the
free dithiolene ligand, which is limited to those where the
2-
free dianions are available such as S2C2(CN)2 (mnt2-),9
S2C2H2 (edt2-),10 and C3S52- (dmit2-),11 or those that can be
prepared from 1,3-dithiole-2-one heterocycles or the related
iminium salts;12 (ii) reaction of metal carbonyls with the
dithiete (CF3)2C2S2, developed by King,13 which suffers from
the fact that this particular dithiete is the only one that is
readily available and sufficiently stable; and (iii) reaction of
metal halides or carbonyls with the solution derived from
the treatment of benzoin or other acyloins with P2S5, as
developed by Schrauzer and Mayweg.14 Other less widely
applicable methods include the combination of metal sulfido
(or di- or polysulfido) complexes with alkynes or of metal
alkyne complexes with sulfur.15 However, one interesting
strategy that we felt had been under-used was the transfer
of dithiolene ligands from one complex to another. This was
also first reported by Schrauzer, who prepared M(CO)2-
(S2C2R2)2 (MdMo, W; R ) aryl, alkyl) by the photochemical
reaction of Ni(S2C2R2)2 with M(CO)6.16 This process was
later improved by Holm, who found that the reaction
proceeded in reasonable yield at room temperature with-
out irradiation when the labile M(CO)3(NCMe)3 was used
as the source of M, leading to typical yields of 30% for Mo
and 70% for W.17 The only other similar reaction was an
attempt to transfer an alkylated dithiolene ligand from Ni to
We decided to investigate the application of the potentially
more general dithiolene transfer reaction to the synthesis of
mononuclear Cp molybdenum dithiolene complexes since
relatively few compounds of the type [CpM(S2C2R2)2]n-
(MdMo, W; n ) 0, 1) have been described in the literature.
In the 1960s, McCleverty and co-workers prepared [Ph4P]-
[CpM(mnt)2] by reaction of CpMo(CO)3I or CpW(CO)3Cl
with Na2mnt, in yields of 15 and 35%, respectively. This
was, however, accompanied by displacement of the Cp lig-
and and formation of the tris-dithiolene species [Ph4P]2-
[M(mnt)3].22,23 More recently, Fourmigue´ and Coulon have
used a similar route to prepare [Ph4P][Cp*Mo(dmit)2], which
was then oxidized by electrocrystallization to neutral Cp*Mo-
(dmit)2; the structures of both compounds were determined.24
The same group has since prepared the tungsten analogue.25
The only other complexes of this type, [CpM{S2C2(CF3)2}2]n-
(MdW, n ) 0; MdMo, n ) 1), were prepared by treating
nitrosyl complexes with the dithiete S2C2(CF3)2.26,27 A low-
yield synthesis of CpMo{S2C2(CO2Me)2}2 by a similar
procedure using a combination of sulfur and dimethylacety-
lene dicarboxylate in place of the dithiete has just been
published.28 We now describe the synthesis of CpMo(S2C2-
Ph2)2 by dithiolene transfer, together with reactions leading
to a family of di- and trinuclear heterometallic dithiolene
complexes derived from it.
(6) Fourmigue´, M. Coord. Chem. ReV. 1998, 178-180, 823.
(7) Rakowski Dubois, M.; Haltiwanger, R. C.; Miller, D. J.; Glatzmeier,
G. J. Am. Chem. Soc. 1979, 101, 5245.
(8) Rauchfuss, T. B. Prog. Inorg. Chem. 2004, 52, 1.
(9) Davison, A.; Holm, R. H. Inorg. Synth. 1967, 10, 8.
(10) (a) Hoyer, E.; Dietzsch, W.; Henning, H.; Schroth, W. Chem. Ber.
1969, 102, 603. (b) Schrauzer, G. N.; Mayweg, V. P. J. Am. Chem.
Soc. 1965, 87, 3585. (c) King, R. B.; Eggers, C. A. Inorg. Chem.
1968, 7, 340.
(11) (a) Svenstrup, N.; Becher, J. Synthesis 1995, 215. (b) Pullen, A. E.;
Olk, R.-M. Coord. Chem. ReV. 1999, 188, 211. (c) Cassoux, P.; Valade,
L.; Kobayashi, H.; Kobayashi, A.; Clark, R. A.; Underhill, A. E. Coord.
Chem. ReV. 1991, 110, 115. (d) Olk, R.-M.; Olk, B.; Dietzsch, W.;
Kirmse, R.; Hoyer, E. Coord. Chem. ReV. 1992, 117, 99.
(12) (a) Mueller-Westerhoff, U. T.; Sanders, R. W. Organometallics 2003,
22, 4778. (b) Boyde, S.; Garner, C. D.; Joule, J. A.; Rowe, D. J. J.
Chem. Soc., Chem. Commun. 1987, 800. (c) Rowe, D. J.; Garner, C.
D.; Joule, J. A. J. Chem. Soc., Perkin Trans. 1 1985, 1907.
(13) King, R. B. J. Am. Chem. Soc. 1963, 85, 1587.
(14) (a) Schrauzer, G. N.; Mayweg, V. P.; Heinrich, W. Inorg. Chem. 1965,
4, 1615. (b) Schrauzer, G. N.; Mayweg, V. P. J. Am. Chem. Soc. 1965,
87, 1483.
(15) (a) Bolinger, C. M.; Rauchfuss, T. B. Inorg. Chem. 1982, 21, 3947.
(b) Rauchfuss, T. B.; Rodgers, D. P. S.; Wilson, S. R. J. Am. Chem.
Soc. 1986, 108, 3114. (c) Abbott, A.; Bancroft, M. N.; Morris, M. J.;
Hogarth, G.; Redmond, S. P. Chem. Commun. 1998, 389.
(16) Schrauzer, G. N.; Mayweg, V. P.; Heinrich, W. J. Am. Chem. Soc.
1966, 88, 5174.
Results and Discussion
Synthesis of CpMo(S2C2Ph2)2 by Dithiolene Transfer.
Treatment of CpMo(CO)3Cl (2) with 1 or 2 molar equiv of
Ni(S2C2Ph2)2 (1) in refluxing toluene for 2 h produced a dark
blue-purple solution that contained two new complexes,
(18) (a) Schrauzer, G. N.; Kisch, H. J. Am. Chem. Soc. 1973, 95, 2501.
(b) Schrauzer, G. N.; Rabinowitz, H. N.; Frank, J. K.; Paul, I. C. J.
Am. Chem. Soc. 1970, 92, 212.
(19) Kuge, K.; Inomata, S.; Tobita, H.; Ogino, H. Chem. Lett. 1999, 1075.
(20) Adams, H.; Morris, M. J.; Morris, S. A.; Motley, J. C. J. Organomet.
Chem. 2004, 689, 522.
(21) Nomura, M.; Okuyama, R.; Fujita-Takayama, C.; Kajitani, M. Orga-
nometallics 2005, 24, 5110.
(22) (a) Locke, J.; McCleverty, J. A. Inorg. Chem. 1966, 5, 1157. (b)
McCleverty, J. A.; James, T. A.; Wharton, E. J. Inorg. Chem. 1969,
8, 1340.
(23) Churchill, M. R.; Coake, J. J. Chem. Soc. A 1970, 2046.
(24) Fourmigue´, M.; Coulon, C. AdV. Mater. 1994, 6, 948.
(25) Domercq, B.; Coulon, C.; Feneyrou, P.; Dentan, V.; Robin, P.;
Fourmigue´, M. AdV. Funct. Mater. 2002, 12, 359.
(26) King, R. B.; Bisnette, M. B. Inorg. Chem. 1967, 6, 469.
(27) James, T. A.; McCleverty, J. A. J. Chem. Soc. A 1970, 3308.
(28) Nomura, M.; Sasaki, S.; Fujita-Takayama, C.; Hoshino, Y.; Kajitani,
M. J. Organomet. Chem. 2006, 691, 3274.
(17) (a) Lim, B. S.; Donahue, J. P.; Holm, R. H. Inorg. Chem. 2000, 39,
263. (b) Goddard, C. A.; Holm, R. H. Inorg. Chem. 1999, 38,
5389.
10968 Inorganic Chemistry, Vol. 45, No. 26, 2006

Heterometallic Dithiolene Complexes
Scheme 2. Dithiolene Transfer from Ni(S2C2Ph2)2 to CpMo(CO)3Cl
Chart 1. Structure of A, One Possible Intermediate in Dithiolene
Transfer Reaction
reaction, the interception of A might be rendered more
effective and the yield of 4 increased. In the event, however,
heating equimolar quantities of CpMo(CO)3Cl, Ni(S2C2Ph2)2,
and CpMo(S2C2Ph2)2 under similar conditions produced
exactly the opposite effect: the yield of 4 dropped to 8%,
and the entire reaction was retarded, with much starting
material still present after 3 h (81% of the initial Ni complex
was reclaimed). However, only 39% of the added molyb-
denum bis(dithiolene) 3 was recovered, and several new
unidentified products were also observed. Clearly, the
additional 3 did not react with A to give 4, and moreover,
its presence interfered in some way in the course of the
reaction between CpMo(CO)3Cl and Ni(S2C2Ph2)2.29 One
possibility is that an electron-transfer process is involved
during the reaction that might be disrupted by the addition
of 3, which is relatively easily reduced. Despite this outcome,
the involvement of a dinuclear complex in the dithiolene
transfer process still appears likely given the isolation of
heterometallic species in the reaction.
dark blue-purple CpMo(S2C2Ph2)2 (3) and royal blue
trinuclear Ni[Mo(S2C2Ph2)2Cp]2 (4) (Scheme 2). The two
compounds were formed in a combined yield of 35-40%,
but their relative isolated yields can vary considerably.
This is because during separation of the constituents by
column chromatography on silica, 4 gradually decomposes
to give more 3, so to obtain the maximum amount of 4,
the purification should be carried out relatively quickly; if
this is done, both compounds can be isolated in yields
of around 20%. A further practical consideration is that
although unreacted Ni(S2C2Ph2)2 is eluted first from the
column, it is rather insoluble; hence, if large amounts remain
at the end of the reaction, it can dissolve slowly from the
top of the column and contaminate the subsequent bands.
Consequently, the use of 1 equiv of the Ni complex in the
reaction is recommended. No trace was found of any products
arising from displacement of the Cp ring from molybde-
num in the current reaction, possibly because it involves
only neutral complexes and is carried out in a nonpolar
solvent.
There are two possible ways in which the dithiolene
ligands might be transferred from nickel to molybdenum:
either by release of free dithiobenzil from the nickel center
into solution, a process that would essentially be analogous
to the reaction of CpMo(CO)3Cl with the dithiete S2C2(CF3)2
reported earlier; or by the formation of a heterodinuclear
NiMo complex followed by transfer of the ligands and
release of the Ni in an unspecified form. Additional experi-
ments were carried out to investigate the mechanism of the
reaction. First, heating pure CpMo(S2C2Ph2)2 with Ni(S2C2-
Ph2)2 did not produce 4, and moreover, 4 did not decompose
thermally over the time scale of the reaction to give 3. Hence,
trinuclear 4 does not appear to be an intermediate in the
formation of bis(dithiolene) complex 3. Second, if one
postulates the existence of a common dinuclear intermediate
complex in the formation of 3 and 4, such as that illustrated
as A (Chart 1), which might either release the Ni to give 3
or react further with 3 to give 4, we reasoned that if additional
3 was already present in the solution at the start of the
Characterization and Structure of CpMo(S2C2Ph2)2 (3).
The nature of CpMo(S2C2Ph2)2 was initially deduced from
its mass spectral and analytical data. Formally, 3 contains
Mo(V) (d1 configuration) and, as befits its paramagnetic
1
nature, displays a featureless H NMR spectrum in the δ
0-10 region. On an expanded scale, two broad singlets were
observed at δ 15 and -4 ppm, presumably corresponding
to the phenyl and Cp protons, respectively. Its X-band EPR
spectrum in a toluene/dimethyl formamide (9:1) solution at
220 K displays a peak at g ) 2.0122 with molybdenum
satellites (AMo ) 9.15 G). The magnitude of this coupling
indicates considerable delocalization of the unpaired electron
onto the dithiolene ligands (d1 molybdenum complexes
typically have AMo of 30-50 G).30 In a frozen toluene/
dimethyl formamide glass (111 K), the compound gives a
rhombic spectrum with g values of 2.0275, 2.0074, and
1.9936, all of which display noticeable satellites (|AMo| )
14, 10.5, and 18 G, respectively). These g values are almost
identical to those reported for the single-crystal EPR study
of the analogous Cp*Mo(dmit)2 radical.24
The molecular structure of 3 is shown in Figure 1, with
selected bond lengths and angles collected in Table 1. The
(29) A control reaction was also carried out between 3 and CpMo(CO)3Cl,
which showed that these two complexes do react but over a much
slower timescale than that of the original reaction.
(30) Cleland, W. E., Jr.; Barnhart, K. M.; Yamanouchi, K.; Collison, D.;
Mabbs, F. E.; Ortega, R. B.; Enemark, J. H. Inorg. Chem. 1987, 26,
1017.
Inorganic Chemistry, Vol. 45, No. 26, 2006 10969

Adams et al.
Figure 1. Molecular structure of complex 3 in the crystal (ORTEP plot, 50% probability ellipsoids). Hydrogen atoms have been omitted for clarity.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for Complex 3
Characterization and Structure of Ni[Mo(S2C2Ph2)2Cp]2
(4). The first indication of the heterometallic nature of 4 came
with the observation of a mass ion envelope centered at m/z
1349 in its mass spectrum, and atomic absorption spectros-
copy subsequently confirmed the presence of Ni and Mo in
a 1:2 ratio. The compound is diamagnetic and displays peaks
Mo(1)-S(2)
Mo(1)-S(1)
S(1)-C(6)
S(3)-C(8)
C(6)-C(7)
2.3625(6) Mo(1)-S(3)
2.3788(6) Mo(1)-S(4)
2.3668(6)
2.3999(7)
1.7362(19)
1.740(2)
1.371(3)
80.768(19)
84.372(17)
1.732(2)
1.728(2)
1.366(3)
S(2)-C(7)
S(4)-C(9)
C(8)-C(9)
S(2)-Mo(1)-S(3) 132.841(19) S(2)-Mo(1)-S(1)
S(3)-Mo(1)-S(1)
S(3)-Mo(1)-S(4)
C(6)-S(1)-Mo(1) 110.01(7)
C(8)-S(3)-Mo(1) 105.40(7)
78.294(19) S(2)-Mo(1)-S(4)
1
for phenyl and Cp protons in a 4:1 intensity ratio in its H
80.969(17) S(1)-Mo(1)-S(4) 134.28(2)
1
NMR spectrum. The simplicity of both the H and the 13C
C(7)-S(2)-Mo(1) 110.26(7)
C(9)-S(4)-Mo(1) 104.82(7)
NMR spectra indicate the equivalence of the dithiolene
ligands in solution, although in the latter, the dithiolene
carbon atoms could not be definitively observed.31 When the
1H and 13C NMR spectra were recorded at a low temperature
(223 K), the phenyl and Cp resonances in both spectra were
broadened considerably, indicating the possible operation of
a fluxional process.
molybdenum atom is situated in a four-legged piano-stool
environment made up of the Cp ligand and the four sulfur
atoms. The Mo(1)-S(2) and Mo(1)-S(3) bonds are shorter
than Mo(1)-S(1) and, particularly, Mo(1)-S(4). As noted
before for complexes of this type, the C-S bonds in the
dithiolene rings are relatively short (av. 1.734 Å), and the
CdC bonds relatively long (av. 1.369 Å), indicating a
considerable contribution of the radical monoanion reso-
nance structure shown in the center of Scheme 1. The
most noticeable feature, however, is the folding of the
dithiolene ligands: that containing S(1) and S(2) is almost
planar, with the angle between the Mo(1)-S(1)-S(2)
plane and the S(1)-C(6)-C(7)-S(2) plane being only 1.1°,
whereas the other dithiolene ligand is folded up toward
the Cp ligand with a corresponding fold angle of 27.9°. The
same phenomenon was observed in the structures of
[Cp*M(dmit)2]n- (n ) 0, 1): in the neutral complex, one
dithiolene was planar and the other folded, as in 3, whereas
in the anion, both were folded toward the Cp ligand.24,25 It
has been shown that in d2 molecules such as [CpMo-
(S2C2R2)2]-, the folding is due to the interaction of both
Complex 4 is air-stable in the solid state, but it decomposes
slowly in solution to give 3, although this decomposition is
slower than during the chromatographic purification. Crystal-
lization by diffusion of pentane into a THF solution produced
large blue blocks of 4‚THF suitable for X-ray analysis. The
unit cell contains two independent molecules with only
relatively minor differences between them; the molecular
structure of one of these is shown in Figure 2 with selected
bond lengths and angles given in Table 2. The core of the
molecule consists of a Mo-Ni-Mo axis, which is virtually
linear with a Mo(1)-Ni(1)-Mo(2) angle of 174.725(18)°.
The Mo(1)-Ni(1) bond [2.7514(5) Å] is considerably shorter
than Mo(2)-Ni(1) [2.8654(5) Å], but both of these are quite
long when compared to the 2.55-2.65 Å length quoted for
typical Ni-Mo single bonds in heterodinuclear compounds.32
They are, however, very similar to the 2.798(8) Å length
found in the trinuclear species [Ph4P]2[Ni(MoS4)2].33
Notwithstanding the solution structure, the molecule
exhibits three different bonding modes for the dithiolene
2
π-donor dithiolenes with the empty dz orbital; on oxidation
to the d1 neutral species, one of the dithiolenes begins to
bend away from the Cp ligand to interact with the half-filled
dxy orbital instead and becomes planar. This trend is
continued in d0 complexes of the type [CpTi(S2C2R2)2]-,
where one dithiolene is folded toward the Cp ring to interact
(31) In the 13C NMR spectra of 4, a broad hump was consistently observed
at 158.5 ppm, which we tentatively assign to the dithiolene carbons.
(32) (a) Chetcuti, M. J.; Eigenbrot, C.; Green, K. A. Organometallics 1987,
6, 2298. (b) Chetcuti, M. J.; Grant, B. E.; Fanwick, P. E. Organome-
tallics 1995, 14, 2937. (c) Chetcuti, M. J.; Fanwick, P. E.; McDonald,
S. R.; Rath, N. P. Organometallics 1991, 10, 1551.
2
with the dz orbital and the other away from it to interact
with the dxy orbital.6
10970 Inorganic Chemistry, Vol. 45, No. 26, 2006

Heterometallic Dithiolene Complexes
Figure 2. Structure of one of the two independent molecules of complex 4 in the crystal (ORTEP plot, 50% probability ellipsoids). Hydrogen atoms and
THF of crystallization have been omitted for clarity.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for One of the
since it allows the two Mo(dithiolene)2 units to lie orthogonal
to each other, with the central Ni atom bonded to two cis-
sulfurs of each [one sulfur atom from each dithiolene attached
Two Independent Molecules of Complex 4‚THFa Present in the Unit
Cell
Mo(2)-S(5)
2.3262(9) Mo(2)-S(6)
2.4715(8) Mo(2)-S(8)
2.8654(5) Mo(1)-S(1)
2.3876(8) Mo(1)-S(2)
2.3923(8) Mo(1)-Ni(1)
2.2286(9) Ni(1)-S(7)
2.2703(9) Ni(1)-S(3)
2.3452(8)
2.4807(8)
2.3861(8)
2.3914(8)
2.7514(5)
2.2385(9)
2.2733(9)
1.758(3)
1.754(3)
1.750(3)
1.812(3)
1.341(4)
1.370(4)
to Mo(1) and both sulfur atoms of one dithiolene attached
to Mo(2)]. The nickel atom thus attains a distorted square
planar environment if the metal-metal bonds are disre-
garded; two of the S-Ni-S angles are approximately 97°,
and the other two approximately 83°. This arrangement is
reminiscent of that found in the dication [Cp2Mo(µ-SMe)2Ni-
(µ-SMe)2MoCp2]2+, although in this complex the Mo‚‚‚Ni
distance is much longer (3.39 Å), precluding any metal-
metal bonding.35 As expected, the Mo-S bonds in the
terminal dithiolene ligand are the shortest (av. 2.336 Å), and
those in the bridging dithiolene the longest (av. 2.476 Å),
with those involving the semi-bridging dithiolene intermedi-
ate in value (av. 2.389 Å).
Mo(2)-S(7)
Mo(2)-Ni(1)
Mo(1)-S(3)
Mo(1)-S(4)
Ni(1)-S(8)
Ni(1)-S(1)
S(1)-C(17)
1.766(3)
1.765(3)
1.747(3)
1.813(3)
1.358(4)
1.365(4)
81.31(3)
81.70(3)
130.38(3)
78.37(3)
133.06(3)
81.30(3)
82.07(3)
97.90(3)
172.78(3)
S(2)-C(18)
S(4)-C(11)
S(6)-C(16)
S(8)-C(13)
C(13)-C(14)
C(17)-C(18)
S(3)-C(12)
S(5)-C(15)
S(7)-C(14)
C(11)-C(12)
C(15)-C(16)
S(5)-Mo(2)-S(6)
S(6)-Mo(2)-S(7)
S(6)-Mo(2)-S(8)
S(1)-Mo(1)-S(3)
S(3)-Mo(1)-S(2)
S(3)-Mo(1)-S(4)
S(8)-Ni(1)-S(7)
S(7)-Ni(1)-S(1)
S(7)-Ni(1)-S(3)
S(5)-Mo(2)-S(7) 127.20(3)
S(5)-Mo(2)-S(8)
S(7)-Mo(2)-S(8)
S(1)-Mo(1)-S(2)
81.65(3)
72.63(3)
80.94(3)
S(1)-Mo(1)-S(4) 133.16(3)
The structure of 4 is also reminiscent of the products of
several recently reported reactions in which mono-dithiolene
complexes of the type CpM(S2C2R2) (MdCo, Rh) have been
treated with low-valent metal fragments to give the dithi-
olene-bridged heterotrinuclear species. It is interesting to note
that in these products, such as Mo(CO)2[Co(S2C6H4)Cp]2,
in which two benzenedithiolate ligands bridge a CoMoCo
S(2)-Mo(1)-S(4)
S(8)-Ni(1)-S(1)
S(8)-Ni(1)-S(3)
S(1)-Ni(1)-S(3)
83.05(3)
177.06(3)
96.47(3)
83.19(3)
72.39(2)
74.76(2)
Mo(1)-Ni(1)-Mo(2) 174.725(18) Ni(1)-S(1)-Mo(1)
Ni(1)-S(3)-Mo(1)
Ni(1)-S(8)-Mo(2)
72.31(2)
74.74(2)
Ni(1)-S(7)-Mo(2)
a These relate to the molecule shown in Figure 2.
t
framework,36 or Ni[Rh(S2C2B10H10)(η-C5H3 Bu2)]2, in which
ligands in the solid state. The two ligands that bridge the
Mo(1)-Ni(1) bond are both bonded in what we term semi-
bridging mode, in which one sulfur atom bridges the two
metals but the other is joined solely to Mo. This bonding
mode has been frequently encountered before in dimolyb-
denum chemistry3,5,34 but is rare in heterodinuclear systems.19
In contrast, one of the dithiolene ligands bonded to Mo(2)
is terminal, and the other is fully bridging, lying effectively
perpendicular to the Ni-Mo bond. This unusual arrangement
may be a consequence of the steric bulk of the phenyl groups
(34) (a) Sugiyama, T.; Yamanaka, T.; Shibuya, M.; Nakase, R.; Kajitani,
M.; Akiyama, T.; Sugimori, A. Chem. Lett. 1998, 501. (b) Shibahara,
T.; Tsuboi, M.; Nakaoka, S.; Ide, Y. Inorg. Chem. 2003, 42, 935. (c)
Roesselet, K.; Doan, K. E.; Johnson, S. D.; Nicholls, P.; Miessler, G.
L.; Kroeker, R.; Wheeler, S. H. Organometallics 1987, 6, 480. (d)
Miki, Y.; Takagi, H.; Ichimura, A.; Akashi, H.; Shibahara, T. Chem.
Lett. 2002, 482.
(35) (a) Prout, K.; Critchley, S. R.; Rees, G. V. Acta Crystallogr., Sect. B
1974, 30, 2305. (b) Dias, A. R.; Green, M. L. H. Chem. Commun.
1969, 962. (c) Dias, A. R.; Green, M. L. H. J. Chem. Soc. A 1971,
1951.
(36) (a) Nihei, M.; Nankawa, T.; Kurihara, M.; Nishihara, H. Angew. Chem.,
Int. Ed. 1999, 38, 1098. (b) Nakagawa, N.; Yamada, T.; Murata, M.;
Sugimoto, M.; Nishihara, H. Inorg. Chem. 2006, 45, 14. (c) Murata,
M.; Habe, S.; Araki, S.; Namiki, K.; Yamada, T.; Nakagawa, N.;
Nankawa, T.; Nihei, M.; Mizutani, J.; Kurihara, M.; Nishihara, H.
Inorg. Chem. 2006, 45, 1108.
(33) (a) Chetcuti, M. J. J. Cluster Sci. 1996, 7, 225. (b) Søtofte, I. Acta
Chem. Scand. 1976, 30, 157. (c) Mu¨ller, A.; Diemann, E.; Jostes, R.;
Bo¨gge, H. Angew. Chem., Int. Ed. Engl. 1981, 10, 934.
Inorganic Chemistry, Vol. 45, No. 26, 2006 10971

Adams et al.
Scheme 3. Synthesis of NiMo and NiMo2 Complexes from
Nickelocene
This chemical shift is, in our experience, unusually low for
a Cp ligand attached to molybdenum. The 13C NMR
spectrum contains two peaks for the dithiolene carbons, one
of which is at δ 170.2 and the other at 135.1, consistent with
the fact that one end of the dithiolene ligand bridges the two
metals and the other is attached only to Mo. Two peaks due
to the ipso carbons of the phenyl groups are also evident,
indicating that the solid state structure is retained in solution.
Comparison of the UV-vis spectrum of 5 with that of 4
indicates that the same chromophore is involved in both
cases, although assignment of the transitions occurring is
problematic.
The molecular structure of 5 in the crystal is shown in
Figure 3, with selected bond lengths and angles collected in
Table 3. The molecule contains one nickel atom and one
molybdenum, each of which bears a Cp ligand. The metals
are joined by a bond of length 2.7201(7) Å, which is shorter
than either of those in 4. The bond is spanned by two
dithiolene ligands that are bonded in the same semi-bridging
mode as those that bridged the Mo(1)-Ni(1) bond in 4, and
the Mo-S and Ni-S bond lengths within this unit are
comparable to those in the NiMo2 complex. In fact, the
geometry of the CpMo(dithiolene)2 portion of the molecule
is also largely unchanged from that in 3, with the exception
that both dithiolene ligands are now folded as a result of the
attachment of the CpNi fragment.
Since 5 results from the replacement of one of the Cp
ligands in nickelocene by a CpMo(S2C2Ph2)2 fragment, our
next step was to see whether the remaining Cp ring could
also be replaced to give 4. In fact, displacement of the second
ring is much more difficult in this case. Thus, TLC
monitoring of a reaction between equimolar amounts of 5
and 3 showed that the reaction was almost complete after 7
days in refluxing toluene. Column chromatography then
produced a 21% yield of 4 (which is difficult to separate
from unreacted 5).
the dithiolene ligand is incorporated into a carborane unit,
the trimetal axis tends to be bent rather than linear, and in
the case of the latter compound, the nickel atom adopts a
distorted tetrahedral arrangement coordinated by the four
sulfurs.37
Synthesis of NiMo(µ-S2C2Ph2)2Cp2 (5). Consideration of
the structure of the NiMo2 complex 4 suggested that it might
formally be regarded as two molecules of 3 complexed to a
Ni(0) fragment or, alternatively, as two [CpMo(S2C2Ph2)2]-
anions complexed to a Ni(II) center. Even though the square
planar coordination of the four sulfur atoms to the Ni might
be considered to favor the latter view, we decided to
investigate whether the compound could also be prepared
from 3 and a suitable source of Ni(0). Indeed, the reaction
of 2 equiv of 3 with Ni(cod)2 (cod ) 1,5-cyclooctadiene) in
toluene at room temperature was found to produce 4 in 64%
yield. Although, as mentioned previously, such reactions have
been carried out previously with mono-dithiolene complexes,
this appears to be the first of this type involving a bis-
(dithiolene) precursor. On the other hand, by heating 4 with
elemental sulfur in toluene solution, the Ni atom can be
readily abstracted as insoluble nickel sulfide to give 3 in
70% yield.
Since Ni(cod)2 is relatively difficult to make and handle,
an alternative source of Ni(0) was then investigated. It is
known that nickelocene, which is much easier to prepare,
can act as a precursor to complexes of the type Ni(PR3)4 for
use in catalytic reactions; both Cp rings are relatively easily
displaced by phosphines.38 Therefore, the reaction of Cp2Ni
with 3 was attempted. Surprisingly, after 1 h in refluxing
toluene, the purple color of the starting solution had changed
not to the blue of 4 but to a bright red-purple. Column
chromatography allowed the isolation of the dinuclear
complex NiMo(µ-S2C2Ph2)2Cp2 5 as an air-stable crystalline
solid in 85% yield (Scheme 3). The fate of the displaced Cp
ligand is unknown, but it seems likely that it is released as
a radical that either dimerizes to fulvalene or abstracts a
hydrogen atom to give cyclopentadiene.
Electrochemistry. Cyclic voltammetry studies of the new
complexes were carried out in dichloromethane solution with
0.1 M Bu4NBF4 as the supporting electrolyte. The cyclic
voltammogram of CpMo(S2C2Ph2)2 shows three reversible
processes: a very facile reduction to the monoanion (formally
d2) at -0.134 V (vs Ag/AgCl), a second reduction to a
dianion (d3) at -1.175 V, and an oxidation to a cation (d0)
at +0.447 V. These processes were also investigated spec-
troelectrochemically in an optically transparent thin layer
electrochemical (OTTLE) cell (CH2Cl2 solution, -20 °C).
The UV-vis/NIR spectrum of neutral 3 shows peaks at 827
and 574 nm, together with much weaker features at 1020
and 1120 nm; in the analogous Cp*Mo(dmit)2 radical, these
features were observed as a strong peak at 941 nm and a
weaker one at 1153 nm.25 On oxidation to the cation 3+, as
shown in Figure 4, the stronger peaks shift to higher energy
at 725 and 554 nm, retaining their relative intensities, and
the weak features disappear. However, on reduction of 3 to
the anion 3-, shown in Figure 5, the main peak is somewhat
quenched, leading to a broad double-humped feature at 707
and 639 nm, and the weak low-energy peaks again disappear.
The appearance of this spectrum is again very similar to that
The 1H NMR spectrum of diamagnetic 5 displays phenyl
group resonances together with two closely spaced peaks
for the Cp ligands at δ 4.80 and 4.77, in a ratio of 4:1:1.
(37) (a) Cai, S.; Wang, J.-Q.; Jin, G.-X. Organometallics 2005, 24, 4226.
(b) Wang, J.-Q.; Hou, X. F.; Weng, L.-H.; Jin, G.-X. J. Organomet.
Chem. 2005, 690, 249. (c) Liu, S.; Wang, X.; Jin, G.-X. J. Organomet.
Chem. 2006, 691, 261.
(38) Leadbeater, N. E. J. Org. Chem. 2001, 66, 7539.
10972 Inorganic Chemistry, Vol. 45, No. 26, 2006

Heterometallic Dithiolene Complexes
Figure 3. Molecular structure of complex 5 in the crystal (ORTEP plot, 50% probability ellipsoids). Hydrogen atoms have been omitted for clarity.
the spectrum of 3- shows very little further change on
reduction to the dianion.
The electrochemistry of the heteronuclear complexes is
more complicated. Dinuclear 5 shows one fully reversible
reduction at -0.905 V, together with an irreversible oxidation
at Epa ) 0.748 V. Trinuclear 4 shows two reductions, the
first one being fully reversible at -0.132 V, and the second
being irreversible at Epc ) -0.666 V. The similarity of the
first reduction potential to that of 3 might indicate that it is
localized on the molybdenum dithiolene moieties, while the
second has a broader line shape and could be due to a nickel-
based reduction. Complex 4 also shows two oxidation waves,
the first of which at 0.454 V is broad and partially reversible,
whereas the second, at Epa ) 1.032 V, is irreversible. No
attempt was made to investigate the spectroelectrochemistry
of either 4 or 5.
Figure 4. OTTLE plot of redox process occurring on oxidation of 3 to
3+ (potential held at 0.8 V vs Ag/AgCl).
Conclusion. The chemistry reported here again demon-
strates the utility of the dithiolene ligand transfer reaction,
which in this case provides a useful route to the new bis-
(dithiolene) Mo(V) complex CpMo(S2C2Ph2)2 from the
readily available precursors Ni(S2C2Ph2)2 and CpMo(CO)3Cl.
The isolation of the unusual Mo2Ni complex 4 was an
unexpected bonus. We have also shown that one of the Cp
ligands of nickelocene can be readily displaced by the bis-
(dithiolene) complex to give an excellent yield of the
heterobimetallic dithiolene-bridged compound 5, whereas the
removal of the second ring to give 4 is a much slower
process. We are currently investigating the reactions of
nickelocene with other suitable dithiolene precursors, and
of CpMo(S2C2Ph2)2 with a range of other suitably labile
metal-ligand fragments, the results of which will be reported
separately.
Figure 5. OTTLE plot of redox process occurring on reduction of 3 to
3- (potential held at -0.5 V vs Ag/AgCl).
Table 3. Selected Bond Lengths (Å) and Angles (deg) for Complex 5
Mo(2)-S(6)
2.3814(8) Mo(2)-S(3)
2.4011(8) Mo(2)-S(4)
2.7201(7) Ni(2)-S(6)
2.2155(9) S(3)-C(13)
2.3830(8)
2.4098(8)
2.1990(9)
1.782(3)
1.738(3)
1.354(4)
Mo(2)-S(5)
Mo(2)-Ni(2)
Ni(2)-S(3)
S(4)-C(11)
1.753(3)
1.768(3)
1.363(4)
79.76(3)
81.58(3)
135.03(3)
87.58(3)
72.74(3)
S(5)-C(14)
S(6)-C(12)
C(11)-C(12)
C(13)-C(14)
S(6)-Mo(2)-S(3)
S(3)-Mo(2)-S(5)
S(3)-Mo(2)-S(4)
S(6)-Ni(2)-S(3)
Ni(2)-S(6)-Mo(2)
S(6)-Mo(2)-S(5)
S(6)-Mo(2)-S(4)
S(5)-Mo(2)-S(4)
Ni(2)-S(3)-Mo(2)
135.33(3)
Experimental Procedures
81.72(3)
83.57(3)
72.43(3)
Materials. General experimental techniques were as described
in recent work from this laboratory.20 All reactions were routinely
carried out under an argon or nitrogen atmosphere, although
separation procedures were carried out without any special precau-
tions since the products described are all relatively air-stable.
Solvents were purified with a Grubbs-type purification system
manufactured by Innovative Technology, Newburyport, MA. The
complexes Ni(S2C2Ph2)2 and CpMo(CO)3Cl were prepared by the
of [Cp*Mo(dmit)2]-, in which the peaks have been assigned
to transitions from the HOMO (essentially dithiolene π-based)
2
to the LUMO (predominantly the Mo dz orbital). Both
couples are clearly fully reversible as shown by the occur-
rence of clear isosbestic points in the spectra. Interestingly,
Inorganic Chemistry, Vol. 45, No. 26, 2006 10973

Adams et al.
Table 4. Summary of Crystallographic Data for Complexes 3, 4‚THF, and 5
3
4‚THF
5
empirical formula
Fw
C33H25MoS4
645.71
C70H58Mo2Ni OS8
1422.23
C38H30MoNiS4
769.51
T (K)
150(2)
150(2)
150(2)
cryst syst
space group
a (Å)
b (Å)
triclinic
P1h
triclinic
P1h
monoclinic
P21/c
15.229(4)
28.544(6)
7.4346(18)
90
92.086(4)
90
3229.8(13)
4
1.583
1.258
1568
0.34 × 0.23 × 0.21
1.34-28.57
37004
11.1395(19)
11.408(2)
11.938(2)
79.504(3)
81.005(3)
70.743(3)
1400.7(4)
2
14.4954(8)
15.5339(9)
28.2119(17)
93.8560(10)
92.7860(10)
104.4510(10)
6123.5(6)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
4
density (calcd)/mg m-3
1.531
0.789
658
0.43 × 0.31 × 0.12
1.74-28.32
8960
1.543
1.026
2904
0.48 × 0.48 × 0.40
1.36-27.54
51432
µ (mm-1
F(000)
)
cryst size (mm3)
θ range for data collection (deg)
reflns collected
independent reflns
data/restraints/params
GOF on F2
6350 [Rint ) 0.0237]
6350/0/343
1.057
26550 [Rint ) 0.0683]
26550/0/1477
0.922
7686 [Rint ) 0.0768]
7686/0/397
0.926
final R1, wR2 [I > 2σ(I)]
R1 ) 0.0314
wR2 ) 0.0850
R1 ) 0.0339
wR2 ) 0.0870
1.104 and -1.253
R1 ) 0.0411
wR2 ) 0.0850
R1 ) 0.0723
wR2 ) 0.0937
0.937 and -0.706
R1 ) 0.0364
wR2 ) 0.0743
R1 ) 0.0643
wR2 ) 0.0816
0.646 and -0.420
all data
largest diff. peak and hole (e Å-3
)
literature procedures.14,39 All other chemicals were obtained from
commercial sources and used as supplied.
removed from the resulting dark solution on the vacuum line.
(Note: We haVe no eVidence for the formation of highly toxic Ni-
(CO)4 in this reaction, but this possibility should be considered
during workup and appropriate precautions taken.) The solid
residue was redissolved in dichloromethane and adsorbed onto 5 g
of chromatographic silica, which was then loaded onto a silica
column prepared in light petroleum or hexanes. Elution of the
column with hexane-dichloromethane (4:1 v/v) produced a green
band of unreacted Ni(S2C2Ph2)2 (139.8 mg, 29.5% recovery). A
13:7 mixture of the same solvents was then used to elute a dark
blue-purple band of CpMo(S2C2Ph2)2 (3) (111.2 mg, 19.8% based
on Mo). The eluting solvent was then changed to a 2:3 mixture to
elute the royal blue band of Ni[Mo(S2C2Ph2)2Cp]2 (4) (124.5 mg,
21.1% based on Mo). These yields are for a total chromatography
time of 1.5 h; as noted in the text, longer times led to increased
amounts of 3 but reduced amounts of 4.
Physical Measurements. 1H and 13C NMR spectra were obtained
in CDCl3 solution on a Bruker AC250 Fourier transform machine
with automated sample-changer or on Bruker AMX400 or DRX-
500 spectrometers. Chemical shifts are given on the δ scale relative
to SiMe4 ) 0.0 ppm. The 13C{1H} NMR spectra were routinely
recorded using an attached proton test technique (JMOD pulse
sequence). IR spectra were recorded on a Perkin-Elmer 1600 FT
machine. The EPR spectrum of 3 was recorded at the University
of Manchester on a Bruker EMX hybrid spectrometer and simulated
with Bruker’s Xsophe software. Mass spectra were recorded on a
Fisons/BG Prospec 3000 instrument operating in fast atom bom-
bardment mode with m-nitrobenzyl alcohol as a matrix; the figures
reported are the highest intensity peak of each isotope envelope.
UV-vis absorption spectra were recorded on a Varian Cary 50
instrument in the range of 200-800 nm in dichloromethane solution
with a path length of 1 cm. Elemental analyses were carried out
by the Microanalytical Service of the Department of Chemistry with
a Perkin-Elmer 2400 analyzer. Cyclic voltammetry was carried out
using an EG&G 273A potentiostat. Measurements were carried out
under dinitrogen in dry freshly distilled dichloromethane solutions
of approximate concentration 1 mM, containing 0.1 M Bu4NBF4
as a supporting electrolyte. Potentials were measured relative to a
Ag/AgCl electrode. Processes are described as reversible if ∆E <
100 mV and |Ipa/Ipc| ) 1. UV-vis/NIR spectroelectrochemistry
was also carried out in CH2Cl2 solution in an OTTLE cell mounted
in a Cary 5000 spectrometer, thermostatically held at 253 K.
Synthesis. CpMo(S2C2Ph2)2 (3) and Ni[Mo(S2C2Ph2)2Cp]2 (4).
The complexes CpMo(CO)3Cl (244.8 mg, 0.873 mmol) and Ni-
(S2C2Ph2)2 (474.1 mg, 0.873 mmol) were dissolved in toluene (150
mL), and the solution was refluxed for 2 h. The solvent was
Data for 3: Mp 237-240 °C. IR (KBr): 3106 m, 3052 m, 2925
m, 2854 m, 1676s, 1661s, 1594 m, 1448vs (CdC), 1428vs
(CdC), 1211s, 1175s, 1164s, 1072w, 1027w, 999w, 875 m
(CsS), 865 m (CsS), 816 m cm-1. 1H NMR: δ 15 (br s), -4 (br
s). EPR (toluene, 298 K): g ) 2.010 (AMo ) 9.6 G). Anal. Found:
C, 61.06; H, 3.95; S, 19.82. Required for C33H25MoS4: C, 61.40;
H, 3.88; S, 19.84%. MS: m/z 647 (M+). UV-vis spectrum 574
nm (ꢀ ) 5535 M-1 cm-1), 442 nm (ꢀ ) 3560 M-1 cm-1).
Data for 4: Mp 202-205 °C. 1H NMR: δ 7.15-6.90 (m, 40 H,
Ph), 5.04 (s, 10 H, Cp). 13C NMR: 158.5 (br s, possibly C of
dithiolene), 141.0 (Cipso of Ph), 129.6, 127.5, 126.8 (Ph), 94.1 (Cp).
Anal. Found: C, 59.51; H, 4.08; S, 18.11. Required for 4‚THF
C70H58Mo2NiOS8: C, 59.13; H, 4.08; S, 18.02%. MS: m/z 1349
(M+), 1107 (M--S2C2Ph2)+, 647 [CpMo(S2C2Ph2)2]+. UV-vis
spectrum 587 nm (ꢀ ) 13 230 M-1 cm-1), 358 nm (ꢀ ) 17 360
M-1 cm-1).
Reaction of CpMo(CO)3Cl with Ni(S2C2Ph2)2 in the Presence
of Additional CpMo(S2C2Ph2)2. A Schlenk tube was charged with
CpMo(CO)3Cl (74.4 mg, 0.27 mmol), Ni(S2C2Ph2)2 (147.8 mg, 0.27
mmol), and CpMo(S2C2Ph2)2 (169.3 mg, 0.26 mmol). The com-
plexes were dissolved in toluene (50 mL), and the solution was
(39) Hoffmann, N. W. Inorg. Chim. Acta 1984, 88, 59. This procedure
was modified in that the NaCp solution was treated with Mo(CO)6 in
refluxing THF for 24 h; we did not use Mo(CO)3(NCMe)3 as an
intermediate. A detailed description of our procedure has been posted
at http://www.mjmorris.staff.shef.ac.uk/preps.html and is also included
in the Supporting Information.
10974 Inorganic Chemistry, Vol. 45, No. 26, 2006

Heterometallic Dithiolene Complexes
heated to reflux for 3 h. Column chromatography as stated
previously afforded green Ni(S2C2Ph2)2 (89.8 mg, 81% recovery),
purple CpMo(S2C2Ph2)2 (66.4 mg, 39% recovery), and a small
amount of blue Ni[Mo(S2C2Ph2)2Cp]2 (13.8 mg, 3.7% based on
Ni). Several other unidentified minor bands were observed, and
much decomposed material remained uneluted.
Reaction of Ni(cod)2 with CpMo(S2C2Ph2)2. In a glove box,
Ni(cod)2 (0.260 g, 0.946 mmol) and CpMo(S2C2Ph2)2 (1.172 g, 1.82
mmol) were dissolved in toluene (50 mL). After stirring for 20.5
h, the solution was removed from the glove box and evaporated to
dryness. Column chromatography as stated previously produced a
purple band of unchanged 3 followed by a blue zone of Ni[Mo-
(S2C2Ph2)2Cp]2 (0.7893 g, 62%).
Reaction of Ni[Mo(S2C2Ph2)2Cp]2 with Sulfur. A solution of
Ni[Mo(S2C2Ph2)2Cp]2 (100.9 mg, 0.074 mmol) and elemental sulfur
(5.3 mg, 0.167 mmol) in toluene (20 mL) was heated to reflux for
2.5 h. After removal of the solvent, column chromatography
produced CpMo(S2C2Ph2)2 (71.1 mg, 0.11 mmol, 74%). A black
insoluble residue remained at the top of the column.
in toluene (20 mL) was heated to reflux for 7 days, during which
the solution took on a blue color. Monitoring the solution by TLC
revealed the red spot due to 5 gradually being replaced by a blue
one. At the end of the reaction, column chromatography produced
two minor bands followed by a purple band of residual 3 (18.5
mg, 22% recovery). Careful elution with a 1:1 mixture of hexane-
CH2Cl2 produced a blue band of 4, which could not be completely
separated from the red band of residual 5 that immediately followed
1
it. The total mass collected was 65 mg, and H NMR integration
revealed that this consisted of a 3:1 mixture of 4 and 5. Hence, the
yield of 4 is approximately 21%. Two further minor green bands
were eluted subsequently, but these have yet to be identified.
Crystal Structure Determinations. Crystal data for the three
structures are summarized in Table 4 . The data were collected at
150 K on a Bruker Smart CCD area detector equipped with an
Oxford Systems cryostat and refined with the program package
SHELXTL40 implemented on a Viglen Pentium computer. Hydrogen
atoms were placed geometrically and refined in riding mode with
Uiso constrained to be 1.2 times Ueq of the carrier atom.
Synthesis of NiMo(µ-S2C2Ph2)2Cp2. A solution of Cp2Ni (30.0
mg, 0.16 mmol) and CpMo(S2C2Ph2)2 (96.5 mg, 0.15 mmol) in
toluene (100 mL) was heated to reflux for 1 h. Column chroma-
tography produced two minor bands (yellow and green) followed
by a large red zone of NiMo(µ-S2C2Ph2)2Cp2 (97.7 mg, 85%). Mp
dec at 230 °C. 1H NMR: δ 7.25-7.15 (m, 20 H, Ph), 4.80 (s, 5 H,
Cp), 4.77 (s, 5 H, Cp). 13C NMR: 170.2 (CPh), 143.5 (Cipso), 141.4
(Cipso), 135.1 (CPh), 129.6-126.3 (m, Ph), 95.7 (Cp), 93.3 (Cp).
Anal. Found: C, 59.06; H, 3.91; S, 16.49. Required for C38H30-
MoNiS4: C, 59.38; H, 3.90; S, 16.67%. MS m/z 770 (M+), 647
(M-NiCp)+. UV-vis spectrum 534 nm (ꢀ ) 13 445 M-1 cm-1),
339 nm (ꢀ ) 17 772 M-1 cm-1).
Acknowledgment. We thank the EPSRC and the Uni-
versity of Sheffield for support, Prof. M.D. Ward for
provision of electrochemical facilities, and Drs. D. Collison
and J. Wolowska (University of Manchester) for recording
and simulating the EPR spectrum.
Supporting Information Available: Crystallographic informa-
tion files for structures 3-5 and a detailed preparation of CpMo-
(CO)3Cl. This material is available free of charge via the Internet
at http://pubs.acs.org.
IC0606227
Reaction of NiMo(µ-S2C2Ph2)2Cp2 with CpMo(S2C2Ph2)2 To
Give Ni[Mo(S2C2Ph2)2Cp]2. A solution of NiMo(µ-S2C2Ph2)2Cp2
(100.0 mg, 0.13 mmol) and CpMo(S2C2Ph2)2 (85.0 mg, 0.13 mmol)
(40) SHELXTL, an integrated system for solving and refining crystal
structures from diffraction data (Revision 5.1), Bruker AXS Ltd.
Inorganic Chemistry, Vol. 45, No. 26, 2006 10975