C-C, C-S, and C-N coupling versus dealkylation processes in the cationic tris(thiolato)dimolybdenum(III) complexes [Mo2Cp2(μ- SMe)3L2]+ (L= xyINC, t-BuNC, CO, MeCN)

Article abstract of DOI:10.1021/om8003702

Reductive coupling between isocyanide ligands attached to adjacent molybdenum atoms in the bis(aryl isocyanide) complex [Mo₂Cp ₂(μ-SMe)₃(xylNC)₂](BF₄) (1) was initiated by addition of the hydrosulfide anion (HS^-) to 1 under reflux in tetrahydrofuran, affording, in nearly quantitative yields, the dimetallaimidoyl(amino)carbene derivative [Mo₂Cp₂(μ- SMe)₃{μ-η¹(C):η¹(C)-C(NHxyl)C(Nxyl)} ] (7), in which both isocyanide groups of 1 are now linked by a new C-C bond. When the previous reaction was conducted in the presence of a large excess of hydrosulfide (20 equiv), under similar experimental conditions, the dithiocarbonimidate compound [Mo₂Cp₂(μ-SMe) ₂(μ-S₂CNXyl)] (8) was obtained in quantitative yields. This product results from subsequent thiolate exchange and substitution reactions to afford a quadruply sulfur bridged intermediate, followed by free isonitrile addition to sulfido S atoms. Treatment of the coupled isocyanide derivative 7 with HBF₄ led exclusively to the formation of the starting complex 1 by reversible isocyanide ligand decoupling. The heating of a tetrahydrofuran solution of 1 with the base NaC≡CH gave, in high yields, the μ-alkylidyne and μ-acetylide product [Mo₂Cp(μ-SMe) ₂ {μ-(η⁵-C₅H₄)(xylN)CN(xyl)C} (μ-CCH)] (9), in which a deprotonated Cp and both isocyanide ligands of 1 are now linked by new C-C and C-N bonds, and in addition an acetylide has replaced a thiolate ligand of 5. Reaction of the μ-alkylidyne complex [Mo ₂Cp(μ-SMe)₃(μ-(η⁵C₅H ₄)(xylN)CN(xyl)C}] (5) with NaC≡CH under reflux in tetrahydrofuran produced, in high yields, the μ-alkylidyne and bis(μ-acetylide) cationic compound [Mo₂Cp(μ-SMe)₂ {μ-(η⁵-C₅H₄)(xylN)CN(xylI)C}(μCCH) ₂]Br (10), in which two xylNC ligands have replaced a thiolate group of 5. Further reactions of the bis(μ-isocyanide) complex 10 with NaOH (suspension), on the one hand, and HBF₄, on the other hand, under reflux in tetrahydrofuran or at room temperature in dichloromethane, respectively, led to the formation in high yields of the known mixed μ-alkylidyne and μ-amino-oxycarbene species [Mo₂Cp(μ-SMe) ₂(μ-(η⁵C₅H₄)(xylN)CN(xyl)C} {μ-η¹(O):η¹(C)-OCNHxyl}} (12) and the new tetrakis(isocyanide) dicationic derivative [Mo₂Cp₂(μ- SMe)₂(xylNC)₄](BF₄)₂ (11), respectively. The latter complex results from successive protonation at one carbon atom of the cyclopentadienyl ligand linked with isocyanides of 10 and decoupling between deprotonated Cp and isocyanide ligands. The heating of a tetrahydrofuran solution of a mixture of the bis(alkyl isocyanide) complex [Mo₂Cp₂(μ-SMe)₃(t-BuNC)₂](BF ₄) (2) and NaSH proceeded exclusively through the dealkylation of one tert-butyl isocyanide ligand to afford the known product [Mo₂Cp ₂(μ-SMe)₃(t-BuNC)](CN)] (13). Similar reaction of the dicarbonyl derivative [Mo₂Cp₂(μ-SMe) ₃(CO)₂]Cl (3) with NaSH proceeded through dealkylation of one thiolate group to yield the new neutral sulfido species [Mo ₂Cp₂(μ-SMe)₂(μ-S)(CO)₂] (14). Further heating of 14 in dichloromethane led to the formation of the chloromethanethiolate derivative [Mo₂Cp₂(μ-SMe) ₂(μ-SCH₂Cl)(CO)₂]Cl (15). Treatment of the bis(nitrile) species [Mo₂Cp₂(μSMe)₃(MeCN) ₂]BF₄ (4) under reflux in tetrahydrofuran with NaSH afforded, in valuable yields, the thioamidato derivative [Mo₂Cp ₂(μ-SMe)₃(μ-MeCSNH)] (18). All new complexes have been characterized by elemental analyses and spectroscopic methods, supplemented for 7-10, 11′, 14, and 15 by X-ray diffraction studies.

Full text of DOI:10.1021/om8003702

Organometallics 2008, 27, 4207–4222
4207
C-C, C-S, and C-N Coupling versus Dealkylation Processes in the
Cationic Tris(thiolato)dimolybdenum(III) Complexes
[Mo2Cp2(µ-SMe)3L2]+ (L ) xylNC, t-BuNC, CO, MeCN)
Wilfried-Solo Ojo, Franc¸ois Y. Pe´tillon,* P. Schollhammer,* and Jean Talarmin
UMR CNRS 6521, Chimie, Electrochimie Mole´culaires et Chimie Analytique, UFR Sciences et Techniques,
UniVersite´ de Bretagne Occidentale, CS 93837, 29238 Brest-Cedex 3, France
ReceiVed April 28, 2008
Reductive coupling between isocyanide ligands attached to adjacent molybdenum atoms in the bis(aryl
isocyanide) complex [Mo2Cp2(µ-SMe)3(xylNC)2](BF4) (1) was initiated by addition of the hydrosulfide anion
(HS-) to 1 under reflux in tetrahydrofuran, affording, in nearly quantitative yields, the dimetallaimidoyl(ami-
no)carbene derivative [Mo2Cp2(µ-SMe)3{µ-η1(C):η1(C)-C(NHxyl)C(Nxyl)}] (7), in which both isocyanide
groups of 1 are now linked by a new C-C bond. When the previous reaction was conducted in the presence
of a large excess of hydrosulfide (20 equiv), under similar experimental conditions, the dithiocarbonimidate
compound [Mo2Cp2(µ-SMe)2(µ-S2CNxyl)] (8) was obtained in quantitative yields. This product results from
subsequent thiolate exchange and substitution reactions to afford a quadruply sulfur bridged intermediate,
followed by free isonitrile addition to sulfido S atoms. Treatment of the coupled isocyanide derivative 7 with
HBF4 led exclusively to the formation of the starting complex 1 by reversible isocyanide ligand decoupling.
The heating of a tetrahydrofuran solution of 1 with the base NaCtCH gave, in high yields, the µ-alkylidyne
and µ-acetylide product [Mo2Cp(µ-SMe)2{µ-(η5-C5H4)(xylN)CN(xyl)C}(µ-CCH)] (9), in which a deprotonated
Cp and both isocyanide ligands of 1 are now linked by new C-C and C-N bonds, and in addition an acetylide
has replaced a thiolate ligand of 5. Reaction of the µ-alkylidyne complex [Mo2Cp(µ-SMe)3{µ-(η5-
C5H4)(xylN)CN(xyl)C}] (5) with NaCtCH under reflux in tetrahydrofuran produced, in high yields, the
µ-alkylidyne and bis(µ-acetylide) cationic compound [Mo2Cp(µ-SMe)2{µ-(η5-C5H4)(xylN)CN(xyl)C}(µ-
CCH)2]Br (10), in which two xylNC ligands have replaced a thiolate group of 5. Further reactions of the
bis(µ-isocyanide) complex 10 with NaOH (suspension), on the one hand, and HBF4, on the other hand, under
reflux in tetrahydrofuran or at room temperature in dichloromethane, respectively, led to the formation in
high yields of the known mixed µ-alkylidyne and µ-amino-oxycarbene species [Mo2Cp(µ-SMe)2{µ-(η5-
C5H4)(xylN)CN(xyl)C}{µ-η1(O):η1(C)-OCNHxyl}] (12) and the new tetrakis(isocyanide) dicationic derivative
[Mo2Cp2(µ-SMe)2(xylNC)4](BF4)2 (11), respectively. The latter complex results from successive protonation
at one carbon atom of the cyclopentadienyl ligand linked with isocyanides of 10 and decoupling between
deprotonated Cp and isocyanide ligands. The heating of a tetrahydrofuran solution of a mixture of the bis(alkyl
isocyanide) complex [Mo2Cp2(µ-SMe)3(t-BuNC)2](BF4) (2) and NaSH proceeded exclusively through the
dealkylation of one tert-butyl isocyanide ligand to afford the known product [Mo2Cp2(µ-SMe)3(t-BuNC)](CN)]
(13). Similar reaction of the dicarbonyl derivative [Mo2Cp2(µ-SMe)3(CO)2]Cl (3) with NaSH proceeded through
dealkylation of one thiolate group to yield the new neutral sulfido species [Mo2Cp2(µ-SMe)2(µ-S)(CO)2] (14).
Further heating of 14 in dichloromethane led to the formation of the chloromethanethiolate derivative
[Mo2Cp2(µ-SMe)2(µ-SCH2Cl)(CO)2]Cl (15). Treatment of the bis(nitrile) species [Mo2Cp2(µ-
SMe)3(MeCN)2]BF4 (4) under reflux in tetrahydrofuran with NaSH afforded, in valuable yields, the thio-
amidato derivative [Mo2Cp2(µ-SMe)3(µ-MeCSNH)] (18). All new complexes have been characterized by
elemental analyses and spectroscopic methods, supplemented for 7-10, 11′, 14, and 15 by X-ray diffraction
studies.
consecutive insertions of these unsaturated molecules into M-C
bonds. These insertion reactions are mostly initiated by oxidative
addition of alkyl halides to [MLn] complexes (L ) RNC, RCN,
CO,...), by addition of an excess of two-electron-donor mol-
ecules to metal complexes, and also by thermolysis.5 Among
the previously cited potential coupling molecules, isocyanides
(RNC) are isoelectronic with CO and, accordingly, are expected
to display similar chemical behavior. Indeed, many such
similarities are apparent, but differences between the two are
also observed, resulting from the fact that isocyanides are better
σ-donors and weaker π-acceptors than carbon monoxide.6 In
particular, almost all the carbonylation reactions are intramo-
Introduction
Coupling reactions involving alkynes,1 isocyanides,1,2 ni-
triles,3 and carbon monoxide,4 through the mediation of transi-
tion-metal complexes, lead to metallacyclic compounds via
(1) (a) Albano, V.G.; Busetto, L.; Marchetti, F.; Monari, M.; Zacchini,
S.; Zanotti, V. Organometallics 2007, 26, 3443. (b) Antin˜olo, A.; García-
Yuste, S.; Lopez-Selera, M. I.; Otero, A.; Pe´rez-Flores, J. C.; Reguillo-
Carmona, R.; Villasen˜or, E. Dalton Trans. 2006, 1495. (c) Jeffery, J. C.;
Green, M.; Lynam, J. M. Chem. Commun. 2002, 3056. (d) Adams, R. D.;
Huang, M. Organometallics 1995, 14, 506. (e) Davidson, J. L.; Wilson,
W. F. J. Chem. Soc., Dalton Trans. 1998, 27. (f) Homrighausen, C. L.;
Alexander, J. J.; Krause-Bauer, J. A. Inorg. Chim. Acta 2002, 334, 419.
10.1021/om8003702 CCC: $40.75
2008 American Chemical Society
Publication on Web 07/30/2008

4208 Organometallics, Vol. 27, No. 16, 2008
Ojo et al.
lecular, while most of the insertions of isocyanides into
metal-carbon bonds are, in contrast, intermolecular,2 in which
the incoming ligand is the one inserted. Interestingly, almost
all the examples of intramolecular coupling reactions between
two isocyanides that have been investigated experimentally are
induced in mononuclear transition-metal complexes by the
carbon-carbon reductive coupling of adjacent ligands.7 Such
reactions, which are reported in the literature, may be viewed
formally as the addition of one electron and one proton to each
of two isocyanide ligands, which then couple to one another. It
has been demonstrated that the close nonbonded contact between
ligands in mononuclear poly(isocyanide) complexes is a pre-
requisite for carbon-carbon bond formation.8 With this in mind,
one can explain the lack, until now, of ligands resulting from
C-C coupling between two isocyanides coordinated to adjacent
metals in binuclear transition-metal complexes, in which the
nonbonded distance between isocyanides is obviously expected
to be much longer than that observed in related mononuclear
derivatives. Nevertheless, a few C-C coupling reactions on
dinuclear transition-metal complexes have been reported; they
involve either incoming isocyanides and unsaturated/saturated
molecules already coordinated to the metals9 or both incoming
isocyanides.10 In all these cases, the isolated products result from
successive insertions of RNC into transition-metal-carbon
bonds.
As part of our ongoing studies of metal-assisted coupling
reactions involving RNC or/and R′CN, we have recently
explored the reactivity toward bases having variable strengths
of such systems coordinated to the bimetallic core {Mo2Cp2(µ-
SMe)3}. We have found, among other features, that on reacting
the bis(tert-butyl isocyanide) complex [Mo2Cp2(µ-SMe)3(t-
BuNC)2](BF4) with n-BuLi the mixed isocyanide-cyanide
derivative [Mo2Cp2(µ-SMe)3(t-BuNC)(CN)] is exclusively formed
by dealkylation of one isocyanide group. However, when
n-butyllithium is replaced by milder bases, a mixture of two
complexes is hence obtained in the reaction of [Mo2Cp2(µ-
SMe)3(t-BuNC)2](BF4) wih NaOH or (Me4N)OH: in addition
to the previous dealkylated derivative, a µ-alkylidyne species,
resulting from the coupling of a deprotonated Cp and two
isocyanide ligands, is formed as a minor product. The yield of
the latter compound is improved by conducting the reaction in
the presence of an excess of tert-butyl isocyanide. It has been
shown that the formation of the µ-alkylidyne ligand in these
experiments involves first the deprotonation by the base of one
Cp carbon atom, followed by its stepwise 1,1-migration to the
carbon of an adjacent RNC ligand, and finally an isocyanide
dimerization occurring via a C,N coupling reaction.11 Interest-
ingly, when the ligand L is xylNC, the formation in high yields
of C,C and C,N coupling products is observed in the reaction
of [Mo2Cp2(µ-SMe)3L2](BF4) with bases (NaOH, (Me4N)OH).
When the latter reactions are conducted in the presence of RNC
(R ) xyl, t-Bu), µ-alkylidyne µ-aminocarbene complexes are
produced by linking first a cyclopentadienyl and two isocyanide
ligands and then a second isocyanide and hydroxide. All these
reactions serve as a striking illustration of the importance of
the nature of both isocyanide or nitrile ligands and bases for
studies involving intramolecular coupling reactions. As an
extension of the above studies, we have now investigated the
reactivity of [Mo2Cp2(µ-SMe)3L2]A (1-4) and [Mo2Cp2(µ-
SMe)3{µ-(η5-C5H4)(xylCN)(xyl)C}] (5) (see Scheme 1) with
several bases (NaSH, NaCtCH, LiOCH2CH2Br, NaOH). We
have found a remarkable variety of products with new func-
tionalities. The results are also used to evaluate how both the
strength of the bases and the nature of the terminal ligands L
in [Mo2Cp2(µ-SMe)3L2]A influence whether or not coupling
products are formed.
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T. R.; Boyle, P. D.; Petersen, J. L. Angew. Chem., Int. Ed. 2008, 47, 726.
(b) Suzuki, S.; Komuro, T; Okazaki, M.; Tobita, H. Organometallics 2007,
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Int. Ed. 2006, 45, 5533. (e) Khripun, A. V.; Kukushkin, V. Y.; Selivanov,
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Results and Discussion
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Reaction of 1 with Sodium Hydrosulfide. Previously, we
have shown that the bis(xylyl isocyanide) complex 1 reacts with
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Cationic Tris(thiolato)dimolybdenum(III) Complexes
Organometallics, Vol. 27, No. 16, 2008 4209
Scheme 1. Tris(thiolato-bridged) Dimolybdenum Precursors
Relevant to This Work
Mo1-Mo2 distance of 2.7254(7) Å is comparable to that of
2.705(7) Å in the cation [Mo2Cp2(µ-SMe)3(µ-η1:η1-HCCCO2-
Me)]+,13 hence indicating a single bond. We consider that the
X-ray study establishes 7 as a µ-η1(C):η1(C) complex and
therefore formulate 7 as a dimetallaimidoyl(amino)carbene
derivative, with a parallel orientation of the C-C axis of the
coupled ligand relative to that of the Mo-Mo bond (C4-C5-
Mo1-Mo2 torsion angle 1.2(3)°).
The present reaction (Scheme 2a) may be viewed as the
addition of two electrons and one proton to the two isocyanide
ligands in 1, which then couple with one another through the
carbon atom of each isocyanide to form a metallaimidoyl(ami-
no)carbene complex. To the best of our knowledge, compound
1 is the first example of a dinuclear transition-metal derivative
that promotes the reductive coupling of isocyanide ligands by
use of an added anionic reagent, HS-, acting as a reductant.
The mechanism by which two isocyanide ligands are reductively
coupled is presently uncertain, but it probably involves a
pathway that facilitates a close nonbonded contact between the
isocyanide ligands in 1, which enhances the propensity for
carbon-carbon bond formation. Accordingly, the first step of
formation of 7 is postulated to be the one-electron reduction of
[Mo2Cp2(µ-SMe)3(xylNC)2]+ by HS- (or S2-). Hence, the
electron back-donation from the metal into isocyanide π-ac-
ceptor orbitals favors the bending of the latter ligand, which in
turn creates a basic nitrogen center that can be protonated to
form the putative, transient aminocarbyne cation [Mo2Cp2(µ-
SMe)3(xylNC)(xylNHC)]+ (A). Thus, addition of a second
electron to the cation A promotes the formation of a second
carbeno¨ıd-type ligand, which activates the resulting molybdenum
derivative for reductive coupling of two isocyanides attached
to adjacent metals to afford the dimetallaimidoyl(amino)carbene
complex 7. It appears that the last step of formation of 7 is
kinetically favored relative to that of the protonation of the
second nitrogen atom of the carbenoid-type group resulting from
the one-electron reduction. This prevents the formation of a
bis(alkylamido)acetylene derivative, as found by Lippard et al.
in several reductive coupling reactions involving mononuclear
polycoordinate transition-metal isocyanide complexes and a
reductant (Zn). Requisite protons to react with the nitrogen of
the isocyanide come from either wet tetrahydrofuran or, more
probably, water present in the sodium sulfide reagent
(NaSH · xH2O). It should be noted that several attempts to react
the bis(isocyanide) cationic compound 1 with zinc under reflux
in wet tetrahydrofuran failed.
hydroxides to afford in nearly quantitative yields (84%) the
µ-alkylidyne
product
[Mo2Cp(µ-SMe)3{µ-(η5-
C5H4)(xylN)CN(xyl)C}] (5) by cyclopentadienyl and isocyanide
coupling.5 It is noteworthy that in this case reductive coupling
of xylNC does not occur. We, therefore, decided to choose
another added anionic reagent to perform the reaction. Accord-
ingly, the hydrosulfide anion (HS-), which can act as a base
or/and a reductant, would seem to be a suitable reagent for
reaction with the bis(isocyanide) compound 1. Indeed, reaction
of 1 with 10 equiv of NaSH · xH2O in tetrahydrofuran under
reflux for 72 h proceeded with high selectivity, and the targeted
reductive coupled-isocyanide derivative 7 was obtained (Scheme
2a).
The elemental analysis confirms the presence of two isocya-
nide units in 7, while its NMR spectra clearly indicate a structure
different from that of 5. Particularly informative is the absence
in the 1H NMR pattern of the four resonances of relative
intensity 1 expected for the four hydrogen atoms of a modified
cyclopentadienyl ring. Instead, a single peak of relative intensity
10, detected at 5.09 ppm, is indicative of two unmodified
cyclopentadienyl ligands in a symmetrical molecule. The
spectroscopic features of 7 are consistent with protonation of a
sole isocyanide at the nitrogen atom. Indeed, a single resonance
assignable to an amino group is observed at 12.07 ppm in the
1H NMR spectrum, in accordance with the presence of only
one N-H stretching frequency at 3431 cm-1. Moreover, a
resonance characteristic of the Mo-bound 13C atom of a carbene-
like species appears at low field (δ 248.2). In order to establish
without any ambiguity the molecular structure of 7, an X-ray
analysis of a single crystal of that complex was undertaken.
This structure is shown in Figure 1, in which the well-known
{Mo2Cp2(µ-SMe)3} unit is bridged by an imidoyl(amino)carbene
group bonded to the Mo2 unit through both carbon atoms
(Mo-C ) 2.093(5) and 2.144(5) Å). These two molybdenum-
carbon lengths are consistent with multiple-bond character. The
resulting C-N (1.317(7) and 1.286(6) Å) distances in the
coupled ligand require multiple-bond character, while the mean
C-N-C angle of 131.5° is consistent with the presence of N-H
bonds. It should be noted that the C4-C5 distance (1.543(7)
Å) is indicative of a single bond. That set of information is in
accord with a coupled isocyanide ligand, showing substantial
bond delocalization (see Chart 1). The complex achieves a
closed-shell configuration if the ligand is viewed as a mono-
carbene, as depicted by the two extreme forms in Chart 1. The
As suggested above, the closest parallel to the work reported
in this part would appear to be the studies by Lippard et al. of
reductive coupling of isocyanide ligands in mononuclear seven-
coordinate metal complexes.7 In particular, these authors have
also postulated a cationic aminocarbyne complex as an inter-
mediate in related coupling reactions, in accordance with many
examples in the literature where electron-rich isocyanide
complexes have been converted to aminocarbynes by electro-
philic attack (H+) at the nitrogen atom.14 However, notable
differences are observed between the two chemistries. For
example, though complex 1 has the majority of the requisite
(12) (a) Cabon, N.; Pe´tillon, F. Y.; Orain, P.-Y.; Schollhammer, P.;
Talarmin, J.; Muir, K. W. J. Organomet. Chem. 2005, 690, 4583. (b) Gomes
de Lima, M. B.; Guerchais, J. E.; Mercier, R.; Pe´tillon, F. Y. Organome-
tallics 1986, 5, 1952. (c) Barrie`re, F.; Le Mest, Y.; Pe´tillon, F. Y.; Poder-
Guillou, S.; Schollhammer, P.; Talarmin, J. J. Chem. Soc., Dalton Trans.
1996, 3967.
(13) Ojo, W.-S.; Capon, J.-F.; Le Goff, A.; Pe´tillon, F. Y.; Schollham-
mer, P.; Talarmin, J.; Muir, K. W. J. Organomet. Chem. 2007, 692, 5351.
(14) Kukushkin, V. Y.; Pombeiro, A. J. L. Chem. ReV. 2002, 102, 1771,
and references therein.

4210 Organometallics, Vol. 27, No. 16, 2008
Ojo et al.
Scheme 2
electronic (high electron density at the metal center owing to
both the reduced complex and the electron-releasing thiolate
groups; presence of both Lewis acid (H+) and reductant in
solution) and steric (high coordination number of the metal
atom) properties to undergo reductive coupling, it does not,
however, afford the bis(alkylamino)acetylene derivative7 but
instead a dimetallaimidoyl(amino)carbene product, by reaction
with a reductant. Moreover, in our case the coupling reaction
requires only one proton instead of two in Lippard’s reactions,
precluding the formation of bis(alkylamino) groups. Finally, it
has been demonstrated that a prerequisite to carbon-carbon
bond formation is a close contact of two isocyanide ligands in
the parent complex,7e which we concede is more easily reached
in mononuclear than in dinuclear derivatives. Indeed, all the
Figure 1. Molecular structure of 7. Here and elsewhere non-hydrogen atoms are shown with ellipsoids at the 30% probability level. H
atoms bonded to C atoms are omitted for clarity. Selected distances (Å), angles (deg), and torsion angles (deg): Mo1-Mo2 ) 2.7254(7),
Mo1-C5 ) 2.093(5), Mo2-C4 ) 2.144(5), C4-C5 ) 1.543(7), C4-N1 ) 1.286(6), C5-N2 ) 1.317(7), N1-C40 ) 1.414(7), N2-C30
) 1.430(7), Mo-S1 ) 2.4533(15), Mo1-S2 ) 2.4659(15), Mo1-S3 ) 2.4623(15), Mo2-S1 ) 2.4642(15), Mo2-S2 ) 2.4488(15),
Mo2-S3 ) 2.4552(15); Mo1-C5-C4 ) 107.1(3), Mo1-C5-N2 ) 141.2(4), C4-C5-N2 ) 111.5(4), C5-N2-C30 ) 130.9(5),
C5-Mo1-Mo2 ) 74.31(15), Mo2-C4-C5 ) 105.3(3), Mo2-C4-N1 ) 142.3(4), C5-C4-N1 ) 112.3(5), C4-N1-C40 ) 132.2(5),
C4-Mo2-Mo1 ) 73.27(14); C4-C5-Mo1-Mo2 ) 1.2(3), Mo1-S2-Mo2-S1 ) 5.49(5), C4-C5-Mo1-S3 ) -1.1(4).

Cationic Tris(thiolato)dimolybdenum(III) Complexes
Organometallics, Vol. 27, No. 16, 2008 4211
Chart 1
Scheme 3. Proposed Route for the Formation of 8 from the
Bis(isocyanide) Complex 1
mononuclear poly(isocyanide) complexes, having reductive
carbon-carbon coupling behavior, contain nonbonded CsC
contacts of 2.25-2.86 Å,7d,f,15 while such a distance in 1 could
be evaluated, in the absence of X-ray structural data for 1, at
about 3.00 Å in comparison with that observed in the related
bis(xylNC) complex 10 (see below). Interestingly, in spite of
this longer nonbonded CsC contact in 1, its reaction with
sodium hydrosulfide in protic solvents leads to the formation
of coupled-isocyanide product. It could be suggested that both
reduction and protonation of the starting complex bring the two
isocyanide ligands closer and, hence, allow the coupling
reaction.
When the bis(isocyanide) complex 1 was heated with a large
excess of sodium hydrosulfide (20 equiv) under conditions
similar to those used in Scheme 2a, the new complex 8 was
obtained in nearly quantitative yield (95%) instead of the
coupled-isocyanide product 7 (Scheme 2c). Elemental analysis
and NMR spectroscopy (see the Experimental Section) indicate
the presence of only one isocyanide and two thiolate ligands in
8. Therefore, this compound was identified as a molybdenum
dimer bridged by a dithiocarbonimidate ligand and two SMe
groups on the basis of these analytical and spectroscopic data
and the solid-state structure, as shown in Scheme 2c and Figure
2. The NMR data provided evidence for the presence of two
isomers in solution, which differ only in the orientation (syn or
dithiocarbonimidate ligand to Mo1 and Mo2 through both S3
and S2, respectively. Otherwise, the Mo-S bond distances
(average 2.448 Å) and Mo-S-Mo angles (average 63.8°) are
in the ranges (2.42-2.49 Å and 62-66°) generally observed
for quadruply bridged dimolybdenum derivatives with a variable
number of µ-thiolato ligands.19 Several examples of related
dimolybdenum cyclopentadienyl complexes featuring bridging
dithiocarbonimidate ligands have been reported,20 but to the best
of our knowledge 8 is the first compound of this series to be
structurally characterized by X-ray analysis.
1
anti) of the bridging SMe groups. The H NMR spectra of
isomers 8a and 8b (2:3 ratio), at room temperature, each exhibit
a single resonance (relative intensity 10) at about 5.5 ppm for
the two cyclopentadienyl ligands, suggesting a chemically
symmetrical molecule. In other respects, the 13C{1H} NMR
spectra of 8 display a low-field resonance pointed at about 171.1
ppm, typical for a CdN group. Thus, the formulation of 8 as a
µ-dithiocarbonimidate derivative was confirmed by X-ray
analysis of a single crystal of 8a obtained from a diethyl ether
solution at room temperature (Figure 2). The structure contains
two CpMo fragments bridged quasi-symmetrically by one
dithiocarbonimidate and two SMe ligands, so that each Mo atom
has a four-legged piano-stool coordination. The Mo-Mo
distance(2.5897(6)Å)istypicalforquadruplybridged{Mo2IIICp2(µ-
SR)n} systems (n ) 3, 4) with single metal-metal bonds.16 The
dithiocarbonimidate N1-C5 bond distance (1.262(8) Å) is in
accord with a bond order of 2; however, the angles at C5
(132.6(5) and 126.5(5)°) show some deviations from sp2
hybridization but broadly agree with those found in a dithio-
carbonimidato complex of palladium(II), [Pd(S2CNCO2-
Et)(PPh3)2] (128.2(4) and 123.3(4)°),17 and the anion
[Ni(S2CNCN)2]2- (132(2) and 120(2)°).18 Trends in bond angles
at C5 reflect the constraint imposed by the attachment of the
The presence of a large excess of NaSH prevents the coupling
of the isocyanide ligands in 1, when this complex reacts with
this basic nucleophile. Although no transient species has been
detected, the pathway of formation of 8 can be accounted for
as summarized in Scheme 3. Indeed, there is precedent for the
first step of the mechanism that involves subsequent thiolate
exchange20b and substitution reactions to afford the quadruply
(19) (a) Le Roy, C.; Pe´tillon, F. Y.; Muir, K. W.; Schollhammer, P.;
Talarmin, J. J. Organomet. Chem. 2006, 691, 898. (b) Cabon, N.; Pe´tillon,
F. Y.; Schollhammer, P.; Talarmin, J.; Muir, K. W. Dalton Trans. 2004,
2708. (c) Schollhammer, P.; Cabon, N.; Capon, J.-F.; Pe´tillon, F. Y.;
Talarmin, J.; Muir, K. W. Organometallic 2001, 20, 1230. (d) Schollham-
mer, P.; Gu´enin, E.; Pe´tillon, F. Y.; Talarmin, J.; Muir, K. W.; Yufit, D. S.
Organometallics 1998, 17, 1922. (e) Schollhammer, P.; Pichon, M.; Muir,
K. W.; Pe´tillon, F. Y.; Pichon, R.; Talarmin, J. Eur. J. Inorg. Chem. 1999,
221. (f) Connelly, N. G.; Dahl, L. F. J. Am. Chem. Soc. 1970, 92, 7470. (g)
Newell, R.; Ohman, C.; Rakowski DuBois, M. Organometallics 2005, 24,
4406. (h) Kaul, B. B.; Noll, B.; Renshaw, S.; Rakowski DuBois, M.
Organometallics 1997, 16, 1604. (i) Tucker, D. S.; Dietz, S.; Parker, K. G.;
Carperos, V.; Gabay, J.; Noll, B.; Rakowski DuBois, M.; Campana, C. F.
Organometallics 1995, 14, 4325. (j) Adams, H.; Morris, M. J.; Riddiough,
A. E.; Yellowlees, L. J.; Lever, A. B. P. Inorg. Chem. 2007, 46, 9790. (k)
Adams, H.; Bailey, N. A.; Bancroft, M. N.; Bisson, A. P.; Morris, M. J. J.
Organomet. Chem. 1997, 542, 131. (l) Wong, R. C. S.; Ooi, M. L.; Tan,
G. H.; Ng, S. W. Inorg. Chim. Acta 2007, 360, 3113. (m) Song, L.-C.;
Wang, J.-Q.; Huang, X.-Y. Polyhedron 1998, 17, 3759.
(15) Warner, S.; Lippard, S. J. Organometallics 1989, 8, 228.
(16) Pe´tillon, F. Y.; Schollhammer, P.; Talarmin, J.; Muir, K. W. Coord.
Chem. ReV. 1998, 178-180, 203.
(20) (a) Miller, D. J.; Rakowski DuBois, M. J. Am. Chem. Soc. 1980,
102, 4925. (b) Rakowski DuBois, M.; VanDerveer, M. C.; DuBois, D. L.;
Miller, W. K. J. Am. Chem. Soc. 1980, 102, 7456. (c) Bernatis, P.; Laurie,
J. C. V.; Rakowski DuBois, M. Organometallics 1990, 9, 1607.
(17) Ahmed, J.; Itoh, K.; Matsuda, I.; Ueda, F.; Ishii, Y.; Ibers, J. A.
Inorg. Chem. 1977, 16, 620.
(18) Cotton, F. A.; Harris, C. B. Inorg. Chem. 1968, 7, 2140.

4212 Organometallics, Vol. 27, No. 16, 2008
Ojo et al.
Scheme 4
bridged intermediate [Mo2Cp2(µ-SMe)2(µ-SH)2] (B). Concerted
dissociation from hydrosulfido ligands and free isonitrile addi-
tion to sulfido S atoms finally leads to the formation of the
bridging dithiocarbonimidate ligand in complex 8. It is known
that the elimination of hydrogen from bis(hydrosulfido) com-
plexes is facilitated by the presence of unsaturated molecules.21
The proposed pathway is consistent with the observation that a
large excess of basic nucleophile must be present in order to
account for the first step, leading finally to 8 via elimination of
dihydrogen. It is worth noting that under similar reaction
conditions complex 8 was also obtained in good yields (80%)
from 7 (Scheme 2d). We assume that this transformation
proceeds logically via a mechanism involving the same bis(hy-
drosulfido) intermediate B (Scheme 3) as that postulated in
Scheme 2c. Another possible pathway involving attack of SH-
on the coordinated isocyanide ligand to give thioaminocarbene
intermediates has also been considered, but the absence of such
complexes in reactions of 1 with a very large excess of
hydrosulfide makes such a mechanism unlikely.
We have shown previously that reaction of 1 with hydroxides
leads to the formation of µ-aminocarbyne products, (e.g., 5),
which involves the coupling of one cyclopentadienyl and two
isocyanide ligands at the {Mo2(µ-SMe)3}nucleus. Hence, when
this reaction is undertaken in the presence of a large excess of
isocyanide, complexes are formed containing at one and the
same time bridging aminocarbyne and amino-oxycarbene
ligands.5 These products result from coupling reactions involving
cyclopentadienyl and isocyanide ligands, on the one hand, and
hydroxide and isocyanide groups, on the other hand. In the hope
of getting amino-thiocarbene adducts, we reacted complex 1 in
tetrahydrofuran with sodium hydrosulfide in the presence of 3
equiv of xylNC under reflux for 72 h. The desired product was
not formed; instead, the coupled-isocyanide derivative 7 was
obtained in good yields (73%) (Scheme 2b). These data indicate
clearly that the imidoyl(amino)carbene ligand in 7 is unable to
activatethe{Mo2(µ-SMe)3}nucleustoundergothesulfide-isocyanide
coupling; this is in contrast with the aminocarbyne group in 5
that clearly performs the related hydroxide-isocyanide coupling.
Interestingly, complex 7 reacted with 1 equiv of HBF4 at low
temperature (-40 °C) to give the starting compound 1 in high
yields (86%) (Scheme 2e). When the reaction was conducted
at room temperature, severe decomposition was observed:
complex 1 (50% yield) was obtained together with the side
product 19, which was characterized only by its NMR data (see
the Experimental Section). Thus, the treatment of the coupled-
isocyanide derivative 7 with H+ leads to the decoupling of the
isocyanide ligands via carbon-carbon bond cleavage and
dihydrogen elimination. These results contrast strongly with
those reported by Lippard et al.,7 which indicate that the double
protonation of the isocyanide ligands in mononuclear polyco-
ordinate transition-metal isocyanide complexes affords coupled-
isocyanide products.
and acetylide ligands. Accordingly, compound 1 reacted with
an excess of sodium acetylide (5 equiv) in tetrahydrofuran under
reflux for 2 h, to give the coupled-isocyanide product [Mo2Cp2(µ-
SMe)2{µ-(η5-C5H4)(xylN)CN(xyl)C}(µ-CCH)] (9) in high yields
(84%) (Scheme 4a). The formation of this compound was
initiated by the deprotonation of one cyclopentadienyl ligand
by reaction of 1 with acetylide, which acted as a base. This
was followed by C-C and C-N coupling between the depro-
tonated Cp and the two isocyanide groups, generating a bridging
aminocarbyne ligand. An additional, relevant feature of the
reaction of formation of 9 was the substitution of acetylide for
one thiolate group. However, the desired isocyanide-acetylide
coupling reaction was not observed. Nevertheless, this result
clearly shows that the bridging alkylidyne ligand in the
µ-aminocarbyne transient complex has the expected labilizing,
trans effect toward one SMe group. Surprisingly, no reaction
was observed when complex 1 was heated with an excess of
sodium acetylide (5 equiv) in the presence of xylNC (5 equiv)
(Scheme 4b). In particular, no trace of a complex showing
isocyanide-acetylide coupling was detected in the 1H and 13
C
NMR spectra of solutions of the crude product. This behavior
contrasts unaccountably with that noted for previous reactions
of 1 with hydroxides in the presence of excess isocyanide, which
give µ-aminocarbyne (amino-oxycarbene) compounds in high
yields.5
The structure of compound 9 was confirmed through a single-
crystal X-ray diffraction study (Figure 3). The molecule of 9
contains an Mo2(µ-SMe)2Cp moiety, stabilized by bridging (η5-
C5H4)(xylN)CN(xyl)C alkylidyne and acetylide ligands. The
(C5H4)(xylN)CN(xyl)C alkylidyne ligand arises from condensa-
tion of a Cp and two xylNC ligands. Thus, the structure of 9
strongly resembles those of the related bridging aminocarbyne
compound [Mo2Cp(µ-SMe)3{µ-(η5-C5H4)(xylN)CN(xyl)C}] (5)
and µ-aminocarbyne (µ-amino-oxycarbene) derivatives [Mo2Cp(µ-
SMe)2{µ-(η5-C5H4)(xylN)CN(xyl)C}(µ-CCNRR′)] that we have
described previously.5 The three-electron-donor acetylide in 9
σ-bonds terminally to Mo2 and π-bonds unsymmetrically via
its C3-C4 triple bond to Mo1. Valuable back-donation from
Mo2 is responsible for the shortening of the Mo2-C3 to
2.096(7) Å and the lengthening of the C3-C4 bond to 1.176(9)
Å. In 9, the coordination of the sp-hybridized C4 carbon atom
Reaction of 1 with Sodium Acetylide. As stated in the
Introduction, the reactivity of bis(isocyanide) derivatives toward
basic nucleophiles depends markedly on the nature of these
reagents. In particular, we have shown above that the hydro-
sulfide anion (HS-) is unable to deprotonate one cyclopenta-
dienylligandin1and,therefore,topromoteacyclopentadienyl-iso-
cyanide coupling, instead it acts as a reductive coupling agent.
We thus decided to check whether the reaction of complex 1
with distinct types of basic nucleophiles, e.g. NaCtCH, induce
C-C or C-N coupling among cyclopentadienyl, isocyanide,
(21) Casewit, C. J.; Coons, D. E.; Wright, L. L.; Miller, W. K.; Rakowski
DuBois, M. Organometallics 1986, 5, 951.

Cationic Tris(thiolato)dimolybdenum(III) Complexes
Organometallics, Vol. 27, No. 16, 2008 4213
Figure 3. Molecular structure of 9. Selected distances (Å) and
angles (deg): Mo1-Mo2 ) 2.6352(8), Mo1-C39 ) 1.999(6),
Mo2-C39 ) 1.997(6), C39-N3 ) 1.369(7), N3-C31 ) 1.454(7),
N3-C49 ) 1.410(7), C49-N4 ) 1.263(7), N4-C41 ) 1.420(7),
C49-C21 ) 1.513(8), Mo1-C3 ) 2.353(6), Mo2-C3 ) 2.096(7),
C3-C4 ) 1.176(9); Mo1-C39-Mo2 ) 82.5(2), Mo1-C39-N3
) 124.0(4), Mo2-C39-N3 ) 153.2(4), C39-N3-C49 ) 118.3(5),
C39-N3-C31)119.7(5),C31-N3-C49)122.0(5),N3-C49-N4
) 120.7(5), N4-C49-C21 ) 129.4(5), Mo1-C3-Mo2 )
72.38(18), Mo1-C3-C4 ) 78.8(5), Mo1-C4-C3 ) 72.7(4),
Mo2-C3-C4 ) 151.2(5).
Figure 2. Molecular structure of 8a. H atoms are omitted for clarity.
Selected distances (Å) and angles (deg): Mo1-Mo2 ) 2.5897(6),
Mo1-S1 ) 2.4400(17), Mo1-S2 ) 2.465(3), Mo1-S3 )
2.4524(15), Mo1-S4 ) 2.433(3), Mo2-S1 ) 2.4422(17), Mo2-S2
) 2.466(2), Mo2-S3 ) 2.4662(15), Mo2-S4 ) 2.433(3), C5-S2
) 1.786(7), C5-S3 ) 1.770(7), C5-N1 ) 1.262(8), N1-C30 )
1.440(9); Mo1-S2-C5 ) 88.3(2), Mo2-S2-C5 ) 88.5(2),
Mo1-S3-C5 ) 89.1(2), Mo2-S3-C5 ) 89.2(2), S2-C5-S3 )
100.9(3), S2-C5-N1 ) 132.6(5), S3-C5-N1 ) 126.5(5),
C5-N1-C30)122.3(6),Mo1-S1-Mo2)64.07(4),Mo1-S2-Mo2
) 63.36(6), Mo1-S3-Mo2 ) 63.69(4), Mo1-S4-Mo2 )
64.31(7).
that 5 already contains a µ-aminocarbyne group that could favor
the desired metal-assisted couplings. Unfortunately, perhaps due
to its neutral nature, complex 5 did not react with a large excess
of sodium sulfide, in the presence of 2 equiv of xylNC in
tetrahydrofuran under reflux for 24 h (Scheme 5a). However,
when 5 was heated with a stronger base, e.g. an excess of
sodium acetylide, in tretrahydrofuran for 1 h, complex 9 was
obtained in high yields (86%) via the substitution of acetylide
for one thiolate ligand (Scheme 5b). This last result shows
clearly that complex 5 serves as an intermediate in the reaction
of formation of 9 when 1 is heated with NaCtCH (see Scheme
4a). Like the bis(isocyanide) derivative 1, complex 5 unexpect-
edly did not react with an excess of sodium acetylide upon
heating a tetrahydrofuran solution of the related mixture for 24 h
in the presence of 5 equiv of xylNC, the starting compound
being totally recovered (Scheme 5c). In contrast with the data
for the two precedents (Scheme 5a,c), the neutral compound 5
readily reacted with 2 equiv of lithium bromoethylate, probably
due to a higher strength of this basic nucleophile, in the presence
of 2 equiv of xylNC to give the new cationic bis(isocyanide)
complex [Mo2Cp(µ-SMe)2{µ-(η5- C5H4)(xylN)CN(xyl)C}-
(xylNC)2]Br (10) in high yields (83%) (Scheme 5d). Interest-
ingly, subsequent addition of a large excess of sodium hydroxide
(10 equiv) afforded the already known µ-aminocarbyne (amino-
oxycarbene) complex [Mo2Cp(µ-SMe)2{µ-(η5-C5H4)(xylN)-
CN(xyl)C}(µ-η1(O):η1(C)-OCNHxyl}] (12)5 in high yields
(83%) (Scheme 5e). Thus, compound 10 experiences an easy
substitution of hydroxide anion for one xylNC ligand and then
subsequent hydroxide-isocyanide coupling to yield complex
12. However, a pathway involving direct attack of OH- at the
metal-coordinated isocyanide, followed by displacement of the
second coordinated isocyanide by the new amino-hydroxide
ligand, could not be excluded. Indeed, it is well-known that
metal-isocyanide binding renders the related carbon atom
electrophilic. Addition of 2 equiv of HBF4 to compound 10 led
deviates notably from linearity and the Mo2-C3-C4 angle
(151.2(5)°) is somewhat outside of the range (158-162°)22
expected for the M2(µ-η1:η2-CCR) moiety.16 Lastly, the S-
methyl groups are syn to the Mo2S2 plane and enfold the CCH
ligand.
The spectroscopic data in solution for compound 9 are
essentially consistent with its solid-state structure (see the
Experimental Section). The results are in agreement with the
coupling of one cyclopentadienyl ring via one of its carbon
1
atoms with an adjacent coordinated isocyanide. The H NMR
pattern shows a singlet of relative intensity 1 at 4.78 ppm,
consistent with an acetylide hydrogen atom in 9. Moreover, a
resonance characteristic of the Mo-bound 13C atom of an
µ-alkylidyne moiety appears at low field (δ 362.9), and a signal
that could be assigned to an imine-like carbon (CdNxyl) is
detected at 156.0 ppm. Salient characterization features of 9
include 1H-13C HMBC and HMQC experiments, which allow
the assignment of resonances detected at 142.5 and 101.8 ppm
to CR and Cꢀ atoms of the Mo-CRtCꢀ-H moiety, respectively.
Reaction of 5 with Basic Nucleophiles. Upon heating the
bis(isocyanide) µ-trithiolato complex 1 with sodium acetylide,
we have shown in the previous section that any attempt to couple
isocyanide and acetylide via this way failed. Instead, compound
1 had been found to readily undergo consecutive couplings of
cyclopentadienyl and isocyanides in addition to the substitution
of an acetylide for a thiolate group. Thus, we were interested
in whether coupled isocyanide-acetylide, isocyanide-sulfide,
and isocyanide-halogenoalkyl ligands could be prepared by
reaction of compound 5 with various basic nucleophiles, given
(22) (a) Carty, A. J. Pure Appl. Chem. 1982, 54, 113. (b) Froom, S. F. T.;
Green, M.; Mercer, R. J.; Nagle, K. R.; Orpen, A. G.; Rodrigues, R. A.
J. Chem. Soc., Dalton Trans. 1991, 3171.

4214 Organometallics, Vol. 27, No. 16, 2008
Ojo et al.
Scheme 5
Figure 4. View of the [Mo2Cp2(µ-SMe)2{µ-(η5-C5H4)-
(Nxyl)CN(xyl)C}(xylNC)2]+ cation in the crystal of 10 · 2CH2Cl2,
showing 30% probability ellipsoids and a partial atom-labeling
scheme. Selected distances (Å) and angles (deg): Mo1-Mo2 )
2.7720(4), Mo2-C3 ) 2.032(3), Mo1-C3 ) 2.049(3), C3-N1
) 1.363(3), N1-C4 ) 1.409(4), N1-C30 ) 1.454(3), C4-C11
) 1.499(4), C4-N2 ) 1.259(4), N2-C40 ) 1.430(4), Mo1-C5
) 2.113(3), C5-N3 ) 1.153(4), N3-C50 ) 1.397(4), C5-C6 )
2.9872(1), Mo2-C6 ) 2.131(3), C6-N4 ) 1.151(4), N4-C60 )
1.397(4); Mo1-C3-Mo2 ) 85.58(10), Mo2-C3-N1 ) 149.7(2),
Mo1-C3-N1 ) 124.62(19), C3-N1-C30 ) 125.2(2), C3-N1-C4
) 116.6(2), C4-N1-C30 ) 117.6(2), N1-C4-C11 ) 111.3(2),
C11-C4-N2 ) 126.8(3), N1-C4-N2 ) 121.9(3), C4-N2-C40
) 116.1(3), Mo1-C5-N3 ) 169.6(3), C5-N3-C50 ) 167.1(3),
Mo2-C6-N4 ) 174.9(3), C6-N4-C60 ) 175.4(3).
to the formation of the tetrakis(isocyanide) dicationic derivative
[Mo2Cp2(µ-SMe)2(xylN)4](BF4)2 (11) in good yields (73%)
(Scheme 5f). This rearrangement is unexpected, although it
offers some similarities with that observed in the reaction of
the dimetallaimidoyl(amino)carbene complex 7 with HBF4 (see
Scheme 2e); it could involve concomitant proton addition at
the Cp-substituted carbon and decoupling between isocyanide
and cyclopentadienyl ligands. Therefore, it appears from the
data summarized in Scheme 5 that coupling reactions involving
isocyanide ligands are only observed when the reagents utilized
in this study have appreciable or even high basicities (NaCtCH,
NaOH). Moreover, it should be noted that metal-assisted
coupling reactions involving isocyanide do not occur when 5
reacts with a moderate base such as the bromoethylate ion;
however, substitution of isocyanides for one thiolate ligand is
observed in this case. Finally, the basicity of the hydrosulfide
ion is apparently too low to undergo any reaction with 5.
The characterization of compounds 9 and 12 was made by
comparison of their spectroscopic data with those of authentic
samples (see above for 9 and ref 5 for 12). The formulation of
the cation of 10 as a bis(isocyanide) µ-aminocarbyne complex
was confirmed through a single-crystal X-ray diffraction study
of 10 · 2CH2Cl2 (Figure 4). The results are unambiguous, the
composition and connectivity being consistent with the structure
presented, in which the original Cp-aminocarbyne group is
retained and the bridging thiolate located trans to that ligand
has been displaced by two xylNC ligands pendant from the
molybdenum atoms. The coordination geometry around each
Mo atom is that of a distorted square pyramid, with two sulfur
atoms, one isocyanide carbon atom, and one carbyne carbon
atom in the basal plane and the centroid of an η5-cyclopenta-
dienyl ring at the apical position. The S1 and S2 methyl groups
adopt an anti orientation relative to the Mo2S1S3 plane, in
contrast with the syn orientation of the related S-methyl groups
in 9. The intermetallic length (2.7720(4) Å) in 10 is consistent
with the formulation of a single Mo-Mo bond for a triply
bridging thiolato-dimolybdenum(III) complex12b under the
EAN formalism. This distance is somewhat longer than those
observed in related quadruply bridged thiolato-dimolybdenum(III)
derivatives (range 2.584(1)-2.660(1) Å for eight compounds5,11),
this reflects the lowering of the number (three) of bridging
ligands in 10 with regard to that in the latter complexes. The
two Mo-C3 bond distances (2.032(3) and 2.049(3) Å) are close,
and although they are somewhat long, they lie between the value
of 1.894(5) Å for the formal double bond ModC in the
vinylidene compound [Mo2Cp2(µ-SMe)3(µ-η1:η2-CdCHTol)]-
(BF4) and that of 2.068(3) Å for the single Mo-C bond in the
acetylide derivative [Mo2Cp2(µ-SMe)3(µ-η1:η2-CtCPh)];19c
they thus indicate a nearly symmetrical coordination of the
alkylidyne group through Mo-C bonds of order 1.5-2. The
presence in the 13C{1H} NMR spectrum of 10 of a low -field
resonance at 386.8 ppm, characteristic of a Mo-bound 13C atom
of an µ-alkylidyne moiety, confirms the above crystallographic
observation. The angles at C3 show severe deviations (see the
caption for Figure 4) from sp2 hybridization but closely agree
with those found in 9 (see above) and related µ-alkylidyne
derivatives [Mo2Cp2(µ-SMe)2{µ-(η5-C5H4)(xylN)CN(xyl)C}X]
(X ) SMe,11 µ-η1(O):η2(C,O)-CNRR′5). The aromatic rings of
the xylNC ligands are nearly parallel (dihedral angle 8.11(17)°).
Departures from linear coordination at C5 and C6 and more
especially at N3 and N4 (C-N-C ) 167.1(3) and 175.4(3)°)

Cationic Tris(thiolato)dimolybdenum(III) Complexes
Organometallics, Vol. 27, No. 16, 2008 4215
(see the caption to Figure 4) ensure that there are no short
intramolecular contacts between these rings. As for compound
9, the spectroscopic data in solution for 10 (see the
Experimental Section) are consistent with its solid-state structure.
In particular, the presence of a µ-alkylidyne ligand, (η5-
C5H4)(xylN)CN(xyl)C, in the complex can be deduced from
the NMR spectra, which closely resemble those of 9, except in
the xylNC region. Thus, typical Mo-bound 13C isocyanide
resonances are detected at 180.95 and 176.95 ppm, which
obviously are absent in the related spectrum of compound 9.
1
Other distinctive features of the H NMR spectra of 10 and 9
are the S-methyl resonances: these appear in the 2.31-1.44 ppm
range as two singlets for 10 and a singlet for 9. This difference
may be ascribed to the orientations of the bridging SMe groups:
anti in the bis(isocyanide) derivative 10 and syn in the acetylide
compound 9.
Complex 11 has been characterized by spectroscopy (1H
NMR and IR) and elemental analysis (see the Experimental
1
Section). H NMR spectroscopy shows the equivalence of the
Cp rings, but not that of the two SMe groups, consistent with
a cis disposition of the cyclopentadienyl rings relative to the
Mo-Mo axis and with a mutually anti orientation of the methyl
groups, respectively. The latter observation contrasts with that
made for the related tetrakis(nitrile) complex [Mo2Cp2(µ-
SMe)2(CH3CN)4](BF4)2 (6), in which the SMe groups adopt a
mutually syn orientation.23 The formulation of 11 as a tetraki-
s(isocyanide) dicationic derivative was confirmed by a X-ray
analysis of crystals of the tetraphenylborate salt [Mo2Cp2(µ-
SMe)2(xylNC)4](BPh4)2 (11′ · 0.5OEt2), obtained as described
in the Experimental Section. The cation of 11′ (Figure 5)
contains two nearly similar CpMo(xylNC)2 units linked through
SMe bridging groups supported by a rather long Mo-Mo bond
of 3.0642(5) Å. This intermetallic length in 11′ is, however,
consistent with the formulation of a single Mo-Mo bond for
the doubly bridged thiolato-dimolybdenum compounds
[Mo2Cp2(µ-SR)2L2](BF4)2, for which values in the range of
3.008(3)-3.0000(6) Å were found.23,24 The dication of 11′ is
structurally close to that of [Mo2Cp2(µ-SMe)2(MeCN)4](BF4)2
(6),23 with a similar butterfly Mo2(µ-S)2 core. The geometry
around each molybdenum atom is based on a four-legged piano
stool with a cis-C2S2 base. The Mo-N-C-C isocyanide
groups are slightly bent: substantial deviations from 180° are
noted for Mo-C-N angles (average 171.5°) and C-N-C
angles (average 170.9°).
Figure 5. View of the [Mo2Cp2(µ-SMe)2(xylNC)4]+ cation in
crystals of 11′ · 0.5OEt2, showing 30% probability ellipsoids and
partial atom-labeling scheme. Selected distances (Å) and angles
(deg): Mo1-Mo2 ) 3.0642(5), Mo1-C3 ) 2.062(5), C3-N1 )
1.158(5), N1-C30 ) 1.407(6), Mo1-C5 ) 2.079(5), C5-N3
) 1.149(5), N3-C50 ) 1.417(6), Mo2-C4 ) 2.085(5), C4-N2
) 1.172(5), N2-C40 ) 1.403(6), Mo2-C6 ) 2.081(5), C6-N4
) 1.158(5), N4-C60 ) 1.406(6), Mo1-S1 ) 2.4393(12), Mo1-S2
) 2.4573(12), Mo2-S1 ) 2.4241(12), Mo2-S2 ) 2.4645(12);
Mo1-C3-N1 ) 172.0(4), C3-N1-C30 ) 175.6(4), Mo1-C5-N3
) 169.6(4), C5-N3-C50 ) 172.6(5), Mo2-C4-N2 ) 172.1(4),
C4-N2-C40 ) 168.3(5), Mo2-C6-N4 ) 172.5(4), C6-N4-C60
) 167.2(5).
Scheme 6
formed previously with strong bases.11 Therefore, whatever the
base may be, reaction of a bis(alkyl isocyanide) dinuclear
transition-metal complex with bases results mainly in dealky-
lation of the isocyanide ligand.
Reaction of 2-4 with Bases. In a previous paper,11 we have
shown that the reaction of strong bases (n-BuLi, NaOH) with
the bis(alkyl isocyanide) complex [Mo2Cp2(µ-SMe)3(t-
BuNC)2](BF4) (2) mainly resulted in dealkylation at one of its
isocyanide ligands, together with formation of a small quantity
of coupled Cp-isocyanide product in the case of sodium
hydroxide. Thus, we were interested in whether coupled ligands
could be formed on reacting the bis(tert-butyl isocyanide)
derivative 2 with bases weaker than n-BuLi or NaOH, given
that small amounts of coupled Cp-isocyanide compounds were
obtained in the reaction of 2 with sodium hydroxide. Unfortu-
nately, treatment of solutions of complex 2 in tetrahydrofuran
under reflux with 10 equiv of NaSH · xH2O gave only the
dealkylated complex [Mo2Cp2(µ-SMe)3(t-BuNC)(CN] (13) in
good yields (69%) (Scheme 6): i.e., the same product that was
As shown in the first part of this work, reductive couplings
of isocyanide ligands are mediated by transition metals in
reactions of the related complexes with anionic reagents. As
carbon monoxide and isocyanide are isolobal, similar types of
reactivity are expected for each. Thus, good π-back-donation
from thiolato-molybdenum centers, {CpMo(µ-SMe)3MoCp},
could have sufficient strength to render the carbonyl carbon
atoms electrophilic in the related complexes to be susceptible
to nucleophilic attack and then to undergo reductive C-C
coupling reactions.4c Accordingly, the cationic bis(carbonyl)
complex [Mo2Cp2(µ-SMe)3(CO)2]Cl (3) was allowed to react
with a large excess of a good reducing agent such as
NaSH · xH2O. Unhappily, no reductive coupling of carbonyl
ligands was observed; instead, dealkylation at one sulfur atom
occurred with loss of MeSH to give the new neutral bridging
sulfido derivative [Mo2Cp2(µ-SMe)2(µ-S)(CO)2] (14) in high
yields (95%) (Scheme 7a). Cleavage of S-CH3 bonds has been
reported previously; it was electrochemically induced in dimo-
(23) Schollhammer, P.; Pe´tillon, F. Y.; Talarmin, J.; Muir, K. W. Inorg.
Chim. Acta 1999, 284, 107.
(24) (a) Courtot-Coupez, J.; Gue´guen, J.; Guerchais, M.; Pe´tillon, J. E.;
Talarmin, F. Y.; Mercier, J. J. Organomet. Chem. 1986, 312, 81. (b) El
Khalifa, M.; Gue´guen, M.; Mercier, R.; Pe´tillon, F. Y.; Saillard, J. Y.;
Talarmin, J. Organometallics 1989, 8, 140.

4216 Organometallics, Vol. 27, No. 16, 2008
Ojo et al.
Scheme 7
lybdenum thiolate/thioether- and bis(thioether)- bridged com-
plexes, [Mo2Cp2(µ-SMe)(µ-SMe2)(CO)(CN)] and [Mo2Cp2(µ-
SMe2)2(CO)(CN)], by increasing the electron density on the
Mo2S2 core to give the anionic derivatives [Mo2Cp2(µ-
SMe)2(CO)(CN)]-.25 Similar S-C(alkyl) bond cleavage was
also observed in the bis(µ-thiolate) µ-sulfido cationic complex
[Mo2Cp2(µ-S2CH2)(µ-SCMe3)(µ-S)]+ by reaction with bromide
salts, to afford the bis(µ-sulfido) compound [Mo2Cp2(µ-S2CH2)(µ-
S)2] and Me3CBr.26 The reaction was proposed to proceed via
either the dissociation of the carbenium ion, whose stability is
well-known,27 or a dissociative mechanism involving the
reversible elimination of isobutene and formation of a µ-hy-
drogenosulfide transient complex, which in turn was deproto-
nated by Br-, and finally addition of the resulting HBr to the
olefin would give the final products.26 In light of these
observations, we suggest that the driving force of the demethy-
lation reaction of a thiolate group in 3 could be the nature of
the reactant, associated with the stability of the thiol product
(MeSH). Further reaction of the bis(carbonyl) complex 3 with
a good basic nucleophile such as hydroxide anion gave neither
reductive coupling of the carbonyl ligand nor dealkylated
products; instead, a mixture of the two already known complexes
[Mo2Cp2(µ-SMe)2(CO)2]28 (16) and [Mo2Cp2(µ-SMe)4]29 (17)
was obtained (Scheme 7b). These two compounds were
characterized by comparing their spectroscopic data with those
of authentic samples.
chain into the dimolybdenum framework, we decided to heat
the µ-sulfido derivative 14 in dichloromethane at reflux. Within
1 h, the resonances (1H NMR) associated with this compound
disappeared, and the single product that resulted from the
reaction was the monocationic dimer 15 with the SCH2Cl
resonance at ca. 4.6 ppm (see Scheme 7b). The alkylation of
sulfido ligands by organic halides has been observed previously
for related permethylcyclopentadienyl dimolybdenum com-
plexes.30 A priori, a higher electron density in the {Mo2Sn} (n
) 1, 2) core would enhance the nucleophilicity of sulfido
ligands, as a result of the electron-releasing C5Me5 group. The
reactions involving the molybdenum(III) carbonyl complexes
[Mo2Cp′2(µ-SMe)2(µ-S)(CO)2] (Cp′ ) η5 -C5Me5,30c,d η5-C5H5
(this work)) illustrate this trend. Thus, alkylation of the sulfido
bridge in the pentamethylcyclopentadienyl complex is achieved
at room temperature,30c,d while in the related cyclopentadienyl
derivative it requires heating. It is known that the presence of
carbonyl ligands in bimetallic compounds tends to remove the
electronic density from the metal, which by transmission reduces
the nucleophilic character of the sulfido ligand in carbonyl
derivatives compared to that in non-carbonyl complexes. In spite
of all this, the displacement of a chloride from dichloromethane
is similarly observed in both reactions with sulfido ligands in
the dicarbonyl derivative 14 and the non-carbonyl complex
[Mo2Cp2*(µ-S2CH2)(µ-S)2]30b (Cp* ) η5 -C5Me5), by heating
dichloromethane solutions of these complexes. These results
indicate that the lower electron density in the {Mo2Sn} core,
induced by CO ligands in 14, with respect to that present in the
non-carbonyl derivative [Mo2Cp2*(µ-S2CH2)(µ-S)2] is balanced
by the lower formal oxidation state of the metal in 14 relative
to that in the related noncarbonyl complex: i.e., III and IV,
respectively.
The first attempts to crystallize the bridging sulfido complex
14, carried out at room temperature from dichloromethane
solutions of 14, failed. Instead, crystals of the complex 15 were
isolated, in which 1H NMR spectroscopy indicated the presence
of a SCH2X ligand. This was confirmed after an X-ray analysis,
whose results are consistent with a structure based on a
{Mo2Cp2(µ-SMe)2(µ-SCH2Cl)+} core bridged by a chlo-
romethane thiolate ligand (see below). In order to find a
convenient method for introducing such a functionalized organic
The new compound 14 has been characterized by spectros-
copy (1H and 13C NMR and IR) and elemental analysis (see
the Experimental Section). 1H and 13C NMR spectra of 14 show
the equivalence of the Cp rings and SMe groups, which implies
that this complex is a cis,syn isomer. Crystals of 14 · 0.5(tolu-
(25) Abasq, M.-L.; Pe´tillon, F. Y.; Schollhammer, P.; Talarmin, J. New
J. Chem. 1996, 20, 1221.
(26) Birnbaum, J.; Rakowski DuBois, M. Organometallics 1994, 13,
1014.
(30) (a) Casewit, C. J.; Haltiwanger, R. C.; Noordik, J.; Rakowski
DuBois, M. Organometallics 1985, 4, 119, and references cited therein.
(b) Maciejewski-Farmer, M.; Haltiwanger, R. C.; Kvietok, F.; Rakowski
DuBois, M. Organometallics 1991, 10, 4066, and references cited therein.
(c) Schollhammer, P.; Pe´tillon, F. Y.; Pichon, R.; Poder-Guillou, S.;
Talarmin, J.; Muir, K. W.; Manojlovic´-Muir, Lj. Organometallics 1995,
14, 2277. (d) Schollhammer, P.; Pe´tillon, F. Y.; Talarmin, J.; Muir, K. W.;
Fun, H. K.; Chinnakali, K. Inorg. Chem. 2000, 39, 5879.
(27) Yamamoto, Y. Coord. Chem. ReV. 1980, 32, 193.
(28) (a) Pe´tillon, F. Y.; Le Que´re´, J. L.; Roue´, J.; Guerchais, J. E.; Sharp,
D. W. A. J. Organomet. Chem. 1980, 204, 207. (b) Guerchais, J. E.; Le
Que´re´, J. L.; Pe´tillon, F. Y.; Manojlovic´-Muir, Lj.; Muir, K. W.; Sharp,
D. W. A. J. Chem. Soc., Dalton Trans. 1982, 283.
(29) (a) King, R. B. J. Am. Chem. Soc. 1963, 85, 1587. (b) Reference
9.

Cationic Tris(thiolato)dimolybdenum(III) Complexes
Organometallics, Vol. 27, No. 16, 2008 4217
Figure 6. Molecular structure of 14 · 0.5(toluene). Selected distances
(Å) and angles (deg): Mo1-Mo2 ) 2.7891(10), Mo1-C3 )
2.012(9), C3-O1 ) 1.144(10), Mo2-C4 ) 1.995(12), C4-O2 )
1.149(11), Mo1-S1 ) 2.454(2), Mo2-S1 ) 2.454(2), Mo1-S2
) 2.468(2), Mo2-S2 ) 2.470(2), Mo1-S3 ) 2.437(2), Mo2-S3
) 2.436(2); Mo1-S1-Mo2 ) 69.26(6), Mo1-S2-Mo2 ) 68.78(6),
Mo1-S3-Mo2)69.84(6),S1-Mo1-S2)111.03(9),S1-Mo2-S2
) 110.92(7), S3-Mo1-C3 ) 145.7(3), S3-Mo2-C4 ) 143.8(3).
Figure 7. Molecular structure of 15 · H2O. Selected distances (Å),
angles (deg), and torsion angles (deg): Mo1-Mo2 ) 2.7805(5),
Mo1-C4 ) 2.006(4), C4-O4 ) 1.149(5), Mo2-C5 ) 2.027(4),
C5-O5 ) 1.124(5), Mo1-S1 ) 2.4538(10), Mo2-S1 ) 2.4489(11),
Mo1-S2 ) 2.4732(11), Mo2-S2 ) 2.4569(11), Mo1-S3 )
2.4658(10), Mo2-S3 ) 2.4573(10), S3-C3 ) 1.812(3), C3-Cl1
) 1.785(4); Mo1-C4-O4 ) 177.6(4), Mo2-C5-O5 ) 176.8(4),
Mo1-S1-Mo2)69.10(3),Mo1-S2-Mo2)68.66(3),Mo1-S3-Mo2
) 68.77(3), S3-C3-Cl1 ) 110.34(18); S1-Mo1-S2-Mo2 )
-4.389(39), S2-S1-S3-Cl1 ) -153.607(53).
ene), suitable for X-ray analysis, were formed in a cold toluene
solution of the complex. The results (Figure 6) reveal that the
[Mo2Cp2(µ-SMe)2(µ-S)(CO)2] (14) molecule is structurally
closely analogous to the cation in the pentamethylcyclopenta-
dienyl complex [Mo2Cp2*(µ-SMe)2(µ-SH)(CO)2](BF4).30c The
metal coordination can be described as a CpMo(CO)S3 piano
stool with S1-Mo-S2 (average 110.97(7)°) being somewhat
narrowed by the bridge constraint and S3-Mo-CO being rather
obtuse (average 144.7(4)°). The Mo-Mo distance (2.7891(12)
Å) in 14 is in the range 2.755-2.800 Å expected for a single
Mo-Mo bond in triply bridged thiolato-dimolybdenum
complexes.12b,30c This type of molecular structure is unprec-
edented for neutral carbonyl tris(sulfur)-bridged derivatives of
molybdenum(III): i.e., of type Mo2Cp2(µ-SR)3-x(µ-S)x(CO)2 (x
) 1, 2). However, several neutral or cationic bridged non-
carbonyl complexes, containing sulfido-bridged groups, have
been previously characterized by X-ray analyses: e.g., [Mo2Cp2′(µ-
S2CH2)(µ-S)2] (Cp′ ) C5H4(C2H4NMe2)19h), [Mo2Cp′2(µ-
S2CH2)(µ-SR)(µ-S)]+ (Cp′, R ) MeCp, C4H3S;32a Cp, Me;30a
Cp, PhCCH2;32b Cp, HCCPhH32c), [Mo2Cp′2(µ-SH)2(µ-SR)(µ-
S)]+ (Cp′ ) Cp; R ) PhCCH232b), [Mo2Cp′2(µ-S2)(µ-SSOx)(µ-
S)] (Cp′ ) C5Me5; x ) 2, 332d), [Mo2Cp′2(µ-S2)(µ-SR)2-x(µ-
S)x]n+ (Cp′ ) C5Me5, x ) 2, n ) 0;32e Cp′ ) MeCp, x ) 1, R
) CH2CO2Me32f), and [Mo2Cp′2(µ-SMe)2(µ-S)2] (Cp′ )
MeCp20b).
previously reported complex [Mo2Cp′2(µ-SMe)2(µ-SI)(CO)2]I5
(Cp′ ) C5Me5).30d Thus, two nearly eclipsed CpMo(CO) units
are linked by a Mo-Mo bond whose length (2.7805(5) Å) is
typical of the values found in dimeric MoIII complexes contain-
ing three bridging groups.12b,16,30c The resulting metal coordina-
tion can be described as a distorted four-legged piano stool
supplemented by a metal-metal bond. The molybdenum atoms
are nearly coplanar with the methanethiolate sulfur atoms
(S1-Mo1-S2-Mo2 ) -4.39(4)°), and the carbonyl ligands
and the thiolate methyl groups lie on the same side of this plane.
In addition, the methanethiolate chloride stands outside of the
plane defined by the three sulfur atoms (S2-S1-S3-Cl1 )
-153.61(5)°). Finally, the S1 and S3 sulfur bridges are nearly
symmetrical, but not the S2 bridge; indeed, in contrast with the
Mo-S distances involving S1 and S3, the Mo-S2 distances
are somewhat different (see the caption to Figure 7).
As stated above, competitive processes occur when the
dinuclear thiolato-molybdenum precursors [Mo2Cp2(µ-
SMe)3L2]+, containing terminal, isolobal isocyanide (1 and 2)
and carbonyl (3) groups, react with basic nucleophiles or/and
reductants to give either coupled ligands or dealkylated products.
Thus, in light of these results, we decided to replace terminal
isocyanide or carbonyl ligands by nitrile groups, in order to
check the reactivity of bis(nitrile) derivatives toward sodium
hydrosulfide. Accordingly, treatment of solution of complex 4,
[Mo2Cp2(µ-SMe)3(CH3CN)2](BF4), in tetrahydrofuran at room
1
The H NMR pattern of 15 indicates the presence of two
isomers (8:1 ratio) in the solution, which probably differ by
the orientation of the SMe groups (syn/anti) in the molecule.
Although chloromethanethiolate complexes have been previ-
ously formed by displacement of a chloride from dichlo-
romethane in reactions with nucleophilic sulfido ligands in metal
compounds,30b,d,33 no related complex has been characterized
until now by X-ray spectroscopy. Thus, a crystal of 15 · H2O,
suitable for X-ray analysis, was obtained from a CH2Cl2-Et2O
solution of 14. Crystals of 15 are built from discrete [Mo2Cp2(µ-
SMe)2(µ-SCH2Cl)(CO)2]+ cations (Figure 7) and H2O-Cl-
anions. The cation is structurally closely analogous to the
(32) (a) Lopez, L. L.; Bernatis, P.; Birnbaum, J.; Haltiwanger, R. C.;
Rakowski DuBois, M. Organometallics 1992, 11, 2424. (b) Laurie, J. C. V.;
Duncan, L.; Haltiwanger, R. C.; Weberg, R. T.; Rakowski DuBois, M. J. Am.
Chem. Soc. 1986, 108, 6234. (c) Weberg, R. T.; Haltiwanger, R. C.; Laurie,
J. C. V.; Rakowski DuBois, M. J. Am. Chem. Soc. 1986, 108, 6242. (d)
Kubas, G. J.; Ryan, R. R.; Kubat-Martin, K. A. J. Am. Chem. Soc. 1989,
111, 7823. (e) Brunner, J.; Meier, W.; Wachter, J.; Guggolz, E.; Zahn, T.;
Ziegler, M. L. Organometallics 1982, 1, 1107. (f) Lopez, L. L.; Gabay, J.;
Haltiwanger, R. C.; Green, K.; Allshouse, J.; Casewit, C.; Rakowski DuBois,
M. Organometallics 1993, 12, 4764.
(33) (a) Lizano, A. C.; Noble, M. E. Inorg. Chem. 1988, 27, 747. (b)
Briant, C. E.; Gardner, C. J.; Hor, T. S. A.; Howells, N. D.; Mingos, D. M. P.
J. Chem. Soc., Dalton Trans. 1984, 2645.
(31) Kuwata, S.; Hidai, M. Coord. Chem. ReV. 2001, 213, 211.

4218 Organometallics, Vol. 27, No. 16, 2008
Ojo et al.
Scheme 8
replacement of a thiolate in 5 by an acetylide group, affording
9, or to no reaction, respectively. The attempted isocyanide
coupling in bis(alkyl isocyanide) derivative 2 by its reaction
with hydrosulfide anion proceeds through dealkylation of one
tert-butyl isocyanide to yield compound 13. In contrast, when
electron-attracting carbonyl groups are bounded to the molyb-
denum atoms in the tris(µ-thiolate) complex, the dealkylation
at the sulfur atoms is favored on reacting 3 with NaSH. This is
not obtained when the carbonyl groups are replaced by nitrile
as ligands in the tris(µ-thiolate) dimolybdenum derivatives.
Indeed, the reaction of the base NaSH (in excess) with the
bis(nitrile) complex 4 affords instead the thio-amido complex
18. Finally,it should be noted that couplings of ligands are
observed in the reactions of the tris(µ-thiolate) cationic complex
[Mo2Cp2(µ-SMe)3L2]+ with bases, only when L is an aryl
isocyanide.
temperature with a large excess of NaSH · xH2O (10 equiv)
readily led to the formation of the thio-amidato derivative
[Mo2Cp2(µ-SMe)3(MeCSNH)] (18) as the major product (Scheme
8). As all attempts to obtain crystals of 18 suitable for X-ray
analysis failed, the formulation of this complex was deduced
1
from the IR and NMR data. The H NMR spectrum displays
two resonances for the cyclopentadienyl groups and four peaks
in the SMe and MeCN regions, indicating that the {Mo2Cp2(µ-
SMe)3} core is retained in 18, that one MeCN is lost relative to
4, and that the fourth bridge is unsymmetric (see the Experi-
mental Section). In addition, a resonance of relative intensity 1
is detected at δ 4.80, which can be assigned to the NH group
of a thio-amidato ligand. This assignment is confirmed by a
typical broad band in the IR spectrum of 18 at 3094 cm-1
attributable to ν(NH) of the amine group. The absence in this
Experimental Section
General Procedures. All reactions were routinely carried out
under a nitrogen atmosphere using standard Schlenk techniques.
Solvents were distilled immediately before use under nitrogen from
appropriate drying agents. Some of the starting materials, [Mo2Cp2(µ-
SMe)3L2](BF4) (L ) xylNC (1),12a t-BuNC (2),11 CO (3),12b MeCN
(4)12c),[Mo2Cp(µ-SMe)3{µ-(η5-C5H4)(xylN)CN(xyl)C}](5),5[Mo2Cp2(µ-
SMe)2(MeCN)4](BF4)2 (6),23 and LiOCH2CH2Br,35 were prepared
as described previously. NaSH · xH2O (Aldrich) and other reagents
were purchased commercially and used as received. Infrared spectra
were recorded on a Nicolet-Nexus FT IR spectrophotometer from
KBr pellets. Chemical analyses were performed by the Service de
Microanalyse ICSN-CNRS, Gif sur Yvette, France. Yields of all
products are relative to the starting dimolybdenum complexes. The
NMR spectra (1H, 13C) were recorded at room temperature in
CDCl3, CD2Cl2, C6D6, or CD3CN solutions with a Bruker AMX
IR spectrum of a broad band between 1200 and 900 cm-1
,
expected for a ν(BF) of the tetrafluoroborate ion, indicates
clearly that 18 does not contain this counterion and is therefore
neutral. Formation of 18 could involve, in the initial step, the
replacement of the two nitrile ligands by one hydrosulfido group
to give the neutral intermediate [Mo2Cp2(µ-SH)(µ-SMe)3]. This
further reacts with free nitrile to undergo 1,2-addition of the
SH group in the tetrakis(µ-thiolate) species to the CtN bond
in nitrile; subsequent internal rearrangement finally gives 18.
This pathway is supported by the well-established tendency for
nitriles to undergo 1,2-addition reactions.20c However, a mech-
anism similar to that proposed for the formation of the related
1
400 spectrometer and were referenced to SiMe4. H-13C experi-
ments were carried out on a Bruker DRX 500 spectrometer.
Reaction of [Mo2Cp2(µ-SMe)3(xylNC)2](BF4) (1) with an
Excess of NaSH: Synthesis of [Mo2Cp2(µ-SMe)3{µ-η1:η1-C(N-
Hxyl)C(Nxyl)}] (7) and [Mo2Cp2(µ-SMe)2{µ-S2C(Nxyl)}] (8).
Complex 1 (400 mg, 0.492 mmol) and 10 equiv of NaSH (276
mg) were heated in tetrahydrofuran (30 mL) at reflux for 72 h.
After filtration the solvent was removed under vacuum and the
residue was washed with diethyl ether (3 × 15 mL), giving complex
7 as a maroon powder (329 mg, 92% yield). Crystals of 7 suitable
for X-ray analysis were obtained by crystallization from a cold
CH2Cl2-Et2O (1:1) solution.
amidato-molybdenum
complex
[Mo2Cp2(µ-SMe)3(µ-
MeCONH)]34 cannot be ruled out. It would involve a direct
attack of the nucleophile SH- at the carbon atom of a nitrile
group, followed by a tautomerization reaction affording the thio-
amidato complex 18.
Concluding Remarks
Because of its reductant and basic nucleophile characters, the
hydrosulfide anion (HS-) reacts with the bis(xylyl isocyanide)
complex [Mo2Cp2(µ-SMe)3(xylNC)2](BF4) (1) to give quanti-
tatively the reductive coupled isocyanide derivative [Mo2Cp2(µ-
SMe)3{µ-η1(C):η1(C)-C(NHxyl)C(Nxyl)}] (7). The presence of
electron-releasing ligands in 1, such as thiolates, could have
promoted this reductive coupling of isocyanide ligands attached
to adjacent molybdenum atoms. However, when the same
reaction is conducted in the presence of a large excess of
hydrosulfide, no coupled isocyanide product could be isolated;
instead, the dithiocarbonimidate derivative [Mo2Cp2(µ-SMe)3(µ-
S2CNxyl)] (8) is obtained. Thus, the use of a distinct type of
basic nucleophile as reagent with 1, e.g. NaCtCH, promotes
the deprotonation of one cyclopentadienyl ligand, and hence
successive couplings between deprotonated cyclopentadienyl and
two isocyanide ligands afford compound 9. Additional reactions
of either hydrosulfide or acetylide anions to the coupled ligand
adduct 5, in the absence or presence of isocyanide, give rise to
Similarly, compound 1 (200 mg, 0.246 mmol) was treated with
a large excess of NaSH (20 equiv, 276 mg) in refluxing tetrahy-
drofuran (20 mL) for 72 h. After filtration the solvent was removed
under reduced pressure and the residue washed three times with
cold pentane (3 × 15 mL), affording a violet powder of 8 (143
mg, 95% yield). Complex 8 was formed as a mixture of two
isomers, 8a and 8b, in a 2:3 ratio inseparable by chromatography.
Crystals of 8, suitable for X-ray analysis, were obtained by
crystallization at room temperature from a diethyl ether solution.
Data for 7 are as follows. Anal. Calcd for C31H38Mo2N2S3: C,
51.23; H, 5.27; N, 3.85. Found: C, 52.00; H, 4.90; N, 4.00. IR
(KBr, cm-1): ν(NH) 3431 (m), ν(CN) 1590 (s). 1H NMR (CDCl3):
δ 12.07 (s, 1H, NH), 7.07-6.98 (m, 6H, C6H3Me2), 5.09 (s, 10H,
C5H5), 2.19 and 2.09 (s, 6H, CH3 (xyl)), 2.02, 1.73, and 1.72
(SCH3). 13C{1H} NMR (CDCl3): δ 248.2 (MoC), 147.7 (Ci (xyl)),
131.0 and 130.6 (Co (xyl)), 127.7, 127.6, and 124.3 (C6H3Me2),
89.9 (C5H5), 24.5 (SCH3), 19.7 and 19.2 (C6H3Me2), 10.4 and 8.9
(SCH3).
(34) Schollhammer, P.; Le He´nanf, M.; Le Roy-LeFloch, C.; Pe´tillon,
F. Y.; Talarmin, J.; Muir, K. W. Dalton Trans. 2001, 1573.
(35) Michelin, R. A.; Zonotto, L.; Braga, D.; Sabatino, P.; Angelici,
R. J. Inorg. Chem. 1988, 27, 85.

Cationic Tris(thiolato)dimolybdenum(III) Complexes
Organometallics, Vol. 27, No. 16, 2008 4219
Data for 8 are as follows. Anal. Calcd for C21H25Mo2NS4: C,
41.24; H, 4.12; N, 2.29. Found: C, 42.18; H, 4.23; N, 2.03. IR
(KBr, cm-1): ν(CN) 1624 (m). 1H NMR (CDCl3): 8a, δ 7.05-6.95
(m, 3H, C6H3Me2), 5.51 (s, 10H, C5H5), 2.07 (s, 6H, CH3(xyl)),
1.62 (s, 6H, SCH3); 8b, δ 6.90-6.81 (m, 3H, C6H3Me2), 5.50 (s,
10H, C5H5), 2.06 (s, 6H, CH3 (xyl)), 1.70 and 1.66 (s, 3H, SCH3).
13C{1H} NMR (CDCl3): 8a, δ 171.05 (S2CN), 143.8 (Ci (xyl)),
135.2 (Cp (xyl)), 127.9 and 123.45 (C6H3Me2), 91.45 (C5H5), 25.4
(SCH3), 18.65 (C6H3Me2); 8b, δ 171.2 (S2CN), 143.7 (Ci (xyl)),
135.0 (Cp (xyl)), 127.8 and 127.4 (C6H3Me2), 91.5 (C5H5), 25.2
(SCH3), 18.25 (CH3 (xyl)), 10.95 (SCH3).
127.9, 127.5, and 123.0 (C6H3Me2), 109.6 and 99.8 (C5H4), 101.8
(HCtCMo), 91.75 (C5H5), 90.0 and 84.1 (C5H4), 19.1 and 18.4
(C6H5Me2), 10.3 (SCH3).
Reaction of [Mo2Cp2(µ-SMe)3(xylNC)2](BF4) (1) with an
Excess of NaCtCH in the Presence of Excess xylNC. Complex
1 (100 mg, 0.123 mmol) was treated with 5 equiv of sodium
acetylide (29.6 mg) in the presence of excess xylNC (81 mg, 5
equiv) in refluxing tetrahydrofuran (20 mL) for 72 h. The solution
was then filtered, and the solvent was removed from the filtrate.
The resulting residue was analyzed by 1H NMR spectroscopy,
which indicated the presence of only one NMR detectable orga-
nometallic starting compound, 1.
Reaction of [Mo2Cp(µ-SMe)3{µ-(η5-C5H4)(xylN)CN(xyl)C}]
(5) with an Excess of NaCtCH: Formation of 9. Complex 5
(120 mg, 0.165 mmol) was treated with a large excess of sodium
acetylide (40 mg, 0.833 mmol) in refluxing tetrahydrofuran (20 mL)
for 1 h. After filtration, the solvent was removed and the residue
washed three times with diethyl ether (3 × 15 mL), affording a
orange powder of 9 (100 mg, 86% yield).
Reaction of [Mo2Cp2(µ-SMe)3(xylNC)2](BF4) (1) with NaSH
in the Presence of Excess xylNC: Formation of 7. Complex 1
(200 mg, 0.246 mmol) was treated with an excess of NaSH (138
mg, 10 equiv) in the presence of 3 equiv of xylNC (97 mg) in
refluxing tetrahydrofuran (30 mL) for 72 h. After filtration, the
solvent was removed and the residue analyzed in CDCl3 by 1H
NMR spectroscopy, which indicated the presence of only one NMR-
detectable organometallic product, 7. Then, the crude product was
washed three times with diethyl ether (3 × 15 mL), affording 7 as
a maroon powder (130 mg, 73% yield).
Reaction of [Mo2Cp2(µ-SMe)3{µ-η1:η1-C(NHxyl)C(Nxyl)}]
(7) with an Excess of NaSH: Formation of 8. To a tetrahydrofuran
solution (20 mL) of 7 (100 mg, 0.163 mmol) was added 10 equiv
of NaSH (77 mg), and the mixture was heated under reflux for
24 h. The solution was then filtered. Removal of the solvent from
the filtrate under vacuum yielded a dark residue, which was washed
with pentane (3 × 15 mL) to give compound 8 as a dark violet
powder (67.3 mg, 80% yield).
Reaction of [Mo2Cp(µ-SMe)3{µ-(η5-C5H4)(xylN)CN(xyl)C}]
(5) with an Excess of NaCtCH in the Presence of Excess xylNC.
Complex 5 (100 mg, 0.138 mmol) was treated with 5 equiv of
sodium acetylide (33 mg) in the presence of 5 equiv of xylNC (90.5
mg) in refluxing tetrahydrofuran (20 mL) for 24 h. After filtration,
the solvent was removed under pressure and the resulting solid
1
analyzed by H NMR spectroscopy, which showed the presence
of only the starting material 5 in acetone-d solution.
Reaction of [Mo2Cp(µ-SMe)3{µ-(η5-C5H4)(xylN)CN(xyl)C}]
(5) with Lithium Bromoethanolate in the Presence of xylNC:
Synthesis of [Mo2Cp(µ-SMe)2{µ-(η5-C5H4)C(Nxyl)N(xyl)C}-
(xylNC)2]Br (10). To a tetrahydrofuran solution (20 mL) of 5 (200
mg, 0.276 mmol) were added 2 equiv of LiOCH2CH2Br (40 µL)
and 2 equiv of xylNC (72 mg), and the mixture was stirred at room
temperature for 1 h. After evaporation of the solvent, the product
was extracted from the residue with dichloromethane (10 mL).
Then, diethyl ether (30 mL) was added to precipitate 10 as a powder
(233.5 mg, 83% yield).
Reaction of [Mo2Cp2(µ-SMe)3{µ-η1:η1-C(NHxyl)C(Nxyl)}]
(7) with an Excess of HBF4 · OEt2: Formation of 1. To a cold
solution of 7 (100 mg, 0.137 mmol) in dichloromethane (5 mL)
was added a drop of HBF4 · OEt2. The mixture was stirred for 20
min at -40 °C, and the solution turned from maroon to gray. A
powder was then precipitated from the solution by addition of
diethyl ether (20 mL), collected by filtration, and washed with
diethyl ether (2 × 15 mL), affording compound 1 as a light brown
powder (95.7 mg, 86% yield). Complex 1 was identified as the
bis(isonitrile) [Mo2Cp2(µ-SMe)3(xylNC)2](BF4) by comparison of
In order to facilitate the formation of crystals of 10+, we first
synthesized the tetraphenylborate complex [Mo2Cp2(µ-SMe)2{µ-
(η5-C5H4)C(Nxyl)N(xyl)C}(xylNC)2](BPh4) (10′) via a metathetical
reaction involving compound 10 as starting material. The formula-
tion of 10′ was proved by 1H NMR spectroscopy. The first attempt
to crystallize 10′ from a CH2Cl2 solution layered with diethyl ether
failed; instead, crystals of the tetrakis(isonitrile) derivative [Mo2Cp2(µ-
SMe)2(xylNC)4](BPh4)2 (11′) were formed. Finally, in a second
attempt we got crystals of 10 · 2CH2Cl2, suitable for X-ray analysis,
by crystallization at room temperature from a CH2Cl2 solution of
10 layered with diethyl ether. Data for 10 are as follows. Anal.
Calcd for C48H51BrMo2N4S2: C, 56.53; H, 5.04; N, 5.49. Found:
C, 56.75; H, 5.14; N, 4.65. IR (KBr, cm-1): ν(CtN) 2113 (s) and
1
its H NMR spectra with that of an authentic sample.12a
When the reaction was conducted at room temperature, the
bis(isonitrile) derivative 1 was formed in lower yields, together with
the byproduct 19 in the molar ratio 1.6:1 according to the 1H NMR
analysis of an acetonitrile-d solution of the mixture. Attempts to
separate cleanly the two complexes by chromatography failed.
However, on the basis of 1H NMR spectra of the mixture the yields
of 1 were estimated at 50%. The other compound, 19, was
1
characterized by its H NMR pattern (δ 6.53 (s, 10H), 2.40 (s br,
6H), and 2.31 (s, 6H)), but no more effort to identify that complex
has been made.
Reaction of [Mo2Cp2(µ-SMe)3(xylNC)2](BF4) (1) with an
Excess of NaCtCH: Synthesis of [Mo2Cp(µ-SMe)2{µ-(η5-
C5H4)(xylN)CN(xyl)C}(µ-CCH)] (9). To a tetrahydrofuran solution
(30 mL) of [Mo2Cp2(µ-SMe)3(xylNC)2](BF4) (1; 150 mg, 0.185
mmol) was added a large excess of sodium acetylide (300 µL),
and the mixture was heated under reflux for ca. 3 h. The solution
was then filtered to remove Na(BF4), and the residue was washed
with diethyl ether (3 × 15 mL), affording an orange powder of 9
(109 mg, 84% yield). Orange crystals of 9, suitable for X-ray
analysis, were obtained at room temperature by slow evaporation
1
2095 (s), ν(CdN) 1666 (s). H NMR (CD2Cl2): δ 7.35-6.81 (m,
12H, C6H3Me2), 5.64, 5.59, 5.47, and 5.25 (m, 1H, C5H4), 5.12 (s,
5H, C5H5), 2.56 and 2.23 (s, 3H, C6H5Me2), 2.31 (s, 3H, SCH3),
2.21 (s, 6H, C6H3Me2), 2.15 (s, 3H, SCH3), 2.13 (s, 6H, C6H3Me2),
2.10 (s, 6H, C6H3Me2). 13C{1H} NMR (CD2Cl2): δ 386.8 (Mo2(µ-
C)), 180.95 and 176.95 (MoCNxyl), 155.45 (xylNdC), 145.2,
142.4, 136.35, 135.65, 135.5, 135.1, 130.55, 130.35, 129.75, 129.5,
129.35, 128.65, 128.45, 128.4, 126.7, and 124.2 (C6H3Me2), 109.75,
99.0, and 97.0 (C5H4), 92.2 (C5H5), 87.2 and 83.8 (C5H4), 30.3,
29.25, 19.80, and 19.10 (CH3 (xyl)), 19.25 (SCH3).
from
a
CH2Cl2-Et2O (1:1) solution. Anal. Calcd for
Reaction of [Mo2Cp(µ-SMe)3{µ-(η5-C5H4)(xylN)CN(xyl)C}]
(5) with NaSH in the Presence of Excess xylNC. A mixture of 5
(120 mg, 0.165 mmol) and NaSH (93 mg, 10 equiv) was heated in
the presence of 2 equiv of xylNC (43.4 mg) in tetrahydrofuran (20
mL) at reflux for 24 h. After filtration the solvent was removed
under reduced pressure and the residue analyzed by 1H NMR
C32H34Mo2N2S2: C, 54.70; H, 4.88; N, 3.98. Found: C, 55.25; H,
5.05; N, 3.14. IR (KBr, cm-1): ν(CN) 1650 (s). 1H NMR (CDCl3):
δ 7.26-6.82 (m, 6H, C6H3Me2), 5.86 and 5.10 (m, 2H, C5H4), 5.11
(s, 5H, C5H5), 4.78 (s, 1H, CtCH), 2.23 and 2.17 (s, 6H, CH3
(xyl)), 1.44 (s, 6H, SCH3). 13C{1H} (CDCl3): δ 362.9 (Mo2C), 156.0
(CdN), 142.5 (CtCMo), 146.85, 142.8, 135.5, 128.55, 128.4,

4220 Organometallics, Vol. 27, No. 16, 2008
Ojo et al.

Cationic Tris(thiolato)dimolybdenum(III) Complexes
Organometallics, Vol. 27, No. 16, 2008 4221
spectroscopy, which indicated the presence of only the starting
complex 5 in acetone-d solution.
15b (in about an 8:1 ratio) by chromatography. Crystals of 15 · H2O,
suitable for X-ray analysis, were obtained at room temperature by
slow evaporation of a CH2Cl2-OEt2 solution of 14.
Reaction of [Mo2Cp(µ-SMe)2{µ-(η5-C5H4)C(Nxyl)N(xyl)C}-
(xylNC)2]Br (10) with NaOH: Formation of [Mo2Cp(µ-SMe)2{µ-
(η5-C5H4)C(Nxyl)N(xyl)C}(µ-OCNHxyl)] (12). Complex 10 (200
mg, 0.196 mmol) was treated with a large excess of NaOH (201
mg) in refluxing tetrahydrofuran (20 mL) for 24 h. After filtration
the solvent was removed under reduced pressure and the residue
washed three times with diethyl ether (3 × 15 mL), affording a
orange powder of the already known compound 125 (132 mg, 83%
yield).
Data for 14 are as follows. Anal. Calcd for C14H16Mo2O2S3: C,
33.34; H, 3.20. Found: C, 33.03; H, 3.31. IR (KBr, cm-1): ν(CO)
1
1946 (s). H NMR (CDCl3): δ 5.43 (s, 10H, C5H5), 2.43 (s, 6H,
SCH3). 13C{1H} NMR (CDCl3): δ 240.95 (CO), 90.95 (C5H5),
28.45 (SCH3).
Data for 15 are as follows. Anal. Calcd for C15H18Cl2Mo2O2S3:
1
C, 30.57: H, 3.08. Found: C, 30.76; H, 3.51. H NMR (CD2Cl2):
15a (major isomer), δ 5.99 (s, 10H, C5H5), 4.60 (s, 2H, SCH2Cl),
2.68 and 2.65 (s, 3H, SCH3); 15b (minor isomer), δ 6.00 (s, 10H,
C5H5), 4.69 (s, 2H, SCH2Cl), 2.67 and 2.63 (s, 3H, SCH3).
Reaction of [Mo2Cp(µ-SMe)2{µ-(η5-C5H4)C(Nxyl)N(xyl)C}-
(xylNC)2]Br (10) with HBF4 · OEt2. Synthesis of the Tetraki-
s(isonitrile) Complex [Mo2Cp2(µ-SMe)2(xylNC)4](BF4)2(11). A
solution of 10 (233 mg, 0.228 mmol) in dichloromethane (20 mL)
was stirred in the presence of 2 equiv of HBF4 · OEt2 (100 µL) for
15 min at room temperature. The solvent was then removed under
Reaction of [Mo2Cp2(µ-SMe)3(CO)2]Cl (3) with an Excess
of NaOH: Formation of [Mo2Cp2(µ-SMe)2(CO)2] (16) and
[Mo2Cp2(µ-SMe)4] (17). Complex 3 (200 mg, 0.360 mmol) was
treated with a large excess of NaOH (201 mg) in refluxing
tetrahydrofuran (20 mL) for 24 h. Then NaOH in excess and NaCl
were eliminated by filtration, and the solvent was removed under
reduced pressure. The resulting residue was washed three times
with cold pentane (3 × 15 mL), affording a brown greenish solid.
The 1H NMR spectrum of the resultant powder (176 mg) in CDCl3
indicated the presence of the two organometallic compounds 1625
and 17,26 together with small amounts of the trans,syn/anti-
[Mo2Cp2(µ-SMe)2(O)(CO)]36 byproduct, in the molar ratio 1:1:0.12.
These three complexes have been identified by comparison of their
NMR data with those of pure samples. On the basis of the 1H NMR
spectra of the mixture the yields of trans,syn/anti 16 and 17 were
both estimated at about 47%.
1
vacuum, and the crude products were analyzed in CD3CN by H
NMR spectroscopy. Compound 11 and an uncharacterized byprod-
uct were respectively formed in about a 2.75:1 ratio. On the basis
of 1H NMR spectra of the mixture the yields of 11 were estimated
at 73%. Compound 11 was characterized by comparison of its 1H
NMR data with those of an authentic sample, which was synthesized
via a more improved way, as described below.
The complex [Mo2Cp2(µ-SMe)2(MeCN)4](BF4)2 (6)23 (100 mg,
0.132 mmol) was treated with 4 equiv of xylNC (148 µL) in
refluxing dichloromethane (50 mL) for 6 h. The volume of the
solution was then reduced under vacuum, and diethyl ether (20 mL)
was added to precipitate a red-brown powder that was washed with
diethyl ether (4 × 15 mL). After drying, 11 was obtained in good
yields (119.2 mg, 81%) as an analytically pure solid.
Reaction of [Mo2Cp2(µ-SMe)3(MeCN)2](BF4) (4) with an
Excess of NaSH: Synthesis of [Mo2Cp2(µ-SMe)3{µ-CH3CSNH}]
(18). A solution of 4 (100 mg, 0.153 mmol) in tetrahydrofuran
(20 mL) was stirred in the presence of 5 equiv of NaSH (44
mg) for 15 min at room temperature. After filtration the solvent
was removed under vacuum, and the organometallic products
were extracted with diethyl ether (3 × 15 mL). The diethyl ether
was removed, and the greenish crude product (61 mg) was
Crystals of the tetraphenylborate salt [Mo2Cp2(µ-
SMe)2(xylNC)4](BPh4)2 (11′ · OEt2), suitable for X-ray analysis,
were obtained as described above. Data for 11 are as follows. Anal.
Calcd for C48H52B2F8Mo2N4S2: C, 51.72; H, 4.70; N, 5.02. Found:
C, 51.15; H, 4.98; N, 4.51. IR (CH2Cl2, cm-1): ν(CN) 2097(s). 1H
NMR (CD3CN): δ 7.17-6.76 (m, 12H, C6H3Me2), 5.75 (s, 10H,
C5H5), 2.85 (s, 3H, SCH3), 2.25 and 2.20 (s, 12H, C6H3Me2), 1.99
(s, 3H, SCH3).
Reaction of [Mo2Cp2(µ-SMe)3(t-BuNC)2](BF4) (2) with an
Excess of NaSH: Formation of [Mo2Cp2(µ-SMe)3(t-BuNC)(NC)]
(13). A tetrahydrofuran solution (20 mL) of 2 (185 mg, 0.258 mmol)
and 10 equiv of NaSH (144.7 mg) were heated under reflux for ca.
72 h. After filtration and evaporation of the solvent, the products
were extracted with diethyl ether (3 × 15 mL). The diethyl ether
was then removed in vacuo from the pooled extracts. Spectroscopic
(1H NMR) analysis of the residue showed the presence in CDCl3
of only one NMR detectable organometallic compound, 13,
previously characterized by us.11 After the usual workup, 13 was
obtained as a maroon powder (102 mg, 69% yield).
Reaction of [Mo2Cp2(µ-SMe)3(CO)2]Cl (3) with an Excess
of NaSH: Synthesis of [Mo2Cp2(µ-SMe)2(µ-S)(CO)2] (14). Reac-
tion of 14 with CH2Cl2: Synthesis of [Mo2Cp2(µ-SMe)2(µ-
SCH2Cl)]Cl (15). A solution of 3 (400 mg, 0.72 mmol) in
tetrahydrofuran (20 mL) was stirred in the presence of 5 equiv of
NaSH (202 mg) for 2 h at room temperature. After filtration and
evaporation of the solvent, the residue was washed three times with
diethyl ether (3 × 15 mL), affording compound 14 as a green
powder (346.5 mg, 95% yield). Crystals of 14 · 0.5(toluene) suitable
for X-ray analysis were formed in a cold toluene solution of 14.
Complex 14 (150 mg, 0.297 mmol) was heated in dichlo-
romethane (20 mL) at reflux for 1 h. The solution turned from light
green to green -yellow. Then, the solution was concentrated and
20 mL of diethyl ether was added to give a green-yellow solid.
After filtration the residue was washed with OEt2 (3 × 15 mL),
affording a dark yellow powder of 15 (136 mg, 78% yield). 15
was obtained as a mixture of the two inseparable isomers 15a and
1
analyzed in C6D6 by H NMR spectroscopy. Compound 18 and
one uncharacterized side product were respectively formed in a
4:1 ratio. On the basis of 1H NMR spectra of the mixture the
yield of 18 was estimated at 58%. Attempts to cleanly separate
the complexes by chromatography failed, owing to severe
decomposition on the column. For this reason, no elemental
analysis is available for 18 and, therefore, that compound was
only characterized by spectroscopy. Data for 18 are as follows.
1
IR (KBr, cm-1): ν(N-H) 3094 (m, br). H NMR (C6D6): 5.27
and 5.21 (s, 5H, C5H5), 4.80 (s, 1H, NH), 1.81, 1.72, 1.65, and
1.61 (s, 3H, CCH3 and SCH3).
X-ray Structural Determinations. Measurements for com-
pounds 7-9, 10 · 2CH2Cl2, 11′ · 0.5OEt2, 14 · 0.5(toluene), and
15 · H2O were carried out on a Oxford Diffraction X-Calibur-2
CCD diffractometer equipped with a jet cooler device. Graphite-
monochromated Mo KR radiation (λ ) 0.710 73 Å) was used
in all experiments. The structures were solved and refined by
standard procedures.37 H atoms were positioned using stereo-
chemical considerations. For 14 · 0.5(toluene), the CH3 group
attached to the toluene ring is distributed over two alternative
sites, suggesting 0.50:0.50 disorder. Selected bond lengths and
angles are collected in the caption to Figures 1–7. Crystal data
and data collection and processing parameters are given in Table
1.
(36) (a) Riguer, P.; Pe´tillon, F. Y. ; Schollhammer, P. Unpublished
results. (b) Riguer, P. D. E. A. Report; University of Bretagne Occidentale,
1993.
(37) (a) Sheldrick, G. M. SHELX-97; University of Go¨ttingen, Go¨ttin-
gen, Germany, 1998. (b) Farrugia, L. J. WinGX-A Windows Program for
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4222 Organometallics, Vol. 27, No. 16, 2008
Ojo et al.
Acknowledgment. We are grateful to Dr. F. Michaud
for the crystallographic measurements, and to Dr. R.
Pichon and N. Kervarec for recording two-dimensional
NMR spectra on a Bruker DRX 500 (500 MHz) spec-
trometer. We also thank Mrs J. L’Helgouarc’h for techni-
cal assistance. The CNRS and the University of Bretagne
Occidentale (Brest) are acknowledged for financial sup-
port. The Ministe`re de l’Enseignement Supe´rieur et de la
Recherche du Gabon is acknowledged for providing
studentships (W.-S.O).
Supporting Information Available: CIF files giving X-ray
crystallographic data for 7, 8a, 9, 10 · 2CH2Cl2, 11′ · 0.5OEt2,
14 · 0.5(toluene), and 15 · H2O. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM8003702