Activation of terminal alkynes at the sulfur-rich bimetallic site [MoIII2Cp2(μ-SMe)3]+: Alkyne-vinylidene conversion and C-S and C-C couplings promoted by addition of unsaturated substrates (RC≡CH, RN≡C, S=C=S).

Article abstract of DOI:10.1021/om000966j

Reactions of the bis(nitrile) compound [Mo₂Cp₂ (MeCN)₂(μ-SMe)₃](BF₄) (1) with terminal alkynes in a 1:1 ratio in dichloromethane at room temperature led to the alkyne adduct [Mo₂Cp₂(μ-SMe)₃(RCCH)] (BF₄) (2: R = Tol (2a), Ph (2b), CH₃C=CH₂ (2c), nPr (2d), CO₂Me (2e), CF₃ (2f)). Compounds 2a-d were readily deprotonated with Et₃N to give neutral acetylide derivatives [Mo₂Cp₂(μ-η¹:η²- C≡CR)(μ-SMe)₃] (3). Protonation of 3 afforded exclusively the vinylidene complexes [Mo₂Cp₂(μ-η¹: η²-C=CHR) (μ-SMe)₃](BF₃) (4). Reaction of 1 with an excess of terminal alkyne RCCH in dichloromethane gave either the six-membered metallacycle compounds [Mo₂Cp₂(μ- η²:η⁴-CR=CHCR=CHSMe)(μ-SMe)₂] (BF₄) (5) or the S-methylthiophenium derivatives [Mo₂Cp₂(μ-η²:η⁴- C₄H₂R₂SMe)(μ-SMe)₂] (BF₄) (6), depending on the nature of the R groups. Further reactions of the alkyne adducts 2 with isocyanide and carbon disulfide led to the vinyl-thioether complexes [Mo₂Cp₂(μ- η¹:η³-CR=CR′-SMe)-(μSMe)₂ (RNC)](BF₄) (7, 8) and to their CS₂ adducts [Mo₂Cp₂(S₂C-CR′=CRSMe)(μ- SMe)₂]-(BF₄) (9, 10), which arise from regioselective C-S coupling. A mechanism is proposed for the formation of the cyclic thiometalla compounds 5, 9, and 10 and of the thiophenium species 6 which assigns a key intermediate role to vinyl-thioether species. The molecular structures of 3a, 4b, and 7a have been established by X-ray diffraction studies.

Full text of DOI:10.1021/om000966j

1230
Organometallics 2001, 20, 1230-1242
Activa tion of Ter m in a l Alk yn es a t th e Su lfu r -Rich
Bim eta llic Site [MoIII2Cp 2(µ-SMe)3]+: Alk yn e-Vin ylid en e
Con ver sion a n d C-S a n d C-C Cou p lin gs P r om oted by
Ad d ition of Un sa tu r a ted Su bstr a tes (RCtCH, RNtC,
SdCdS). Cr ysta l Str u ctu r es of µ-η1:η2-Vin ylid en e,
µ-η1:η2-Acetylid e, a n d µ-η1:η3-Vin yl-Th ioeth er
Com p ou n d s
Philippe Schollhammer, Nolwenn Cabon, J ean-Franc¸ois Capon,
Franc¸ois Y. Pe´tillon,* and J ean Talarmin
UMR CNRS 6521, Chimie, Electrochimie Mole´culaires et Chimie Analytique, Faculte´ des
Sciences, Universite´ de Bretagne Occidentale, BP 809, 29285 Brest-Ce´dex, France
Kenneth W. Muir*
Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, Great Britain
Received November 14, 2000
Reactions of the bis(nitrile) compound [Mo2Cp2(MeCN)2(µ-SMe)3](BF4) (1) with terminal
alkynes in a 1:1 ratio in dichloromethane at room temperature led to the alkyne adduct
[Mo2Cp2(µ-SMe)3(RCCH)](BF4) (2: R ) Tol (2a ), Ph (2b), CH3CdCH2 (2c), nPr (2d ), CO2Me
(2e), CF3 (2f)). Compounds 2a -d were readily deprotonated with Et3N to give neutral
acetylide derivatives [Mo2Cp2(µ-η1:η2-CtCR)(µ-SMe)3] (3). Protonation of 3 afforded exclu-
sively the vinylidene complexes [Mo2Cp2(µ-η1:η2-CdCHR)(µ-SMe)3](BF3) (4). Reaction of 1
with an excess of terminal alkyne RCCH in dichloromethane gave either the six-membered
metallacycle compounds [Mo2Cp2(µ-η2:η4-CRdCHCRdCHSMe)(µ-SMe)2](BF4) (5) or the
S-methylthiophenium derivatives [Mo2Cp2(µ-η2:η4-C4H2R2SMe)(µ-SMe)2](BF4) (6), depending
on the nature of the R groups. Further reactions of the alkyne adducts 2 with isocyanide
and carbon disulfide led to the vinyl-thioether complexes [Mo2Cp2(µ-η1:η3-CRdCR′-SMe)-
(µ-SMe)2(RNC)](BF4) (7, 8) and to their CS2 adducts [Mo2Cp2(S2C-CR′dCRSMe)(µ-SMe)2]-
(BF4) (9, 10), which arise from regioselective C-S coupling. A mechanism is proposed for
the formation of the cyclic thiometalla compounds 5, 9, and 10 and of the thiophenium species
6 which assigns a key intermediate role to vinyl-thioether species. The molecular structures
of 3a , 4b, and 7a have been established by X-ray diffraction studies.
In tr od u ction
fragmentation but may also affect the activity of the
metal site.4 Though sulfur-containing bridges can sta-
bilize robust polymetallic complexes, their activity has
been relatively little explored because of the notoriety
of sulfur derivatives as catalyst poisons.4b,c In this
respect, the sulfur-rich environment of the cofactors of
some metalloenzymes5 and the well-developed chemis-
try of thiolato-bridged diruthenium and dimolybdenum
systems are noteworthy.1c,d,4b,c
This study of the interaction of alkynes with the
sulfur-rich dimolybdenum system Cp2Mo2(µ-SMe)3 was
aimed at eliciting cooperative activation by the adjacent
metals, leading to chemical transformations unattain-
able with a single metal atom.1 Such studies also afford
simple structural and chemical precedents for the
behavior of less accessible natural or industrial catalyst
systems.2 Bimetallic complexes offer an attractive com-
promise between polymetallic activity and structural
simplicity.3 The incorporation of bridging groups inhibits
Recently, Rakowski DuBois and co-workers reported
that the thermal lability of the thioether bridge in
[Mo2Cp2(µ-S2CH2)(µ-SMe)(µ-SMe2)]+ gave rise to sub-
(1) (a) Catalysis by Di- and Polynuclear Metal Cluster Complexes;
Adams, R. D., Cotton, F. A., Eds.; Wiley-VCH: New York, 1998. (b)
Braunstein, P.; Rose, J . In Chemical Bonds-Better Ways to Make Them
and Break Them; Bernal, I., Ed.; Elsevier: Amsterdam, 1989; p 5. (c)
Hidai, M.; Mizobe, Y. In Transition Metal Sulfur Chemistry-Biological
and Industrial Significance; Stiefel, E. I., Matsumoto, K., Eds.; ACS
Symposium Series 653; American Chemical Society: Washington, DC,
1996; p 310. (d) Hidai, M.; Mizobe, Y.; Matsuzaka, H. J . Organomet.
Chem. 1994, 473, 1 and references therein.
(3) For example: (a) Curtis, M. D. Polyhedron 1987, 6, 759. (b)
Winter, M. J . Adv. Organomet. Chem. 1991, 29, 101.
(4) For example: (a) King, J . D.; Mays, M. J .; Mo, C.-Y.; Raithby,
P. R.; Rennie, M. A.; Solan, G. A.; Adatia, T.; Conole, G. J . Organomet.
Chem. 2000, 601, 271 and references therein. (b) Rakowski DuBois,
M. Polyhedron 1997, 16, 3089. (c) Rakowski DuBois, M. J . Cluster Sci.
1996, 7, 293.
(5) (a) Richards, R. L. New J . Chem. 1997, 21, 727. (b) Sellmann,
D.; Sutter, J . Acc. Chem. Res. 1997, 30, 460. (c) Coucouvanis, D. J .
Bio. Inorg. Chem. 1996, 1, 594.
(2) Henderson, R. A. J . Chem. Soc., Dalton Trans. 1995, 503.
10.1021/om000966j CCC: $20.00 © 2001 American Chemical Society
Publication on Web 02/22/2001

Activation of Terminal Alkynes
Organometallics, Vol. 20, No. 6, 2001 1231
stitution and desulfurization reactions. They speculated
that the active intermediate, which could be neither
isolated nor characterized, was the unsaturated species
[Mo2Cp2(µ-S2CH2)(µ-SMe)]+, stabilized by coordinated
solvent molecules.6,7 We have reported stoichiometric
reactions which occur at a similar tris(µ-thiolato) bi-
metallic site in the µ-chloro complex [Mo2Cp2(µ-Cl)(µ-
SMe)3].8 This complex in MeCN solution afforded the
stable and tractable bis(acetonitrile) species9 [Mo2Cp2-
(MeCN)2(µ-SMe)3](BF4) (1), which is similar to the
unsaturated intermediate postulated by Rakowski
DuBois. Recently, we have shown that 1 can add two
terminal alkynes to its coordination sphere: formally
regioselective head-to-tail and tail-to-tail linkage of the
alkynes and their coupling to the sulfur atom of a
thiolate bridge gave six-membered metallacycles or
thiophenium derivatives.10 These results suggest that
1 may undergo formal insertion of alkynes into a Mo-S
bond. The rarity of such processes, which are known
only for certain mono- and bimetallic complexes con-
taining fluorinated alkynes11 and for diruthenium com-
pounds,12 and the opportunity to develop new routes to
S-heterocycles13 have led us to investigate the reactivity
of 1 toward terminal alkynes RCtCH.
Resu lts a n d Discu ssion
1. Rea ction of [Mo2Cp 2(MeCN)2(µ-SMe)3](BF 4) (1)
w ith a n Equ im ola r Am ou n t of Ter m in a l Alk yn e
RCtCH. A red solution of 1 in dichloromethane reacted
quantitatively with 1 equiv of RCCH (R ) Tol, Ph,
C(CH3)dCH2, nPr, CO2Me) and with 2-3 equiv of
CF3CCH at room temperature within 30 min to give
brown or green solutions. Addition of diethyl ether
precipitated complexes 2a -f (eq 1) as brown or green
solids. Under the same conditions no reaction occurred
with either the more sterically hindered tBuCtCH or
with disubstituted alkynes RCtCR. The complexes 2
were unambiguously formulated by spectroscopic stud-
ies as the MoIII-MoIII alkyne adducts [Mo2Cp2(RCCH)-
(µ-SMe)3](BF4), but the mode of coordination of the
alkyne has not been reliably established, since mono-
crystals of diffraction quality could not be obtained. At
We shall show that 1 reacts with various alkynes to
afford the dinuclear alkyne adducts [Mo2Cp2(µ-SMe)3-
(RCCH)]+ (2), which are intermediates in the formation
of thiametallacycles at the {Mo2Cp2(µ-SMe)3}+ site, and
in which the alkyne group may also undergo an 1,2-H
shift, giving rise to vinylidene species. Furthermore,
addition of unsaturated molecules (e.g., isocyanides) to
2 results in the formation of vinyl-thioether derivatives
with an unprecedented µ-η1:η3-coordination. A prelimi-
nary communication of a part of this work has already
appeared.10
1
room temperature the H NMR spectra of 2 displayed
both the resonances expected for the alkyne substituent,
R, and a low-field signal (between 12 and 14 ppm) for
the CH end of the alkyne, indicating coordination of an
RCCH ligand to the molybdenum atoms. The single
broad resonance which was observed for the two cyclo-
pentadienyl groups suggested that a dynamic process
was operative in solution at room temperature for
complexes 2a -d . Two cyclopentadienyl resonances were
observed at room temperature for complexes 2e,f, which
contain alkynes with the more electron-withdrawing
groups COOMe and CF3. 13C NMR spectra were re-
corded to get more information about the mode of
coordination of the alkyne in 2. The two resonances of
the sp-hybridized carbon atoms of the alkyne RCCH
display some of the largest downfield chemical shifts
yet reported for M2(alkyne) complexes (between 254 and
291 ppm),14 lying in the carbene range but slightly lower
than expected for four-electron-donor alkynes in mono-
nuclear compounds.15 Such data do not allow the nature
of the alkyne-metal bonding to be defined without
ambiguity, especially as the strong deshielding observed
in 2 may partially reflect the electronic behavior of the
thiolato-bridged bimetallic cation. Nevertheless, they
suggest that the alkyne acts as a four-electron donor
with a significant π contribution,15 as required by the
electron-counting rules to saturate the {Mo2Cp2(µ-
SMe)3}+ core. The alkyne coordination in 2 may not be
completely described by either the classical tetrahe-
drane µ-η2:η2 coordination mode (I; Chart 1)16 or the
dimetallacyclobutene µ-η1:η1 coordination mode (II;
(6) Gabay, J .; Dietz, S.; Bernatis, P.; Rakowski DuBois, M. Or-
ganometallics 1993, 12, 3630.
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J . Y.; Talarmin, J .; Muir, K. W. Chem. Commun. 1996, 2633. (b)
Schollhammer, P.; Gue´nin, E.; Pe´tillon, F. Y.; Talarmin, J .; Muir, K.
W.; Yufit, D. S. Organometallics 1998, 17, 1922.
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3967.
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metallics 1995, 14, 703. (d) Adams, H.; Allott, M.; Bancroft, M. N.;
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32, 1. (c) Kondo, T.; Mitsudo, T. A. Chem. Rev. 2000, 100, 3205.
(14) (a) Bott, S. G.; Clark, D. L.; Green, M. L. H.; Mountford, P. J .
Chem. Soc., Dalton Trans. 1991, 471. (b) Feng, Q.; Green, M. L. H.;
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1232 Organometallics, Vol. 20, No. 6, 2001
Schollhammer et al.
Ch a r t 1. Su ggested Lim itin g F or m Con tr ibu tion s
Sch em e 2
to th e Str u ctu r e of th e Alk yn e Ad d u ct Com p lexes
2
electron-withdrawing substituents inhibit the fluxion-
ality. Moderate values for the energy barriers, of 46.8
kJ mol-1 for 2a (R ) Tol) and 50.0 ( 1 kJ mol-1 for 2b
(R ) Ph),21 were determined from variable-temperature
1H NMR studies but are difficult to interpret without a
reliable structural model for 2.
Sch em e 1
2. P r oton Tr a n sfer in th e Alk yn e Ad d u cts [Mo2-
Cp 2(RCCH)(µ-SMe)3]+ (2). Compounds 2a -d were
readily deprotonated in the presence of Et3N to give
green solutions of the neutral acetylide derivatives
[Mo2Cp2(µ-η1:η2-CtCR)(µ-SMe)3] (3). Addition of HBF4
to dichloromethane solutions of 3 afforded exclusively
the expected Câ-protonated vinylidene complexes
[Mo2Cp2(µ-η1:η2-CdCHR)(µ-SMe)3](BF4) (4), which were
easily deprotonated to regenerate 3 (Scheme 2). The
conversion of the Mo2(III) alkyne adducts 2 into µ-vi-
Chart 1)17 but may also involve contributions from the
µ-η2:η1 or µ-η1:η1 bis(carbene) limiting forms (III and IV;
Chart 1);18a III resembles structures found in ynamine
complexes.18b,c A final possibility is the unbridged four-
1
electron-donor alkyne V (Chart 1).15,19 The J CH value
(156.5 Hz) suggests a significant C(sp) f C(sp2) rehy-
bridization in 2e (1J CH ) 156 Hz in CH2dCH2 and 249
Hz in HCtCH).15,16 Interactions of alkynes with di-
nuclear complexes containing tripositive group 6 metals
have been reported:14,20 they generally give rise to
adducts whose structures deviate from the ideal per-
pendicular bridge geometry, with an unsymmetrical
M2(µ-C2R2) unit and a C-C bond slightly twisted with
respect to the M-M axis. The internal carbon chemical
shifts of the alkyne bridge carbon atoms in such
complexes are <200 ppm, indicating strong deshielding.
Examination of the line shapes in variable-temperature
1H NMR spectra of complexes 2a ,b revealed that only
the cyclopentadienyl resonances are temperature-de-
pendent. This suggests strongly that the alkyne vector
is not perpendicular to the Mo-Mo axis in the typical
{Mo2Cp2(RCCH)(µ-SMe)3}+ framework;8 consequently,
the fluxional motion requires either inversion of the
alkyne RCtCH relative to the Mo-Mo axis and/or an
exchange of this ligand from one molybdenum site to
the other (Scheme 1). In addition, the two cyclopenta-
dienyl signals did not coalesce on warming CD3CN
solutions of 2e,f, suggesting that alkynes with strongly
1
nylidene species was revealed by H NMR monitoring
for complexes 2a -d . A total of 75% of 2a (R ) tolyl)
slowly transformed into 4a within 3 days at room
temperature, but over the same time solutions of 2e and
2f did not change. It is worth noting that, unlike tBuCt
CH, an excess of the terminal alkyne Me3SiCtCH
reacted with 1 at room temperature within 1 h and
afforded the µ-vinylidene complex [Mo2Cp2(µ-η1:η2dCd
CH2)(µ-SMe)3](BF4) (4e). We assume that a 1,2-silyl
shift helps to reduce steric crowding and that the
product hydrolyzes under moist conditions to yield 4e.
Analogous transformations with mononuclear com-
plexes have been reported.22 When it is warmed in
acetonitrile, 4e regenerated the bis(acetonitrile) deriva-
tive 1, possibly losing acetylene via the reverse vi-
nylidene-alkyne tautomerization. These results indi-
cate that the MoIII alkyne complexes isomerize to the
2
more stable vinylidene adducts at room temperature.
However, the reverse reaction, which has been reported
for the conversion of the vinylidene species [Mo2Cp2-
(CO)4(µ-η1:η2-CdCHR)] into the related MoI2 alkyne
derivative [Mo2Cp2(CO)4(RCCH)],24 may operate at
higher temperature. This alkyne-vinylidene isomer-
(16) Bailey, W. I.; Chisholm, M. H.; Cotton, F. A.; Rankel, L. A. J .
Am. Chem. Soc. 1978, 100, 5765.
(17) Hoffman, D. M.; Hoffman, R.; Fisel, C. R. J . Am. Chem. Soc.
1982, 104, 3858.
(18) (a) Spaltenstein, E.; Mayer, J . M. J . Am. Chem. Soc. 1991, 113,
7744. (b) Cabrera, E.; Daran, J .-C.; J eannin, Y. Organometallics 1988,
7, 2010. (c) Adams, R. D.; Chen, G.; Yin, J . Organometallics 1991, 10,
1278.
(19) (a) Chisholm, M. H.; Huffman, J . C.; Heppert, J . A. J . Am.
Chem. Soc. 1985, 107, 5116. (b) J effery, J . C.; Moore, I.; Razay, H.;
Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1984, 1581.
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Trans. 2000, 1499. (b) Green, M. L. H.; Mountford, P. Chem. Soc. Rev.
1992, 29. (c) Mountord, P. J . Chem. Soc., Dalton Trans. 1994, 1843.
(d) Buhro, W. E.; Chisholm, M. H. Adv. Organomet. Chem. 1987, 27,
311.
(21) Gutowski, H. S.; Holm, C. H. J . Chem. Phys. 1956, 25, 1228.
(22) (a) Werner, H.; Baum, M.; Schneider, D.; Windmu¨ller, B.
Organometallics 1994, 13, 1089. (b) Bullock, R. M. J . Chem. Soc., Chem.
Commun. 1989, 165.
(23) (a) Silvestre, J .; Hoffman, R. Helv. Chim. Acta 1985, 68, 1461.
(b) Cadierno, V.; Pilar Gamasa, M.; Gimeno, J .; Pe´rez-Carreno, E.;
Garcia-Granda, S. (c) Connely, N. G.; Geiger, W. E.; Lagunas, M. C.;
Metz, B.; Rieger, A. L.; Shaw, M. J . J . Am. Chem. Soc. 1995, 117,
12202. (d) Pe´rez-Carreno, E.; Paoli, P.; Ienco, A.; Mealli, C. Eur. J .
Inorg. Chem. 1999, 1315. (e) Bruce, M. I. Chem. Rev. 1991, 91, 197. (f)
El Amouri, H.; Gruselle, M. Chem. Rev. 1996, 96, 1077. (g) Bruce, M.
I. Chem. Rev. 1998, 98, 2797.
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A. G.; Rodrigues, A. G. J . Chem. Soc., Dalton Trans. 1991, 3171.

Activation of Terminal Alkynes
Organometallics, Vol. 20, No. 6, 2001 1233
F igu r e 1. View of a molecule of complex 3a showing 20%
probability ellipsoids for non-hydrogen atoms.
F igu r e 2. View of the 4b cation showing 20% probability
ellipsoids for non-hydrogen atoms.
ization at the {Mo2(µ-SMe)3} core depends on the
electronic properties of the group which is borne by the
alkyne as well as on those of the metallic fragment.22,23
The 1,2-H shift does not occur when a strongly electron-
withdrawing group (e.g., CO2Me or CF3) is present in
the alkynes, whereas the tautomerization occurs readily
when the alkyne contains the electron-releasing n-
propyl group. In addition, the formation of the initial
alkyne adduct 2e upon addition of HBF4 to 3e (R
dCO2Me) shows that the electronic characteristics of
the R group may control both the polarity of the
acetylide µ-η1:η2-CtCR bridge and the regiospecificity
of the electrophilic attack, as has been previously
reported for nucleophilic attack.25
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in Com p ou n d s 3a a n d 4b
3a
4b
3a
4b
Mo1-Mo2
Mo1-S1
Mo1-S2
Mo1-S3
Mo2-S1
Mo2-S2
2.616(1) 2.622(1) Mo2-S3
2.458(1) 2.482(1) Mo1-C4
2.449(1) 2.449(1) Mo1-C5
2.483(1) 2.462(1) Mo2-C4
2.453(1) 2.489(1) C4-C5
2.449(1) 2.445(1) C5-C6
2.472(1) 2.481(1)
2.360(3) 2.268(5)
2.661(3) 2.589(5)
2.068(3) 1.894(5)
1.238(4) 1.356(6)
1.443(4) 1.470(7)
Mo1-C4-Mo2 72.1(1) 77.5(2) C4-C5-C6
168.5(3) 124.9(5)
Mo1-C4-C5
Mo2-C4-C5
89.8(2) 87.4(3) C4-C5-Mo1 62.5(2) 61.3(3)
160.9(3) 164.6(4) Mo1-C5-C6 125.2(2) 117.6(3)
denum(I) vinylidene species [Mo2Cp2(CO)4(µ-η2:η1-
CdCHR)],24 suggesting stronger binding of the CdCH2
moiety to the bimetallic site.
The acetylide and vinylidene compounds were identi-
fied by NMR spectroscopy, and their structures were
confirmed by X-ray analyses of crystals of 3a (R ) Tol)
X-ray analyses of 3a and 4b confirm the unsym-
metrical side-on coordination of the acetylide (Figure 1)
and vinylidene (Figure 2) groups which bridge the Mo-
Mo bond. The geometries of these complexes will be
discussed together (Table 1), since 3a is the depro-
tonated form of the tolyl analogue of 4b. The lengths of
the Mo-Mo single bonds in 3a and 4b are typical of
values in [MoIII2Cp2(µ-SR)3] complexes (the mean length
of 42 such bonds is 2.612 Å) and those of the µ-Mo-S
bonds are unexceptional.26 The three-electron-donor
acetylide ligand in 3a bonds terminally to Mo2 and
bonds via the π-electrons of its CtC triple bond to Mo1.
The terminal Mo-CtCR interaction involves enough
back-donation from Mo2 to shorten the Mo2-C4 dis-
tance to 2.068(3) Å and lengthen the C4-C5 bond
(which is also perturbed by its interaction with Mo1) to
1.238(4) Å: for comparison, in [Mo2(CCR)4(PR′3)4] com-
plexes back-donation into the terminal acetylide ligands
is thought to be slight and the average Mo-C and CtC
bond lengths are 2.149 and 1.205 Å.27 The π-interaction
1
and 4b (R ) Ph). The H NMR spectra of the acetylide
(3) and vinylidene (4) compounds exhibited the two sets
of resonances respectively expected for the [Mo2Cp2(µ-
SMe)3] core and for the R group. The vinylidene bridge
µ-η2:η1-CRdCâHR was characterized by the observation
of a 1H resonance between 6 and 8 ppm, which was
assigned to the dCâHR group, and of two resonances
in the 13C NMR spectra, at low field in the carbene (ca.
366 ppm) and in the vinyl (ca. 115 ppm) ranges, which
were assigned to CR and Câ, respectively. A single
resonance was observed for the two cyclopentadienyl
groups in the acetylide and vinylidene compounds,
suggesting that windshield wiper fluxionality occurs in
solution at room temperature.24 The dynamic process
could be studied on the NMR time scale only for the
vinylidene species: energy barriers of 34.2, 35.9, 42.3,
and 61.0 ( 1 kJ mol-1 were determined21 for 4a (R )
Tol), 4b (R ) Ph), 4d (R ) nPr), and 4e (R ) H),
respectively. Replacement of a hydrogen substituent by
an alkyl or aryl group appears to lower the barrier
energy for the vinylidene fluxional motion, suggesting
that π-electron delocalization through a tolyl or phenyl
group facilitates the motion. When R ) H, the value is
in the range of values determined for neutral dimolyb-
(26) (a) Allen, F. H.; Kennard, O. Chem. Des. Automation News 1993,
8, 31. Version 5.20 of the Cambridge Structural Database with 224 400
structures was used. (b) Orpen, A. G.; Brammer, L.; Allen, F. H.;
Kennard, O.; Watson, D. G.; Taylor, R. International Tables for
Crystallography; Kluwer Academic: Dordrecht, The Netherlands, 1992;
Vol. C, I.U.Cr.; Table 9.6.
(27) J ohn, K. D.; Miskowski, V. M.; Vance, M. A.; Dallinger, R. F.;
Wang, L. C.; Geib, S. J .; Hopkins, M. D. Inorg. Chem. 1998, 37, 6858.
(25) Mott, G. N.; Carty, A. J . Inorg. Chem. 1983, 22, 2726.

1234 Organometallics, Vol. 20, No. 6, 2001
Schollhammer et al.
Sch em e 3
between Mo1 and the CtC bond is extremely unsym-
metrical (Mo1-C4 ) 2.360(3), Mo1-C5 ) 2.661(3) Å)
and also weak, since the mean length for 2e-donor Mo-
C(η2-C2R2) bonds is 2.129 Å.26b Protonation of an ana-
logue of 3a at C5 generates the four-electron-donor
ModCdCHR vinylidene ligand present in 4b. The
Mo2-C4 distance (1.894(5) Å) now formally represents
a double bond, and it is 0.17 Å shorter than the
comparable distance in 3a . Similarly, the C4-C5 bond
length (1.356(6) Å) increases, as its order decreases from
3 to 2, and the Mo1-C π-bonds shorten (Mo1-C4
2.268(5), Mo1-C5 2.589(5) Å), presumably as a result
of greater back-donation from Mo1. Thus, all three
Mo-C distances are shorter in 4b than 3a . In 4b, C5 is
sp2 hybridized and its attached aromatic ring is in
conjugation with the C4-C5 double bond (C4-C5-C6-
C11 ) 17.3(8)°). In 3a and 4b the coordination of sp-
hybridized C4 carbon atoms is slightly nonlinear but
the Mo2-C4-C5 angles (160.9(3)° and 164.6(4)°) are
within the range expected for M2(µ-η1:η2-CCR) and M2(µ-
η1:η2-CCHR) groups.23e,24 Apart from C4-C5-C6, which
changes from 168.5(3) to 124.9(5)°, corresponding bond
angles in 3a and 4b are remarkably similar (Table 1).
The bridging organic ligands in 3a and 4b resemble
those in the zerovalent Mo2(µ-η1:η2-CCR) and Mo2(µ-η1:
η2-CCHR) complexes described by Froom et al., but the
Mo0-C bond lengths are in general shorter than those
in 3a and 4b and the Mo0-Mo0 bond lengths of 3.10-
3.12 Å are much longer.24
3. C-S a n d C-C Cou p lin gs In d u ced by th e
Ad d ition of RCCH, RNC, a n d CS2 to th e Alk yn e
Ad d u ct [Mo2Cp 2(RCCH)(µ-SMe)3](BF 4) (2). Reaction
of the bis(acetonitrile) compound 1 in dichloromethane
with 2 equiv or with a large excess of terminal alkyne
RCCH led to brownish green solutions from which six-
membered metallacycle (5) or S-methylthiophenium (6)
derivatives were isolated, depending on the nature of
the R groups. Interestingly, the same products were
formed on reacting the alkyne adducts 2 with an excess
(4 equiv) of RCCH (Scheme 3). In contrast, when an
excess of RCCH was added to complexes 3a -d or 4a -
d , no reaction was observed. Complexes 5 and 6 were
formulated by a combination of X-ray diffraction and
spectroscopic studies. Their molecular structures (see
Figures 3 and 4) were reported in a preliminary com-
munication10 and will not therefore be described here
in detail. The structure of the cation in 5a is based on
a {Mo2Cp2(µ-SMe)2} unit which is bridged by an eight-
electron-donor CRdCHCRdCHSMe ligand (R ) Ph)
formed by linking together one SMe bridge and two
alkynes, the latter being coupled head-to-tail (Mo1-C4
F igu r e 3. View of the 5a cation showing 20% probability
ellipsoids for non-hydrogen atoms.10 As discussed in the
text, Mo1 is π-bonded to the C4-C7 butadiene unit.
) 2.24(2) Å, Mo1-C5 ) 2.30(2) Å, Mo1-C6 ) 2.40(2)
Å, Mo1-C7 ) 2.45(2) Å; see Figure 3). NMR spectros-
1
copy is in accord with this structure. H NMR spectra
exhibited two resonances for the two inequivalent
cyclopentadienyl ligands and the set of resonances
expected for two R and three SMe groups. The chemical
shifts of the SMe groups did not prove unambiguously
that one of them had coupled to an alkyne. Two doublets
at δ 7.12 and 5.03 (4J HH ) 1.4 Hz) were detected in the
1H NMR spectrum of 5a and were assigned to the two
protons of the bridging ligand C(R)dCHC(R)dCHSMe.
It is worth noting that similar patterns were observed
for 5c, suggesting that the same head-to-tail coupling
occurs when R is an aliphatic group. The thiophenium
derivatives 6 were obtained, but with diminished yields
(40-50%) compared to the reactions giving the thia-
metallacyclic complexes 5a ,b (70-75%), when the reac-
tions were conducted at room temperature. This may
indicate that the pathway leading to tail-to-tail coupling
of the alkyne followed by ring closure was slower than
that affording complexes 5a ,b. Nevertheless, in the
reactions of 2e and 2f with excess alkyne RCtCH (R )
1
CO2Me, CF3), the only products detectable by H NMR
spectroscopy were 6 and an appreciable amount of
unreacted alkyne adduct 2e,f (about 30% after 24 h at
room temperature). We have previously noted that
warming increases the yield of 6a .10 The principal
structural feature of complex 6a was the presence of
the thiophenium ring {C4H2(CF3)2SCH3}+ in a shallow
envelope conformation which is bound to a {Mo2Cp2(µ-

Activation of Terminal Alkynes
Organometallics, Vol. 20, No. 6, 2001 1235
F igu r e 5. View of the 7a cation showing 20% probability
ellipsoids for non-hydrogen atoms.
F igu r e 4. View of a 6a cation showing 20% probability
ellipsoids for non-hydrogen atoms.10 In the solid there are
two crystallographically independent but structurally equiva-
lent cations. One straddles a crystallographic mirror plane;
the other (shown here) has no crystallographically imposed
symmetry..
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in 7a
Mo1-Mo2
Mo1-C4
Mo1-C9
Mo2-C9
Mo2-C10
C9-C10
S3-C10
S3-C3
2.825(1)
2.104(4)
2.128(4)
2.293(4)
2.308(4)
1.399(6)
1.782(4)
1.811(5)
N1-C4
1.151(5)
1.470(6)
2.463(1)
2.441(1)
2.431(1)
2.434(1)
2.540(1)
N1-C5
Mo1-S1
Mo1-S2
Mo2-S1
Mo2-S2
Mo2-S3
Sch em e 4
N1-C4-Mo1
C4-N1-C5
C11-C10-Mo2
C10-S3-C3
C10-C9-Mo1
C3-S3-Mo2
C10-S3-Mo2
172.7(4)
175.0(5)
131.0(3)
107.1(2)
130.1(3)
113.2(2)
61.6(1)
S3-C10-Mo2
Mo1-C9-Mo2
C11-C10-S3
C9-C10-Mo2
C10-C9-Mo2
C9-C10-S3
75.6(2)
79.3(1)
122.2(3)
71.7(2)
72.9(2)
114.0(3)
ligands were detected in the H and 13C NMR spectra.
In particular, the signals of the CN groups were
observed at 166.3 ppm (7a ) and 187.1 ppm (7b), in
accord with a terminal bonding mode of the isocyanide
(Mo-CN-R). The chemical shifts of the unsaturated
carbon atoms of the alkyne fall in the sp2-hybridized
carbon range (160-100 ppm). The 13C chemical shifts
for the σ-bonded (CR) and the non-σ-bonded (Câ) carbon
atoms of the µ-vinyl appear at about 152-150 and 112
ppm, respectively, which are in accord with carbene-
like character for CR and sp3 hybridization at Câ.29 X-ray
analysis of 7a revealed a C-S bond between the carbon
atom bearing the R group of the alkyne ligand and the
sulfur atom of one SMe group (S3-C10 ) 1.782(4) Å).
The structure of 7a (Figure 5 and Table 2) can be
regarded as that of a µ-η1:η3 vinyl-thioether complex
in which the vinylic C9-C10 unit is σ-bonded to Mo1
(Mo1-C9 ) 2.128(4) Å) and π-bonded to Mo2 (Mo2-C9
) 2.293(4) Å, Mo2-C10 ) 2.308(4) Å) and the S3 atom
is σ-bonded to Mo2 (Mo2-S3 ) 2.540(1) Å). The Mo(1)-
Mo(2) length (2.825(1) Å) in 7a is in accord with the
electron-counting rules, which require an order of 1 for
the Mo(1)-Mo(2) bond, and with the presence of the less
sterically constraining MeSCRdCH- bridging group.
1
SMe)2} bimetallic core through the CdC double bonds
(Mo‚‚‚S ) 3.386(2)-3.395(2) Å; Mo-CR ) 2.161(5)-
2.184(6) Å; Mo-Câ ) 2.249(5)-2.261(6) Å). The 1H NMR
spectrum of 6 displayed one resonance for the two Cp
ligands, which is in accord with the symmetrical solid-
state structure (Figure 4); a single resonance detected
for two protons at about 3.3 ppm indicated the formally
tail-to-tail coupling of the two alkynes.
To get additional information on the mechanistic
pathway leading to complexes 5 and 6 via C-C and C-S
bond formation, we investigated reactions of the alkyne
adduct 2b (R ) Ph) with isocyanide substrates. 2b
reacted quantitatively in dichloromethane with 1 equiv
of tBuNC or xylylNC to give, within 1 h, orange
solutions. Orange solids, 7a ,b, were obtained upon
addition of diethyl ether to the concentrated solution
(Scheme 4). Infrared spectra of 7 showed the presence
of typical ν(CN) bands at frequencies lower than those
of the free ligands;28 these data indicate that an iso-
cyanide molecule is coordinated to a molybdenum atom
in 7. The expected set of resonances of the isocyanide
(28) Pe´tillon, F. Y.; Schollhammer, P.; Talarmin, J . J . Organomet.
Chem. 1991, 411, 159.
(29) Schollhammer, P.; Pe´tillon, F. Y.; Poder-Guillou, S.; Talarmin,
J .; Muir, K. W.; Yufit, D. S. J . Organomet. Chem. 1996, 513, 181.

1236 Organometallics, Vol. 20, No. 6, 2001
Schollhammer et al.
F igu r e 6. 1H-13C 2D HMBC spectrum of 8 (298 K, CDCl3).
The Mo1-C9 distance is comparable with that observed
in the µ-σ:η2-vinyl dimolybdenum(II) complex [Mo2Cp-
(µ-SPh)(µ-σ:η2-C(CH3)dCH(CH3))]29 (2.121(8) Å), whereas
the Mo2-C9 and Mo2-C10 π bonds in 7a are slightly
atoms.11g To our knowledge, 7a provides the first
crystallographic example of a µ-η1:η3-CR1dCR2-SR3
ligand, though µ-η1:η3-bonding has been proposed to
explain the isomerism in [Fe2(CO)4{µ-C(CF3)dC(CF3)-
SMe}].32
shorter than those in the µ-σ:η2-vinyl MoII complex
2
(2.359(8) and 2.397(7) Å), perhaps reflecting the differ-
ence in the oxidation states of the molybdenum atoms.
The C9-C10 double bond (1.399(6) Å) appears to be
lengthened by its coordination to Mo2. Structural
features of the terminal tBuNC ligand are unexcep-
tional.30 The µ-η1:η3 structure of the five-membered
dimolybdenacycle in 7a differs from the µ-η2:η2 arrange-
ment found in most related complexes, where the vinyl-
thioether forms part of a thiametallacyclobutene system
which is linked to the second metal atom through the
vinylic double bond.12b-c,31 The µ-η1:η1 coordination of
the -C(CF3)dCHSMe unit in the eight-membered di-
molybdenacycle complex [Mo2Cp2{µ-η1:η1-C(CF3)d
CHSMe}2] shows how the vinyl-thioether ligand can
tailor its electron donation to the demands of the metal
To find if the regioselectivity of the C-S coupling
depends on the nature of the alkyne substituent, as has
been previously observed for the coupling of SMe with
two alkynes (see above), a solution of the complex 2e in
CH2Cl2 was treated with 1 equiv of tBuNC. A compound
8 in which the isocyanide was coordinated to one
1
molybdenum atom (Scheme 4) was formed. The H-13C
HMQC and 1H-13C HMBC 2D NMR spectra allowed
full assignment of 13C chemical shifts and indicated
unambiguously that in 8 the sulfur atom of one SMe
group was bonded to the carbon of the alkyne bearing
the hydrogen atom (Figure 6). The correlation peaks
between the methyl protons at 2.37 ppm and the carbon
at 100.2 ppm (3J CH) and those between the proton of
the CH group at 6.83 ppm, the methanethiolate carbon
at 21.7 ppm (3J CH), the carbon bearing the CO2Me group
at 129.6 ppm (2J CH), and the carbon of the CO2Me group
at 175.6 ppm (3J CH), are in accord with a MeSCHdCR-
(30) McDermott, L. C.; Muir, K. W.; Pe´tillon, F. Y.; Poder-Guillou,
S.; Schollhammer, P. Acta Crystallogr. 1996, C52, 74.
(31) (a) King, J . D.; Mays, M. J .; Pateman, G. E.; Raithby, P. R.;
Rennie, M. A.; Solan, G. A.; Choi, N.; Conole, G.; McPartlin, M. J .
Chem. Soc., Dalton Trans. 1999, 4447. (b) Rumin, R.; Guennou, K.;
Pe´tillon, F. Y.; Muir, K. W. J . Chem. Soc., Dalton Trans. 1997, 1381.
(32) Rumin, R.; Pe´tillon, F.; Manojlovic-Muir, L.; Muir, K. W.
Organometallics 1990, 9, 944.

Activation of Terminal Alkynes
Organometallics, Vol. 20, No. 6, 2001 1237
Sch em e 5
addition of HSMe to the alkyne. The residual organo-
metallic species was not identified (eq 2).
Investigations of the reactivity of the alkyne adducts
with carbon disulfide again indicated that the regio-
selective formation of products with new C-S and C-C
bonds was controlled by the R substituent of the alkyne.
An excess of CS2 was added to dichloromethane solu-
tions of complexes 2a ,b,e (Scheme 5). The solutions
turned brownish red within 2 h and afforded compounds
9 and 10, which were identified by NMR spectroscopy,
since diffraction-quality crystals could not be obtained.
1H NMR spectra of 9 and 10 displayed two broad
resonances, which were assigned to the cyclopentadienyl
ligands. These resonances coalesced upon warming,
showing that the complexes were fluxional. Energy
backbone. Very weak correlations were also detected
between the C(CH3)3 signal at 1.41 ppm and both the
C5H5 signal at 5.11 ppm and the carbon signal of the
3
isocyanide at 164.2 ppm (4J CH and J CH). When 8 was
left overnight in CDCl3, quantitative evolution of an
organic product was observed. It was identified by its
1
1H NMR spectrum and H-13C HMBC 2D NMR experi-
ments as the E isomer of the vinyl-thioether MeSCHd
CHCO2Me, formally the product of anti-Markownikoff
F igu r e 7. 1H-13C 2D HMBC spectrum of 10 (298 K, CD3COCD3).

1238 Organometallics, Vol. 20, No. 6, 2001
Schollhammer et al.
Sch em e 6
the bimetallic site through the three sulfur atoms and
the CdC double bond, giving the formally eight-electron-
donor ligand (Scheme 5) required by the electron-
counting rules.33 The motion of such a ligand shown in
Scheme 6 may explain the temperature dependence of
1
the H NMR spectra of complexes 9 and 10.
4. P ossible Mech a n ism of Oligom er iza tion of
Alk yn es a t th e {Mo2Cp 2(µ-SMe}3 Cor e. Reaction of
monosubstituted acetylenes with the bis(nitrile) complex
1 gives first the alkyne complexes 2. This reaction is
reversible, since 2 can be converted back to 1 by
dissolving it in acetonitrile solution (Scheme 7).The
nature of the bonding of the alkyne to the dimolybde-
num framework of 2 has not been established in detail.
We suggest that the further addition to 2 of an unsat-
urated molecule L (L ) RCtCH, RNtC, SdCdS)
produces the intermediate vinyl-thioether complexes
11. The incoming ligand L bonds to only one of the metal
atoms and thereby labilizes a bridging Mo-S bond, into
which is inserted the RCCH added in the previous step.
Several examples of insertion of an alkyne into an
M-SR bond in mononuclear11 and dinuclear com-
plexes12 have been reported, and it has been shown that
vinyl-thioether compounds are intermediates in the
formation of thiometallacycles. It is worth noting that
under very mild conditions only one isomer of most of
the products was obtained in appreciable yield. This
strongly suggests that these reactions are highly regio-
selective and that they depend on a delicate balance
involving the electronic and steric properties of both the
metallic framework and the alkyne substituents, as is
barrier values of 63.1, 63.8, and 66.3 ( 1 kJ .mol-1 were
determined for 9a ,b and 10, respectively.21 The signals
of the CH groups were detected at about 6 ppm. Two-
1
dimensional heteronuclear H-13C inverse-correlation
experiments were carried out to characterize 9a and 10.
Full assignment of the 13C chemical shifts was achieved
by means of 1H-13C HMQC and 1H-13C HMBC 2D
NMR experiments, which revealed that one carbon atom
of the alkyne binds to the sulfur atom of a SMe group
and the other to the carbon of CS2 and, in addition, that
the regioselectivity of the C-S coupling depends on the
1
nature of the alkyne substituent. The H-13C HMBC
2D NMR spectra of 9a (Figure 7) and 10 are in accord
-
with the respective formation of MeS-C(tol)dCHCS2
and MeSCHdC(CO2Me)CS2. No correlation peak be-
tween the CH signal and any SMe resonances was
detected when R ) Tol, whereas in the CO2Me case,
correlations were observed between the SCH3 signal at
2.66 ppm and the CH resonance at 152.0 ppm (3J CH
)
and between the CH signal at 7.93 ppm and the carbon
of the CS2 group at 142.5 ppm (3J CH) and the carbon
resonance of CO2Me at 163.3 ppm (3J CH) (Figure 7). The
vinyl-thioether dithiocarboxylate ligand may bind to
Sch em e 7. P ossible P a th w a ys to th e F or m a tion of (a ) Six-Mem ber ed Meta lla cycle Com p lexes 5 a n d
th iop h en iu m Com p lexes 6 a n d (b) Com p lexes 7, 8 a n d 9, 10

Activation of Terminal Alkynes
Organometallics, Vol. 20, No. 6, 2001 1239
Syn th esis of [Mo2Cp 2(µ-SMe)3(RCCH)](BF 4) (2). A solu-
tion of complex 1 (0.2 g, 0.32 mmol) in CH2Cl2 (15 mL) was
stirred in the presence of 1 equiv of RCCH (R ) Tol, v ) 41
µL; R ) Ph, v ) 35 µL; R ) CH3CdCH2, v ) 30.5 µL; R ) nPr,
v ) 31.5 µL; R ) CO2Me, v ) 28.5 µL) for 30 min at room
temperature. The solution turned from red to green (R d
CO2Me) or brownish purple (R ) Tol, Ph, CH3CdCH2, nPr).
The solvent was then concentrated, and Et2O was added.
Brown or green solids precipitated, were collected by filtration,
and then were washed with pentane. In a similar procedure,
the complex 2f was obtained by reacting 3 equiv of CF3CCH
with complex 1 as a green powder. Yields: 2a (R ) Tol), 202
mg, 95%; 2b (R ) Ph), 198 mg, 95%; 2c (R ) CH3CdCH2),
178 mg, 95%; 2d (R ) nPr), 184 mg, 90%; 2e (R ) CO2Me),
195 mg, 85%; 2f (R ) CF3), 165 mg, 80%.
often observed in coupling or insertion processes. In the
products the most electron-releasing alkyne substituent
is adjacent to S: thus, if R ) Ph, Tol, nPr the MeSCRd
CH ether is formed (11a ) via a 1,2-insertion, but when
R ) CO2Me, CF3, i.e., is strongly electronegative, then
the MeSCHdCR ether is formed (11b) via a 2,1-
insertion (Scheme 2). When L ) CNR, complexes 7 and
8 are the final products. When L ) CS2 is added to 2,
the initially formed 11a or 11b gives the expected final
product 9 or 10 by insertion of CS2 into the Mo-C σ
bond. When L ) RCCH, the second alkyne again inserts
into the Mo-C σ-bond of 11a or 11b in such a way that
the hydrogen-bearing alkyne carbon atom always ends
up σ-bonded to molybdenum. For R ) CO2Me, CF3, the
outcome is therefore 12b and reductive elimination
gives the thiophenium complexes 6. When R ) Ph, Tol,
the same insertion gives 12a and a further 1,4-SMe
migration through the metallacycle is needed to get the
six-membered metallacycle 5 in which the SMe is borne
by the less sterically hindered carbon atom (Scheme 2).
This step is strongly reminiscent of the mechanism
suggested by Davidson et al. for the formal insertion of
an alkyne into the C-S bond of a thio-alkenyl
species.11d,34
1
2a . H NMR (CD3COCD3, room temperature; δ): 12.90 (s,
1H, TolCCH), 7.15, 6.57 (2 × d, 4H, CH3C6H4), 6.64 (s, 10H,
C5H5), 2.44 (s, 3H, CH3C6H4), 2.31 (s, 3H, SCH3), 2.14 (s, 3H,
1
SCH3), 2.09 (s, 3H, SCH3). H NMR (CD2Cl2, 204 K; δ): 12.89
(s, 1H, TolCCH), 7.07, 6.35 (2d, J HH ) 8 Hz, 2 × 2H, CH3C6H4),
6.46 (s, 5H, C5H5), 6.27 (s, 5H, C5H5), 2.28 (s, 3H, CH3C6H4),
2.10 (s, 3H, SCH3), 1.96 (s, 3H, SCH3), 1.90 (s, 3H, SCH3).
13C{1H} NMR (CD2Cl2, 25 °C; δ): RCCH not observed, 150.0,
137.8, 128.5, 121.6 (CH3C6H4), 101.6 (C5H5), 43.1, 21.1, 19.2,
18.9 (CH3C6H4, 3 × SCH3). Anal. Calcd for C22H27BF4Mo2S3:
C, 39.6; H, 4.0. Found: C, 38.4; H, 4.0.
2b. 1H NMR (CD2Cl2, 25 °C; δ): 12.77 (s, 1H, PhCCH), 7.32,
7.19, 6.51 (m, 5H, C6H5), 6.38 (s, 10H, C5H5), 2.37 (s, 3H,
SCH3), 2.06 (s, 3H, SCH3), 1.98 (s, 3H, SCH3). 1H NMR
(CD2Cl2, 215 K; δ): 12.88 (s, 1H, PhCCH), 7.28-6.44 (m, 5H,
C6H5), 6.47 (s, 5H, C5H5), 6.27(s, 5H, C5H5), 2.32 (s, 3H, SCH3),
1.98 (s, 3H, SCH3), 1.92 (s, 3H, SCH3). 13C{1H} NMR (CD2Cl2,
25 °C; δ): RCCH not observed, 153.1, 128.4, 127.4, 121.3
(C6H5), 101.7 (C5H5), 43.6 (SCH3), 19.5 (SCH3), 19.1 (SCH3).
13C{1H} NMR (CD2Cl2, 208 K; δ): 290.1 and 279.0 (RCCH),
152.9, 127.6, 126.5, 120.2 (C6H5), 101.8, 100.1 (C5H5), 30.9
(SCH3), 20.0 (SCH3), 19.4 (SCH3). Anal. Calcd for C21H25BF4-
Mo2S3: C, 38.6; H, 3.8.Found: C, 37.4; H, 3.8.
Elemental analyses for 2a ,b were obtained under nitrogen
on three independently prepared pure samples (NMR grade),
but unreliable data were obtained, probably because the
compounds slowly evolved with partial loss of alkyne, which
could explain the slight lowering of the amount percent of
carbon.
2c. 1H NMR (CD2Cl2, 25 °C; δ): 12.92 (s, 1H, CH2dC(CH3)-
CCH), 6.40 (s, 10H, C5H5), 4.64, 4.09 (2s, 2 × 1H, CH3CdCH2),
2.22 (s, 3H, CH3CdCH2), 2.10 (s, 3H, SCH3), 2.01 (s, 3H, SCH3),
1.91 (s, 3H, SCH3).
Con clu sion
Transformations of terminal alkynes at the {Mo2Cp2-
(µ-SMe)3+} core show that the bis(nitrile) complex
[Mo2Cp2(µ-SMe)3(CH3CN)2](BF4) (1) provides a pro-
tected but readily accessible bimetallic site for substrate
transformations. Hydrocarbon ligands weaken one Mo-S
bond to generate a coordination site together with C-S
coupling. Our studies have demonstrated that alkyne
dimerization or functionalization can be promoted by a
C-S coupling at the bimetallic framework {Mo2Cp2(µ-
SMe)3}. It is noteworthy that fine modifications of such
a bimetallic site, involving steric constraint by replace-
ment of two thiolate bridges (µ-SMe)2 with a µ-η2-S2CH2
ligand, seem to have a significant influence on its
activity.7 In conclusion, we have described well-defined
syntheses of sulfur-rich dimolybdenum compounds con-
taining alkyne, acetylide, and vinylidene ligands and
established their structural relationships using spec-
troscopic and X-ray diffraction methods. Further trans-
formations of these species are now under investigation.
2d . 1H NMR (CD3COCD3, 25 °C; δ): 12.24 (s, 1H, nPrCCH),
6.54 (s, 10H, C5H5), 2.23 (s, 3H, SCH3), 2.04 (s, 3H, SCH3),
1.90 (s, 3H, SCH3), 1.14 (m, 2H, (CH2)2), 0.80 (t, J HH ) 7.4 Hz,
3H, (CH2)2CH3).
2e. 1H NMR (CD3COCD3, 25 °C; δ): 13.17 (s, 1H MeCO2-
CCH), 6.82, 6.77 (2 × s, 2 × 5H, 2 × C5H5), 3.67 (s, 3H, CH3-
COOMe), 2.31 (s, 3H, SCH3), 2.17 (s, 3H, SCH3), 2.12 (s, 3H,
SCH3). 13C NMR (CD2Cl2, 25 °C; δ): 272.3 (d, J CH ) 156.5 Hz,
Exp er im en ta l Section
Gen er a l P r oced u r es. The reactions were performed under
nitrogen using standard Schlenk techniques. Solvents were
deoxygenated and dried by standard methods. IR spectra were
recorded on a Perkin-Elmer 1430 spectrophotometer from KBr
pellets. Chemical analyses were performed by the Centre de
Microanalyses du CNRS, Vernaison, France. NMR spectra (1H,
13C,19F) were recorded on either a Bruker AC300 or AMX3 400
spectrometer and were referenced to SiMe4 (1H, 13C) or CFCl3
(19F). The spectroscopic data for 2d and 5a have been revised10
RCCH), 266.0 (s, RCCH), 185.7 (s, CO2Me), 103.2 (d, J CH
)
181.0 Hz, C5H5), 101.7 (d, J CH ) 181.0 Hz, C5H5), 43.6 (q, J CH
) 142.0 Hz, CO2CH3), 21.3, 21.2 (q, J CH ) 142.0 Hz, SCH3).
IR (KBr pellets; cm-1): 1690 (s) ν(CO), 1150-1050 (s) ν(BF).
2f. 1H NMR (CD2Cl2, 25 °C; δ): 12.96 (s, 1H, CF3CCH), 6.68
(s, 5H, C5H5), 6.61 (s, 5H, C5H5), 2.17 (s, 3H, SCH3), 2.15 (s,
3H, SCH3), 2.10 (s, 3H, SCH3). 19F NMR (CD2Cl2, 25 °C; δ):
-61.1 (s, CF3CCH), -149.7 (BF4-). 13C{1H} NMR (CD3COCD3,
25 °C; δ): 254.0 (q, J CF ) 30.3 Hz, CF3CCH), 263.5 (m,
CF3CCH), 104.2 (C5H5), 103.5 (C5H5), 22.9 (SCH3), 22.3 (SCH3).
Anal. Calcd for C16H20BF7Mo2S3: C, 29.8; H, 3.1. Found: C,
29.9; H, 3.3.
using new H and 13C spectra. Literature methods were used
1
for the preparation of [Cp2Mo2(µ-SMe)3(CH3CN)2](BF4) (1).9
(33) (a) Adams, R. A.; Chen, L.; Wu, W. Organometallics 1994, 13,
1257. (b) Torres, M. R.; Perales, A.; Ros, J . Organometallics 1988, 7,
Syn th esis of [Mo2Cp 2(µ-SMe)3(µ-η1: η2-CCR] (3). To a
solution of [Mo2Cp2(µ-SMe)3(RCCH)](BF4) (0.2 g: 2a , 0.30
mmol; 2b, 0.31 mmol; 2c, 0.32 mmol; 2d , 0.32 mmol; 2e, 0.31
1223.
(34) Agh-Atabay, N. M.; Davidson, J . L. J . Chem. Soc., Dalton Trans.
1992, 3531.

1240 Organometallics, Vol. 20, No. 6, 2001
Schollhammer et al.
mmol) in CH2Cl2 was added a slight excess of Et3N (1.5 equiv).
The solution quickly turned green. After the mixture was
stirred for a few minutes at ambient temperature, the solvent
was evaporated and the compounds 3 were extracted with
diethyl ether (3 × 10 mL). The diethyl ether was then removed
in vacuo from the pooled extracts. Washing the residue with
cold pentane gave 3 as brownish powders. Yields: 3a (R )
Tol), 121 mg, 70%; 3b (R ) Ph), 131 mg, 75%; 3c (R ) CH3Cd
CH2), 118 mg, 70%; 3d (R ) nPr), 110 mg, 65%; 3e (R )
CO2Me), 68 mg, 40%.
solid precipitated. It was collected by filtration and then
washed with pentane. Yield: 4e (R ) H), 175 mg, 95%,
1
4e. H NMR (CD2Cl2, 25 °C; δ): 6.44 (s, broad, 5H, C5H5),
6.00 (s, broad, 5H, C5H5), 5.64 and 5.20 (AB, J HH ) 18.7 Hz,
2H, dCdCH2), 1.95 (s, 3H, SCH3), 1.60 (s, 3H, SCH3), 1.42 (s,
3H, SCH3). 13C{1H} NMR (CDCl3, 25 °C; δ): 371.5 (dCdCH2),
99.9 (C5H5), 94.3 (C5H5), 87.1 (dCdCH2), 21.8 (SCH3), 9.4
(SCH3), 6.8 (SCH3).
Rea ction of [Mo2Cp 2(µ-SMe)3(RCCH)](BF 4) (2a ,b,d -f)
w ith Ad d ition a l RCCH. A solution of the alkyne complex
[Mo2Cp2(µ-SMe)3(RCCH)](BF4) (0.2 g: 2a , 0.30 mmol; 2b, 0.31
mmol; 2d , 0.32 mmol; 2e, 0.31 mmol; 2f, 0.31 mmol) in CH2Cl2
(15 mL) was stirred in the presence of an excess (4 equiv) of
the same RCCH alkyne (R ) Tol, v ) 154 µL; R ) Ph, v ) 136
µL; R ) nPr, v ) 126 µL; R ) CO2Me, v ) 110 µL; CF310) for
24 h at room temperature. The solution turned brownish green.
The solvent was then concentrated, and Et2O was added.
Brownish green solids precipitated. They were collected by
filtration and then washed with pentane. Yields: 5a (R ) Tol),
164 mg, 70%; 5b (R ) Ph), 175 mg, 75%; 5c (R ) nPr), 143
mg, 65%; 6a (R ) CF3), 96 mg, 42% yield; 6b (R ) CO2Me),
100 mg, 45%.
5a .10 1H NMR (CD3COCD3, 25 °C; δ): [7.80 (d, J HH ) 8.5
Hz, 2H), 7.36 (d, J HH ) 8.5 Hz, 2H), 7.02 (d, J HH ) 8.5 Hz,
2H), 6.58 (J HH ) 8.5 Hz, 2H, d)] 2 × C6H4CH3, 7.12 and 5.03
(2 × d, J HH ) 1.4 Hz, 2 × 1H, -CHdCRCHdCR-), 5.56 (s,
5H, C5H5), 5.39 (s, 5H, C5H5), 2.45, 2.42, 2.28, 2.24, 1.86 (5 s,
5 × 3H, 2 × C6H4CH3 and 3 × SCH3). 13C{1H} NMR (CD2Cl2,
25 °C; δ): 141.7, 136.6, 136.5, 136.0, 132.2, 130.1, 129.4, 128.4,
127.2, 126.7 (TolCdCHdCToldCHSMe), 98.5 (C5H5), 94.3
(C5H5), 21.2, 20.9, 26.1, 22.9, 19.7 (2 × C6H4CH3 + 3 × SCH3).
Anal. Calcd for C31H35BF4Mo2S3: C, 47.6; H, 4.5. Found: C,
47.3; H, 4.4.
1
3a . H NMR (CDCl3, 25 °C; δ): 6.97 (2d, 4H, J HH ) 8.0 Hz,
CH3C6H4), 5.18 (s, 10H, C5H5), 2.29 (s, 3H, CH3C6H4), 1.72 (s,
3H, SCH3), 1.62 (s, 3H, SCH3), 1.48 (s, 3H, SCH3).
3b. 1H NMR (CDCl3, 25 °C; δ): 7.26 & 7.06 (2m, 5H, C6H5),
5.20 (s, 10H, C5H5), 1.69 (s, 3H, SCH3), 1.63 (s, 3H, SCH3),
1.48 (s, 3H, SCH3). Anal. Calcd for C21H24Mo2S3: C, 44.7; H,
4.0. Found: C, 44.6; H, 4.4.
3c. 1H NMR (CDCl3, 25 °C; δ): 5.26 (s, 10H, C5H5), 5.15,
4.80 (2s, 2 × 1H, CH3CdCH2), 1.72. (s, 3H, SCH3), 1.60 (s,
6H, 2 × SCH3), 1.42 (s, 3H, CH3CdCH2).
1
3d . H NMR (Tol-d8, 25 °C; δ): 5.07 (s, 10H, C5H5), 1.81 (t,
J HH ) 7.0 Hz, 2H, CH2CH2CH3), 1.62 (s, 3H, SCH3), 1.59 (s,
3H, SCH3), 1.54 (s, 3H, SCH3), 1.32 (sext, J HH ) 7.2 Hz, 2H,
CH2CH2CH3), 0.84 (t, J ) 7.4 Hz, 3H, CH2CH2CH3).
1
3e. H NMR (CDCl3, 25 °C; δ): 5.52 (s, 10H, C5H5), 3.63 (s,
3H, CO2CH3), 1.61 (s, 3H, SCH3), 1.48 (s, 3H, CH3), 1.37 (s,
3H, CH3).
Syn th esis of [Mo2Cp2(µ-SMe)3(µ-η1:η2-CdCHR](BF4) (4a-
d ). To a solution of [Mo2Cp2(µ-SMe)3(µ-CCR)] (0.2 g: 3a , 0.35
mmol; 3b, 0.35 mmol; 3c, 0.38 mmol; 3d , 0.38 mmol) in Et2O
was added 1 equiv of H[BF4]‚Et2O. Blue solids of [Mo2Cp2(µ-
SMe)3(µ-CdCHR](BF4) precipitated from the solution and were
collected by filtration and then washed with pentane Yields:
4a (R ) Tol), 228 mg, 98%; 4b (R ) Ph), 217 mg, 95%; 4c (R
) CH3CdCH2), 222 mg, 95%; 4d (R ) nPr), 225 mg, 96%.
5b. 1H NMR (CD3COCD3, 25 °C; δ): δ 7.91 and 7.53 (m,
5H, PhCdCHdCPhdCHSMe), 7.19 & 6.70 (m, 5H, PhCdCHd
CPhdCHSMe), 7.14 (d, J HH ) 1.3 Hz, 1H, PhCdCHdC(Ph)d
1
4a . H NMR (CD2Cl2, 25 °C; δ): 7.65 (s, 1H, dCdC(Tol)H),
7.09 (d, 2H, CH3C6H4), 6.90 (d, 2H, CH3C6H4), 6.02 (s, 10H,
C5H5), 2.29 (s, 3H, CH3C6H4), 1.85 (s, 3H, SCH3), 1.68 (s, 3H,
SCH3), 1.50 (s, 3H, SCH3). Anal. Calcd for C22H27BF4Mo2S3:
C, 39.6; H, 4.0. Found: C, 37.4; H, 4.7.
4b. 1H NMR (CD3COCD3, 25 °C; δ): 7.99 (1H, s, dCdC(Ph)-
H), 4.78-7.15 (5H, m, C6H5), 6.28 (10H, s, C5H5), 1.93 (3H, s,
SCH3), 1.76 (3H, s, SCH3), 1.55 (3H, s, SCH3). 13C{1H} NMR
(CDCl3, 25 °C; δ): 368.4 (dCdCHPh), {(131.6, s), (130.3, dt,
J CH ) 162.0 Hz, J CH ) 7.3 Hz), (129.1, dm, J CH ) 164.0 Hz),
(128.9, dm, J CH ) 165.0 Hz) C6H5}, 115.4 (d, J CH ) 163.0 Hz,
CHSMe), 5.60 (s, 5H, C5H5), 5.40 (s, 5H, C5H5), 5.05 (d, J HH
)
1.3 Hz, 1H, PhCdCHdC(Ph)dCHSMe), 2.45 (s, 3H, SCH3),
2.27 (s, 3H, SCH3), 1.87 (s, 3H, SCH3). 13C{1H} NMR (CD2Cl2,
25 °C; δ): 152.8, 138.9, 132.4, 130.9, 130.0, 129.2, 127.9, 127.1,
126.9, 126.8 (PhCdCHdCPhdCHSMe), 98.6 (C5H5), 94.4
(C5H5), 23.8 (SCH3), 15.7 (SCH3), 11.1 (SCH3). Anal. Calcd for
C
29H31BF4Mo2S3: C, 46.2; H, 4.1. Found: C, 46.4; H, 4.2.
1
5c. H NMR (CDCl3, 25 °C; δ): 6.35 (s, broad, 1H, (nPr)Cd
CHdC(nPr)dCHSMe), 5.50 (s, 5H, C5H5), 5.13 (s, 5H, C5H5),
4.29 (s, broad, 1H, (nPr)CdCHdC(nPr)dCHSMe), 2.40 (m, 2H,
(CH2)2), 2.26 (s, 3H, SCH3), 1.90 (m, 4H, (CH2)2), 1.88 (s, 3H,
dCdCHPh), 98.2 (d, J CH ) 181.0 Hz, C5H5), 19.4 (q, J CH
141.0 Hz, SCH3), 10.6 (q, J CH ) 141.0 Hz, SCH3), 6.7 (q, J CH
)
)
141.0 Hz, SCH3). Anal. Calcd for C21H25BF4Mo2S3: C, 38.6;
H, 3.8. Found: C, 37.8; H, 4.0.
Repeated poor analytical results were obtained for spec-
trospically (NMR) pure samples of 4a ,b for reasons similar to
those for 2a ,b (see above).
4c. 1H NMR (CD3COCD3, 25 °C; δ): 7.46 (s, 1H, dCdCRH),
6.27 (s, 10H, C5H5), 5.31, 4.97 (2 × m, 2 × 1H, CH3CdCH2),
1.92. (s, 3H, SCH3), 1.68 (s, 3H, SCH3), 1.58 (s, 3H, SCH3),
1.52 (q, J HH ) 0.7 Hz, 3H, CH3CdCH2).
SCH3), 1.79 (s, 3H, SCH3), 1.40 (m, 2H, (CH2)2), 1.17 (t, J HH
7.2 Hz, 3H, CH3), 0.96 (t, J HH ) 7.2 Hz, 3H, CH3).
)
6a .10 1H NMR (CD3COCD3, 25 °C; δ): 5.97 (s, 10H, C5H5),
3.38 (s, 2H, C4(CF3)2H2SCH3+), 2.73 (s, 3H, C4(CF3)2H2SCH3+),
2.33 (s, 3H, SCH3), 2.10 (s, 3H, SCH3). 19F NMR (CD3COCD3,
25 °C; δ): -51.3 (s, C4(CF3)2H2SCH3+), -150.3 (s, BF4-). Anal.
Calcd for C19H21BF10Mo2S3: C, 30.9; H, 2.8. Found: C, 30.6;
H, 3.0.
6b. 1H NMR (CD3COCD3, 25 °C, δ): 5.84 (s, 10H, C5H5),
3.67 (s, 2H, C4(CO2CH3)2H2SCH3+), 3.33 (s, 2H, C4(CO2-
CH3)2H2SCH3+), 2.70 (s, 3H, C4(CO2CH3)2H2SCH3+), 2.13 (s,
3H, SCH3), 1.95 (s, 3H, SCH3).
4d . 1H NMR (CD2Cl2, 25 °C; δ): 6.60 (s, broad, 1H, dCd
C(nPr)H), 6.07 (s, 10H, C5H5), 1.89 (s, 3H, SCH3), 1.68 (m, 2H,
(CH2)2), 1.57 (s, 3H, SCH3), 1.48 (m, 2H, (CH2)2), 1.45 (s, 3H,
SCH3), 0.93 (t, J HH ) 7.2 Hz, 3H, (CH2)2CH3). 13C NMR
(CD2Cl2, 25 °C; δ): 365.3 (dCdCH(nPr)), 114.2 (d, J CH ) 163.2
Hz, dCdCH(nPr)), 97.4 (d, J CH ) 168.0 Hz, C5H5), 25.0 (t, J CH
Rea ction of [Mo2Cp 2(µ-SMe)3(RCCH)](BF 4) (2b,e) w ith
RNC (R ) tBu , Xylyl). A solution of [Mo2Cp2(µ-SMe)3-
(PhCCH)](BF4) (2b; 0.2 g, 0.30 mmol) in CH2Cl2 (15 mL) was
stirred with 1 equiv of RNC (R ) tBu, v ) 34 µL; R ) xylyl, m
) 39.3 mg) for 1 h at room temperature. The solution readily
turned orange. The solvent was then concentrated, and Et2O
was added. Orange solids precipitated. They were collected by
filtration and then washed with pentane. Yields: 7a (R ) Ph,
L ) tBuNC), 198 mg, 90%; 7b (R ) Ph, L ) xylylNC), 200 mg,
85%. The same procedure was applied to 2e (0.2 g, 0.31 mmol)
) 128.5 Hz, CH2), 13.4 (q, J CH ) 125.5 Hz, CH3), 9.9 (q, J CH
)
142.0 Hz, SCH3), 6.3 (q, J CH ) 141.1 Hz, SCH3). One SCH3
has not been assigned.
Syn th esis of [Mo2Cp 2(µ-SMe)3(µ-η1: η2-CdCH2](BF 4)
(4e). A solution of complex 1 (0.2 g, 0.32 mmol) in CH2Cl2 (15
mL) was stirred with an excess of Me3SiCCH (v ) 250 µL) for
1 h at 25 °C. The solution turned from red to blue-green. The
solvent was then concentrated, and Et2O was added. A blue

Activation of Terminal Alkynes
Organometallics, Vol. 20, No. 6, 2001 1241
Ta ble 3. Cr ysta l Da ta a n d Str u ctu r e Refin em en t Deta ilsa
3a
4b
7a
empirical formula
fw
C
22H26Mo2S3‚0.5C5H12
C21H25BF4Mo2S3
652.28
C27H36BCl2F4Mo2NS3
820.34
614.56
cryst syst
space group
a, Å
b, Å
c, Å
monoclinic
Cc
monoclinic
P21/c
monoclinic
P21/c
14.1852(8)
22.5726(10)
7.9974(3)
90.695(4)
2560.6(2)
4
1.594
1.234
1244
15.7730(15)
8.5305(6)
17.7108(7)
90.285(6)
2383.0(3)
4
1.818
1.354
1296
10.2490(6)
12.2493(12)
25.9798(17)
91.212(5)
3260.9(4)
4
1.671
1.167
1648
â, deg
V, Å3
Z
D
calcd, Mg/m3
µ, mm-1
F(000)
cryst size, mm
θ range, deg
index ranges
0.47 × 0.16 × 0.11
2.9-30.4
-20 e h e 20
-19 e k e 32
-11 e l e 6
8598
0.30 × 0.28 × 0.13
2.3-27.0
-20 e h e 2
-10 e k e 1
-22 e l e 22
6768
5206 (Rint ) 0.035)
3502
ι-scans
0.769-0.709
5206/284
0.918
0.042, 0.073
0.101, 0.083
0.30 × 0.13 × 0.05
2.3-26.9
-13 e h e 13
-2 e k e 15
-3 e l e 33
8766
7037 (Rint ) 0.020)
5077
analytical
0.950-0.906
7037/365
1.010
0.039, 0.093
0.071, 0.106
no. of rflns collected
no. of indep rflns
no. of obsd rflns with I > 2σ(I)
abs cor
5221 (Rint ) 0.015)
4835
analytical
0.896-0.669
5221/255
1.033
0.022, 0.056
0.028, 0.058
0.07(3)
T
max, Tmin
no. of data/params
goodness of fit on F2
R1, wR2 (I > 2σ(I))
R1, wR2 (all data)
Flack param
∆F range, e Å-3
+0.43 to -0.30
+0.66 to -0.50
+0.85 to -0.88
a
All measurements were made at 20 °C with Mo KR radiation, λ ) 0.710 73 Å, on a Nonius CAD4 diffractometer.
and afforded in the presence of an equimolar amount of tBuNC
(v ) 35 µL) the complex 8 as an orange powder Yield: 204
mg, 92%.
9a . 1H NMR (CD3COCD3, 25 °C; δ): 7.31-7.26 (m, 4H,
C6H4), 6.44 (s, broad, 5H, C5H5), 6.08 (s, 1H, -CHdCRSCH3),
5.76 (s, broad, 5H, C5H5), 2.36 (s, 3H, C6H4CH3), 2.19 (s, 3H,
SCH3), 2.14 (s, 3H, SCH3), 2.06 (s, 3H, -CHdCRSCH3).
13C{1H} NMR (CD2Cl2, 25 °C; δ): 146.6 (-CHdCR-SCH3),
142.6 (CS2), 140.0, 135.2, 130.1, 129.3 (C6H4), 133.3 (-CHd
CRSCH3), 103.1 (C5H5), 94.6 (C5H5), 26.2 (SCH3), 21.1
(C6H4CH3), 16.8 (-CHdCRSCH3), 10.3 (SCH3). Anal. Calcd for
23H27BF4Mo2S5‚CH2Cl2: C, 34.7; H, 3.7. Found: C, 34.8; H,
3.5.
9b. 1H NMR (CD3COCD3, 25 °C; δ): 7.42 (m, 5H, C6H5), 6.28
(s, broad, 5H, C5H5), 6.09 (s, 1H, -CHdCR-), 5.76 (s, broad,
5H, C5H5), 2.14 (s, 3H, SCH3), 2.10 (s, 3H, SCH3), 2.05 (s, 3H,
SCH3). 13C{1H} NMR (CD2Cl2, 25 °C; δ): 147.6, 142.3, 137.3,
132.3, 129.7, 129.2, 129.0 (C6H5 + -CHdCR- + CS2), 102.2
(C5H5), 93.9 (C5H5), 26.5 (SCH3), 19.7 (SCH3), 10.9 (SCH3). IR
(KBr pellets; cm-1): 1150-1050 (s) ν(BF). Anal. Calcd for
1
7a . H NMR (CD2Cl2, 25 °C; δ): 7.37 & 7.0 (m, 5H, C6H5),
6.76 (s, 1H, MeSCRdCH), 5.21 (s, 5H, C5H5), 5.11 (s, 5H, C5H5),
2.16 (s, 3H, SCH3), 1.96 (s, 3H, SCH3), 1.59 (s, 3H, SCH3), 1.36
(s, 9H, C(CH3)3). 13C{1H} NMR (CD2Cl2, 25 °C; δ): 166.3 (CNC-
(CH3)3), 151.8 (MeSCRdCH), 139.0, 129.2, 128.9, 127.9 (C6H5),
111.7 (MeSCRdCH), 93.8 (C5H5), 91.4 (C5H5), 59.1 (C(CH3)3),
29.9 (C(CH3)3), 23.9 (SCH3), 22.4 (SCH3), 14.1 (SCH3). IR (KBr
pellets; cm-1): 2120 (s) ν(CN), 1150-1050 (s) ν(BF). Anal.
Calcd for C26H34NBF4Mo2S3‚CH2Cl2: C, 39.5; H, 4.4; N, 1.7.
Found: C, 39.4; H, 4.4, N, 2.2.
C
7b. 1H NMR (CD2Cl2, 25 °C; δ): 7.4-6.9 (m, 8H, C6H3(CH3)2
and C6H5), 6.86 (s, 1H, MeSCRdCH), 5.27 (s, 5H, C5H5), 5.26
(s, 5H, C5H5), 2.37 (s, 6H, C6H3(CH3)2), 2.28 (s, 3H, SCH3), 1.88
(s, 3H, SCH3), 1.67 (s, 3H, SCH3). 13C{1H} NMR (CD2Cl2, 25
°C; δ): 187.1 (CNC6H3(CH3)2), 150.8 (MeSCRdCH), 139.0-
127.0 (C6H3(CH3)2 and C6H5), 111.7 (MeSCRdCH), 94.2 (C5H5),
92.1 (C5H5), 24.9 (SCH3), 23.1 (SCH3), 19.5 (CNC6H3(CH3)2),
14.5 (SCH3). IR (KBr pellets; cm-1): 2060 (s) ν(CN), 1150-
1050(s) ν(BF). Anal. Calcd for C30H34NBF4Mo2S3‚CH2Cl2: C,
42.8; H, 4.1; N, 1.6. Found: C, 42.6; H, 4.1, N, 1.7.
C
22H25BF4Mo2S5‚CH2Cl2: C, 33.9; H, 3.3. Found: C, 34.2; H,
3.5.
10. 1H NMR (CD3COCD3, 25 °C; δ): 7.93 (s, 1H, CH3SCHd
CR-), 6.34 (s, broad, 5H, C5H5), 5.74 (s, broad, 5H, C5H5), 3.72
(s, 3H, CO2CH3), 2.66 (s, 3H, CH3SCHdCR), 2.17 (s, 3H,
SCH3), 2.15 (s, 3H, SCH3). 13C{1H} NMR (CD3COCD3, 25 °C;
δ): 152.0 (CH3SCHdCR-), 163.3 (CO2CH3), 142.5 (CS2), 127.1
(CH3SCHdCR-), 102.9 (C5H5), 94.4 (C5H5), 52.6 (CO2CH3),
25.7 (CH3SCHdCR), 20.5 (SCH3), 10.2 (SCH3). Anal. Calcd for
1
8. H NMR (CDCl3, 25 °C; δ): 6.83 (s, 1H, CRdCHSCH3),
5.45 (s, 5H, C5H5), 5.11 (s, 5H, C5H5), 3.58 (s, 3H, CO2CH3),
2.37 (s, 3H, CRdCHSCH3), 2.26 (s, 3H, SCH3), 1.71 (s, 3H,
SCH3), 1.41 (s, 9H, C(CH3)3). 13C NMR (CDCl3, 25 °C; δ): 175.6
(CO2CH3), 164.2 (CNC(CH3)3), 129.6 (CRdCHSCH3), 100.2
(CRdCHSCH3), 93.7 (C5H5), 91.5 (C5H5), 58.5 (C(CH3)3), 51.8
(CO2CH3), 29.6 (C(CH3)3), 23.6 (SCH3), 21.7 (CRdCHSCH3),
13.4 (SCH3).
Reaction of [Mo2Cp2(µ-SMe)3(RCCH)](BF4) (2a,b,e) with
CS2. A solution of the complex [Mo2Cp2(µ-SMe)3(RCCH)](BF4)
(0.2 g: 2a , 0.30 mmol; 2b, 0.31 mmol; 2e, 0.31 mmol) in CH2Cl2
(15 mL) was stirred with excess CS2 (2 mL) for 2 h at room
temperature. The solution turned brownish red. The solvent
was then concentrated, and Et2O was added. Brown solids
precipitated. They were collected by filtration and then washed
with pentane. Yields: 9a (R ) Tol), 184 mg, 80%; 9b (R )
Ph), 186 mg, 85%; 10 (R ) CO2Me), 189 mg, 86%.
C
18H23BF4Mo2O2S5: C, 30.4; H, 3.2. Found: C, 30.2; H, 3.3.
Cr ysta l Str u ctu r e Deter m in a tion s of 3a , 4b, a n d 7a .
Pertinent data are summarized in Table 3. In general, the
structures were refined with anisotropic displacement param-
eters for non-hydrogen atoms and hydrogen atoms were subject
to riding constraints during refinement.35 However, the hy-
drogen atoms attached to C5 in 4b and to C9 in 7a were
located in difference syntheses and their parameters were then
(35) Programs used: Sheldrick, G. M. SHELX97-Programs for
Crystal Structure Analysis (Release 97-2); Institu¨t fu¨r Anorganische
Chemie der Universita¨t, Tammanstrasse 4, D-3400 Go¨ttingen, Ger-
many, 1998. Farrugia, L. J . WinGX-A Windows Program for Crystal
Structure Analysis. J . Appl. Crystallogr. 1999, 32, 837.

1242 Organometallics, Vol. 20, No. 6, 2001
Schollhammer et al.
successfully refined. The crystal of 3a contained highly dis-
ordered solvent, believed to be n-pentane, which was modeled
approximately by including the seven most highly populated
atomic sites in the structure factor calculations as C atoms
with 50% occupancy. The position of each site was taken from
a difference synthesis, and subsequently, only its Uiso param-
eter was refined. Crystals of 7a contain ordered dichloro-
methane.
We thank the CNRS, the EPSRC, Glasgow University,
and the University of Brest for financial support.
Su p p or tin g In for m a tion Ava ila ble: For 3a , 4b, and 7a ,
tables giving details of structure determinations, non-hydrogen
atomic positional parameters, all bond distances and angles,
anisotropic displacement parameters, and hydrogen atomic
coordinates. This material is available free of charge via the
Internet at http://pubs.acs.org.
Ack n ow led gm en t. We are grateful to N. Kervarec
and R. Pichon for the recording of two-dimensional NMR
spectra on a Bruker DRX 500 (500 MHz) spectrometer.
OM000966J