Metallathiirenes. 4. Thioaroyl complexes of molybdenum(II) and tungsten(II)

Article abstract of DOI:10.1021/om030261s

Synthetic routes to a range of thioaroyl complexes of tungsten and molybdenum were reported. The synthesis precludes hyperconjugation into the metallathiirene system which reduces the stability but significantly enhances the reactivity and synthetic utility. Results showed that methylthiirane can be used as an effective sulfur transfer reagent too.

Full text of DOI:10.1021/om030261s

3502
Organometallics 2003, 22, 3502-3512
Meta lla th iir en es. 4.1 Th ioa r oyl Com p lexes of
Molybd en u m (II) a n d Tu n gsten (II)
Darren J . Cook and Anthony F. Hill*
Research School of Chemistry, Institute of Advanced Studies, Australian National University,
Canberra, Australian Central Territory, Australia
Received April 9, 2003
Synthetic routes to a range of thioaroyl complexes of tungsten and molybdenum are
reported. Successive treatment of [M(CO)6] (M ) Mo, W) with LiC6H4OMe-4‚LiBr, (CF3-
CO)2O, and 2,2-bipyridyl (bipy) provides [M(tCC6H4OMe-4)Br(CO)2(bipy)], which react with
methylthiirane to provide the thioaroyl complexes [M(η2-SCC6H4OMe-4)Br(CO)2(bipy)] and
the dithiocarboxylate complexes [M(η2-S2CC6H4OMe-4)Br(CO)2(bipy)]. [Mo(tCC6H4Me-4)-
(CO)2{HB(pz)3}] (pz ) pyrazol-1-yl), [Mo(tCC6H4OMe-4)(CO)2{HB(pz)3}] (obtained from [Mo-
(tCC6H4OMe-4)Br(CO)2(γ-picoline)2] and K[HB(pz)3]), and [Mo(tC4H3S-2)(CO)2{HB(pz)3}]
(obtained directly from [Mo(CO)6], 2-thienyllithium, (CF3CO)2O, and K[HB(pz)3]) react with
methylthiirane to provide primarily [Mo(η2-SCR)(CO)2{HB(pz)3}] in addition to small
amounts of the corresponding dithiocarboxylates [Mo(η2-S2CR)(CO)2{HB(pz)3}], which also
arise from treatment of [Mo(η2-SCR)(CO)2{HB(pz)3}] with methylthiirane or elemental sulfur.
[Mo(tCC6H2Me3-2,4,6)(CO)2{HB(pz)3}] failed to react with methyllirane, while [Mo(tCC6H4-
OMe-4)(CO)2(η-C5H5)] provided exclusively the dithiocarboxylate derivative. The mixed
selenothiocarboxylates [Mo(η2-SSeCR)(CO)2{HB(pz)3}] (R ) C6H4OMe-4, C4H3S-2) are
obtained by treating [Mo(η2-SCR)(CO)2{HB(pz)3}] with Li2Se2, while [Mo(η2-SOCC6H4Me-
4)(CO)2{HB(pz)3}] results from hydrolysis of the product of the reaction of [Mo(η2-SCC6H4-
Me-4)(CO)2{HB(pz)3}] with [Me2SSMe]BF4. Alkylation of [Mo(η2-SCC6H4Me-4)(CO)2{HB-
(pz)3}] with [Et3O]BF4 provides the thiolatocarbene salt [Mo(η2-EtSCC6H4Me-4)(CO)2{HB(pz)3}],
while the analogues [Mo(η2-MeSCC6H4Me-4)(CO)2{HB(pz)3}]BF4 and [Mo(η2-MeSCC4H3S-
2)(CO)2{HB(pz)3}]BF4 result from the reactions of [Mo(tCR)(CO)2{HB(pz)3}] with [Me2SSMe]-
BF4. The reactions of these salts with the nucleophiles Li[Et3BH] and Me3CSH provide the
thioalkyl complexes [Mo(η2-MeSCHC4H3S-2)(CO)2{HB(pz)3}], [Mo(η2-MeSCHC6H4OMe-4)-
(CO)2{HB(pz)3}], and [Mo(η2-MeSC(SCMe3)C6H4OMe-4)(CO)2{HB(pz)3}]. The heterobimetallic
thioaroyl complex [MoFe(µ-SCC6H4Me-4)(CO)5{HB(pz)3}] is obtained from the reaction of
[Mo(η2-SCC6H4Me-4)(CO)2{HB(pz)3}] with [Fe2(CO)9].
Sch em e 1. Acyl a n d Heter oa cyl Liga n d sa
In tr od u ction
The acyl ligand is ubiquitous in organotransition-
metal chemistry, while iminoacyls provide a commonly
encountered tangent to the σ-organometallic chemistry
of isonitriles. However, acyl analogues based on replace-
ment of oxygen by the heavier chalcogens (Scheme 1)
remain rare. We have recently reported general routes
to thiocarbamoyl complexes of molybdenum and tung-
sten and suggested that the thiocarbamoyl amino sub-
stituent is intimately involved in the bonding in such
“metallathiirenes”.1 We now wish to report the synthesis
of thioaroyl complexes of these metals, wherein hyper-
conjugation into the metallathiirene system is pre-
cluded, reducing the stability but significantly enhanc-
ing the reactivity and synthetic utility.
a
A ) O, S, Se, Te, NR.
densed phases, although a variety of routes exist for
their construction within a coordination complex.2 In-
deed, the first examples of thioaroyl ligands arose from
the migratory insertion reactions of σ-aryl-thiocarbonyl
complexes.3 It was shown, furthermore, that even hy-
dride ligands may undergo such processes to provide
isolable thioformyl complexes.4 Such a process is not
generally observed for hydrido-carbonyl complexes,
although it is often inferred. Since these initial studies
by Roper and co-workers, further examples have arisen
in related systems within group 8,5,6 including the
In contrast to acyl and iminoacyl chemistry, where
CO and isonitriles are readily introduced as ligands for
subsequent coupling with σ-organyls, the molecules CA
(A ) S, Se, Te) are not independently stable in con-
(2) For a review of thiocarbonyl ligands see: Broadhurst, P. V.
Polyhedron 1985, 4, 1801.
* To whom correspondence should be addressed: E-mail: a.hill@
rsc.anu.edu.au.
(1) Part 3: Anderson, S.; Cook, D. J .; Hill, A. F. Organometallics
2001, 20, 2468.
(3) (a) Clark, G. R.; Collins, T. J .; Marsden, K.; Roper, W. R. J .
Organomet. Chem. 1983, 259, 215. (b) Clark, G. R.; Collins, T. J .;
Marsden, K.; Roper, W. R. J . Organomet. Chem. 1978, 157, 23.
(4) Collins, T. J .; Roper, W. R. J . Organomet. Chem. 1978, 159, 73.
10.1021/om030261s CCC: $25.00 © 2003 American Chemical Society
Publication on Web 07/24/2003

Metallathiirenes
Organometallics, Vol. 22, No. 17, 2003 3503
Sch em e 2. Ch a lcoa cyl a n d Ar oyl Com p lexesa
Sch em e 3. P r op osed In ter m ed ia cy of Th ioa cyl
Com p lexesa
a
a
M ) Ru, Os; L ) PPh3; R ) aryl, vinyl, silyl (not all
L ) PPh3.
combinations).
SCCHR2)Cl(η-C5H5)2] (CR2 ) C(CMe3)2, cyclo-CCMe2-
(CH2)3CMe2)12a arise from the sequential treatment of
[Zr(Bu)2(η-C5H5)2] with thioketenes SdCdCR2 and HCl,
and a similar thioketene protonation sequence provides
[Co(η2-SCCHR2)(PMe3)(η-C5H5)]+ from [Co(η2-SCCR2)-
coupling of silyl and thiocarbonyl ligands;7 once again,
this is a reaction rarely observed for silyl-carbonyl
complexes.8 These transformations are summarized in
Scheme 2. The key to the stability and ready formation
of these thioacyl complexes appears to lie in the com-
bination of (i) the HSAB compatibility of sulfur and
divalent ruthenium or osmium and (ii) the adopted
pseudo-octahedral geometry, placing a π-acid (CO) trans
to the π-donor sulfur and a π-donor halide trans to the
π-acidic acyl carbon. Indeed, this arrangement is also
observed in related acyl and aroyl complexes, where the
HSAB argument alone is less convincing.9 Thus, the
unusual stability of these thioacyl examples appears
peculiar to group 8.
For earlier transition-metal triads, the migratory
insertion approach, while applicable in principle, is in
practice not suitable because no σ-organyl-thiocarbonyl
complexes exist yet for these metals. Accordingly, with
the exception of bimetallic thioacyl complexes,10,11 there
have been very few reports12 of simple mononuclear
thioacyl ligands outside group 8: the complexes [Zr(η2-
(PMe3)(η-C5H5)] (CR2 ) cyclo-CCMe2(CH2)3CMe2).12b
A
thioformyl complex has been proposed as an intermedi-
ate in the hydrogenation of [IrH(CS)(PPh3)3] to provide
[IrH2(SCH3)(PPh3)3], and in support of this, the isolable
thioformyl complex [IrCl2{C(H)dS}(CO)(PPh3)2] was
obtained by nucleophilic (hydride) attack on the thio-
carbonyl ligand of [IrCl2(CS)(CO)(PPh3)2]+.12c Thioacyl
intermediates have also been proposed in the reactions
of [M(C6F5)(CS)(PPh3)2] (M ) Rh, Ir) and [Rh(CS)(PPh3)-
(η-C5H5)] with iodomethane to provide (methylthio)-
ethylidene complexes.12d,e We have also had reason to
invoke thioaroyl intermediates in the formation of the
unusual scorpionate complex [W(η2-S2CR′)(CO)2{κ3-HB-
(SCH2R)(pz)2}] (Scheme 3; hereafter R1 ) C6H4Me-4,
R2 ) C6H4OMe-4, R3 ) C4H3S-2, pz ) pyrazolyl).13
Roper’s alternative synthetic approach to thioacyls
involved the addition of elemental chalcogens to the
alkylidyne complex [Os(tCR)Cl(CO)(PPh3)2] to provide
what remains, after two decades, the only complete
series of chalcoacyl complexes [Os(η2-ACR)Cl(CO)-
(PPh3)2] (Scheme 2; A ) S, Se, Te).14 This approach
would appear attractive for groups 5-7, wherein alkyli-
dyne complexes are readily available in a range of
oxidation states, geometries, and coordination environ-
ments via a variety of synthetic protocols.15 This has,
however, not proven to be the case: Stone showed that
elemental sulfur or selenium adds to the alkylidyne
(5) (a) Elliott, G. P.; Roper, W. R. J . Organomet. Chem. 1983, 250,
C5. (b) Elliott, G. P.; Roper, W. R.; Waters, J . M. Chem. Commun. 1982,
811. (c) Rickard, C. E. F.; Roper, W. R.; Woodgate, S. D.; Wright, L. J .
J . Organomet. Chem. 2001, 623, 109. (d) Rickard, C. E. F.; Roper, W.
R.; Woodgate, S. D.; Wright, L. J . J . Organomet. Chem. 2000, 607, 27.
(6) (a) Bedford, R. B.; Hill, A. F.; White, A. J . P.; Williams, D. J .
Angew. Chem., Int. Ed. Engl. 1996, 35, 95. (b) Cannadine, J .; Hector,
A. L.; Hill, A. F., Organometallics 1992, 11, 2323.
(7) (a) Rickard, C. E. F.; Roper, W. R.; Salter, D. M.; Wright, L. J .
Organometallics 1992, 11, 3931. (b) Attar-Bashi, M. T.; Rickard, C. E.
F.; Roper, W. R.; Wright, L. J .; Woodgate, S. D. Organometallics 1998,
17, 504.
(8) Woo, H.-G.; Freeman, W. P.; Tilley, T. D. Organometallics 1992,
11, 2198.
(9) (a) Roper, W. R.; Wright, L. J . J . Organomet. Chem. 1977, 142,
C1. (b) Roper, W. R.; Taylor, G. E.; Waters, J . M.; Wright, L. J . J .
Organomet. Chem. 1978, 157, C27. (c) Roper, W. R.; Taylor, G. E.;
Waters, J . M.; Wright, L. J . J . Organomet. Chem. 1978, 157, 23. (d)
Bohle, D. S.; Clark, G. R.; Rickard, C. E. F.; Roper, W. R.; Wright, L.
J . J . Organomet. Chem. 1988, 358, 411. (e) Rickard, C. E. F.; Roper,
W. R.; Taylor, G. E.; Waters, J . M.; Wright, L. J . J . Organomet. Chem.
1990, 389, 375. (f) Grundy, K. R.; J enkins, J . J . Organomet. Chem.
1984, 265, 77.
(10) (a) Byrne, P. G.; Garcia, M. E.; J effery, J . C.; Sherwood, P.;
Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1987, 1215. (b) Hill, A.
F.; Nasir, B. A.; Stone, F. G. A. Polyhedron 1989, 8, 179. (c) Ellis, D.
D.; Farmer, J . M.; Malget, J . M.; Mullica, D. F.; Stone, F. G. A.
Organometallics 1998, 17, 5540.
(12) (a) Andon, W.; Ohtaki, T.; Suzuki, T.; Kabe, Y. J . Am. Chem.
Soc. 1991, 113, 7782. (b) Drews, R.; Edelmann, F.; Behrens, U. J .
Organomet. Chem. 1986, 315, 369. (c) Roper, W. R.; Town, K. G. J .
Chem. Soc., Chem. Commun. 1977, 781. (d) Faraone, F.; Tresoldi, G.;
Loprete, G. A. J . Chem. Soc., Dalton Trans. 1979, 933. (e) Tresoldi,
G.; Faraone, F.; Piraino, P. J . Chem. Soc., Dalton Trans. 1979, 1053.
(13) Hill, A. F.; Malget, J . M. J . Chem. Soc., Dalton Trans. 1997,
2003.
(14) Clark, G. R.; Marsden, K.; Roper, W. R.; Wright, L. J . J . Am.
Chem. Soc. 1980, 102, 6570. N.B.: for A ) O, the σ-aryl/carbonyl
tautomer [OsCl(R1)(CO)2(PPh3)2] is preferentially adopted. The chal-
cocarbamoyl series [Ru(η2-ACNMe2)Cl(CO)(PPh3)2] has also been
obtained from the reactions of [RuCl2(dCClNMe2)(CO)(PPh3)2] (A )
S, Se, Te) with NaAH: Roper, W. R.; Wright, A. H. J . Organomet.
Chem. 1982, 223, C59.
(11) Umland, H.; Behrens, U. J . Organomet. Chem. 1985, 287, 109.

3504 Organometallics, Vol. 22, No. 17, 2003
Cook and Hill
Sch em e 5. Bip yr id yl Th ioa r oyl Com p lexesa
Sch em e 4. Dich a lcoca r boxyla te Com p lex
F or m a tion a
a
M ) Mo, W; R ) C6H4OMe-4.
a
R ) C6H4Me-4, A ) S, Se.
(CO)2(bipy)] (M ) Cr, Mo, W) with methylthiirane were
studied. These complexes are obtained in “one pot” via
a modified Mayr synthesis: the reaction of the ap-
propriate metal hexacarbonyl with a diethyl ether
solution of LiR2 (obtained from Li and BrR2) provides
the acylate [M{dC(OLi)R2}(CO)5]. This was not isolated
but treated with trifluoroacetic anyhdride at low tem-
perature (dry ice/propanone) followed by 2,2′-bipyridyl.
This approach conveniently provides the alkylidyne
complexes in high to moderate yields (M ) W (86%),
Mo (70%), Cr (52%)) and usually in sufficient purity for
further synthetic work.
complexes [W(tCR)(CO)2(η-C5H5)] and [Mo(tCCH2-
CMe3){P(OMe)3}2(η-C5H5)] to provide dithio- or disele-
nocarboxylato complexes. Thioacyl intermediates could
be neither isolated nor observed, even when steric
encumbrance was exaggerated about the metal, e.g., in
the complexes [M(tCR)(CO)2(η-C5Me5)] (R ) C6H3Me2-
2,6),17 or when the milder sulfur transfer agent cyclo-
hexene episulfide was employed.18 Notably, in the case
of [W(η2-S2CR)(CO)2(η-C5H5)] (R ) C6H5, R1), one sulfur
can be removed by heating with excess PMe3, although
this reagent ultimately traps the resulting thioacyl
complex as the phosphosphium ylide [W{η2-SC(PMe3)R}-
(CO)2(η-C5H5)].19 Similarly, the cationic rhenium com-
plex [Re(tCR)(CO)2(η-C5H5)]+ reacted with methylthi-
irane to provide a dithiocarboxylate, for which the
intermediacies of a sulfonium carbene and a thioether-
stabilized thioaroyl were invoked (Scheme 4).20
We wish to report herein that methylthiirane can
indeed be used as an effective sulfur transfer reagent
for the synthesis of group 6 thioaroyl complexes and
that, in contrast to related thiocarbamoyl complexes, the
metallathiirene unit is synthetically versatile. Aspects
of this work have provided the basis of a preliminary
report.21
Both the molybdenum and tungsten alkylidyne com-
plexes react with methylthiirane in dichloromethane to
provide a blue precipitate and a purple supernatant. In
both cases, the precipitate is by far the major product
and is formulated as the thioaroyl complex [M(η2-SCR2)-
Br(CO)2(bipy)]. The supernatant contained approxi-
mately 5% of a complex formulated as the dithiocar-
boxylate [M(η2-S2CR2)Br(CO)2(bipy)], which is also the
sole product of the reaction of these alkylidyne com-
plexes with elemental sulfur (Scheme 5). The feature
of the thiocarbamoyl complexes which allowed their
isolation, i.e., very low solubility, also compromised full
spectroscopic characterization. The complexes are es-
sentially insoluble in all common solvents, although a
1H NMR spectrum can be obtained in d6-DMSO. This
confirms the presence of the bipyridyl and anisyl groups
but is otherwise uninformative. The appearance of four
signals for the bipyridyl ligand suggests that the
complex contains a plane of symmetry that includes the
thioaroyl ligand. This is the geometry that was observed
for the recently reported and corresponding thiocar-
bamoyl complex [Mo(η2-SCNMe2)Cl(CO)2(bipy)].1 The
complexes are, however, not sufficiently stable in DMSO
for the acquisition of useful 13C{1H} NMR data; com-
plete decomposition occurrs over a period of 30 min. The
FAB mass spectrum, however, provides confirmation of
the gross formulation with isotopic clusters observed for
the molecular ion, in addition to identifiable fragments
arising from sequential loss of the bromide and/or
carbonyl ligands. The infrared spectrum features two
carbonyl associated absorptions at 1973 s and 1870 vs
cm-1 for the molybdenum complex and 1952 s and 1856
vs cm-1 for the tungsten complex. Interestingly, the
Resu lts a n d Discu ssion
A range of alkylidyne complexes of low-valent tung-
sten and molybdenum have been investigated. Initially,
the reactions of the alkylidyne complexes [M(tCR2)Br-
(15) (a) Kim, H.-S.; Angelici, R. J . Adv. Organomet. Chem. 1987,
27, 51. (b) Mayr, A.; Hoffmeister, H. Adv. Organomet. Chem. 1991,
32, 227. (c) Mayr, A.; Ahn, S. Adv. Transition Met. Coord. Chem. 1996,
1, 1. (d) Transition Metal Carbyne Complexes; Kreissl, F. R., Ed.; NATO
ASI Series C392, Kluwer: Dordrecht, The Netherlands, 1992.
(16) Gill, D. S.; Green, M.; Marsden, K.; Moore, K.; Orpen, A. G.;
Stone, F. G. A.; Williams, I. D.; Woodward, P. J . Chem. Soc., Dalton
Trans. 1984, 1343.
(17) Anderson, S.; Hill, A. F.; Nasir, B. A. Organometallics 1995,
14, 2987.
(18) Kreissl, F. R.; Ulrich, N. J . Organomet. Chem. 1989, 361, C30.
(19) Kreissl, F. R.; Ullrich, N.; Wirsing, A.; Thewalt, U. Organome-
tallics 1991, 10, 3275.
(20) Mercando, L. A.; Handwerker, B. M.; MacMillan, Geoffroy, G.
L.; Rheingold, A. L.; Owens-Waltermire, B. E. Organometallics 1993,
12, 1559.
(21) Cook, D. J .; Hill, A. F. J . Chem. Soc., Chem. Commun. 1997,
955.

Metallathiirenes
Organometallics, Vol. 22, No. 17, 2003 3505
Sch em e 6. HB(p z)3 Th ioa r oyl Com p lexesa
ratio of intensities is reversed for the corresponding
dithiocarboxylates, such that the higher frequency
absorption is more intense, providing a profile similar
to that observed for the complex [W(η2-S2CR1)(CO)2(η-
C5H5)].16
In the case of the analogous chromium alkylidyne
complex, no reaction was observed (IR) after 3 days at
room temperature. Although curtailing our efforts in
chromium chemistry, this observation did, however,
afford some economy. Commercially available Mo(CO)6
containing 5% Cr(CO)6 could be used for the preparation
of the molybdenum thioaroyl complex, with the unre-
acted chromium alkylidyne remaining in solution.
The insolubility of the bipyridyl complexes not only
compromised their characterization but also limited
their synthetic utility, and these were not pursued
further. The complex [Mo(tCR2)Br(CO)2(γ-picoline)2]
was also investigated; however, intractable brown oils
were obtained, which were also not pursued. Suspecting
that picoline lability might have been a factor contribut-
ing to this problem, the substitution-inert complex [Mo-
(tCR2)(CO)2{HB(pz)3}] (pz ) pyrazol-1-yl) was prepared
from the reaction of [Mo(tCR2)Br(CO)2(γ-picoline)2]
with K[HB(pz)3]. The characterization of [Mo(tCR2)-
(CO)2{HB(pz)3}] does not call for comment, related
complexes having been previously reported by Stone.23
A slow reaction ensues between [Mo(tCR2)(CO)2{HB-
(pz)3}] and methylthiirane in dichloromethane to pro-
vide a dark solution which, as in the case of the bipyridyl
complexes above, contains a blue major compound in
addition to a minor purple compound. These are for-
mulated as the thioaroyl and dithiocarboxylate com-
plexes, respectively, on the basis of spectroscopic data
(vide infra). Various attempts were made to eliminate
the dithiocarboxylate side product, with only limited
success. Addition of [Bu4N]Br to activate the thiirane
leads to an increase in reaction rate, which is ac-
companied by a loss of selectivity and increase in the
proportion of dithiocarboxylate. Heating the reaction
mixture under reflux results in intractable brown oils.
Reducing the proportion of methylthiirane to 0.8 equiv
leads to a mixture of starting material and the two
products. The one intriguing observation was, however,
that by carrying out the reaction in the dark, the
dithiocarboxylate formation could be minimized. Thus,
it appears that the first sulfur addition is faster than
the second, which is also photoassisted. Pure samples
of each complex were obtained by careful cryostatic
chromatography (-40 °C) on silica gel.
a
R ) C6H4Me-4, C6H4OMe-4, C4H3S-2.
NMR time scale(s). A similar fluxionality is observed
in the case of the related thiocarbamoyl complex [Mo-
(η2-SCNMe2)(CO)2{RB(pz)3}] (R ) H,1 pz24a) and the
acyls [Mo(η2-OCR)(CO)2{HB(pz)3}] (R ) Me, Ph).24b It
is not yet clear whether this arises from a Bailar twist
process or whether interconversion is via intermediates
of reduced coordination number arising from dissocia-
tion of a pyrazolyl chelate or monodentate coordination
of the thioaroyl/thiocarbamoyl ligand. The 13C{1H} NMR
spectrum is unremarkable, other than further indicating
the chemical equivalence of the three pyrazolyl groups
and the resonance due to the thioaroyl carbon. This
appears at δ 278.0 and is downfield from that of the
corresponding dithiocarboxylate (δ 250.4). We have
recently collated data for a range of heteroacyl ana-
logues of the form [M(η2-SCR)(CO)2{HB(pz)3}] (M ) Mo,
W; R ) NR2, SR, OR, R) (see Scheme 6) and the related
thioaroyl complexes1 and find that the thioaroyl carbons
resonate to lower field of analogous thiocarbamoyl
resonances but to higher field of monothioalkoxycar-
bonyls. The infrared spectrum of [M(η2-SCR2)(CO)2{HB-
(pz)3}] includes two carbonyl-associated absorptions at
1976 and 1891 cm-1, to lower frequency of the alkyli-
dyne precursor but to substantially higher frequency of
those for the related thiocarbamoyl complex [Mo(η2-
SCNMe2)(CO)2{HB(pz)3}] (CH2Cl2: 1942, 1848 cm-1),1
suggesting a strong net acceptor role for the thioaroyl
ligand.
In a manner similar to the synthesis of [Mo(η2-SCR2)-
(CO)2{HB(pz)3}], the analogous complexes [Mo(η2-SCR)-
(CO)2{HB(pz)3}] (R ) R1, R3) were prepared from the
alkylidyne precursors [Mo(tCR)(CO)2{HB(pz)3}] and
methylthiirane in high yields. Again, dithiocarboxylate
derivatives were obtained as minor side products, which
could be removed only by low-temperature chromatog-
raphy. The spectroscopic data for these thioaroyls were
essentially comparable to those for the thioanisyl com-
plex and require no further discussion. It should,
however, be pointed out that the 2-thienyl derivative
reacted more rapidly than the tolyl and anisyl deriva-
tives, possibly due to a modest decrease in the steric
bulk of the five-membered heterocycle ring. In support
of this, we note that there is no reaction between
methylthiirane and the sterically congested complex
[Mo(tCC6H2Me3-2,4,6)(CO)2{HB(pz)3}], while the reac-
tion of [Mo(tCR2)(CO)2(η-C5H5)] with methylthiirane
provided only the dithiocarboxylate derivative [Mo(S2-
The complex [Mo(η2-SCR2)(CO)2{HB(pz)3}] is suf-
ficiently soluble to obtain satisfactory spectroscopic
data: the 1H NMR spectrum includes characteristic
resonances due to the 4-anisyl group, in addition to
three unresolved broad singlets due to the H3, H4, and
H5 protons of the pyrazolyl groups. In principle, the
three pyrazolyl groups should be chemically distinct or
have environments in the ratio of 2:1, depending on the
ground-state orientation of the thioaroyl ligand. The
observation that these are chemically equivalent sug-
1
gests that the complex is fluxional on the H (and 13C)
(22) (a) McDermott, G. A.; Dorries, A. M.; Mayr, A. Organometallics
1987, 6, 925. (b) Mayr, A.; McDermott, G. A.; Dorries, A. M. Organo-
metallics 1985, 4, 608.
(23) Bermudez, M. D.; Delgado, E.; Elliott, G. P.; Tran-Huy, N. H.;
Mayor-Real, F.; Winter, M. J . Chem. Soc., Dalton Trans. 1987, 1235.
(24) (a) Desmond, T.; Lalor, F. J .; O’Sullivan, B.; Ferguson, G. J .
Organomet. Chem. 1990, 381, C33. (b) Curtis, M. D.; Shiu, K.-B.;
Butler, W. M. J . Am. Chem. Soc. 1986, 108, 1550.

3506 Organometallics, Vol. 22, No. 17, 2003
Cook and Hill
CR2)(CO)2(η-C5H5)], which was obtained directly from
[Mo(tCR2)(CO)2(η-C5H5)] and elemental sulfur. Pre-
sumably the second sulfur addition to this complex is
considerably more rapid than for the tris(pyrazolyl)-
borate complexes, possibly due to less steric crowding
around the molybdenum center.
Sch em e 7. Electr op h ilic Beh a vior of cyclo-S8
The observed success of methylthiirane in the syn-
thesis of thioaroyl complexes can only be descibed as
fortuitous, given the failure of cyclohexene episulfide to
allow the isolation of these intermediates en route to
dithiocarboxylates18 and the failure of methylthiirane
to provide thioacyls of rhenium. The actual mechanism
for sulfur atom transfer remains unclear. The complexes
[Mo(tCR)(CO)2L] (L ) η-C5H5, η-C5Me5, HB(pz)3, HB-
(pzMe2)3) are generally inert to associative ligand
substitution at the 18-electron molybdenum centers
under these mild conditions, although substitution may
be effected photochemically via the intermediacy of
ketenyl complexes.25 The present reactions, however,
proceed in the dark, and so direct attack at the metal
center seems unlikely. Indeed, the isolable and substi-
tution-labile ketenyl complex [Mo{η2-C(dO)CR2}(NCMe)-
(CO){HB(pzMe3)3}] failed to react with methylthiirane
to generate either thioaroyl or dithiocarboxylate com-
plexes. Attack at the carbyne carbon by the sulfur seems
most likely, as proposed by Geoffroy20 for the isoelec-
tronic, though far more electrophilic, rhenium complex
[Re(tCR1)(CO)2(η-C5H5)]+. The resulting sulfonio car-
bene was then proposed to eliminate propene, to gener-
ate a putative thiaroyl complex analogous to those
described above. However, in the rhenium case this
cationic metallathiirene is presumably more prone to
nucleophilic attack by a second thiirane to generate the
final dithiocarboxylate. In the (neutral) molybdenum
chemistry, the electrophilicity appears sufficiently re-
duced to slow this second reaction and allow the
interception of the thioaroyl complex. When isolated
thiaroyl complexes were exposed to methylthiirane (or
elemental sulfur), complete conversion to the dithiocar-
boxylate was observed, although this required between
5 (C3H6S) and 7 days (S8) to proceed to completion. This
mechanism would seem plausible for sulfur atom trans-
fer from episulfides. However, one more observation
needs to be explained, and that is the slow reaction of
the thioacyl complexes with thiiranes or elemental
sulfur, when the direct synthesis of dithiocarboxylate
complexes from alkylidynes and elemental sulfur is
substantially faster, complete in hours rather than days.
It seems likely that while thiiranes may only transfer
one atom of sulfur, cyclo-S8 cannot undergo a concerted
extrusion of a single sulfur atom. cyclo-S8 may serve as
a nucleophile, illustrated by the isolation of transition-
metal complexes, e.g., [Ag(S8)2]AsF6.26 Alternatively, it
may act as an electrophile in reactions with lithium
organyls, phosphines, and cyanide. In these reactions,
the solvent dependence of kinetic data has been taken
to support rate-limiting ring opening of the S8 ring by
the nucleophile (Nu) to generate dipolar linear +Nu-
S7-S- species (Scheme 7).27 It seems plausible that the
Sch em e 8. P er ch a lcom eta lla cyclesa
a
A ) O, NR.
alkylidyne acts as a nucleophile in reactions with
elemental sulfur and that the intermediate cleaves by
delivering two atoms of sulfur in the case of group 6
metals and one atom in the case of group 8 metals
(Scheme 7). This interpretation is consistent with the
nucleophilic role of such alkylidyne complexes in their
reactions with unsaturated metal complexes23 and bo-
ranes.28 While d6 alkylidynes of the form [W(tCR)-
(CO)2L] (L ) η-C5R′5, HB(pz)3, η5-C2B9H9R′2; R′ ) H,
Me)) show ambiphilic behavior, Roper’s d8 alkylidynes
[M(tCR)Cl(CO)(PPh3)2] (M ) Ru, Os) are generally
unreactive toward nucleophiles, suggesting an electro-
philic role for the attacking chalcogen. The suggested
intermediacy of a perthioacyl ligand (A, Scheme 7) is
novel; however, support comes from related chalcomet-
allacycles (Scheme 8), which include Roper’s peroxycar-
bonyl,30 Kubota’s perthiothiocarbonyl,31 and the metal-
(28) (a) Carriedo, G. A.; Elliott, G. P.; Howard, J . A. K.; Lewis, D.
B.; Stone, F. G. A. J . Chem. Soc., Chem. Commun. 1984, 1585. (b)
Wadepohl, H.; Elliott, G. P.; Pritzkow, H.; Stone, F. G. A.; Wolf, A. J .
Organomet. Chem. 1994, 482, 243. (c) Wadepohl, H.; Arnold, U.; Kohl,
U.; Pritzkow, H.; Wolf, A. J . Chem. Soc., Dalton Trans. 2000, 3553.
(d) Wadepohl, H.; Arnold, U.; Pritzkow, H. Angew. Chem., Int. Ed.
1997, 36, 974.
(25) For a review of ketenyl complexes see: Mayr, A.; Bastos, C. M.
Prog. Inorg. Chem. 1992, 40, 1.
(26) Roesky, H. W.; Thomas, M.; Schimkowiak, J .; J ones, P. G.;
Pinkert, W.; Sheldrick, G. M. J . Chem. Soc., Chem. Commun. 1982,
895.
(29) Hill, A. F.; Wilton-Ely, J . D. E. T. Organometallics 1996, 15,
3791.
(27) (a) Bartlett, P. D.; Meguerian, G. J . Am. Chem. Soc. 1956, 78,
3710. (b) Bartlett, P. D.; Davis, R. E. J . Am. Chem. Soc. 1958, 80, 2513.
(30) Laing, K. R.; Roper, W. R. J . Chem. Soc. D 1968, 1568. (b)
Roper, W. R. J . Organomet. Chem. 1986, 300, 167.

Metallathiirenes
Organometallics, Vol. 22, No. 17, 2003 3507
Sch em e 9. Rea ction s of Th ioa r oyl Com p lexes
w ith Electr op h ilesa
lacycles arising from the cycloaddition of iminooxosul-
furanes or sulfur dioxide to group 8 alkylidynes.32
Notably, the thermal peroxycarbonyl/carbonate inter-
conversion is akin to the perthioacyl/dithiocarboxylate
rearrangement proposed in Scheme 7.
No reaction was observed between the complex [Mo-
(η2-SCR2)(CO)2{HB(pz)3}] and elemental selenium or
tellurium, even when ultrasonic irradiation was em-
ployed for a prolonged period. This observation supports
the argument that monochalcoacyl complexes are not
intermediates in the synthesis of dichalcocarboxylates
from elemental chalcogens. It was, however, possible to
add selenium to the thioacyl complex by delivering it
in a more nucleophilic form. For this purpose a solution
of dilithiodiselenide proved effective, providing instan-
taneously the mixed selenothiocarboxylate complex [Mo-
(κ2-SSeCR2)(CO)2{HB(pz)3}]. The solution of Li2Se2 could
be prepared in a separate vessel (from selenium and Li-
[Et3BH]), or alternatively, addition of Li[Et3BH] directly
to a mixture of the thioaroyl complex and elemental
selenium achieved similar yields. We are unaware of
any other examples of mixed thio-/selenocarboxylate
complexes; however, spectroscopic data confirm the
formulation, including the appearance of a molecular
ion in the FAB mass spectrum and the low-field 13C-
{1H} resonance (249.7 ppm) showing coupling to sele-
nium (1J (77Se13C) ) 23 Hz). Unfortunately, a similar
reaction was not observed using Li2Te2, and accordingly,
tellurocarboxylate ligands remain unknown.33 We have
previously noted the facile extrusion of tellurium from
LnMTeC(dS) rings.37 This contrasts with the addition
of tellurium to the metal-carbon multiple bonds of [Os-
(tCR1)Cl(CO)(PPh3)2]14 and [Os(dCH2)Cl(NO)(PPh3)2]38
to provide the telluroacyl and telluroformaldehyde
complexes [Os(η2-TeCR1)Cl(CO)(PPh3)2] and [Os(η2-
TeCH2)Cl(NO)(PPh3)2], respectively. Within group 6,
this has provided an important access to the chemistry
of telluroaldehyde and telluroketone complexes.39 The
failure of either [Mo(η2-SCR2)(CO)2{HB(pz)3}] to react
with selenium or tellurium or [Mo(tCR2)(CO)2{HB-
(pz)3}] to react with tellurium would therefore appear
to be a kinetic phenomenon rather than a reflection of
thermodynamic instability of the anticipated dichalco-
carboxylates, given that [Mo(η2-SSeCR2)(CO)2{HB(pz)3}]
was obtained via an alternative route (vide supra).
With these thioaroyl complexes in hand, we have
briefly investigated their reactivity. Roper’s group 8
examples can be alkylated on sulfur, but only by potent
alkylating agents (e.g., MeOSO2CF3),3 presumably since
a
R ) C6H4Me-4, C6H4OMe-4 (not all combinations).
coordination of the sulfur to the metal center reduces
its nucleophilicity. Furthermore, this bidentate coor-
dination, once adopted, appears to be very strongly
adhered to: e.g., the reaction of [Os(η2-SCR1)Cl(CO)-
(PPh3)2] with dithiocarbamate results in halide replace-
ment and phosphine loss rather than opening of the
osmathiirene ring.3 The alkylation of [Mo(η2-SCR1)-
(CO)2{HB(pz)3}] with Meerwein’s reagent [Et3O]BF4
occurs readily at sulfur to provide the bidentate thio-
latocarbene carbene complex [Mo(η2-EtSCR1)(CO)2{HB-
(pz)}]BF4 in 53% yield (Scheme 9). No reaction, however,
occurs with the milder alkylating agent iodomethane.
The first example of a mononuclear bidentate thiolato
carbene3 arose from alkylation of [Os(η2-SCR1)Cl(CA)-
(PPh3)2] (A ) O, NR1), although in this case the
thioether coordination was hemilabile and could be
opened by reaction with halides. More closely related
to the present example are the complexes [W(η2-MeSCH)-
(CO)2{HB(pz)3}]+ and [M(η2-MeSCR1)(CO)(L)(η-C5H5)]+
(M ) W, Mo; L ) CO, PMe3). The former40 arises from
the protonation of the thiolatocarbyne complex [W(tCS-
Me)(CO)2{HB(pz)3}], while the latter41 is obtained via
the electrophilic attack by [MeSSMe2]BF4 (synthetically
equivalent to “MeS+”) on the MtC bonds of [M(tCR1)-
(CO)L(η-C5H5)]. Accordingly, there exist sufficient pub-
lished spectroscopic data to make characterization of
[Mo(η2-EtSCR1)(CO)2{HB(pz)}]BF4 both straightforward
and unambiguous. In addition to routine characteriza-
tional data, the 13C NMR resonance attributable to the
carbene carbon appears at 248.1 ppm. This is moved to
higher field of the precursor complex and may be
(31) Kubota, M.; Carey, C. R. J . Organomet. Chem. 1970, 24, 491.
(32) (a) Hill, A. F. J . Mol. Catal. 1991, 65, 85. (b) Hill, A. F. Adv.
Organomet. Chem. 1994, 36, 159.
(33) N.B.: monotellurocarboxylate complexes have recently been
isolated for platinum and palladium, involving monodentate coordina-
tion through tellurium.34 Ditellurocarbamates and xanthates have been
mentioned in the patent literature as precursors to zinc telluride,35
and hypothetical tetratellurooxalate complexes have been the subject
of theoretical studies.36
(34) Kato, S.; Niyomura, O.; Kawahara, Y.; Kanda, T. J . Chem. Soc.,
Dalton Trans. 1999, 1677.
(35) Hiroto, U. J pn. Patent 88-126944, 1991.
(36) Mire, L. W.; Marynick, D. S. Inorg. Chem. 2000, 39, 5970.
(37) Herberhold, M.; Hill, A. F.; McAuley, N.; Roper, W. R. J .
Organomet. Chem. 1986, 310, 95.
(38) Hill, A. F.; Roper, W. R.; Waters, J . M.; Wright, A. H. J . Am.
Chem. Soc., 1983, 105, 5939.
(40) (a) Kim, H. P.; Angelici, R. J . Organometallics 1986, 5, 2489.
(b) Yu, Y. S.; Angelici, R. J . Organometallics 1983, 2, 1018. (c) Yu, Y.
S.; Angelici, R. J . Organometallics 1983, 2, 1583.
(41) (a) Kreissl, F. R.; Keller, H. Angew. Chem., Int. Ed. Engl. 1986,
25, 904. (b) Kreissl, F. R.; Schu¨tt, W.; Stegmair, C. M.; Ullrich, N.;
Keller, H.; Ostermeier, J .; Herdtweck, E. Chem. Ber. 1993, 126, 1609.
(c) Kreissl, F. R.; Schu¨tt, W.; Ostermeier, J .; Stefmair, C. M.; Ullrich,
W.; Herdtweck, E. Z. Naturforsch. 1993, 48b, 1481. (d) Kreissl, F. R.;
Stegmair, C. M. Chem. Ber. 1991, 124, 2747. (e) Ostermeier, J .; Schu¨tt,
W.; Kreissl, F. R. J . Organomet. Chem. 1992, 436, C17. (f) Schu¨tt, W.;
Ullrich, N.; Kreissl, F. R. J . Organomet. Chem. 1991, 408, C5. (g)
Ullrich, N.; Keller, H.; Stegmair, C.; Kreissl, F. R. J . Organomet. Chem.
1989, 378, C19. (h) Kreissl, F. R.; Ullrich, N. Chem. Ber. 1989, 122,
1487. (i) Ullrich, N.; Stegmair, C.; Keller, H.; Herdtweck, E.; Kreissl,
F. R. Z. Naturforsch. 1990, 45b, 921.
(39) For a review of telluroaldehyde and ketone complexes see:
Fischer, H.; Stumpf, R.; Roth, G. Adv. Organomet. Chem. 1999, 43,
125.

3508 Organometallics, Vol. 22, No. 17, 2003
Cook and Hill
compared to that observed for [Mo(η2-MeSCPh)(CO)2-
(η-C5H5)]BF4 (249.5 ppm).41i The salts [Mo(η2-MeSCR)-
(CO)2{HB(pz)3}]BF4 (R ) R2, R3) were also obtained
from the reactions of the carbyne complexes [Mo(tCR)-
(CO)2{HB(pz)3}] with [MeSSMe2]BF4. Notably, although
the thiocarbamoyl complex [Mo(η2-SCNMe2)(CO)2(η-
C5H5)] may be alkylated on sulfur with [Me3O]BF4 to
provide [Mo(η2-MeSCNMe2)(CO)2(η-C5H5)]BF4,42 the cor-
responding reaction of [Mo(η2-SCNMe2)(CO)2{HB(pz)3}
with [Et3O]BF4 fails.1
Kreissl showed that methylthiolato carbene com-
plexes obtained from the reactions of alkylidynes with
[MeSSMe2]BF4 react with a further 1 equiv of this
methylsulfonium transfer reagent to provide [W{η3-
(MeS)2CR1}(CO)2(η-C5H5)](BF4)2. The reaction of [Mo-
(η2-SCR1)(CO)2{HB(pz)3}] with [MeSSMe2]BF4 was there-
fore investigated and found to yield, after chromatog-
raphy, the neutral thiocarboxylate complex [Mo(η2-
OSCR1)(CO)2{HB(pz)3}]. This result is consistent with
the successful transfer of ‘MeS+’ to the ModC bond to
generate a cationic complex of a methyldithiotoluate,
which hydrolyzed during chromatography, presumably
due to activation at the dithioester through coordination
to the electrophilic “Mo(CO)2{HB(pz)3}+” center. This
complex extends the series [Mo(η2-SACR)(CO)2{HB-
(pz)3}] (A ) O, S, Se) and is an isomer of the aryloxy-
thiocarbonyl complex [Mo(η2-SCOR1)(CO)2{HB(pz)3}],
which we have recently reported.1 The difference in
ν(CO) frequencies for these two isomers reflects the
π-acidity of the aryloxythiocarbonyl ligand (CH2Cl2:
1994, 1878 cm-1) and the π-basicity of the thiocarbox-
ylate ligand (CH2Cl2 1959, 1855 cm-1).
[Mo(tCR3)(CO)2{HB(pz)3}], albeit in low yield (15%)
after chromatographic purification. The re-formation of
the metal-carbon triple bond via sulfur abstraction is
of interest, given that the majority of thiocarbonyl ligand
syntheses rely on the extrusion of sulfur from η2-
coordinated carbon disulfide.2
The reactivities of the bidentate methylthiolato car-
bene complexes [Mo(η2-MeSCR)(CO)2{HB(pz)3}]BF4 were
briefly investigated. Although Roper had shown that
chloride would open the osmacycle of [Os(η2-ΜeSCR1)-
Cl(CNR1)(PPh3)2]O3CF3 to provide the neutral mono-
dentate carbene complex [OsCl2{dC(SMe)R1}(CNR1)-
(PPh3)2],3 the majority of reactions of the monodentate
thiolatocarbenes LnMdCH(SMe)+ (LnM ) OsCl(CO)2-
(PPh3)2,4 OsCl(CO)(CNR1)(PPh3)2,4 Fe(CO)2(η-C5H5)43)
involve direct nucleophilic attack at the carbene carbon.
The majority of reactions of the tungsten complex [W(η2-
MeSCH)(CO)2{HB(pz)3}]+ with nucleophiles resulted in
complexes which (ultimately) retain the WCS metalla-
cyclic motif and also arise from nucleophilic attack at
the carbene carbon. Thus, e.g., the reactions with thiols
(RSH) under basic conditions provide [W(η2-MeSCHSR)-
(CO)2{HB(pz)3}], with the exceptions of hydrosulfide and
benzyl mercaptide, which instead each provide a mix-
ture of [W(tCSMe)(CO)2{HB(pz)3}] and [W(η2-MeSC-
HSMe)(CO)2{HB(pz)3}].40a A similar mixture is obtained
from the reaction of [W(η2-MeSCH)(CO)2{HB(pz)3}]+
with hydride donors (NaH, NaBH4) rather than forma-
tion of the thiolatomethyl complex [W(η2-CH2SMe)(CO)2-
{HB(pz)3}], although related complexes are known to
be stable, resulting from, e.g., the reaction of metal
carbonylates with ClCH2SMe.44
The reaction of [Mo(η2-MeSCR2)(CO)2{HB(pz)3}]BF4
with tert-butyl mercaptan in the presence of a nonnu-
cleophilic base (DBU) results in the formation of the
neutral orange bis(thioalkyl)alkyl complex [Mo{η2-MeSC-
(SCMe3)R2}(CO)2{HB(pz)3}] in high yield after chroma-
tography on alumina. In principle, two isomers are
possible, depending on which of the SMe and SCMe3
groups coordinate to the molybdenum center. Only one
isomer is apparent from the IR spectrum of the product
both in solution and in the solid state, on the basis of
the observation of two ν(CO) bands (CH2Cl2: 1950, 1820
cm-1). In contrast, Angelici obtained two isomers in a
temperature- and solvent-dependent ratio from the
reactions of the tungsten complex [W(η2-MeSCH)(CO)2-
Heterobimetallic thioacyl complexes [MFe(µ-SCR1)-
(CO)5L] (M ) Mo, W; L ) η-C5H5, η-C5Me5) result from
the addition of elemental sulfur to the bridging carbyne
ligands of the complexes [MFe(µ-CR1)(CO)5L].10,17,23 The
analogous bridging thiocarbamoyl complex [MoFe(µ-
SCNiPr2)(CO)5{HB(pz)3}] may be prepared similarly via
the sequential treatment of [Mo(tCNiPr2)(CO)2{HB-
(pz)3}] with [Fe2(CO)9] and sulfur. However, the reverse
sequence, i.e., initial addition of sulfur to generate [Mo-
(η2-SCNiPr2)(CO)2{HB(pz)3}], fails, as does the reaction
of [Mo(η2-SCNMe2)(CO)2{HB(pz)3}] with [Fe2(CO)9].1 In
contrast, treating a dichloromethane solution of [Mo-
(η2-SCR1)(CO)2{HB(pz)3}] with [Fe2(CO)9] leads to a
slow reaction, which may be accelerated ultrasonically,
to provide an orange complex. Spectroscopic data (IR,
1H and 13C{1H} NMR) confirm the identity of the
product as [MoFe(µ-SCR1)(CO)5{HB(pz)3}] by compari-
son with those previously published for the alternative
route.23 Furthermore, a molecular ion is observed in the
FAB mass spectrum, in addition to fragments arising
from loss of three, four, and five carbonyl ligands. These
two reactions, alkylation and Fe(CO)3 addition to the
thioaroyl ligand, succeed where they fail for thiocar-
bamoyl complexes, a result which is perhaps counter-
intuitive, given that the π-dative amino group of thio-
carbamoyl ligands might be expected to increase the
nucleophilicity of sulfur, relative to thioaroyl ligands.
A curious reaction occurs between [Mo(η2-SCR3)(CO)2-
{HB(pz)3}] and CuCl2 in dichloromethane; the only
isolable product is the precursor alkylidyne complex
i
{HB(pz)3}]+ with mercaptides (RS-: R ) Me, Et, Pr).
The isomerism arose from the relative positions of the
SCH3 and thiolate substituents straddling the WCS
metallacycle.40 This appears to occur in the present
example, presumably because the added steric bulk of
the anisyl (vs H) substituent exaggerates steric factors,
which are also augmented by the use of the bulky
SCMe3 group. It seems most likely that the thiolate
nucelophile attacks the WCS face opposite the sterically
cumbersome HB(pz)3 ligand, such that the SCMe3 and
Me groups are anti with respect to the WCS metalla-
cycle. The FAB mass spectrum of the complex [Mo{η2-
MeSC(SCMe3)R2}(CO)2{HB(pz)3}] includes substantial
isotope clusters attributable to the molecular ion, in
addition to loss of two carbonyl ligands and, most
(43) (a) Yu, Y. S.; Angelici, R. J . Organometallics 1983, 2, 1018. (b)
Yu, Y. S.; Angelici, R. J . Organometallics 1983, 2, 1583.
(42) Dean, W. K.; Treichel, P. M. J . Organomet. Chem. 1974, 66,
87.
(44) (a) King, R. B.; Bisnette, M. B. Inorg. Chem. 1965, 4, 486. (b)
Rudolpho de Gil, E.; Dahl, L. F. J . Am. Chem. Soc. 1969, 91, 3751.

Metallathiirenes
Organometallics, Vol. 22, No. 17, 2003 3509
Ta ble 1. Com p a r a tive Sp ectr oscop ic Da ta for
Th ioa r oyl a n d Dich a lcoca r boxyla te Com p lexes
Exp er im en ta l Section
Gen er a l P r oced u r es. All manipulations were carried out
under an atmosphere of prepurified dinitrogen using conven-
tional Schlenk and vacuum-line techniques. Solvents were
purified by distillation from an appropriate drying agent
(ethers and paraffins from sodium/potassium alloy with ben-
zophenone as indicator; halocarbons from CaH2). Light petro-
leum refers to that fraction with bp 40-60 °C.
a
δ(13C) (ppm)
ν(CO) (cm-1
)
[Mo]CR1 b
[Mo]CR2
[Mo]CR3
[Mo]SCR1
[Mo]SCR2
[Mo]SCR3
293.1
294.2
276.8
1998, 1921
1991, 1906
1996, 1913
280.4
278.0
261.6
1979, 1893
1976, 1891
1980, 1897
1H and 13C{1H} NMR spectra were recorded on Bruker WH-
400 NMR and J EOL J NM EX270 NMR spectrometers and
calibrated against internal Me4Si (1H) or CDCl3 (13C{1H}).
Unless otherwise indicated, NMR data were acquired from
saturated solutions in CDCl3 at room temperature. Infrared
spectra were recorded using Perkin-Elmer 1720-X FT-IR and
Mattson Research Series 1 spectrometers. FAB mass spec-
trometry was carried out with an Autospec Q mass spectrom-
eter using 3-nitrobenzyl alcohol as matrix. Elemental micro-
analytical data were obtained from the ICSTM microanalytical
service. Unless indicated, reagents were commercially avail-
able and used as received from commercial sources (Aldrich).
The salt K[HB(pz)3]45 was prepared according to a published
procedure. Alkylidyne precusors were generally prepared via
minor modifications of the Mayr protocol.22
[Mo]OSCR1
[Mo]SSCR1
[Mo]SSCR2
[Mo]SeSCR2
[Mo]SeSCR3
[Mo]CSOR1
251.6
249.1
250.9
249.7
249.6
284.6
1959, 1855
1953, 1871
1965, 1890
1943, 1861
1945, 1857
1993, 1879
In CH2Cl2. b Taken from ref 23. Legend: [Mo] ) Mo(CO)2{HB-
a
(pz)3}; R1 ) C6H4Me-4; R2 ) C6H4OMe-4; R3 ) C4H3S-2.
abundantly, one SCMe3 group. No peaks were assign-
able to fragmentations involving loss of the SMe group,
which is therefore presumed to be bound to the metal.
This suggests that scrambling of SMe and SCMe3
groups between coordinated and pendant positions does
not occur. The 13C NMR features a peak at δ 65.88
attributable to the tungsten-bound carbon of the alkyl
ligand, which may be compared with the values of δ
61.79 and 71.69 reported for the two isomers of [W{η2-
MeSC(SMe)H}(CO)2{HB(pz)3}].40a
P r ep a r a tion of tr a n s,cis,cis-[W(tCR2)Br (CO)2(bip y)].
Tungsten hexacarbonyl (5.30 g, 15.1 mmol) was suspended in
diethyl ether (40 mL), and 4-anisolyllithium (from Li and BrR2,
15.1 mL, 1.0 mol dm-3, 15.1 mmol) was added dropwise over
a 15 min period. The resulting dark orange solution was cooled
(dry ice/propanone) and trifluoroacetic anhydride (2.1 mL, 15
mmol) added in small portions, with stirring, until the initial
deep purple color dissipated after each addition. The resulting
deep red solution was warmed gradually to room temperature
and 2,2′-bipyridyl (2.40 g, 15.1 mmol) added, resulting in the
precipitation of crude product. The supernatant was decanted,
the solid extracted with a mixture of dichloromethane and light
petroleum (2:1), and the extract filtered through a plug of
alumina (ca. 10 × 4 cm). Concentration of the red solution and
storage at -20 °C yielded crystals of trans,cis,cis-[W(tCR2)-
Br(CO)2(bipy)]. Yield: 7.71 g (86%). IR (CH2Cl2): ν(CO) 1985
In contrast to the reaction of [W(η2-MeSCH)(CO)2-
{HB(pz)3}] with NaBH4, which provides [W(tCSMe)-
(CO)2{HB(pz)3}] and [W{η2-CH(SMe)2}(CO)2{HB(pz)3}]
(vide supra),40a a clean reaction occurs between [Mo(η2-
MeSCR)(CO)2{HB(pz)3}]BF4 and Li[Et3BH] to provide
the thiolatoalkyl complexes [Mo(η2-MeSCHR)(CO)2{HB-
(pz)3}] (R ) R2, R3) in high yield. Once again, attack by
the nucleophile (“H-”) would seem most likely to occur
opposite the bulky HB(pz)3 ligand, although this could
not be confirmed unequivocally from the spectroscopic
data. Nevertheless, these data do confirm that, in both
cases, two isomers are present in solution. In the case
of R ) 2-thienyl, the ratio of isomers is close to
comparable (ca 5:4), while for the slightly bulkier R )
C6H4OMe-2 the ratio is approximately 15:1 (in CH2Cl2).
Angelici has discussed this type of isomerism and
concluded that interconversion most probably proceeds
via simple inversion at the coordinated sulfur, rather
than dissociation of the thiolate group from tungsten.40a
The isolation of moderately stable thioaroyl complexes
of tungsten and molybdenum establishes that there is
nothing inherently unstable about them, merely that
they are reactive and that this requires careful control
of conditions during their synthesis. The reactivity is
primarily associated with the nucleophilicity of the
sulfur atom, although some reactions, such as the
addition of further methylthiirane to provide dithiocar-
boxylates, points toward electrophilic character for the
thioacyl carbon. This is further supported by the syn-
thesis of a mixed selenothiocarboxylate complex by
employing the nucleophilic reagent Li2Se2 as a selenium
delivery agent. Data for this range of dichalcocarbox-
ylate complexes are collected in Table 1. The thioaroyl
ligand, once constructed, serves as a precursor for
heterobimetallic thioaroyl complexes (bridge-assisted
metal-metal bond formation) and for thiolatocarbenes
upon electrophilic alkylation, complementing existing
routes to such complexes.
s, 1899 vs cm-1. IR (Nujol): ν(CO) 1974 s, 1875 vs cm-1 1H
.
NMR: δ 3.75 [s, 3 H, CH3], 6.69, 7.20 [(AB)2, 4 H, 3J (AB) ) 8.0
Hz, C6H4], 7.56, 8.08, 8.23, 9.22 [8 H, bipy]. FAB-MS: m/z 596
[M]+, 568 [M - CO + H]+, 538 [M - 2CO]+, 515 [M - Br]+,
369 [M - CO - Br - R2]+. Anal. Found: C, 39.4; H, 2.5; N,
4.7. Calcd for C20H15BrNO3W: C, 40.37; H, 2.54; N, 4.71.
P r ep a r a tion of [Mo(tCR2)(CO)2{HB(p z)3}]. A solution
of [Mo(tCR2)Br(CO)2(γ-picoline)2] (3.00 g, 5.6 mmol) in dichlo-
romethane (60 mL) was treated with potassium hydrotris-
(pyrazol-1-yl)borate (1.44 g, 5.70 mmol). The orange suspension
was stirred for 12 h and allowed to settle. The orange
supernatant was decanted from the solid residue and chro-
matographed on alumina (ca 15 × 4 cm) using diethyl ether
as the eluant. The bright orange fraction was diluted with light
petroleum (60 mL) and concentrated under reduced pressure
to the point of crystallization. Subsequent storage of the
solution at -20 °C produced orange microcrystals of [Mo(t
CR2)(CO)2{HB(pz)3}]. Yield: 2.40 g (87%). IR (CH2Cl2): ν(CO)
1991 s, 1906 vs cm-1. IR (Nujol): ν(CO) 1978 s, 1913 s cm-1
.
1H NMR: δ 3.83 [s, 3 H, CH3], 6.17, 6.22 [t × 2, 3 H, H4(pz)],
6.81, 7.51 [(AB)2, 4 H, 3J (AB) ) 8.0 Hz, C6H4]; 7.64, 7.67, 7.91
[s, d × 2, 6 H, H3,5(pz)]. 13C{1H} NMR: δ 294.2 [MotC], 226.0
[CO], 159.9 [C1(C6H4)], 149.4, 140.1 [C2,3,5,6(C6H4)], 143.0, 135.4,
131.2, 113.5, 105.2 [C(pz)], 124.7 [C4(C6H4)], 55.4 [CH3] ppm.
FAB-MS: m/z 484 [M]+, 456 [M - CO]+, 428 [M - 2CO]+. Anal.
Found: C, 47.5; H, 3.2; N, 17.7. Calcd for C19H17BMoN6O3: C,
47.14; H, 3.54; N, 17.36.
(45) (a) Trofimenko, S. J . Am. Chem. Soc. 1967, 89, 6288. (b)
Trofimenko, S. Scorpionates: The Coordination Chemistry of Poly-
pyrazolylborate Ligands; Imperial College Press: London, 1999.

3510 Organometallics, Vol. 22, No. 17, 2003
Cook and Hill
P r ep a r a tion of [Mo(tCR3)(CO)2{HB(p z)3}]. Molybde-
num hexacarbonyl (3.00 g, 11.4 mmol) was suspended in
diethyl ether (50 mL), and 2-thienyllithium (11.4 mL, 1.0 mol
dm-3, 11.4 mmol, Aldrich) was added dropwise over a 15 min
period, resulting in an orange solution. The mixture was cooled
(dry ice/propanone) and then treated with trifluoroacetic
anhydride (1.2 mL, 11.4 mmol), resulting in the immediate
formation of a deep purple solution. The cooling bath was
removed and the mixture warmed slowly. At the point where
the last vestige of purple coloration dissipated, potassium
hydrotris(pyrazolyl)borate (3.05 g, 12.1 mmol) was added in
one portion and the mixture warmed gradually with stirring
to room temperature, resulting in the vigorous evolution of
carbon monoxide and the formation of a deep orange-red
suspension. After it was stirred for 30 min at room tempera-
ture, the solution was transferred via cannula filtration to a
second Schlenk vessel and concentrated under reduced pres-
sure to ca. 20 mL. The solution was then transferred to a
chromatography column (ca. 30 × 3 cm, silica) and eluted with
a mixture of diethyl ether and hexane (1:1) to provide an
orange eluate, which was diluted with light petroleum (50 mL)
and reduced in vacuo, yielding bright orange microcrystals.
a dark blue-purple fraction. Dilution with hexane, concentra-
tion, and storage of the solution at -20 °C resulted in the
deposition of pure, crystalline [Mo(η2-SCR2)(CO)2{HB(pz)3}].
Yield: 0.99 g (93%). IR (CH2Cl2): ν(CO) 1976 s, 1891 vs cm-1
.
1
IR (Nujol): ν(CO) 1974 s, 1895 vs cm-1. H NMR: δ 3.94 [s, 3
H, OCH3], 6.24, 7.39, 7.74 [s(br) × 3, 9 H, pz], 7.09, 8.04 [(AB)2,
4 H, 3J (AB) ) 8.0 Hz, C6H4]. 13C{1H} NMR: δ 278.0 [CS], 233.6
[CO], 162.5 [Cl(C6H4)], 136.8, 113.8, 106.0 [C(pz)], 137.0, 136.9
[C2,3,5,6(C6H4)], 124.8 [C4(C6H4)], 55.6 [CH3] ppm. FAB-MS: m/z
518 [M]+, 592 [M - CO]+, 562 [M - 2CO]+. Anal. Found: C,
43.3; H, 3.2; N, 16.7. Calcd for C19H17BMoN6O3S: C, 44.21;
H, 3.32; N, 16.28. Under these experimental conditions, the
second purple fraction was obtained only in sufficient quanti-
ties (1-3%) to identify it, by comparison of infrared and 1H
NMR data, as the dithiocarboxylate complex [Mo(κ2-S2CR2)-
(CO)2{HB(pz)3}], described below.
P r ep a r a t ion of [Mo(η2-SCR 3)(CO)2{H B(p z)3}]. [Mo-
(tCR3)(CO)2{HB(pz)3}] (2.00 g, 4.30 mmol) was dissolved in
dichloromethane (20 mL) and methylthiirane (0.31 mL, 4.30
mmol) added. The initially orange solution was stirred for 4
h. resulting in the formation of an intense blue-purple solution.
Concentration of this solution followed by chromatographic
purification on silica gel (30 × 3 cm) using diethyl ether as
the eluant yielded a dark blue band. This was diluted with
hexane (30 mL), concentrated under reduced pressure to ca.
10 mL, and stored at -20 °C for 24 h. The resulting dark blue
crystals were filtered off and dried in vacuo. Yield: 1.92 g
(90%). IR (CH2Cl2): ν(CO) 1980 s, 1897 vs cm-1. IR (Nujol):
Yield: 5.02 g (96%). IR (CH2Cl2): ν(CO) 1996 s, 1913 s cm-1
.
1
IR (Nujol): ν(CO) 1992 s, 1899 s cm-1. H NMR: δ 6.21, 6.26
[s × 2, 3 H, H4(pz)], 6.94, 7.21, 7.36 [3 H, C4H3S], 7.70 [H3,5
-
(pz)]. 13C{1H} NMR: 276.8 [MotC], 225.9 [CO], 144.3, 135.5,
105.5 [C(pz)], 143.1, 130.6, 127.7, 126.6 [C(C4H3S)]. FAB-MS:
m/z 462 [M]+, 434 [M - CO]+, 406 [M - 2CO]+. Anal. Found:
C, 41.6; H, 2.6; N, 18.3. Calcd for C16H13BMoN6O2S: C, 41.77;
H, 2.85; N, 18.26.
1
ν(CO) 1988 s, 1878 vs cm-1. H NMR: δ 6.24 [t, 3 H, H4(pz)],
7.27-8.05 [9 H, H3,5(pz) and C4H3S]. 13C{1H} NMR: δ 261.6
[CS], 233.7 [CO], 149.5, 145.2, 143.6, 142.2 [C2-4(C4H3S)],
135.6, 129.1, 105.9 [C(pz)] ppm. FAB-MS: m/z 494 [M]+, 466
[M - CO]+, 438 [M - 2CO]+. Anal. Found: C, 39.1; H, 3.0; N,
17.0. Calcd for C16H13BMoN6O2S2: C, 39.05; H, 2.66; N, 17.07.
P r epar ation of tr a n s,cis,cis-[W(η2-SCR2)Br (CO)2(bipy)].
[W(tCR2)Br(CO)2(bipy)] (0.48 g, 0.80 mmol) was dissolved in
dichloromethane (40 mL), methylthiirane (0.06 mL, 0.80 mmol)
was added, and the mixture was stirred for 10 min. The red
solution was then left to stand without stirring for 24 h,
resulting in the precipitation of dark blue microcrystals from
the resulting purple solution. The product was isolated by
decantation, washed with diethyl ether (3 × 30 mL), and dried
in vacuo. Yield: 0.35 g (69%). IR (CH2Cl2): ν(CO) 1952 s, 1856
s cm-1. IR (Nujol): ν(CO) 1954 s, 1871 s cm-1. 1H NMR: δ 3.87
P r ep a r a tion of [MoF e(µ-SCR1)(CO)5[HB(p z)3}]. [Mo(η2-
SCR1)(CO)2{HB(pz)3}] (0.50 g, 1.00 mmol) was dissolved in
dichloromethane (30 mL) and diiron nonacarbonyl (0.40 g, 1.10
mmol) added. The suspension was stirred for 12 h and then
placed in an ultrasonic bath for a further 6 h. The supernatant
was decanted from solid biproducts and unreacted [Fe2(CO)9],
concentrated under reduced pressure, and chromatographed
(alumina, diethyl ether eluant). The major orange fraction was
collected, diluted with hexane, and then concentrated under
reduced pressure to ca. 15 mL. Storage at -20 °C provided
orange microcrystals. Yield: 0.28 g (44%). IR (CH2Cl2): ν(CO)
2051 s, 1982 vs, 1843 br cm-1 (lit.23 IR (CH2Cl2): 2058 s, 1985
s, 1859 s cm-1).23 IR (Nujol): ν(BH) 2489, ν(CO) 2047 s, 1969
3
[s, 3 H, CH3], 6.94, 7.88 [(AB)2, 4 H, J (AB) ) 8.0 Hz, C6H4],
7.22, 7.89, 8.31, 8.95 [8 H, bipy]. Useful 13C{1H} NMR data
were not obtained, due to insolubility and solution instability
(vide supra). FAB-MS: m/z 628 [M]+, 600 [M - CO]+, 572
[M - 2CO]+, 538 [M - 2CO - S]+. Anal. Found: C, 38.3; H,
2.3; N, 4.4. Calcd for C20H15BrN2O3SW: C, 38.30; H, 2.41; N,
4.47.
P r epar ation of tr a n s,cis,cis-[Mo(η2-SCR2)Br (CO)2(bipy)].
[Mo(tCR2)Br(CO)2(bipy)] (2.00 g, 4.00 mmol) was dissolved in
dichloromethane (100 mL) and methylthiirane (0.29 mL, 4.0
mmol) added. The orange solution was stirred for 10 min and
then left to stand without stirring for 20 h, whereupon a purple
solution formed and blue crystals separated. The mother liquor
was removed using a cannula, and the crystals were washed
with diethyl ether (3 × 30 mL) and dried in vacuo. Yield: 1.70
g (79%). IR (CH2Cl2): ν(CO) 1962 s, 1870 vs cm-1. IR (Nujol):
1
vs, 1958 vs, 1839 s cm-1. H NMR: δ 2.41 [s, 3 H, CH3], 6.10,
6.25, 6.33 [t × 3, 3 H, H4(pz)], 7.19-7.86 [10 H, H3,5(pz)]. 13C-
{1H} NMR: δ 231.8, 226.8, 209.9, 209.7, 208.0 [CO], 144.7,
129.4, 106.0 [C(pz)], 142.9 [C1(C6H4)], 136.6, 135.7 [C2,3,5,6
-
(C6H4)], 105.7 [FeWSC], 21.3 [CH3] ppm (N.B.: literature
values23 in CD2Cl2/CH2Cl2). FAB-MS: m/z 640 [M]+, 558
[M - 3CO]+, 530 [M - 4CO]+, 502 [M - Fe(CO)3]+.
P r ep a r a tion of [Mo(K2-S2CR2)(CO)2{HB(p z)3}]. [Mo{η2-
SCR2)(CO)2{HB(pz)3}] (0.20 g, 0.38 mmol) was dissolved in
diethyl ether (30 mL) and (i) elemental sulfur (0.20 g, 0.76
mmol) or (ii) methylthiirane (0.03 mL, 0.38 mmol) added. The
solutions were stirred for (i) 7 days and (ii) 5 days, respectively.
The resulting purple solutions were chromatographed on a
water-cooled column loaded with alumina, with diethyl ether
as eluant, to obtain purple fractions. Addition of ethanol and
concentration of the solutions to minimum volume yielded [Mo-
(κ2-S2CR2)(CO)2{HB(pz)3}] Yield: (i) 0.15 g (74%); (ii) 0.17 g
(80%). IR (CH2Cl2): ν(CO) 1951 vs, 1867 s cm-1. IR (Nujol):
1
ν(CO) 1962 s, 1872 vs cm-1. H NMR (ppm, 25 °C, d6-DMSO):
3
δ 4.14 [s, 3 H, CH3], 8.38, 7.49 [(AB)2, 4 H, J (AB) ) 8.0 Hz,
C6H4], 9.13, 8.87, 8.55, 8.03 [8 H, bipy]. Useful 13C{1H} NMR
data were not obtained, due to insolubility and solution
instability (vide supra). FAB-MS: m/z 540 [M]+, 511 [M -
CO]+, 484 [M - 2CO]+, 453 [M - CO - Br]+, 407 [M - 2CO -
Br]+, 329 [M - 2CO - bipy]+. Anal. Found: C; 43.8, H; 2.2,
N; 5.2. Calcd for C20H15BrMoN2O3S: C, 44.55; H, 2.80; N, 5.19.
P r ep a r a t ion of [Mo(η2-SCR 2)(CO)2{H B(p z)3}]. [Mo-
(tCR2)(CO)2{HB(pz)3}] (1.00 g, 1.90 mmol) was dissolved in
dichloromethane (20 mL) and methylthiirane (0.14 mL, 1.9
mmol) added. The orange solution was stirred in the dark for
12 h. The resulting intense purple solution was chromato-
graphed on a water-cooled column (50 × 4 cm) loaded with
alumina. Elution with diethyl ether allowed the separation of
ν(CO) 1940 vs, 1868 s cm-1 1H NMR: δ 3.88 [s, 3 H, CH3],
.
6.25 [t, 3 H, H4(pz)], 6.91, 8.00 [(AB)2, 4 H, C6H4], 7.68, 8.16
[d × 2, 6 H, H3,5(pz)]. 13C{1H} NMR: δ 250.4 [S2C], 222.3 [CO],
163.6 [C1(C6H4)], 145.2, 135.9 [C2,3,5,6(C6H4)], 124.8 [C4(C6H4)],
136.8, 113.7, 105.9 [C(pz)], 55.6 [CH3] ppm. FAB-MS: m/z 494

Metallathiirenes
Organometallics, Vol. 22, No. 17, 2003 3511
[M - 2CO]+. Anal. Found: C, 39.6; H, 2.7; N, 16.2. Calcd for
P r epar ation of [Mo(K2-S2CR2)(CO)2(η-C5H5)]. [Mo(tCR2)-
(CO)2(η-C5H5)] (0.60 g, 1.80 mmol) was dissolved in dichlo-
romethane (20 mL) and methylthiirane (0.13 mL, 1.8 mmol)
added. The initially bright orange solution became deep red
over 15 min. A further 0.26 mL (3.6 mmol) of methylthiirane
was added and the solution stirred for 4 h. Concentration of
the solution and addition of an equal volume of hexane gave
a red solution, which was purified by chromatographic separa-
tion on silica (15 × 3 cm). Eluting with a mixture of dichlo-
romethane and hexane (1:1) provided a red eluate, the volume
of which was reduced to ca. 10 mL in vacuo. Storage at
-20 °C yielded purple microcrystals. Yield: 0.61 g (85%). IR
(CH2Cl2): ν(CO) 1965 vs, 1890 s cm-1. IR (Nujol): ν(CO) 1945
C
19H17BMoN6O3S2: C, 41.62; H, 3.13; N, 15.33.
P r ep a r a tion of [Mo(K2-S2CR1)(CO)2{HB(p z)3}]. [Mo(η2-
SCR1)(CO)2{HB(pz)3}] (0.50 g, 1.00 mmol) was dissolved in
diethyl ether (30 mL) and methylthiirane (0.08 mL, 1.0 mmol)
added. The solution was stirred for 5 days. Purification of the
resulting deep purple solution was achieved by column chro-
matography (alumina, diethyl ether eluant). The product was
recrystallized from ethanol solution at -20 °C. Yield: 0.45 g
(85%). IR (CH2Cl2): ν(CO) 1953 vs, 1871 s cm-1. IR (Nujol):
ν(CO) 1932 vs, 1857 s cm-1 1H NMR: δ 2.40 [s, 3 H, CH3],
.
6.27, 6.63 [t × 2, 3 H, H4(pz)], 7.23, 7.98 [(AB)2, 4 H, 3J (AB) )
8.1 Hz, C6H4], 7.73, 8.25 [d × 2, 6 H, H3,5(pz)]. 13C{1H} NMR:
δ 249.1 [S2C], 222.4 [CO], 146.4, 135.9 [C2,3,5,6(C6H4)], 143.3
[C1(C6H4)], 140.5 [C4(C6H4)], 129.1, 122.8, 106.3 [C(pz)], 21.7
[CH3] ppm. FAB-MS: m/z 478 [M - 2CO]+. Anal. Found: C,
43.2; H, 3.1; N, 16.4. Calcd for C19H17BMoN6O2S2: C, 42.88;
H, 3.22; N, 15.79. The tungsten analogue [W(η2-S2CR1)(CO)2-
{HB(pz)3}] has been described.13 N.B.: the reaction of [Mo-
(tCR1)(CO)2{HB(pz)3}] with sulfur in refluxing tetrahydro-
furan provides [Mo(η3-S2CR1)(dO){HB(pz)3}].46
vs, 1859 s cm-1 1H NMR: δ 3.84 [s, 3 H, CH3], 5.51 [s, 5 H,
.
C5H5], 6.84, 7.88 [(AB)2, 4 H, C6H4]. 13C{1H} NMR: δ 250.9
[S2C], 231.9 [CO], 163.4 [C1(C6H4)], 137.7 [C4(C6H4)], 123.8,
113.5 [C2,3,5,6(C6H4)], 92.9 [C5H5], 55.6 [CH3] ppm. FAB-MS:
m/z 406 [M]+, 346 [M - 2CO]+. Anal. Found: C, 44.6; H, 2.8.
Calcd for C15H12MoO3S2: C, 45.01; H, 3.02.
P r ep a r a tion of [Mo(K2-SSeCR3)(CO)2{HB(p z)3}] [Mo(η2-
SCR3)(CO)2{HB(pz)3}] (0.20 g, 0.41 mmol) was dissolved in
tetrahydrofuran (10 mL) and gray selenium (0.04 g, 0.51 mmol)
added. Dropwise addition of a solution of lithium triethylboro-
hydride (0.41 mL, 1.0 mol dm-3, 0.41 mmol, Aldrich) resulted
in an instantaneous reaction, producing a bright blue solution.
After the mixture was stirred for 1 h, the solvent was removed
under reduced pressure. The residue was then redissolved in
diethyl ether (10 mL). Purification by column chromatography
(alumina, 15 × 3 cm) with diethyl ether as eluant produced a
blue initial fraction, which was collected, diluted with hexane
(20 mL), and concentrated under reduced pressure. Storage
at -20 °C resulted in the deposition of dark blue crystals
P r ep a r a tion of [Mo(K2-OSCR1)(CO)2{HB(p z)3}]. [Mo(η2-
SCR1)(CO)2{HB(pz)3}] (0.50 g, 1.00 mmol) was dissolved in
dichloromethane (20 mL) and excess dimethyl(methylthio)-
sulfonium tetrafluoroborate (0.39 g, 2.0 mmol) added until no
more starting material was observable in the IR spectrum and
a red solution had formed. The solution was chromatographed
on a column loaded with silica (ca. 20 × 6 cm) using a mixture
of dichloromethane and hexane (1:1) as the eluant. The initial
red-orange fraction was collected and concentrated under
reduced pressure, yielding red crystals of the dichloromethane
hemisolvate (1H NMR). Yield: 0.34 g (65%). IR (CH2Cl2): ν(CO)
1959 vs, 1855 s cm-1. IR (Nujol): ν(CO) 1946 vs, 1860 s; ν(C-
Yield: 0.21 g (90%). IR (CH2Cl2): ν(CO) 1945 vs, 1864 s cm-1
.
IR (Nujol): ν(CO) 1928 vs, 1857 s cm-1. H NMR: δ 6.26 [t, 3
H, H4(pz)], 7.09 [t, 1 H, H4(C4H3S)], 7.56 [d, 1 H, H3(C4H3S)],
7.70, 8.18 [d × 2, 6 H, H3,5(pz)]. 13C{1H} NMR: δ 249.6 [SeSC],
211.3 [CO], 145.5, 135.9, 106.0 [C(pz)], 131.3, 128.8, 124.2
[C(C4H3S)] ppm. FAB-MS: m/z 572 [M + H]+, 516 [M - 2CO]+.
1
1
O) 1603 w cm-1. H NMR: δ 2.38 [s, 3 H, CH3], 6.24 [t, 3 H,
3
H4(pz)], 7.18, 7.83 [(AB)2, 4 H, J (AB) ) 8.0 Hz, C6H4], 7.73,
8.10 [H3,5(pz)]. 13C{1H} NMR: δ 251.6 [SOC], 209.7 [CO], 144.9,
136.0, 105.7 [C(pz)], 128.9, 125.4 [C2,3,5,6(C6H4)], 21.8 [CH3]
ppm. FAB-MS: m/z 462 [M - 2CO]+. Anal. Found: C, 42.4;
H, 3.4; N, 14.7. Calcd for C19H17BMoN6O3S‚0.5CH2Cl2: C,
41.92; H, 3.25; N, 15.04.
Anal. Found: C, 33.4; H, 2.2; N, 14.4. Calcd for C16H13
BMoN6O2S2Se: C, 33.65; H, 2.29; N, 14.71.
-
P r epar ation of [Mo(η2-EtSCR1)(CO)2{HB(pz)3}]BF4. [Mo-
(η2-SCR1)(CO)2{HB(pz)3}] (0.20 g, 0.40 mmol) was dissolved
in a mixture of dichloromethane and diethyl ether (1:1, 10 mL)
and then treated with a solution of triethyloxonium tetrafluo-
roborate in dichloromethane (0.40 mL, 1.0 mol dm-3, 0.40
mmol, Aldrich). A slow color change from blue-purple to yellow
occurred over a 5 h period, as a yellow product precipitated.
The reaction liquor was decanted off and the product washed
with diethyl ether (2 × 10 mL) and dried in vacuo. The product
could be recrystallized from a mixture of dichloromethane and
hexane at -20 °C. Yield: 0.13 g (53%). IR (CH2Cl2): ν(CO)
P r ep a r a t ion of [Mo(K2-SSeCR2)(CO)2{HB(p z)3}]. [Mo-
(η2-SCR2)(CO)2{HB(pz)3}] (0.20 g, 0.40 mmol) was dissolved
in tetrahydrofuran (10 mL) and gray selenium (0.04 g, 0.50
mmol) added. Dropwise addition of a solution of lithium
triethylborohydride (0.40 mL, 1.0 mol dm-3, 0.40 mmol,
Aldrich) resulted in an instantaneous reaction, producing a
bright purple solution. After the mixture was stirred for 30
min, the solvent was removed in vacuo and the residue
redissolved in diethyl ether (10 mL). Purification via column
chromatography (alumina, 15 × 3 cm, diethyl ether eluant)
provided an initial bright purple fraction, which was diluted
with hexane (20 mL) and concentrated under reduced pres-
sure. Storage at -20 °C resulted in the deposition of dark
purple crystals. Yield: 0.20 g (87%). An analytical sample of
the dichloromethane monosolvate (1H NMR) was crystallized
from a mixture of dichloromethane and hexane. Alternatively,
a solution of Li2Se2 could be prepared in a separate Schlenk
flask from Li[Et3BH] and selenium and added to give the
product in comparable yield. IR (CH2Cl2): ν(CO) 1943 vs, 1861
2056 s, 1992 vs cm-1. IR (Nujol): ν(CO) 2050 s, 1973 vs cm-1
.
1H NMR (CD2Cl2): δ 1.40 [t, 3 H, CH2CH3, 3J (HH) ) 7.6], 2.57
[s, 3 H, C6H4CH3], 2.83 [q, 2 H, 3J (HH) ) 7.6, SCH2], 6.45,
6.49, 6.52 [t × 3, 1 H × 3, H4(pz), 3J (HH) ) 2.3]. 7.33, 7.57,
3
7.97, 7.99, 7.80, 8.14 [d × 6, 1 H × 6, H3,5(pz), J (HH) ) 2.3],
3
7.61, 8.04 [(AB)2, 4 H, C6H4, J (AB) ) 8.3 Hz]. 13C{1H} NMR
(CD2Cl2): δ 248.1 [CS], 219.1 [CO], 148.8 [C1(C6H4)], 147.9 [C4-
(C6H4)], 145.6, 140.3, 109.6 [s(br) × 3, pz], 136.7, 133.2 [C2,3,5,6
-
s cm-1. IR (Nujol): ν(CO) 1934 vs, 1861 s cm-1 1H NMR: δ
.
(C6H4)], 40.4 [SCH2], 23.9 [C6H4CH3], 15.9 [CH2CH3] ppm.
FAB-MS: m/z 531 [M]+, 500 [M - S]+, 475 [M - 2CO]+, 343
[SMoHB(pz)3]+. Anal. Found: C, 40.8; H, 3.4; N, 14.3. Calcd
for C21H22B2F4MoN6O2S: C, 40.94; H, 3.60; N, 13.64.
3.87 [s, 3 H, CH3], 6.25 [t, 3 H, H4(pz)], 6.89, 7.99 [(AB)2, 4 H,
3
C6H4, J (AB) ) 8.2 Hz], 7.69, 8.20 [d × 2, 6 H, H3,5(pz)]. 13C-
{1H} NMR: δ 249.7 [SeSC, 1J (SeC) ) 23 Hz], 223.5 [CO], 163.7
[C1(C6H4)], 145.5, 135.9, 105.9 [C(pz)], 138.8 [C4(C6H4)], 124.6,
113.9 [C2,3,5,6(C6H4)], 55.5 [CH3] ppm. FAB-MS: m/z 597 [M +
H]+, 568 [M - CO]+, 540 [M - 2CO]+. Anal. Found: C, 35.6;
H, 2.0; N, 12.0. Calcd for C19H17BMoN6O3SSe‚CH2Cl2: C,
35.32; H, 2.82; N, 12.36.
P r ep a r a t ion of [Mo(η2-MeSCR2)(CO)2{H B(p z)3}]BF 4.
[Mo(tCR2)(CO)2{HB(pz)3}] (0.30 g, 0.60 mmol) was dissolved
in dichloromethane (15 mL), forming a bright orange solution.
Slow addition of dimethyl(methylthio)sulfonium tetrafluorobo-
rate (0.12 g, 0.60 mmol) resulted in a change in solution color
to light brown. While the solution was stirred for 30 min, a
yellow solid precipitated. Recrystallization of the crude pre-
cipitate from a mixture of propanone and hexane at -20 °C
(46) Hughes, A. K.; Malget, J . M.; Goeta, A. E. J . Chem. Soc., Dalton
Trans. 2001, 1927.

3512 Organometallics, Vol. 22, No. 17, 2003
Cook and Hill
provided bright yellow microcrystals. Yield: 0.36 g (94%). IR
(CH2Cl2): ν(CO) 2053 s, 1986 vs cm-1. IR (Nujol): ν(CO) 2055
s, 1988 vs cm-1. FAB-MS: m/z 533 [M]+, 503 [M - CO]+, 477
[M - 2CO]+, 343 [M - 2CO - Me - CR2]+. These data may
be compared with those for the SEt derivative described above.
NMR data were not obtained due to low solubility.
solvent was removed under reduced pressure. The residue was
recrystallized from a mixture of dichloromethane and light
petroleum at -20 °C. Yield: 0.08 g (80%). IR (CH2Cl2): ν(CO)
1950 s, 1820 vs cm-1. IR (Nujol): ν(CO) 1950 s, 1831 s cm-1
.
1H NMR: δ 1.11 [s, 9 H, CCH3], 2.68 [s, 3 H, SCH3], 3.70 [s, 3
H, OCH3], 6.03-7.95 [m, 13 H, H(pz) and C6H4]. 13C{1H}
NMR: δ 237.9, 233.6 [CO], 157.9 [C1(C6H4)], 145.4-104.9
[C(pz) and C6H4], 55.2 [OCH3], 51.1 [SCMe3], 31.2 [CCH3], 23.7
[SCH3] ppm. FAB-MS: m/z 622 [M]+, 594 [M - CO]+, 566
[M - 2CO]+, 533 [M - SCMe3]+, 477 [M - 2CO - CMe3]+.
P r ep a r a tion of [Mo(η2-MeSCHR2)(CO)2{HB(p z)3}]. [Mo-
(η2-CH3SCR2)(CO)2{HB(pz)3)]BF4 (0.36 g, 0.60 mmol) was
suspended in dichloromethane (15 mL), and a solution of
lithium triethylborohydride (0.60 mL, 1.0 mol dm-3, 0.60
mmol, Aldrich) was added dropwise. When the mixture was
stirred for 1 h, a dark orange solution formed. The solution
was concentrated and chromatographed on alumina (15 × 3
cm) at room temperature using diethyl ether as the eluant.
Addition of light petroleum (20 mL) to the initial orange band
and concentration under reduced pressure afforded orange
microcrystals. An analytical sample of a dichloromethane
Anal. Found: C, 46.5; H, 4.2; N, 13.0. Calcd for C24H29
-
BMoN6O3S2: C, 46.46; H, 4.71; N, 13.55.
P r ep a r a tion of [Mo(η2-MeSCHR3)(CO)2{HB(p z)3}]. [Mo-
(tCR3)(CO)2{HB(pz)3}] (0.30 g, 0.70 mmol) was dissolved in
dichloromethane (15 mL) and dimethyl(methylthio)sulfonium
tetrafluoroborate (0.13 g, 0.70 mmol) added in small quantities,
providing in situ a yellow solution of [Mo(η2-CH3SCR3)(CO)2-
{HB(pz)3}]BF4, identified by IR spectroscopy. The solvent was
removed and the oily residue suspended in diethyl ether
(10 mL). Treatment of this suspension with a solution of
lithium triethylborohydride (0.70 mL, 1.0 mol dm-3, 0.70
mmol, Aldrich) resulted in the immediate darkening of the
solution color to an intense orange. The supernatant was
transferred to a chromatography column (alumina) by cannula
filtration. Elution with diethyl ether provided an intense
orange eluate, which was subsequently diluted with hexane.
Slow concentration of the solution resulted in the precipitation
of bright orange crystals. Yield: 0.27 g (82%). IR (CH2Cl2):
hemisolvate (1H NMR) was obtained from
a mixture of
dichloromethane and hexane at -20 °C. Yield: 0.25 g (76%).
IR (CH2Cl2): ν(CO) 1949 s, 1812 vs cm-1. IR (Nujol): ν(CO)
1
1941 s, 1806 s cm-1. H NMR: δ 2.10 [s, 3 H, SCH3], 3.86 [s, 3
H, OCH3], 5.79 [s, 1 H, MoCH], 6.10 [s(br), 3 H, H4(pz)], 6.98,
7.47 [(AB)2, 4 H, C6H4], 7.59-8.10 [m, 6 H, H3,5(pz)]. 13C{1H}
NMR: δ 234.8, 229.7 [CO], 158.8 [C1(C6H4)], 146.3, 144.3,
139.7, 135.6 [C2,3,5,6(C6H4)], 131.9 [C4(C6H4)], 133.3, 113.6, 105.7
[C(pz)], 72.4 [MoCH], 55.3 [OCH3], 19.9 [SCH3] ppm. FAB-
MS: m/z 534 [M]+, 506 [M - CO]+, 478 [M - 2CO]+, 458
[M - CO - SCH3]+, 428 [M - C6H4OCH3]+. Anal. Found: C,
42.3; H, 3.3; N, 14.6. Calcd for C20H21BMoN6O3S‚0.5CH2Cl2:
C, 42.8; H, 3.9; N, 14.6.
ν(CO) 1957 s, 1818 vs cm-1. IR (Nujol): 1944 s, 1804 s cm-1
.
1H NMR: δ 2.10 [s, 3 H, SCH3], 5.59, 5.75 [s × 2, 1 H, MoCHS],
6.14 [s(br), 3 H, H4(pz)], 6.82-7.22 [m, 3 H, C4H3S], 7.57-
7.97 [m, 6 H, H3,5(pz)]. 13C{1H} NMR: δ 235.3, 233.8, 228.8,
226.1 [CO], 146.6-105.7 [C(pz) and C4H3S], 21.4, 20.6 [SCH3]
ppm. FAB-MS: m/z 510 [M]+, 482 [M - CO]+, 454 [M - 2CO]+,
435 [M - CO, SCH3]+, 406 [M - 2CO, SCH3]+. Anal. Found:
C, 40.7; H, 2.7; N, 15.5. Calcd for C17H17BMoN6O2S2: C, 40.18;
H, 3.37; N, 16.54.
P r ep a r a t ion of [Mo{η2-MeSC(SCMe3)R 2}(CO)2{H B-
(p z)3)]. [Mo(η2-CH3SCR2)(CO)2{HB(pz)3}]BF4 (0.10 g, 0.20
mmol) was suspended in dichloromethane (10 mL) and then
treated with 2-methyl-2-propanethiol (0.02 mL, 0.20 mmol)
and DBU (0.20 mL, excess). An immediate reaction was
observed with the formation of a deep orange solution. After
it was stirred for 15 min, the mixture was transferred to a
chromatography column loaded with alumina. Elution with
diethyl ether provided an orange fraction, from which the
OM030261S