Metallathiirenes. 3.1 thiocarbamoyl and alkoxythiocarbonyl complexes of molybdenum(II) and tungsten(II)

Article abstract of DOI:10.1021/om991019h

Synthetic routes to thiocarbamoyl (thiocarboxamide) complexes of divalent molybdenum and tungsten are reported: The reaction of fac-[Mo(CO)₃(NCMe)₃] with N,N-dimethyl thiocarbamoyl chloride (Me₂NC(=S)Cl) at low temperature provides a thermally labile intermediate (1) presumed on the basis of subsequent transformations to be [Mo(η²-SCNMe₂)-Cl(CO)₃(NCMe)]. Reactions of 1 with K[HB(pz)₃] (pz = pyrazol-1-yl), NaC₅H₅, bipy, or tmeda provide the complexes [Mo(η²-SCNMe₂)(CO)₂{HB(pz)₃}] (2), [Mo(η²-SCNMe₂)(CO)₂(η-C₅ H₅)] (3), [Mo(η²-SCNMe₂)Cl(CO)₂(bipy)] (4), and [Mo(η²-SCNMe₂)Cl(CO)₂(tmeda)] (5), respectively. The complex cis,cis,trans-[Mo(η²-SCNMe₂)Cl(CO)₂ (PPh₃)₂] (6) results from the oxidative addition of Me₂NC(=S)Cl to [Mo(NCMe)₂(CO)₂(PPh₃)₂] and is one of two isomers obtained from the reaction of 1 with PPh₃. The complex 2 may also be obtained from reaction of (i) K[Mo(CO)₃{HB(pz)₃}] with Me₂NC(=S)Cl; (ii) [Mo(CO)₃(η⁶-C₇H₈)] with Me₂NC(=S)Cl and K[HB(pz)₃]; and (iii) K[HB(pz)₃] with either 5 or 6. Sequential treatment of either [Mo(CO)₃-(NCMe)₃] or [Mo(CO)₃(η⁶-C₇H₈)] with ClC(=S)OR (R = C₆H₄Me-4, C₆H₅) and K[HB(pz)₃] provides the complexes [Mo(η²-SCOR)(CO)₂{HB(pz)₃}] [R = C₆H₄Me-4 (7a), C₆H₅ (7b)]. Attempts to prepare a mononuclear thiocarbamoyl complex by addition of elemental sulfur or propene episulfide to the aminomethylidyne complex [Mo(≡CNⁱPr₂)(CO)₂{HB(pz)₃}] (8) were unsuccessful; however addition of [Fe₂(CO)₉] to 8 provided the thermally unstable complex [MoFe(μ-CNⁱPr₂)(CO)₅{HB(pz)₃}] (9), which reacts with sulfur to provide the heterobimetallic bridging thiocarbamoyl complex [MoFe(μ-SCNⁱPr₂)(CO)₅{HB(pz)₃}] (10). Treating fac-[W(CO)₃(NCMe)₃] sequentially with Me₂NC(=S)Cl and K[HB(pz)₃] provided [W(η²-SCNMe₂)(CO)₂{HB(pz)₃}] (11); however replacing Me₂NC(=S)Cl with ClC(=S)OC₆H₄-Me-4 led to [WCl(CO)₃{HB(pz)₃}] (12).

Full text of DOI:10.1021/om991019h

2468
Organometallics 2001, 20, 2468-2476
Meta lla th iir en es. 3.1 Th ioca r ba m oyl a n d
Alk oxyth ioca r bon yl Com p lexes of Molybd en u m (II) a n d
Tu n gsten (II)
Stephen Anderson,† Darren J . Cook,† and Anthony F. Hill*,†,‡
Department of Chemistry, Imperial College of Science, Technology and Medicine,
London SW7 2AY, U.K., and Research School of Chemistry, Australian National University,
Canberra ACT, Australia
Received December 21, 1999
Synthetic routes to thiocarbamoyl (thiocarboxamide) complexes of divalent molybdenum
and tungsten are reported: The reaction of fac-[Mo(CO)3(NCMe)3] with N,N-dimethyl
thiocarbamoyl chloride (Me2NC(dS)Cl) at low temperature provides a thermally labile
intermediate (1) presumed on the basis of subsequent transformations to be [Mo(η2-SCNMe2)-
Cl(CO)3(NCMe)]. Reactions of 1 with K[HB(pz)3] (pz ) pyrazol-1-yl), NaC5H5, bipy, or tmeda
provide the complexes [Mo(η2-SCNMe2)(CO)2{HB(pz)3}] (2), [Mo(η2-SCNMe2)(CO)2(η-C5H5)]
(3), [Mo(η2-SCNMe2)Cl(CO)2(bipy)] (4), and [Mo(η2-SCNMe2)Cl(CO)2(tmeda)] (5), respectively.
The complex cis,cis,trans-[Mo(η2-SCNMe2)Cl(CO)2(PPh3)2] (6) results from the oxidative
addition of Me2NC(dS)Cl to [Mo(NCMe)2(CO)2(PPh3)2] and is one of two isomers obtained
from the reaction of 1 with PPh3. The complex 2 may also be obtained from reaction of (i)
K[Mo(CO)3{HB(pz)3}] with Me2NC(dS)Cl; (ii) [Mo(CO)3(η6-C7H8)] with Me2NC(dS)Cl and
K[HB(pz)3]; and (iii) K[HB(pz)3] with either 5 or 6. Sequential treatment of either [Mo(CO)3-
(NCMe)3] or [Mo(CO)3(η6-C7H8)] with ClC(dS)OR (R ) C6H4Me-4, C6H5) and K[HB(pz)3]
provides the complexes [Mo(η2-SCOR)(CO)2{HB(pz)3}] [R ) C6H4Me-4 (7a ), C6H5 (7b)].
Attempts to prepare a mononuclear thiocarbamoyl complex by addition of elemental sulfur
or propene episulfide to the aminomethylidyne complex [Mo(tCNiPr2)(CO)2{HB(pz)3}] (8)
were unsuccessful; however addition of [Fe2(CO)9] to 8 provided the thermally unstable
complex [MoFe(µ-CNiPr2)(CO)5{HB(pz)3}] (9), which reacts with sulfur to provide the
heterobimetallic bridging thiocarbamoyl complex [MoFe(µ-SCNiPr2)(CO)5{HB(pz)3}] (10).
Treating fac-[W(CO)3(NCMe)3] sequentially with Me2NC(dS)Cl and K[HB(pz)3] provided
[W(η2-SCNMe2)(CO)2{HB(pz)3}] (11); however replacing Me2NC(dS)Cl with ClC(dS)OC6H4-
Me-4 led to [WCl(CO)3{HB(pz)3}] (12).
In tr od u ction
lecular hydroboration by a dihydrobis(pyrazolyl)borate
co-ligand.5 To further investigate the reasons for this
dichotomy in stability and reactivity, we have turned
our attention to the synthesis of heteroatom-substituted
thioacyl complexes of tungsten and molybdenum, i.e.,
those featuring thiocarbamoyl and alkoxythiocarbonyl
ligands (Chart 1).
Thiocarbamoyl ligands show a strong tendency to
adopt bidentate coordination, more so than alkoxythio-
carbonyl or thioacyl ligands. This is presumably due to
the ability of the amino “lone pair” to contribute via
conjugation to the metal-ligand bonding. Further to the
valence bond representations for thiocarbamoyl ligands
indicated in Chart 1, a consideration of the valence
orbitals of the [SCNMe2]+ cation (Figure 1) is useful.
This suggests that in addition to σ-donation and π-ac-
ceptance, which fall within the conventional Dewar-
Chatt-Duncanson model for side-on coordination of a
multiple bond, there also exists the possibility of π-do-
nation from sulfur to the metal, perpendicular to the
MCS plane. The topology of this π-donation depicted
in Figure 1 reveals the contribution from the nitrogen
We have recently shown that thioaroyl complexes of
group 6 and 8 metals are accessible via the addition of
propene episufide to benzylidyne complexes.1 In contrast
to thioacyl complexes of group 8 metals,1-3 the group 6
examples are thermally labile. Furthermore, they are
particularly reactive species and are prone to the
addition of excess sulfur or propene episulfide to provide
dithiocarboxylate ligands1,4 or, in one case, intramo-
* To whom correspondence should be addressed. E-mail:
a.hill@rsc.anu.edu.au.
† Imperial College.
‡ Australian National University.
(1) Part 2: Cook, D. J .; Hill, A. F., Chem. Commun. 1997, 955.
(2) (a) Clark, G. R.; Collins, T. J .; Marsden, K.; Roper, W. R. J .
Organomet. Chem. 1983, 259, 215. (b) Elliott, G. P.; Roper, W. R.;
Waters, J . M. Chem. Commun. 1982, 811. (c) Elliott, G. P.; Roper, W.
R. J . Organomet. Chem. 1983, 250, C5. (d) Rickard, C. E. F.; Roper,
W. R.; Salter, D. M.; Wright, L. J . Organometallics 1992, 11, 3931. (e)
Clark, G. R.; Marsden, K.; Roper, W. R.; Wright, L. J . J . Am. Chem.
Soc. 1980, 102, 6570.
(3) (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.
(4) (a) 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. (b) Kreissl, F. R.; Ullrich, N. J . Organomet. Chem.
1989, 361, C30.
(5) Hill, A. F.; Malget, J . M. J . Chem. Soc., Dalton Trans. 1997, 2003.
10.1021/om991019h CCC: $20.00 © 2001 American Chemical Society
Publication on Web 05/15/2001

Metallathiirenes
Organometallics, Vol. 20, No. 12, 2001 2469
philic attack at a coordinated isothiocyanate;12 (iv)
cleavage of a dithiocarbamate ligand;13 and (v) C-H
activation of thioformamides.14
Resu lts a n d Discu ssion
Baker has reported and extensively exploited the
versatile complexes [MI2(CO)3(NCMe)2] (M ) Mo, W),15
which are conveniently obtained by halogenation of
[M(CO)3(NCMe)3].16 We hoped that a similar oxidative
addition of Me2NC(dS)Cl to [Mo(CO)3(NCMe)3] would
lead to a complex of the form [Mo(η2-SCNMe2)Cl(CO)x-
(NCMe)y] (x + y ) 4). This indeed appears to be the case;
however the complex formed is quite thermally labile:
Addition of Me2NC(dS)Cl to a cold (-30 °C) solution of
[Mo(CO)3(NCMe)3] in acetonitrile led to a gradual color
change from pale yellow to orange. Attempts to isolate
the resulting complex met with comprehensive failure.
Removal of solvent or prolonged stirring at room tem-
perature led to the formation of a completely insoluble
blue compound, which is presumably polymeric in
nature. Thiocarbamoyl ligands have already been shown
to have a strong propensity for bridging two metals,6,17
and in this case the oligomerization appears to be
irreversible, at least in acetonitrile under ambient
conditions. Nevertheless, subsequent ligand exchange
reactions carried out on the intermediate are consistent
with it being [Mo(η2-SCNMe2)Cl(CO)3(NCMe)] (1). Treat-
ing a solution of 1 generated in situ with K[HB(pz)3]
(pz ) pyrazol-1-yl) results in the formation of the ther-
mally stable complex [Mo(η2-SCNMe2)(CO)2{HB(pz)3}]
(2) in modest yield (45% based on [Mo(CO)6]) (Scheme
1). This complex has been prepared previously by Lalor
via an alternative route.18 The complex 2 may also be
prepared via the reaction of [Mo(CO)3(NCMe)3] with
K[HB(pz)3] (to provide K[Mo(CO)3{HB(pz)3}] in situ)
followed by Me2NC(dS)Cl; however this sequence only
proceeds in an overall yield of 15%. The approach follows
that described previously for the cyclopentadienyl ana-
logue [Mo(η2-SCNMe2)(CO)2(η-C5H5)] (3),7a which re-
sults from the reaction of Na[Mo(CO)3(η-C5H5)] with
Me2NC(dS)Cl. More conveniently, the reaction of
[Mo(η2-SCNMe2)Cl(CO)2(tmeda)] (5) (vide infra) with
NaC5H5 provides 3 in 84% yield. Better yields (46%) of
2 are also obtained from the reaction of [Mo(η6-C7H8)-
(CO)3] with Me2NC(dS)Cl in dichloromethane followed
by treatment with K[HB(pz)3]. In this case the reaction
takes 48 h to proceed to completion in contrast to the
F igu r e 1. [Me2NCS]+ frontier orbitals.
Ch a r t 1
p orbital, which is orthogonal to the MCS plane and
absent in simple thioacyl and thioaryl ligands.
Thiocarbamoyl (thiocarboxamide) complexes have
previously been prepared by a variety of synthetic
routes.6 Most generally, metal carbonylates have been
shown to react with N,N-dimethylthiocarbamoyl chlo-
ride, Me2NC(dS)Cl, via nucleophilic displacement of the
chloride7 or by oxidative addition such that both chloride
and thiocarbamoyl ligands result.8 These two ap-
proaches are most relevant to the work to be described
herein; however alternative approaches have included
(i) nucleophilic attack by an amine on an electrophilic
thiocarbonyl complex;9 (ii) reaction of hydrosulfide with
haloaminocarbene10 or isonitrile11 ligands; (iii) electro-
(11) Treichel, P. M.; Knebel, W. J .; Hess, R. W. J . Am. Chem. Soc.
1971, 93, 5424.
(12) Roper, W. R.; Grundy, K. R. J . Organomet. Chem. 1976, 113,
C45.
(13) (a) Brower, D. C.; Tonker, T. L.; Templeton, J . L. Organome-
tallics 1985, 4, 745. (b) Herrick, R. S.; Burgmayer, S. J . N.; Templeton,
J . L. J . Am. Chem. Soc. 1983, 105, 2599. (c) Mayr, A.; McDermott, G.
A.; Dorries, A. M.; Holder, A. K. J . Am. Chem. Soc. 1986, 108, 310. (d)
Anderson, S.; Hill, A. F. J . Chem. Soc., Dalton Trans. 1993, 587. (e)
Ichimura, A.; Yamamoto, Y.; Kajino, T.; Kitigawa, T.; Kuma, H.; Kushi,
Y. Chem. Commun. 1988, 1130.
(6) For a review of carbamoyl and thiocarbamoyl complexes see:
Angelici, R. J . Acc. Chem. Res. 1972, 18, 335.
(7) (a) Dean, W. K.; Treichel, P. M. J . Organomet. Chem. 1974, 66,
87. Dean, W. K.; Treichel, P. M. Chem. Commun. 1972, 803. (b) Dean,
W. K. J . Organomet. Chem., 1977, 135, 195.
(14) Luo, X.-L.; Kubas, G. J .; Burns, C. J .; Butcher, R. J . Organo-
metallics 1995, 14, 3370.
(15) For a review see: Baker, P. K. Adv. Organomet. Chem. 1996,
40, 46.
(16) Baker, P. K.; Fraser, S. G.; Keys, E. M. J . Organomet. Chem.
1986, 309, 319.
(17) (a) Green, C. R.; Angelici, R. J . Inorg. Chem. 1972, 11, 2095.
(b) Gal, A. W.; Ambrosius, H. P. M. M.; Van der Ploeg, A. F. M. J .;
Bosman, W. P. J . Organomet. Chem. 1978, 149, 81.
(18) Desmond, T.; Lalor, F. J .; Osullivan, B.; Ferguson, G. J .
Organomet. Chem. 1990, 381, C 33.
(8) (a) Gibson, J . A. E.; Cowie, M. Organometallics 1984, 3, 722. (b)
Corain, B.; Martelli, M. Inorg. Nucl. Chem. Lett. 1972, 8, 39. (c) Gal,
W. K. J . Organomet. Chem. 1980, 190, 353. (d) Dean, W. K.; Charles,
R. S.; Van Derveer, D. G. Inorg. Chem. 1977, 16, 3328.
(9) (a) Busetto, L.; Grazianin, M.; Belluco, U. Inorg. Chem. 1971,
10, 78. (b) Petz, W. J . Organomet. Chem. 1981, 205, 203.
(10) Roper, W. R.; Wright, A. H. J . Organomet. Chem. 1982, 233,
C59.

2470 Organometallics, Vol. 20, No. 12, 2001
Anderson et al.
Sch em e 1
F igu r e 2. Fluxionality of η2-thiocarbamoyl ligands. Pro-
cess A equilibrates sites LX and LY. Process B equilibrates
sites RX and RY.
perpendicular to a molecular plane of symmetry. The
low-field section of the 13C{1H} NMR spectrum consists
of two peaks attributable on intensity grounds to the
thiocarbamoyl (223.0) and carbonyl (204.7 ppm) carbon
nuclei, respectively. This would appear to suggest that
either (i) assuming a static structure, the plane of the
thiocarbamoyl ligand lies between the two chemically
equivalent cis carbonyl ligands or (ii) rotation of the
carbamoyl ligand is rapid on the 13C NMR time scale.
FAB-mass spectroscopy reveals, in addition to a well-
resolved molecular ion, isotope clusters attributable to
loss of carbonyl and chloride ligands. No peaks could
however be identified that correspond to loss of or
fragmentation of the thiocarbamoyl ligand.
Sch em e 2
A similar reaction ensues between 1 and N,N,N′,N′-
tetramethylethylenediamine (tmeda) at low tempera-
ture to provide a deep orange complex [Mo(η2-SCNMe2)-
Cl(CO)2(tmeda)] (5) in high yield (79%). The complex 5
is thermally stable, and in general spectroscopic data
for 5 are comparable to those for 4 with the exception
1
that broadening of the H NMR resonances due to the
tmeda (δ 2.88, 3.11) and thiocarbamoyl (δ 3.61, 3.73)
ligands is apparent at room temperature, suggesting the
onset of a fluxional process. The fluxionality apparent
in this and subsequently described complexes appears
to involve rotation of the entire thiocarbamoyl ligand
about an axis approximately normal to the C-S bond
since the effect is to chemically equilibrate the environ-
ments of similar co-ligands, but leaves the methyl
groups of the thiocarbamoyl ligand chemically distinct
(Figure 2). Thus at no time have we observed a process
consistent with rotation about the C-N multiple bond.
Similar fluxionality has been discussed previously for
thiocarbamoyl complexes.18 Once again the thiocarbonyl
13C{1H} NMR resonance (245.2 ppm) appears to low
field of the single carbonyl resonance (230.9 ppm). In
parallel studies19 we have recently prepared the complex
[Mo{σ-C(dO)NiPr2}I(CO)3(tmeda)] from the reaction of
[Mo(η2-OCNiPr2)I(CO)4] with tmeda, and it is of interest
to note the failure of a carbonyl ligand in this complex
to dissociate and thereby allow bidentate carbamoyl
coordination. The complex 5 serves as a thermally stable
but reactive precursor for ligand exchange reactions.
Thus, for example, reactions of 5 with K[HB(pz)3] or
NaC5H5 provide the complexes 2 and 3 in spectroscopi-
cally quantitative yields.
reaction of 1 with K[HB(pz)3], which is virtually instan-
taneous. Presumably the reaction rate is controlled by
the partial dissociation of the cycloheptatriene ring prior
to oxidative addition of the thiocarbamoyl chloride.
The complex 1 also serves as a precursor to new
thiocarbamoyl complexes (Scheme 2). Treating an aceto-
nitrile solution of 1 (generated in situ) with 2,2′-
bipyridyl leads to the precipitation of a brown crude
product. From this can be extracted (thf) a deep orange
complex formulated as [Mo(η2-SCNMe2)Cl(CO)2(bipy)]
(4) in 58% yield (based on [Mo(CO)6]). The infrared
spectrum includes two carbonyl absorptions at 1910 and
1828 cm-1 (CH2Cl2 solution), suggesting that while the
molybdenum center is formally divalent, it is compara-
tively π-basic. Two methyl resonances are observed in
1
the H NMR spectrum, consistent with hindered rota-
tion about the (partially multiple) C-N bond of the
thiocarbamoyl ligand, while the appearance of only four
resonances for the bipy protons suggests this ligand lies
(19) Anderson, S.; Cook, D. J .; Hill, A. F. Organometallics 1997, 16,
5595.

Metallathiirenes
Organometallics, Vol. 20, No. 12, 2001 2471
The unstable complex [Mo(η2-OCNiPr2)I(CO)4] reacts
with triphenylphosphine to provide a stable monosub-
stitution product, mer-[Mo(η2-OCNiPr2)I(CO)3(PPh3)],19
and it seemed that an analogous complex, [Mo(η2-
SCNMe2)Cl(CO)3(PPh3)], would be readily accessible.
Attempts to introduce triphenylphosphine into the
coordination sphere of 1 were however complicated by
the apparent formation of an inseparable mixture of two
isomers of [Mo(η2-SCNMe2)Cl(CO)2(PPh3)2], which vary
in the cis or trans disposition of the two phosphine
ligands. An alternative approach however allowed the
isolation of the cis, cis, trans isomer specifically. The
complex [Mo(NCMe)2(CO)2(PPh3)2] results from the
reaction of [Mo(η3-CH2CHCH2)Br(NCMe)2(CO)2] with
excess triphenylphoshine.20 Treating this complex with
Me2NC(dS)Cl leads to a smooth oxidative addition and
formation of cis,cis,trans-[Mo(η2-SCNMe2)Cl(CO)2(PPh3)2]
(6) in moderate yield (52%) (Scheme 2). Characterization
of this complex remains incomplete due to its low
solubility in all common solvents and its slow decom-
position in those in which it is soluble. As with the
previous complexes, however, 6 reacts with K[HB(pz)3]
to provide 2 in 88% yield, a conversion that supports
its formulation.
While thiocarbamoyl ligands are comparatively re-
sistant to amine protonolysis, alkoxythiocarbonyls may
often be converted to thiocarbonyls by treatment with
Brønstead or Lewis acids. For example, we have recently
described a convenient preparation of [IrCl(CS)(PPh3)2]
based on the protonolysis of the aryloxythiocarbonyl
complex [IrHCl{C(dS)OC6H4Me-4)(CO)(PPh3)2].21 The
thiocarbonyl chemistry of tungsten has been extensively
studied by Angelici,22,23 revealing an impressive syn-
thetic utility for the preparation of a wide range of
organosulfur ligands. Unfortunately, the key starting
material for this work is [W(CS)(CO)5],23 which is only
obtained in 12% yield. The yield for the corresponding
molybdenum complex is only 2-4%, a fact that some-
what curtails the study of molybdenum thiocarbonyl
chemistry. We therefore hoped that the strategies
employed above, if applied to the synthesis of alkoxy-
thiocarbonyl complexes, might provide an alternative
entry point for molybdenum thiocarbonyl chemistry.24
Sch em e 3
troscopic data, these being generally similar to those
for 2. Thus two carbonyl infrared absorptions are
observed at 1993 and 1876 cm-1, to somewhat higher
frequency of those observed for 2, suggesting an en-
hanced π-acidity for alkoxythiocarbonyl ligands relative
1
to thiocarbamoyls (vide infra). The H NMR spectrum
of 7a clearly reveals the operation of a fluxional process
at room temperature: The pyrazolyl protons give rise
to only two peaks [δ 7.73 (6 H), 6.24 (3 H)] and the
AA′BB′ system of the tolyl group appears as only a broad
single resonance [δ 7.25]. While the 13C{1H} resonance
for the carbonyl ligands (233.3) is shifted to high field
of that for 2, the thiocarbonyl resonance (284.6 ppm) is
moved dramatically to lower field. FAB-MS data confirm
the gross formulation of 7a and also include fragmenta-
tions due to loss of carbonyl ligands and the entire
aryloxythiocarbonyl ligand. Perhaps surprisingly, there
are no fragmentations attributable to loss of the aryl-
oxide group. We have observed the prevalence of frag-
mentations due to aryloxide elimination among the
FAB-MS data for aryloxythiocarbonyl complexes of
iridium and noted that such processes are also reflected
in the solution chemistry.21 Unfortunately for our
present purposes, the absence of such fragmentations
for 7a is also mirrored in its reactivity: The complex
fails to react with either HCl or HBF4 to provide
thiocarbonyl complexes. In a similar manner, the thio-
carbamoyl complex 2 failed to react with HCl, HBF4, or
[Et3O]BF4 under ambient conditions. Heating 2 with
elemental sulfur or propene episulfide in refluxing thf
also failed to provide the dithiocarbamate complex [Mo-
(S2CNMe2)(CO)2{HB(pz)3}], while the reactions of sulfur
with either [Mo(η2-SCC6H4OMe)(CO)2{HB(pz)3}] or [Mo-
(tCC6H4OMe-4)(CO)2{HB(pz)3}] readily provide the
dithiocarboxylate complex [Mo(S2CC6H4OMe-4)(CO)2-
{HB(pz)3}].1 The anticipated ultimate products of elec-
trophilic attack at the sulfur of bidentate thiocarbamoyl
ligands would be bidentate thiolatocarbene complexes.
These would appear entirely reasonable and have
copious precedent, via alternative synthetic strate-
gies.1,7,25,26 The bidentate thiocarbamoyl and thioalkoxy-
carbonyl binding mode in these complexes however
appears particular unreactive. This reinforces observa-
Treating an acetonitrile solution of [Mo(CO)3(NCMe)3]
with 4-tolyl chlorothionoformate (ClC(dS)OC6H4Me-4)
results in the formation of a deep red solution. No
attempt was made to isolate the intermediate; however
subsequent treatment with K[HB(pz)3] resulted in the
formation of the deep red complex, [Mo(η2-SCOC6H4Me-
4)(CO)2{HB(pz)3}] (7a ), in reasonable yield (69% based
on [Mo(CO)6]). A similar process employing ClC(dS)-
OC6H5 provides [Mo(η2-SCOC6H5)(CO)2{HB(pz)3}] (7b)
in lower yield (49%). Lower yields (52%) of 7a are also
obtained when [Mo(η6-C7H8)(CO)3] is treated with ClC-
(dS)OC6H4Me-4 and K[HB(pz)3] in dichloromethane
(Scheme 3). The formulation of 7a follows from spec-
(20) Deick, H. T.; Freidel, H. J . Organomet. Chem. 1968, 14, 375.
(21) Hill, A. F.; Wilton-Ely, J . D. E. T. Organometallics 1996, 15,
3791.
(22) For a general review of thiocarbonyl ligands see: Broadhurst,
P. V. Polyhedron 1985, 4, 1801.
(23) Dombek, B. D.; Angelici, R. J . Inorg. Chem. 1976, 15, 1089.
(24) For chromium an alternative entry is already available employ-
ing the desulfurization of coordinated CS2: (a) Fenster, A. E.; Butler,
I. S. J . Organomet. Chem. 1974, 13, 915. (b) Caillet, P.; J aouen, G. J .
Organomet. Chem. 1975, 91, C53.

2472 Organometallics, Vol. 20, No. 12, 2001
Anderson et al.
tions by Roper27 that in the case of dithioalkoxycarbo-
nyls the mode of coordination, i.e., monohapto or di-
hapto, effects the acid lability of the thiolate substituent,
the latter being generally deactivated toward electro-
philic attack. In the case of 6a the mode of coordination
of the thioalkoxycarbonyl ligand is dihapto and accord-
ingly deactivated toward acids.
As noted above, thioaroyl complexes, e.g., [Mo(η2-
SCC6H4OMe-4)(CO)2{HB(pz)3}] related to 2 and 7, are
readily obtained by addition of propene episulfide to
appropriate alkylidyne complexes.1 Given the stability
of thiocarbamoyl complexes discussed above, it seemed
reasonable that a similar addition of sulfur to an
aminomethylidyne complex would also provide access
to thiocarbamoyls. The reaction of [Mo(dCNiPr2)(CO)2-
{HB(pz)3}] (8) with elemental sulfur was therefore
investigated and found not to occur. In a similar
manner, propene episulfide fails to react with 8. This
may be for one of two possible reasons: First the NiPr2
group is sterically cumbersome and might be expected
to offer some kinetic protection to the MotC multiple
bond. This seems however unlikely since the sterically
encumbered complex [Mo(tCC6H3Me2-2,6)(CO)2(η-C5-
Me5)] reacts readily with sulfur to provide [Mo(S2CC6H3-
Me2-2,6)(CO)2(η-C5Me5)].28 It seems more likely that the
initial step involves nucleophilic attack by the sulfur of
S8 or SC3H6, and this is disfavored by the less electro-
philic amino-substituted alkylidyne. Furthermore, argu-
ing against steric factors, the complex 8 does react with
[Fe2(CO)9] to provide the thermally labile hetero-
bimetallic alkylidyne complex [MoFe(µ-CNiPr2)(CO)5]
(9) (Scheme 4). Although this appears to be the first
example of the use of a terminal mononuclear amino-
methylidyne complex in bridge-assisted metal-metal
bond formation, the process follows the copious prece-
dent provided by Stone for hydrocarbon-based alkyli-
dyne ligands.29 Thus the formulation of 9 rests on a
comparison of spectroscopic data with those for the
general class of compounds [MFe(µ-CR)(CO)5(L)] (M )
Cr, Mo, W; R ) Me, Ph, C6H4NMe2, C6H4Me-4, C6H3-
Me2-2,6; L ) η-C5H5, η-C5Me5, HB(pz)3). The complex 9
gives rise to five carbonyl absorptions in an intensity
ratio [CH2Cl2: 2036s, 1969m, 1945m, 1891w, 1827w(br)]
similar to those observed for the complex [MoFe(µ-
CC6H3Me2-2,6)(CO)5(η-C5R5)] [R ) H: 2053s, 1995s,
1977s, 1933w, 1896w(br);30 R ) Me: 2038vs, 1975s,
1965s, 1859w(br)28] although shifted to slightly lower
frequency, consistent with the increased electron-donat-
ing ability of the amino substituent. While the precursor
8 gives rise to one doublet and one heptet 1H NMR
resonance, the spectrum for the complex 9 includes two
heptets and two doublets for the NiPr2 group. Thus the
two isopropyl groups are chemically distinct but straddle
a molecular mirror plane. This is consistent with the
F igu r e 3. Orientational possibilities for the bridging
aminomethylidyne ligand in 8.
Sch em e 4
C-N-C and Fe-C-Mo units being coplanar (Figure 3),
even though this might be expected to be disfavored on
steric grounds. The role of the MotC group as “four-
electron” donor31 to the “Fe(CO)3” fragment would
clearly be enhanced were the nitrogen to also conjugate
into the unsaturated MoCFe system, and this is possible
with such an arrangement. Attempts to obtain 13C{1H}
NMR data for 9 were unsuccessful due to decomposition
during the acquisition, the major product being regener-
(25) (a) Doyle, R. A.; Angelici, R. J . Organometallics 1989, 8, 2207.
(b) Kim, H. P.; Kim, S.; J acobson, R. A.; Angelici, R. J . Organometallics
1984, 3, 1124.
(26) (a) Kreissl, F. R.; Keller, H. Angew. Chem., Int. Ed. Engl. 1986,
25, 904. (b) Ullrich, N.; Steigmair, C.; Keller, H.; Hertweck, E.; Kreissl,
F. R. Z. Naturforsch. 1990, B45, 921. (c) Kreissl, F. R.; Stegmair, C.
M. Chem. Ber. 1991, 124, 2747.
(27) Collins, T. J .; Roper, W. R.; Town, K. G. J . Organomet. Chem.
1976, 121, C41.
(28) Anderson, S.; Hill, A. F.; Nasir, B. A. Organometallics 1995,
14, 2987.
(29) Stone, F. G. A. Angew. Chem., Int. Ed. Engl. 1984, 23, 89.
(30) Dossett, S. J .; Hill, A. F.; J effery, J . C.; Marken, F.; Sherwood,
P.; Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1988, 2453.
(31) For theoretical treatments of alkylidyne complexes acting as
“four-electron donors” see ref 30 and: Dossett, S. J .; Hill, A. F.; Howard,
J . A. K.; Nasir, B. A.; Spaniol, T. P.; Sherwood, P.; Stone, F. G. A. J .
Chem. Soc., Dalton Trans. 1989, 1871.

Metallathiirenes
Organometallics, Vol. 20, No. 12, 2001 2473
Ta ble 1. Selected In fr a r ed a n d Ca r bon -13 NMR
Da ta for th e Com p lexes
ated 8. This loss of the “Fe(CO)3” group is unexpected;
however we note that 8 also fails to react with [Co2-
(CO)8], despite this being one of the most general
reactions for alkylidynes of the form [M(dCR)(CO)2-
(L)].29
[M(η2-XdC-Y)(CO)2{HB(p z)3}]
IR (CH2Cl2)
NMR (CDCl3)
13C(XCY) 13C(CO)
a
ν(CO)
kCK
(Nm-1
δ
δ
M
X
Y
(cm-1
)
)
(ppm)
(ppm)
Despite the instability of 9, it is possible to convert it
to a heterodinuclear thiocarbamoyl complex. Thus a
purple solution of 9 reacts rapidly with elemental sulfur
to provide the yellow and thermally stable thiocarbam-
oyl complex [MoFe(µ-SCNiPr2)(CO)5{HB(pz)3}] (10). Simi-
lar reactions have been described for related bimetallic
hydrocarbon-based alkylidyne complexes.28,32,33 In the
present case, the addition of sulfur to one of the
prochiral FeCMo faces provides a tetrahedral FeMoCS
core, and the resulting chirality is manifest in the
appearance of two methine heptets and four methyl
doublets (δ 0.87, 1.42, 1.50, 1.59) in the 1H NMR
spectrum of 10. The infrared spectrum of 10 includes
four carbonyl absorptions (1948, 1932, 1850, and 1832
cm-1), and while the intensity profile is similar to that
for [MoFe(µ-SCC6H3Me2-2,6)(CO)5(η-C5H5)],33a the ab-
sorptions are moved to significantly lower frequency.
Although thiocarbamoyl ligands have been previously
observed in bi-34 and trinuclear35 complexes, we believe
this is the first heterobimetallic example with a trans-
verse arrangement of C-S and metal-metal vectors.
The thioaroyl complex [Mo(η2-SCC6H4OMe-4)(CO)2{HB-
(pz)3}] reacts with [Fe2(CO)9] to provide the thioaroyl-
bridged bimetallic complex [MoFe(µ-SCC6H4OMe-4)-
(CO)5{HB(pz)3}].1 It is therefore somewhat surprising
that the thiocarbamoyl complex 2 fails to react with [Fe2-
(CO)9] to provide [MoFe(µ-SCNMe2)(CO)5{HB(pz)3}]
given the isolation of 10. These results taken together
tend to encourage caution in drawing too strong an
analogy between thioacyl and thiocarbamoyl ligands.
Thus each of the structural motifs detailed in Scheme
4 can be constructed; however some of the apparent
kinetic barriers preventing their interconversion are
surprising.
Mo
Mo
Mo
Mo
Mo
Mo
Mo
Mo
W
S
S
S
OC6H4Me-4 1993 1879 15.15
284.6
284.0
280.4
278.0
268
233.3
233.1
233.2
233.6
236
OC6H5
C6H4Me-4
1994 1878 15.15
1979 1893 15.14
S
C6H4OMe-4 1976 1891 15.10
O
O
S
O
S
Meb
1980 1850 14.82
1965 1852 14.72
1942 1848 14.51
1937 1820 14.26
1923 1818 14.14
1924 1803 14.04
Phb
254
239
NMe2
NiPr2
NMe2
NiPr2
251.3
204.8
249.7
205.7
242.7
245.1
241.5
245.3
W
O
a
b
Cotton Kraihanzel force constant. Taken from ref 37.
[W(η2-SCNMe2)(CO)2{HB(pz)3}] (11) in reasonable yield
(60%) (Scheme 3). Spectroscopic data for 11 are es-
sentially comparable to those for 2: Two carbonyl
absorptions are observed in the infrared spectrum at
1923 and 1818 cm-1 (CH2Cl2). As with 2, the operation
of a fluxional process is evident from the appearance of
1
the pyrazolyl-derived H NMR resonances as a triplet
(δ 6.20) and two doublets (δ 7.74, 7.64). Only at
temperatures below -40 °C do the pyrazolyl environ-
ments become resolved. This fluxionality does not
however chemically equilibrate the methyl groups,
which remain distinct (δ 3.78, 3.73). On intensity
grounds, the two closely positioned low-field 13C{1H}
resonances at 249.7 and 241.5 ppm are assigned to the
thiocarbamoyl and carbonyl nuclei, respectively. Treat-
ing an acetonitrile solution of [W(CO)3(NCMe)3] with
ClC(dS)OC6H4Me-4 (-30 °C) followed by addition of
K[HB(pz)3}] fails to result in the isolation of an aryloxy-
thiocarbonyl complex. Rather, spectroscopic data for the
yellow product reveal it to be [WCl(CO)3{HB(pz)3}] (12),
which has been described previously by Angelici.36
Con clu d in g Rem a r k s. The isolation of the com-
plexes 2, 6, 11, our recent report on the complexes [Mo-
(η2-SCR)(CO)2{HB(pz)3}] (R ) C6H4OMe-4, C6H4Me-4,
C4H3S-2),1 and related carbamoyl complexes [M(η2-
OCNiPr2)(CO)2{HB(pz)3}] (M ) Mo, W)19 allow for a
Tu n gsten Com p lexes. Preliminary attempts to ex-
tend the above methods to tungsten met with varied
success. The synthesis of a thiocarbamoyl complex was
readily achieved; however the approach has failed so
far for the introduction of aryloxythiocarbonyl ligands.
Treating a solution of [W(CO)3(NCMe)3] with Me2NC-
(dS)Cl resulted in an oxidative addition similar to that
described for the formation of 1; however while the
formation of 1 requires approximately 5 min at (-30
°C), the formation of the tungsten analogue requires 30
min at this temperature to go to completion. Subsequent
addition of K[HB(pz)3] resulted in the formation of
comparison of spectroscopic data for
a range of
“metallathiirene” and “metallaoxirene” LnM(η2-XdC-Y)
(X ) O, S; Y ) amino, alkoxy, aryl) compounds. Thus
Table 1 collates infrared and 13C{1H} NMR data for
the various analogues, including the complexes [Mo-
(η2-OCR)(CO)2{HB(pz)3}] (R ) Me, Ph) described by
Curtis.37 The infrared data provide a rough indication
of the variation in metal basicity which is reflected in
the force constants38 of the carbonyl co-ligands. From
this the following points may be noted within this
series: (i) As expected the ν(CO) and k(CK) values for
tungsten analogues are lower than those for the related
molybdenum examples, this being a generally observed
phenomenon for isostructural pairs of carbonyl com-
plexes of 4d and 5d metals.39 (ii) The aryloxythiocarbo-
nyl ligand appears the most strongly π-acidic, although
(32) (a) Bermudez, M. D.; Delgado, E.; Elliott, G. P.; Tran-Huy, N.
H.; Mayor-Real, F.; Stone, F. G. A.; Winter, M. J . J . Chem. Soc., Dalton
Trans. 1987, 1235. (b) Delgado, E.; Hein, J .; J effery, J . C.; Ratermann,
A. L.; Stone, F. G. A.; Farrugia, L. J . J . Chem. Soc., Dalton Trans.
1987, 1191. (c) Green, M.; Howard, J . A. K.; J ames, A. P.; Nunn, C.
M.; Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1986, 187. (d) Chetcuti,
M. J .; Chetcuti, P. A. M.; J effery, J . C.; Mills, R. M.; Mitrprachachon,
P.; Pickering, S. J .; Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1982,
699.
(33) (a) Hill, A. F.; Nasir, B. A.; Stone, F. G. A. Polyhedron 1989, 8,
179. (b) Byrne, P. G.; Garcia, M. E.; J effery, J . C.; Sherwood, P.; Stone,
F. G. A. J . Chem. Soc., Dalton Trans. 1987, 1215.
(34) (a) Dean, W. K.; Van der Veer, D. G. J . Organomet. Chem. 1978,
146, 143. (b) Mahe, C.; Patin, H.; Benoit, A.; Le Marouille, J . Y. J .
Organomet. Chem. 1981, 216, 15. (c) Porter, S. K.; White, H.; Green,
C. R.; Angelici, R. J .; Clardy, J . Chem. Commun. 1973, 493.
(35) J effery, J . C.; Went, M. J . J . Chem. Soc., Dalton Trans. 1990,
567. J effery, J . C.; Went, M. J . Chem. Commun. 1987, 1766.
(36) Kim, H. P.; Kim, S.; J acobson, R. A.; Angelici, R. J . Organo-
metallics 1986, 5, 2481.
(37) Butler, W. M.; Curtis, M. D.; Shiu, K. B. Organometallics 1983,
2, 1475. Curtis, M. D.; Shiu, K. B.; Butler, W. M. J . Am. Chem. Soc.
1986, 108, 1550.
(38) Cotton, F. A.; Kraihanzel, C. S. J . Am. Chem. Soc. 1962, 84,
4432.

2474 Organometallics, Vol. 20, No. 12, 2001
Anderson et al.
addition of K[HB(pz)3] (3.05 g, 12.1 mmol) at this point and
slow warming to room temperature resulted in the formation
of a deep red/orange suspension. The solid byproducts were
allowed to settle, and the reaction liquor was transferred to a
second Schlenk tube via a cannula. Removal of the solvent in
vacuo afforded a dark oil, which was extracted with dichloro-
methane (2 × 10 mL). The combined extracts were chromato-
graphed on alumina (ca. 50 × 6 cm) at -30 °C eluting with a
mixture of diethyl ether and hexane (2:1). The initial intense
orange band was collected, reduced in volume to ca. 20 mL,
and diluted with hexane (20 mL). Slow removal of solvent led
to the solution becoming cloudy. Storage of the concentrated
solution at -20 °C (24 h) yielded orange microcrystals of [Mo-
(η2-SCNMe2)(CO)2{HB(pz)3}] (2). Yield: 2.30 g (45%).
(ii) Molybdenum hexacarbonyl (3.00 g, 11.4 mmol) and
K[HB(pz)3] (3.05 g, 12.1 mmol) were suspended in acetonitrile
and heated under reflux for 24 h. The resulting orange solution
was slowly cooled to 0 °C in an ice bath and N,N-dimethylthio-
carbamoyl chloride (1.39 g, 11.4 mmol) added in one portion.
The suspension gradually became dark red-brown in color.
Removal of the solvent and dissolution with dichloromethane
followed by chromatography (alumina, diethyl ether eluant,
-20 °C) resulted in the elution of an orange fraction, from
which [Mo(η2-SCNMe2)(CO)2{HB(pz)3}] (2) was isolated as
described in (i) above. Yield: 0.35 g (14%).
(iii) [Mo(η2-SCNMe2)Cl(CO)2(tmeda)] (4) (vide infra, 0.20 g,
0.50 mmol) was dissolved in dichloromethane (20 mL) and
K[HB(pz)3] (0.13 g, 0.50 mmol) added. An instantaneous
reaction occurred with the visible darkening of the solution to
deep orange. Chromatographic separation (alumina, diethyl
ether eluant, 25 °C) yielded a bright orange fraction, from
which [Mo(η2-SCNMe2)(CO)2{HB(pz)3}] (2) was isolated as in
(i) above. Yield: 0.22 g (95%).
(iv) A suspension of trans-[Mo(η2-SCNMe2)(Cl)(CO)2(PPh3)2]
(5) (vide infra, 0.20 g, 0.30 mmol) in tetrahydrofuran (20 mL)
was treated with K[HB(pz)3] (0.06 g, 0.30 mmol) and stirred
for 1 h. The resulting orange suspension was freed of solvent
under reduced pressure and the residue extracted with a
mixture of dichloromethane and light petroleum (1:1, 10 mL)
and purified by chromatography (alumina, -20 °C) eluting
with the same solvent mixture. The bright orange zone was
collected and reduced to a small volume, resulting in the
crystallization of bright orange [Mo(η2-SCNMe2)(CO)2{HB-
(pz)3}] (2). Yield: 0.10 g (88%).
this is essentially comparable to that of thioaroyl ligands
and greater than for aroyl and acyl ligands. (iii) Thio-
carbamoyls are comparatively π-basic ligands, while
carbamoyls themselves are the most electron releasing.
From the 13C{1H} NMR data it can be seen that for the
thioacyl, thioaroyl, and aryloxythiocarbonyl complexes
the resonances attributed to these ligands appear to low
field of that for the carbonyl ligand and the trend in
their chemical shift parallels that for the infrared data.
In the case of carbamoyl ligands this resonance is
dramatically shifted to high field of the carbonyl ligand.
The carbonyl resonance appears somewhat insensitive
to the nature of the metallathiirene/oxirene substitu-
ents, but correlates loosely with the infrared data.
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-tube techniques. Solvents were purified by
distillation from an appropriate drying agent [ethers and
paraffins from sodium/potassium alloy with benzophenone as
indicator; halocarbons and acetonitrile from CaH2]. With the
exception of the intermediate 1, which was not isolated, all
other new compounds described were indefinitely stable as
solids under air in ambient conditions, although these were
routinely stored in a freezer. Solutions of compound 6 and 9
gradually decomposed; however all other products showed no
apparent air sensitivity. Schlenk-line techniques were never-
theless routinely employed. The use of low-temperature col-
umn chromatography does not reflect thermal instability of
the compounds, but rather a tendency to elute poorly at room
temperature, in addition to the general improvement in
resolution offered by thermostatically controlled low temper-
atures. Reactions were monitored by thin-layer chromatogra-
phy (and FT-IR spectroscopy) under ambient conditions. In
most cases chromatography could be replaced by repeated
fractional crystallizations; however this resulted in substan-
tially lower yields and occasional reductions in product purity.
1H, 13C{1H}, and 31P{1H} NMR spectra were recorded on
Bruker WH-400 NMR or J EOL J NM EX270 NMR spectrom-
eters and calibrated against internal Me4Si (1H), internal
CDCl3 (13C), or external H3PO4 (31P). Infrared spectra were
recorded using Perkin-Elmer 1720-X FT-IR or Mattson Re-
search Series 1 spectrometers. FAB mass spectrometry was
carried out with an Autospec Q mass spectrometer using
3-nitrobenzyl alcohol as matrix. Elemental microanalytical
data were obtained from the ICSTM microanalytical service.
All reagents were commercially available and used as received
from commercial sources (Aldrich). The compounds [Mo(η6-
C7H8)(CO)3],40 [Mo(CO)3(NCMe)3],41 [W(CO)3(NCMe)3],41 and
K[HB(pz)3]42 were prepared according to published procedures.
P r ep a r a tion of [Mo(η2-SCNMe2)(CO)2{HB(p z)3}] (2). (i)
Molybdenum hexacarbonyl (3.00 g, 11.4 mmol) was suspended
in acetonitrile (40 mL) and heated under reflux for 24 h, to
generate fac-[Mo(NCMe)3(CO)3]. The yellow solution was
cooled to -30 °C and N,N-dimethylthiocarbamoyl chloride
(1.39 g, 11.4 mmol) added in one portion. A darkening of the
yellow solution was observed immediately. After stirring for
5 min, a dark orange solution had resulted. Subsequent
(v) A solution of [Mo(η6-C7H8)(CO)3] (1.00 g, 3.7 mmol) in
dichloromethane (20 mL) was treated with N,N-dimethylthio-
carbamoyl chloride (0.45 g, 3.7 mmol) and K[HB(pz)3] (0.93 g,
3.7 mmol), and the mixture stirred for 48 h. Purification was
achieved by chromatography on silica gel (ca. 50 × 4 cm) using
diethyl ether as the eluant. The major orange band was
collected and the product isolated as for (i) above. Yield: 0.77
g (46%). IR CH2Cl2: ν(CO) 1942vs, 1848s [ν(CO)] cm-1; Nujol:
1912s, 1812s [ν(CO)] cm-1. NMR (CDCl3, 25 °C) 1H: δ 3.75,
3.83 [s × 2, 3 H × 2, CH3], 6.20 [t, 3 H, H4(pz)], 7.64, 7.74 [d
× 2, 3 H × 2, H3, H5(pz)] ppm. 13C{1H}: 251.3 [CS], 242.7 [CO],
145.5, 144.4, 136.2, 135.3, 107.1, 105.9 [pz], 50.7, 45.5 [CH3]
ppm. FAB-MS m/z 455 [M]+, 425 [M - CO]+, 399 [M - 2CO]+.
Anal. Found: C, 37.0; H, 3.4; N, 21.2. Calcd for C14H16
BMoN7O2S: C, 37.1; H, 3.6; N, 21.6.
-
P r ep a r a tion of [Mo(η2-SCNMe2)(CO)2(η2-C5H5)] (3). A
suspension of [Mo(η2-SCNMe2)Cl(CO)2(tmeda)] (0.20 g, 0.50
mmol) in tetrahydrofuran (20 mL) was treated with a solution
(39) Kirtley, S. W. In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Perganomn Press
Ltd.: Oxford, 1982; Vol. 3, p 1079.
(40) Abel, E. W.; Bennet, M. A.; Burton, R.; Wilkinson, G. J . Chem.
Soc., A 1958, 4559. Cotton, F. A.; McCleverty, J . A.; White, J . E.; King,
R. B.; Fronzaglia, A. F.; Bisnette, M. B. Inorg. Synth. 1967, 9, 121.
(41) Tate, D. P.; Knipple, W. R.; Augl, J . M. Inorg. Chem. 1962, 1,
433.
of NaC5H5 also in tetrahydrofuran (0.50 mL, 1.0 mol dm-3
,
0.50 mmol). An immediate darkening of the solution to red
was observed. After stirring for 1 h, the reaction liquor was
passed through a short plug of alumina (ca. 15 × 2 cm) and
[Mo(η2-SCNMe2)(CO)2(η2-C5H5)] crystallized from the eluate
by addition of hexane and cooling to -30 °C. Yield: 0.13 g
(84%). IR CH2Cl2: 1943vs, 1847s [ν(CO)] cm-1. NMR (CDCl3,
25 °C) 1H: δ 3.61, 3.73 [s × 2, 3 H × 2, CH3], 5.42 [s, 5 H,
C5H5]. 13C{1H}: 243.5 [CS], 222.6 [CO], 93.6 [C5H5], 49.7, 46.6
(42) Trofimenko, S. J . Am. Chem. Soc. 1967, 89, 6288. Trofimenko,
S. Scorpionates: The Coordination Chemistry of Polypyrazolylborate
Ligands; Imperial College Press: London, 1999.

Metallathiirenes
Organometallics, Vol. 20, No. 12, 2001 2475
1
[CH3] ppm. IR and H NMR data may be compared with those
reported previously.7
its formulation however comes from the reaction of 6 with
K[HB(pz)3] to provide 2.
P r epar ation [Mo(η2-SCOC6H4Me-4)(CO)2{HB(pz)3}] (7a).
(i) Molybdenum hexacarbonyl (1.50 g, 5.70 mmol) in acetoni-
trile (30 mL) was heated under reflux for 24 h. The resulting
yellow solution was cooled to -30 °C and p-tolyl chlorothiono-
formate (0.9 mL, 5.7 mmol) added. Stirring at this temperature
for 15 min resulted in the formation of an intense orange
solution. Addition of K[HB(pz)3] (1.45 g, 5.8 mmol) resulted
in vigorous evolution of carbon monoxide and the formation
of a red suspension, which was allowed to return to ambient
temperature. The reaction liquor was freed of solvent and
extracted with diethyl ether (3 × 10 mL), and the combined
extracts were purified by chromatography (alumina, ca. 30 ×
6 cm, diethyl ether eluant). The orange zone, which eluted with
diethyl ether, was diluted with ethanol, concentrated, and
cooled (-30 °C) to provide deep red crystals of [Mo(η2-
SCOC6H4Me-4)(CO)2{HB(pz)3}] (7a ). Yield: 2.02 g (69%).
(ii) A solution of [Mo(η6-C7H8)(CO)3] (1.00 g, 3.7 mmol) in
dichloromethane (20 mL) was treated with K[HB(pz)3] (0.93
g, 3.7 mmol) followed by p-tolyl chlorothionoformate (0.5 mL,
3.7 mmol). The orange suspension was stirred for 24 h and
the resulting mixture chromatographed on silica gel (ca. 50 ×
6 cm). Slow elution with a mixture of light petroleum and
dichloromethane (2:1) facilitated the separation of the major
orange product from several minor side-product bands. Reduc-
ing the eluate volume resulted in the deposition of red [Mo-
(η2-SCOC6H4Me-4)(CO)2{κ3-HB(pz)3}] (7a ) (0.99 g, 52%). IR
CH2Cl2: 1993s, 1879vs [ν(CO)] cm-1. Nujol: 1985s, 1855s [ν-
(CO)] cm-1. NMR (CDCl3, 25 °C) 1H: δ 2.41 [s, 3 H, CH3], 6.24,
7.73 [s(br) × 2, 9 H, H(pz)], 7.25 [s(br), 4 H, C6H4]. 13C{1H}:
284.6 [CS], 233.3 [CO], 159.2 [C1(C6H4)], 144.4 [C4(C6H4)],
136.7, 135.6 [C2,3,5,6(C6H4)], 130.0, 119.3, 105.8 [pz], 21.0 [CH3]
ppm. FAB-MS m/z 518 [M]+, 490 [M - CO]+, 460 [M - 2CO]+,
366 [M - CSOC6H4Me]+ Anal. Found: C, 39.3; H, 2.9; N, 14.5.
Calcd for C19H17BMoN6O3S.CH2Cl2 C, 40.0; H, 3.2; N, 14.0.
Unsatisfactory analytical data presumably reflect variable
solvation.
P r ep a r a tion of [Mo(η2-SCOP h )(CO)2{HB(p z)3}] (7b). A
suspension of molybdenum hexacarbonyl (1.50 g, 5.70 mmol)
in acetonitrile (30 mL) was heated under reflux for 24 h. The
resulting yellow solution was cooled to -30 °C and phenyl
chlorothionoformate (0.6 mL, 5.7 mmol) added. Stirring at this
temperature for 15 min resulted in the formation of an intense
orange solution. Addition of K[HB(pz)3] (1.45 g, 5.8 mmol)
resulted in vigorous evolution of carbon monoxide and the
formation of a red suspension. The mixture was then allowed
to return to ambient temperature. The reaction liquor was
freed of solvent, the residue was extracted with diethyl ether
(3 × 10 mL), and the combined extracts were purified by
chromatography on alumina (ca. 30 × 6 cm, -20 °C). The
orange zone was eluted and the product isolated as for 6a
above to provide red crystals of [Mo(η2-SCOPh)(CO)2{HB(pz)3}]
(7b). Yield: 1.41 g (49%). IR CH2Cl2: 1994vs, 1878s [ν(CO)]
cm-1. Nujol: 1989s, 1857s [ν(CO)] cm-1. NMR (CDCl3, 25 °C)
1H: δ 6.25, 7.73 [s(br) × 2, 9 H, pz], 7.34-7.46 [m, 5 H, C6H5].
13C{1H}: 284.0 [CS], 233.1 [CO], 160.9 [C1(C6H5)], 144.6 [C4-
(C6H5)], 135.6, 126.9 [C2,3,5,6(C6H5)], 129.5, 119.6, 105.8 [pz]
ppm. FAB-MS m/z 504 [M]+, 476 [M - CO]+, 448 [M - 2CO]+.
P r ep a r a tion of [Mo(η2-SCNMe2)Cl(CO)2(bip y)] (4). Mo-
lybdenum hexacarbonyl (3.00 g, 11.4 mmol) was suspended
in acetonitrile (40 mL) and heated under reflux for 24 h, to
generate fac-[Mo(NCMe)3(CO)3]. The yellow solution was
cooled to -30 °C and N,N-dimethylthiocarbamoyl chloride
(1.39 g, 11.4 mmol) added. A darkening of the yellow solution
was observed immediately, and, after stirring for 5 min, 2,2-
bipyridyl (1.80 g, 11.4 mmol) was added. This resulted in a
further darkening of the solution. A dark brown precipitate
had formed after stirring for 1 h. The crude solid was filtered
off and washed with acetonitrile (3 × 40 mL). Purification was
achieved by extraction of this solid with tetrahydrofuran (3 ×
20 mL) and elution of the combined extracts through alumina
(ca. 15 × 6 cm). The orange fraction was collected, diluted with
hexane, and then concentrated under reduced pressure to
provide [Mo(η2-SCNMe2)Cl(CO)2(bipy)] (3). Yield: 2.60 g (58%).
IR CH2Cl2: 1937 s, 1840s [ν(CO)] cm-1. Nujol: 1931s, 1846s
[ν(CO)] cm-1. NMR (CDCl3, 25 °C) 1H: δ 3.41, 3.74 [s × 2, 3 H
× 2, CH3], 7.40, 7.94, 8.13, 9.15 [bipy]. 13C{1H}: 223.0 [CS],
204.7 [CO], 153.1, 137.2, 125.2, 123.2, 121.9 [C(bipy)], 29.7,
29.6 [CH3] ppm. FAB-MS m/z 433 [M]+, 407 [M - CO]+, 398
[M - Cl]+, 377 [M - 2CO]+, 342 [M - 2CO, Cl]+. Anal. Found:
C, 41.8; H, 3.0; N, 10.7. Calcd for C15H14ClMoN3O2S: C, 42.0;
H, 3.3; N, 9.8.
P r ep a r a tion of [Mo(η2-SCNMe2)Cl(CO)2(tm ed a )] (5).
Molybdenum hexacarbonyl (1.50 g, 5.7 mmol) was suspended
in acetonitrile (30 mL) in a flame-dried Schlenk tube and
heated under reflux for 24 h. The resulting yellow solution
was cooled to -40 °C and N,N-dimethylthiocarbamoyl chloride
(0.68 g, 5.70 mmol) added. The solution was stirred for 10 min,
becoming deep orange. N,N,N′,N′-Tetramethylethylenediamine
(tmeda, 0.83 mL, 5.7 mmol) was then added and the mixture
stirred while warming to room temperature. The solution was
concentrated in volume under reduced pressure to ca. 15 mL,
yielding a bright orange precipitate of pure [Mo(η2-SCNMe2)-
Cl(CO)2(tmeda)] (4). Yield: 3.20 g (79%). IR CH2Cl2: 1923s,
1810s [ν(CO)] cm-1. Nujol: 1911s, 1797s [ν(CO)] cm-1. NMR
1
(CDCl3, 25 °C) H: δ 2.88, 3.11 [s(br) × 2, 16 H, tmeda]; 3.61,
3.73 [s × 2, 3 H × 2, SCNCH3]. 13C{1H}: 245.2 [CS], 230.9 [CO],
59.8, 57.1, 55.7, 52.4 [tmeda], 51.1, 45.0 [SCNCH3] ppm. FAB-
MS m/z 393 [M]+, 365 [M - CO]+, 358 [M - Cl]+, 337 [M -
2CO]+, 302 [M - 2CO, Cl]+, 269 [M - 2CO, Cl, S]+. Anal.
Found: C, 33.5; H, 5.4; N, 10.9. Calcd for C11H22ClMoN3O2S:
C, 33.7; H, 5.7; N, 10.7.
P r ep a r a t ion of [Mo(η2-SCNMe2)Cl(CO)2(P P h 3)2] (6).
Molybdenum hexacarbonyl (5.28 g, 20.0 mmol) and 3-bromo-
prop-1-ene (2.6 mL, 20.0 mmol) were suspended in acetonitrile
(40 mL) and benzene (40 mL) and heated under reflux for
24 h. Upon cooling, an orange precipitate of [Mo(η-C3H5)(Br)-
(CH3CN)2(CO)2] was isolated by filtration. This precipitate and
triphenylphosphine (15.8 g, 60.3 mmol) were suspended in
acetonitrile (60 mL) and heated under reflux for 15 min,
resulting in the deposition of a bright yellow precipitate of
[Mo(CH3CN)2(CO)2(PPh3)2].
[Mo(CH3CN)2(CO)2(PPh3)2] (1.00 g, 1.30 mmol) was sus-
pended in dichloromethane (15 mL) and N,N-dimethylthio-
carbamoyl chloride (0.16 g, 1.3 mmol) added. An immediate
darkening of the reaction liquor was observed, followed by
the deposition of an orange precipitate, which was complete
after 20 min. The product was isolated by filtration and
washed successively with acetonitrile (10 mL), dichloro-
methane (2 × 10 mL), and diethyl ether (2 × 10 mL) to provide
[Mo(η2-SCNMe2)Cl(CO)2(PPh3)2]. Yield: 0.55 g (52%). IR CH2-
Cl2: 1952s, 1848vs [ν(CO)] cm-1. Nujol: 1952s, 1849s [ν(CO)]
cm-1. NMR (CDCl3, 25 °C) 31P: 40.1 ppm. FAB-MS m/z 766
[M - Cl]+, 678 [M - Cl, CSNMe2]+, 538 [M - PPh3]+, 505
[M - PPh3, Cl]+. The compound was not completely character-
ized due to its low solubility and solution stability, which
precluded satisfactory recrystallization. Further support for
Anal. Found: C, 42.5; H, 3.0; N, 16.4. Calcd for C18H15
BMoN6O3S: C, 43.0; H, 3.0; N, 16.7.
-
P r ep a r a tion of [Mo(tCNiP r 2)Br (CO)3(P P h 3)]. This in-
termediate in the preparation of 8 was prepared by Mayr’s
acyl-oxide abstraction approach43 applied to the synthesis of
aminomethylideyne complexes:44 Diisopropylamine (3.00 g, 30
(43) For a general review of the chemistry of alkylidyne complexes
including a discussion of oxide-absrtaction strategies see: Mayr, A.;
Hoffmeister, H. Adv. Organomet. Chem. 1991, 32, 227.
(44) (a) Anderson, S.; Hill, A. F. J . Organomet. Chem. 1990, 394,
C24. (b) Anderson, S.; Cook, D. J .; Hill, A. F. J . Organomet. Chem.
1993, 463, C3.

2476 Organometallics, Vol. 20, No. 12, 2001
Anderson et al.
mmol) was added to diethyl ether (40 mL) and cooled in an
complex was insufficiently stable for the acquisition of satis-
factory 13C{1H} NMR and elemental microanalytical data.
P r ep a r a tion of [MoF e(µ-SCNiP r 2)(CO)5{HB(p z)3] (10).
[MoFe{µ-CNiPr2}(CO)5{HB(pz)3}] (9, 0.035 g, 0.06 mmol) was
dissolved in tetrahydrofuran (20 mL) and sulfur (14 mg, 0.06
mmol) added. After stirring at room temperature overnight,
the reaction mixture changed from purple to yellow. The
solvent was then removed under vacuum, and the residue
chromatographed at low temperature (-30 °C, alumina, di-
ethyl ether eluant). The product was then isolated from the
first yellow band. Yield: 0.03 g (80%). IR Nujol: 2481 [ν(BH)],
1938, 1926, 1845, 1827 [ν(CO)] cm-1. CH2Cl2: 2485 [ν(BH)],
1948, 1932, 1850, 1832 [ν(CO)] cm-1. NMR 1H: δ 0.87, 1.42,
1.50, 1.59 [d × 4, 3 H × 4, CH3, J (HH) ) 6.9 Hz], 3.49, 4.11 [h
× 2, 2 H, NCH], 6.15, 6.19 [t × 2, 3 H, H4(pz)], 7.31 [m, 3 H,
H5(pz)], 7.71 [m, 3H, H3(pz)]. Anal. Found: C, 40.2; H, 4.0; N,
12.8. Calcd for C21H24BFeMoN6O5S: C, 39.7; H, 3.8; N, 13.3.
P r ep a r a tion of [W(η2-SCNMe2)(CO)2{HB(p z)3}] (11).
Tungsten hexacarbonyl (1.00 g, 2.8 mmol) was suspended in
acetonitrile (20 mL) and heated under reflux for 72 h. The
solution was cooled to -30 °C and treated with N,N-dimeth-
ylthiocarbamoyl chloride (0.35 g, 2.8 mmol), resulting in a slow
darkening of the solution to orange over a 30 min period.
Addition of K[HB(pz)3] (0.72 g, 2.9 mmol) resulted in a further
darkening of color. The mixture was allowed to return to
ambient temperature and stirred for 2 h. The solvent was
removed under reduced pressure, and the orange residue
redissolved in dichloromethane (15 mL). Purification by chro-
matography (alumina, dichloromethane eluant, -20 °C) yielded
a bright orange eluate, which was diluted with hexane (50 mL)
and reduced in volume to effect crystallization of [W(η2-
SCNMe2)(CO)2{HB(pz)3}] (9). Yield: 0.92 g (60%). IR CH2Cl2:
ice bath. A solution of methyllithium (19.5 mL, 1.54 mol dm-3
30 mmol) prepared from bromomethane and lithium was then
added dropwise and the resulting solution of “LiNiPr2‚LiBr”
allowed to warm to room temperature. In a separate flask,
molybdenum hexacarbonyl (5.28 g, 20 mmol) was suspended
in diethyl ether (20 mL). The solution of the lithium reagent
was added dropwise until the metal carbonyl had been
consumed (monitored by IR spectroscopy). The resulting yellow
solution was cooled (dry ice/propanone) and then treated with
a solution of trifluoroacetic anhydride (3.10 mL, 22 mmol) in
diethyl ether (20 mL). After stirring at low temperature for
15 min, the mixture was allowed to warm slowly to 0 °C. At
this point triphenylphosphine (7.86 g, 30 mmol) was added
and the mixture left to warm to ambient temperature. The
mixture was stirred for 10 h to provide a yellow precipitate.
The supernatant was discarded by decantation and the residue
extracted with a mixture of dichloromethane and light petro-
leum (2:1, 5 × 20 mL). The combined extracts were filtered
through diatomaceous earth, concentrated, and chromato-
graphed (silica gel, -30 °C, dichloromethane eluant) to provide
[Mo(tCNiPr2)Br(CO)3(PPh3)]. Yield: 6.89 g (54%). IR Nujol:
2043, 1973, 1932 [ν(CO)], 1564 [ν(CN)] cm-1. CH2Cl2: 2054,
1983, 1948 [ν(CO)], 1534 [ν(CN)] cm-1. NMR (CDCl3, 25 °C)
1H: δ 1.12 [d, 12 H, CH3, J (HH) ) 6.9 Hz], 2.97 [h, 2 H, NCH],
7.33-7.72 [m, 15 H, P(C6H5)3]. 13C{1H}: 249.1 [d, MotC, J (PC)
) 12.5], 212.1 [d, MoCO (trans to P), J (PC) ) 41.1], 205.5 [d,
MoCO (cis to P), J (PC) ) 9.0 Hz], 135.1-127.9 [C6H5], 50.6
[NCH], 22.1 [CH3] ppm. 31P{1H}: 27.2 ppm. FAB-MS: m/z 635
[HM]+, 579 [M - 2CO]+, 556 [M - Br]+, 528 [M - CO,Br]+,
507 [MoBrPPh3CNiPr]+, 439 [MoPPh3Br]+, 358 [MoPPh3]+, 102
,
i
[NH2 Pr2]+. Anal. Found: C, 52.9; H, 4.6; N, 2.2. Calcd for
C
28H29BrMoNO3P: C, 53.0; H, 4.6; N, 2.2.
1923vs, 1818s [ν(CO)] cm-1. Nujol: 1904s, 1795s [ν(CO)] cm-1
.
P r ep a r a tion of [Mo(tCNiP r 2)(CO)2{HB(p z)3}] (8). [Mo-
NMR (CDCl3, 25 °C) H: δ 3.73, 3.78 [s × 2, 3 H × 2, CH3],
6.20 [t, 3 H, H4(pz)], 7.65, 7.84 [d × 2, 3 H × 2, H3, H5(pz)].
13C{1H}: 249.7 [CS], 241.5 [CO], 145.5, 135.4, 106.2 [C(pz)],
50.3, 45.2 [CH3] ppm. FAB-MS m/z 541 [M]+, 485 [M - 2CO]+.
Anal. Found: C, 31.0; H, 3.0; N, 17.9. Calcd for C14H16BN7O2-
SW C, 31.0; H, 3.0; N, 18.1.
1
(tCNiPr2)(CO)3(PPh3)Br] (0.63 g, 1.00 mmol) was placed in a
Schlenk tube with K[HB(pz)3] (0.27 g, 1.10 mmol) and the
vessel evacuated for several minutes, then back-filled with
nitrogen. Tetrahydrofuran (25 mL) was added, and the mixture
stirred at room temperature for 1 h. The solvent was removed
under reduced pressure and the residue chromatographed
(silica gel, -30 °C), eluting with a mixture of dichloromethane
and hexane (2:3). The product was then isolated by concentra-
tion and cooling (-30 °C) of the major orange fraction. Yield:
0.38 g (80%). IR Nujol: 2469 [ν(BH)], 1937, 1835 [ν(CO)], 1516
[νCN)] cm-1. CH2Cl2: 2480 [ν(BH)], 1951, 1852 [ν(CO)], 1527
[ν(CN)] cm-1. NMR (CDCl3, 25 °C). 1H δ 1.44 [d, 12 H, CH3,
J (HH) ) 7.0 Hz], 3.55 [h, 2H, NCH], 6.15. 6.16 [t × 2, 3 H,
H4(pz)], 7.35 [m, 3 H, H5(pz)], 7.64, 7.74 [d × 2, 3 H, H3(pz)].
13C{1H}: 260.5 [MotC], 230.2 [MoCO], 143.8 [C3(pz)], 134.8
[C5(pz)], 104.8 [C4(pz)], 52.7 [NCH], 23.3 [CH3] ppm. FAB-
MS: m/z 479 [M]+, 451 [M - CO]+, 423 [M - 2CO]+, 380 [Mo-
{HB(pz)3}CNiPr]+, 309 [Mo{HB(pz)3}]+. Anal. Found: C, 45.1;
H, 5.5; N, 20.3. Calcd for C18H24BMoN7O2: C, 45.3; H, 5.1;
N, 20.6.
P r ep a r a tion of [WCl(CO)3{HB(p z)3}] (12). A suspension
of tungsten hexacarbonyl (2.00 g, 5.7 mmol) in acetonitrile (30
mL) was heated under reflux for 72 h. Upon cooling to -30 °C
the yellow solution was treated with p-tolyl chlorothiono-
formate (0.87 mL, 5.7 mmol), followed by K[HB(pz)3] (1.45 g,
5.8 mmol). After stirring for 1 h, the reaction liquor was passed
through a short plug of alumina (ca. 20 × 4 cm) and reduced
in volume, resulting in the precipitation of a golden yellow
product. The crude product was recrystallized from a mixture
of dichloromethane and hexane (-20 °C). Yield: 1.62 g (55%).
IR CH2Cl2: 2035s, 1947vs, 1902br [ν(CO)] cm-1. Nujol: 2036m,
1
1940vs, 1894s [ν(CO)] cm-1. NMR (CDCl3, 25 °C) H: δ 6.31
[t, 3 H, H4(pz)], 7.70 [d, 3 H, H5(pz)], 8.24 [d, 3 H, H3(pz)].
13C{1H}: 238.5 [CO], 146.2 [C3(pz)], 136.6 [C5(pz)], 107.1 [C4-
(pz)] ppm. FAB-MS m/z 488 [M - CO]+, 462 [M - 2CO]+, 432
[M - 3CO]+, 397 [M - 3CO, Cl]+. Anal. Found: C, 28.2; H,
2.0; N, 16.0. Calcd for C12H10BClN6O3W: C, 27.9; H, 2.0; N,
16.3. These data may be compared with those previously
reported.36
P r ep a r a tion of [MoF e(µ-CNiP r 2)(CO)5{HB(p z)3] (9).
[Mo(tCNiPr2)(CO)2{HB(pz)3}] (8, 0.10 g, 0.20 mmol) was
dissolved in diethyl ether (20 mL), and [Fe2(CO)9] (0.20 g, 0.50
mmol) added. On stirring at room temperature overnight, a
purple solution resulted. The ether was then removed under
vacuum, and the residue chromatographed at low temperature
(-30 °C, alumina, diethyl ether eluant). The product [MoFe-
{µ-CNiPr2}(CO)5{HB(pz)3}] was then isolated from the initial
purple band. Yield: 0.09 g (70%). IR Nujol: 2471 [ν(BH)], 2041,
1966, 1943, 1877, 1817 [ν(CO)] cm-1. CH2Cl2: 2487 [ν(BH)],
2036, 1969, 1945, 1891, 1827 [ν(CO)] cm-1. NMR 1H: δ 0.91
[d, 6 H, CH3, J (HH) ) 6.9 Hz], 1.73 [d, 6 H, CH3, J (HH) ) 6.9
Hz], 3.75, 4.38 [h × 2, 2 H, NCH], 6.10, 6.67 [2 × t, 3H, H4-
(pz)], 7.35 [m, 3H, H5(pz)], 7.70, 8.62 [m, s, 2H, H3(pz)]. The
Ack n ow led gm en t. We wish to thank the E.P.S.R.C.
(U.K.) for the award of post graduate studentships (to
S.A. and D.J .C.). A.F.H. gratefully acknowledges the
award of a Senior Research Fellowship by the Lever-
hulme Trust and the Royal Society.
OM991019H