Synthesis, structures, and properties of mixed dithiolene-carbonyl and dithiolene-phosphine complexes of tungsten

Article abstract of DOI:10.1021/ic802016b

A new, high yield synthesis of [Ni(S₂C₂Me ₂)2] (3) is described using 4,5-dimethyl-1,3-dithiol-2-one, Me ₂C₂S₂C=O (1), as dithiolene ligand precursor. Reaction of (Me₂C₂

Full text of DOI:10.1021/ic802016b

Inorg. Chem. 2009, 48, 2103-2113
Synthesis, Structures, and Properties of Mixed Dithiolene-Carbonyl and
Dithiolene-Phosphine Complexes of Tungsten
P. Chandrasekaran,† Kuppuswamy Arumugam,† Upul Jayarathne,† Lisa M. Pe´rez,‡ Joel T. Mague,†
and James P. Donahue*,†
Department of Chemistry, Tulane UniVersity, 6400 Freret Street, New Orleans, Louisiana
70118-5698, and Laboratory for Molecular Simulation, Texas A&M UniVersity, P.O. Box 30012,
College Station, Texas 77842-3012
Received October 21, 2008
A new, high yield synthesis of [Ni(S2C2Me2)2] (3) is described using 4,5-dimethyl-1,3-dithiol-2-one, Me2C2S2CdO
(1), as dithiolene ligand precursor. Reaction of (Me2C2S2)SnnBu2, 2, with WCl6 produces tris(dithiolene) [W(S2C2Me2)3]
(6) and demonstrates the potential synthetic utility of this compound in metallodithiolene synthesis. The series of
compounds [W(S2C2Me2)x(CO)6-2x] (x ) 1-3), obtained as a mixture via the reaction of [Ni(S2C2Me2)2] with
[W(MeCN)3(CO)3], has been characterized structurally. A trigonal prismatic geometry is observed for
[W(S2C2Me2)(CO)4] (4) and confirmed by a DFT geometry optimization to be lower in energy than an octahedron
by 5.1 kcal/mol. The tris(dithiolene) compound [W(S2C2Me2)3] crystallizes in disordered fashion upon a 2-fold axis
¯
in C2/c, a different space group than that observed for its molybdenum homologue (P1), which is attributed to a
slightly smaller chelate fold angle, R, in the former. The reactivity of 4 and [W(S2C2Me2)2(CO)2] (5) toward PMe3
has been examined. Compound 4 yields only [W(S2C2Me2)(CO)2(PMe3)2] (7), while 5 produces either
[W(S2C2Me2)2(CO)(PMe3)] (8) or [W(S2C2Me2)2(PMe3)2] (9) depending upon reaction conditions. Crystallographic
characterization of 5, 8, and 9 reveals a trend toward greater reduction of the dithiolene ligand (i.e., more ene-
1,2-dithiolate character) across the series, as manifested by C-C and C-S bond lengths. These structural data
indicate a profound effect exerted by the π-acidic CO ligands upon the apparent state of reduction of the dithiolene
ligand in compounds with ostensibly the same oxidation state.
Introduction
this work has been the [W(S2C2R2)2(CO)2] (R ) Me, Ph)
complexes originally described by Schrauzer9 and examined
more recently by Holm.10,11 The reaction types by which
[W(S2C2R2)2(CO)2] have been converted to biologically
relevant catalytic site analogues have been non-redox car-
bonyl displacement reactions.
The prevalence of dithiolene supporting ligands for mo-
lybdo- and tungstoenzyme catalytic sites suggests the pos-
sible utility of this ligand type in supporting non-biological
redox catalysis. This possibility has not been explored. An
Heteroleptic tungsten dithiolene complexes have been
explored almost exclusively in the context of modeling the
structures, spectroscopy, and reactivity of the catalytic sites
of tungstoenzymes and molybdenum isosymes. A consider-
able body of synthesis has now been developed in which a
bis(dithiolene) tungsten1-5 or mono(dithiolene) tungsten
unit6-8 is constant and supporting chalcogenide or chalco-
genate coligands are varied. The starting point for much of
* To whom correspondence should be addressed. E-mail: donahue@
tulane.edu.
†
Tulane University.
Texas A&M University.
(6) Wang, J.-J.; Holm, R. H. Inorg. Chem. 2007, 46, 11156–11164.
(7) Wang, J.-J.; Groysman, S.; Lee, S. C.; Holm, R. H. J. Am. Chem.
Soc. 2007, 129, 7512–7513.
(8) Groysman, S.; Wang, J.-J.; Tagore, R.; Lee, S. C.; Holm, R. H. J. Am.
Chem. Soc. 2008, 130, 12794–12807.
(9) Schrauzer, G. N.; Mayweg, V. P.; Heinrich, W. J. Am. Chem. Soc.
1966, 88, 5174–5179.
(10) Goddard, C. A.; Holm, R. H. Inorg. Chem. 1999, 38, 5389–5398.
(11) Fomitchev, D. V.; Lim, B. S.; Holm, R. H. Inorg. Chem. 2001, 40,
645–654.
‡
(1) Enemark, J. H.; Cooney, J. J. A.; Wang, J.-J.; Holm, R. H. Chem.
ReV. 2004, 104, 1175–1200, and references cited therein.
(2) Wang, J.-J.; Kryatova, O. P.; Rybak-Akimova, E. V.; Holm, R. H.
Inorg. Chem. 2004, 43, 8092–8101.
(3) Jiang, J.; Holm, R. H. Inorg. Chem. 2004, 43, 1302–1310.
(4) Wang, J.-J.; Tessier, C.; Holm, R. H. Inorg. Chem. 2006, 45, 2979–
2988.
(5) Grosyman, S.; Holm, R. H. Inorg. Chem. 2007, 46, 4090–4102.
10.1021/ic802016b CCC: $40.75  2009 American Chemical Society
Inorganic Chemistry, Vol. 48, No. 5, 2009 2103
Published on Web 02/04/2009

Chandrasekaran et al.
freshly cut Na metal (6.29 g, 0.274 mol) were added to freshly
distilled MeOH (300 mL) with rapid stirring at 0 °C under a N2
atmosphere. Stirring was continued for 2 h to allow for complete
reaction. A solution of 4,5-dimethyl-1,3-dithiol-2-one (20.0 g, 0.137
mol) in MeOH (50 mL) was added via cannula to the NaOMe
solution, and the resulting mixture was stirred an additional 2 h at
ambient temperature. Under nitrogen flow, anhydrous NiCl2 (8.87
g, 0.068 mol) was added as a single portion, producing a change
in color to dark brown. After stirring for 6 h, one ½ equiv of solid
I2 (17.4 g, 0.0684 mol) was added under nitrogen flow, and stirring
was continued for an additional 6 h. The precipitate that developed
in the reaction vessel was collected by vacuum filtration and washed
with portions of deionized H2O (2 × 50 mL) followed by MeOH
(2 × 50 mL) and Et2O (3 × 50 mL). The dark blue solid was dried
under vacuum for 24 h to afford pure [Ni(S2C2Me2)2] (17.5 g, 0.059
mol, 87% yield) that was spectroscopically identical to samples
prepared via the method of Schrauzer.15,16
obstacle to the use of dithiolenes as supporting ligands in
homogeneous catalysis is a paucity of starting materials and
methods which would lead one to reactive compounds other
than coordinatively saturated tris(dithiolene) or, for the Group
VIII metals, bis(dithiolene) complexes. For this reason,
[W(S2C2Me2)2(CO)2] invites further scrutiny of its behavior,
for example, toward direct oxidative addition reactions. The
preparation of [W(S2C2Me2)2(CO)2] is attended by the
formation of modest quantities of the unusual mono(dithi-
olene) compound [W(S2C2Me2)(CO)4], a species of interest
for similar reasons. The following are selected initial results
from a broad survey of the reactivity of [W(S2C2Me2)x-
(CO)6-2x] (x ) 1 or 2) with a variety of small molecule
substrates under a range of conditions.
Experimental Section
[W(S2C2Me2)(CO)4] (4), [W(S2C2Me2)2(CO)2] (5), [W(S2C2-
Me2)3] (6) (Method 1). The following procedure is a slight
4,5-Dimethyl-1,3-dithiol-2-one (1) was prepared by a modified
version of a literature procedure.12 All other reagents were either
purchased from commercial sources and used as received (Na metal,
adaptation of the procedure described by Holm and Goddard.10
A
solution of [Ni(S2C2Me2)2] (1.51 g, 5.12 mmol) and
[W(CO)3(MeCN)3] (1.00 g, 2.56 mmol) in 250 mL of dry CH2Cl2
was stirred overnight under a N2 atmosphere. The mixture was
filtered to remove polymeric [Ni(S2C2Me2)]x, and the dark filtrate
was reduced to dryness in vacuo. The dark residual solid was
extracted with n-pentane (2 × 50 mL). The pentane extracts were
filtered, reduced to dryness, and redissolved in a minimal volume
of pentane (∼30 mL). This solution was directly loaded onto a
silica column packed as a slurry in n-pentane and eluted with the
same solvent. An orange band corresponding to [W(S2C2Me2)(CO)4]
rapidly eluted and was followed by a slower red-violet band
corresponding to [W(S2C2Me2)2(CO)2]. These bands were separately
collected and reduced to dryness. The dark solids remaining after
the first n-pentane extraction were extracted with a minimal portion
of 30% C6H6 in pentane, and the extracts were directly pipeted
onto a column containing the same solvent mixture. Elution brought
down a red-violet band of additional [W(S2C2Me2)2(CO)2], which
was collected and combined with the material obtained from the
first silica column, followed by a dark greenish-blue band of
[W(S2C2Me2)3].
n
SnCl2 Bu2, WCl6, NiCl2, I2, 1.0 M PMe3 in toluene, Me3NO) or
prepared using literature methods ([W(CO)3(MeCN)3]13). Solvents
either were dried with a system of drying columns from the Glass
Contour Company (CH2Cl2, n-pentane, hexanes, Et2O, THF, C6H6,
toluene) or freshly distilled according to standard procedures14
(MeOH, CH3CN). Silica columns were run in the open air using
60-230 µm silica (Dynamic Adsorbents).
Syntheses. 2,2-Di-n-butyl-4,5-dimethyl-1,3,2-dithiastannole
(2). Pieces of freshly cut sodium metal (1.96 g, 0.085 mol) were added
to dry, distilled MeOH (200 mL) under a N2 atmosphere at 0 °C. The
resulting mixture was stirred for 30 min to allow complete consumption
of the Na metal. Under an outward nitrogen flow, 4,5-dimethyl-1,3-
dithiol-2-one (5.0 g, 0.034 mol) was then added to the NaOMe/MeOH
solution. Stirring was continued for 2 h at 25 °C, during which time
the homogeneous colorless solution developed a slight yellowish aspect.
Under an outward flow of N2, solid SnCl2nBu2 (10.4 g, 0.034 mol)
was added, which produced the immediate formation of a colorless
precipitate. This heterogeneous mixture was stirred overnight at
ambient temperature. The precipitate was separated by filtration, and
the filtrate was reduced to dryness under reduced pressure. The crude
solid was redissolved in a minimal volume of CH2Cl2 and evaporated
onto ∼4 g of SiO2. This coated silica was loaded as a dry solid onto
a silica column packed as a slurry in hexanes. Elution began with
n-hexanes (100 mL) and was continued with 100 mL portions of a
CH2Cl2:hexanes mixture that incrementally increased from 1% to 5%
CH2Cl2 in hexanes (v/v). Compound 2 was collected as the leading
fraction from the column. Yield: 4.5 g, 0.013 mol, 38%. Rf ) 0.54
[W(S2C2Me2)(CO)4]: 0.192 g, 0.46 mmol, 18.1% yield. Rf (n-
1
pentane) ) 0.91. H NMR (δ, ppm in C6D6): 2.37 (s, dithiolene
CH3). 13C NMR (δ, ppm in C6D6): 216.31 (CO), 155.14 (olefinic
C), 24.79 (dithiolene CH3). Absorption spectrum (CH2Cl2): λmax
(εM) 236 (sh, 35700), 268 (sh, 11300), 316 (7400), 406 (12100).
IR (ν, cm-1): 2074 (s, CO), 1987, (s, CO), 1967 (s, CO), 1262
(w), 1094 (w), 1018 (w), 802 (w), 548 (w), 506 (w), 447 (w). Anal.
Calcd for C8H6O4S2W: C, 23.20; H, 1.46; O, 15.45. Found: C,
23.41; H, 1.42; O, 15.50.
1
(2:3 CH2Cl2:hexanes). H NMR (δ, ppm in CDCl3): 1.99 (s, 6H,
dithiolene CH3), 1.68 (quintet, 4H, -CH2CH2CH2-), 1.53 (t, 4H,
[W(S2C2Me2)2(CO)2]: 0.240 g, 0.504 mmol, 19.7% yield. Rf (40%
C6H6 in n-pentane) ) 0.78. H NMR (δ, ppm in C6D6): 2.35 (s,
1
-SnCH2-), 1.34 (sextet, 4H, J ) 7.3 Hz, -CH2CH2CH3), 0.90 (t, 6H, J
n
) 7.3 Hz, Bu CH3). 13C NMR (δ, ppm in CDCl3): 123.2 (olefinic
dithiolene CH3). 13C NMR (δ, ppm in C6D6): 219.12 (CO), 160.84
(olefinic C), 24.53 (dithiolene CH3). Absorption spectrum (CH2Cl2):
λmax (εM) 358 (5820), 508 (17500), 636 (405). IR (ν, cm-1): 2022
(s, CO), 1949 (s, CO), 1475 (m), 1363 (w), 934 (m), 558 (w), 446
(s). Anal. Calcd for C10H12O2S4W: C, 25.22; H, 2.54; O, 6.72.
Found: C, 25.22; H, 2.51; O, 6.82.
C), 28.1, 26.9, 22.9, 21.5, 13.8. ESI-MS+: m/z 352 (M + H+).
[Ni(S2C2Me2)2] (3). The following procedure is an alternative
to the original preparation described by Schrauzer.15 Portions of
(12) Chandrasekaran, P.; Donahue, J. P. Org. Synth.; submitted for
publication.
[W(S2C2Me2)3]: 0.034 g, 0.063 mmol, 2.5% yield. Rf (40% C6H6
(13) Tate, D. P.; Knipple, W. R.; Augl, J. M. Inorg. Chem. 1962, 1, 433–
1
in n-pentane) ) 0.59. H NMR (δ, ppm in CDCl3): 2.72 (s, 18H,
434.
dithiolene CH3). 1H NMR (δ, ppm in C6D6): 2.25 (s, 18H, dithiolene
(14) Armarego, W. L. F.; Perrin, D. D. Purification of Laboratory
Chemicals, 4th ed.; Butterworth-Heinemann: Oxford, Great Britain,
2000.
(15) Schrauzer, G. N.; Mayweg, V. P. J. Am. Chem. Soc. 1965, 87, 1483–
(16) Lim, B. S.; Fomitchev, D. V.; Holm, R. H. Inorg. Chem. 2001, 40,
1489.
4257–4262.
2104 Inorganic Chemistry, Vol. 48, No. 5, 2009

Dithiolene-Carbonyl and Dithiolene-Phosphine Complexes
CH3). 13C NMR (δ, ppm in CDCl3): 167.6 (olefinic C), 25.5
(dithiolene CH3). Absorption spectrum (CH2Cl2): 254 (12900), 268
(sh, 4840), 310 (3730), 402 (10800), 508 (4710), 608 (19700).
[W(S2C2Me2)3] (6) (Method 2). A 50 mL Schlenk flask was
charged with a stir bar, (Me2C2S2)Sn(nBu)2 (0.465 g, 1.3 mmol)
and WCl6 (0.175 g, 0.44 mmol). Dry toluene (40 mL) was added
via syringe; a dark green color immediately became apparent. The
flask septum was exchanged with an oven-dried condenser leading
to a Schlenk line equipped with mercury bubbler. The reaction
mixture was heated to reflux for 12 h under N2, whereupon it was
cooled to room temperature, and the solvent was removed under
reduced pressure. The solid residue was washed with MeOH (3 ×
10 mL) to remove the di(n-butyl)tin dichloride byproduct and then
dried in vacuo. Yield: 0.190 g, 0.35 mmol, 80% yield. ESI-MS-:
m/z 538 (M-). Anal. Calcd for C12H18S6W: C, 26.76; H, 3.37; S,
35.73. Found: C, 26.97; H, 3.37; S, 35.44.
[W(S2C2Me2)(CO)2(PMe3)2] (7). A 50 mL Schlenk flask with
stir bar was charged with [W(S2C2Me2)(CO)4] (0.088 g, 0.214
mmol) under an atmosphere of N2. Toluene (15 mL) was added
via syringe to afford a yellow solution, followed by addition of
PMe3 (1.5 mL of 1.0 M toluene solution, 1.5 mmol). A color change
to red developed immediately. After heating to 75 °C with stirring
for 8 h, the solvent was removed in vacuo to afford a red solid.
Recrystallization was accomplished by slow evaporation of a C6H6
solution under nitrogen. Yield: 0.104 g, 0.204 mmol, 95% yield.
1H NMR (δ, ppm in CDCl3): 2.53 (s, 6H, dithiolene CH3), 1.77 (d,
JPH ) 10 Hz, 18H, P(CH3)3). 13C NMR (δ, ppm in CDCl3): 237.33
(t, JPC) 21.8 Hz, CO), 145.16 (t, olefinic C), 24.52 (t, dithiolene
CH3), 20.95 (m, P(CH3)3). 31P NMR (δ, ppm in CDCl3): -4.87 (s,
JPW ) 171.9 Hz). Absorption spectrum (CH2Cl2): 342 (sh, 4410),
372 (7110), 454 (sh, 1200). IR (ν, cm-1): 1910 (vs, CO), 1844 (vs,
CO), 1811 (vs, CO), 1415 (m), 1277 (s), 934 (vs), 855 (w), 723
(w), 670 (m), 571 (w), 473 (w). Anal. Calcd for C12H24O2P2S2W:
C, 28.25; H, 4.74; P, 12.14. Found: C, 28.43; H, 4.62; P, 12.29.
C6H6 solution under nitrogen. Yield: 0.270 g, 0.472 mmol, 75%
yield. 1H NMR (δ, ppm in CDCl3): 2.63 (s, 12H, dithiolene CH3),
1.80 (d, JPH ) 8.8 Hz, 18H, P(CH3)3). 13C NMR (δ, ppm in CDCl3):
149.95 (s, olefinic C), 23.76 (m, P(CH3)3), 23.0 (s, dithiolene CH3).
31P NMR (δ, ppm in CDCl3): -5.43 (s, JPW ) 239.43 Hz).
Absorption spectrum (CH2Cl2) λmax (εM): ∼270 (sh, 16500), ∼344
(sh, 7800), ∼382 (sh, 11800), 410 (13100), ∼462 (sh, 7500). IR
(ν, cm-1): 2905 (m), 1534 (w), 1408 (m), 1276 (s), 947 (vs), 723
(m), 670 (m). Anal. Calcd for C14H30P2S4W: C, 29.37; H, 5.28; P,
10.82. Found: C, 29.29; H, 5.14, P, 10.64.
X-ray Structures. The numbering system by which the com-
pounds are hereafter identified is defined in the preceding Experi-
mental Section and in Scheme 1. Colorless plate crystals of 1 were
obtained directly from the receiving flask used in the vacuum
distillation of 1,12 while colorless column-shaped crystals of 2
deposited upon slow evaporation of a hexanes solution. Dark
orange-red plate crystals of 4 grew from a concentrated n-pentane
solution cooled to -20 °C. Slow evaporation of a benzene solution
of 5 yielded red-violet block-shaped crystals of 5. Dark bluish-red
block-shaped crystals of 6 grew by the slow diffusion of MeOH
vapor into a nitrobenzene solution. Crystals of 7 (red blocks) and
8 (orange blocks) were grown by evaporation of benzene and Et2O
solutions, respectively, while crystals of 9 were grown by diffusion
of hexanes vapor into a benzene solution. All crystals were coated
in Paratone oil and mounted onto a nylon cryoloop attached to a
goniometer.
Data were collected with a Bruker APEX CCD diffractometer
equipped with a Kryoflex attachment supplying a nitrogen stream
at 100 K. Full spheres of data were obtained by collecting either
three sets of 606 frames in ω (0.3°/scan) with ꢀ held constant at 0,
120, and then 240° (for 4 and 8) or a combination of three sets of
400 scans in ω (0.5°/scan) at ꢀ ) 0, 90, and 180° with two sets of
800 scans in ꢀ (0.45°/scan) at ω ) -30 and 210° (for 1, 2, 5-7
and 9) under control of either the SMART software package17a or
the APEX2 program suite.17b The crystal of 6 used for data
collection proved to be twinned; approximately 95% of the available
reflections could be fit to a two-component twin with lattice
orientations offset by a 1.2° rotation about the c axis as determined
by CELL_NOW.18 The raw data were reduced to F2 values using
the SAINT+ software,19 and a global refinement of unit cell
parameters was performed using 4054-9991 selected reflections
from the full data set. Multiple measurements of symmetry
equivalent reflections provided the basis for an empirical absorption
correction as well as a correction for any crystal decomposition
during the course of the data collection (SADABS20a for 1-2, 4-5,
7-9; TWINABS20b for 6). Structure solutions were obtained by
direct methods (1, 4 and 6-8) or by Patterson methods (2, 5, and
9), and refinements were accomplished by full-matrix least-squares
procedures using the SHELXTL software suite.21 Compound 6
revealed two distinct forms of disorder, one being a whole molecule
disorder over two positions, both upon a crystallographic 2-fold
axis, which was modeled as a 9:1 distribution. Only the positions
[W(S2C2Me2)2(CO)(PMe3)]
(8).
A
solution
of
[W(S2C2Me2)2(CO)2] (0.173 g, 0.363 mmol) in toluene (20 mL)
was treated with PMe3 (0.425 mL of 1 M toluene solution, 0.425
mmol) at ambient temperature. An immediate change in color from
magenta to intense orange ensued, and the resulting solution was
stirred 2 h. The solvent was removed in vacuo to afford an orange
solid that was recrystallized by slow evaporation of a C6H6 solution.
Yield: 0.175 g, 0.333 mmol, 92% yield. 1H NMR (δ, ppm in
CDCl3): 2.71 (s, 12H, dithiolene CH3), 1.65 (d, JPH ) 9.6 Hz, 9H,
P(CH3)3). 13C NMR (δ, ppm in CDCl3): 232.65 (s, CO), 155.09
(br s, olefinic C), 24.04 (s, dithiolene CH3), 21.09 (d, JPC ) 35.9
Hz, P(CH3)3). 31P NMR (δ, ppm in CDCl3): 1.95 (s, JPW ) 217.6
Hz). Absorption spectrum (CH2Cl2) λmax (εM): 484 (29000), 358
(15600), 324 (sh, 7900), 276 (sh, 14500). IR (ν, cm-1): 1929 (s,
CO), 1501 (w), 1270 (m), 953 (m), 670 (w), 446 (s). Anal. Calcd
for C12H21OPS4W: C, 27.49; H, 4.04; P, 5.91. Found: C, 27.65; H,
4.00, P, 5.72.
[W(S2C2Me2)2(PMe3)2] (9). A solution of [W(S2C2Me2)2(CO)2]
(0.30 g, 0.630 mmol) in 30 mL of toluene was treated with PMe3
(2.5 mL of 1 M toluene solution, 2.5 mmol) delivered via syringe.
A single portion of freshly sublimed Me3NO (0.095 g, 1.26 mmol)
was added under N2 flow, and the resulting mixture was stirred for
2 h. A second portion of PMe3 (2.5 mL of 1 M toluene solution,
2.5 mmol) was added, and the mixture was then heated to reflux
for 4 h. During this time period, a yellow precipitate developed.
The reaction mixture was cooled to ambient temperature, and the
yellow solid was isolated by filter cannulation, washed with
n-pentane (20 mL) and dried in vacuo. Crystallization of this crude
product was accomplished by diffusion of hexanes vapor into a
(17) (a) SMART, Version 5.625; Bruker-AXS: Madison, WI, 2000. (b)
APEX2Version 2.1-4; Bruker-AXS: Madison, WI, 2007.
(18) Sheldrick, G. M. CELL_NOW; University of Go¨ttingen: Go¨ttingen,
Germany, 2005.
(19) SAINT+, Versions 6.35A and 7.34A; Bruker-AXS: Madison, WI, 2002,
2006.
(20) (a) Sheldrick, G. M. SADABS, Version 2.05 and Version 2007/2;
University of Go¨ttingen: Go¨ttingen, Germany, 2002, 2007. (b)
Sheldrick, G. M. TWINABS, Version 2007/5; University of Go¨ttingen:
Go¨ttingen, Germany, 2007.
(21) (a) SHELXTL, Version 6.10; Bruker-AXS: Madison, WI, 2000. (b)
Sheldrick, G. M. SHELXS97 and SHELXL97; University of Go¨ttingen:
Go¨ttingen, Germany, 1997.
Inorganic Chemistry, Vol. 48, No. 5, 2009 2105

Chandrasekaran et al.
Scheme 1. (A) High-Yield Syntheses for [Ni(S2C2Me2)2] (3) and [W(S2C2Me2)3] (6) and (B) Synthesis of Mixed Dithiolene Carbonyl and Dithiolene
Phosphine Tungsten Compounds [W(S2C2Me2)x(CO)y(PMe3)z]
Table 1. Crystal and Refinement Data for Compounds 1, 2, and 4-9
1
2
4
5
6
7
8
9
formula
C5H6OS2
146.22
100 K
0.71073
white plate
monoclinic
C12H24S2Sn
351.12
195 K
C8H6O4S2W
414.10
100 K
C10H12O2S4W
476.29
100 K
C12H18S6W
538.47
100 K
C12H24O2P2S2W C12H21OPS4W C14H30P2S4W
formula wt
temperature
wavelength, Å
color, habit
crystal system
space group
a, Å
510.22
100 K
524.35
100 K
572.41
100 K
0.71073
0.71073
0.71073
0.71073
0.71073
0.71073
0.71073
white column orange plates red-purple block blue-red block red block
triclinic
j
orange block
monoclinic
orange column
monoclinic
triclinic
triclinic
monoclinic
monoclinic
j
j
P21/c (No. 14) P1 (No. 2)
P1 (No. 2)
P1 (No. 2)
C2/c (No. 15) P21/c (No. 14) P21/c (No. 14) C2/c (No. 15)
3.9068(3)
12.1944(8)
13.4159(9)
90
92.044(1)
90
638.74(8)
4
1.520
10.099(1)
10.475(1)
15.224(2)
82.493(2)
86.660(2)
77.971(2)
1560.8(3)
4
1.494
1.878
19383
4942
6.878(1)
7.600(1)
12.318(2)
94.916(2)
97.976(2)
114.880(2)
571.0(2)
2
7.0364(3)
7.6373(3)
13.5606(6)
93.506(1)
93.891(1)
95.516(1)
722.01(5)
2
2.191
8.564
12457
3434
15.344(2)
8.918(1)
13.669(2)
90
108.089(2)
90
1778.0(4)
4
2.012
7.186
4235
13.633(4)
10.553(3)
13.062(4)
90
8.922(1)
9.574(1)
21.246(3)
90
18.384(1)
7.4904(5)
17.380(2)
90
b, Å
c, Å
R, deg.
ꢁ, deg.
105.522(4)
90
91.982(2)
90
121.368(1)
90
γ, deg.
V, Å3
1810.6(9)
4
1813.8(4)
4
2043.5(3)
4
Z
density, g/cm3
2.408
10.469
4975
1.872
6.783
30894
4497
1.920
6.908
31081
4513
1.861
6.211
17347
2546
µ, mm-1
0.725
total reflections 10389
indep. reflections 1566
2603
2206
parameters
R1a, wR2b
(I > 2σ)
R1a, wR2b
(all data)
GoF
75
279
138
157
128
180
179
101
0.0281, 0.0696 0.0394, 0.0976 0.0327, 0.0807 0.0175, 0.0393 0.0377, 0.0883 0.0145, 0.0352 0.0148, 0.0342 0.0131, 0.0302
0.0363, 0.0724 0.0521, 0.1084 0.0363, 0.0824 0.0197, 0.0402 0.0436, 0.0907 0.0153, 0.0355 0.0155, 0.0345 0.0138, 0.0304
1.356
1.088
1.052
1.055
1.040
1.151
1.128
1.069
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) {∑[w(Fo - Fc2)2]/∑w(Fo )2}1/2; w ) 1/[σ2(Fo ) + (xP)2], where P ) (Fo + 2Fc2)/3.
2
2
2
2
of the tungsten and sulfur atoms were identified and refined for
the minor contributor. The crystallographic 2-fold axis bisects one
dithiolene ligand, passes through the tungsten atom, and interrelates
the remaining two dithiolene ligands by the 2-fold rotation. Because
6 has only C3h symmetry because of a slight fold of the dithiolene
chelate along each intraligand S-S vector, its location on the
crystallographic 2-fold axis imposes a second disorder between two
highly overlapped rotational variants. This disorder was treated with
a ∼1:1 split atom model. Anisotropic refinement of the structure
was limited to the tungsten and sulfur atoms only. All hydrogen
atoms were added in calculated positions and included as riding
contributions with isotropic displacement parameters tied to those
of the carbon atoms to which they were attached. Methyl substit-
uents have been allowed to refine an orientation around the C-C
bond that optimizes the model for electron density for this group.
Crystal and refinement data for 1, 2, and 4-9 are summarized in
Table 1.
Other Physical Methods. UV-vis spectra were obtained at
ambient temperature with a Hewlett-Packard 8452A diode array
spectrometer, while IR spectra were taken as pressed KBr pellets
with a Thermo Nicolet Nexus 670 FTIR instrument in absorption
mode. All NMR spectra were recorded at 25 °C with a Varian Unity
Inova spectrometer operating at 400, 100.5, or 161.8 MHz for 1H,
13C, and 31P, respectively. Spectra were referenced to the solvent
2106 Inorganic Chemistry, Vol. 48, No. 5, 2009

Dithiolene-Carbonyl and Dithiolene-Phosphine Complexes
residual (1H, 13C) or to a value loaded from a reference file (31P).
Electrospray ionization mass spectra were obtained either with a
Bruker Daltonics or with a PESciex Qstar instrument. Electro-
chemical measurements were made with a CHI620C electroanalyzer
workstation using a Ag/AgCl reference electrode, a platinum disk
working electrode, Pt wire as auxiliary electrode, and Bu4NPF6 as
the supporting electrolyte. Under these conditions, the Cp2Fe+/
Cp2Fe couple consistently occurred at +440 mV. Elemental
analyses were performed by Canadian Microanalytical of Delta,
British Columbia or by Midwest Microlab, LLC of Indianapolis,
IN.
yields, is attended by the unpleasant smells invariably
associated with phosphorus sulfides, and generally requires
a further degree of purification of the metallodithiolene
product by Soxhlet extraction. Beginning with 4,5-dimethyl-
1,3-dithiol-2-one, a compound whose preparation we have
simplified and amplified to a scale of tens of grams,12
straightforward base hydrolysis liberates the fully reduced
ene-1,2-dithiolate. Subsequent addition of NiCl2, followed
by iodine to oxidize the resulting dianion, yields
[Ni(S2C2Me2)2] on a preparative scale in a minimal time and
without the need for additional purification. This synthetic
approach supersedes the method of Schrauzer.15,28
Calculations
An alternative useful form to the methyl-substituted
dithiolene ligand is the di-n-butyltin compound 2,2-di-n-
butyl-4,5-dimethyl-1,3,2-dithiastannole, 2. Compound 2 is
readily generated from 1 by treatment of the ene-1,2-
dithiolate dianion with di-n-butyltin dichloride. A slightly
different preparation of 2 has been described earlier,29 but
the utility of this compound as a dithiolene ligand precursor
or ligand transfer reagent was not probed. Having noted the
use made of other dialkyl tin protected dithiolene-type
ligands, particularly in ligand exchange reactions with
transition metal chlorides,30-33 the utility of 2 was tested in
the synthesis of another homoleptic metal dithiolene com-
pound, [W(S2C2Me2)3]. For reasons that are unclear,
[W(S2C2Me2)3] could not be isolated by introducing WCl6
to 3 equiv of in situ generated Na2[Me2C2S2]. However,
[W(S2C2Me2)3] was isolated in 80% yield after treatment of
WCl6 with 3 equiv of 2 (Scheme 1), separation of the
nBu2SnCl2 byproduct by simple MeOH extraction, and
purification of the remaining solid by recrystallization. This
procedure is analogous to the use of bis((trialkylsilyl)sulfa-
nyl)alkenes as protected dithiolene ligands34 in that metal-
lodithiolene complex formation is driven, at least in part,
by formation of a strong metallodithiolene chelate.
The mixed dithiolene carbonyl compounds [M(S2C2-
R2)2(CO)2] (M ) Mo, W; R ) Me, Ph) were first reported
by Schrauzer as products arising from dithiolene ligand
transfer from [Ni(S2C2Me2)2] to M(CO)6 under photolytic
conditions.9 The yields and ease of synthesis were consider-
ably improved by Goddard and Holm,10 who noted that use
of [M(CO)3(MeCN)3] (M ) Mo, W) in lieu of the hexa-
carbonyl resulted in cleaner reactivity without the need for
photolysis. In the tungsten system, modest quantities of
[W(S2C2R2)(CO)4], a moderately stable intermediate appear-
ing in the course of formation of [W(S2C2R2)2(CO)2], can
be isolated. This mono(dithiolene) intermediate is not
observed in the molybdenum system, probably because the
All calculations were performed using the Gaussian 03
suite of software22 at the B3LYP23 (Becke-3 exchange24 and
Lee-Yang-Parr correlation25 functional) level of theory.
Full geometry optimizations were performed in C2V sym-
metry, and stationary points were characterized via analytical
frequency calculations. For the S, O, C, and H atoms, the
Pople triple-ꢂ quality basis set (6-311++G(2d,p))26 with
1 diffuse and 2 polarization functions (d) on the S, C, and O
atoms and 1 diffuse and 1 polarization function (p) on the
H atoms was used. For the W atom, the Stuttgart triple-ꢂ
quality basis set (SDD) with an Effective Core Potential
(ECP) was used.27
Discussion
Syntheses. Reported herein is a new and more efficient
synthesis of [Ni(S2C2Me2)2], which considerably improves
access to preparative-scale quantities of this useful compound
and thus facilitates further exploration of the reactivity of
[W(S2C2Me2)(CO)4] and [W(S2C2Me2)2(CO)2]. To the best
of our knowledge, the P4S10/acetoin protocol originally
described by Schrauzer has remained until now the exclusive
method by which transition metal complexes with the methyl
substituted dithiolene ligand have been generated. Although
it is reproducible, Schrauzer’s method suffers from low
(22) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin,
K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone,
V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada,, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai,
H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.;
Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.;
Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.;
Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg,
J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.;
Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman,
J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.;
Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.;
Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.;
Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen,
W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03,, Revision
D.02; Gaussian, Inc.: Wallingford, CT, 2004.
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Phys. Chem. 1994, 98, 11623–11627.
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(26) (a) Krishnan, R.; Binkley, J. S.; Seeger, R.; Pople, J. A. J. Chem.
Phys. 1980, 72, 650–654. (b) McLean, A. D.; Chandler, G. S. J. Chem.
Phys. 1980, 72, 5639–5648. (c) Frisch, M. J.; Pople, J. A.; Binkley,
J. S. J. Chem. Phys. 1984, 80, 3265–3269.
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2007, 46, 3823–3288.
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Masuda, N.; Nishimoto, Y.; Takasaki, S.; Anzai, H. J. Org. Chem.
1996, 61, 3987–3995.
(30) Nomura, M.; Fourmigue´, M. Inorg. Chem. 2008, 47, 1301–1312.
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Terroba, R. Organometallics 1995, 14, 5537–5543.
(32) Cerrada, E.; Fernández, E. J.; Gimeno, M. C.; Laguna, A.; Laguna,
M.; Terroba, R.; Villacampa, M. D. J. Organomet. Chem. 1995, 492,
105–110.
(27) Andrae, D.; Häußermann, U.; Dolg, M.; Stoll, H.; Preuß, H. Theor.
Chim. Acta 1990, 77, 123–141.
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A. G. M.; Hoffman, B. M. J. Am. Chem. Soc. 1993, 115, 9997–10003.
Inorganic Chemistry, Vol. 48, No. 5, 2009 2107

Chandrasekaran et al.
Figure 2. Thermal ellipsoid plot at the 50% probability level for
4,5-dimethyl-1,3-dithiol-2-one (1) and 30% level for 2,2-di-n-butyl-4,5-
dimethyl-1,3,2-dithiastannole (2). For 2, only one of two independent
molecules in the asymmetric unit is shown. H atoms are omitted for clarity.
of these transitions will later be made with the use of TD-
DFT calculations.
Figure 1. UV-vis spectra (CH2Cl2) of the compounds
[W(S2C2Me2)x(CO)6-2x] (x ) 1-3). The UV-vis traces are shown with
the approximate colors of the compounds.
Schrauzer noted the propensity of both [W(S2C2Me2)-
(CO)4] and [W(S2C2Me2)2(CO)2] to undergo carbonyl dis-
placement reactions by phosphines.9 As the first part of broad
survey of the reactivity of these compounds, we have noted
that [W(S2C2Me2)(CO)4] readily undergoes the displacement
of only two CO ligands when introduced to an excess of
relatively basic PMe3 and subjected to vigorous reflux
(Scheme 1). Similarly, [W(S2C2Me2)2(CO)2] readily under-
goes displacement of one CO ligand by PMe3 to afford the
mixed carbonyl phosphine complex 8. With the use of excess
PMe3, accompanied by Me3NO to facilitate displacement of
CO by its oxidation to CO2, good yields of
[W(S2C2Me2)2(PMe3)2] are obtained. The promotion of CO
substitution by phosphine with use of Me3NO has been
previously noted.37-40 Phosphine basicity appears to be an
important factor in enabling the formation of this bis(phos-
phine) adduct. Reaction of the modestly basic 1,2-bis(diphen-
ylphosphino)ethane ligand with 5 under forcing conditions,
despite a chelate effect which would favor CO displacement,
produces only trace amounts of [W(S2C2Me2)2(dppe)]. The
only other bis(dithiolene) bis(phosphine) complexes of
tungsten that are known are [W(S2C2Ph2)2(dppe)]9 and
[W(bdt)2(P(OEt)3)2] (bdt ) benzene-1,2-dithiolate), the latter
of which is formed in an oxygen atom abstraction reaction
between [WO(bdt)2Cl]1- and excess P(OEt)3.41
M-CO bonds in [M(S2C2R2)(CO)4] are inherently weaker
for Mo versus W and render this species unstable against a
second dithiolene ligand transfer. Both experiment35 and
theory36 indicate a ∼5-6 kcal/mol greater M-CO bond
strength for W over Mo in the corresponding hexacarbonyls.
Mono(dithiolene) complexes of Mo and W are relatively
scarce, particularly in compounds bearing other ligands
potentially subject to further substitution reactions. For this
reason, [W(S2C2Me2)(CO)4] may have value in the synthesis
of tungsten analogues of the catalytic sites of molydoenzymes
in the xanthine oxidase family.
The original preparation and isolation of [W(S2C2Me2)-
(CO)4] from the reaction of [W(CO)6] with [Ni(S2C2Me2)2]
as described by Schrauzer was complicated by difficulty in
separating it from unreacted W(CO)6 by chromatography and
by its intrinsic solution lability, which made recrystallization
impractical. Consequently, no yield was determined, and only
limited physical data were reported. The reaction of
[W(CO)3(MeCN)3] with [Ni(S2C2Me2)2] in CH2Cl2 solution
according to Goddard and Holm, but with 8-12 h rather
than 72 h reaction times, results in modest but consistent
18-20% yields of [W(S2C2Me2)(CO)4] that are unmixed with
residual [W(CO)6]. After separation from [W(S2C2Me2)2-
(CO)2] by elution from a silica column with pure n-pentane,
recrystallization is readily accomplished from this same
solvent at reduced temperature. Under these conditions,
[W(S2C2Me2)2(CO)2] is produced in similar amounts (∼20%
yield), and [W(S2C2Me2)3] is invariably formed in small
quantities (∼2-3%) as well.
Structures. The crystal structure of protected ligand 1 has
been determined and is presented in Figure 2. This molecule
offers baseline C-S single and CdC double bond lengths
(Table 2) that are uncomplicated by the potentially “non-
innocent” behavior of the dithiolene ligand in its metal
complexes. The C-Save bond length of 1.754[1] Å42 and the
CdC bond length of 1.340(2) Å in 1 agree closely with the
typical values of 1.751[17] Å for S-C(sp2) and 1.331[9] Å
The UV-vis spectra of the series [W(S2C2Me2)x(CO)6-2x
]
(x ) 1-3) are displayed in Figure 1 and reveal a trend toward
lower energy absorption and greater intensity as the number
of dithiolene ligands is increased. These absorptions are likely
transitions involving orbitals that are mixed in composition
and are thus not the MLCT or LMCT transitions of more
classical inorganic compounds. A more definitive assignment
(36) Ehlers, A. W.; Frenking, G. J. Chem. Soc., Chem. Commun. 1993,
1709–1711.
(37) Blumer, D. J.; Barnett, K. W.; Brown, T. L. J. Organomet. Chem.
1979, 173, 71–76.
(38) Shi, Y.-L.; Gao, Y.-C.; Shi, Q.-Z.; Kershner, D. L.; Basolo, F.
Organometallics 1987, 6, 1528–1531.
(39) Gao, Y.-C.; Shi, Q.-Z.; Kershner, D. L.; Basolo, F. Inorg. Chem. 1988,
27, 188–191.
(34) Friedle, S.; Partyka, D. V.; Bennett, M. V.; Holm, R. H. Inorg. Chim.
Acta 2006, 359, 1427–1434.
(35) Lewis, K. E.; Golden, D. M.; Smith, G. P. J. Am. Chem. Soc. 1984,
106, 3905–3912.
(40) Shen, J.-K.; Shi, Y.-L.; Gao, Y.-C.; Shi, Q.-Z.; Basolo, F. J. Am. Chem.
Soc. 1988, 110, 2414–2418.
(41) Lorber, C.; Donahue, J. P.; Goddard, C. A.; Nordlander, E.; Holm,
R. H. J. Am. Chem. Soc. 1998, 120, 8102–8112.
2108 Inorganic Chemistry, Vol. 48, No. 5, 2009

Dithiolene-Carbonyl and Dithiolene-Phosphine Complexes
Table 2. Bond Lengths (Å) and Selected Angles (deg) for 4,5-Dimethyl-1,3-dithiol-2-one (1) and for 2,2-Di-n-butyl-4,5-dimethyl-1,3,2-dithiastannole
(2)a
1
2
S(1)-C(1)
S(2)-C(2)
S(1)-C(5)
S(2)-C(5)
C(5)-O(1)
C(1)-C(2)
C(1)-C(3)
C(2)-C(4)
1.755(1)
1.752(2)
1.770(2)
1.769(2)
1.211(2)
1.340(2)
1.503(2)
1.506(2)
C(1)-S(1)-C(5)
97.20(7)
97.36(7)
116.9(1)
116.9(1)
111.62(8)
124.3(1)
124.1(1)
Sn(1)-S(1)
Sn(1)-S(2)
S(1)-C(1)
S(2)-C(2)
C(1)-C(2)
C(1)-C(3)
C(2)-C(4)
2.455(1)
2.408(2)
1.778(6)
1.784(6)
1.338(8)
1.500(8)
1.502(8)
S(1)-Sn(1)-S(2)
S(1)-Sn(1)-C(5)
S(1)-Sn(1)-C(9)
S(2)-Sn(1)-C(5)
S(2)-Sn(1)-C(9)
C(5)-Sn(1)-C(9)
C(1)-S(1)-Sn(1)
C(2)-S(2)-Sn(1)
88.89(5)
103.8(1)
106.0(2)
110.7(2)
114.3(2)
125.6(2)
99.5(2)
C(2)-S(2)-C(5)
S(1)-C(1)-C(2)
S(2)-C(2)-C(1)
S(1)-C(5)-S(2)
S(1)-C(5)-O(1)
S(2)-C(5)-O(1)
100.4(2)
a Data for 2 are for one of two independent molecules in the asymmetric unit.
Scheme 2. Possible Oxidation States of a Dithiolene Ligand
dithiolate; R ) Me or Et)],45 although the latter set of
molecules are pseudo pentacoordinate owing to intermo-
lecular Sn · · · S interactions.
Of the three-member series [W(S2C2Me2)x(CO)6-2x] (x )
1-3), structural data have only been available for the
dicarbonyl compound (x ) 2).10 Reported here are crystal
structures of compounds 4 (x ) 1) and 6 (x ) 3) as well as
that of 5 (x ) 2) at slightly higher resolution than the
previous structural characterization (Figure 3, Tables 1 and
3). The structure of 4 was proposed by Schrauzer to be
octahedral9 but in fact has been found to be a near-perfect
trigonal prism (Figure 3) with a Bailar twist angle of 4.0°.
This trigonal prismatic coordination geometry is unique
among monodithiolene complexes of Mo and W and will
later be the subject of a more detailed computational study.
Preliminarily, a geometry optimization of trigonal prismatic
and octahedral [W(S2C2Me2)(CO)4] at the B3LYP level of
theory calculates the trigonal prismatic geometry to be 5.12
kcal/mol lower in free energy than the octahedral structure.
The calculations also reveal that the octahedral structure is
a transition state with one imaginary mode (34.3i cm-1)
whose reactant and product are trigonal prismatic structures.
for (sp2)CdC(sp2) that have been tabulated from a large body
of structurally identified compounds.43 Dithiolene ligand
C-S bond lengths that are shorter than 1.751[17] Å by the
3σ criterion that is generally accepted as limiting the
confidence of bond length measurements (i.e., C-S bond
lengths <1.73 Å) may be taken as indicative of partial thione
character to the dithiolene ligand because of some degree
of ligand oxidation (b in Scheme 2). Similarly, dithiolene
C-C bond lengths longer than the typical C-C olefinic bond
length of 1.331[9] Å by the same threshold (i.e., > 1.358
Å) may be interpreted as evidence for some thienyl radical
monoanion (b in Scheme 2) involvement, which lowers the
carbon-carbon bond order.
Compound 2 was characterized structurally (Figure 2) and
j
found to crystallize in triclinic space group P1 with two
46
A species related to 4 is the dianion [W(bdt)(CO)4],2-
independent molecules in the asymmetric unit, data for only
one of which are shown in Table 2. The coordination
geometry at Sn in 2 is distorted tetrahedral, the greatest
deviation from the idealized value of 109.5° being the
S(1)-Sn(1)-S(2) angle (88.89(5)°) because of the con-
straints of the ligand chelate. The averaged C-S bond length
for 2 is 1.776[3] Å, a value somewhat longer than those
observed in 1. This difference may be attributable, at least
in part, to an absence of a complete set of π bonds around
the 1,3,2-dithiastannole ring system, compared to the 1,3-
dithiol-2-one ring system, because of the sp3 hybridization
at the tin center. However, the C-C olefinic bond lengths
in 2 (1.341[5] Å) are essentially the same as in 1. Compounds
related to 2 that have been structurally identified include
which crystallography revealed to have an octahedral ge-
ometry.
The C-S and C-C (olefinic) bond lengths in 4 are, within
the error of the experiment, similar to the corresponding
values in 1 and imply a dithiolene ligand in 4 that is closer
to a fully reduced ene-1,2-dithiolate description than other-
wise. Thus a W(II) oxidation description would appear
pertinent to 4. In contrast, compound 5 reveals C-S and
dithiolene C-C bond lengths that are appreciably shorter
(C-Save ) 1.722[2] Å) and longer (C-Cave ) 1.363[3] Å),
respectively, within the resolution limit of the data than those
in 1 (1.754[1] Å and 1.340(2) Å, respectively) which strongly
points toward the involvement of thienyl radical monoanion
character to both dithiolene ligands and consequently a W(II)
oxidation state for this compound as well. This W(II)
oxidation state formulation for 5 has also been implicated
by calculations of the electronic structures of the series
[W(S2C2Me2)2(CO)2]n (n ) 0, 1-, 2-).11
n
[(mnt)SnR2] (mnt ) maleonitriledithiolate; R ) CH3, Bu
or Ph)44 and [(dmit)SnR2] (dmit ) 1,3-dithiol-2-thione-4,5-
(42) Uncertainties for averaged bond lengths were determined using the
general formula for uncertainty in a function of multiple variables as
described by Taylor, J. R. An Introduction to Error Analysis;
University Science Books: Sausalito, CA, 1997; pp 73-77.
(43) Allen, F. H.; Kennard, O.; Watsoc, D. G.; Brammer, L.; Orpen, A. G.;
Taylor, R. In International Tables of Crystallography; Wilson, A. J. C.,
Ed.; Kluwer Academic Publishers: Boston, 1995; Vol. C, Mathemati-
cal, Physical, and Chemical Tables, Sect. 9.5.
Tris(dithiolene) compound 6 proved to be surprisingly
difficult to crystallize in a diffraction quality form, a stark
contrast to its molybdenum homologue, which readily
(45) Allan, G. M.; Howie, R. A.; Skakle, J. M. S.; Wardell, J. L.; Wardell,
(44) Ma, C.; Han, Y.; Li, D. Polyhedron 2004, 23, 1207–1216.
S. M. S. V. J. Organomet. Chem. 2001, 627, 189–200.
Inorganic Chemistry, Vol. 48, No. 5, 2009 2109

Chandrasekaran et al.
Figure 3. Thermal ellipsoid plots at the 50% (4, 5, 7-9) or 30% (6) level. Compounds 6 and 7 are presented in two orientations. For 6, only the tungsten
and sulfur ellipsoids are anisotropic. H atoms are omitted for clarity.
crystallizes by evaporation of benzene solutions.47 Invariably,
crystals of 6 were twinned and demonstrated a high mosa-
icity. After screening a broad variety of solvents systems
and methods, crystals of 6 that showed strong diffraction of
X-rays were obtained by the diffusion of MeOH into a
nitrobenzene solution. Regrettably, in addition to the twinning
complications, the structure of 6 proved to be afflicted with
disorder problems which militated against the attainment of
low uncertainties in any bond lengths and angles despite an
overall acceptably low R factor in the final refinement of
the molecule. Consequently, no insight is available into the
state of oxidation of the dithiolene ligands in this compound
on the basis of C-S and C-C bond lengths (Table 3). Recent
XAS and spectroscopic work by Wieghardt and co-workers
upon [W(3,5-tBu2-C6H2S2)3]n (n ) 0, 1-) have identified
W(V) as the metal oxidation occurring in both compounds.48
However, a sulfur K-edge XAS study and detailed compu-
tational analysis of the related [Mo(S2C2Me2)3]0,1-,2- series
(46) Darensbourg, D. J.; Draper, J. D.; Frost, B. J.; Reibenspies, J. H. Inorg.
Chem. 1999, 38, 4705–4714.
(47) Lim, B. S.; Donahue, J. P.; Holm, R. H. Inorg. Chem. 2000, 39, 263–
273.
2110 Inorganic Chemistry, Vol. 48, No. 5, 2009

Dithiolene-Carbonyl and Dithiolene-Phosphine Complexes
Table 3. Selected Bond Lengths (Å) and Angles (deg) for Compounds 4-6a
[W(S2C2Me2)(CO)4], 4
[W(S2C2Me2)2(CO)2], 5
[W(S2C2Me2)3], 6
W(1)-S(1)
2.358(2)
2.364(2)
2.038(7)
2.043(6)
2.035(6)
2.038(7)
1.739(6)
1.749(6)
1.744[4]
1.351(8)
1.137(8)
1.126(8)
1.137(8)
1.142(8)
1.507(8)
1.494(8)
82.38(5)
84.7(2)
142.3(2)
86.9(2)
137.5(2)
137.5(2)
88.0(2)
141.7(2)
85.5(2)
78.1(8)
W(1)-S(1)
W(1)-S(2)
W(1)-S(3)
W(1)-S(4)
W(1)-C(9)
W(1)-C(10)
S(1)-C(1)
S(2)-C(2)
S(3)-C(3)
S(4)-C(4)
2.3711(7)
2.3722(7)
2.3657(7)
2.3699(7)
2.019(3)
2.020(3)
1.720(3)
1.722(3)
1.721(3)
1.726(3)
1.722[2]
1.365(4)
1.361(4)
1.363[3]
1.142(4)
1.141(3)
81.05(2)
88.34(3)
148.03(3)
76.77(9)
129.44(9)
141.56(3)
88.80(2)
133.22(8)
79.01(8)
80.96(2)
78.49(8)
133.05(8)
129.32(9)
77.15(9)
84.2(1)
W(1A)-S(1A)
2.35(2)
2.354(7)
2.33(1)
2.38(1)
2.381(5)
2.381(9)
1.73(2)
1.73(2)
1.75(2)
1.36(2)
1.387
81.8(4)
136.4(4)
132.9(2)
82.1(4)
83.9(4)
81.9(3)
79.5(3)
134.5(2)
137.6(2)
82.7(4)
135.4(2)
81.6(1)
81.1(3)
136.0(3)
81.9(2)
109.4(9)
108.6(5)
107.7(8)
119(1)
W(1)-S(2)
W(1)-C(5)
W(1)-C(6)
W(1)-C(7)
W(1)-C(8)
S(1)-C(1)
S(2)-C(2)
W(1A)-S(2A)
W(1A)-S(3A)
W(1A)-S(1BA)
W(1A)-S(2BA)
W(1A)-S(3BA)
S(1A)-C(1A)
S(2A)-C(2A)
b
S-Cave
S(3A)-C(3A)
C(1)-C(2)
C(1A)-C(2A)
b
C(5)-O(1)
S-Cave
C(3A)-C(3BA)
C(6)-O(2)
C(1)-C(2)
C(3)-C(4)
olefinic C-Cave
C(9)-O(1)
C(10)-O(2)
S(1A)-W(1A)-S(2A)
S(1A)-W(1A)-S(3A)
S(1A)-W(1A)-S(1BA)
S(1A)-W(1A)-S(2BA)
S(1A)-W(1A)-S(3BA)
S(2A)-W(1A)-S(3A)
S(2A)-W(1A)-S(1BA)
S(2A)-W(1A)-S(2BA)
S(2A)-W(1A)-S(3BA)
S(3A)-W(1A)-S(1BA)
S(3A)-W(1A)-S(2BA)
S(3A)-W(1A)-S(3BA)
S(1BA)-W(1A)-S(2BA)
S(1BA)-W(1A)-S(3BA)
S(2BA)-W(1A)-S(3BA)
W(1A)-S(1A)-C(1A)
W(1A)-S(2A)-C(2A)
W(1A)-S(3A)-C(3A)
S(1A)-C(1A)-C(2A)
S(2A)-C(2A)-C(1A)
S(3A)-C(3A)-C(3BA)
S(1A)-C(1A)-C(4A)
S(2A)-C(2A)-C(5A)
S(3A)-C(3A)-C(6A)
θc
C(7)-O(3)
b
C(8)-O(4)
C(1)-C(3)
C(2)-C(4)
S(1)-W(1)-S(2)
S(1)-W(1)-C(5)
S(1)-W(1)-C(6)
S(1)-W(1)-C(7)
S(1)-W(1)-C(8)
S(2)-W(1)-C(5)
S(2)-W(1)-C(6)
S(2)-W(1)-C(7)
S(2)-W(1)-C(8)
C(5)-W(1)-C(6)
C(5)-W(1)-C(7)
C(5)-W(1)-C(8)
C(6)-W(1)-C(7)
C(6)-W(1)-C(8)
C(7)-W(1)-C(8)
W(1)-S(1)-C(1)
W(1)-S(2)-C(2)
W(1)-C(5)-O(1)
W(1)-C(6)-O(2)
W(1)-C(7)-O(3)
W(1)-C(8)-O(4)
θc
S(1)-W(1)-S(2)
S(1)-W(1)-S(3)
S(1)-W(1)-S(4)
S(1)-W(1)-C(9)
S(1)-W(1)-C(10)
S(2)-W(1)-S(3)
S(2)-W(1)-S(4)
S(2)-W(1)-C(9)
S(2)-W(1)-C(10)
S(3)-W(1)-S(4)
S(3)-W(1)-C(9)
S(3)-W(1)-C(10)
S(4)-W(1)-C(9)
S(4)-W(1)-C(10)
C(9)-W(1)-C(10)
W(1)-S(1)-C(1)
W(1)-S(2)-C(2)
W(1)-S(3)-C(3)
W(1)-S(4)-C(4)
W(1)-C(9)-O(1)
W(1)-C(10)-O(2)
θc
77.2(2)
128.7(2)
120.7(2)
77.3(2)
78.0(2)
120(1)
120.4
118(1)
115(1)
108.6(2)
108.5(2)
177.1(5)
177.7(6)
176.8(6)
177.2(6)
4.0°
109.7(1)
109.3(1)
109.6(1)
109.7(1)
178.7(3)
178.6(3)
3.4°
116(1)
0.7°e
Rd
7.8°
Rd
0.7°
Rd
2.7°
a Averaged bond lengths are in bold faced type. b See footnote of reference 42. c Bailar twist angle, defined as the twist angle between triangular faces
of the trigonal prism. d Chelate fold angle, defined as the angle between the WS2 and S2C2 planes. For 5 and 6, these are averaged values. e See text for
discussion.
by Solomon and co-workers concluded that the both redox
processes in this series are ligand-based and that the metal
center is Mo(IV) throughout.49 While it is unclear what
formulation is best suited to describe the oxidation state of
tungsten in [W(S2C2Me2)3], the foregoing studies indicate
that fully reduced ene-1,2-dithiolate ligands are not pertinent
here and that some degree of partial ligand oxidation is
operative.
Figure 4 illustrates the disorder occurring in 6 as a
consequence of its location on a crystallographic 2-fold axis
(vertical and in the plane of the paper) in space group C2/c.
Despite this disorder, it appears that the true Bailar twist
angle, defined as the twist angle between triangular faces in
the trigonal prism, is 1.8°. This number is close to the value
of 2.4° observed in [Mo(S2C2Me2)3].47,49 Other, slightly
different, split atom models that could be devised to model
the disorder in 6 lead to larger Bailar twist angles but also
lead to dithiolene C-C and C-S bond distances that are
not chemically reasonable. Also of interest is the dithiolene
chelate fold angle, R, the angle between the WS2 and S2C2
mean planes. The dithiolene C-S and C-C bond lengths
Figure 4. Illustration of the disorder in tris(dithiolene) compound 6 about
a crystallographic 2-fold axis.
are somewhat less decisive in pointing toward one value or
another for R among the possibilities that exist depending
on how the ligand disorder is partitioned, but the smaller of
the possible values for R, 7.8°, also appears to be most likely.
Another point suggesting the smallest possible value for R
is the consideration that this molecule is more likely to
crystallize on a 2-fold axis if the compound is closer to true
D3h symmetry, which has 2-fold symmetry, rather than
further from D3h symmetry, with a larger R value. In fact, it
(48) Kapre, R. R.; Bothe, E.; Weyhermu¨ller, T.; DeBeer George, S.;
Wieghardt, K. Inorg. Chem. 2007, 46, 5642–5650.
Inorganic Chemistry, Vol. 48, No. 5, 2009 2111

Chandrasekaran et al.
Table 4. Selected Bond Lengths (Å) and Angles (deg) for Compounds 7-9a
[W(S2C2Me2)(CO)2(PMe3)2], 7 [W(S2C2Me2)2(CO)(PMe3)], 8
W(1)-S(1)
[W(S2C2Me2)2(PMe3)2], 9
2.3775(7)
2.3841(7)
2.4794(8)
2.4628(8)
1.970(2)
1.979(2)
1.750(2)
1.758(2)
1.754[1]
1.349(3)
1.164(2)
1.159(3)
1.509(3)
1.505(3)
81.44(2)
85.77(2)
134.40(2)
91.92(6)
148.41(6)
135.84(2)
83.51(2)
144.67(6)
92.89(6)
132.11(2)
77.45(6)
76.78(6)
76.60(6)
74.89(6)
109.32(8)
109.34(7)
109.07(7)
174.7(2)
176.2(2)
9.8°
W(1)-S(1)
W(1)-S(2)
W(1)-S(3)
W(1)-S(4)
W(1)-P(1)
W(1)-C(9)
S(1)-C(1)
S(2)-C(2)
S(3)-C(3)
S(4)-C(4)
2.3588(6)
2.3550(5)
2.3626(6)
2.3514(5)
2.4762(6)
2.000(2)
1.735(2)
1.736(2)
1.730(2)
1.730(2)
1.733[1]
1.353(3)
1.354(3)
1.354[2]
1.153(3)
81.02(2)
86.89(2)
139.80(2)
80.64(2)
136.27(6)
144.93(2)
87.73(2)
130.62(2)
80.06(6)
80.56(2)
78.73(2)
128.52(6)
132.72(2)
78.12(6)
82.49(6)
109.30(7)
109.67(7)
110.19(8)
110.64(7)
179.0(2)
3.7°
W(1)-S(1)
W(1)-S(2)
W(1)-P(1)
S(1)-C(1)
S(2)-C(2)
2.3627(5)
2.3506(5)
2.4949(5)
1.741(2)
1.745(2)
1.743[1]
1.346(3)
80.27(2)
137.93(2)
86.64(2)
76.89(2)
137.93(2)
86.64(2)
143.02(2)
129.48(2)
79.61(2)
80.27(2)
137.93(2)
76.89(2)
79.61(2)
129.48(2)
88.22(2)
110.72(7)
110.83(7)
118.9(1)
119.2(1)
5.1°
W(1)-S(2)
W(1)-P(1)
W(1)-P(2)
W(1)-C(5)
W(1)-C(6)
S(1)-C(1)
S(2)-C(2)
b
S-Cave
C(1)-C(2)
S(1)-W(1)-S(2)
S(1)-W(1)-S(1A)
S(1)-W(1)-S(2A)
S(1)-W(1)-P(1)
S(1)-W(1)-P(1A)
S(2)-W(1)-S(1A)
S(2)-W(1)-S(2A)
S(2)-W(1)-P(1)
S(2)-W(1)-P(1A)
S(1A)-W(1)-S(2A)
S(1A)-W(1)-P(1)
S(1A)-W(1)-P(1A)
S(2A)-W(1)-P(1)
S(2A)-W(1)-P(1A)
P(1)-W(1)-P(1A)
W(1)-S(1)-C(1)
W(1)-S(2)-C(2)
S(1)-C(1)-C(2)
S(2)-C(2)-C(1)
θc
b
S-Cave
C(1)-C(2)
b
C(5)-O(1)
S-Cave
C(6)-O(2)
C(1)-C(2)
C(3)-C(4)
olefinic C-Cave
C(9)-O(1)
C(1)-C(3)
b
C(2)-C(4)
S(1)-W(1)-S(2)
S(1)-W(1)-P(1)
S(1)-W(1)-P(2)
S(1)-W(1)-C(5)
S(1)-W(1)-C(6)
S(2)-W(1)-P(1)
S(2)-W(1)-P(2)
S(2)-W(1)-C(5)
S(2)-W(1)-C(6)
P(1)-W(1)-P(2)
P(1)-W(1)-C(5)
P(1)-W(1)-C(6)
P(2)-W(1)-C(5)
P(2)-W(1)-C(6)
C(5)-W(1)-C(6)
W(1)-S(1)-C(1)
W(1)-S(2)-C(2)
W(1)-C(5)-O(1)
W(1)-C(6)-O(2)
θc
S(1)-W(1)-S(2)
S(1)-W(1)-S(3)
S(1)-W(1)-S(4)
S(1)-W(1)-P(1)
S(1)-W(1)-C(9)
S(2)-W(1)-S(3)
S(2)-W(1)-S(4)
S(2)-W(1)-P(1)
S(2)-W(1)-C(9)
S(3)-W(1)-S(4)
S(3)-W(1)-P(1)
S(3)-W(1)-C(9)
S(4)-W(1)-P(1)
S(4)-W(1)-C(9)
P(1)-W(1)-C(9)
W(1)-S(1)-C(1)
W(1)-S(2)-C(2)
W(1)-S(3)-C(3)
W(1)-S(4)-C(4)
W(1)-C(9)-O(1)
θc
Rd
2.8°
Rd
0.9°
Rd
4.5°
a Averaged bond lengths are in bold faced type. b See footnote reference 42. c Bailar twist angle, defined as the twist angle between triangular faces of
the trigonal prism. d Chelate fold angle, defined as the angle between the WS2 and S2C2 planes. The value for compound 8 is an average of two values.
is a slight difference in R which appears to be the principal
distinction between the structures of 6 and [Mo(S2C2Me2)3],
for which R ) 15.8°.47,49 Modest though the difference may
be, a larger chelate fold for [Mo(S2C2Me2)3] apparently leads
[M(CO)6] (M ) Mo,55 W56). The chelate fold angle, R, in
trigonal prismatic tris(dithiolene) complexes has been identi-
fied as arising from configuration interaction between the
2
metal dz orbital, which is doubly occupied, and a ligand-
j
it to crystallize on a general position in P1 without disorder,
based MO constituted of an interligand antibonding combi-
nation of the three dithiolene π-systems.49,57 As such, the
degree of configuration interaction, and hence the magnitude
of the ligand chelate fold, might be expected to differ
between the Mo and W systems because of an intrinsic
while a smaller chelate fold for 6 brings it close enough to
idealized D3h symmetry that it can crystallize, albeit with
disorder, in the higher symmetry of monoclinic C2/c. This
divergence in crystal behavior between homologous molyb-
denum and tungsten compound is unusual. Almost invariably,
homologous Mo and W compounds (provided counterions
and molecules of solvation are the same) crystallize in the
same space group with nearly isometric unit cell parameters.
Examples include, to name a select few, [Et4N][M(S2-
C2Me2)3] (M ) Mo,47 W11), [Et4N]2[M(S2C2Me2)3] (M )
Mo,11 W11), [Et4N][M(O)(OSitBuPh2)(bdt)2] (M ) Mo,50
W41), [M(bdt)3] (M ) Mo,51 W52), [M2(DAniF)4] (DAniF
) N,N′-di-p-anisylformamidinate; M ) Mo,53 W54), and
2
2
difference in energy between the 4dz and 5dz orbitals in
these molecules.
The mixed dithiolene phosphine compounds 7, 8, and 9
have all been characterized structurally as well (Figure 3,
Table 4). The preparation and structures of several com-
pounds similar to 7 have been previously described, although
their synthesis proceeded by displacement of iodide and CO
from [WI2(CO)3(PR3)2] (R ) Et, Ph) by reduced dithiolene
ligand.58 The coordination geometry of 7 is distorted trigonal
prismatic, with a twist angle of 9.8° between triangular faces.
(49) Tenderholt, A. L.; Szilagyi, R. K.; Holm, R. H.; Hodgson, K. O.;
Hedman, B.; Solomon, E. I. Inorg. Chem. 2008, 47, 6382–6392.
(50) Donahue, J. P.; Goldsmith, C. R.; Nadiminti, U.; Holm, R. H. J. Am.
Chem. Soc. 1998, 120, 12869–12881.
(51) Cowie, M.; Bennett, M. J. Inorg. Chem. 1976, 15, 1584–1589.
(52) Huynh, H. V.; Lu¨gger, T.; Hahn, F. E. Eur. J. Inorg. Chem. 2002,
3007–3009.
(54) Cotton, F. A.; Donahue, J. P.; Hall, M. B.; Murillo, C. A.; Villagra´n,
D. Inorg. Chem. 2004, 43, 6954–6964.
(55) Mak, T. C. W. Z. Kristallogr. 1984, 166, 277–281.
(56) Heinemann, F.; Schmidt, H.; Peters, K.; Thiery, D. Z. Kristallogr.
1992, 198, 123–124.
(57) Campbell, S.; Harris, S. Inorg. Chem. 1996, 35, 3285–3288.
(58) Baker, P. K.; Drew, M. G. B.; Parker, E. E.; Robertson, N.; Underhill,
A. E. J. Chem. Soc., Dalton Trans. 1997, 1429–1433.
(53) Lin, C.; Protasiewicz, J. D.; Smith, E. T.; Ren, T. Inorg. Chem. 1996,
35, 6422–6428.
2112 Inorganic Chemistry, Vol. 48, No. 5, 2009

Dithiolene-Carbonyl and Dithiolene-Phosphine Complexes
This distortion is appreciably less than that observed in
syntheses of the classical compounds [Ni(S2C2Me2)2] (3) and
[W(S2C2Me2)3] (6), previously only available via the P4S10/
acetoin method. The former is prepared via base hydrolysis
of Me2C2S2CdO, followed by addition of NiCl2 and I2, while
the latter is formed in the reaction between WCl6 and
(Me2C2S2)SnnBu2.
related structurally characterized compounds (θ
)
12-23°).58 Compounds 8 and 9 adopt the nearly perfect
trigonal prismatic coordination geometry that is by now well
precedented for bis(dithiolene) complexes of tungsten and
molybdenum.1 The C-S and C-C bond lengths in the series
5, 8, and 9 (Tables 3 and 4) reveal a definite trend toward
longer (1.722[2] Å f 1.733[1] Å f 1.743[1] Å) and shorter
(1.363[3] Å f 1.354[2] Å f 1.346(3) Å) values, respec-
tively. These trends imply that the presence of the strongly
π-acidic CO ligands stabilizes the thienyl radical monoan-
ionic form of the dithiolene ligand (Scheme 2), while their
removal forces more electron density back upon the dithi-
olene ligands and causes the ene-1,2-dithiolate description
to become operative. These trends are currently being probed
by sulfur K-edge XAS spectroscopy, the results of which
will be published in a forthcoming study.
Improved access to [Ni(S2C2Me2)2] has enabled further
study of the series [W(S2C2Me2)x(CO)6-2x] (x ) 1 (4), x )
2, (5), x ) 3 (6)), which is formed as a mixture in reactions
between [W(MeCN)3(CO)3] and 3. This series has been fully
characterized here for the first time, both structurally and
spectroscopically. Near perfect trigonal prismatic coordina-
tion geometries are observed for all three compounds.
Compound 4 is a rare, if not unique, instance of a mon-
o(dithiolene) compound in this coordination geometry.
Compound 6 crystallizes in disordered fashion upon a 2-fold
axis and appears to differ from its molybdenum homologue
by having a smaller dithiolene chelate fold angle (R).
Mono(dithiolene) compound [W(S2C2Me2)(CO)4] is sub-
ject to carbonyl displacement by PMe3, affording distorted
trigonal prismatic [W(S2C2Me2)(CO)2(PMe3)2]. Similarly,
treatment of [W(S2C2Me2)2(CO)2] with PMe3 or PMe3/
Electrochemistry. Compounds 5 and 6 have previously
been examined by cyclic voltammetry and found to undergo
two highly reversible reductions.11 Spectroscopic, structural,
and computational data indicate that these processes are
ligand based for 5. A similar situation may pertain for 6
inasmuch as the two reversible reductions observed for its
molybdenum counterpart, [Mo(S2C2Me2)3], have also been
assigned as ligand-based events. Compound 4 does not
display any reversible reduction in either MeCN or CH2Cl2,
a somewhat surprising observation in view of the presence
of four CO ligands that might be expected to accept some
amount of charge density. Considering the existence of the
related octahedral dianion [W(S2C6H4)(CO)4],2- 46 one pos-
sible explanation for this lack of reversibility is a facile
structural reorganization to an octahedral geometry, with a
consequent change in the compound’s redox potentials.
Compound 8 displays one reversible reduction at a fairly
reducing potential of -1.04 V (vs Ag/AgCl), while 7 and 9
reveal only irreversible behavior in both the oxidizing and
the reducing directions (see Supporting Information). No
improvement in the behavior of 9 is observed upon perform-
ing the scan in the presence of excess PMe3, indicating that
dissociation of phosphine upon reduction is not the reason
for the observed irreversibility, as has been noted in related
iron and cobalt dithiolene systems.59 Thus, electrochemical
reversibility in the series [W(S2C2Me2)2(CO)2-x(PMe3)x] (x
) 0, 1, 2) correlates directly with the presence of CO ligand.
While this trend may be rationalized simply as the ability to
absorb additional charge with a π-acid ligand, the structural
data suggest a different nuance in which CO ligand(s)
supports some oxidized character to the dithiolene ligands,
which are themselves the principal sites of reduction.
Me3NO
produces
[W(S2C2Me2)2(CO)(PMe3)]
or
[W(S2C2Me2)2(PMe3)2], respectively. Structural data for these
compounds identify a correlation between the presence of
CO ligand and partially oxidized (thienyl radical monoanion)
dithiolene ligand, as manifested by C-S and C-C bond
lengths. Of this set of mixed dithiolene-phosphine com-
pounds 7-9, only 8 displays any reversible electrochemistry,
a reduction at -1.04 V (vs Ag/AgCl).
With [W(S2C2Me2)(CO)4] and [W(S2C2Me2)2(CO)2] now
more available because of the improved access to the key
[Ni(S2C2Me2)2] synthon, an exploration of their reactivity
in direct oxidative addition reactions toward a variety of
small organic molecules is being probed.
Acknowledgment. The Louisiana Board of Regents is
gratefully acknowledged for the support through which
Tulane’s CCD diffractometer was purchased (Grant LEQSF-
(2002-03)-ENH-TR-67), and the Tulane Department of
Chemistry is thanked for its ongoing support of the X-ray
diffraction laboratory. J.P.D. thanks the Petroleum Research
Fund (Award 45685-G3) and Tulane University for start-up
funding and for a Committee on Research Fellowship
supporting this work. The Supercomputing Facility at Texas
A&M is thanked for providing computer time.
Supporting Information Available: X-ray crystallographic files
in CIF format and thermal ellipsoid plots with full atom labeling
for 1, 2 and 4-9. Selected spectroscopic and electrochemical data
for 1, 2 and 4-9. This material is available free of charge via the
Internet at http://pubs.acs.org.
Conclusions
This work describes the use of two protected forms of the
dimethyl-substituted dithiolene ligand for much improved
(59) Yu, R.; Arumugam, K.; Manepalli, A.; Tran, Y.; Schmehl, R.;
Jacobsen, H.; Donahue, J. P. Inorg. Chem. 2007, 46, 5131–5133.
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