Preparation of trichloro- and tribromocyclopentadienyltungsten(IV)

Article abstract of DOI:10.1016/S0022-328X(99)00292-2

The thermal decarbonylation of (Ring)WX₃(CO)₂ in refluxing toluene has led to the preparation of the CO-free compounds [(Ring)WX₃]₂ [Ring=η⁵-C₅H₅ (Cp) and X=Cl (1a) or Br (1b); Ring=η⁵-C₅H₄Me (Cp′), X=Cl (2a) or Br (2b); Ring=η⁵-C₅Me₅ (Cp*), X=Cl (3)]. The NMR properties of these molecules are consistent with diamagnetism and thereby indicate a different structure from that of the paramagnetic molybdenum analogues. Compounds 1a and 2a react with dppe to afford mononuclear 18-electron adducts, (Ring)WCl₃(dppe) (Ring=Cp (4) or Cp′ (5)). The X-ray structure of 5 shows a pseudo-fac-octahedral geometry with the dppe ligand occupying two equatorial (e.g. cis relative to Cp′) coordination sites. The X-ray structure of two by-products of the synthetic processes are also reported, e.g. Cp′₃W₃Cl₃(μ₂-Cl)₂(μ₃-O) (6) and [Cp*WCl₃]₂(μ-O) (7).

Full text of DOI:10.1016/S0022-328X(99)00292-2

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 593–594 (2000) 27–35
Preparation of trichloro- and tribromocyclopentadienyltungsten(IV)
Haley Blackburn a, James C. Fettinger a, Heinz-Bernhard Kraatz a,1, Rinaldo Poli b,*,
Raymund C. Torralba a
a Department of Chemistry and Biochemistry, Uni6ersity of Maryland, College Park, MD 20742, USA
b Laboratoire de Synthe`se et d’Electrosynthe`se Organome´talliques, Uni6ersite´ de Bourgogne, 6 Boule6ard Gabriel, F-21100 Dijon, France
Received 20 March 1999; accepted 19 May 1999
Dedicated to Professor Fausto Calderazzo in recognition of his outstanding contribution to organometallic chemistry.
Abstract
The thermal decarbonylation of (Ring)WX3(CO)2 in refluxing toluene has led to the preparation of the CO-free compounds
[(Ring)WX3]2 [Ring=h5-C5H5 (Cp) and X=Cl (1a) or Br (1b); Ring=h5-C5H4Me (Cp%), X=Cl (2a) or Br (2b); Ring=h5-
C5Me5 (Cp*), X=Cl (3)]. The NMR properties of these molecules are consistent with diamagnetism and thereby indicate a
different structure from that of the paramagnetic molybdenum analogues. Compounds 1a and 2a react with dppe to afford
mononuclear 18-electron adducts, (Ring)WCl3(dppe) (Ring=Cp (4) or Cp% (5)). The X-ray structure of 5 shows a pseudo-fac-oc-
tahedral geometry with the dppe ligand occupying two equatorial (e.g. cis relative to Cp%) coordination sites. The X-ray structure
of two by-products of the synthetic processes are also reported, e.g. Cp%W3Cl3(m2-Cl)2(m3-O) (6) and [Cp*WCl3]2(m-O) (7). © 2000
3
Elsevier Science S.A. All rights reserved.
Keywords: CO-free compounds; Diamagnetism; Metal–metal bonds; Tungsten; X-ray structures
1. Introduction
their structural and bonding features. Compounds of
Mo and W having the same stoichiometry are not
always necessarily isostructural. This is exemplified by
Monoyclopentadienylmetal halide systems are excel-
lent synthons to a variety of other organometallic com-
pounds [1]. For the heavier Group 6 metals (Mo and
W), systems with the metal in the oxidation states V,
(Ring)MX4 (Ring=Cp or substituted analogue) [2–5],
and III, [(Ring)MX2]2 [5–8], have been known for some
time. The corresponding systems of Mo(IV),
[(Ring)MoX3]2, have been more recently developed [9–
13]. Here, we report on the corresponding development
of the previously unknown systems of W(IV). These
systems have attracted our attention not only because
of their potential utility as starting compounds for
further organometallic transformations, but also for
the structure of [(h5-C5H4 Pr)MCl2]2 (type I [6] for
i
M=Mo and type II [7] for M=W). The W compound
has a tendency to maximize the metal–metal bonding
at the expense of metal–ligand bonding. The structure
of [Cp*MoX3]2 (X=Cl, Br) was shown to be of type
III with no direct metal–metal bonding interaction and
the compounds show magnetic properties consistent
with antiferromagnetic coupling between two S=1 d2
metal centers [11,12]. This structure is also found for
the corresponding d1–d1 Ta(IV) system, [(h5-
C5Me4Et)TaBr3]2 [14], which similarly has no metal–
metal bond. However, the corresponding d3–d3
[(h5-C5Me4Et)ReCl3]2 is diamagnetic and adopts a dif-
ferent structure, i.e. IV, with a metal–metal bonding
interaction. We have previously advanced the hypothe-
sis [11] that an analogous compound of W(IV) could
adopt a structure analogous to that of the Re system,
since W is known to form stronger metal–metal bonds
* Corresponding author. Tel.: +33-380-396-881; fax: +33-380-
396-098.
E-mail address: poli@u-bourgogne.fr (R. Poli)
1 Present address: Department of Chemistry, University of
Saskatchewan, Saskatoon, SK S7N 5C9, Canada.
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00292-2

28
H. Blackburn et al. / Journal of Organometallic Chemistry 593–594 (2000) 27–35
than Mo. In this contribution, we present a simple
synthetic procedure for the preparation of these W(IV)
systems and the structure of their phosphine addition
products. The diamagnetism found for [(Ring)WX3]2
suggest that they indeed adopt a metal–metal bonded
structure. The high oxophilicity of these materials leads
to the formation of oxygen-containing by-products, two
of which have been crystallographically characterized
and are also described here.
2.2. Thermal decarbonylation of (p5-Ring)WX3(CO)2
(Ring=C5H5, C5H4Me; X=Cl, Br). Formation of
[(p5-Ring)WX3]2
The products of these reactions are only sparingly
soluble in all common solvents and cannot be easily
recrystallized. The spectroscopic and analytical data
have been obtained for the crude materials and have
been tabulated in Table 1.
(a) [(h5-C5H5)WCl3]2 (1a). (h5-C5H5)WCl3(CO)2 (534
mg, 1.30 mmol) was placed in a silylated Schlenk tube
equipped with a magnetic stir bar and a silylated reflux
condenser. Toluene (20 ml) was added and the resulting
yellow–green slurry was refluxed for 3 h, yielding a
dark emerald-green slurry. An IR spectrum on an
aliquot of the mother solution showed no carbonyl
stretching frequencies. The solution was evaporated
under reduced pressure to ca. 2–3 ml and the precipita-
tion of the product was completed by the addition of
heptane (50 ml). After filtration, the solid was washed
with heptane (3×10 ml) until the washings were color-
less. The washings were cannulated off and discarded.
The solid was then dried under vacuum and stored in
flame-sealed vials under dinitrogen. An IR spectrum on
the residual solid showed no CO stretching vibrations.
Yield: 463 mg (87%).
(b) [(h5-C5H4Me)WCl3]2 (2a). By a procedure identi-
cal with that described in the preceding section, (h5-
C5H4Me)WCl3(CO)2 (525 mg, 1.24 mmol) gave 442 mg
of product (84%).
2. Experimental
An identical reaction with similar quantities of all
materials was performed. After the reflux in toluene,
the solution was filtered and cooled to −20°C, afford-
ing a few dark-green crystals. A single crystal of this
batch was used for the X-ray analysis, revealing the
trinuclear by-product (h5-C5H4Me)3W3Cl5O (6).
(c) [(h5-C5H5)WBr3]2 (1b). (h5-C5H5)WBr3(CO)2 was
prepared in situ from [(h5-C5H5)W(CO)3]2 (1.04 g, 1.56
mmol) and Br2 (242 ml, 4.69 mmol) in a silylated
2.1. General data
All operations were carried out under an atmosphere
of argon with standard Schlenk-line techniques. All
glassware was silylated with a 1:10 v/v solution of
dichlorodimethylsilane in CCl4. Solvents were distilled
directly from the drying agent (toluene and heptane
from Na, THF from Na/K/benzophenone, CH2Cl2
from P4O10) under argon prior to use. FT-IR spectra
were recorded with KBr cells on a Perkin–Elmer 1800
spectrophotometer. NMR spectra were recorded on
Bruker WP200, AF200, and AM400 spectrometers; the
peak positions are reported with positive shifts
downfield of TMS as calculated from the residual sol-
vent peaks (1H), or downfield of external 85% H3PO4
(31P). For each 31P-NMR spectrum a sealed capillary
containing H3PO4 was immersed in the same NMR
solvent used for the measurement and this was used as
the reference. The elemental analyses were carried out
by M-H-W Laboratories, Phoenix, AZ, Galbraith Lab-
oratories, Knoxville, TN, and Desert Analytics Labora-
tory, Tucson, AZ. Compounds (h5-Ring)WX3(CO)2
(Ring=C5H5, C5H4Me, C5Me5; X=Cl, Br) were pre-
pared as previously described [15]. Dppe (Strem) was
used without any further purification.
Table 1
Spectroscopic and analytical data for [(h5-Ring)WX3]2
Compound
1H-NMR l (ppm) Elemental analyses % found
(% calculated)
C
H
[CpWCl3]2
[CpWBr3]2
[Cp%WCl3]2
5.58 (s) a
16.9 (16.9)
11.9 (12.3)
19.7 (19.5)
1.4 (1.4)
1.0 (1.0)
1.8 (1.9)
5.62 (s) a
5.72 (br, 2H) b
5.31 (br, 2H)
1.74 (s, 3H)
6.51 (br, 2H) b
6.07 (br, 2H)
1.95 (s, 3H)
[Cp%WBr3]2
14.8 (14.3)
1.5 (1.4)
a Solvent=CD2Cl2.
b Solvent=C6D6.

H. Blackburn et al. / Journal of Organometallic Chemistry 593–594 (2000) 27–35
29
Schlenk tube as described above in (a). The Schlenk
tube was then equipped with a magnetic stir bar and a
silylated reflux condenser. Toluene (20 ml) was added
and the resulting brown–yellow slurry was refluxed
overnight, yielding a red–brown slurry. An IR spec-
trum on an aliquot of the mother solution showed no
carbonyl stretching frequencies. The solution was evap-
orated under reduced pressure to ca. 2–3 ml. The
precipitation of the product was completed by the
addition of heptane (50 ml). The solid was washed with
heptane (3×10 ml) until the washings were colorless,
dried under vacuum, and stored in flame-sealed vials
under dinitrogen. An IR spectrum on the residual
brown solid did not show CO stretching vibrations.
Yield: 434 mg (57%).
investigated by 1H-NMR spectrometry. 1H-NMR
(CD2Cl2): l 8.33–7.34 (m, Ph, 20H), 4.85 (t, Cp, 5H,
J
PH=4 Hz), 3.41 (br, CH2, 2H), 2.77 (br, CH2, 2H);
1
31P-NMR (CD2Cl2): l 12.14 (s, JPW=229 Hz).
(b) (h5-C5H4Me)WCl3(dppe) (5). By using a proce-
dure identical with that described above for the corre-
sponding Cp compound, [(h5-C5H4Me)WCl3]2 (610 mg,
1.65 mmol) and dppe (658 mg, 1.65 mmol) yielded a
brown solution, from which 925 mg of crude product
(79%) was obtained after filtration, evaporation to ca. 5
ml, and addition of pentane (50 ml). 1H-NMR
(CD2Cl2): l 7.70–7.27 (m, Ph, 20H), 4.44 (br, Cp%, 4H),
3.47 (br, CH2, 2H), 3.11 (br, CH2, 2H), 2.17 (s, Cp%,
1
3H); 31P-NMR (CD2Cl2): l 12.96 (s, JPW=226 Hz). A
single crystal of this compound was obtained by slow
diffusion of an n-pentane layer into a CH2Cl2 solution.
(d) [(h5-C5H4Me)WBr3]2 (2b). By a procedure identi-
cal with that described in (a) above, (h5-
C5H4Me)WBr3(CO)2 (283 mg, 0.507 mmol) gave 160
mg of brown solid (63%).
2.5. X-ray crystallography
(a) Compound 5. A dark-red parallelepiped crystal
with dimensions 0.20×0.20×0.40 mm was placed on
the Enraf–Nonius CAD-4 diffractometer. The cell
parameters and crystal orientation matrix were deter-
mined from 25 reflections in the range 6.1BqB13.9°
and confirmed with axial photographs. Data were col-
lected [Mo–Ka] with ꢀ–2q scans over the q range
1.6–22.5° with a scan width of (1.26+1.05 tan q)° and
a fixed scan speed of 4.12° min−1 with each scan
recorded in 96 steps with the outermost 16 steps on
each end of the scan being used for background deter-
mination. No decay correction was necessary (B3%
decay). Intensity statistics clearly favored the non-cen-
trosymmetric case. The structure was determined by
direct methods with the successful location of the tung-
sten atom in the space group P21. Subsequent differ-
ence-Fourier maps revealed the location of all
remaining non-hydrogen atoms within the main
molecule and also the two methylene chloride molecules
in the asymmetric unit. Hydrogen atoms were placed in
calculated positions as described in section (a) above.
After convergence, a final difference-Fourier map ex-
2.3. Thermal decarbonylation of (p5-C5Me5)WCl3-
(CO)2. Formation of [(p5-C5Me5)WCl3]2(v-O) (7)
(h5-C5Me5)WCl3(CO)2 (352 mg, 0.731 mmol) was
placed in a silylated Schlenk tube equipped with a
magnetic stir bar and a silylated reflux condenser.
Toluene (20 ml) was added and the resulting dark-yel-
low slurry was refluxed for 3 h, yielding a dark olive-
green slurry. An IR spectrum on an aliquot of the
mother solution showed no carbonyl stretching fre-
quencies. After evaporation to dryness at reduced pres-
sure, the residue was extracted with dichloromethane
affording an emerald-green solution and an olive-green
residue. The olive-green residue was sparingly soluble in
toluene and moderately soluble in dichloromethane.
1H-NMR (CD2Cl2): l 2.24 (s). The emerald-green solu-
tion was evaporated to dryness under reduced pressure
and redissolved in toluene. The solution was heated to
reflux and filtered while hot. The filtrate was allowed to
cool slowly to room temperature affording dark green–
1
black crystals. Yield: 64 mg. H-NMR (CD2Cl2): l 1.30
,
(s); (C6D6) l 1.73 (s). A single crystal of this batch was
used for the X-ray analysis.
hibited three peaks in the vicinity, i.e. within 1.2 A, of
the tungsten atom with ꢀDrꢀ52.71 e A−3. Selected
,
crystal data and refinement parameters are collected in
Table 2, and relevant bond distances and angles are
listed in Table 3.
2.4. Reaction between [(p5-Ring)WCl3]2 (Ring=C5H5,
C5HMe) and dppe. Formation of (p5-Ring)WCl3(dppe)
(b) Compound 6. A black crystal with dimensions
0.13×0.08×0.08 mm was placed and optically cen-
tered on the Enraf–Nonius CAD-4 diffractometer. The
cell parameters and crystal orientation matrix were
determined from 25 reflections in the range 8.6BqB
20.7° and confirmed with axial photographs. Data col-
lection and reduction was carried out as described in (a)
above. Two forms of data were collected in the hemi-
sphere 9hk9l, resulting in the measurement of 5392
reflections, 2707 of which were unique. Minor (1–4%)
(a) (h5-C5H5)WCl3(dppe) (4). [(h5-C5H5)WCl3]2 (358
mg, 1.01 mmol) was placed in a Schlenk tube with 20
ml dichloromethane and to the resulting green suspen-
sion was added solid dppe (402 mg, 1.01 mmol). The
Schlenk tube was equipped with a reflux condenser and
magnetic stir bar and the mixture was refluxed for 3 h.
The starting material dissolved to yield a dark-brown
solution. An aliquot of this solution was evaporated to
dryness and the residue was redissolved in CD2Cl2 and

30
H. Blackburn et al. / Journal of Organometallic Chemistry 593–594 (2000) 27–35
Table 2
Crystal data for all compounds
Compound
5·2CH2Cl2
6
7
Empirical formula
C34H35Cl7P2W
C18H21Cl5OW3
C20H30Cl6OW2
Formula weight
Space group
937.56
P21
982.15
P21/c
866.84
Pbca
Unit cell dimensions
,
a (A)
12.593(4)
12.722(4)
12.731(4)
115.68(2)
1838.2(10)
2
14.434(3)
10.129(2)
14.534(3)
100.61(2)
2088.6(7)
4
12.745(5)
15.275(2)
12.9129(8)
,
b (A)
,
c (A)
i (°)
V (A )
3
,
2513.8(10)
4
2.290
0.723
Z
Dcalc. (g cm−3
)
1.694
0.661
3.123
0.753
m (Mo–Ka), (mm−1
)
,
Radiation (monochromated in incident beam)
Temperature (°C)
[I\2|(I)]
Rw [I\2|(I)]
Mo–Ka (u=0.71073 A)
293(2)
0.0711
0.1964
153(2)
0.0469
0.0825
293(2)
0.0306
0.0746
a
R
b
a R=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ.
b Rw=[Sw(ꢀFoꢀ−ꢀFcꢀ)2/SwꢀFoꢀ2]1/2; w=1/|2(ꢀFoꢀ).
variations in intensity were observed for three nearly
orthogonal standard reflections monitored at 1-h inter-
vals of X-ray exposure, thus the data were not cor-
rected for decay. The data were corrected for Lorentz
and polarization factors, and for absorption on the
basis of the c-scan method. Intensity statistics clearly
determined the centrosymmetric monoclinic space
group P21/c (no. 14). The structure was solved by direct
methods with the successful location of the three tung-
sten atoms. Subsequent difference-Fourier maps re-
vealed the location of all remaining non-hydrogen
atoms within the molecule. Hydrogen atoms were
placed in calculated positions, with the aromatic hydro-
mined by direct methods with the successful location of
the tungsten and chlorine atoms. Subsequent difference-
Fourier maps revealed the location of all remaining
non-hydrogen atoms within the molecule. Hydrogen
atoms were inserted and handled as described in the
previous section. After convergence, a final difference-
Fourier map possessed three peaks in the vicinity, i.e.
,
within 1.2 A of the tungsten atom with ꢀDzꢀ51.29 e
A−3 and the largest remaining peaks had ꢀDzꢀ50.65 e
A
−3. Selected crystal data and refinement parameters
are collected in Table 2, and relevant bond distances
and angles are listed in Table 5.
,
gens at d(CꢀH)=0.950 A and UH=1.2 U (parent)
while methyl hydrogens were initially determined with a
rotational Fourier about the central carbon atom that
was further optimized for tetrahedral geometry with
Table 3
,
Selected bond distances (A) and bond angles (°) for compound
5·2CH2Cl2
,
d(CꢀH)=0.980 A and UH=1.5 U (parent). After con-
vergence, a final difference-Fourier map exhibited sev-
,
Bond distances (A)
,
eral peaks in the vicinity, i.e. within 1.2 A of the
W(1)–Cl(1)
W(1)–Cl(2)
W(1)–Cl(3)
W(1)–P(1)
W(1)–P(2)
W(1)–CNT(1)
2.456(8)
2.429(7)
2.490(9)
2.570(8)
2.567(8)
2.000(3)
W(1)–C(2)
W(1)–C(3)
W(1)–C(4)
W(1)–C(5)
W(1)–C(6)
2.50(3)
2.35(3)
2.22(3)
2.19(3)
2.31(3)
tungsten atoms with ꢀDzꢀ51.58 e A−3. Selected crystal
,
data and refinement parameters are collected in Table
2, and relevant bond distances and angles are listed in
Table 4.
(c) Compound 7. A reddish–black crystal with di-
mensions 0.20×0.20×0.25 mm was placed on the
Enraf–Nonius CAD-4 diffractometer. The cell parame-
ters and crystal orientation matrix were determined
from 25 reflections in the range 12.9BqB15.2° and
confirmed with axial photographs. Data collection and
reduction was carried out as described in (a) above. No
decay correction was necessary (B3% decay). System-
atic absences clearly indicated the centrosymmetric
space group Pbca (no. 61). The structure was deter-
Bond angles (°)
Cl(1)–W(1)–Cl(2)
Cl(1)–W(1)–Cl(3)
Cl(1)–W(1)–P(1)
Cl(1)–W(1)–P(2)
Cl(1)–W(1)–CNT
Cl(2)–W(1)–Cl(3)
Cl(2)–W(1)–P(1)
Cl(2)–W(1)–P(2)
80.8(3)
84.1(3)
89.0(3)
150.7(4)
103.9(9)
79.5(3)
74.5(3)
70.1(3)
Cl(2)–W(1)–CNT
Cl(3)–W(1)–P(1)
Cl(3)–W(1)–P(2)
Cl(3)–W(1)–CNT
P(1)–W(1)–P(2)
P(1)–W(1)–CNT
P(2)–W(2)–CNT
175.3(9)
153.8(3)
93.6(3)
101.5(9)
80.2(3)
104.6(9)
105.2(9)

H. Blackburn et al. / Journal of Organometallic Chemistry 593–594 (2000) 27–35
31
Table 4
Selected bond distances (A) and bond angles (°) for Cp%3W3Cl7O
pared with refluxing CH2Cl2 for the Mo systems), is
somewhat remarkable because the strength of the
MꢀCO bond increases upon descending a group of
transition metals. For instance, while thermal decar-
bonylation of MoI2(CO)3(dppm) cleanly affords
Mo2I4(dppm)2 [16], the corresponding WI2(CO)3-
(dppm) affords only WI2(CO)(dmpm)2 in small yields
[17].
,
,
Bond distances (A)
W(1)–W(2)
W(1)–W(3)
W(1)–Cl(1)
W(1)–Cl(12)
W(1)–Cl(13)
W(1)–O(123)
W(1)–C(CNT1)
W(2)–W(3)
2.7466(12) W(2)–Cl(2)
2.7741(11) W(2)–Cl(12)
2.412(4)
2.459(5)
2.036(12)
1.973(9)
2.404(5)
2.445(5)
2.030(12)
2.018(8)
2.438(5)
2.491(5)
2.488(5)
W(2)–O(123)
W(2)–C(CNT2)
W(3)–Cl(3)
2.010(11) W(3)–Cl(13)
2.004(7) W(3)–O(123)
The solubility of the W(IV) trichloride products in-
1
2.6114(12) W(3)–C(CNT3)
creases, as expected, in the order CpBCp%. H-NMR
characterization for the Cp compounds could only be
carried out in dilute CD2Cl2 solutions, whereas the
Cp% derivatives are sufficiently soluble in aromatic hy-
drocarbons. The 1H-NMR properties of the isolated
materials (see Table 1) indicate diamagnetism, in con-
trast with the corresponding Mo analogues [11,12],
this hinting to a different structure for the Mo and
W analogues (see Section 1). Unfortunately, suitable
single crystals could not be obtained for any of these
derivatives. During one of the various crystallization
attempts, crystals of an oxygenated by-product were
Bond angles (°)
W(2)n˜W(1)n˜W(3)
W(2)n˜W(1)n˜Cl(1)
W(2)n˜W(1)n˜Cl(12)
W(2)n˜W(1)n˜Cl(13) 109.12(12) Cl(2)–W(2)–O(123)
W(2)n˜W(1)n˜O(123)
56.46(3) W(3)–W(2)–O(123)
119.82(12) W(3)–W(2)–CNT2
55.75(11) Cl(2)–W(2)–Cl(12)
49.9(3)
114.2(3)
90.41(16)
81.4(3)
109.1(3)
76.3(3)
47.6(3)
Cl(2)–W(2)–CNT2
Cl(12)–W(2)–O(123)
W(2)n˜W(1)n˜CNT1 120.5(3)
W(3)n˜W(1)n˜Cl(1)
W(3)–W(1)–Cl(12)
W(3)–W(1)–Cl(13)
W(3)–W(1)–O(123)
120.70(11) Cl(12)–W(2)–CNT2 114.8(3)
110.29(11) O(123)–W(2)–CNT2 163.9(4)
55.05(12) W(1)–W(3)–W(2)
61.24(3)
94.72(12)
56.52(11)
46.3(3)
158.4(3)
112.27(14)
115.08(11)
50.1(3)
114.5(2)
89.79(17)
140.7(3)
105.9(3)
73.8(3)
46.9(3)
W(1)–W(3)–Cl(3)
W(1)–W(3)–Cl(13)
W(3)–W(1)–CNT1 119.5(2)
Cl(1)–W(1)–Cl(12)
Cl(1)–W(1)–Cl(13)
Cl(1)–W(1)–O(123)
Cl(1)–W(1)–CNT1 110.6(3)
Cl(12)–W(1)–Cl(13) 146.21(15) W(2)–W(3)–O(123)
Cl(12)–W(1)–O(123) 76.0(3)
Cl(12)–W(1)–CNT1 106.7(3)
Cl(13)–W(1)–O(123) 73.1(4)
Cl(13)–W(1)–CNT1 106.8(3)
O(123)–W(1)–CNT1 164.2(4)
81.67(16) W(1)–W(3)–O(123)
82.46(16) W(1)–W(3)–CNT3
obtained for the Cp%-chloro system (Cp%W3Cl5O, com-
3
85.2(4)
W(2)–W(3)–Cl(3)
W(2)–W(3)–Cl(13)
pound 6). The structure of this compound, showing
several remarkable features, is discussed later. It is
noteworthy that oxygen incorporation in these sys-
tems is associated with formal metal reduction. We
have not been able to elucidate the nature of the
concomitant oxidation products.
W(2)–W(3)–CNT3
Cl(3)–W(3)–Cl(13)
Cl(3)–W(3)–O(123)
Cl(3)–W(3)–CNT3
Cl(13)–W(3)–O(123)
In an attempt to facilitate the crystallization pro-
cess, the synthesis of the more methyl-substituted
(thus presumably more soluble) Cp*-chloro derivative
was attempted by the same decarbonylation method
shown in Eq. (1). Indeed, the decarbonylation of
Cp*WCl3(CO)2 yielded an intensely colored green so-
lution, which contains two diamagnetic products ac-
W(1)–W(2)–W(3)
W(1)–W(2)–Cl(2)
W(1)–W(2)–Cl(12)
W(1)n˜W(2)n˜O(123)
W(1)–W(2)–CNT2 128.0(3)
W(3)–W(2)–Cl(2)
W(3)–W(2)–Cl(12)
62.30(3) Cl(13)–W(3)–CNT3 116.1(3)
121.35(12) O(123)–W(3)–CNT3 113.4(4)
56.85(11) W(1)–Cl(12)–W(2)
67.40(13)
46.8(3)
W(1)–Cl(13)–W(3)
W(1)–O(123)–W(3)
68.43(13)
86.7(4)
85.5(5)
79.9(4)
108.34(12) W(1)–O(123)–W(2)
116.98(12) W(2)–O(123)–W(3)
1
cording to H-NMR spectroscopy. The major product
could be obtained in the form of single crystals and
was shown by X-ray crystallography to correspond to
the oxo compound [Cp*WCl3]2O (7), vide infra. This
result was reproduced several times, in spite of our
best attempts to rigorously exclude air and moisture
(see Section 2). The oxygen atom could be originating
from a CO ligand by a process of metal-mediated CO
bond breaking, which is not unprecedented for tung-
sten [18,19]. If this is the case, a carbido ligand could
possibly be incorporated into the other observed
product which, unfortunately, could not be obtained
in a pure, crystalline form suitable to full characteri-
zation [20].
For the less methyl-substituted Cp and Cp% systems,
only a single compound could be detected by 1H-
NMR investigations of the crude products and satis-
factory C, H analyses were obtained. The identity of
the compounds is further confirmed by the derivatiza-
tion reactions discussed in the next section.
3. Results and discussion
3.1. Synthesis and physical properties
The preparation of the trihalocyclopentadienyltung-
sten(IV) compounds follows one of the strategies pre-
viously adopted for the synthesis of the corresponding
Mo(IV) compounds [10–12], i.e. thermal decarbonyla-
tion of the dicarbonyl adducts, see Eq. (1). The latter
compounds are easily available by dihalogen oxida-
tion of the corresponding [(Ring)W(CO)3]2 com-
pounds [15].
D
(Ring)WX3(CO)2tꢀolꢀuꢀenꢁe1/2[(Ring)WX3]2+2Co
(1)
(Ring=Cp, Cp%; X=Cl, Br)
The occurrence of a complete decarbonylation of
these tungsten carbonyl derivatives, albeit under
rather forcing conditions (refluxing toluene as com-

32
H. Blackburn et al. / Journal of Organometallic Chemistry 593–594 (2000) 27–35
3.2. Formation of ligand adducts and X-ray structure
of Cp%WCl3(dppe)
Compounds [CpWCl3]2 and [Cp%WCl3]2 slowly add
dppe in refluxing dichloromethane, to afford the 18-
electron adducts, see Eq. (2):
[(Ring)WCl3]2+2dppe“2(Ring)WCl3(dppe)
(Ring=Cp, 4; Cp%, 5)
(2)
These reactions show that the WꢀW bonds in these
systems are sufficiently weak to allow their rupture and
the formation of mononuclear ligand adducts. How-
ever, the reactions are quite slow when compared with
those of the corresponding [(Ring)MoCl3]2 complexes
in which the metal centers are held together only by
two bridging chloride ligands [9,11]. Both products of
reaction 2 are diamagnetic compounds and are stoi-
chiometric analogues of the previously reported
CpMoCl3(dppe), which was shown to adopt the
pseudo-mer-octahedral structure V in the solid state
[21]. The same stereochemistry was also established for
compound CpMoCl3(dmpe) [22]. The NMR properties
of the W derivatives, however, indicate equivalence for
the two P nuclei (singlet resonance in the 31P-NMR
spectrum and triplet resonance for the Cp protons in
Fig. 1.
Cp%WCl3(dppe).
A
view of the molecular structure of compound
1
the H-NMR spectrum of 4) and are therefore more
consistent with the alternative fac stereochemistry illus-
trated in VI, which is common, on the other hand, to
the previously reported Mo(IV) bis-phosphite derivative
CpMoCl3[P(OCH2)3CEt]2 [9], and to the W(IV) car-
Selected distances and angles are reported in Table 3.
The cyclopentadienyl ring is significantly distorted from
the ideal five-fold symmetry, the difference between the
i
bonyl derivatives (C5H4 Pr)WBr3(CO)2 [23] and
,
shortest and longest WꢀC distance being 0.31(4) A. The
Cp*WBr3(CO)2 [15]. The fac geometry of compound 5
has been unambiguously confirmed by an X-ray struc-
tural determination (see Fig. 1).
longest distance is to the methyl-substituted C atom
,
[W(1)–C(2), 2.50(3) A], while the shortest ones are
those to the opposite C atoms, C(4) and C(5), 2.22(3)
,
and 2.19(3) A, respectively. This distortion could be
induced sterically by the proximity of the ring Me
substituent and the Cl(1) atom and/or electronically by
the back-donation from the metal dxy orbital to one of
the ring d acceptor orbitals, as previously described
[24]. A similar distortion has been noted for (h5-
Table 5
,
Selected bond distances (A) and bond angles (°) for [Cp*WCl3]2(m-O)
,
Bond distances (A)
W–Cl(1)
W–Cl(3)
W–Cl(2)
W–CNT
W–O
2.371(3)
2.372(3)
2.375(3)
2.031(11)
1.8709(4)
i
C5H4 Pr)WBr3(CO)2, whose stereochemistry is identical
to that of compound 6 [23]. We are not aware of other
crystal structures of monocyclopentadienyltungsten(IV)
chloride or phosphine derivatives. The average W–Cl
,
distance [2.46(3)A] is similar to the average Mo–Cl
distance in the corresponding CpMoCl3(dppe) [2.48(1)
Bond angles (°)
Cl(1)–W–Cl(2)
Cl(1)–W–Cl(3)
Cl(1)–W–O
Cl(1)–W–CNT
Cl(2)–W–Cl(3)
Cl(2)–W–O
Cl(2)–W–CNT
Cl(3)–W–O
Cl(3)–W–CNT
O–W–CNT
80.17(11)
139.45(12)
84.69(8)
110.1(3)
79.96(12)
135.17(10)
112.2(3)
85.04(7)
110.1(3)
112.6(2)
180.0
,
,
A] [21], CpMoCl3[P(OCH2)3CEt]2 [2.47(4) A] [9], and
CpMoCl3(dmpe) [2.494(7) A] [22] compounds. The ax-
ial (trans to Cp) W–Cl distance is slightly shorter than
the equatorial (trans to P) distances, as previously seen
also for CpMoCl3[P(OCH2)3CEt]2 [9]. The W–P dis-
tances are essentially equivalent and their average
[2.568(8) A] is similar to the average Mo–P distance in
CpMoCl3(dppe) [2.604 A] [21] and CpMoCl3(dmpe)
[2.548 A] [22], although in the latter cases the two
,
,
,
W–O–W%
,

H. Blackburn et al. / Journal of Organometallic Chemistry 593–594 (2000) 27–35
33
individual distances are quite different from each other
because of the different geometry (e.g. V).
The different solid state structure of the homologous
CpMCl3(dppe) compounds (V for Mo, VI for W) is an
interesting phenomenon that does not have a clear-cut
explanation. In solution, structure VI appears to be
strongly favored for the W system (no other isomer can
be detected by 31P-NMR), whereas a more delicate
balance is present for the Mo compound, an 80:20
mixture of isomers favoring V being established by
31P-NMR in CD2Cl2 [21].
Scheme 1.
with essentially equal distances to the three W atoms
[average 2.02(2) A]. The average oxidation state of the
,
metal in this compound is 3 and 1/3. A valence-trapped
assignment as +4 for W(1) and +3 for W(2) and
W(3) is indicated by the structure. Mononuclear four-
legged piano stool compounds for W(IV) (e.g. having a
16-electron configuration) are not precedented, but this
is a common geometry for analogous complexes of
Mo(IV), for instance [CpMoCl2L2]+ and CpMoCl3L
(L=tertiary phosphine) [25,26]. The two d electrons of
the W(1) atom can be imagined to become involved in
metal–metal bonding through participation of the dxy
orbital, which is of suitable symmetry. If, at this point,
the Cp%WCl2+ unit of atom W(1) is removed from the
cluster, the remaining fragment corresponds to a
3.3. Structure of Cp%W3Cl5O
3
A view of this compound is shown in Fig. 2 and
selected bond distances and angles are given in Table 4.
The structure of this molecule is quite remarkable; the
three metal centers display three different coordination
geometries, none of which appears to have any prece-
dent in the literature for W systems. These geometries
can be roughly described as a Cp%WCl3O four-legged
piano stool for W(1) and four-coordinate (when consid-
ering the Cp% ligands as occupying a single coordination
geometry) Cp%WCl2O for W(2) and W(3). The ge-
ometries around W(2) and W(3) differ for the relative
ligand arrangement, e.g. the CNT(2)–W(2)–O(123)
and CNT(3)–W(3)–O(123) angles [CNT(n) is the cen-
troid of the Cp% ring attached to the W(n) atom] are
163.9 and 113.5°, respectively. The W atoms define an
isosceles triangle, the two longer W(1)–W(2) and
[Cp%W2Cl4(m-O)]2− ion as illustrated in Scheme 1(a).
2
The geometry of this ion strongly resembles that of the
dinuclear Mo(III) ion [CpMoCl4(m-Cl)]− [27], shown
schematically in Scheme 1(b), giving credit to our oxi-
dation state assignment for atoms W(2) and W(3). The
two geometries in Scheme 1 differ only in the relative
disposition and angular relationships of the ligands
(cisoid Cp% and transoid terminal Cl ligands in the W
structure; transoid Cp ligands in the Mo structure). This
difference probably results from the steric repulsion
,
W(1)–W(3) vectors [2.747(1) and 2.774(1) A, respec-
tively] being bridged by a chlorine atom and the unique
shorter W(2)–W(3) vector [2.611(1) A] having no bridg-
ing Cl atom. The oxygen atom caps the W3 triangle
,
between the Cp% rings in the Cp%W3Cl5O structure and
3
by the forced relative configuration of the Cl(12) and
Cl(13) ligands, these being locked into place by the
need to bridge the W(2) and W(3) atoms, respectively,
with W(1). The W(2)–W(3) bond is slightly longer than
the MoꢀMo bond in [Cp2Mo2Cl5]− [2.413(1) A] [27],
,
which was described as a weakened metal–metal triple
bond. Other parallels may be drawn between the struc-
ture of 6 and other oxo-capped, trimetallic clusters such
as
Cp3Mo3Cl7O,
[28]
(Ring)3Nb3Clx(OH)7−xO
(Ring=Cp, Cp%; X=Cl, OH), [29,30] and
Cp3*Ta3O4Cl4, [31,32] but none of these show coordina-
tion geometries or a d-electron count as 6.
The terminal W(1)–Cl bond is longer than the other
terminal WꢀCl bonds, contrary to what would be ex-
pected on the basis of the oxidation state assignment
given above. However, while the Cl(1) ligand is bonded
to an effectively saturated W(1) center, the Cl(2) and
Cl(3) are bonded to electronically unsaturated metal
centers. The shorter W(2)–Cl(2) and W(3)–Cl(3) dis-
tances may therefore reflect the involvement of some
Fig. 2. A view of the molecular structure of compound Cp%3W3Cl5O.

34
H. Blackburn et al. / Journal of Organometallic Chemistry 593–594 (2000) 27–35
enyl halides of W(IV). A comparison with the previ-
ously developed Mo systems indicates two main
differences. The decarbonylation of (Ring)MX3(CO)2
is, as expected, less facile for W than for Mo. It does
proceed to completion, however, in refluxing toluene.
The structure of the two [(Ring)MX3]3 systems is quite
different, the lack of metal–metal bonding leading to
paramagnetism for M=Mo whereas diamagnetic com-
pounds, presumably containing metal–metal bonds
[20], are obtained for M=W. These compounds are
able, however, to add neutral donors with formation of
diamagnetic mononuclear derivatives (albeit more
slowly than the corresponding Mo systems), as exem-
plified by the formation of the dppe adducts
(Ring)WCl3(dppe) (Ring=Cp, Cp%). Finally, these
W(IV) systems are quite reactive toward oxygen con-
taining compounds, leading to the facile formation of
oxygen-containing derivatives.
Fig. 3. A view of the molecular structure of compound [Cp*WCl3]2(m-
O).
5. Supplementary material
WꢀCl p bonding. For the same reason, the W–Cl
distances to the bridging Cl ligands are shorter on the
W(2) and W(3) sides with respect to the W(1) side. All
bridging WꢀCl bonds are, as expected, longer than the
terminal ones.
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 116644 for 5·2CH2Cl2, CCDC
No. 116646 for 6, and CCDC No. 116645 for 7. Copies
of this information may be obtained free of charge
from the Director, CCDC, 12 Union Road, Cambridge,
CB2 1EZ, UK (Fax: +44-1223-336033; e-mail: de-
posit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk).
3.4. Structure of [Cp*WCl3]2(v-O)
A view of this compound is shown in Fig. 3 and
selected bond distances and angles are given in Table 5.
The compound crystallizes with the oxygen atom sitting
on a center of symmetry, thus the linearity of the
W–O–W moiety is crystallographically imposed. The
geometry around each W atom is of the four-legged
piano stool type, the four legs being the three terminal
chlorine and the bridging O atoms. The three W–Cl
Acknowledgements
Support of this work from the US Department of
Energy-Office of Energy Research (DEFG0295ER-
14550) and the Re´gion Bourgogne is gratefully ac-
knowledged. The authors thank Dr Peter Burger for
disclosing to us the results of his work on [Cp*WCl3]2
[20].
,
distances are essentially equivalent [average 2.373(3) A].
These W–Cl distances and the W–O distance are sig-
nificantly shorter than the corresponding parameters in
the above described Cp%W3Cl5O, in agreement with the
3
higher metal oxidation state in [Cp*WCl3]2O. In addi-
tion, WꢀO multiple bonding is allowed in the dinuclear
W(V) compound, further shortening the bonds,
whereas only s bonds are allowed for the capping
oxygen in the trinuclear cluster described above. The
W–O distance is comparable with that of the isoelec-
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[20] (a) Dr Peter Burger (University of Zurich) has informed us that
compound [Cp*WCl3]2 has been obtained in his laboratory by
sodium reduction of Cp*WCl4 and that its X-ray structure is as
shown in IV. (b) C. Cremer, Diplomarbeit, Universities of
Kostanz and Zu¨rich, 1996.
.