Alkynylcarbyne complexes containing various tri- and bidentate ligands such as cyclopentadienide, tris(pyrazolyl)borate, bis(pyrazolyl)acetate and tmeda: synthesis and spectroscopic properties

Article abstract of DOI:10.1016/S0022-328X(01)01310-9

The (alkynylcarbyne)tungsten complexes [L₃(CO)₂WCCCR] (3a,b-6a,b) [L₃=hydro[tris(3,5-dimethylpyrazol-1-yl)]borato (Tp′, 3), hydro[tris(pyrazol-1-yl)]borato (Tp, 4), cyclopentadienyl (Cp, 5), bis(3,5-dimethylpyrazol-1-yl)ac

Full text of DOI:10.1016/S0022-328X(01)01310-9

Journal of Organometallic Chemistry 641 (2002) 134–141
www.elsevier.com/locate/jorganchem
Alkynylcarbyne complexes containing various tri- and bidentate
ligands such as cyclopentadienide, tris(pyrazolyl)borate,
bis(pyrazolyl)acetate and tmeda: synthesis and spectroscopic
properties
Birgit Schwenzer, Joachim Schleu, Nicolai Burzlaff, Christoph Karl, Helmut Fischer *
Fachbereich Chemie, Uni6ersita¨t Konstanz, Fach M727, D-78457 Konstanz, Germany
Received 4 July 2001; accepted 7 August 2001
Abstract
The (alkynylcarbyne)tungsten complexes [L3(CO)2WꢀCꢁCꢀCꢁR] (3a,b–6a,b) [L3=hydro[tris(3,5-dimethylpyrazol-1-yl)]borato
(Tp%, 3), hydro[tris(pyrazol-1-yl)]borato (Tp, 4), cyclopentadienyl (Cp, 5), bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza, 6);
R=SiMe3 (a), Ph (b)] were prepared in a stepwise fashion from [W(CO)6] and Li[CꢀCR], (CF3CO)2O and M[L3] (M=Na, K).
The formation of 6a,b was highly selective, only complexes with a trans arrangement of the carboxylate group of bdmpza and the
alkynylcarbyne ligand were detected. The reaction of [W(CO)6] with Li[CꢀCR], C2O2Cl2 and tmeda afforded trans-
[Cl(CO)2(tmeda)WꢀCꢁCꢀCꢁR] (7a,b). The electron-donating potential of the different tripodal ligands L3 was studied by IR- and
13C-NMR spectroscopy and compared to that of the ligand combination Cl/tmeda. The IR data suggest that in these complexes
bdmpza is a weaker electron donor than Tp% and Tp but displays stronger electron-donating abilities than Cp. The structures of
6b and 7b were established by X-ray structural analyses. © 2002 Elsevier Science B.V. All rights reserved.
Keywords: Carbyne complexes; Tripodal ligands; Tungsten; Electron donating ability
an even number of carbon atoms are derived from
alkynes and alkynyl complexes via coupling reactions.
In contrast, precursors for the synthesis of complexes
with an odd number of bridging carbon atoms are
much less readily available.
Alkynylcarbyne complexes (alkynylidyne complexes),
LnMꢀCꢁ(CꢀC)mꢁR, might be suitable starting com-
pounds for the synthesis of complexes with an odd
number of bridging carbon atoms. In addition, they
also might constitute interesting terminating groups.
However, until now there are only a few reports on
alkynylcarbyne complexes. The first complexes, trans-
X(CO)4WꢀCꢁCꢀCꢁPh (X=Cl, Br, I), were prepared by
Fischer et al. already in 1974 [4]. Since then, only a few
more alkynylcarbyne complexes containing bi- and tri-
dentate ligands, LnMꢀCꢁCꢀCnBu (M=Mo, W), have
been reported by Stone and coworkers [5].
1. Introduction
Organometallic compounds with extended p-conju-
gated ligands have attracted considerable interest [1],
since bi- and polynuclear complexes containing p-un-
saturated conjugated bridges are expected to exhibit
potentially useful physical and chemical properties. In
such bi- and polynuclear complexes the metal–ligand
fragment LnM can occupy an internal or/and a termi-
nating position in the chain. Various types of bridging
ligands have been proposed. In recent years attention
has focused on complexes with carbon-rich bridges,
[LnM(C)mM%L% ] [2]. Until now, complexes with an
n%
even number of carbon atoms linking the metals (m up
to 20 [3]) are more readily accessible than those with an
odd number of carbon atoms. Usually, complexes with
We now report on the synthesis and the spectro-
scopic properties of a series of alkynylcarbyne com-
plexes of tungsten containing tripodal ligands,
* Corresponding author. Tel.: +49-7531-882783; fax: +49-7531-
883136.
E-mail address: helmut.fischer@uni-konstanz.de (H. Fischer).
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01310-9

B. Schwenzer et al. / Journal of Organometallic Chemistry 641 (2002) 134–141
135
L3(CO)2WꢀCꢁCꢀCR, as well as of two tmeda com-
plexes. To have a rather broad range of electronic
properties available, in addition to cyclopentadienide
(Cp), hydro[tris(pyrazol-1-yl)]borate (Tp), hydro-
[tris(3,5-dimethylpyrazol-1-yl)]borate (Tp%) [6] and the
new scorpionate ligand bis(3,5-dimethylpyrazol-1-
yl)acetate (bdmpza) recently reported by Otero et al. [7]
and Burzlaff and coworkers [8] were used as coligands
(Scheme 1). The alkynylcarbyne substituent R (SiMe3,
Ph) was chosen in such a way as to be able to further
functionalize the complexes and use them as precursors
for the synthesis of bi- and polynuclear complexes.
Scheme 1.
2. Results and discussion
Fischer-type carbyne complexes are usually prepared
by either one of the two following pathways:
(a) transformation of carbene into carbyne complexes
by reaction with trihalides of Group III elements (B
[9], Al [10], Ga [11]) or
(b) abstraction of an oxide, O2−, from an acyl metal-
late by e.g. Ph3PBr2 [12], SOCl2 [13], COCl2, oxalyl
halides, or (CF3CO)2O [14].
For the synthesis of alkynylcarbyne complexes path-
way (b) turned out to be more efficient than pathway
(a) affording higher yields. Addition of Li[CꢀCꢁR] to
[W(CO)6] in THF or Et2O gave the acyl tungstates 1a,b
[15,16]. Subsequent oxide abstraction with trifluoracetic
anhydride at −80 °C [14] afforded the trans-tetracar-
bonyl(trifluoracetato)tungsten complexes 2a,b. The trifl-
uoracetato ligand is only weakly coordinated and,
therefore, is easily replaced by other anions. The te-
tracarbonyl complexes 2a,b were not isolated but imme-
diately transformed at −50 °C into the complexes
3a,b–6a,b (Scheme 2) by reaction with the sodium or
potassium salts of the tripodal ligand (NaTp%, KTp,
NaCp or K[bdmpza]). The reaction was accompanied
by CO evolution. Column chromatography of the crude
products of 3a,b–5a,b finally afforded the pure com-
plexes in moderate yield (14–56% overall yield, three
steps). Deviating from this purification procedure com-
plexes 6a,b were obtained in 83 and 91% yield by
precipitation from the reaction mixture (addition of
pentane to solutions in diethyl ether) and subsequent
recrystallization.
Scheme 2.
All complexes are poorly soluble in unpolar organic
solvents but readily soluble in polar solvents. In the
solid state, all compounds are stable at room tempera-
ture. At −30 °C, they can be stored under inert gas
for prolonged periods without noticeable decomposi-
tion. In solution at room temperature, however, com-
plexes 3a,b–5a,b slowly decompose.
For comparison, additionally the alkynylcarbyne
complexes 7a,b containing a bidentate ligand (tmeda)
were synthesized from [W(CO)6] and Li[CꢀCR] (R=
Scheme 3.

136
B. Schwenzer et al. / Journal of Organometallic Chemistry 641 (2002) 134–141
3a,b–6a,b. Nevertheless, they can be heated to at least
80 °C but start to decompose quickly above ca.
120 °C.
The metal in these complexes 3a,b–6a,b and 7a,b is
pseudo-octahedrally coordinated, the tripodal ligand in
3a,b–6a,b occupying a facial position. In contrast to
3a,b–5a,b, two isomers are conceivable for complexes
6a and 6b: there is either a trans arrangement of a
3,5-dimethylpyrazolyl group and the alkynylcarbyne
ligand (isomer A) or of the carboxylate and the alkynyl-
carbyne ligand (isomer B). IR, 1H- and 13C-NMR
spectra indicate that a single isomer is formed. The
1H-NMR spectra of 6a and 6b exhibit a single set of
resonances for the pyrazolyl groups (e.g. two Me
peaks). In contrast, for 3a and 3b four N-methyl reso-
nances are observed. The 13C-NMR spectra show only
one peak for the two CO ligands at a position [l=
225.9 (6a) and 226.0 ppm (6b)] similar to that of the CO
resonances in 3a,b and 4a,b (l=226.1–227.3 ppm).
From these observation it follows that in solution iso-
mer B is present. The conclusion is supported by the
results of the X-ray analysis of complex 6b. Until now,
there is no solid-state structure of a complex with a
terminally bonded alkynylcarbyne ligand available.
Only a complex featuring a bridging CꢁCꢀCꢁCMe3
ligand [17] and a binuclear ReꢁW complex with a
Fig. 1. Molecular structure of complex 6b in the crystal (solvent
molecule omitted for clarity).
nearly
linear
C3
bridge,
[Cp*(PPh3)(NO)Reꢁ
CꢀCꢁCꢀW(OtBu)3] (8) [18], have been characterized by
X-ray structural analyses. Therefore, the structure of 7b
was also established by an X-ray analysis.
Fig. 2. Molecular structure of complex 7b in the crystal (hydrogen
atoms and solvent molecule are omitted for clarity).
Table 1
In both complexes, 6b (Fig. 1) and 7b (Fig. 2), the
coordination octahedron is slightly distorted. The CO
ligands are bent towards the alkynylcarbyne ligand.
Conversely, the C(carbyne)ꢁWꢁN angle is \90°. As
has already been deduced from the NMR spectra the
carboxylate in 6b occupies the position trans to the
alkynylcarbyne ligand. The WꢀC(carbyne) distance is
Selected bond distances and angles in 6b and 7b
6b
7b
Bond lengths
W(1)ꢁC(1)
W(1)ꢁC(2)
W(1)ꢁC(3)
W(1)ꢁN(1)
W(1)ꢁN(2)
W(1)ꢁO(3)
W(1)ꢁCl(1)
C(3)ꢁC(4)
C(4)ꢁC(5)
C(5)ꢁC(6)
2.032(14)
2.024(13)
1.839(13)
2.247(8)
2.233(9)
2.222(7)
1.986(6)
1.983(5)
1.834(5)
2.304(4)
2.300(4)
,
,
equal in both compounds [1.839(13) A in 6b, 1.834(5) A
in 7b] (Table 1) and compares well with that in the
tolylcarbyne
complex
[Tp%(CO)2WꢀCꢁC6H4Me-p]
−
2.5098(14)
1.376(6)
1.204(7)
1.427(6)
,
((1.829(3) A) [19]. Obviously, the trans ligand (RCOO
, Cl−, pyrazolyl) does not significantly influence the
WꢀC(carbyne) bond length. However, the (tBuO)3WꢀC
1.429(16)
1.216(15)
1.457(15)
,
distance in 8 is significantly shorter (1.769(8) A) [18].
Bond angles
Due to the p-acceptor properties of the pyrazolyl lig-
C(3)ꢁW(1)ꢁC(1)
C(3)ꢁW(1)ꢁC(2)
C(3)ꢁW(1)ꢁN(1)
C(3)ꢁW(1)ꢁN(2)
W(1)ꢁC(3)ꢁC(4)
C(3)ꢁC(4)ꢁC(5)
C(4)ꢁC(5)ꢁC(6)
88.6(5)
85.1(5)
99.7(4)
102.8(4)
178.1(10)
177.3(12)
179.2(12)
82.4(2)
88.3(2)
ands in 6b the WꢁCO distances in 6b is longer than in
100.16(19)
97.27(17)
168.4(4)
175.7(5)
176.9(5)
,
,
7b (2.024–2.032(14) A in 6b, 1.983–1.986(6) A in 7b).
,
The C(3)ꢁC(4) distance in 6b (1.429(16) A) and 7b
,
(1.376(6) A) compares well with the median value for a
,
C(sp)ꢁC(sp) single bond (1.377 A [20]). The C(4)ꢁC(5)
,
,
distance (1.216(15) A in 6b and 1.204(7) A for 7b) is
also in the range usually observed for CꢀC bonds (1.183
,
A [20]). Whereas the WCCC fragment in 6a is nearly
SiMe3, Ph), oxalyl chloride and tmeda (Scheme 3).
After chromatography, 7a was obtained in 22%, 7b in
24% overall yield. Compounds 7a,b are less stable than
linear (WꢁCꢁC 178.1(10)°, CꢁCꢁC 177.3(12)°), that in
7b is slightly bent (WꢁC(3)ꢁC(4) 168.4(4)°,

B. Schwenzer et al. / Journal of Organometallic Chemistry 641 (2002) 134–141
137
C(3)ꢁC(4)ꢁC(5) 175.7(5)°). The deviation from linearity
is presumably due to packing effects in the crystal.
All alkynylcarbyne complexes display two w(CO) ab-
sorptions of similar intensity as expected for cis-
[L4M(CO)2] complexes. An additional weak absorption
at 2050–2057 cm−1 in the spectra of the trimethylsi-
lylethynylcarbyne complexes 3a–7a is assigned to the
w(CꢀC) vibration. The corresponding absorption of the
phenylethynylcarbyne complexes is at about 50 cm−1
higher wavenumbers indicating stronger p-acceptor
properties of CꢁCꢀCꢁSiMe3 compared to CꢁCꢀCꢁPh.
The conclusion agrees with the observation that the
w(CO) absorptions of the phenylethynylcarbyne com-
plexes 3b–7b are at slightly smaller wavenumbers than
those of 3a–7a.
From the IR data it also follows that bdmpza is
stronger electron-donating than Cp. This result contra-
dicts data published earlier by Burzlaff et al. [22]. Based
mainly on the shorter MꢁCO distances in [Tp%M(CO)3]
and [CpM(CO)3] than in [(bdmpza)M(CO)3] (M=Mn,
Re) they concluded that bdmpza would be less electron-
donating than Cp and Tp%. However, a change in donor
capacity of Tp%, Tp and Cp in compounds of transition
metals belonging to different groups has been recog-
nized before [23]. Apparently this dependence of the
electron-donor ability on the metal also holds true for
bdmpza.
The carbonyl and the carbyne resonances in the
13C-NMR spectra are rather insensitive to changes in
the tripodal ligand (Tp%, Tp and bdmpza) and appear at
l=226.690.7 and l=250.493.1 ppm (Table 2). The
same applies to both alkynyl carbon atoms. Surpris-
ingly, substitution of carboxylate for the trans-pyra-
zolyl group does not significantly affect the WꢀC
resonance. In contrast, in the trans-chloro complexes
7a,b all carbon resonances (CO, WꢀCꢁCꢀC) are shifted
towards higher field, the resonance of the carbyne
carbon even by ca. 20 ppm.
From the shift in the w(CO) absorptions (Table 1) we
can deduce a decrease in the electron donating ability in
the order Tp%\Tp\Cp. The same order has been
reported before by Stone and coworkers [5] for t-
butylethinylcarbyne complexes of molybdenum.
A
higher electron-donating potential of Tp compared to
Cp has also been observed by McElwee-White and
coworkers [21] with some molybdenum carbyne
complexes.
When the pyrazole-containing tripodal ligands are
replaced by cyclopentadienide a significant shift to-
wards higher field for the carbonyl resonance and,
conversely, towards lower field for the carbyne reso-
nance is observed.
Replacement of one strongly s-donating pyrazolyl
group in Tp by the electronegative C(ꢂO)O− group
(4“6) should reduce the electron-donating properties
of the tripodal ligand, although the effect should be less
pronounced for a substitution cis to CO than trans to
CO. The assumption is confirmed by the w(CO) absorp-
tions: the influence of the new bdmpza tripodal ligand
on the carbonyl vibrations is intermediate between that
of Tp and Cp. Thus, with respect to the electronic
influence of various tripodal ligands on the metal bdm-
pza fills in the gap between Tp and Cp. Based on the
w(CO) spectra the s-donor/p-acceptor ratio of the
tripodal bdmpza ligand is comparable to the ligand
combination tmeda/Cl−.
Thus, several metal–ligand fragments are now avail-
able for modifying the properties of the alkynylcarbyne
ligand. Furthermore, due to the CꢂO functionality, a
fine-tuning of the electronic properties of the new bdm-
pza group should be possible through addition of Lewis
acids. These new alkynylcarbyne complexes should con-
stitute good starting compounds for chain extensions
and for the synthesis of binuclear complexes with an
odd number of bridging carbon atoms. The high ther-
mal stability of the complexes 3a,b–7a,b should make
coupling reactions feasible which usually require ele-
vated temperatures. Preliminary results already indicate
that 7a can be desilyated by e.g. [NBu4]F–THF (Table
3).
Table 2
w(CO) and w(CꢀC) absorptions of the complexes 3a,b–7a,b (in cm−1
in THF
)
Complex
A1
B1
w(CꢀC)
2052
[Tp%(CO)2WꢀCꢁCꢀCꢁSiMe3] (3a)
[Tp(CO)2WꢀCꢁCꢀCꢁSiMe3] (4a)
[Cp(CO)2WꢀCꢁCꢀCꢁSiMe3] (5a)
[(bdmpza)(CO)2WꢀCꢁCꢀCꢁSiMe3]
(6a)
1982 1896
1991 1906
1995 1923
1995 1912
3. Experimental
2056
2057
2052
3.1. General
[Cl(tmeda)(CO)2WꢀCꢁCꢀCꢁSiMe3] 1997 1908
2050
All operations were carried out under either nitrogen
or Ar by using conventional Schlenk techniques. Sol-
vents were dried by refluxing over sodium-benzophe-
none ketyl or CaH2 and were freshly distilled prior to
use. The silica gel used for chromatography (J.T.
Baker, silica gel for flash chromatography) was satu-
rated with Ar. The yields refer to analytically pure
compounds and were not optimized. NaTp [6] and
(7a) a
[Tp%(CO)2WꢀCꢁCꢀCꢁPh] (3b)
[Tp(CO)2WꢀCꢁCꢀCꢁPh] (4b)
[Cp(CO)2WꢀCꢁCꢀCꢁPh] (5b)
1979 1893
1988 1904
1992 1920
2101 b
2102
2105
[(bdmpza)(CO)2WꢀCꢁCꢀCꢁPh] (6b) 1992 1910
[Cl(tmeda)(CO)2WꢀCꢁCꢀCꢁPh] (7b) 1993 1909
2097 b
a In CH2Cl2.
b In KBr.

138
B. Schwenzer et al. / Journal of Organometallic Chemistry 641 (2002) 134–141
Table 3
was dissolved in THF and chromatographed at
−20 °C on silica gel.
Selected 13C-NMR resonances (in ppm) of complexes 3a,b–7a,b
Complex
l(CO) l(WꢀC) l(Ca) l(Cb)
3.2.1. Dicarbonyl[hydro(tris-3,5-dimethylpyrazol-
1-yl)borato](trimethylsilylpropynylidyne)-tungsten (3a)
Chromatography with pentane afforded a purple
band. Removal of the solvent from the purple fraction
yielded complex 3a as a red–purple microcrystalline
powder. Yield: 900 mg (28% relative to [W(CO)6]). Dec.
\208 °C. IR (THF, cm−1) w(CꢀC) 2052 w, w(CO)
1982 s, 1896 s. 1H-NMR (CDCl3): l=0.15 (s, 9H,
Si(CH3)3), 2.28 (s, 3H, pz-C3Me), 2.33 (s, 9H, pz-
C5Me), 2.55 (s, 6H, pz-C3Me), 5.71 (s, 1H, pz-C4H),
5.88 (s, 2H, pz-C4H). 13C-NMR (CDCl3): l= −0.5
(Si(CH3)3), 12.6 (pz-C5Me), 15.1 (pz-C3Me), 16.4 (pz-
C3Me), 79.5 (Cb), 106.4 (pz-C4), 120.4 (Ca), 144.4 (pz-
C3), 145.2 (pz-C3), 151.8 (pz-C5), 152.2 (pz-C5), 226.1 (t,
J(WC)=162 Hz, CO), 247.3 (t, J(WC)=198 Hz,
WꢀC). FABMS (NBA); m/z (%): 646 (4) [M+], 618 (10)
[M+−CO], 590 (9) [M+−2CO], 73 (100) [Si(CH3)3].
Anal. Found: C, 42.89; H, 4.90; N, 12.65. Calc. for
C23H31BN6O2SiW (646.3): C, 42.74; H, 4.83; N,
13.00%.
[Tp%(CO)2WꢀCꢁCꢀCꢁSiMe3] 226.1
247.3
253.4
266.3
244.1
120.4 79.5
120.9 80.7
123.0 86.1
121.1 78.8
(3a) a
[Tp(CO)2WꢀCꢁCꢀCꢁSiMe3] 226.5
(4a) b
[Cp(CO)2WꢀCꢁCꢀCꢁSiMe3] 222.2
(5a) b
[(bdmpza)(CO)2−WꢀCꢁ
CꢀCꢁSiMe3] (6a) b
225.9
[Cl(tmeda)(CO)2−WꢀCꢁ
CꢀCꢁSiMe3] (7a) a
[Tp%(CO)2WꢀCꢁCꢀCꢁPh]
(3b) b
222.0
227.3
226.7
222.4
226.0
232.4
247.3
251.4
264.2
248.9
118.8 68.2
122.5 71.4
122.3 72.1
122.3 76.7
122.3 69.8
[Tp(CO)2WꢀCꢁCꢀCꢁPh]
(4b) b
[Cp(CO)2WꢀCꢁCꢀCꢁPh]
(5b) b
[(bdmpza)(CO)2−WꢀCꢁ
CꢀCꢁPh] (6b) b
[Cl(tmeda)(CO)2−WꢀCꢁ
CꢀCꢁPh] (7b) a
222.4
230.4
105.2 68.2
a In CDCl3.
b In d6-acetone.
3.2.2. Dicarbonyl[hydro(tris-3,5-dimethylpyrazol-
1-yl)borato](phenylpropynylidyne)tungsten (3b)
KTp% [24] were prepared according to literature proce-
Chromatography with pentane–CH2Cl2 (4:1) gave a
purple band. Removal of the solvent from the purple
fraction afforded complex 3b as a red–purple micro-
crystalline powder. Yield: 520 mg (14% relative to
[W(CO)6]). Dec. \182 °C. IR (THF, cm−1) w(CO)
1979 s, 1893 s. 1H-NMR (CDCl3): l=2.30 (s, 3H,
pz-C5Me), 2.35 (s, 3H, pz-C3Me), 2.36 (s, 6H, pz-
C5Me), 2.59 (s, 6H, pz-C3Me), 5.73 (s, 1H, pz-C4H),
5.89 (s, 2H, pz-C4H), 7.15–7.50 (m, 5H, C6H5). 13C-
NMR: l=12.6 (s, pz-C5Me), 12.6 (s, pz-C5Me), 15.3 (s,
pz-C3Me), 16.5 (s, pz-C3Me), 71.4 (Cb), 106.6 (C1, Ph),
107.5 (s, pz-C4), 107.7 (s, pz-C4), 122.5 (Ca), 129.7 (Ph),
129.9 (Ph), 133.2 (Ph), 146.0 (s, pz-C3), 146.9 (s, pz-C3),
152.7 (s, pz-C5), 152.9 (s, pz-C5), 227.3 (t, J(WC)=160
Hz, CO), 247.3 (WꢀC). FABMS (NBA); m/z (%): 650
(8) [M+], 622 (10) [M+−CO], 594 (10) [M+−2CO].
Anal. Found: C, 48.00; H, 4.18; N, 12.75. Calc. for
C26H27BN6O2W (650.2): C, 48.03; H, 4.19; N, 12.93%.
dures. K[bdmpza] [8] was supplied by Dr N. Burzlaff.
Trimethylsilylacetylene
(Fluka),
phenylacetylene
(Merck), n-BuLi (Chemetall), [W(CO)6] and trifluo-
racetic anhydride (Aldrich) were commercial products
and were used without further purification. IR: Bio-
1
Rad FT-IR spectrophotometer. H-NMR, 13C-NMR:
Bruker AC 250, Bruker DRX 600. Unless specifically
mentioned, 1H-NMR spectra were recorded at 250
MHz and 13C-NMR at 151 MHz at room temperature
(r.t.). Chemical shifts are reported relative to the resid-
ual solvent peaks [CD3COCD3: l=2.04 (1H) and 29.8
ppm (13C), CDCl3: l=7.24 (1H) and 77.0 ppm (13C)].
MS: Finnigan MAT 312 (EI) or Finnigan MAT 312/
AMD5000 (FAB).
3.2. General procedure for the synthesis of the
complexes 3–6
At −30 °C, 5.0 mmol of trimethylsilylacetylene and
phenylacetylene, respectively, in 30 ml of THF was
lithiated with a 15% solution of n-BuLi in hexane.
After 0.5 h, 5.0 mmol of [W(CO)6] was added to the
solution. The resulting red solution was stirred at r.t.
for 1 h and then cooled to −80 °C. (CF3CO)2O (5.0
mmol) of was added. CO evolution was observed. The
solution was warmed to −50 °C and 5.0 mmol of
NaTp%, KTp and NaCp, respectively, was added. When
the CO evolution stopped after warming to r.t. the
solvent was removed in vacuo. The dark brown residue
3.2.3. Dicarbonyl[hydro(trispyrazol-1-yl)borato](tri-
methylsilylpropynylidyne)tungsten (4a)
Chromatography with pentane–CH2Cl2 (9:1) gave a
red band. Removal of the solvent from the red fraction
afforded complex 4a as a red microcrystalline powder.
Yield: 870 mg (31% relative to [W(CO)6]). Dec. \
164 °C. IR (THF, cm−1) w(CꢀC) 2056 w, w(CO) 1991
s, 1906 s. 1H-NMR (CDCl3): l=0.18 (s, 9H, Si(CH3)3),
6.13 (t, J3=2.1 Hz, 1H, pz-C4H), 6.24 (t, J3=2.2 Hz,
2H, pz-C4H), 7.58 (d, 1H, pz-C5H), 7.60 (d, 1H,
pz-C3H), 7.64 (d, J3=2.2 Hz, 2H, pz-C5H), 8.01 (d,

B. Schwenzer et al. / Journal of Organometallic Chemistry 641 (2002) 134–141
139
J3=1.9 Hz, 2H, pz-C3H). 13C-NMR: l= −0.4
(Si(CH3)3), 80.7 (t, J3=4 Hz, Cb), 107.2 (pz-C4), 120.9
(t, J2=28 Hz, Ca), 137.1 (pz-C3), 145.2 (pz-C5), 146.2
(pz-C5), 226.5 (t, J(WC)=164 Hz, CO), 253.4 (t,
J(WC)=200 Hz, WꢀC). FABMS (NBA); m/z (%): 562
(38) [M+], 534 (24) [M+−CO], 73 (68) [Si(CH3)3], 68
(43) [C3H4N2]. Anal. Found: C, 37.19; H, 3.89; N,
14.59. Calc. for C17H19BN6O2SiW (562.1): C, 36.32; H,
3.41; N, 14.95%.
Hz, WꢀC). EIMS; m/z (%): 418 (43) [M+], 390 (3)
[M+−CO], 362 (100) [M+−2CO]. Anal. Found: C,
45.73; H, 2.71. Calc. for C16H10O2W (418.1): C, 45.96;
H, 2.41%.
3.3. General procedure for the synthesis of the
complexes 6a and 6b
At −30 °C, 5.0 mmol of trimethylsilylacetylene and
phenylacetylene, respectively, in 30 ml of Et2O was
lithiated with a 15% solution of n-BuLi in hexane.
After 0.5 h, 5.0 mmol of [W(CO)6] was added to the
solution. The resulting red solution was stirred at r.t.
for 1 h and then cooled to −80 °C. (CF3CO)2O (5.0
mmol) of was added. CO evolution was observed. The
solution was warmed to −50 °C and 5.0 mmol of the
K[bdmpza] was added. When the CO evolution stopped
after warming to r.t. ca. 50ml of pentane was added. A
pale red precipitate formed. The precipitate was washed
3× with 50 ml of pentane each to remove [W(CO)6].
The powder was dried in vacuo and then recrystallized
from THF.
3.2.4. Dicarbonyl[hydro(trispyrazol-1-yl)borato](phenyl-
propynylidyne)tungsten (4b)
Chromatography with pentane–CH2Cl2 (4:1) gave a
red band. Removal of the solvent from the red fraction
afforded complex 4b as a red microcrystalline powder.
Yield: 780 mg (28% relative to [W(CO)6]). Dec. \
135 °C. IR (THF, cm−1) w(CꢀC) 2102 vw, w(CO) 1988
s, 1904 s. 1H-NMR: l=6.30 (t, J3=2.1 Hz, 1H,
pz-C4H), 6.40 (t, J3=2.3 Hz, 2H, pz-C4H), 7.20–7.60
(m, 5H, Ph), 7.83 (d, J3=2.0 Hz, 1H, pz-C5H), 7.90 (d,
J3=2.2 Hz, 1H, pz-C3H), 7.96 (d, J3=2.3 Hz, 2H,
pz-C5H), 8.11 (d, J3=1.9 Hz, 2H, pz-C3H). 13C-NMR:
l=72.1 (Cb), 107.2 (pz-C4), 107.4 (C1, Ph), 122.3 (Ca),
129.7 (Ph), 130.0 (Ph), 133.2 (Ph), 137.1 (pz-C3), 137.3
(pz-C3), 145.0 (pz-C5), 146.2 (pz-C5), 226.7 (t, J(WC)=
64 Hz, CO), 251.4 (WꢀC). EIMS; m/z (%): 566 (5)
[M+], 538 (6) [M+−CO], 512 (4) [M+−2CO]. Anal.
Found: C, 43.66; H, 3.23; N, 14.12. Calc. for
C20H15BN6O2W (566.0): C, 42.44; H, 2.67; N, 14.85%.
3.3.1. Bis(3,5-dimethylpyrazol-1-yl)acetato-
(dicarbonyl)(trimethylsilylpropynylidyne)tungsten (6a)
Yield: 2.5 g (83% relative to [W(CO)6]). Dec. \
205 °C. IR (THF, cm−1) w(CꢀC) 2052 w, w(CO) 1995
1
s, 1912 s, 1693 m. H-NMR: l=0.14 (s, 9H, Si(CH3)3),
2.59 (s, 6H, pz-CMe), 2.60 (s, 6H, pz-CMe), 6.36 (s,
2H, pz-C4H), 6.62 (s, 1H, CH). 13C-NMR: l= −0.4
(Si(CH3)3), 11.0 (pz-CMe), 16.1 (pz-CMe), 69.0 (CH),
78.8 (Cb), 108.9 (pz-C4), 121.1 (t, J2(WC)=27 Hz; Ca),
144.2 (pz-C5), 154.7 (pz-C3), 163.7 (CO2), 225.9 (t,
J(WC)=172 Hz, CO), 244.1 (t, J(WC)=196 Hz;
WꢀC). FABMS (NBA); m/z (%): 603 (12) [M++Li],
596 (14) [M+], 496 (22) [M+−2CO−CO2], 455 (52)
[M+−2CO−CO2−C2H3N], 108 (100) [C6H8N2].
Anal. Found: C, 39.77; H, 4.09; N, 9.16. Calc. for
C20H24N4O4SiW (596.4): C, 40.28; H, 4.06; N, 9.39%.
3.2.5. Dicarbonyl(cyclopentadienyl)(trimethylsilyl-
propynylidyne)tungsten (5a)
Chromatography with pentane–CH2Cl2 (4:1) gave a
red band. Removal of the solvent from the red fraction
afforded complex 5a as a red microcrystalline powder.
Yield: 1160 mg (56% relative to [W(CO)6]). Dec. \
115 °C. IR (THF, cm−1) w(CꢀC) 2057 w, w(CO) 1995
1
s, 1923 s. H-NMR: l=0.15 (s, 9H, Si(CH3)3), 5.87 (s,
5H, C5H5). 13C-NMR: l= −0.8 (Si(CH3)3), 86.1 (Cb),
93.6 (C5H5), 123.0 (Ca), 222.2 (CO), 266.3 (WꢀC).
FABMS (NBA); m/z (%): 414 (11) [M+], 386 (5) [M+
−CO], 358 (12) [M+−2CO], 73 (100) [Si(CH3)3].
Anal. Found: C, 38.05; H, 3.59. Calc. for C13H14O2SiW
(414.2): C, 37.70; H, 3.41%.
3.3.2. Bis(3,5-dimethylpyrazol-1-yl)acetato(dicarbonyl)-
(phenylpropynylidyne)tungsten (6b)
Yield: 2.7 g (91% relative to [W(CO)6]). Dec. \
206 °C. IR (KBr, cm−1) w(CꢀC) 2097; (THF, cm−1
)
1
w(CO) 1992 s, 1910 s, 1692 m. H-NMR: l=2.61 (s,
6H, Me), 2.64 (s, 6H, Me), 6.37 (s, 2H, C4H), 6.63 (s,
1H, CH), 7.3–7.5 (m, 5H, C6H5). 13C-NMR: l=11.0
(C5Me), 16.2 (C3Me), 69.1 (CH), 69.8 (Cb), 107.4 (C1,
Ph), 108.9 (pz-C4), 122.3 (Ca), 129.6 (Ph), 129.9 (Ph),
133.2 (Ph), 144.2 (pz-C), 154.7 (pz-C), 163.6 (CO2),
226.0 (CO), 248.9 (WꢀC). FABMS (NBA); m/z (%):
600 (4) [M+], 500 (2) [M+−2CO−CO2], 459 (4) [M+
−2CO−CO2−C2H3N]. Anal. Found: C, 46.18; H,
3.46; N, 9.33. Calc. for C23H20N4O4W (600.3): C, 46.02;
H, 3.36; N, 9.33%.
3.2.6. Dicarbonyl(cyclopentadienyl)-
(phenylpropynylidyne)tungsten (5b)
Chromatography with pentane–CH2Cl2 (4:1) gave a
red band. Removal of the solvent from the red fraction
afforded complex 5b as a red microcrystalline powder.
Yield: 794 mg (38% relative to [W(CO)6]). Dec. \
136 °C. IR (THF, cm−1) w(CꢀC) 2105 w, w(CO) 1992
1
s, 1920 s. H-NMR: l=5.89 (s, 5H, C5H5), 7.3–7.5 (m,
5H, C6H5). 13C-NMR: l=76.7 (Cb), 93.3 (C5H5), 109.6
(C1, Ph), 122.3 (Ca), 129.6 (Ph), 130.3 (Ph), 132.5 (Ph),
222.4 (t, J(WC)=194 Hz, CO); 264 (t, J(WC)=226

140
B. Schwenzer et al. / Journal of Organometallic Chemistry 641 (2002) 134–141
3.4. Dicarbonyl(chloro)(trimethylsilylpropynylidyne)-
(tetramethylethylendiamine)tungsten (7a)
solvent was removed in vacuo. The light brown residue
was dissolved in THF and chromatographed at
−20 °C on silica gel. Chromatography with pentane–
CH2Cl2 (1:0) gave a red band. Removal of the solvent
from the red fraction afforded complex 9 as a red
microcrystalline powder. Yield: 550 mg (22% relative to
At −80 °C, 5.0 mmol of 1.6M solution of n-BuLi in
hexane were added dropwise to a solution of 5.0 mmol
of trimethylsilylacetylene in 30 ml of THF. The solu-
tion was stirred for 10 min and then gradually warmed
to r.t. A suspension of 5.0 mmol of [W(CO)6] in 50 ml
of THF cooled to −5 °C was added. The solution
immediately turned orange. It was cooled to −80 °C
and a solution of 5.0 mmol of C2O2Cl2 in 20 ml of THF
was added dropwise. The color of the solution changed
to red–brown and a CO evolution was observed. The
solution was warmed to −60 °C and 5.0 mmol of
tmeda was added. When the CO evolution had ceased
the solution was heated at 40 °C for 1 h. The solvent
was removed in vacuo. The light brown residue was
dissolved in 25 ml of CH2Cl2 and solution filtered over
a 15 cm layer of silica gel. A red–brown band was
eluted which was subsequently chromatographed at
−20 °C on silica gel. With CH2Cl2 three fractions were
obtained: the first, yellow–brown one contained
[W(CO)6]). M.p.\120 °C (dec.). IR (THF, cm−1
)
1
w(CO) 1993 s, 1909 vs. H-NMR (CDCl3): l=2.92 (s,
6H, CH3), 2.93 (s, 4H, CH2), 3.22 (s, 6H, CH3), 7.23–
7.45 (m, 5H, C6H5). 13C-NMR (CDCl3): l=52.31,
58.21, 61.21 (CH3, CH2), 68.2 (Cb), 105.2 (J2(WC)=30
Hz, Ca), 121.8, 128.5, 128.6, 132.7 (Ph), 222.4
(J(WC)=172 Hz, CO), 230.4 (J(WC)=212 Hz, WꢀC).
FABMS (NBA); m/z (%): 504 (21) [M+], 476 (59)
[M+−CO], 469 (37) [M+−Cl], 448 (56) [M+−2CO],
115 (100) [tmedaꢁH+], 89 (21) [C-Ph]. Anal. Found: C,
39.63; H, 4.54; N, 5.07. Calc. for C17H21ClN2O2W
(504.7): C, 40.46; H, 4.19; N, 5.55%.
3.6. X-ray structural analyses of 6b and 7b
6b. C27H28N4O5W, molecular mass (672.38), crystal
size 0.2×0.2×0.05 mm3 (obtained by recrystallization
from THF); crystal system monoclinic, space group
[W(CO)6],
the
second,
yellow–orange
one
[(CO)4W(tmeda)] and the third, orange fraction finally
gave complex yellow–orange 7a as a microcrystalline
powder. Yield: 600 mg (24% relative to [W(CO)6]).
M.p.\124 °C. IR (CH2Cl2, cm−1) w(CꢀC) 2050 vw,
,
,
P21/c, a=20.617(15) A, b=9.680(8) A, c=15.743(14)
3
,
,
A, i=111.99(5)°; V=2913.3(41) A , Z=4, Dcalc
=
,
1.533 g cm−3, absorption coefficient 4.005 mm−1
1
br; w(CO) 1997 s, 1908 vs. H-NMR (CDCl3): l=0.16
F(000) 1328; scan type: adaptive ꢀ, [ range 2.13–
25.0°, scan range 1.6°, scan rate variable 4.0–30.0° per
minute in ꢀ; 5119 independent reflections, 3478 reflec-
tion with I\2|(I); 334 refined parameters; R1=
(s, 9H, SiCH3), 2.90 (s, 6H, NCH3), 2.91 (s, 4H,
NCH2), 3.18 (s, 6H, NCH3). 13C-NMR (CDCl3): l=
−0.0 (SiCH3), 52.3, 58.2, 61.2 (NCH3, CH2), 68.2 (Cb),
118.8 (J2(WC)=28.9 Hz, Ca), 222.0 (J(WC)=173 Hz,
CO), 232.4 (J(WC)=210 Hz, WꢀC). FABMS (NBA);
m/z (%): 500 (18) [M+], 472 (59) [M+−CO], 465 (45)
[M+−Cl], 444 (58) [M+−2CO], 409 (14) [M+−
2CO−Cl], 115 (100) [tmedaꢁH+]. Anal. Found: C,
34.44; H, 5.34; N, 5.28. Calc. for C14H25ClN2O2SiW
(500.8): C, 33.58; H, 5.03; N, 5.59%.
0.0600, wR2=0.1507. Largest difference peak and hole:
−3
,
+1.818 and −1.676 e A
.
7b. C18H23Cl3N2O2W, molecular mass (589.58), crys-
tal size 0.3×0.2×0.3 mm3 (obtained by recrystalliza-
tion from CH2Cl2); crystal system triclinic, space group
(
,
,
,
P1, a=7.704(2) A, b=11.921(3) A, c=12.961(3) A,
h=101.30(1), i=105.21(2), k=105.68(1)°; V=
1059.3(5) A , Z=2, Dcalc=1.848 g cm−3, absorption
3
,
3.5. Dicarbonyl(chloro)(phenylpropynylidyne)-
(tetramethylethylendiamine)tungsten (7b)
coefficient 5.848 mm−1, F(000) 572; scan type: adaptive
ꢀ, [ range 2.12–27.05°, 4579 independent reflections,
4344 reflection with I\2|(I); 220 refined parameters;
At −80 °C, 5.0 mmol of phenylacetylene were lithi-
ated in 30 ml of THF by dropwise adding a 15%
solution of n-BuLi in hexane. After 5 min of stirring
the cooling bath was removed and the solution stirred
until r.t. was reached. At −5 °C, this solution was
combined with 5.0 mmol of a solution of [W(CO)6] in
50 ml of THF. The resulting red solution was stirred
for ca. 20 min while warming to 0 °C and then cooled
to −80 °C. 5.0 mmol of C2O2Cl2 was added dropwise.
The color of the solution changed to red–brown and a
CO evolution was observed. The solution was warmed
to −60 °C and 5.0 mmol of tmeda was added. When
the CO evolution had ceased after warming the solution
to r.t. and successive heating to 40 °C for 1 h, the
R1=0.0301, wR2=0.0775. Largest difference peak and
−3
,
hole: +1.220 and −1.452 e A
.
The measurements were performed at −38 (6b) and
−42 °C (7b) with a crystal mounted in a glass capillary
on a Siemens P4 diffractometer (graphite monochroma-
,
tor, Mo–Ka radiation, u=0.71073 A). The structures
were solved by direct methods using the SHELX-97
program package [25]. The positions of the hydrogen
atoms were calculated by assuming ideal geometry and
their coordinates were refined together with those of the
attached C atoms as ‘riding model’. The positions of all
other atoms were refined anisotropically by the full-ma-
trix least-squares method. Complex 6b crystallized with
one equivalent of THF, complex 7b with one equivalent

B. Schwenzer et al. / Journal of Organometallic Chemistry 641 (2002) 134–141
141
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4. Supplementary material
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Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 166390 and 166389 for com-
pounds 6b and 7b, respectively. Copies of this informa-
tion may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(Fax:
+44-1223-336033;
e-mail:
deposit@ccdc.
cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
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Acknowledgements
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Support of these investigations by the Fonds der
Chemischen Industrie is gratefully acknowledged. We
also thank Mr B. Weibert for collecting the data sets
for the X-ray structural analyses.
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