Preparation, characterization, and properties of various novel ionic derivatives of pentacarbonyltungsten

Article abstract of DOI:10.1002/(sici)1099-0682(199910)1999:10<1813::aid-ejic1813>3.0.co;2-d

The complexes [Li(DIME)₂][W(CO)₅L] [L = OCN 2, NCS 3a, PPh₂ 4, SiMe₂Ph 8, N(SiMe₃)₂ 9, CH₂Ph 10, Si₆Me₁₁ 11; DIME = diethylene glycol dimethyl ether] have been prepared by reaction of [Li(DIME)₂][W(CO)₅I] (1) with KOCN, KSCN, NaPPh₂, LiSiMe₂Ph, LiN(SiMe₃)₂, PhCH₂MgCl, and KSi₆Me₁₁, respectively. Photochemical ligand substitution in W(CO)₆ has been used as an alternative method for the preparation of pentacarbonyl tungstates; [K(DIME)₂][W(CO)₅NCS] (3b), [Na(DIME)₂][W(CO)₅N₃] (5), [Li(DIME)₂][W₂(CO)₁₀(υ-H)] (6), and [K(DIME)₂][W₂(CO)₁₀(υ-CN)] (7) were synthesized in this manner. The molecular structure of [Li(DIME)₂][W(CO)₅Si₆Me₁₁] (11) has been determined by X-ray diffraction analysis. The spectral and chemical properties of 2-11 are discussed. Pyrolysis of 11 leads to tungsten silidde and tungsten carbide.

Full text of DOI:10.1002/(sici)1099-0682(199910)1999:10<1813::aid-ejic1813>3.0.co;2-d

FULL PAPER
Preparation, Characterization, and Properties of Various Novel
Ionic Derivatives of Pentacarbonyltungsten
Wolfram Palitzsch,[a] Christian Beyer,[a] Uwe Böhme,*[a] Ben Rittmeister,[a]
and Gerhard Roewer[a]
Keywords: Tungsten / Carbonyl complexes / Undecamethylcyclohexasilyl / Transition metal silicon compounds / Anions /
Tungsten silicide / Silicon
The complexes [Li(DIME)2][W(CO)5L] [L = OCN 2, NCS 3a,
[Na(DIME)2][W(CO)5N3] (5), [Li(DIME)2][W2(CO)10(µ-H)] (6),
PPh2 4, SiMe2Ph 8, N(SiMe3)2 9, CH2Ph 10, Si6Me11 11; DIME = and [K(DIME)2][W2(CO)10(µ-CN)] (7) were synthesized in this
diethylene glycol dimethyl ether] have been prepared by manner. The molecular structure of [Li(DIME)2][W(CO)5-
reaction of [Li(DIME)2][W(CO)5I] (1) with KOCN, KSCN,
NaPPh2, LiSiMe2Ph, LiN(SiMe3)2, PhCH2MgCl, and KSi6Me11
Si6Me11
] (11) has been determined by X-ray diffraction
,
analysis. The spectral and chemical properties of 2–11 are
respectively. Photochemical ligand substitution in W(CO)6 has discussed. Pyrolysis of 11 leads to tungsten silicide and
been used as an alternative method for the preparation of tungsten carbide.
pentacarbonyl tungstates; [K(DIME)2][W(CO)5NCS] (3b),
compounds including pseudohalide derivatives in order to
further development in this field.
Introduction
For a long time, chemists have been interested in
[M0(CO)5X]Ϫ anions of the Group VIA elements.[1] The
fact that they could easily be prepared from M(CO)6 and
R4NϩXϪ[2] and their role as starting materials in the syn-
thesis of derivatives of the relevant transition metals at-
tracted considerable attention. In 1963, Abel and co-work-
ers reported the synthesis of pentacarbonylhalometallate
anions.[2] They were able to isolate R4Nϩ[M(CO)5X]Ϫ spe-
cies from reactions of tetraalkylammonium halides with
metal hexacarbonyls, but the products were characterized
only by infrared spectroscopy. The authors indicated that
the goal of isolating and purifying these compounds was
frustrated by decomposition. In a recent communication,
we described a cation design that should offer improved
thermal stability.[3]
Accordingly, we decided to introduce the Si6Me11 group
into this anionic complex of tungsten. Some transition me-
tal compounds of undecamethylcyclohexasilane have been
described in the last few years,[6] but as far as we are aware,
only one X-ray structure analysis of a cyclohexasilyl tran-
sition metal compound has hitherto been published.[7] We
report herein on the synthesis and characterization of [Li-
(DIME)2][W(CO)5Si6Me11] (11), for which single-crystal
structural data could be obtained.
Among the transition metal silicides, those of tungsten
offer excellent oxidation resistance. Consequently, they are
being considered as potential high-temperature structural
materials, capable of operating well beyond the stable tem-
perature limits possible with superalloys. WSi2 has a high
melting temperature of 2165°C.[8] The fabrication and
characterization of WϪSiϪC phases is a challenge in mate-
rials science. It would be very desirable if such high-tem-
perature resistant materials could be prepared from poten-
tial precursors such as 11.
Because transition metal silicon compounds are useful
precursors for metal silicides, the design of suitable com-
pounds fulfilling this role is very important.[4] The chemis-
try of ionic transition metal silyl derivatives remains largely
unexplored. Only a few compounds of this type derived
from monosilanes have been reported.[5]
In our laboratory, compounds of the type [Li(DI-
ME)2][M(CO)5I] [M ϭ W (1), Mo] have been synthesized
with a modification of the method described by Abel and
co-workers. It is very easy to substitute the iodine while
retaining the d6-character of the tungsten, and hence the
[W(CO)5I]Ϫ anion represents an interesting and versatile
building block. Silyllithium or Grignard reagents react with
complexes such as the [W(CO)5I]Ϫ anion. In the present
work, we describe the preparation and properties of new
Results and Discussion
The iodide complex 1 was chosen as the starting com-
pound for the synthesis of further [W(CO)5L]Ϫ anions. It
was generated by the reaction of W(CO)6 with anhydrous
lithium iodide diethyl ether complex (LiI · OEt2) in DIME
(diethylene glycol dimethyl ether). Complex 1 reacts with a
variety of reagents under substitution of the iodide by the
incoming nucleophile (see Schemes 1 and 3). Reactions with
potassium cyanate and potassium thiocyanate were per-
formed in DME at room temperature. However, these reac-
tions provide the pseudohalide pentacarbonyltungstates 2
and 3a only as mixtures with the starting material 1.
[a]
Technische Universität Bergakademie Freiberg, Institut für
Anorganische Chemie,
Leipziger Straße 29, D-09596 Freiberg, Germany
E-mail: boehme@silicium.aoch.tu-freiberg.de
Eur. J. Inorg. Chem. 1999, 1813Ϫ1820
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
1434Ϫ1948/99/1010Ϫ1813 $ 17.50ϩ.50/0
1813

W. Palitzsch, C. Beyer, U. Böhme, B. Rittmeister, G. Roewer
FULL PAPER
Scheme 1. Substitution of iodide by pseudohalide ions
Scheme 2. Anionic derivatives starting from W(CO)5THF
The infrared spectra of 2 and 3a feature four bands in
the carbonyl stretching region.[9] While only three infrared
bands are to be expected for rigorous C4v symmetry, the
rather weak band at 1960 cmϪ1 in 3a can be assigned to band for the stretching mode of the NCS ligand as de-
the formally infrared inactive B1 mode.[10] The character- scribed above. Generally, the thiocyanate ion is able to coor-
istic modes of the pseudohalides are found at 2245 cmϪ1 dinate to metals through either the nitrogen or the sulfur
(νNCO in 2) and 2090 cmϪ1 (νNCS in 3a). All attempts to atom. The high frequency νCN band indicates that in this
separate 2 and 3a from the starting compound 1 by recrys- case the thiocyanate is coordinated to the tungsten through
tallization were unsuccessful. As the product mixture con- the nitrogen atom.[13] As mentioned above, the product 3a
tained 1 as the major and 2 as the minor component, we formed by nucleophilic substitution of iodide by SCNϪ was
were unable to obtain a full spectroscopic characterization found to be contaminated with the starting compound 1;
of 2. Specifically, it could not be established whether the however, the product of the photochemical reaction se-
cyanate ion is coordinated through nitrogen or oxygen at quence was free from impurities.
the tungsten atom.
Reaction of potassium selenocyanate (KSeCN) with
Reaction of 1 with sodium diphenylphosphide in THF/ W(CO)5THF in DIME failed to give the desired product
dioxane yielded a red oil, the NMR and IR spectroscopic [K(DIME)2][W(CO)5NCSe] in all cases, even at low tem-
data of which were consistent with the formula [Li(DI- peratures. Instead, a finely divided black precipitate was
ME)2][W(CO)5PPh2]. The infrared spectrum features four formed, which was identified as elemental selenium by
bands attributable to the W(CO)5 fragment at 2045, 1964, flame photometry and its melting point (215Ϫ217°C).
1936, and 1880 cmϪ1. In the 13C-NMR spectrum, the sig-
Sodium azide decomposes in solution if it is exposed to
nals of the CO carbon atoms are split into doublets due to strong light. Therefore, the synthesis of [Na(DIME)2][W(-
coupling with the phosphorus atom bound to the W(CO)5 CO)5N3] 5 was performed in a two-step sequence. The
fragment.
W(CO)5THF adduct was prepared photochemically as
The reaction of the tungsten pentacarbonyl THF adduct above. The solution of W(CO)5THF thus formed was then
with pseudohalides represents an alternative route for pre- added dropwise to a solution of sodium azide protected
paring substitution products of the type [(OC)5WϪX]Ϫ (see from bright light. The product 5 was found to be air- and
Scheme 2). Donor adducts of W(CO)5 have been used pre- light-sensitive and was characterized by its 13C-NMR and
viously as reactive intermediates.[11] It is easy to prepare IR spectra. The 13C-NMR spectrum features the character-
W(CO)5THF from W(CO)6 by photochemical ligand sub- istic 1:4 peak intensity ratio due to the CO carbon atoms
stitution in THF solution.
at low field, as well as additional signals due to the DIME
Reaction of W(CO)5THF with KSCN in DIME yields ligand (for details, see the Experimental Section). Four IR
3b as a yellow microcrystalline powder. The 13C-NMR bands are seen in the carbonyl stretching region. One ad-
spectrum features one signal due to the thiocyanate carbon ditional weak band at 2080 cmϪ1 can be assigned to the
atom at δ ϭ 135.1 and three signals due to the DIME li- asymmetric stretching mode of the azide group. To assess
gand coordinated at the potassium ion. The signals of the the stability of compound 5 in solution, the NMR sample
CO carbon atoms are found at δ ϭ 197.6 and 201.6, with was stored for one week at room temperature. When an
1
an intensity ratio of 1:4. The J(13C,183W) coupling con- NMR spectrum was recorded after this period, the 13C-
stant, which is well resolved in the spectrum of this com- NMR signals of the [W(CO)5N3]Ϫ ion could no longer be
pound, has a value of 129.2 Hz. The spectroscopic data of detected. New signals were seen, which corresponded to
compound 3b correspond well with the data of W(CO)6 and [W(CO)5NCO]Ϫ. The mechanism of de-
[NEt4][W(CO)5NCS], which was described by Buchner and composition of [W(CO)5N3]Ϫ might be analogous to the
Schenk.[12] The infrared spectrum of 3b features four bands Curtius rearrangement.[14] Reactions of metal carbonyls
Ϫ
in the carbonyl stretching region and one characteristic with N3 have been studied extensively.[15]
1814
Eur. J. Inorg. Chem. 1999, 1813Ϫ1820

Various Novel Ionic Derivatives of Pentacarbonyltungsten
Because the tetrahydroborate ion is isoelectronic with the
FULL PAPER
Complexes 8, 9, and 10 were isolated and purified by ex-
fluoride, hydroxide, amide, and methyl ions, we were also traction with pentane. Subsequent recrystallization from di-
interested in carrying out reactions of W(CO)5THF with chloromethane gave yellowish solids. Compounds 8؊11 can
lithium tetrahydroborate. The 13C-NMR data of 6 reveal be safely dried in vacuo at room temperature without loss
the presence of a W(CO)5 unit, since two signals for car- of the DIME ligands. Complex 9 proved to be more air-
bonyl carbon atoms are seen, with an intensity ratio of 1:4. sensitive than compounds 8, 10, and 11. The IR spectra of
One signal at δ ϭ Ϫ12.55 is seen in the 1H-NMR spectrum compounds 8, 9, and 10 exhibit three νCO bands (2A1 and
of 6. It is split into a triplet due to coupling with two tung- E). These stretching modes are in agreement with data
sten atoms [1J(1H,183W) ϭ 42.0 Hz]. The chemical shift and found for the corresponding neutral M(CO)5X species.[18]
1
coupling constant of this proton are characteristic features The H-NMR spectra are indicative of the presence of the
of such µ-hydrogen-bridged ditungsten complexes. A few DIME ligand (3 signals) and also feature characteristic sig-
examples have been described previously, which showed nals for the substituents at the tungsten atom: δ ϭ 7.54 (m,
very similar chemical shifts and coupling constants as those SiPh), 0.58 (SiMe2) for 8; δ ϭ 0.0 (SiMe3) for 9; δ ϭ
found for 6.[16] In addition, we observed signals due to a 7.26 (m, Ph), 1.25 (CH2) for 10. The 13C-NMR data of 9
BH4-containing side-product in the NMR spectra of 6, and 10 confirm the presence of the DIME ligand (3 signals)
which are most probably attributable to a small amount of and of the substituents at the tungsten atom (see Exper-
[Li(DIME)2][W(CO)4(µ2-BH4)]. It was not possible to re- imental Section). The 29Si-NMR peak of 8 at δ ϭ Ϫ6.13
move this impurity by recrystallization.
gives evidence that one silicon atom is present.
Reaction of W(CO)5THF with potassium cyanide in THF
Undecamethylcyclohexasilyl potassium (KSi6Me11) is
in the presence of DIME yielded a yellow microcrystalline well-established as a useful reagent for the synthesis of a
powder. The 13C-NMR spectrum of this substance reveals variety of transition metal silyl complexes. [Li(DIME)2][W(-
the presence of two different W(CO)5 units, since two sets of CO)5Si6Me11] (11) was prepared according to Scheme 4.
carbonyl carbon atom signals with an intensity ratio of 1:4 The reaction of one equivalent of [Li(DIME)2][W(CO)5I]
are seen. This pattern is suggestive of the formation of a with KSi6Me11 in DME at ambient temperature resulted in
dimeric CN-bridged complex. The carbon atom signal of the the novel substance [Li(DIME)2][W(CO)5Si6Me11] (11).
CN group is found at δ ϭ 152.5. Five bands are seen in the
carbonyl stretching region of the IR spectrum (see Exper-
imental Section). There is probably a superposition of the
absorptions of the two different W(CO)5 fragments. The
stretching mode of the cyanide group is observed at 2124
cmϪ1. Comparable compounds, such as the bridged complex
[PPN][W2(CO)10(µ-CN)] and [NEt4][W(CO)5CN], show ab-
sorptions at 2121 cmϪ1 and 2104 cmϪ1, respectively.[17] The
high wavenumber shift of the νCN mode, together with the
aforementioned NMR data, lead us to the conclusion that
the bridged complex [K(DIME)2][(OC)5W(µ-CN)W(CO)5] 7
was formed in this reaction.
Reaction of [Li(DIME)2][W(CO)5I] (1) with 1 molar
equivalent of lithium bis(trimethylsilyl)amide Li[N(SiMe3)2]
in tetrahydrofuran gave [Li(DIME)2][W(CO)5N(SiMe3)2]
(9). Treatment of 1 with the Grignard reagent PhCH2MgCl
in diethyl ether solution afforded complex 10 (Scheme 3).
Complex 8 was prepared by adding a solution of [Li(DI-
ME)2][W(CO)5I] (1) in DME to an excess of LiSiMe2Ph.
Scheme 4. Synthesis of compound 11
The cyclohexasilyl derivative 11 was found to be more
stable than complexes 8؊10. In the solid state, 11 is prone
to very slow decomposition in air. It decomposes thermally
between 160 and 250°C (TG). It is quite soluble in protic
solvents, for example, wet methanol, with no evidence of
decomposition in solution detectable in the NMR spec-
trum. Recrystallization from dichloromethane/pentane at
Ϫ20°C gave analytically pure yellow crystals of 11 suitable
for an X-ray crystallographic study. The structure was
solved and refined in space group P21/n. 11 crystallizes in
Scheme 3. Syntheses of compounds 8Ϫ10 by nucleophilic substitution discrete ionic pairs; the structure of the cation is shown in
Eur. J. Inorg. Chem. 1999, 1813Ϫ1820
1815

W. Palitzsch, C. Beyer, U. Böhme, B. Rittmeister, G. Roewer
˚
FULL PAPER
Figure 1. The lithium atom is coordinated by two DIME Table 1. Selected bond lengths [A] and bond angles [°] in 11
molecules in a distorted octahedral coordination geometry.
The tridentate ether molecules chelate the lithium atom
WϪC(1)
WϪC(2)
WϪC(3)
1.966(6)
2.017(8)
2.011(7)
2.044(8)
2.016(8)
2.670(2)
1.176(8)
1.151(9)
1.163(9)
1.122(9)
1.162(9)
90.2(3)
LiϪO(6)
2.285(10)
2.046(9)
2.138(10)
2.274(11)
2.009(10)
2.118(11)
177.9(6)
79.4(4)
LiϪO(7)
with meridional coordination. The LiϪO bond lengths in
LiϪO(8)
˚
11 of 2.009 to 2.285 A are in the same range as the LiϪO WϪC(4)
LiϪO(9)
distances reported for 1.[3] The structures of these cations
WϪC(5)
LiϪO(10)
WϪSi(1)
LiϪO(11)
are isotypic.
C(1)ϪO(1)
O(10)ϪLiϪO(7)
O(7)ϪLiϪO(8)
O(7)ϪLiϪO(6)
O(7)ϪLiϪO(11)
O(7)ϪLiϪO(9)
C(2)ϪO(2)
C(3)ϪO(3)
75.5(3)
C(4)ϪO(4)
98.1(4)
105.2(4)
C(5)ϪO(5)
C(4)ϪWϪC(3)
C(4)ϪWϪC(5)
C(2)ϪWϪC(3)
C(2)ϪWϪC(5)
C(1)ϪWϪSi(1)
89.7(3)
90.4(3)
89.8(3)
175.3(2)
In the infrared spectrum of 11, four metal carbonyl bands
at 2020 (w), 1915 (m), 1890 (s), and 1860 (m) cmϪ1 are
observed, which are characteristic of a metal pentacarbonyl
anion.[2] The IR bands can be assigned to the three IR-
active fundamental vibrations (2A1 ϩ E) expected for a C4v
metal pentacarbonyl species and to the B1 vibration, al-
though this is IR inactive for rigorous C4v geometry. This
assessment is in agreement with those for the corresponding
M(CO)5X species by Casey.[9a] The 1H-NMR signals of the
DIME ligands are observed at δ ϭ 3.40 (s, CH3) and δ ϭ
Figure 1. Structure of the [Li(DIME)2]ϩ cation in 11
The structure of the undecamethylcyclohexasilylpenta-
carbonyltungsten anion is shown in Figure 2. The [W(CO)5-
Si6Me11]Ϫ anion has approximately C4v symmetry with a
˚
WϪSi bond length of 2.670(2) A, which is slightly longer
1
3.56 and 3.65 (m, CH2CH2). The H-NMR resonances for
the methyl groups bonded to the silicon appear in the typi-
cal range with δ values near to zero (see Table 2).
˚
than the corresponding distance of 2.614(2)
A
in
[PPN][W(CO)5SiMe3].[19] The tungsten atom resides in an
almost regular octahedron with COeqϪWϪCOeq angles
very close to 90° and a COaxϪWϪSiax angle of 175.3(2)°.
The WϪC distances for the four equatorial CO ligands
1
Table 2. H-, 13C-, and 29Si-NMR data of compound 11[a]
˚
δ1H
DIME
δ13C
MeϪSi DIME
δ29Si
range from 2.011 to 2.044 A, while the WϪC bond to the
CO
SiϪMe
˚
axial CO ligand measures only 1.966(6) A. This is possibly
a reflection of a greater π-back-bonding to the CO ligand
situated trans to the silyl group. Two of the four equatorial
COЈs are bent towards the Si6Me11 ligand, resulting in
Si(1)ϪWϪC(4) and Si(1)ϪWϪC(5) angles of 84.6(2) and
80.2(2)°, respectively. The cyclohexasilyl ligand adopts a
chair conformation with the W(CO)5 group in an equa-
torial position.
3.65,
0.49,
70.75,
212.16, Ϫ2.14,
Ϫ75.7,
Ϫ42.0,
Ϫ40.7,
Ϫ30.7
3.56 (CH2), 0.22,
69.30 (CH2), 207.67 Ϫ3.18,
3.40 (CH3) 0.15,
59.31 (CH3)
Ϫ3.79,
Ϫ4.19,
Ϫ4.85,
Ϫ5.95,
Ϫ6.79
0.14,
0.11,
0.10
[a]
Recorded in CDCl3 at 25°C; data in ppm are relative to Me4Si
at δ ϭ 0.0.
Crystallographic data and data collection parameters are
listed in Table 3. Salient bond lengths and angles are listed
in Table 1.
The fact that six signals are observed indicates that the
silicon ring adopts a chair conformation. Single-crystal
structure analysis confirms this assumption. The 29Si-NMR
spectrum of compound 11 features four resonances for the
cyclo-silyl ligand bonded at the metal atom (Table 2). The
29Si-NMR chemical shifts for the anion [W(CO)5Si6Me11]Ϫ
move progressively to higher field relative to the shifts for
the analogous [Mo(CO)5Si6Me11],[7] which is the expected
trend for complexes of this type.[20] The 13C-NMR data of
11 are in agreement with the proposed structure (Table 2).
Pyrolysis of [Li(DIME)2][W(CO)5Si6Me11] (11)
Thermogravimetry (TG) and differential thermal analysis
(DTA) were performed using a MOM Budapest Derivato-
Figure 2. Structure of the [W(CO)5Si6Me11]Ϫ anion in 11
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Eur. J. Inorg. Chem. 1999, 1813Ϫ1820

Various Novel Ionic Derivatives of Pentacarbonyltungsten
FULL PAPER
Figure 3. Comparison of the XRD pattern of the pyrolyzed sample of [Li(DIME)2][W(CO)5Si6Me11] (11) (top) with powder diffraction
files: 11Ϫ0195 WSi2, 25Ϫ1047 WC (bottom)
graph. An atmosphere of Ar (at a flow rate of 200 mL/
Experimental Section
All preparative work and sample handling was carried out under
Ar with dry glassware and in dry solvents. Diethylene glycol di-
methyl ether (DIME) was repeatedly distilled from freshly cut Na
until effervescence was no longer observed. It was distilled once
minϪ1) and a corund open pan were used for the experi-
ment. A sample of 11 was heated at a rate of 5 °C minϪ1
up to 1400°C. Decomposition started at 160°C and reached
a maximum rate at 230°C. The mass lost amounted to 29%
of the sample mass at 250°C, which corresponds to the loss more and then stored in a sealed flask in a drybox prior to use.
Starting materials W(CO)6 and Li[N(SiMe3)2] were purchased from
Fluka Chemie AG. W(CO)6 was vacuum-sublimed prior to use. All
alkaline pseudohalides were dried in vacuo for 4 h prior to use. The
syntheses of PhCH2MgCl,[21] LiSiMe2Ph,[22] and KSi6Me11[23] were
carried out according to established procedures.
of 2 DIME molecules per formula unit. The following sub-
stances could be detected by GC analysis: CO at
400Ϫ1000°C, CH4 at 500Ϫ800°C, and H2 < 1200°C. X-ray
analysis after the pyrolysis indicated that the product was
mainly a mixture of WSi2 and WC (Figure 3).
NMR spectra were recorded on a Bruker MSL 200 spectrometer.
Ϫ
Elemental analyses were performed on a CHN-O-Rapid
(Heraeus). The carbon values recorded were systematically lower
due to carbide formation. Ϫ Infrared spectra were recorded on a
Specord 75 IR instrument in the range 4000 to 400 cmϪ1 for
samples pressed into a KBr disc. Ϫ X-ray powder diffraction pat-
terns were obtained using a Siemens D5000 diffractometer with
Cu-Kα radiation.
Conclusions
In conclusion, [Li(DIME)2][W(CO)5I] (1) reacts readily
with nucleophilic reagents such as alkyls and organoam-
ides, -phosphides, and -silyls. The preferred site of reactivity
is the WϪI bond. Thus, it is evident that 1 is a highly useful
reagent for preparing a wide variety of W(CO)5 derivatives.
Reaction of 1 with pseudohalides leads to mixtures of start-
ing material and product. This is probably due to the weak
nucleophilicity of the pseudohalides. Therefore, the salt
elimination route is not suitable for preparing pure pseudo-
halideϪpentacarbonyltungstate derivatives. However, it is
possible to obtain these derivatives by using the photoch-
emical reaction sequence via W(CO)5THF. The X-ray crys-
tal structure of 11 confirms that the cyclohexasilyl ring is
bound to the tungsten. The production of pure tungsten
silicide is a challenging task with potential applications in
materials science; thus it is noteworthy that thermolysis of
11 produces WSi2 together with WC. Further investigations
concerning the synthesis and thermal decomposition path-
Synthesis of [Li(DIME)2][W(CO)5I] (1): A sample of W(CO)6
(5.0 g, 0.014 mol) was added to a solution of LiI·Et2O (3.0 g, ഠ
0.014 mol) in diethylene glycol dimethyl ether (20 mL). The mixture
was heated at 80°C for 2 days, during which it became bright yel-
low. IR monitoring showed the formation of a species with a ν(CO)
pattern typical for [W(CO)5L] species: ν˜ ϭ 1950, 1915, 1850 cmϪ1
.
The solvent was removed in vacuo to leave a yellow residue. This
was redissolved in dichloromethane and then treated with n-pen-
tane to give yellow crystals of 1 (isolated yield 93.7%). Ϫ 1H NMR
(CDCl3/TMS): δ ϭ 3.75, 3.64, 3.45 (DIME). Ϫ 13C NMR (CDCl3/
TMS): δ ϭ 202.62, 197.18 (CO), 70.58, 69.37, 59.54 (DIME). Ϫ
C17H28ILiO11W (697.8): calcd. C 21.88, H 3.02; found C 21.74,
H 3.10.
Synthesis of [Li(DIME)2][W(CO)5NCO] (2) and [Li(DIME)2][W-
(CO)5NCS] (3a): [Li(DIME)2][W(CO)5I] (1) (0.003 mol) and an
equimolar amount of KOCN or KSCN, respectively, were sus-
ways of metalϪsilicon compounds are currently under way. pended in DME and the mixture was stirred for 24 h at room tem-
Eur. J. Inorg. Chem. 1999, 1813Ϫ1820 1817

W. Palitzsch, C. Beyer, U. Böhme, B. Rittmeister, G. Roewer
FULL PAPER
perature. The solvent was then evaporated in vacuo, and the re-
Synthesis of [Li(DIME)2][W2(CO)10(µ-H)] (6): W(CO)5THF was
maining solid was washed with n-pentane and taken up in dichloro-
prepared as described above. LiBH4 (0.185 g, 0.0085 mol) was dis-
methane. The resulting suspension was filtered to remove insoluble solved in a mixture of THF (60 mL) and DIME (20 mL). The tung-
alkaline halides. Addition of n-pentane to the clear solution and sten pentacarbonyl THF adduct was added dropwise to the LiBH4
cooling to 5°C led to the deposition of 3a as a yellow solid. Ϫ H solution over a period of 15 min. at 0°C and the reaction mixture
NMR (CDCl3/TMS): δ ϭ 3.74, 3.63, 3.46 (DIME). Ϫ 13C NMR
was stirred for 8 h. After evaporation of the solvent, the residue
(CDCl3/TMS): δ ϭ 201.4 (COax), 197.6 (COeq), 135.4 (NCS), 70.7, was redissolved in THF, the resulting solution was filtered, and n-
69.3 (DIME). Ϫ IR (KBr): νCO ϭ 2060 (w), 1960 (w, sh), 1910 (s), pentane was added to the filtrate. The clear solution was cooled to
1860 (m) cmϪ1; νNCS ϭ 2090 (w) cmϪ1. The spectra of 3a prepared Ϫ20°C to crystallize the product. Ϫ 1H NMR (CD3CN/TMS): δ ϭ
1
by this method show additional signals attributable to 1.
3.61, 3.52, 3.35 (DIME), Ϫ12.55 [1J(1H,183W) ϭ 42.0 Hz (WH)].
13C NMR (CD3CN/TMS):
202.0 (COax), 199.7
Ϫ
δ ϭ
Synthesis of [K(DIME)2][W(CO)5NCS] (3b): W(CO)5THF was pre-
pared immediately prior to use by irradiating a solution of W(CO)6
(2.5 g, 0.0071 mol) in dry THF (concentration about 0.1 mol/L)
under Ar for 4 h with a high-pressure Hg lamp (160 W).[24] Mean-
while, a solution of potassium thiocyanate (0.69 g, 0.0071 mol) in
DIME (15 mL) was prepared. The synthesized tungsten pentacar-
bonyl THF adduct was then added to this solution over a period
of 10 min. The resulting mixture was stirred for 24 h at room tem-
perature. The solvent and excess W(CO)6 were then removed in
vacuo. Pentane was added, the product was isolated by filtration,
washed with n-pentane, and dried in vacuo to afford 3b as a yellow
microcrystalline powder. Ϫ 1H NMR (CDCl3/TMS): δ ϭ 3.66,
3.59, 3.42 (DIME). Ϫ 13C NMR (CDCl3/TMS): δ ϭ 201.6 (COax),
197.6 [1J(13C,183W) ϭ 129.2 Hz (COeq)], 135.1 (NCS), 71.5, 69.9,
59.0 (DIME). Ϫ IR (KBr): νCO ϭ 2066 (w), 1975 (w, sh), 1918 (s),
[1J(13C,183W) ϭ 124.2 Hz (COeq)], 71.7, 70.2, 59.1 (DIME); im-
purities: LiBH4: 1H NMR (CD3CN/TMS): δ ϭ Ϫ0.46 [quadruplet,
1J(1H,11B) ϭ 83.2 Hz]. Ϫ 11B NMR (CD3CN/BF3·Et2O): δ ϭ
Ϫ39.43; [Li(DIME)2][W(CO)4(µ2-BH4)]: 1H NMR (CD3CN/TMS):
δ ϭ Ϫ11.84 (weak). Ϫ 13C NMR (CD3CN/TMS): δ ϭ 201.4, 200.8
(CO, weak). Ϫ IR (KBr): νCO ϭ 2071 (w), 2041 (m), 2014 (w), 1966
(m, sh), 1936 (s), 1873 (s, br), 1839 (m), 1802 (w, sh) cmϪ1; νBH
2246 (s, br) cmϪ1
ϭ
.
Synthesis of [K(DIME)2][W2(CO)10(µ-CN)] (7): W(CO)5THF was
prepared as described above. Potassium cyanide (0.55 g, 0.0085
mol) was dissolved in a mixture of THF (40 mL) and DIME
(20 mL). The tungsten pentacarbonyl THF adduct was then added
dropwise to the potassium cyanide solution over a period of
15 min. at 0°C. The resulting mixture was stirred for 4 h and then
the remaining traces of KCN were filtered off. The solvent was
removed under reduced pressure, n-pentane was added to the resi-
due, and the precipitate was collected by filtration. The green-yel-
low solid was taken up in THF and filtered, and the collected solid
was washed with n-pentane and dried in vacuo to afford a yellow
microcrystalline powder 7. The product was found to be sensitive
1864 (m) cmϪ1; νNCS ϭ 2093 (w) cmϪ1
.
Synthesis of [Li(DIME)2][W(CO)5PPh2] (4): [Na(dioxane)n][PPh2]
was prepared according to the method of Issleib.[25] [Li(DI-
ME)2][W(CO)5I] (2.54 g, 0.0035 mol) was dissolved in THF
(40 mL) and a solution of [Na(dioxane)n][PPh2] (ca. 0.01 mol) in
THF/dioxane (23 mL) was added at Ϫ76°C. The resulting mixture
was stirred for a period of 10 h, during which the colour changed
from yellow/orange to red. DIME (20 mL) was then added to the
reaction mixture. The resulting suspension was filtered and the sol-
vents were evaporated in vacuo. All attempts at crystallization led
only to a clear red oil 4. Ϫ 1H NMR (CDCl3/TMS): δ ϭ 7.73, 7.23,
7.04 (Ph), 3.75, 1.86 (THF), 3.72, 3.62, 3.44 (DIME). Ϫ 13C NMR
(CDCl3/TMS): δ ϭ 204.7 [2J(13C,31P) ϭ 12.9 Hz (COax)], 201.2
[1J(13C,183W) ϭ 123.9 Hz (COeq)], 151.2 [1J(13C,31P) ϭ 12.3 Hz
(Cipso)], 133.4 [2J(13C,31P) ϭ 10.9 Hz (Cortho)], 126.8 [3J(13C,31P) ϭ
7.7 Hz (Cmeta)], 125.5 (Cpara), 71.0, 69.7, 59.4 (DIME), 68.0, 25.6
(THF). Ϫ IR (THF): νCO ϭ 2045 (w), 1964 (w, sh), 1936 (s), 1880
1
to light and air. Ϫ H NMR (CDCl3/TMS): δ ϭ 3.65, 3.59, 3.42
(DIME). Ϫ 13C NMR (CDCl3/TMS): δ ϭ 202.3 (COax NC), 197.9
[1J(13C,183W) ϭ 129.0 Hz (COeq NC)], 200.2 (COax CN), 196.9
[1J(13C,183W) ϭ 125.0 Hz (COeq CN)], 152.5 (CN), 71.5, 70.0, 59.0
(DIME). Ϫ IR (THF): νCO ϭ 2057 (w), 1971 (sh), 1934 (s), 1900
(m), 1880 (m); νCN ϭ 2124 (w). Ϫ UV/vis (EtOH): λmax (ε/
l·molϪ1·cmϪ1) ϭ 230 (80870), 248 (54515), 338 (3947), 362 (4021),
384 (2740) nm.
Synthesis of [Li(DIME)2][W(CO)5SiMe2Ph] (8): A solution of 1
(0.005 mol, 3.49 g) in DME (20 mL) was added slowly, over a per-
iod of 4 h, to an excess of LiSiMe2Ph (0.006 mol) in THF. The
mixture was stirred for further 3 h and then the solvents were re-
moved in vacuo. The remaining orange solid was redissolved in
dichloromethane (20 mL) and this solution was filtered. Pentane
(50 mL) was added to the clear yellow filtrate and complex 8 crys-
tallized on cooling. The mother liquor was removed by means of a
cannula. The residue was washed with pentane, dried in a stream
of argon, and then at oil-pump vacuum to afford 2.8 g (79%) of 8
as a yellow solid. Ϫ 1H NMR (CDCl3/TMS): δ ϭ 7.54 (SiPh), 3.68,
3.59, 3.43 (DIME), 0.58 (SiMe2). Ϫ 29Si NMR (dichloromethane/
(m) cmϪ1
.
Synthesis of [Na(DIME)2][W(CO)5N3] (5): W(CO)5THF was pre-
pared as described above. Sodium azide (0.46 g, 0.0071 mol) was
dissolved in methanol (60 mL) and THF (80 mL) and then DIME
(20 mL) was added to the solution. The tungsten pentacarbonyl
THF adduct was added dropwise to this mixture with stirring.
After stirring for 10 h, the solvents were evaporated in vacuo and
excess n-pentane was added to the yellow residue. The resulting
yellow solid was collected by filtration and washed with n-pentane.
The solid residue was redissolved in THF, the resulting solution
was filtered, and n-pentane was added to the filtrate to crystallize
the product. The product was found to be sensitive to light and
air. It decomposes in CH2Cl2 and CHCl3. In solution, the product
D2O): δ ϭ Ϫ6.13. Ϫ IR (CHCl3): νCO ϭ 1925, 1887, 1815 cmϪ1
.
Ϫ C25H39LiO11SiW (706.1): calcd. C 42.52, H 5.51; found C 41.86,
H 5.53.
converts into W(CO)6 and [Na(DIME)2][W(CO)5NCO]. Ϫ 1H Synthesis of [Li(DIME)2][W(CO)5N(SiMe2)2] (9): A solution of 1
NMR (CD3OD/TMS): δ ϭ 3.62, 3.54, 3.36 (DIME). Ϫ 13C NMR (0.005 mol, 3.49 g) in THF was cooled to Ϫ76°C, whereupon 5 mL
(CD3OD/TMS): δ ϭ 203.4 (COax N3), 199.8 [1J(13C,183W) ϭ
(0.005 mol) of a 1  solution of Li[N(SiMe3)2] in THF was added.
129.3 Hz (COeq N3)], 202.2 (COax OCN), 199.4 (COeq OCN), 192.4
The mixture was stirred for 2 h while being allowed to warm to
[W(CO)6], 72.9, 71.3, 59.1 (DIME). Ϫ IR (THF): νCO ϭ 2040 (w), room temperature. After evaporation of the solvent, the residue was
1965 (s), 1910 (s), 1865 (m) cmϪ1, νN3 ϭ 2080 (w) cmϪ1; νOCN
ϭ
redissolved in DME (20 mL) and the resulting solution was filtered.
Pentane was added to the clear yellow solution to start the crystalli-
2245 (w) cmϪ1
.
1818
Eur. J. Inorg. Chem. 1999, 1813Ϫ1820

Various Novel Ionic Derivatives of Pentacarbonyltungsten
FULL PAPER
zation. After cooling, the yield of 9 was 1.4 g (38.3%). The product
was recrystallized from dichloromethane/pentane to afford an or-
ange solid. Ϫ 1H NMR (CDCl3): δ ϭ 3.71, 3.60, 3.40 (DIME),
0.00 (SiMe3). Ϫ 13C NMR (CDCl3): δ ϭ 205.67, 197.04 (CO),
Table 3. Crystal data and structure refinement for [Li(DIME)2]-
[W(CO)5Si6Me11] (11)
11
70.43, 69.19, 59.45 (DIME), 2.39 (SiMe3). Ϫ IR (CDCl3): νCO
ϭ
1928, 1874, 1855 cmϪ1. Ϫ C19H46LiO11Si2W (731.32): calcd.
Empirical formula
Formula weight
Temperature
C28H61LiO11Si6W
933.10
C 31.20, H 6.28; found C 30.76, H 6.22.
190(2) K
˚
Wavelength
1.54180 A
Synthesis of [Li(DIME)2][W(CO)5CH2Ph] (10): PhCH2MgCl
(0.005 mol, 12.8 mL of a 0.4  Grignard solution) was treated with
a solution of 0.005 mol (3.49 g) of 1 in DME (20 mL) and the
resulting mixture was stirred for 2 h at room temperature. Sub-
sequent evaporation of the solvents left a yellow solid, which was
taken up in dichloromethane (30 mL) under cooling. This mixture
was then filtered and the filtrate was concentrated to dryness to
afford 1.7 g (51.4%) of 10. Ϫ 1H NMR (CDCl3/TMS): δ ϭ 7.26
(Ph), 3.74, 3.64, 3.44 (DIME), 1.25 (CH2). Ϫ 13C NMR (CDCl3/
TMS): δ ϭ 138.78, 130.68, 128.73, 126.48 (Ph), 70.85, 69.58, 59.49
(DIME), 45.58 (CH2). Ϫ IR (CDCl3): νCO ϭ 1934, 1916, 1885
cmϪ1. Ϫ C24H35LiO11W (662.04): calcd. C 43.54, H 5.28; found
C 43.45, H 5.24.
Crystal system
Space group
Unit cell dimensions
monoclinic
P21/n
˚
a ϭ 19.116(2) A, α ϭ 90°
˚
b ϭ 14.308(2) A, β ϭ 96.810(10)°
˚
c ϭ 20.264(3) A, γ ϭ 90°
3
˚
Volume
Z
Density (calculated)
Absorption coefficient
F(000)
Crystal size
θ range for data collection
Index ranges
4639.7(11) A
4
1.336 Mg/m3
6.468 mmϪ1
1912
0.4 ϫ 0.3 ϫ 0.15 mm
3.32Ϫ74.77°
Ϫ20 Յ h Յ 20, 0 Յ k Յ 17,
Ϫ25 Յ l Յ 9
Reflections collected
Independent reflections
Refinement method
14335
9517 [R(int) ϭ 0.0944]
Full-matrix least squares on F2
9517/0/439
Synthesis of [Li(DIME)2][W(CO)5Si6Me11] (11): KSi6Me11 was pre-
pared from cyclo-Si6Me12 (2.6 g, 0.007 mol) and KOC(CH3)3
(0.78 g, 0.007 mol) in DME (10 mL) and then added dropwise at
room temperature over a period of 15 min. to a stirred solution of
1 (5.08 g, 0.007 mol) in DME (20 mL). After stirring the mixture at
room temperature for 12 h, the solvent was removed under reduced
pressure. Then, a mixture of n-pentane/dichloromethane (1:1,
20 mL) was added to the residue and the precipitate was filtered
off. The filtrate was concentrated to dryness under reduced pressure
and n-pentane (20 mL) was added to the residue to produce a
slightly yellow suspension. An orange oil separated from the mix-
ture after addition of approximately 10 drops of dichloromethane.
Yellow crystals of 11 deposited from the oil after 1 d at Ϫ20°C.
Yield: 4.82 g (74%). The NMR data are shown in Table 2. Ϫ IR
(nujol): νCO ϭ 2020 (w), 1915 (m), 1890 (s), 1860 (m). Ϫ
C28H61LiO11Si6W: calcd. C 36.04, H 6.58; found C 35.91, H 6.74.
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
R indices (all data)
1.038
R1 ϭ 0.0575, wR2 ϭ 0.1453
R1 ϭ 0.0787, wR2 ϭ 0.1609
0.6843
min. transmission
max transmission
0.9998
2.051 and Ϫ3.071 e·A
Ϫ3
˚
Largest diff. peak and hole
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1819

W. Palitzsch, C. Beyer, U. Böhme, B. Rittmeister, G. Roewer
FULL PAPER
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