Synthesis and structural characterization of metallogermylenes, Cp-substituted germylene, and a germanium(II)-borane adduct from pyridyl-1-azaallyl germanium(II) chloride

Article abstract of DOI:10.1021/om3007739

The reaction of [{N(SiMe₃)C(Ph)C(SiMe₃)(C ₅H₄N-2)}GeCl] (1) with Na[M(η⁵-C ₅H₅)(CO)₃]?2DME (M = Mo, W) afforded the metallogermylenes [{N(SiMe₃)C(Ph)C(SiMe₃)(C ₅H₄N-2)}Ge-M(η⁵-C₅H ₅)(CO)₃] (M = Mo (2), W (3)). Compounds 2 and 3 have been characterized by X-ray crystallography and NMR and IR spectroscopy. Structural analyses of compounds 2 and 3 are consistent with the presence of lone-pair electrons at the germanium(II) center. The Ge-Mo and Ge-W bond distances of 2.875(1) and 2.852(1) A are consistent with Ge-metal single bonds. The chlorogermylene 1 was also used in the synthesis of a substituted germylene, [{N(SiMe₃)C(Ph)C(SiMe₃)(C₅H₄N-2)} Ge(η¹-C₅H₅)] (4), by reaction with sodium cyclopentadienylide. The reaction of compound 1 with tris(pentafluorophenyl) borane led to the formation of a Lewis acid-base adduct, [{N(SiMe ₃)C(Ph)C(SiMe₃)(C₅H₄N-2)}Ge(Cl) →B(C₆F₅)₃] (5).

Full text of DOI:10.1021/om3007739

Article
pubs.acs.org/Organometallics
Synthesis and Structural Characterization of Metallogermylenes, Cp-
Substituted Germylene, and a Germanium(II)-Borane Adduct from
Pyridyl-1-azaallyl Germanium(II) Chloride
Wing-Por Leung,* Wang-Kin Chiu, and Thomas C. W. Mak
Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, People’s Republic of China
S
* Supporting Information
ABSTRACT: The reaction of [{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}GeCl] (1) with
Na[M(η5-C5H5)(CO)3]·2DME (M = Mo, W) afforded the metallogermylenes
[{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Ge-M(η5-C5H5)(CO)3] (M = Mo (2), W
(3)). Compounds 2 and 3 have been characterized by X-ray crystallography and
NMR and IR spectroscopy. Structural analyses of compounds 2 and 3 are consistent with
the presence of lone-pair electrons at the germanium(II) center. The Ge−Mo and Ge−
W bond distances of 2.875(1) and 2.852(1) Å are consistent with Ge−metal single
bonds. The chlorogermylene 1 was also used in the synthesis of a substituted germylene,
[{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Ge(η1-C5H5)] (4), by reaction with sodium
cyclopentadienylide. The reaction of compound 1 with tris(pentafluorophenyl)borane
led to the formation of a Lewis acid−base adduct, [{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-
2)}Ge(Cl)→B(C6F5)3] (5).
importance of heteroleptic germanium(II) chlorides in low-
valent germanium chemistry, and it is not surprising that there
is still intensive research activity focused on developing new
ligands for stabilization of the low-valent germnaium(II) center
in RGeCl or the continuation of the reactivity study of
chlorogermylenes.12
INTRODUCTION
■
In the last three decades, the synthesis of compounds with
group 14 elements in unusual or low oxidation states has
received much attention1 since the first isolation of a germylene
complex by Lappert and co-workers in 1974.2 In particular,
organohalogermylenes (RGeX, R = monoanionic ligand; X =
halogen atom), which constitute an interesting class of
compounds in group 14 metal chemistry, have drawn much
attention, as they are important precursors for the synthesis of
new low-valent germanium compounds.3 For example, Power4
and Tokitoh5 respectively reported the synthesis of 1,2-
diaryldigermynes by the reduction of the chlorogermylenes
supported by terphenyl ligands or the 1,2-diaryl-1,2-dibromo-
digermenes. Recently, Jones reported the synthesis of a
digermyne with a Ge−Ge single bond by reduction of amido
germanium(II) chloride,6 while the facile syntheses of Ge(I)
dimers from the reduction of different chlorogermylenes have
been reported by several research groups.7 In 2006, Driess and
co-workers documented the synthesis and isolation of a ylide-
like germylene by dehydrohalogenation of a chlorogermylene.8
By addition of AlH3·NMe3 or [K{B(Bui)3}H] to a β-
diketiminato germanium(II) chloride,9 a stable monomeric
terminal germanium(II) monohydride was synthesized by
Roesky, and the germanium(II) hydride has played an
important role in synthetic chemistry and the activation of
small molecules.10 In addition, the versatile chlorogermylenes
were also employed in the formation of unusual hetero-
bimetallic metal−metal bonded systems, which provide
valuable structural information on the metal complexes
supported by monodentate or bidentate ligands.11 The
aforementioned reports are only some highlights of the
Our group has recently reported the synthesis of a pyridyl-1-
azaallyl germanium(II) chloride, LGeCl (1) (L = N(SiMe3)-
C(Ph)C(SiMe3)(C5H4N-2)),13a and its reaction with chalco-
gens.13b We have also carried out reactivity studies of
compound 1, which gave novel lithium germinate [{(PhC
C)3Ge}3GeLi(Et2O)3] and Ge(II)−M(I) (M = Cu and Au)
adducts.13c In a recent communication, we reported the
synthesis of a pyridyl-1-azaallyl germanium(I) dimer and its
reaction with sulfur to afford a germadithiocarboxylic acid
anhydride.7d Further to these studies, herein we report the
reactivity studies of compound 1. This includes the reaction
with Na[M(η5-C5H5)(CO)3]·2DME (M = Mo, W; DME = 1,2-
dimethoxyethane), which afforded novel intramolecularly
donor-stabilized metallogermylenes. The salt elimination
reaction of 1 with sodium cyclopentadienylide (NaCp) and
the Lewis acid−base reaction of 1 with B(C6F5)3 will also be
described.
RESULTS AND DISCUSSION
■
Synthesis of Metallogermylenes. The pyridyl-1-azaallyl
germanium(II) chloride LGeCl (1) was prepared according to
the literature procedure.13a Treatment of 1 with 1 equiv of
Received: August 10, 2012
Published: September 14, 2012
© 2012 American Chemical Society
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Na[M(η5-C5H5)(CO)3]·2DME14 (M = Mo or W; DME = 1,2-
dimethoxyethane) in THF afforded compounds 2 and 3
(Scheme 1). The metallogermylenes 2 and 3 [{N(SiMe3)C-
(Ph)C(SiMe3)(C5H4N-2)}Ge-M(η5-C5H5)(CO)3] (M = Mo
or W) were isolated as dark red crystals.
observed at δ 122.12−156.08 ppm. The H and 13C NMR
signals are consistent with the solid-state structures of 2 and 3.
Two sharp singlets due to the SiMe3 groups are observed at δ
−0.20 and −0.14 ppm in the 1H NMR spectrum of compound
4. In addition, a sharp singlet is found at δ 6.07 ppm, which is
the signal for the protons from the Cp ring. Signals due to the
phenyl and pyridyl protons are observed at δ 7.28−8.47 ppm.
The 13C spectrum of 4 displays two singlets at δ 2.17 and 3.16
ppm, which are due to the carbons from the two SiMe3 groups.
Also, in the 13C spectrum, a sharp singlet is observed at δ
113.54 ppm, which corresponds to the carbons from the Cp
ring. The NMR signals suggest that the Cp ring in 4 is fluxional,
with the point of attachment of the Ge atom to the Cp ring
migrating rapidly from one carbon to another via a series of 1,2-
or 1,3-shifts of the Ge atom around the η1-C5H5 ring.15a,b
Therefore, only one signal is observed for the Cp ring in either
the 1H or 13C NMR spectra even at temperatures as low as −80
°C due to the low-energy barrier to the interconversion. The
fluxional behavior of the η1-C5H5 group has also been observed
for [Fe(η1-C5H5)(η5-C5H5)(CO)2]15b and [fac-(η1-C5H5)Re-
(CO)3(P(CH3)3)].15c
1
Scheme 1. Synthesis of Compounds 2−5
The 1H NMR spectrum of 5 displays two sharp singlets at δ
−0.15 and −0.10 ppm due to the two SiMe3 groups in
compound 5. Signals due to the phenyl and pyridyl protons are
observed at δ 7.38−8.72 ppm. The 13C spectrum of 5 displays
two sharp singlets at δ 1.74 and 2.83 ppm, which are due to the
carbons from the two SiMe3 groups. Signals due to the phenyl
and pyridyl carbons in the ligand backbone and the carbons
from B(C6F5)3 are observed at δ 120.44−149.80 ppm. The 11
B
NMR spectrum of 5 shows a broad signal at δ 2.80 ppm, which
shows a downfield shift in comparison to that of the
germanium(II) hydride−borane adduct supported by the
pyridyl-1-azaallyl ligand (δ −38.88 ppm).13c The signal also
shows a downfield shift when compared to those observed for
related complexes containing a Ge(II)−B bond. 11B NMR
chemical shifts for [{2,6-(NMe2)2C6H3}2Ge→BH3] (δ −35
ppm),16 [{HC(CMeNAr)2}GeH(BH3)] (δ −42 ppm; Ar = 2,6-
Pri2C6H3),17 and NHC→(Mes)2Ge→BH3 (δ −28.49 ppm;
NHC = [C{N(Pri)C(CH3)}2], Mes = 2,4,6-Me3C6H2)18 have
been reported.
X-ray Structure. The molecular structures of compounds 2
and 3 are shown in Figures 1 and 2. Selected bond distances
(Å) and angles (deg) are listed in Table 1. The Ge−Mo bond
distance of 2.875(1) Å in 2 is longer than that of 2.271−2.319
Å in the molybdenum−germylyne complexes reported by
groups of Power and Filippou.19 Theoretical calculations and
bonding analysis by Pandey’s research group revealed that the
π-bonding contributions in metallogermylenes are weaker than
those in metallogermylynes and that the σ-bonding contribu-
tions in the former compounds are stronger than those in the
latter.20 The Ge−Mo bond distance of 2.875(1) Å in 2 is also
longer than those reported for molybdenum−germylidene
complexes (2.402−2.537 Å)21 and the calculated Ge−Mo bond
distance of 2.695 Å for [MeGe-Mo(η5-C5H5)(CO)3].20a To the
best of our knowledge, there are no structurally characterized
molybdenum−germylene σ-complexes possessing a Ge(II)−
Mo single bond, although there are recent reports of iron−
germylenes of general formula RGe-Fe(η5-C5H5)(CO)2 by
Driess11h and Jones,11g respectively. Compound 2 is the first
structurally characterized hetero-bimetallic complex featuring a
Ge(II)−Mo σ-bond with the presence of a stereoactive lone-
pair at the germanium(II) center.
Synthesis of Heteroleptic Germylene and
Germanium(II)−Borane Adduct. The salt elimination
reaction with NaCp was performed, which afforded a
monomeric heteroleptic germylene, [{N(SiMe3)C(Ph)C-
(SiMe3)(C5H4N-2)}Ge(η1-C5H5)] (4). We have previously
shown that the reaction of 1 with group 11 metal iodides
afforded the corresponding Ge(II)−Cu(I) or −Au(I) Lewis
acid−base adducts.13c To investigate the Lewis base behavior of
1, compound 1 was treated with tris(pentafluorophenyl)borane,
B(C6F5)3. This reaction afforded the adduct [{N(SiMe3)C-
(Ph)C(SiMe3)(C5H4N-2)}Ge(Cl)→B(C6F5)3] (5) (Scheme
1).
Spectroscopic Properties. Compounds 2−5 were isolated
as dark red or yellow crystalline solids that decompose readily
upon contact with air or moisture. They show good solubility in
THF, ether, and toluene but are sparingly soluble in hexane.
1
The H NMR spectra of compounds 2 and 3 show a similar
pattern. The singlets due to the two SiMe3 groups in 2 are
observed at δ 0.12 and 0.15 ppm, and those for 3 are observed
at δ 0.19 and 0.25 ppm, respectively. Two singlets are found
1
respectively at δ 5.23 and 5.12 ppm in the H NMR spectra of
compounds 2 and 3, which are due to the protons from the Cp
rings coordinated to the molybdenum and tungsten centers.
The 13C NMR spectra of compounds 2 and 3 are similar. The
singlets due to the carbons of the two SiMe3 groups in 2 are
observed at δ 2.10 and 2.88 ppm, while those for 2 are observed
at δ 2.68 and 3.55 ppm, respectively. Signals due to the carbons
from the Cp rings are observed at δ 81.65 and 82.38 ppm,
respectively. Signals due to the pyridyl and phenyl carbons in 2
are observed at δ 126.32−154.08 ppm, while those for 3 are
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Table 1. Selected Bond Distances (Å) and Angles (deg) for
Compounds 2 and 3
[{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Ge-M(η5-C5H5)(CO)3]
M = Mo (2)
M = W(3)
Ge(1)−M(1)
Ge(1)−N(1)
Ge(1)−N(2)
N(1)−C(5)
N(1)−Ge(1)−M(1)
N(2)−Ge(1)−M(1)
N(2)−Ge(1)−N(1)
C(25)−M(1)−Ge(1)
2.875(1)
2.057(4)
1.940(3)
1.346(6)
107.3(1)
113.2(1)
88.7(1)
2.852(1)
2.011(4)
1.978(3)
1.353(6)
106.6(1)
115.9(1)
88.0(2)
73.6(2)
72.7(1)
angles at the Ge(1) atom is 309.2°, which is consistent with a
stereoactive lone-pair at the germanium(II) center. Similarly, in
the tungsten−germylene 3, the sum of the bond angles at the
Ge(1) atom being 310.5° is also consistent with the presence of
a lone-pair at the germanium(II) center. The distorted
structures of compounds 2 and 3 are obviously different from
those observed in the metallogermylyne complexes, which
show almost linear structures (bent angles at Ge range from
170.9(3)° to 178.9(2)o).11c,d,f,19 On the other hand, the N−
Ge−M angles in 2 and 3 are similar to those observed in the
nitrogen-stabilized iron−germylenes.11g,h
Figure 1. Molecular structure of [{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-
2)}Ge-Mo(η5-C5H5)(CO)3] (2). Hydrogen atoms are omitted for
clarity; 30% thermal ellipsoids are shown.
The molecular structure of 4 is depicted in Figure 3, and
selected bond distances and angles are shown in Table 2.
Figure 2. Molecular structure of [{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-
2)}Ge-W(η5-C5H5)(CO)3] (3). Hydrogen atoms are omitted for
clarity; 30% thermal ellipsoids are shown.
There is only one reported example of a structurally
characterized tungsten−germylene σ-complex that has a Ge−
W single bond of 2.681(3) Å.11c The Ge−W bond distance of
2.852(1) Å in 3 is significantly longer than those reported for
tungsten−germylidene complexes (2.402−2.632 Å)22 and
tungsten−germylyne complexes (2.277−2.338 Å).11c,d,f,19a,b
The Mo−CCO and Mo−Cη5‑C5H5 distances (av 1.952(6),
2.358(6) Å) in compound 2 are similar to those observed in the
structure of the dimer {Mo(η5-C5H5)(CO)3}2 (av 1.977(3),
2.338(3) Å). The W−CCO and W−Cη5‑C5H5 distances (av
1.955(6), 2.351(6) Å) in compound 3 are also very similar to
the corresponding ones in the dimer {W(η5-C5H5)(CO)3}2 (av
1.976(6), 2.342(6) Å).23 In compound 2, the germanium(II)
center Ge(1) is bonded to one molybdenum atom Mo(1) and
two nitrogen atoms N(1) and N(2). The sum of the bond
Figure 3. Molecular structure of [{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-
2)}Ge(η1-C5H5)] (4). Hydrogen atoms are omitted for clarity; 30%
thermal ellipsoids are shown.
Compound 4 is a monomeric heteroleptic germylene. The
germanium(II) center in compound 4 adopts a trigonal-
pyramidal geometry with the germanium atom Ge(1) bonding
with one carbon atom, C(20), and two nitrogen atoms, N(1)
and N(2). The Ge(1)−C(20) bond distance of 2.115(3) Å in 4
is comparable to those of 2.040(3) and 2.004(4) Å in
[{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Ge(But)] and [{N-
(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Ge(CCPh)].13c The
Ge(1)−C(20) distance is also comparable to those observed
in the monomeric germanium(II) alkynyl compounds RGe-
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GeH(BH3)] (2.015(7) Å).17 It is noteworthy that the above-
mentioned Ge(II)−borane adducts were formed by using the
corresponding chlorogermylenes as the starting material.
Homoleptic germylenes acting as a Lewis base toward boranes
have also been demonstrated in [{2,6-(NMe2)2C6H3}2Ge→
BH3]16 and a NHC-stabilized dimesitylgermylene−borane
adduct.18
The Ge(1) of compound 5 adopts a tetrahedral geometry
with a Ge−Namide bond distance of 1.860(2) Å. The distance is
shorter when compared to the corresponding bond distance of
compound 1 (1.920(2) Å). The shortening of the Ge−Namide
bond is probably due to the fact that the germanium(II) center
in 5 forms a donor−acceptor interaction with the borane, and
so the electron density at the germanium center is diminished
as compared to compound 1. Similar shortening of the Ge−
Namide bonds is also observed in the Ge(II)−Cu(I) or −Au(I)
Lewis acid−base adduct with 1 (1.888(8), 1.884(2) Å).13c
Table 2. Selected Bond Distances (Å) and Angles (deg) for
Compounds 4 and 5
[{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Ge(η1-C5H5)] (4)
Ge(1)−N(1)
Ge(1)−C(20)
N(2)−Ge(1)−N(1)
N(1)−Ge(1)−C(20)
C(24)−C(20)−Ge(1)
2.052(2)
2.115(3)
86.2(1)
93.5(1)
96.1(2)
Ge(1)−N(2)
N(1)−C(1)
N(2)−Ge(1)−C(20)
C(21)−C(20)−Ge(1)
C(21)−C(20)−C(24)
1.963(2)
1.351(3)
98.2(1)
96.4(2)
105.5(3)
[{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Ge(Cl)→B(C6F5)3] (5)
Ge(1)−B(1)
Ge(1)−N(1)
N(1)−Ge(1)−B(1)
Cl(1)−Ge(1)−B(1)
N(1)−Ge(1)−Cl(1)
2.186(3)
1.981(3)
110.3(1)
104.3(1)
98.7(1)
Ge(1)−Cl(1)
Ge(1)−N(2)
N(2)−Ge(1)−B(1)
N(2)−Ge(1)−N(1)
N(2)−Ge(1)−Cl(1)
2.171(1)
1.860(2)
139.4(1)
90.4(1)
106.6(1)
(CC)R′ (1.976(4)−2.017(2) Å; R = (But)2ATI (ATI =
aminotroponiminate), methylaminomethyl-m-xylyl, HC{C-
(Me)N(2,6-Pri2C6H3)}2; R′ = H, Ph, (C5H4)Fe(C5H5)),12g,24
but significantly longer than that of the germanium(II) alkynyl
complexes (1.911(2), 1.907(2) Å) supported by terphenyl
ligands due to the possible long-range conjugation of the
alkynyl groups through the Ge−Ge linkage.12e The C(21)−
C(22) and C(23)−C(24) distances (1.353(5), 1.346(5) Å) in
4 are typical for a carbon−carbon double bond. Other bond
distances within the ligand backbones are comparable to those
in compound 1.13a
CONCLUSIONS
■
In this paper, we have reported the synthesis and structural
characterization of novel nitrogen-stabilized molybdenum- and
tungsten-germylenes 2 and 3 from the facile reaction of pyridyl-
1-azaallyl germanium(II) chloride (1) with Na[M(η5-C5H5)-
(CO)3]·2DME (M = Mo, W). The salt elimination reaction of
1 with NaCp afforded the monomeric heteroleptic germylene
[{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Ge(η1-C5H5)] (4).
Furthermore, the reaction of 1 with B(C6F5)3 led to the
formation of the Lewis acid−base pair [{N(SiMe3)C(Ph)C-
(SiMe3)(C5H4N-2)}Ge(Cl)→B(C6F5)3] (5).
The molecular structure of 5 is depicted in Figure 4, and
selected bond distances and angles are listed in Table 2. The
EXPERIMENTAL SECTION
■
General Procedures. All manipulations were carried out under an
inert atmosphere of dinitrogen gas by standard Schlenk techniques.
Solvents were dried over and distilled from Na (Et2O, toluene, and
THF). Compound 1 [{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}-
GeCl]13a and Na[M(η5-C5H5)(CO)3]·2DME14 (M = Mo or W;
DME = 1,2-dimethoxyethane) were prepared according to the
literature procedures. Sodium cyclopentadienylide and tris-
(pentafluorophenyl)borane were purchased from Aldrich Chemical
Co. and used without further purification. The NMR spectra were
recorded on Bruker 400 spectrometers and recorded in THF-d . The
̈
8
chemical shifts δ are relative to SiMe4 for 1H and 13C{1H} and
BF3·OEt2 for 11B{1H} NMR. Elemental (C, H, N) analyses were
performed by MEDAC Ltd., United Kingdom. IR spectra were
recorded with a Nicolet Impact 420 FT-IR spectrometer.
Synthesis of [{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Ge-Mo(η5-
C5H5)(CO)3] (2). A solution of 1 (0.81 g, 1.81 mmol) in THF (25
mL) was added slowly to a stirring solution of Na[Mo(η5-
C5H5)(CO)3]·2DME (0.82 g, 1.83 mmol) in THF (30 mL) at −90
°C. The resultant dark red mixture was warmed to ambient
temperature and stirred for 12 h. The solution was filtered, and the
volatiles were removed under reduced pressure. The dark red residue
was extracted with Et2O. After filtration, concentration of the filtrate
afforded dark red crystals. Yield: 0.72 g (61%). Mp: 162 °C. Anal.
Found: C 49.38, H 5.01, N 4.76. Calcd for C27H32GeMoN2O3Si2: C
49.34, H 4.91, N 4.26. 1H NMR (THF-d8): δ 0.12 (s, 9H, SiMe3), 0.15
(s, 9H, SiMe3), 5.23 (s, 5H, C5H5), 6.67 (d, 1H, Py, 2JH−H′ = 6.2 Hz),
Figure 4. Molecular structure of [{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-
2)}Ge(Cl)→B(C6F5)3] (5). Hydrogen atoms are omitted for clarity;
30% thermal ellipsoids are shown.
2
2
7.04 (t, 1H, Py, JH−H′ = 6.2 Hz), 7.20 (d, 1H, Py, JH−H′ = 6.2 Hz),
Ge−B distance of 2.186(3) Å in 5 is similar to that of 2.156(4)
Å in [{Me2ATI}GePh(BPh3)] (ATI = aminotroponiminate).25
However, it is longer than that of 2.064(6) Å in the pyridyl-1-
azaallyl germanium(II) hydride−borane adduct [{N(SiMe3)C-
(Ph)C(SiMe3)(C5H4N-2)}GeH(BH3)] due to the increased
bulkiness of the substituent at the B(1) center.13c Similary, the
Ge(1)−B(1) bond is also longer than that in the β-diketiminato
germanium(II) hydride−borane adduct [{HC(CMeNAr)2}-
2
7.31−7.38 (m, 5H, Ph), 8.03 (t, 1H, Py, JH−H’ = 6.2 Hz). 13C{1H}
NMR (THF-d8): δ 2.10, 2.88 (SiMe3), 81.65 (C5H5), 119.19
(CSiMe3), 126.32, 128.17, 129.89, 132.44, 134.12, 136.58, 138.82,
139.12, 141.35, 146.71, 154.08 (Ph and Py), 166.31 (NCPh), 211.33
(CO). IR (KBr, cm−1): ν (CO) 2005.95 (s), 1927.33 (s), 1889.19 (s).
Synthesis of [{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Ge-W(η5-
C5H5)(CO)3] (3). A solution of 1 (0.65 g, 1.45 mmol) in THF (20
mL) was added slowly to a stirring suspension of Na[W(η5-
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C5H5)(CO)3]·2DME (0.81 g, 1.51 mmol) in THF at −90 °C. The
resultant dark red mixture was warmed to ambient temperature and
stirred for 12 h. The solution was filtered, and the volatiles were
removed under reduced pressure. The dark red residue was extracted
with toluene. After filtration, addition of 5 mL of THF and
concentration of the filtrate afforded dark red crystals. Yield: 0.61 g
(56%). Mp: 198 °C. Anal. Found: C 43.72, H 4.67, N 4.03. Calcd for
C27H32GeWN2O3Si2: C 43.52, H 4.33, N 3.76. 1H NMR (THF-d8): δ
0.19 (s, 9H, SiMe3), 0.25 (s, 9H, SiMe3), 5.12 (s, 5H, C5H5), 6.95 (d,
AUTHOR INFORMATION
Corresponding Author
*E-mail: kevinleung@cuhk.edu.hk.
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Research Grants Council of
The Hong Kong Special Administrative Region, China (Project
No. CUHK 402210).
2
2
1H, Py, JH−H′ = 6.8 Hz), 7.09 (t, 1H, Py, JH−H′ = 6.8 Hz), 7.27 (d,
2
1H, Py, JH−H′ = 6.8 Hz), 7.38−7.45 (m, 5H, Ph), 8.13 (t, 1H, Py,
2JH−H′ = 6.8 Hz). 13C{1H} NMR (THF-d8): δ 2.68, 3.55 (SiMe3),
82.38 (C5H5), 114.91 (CSiMe3), 122.12, 124.36, 127.16, 131.44,
132.98, 135.57, 137.14, 138.93, 143.93, 146.62, 156.08 (Ph and Py),
168.35 (NCPh), 218.90 (CO). IR (KBr, cm−1): ν (CO) 2001.78 (s),
1943.86 (s), 1876.65 (s).
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Synthesis of [{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}Ge(η1-C5H5)]
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̈
2
2
7.87 (t, 1H, Py, JH−H′ = 6.5 Hz), 8.47 (d, 1H, Py, JH−H′ = 6.5 Hz).
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1
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ASSOCIATED CONTENT
■
S
* Supporting Information
X-ray crystallographic files in CIF format for the structure
determinations of compounds 2−5 are available free of charge
via the Internet at http://pubs.acs.org.
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