Metal-template-controlled stabilization of β-functionalized isocyanides

Article abstract of DOI:10.1021/om301067v

Reaction of 2-azidoethyl isocyanide 1, 2-azidophenyl isocyanide 2, or 2-nitrophenyl isocyanide 3 with complexes [Mo(CO)₃(dppe)(py)] [4] or [W(CO)₃(dppe)(Ni-≡CCH₃)] [5] yields the isocyanide complexes [Mo(CO)₃(dp

Full text of DOI:10.1021/om301067v

Article
pubs.acs.org/Organometallics
Metal-Template-Controlled Stabilization of β‑Functionalized
Isocyanides
A. Carolin Dumke, Tania Pape, Jutta Kosters, Kai-Oliver Feldmann, Christian Schulte to Brinke,
̈
and F. Ekkehardt Hahn*
Institut fur Anorganische und Analytische Chemie and NRW Graduate School of Chemistry, Westfalische Wilhelms-Universitat
̈
̈
̈
Munster, Corrensstrasse 30, D-48149 Munster, Germany
̈
̈
S
* Supporting Information
ABSTRACT: Reaction of 2-azidoethyl isocyanide 1, 2-azidophenyl isocyanide 2, or 2-
nitrophenyl isocyanide 3 with complexes [Mo(CO)3(dppe)(py)] [4] or [W-
(CO)3(dppe)(NCCH3)] [5] yields the isocyanide complexes [Mo(CO)3(dppe)-
(CNR)] ([6]: CNR = 1; [12]: CNR = 2; [13]: CNR = 3) and
[W(CO)3(dppe)(CNR)] ([7]: CNR = 1; [14]: CNR = 2; [15]: CNR = 3).
Reduction of the nitro or azido groups attached to the isocyanide ligands by Zn/NH4Cl
(azidoethyl or azidophenyl isocyanides) or Raney-nickel/hydrazine hydrate (nitrophenyl
isocyanide) yields exclusively the complexes bearing the 2-amino-functionalized
isocyanides. The normally unstable 2-amino-functionalized isocyanides are stabilized by
M→CNR back-bonding, which deactivates the isocyanide carbon atom for an
intramolecular nucleophilic attack by the primary amine.
Scheme 1. Reactions of 2-Hydroxyethyl Isocyanide with
Selected Metal Complexes
1. INTRODUCTION
Protic heterocarbene ligands can be generated at suitable metal
templates from coordinated isocyanide ligands. Such coordi-
nated isocyanides are attacked by protonated Lewis bases HX
(X = OR, RNH) in a nucleophilic reaction that leads to carbene
complexes.1 A large number of complexes bearing acyclic
carbenes2 have been generated by this method.3
The use of complexes bearing functionalized isocyanides
containing both the isocyanide group and the nucleophile in
the same molecule gives access to complexes with heterocyclic
carbene ligands via an intramolecular 1,2-addition across the
CNR triple bond.4 While the functionalized isocyanides can
be generated in a template approach,5 their direct use is much
more facile.
Hydroxyalkyl isocyanides, such as 2-hydroxyethyl isocyanide,
are stable molecules but are known to become activated on
contact with selected metal ions where they isomerize to N,O-
heterocycles. Even traces of Zn2+ or Pd2+ can initiate a vigorous
exothermic reaction.6 Fehlhammer et al. used this type of
cyclization for the metal-template-controlled generation of
NH,O-heterocarbene ligands (Scheme 1). The intramolecular
cyclization reaction is strongly dependent on the template
metal complex. At some zerovalent metal centers, such as
{M(CO)5} (M = Cr, Mo, W), the isocyanide ligand
coordinates to the metal atom to give complexes of type A.
Here, the isocyanide ligand is not sufficiently activated for a
complexes of type B bearing the oxazolidin-2-ylidenen ligand
are formed by an intramolecular cyclization reaction.8
A substitution of the ethyl spacer in 2-hydroxyethyl
isocyanide for a 1,2-phenyl group leads to 2-hydroxyphenyl
isocyanide. This ligand, however, contains the isocyanide and
the hydroxyl group in the same molecule, and these two groups
are also arranged in one plane, facilitating an intramolecular
cyclization. Consequently and contrary to 2-hydroxyethyl
isocyanide, 2-hydroxyphenyl isocyanide is not stable in the
free state but spontaneously cyclizes to yield benzoxazole even
in the absence of any metal ions9 (Scheme 2). The benzoxazole
subsequent cyclization reaction (free ligand: νCN
̃
2153 cm−1;
[Cr(CO)5(CNCH2CH2OH]: νCN
̃
2178 cm−1; [Mo-
(CO)5(CNCH2CH2OH]: νCN
2164 cm−1).7 However, if the
̃
metal atom is electron deficient, like in the case of Pd2+ or Pt2+,
Received: November 12, 2012
Published: December 21, 2012
isocyanide complexes cannot be isolated and, instead,
© 2012 American Chemical Society
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the isocyanide prevents the intramolecular cyclization and
allows the characterization of complexes bearing the elusive β-
amino functionalized isocyanide ligands Scheme 3). Such
Scheme 2. Reactions of 2-Hydroxyphenyl Isocyanide
Scheme 3. Reactions of β-Functionalized Ethyl and Phenyl
Isocyanides
heterocycle opens up upon treatment with n-BuLi, and the
isocyanide obtained in this way can be stabilized as 2-
trimethylsiloxyphenyl isocyanide by reaction with trimethylsilyl
chloride.10 Coordination of trimethylsiloxyphenyl isocyanide to
different metal complexes leads to isocyanide complexes, which,
upon cleavage of the O−SiMe3 bond, react to yield complexes
with a 2-hydroxyphenyl isocyanide (C)11 or a benzoxazolin-2-
ylidene ligand (D,12 Scheme 2). As in the case of the 2-
hydroxyethyl isocyanide, the final outcome of the reaction is
determined by the electronic situation at the complex fragment.
Stabilization of the freely unstable 2-hydroxyphenyl isocyanide
in complexes of type C has been achieved at electron-rich
complex fragments that are engaged in strong M→CNR
back-bonding, thereby deactivating the isocyanide for an
intramolecular nucleophilic attack by the hydroxyl group.
Occasionally, an equilibrium between complexes of types C and
D has been observed.13
The amine-substituted derivatives of 2-hydroxyethyl iso-
cyanide (2-aminoethyl isocyanide) and 2-hydroxyphenyl
isocyanide (2-aminophenyl isocyanide) are not stable as free
molecules and immediately cyclize to give, for example,
benzimidazole. As in the case of 2-hydroxyphenyl isocyanide
(Scheme 2), the β-amino-substituted isocyanides can only be
generated in a template-controlled approach at suitable metal
centers. We have used 2-azidoethyl isocyanide 1, 2-azidophenyl
isocyanide 2, and 2-nitrophenyl isocyanide 3 as synthons for 2-
aminoethyl isocyanide and 2-aminophenyl isocyanide, respec-
tively. Coordination of the isocyanides 1−3, followed by
reduction of the azido or nitro groups, leads to complexes
bearing β-amino-functionalized isocyanides (E, F), which, in all
cases described so far, are unstable and rapidly undergo an
intramolecular cyclization reaction to give the complexes
bearing saturated14 (G) or benzannulated15 NH,NH-NHC
ligands (H).
complexes have not been isolated so far, but some related α,ω-
aminoalkyl isocyanides featuring a (CH2)3 or (CH2)4 alkyl
chain between the amine and the isocyanide groups also do not
cyclize to the six- or seven-membered NHCs at the template
metal studied.16 Previous reports on the isolation of the
{Cr(CO)5}complex of β-aminophenyl isocyanide17 must be
taken with caution as this complex has been shown
unequivocally by X-ray diffraction to react with cyclization of
the β-aminophenyl isocyanide to give the complex with an
NH,NH-NHC ligand.15a
2. RESULTS AND DISCUSSION
The stabilization of 2-hydroxyalkyl7 and -phenyl isocya-
nides11,13 has been achieved at electron-rich transition-metal
complex fragments where the M→CNR back-bonding
prevents the intramolecular nucleophilic attack of the hydroxyl
group at the isocyanide carbon atom. The analogous
stabilization of 2-aminoethyl or -phenyl isocyanides has not
been demonstrated yet, which is most likely due to the
enhanced nucleophilicity of the amino group in comparison to
the hydroxyl group. We have tried to identify such metal
templates that would provide enough electron density and M→
CNR back-bonding to stabilize the reactive β-amino-
functionalized isocyanide ligands. Since even complex frag-
ments of zerovalent transition metals, such as {M(CO)5} (M =
Cr, Mo, W), allowed the cyclization of coordinated 2-
aminoethyl isocyanide14 and 2-aminophenyl isocyanide,15 we
envisaged that the substitution of some of the π-acceptor
carbonyl ligands for strong σ-donor and weak π-acceptor
ligands might change the electronic situation at the metal atom
sufficiently to allow the stabilization of coordinated β-amino-
functionalized isocyanides. The chelating diphosphine ligand
dppe was selected for this task.
We became interested in the intermediary complexes bearing
the β-amino-functionalized isocyanides. In this contribution, we
describe electron-rich complexes of types E and F, where
enhanced M→CNR back-bonding from the metal atom to
We have prepared complex [Mo(CO)3(dppe)(py)] [4] from
[Mo(CO)3(py)3]18 and dppe. This complex was not purified
but used for subsequent reactions as obtained. Complex
[W(CO)3 (dppe)(NCCH3)] [5] was prepared from [W-
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(CO)6] and dppe in acetonitrile and isolated as described.19
Both complexes [4] and [5] react with 2-azidoethyl isocyanide
114b,d with substitution of the nitrogen donor to yield the
isocyanide complexes [6] and [7] (Scheme 4). The isocyanide
The formation of the molybdenum complex [6] was
corroborated by an X-ray diffraction analysis (Figure 1, top).
Scheme 4. Stabilization of 2-Aminoethyl Isocyanide at Metal
Templates
Figure 1. Molecular structures of [6] (top) and [6]2 in [6]2·2CH2Cl2
(bottom, 50% displacement ellipsoids, hydrogen atoms and solvent
molecules have been omitted; complex [6]2 resides on a crystallo-
graphic inversion center). Selected bond lengths (Å) and angles (deg)
for [6], [[6]2·2CH2Cl2]: Mo−C1 2.140(2) [2.125(3)], C1−N1
1.163(2) [1.151(3)], N1−C2 1.434(2) [1.439(3)], C3−N2 1.476(3)
[1.464(4)], N2−N3 1.210(3) [1.267(4)], N3−N4 1.333(3)
[1.089(4)]; Mo−C1−N1 174.55(15) [178.5(2)], C1−N1−C2
169.7(2) [177.7(3)], N2−N3−N4 171.1(3) [170.4(4)].
The structure analysis revealed the expected slightly bent
arrangement of the isocyanide group (angle C1−N1−C2
169.7(2)°), which is most likely caused by M→CNR back-
bonding.1 The N2−N3−N4 angle of the azide group measures
171.1(3)°.
Beside the expected mononuclear complex [6], the dinuclear
complex [6]2 was found as a side product upon crystallization
of [6]. The X-ray diffraction analysis of [6]2·2CH2Cl2 revealed
the unexpected coordination of dppe as a bridging ligand.
Normally, the coordination chemistry of dppe is dominated by
the formation of stable complexes featuring five-membered
chelate rings that are thermodynamically favored in comparison
to a bridging coordination mode. In fact, there is only one
report describing the M(μ-dppe)2M structural motif. Homo-
and heterobimetallic complexes of the type [(CO)4M(μ-
dppe)M′(CO)4] (M, M′ = Cr, Mo, W) have been prepared
in a base-catalyzed template synthesis starting from equimolar
amounts of complexes of types [M(CO)4(PPh2H)2] and
[M(CO)4(PPh2CHCH2)2].21 In the 31P{1H} NMR spectra,
the resonance for the dinuclear complex [(CO)4Mo(μ-
dppe)2Mo(CO)4] (s, δ = 29.6 ppm) differs significantly from
that for the mononuclear chelate complex [Mo(CO)4(dppe)]
(s, δ = 55.4 ppm). Since the 31P{1H} NMR spectrum of [6]
revealed only one resonance in the range typical for
mononuclear complexes (δ = 55.48 ppm), we assume that
[6]2 is obtained as a side product during the crystallization of
[6]. Equivalent metric parameters are similar for [6] and [6]2.
CNR resonances in the 13C{1H} NMR spectra were
observed at δ = 167.4 ppm for [6] and at δ = 159.5 ppm for
2
[7]. The resonance for [6] shows JPC(isocyanide) coupling, but
lacks the JCN coupling found for the free ligand 114b and for
1
related aliphatic isocyanides.20 The lack of 1JCN coupling can be
taken as an indication for metal coordination of the isocyanide
ligand.20 The isocyanide stretching vibration for [6] was
observed at ν
̃ ̃
= 2135 cm−1 and at ν = 2129 cm−1 for [7]. These
values represent a shift of 17 and 23 cm−1, respectively, to lower
wavenumbers upon metal coordination compared to the free
ligand 1 (ν
̃
= 2152 cm−1).14b The shift to lower wavenumbers
indicates the desired strong back-bonding from the metal atom
to the isocyanide ligand and a weakening of the CNR bond
of the isocyanide. It was hoped for that the enhanced M→C
NR back-bonding in [6] and [7] proved sufficient to prevent an
intramolecular nucleophilic attack after reduction of the azido
function of the ligand to a primary amine.
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Next, the azido functions in [6] and [7] were reduced to
primary amines (Scheme 4). Previous studies had shown that a
mixture of zinc powder, ammonium chloride, and water in
methanol is particularly useful for this reduction and does not
interfere with the central metal atom.15e,22 The reduction
yielded the ammonium salts [8]X and [9]X (X− = Cl−,
0.5[ZnCl4]2−) as isolable materials, containing a mixture of two
different counterions. Mass spectrometry (ESI and MALDI,
negative ions) of these compounds provided evidence for the
presence of both, chloride and tetrachlorozincate counterions.
The amount of these anions could not be determined, allowing
only a rough estimate of the yield in this reaction step.
be expected for an isocyanide ligand stabilized by Mo→CNR
back-bonding. The back-bonding to the isocyanide also
manifests itself in two short Mo−CO (trans to P, 1.976(2)
and 1.979(2) Å) and a long Mo−CO (trans to CNR,
1.992(2) Å) bond.
Next, we studied the complexes containing the phenyl
isocyanides 2 and 3 (Scheme 5). Reduction of the azido or
Scheme 5. Stabilization of 2-Aminophenyl Isocyanide at
Metal Templates
Treatment of complexes [8]X and [9]X with sodium
hydroxide in methanol finally yielded complexes [10] and
[11] bearing the 2-aminoethyl isocyanide ligand. No indication
for the formation of an equilibrium between the isocyanide and
the NHC complex was observed. Complexes [10] and [11] are
the first examples for which the normally favored intra-
molecular cyclization of 2-aminoethyl isocyanide to the
NH,NH-NHC ligand has been suppressed. Instead, the reactive
isocyanides are stabilized at the metal template.
Complexes [10] and [11] have been characterized
spectroscopically. The IR spectra show no absorptions due to
the N3 group anymore, while the wavenumbers for the CNR
stretching vibrations have been detected at ν
̃
= 2133 cm−1 (for
[10]) and ν
̃
= 2126 cm−1 (for [11]). These absorptions are
shifted only marginally toward lower wavenumbers in
comparison to the azide complexes [6] and [7]. In addition,
̃ ̃
new absorptions at ν =
= 3441 and 3396 cm−1 (for [10]) and ν
3447 and 3363 cm−1 (for [11]) were observed, which have
been assigned to the NH2 group. The 13C{1H} NMR spectra
exhibit the resonance for the isocyanide carbon atom at δ =
164.0 (for [10]) and at δ = 156.0 ppm (for [11]), respectively.
1
The H NMR spectra feature the resonances for the amine
protons at δ = 0.45 ppm for [10] and at δ = 0.61 ppm for [11].
These signals are shifted slightly high field in comparison to
free aliphatic primary amines.23
Formation of the 2-aminoethyl isocyanide complex [10] was
confirmed by an X-ray diffraction analysis. Suitable single
crystals were obtained by slow diffusion of diethyl ether into a
saturated solution of [10] in dichloromethane. The molecular
structure of [10] is depicted in Figure 2 (the ethyl spacer
between the CN and NH2 groups is disordered over two
position, only one of which is depicted). The isocyanide ligand
features no unusual metric parameters. The C1−N1−C2 bond
angle (171.4(4°) deviates significantly from linearity, as would
nitro functions of the coordinated isocyanide ligands would
lead to complexes bearing the 2-aminophenyl isocyanide, a
ligand not known in the free state as it immediately cyclizes to
yield benzimidazole. The reaction of 2-azidophenyl isocyanide
2 with complexes [4] and [5] yielded the isocyanide complexes
[12] and [14], respectively. These complexes, however, are not
stable enough to be isolated in a pure form. Generally, aromatic
isocyanides are less nucleophilic than their aliphatic analogues,
which might contribute to the instability of complexes [12] and
[14]. The crude reaction products were, therefore, used for the
subsequent reduction of the azido function. The related
complexes bearing the 2-nitrophenyl isocyanide [13] and
[15] are more stable and were isolated and spectroscopically
characterized.
Figure 2. Molecular structure of [10] (50% displacement ellipsoids;
hydrogen atoms have been omitted). Selected bond lengths (Å) and
angles (deg): Mo−C1 2.157(2), Mo−C4 1.976(2), Mo−C5 1.979(2),
Mo−C6 1.992(2), C1−N1 1.139(3); Mo−C1−N1 176.0(2), C1−
N1−C2 171.4(4).
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Whereas the 1H and 13C{1H} NMR spectra of [13] and [15]
differ only slightly, the resonances in the 31P{1H} NMR spectra
vary significantly ([13]: δ = 56.45 ppm; [15]: δ = 40.60 ppm,
1JPW = 225.3 Hz). The absorption for the CNR stretching
complexes of the type [M(CO)5(3)], confirming previous
observations that metric parameters associated with isocyanide
ligands are less informative than spectroscopic data in the
assessment of the bonding situation.24
Reduction of the functional groups of the isocyanide ligands
in [12]−[15] was achieved with Zn/NH4Cl/H2O for the 2-
azidophenyl isocyanide complexes or with Raney nickel/
hydrazine hydrate for the 2-nitrophenyl isocyanide complexes.
This led to complexes [16] and [17], respectively, bearing the
2-aminophenyl isocyanide ligand (Scheme 5). Clearly, the
electronic situation and the M→CNR back-bonding in these
complexes prevented the ubiquitous cyclization to the
benzannulated NH,NH-NHC ligand.15
vibration was detected at ν
̃
= 2063 cm−1 for complex [13] and
at ν
wavenumbers compared to the free 2-nitrophenyl isocyanide
315b (ν = 2129 cm−1) by Δν ≈ 70 cm−1 indicate that
̃
= 2059 cm−1 for [15]. These values and the shift to lower
̃
̃
coordination of 3 in the electron-rich complexes [13] and [15]
leads to enhanced M→CNR back-bonding and concurrent
deactivation of the isocyanide for a nucleophilic attack. The
drop in the wavenumber upon metal coordination is even
stronger than that observed for the similar complexes [6] and
Complexes [16] and [17] were studied by NMR and IR
̃
[7] bearing the aliphatic 2-azidoethyl isocyanide ligand (Δν ≈
20 cm−1), which can be attributed to the generally better π-
acceptor properties of aromatic isocyanides.
spectroscopy. The IR spectra showed the isocyanide stretching
vibrations at ν
addition to two absorptions at high wavenumbers ([16]: ν
3484 and 3394 cm−1; [17]: ν = 3482 and 3389 cm−1), which
̃ ̃
= 2097 cm−1 ([16]) or ν = 2093 cm−1 ([17]) in
̃
=
In addition, complexes [13] and [15] were characterized by
X-ray diffraction studies. Suitable crystals of [13]·THF and
[15]·Et2O were obtained by slow evaporation of the solvent
from solutions of the complexes in THF and Et2O, respectively.
The molecular structures of [13] and [15] are depicted in
Figure 3. The molecular structure determinations confirmed
̃
were assigned to the stretching vibrations of the NH2 groups.
The resonances for the isocyanide carbon atoms were found at
δ = 177.1 ppm for [16] and at δ = 169.3 ppm for [17] (in
[D8]THF.
Single crystals of [16] and [17] were obtained by
evaporation of the solvent from a saturated dichloromethane
solution of [16] or a saturated THF solution of [17]. The
molecular structures of [16] and [17] are depicted in Figure 4.
Figure 3. Molecular structure of [13] in [13]·THF (top) and [15] in
[15]·Et2O (bottom, 50% displacement ellipsoids; hydrogen atoms
have been omitted). Selected bond lengths (Å) and angles (deg) for
[13], [15]: M−C1 2.098(2) [2.080(3)], C1−N1 1.171(2) [1.173(4)];
M−C1−N1 174.3(2) [175.8(3)], C1−N1−C2 164.7(2) [167.1(3)].
Figure 4. Molecular structures of [16] (top) and [17] (bottom, 50%
displacement ellipsoids; hydrogen atoms, except for those bound to
N2, have been omitted). Selected bond lengths (Å) and angles (deg)
for [16], [17]: M−C1 2.129(2) [2.113(3)], C1−N1 1.161(3)
[1.161(4)]; M−C1−N1 176.0(2) [176.4(3)], C1−N1−C2 176.5(2)
[176.5(3)].
the expected connectivity. The change from molybdenum in
[13] to tungsten [15] does not lead to significantly different
metric parameters. In comparison to the related, but less
electron-rich complexes of the type [M(CO)5(3)] (M = Mo,
W),15b the enhanced back-bonding in [13] and [15] is reflected
in a further reduction of the C1−N1−C2 angles to 164.7(2)°
for [13] and 167.1(3)° for [15]. The enhanced ability of the
metal centers in [13] and [15] to engage in M→CNR back-
bonding also leads to a general shortening of the M−CO bonds
compared with complexes of the type [M(CO)5(3)]. Generally,
the metric parameters involving the isocyanide ligands in [13]
and [15] do not differ significantly from those observed in
The most significant differences in the metric parameters of the
2-nitrophenyl isocyanide complexes [13] and [15] and the 2-
aminophenyl isocyanide complexes [16] and [17] result from
the reduction of the π-acceptor character of 2-aminophenyl
isocyanide compared to 2-nitrophenyl isocyanide. As the
isocyanide ligands in [16] and [17] are weaker π acids, the
M−CNR bond lengths increase (for example, from 2.098(2)
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Table 1. IR Spectroscopic Data for Isocyanide Complexes
complex fragment
isocyanide ligand
compound
ν
̃
(NC) (cm−1
)
k(NC) (Nm1−
)
after reduction
Mo(CO)5
CNCH2CH2N3 1
CNCH2CH2N3 1
CNCH2CH2NH2
CNC6H4N3 2
[18]
[6]
2176
2135
2133
2077
2133
2063
2097
2187
2129
2126
2141
2075
2134
2059
2093
1803
1736
1733
1643
1733
1621
1675
1822
1726
1721
1746
1640
1734
1615
1668
ylidene
Mo(CO)3(dppe)
Mo(CO)3(dppe)
Mo(CO)3(dppe)
Mo(CO)5
isocyanide
[10]
[12]
15b
isocyanide
ylidene
CNC6H4NO2 3
CNC6H4NO2 3
CNC6H4NH2
Mo(CO)3(dppe)
Mo(CO)3(dppe)
W(CO)5
[13]
[16]
14b
isocyanide
CNCH2CH2N3 1
CNCH2CH2N3 1
CNCH2CH2NH2
CNC6H4N3 2
ylidene
W(CO)3(dppe)
W(CO)3(dppe)
W(CO)5
[7]
isocyanide
[11]
15a
ylidene
W(CO)3(dppe)
W(CO)5
CNC6H4N3 2
[14]
15b
isocyanide
ylidene
CNC6H4NO2 3
CNC6H4NO2 3
CNC6H4NH2
W(CO)3(dppe)
W(CO)3(dppe)
[15]
[17]
isocyanide
Å in [13] to 2.129(2) Å in [16]) and the isocyanide group
becomes more linear (angle C1−N1−C2 164.7(2)° in [13]
and 176.0(2)° in [16]).
bond, where intramolecular nucleophilic attack is prevented,
have been calculated. These values may prove useful in the
prediction of the course of reactions during the template-
controlled synthesis of NH,NH-NHC complexes from
isocyanide complexes.
Isocyanides act, similarly to CO, as σ-donor/π-acceptor
ligands. The reactivity of a coordinated isocyanide ligand is
significantly affected by the metal atom it coordinates to. This
reactivity can be related to the IR absorption frequency or the
force constants of the CNR bond.4a,13a The force constant
can be directly correlated with the positive charge at the CN
carbon atom and, therefore, to its sensibility for a nucleophilic
attack. We have calculated the force constants for the
isocyanides described in this contribution using the method
of Cotton and Kraihanzel25 with corrections for the mass
difference between CO and CN (Table 1; complex [Mo-
(CO)5(CN−CH2−CH2−N3)] [18] was prepared for
comparison only and was not used in reactivity studies).
The calculated force constants are not significantly different
for Mo and W complexes bearing an identical set of ligands and
isocyanide ligands. The substitution of two CO ligands in the
{M(CO)5} complex fragment for dppe leads to force constants
for the CNR bond that are significantly smaller than the ones
calculated for the pentacarbonyl complexes. This trend is
particularly visible for the complexes bearing the aromatic
isocyanide ligands. The substitution of two carbonyl ligands for
a dppe ligand leads to a significantly enhanced electron density
at the metal center and an enhanced propensity for M→C
NR back-bonding. Stabilization of the 2-amino-functionalized
aliphatic isocyanide ligands occurs if the force constant falls in a
range of k < 1733 N m−1. The force constant required for
stabilization of the aromatic 2-aminophenyl isocyanide (k <
1668 N m−1) is even smaller. These are limiting values, and not
only the deactivation of the isocyanide by back-bonding
(indicated by the NC force constant) but also the stability
of the resulting ylidene influences the course of the reaction.13a
4. EXPERIMENTAL SECTION
General Procedures. Caution! Aliphatic azides are high-energy-
density materials. Vigorous heating of 2-azidoethyl isocyanide can cause an
explosive decomposition, and appropriate care is advised when handling
organic azides. All manipulations were carried out under an argon
atmosphere using standard Schlenk techniques. Solvents were dried
1
and degassed by standard methods prior to use. H, 13C{1H}, and
31P{1H} NMR spectra were measured on Bruker AVANCE I 400,
Bruker AVANCE III 400, or Bruker AVANCE II 200 spectrometers.
Chemical shifts (δ) are given in parts per million using the residual
protonated solvent as an internal standard. Coupling constants are
expressed in hertz. Mass spectra were obtained with Orbitrap LTQ XL
(Thermo Scientific), MicroTof (Bruker Daltronics), Finnigan MAT95,
or Bruker Reflex IV MALDI TOF spectrometers. IR spectra were
recorded on a Bruker Vector 22 spectrometer. Compounds 2-
azidoethyl isocyanide 1,14b 2-azidophenyl isocyanide 2,15a 2-nitro-
phenyl isocyanide 3,15b [Mo(CO)3(py)3] [4],18 and [W-
(CO)4(dppe)]19 have been prepared as described in the literature.
Alternatively to the literature procedure,15b isocyanide 3 can be
prepared from 2-nitrophenyl formamide by using POCl3 as
dehydration agent. Complex [Mo(CO)3(dppe)(py)] [4] was
generated in situ from [Mo(CO)3(py)3] and dppe. Elemental analyses
for compounds with azido or nitro groups could not be obtained due
to their potentially explosive decomposition. Instead, HRMS data are
given in the Experimental Section.
[Mo(CO)3(dppe)(CNCH2CH2N3)] [6]. A solution of [Mo-
(CO)3(py)3] (200 mg, 0.48 mmol) in dichloromethane (20 mL)
was treated with dppe (191 mg, 0.48 mmol) and left to stir for 12 h at
ambient temperature. Subsequently, the solvent was removed in vacuo.
The residue (crude complex [4]) was suspended in THF (20 mL),
and to this was added dropwise a solution of 2-azidoethyl isocyanide 1
(56 mg, 0.58 mmol) in dichloromethane (10 mL). The reaction
mixture was heated under reflux for 3 h, followed by removal of the
solvent under reduced pressure. The crude reaction product was
purified by column chromatography on neutral alumina (4% H2O)
with dichloromethane/cyclohexane (2:1, v/v) as eluent to give [6] as a
3. CONCLUSIONS
We presented molybdenum and tungsten complexes of
aliphatic 2-aminoethyl isocyanide and aromatic 2-aminophenyl
isocyanide where the ubiquitous intramolecular nucleophilic
attack of the amino group at the isocyanide carbon atom has
been prevented by enhanced M→CNR back-bonding. This
allowed the isolation of complexes bearing the 2-amino-
functionalized isocyanides that are unknown molecules in the
free state. Limiting values for the force constants k of the CN
1
pale yellow solid. Yield: 250 mg (0.37 mmol, 77%). H NMR (400
MHz, CD2Cl2): δ 7.66 (m, 8H, Ph-Hortho), 7.38 (m, 12H, Ph-Hmeta and
Ph-Hpara), 2.96 (tt, 3J = 5.8 Hz, 5JPH = 1.5 Hz, 2H, CH2NC), 2.72 (t, 3J
= 5.8 Hz, 2H, CH2N3), 2.56 (m, 4H, CH2P). 13C{1H} NMR (101
2
2
MHz, CD2Cl2): δ 221.2 (dd, JPC(trans) = 28.5 Hz, JPC(cis) = 9.5 Hz,
COeq), 215.6 (t, 2JPC(cis) = 8.7 Hz, COax), 167.4 (t, 2JPC = 8.6 Hz, C
294
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Organometallics
Article
1
1
N), 137.9 (d, JPC = 29.4 Hz, Ph-Cipso), 137.7 (d, JPC = 32.0 Hz, Ph-
Cipso), 132.2 (m, Ph-Cortho), 130.0 (Ph-Cpara), 129.7 (Ph-Cpara), 128.8
(m, Ph-Cmeta), 49.7 (CH2N3), 42.9 (CH2NC), 27.9 (m, CH2P).
31P{1H} NMR (162 MHz, CD2Cl2): δ 55.48. HRMS (ESI, positive
ions): m/z 715.03017 [[6] + K]+ (calcd for [[6] + K]+ 715.03415),
699.05752 [[6] + Na]+ (calcd for [[6] + Na]+ 699.05905), 677.07521
[[6] + H]+ (calcd for [[6] + H]+ 677.07635), 649.08085 [[6] − CO +
2JPC(trans) = 35.4 Hz, 2JPC(cis) = 8.4 Hz, COeq), 210.7 (t, 2JPC(cis) = 4.9 Hz,
1
1
COax), 137.6 (d, JPC = 40.4 Hz, Ph-Cipso), 136.6 (d, JPC = 30.2 Hz,
Ph-Cipso), 133.7 (m, Ph-Cortho), 132.9 (m, Ph-Cortho), 130.2 (Ph-Cpara),
129.7 (Ph-Cpara), 129.2 (m, Ph-Cmeta), 129.0 (m, Ph-Cmeta), 123.1 (s br,
NCCH3), 29.5 (m, CH2-P), 1.8 (NCCH3). 31P{1H} NMR (162 MHz,
[D8]THF): δ 46.50 (1JPW = 228.0 Hz). MS (MALDI, positive ions)
m/z: 707 [5]+ (calcd for [M]+ 707). IR (KBr, cm−1): ν
̃
1918 (s, CO),
H]+ (calcd for [[6] − CO + H]+ 649.08335). IR (KBr, cm−1): ν
̃
2135
1825 (s, CO), 1793 (s, CO).
[W(CO)3(dppe)(CNCH2CH2N3)] [7]. A solution of [5] (225 mg,
0.32 mmol) in THF (20 mL) was treated with 1 (38.2 mg, 0.40
mmol). The reaction mixture was heated under reflux for 3 h, followed
by the removal of the solvent under reduced pressure. The crude
reaction product was purified by column chromatography on neutral
alumina (4% H2O) with dichloromethane/cyclohexane (2:1, v/v) as
eluent to give [7] as a pale yellow solid. Yield: 172 mg (0.23 mmol,
(m, CN and N3), 2098 (sh, N3), 1937 (s, CO), 1858 (s, CO), 1835
(s, CO).
[Mo(CO)3(dppe)(CNCH2CH2NH3)]X [8]X. To a suspension made
up from [6] (289 mg, 0.43 mmol), zinc powder (38 mg, 0.58 mmol),
and ammonium chloride (31 mg, 0.58 mmol) in dry methanol (20
mL) were added three drops of degassed water. This mixture was
heated under reflux for 24 h. Subsequent filtration yielded a pale
yellow solid containing the salts [8]Cl and [8]2[ZnCl4], which could
not be separated. Yield: 260 mg (86% for [8]Cl or 78% for
[8]2[ZnCl4]; the actual yield lies in between these two extremes). H
NMR (400 MHz, [D6]DMSO): δ 7.68 (m, 4H, Ph-Hortho), 7.63 (m,
4H, Ph-Hortho), 7.40 (m, 8H, Ph-Hmeta), 7.37 (m, 4H, Ph-Hpara), 3.34
1
72%). H NMR (400 MHz, CD2Cl2): δ 7.65 (m, 8H, Ph-Hortho), 7.38
(m, 8H, Ph-Hmeta), 7.35 (m, 4H, Ph-Hpara), 2.98 (tt, 3J = 5.9 Hz, 5JPH
=
1.5 Hz, 2H, CH2NC), 2.69 (t, 3J = 5.9 Hz, 2H, CH2N3), 2.61 (m, 4H,
1
2
CH2P). 13C{1H} NMR (101 MHz, CD2Cl2): δ 212.6 (dd, JPC(trans)
=
2
2
27.8 Hz, JPC(cis) = 7.5 Hz, COeq), 207.0 (t, JPC(cis) = 6.4 Hz, COax),
1
1
+
3
159.5 (CN), 137.4 (d, JPC = 35.4 Hz, Ph-Cipso), 137.2 (d, JPC
=
(br s, 3H, NH3 ), 2.98 (t, J = 6.9 Hz, 2H, CH2NC), 2.59 (m, 4H,
3
+
CH2P), 2.10 (t, J = 6.9 Hz, 2H, CH2NH3 ). 13C{1H} NMR (101
MHz, [D6]DMSO): δ 221.5 (dd, 2JPC(trans) = 28.3 Hz, 2JPC(cis) = 9.5 Hz,
COeq), 215.6 (t, 2JPC(cis) = 8.8 Hz, COax), 161.1 (t, 2JPC = 9.6 Hz, C
38.1 Hz, Ph-Cipso), 132.3 (m, Ph-Cortho), 130.1 (Ph-Cpara), 129.9 (Ph-
Cpara), 128.9 (m, Ph-Cmeta), 49.8 (CH2N3), 43.0 (CH2NC), 29.5 (m,
CH2P). 31P{1H} NMR (162 MHz, CD2Cl2): δ 40.71 (1JPW = 222.7
Hz). MS (EI): m/z (%) 762 (20) [7]+, 734 (54) [[7] − CO]+, 706
(86) [[7] − 2CO]+, 678 (56) [[7] − 3CO]. HRMS (ESI, positive
ions): m/z 762.11465 [7]+ (calcd for [7]+ 762.11465). IR (KBr,
1
1
N), 136.7 (d, JPC = 32.0 Hz, Ph-Cipso), 136.6 (d, JPC = 29.0 Hz, Ph-
Cipso), 131.5 (m, Ph-Cortho), 131.2 (m, Ph-Cortho), 129.5 (Ph-Cpara),
129.4 (Ph-Cpara), 128.4 (m, Ph-Cmeta), 44.7 (CH2NC), 40.2
cm−1): ν
̃
2129 (m, CN and N3), 2097 (m, N3), 1934 (s, CO), 1852
+
(CH2NH3 ), 26.4 (m, CH2P). 31P{1H} NMR (162 MHz, [D6]-
DMSO): δ 54.71. HRMS (ESI, positive ions): m/z 651.08557 [8]+
(calcd for [8]+ 651.08585), 623.09037 [[8] − CO]+ (calcd for [[8] −
CO]+ 623.09286), 595.09541 [[8] − 2CO]+ (calcd for [[8] − CO]+
595.09795). HRMS (ESI, negative ions): m/z 818.92543 [[8] − H +
ZnCl3]− (calcd for [[8] − H + ZnCl3]− 818.91427), 685.05786 [[8] −
(s, CO), 1821 (s, CO).
[W(CO)3(dppe)(CNCH2CH2NH3)]X [9]X. To a suspension of [7]
(102 mg, 0.13 mmol), zinc powder (18 mg, 0.27 mmol), and NH4Cl
(15 mg, 0.28 mmol) in methanol (20 mL) was added 0.1 mL of
degassed water. The reaction mixture was heated under reflux for 24 h.
After removal of the solvent, the residue was dissolved in
dichloromethane and filtered. Removal of the solvent yielded a pale
yellow powder. The obtained solid is composed of the salts [9]Cl and
H + Cl]− (calcd for [[8] − H + Cl]− 685.04752). IR (KBr, cm−1): ν
̃
+
3134 (m, NH3 ), 2123 (m, CN), 1933 (s, CO), 1845 (s, CO).
[Mo(CO)3(dppe)(CNCH2CH2NH2)] [10]. A methanol solution of
[8]X from the previous reaction was treated with an excess of sodium
hydroxide. After stirring for 1 h at room temperature, the solvent was
removed in vacuo. The solid residue was dissolved in a water/
dichloromethane mixture. The organic layer was separated, washed
several times with water, and dried over MgSO4. Removal of the
solvent yielded [10] as a pale yellow powder. Yield: 230 mg (0.35
mmol, 81%, relative to [6]). 1H NMR (400 MHz, CD2Cl2): δ 7.67 (m,
8H, Ph-Hortho), 7.36 (m, 8H, Ph-Hmeta), 7.34 (m, 4H, Ph-Hpara), 2.83
1
[9]2[ZnCl4], which could not be separated. Yield: 106 mg. H NMR
(400 MHz, CD2Cl2): δ 7.64 (m, 8H, Ph-Hortho), 7.44 (m, 4H, Ph-
Hpara), 7.37 (m, 8H, Ph-Hmeta), 3.12 (t, 3J = 5.6 Hz, 2H, CH2NC), 2.63
3
(m, 4H, CH2P), 2.46 (t, J = 5.6 Hz, 2H, CH2NH3), 2.23 (s br, 3H,
2
NH3). 13C{1H} NMR (101 MHz, CD2Cl2): δ 212.9 (dd, JPC(trans)
=
2
2
27.7 Hz, JPC(cis) = 7.7 Hz, COeq), 207.2 (t, JPC(cis) = 6.6 Hz, COax),
1
1
159.2 (CN), 137.4 (d, JPC = 35.1 Hz, Ph-Cipso), 137.1 (d, JPC
=
37.7 Hz, Ph-Cipso), 132.4 (m, Ph-Cortho), 132.1 (m, Ph-Cortho), 130.2
(Ph-Cpara), 130.2 (Ph-Cpara), 129.2 (m, Ph-Cmeta), 128.9 (m, Ph-Cmeta),
45.4 (CH2NC), 41.1 (CH2NH3), 29.6 (m, CH2P). 31P{1H} NMR
(162 MHz, CD2Cl2): δ 40.80 (1JPW = 222.1 Hz). HRMS (ESI, positive
ions): m/z 737.13228 [9]+ (calcd for [9]+ 737.13190). HRMS (ESI,
3
3
(t, J = 5.7 Hz, 2H, CH2NC), 2.55 (m, 4H, CH2P), 2.18 (t, J = 5.7
Hz, 2H, CH2NH2), 0.45 (br s, 2H, NH2). 13C{1H} NMR (101 MHz,
2
2
CD2Cl2): δ 221.4 (dd, JPC(trans) = 28.5 Hz, JPC(cis) = 9.7 Hz, COeq),
216.0 (t, 2JPC(cis) = 8.8 Hz, COax), 164.0 (CN), 137.9 (d, 1JPC = 27.1
Hz, Ph-Cipso), 137.6 (d, 1JPC = 30.1 Hz, Ph-Cipso), 132.1 (m, Ph-Cortho),
129.9 (Ph-Cpara), 129.7 (Ph-Cpara), 128.8 (m, Ph-Cmeta), 47.6
(CH2NC), 41.4 (CH2NH2), 27.9 (m, CH2P). 31P{1H} NMR (162
MHz, CD2Cl2): δ 55.34. HRMS (ESI, positive ions): m/z 651.08459
[[10] + H]+ (calcd for [[10] + H]+ 651.08585), 623.08979 [[10]
−CO + H]+ (calcd for [[10] − CO + H]+ 623.09286), 595.09484 [M
− 2CO + H]+ (calcd for [[10] − 2CO + H]+ 595.09795). IR (KBr,
negative ions): m/z 771.0997 [[9] − H + Cl]− (calcd for [[9] − H +
+
Cl]− 771.0886). IR (KBr, cm−1): ν
1929 (s, CO), 1849 (s, CO).
̃
3193 (w, NH3 ), 2125 (m, CN),
[W(CO)3(dppe)(CNCH2CH2NH2)] [11]. A solution of [9]X from
the previous reaction in 10 mL of methanol was treated with sodium
hydroxide and stirred for 1 h at room temperature. After removal of
the solvent, the residue was dissolved in water and dichloromethane.
The organic layer was separated, washed several times with water, and
dried over MgSO4. Removal of the solvent yielded [11] as a pale
cm−1): ν
̃
3441 (w, NH2), 3396 (w, NH2), 2133 (m, CN), 1927 (s,
CO), 1831 (s, CO). Anal. Calcd: C, 59.27; H, 4.66; N, 4.32. Found: C,
59.66; H, 4.70; N, 4.00.
1
yellow powder. Yield: 58 mg (0.08 mmol, 62%, relative to [7]). H
NMR (200 MHz, CD2Cl2): δ 7.65 (m, 8H, Ph-Hortho), 7.39 (m, 12H,
[W(CO)3(dppe)(NCCH3)] [5]. A suspension of 1.160 g (1.67
mmol) [W(CO)4(dppe)]19 in acetonitrile (100 mL) was irradiated at
0 °C for 5 h in a photoreactor (high-pressure mercury vapor lamp).
After complete conversion, checked by IR spectroscopy, the solvent
was removed in vacuo, the oily residue was dissolved in THF and
filtered through Celite. The filtrate was cooled to 0 °C and treated
with hexane while stirring. Complex [5] precipitated out of the solvent
mixture. The bright yellow solid residue was isolated by filtration and
dried in vacuo. Yield: 896 mg (1.27 mmol, 76%). 1H NMR (400 MHz,
[D8]THF): δ 7.78 (m, 4H, Ph-Hortho), 7.60 (m, 4H, Ph-Hortho), 7.30
(m, 12H, Ph-Hmeta and Ph-Hpara), 2.59 (m, 4H, CH2-P), 1.37 (s, 3H,
NCCH3). 13C{1H} NMR (101 MHz, [D8]THF): δ 215.5 (dd,
3
5
Ph-Hmeta and Ph-Hpara), 2.85 (tt, J = 5.8 Hz, JPC = 1.5 Hz, 2H,
3
CH2NC), 2.61 (m, 4H, CH2P), 2.16 (t, J = 5.8 Hz, 2H, CH2NH2),
0.61 (s br, 2H, NH2). 13C{1H} NMR (50 MHz, CD2Cl2): δ 212.9 (dd,
2JPC(trans) = 27.9 Hz, 2JPC(cis) = 7.7 Hz, COeq), 207.4 (t, 2JPC(cis) = 6.5 Hz,
1
COax), 156.0 (CN), 137.5 (d, JPC = 34.6 Hz, Ph-Cipso), 137.2 (dd,
1JPC = 38.1 Hz, JPC = 0.9 Hz, Ph-Cipso), 132.2 (m, Ph-Cortho), 130.1
3
(Ph-Cpara), 129.9 (Ph-Cpara), 128.9 (m, Ph-Cmeta), 47.7 (CH2NC), 41.5
(CH2NH2), 29.5 (m, CH2P). 31P{1H} NMR (162 MHz, CD2Cl2): δ
40.63 (1JPW = 222.6 Hz). MS (EI): m/z (%) 736 (85) [11]+, 708
(100) [[11] − CO]+, 680 (62) [[11] − 2CO]+, 652 (30) [[11] −
3CO], 638 (22) [[11] − CNCH2CH2NH2 − CO], 610 (18) [[11] −
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Organometallics
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CNCH2CH2NH2 − 2CO], 582 (7) [[11] − CNCH2CH2NH2
−
purify without decomposition and was, therefore, used as received for
the next reaction. Complex [12] was characterized by IR spectroscopy
3CO]. HRMS (ESI, positive ions): m/z 737.13025 [[11] + H]+ (calcd
for [[11] + H]+ 737.13138). IR (KBr, cm−1): ν
(w, NH2), 2126 (m, CN), 1926 (s, CO), 1838 (s, CO). Anal. Calcd:
C, 52.19; H, 4.11; N, 3.80. Found: C, 51.10; H, 4.00; N, 3.58.
[Mo(CO)3(dppe)(CNC6H4N3)] [12]. See preparation of [16].
̃
3447 (w, NH2), 3363
(KBr, cm−1): ν
̃
2121 (m, N3), 2077 (m, CN), 1929 (s, CO), 1856
(s, CO). The oily residue of [12] was dissolved in THF (20 mL), and
zinc powder (27 mg, 0.42 mmol), ammonium chloride (23 mg, 0.43
mmol), and three drops of degassed water were added. The resulting
suspension was heated under reflux for 24 h. The solvent was then
removed in vacuo. The residue was dissolved in methanol (10 mL)
and treated with sodium hydroxide (22 mg, 0.55 mmol). The reaction
mixture was stirred at ambient temperature for 1 h. After removal of
the solvent, dichloromethane (20 mL) and water (10 mL) were added.
The organic layer was separated, washed several times with water, and
dried over MgSO4. Removal of the solvent gave a solid residue that
was purified by column chromatography on silica gel with dichloro-
methane/cyclohexane (1:1, v/v) as eluent to give [16] as a slightly
yellow powder. Yield: 184 mg (0.26 mmol, 84% over the entire
[Mo(CO)3(dppe)(CNC6H4NO2)] [13]. A solution of [Mo-
(CO)3(py)3] (288 mg, 0.69 mmol) dissolved in dichloromethane
(20 mL) was treated with 275 mg (0.69 mmol) of dppe and left to stir
for 12 h at room temperature. Subsequently, the solvent was removed
in vacuo. The residue (complex [4]) was not further purified but was
suspended in THF (20 mL). To this suspension was added dropwise a
solution of 3 (123 mg, 0.83 mmol) in dichloromethane (10 mL). The
reaction mixture was heated under reflux for 4.5 h, followed by the
removal of the solvents under reduced pressure. The crude reaction
product was purified by column chromatography on neutral alumina
(4% H2O) with dichloromethane/cyclohexane (1:1, v/v) as eluent to
1
reaction sequence starting from [Mo(CO)3(py)3]). H NMR (400
1
give [13] as a deep red solid. Yield: 282 mg (0.39 mmol, 57%). H
MHz, CD2Cl2): δ 7.68 (m, 8H, Ph-Hortho), 7.38 (m, 4H, Ph-Hmeta),
7.37 (m, 2H, Ph-Hpara), 7.28 (m, 4H, Ph-Hmeta), 7.26 (m, 2H, Ph-
Hpara), 6.94 (ddd, 3J = 8.1 Hz, 3J = 7.9 Hz, 4J = 1.2 Hz, 1H, H-4), 6.55
(dd, 3J = 8.1 Hz, 4J = 0.9 Hz, 1H, H-3), 6.45 (ddd, 3J = 7.9 Hz, 3J = 7.8
Hz, 4J = 0.9 Hz, 1H, H-5), 6.26 (dd, 3J = 7.8 Hz, 4J = 1.2 Hz, 1H, H-6),
NMR (400 MHz, [D8]THF): δ 7.91 (dd, 3J = 8.2 Hz, 4J = 0.9 Hz, 1H,
H-3), 7.68 (m, 8H, Ph-Hortho), 7.40 (ddd, 3J = 8.2 Hz, 3J = 8.0 Hz, 4J =
0.9 Hz, H-5), 7.34 (m, 4H, Ph-Hmeta), 7.30 (m, 2H, Ph-Hpara), 7.26
(ddd, 3J = 8.2 Hz, 3J = 8.1 Hz, 4J = 0.9 Hz, 1H, H-4), 7.19 (m, 4H, Ph-
Hmeta), 7.12 (m, 2H, Ph-Hpara), 6.55 (dd, 3J = 7.9 Hz, 4J = 0.9 Hz, 1H,
H-6), 2.64 (m, 4H, CH2P). 13C{1H} NMR (101 MHz, [D8]THF): δ
1
3.40 (br s, 2H, NH2), 2.59 (m, 4H, CH2P). H NMR (400 MHz,
[D8]THF): δ 7.71 (m, 8H, Ph-Hortho), 7.31 (m, 6H, Ph-Hpara and Ph-
Hmeta), 7.25 (m, 4H, Ph-Hmeta), 7.20 (m, 2H, Ph-Hpara), 6.85 (ddd, 3J =
8.2 Hz, 3J = 7.2 Hz, 4J = 1.2 Hz, 1H, H-4), 6.54 (dd, 3J = 8.2 Hz, 4J =
0.9 Hz, 1H, H-3), 6.30 (ddd, 3J = 8.0 Hz, 3J = 7.2 Hz, 4J = 0.9 Hz, 1H,
H-5), 6.17 (dd, 3J = 8.0 Hz, 4J = 1.2 Hz, 1H, H-6), 4.20 (s, 2H, NH2),
2.60 (m, 4H, CH2P). 13C{1H} NMR (101 MHz, CD2Cl2): δ 220.9
2
2
220.3 (dd, JPC(trans) = 27.7 Hz, JPC(cis) = 9.1 Hz, COeq), 214.9 (t,
2JPC(cis) = 8.8 Hz, COax), 188.0 (t, 2JPC = 10.3 Hz, CN), 143.2 (C-2),
138.5 (d, 1JPC = 32.2 Hz, Ph-Cipso), 138.4 (d, 1JPC = 31.4 Hz, Ph-Cipso),
134.7 (C-5), 132.7 (m, Ph-Cortho), 130.7 (C-6), 130.3 (Ph-Cpara), 129.8
(Ph-Cpara), 129.1 (m, Ph-Cmeta), 127.6 (C-4), 126.0 (C-3), 123.5 (C-
1), 28.6 (m, CH2P). 31P{1H} NMR (162 MHz, [D8]THF): δ 56.45.
HRMS (ESI, positive ions): m/z 751.04371 [[13] + Na]+ (calcd for
[[13] + Na]+ 751.04283). HRMS (ESI, negative ions): m/z 763.02591
2
2
2
(dd, JPC(trans) = 28.4 Hz, JPC(cis) = 9.6 Hz, COeq), 215.9 (t, JPC(cis)
=
8.6 Hz, COax), 176.4 (t, 2JPC = 10.0 Hz, CN), 142.9 (C-2), 138.0 (d,
1JPC = 29.8 Hz, Ph-Cipso), 137.5 (d, 1JPC = 32.1 Hz, Ph-Cipso), 132.3 (m,
Ph-Cortho), 131.9 (m, Ph-Cortho), 130.1 (Ph-Cpara), 129.7 (Ph-Cpara),
128.9 (m, Ph-Cmeta), 128.9 (C-4), 126.2 (C-6), 117.9 (C-5), 115.3 (C-
3), 115.1 (C-1), 27.9 (m, CH2P). 13C{1H} NMR (101 MHz,
[[13] + Cl]− (calcd for [[13] + Cl]− 763.02128). IR (KBr, cm−1): ν
̃
2063 (m, CN), 1925 (s, CO), 1876 (s, CO).
[W(CO)3(dppe)(CNC6H4N3)] [14]. See preparation of [17].
[W(CO)3(dppe)(CNC6H4NO2)] [15]. A solution of [5] (239 mg,
0.34 mmol) dissolved in THF (40 mL) was treated dropwise with a
solution of 3 (50 mg, 0.34 mmol) in THF (20 mL). The reaction
mixture was stirred for 20 h at ambient temperature, and the solvent
was subsequently removed under reduced pressure. The obtained solid
was purified by column chromatography on neutral alumina (4%
H2O) with dichloromethane as eluent to give [15] as a red solid. Yield:
246 mg (0.30 mmol, 88%). 1H NMR (400 MHz, CD2Cl2): δ 7.89 (dd,
[D8]THF): δ 221.1 (dd, JPC(trans) = 28.3 Hz, 2JPC(cis) = 9.4 Hz, COeq),
2
2
216.0 (t, JPC(cis) = 8.7 Hz, COax), 177.1 (CN), 144.7 (C-2), 139.0
(d, 1JPC = 29.6 Hz, Ph−Cipso), 138.5 (d, 1JPC = 31.7 Hz, Ph-Cipso), 132.9
(m, Ph-Cortho), 132.5 (m, Ph-Cortho), 130.2 (Ph-Cpara), 129.9 (Ph-Cpara),
129.1 (m, Ph-Cmeta), 129.1 (C-4), 126.5 (C-6), 116.9 (C-5), 115.3 (C-
3), 115.2 (C-1), 28.4 (m, CH2P). 31P{1H} NMR (162 MHz, CD2Cl2):
δ 55.10. 31P{1H} NMR (162 MHz, [D8]THF): δ 55.82. MS (EI): m/z
(%) 698 (5) [16]+, 670 (13) [[16] − CO]+, 642 (9) [[16] − 2CO]+,
614 (5) [[16] − 3CO]+, 580 (17) [[16] − CNC6H4NH2]+, 552 (25)
[[16] − CO − CNC6H4NH2]+, 524 (30) [[16] − 2CO
−CNC6H4NH2]+, 496 (50) [[16] − 3CO − CNC6H4NH2]+.
HRMS (ESI, positive ions): m/z 721.06882 [[16] + Na]+ (calcd for
[[16] + Na]+ 721.06863). HRMS (ESI, negative ions): m/z 733.05107
4
3J = 8.3 Hz, J = 1.4 Hz, 1H, H-3), 7.64 (m, 8H, Ph-Hortho), 7.38 (m,
4H, Ph-Hmeta), 7.37 (m, 2H, Ph-Hpara), 7.34 (m, 1H, H-5), 7.23 (m,
1H, H-4), 7.23 (m, 4H, Ph-Hmeta), 7.16 (m, 2H, Ph-Hpara), 6.50 (dd, 3J
= 8.0 Hz, 4J = 1.3 Hz, H-6), 2.69 (m, 4H, CH2P). 13C{1H} NMR (101
2
2
MHz, CD2Cl2): δ 211.4 (dd, JPC(trans) = 26.9 Hz, JPC(cis) = 7.5 Hz,
COeq), 206.8 (t, 2JPC(cis) = 6.7 Hz, COax), 179.0 (CN), 142.5 (C-2),
137.0 (d, 1JPC = 38.8 Hz, Ph-Cipso), 136.9 (d, 1JPC = 37.4 Hz, Ph-Cipso),
134.3 (C-5), 132.2 (m, Ph-Cortho), 130.3 (Ph-Cpara), 130.2 (C-6), 129.8
(Ph-Cpara), 128.9 (m, Ph-Cmeta), 126.9 (C-4), 125.6 (C-3), 123.6 (C-
1), 29.8 (m, CH2P). 31P{1H} NMR (162 MHz, CD2Cl2): δ 40.60
(1JPW = 225.3 Hz). HRMS (ESI, positive ions): m/z 837.0843 [[15] +
Na]+ (calcd for [[15] + Na]+ 837.0881), 815.1061 [[15] + H]+ (calcd
for [[15] + H]+ 815.1061). MS (MALDI, positive ions): m/z: 814
[[16] + Cl]− (calcd for [[16] + Cl]− 733.05107). IR (KBr, cm−1): ν
3484 (m, NH2), 3394 (m, NH2), 2097 (m, NC), 1924 (s, CO), 1848
(s, CO), 1822 (s, CO). Anal. Calcd: C, 62.08; H, 4.34; N, 4.02. Found:
C, 61.76; H, 4.54; N, 3.76.
̃
[Mo(CO)3(dppe)(CNC6H4NH2)] [16] by Reduction of the
Nitrophenyl Isocyanide in [13]. A solution of [13] (212 mg,
0.29 mmol) in THF (20 mL) was treated with a catalytic amount of
Raney nickel. The mixture was cooled to 0 °C and treated dropwise
with hydrazine hydrate (0.3 mL, 5.80 mmol). After warm-up, the
reaction mixture was stirred for 48 h at ambient temperature. Removal
of insolubles by filtration and stripping of the solvent gave an off-white
powder that was purified by column chromatography on silica gel with
dichloromethane/cyclohexane (1:1, v/v) as eluent to give [16] as a
slightly yellow powder. Yield: 141 mg (0.20 mmol, 69%). The
analytical data are identical to those of [16] obtained from [12].
[W(CO)3(dppe)(CNC6H4NH2)] [17] by Reduction of the
Azidophenyl Isocyanide in [14]. A sample of complex [5] (180
mg, 0.25 mmol) dissolved in THF (20 mL) was treated with a solution
of 2 (44 mg, 0.30 mmol) in THF (5 mL). The reaction mixture was
heated under reflux for 12 h. Removal of the solvent gave complex
[14] as an oily residue that proved difficult to purify without
decomposition. The complex was, therefore, used as received for the
[15]+, 730 [[15] − 3CO]+. IR (KBr, cm−1): ν
̃
2059 (m, CN), 1919
(s, CO), 1857 (s, CO).
[Mo(CO)3(dppe)(CNC6H4NH2)] [16] by Reduction of the
Azidophenyl Isocyanide in [12]. Complex [12] was prepared as
described below and used without further purification for the
subsequent reduction. A solution of [Mo(CO)3(py)3] (129 mg, 0.31
mmol) in dichloromethane (20 mL) was treated with dppe (123 mg,
0.31 mmol) and left to stir for 12 h at ambient temperature.
Subsequently, the solvent was removed in vacuo. The solid residue
(complex [4]) was suspended in THF (20 mL), and to this solution
was added dropwise 2-azidophenyl isocyanide 2 (53 mg, 0.37 mmol)
dissolved in THF (20 mL). The reaction mixture was heated under
reflux for 12 h, followed by the removal of the solvent under reduced
pressure. The oily residue of [12] obtained this way proved difficult to
296
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Organometallics
Article
3
subsequent reduction. Crude complex [14] was characterized by IR
5.6 Hz, 2H, CH2N3), 3.60 (t, J = 5.6 Hz, 2H, CH2NC). 13C{1H}
NMR (101 MHz, CDCl3): δ 206.4 (COax), 203.6 (COeq), 157.3 (C
N), 49.5 (CH2N3), 43.7 (CH2NC). MS (EI): m/z (%) 334 (100)
[18]+ 306 (27) [[18] − CO]+, 278 (11) [[18] − 2CO]+, 250 (49)
[[18] − 3CO]+, 222 (75) [[18] − 4CO]+, 194 (44) [[18] − 5CO]+.
spectroscopy (KBr, cm−1): ν
̃
2123 (m, N3), 2075 (m, CN), 1921 (s,
CO), 1851 (s, CO). The crude complex [14] was dissolved in THF
(20 mL), and zinc powder (23 mg, 0.35 mmol), ammonium chloride
(19 mg, 0.35 mmol), and three drops of degassed water were added.
The suspension was heated for 24 h under reflux. Subsequently, the
solvent was removed in vacuo and the solid residue was dissolved in
methanol (10 mL) and treated with sodium hydroxide (22 mg, 55
mmol) dissolved in methanol (10 mL). The reaction mixture was
stirred for 1 h at ambient temperature, followed by removal of the
solvent in vacuo at ambient temperature. Dichloromethane (20 mL)
and water (10 mL) were added. The organic layer was separated,
washed several times with water, and dried over MgSO4. Removal of
the solvent gave a yellow powder. This powder was purified by column
chromatography on silica gel with dichloromethane/cyclohexane (3:1,
v/v) as eluent to give [17] as a slightly yellow powder. Yield: 60 mg
(0.08 mmol, 31%). For analytical data, see below.
IR (KBr, cm−1): ν
̃
2176 (s, CN), 2132 (sh, N3), 2106 (s, N3), 2072
(s, CO), 1929 (s, CO).
X-ray Diffraction Studies. Diffraction data were collected at T =
153(2) K with a Bruker AXS APEX CCD diffractometer ([6],
[6]2·2CH2Cl2, [10], [13]·THF, and [15]·Et2O) or a STOE IPDS 2
([16] and [17]) diffractometer using graphite-monochromated Mo
Kα radiation (λ = 0.71073 Å). Diffraction data were collected over the
full sphere and were corrected for absorption. Structure solutions were
found with the SHELXS-9726 package using direct methods and were
refined with SHELXL-9726 against |F2| using first isotropic and later
anisotropic thermal parameters for all non-hydrogen atoms. Hydrogen
atoms were added to the structure models in calculated positions.
[6]. Crystals suitable for a X-ray diffraction study were obtained by
slow evaporation of the solvent from a THF solution of [6].
C32H28N4MoO3P2, M = 674.46 g·mol−1, light yellow crystal, 0.07 ×
0.06 × 0.05 mm3, orthorhombic, space group Pna21, Z = 4, a =
22.5033(8) Å, b = 9.8583(4) Å, c = 13.5324(5) Å, V = 3002.1(2) Å3,
ρcalc = 1.492 g·cm−3, μ = 0.584 mm−1, ω- and φ-scans, 34 439
measured intensities (3.6° ≤ 2θ ≤ 60.5°), semiempirical absorption
correction (0.960 ≤ T ≤ 0.971), 8868 independent (Rint = 0.0285) and
8207 observed intensities (I ≥ 2σ(I)), refinement of 379 parameters
against |F2| of all measured intensities with hydrogen atoms on
[W(CO)3(dppe)(CNC6H4NH2)] [17] by Reduction of the
Nitrophenyl Isocyanide in [15]. A solution of [15] (176 mg,
0.22 mmol) in THF (20 mL) was treated with a catalytic amount of
Raney nickel. The mixture was cooled to 0 °C and treated dropwise
with hydrazine hydrate (0.3 mL, 5.80 mmol). After warm-up, the
reaction mixture was stirred for 72 h at ambient temperature. Removal
of insolubles by filtration and stripping of the solvent gave an off-white
powder that was purified by column chromatography on silica gel with
dichloromethane/cyclohexane (1:1, v/v) as eluent to give [17] as a
1
slightly yellow powder. Yield: 78 mg (0.10 mmol, 45%). H NMR
(400 MHz, CD2Cl2): δ 7.65 (m, 8H, Ph-Hortho), 7.39 (m, 6H, Ph-Hpara
and Ph-Hmeta), 7.29 (m, 4H, Ph-Hmeta), 7.27 (m, 2H, Ph-Hpara), 6.93
(ddd, 3J = 7.9 Hz, 3J = 7.7 Hz, 4J = 1.2 Hz, 1H, H-4), 6.54 (dd, 3J = 7.9
Hz, 4J = 0.8 Hz, 1H, H-3), 6.44 (ddd, 3J = 7.9 Hz, 3J = 7.7 Hz, 4J = 0.8
calculated positions. R = 0.0224, wR = 0.0481, Rall = 0.0266, wRall
0.0499. The asymmetric unit contains one formula unit.
=
[6]2·2CH2Cl2. Crystals of [6]2·2CH2Cl2 suitable for an X-ray
diffraction study were obtained by slow evaporation of the solvent
from a dichloromethane solution of [6]2. C66H60N8Cl4Mo2O6P4, M =
1518.78 g·mol−1, colorless stick, 0.07 × 0.03 × 0.03 mm3, monoclinic,
space group P21/n, Z = 2, a = 18.5649(7) Å, b = 9.7263(3) Å, c =
19.0379(7) Å, β = 97.8670(10)°, V = 3405.3(2) Å3, ρcalc = 1.481
g·cm−3, μ = 0.675 mm−1, ω- and φ-scans, 35 449 measured intensities
(2.9° ≤ 2θ ≤ 59.5°), semiempirical absorption correction (0.954 ≤ T
≤ 0.980), 9606 independent (Rint = 0.0506) and 7352 observed
intensities (I ≥ 2σ(I)), refinement of 406 parameters against |F2| of all
measured intensities with hydrogen atoms on calculated positions. R =
0.0395, wR = 0.0894, Rall = 0.0610, wRall = 0.0988. The asymmetric
unit contains one-half a formula unit related to the other half by a
crystallographic inversion center.
[10]. Crystals suitable for an X-ray diffraction study were obtained
by slow diffusion of diethyl ether into a saturated solution of [10] in
dichloromethane. C32H30N2MoO3P2, M = 648.46 g·mol−1, light yellow
crystal, 0.10 × 0.07 × 0.03 mm3, monoclinic, space group Cc, Z = 4, a
= 22.1752(10) Å, b = 8.6798(4) Å, c = 15.6483(7) Å, β =
104.3190(10)°, V = 2918.4(2) Å3, ρcalc = 1.476 g·cm−3, μ = 0.595
mm−1, ω- and φ-scans, 16 832 measured intensities (3.8° ≤ 2θ ≤
60.6°), semiempirical absorption correction (0.943 ≤ T ≤ 0.982),
8406 independent (Rint = 0.0192) and 8036 observed intensities (I ≥
2σ(I)), refinement of 389 parameters against |F2| of all measured
intensities with hydrogen atoms on calculated positions. R = 0.0220,
wR = 0.0523, Rall = 0.0239, wRall = 0.0530. The asymmetric unit
contains one formula unit.
3
4
Hz, 1H, H-5), 6.21 (dd, J = 7.9 Hz, J = 1.2 Hz, 1H, H-6), 3.39 (s,
1
2H, NH2), 2.65 (m, 4H, CH2P). H NMR (400 MHz, [D8]THF): δ
7.70 (m, 8H, Ph-Hortho), 7.32 (m, 6H, Ph-Hpara and Ph-Hmeta), 7.26 (m,
4H, Ph-Hmeta), 7.19 (m, 2H, Ph-Hpara), 6.83 (ddd, 3J = 8.2 Hz, 3J = 7.3
Hz, 4J = 1.5 Hz, 1H, H-4), 6.52 (dd, 3J = 8.2 Hz, 4J = 1.2 Hz, 1H, H-3),
6.29 (ddd, 3J = 7.9 Hz, 3J = 7.3 Hz, 4J = 1.2 Hz, 1H, H-5), 6.12 (dd, 3J
4
= 7.9 Hz, J = 1.5 Hz, 1H, H-6), 4.19 (s, 2H, NH2), 2.67 (m, 4H,
2
CH2P). 13C{1H} NMR (101 MHz, CD2Cl2): δ 212.3 (dd, JPC(trans)
=
2
2
27.5 Hz, JPC(cis) = 7.2 Hz, COeq), 207.7 (t, JPC(cis) = 6.5 Hz, COax),
168.9 (t, 2JPC) = 8.2 Hz, CN), 143.0 (C-2), 137.5 (d, 1JPC = 36.2 Hz,
1
Ph-Cipso), 137.0 (d, JPC = 38.2 Hz, Ph-Cipso), 132.4 (m, Ph-Cortho),
131.9 (m, Ph-Cortho), 130.3 (Ph-Cpara), 129.9 (Ph-Cpara), 129.0 (m, Ph-
Cmeta), 128.7 (C-4), 126.2 (C-6), 117.9 (C-5), 115.4 (C-1), 115.3 (C-
3), 29.5 (m, CH2P). 13C{1H} NMR (101 MHz, [D8]THF): δ 212.3
2
2
2
(dd, JPC(trans) = 27.7 Hz, JPC(cis) = 7.5 Hz, COeq), 207.7 (t, JPC(cis)
=
6.3 Hz, COax), 169.3 (t, 2JPC = 7.8 Hz, CN), 144.8 (C-2), 138.5 (d,
1JPC = 35.7 Hz, Ph-Cipso), 138.1 (d, 1JPC = 38.3 Hz, Ph-Cipso), 133.0 (m,
Ph-Cortho), 132.5 (m, Ph-Cortho), 130.4 (Ph-Cpara), 130.1 (Ph-Cpara),
129.2 (m, Ph-Cmeta), 129.1 (m, Ph-Cmeta), 128.8 (C-4), 126.4 (C-6),
116.9 (C-5), 115.5 (C-1), 115.3 (C-3), 30.0 (m, CH2P). 31P{1H}
NMR (162 MHz, CD2Cl2): δ 40.25 (1JPW = 223.7 Hz). 31P{1H} NMR
(162 MHz, [D8]THF): δ 40.95 (1JPW = 225.3 Hz). HRMS (ESI,
positive Ions): m/z 807.11346 [[17] + Na]+ (calcd for [[17] + Na]+
807.11391), 785.13149 [[17] + H]+ (calcd for [[17] + H]+
785.13197). HRMS (ESI, negative Ions): m/z 819.10153 [[17] +
Cl]− (calcd for [[17] + Cl]− 819.09187). MS (MALDI, positive ions):
m/z 784 [17]+. IR (KBr, cm−1): ν
̃
3482 (w, NH2), 3389 (w, NH2),
[13]·THF. Crystals of [13]·THF suitable for an X-ray diffraction
study were obtained by slow evaporation of the solvent from a THF
solution of [13]. C40H36N2MoO6P2, M = 798.59 g·mol−1, dark red
2093 (m, CN), 1917 (s, CO), 1841 (s, CO), 1817 (s, CO). Anal.
Calcd: C, 55.12; H, 3.85; N, 3.57. Found: C, 55.06; H, 3.93; N, 3.31.
[Mo(CO)5(CNCH2CH2N3)] [18]. A solution of [Mo(CO)6] (200
mg, 0.76 mmol) and 2-azidoethyl isocyanide 1 (73 mg, 0.76 mmol) in
THF (15 mL) was treated dropwise with a solution of trimethylamine
oxide (84 mg, 1.12 mmol) in dichloromethane (30 mL). The reaction
mixture was stirred at ambient temperature for 6 h. After removal of
the solvent, the residue was extracted with diethyl ether. Stripping of
the solvent gave a purple powder that was purified by column
chromatography on neutral alumina with dichloromethane/cyclo-
hexane (1:1, v/v) as eluent to give [18] as a pink to purple solid. Yield:
56 mg (0.17 mmol, 22%). 1H NMR (400 MHz, CDCl3): δ 3.78 (t, 3J =
crystal, 0.13 × 0.09 × 0.08 mm3, triclinic, space group P1, Z = 2, a =
̅
11.9644(5) Å, b = 12.2905(5) Å, c = 13.6395(6) Å, α = 98.6020(10)°,
β = 105.1870(10)°, γ = 103.3640(10)°, V = 1835.45(13) Å3, ρcalc
=
1.445 g·cm−3, μ = 0.494 mm−1, ω- and φ-scans, 21 265 measured
intensities (3.2° ≤ 2θ ≤ 60.0°), semiempirical absorption correction
(0.939 ≤ T ≤ 0.962), 10 572 independent (Rint = 0.0241) and 9444
observed intensities (I ≥ 2σ(I)), refinement of 460 parameters against
|F2| of all measured intensities with hydrogen atoms on calculated
positions. R = 0.0313, wR = 0.1053, Rall = 0.0355, wRall = 0.1086. The
asymmetric unit contains one formula unit.
297
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Organometallics
Article
[15]·Et2O. Crystals of [15]·Et2O suitable for an X-ray diffraction
study were obtained by slow evaporation of the solvent from a diethyl
ether solution of [15]. C40H38N2O6P2W, M = 888.51 g·mol−1, brown
(3) (a) Handa, S.; Slaughter, L. M. Angew. Chem., Int. Ed. 2012, 51,
2912−2915. (b) Wanniarachchi, Y. A.; Kogiso, Y.; Slaughter, L. M.
Organometallics 2008, 27, 21−24. (c) For a comprehensive review on
the subject, see: Slaughter, L. M. Comments Inorg. Chem. 2008, 29,
46−72.
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209. (b) Michelin, R. A.; Pombeiro, A. J. L.; Guedes da Silva, M. F. C.
Coord. Chem. Rev. 2001, 218, 75−112. (c) Hahn, F. E.; Jahnke, M.
Angew. Chem., Int. Ed. 2008, 47, 3122−3172. (d) Hahn, F. E.
ChemCatChem 2012, in press. DOI: 10.1002/cctc.201200567.
(5) (a) Beck, W.; Weigand, W.; Nagel, U.; Schaal, M. Angew. Chem.,
crystal, 0.05 × 0.03 × 0.02 mm3, triclinic; space group P1, Z = 2, a =
̅
11.9808(10) Å, b = 12.1509(10) Å, c = 13.7515(11) Å, α =
100.148(1)°, β = 100.671(1)°, γ = 103.831(1)°, V = 1858.6(3) Å3, ρcalc
= 1.588 g·cm−3, μ = 3.243 mm−1, ω- and φ-scans, 19 135 measured
intensities (3.1° ≤ 2θ ≤ 55.8°), semiempirical absorption correction
(0.855 ≤ T ≤ 0.938), 8836 independent (Rint = 0.0298) and 7775
observed intensities (I ≥ 2σ(I)), refinement of 460 parameters against
|F2| of all measured intensities with hydrogen atoms on calculated
positions. R = 0.0281, wR = 0.0591, Rall = 0.0355, wRall = 0.0615. The
asymmetric unit contains one formula unit. The diethyl ether molecule
in the asymmetric unit is disordered.
Int. Ed. Engl. 1984, 23, 377−378. (b) Bar, E.; Volkl, A.; Beck, F.;
̈
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Fehlhammer, W. P.; Robert, A. J. Chem. Soc., Dalton Trans. 1986, 863−
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Trans. 1996, 3231−3236. (d) Bertani, R.; Mozzon, M.; Michelin, R. A.
Inorg. Chem. 1988, 27, 2809−2815. (e) Bertani, R.; Mozzon, M.;
Michelin, R. A.; Benetollo, F.; Bombieri, G.; Castilho, T. J.; Pombeiro,
A. J. L. Inorg. Chim. Acta 1991, 189, 175−187. (f) Beck, G.;
Fehlhammer, W. P. Angew. Chem., Int. Ed. Engl. 1988, 27, 1344−1347.
(g) Motschi, H.; Angelici, R. J. Organometallics 1982, 1, 343−349.
(h) Michelin, R. A.; Zanotto, L.; Braga, D.; Sabatino, P.; Angelici, R. J.
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[16]. Crystals suitable for an X-ray diffraction study were obtained
by slow evaporation of the solvent from a dichloromethane solution of
[16]. C36H30MoN2O3P2, M = 696.50 g·mol−1, colorless crystal, 0.28 ×
0.22 × 0.04 mm3, orthorhombic, space group Pbca, Z = 8, a =
16.810(3) Å, b = 16.578(3) Å, c = 22.578(5) Å, V = 6292(2) Å3, ρcalc
=
1.471 g·cm−3, μ = 0.558 mm−1, ω- and φ-scans, 44 365 measured
intensities (3.6° ≤ 2θ ≤ 56.0°), semiempirical absorption correction
(0.859 ≤ T ≤ 0.978), 7496 independent (Rint = 0.0450) and 5636
observed intensities (I ≥ 2σ(I)), refinement of 405 parameters against
|F2| of all measured intensities with hydrogen atoms on calculated
positions. R = 0.0312, wR = 0.0607, Rall = 0.0531, wRall = 0.0653. The
asymmetric unit contains one formula unit.
(6) Bartel, K.; Fehlhammer, W. P. Angew. Chem., Int. Ed. Engl. 1974,
13, 599−600.
[17]. Crystals suitable for an X-ray diffraction study were obtained
by slow evaporation of the solvent from a THF solution of [17].
C36H30N2O3P2W, M = 784.41 g·mol−1, colorless crystal, 0.46 × 0.16 ×
0.06 mm3, orthorhombic, space group Pbca, Z = 8, a = 16.766(3) Å, b
= 16.528(3) Å, c = 22.564(5) Å, V = 6253(2) Å3, ρcalc = 1.667 g·cm−3,
μ = 3.837 mm−1, ω- and φ-scans, 59 375 measured intensities (3.6° ≤
2θ ≤ 55.9°), semiempirical absorption correction (0.271 ≤ T ≤
0.802), 7398 independent (Rint = 0.0688) and 5348 observed
intensities (I ≥ 2σ(I)), refinement of 405 parameters against |F2| of
all measured intensities with hydrogen atoms on calculated positions.
R = 0.0289, wR = 0.0603, Rall = 0.0493, wRall = 0.0658. The asymmetric
unit contains one formula unit.
(7) Fehlhammer, W. P.; Bartel, K.; Weinberger, B.; Plaia, U. Chem.
Ber. 1985, 118, 2220−2234.
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Chem. Ber. 1985, 118, 2235−2254. (b) Plaia, U.; Stolzenberg, H.;
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569−570. (b) Barluenga, J.; Aznar, F.; Weyershausen, B.; García-
Granda, S.; Martín, E. Chem. Commun. 1996, 2455−2456. (c) Hahn, F.
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ASSOCIATED CONTENT
* Supporting Information
■
(12) (a) Hahn, F. E.; Tamm, M. J. Organomet. Chem. 1993, 456,
C11−C14. (b) Hahn, F. E.; Tamm, M. J. Chem. Soc., Chem. Commun.
S
X-ray crystallographic files for [6], [6]2·2CH2Cl2, [10],
[13]·THF, [15]·Et2O, [16], and [17] (CIF files). This material
is available free of charge via the Internet at http://pubs.acs.org.
1993, 842−844. (c) Tamm, M.; Lugger, T.; Hahn, F. E. Organo-
̈
metallics 1996, 15, 1251−1256. (d) Kernbach, U.; Lugger, T.; Hahn, F.
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̈
AUTHOR INFORMATION
Corresponding Author
*E-mail: fehahn@uni-muenster.de.
■
̈
Notes
The authors declare no competing financial interest.
̈
ACKNOWLEDGMENTS
The authors thank the Graduate School of Chemistry Munster
and the International Research Training Group (IRTG 1444)
for predoctoral grants to A.C.D., K.-O.F. and C.S.B.
■
Engl. 1994, 33, 1356−1359.
̈
(14) (a) Liu, C.-Y.; Chen, D.-Y.; Lee, G.-H.; Peng, S.-M.; Liu, S.-T.
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