[3+2] Cycloadditions of molybdenum(II) azide complexes with nitriles and an alkyne

Article abstract of DOI:10.1021/om1007083

A series of products of [3+2] cycloaddition reactions of molybdenum azide complexes with nitriles and an alkyne were prepared and characterized. These include the tetrazolate complexes Mo(η³-C₃H ₅)(CO)₂(en)(N₄CR) (R = CH₃ (1), C₆H₅ (2), C(CH₃)₃ (3), CH=CHCN (4)) and the triazolate complexes Mo(η³-C₃H ₅)(CO)₂(L₂){N₃C₂(CO ₂CH₃)₂} (L₂ = en (6), dppe (7)). They are the first examples of a complex with a heterocyclic ligand prepared via a reaction of a group VIB metal azide with an unsaturated dipolarophile. All these complexes are fluxional in solution, with those containing en ligands displaying broad unresolved proton NMR signals at room temperature. With the exception of 1, their solution behavior was studied by low-temperature NMR spectroscopy. In contrast, the dppe complexes display average NMR signals at room temperature due to a fast exchange. The solid-state structures of these cycloaddition products were also determined by single-crystal X-ray diffraction analysis. The tetrazolate complexes 1, 2, and 4 adopt an asymmetric endo-conformation, while complex 3 adopts a symmetric endo-conformation. The tetrazolate ligand is N(1)-bonded in 1 and N(2)-bonded in complexes 2-4. The steric effect is the main reason for the N(2)-bonding mode found in 3. Complex 4 is the first structurally characterized product of a [3+2] cycloaddition reaction involving the C≡N bond of fumaronitrile. The triazolate complexes 6 and 7 adopt an asymmetric endo-conformation, with their heterocyclic ligands being bonded to the metal via N(2).

Full text of DOI:10.1021/om1007083

4282 Organometallics 2010, 29, 4282–4290
DOI: 10.1021/om1007083
[3þ2] Cycloadditions of Molybdenum(II) Azide Complexes with Nitriles
and an Alkyne
Fu-Chen Liu,* Yu-Liang Lin, and Pei-Shan Yang
Department of Chemistry, National Dong Hwa University, Hualien 974, Taiwan, Republic of China
Gene-Hsian Lee and Shie-Ming Peng
Department of Chemistry, National Taiwan University, Taipei 106, Taiwan, Republic of China
Received July 20, 2010
A series of products of [3þ2] cycloaddition reactions of molybdenum azide complexes with nitriles
and an alkyne were prepared and characterized. These include the tetrazolate complexes Mo(η3-
C3H5)(CO)2(en)(N4CR) (R=CH3 (1), C6H5 (2), C(CH3)3 (3), CHdCHCN (4)) and the triazolate
complexes Mo(η3-C3H5)(CO)2(L2){N3C2(CO2CH3)2} (L2 = en (6), dppe (7)). They are the first
examples of a complex with a heterocyclic ligand prepared via a reaction of a group VIB metal azide
with an unsaturated dipolarophile. All these complexes are fluxional in solution, with those
containing en ligands displaying broad unresolved proton NMR signals at room temperature. With
the exception of 1, their solution behavior was studied by low-temperature NMR spectroscopy. In
contrast, the dppe complexes display average NMR signals at room temperature due to a fast
exchange. The solid-state structures of these cycloaddition products were also determined by single-
crystal X-ray diffraction analysis. The tetrazolate complexes 1, 2, and 4 adopt an asymmetric endo-
conformation, while complex 3 adopts a symmetric endo-conformation. The tetrazolate ligand is
N(1)-bonded in 1 and N(2)-bonded in complexes 2-4. The steric effect is the main reason for the
N(2)-bonding mode found in 3. Complex 4 is the first structurally characterized product of a [3þ2]
cycloaddition reaction involving the CtN bond of fumaronitrile. The triazolate complexes 6 and 7
adopt an asymmetric endo-conformation, with their heterocyclic ligands being bonded to the metal
via N(2).
Introduction
a range of important applications in pharmaceutical and
biomedical applications,3 corrosion inhibitors,4 and ener-
getic materials.5 The [3þ2] dipolar cycloaddition of metal
azide complexes with unsaturated organic compounds has
also been a subject of interest for many decades.6 These azide
complexes have been reported to react with nitriles7 and
1,3-Dipolar cycloaddition, a common process in organic
chemistry,1 involves a reaction of 1,3-dipoles with unsatu-
rated dipolarophiles. Among various types of 1,3-dipoles,
the organic azides are particularly important, as they provide
an entry into the synthesis of triazoles and tetrazoles.2 These
heterocycles and their metal complex derivatives have found
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3-8633570.
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Published on Web 09/02/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 19, 2010 4283
isonitriles8 to produce metal-nitrogen- and metal-carbon-
bonded tetrazolate complexes, respectively, and with
alkynes9 to furnish triazolate metal complexes. In addition,
reactions of metal azide complexes with other unsaturated
substrates such as carbon monoxide, carbon disulfide, thio-
cyanates, and isothiocyanates have also been reported.8b,c,10
In general, these reactions involve electron-rich azide com-
plexes. During the past decades many main group metal11 as
well as late transition metal azide complexes of groups VIIB
to IIB have been examined in their reactions with unsatu-
rated substrates.7b,c,8a-8c,12 However, [3þ2] dipolar cycload-
dition has never been extended to the less electron-rich group
VIB metal azide complexes.13 Here we would like to report
our recent findings with respect to the reactivity of the
molybdenum azides toward nitriles and an alkyne.
could be a reason for such a difference in reaction tempera-
tures. These reactions, shown in eq 1, were monitored for
completeness by observing the disappearance of the asym-
metric N3 stretching band of azide complex Mo(η3-C3H5)-
(CO)2(en)(N3) in the IR spectrum.14 The tetrazolate com-
plexes prepared display different degrees of solubility in
commonly used polar organic solvents. Thus, complex 4
has a good solubility, while only DMSO and methanol
(sparingly) can dissolve complex 1, with complexes 2 and 3
being moderately soluble. Two carbonyl absorption bands of
about equal intensity consistent with the presence of a cis-
M(CO)2 unit15 were observed in the IR spectrum of each
complex. The CtN (2219 cm-1) and CdC (1637 cm-1
)
stretching bands in 4 are consistent with those found in
the tetrazole complexes In(tpp)[N4C(CHdCHCN)] (tpp =
dianionic tetraphenylporphyrin)16 and Mn(tpp)[N4C-
(CHdCHCN)].17
Results and Discussion
Preparations and Properties of Mo(η3-C3H5)(CO)2(en)-
(N4CR) (R = CH3 (1); C6H5 (2); C(CH3)3 (3); CHdCHCN
(4)). Tetrazolate molybdenum complexes Mo(η3-C3H5)(CO)2-
(en){N4C(CH3)}, 1, Mo(η3-C3H5)(CO)2(en){N4C(C6H5)}, 2,
and Mo(η3-C3H5)(CO)2(en){N4CC(CH3)3}, 3, were isolated
from reactions of Mo(η3-C3H5)(CO)2(en)(N3)14 with aceto-
nitrile, benzonitrile, and trimethylacetonitrile, respectively,
at elevated temperatures. In contrast, the reaction of Mo(η3-
C3H5)(CO)2(en)(N3) with fumaronitrile produced Mo(η3-
C3H5)(CO)2(en){N4C(CHdCHCN)}, 4, at room tempera-
ture. The more electron-withdrawing nature of fumaronitrile
Due to the Bailar pseudorotation, fluxional behavior is a
general phenomenon observed in a M(η3-C3H5)(CO)2(L2)-
(X) (M=Mo, W; L2=nonrigid bidentate ligand; X=anionic
monodentate ligand) type of complex in solution.18 Com-
plexes 1-4 displayed broad unresolved proton NMR signals
at room temperature. Further characterization of the solu-
tion behavior of 1 was performed at elevated temperature. As
the temperature was raised, the broad signals sharpened
gradually, with average NMR signals being observed at
115 °C. At this temperature the proton spectrum displayed
only three signals for the allyl group hydrogens (a symmetric
pattern). The spectrum averaging resulted from a fast rota-
tion of the triangular face formed by the tetrazole ligand and
the chelating en ligand with respect to the face formed by the
allyl and two carbonyl ligands.19 In the 13C NMR spectrum
the tetrazolate N4C carbon appeared at 159.04 ppm.
Complexes 2-4 were characterized by 1H-1H COSY and
1H-13C HMQC 2D NMR analyses at low temperature
(-40 °C for 2; -60 °C for 3 and 4). For each complex a pro-
ton spectrum with five allyl, four NH2, and four CH2 proton
resonances was observed, suggesting the existence of an
asymmetric conformation at low temperature. Two vinyl
hydrogens on the substituted tetrazolate ligand of 4 ap-
peared at 7.64 and 6.50 ppm (d, JH-H = 16.4 Hz), consistent
with their anti-arrangement. In the 13C NMR spectra, two
carbonyl resonances were observed for each complex, and
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4284 Organometallics, Vol. 29, No. 19, 2010
Liu et al.
Figure 1. Molecular structure of Mo(η3-C3H5)(CO)2(en){N4C-
(CH3)}, 1, with 30% probability thermal ellipsoids.
Figure 3. Molecular structure of Mo(η3-C3H5)(CO)2(en)-
{N4CC(CH3)3}, 3, with 50% probability thermal ellipsoids.
Figure 2. Molecular structure of Mo(η3-C3H5)(CO)2(en){N4C-
(C6H5)}, 2, with 50% probability thermal ellipsoids.
the tetrazolate ligand carbon atom appeared at 162.38,
170.8, and 159.0 ppm for 2, 3, and 4, respectively.
Figure 4. Molecular structure of Mo(η3-C3H5)(CO)2(en){N4C-
(CHdCHCN)}, 4, with 50% probability thermal ellipsoids.
The molecular structures of 1-4 were analyzed by single-
crystal X-ray crystallography. The molecular structures of
1-4 are shown in Figures 1-4. Although the unit cell of 4
contains two crystallographically different molecules, only
one molecule is displayed due to the difference being insig-
nificant. The crystallographic data and selected bond dis-
tances and bond angles are given in Tables 1-5. The
molecular structure of each complex can be described as a
distorted octahedral, with the central atom being surrounded
by allyl, tetrazolate, en, and two carbonyl ligands. The two
carbonyls are cis to each other and occupy the equatorial
positions. The allyl occupies an axial position with its open
face eclipsing the two carbonyl ligands. Complexes 1, 2, and
4 adopt an asymmetric endo-conformation, with two nitro-
gen atoms of the en ligand occupying an equatorial and an
axial positions and the tetrazolate ligand occupying another
equatorial position trans to a carbonyl ligand. Complex 3
adopts a symmetric endo-conformation, in which two nitro-
gen atoms of the en ligand occupy the equatorial positions,
each of them trans to a carbonyl ligand, and the tetrazolate
ligand occupies the axial position trans to the allyl ligand.
According to our previous study, the solid-state structures of
Mo(η3-C3H5)(CO)2(en)(X)14 appear to be dependent on the
anionic ligand X-. The asymmetric endo-forms were found
for compounds containing a weak field ligand, while the
symmetric endo-forms were found in the case of a strong field
ligand. A strong donor ability of the tert-butyl group
may have induced a strong interaction between the metal
and the tetrazolate ligand, resulting in the symmetric endo-
conformation in the solid state.
The tetrazolate ligand in 1 is bonded to the Mo via its N(1)
˚
atom. The Mo-N(1) bond distance (2.247(12) A) is slightly
longer than that of the azide complex Mo(η3-C3H5)(CO)2-
(en)(N3) (2.233(3) A).14 The five-membered tetrazolate ring
˚
exhibits an irregular pentagonal structure. The NdN bond
˚
distances are in the range 1.33(2)-1.40(2) A, and the CdN
bond distances are 1.29(2) and 1.31(3) A, respectively,
˚
suggesting a localization of π-electrons on the CdN bond.
The short CdN distance has also been found in the tetra-
zolate complex (2,3,7,8,12,13,17,18-octaethylprophinato)-
In(N4CMe) (1.28(1) A).2d The tetrazolate ligands in 2-4 are
˚
N(2)-bonded to the metal. The Mo-N(2) bond distances are
2.2663(17) A in 2, 2.2120(16) A in 3, and 2.2454(17) and
˚
˚
˚
2.2688(18) A in 4. The short Mo-N(2) bond distance in 3
confirmed a strong interaction between Mo and the tetra-
zolate ligand.
The tetrazolate ligand could be coordinated to a metal
through either its N(1) or N(2) nitrogen. The theoretic calcu-
lation has suggested both types of bonding modes to be essen-
tially energetically equivalent.20 It has been observed that elec-
tronegative substituents in the 5-position give predominantly

Article
Organometallics, Vol. 29, No. 19, 2010 4285
Table 1. Crystallographic Data for Mo(η3-C3H5)(CO)2(en){N4C(CH3)}, 1, Mo(η3-C3H5)(CO)2(en){N4C(C6H5)}, 2, Mo(η3-C3H5)-
(CO)2(en){N4CC(CH3)3}, 3, and Mo(η3-C3H5)(CO)2(en){N4C(CHdCHCN)}, 4
empirical formula
fw
T (K)
C9H16MoN6O2
336.22
150(2)
C14H18MoN6O2
398.28
150(2)
C12H22MoN6O2
378.30
150(2)
C11H15MoN7O2
373.24
150(2)
cryst syst
space group
orthorhombic
Pnnm
triclinic
P1
monoclinic
P2(1)/c
11.1095(5)
12.4776(5)
12.1090(5)
triclinic
P1
10.6504(7)
10.7583(7)
14.8762(9)
˚
a (A)
15.1003(5)
11.6868(4)
7.3957(2)
110.416(2)
90
91.906(2)
1305.15(7)
4
7.6295(7)
9.8074(9)
11.8453(11)
94.424(1)
102.060(2)
118.888(1)
806.86(13)
2
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
101.432(1)
90.975(1)
3
˚
V (A )
Z
F
1645.25(12)
4
1.527
0.30 ꢀ 0.30 ꢀ 0.10
Mo KR (0.71073)
2.37-27.50
-14 e h e 14
-16 e k e 15
-15 e l e 15
12 313
1485.09(16)
4
1.669
0.40 ꢀ 0.35 ꢀ 0.10
Mo KR (0.71073)
1.38-27.50
-13 e h e 13
-13 e k e 13
-19 e l e 19
19 210
calcd (g/cm3)
1.711
1.639
cryst size (mm3)
0.15 ꢀ 0.12 ꢀ 0.05
Mo KR (0.71073)
2.20-27.49
-17 e h e 19
-15 e k e 12
-9 e l e 9
6670
1611
680
99.6
1.010
0.25 ꢀ 0.25 ꢀ 0.12
Mo KR (0.71073)
1.89-27.50
-9 e h e 9
-12 e k e 12
-15 e l e 15
10 455
3689
404
99.9
0.832
˚
radiation (λ, A)
θ limits (deg)
index ranges
reflns collected
unique reflns
3762
776
99.8
0.811
6790
752
99.7
0.899
unique reflns [I > 2.0σ(I )]
completeness to θ (%)
μ (mm-1
)
data/restraints/params
R1a [I > 2.0σ(I )]
wR2b (all data)
Rint
1611/0/137
0.0857
0.2084
0.0507
1.220
3689/0/208
0.0273
0.0676
0.0307
1.021
3762/0/193
0.0259
0.0622
0.0325
1.059
6790/0/379
0.0263
0.0626
0.0186
1.119
GOF on F2
P
P
P
P
aR1 = ||Fo|| - |Fc||/ ||Fo|. bwR2 = { w(Fo2 - Fc2)2/ w(Fo2)2}1/2
.
˚
˚
Table 2. Selected Bond Distances (A) and Bond Angles (deg) for
Table 3. Selected Bond Distances (A) and Bond Angles (deg) for
Mo(η3-C3H5)(CO)2(en){N4C(C6H5)}, 2
Mo(η3-C3H5)(CO)2(en){N4C(CH3)}, 1
Mo-C(1)
Mo-N(1)
C(1)-O(1)
C(8)-N(1)
N(2)-N(3)
N(4)-C(8)
1.85(2)
2.247(12)
1.21(2)
1.29(2)
1.33(2)
1.31(3)
Mo-C(2)
Mo-N(5)
C(2)-O(2)
N(2)-N(1)
N(3)-N(4)
1.957(17)
2.254(9)
1.147(19)
1.40(2)
Mo-C(1)
Mo-N(2)
Mo-N(6)
C(2)-O(2)
N(2)-N(1)
N(3)-N(4)
1.952(2)
2.2663(17)
2.2762(18)
1.158(3)
1.345(2)
1.339(2)
Mo-C(2)
Mo-N(5)
C(1)-O(1)
C(8)-N(1)
N(2)-N(3)
N(4)-C(8)
1.950(2)
2.2333(18)
1.154(3)
1.328(3)
1.317(2)
1.334(3)
1.38(3)
C(1)-Mo-C(2)
C(1)-Mo-N(5A)
C(2)-Mo-N(5A)
N(5)-Mo-N(5A)
C(4)-Mo-N(5)
C(2)-Mo-N(1)
N(3)-N(2)-N(1)
Mo-C(1)-O(1)
C(3)-C(4)-C(5)
75.8(7)
97.5(7)
94.8(5)
75.5(5)
86.7(6)
171.7(4)
108.0(14)
174.7(17)
115.3(19)
C(1)-Mo-N(1)
C(2)-Mo-N(5)
N(5)-Mo-N(1)
N(1)-Mo-N(5A)
C(1)-Mo-N(5)
C(8)-N(1)-N(2)
N(2)-N(3)-N(4)
Mo-C(2)-O(2)
112.1(7)
94.8(5)
77.6(4)
C(1)-Mo-C(2)
C(2)-Mo-N(2)
N(5)-Mo-N(6)
N(5)-Mo-N(2)
C(1)-Mo-N(6)
C(8)-N(1)-N(2)
N(2)-N(3)-N(4)
Mo-C(2)-O(2)
80.08(9)
167.79(8)
75.19(7)
C(1)-Mo-N(2)
C(2)-Mo-N(5)
N(2)-Mo-N(6)
C(1)-Mo-N(5)
C(2)-Mo-N(6)
N(3)-N(2)-N(1)
Mo-C(1)-O(1)
C(3)-C(4)-C(5)
94.59(8)
91.45(8)
86.23(6)
92.15(8)
96.49(8)
110.55(17)
177.20(19)
114.3(2)
86.6(4)
77.69(7)
168.0(6)
103.7(14)
108.4(17)
174.3(14)
166.86(8)
103.7(14)
108.18(18)
176.0(2)
˚
Table 4. Selected Bond Distances (A) and Bond Angles (deg) for
Mo(η3-C3H5)(CO)2(en){N4CC(CH3)3}, 3
N(2)-bonded isomers, while those with electropositive groups
in the 5-position lead predominantly to the N(1)-bonding
mode.6c,20b,21 Thus, the steric hindrance of the bulky tert-butyl
substituent is the main driving force in determining the N(2)-
bonding mode for complex 3. The interatomic distances within
the five-membered tetrazolate ring are more typical than those
found in 1, consistent with the delocalization of the π-electrons
within the heterocycle. They are in the range 1.317(2)-1.345(2)
Mo-C(1)
Mo-N(2)
Mo-N(6)
C(2)-O(2)
N(2)-N(1)
N(3)-N(4)
1.942(2)
2.2120(16)
2.2916(16)
1.152(3)
1.343(2)
1.342(2)
Mo-C(2)
Mo-N(5)
C(1)-O(1)
C(8)-N(1)
N(2)-N(3)
N(4)-C(8)
1.973(2)
2.2571(17)
1.164(2)
1.329(3)
1.309(2)
1.337(3)
C(1)-Mo-C(2)
C(2)-Mo-N(2)
N(5)-Mo-N(6)
N(5)-Mo-N(2)
C(1)-Mo-N(6)
C(8)-N(1)-N(2)
N(2)-N(3)-N(4)
Mo-C(2)-O(2)
79.64(9)
87.49(7)
75.25(6)
C(1)-Mo-N(2)
C(2)-Mo-N(5)
N(2)-Mo-N(6)
C(1)-Mo-N(5)
C(2)-Mo-N(6)
N(3)-N(2)-N(1)
Mo-C(1)-O(1)
C(3)-C(4)-C(5)
88.36(7)
79.17(6)
81.52(6)
103.28(7)
99.46(7)
110.72(15)
177.10(19)
115.4(2)
˚
˚
A in 2, 1.309(2)-1.343(2) A in 3, and 1.324(2)-1.338(3) or
˚
1.321(2)-1.342(2) A in 4 (two independent molecules in the unit
cell). In complex 2, the tetrazolate and the phenyl rings are not
99.46(7)
169.88(7)
104.10(15)
108.22(15)
177.69(18)
coplanar. The C(tetrazolate)-C(phenyl) inter-ring distance is
(20) (a) Kieft, R. L.; Peterson, W. M.; Blundell, G. L.; Horton, S.;
Hendry, R. A.; Jonasson, H. B. Inorg. Chem. 1976, 15, 1721. (b) Redfield,
D. A.; Nelson, J. H.; Henry, R. A.; Moore, D. W.; Jonassen, H. B. J. Am.
Chem. Soc. 1974, 96, 6298. (c) Nelson, J. H.; Schmitt, D. L.; Henty, R. A.;
Moore, D. W.; Jonassen, H. B. Inorg. Chem. 1970, 9, 2678.
˚
1.477 A, and the dihedral angle between the rings is 16.74°,
suggesting no interannular conjugation between them. The
intermolecular hydrogen bonds were found in 2 and 3.
(21) Paul, P.; Chakladar, S.; Nag, K. Inorg. Chim. Acta 1990, 170, 27.

4286 Organometallics, Vol. 29, No. 19, 2010
Liu et al.
3
˚
Table 5. Selected Bond Distances (A) and Bond Angles (deg) for Mo(η -C3H5)(CO)2(en){N4C(CHdCHCN)}, 4
molecule 1
molecule 2
molecule 1
molecule 2
Mo-C(1)
Mo-N(2)
Mo-N(6)
C(2)-O(2)
N(2)-N(1)
N(3)-N(4)
C(9)-C(10)
1.949(2)
2.2454(17)
2.2794(17)
1.156(3)
1.338(2)
1.327(3)
1.326(3)
1.959(2)
2.2688(18)
2.2768(18)
1.159(3)
1.342(2)
1.332(3)
1.326(4)
Mo-C(2)
Mo-N(5)
C(1)-O(1)
C(8)-N(1)
N(2)-N(3)
N(4)-C(8)
N(7)-C(11)
1.950(2)
2.2371(18)
1.158(3)
1.335(3)
1.324(2)
1.338(3)
1.149(3)
1.939(2)
2.2384(18)
1.157(3)
1.341(3)
1.321(2)
1.333(3)
1.148(3)
C(1)-Mo-C(2)
C(2)-Mo-N(2)
N(5)-Mo-N(6)
N(5)-Mo-N(2)
C(1)-Mo-N(6)
C(8)-N(1)-N(2)
N(2)-N(3)-N(4)
Mo-C(2)-O(2)
79.30(9)
81.35(9)
169.95(8)
75.59(6)
C(1)-Mo-N(2)
C(2)-Mo-N(5)
N(2)-Mo-N(6)
C(1)-Mo-N(5)
C(2)-Mo-N(6)
N(3)-N(2)-N(1)
Mo-C(1)-O(1)
C(3)-C(4)-C(5)
96.42(8)
90.51(8)
82.44(6)
94.82(8)
100.07(8)
110.39(17)
177.2(2)
114.3(2)
98.35(8)
91.58(8)
82.06(6)
90.62(8)
95.78(8)
110.16(17)
177.3(2)
115.9(2)
168.95(8)
75.59(7)
79.64(7)
170.39(8)
103.66(17)
108.80(17)
175.0(2)
78.37(7)
165.87(8)
103.44(18)
109.22(18)
178.4(2)
In compound 2, two kinds of intermolecular hydrogen bonds
˚
bond angles are given in Tables 6 and 7. Complex 5 adopts an
asymmetric endo-conformation. The Mo-N3 bond distance
between N(6)H N(4) (N(4)-N(6) = 3.009 A) and CO-
3 3 3
˚
˚
(1) HN(5) (N(5)-O(1)=3.017 A) result in a bilayered one-
is 2.253(2) A. The N-N bond distances are 1.153(4) and
1.190(3) A, the shorter one being between the middle nitro-
3 3 3
˚
dimensional polymer. In compound 3, two pairs of intermole-
cular hydrogen bonds between N(6)H N(3) (N(3)-N(6) =
gen and the nitrogen bonded to the metal. These bond
distances are similar to those found in the azide complex
3 3 3
˚
3.023 A) lead to a dimeric structure.
3
W(CO)2(η -C3H5)(en)(N3) (1.152(6) and 1.191(6) A).14 The
˚
In principle, the cycloaddition of fumaronitrile with a
metal azide can take place via either the CdC or CtN bond.
If the CdC bond is involved, a triazolate complex is formed
accompanied by removal of one HCN molecule. In contrast,
if the CtN bond is involved, a tetrazolate complex is formed.
Among the literature reports, most of these cycloadditions
involve the CdC bond of fumaronitrile.9b,c,12f,12i,22 To our
knowledge, there are only two reports16,17 in which the CtN
bonds were involved, and complex 4 is the first structurally
characterized product of such a reaction.
azide moiety exhibits a nearly linear arrangement. The
N-N-N bond angle of the azide ligand is 177.4(3)°, which
is consistent with the range observed for coordinated azide
ligands (173-180°).14,24
Preparations and Properties of Mo(η3-C3H5)(CO)2(en)-
{N3C2(CO2CH3)2}, 6, and Mo(η3-C3H5)(CO)2(dppe){N3C2-
(CO2CH3)2}, 7. Dppe complex 5 did not react with
fumaronitrile. In its reactions with acetonitrile, benzonitrile,
and trimethylacetonitrile under reflux conditions it decom-
posed, with no cycloaddition products being detected. How-
ever, it did react with an activated alkyne, dimethyl
acetylenedicarboxylate. The triazolate complexes Mo(η3-
C3H5)(CO)2(en){N3C2(CO2CH3)2}, 6, and Mo η3-C3H5)-
(CO)2(dppe){N3C2(CO2CH3)2}, 7, were prepared from the
reactions of Mo(η3-C3H5)(CO)2(L2)(N3) (L2 = en, dppe) with
dimethyl acetylenedicarboxylate at room temperature (eq 3).
The reaction completeness was confirmed by the disappear-
ance of the asymmetric N3 stretching band of the starting azide
complex. Both complexes are air-stable and have better solu-
bility in generally used polar organic solvent compared with
the tetrazolate complexes prepared in this work. In the IR
spectrum, two carbonyl absorption bands of about equal
intensity were observed for 6 (1928 and 1828 cm-1) and 7
(1940 and 1849 cm-1). The higher carbonyl absorption energy
of 7 is due to the π back-bonding ability of the dppe ligand
competing for the electron density with the carbonyl ligands.
The NdN absorption of the triazolate ring and that of CdO
are at 1450 and 1700 cm-1 in 6 and 1434 and 1716 cm-1 in 7.
Preparations and Properties of Mo(η3-C3H5)(CO)2(dppe)-
(N3), 5. Treatment of the molybdenum complex Mo(η3-
C3H5)(CO)2(CH3CN)2(Br)23 with 1,2-bis(diphenylphos-
phino)ethane (dppe) and excess NaN3 affords red azide
compound Mo(η3-C3H5)(CO)2(dppe)(N3), 5 (eq 2). It is air-
stable and soluble in CH2Cl2, CHCl3, and acetone.
In general, the energy barrier of the fluxional behavior of
the dppe complexes is lower than that of their en analogues.
Complex 5 displays average NMR signals at room temper-
ature. Its 31P resonance appears at 44.7 ppm as a singlet. As
the temperature was lowered, the signal broadened and
eventually split into two signals at 45.19 and 41.72 ppm at
-90 °C, due to the nonequivalence of the two phosphorus
atoms. In the 13C NMR spectrum, the methylene carbon of
the dppe ligand appears at 24.87 ppm as a triplet (Jc-p=19.2
Hz), due to a virtual coupling with two phosphorus atoms.20
This phenomenon also occurs in complex 7 and has been
previously observed in other dppe complexes.9c,d,12f In the IR
spectrum, the asymmetric N3 stretching band appears at
2057 cm-1, consistent with the generally observed range of
2050-2070 cm-1 10a
.
The molecular structure of 5 is shown in Figure 5, and the
crystallographic data and the selected bond distances and
Complex 6 adopts an asymmetric conformation in solu-
tion at low temperature (-100 °C). In the 1H NMR spectrum
(22) Singh, K. S.; Kreisel, K. A.; Yap, G. P. A.; Kollipara, M. R.
J. Organomet. Chem. 2006, 691, 3509.
(23) Dieck, H. T.; Friedel, H. J. Organomet. Chem. 1968, 14, 375.
(24) Palenik, G. H. Acta Crystallogr. 1964, 17, 360.

Article
Organometallics, Vol. 29, No. 19, 2010 4287
Figure 5. Molecular structure of Mo(η3-C3H5)(CO)2(dppe)(N3), 5, with 50% probability thermal ellipsoids.
Table 6. Crystallographic Data for Mo(η3-C3H5)(CO)2(dppe)(N3), 5, Mo(η3-C3H5)(CO)2(en){N3C2(CO2CH3)2}, 6, and Mo(η3-C3H5)-
(CO)2(dppe){N3C2(CO2CH3)2}, 7
empirical formula
fw
T (K)
C31H29MoN3O2P2
633.45
150(2)
C13H19MoN5O6
437.27
298(2)
C37H35MoN3O6P2
775.56
298(2)
cryst syst
space group
orthorhombic
P2(1)2(1)2(1)
9.2366(6)
11.6243(7)
26.1056(17)
90
2802.9(3)
4
1.501
0.25 ꢀ 0.18 ꢀ 0.15
Mo KR (0.71073)
1.56-27.50
-12 e h e 12
-14 e k e 15
-33 e l e 33
21 657
monoclinic
P2(1)/c
monoclinic
P2(1)/n
˚
a (A)
7.9487(2)
11.2699(4)
19.7532(6)
91.5180(10)
1768.89(9)
4
14.3865(6)
12.1193(5)
21.6669(9)
108.286(1)
3586.9(3)
4
˚
b (A)
˚
c (A)
β (deg)
3
V (A )
˚
Z
F
calcd (g/cm3)
1.646
1.436
cryst size (mm3)
0.47 ꢀ 0.14 ꢀ 0.12
Mo KR (0.71073)
2.06-28.32
-10 e h e 10
-15 e k e 15
-26 e l e 26
19 804
4407
888
100.0
0.781
0.40 ꢀ 0.40 ꢀ 0.25
Mo KR (0.71073)
1.51-27.50
-18 e h e 18
-15 e k e 15
-27 e l e 28
27 248
8248
1592
99.9
0.504
˚
radiation (λ, A)
θ limits (deg)
index ranges
reflns collected
unique reflns
6424
1296
100.0
0.616
unique reflns [I > 2.0σ(I )]
completeness to θ (%)
μ (mm-1
)
data/restraints/params
R1a [I > 2.0σ(I )]
wR2b (all data)
Rint
6424/0/352
0.0319
0.0708
0.0427
1.108
4407/0/228
0.0216
0.0618
0.0249
1.050
8248/0/444
0.0366
0.0943
0.0360
1.034
GOF on F2
P
P
P
P
aR1 = ||Fo|| - |Fc||/ ||Fo|. bwR2 = { w(Fo2 - Fc2)2/ w(Fo2)2}1/2
.
asymmetric patterns were observed for both allyl and en
hydrogens. In the 13C NMR spectrum the triazolate carbons
appeared at 137.3 and 126.2 ppm.
Similar to the dppe complex 5, complex 7 also displays
average NMR signals at room temperature. Its 31P reso-
nance appears at 51.10 ppm at room temperature and splits
into two broad signals at 47.07 and 46.10 ppm at -90 °C, due
to the nonequivalence of the two phosphorus atoms at low
temperature. In the 13C NMR spectrum, the triazolate
carbon signal appears at 138.47 ppm and the methylene
carbon of the dppe ligand appears at 26.19 ppm (t, Jc-p =
20.3 Hz).
The molecular structures of 6 and 7 are shown in Figures 6
and 7, and the crystallographic data and selected bond
distances and bond angles are given in Tables 6, 8, and 9.
These two molecules have similar structures. Both complexes
adopt asymmetric endo-conformations, with the triazolate
being N(2)-bonded to the metal. The Mo-N(2) bond
˚
˚
distance is 2.2636(13) A in 6 and 2.2228(18) A in 7. Com-
pared with the en ligand, the dppe ligand is more sterically

4288 Organometallics, Vol. 29, No. 19, 2010
Liu et al.
˚
Table 7. Selected Bond Distances (A) and Bond Angles (deg) for
Mo(η3-C3H5)(CO)2(dppe)(N3), 5
Mo-C(1)
Mo-N(1)
Mo-P(2)
C(2)-O(2)
N(2)-N(3)
1.948(3)
2.253(2)
2.5978(7)
1.145(3)
1.153(4)
Mo-C(2)
Mo-P(1)
C(1)-O(1)
N(1)-N(2)
1.956(3)
2.4919(7)
1.159(4)
1.190(3)
C(1)-Mo-C(2)
C(1)-Mo-P(2)
C(2)-Mo-P(1)
N(1)-Mo-P(1)
C(2)-Mo-N(1)
N(3)-N(2)-N(1)
Mo-C(1)-O(1)
C(3)-C(4)-C(5)
79.26(12)
C(1)-Mo-P(1)
C(1)-Mo-N(1)
C(2)-Mo-P(2)
N(1)-Mo-P(2)
N(2)-N(1)-Mo
P(1)-Mo-P(2)
Mo-C(2)-O(2)
82.76(8)
104.50(10)
94.79(9)
78.18(6)
130.6(2)
77.23(2)
177.6(3)
158.75(9)
93.57(9)
77.40(7)
169.53(10)
177.4(3)
174.6(3)
117.3(3)
Figure 7. Molecular structure of Mo(η3-C3H5)(CO)2(dppe)-
{N3C2(CO2CH3)2}, 7, with 30% probability thermal ellipsoids.
˚
Table 8. Selected Bond Distances (A) and Bond Angles (deg) for
Mo(η3-C3H5)(CO)2(en){N3C2(CO2CH3)2}, 6
Figure 6. Molecular structure of Mo(η3-C3H5)(CO)2(en)-
{N3C2(CO2CH3)2}, 6, with 50% probability thermal ellipsoids.
Mo-C(1)
Mo-N(2)
Mo-N(5)
C(2)-O(2)
N(2)-N(3)
N(1)-C(8)
1.9444(17)
2.2636(13)
2.2781(14)
1.149(2)
1.3434(19)
1.3472(19)
Mo-C(2)
Mo-N(4)
C(1)-O(1)
N(1)-N(2)
N(3)-C(9)
C(8)-C(9)
1.9556(17)
2.2404(13)
1.161(2)
1.3282(18)
1.342(2)
1.391(2)
demanding; therefore, the shorter Mo-N(2) bond distance
in 7 may suggest a stronger bonding interaction between the
triazolate ligand and the metal. The interatomic distances of
the five-membered triazolate ring are similar in both mole-
C(1)-Mo-C(2)
C(2)-Mo-N(2)
Mo-C(1)-O(1)
C(3)-C(4)-C(5)
79.66(8)
171.69(6)
176.40(18)
114.82(18)
C(1)-Mo-N(2)
N(4)-Mo-N(5)
Mo-C(2)-O(2)
99.47(7)
75.10(5)
176.88(17)
˚
cules. They are in the range 1.3282(18)-1.391(2) A in 6 and
˚
1.327(3)-1.387(3) A in 7. Compound 6 also contains inter-
molecular hydrogen bond CO(4) HN(4) (N(4)-O(4) =
3 3 3
˚
2.957 A), resulting in a one-dimensional polymer.
˚
Table 9. Selected Bond Distances (A) and Bond Angles (deg) for
Mo(η3-C3H5)(CO)2(dppe){N3C2(CO2CH3)2}, 7
It has been reported that the N(1)-bonded triazolate
ligand (N3C2(CO2CH3)2) complex is a kinetic product, while
its N(2)-bonded isomer is a thermodynamic product.7d,12d
The transformation of the N(1) mode to the N(2) mode has
been observed during the formation of ruthenium triazolate
complexes,9b,c and in several cases both the N(1)- and N(2)-
bonded isomers have been found to coexist in the reaction.25
In our case, the time-elapsed 31P NMR study of the forma-
tion of 7 did not provide any evidence for the existence of the
N(1)-bonded isomer during the reaction.
Mo-C(1)
Mo-N(2)
Mo-P(2)
C(2)-O(2)
N(1)-N(2)
N(3)-C(7)
1.950(3)
2.2228(18)
2.6059(6)
1.151(3)
1.327(3)
1.333(3)
Mo-C(2)
Mo-P(1)
C(1)-O(1)
N(1)-C(6)
N(2)-N(3)
C(6)-C(7)
1.977(3)
2.5526(6)
1.147(3)
1.338(3)
1.345(3)
1.387(3)
C(1)-Mo-C(2)
C(2)-Mo-N(2)
C(1)-Mo-P(2)
C(2)-Mo-P(2)
N(2)-Mo-P(1)
N(2)-N(1)-C(6)
N(1)-C(6)-C(7)
P(1)-Mo-P(2)
Mo-C(2)-O(2)
79.63(11)
165.21(10)
168.90(9)
102.06(8)
83.89(5)
106.16(18)
107.7(2)
76.62(2)
C(1)-Mo-N(2)
C(1)-Mo-P(1)
C(2)-Mo-P(1)
N(2)-Mo-P(2)
N(3)-N(2)-N(1)
C(7)-N(3)-N(2)
N(3)-C(7)-C(6)
Mo-C(1)-O(1)
C(3)-C(4)-C(5)
90.46(10)
92.65(9)
85.62(8)
85.62(5)
112.22(18)
105.37(19)
108.5(2)
176.1(3)
116.4(3)
Conclusion
This study describes the first examples of [3þ2] cycloaddi-
tion reactions of a group VIB metal azide complex Mo(η3-
C3H5)(CO)2(L2)(N3) (L2 = en, dppe) with nitriles and an
alkyne, respectively, to generate tetrazolate complexes 1-4
and triazolate complexes 6 and 7. The heterocyclic ligand is
N(1)-bonded in 1 and N(2)-bonded in other tetrazolate and
triazolate complexes. The steric effect is the predominant
factor in determining the N(2)-bonding mode in 3; however,
the electronic effect could account for its symmetric endo-
conformation. In general, the [3þ2] cycloaddition of fumar-
onitrile involves the addition of a CdC bond, and the
examples involving the CtN bond to form a tetrazolate
174.3(2)
complex are rare. Complex 4 represents the first structurally
characterized product of the latter addition mode. The dppe
complex 5 reacted with an activated alkyne, dimethyl acet-
ylenedicarboxylate, but failed to react with nitriles. Poor
reactivity of 5 toward nitriles can be explained by a lower
electron density on the metal in the case of dppe, a good
π-acceptor ligand, compared with en.
Experimental Section
General Procedures. All manipulations were carried out on a
standard high-vacuum line or in a drybox under nitrogen.
(25) Parimal, P.; Kamalaksha, N. Inorg. Chem. 1987, 26, 2969.

Article
Organometallics, Vol. 29, No. 19, 2010 4289
Reagents were used as obtained from the commercial suppliers,
and solvents were dried and freshly distilled prior to use.
Mo(CO)2(η3-C3H5)(en)(N3)11 and Mo(CO)2(η3-C3H5)(CH3-
CN)2(Br)23 were prepared according to the literature proce-
dures. Elemental analyses were obtained on a Hitachi 270-30
instrument. Proton spectra (internally referenced to TMS, δ
0.00 ppm) were recorded on either a Bruker Avance DPX300 or
a Bruker Avance II 400 spectrometer operating at 300.130 and
400.132 MHz, respectively. 31P spectra (externally referenced to
85% H3PO4, δ 0.00 ppm) were recorded on a Bruker Avance II
400 spectrometer operating at 161.976 MHz. Infrared spectra
were recorded on a JASCO FT-IR 401 spectrometer with 4 cm-1
resolution.
Crystallization of the resulting yellow solid from a CH3OH/
ether/hexane mixture led to the isolation of 294.4 mg (73.6%
yield) of the title product as yellow crystals. 1H NMR (CD3OD,
-40 °C): δ 8.05-7.43 (m, 5H, C6H5), 6.46 (br s, 1H, NH2), 4.29
(br s, 1H, NH2), 4.13 (m, 1H, Hc), 3.96 (br s, 1H, NH2), 3.48
(br s, 1H, NH2), 3.32 (br s, 1H, Hs), 2.92 (br s, 1H, Hs), 2.66 (br s,
1H, CH2), 2.51(br s, 1H, CH2), 2.36 (br s, 1H, CH2), 2.04 (br s,
1H, CH2), 1.29 (d, J = 7.2 Hz, 1H, Ha), 1.02 (d, J = 7.2 Hz, 1H,
Ha). 13C NMR (CD3OD, -40 °C): δ 226.19, 225.11 (CO), 162.38
(N4C), 128.98, 128.86, 128.60, 126.12 (C6H5), 69.58 (Cc), 55.79,
55.16 (Ct), 43.44, 41.49 (CH2). IR (KBr): 3318(w), 3308(w),
3208(vw), 3125(w), 3065(vw), 2989(vw), 2964(vw), 2939(vw),
2884(vw), 2862(vw), 1930(vs), 1825(vs), 1607(w), 1456(w),
1443(w), 1384(vw), 1364(vw), 1352(vw), 1333(vw), 1302(vw),
1281(vw), 1263(vw), 1224(vw), 1185(vw), 1176(vw), 1154(vw),
1138(w), 1106(w), 1071(vw), 1053(w), 1038(vw), 1021(vw),
1011(vw), 997(vw), 963(vw), 948(vw), 919(vw), 900(vw), 874-
(vw), 834(vw), 800(vw), 788(vw), 731(w), 693(w), 670(vw), 666-
(vw), 626(vw), 604(vw), 577(vw), 566(vw), 537(vw), 508(vw),
497(vw), 472(vw), 465(vw) cm-1. Anal. Calcd for C14H18Mo-
N6O2: N, 21.10; C, 42.22; H, 4.56. Found: N, 21.00; C, 42.29; H,
4.60.
X-ray Crystal Structure Determination. Suitable crystals of
1-7 were mounted and sealed inside glass capillaries under
nitrogen. Crystallographic data collections were carried out on a
Nonius KappaCCD diffractometer with graphite-monochro-
˚
mated Mo KR radiation (λ = 0.71073 A) at 150(2) or 298(2) K.
Unit cell parameters were retrieved and refined using DENZO-
SMN26 software on all reflections. Data reduction was per-
formed with the DENZO-SMN26 software. An empirical
absorption was based on the symmetry-equivalent reflections
and was applied to the data using the SORTAV27,28 program.
The structure was solved using the SHELXS-9729 program and
refined using SHELXL-9730 by full-matrix least-squares on F2
values. All non-hydrogen atoms in each structure were located
and refined anisotropically. All hydrogen atoms were fixed at
calculated positions and refined using a riding mode. Crystal-
lographic data of 1-7 are summarized in Tables 1-9.
Preparation of Mo(η3-C3H5)(CO)2(en){N4CC(CH3)3}, 3.
Mo(η3-C3H5)(CO)2(en)(N3) (147.5 mg, 0.5 mmol) and 3.0 mL
(37 mmol) of trimethylacetonitrile were placed in a 50 mL flask.
After degassing, the mixture was refluxed at 110 °C for three
days, giving rise to a yellow, cloudy solution. The solvent was
removed under a dynamic vacuum followed by the extraction of
the resulting yellow solid with dichloromethane. After removal
of dichloromethane the yellow solid was dissolved in a dichlor-
omethane/acetonitrile mixture and layered with hexane for
crystallization, furnishing 136.5 mg (72.2% yield) of 3 as yellow
CAUTION: Owing to their potentially explosive nature, reac-
tions with azide salts and their complexes should be performed
with extreme care.
Preparation of Mo(η3-C3H5)(CO)2(en){N4C(CH3)}, 1. Mo-
(η3-C3H5)(CO)2(en)(N3) (295.1 mg, 1.0 mmol) and about 20 mL
of acetonitrile were placed in a 50 mL flask. After degassing, the
solution was refluxed for three days, resulting in a yellow, cloudy
solution. The solvent was removed under a dynamic vacuum,
leaving behind a yellow solid. Crystallization from methanol
furnished 216.2 mg (64.3% yield) of the title compound as
yellow crystals. 1H NMR (d6-DMSO, 115 °C): δ 4.72 (br s, 2H,
NH2), 3.87 (m, 1H, Hc), 3.40 (br s, 2H, NH2), 3.10 (d, J = 5.9 Hz,
2H, Hs), 2.50 (br s, 2H, CH2), 2.32 (s, 3H, CH3), 2.10 (br s, 2H,
CH2), 1.04 (d, J=9.9 Hz, 2H, Ha). 13C NMR (d-DMSO, 115 °C):
δ 227.54 (CO), 159.04 (N4C), 71.07(Cc), 56.83 (Ct), 42.82 (en),
10.98 (CH3). IR (KBr): 3309(m), 3279(vw), 3230(w), 3127(w),
2980(w), 2961(vw), 2892(vw), 1914(vs), 1820(vs), 1610(vw),
1587(vw), 1483(vw), 1457(vw), 1370(w), 1327(vw), 1288(vw),
1262(vw), 1232(vw), 1187(vw), 1132(vw), 1116(w), 1056(m),
1017(vw), 998(vw), 954(vw), 931(vw), 913(vw), 883(vw), 869-
(vw), 803(vw), 690(vw), 651(vw), 625(vw), 607(vw), 576(vw),
555(vw), 533(vw), 507(w), 469(w), 448(vw) cm-1. Anal. Calcd
for C9H16MoN6O2: N, 24.99; C, 32.15; H, 4.80. Found: N,
24.87; C, 32.07; H, 4.82.
1
crystals. H NMR (CD3OD, -60 °C): δ 6.35 (br s, 1H, NH2),
4.19 (br s, 1H, NH2), 3.99 (m, 1H, Hc), 3.93 (br s, 1H, NH2), 3.38
(br s, 1H, NH2), 3.24 (br s, 1H, Hs), 2.80 (br s, 1H, Hs), 2.61 (br s,
1H, CH2), 2.44 (br s, 1H, CH2), 2.18 (br s, 1H, CH2), 1.96 (br s,
1H, CH2), 1.37(s, 9H, CH3), 1.22 (d, J = 9.5 Hz, 1H, Ha), 0.99
(d, J = 8.5 Hz, 1H, Ha). 13C NMR (MeOD, -60 °C): δ 226.1,
225.1 (CO), 170.8 (N4C), 69.4 (Cc), 55.6, 55.1 (Ct), 43.3, 43.1
(en), 30.7 (C(CH3)3), 29.0 (CH3). IR (KBr): 3324(m), 3302(m),
3247(m), 3219(m), 3148(w), 3034(w), 2961(m), 2958(w),
2930(w), 2895(w), 2868(w), 1945(vs), 1832(vs), 1596(m),
1574(m), 1492(m), 1476(m), 1426(w), 1459(m), 1426(w),
1385(w), 1377(w), 1358(m), 1330(vw), 1286(w), 1262(vw),
1234(w), 1190(w), 1160(w), 1146(w), 1119(m), 1094(m),
1045(s), 1034(s), 1017(m), 987(m), 954(w), 921(vw), 902(vw),
872(vw), 861(w), 828(vw), 781(vw), 732(vw), 688(vw), 636(vw),
603(vw), 576(w), 554(w), 529(w), 491(m) cm-1. Anal. Calcd for
C12H22MoN6O2: N, 22.50; C, 37.80; H, 6.10. Found: N, 22.48; C,
37.69; H, 6.06.
Preparation of Mo(η3-C3H5)(CO)2(en){N4C(CHdCHCN)},
4. Mo(η3-C3H5)(CO)2(en)(N3) (295.1 mg, 1.0 mmol) and fumar-
onitrile (85.54 mg, 1.1 mmol) were placed in a 50 mL flask. After
degassing, about 25 mL of THF was transferred into the flask.
The solution was warmed to room temperature and stirred at
room temperature for 24 h, leading to a yellow-orange solution.
The solvent removal gave rise to a yellow solid, which was
washed with ether several times to remove the unreacted fumar-
onitrile followed by extraction with dichloromethane. The
dichloromethane was removed, and the yellow solid was dis-
solved in a dichloromethane/acetonitrile mixture and layered
with hexane for crystallization, affording 150.13 mg (40.2%
yield) of 4 as yellow crystals. 1H NMR (CD3OD, -60 °C): δ 7.64
(d, 1H, J = 16.4 Hz, CH), 6.50 (d, 2H, J = 16.4 Hz, CH and
NH2), 4.29 (br s, 1H, NH2), 4.09 (m, 1H, Hc), 3.91 (br s, 1H,
NH2), 3.52 (br s, 1H, NH2), 3.28 (br s, 1H, Hs), 2.83 (br s, 1H,
Hs), 2.63 (br s, 1H, CH2), 2.50 (br s, 1H, CH2), 2.39 (br s, 1H,
CH2), 1.94 (br s, 1H, CH2) 1.30 (d, 1H, J = 9.6 Hz, Ha), 0.99
(d, 1H, J = 8.8 Hz Ha). 13C NMR (CD3OD, -60 °C): δ 226.1,
225.0 (CO), 159.0 (N4C), 137.0 (Cm), 117.2 (CN), 100.1 (Cp),
Preparation of Mo(η3-C3H5)(CO)2(en){N4C(C6H5)}, 2. In a
drybox, 295.1 mg (1.0 mmol) of Mo(η3-C3H5)(CO)2(en)(N3),
210.0 mg (2.0 mmol) of C6H5CN, and about 20 mL of THF were
added into a 50 mL flask. The flask was evacuated, and the
mixture was refluxed for 4 days. The resulting orange solution
was concentrated, furnishing a viscous, yellow solution, which
was washed with hexane several times and dried under vacuum.
(26) DENZO-SMN: Otwinowsky, Z.; Minor, W. Processing of X-ray
Diffraction Data Collected in Oscillation Mode. In Methods in Enzy-
mology, Vol. 276: Macromolecular Crystllography, Part A; Carter, C. W.,
Jr., Sweet, R. M., Eds.; Academic Press: New York, 1997; pp 307-326.
(27) Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33.
(28) Blessing, R. H. J. Appl. Crystallogr. 1997, 30, 421.
(29) SHELXS-97: Sheldrick, G. M. Acta Crystallogr., Sect. A 1990,
46, 467.
€
€
(30) Sheldrick, G. M. SHELXL-97; University of Gottingen: Gottingen,
Germany, 1997.

4290 Organometallics, Vol. 29, No. 19, 2010
Liu et al.
69.4 (Cc), 55.4, 54.8 (Ct), 43.3, 41.2 (en). IR (KBr): 3335(m),
3291(m), 3247(m), 3219(m), 3159(w), 3034(w), 2989(m),
2956(w), 2939(w), 2890(w), 2879(w), 2219(m), 1917(vs), 1816-
(vs), 1637(m), 1604(m), 1588(m), 1456(m), 1403(vw), 1385(m),
1369(vw), 1319(w), 1286(w), 1262(vw), 1229(w), 1171(w),
1160(w), 1122(m), 1089(m), 1078(w), 1053(s), 1039(s),
1012(m), 982(m), 954(w), 927(vw), 902(vw), 880(vw), 869(w),
834(vw), 803(vw), 738(vw), 705(w), 677(vw), 666(vw), 644(vw),
611(vw), 576(w), 556(w), 529(w), 493(m), 471(w) cm-1. Anal.
Calcd for C11H15MoN7O2: N, 26.27; C, 35.39; H, 4.05. Found:
N, 26.19; C, 35.32; H, 4.10.
-100 °C): δ 6.40 (br s, 1H, NH2), 4.39 (br s, 1H, NH2), 4.22
(m, 1H, Hc), 4.04 (br s, 1H, NH2), 3.74 (s, 6H, CH3), 3.42 (br s,
1H, NH2), 3.12 (br s, 1H, Hs), 2.95 (br s, 1H, Hs), 2.52 (br s, 2H,
CH2), 2.40 (br s, 1H, CH2) 1.64 (br s, 1H, CH2) 1.21 (d, J = 9.5
Hz, 1H, Ha), 0.92 (d, J = 8.9 Hz, 1H, Ha). 13C NMR (d8-THF,
-100 °C): δ 225.3, 223.8 (CtO), 160.5 (CdO), 137.3, 126.2
(N3C2), 68.5 (Cc), 54.0 (Ct), 49.3 (CH3), 42.1, 39.5 (en). IR
(KBr): 3440(m), 3394(w), 3309(m), 3293(m), 3266(m), 3220(m),
3127(w), 3070(vw), 3031(vw), 3008(w), 2973(w), 2950(w),
2911(w), 2896(w), 2842(w), 1928(vs), 1828(vs), 1700(s),
1650(m), 1577(m), 1554(w), 1515(m), 1450(m), 1411(w),
1369(w), 1334(m), 1288(w), 1241(m), 1207(m), 1176(m),
1145(m), 1099(m), 1049(m), 1018(w), 998(w), 968(w), 937(w),
Preparation of Mo(η3-C3H5)(CO)2(dppe)(N3), 5. In a drybox,
362.1 mg (1.0 mmol) of Mo(η3-C3H5)(CO)2(CH3CN)2(Br) and
420.5 mg (1.0 mmol) of 1, 2-bis(diphenylphosphino)ethane were
placed in a 50 mL flask. The flask was evacuated, and about
25 mL of CH2Cl2 was transferred into the flask at -78 °C. The
flask was warmed to room temperature, and the stirring was
continued for an additional 6 h, giving rise to a red solution
of Mo(η3-C3H5)(CO)2(dppe)Br. A NaN3 solution (131.0 mg,
2.0 mmol of NaN3 in 10 mL of CH3OH) was added dropwise
into this red solution within a 5 min period. The mixture was
kept stirring at room temperature for an additional 24 h, leading
to a clear red solution. Following the solvent removal the
resulting red solid was extracted with CH2Cl2 several times.
The red-orange solid obtained from the extract after dichlor-
omethane removal was dissolved in CH2Cl2 and layered with
CH3OH for crystallization, giving rise to 410.9 mg (64.1% yield)
of 5 as red crystals. 31P NMR (d6-acetone): δ 44.7. 31P NMR (d6-
acetone, -90 °C): δ 44.31, 41.09. 1H NMR (d6-acetone): δ
7.46-7.75 (m, 20H, C6H5), 3.57 (m, 1H, Hc), 3.42 (m, 2H, Hs),
2.86 (m, 2H, Hb), 2.32 (m, 2H, Hd), 1.74 ppm (d, J = 10.0 Hz,
2H, Ha). 13C NMR (d6-acetone): δ 224.14 (CO), 133.20, 133.15,
133.10, 132.19, 132.15, 132.10, 130.87, 130.12, 129.02, 128.98,
128.66, 128.62, 128.57 (C6H5), 79.48 (Cc), 57.65 (Ct), 24.87
(t, JC-P = 19.2 Hz, CH2). IR (KBr): 3380(vw), 3332(vw),
3139(vw), 3079(vw), 3052(vw), 3023(vw), 2994(vw), 2960(vw),
2925(vw), 2672(vw), 2057(vs), 1984(vw), 1930(vs), 1851(vs),
1583(vw), 1569(vw), 1542(vw), 1482(w), 1465(vw), 1432(m),
1405(vw), 1384(vw), 1338(vw), 1307(vw), 1278(vw), 1263(vw),
1245(vw), 1230(vw), 1186(w), 1159(vw), 1095(vw), 1068(vw),
1025(vw), 995(vw), 970(vw), 948(vw), 919(vw), 871(w), 808(vw),
816(vw), 744(m), 696(s), 667(w), 646(w), 615(vw), 592(vw),
561(vw), 526(m), 476(w), 462(vw), 422(w) cm-1. Anal. Calcd
for C31H29MoN3O2P2: N, 6.63; C, 58.78; H, 4.61. Found: N,
6.63; C, 58.74; H, 4.62.
921(vw), 887(w), 871(w), 829(w), 806(m), 775(w), 732(w) cm-1
.
Anal. Calcd for C13H19MoN5O6: N, 16.01; C, 35.71; H, 4.38.
Found: N, 16.00; C, 35.62; H, 4.42.
Preparation of Mo(η3-C3H5)(CO)2(dppe){N3C2(CO2CH3)2},
7. Mo(η3-C3H5)(CO)2(dppe)(N3) (637.1 mg, 1.0 mmol) and
dimethyl acetylenedicarboxylate (142.3 mg, 1.0 mmol) were
placed in a 50 mL flask. After degassing, about 20 mL of
CH2Cl2 was transferred into the flask at -78 °C. The flask
was warmed to room temperature, and the stirring was con-
tinued for one day. This deep-red solution was concentrated and
evaporated at room temperature for crystallization, giving rise
to 608.0 mg (78.2% yield) of 7 as orange crystals. 31P NMR
(CD2Cl2): δ 51.10. 31P NMR (CD2Cl2, -90 °C): δ 47.07, 46.10.
1H NMR (CDCl3): δ 7.65-7.13 (m, 20H, C6H5), 4.19 (m, 1H,
Hc), 4.13 (br s, 2H, Hs), 3.73 (s, 6H, CH3), 3.41 (m, 2H, Hb), 2.45
(m, 2H, Hd), 2.23 (d, J = 9.2 Hz, 2H, Ha). 13C NMR (CDCl3):
δ 224.86 (CtO), 162.38 (CdO), 138.47 (N3C2), 135.49, 135.12,
132.69, 132.64, 132.59, 131.98, 131.94, 131.89, 131.70, 131.50,
131.32, 130.37, 129.79, 128.87, 128.83, 128.78, 128.13, 128.09,
128.04 (C6H5), 86.61 (Cc), 61.19 (Ct), 51.46 (CH3), 26.19 (t,
JC-P = 20.3 Hz, CH2). IR (KBr): 3424(vw), 3139(vw), 3073-
(vw), 3058(vw), 3021(vw), 3000(vw), 2948(w), 2931(vw), 2906-
(vw), 2861(vw), 2832(vw), 2088(vw), 2073(vw), 2042(vw),
2015(vw), 1940(vs), 1849(vs), 1716(s), 1655(vw), 1637(vw),
1585(vw), 1571(vw), 1542(vw), 1502(vw), 1484(w), 1446(w),
1434(m), 1386(vw), 1336(vw), 1315(vw), 1272(w), 1230(s),
1197(s), 1172(s), 1128(vw), 1091(s), 1025(w), 998(w), 989(w),
968(vw), 954(w), 921(vw), 879(w), 833(w), 821(w), 800(w),
775(w), 754(m), 742(w), 734(w), 713(w), 700(s), 659(w),
615(w), 595(w), 586(w), 563(w), 536(w), 524(s), 482(m),
455(w), 412(w) cm-1. Anal. Calcd for C37H35MoN3O6P2: N,
5.42; C, 57.30; H, 4.55. Found: N, 5.38; C, 57.17; H, 4.56.
Preparation of Mo(η3-C3H5)(CO)2(en){(N3C2)(CO2CH3)2},
6. Mo(η3-C3H5)(CO)2(en)(N3) (295.1 mg, 1.0 mmol) and di-
methyl acetylenedicarboxylate (156.53 mg, 1.1 mmol) were
placed in a 50 mL flask. After degassing, about 25 mL of
CH3CN was transferred into the flask. The flask was warmed
to room temperature, and the stirring was continued for an
additional 12 h when the mixture turned red-brown. The solu-
tion was concentrated, and the solvent was allowed to evaporate
slowly at room temperature. Crystallization afforded 200.2 mg
(46.0% yield) of 6 as yellow crystals. 1H NMR (d8-THF,
Acknowledgment. This work was supported by the
National Science Council of the ROC through Grant
NSC 99-2113-M-259-001-MY3.
Supporting Information Available: Tables of crystallographic
data, positional and thermal parameters, and interatomic dis-
tances and angles for 1-7. This material is available free of
charge via the Internet at http://pubs.acs.org.