Synthesis and reactivity of molybdenum complexes containing functionalized alkynyl ligands: A photochemically activated CO-releasing molecule (PhotoCO-RM)

Article abstract of DOI:10.1021/om200495h

Reaction of [MoCl(η⁵-C₅H₅)(CO) ₃] with propargyl alcohols HC≡CCR¹R²OH in the presence of catalytic amounts of CuI and using NEt₂H as solvent results in the formation of alkynyl c

Full text of DOI:10.1021/om200495h

ARTICLE
pubs.acs.org/Organometallics
Synthesis and Reactivity of Molybdenum Complexes Containing
Functionalized Alkynyl Ligands: A Photochemically Activated
CO-Releasing Molecule (PhotoCO-RM)
Wei-Qiang Zhang, Anthony J. Atkin, Ian J. S. Fairlamb, Adrian C. Whitwood, and Jason M. Lynam*
Department of Chemistry, University of York, Heslington, York, YO10 5DD, U.K.
S Supporting Information
b
ABSTRACT: Reaction of [MoCl(η5-C5H5)(CO)3] with pro-
pargyl alcohols HCtCCR1R2OH in the presence of catalytic
amounts of CuI and using NEt2H as solvent results in the
formation of alkynyl complexes [Mo(CtCCR1R2OH)(η5-
C5H5)(CO)3]. The structure of the complexes where R1 = R2
= Me and R1 = Me, R2 = Ph were confirmed by single-crystal
X-ray diffraction. The method could be extended to a range of
propargyl ethers and propargyl esters, which allowed for the
preparation of molybdenum complexes containing pendant
salicylate and β-D-fructopyranose groups. The alkynyl complex
[Mo(CtCCH2OH)(η5-C5H5)(CO)3] undergoes a further
reaction with NEt2H to give the substituted allyl complex
[Mo(η3-H2CC{NEt2}CHC{O}NEt2)(η5-C5H5)(CO)3]. Similar products could be obtained from the reaction of [MoCl(η5-
C5H5)(CO)3] with HCtCCH2OH in the presence of CuI using pyrrolidine or piperidine as solvent. In the case of the reaction with
piperidine a further product could be isolated that has arisen from the coupling of two propargyl alcohol molecules to afford a
butadienyl ligand. The CO-releasing properties of a number of these novel complexes have been investigated. In the case of the
water-soluble alkynyl complex containing a β-D-fructopyranose group CO release was shown to be promoted by exposure to UV
light, revealing a new class of photochemically activated CO-releasing molecules (PhotoCO-RMs).
’ INTRODUCTION
an attractive method for the preparation of metal alkynyl com-
plexes, as it does not require the preformation of the transme-
talating agent.8 This method has found a number of applications,
for example, in the synthesis of carbon-rich metal diynyl
complexes,9 half-sandwich iron,10 ruthenium, and tungsten alky-
nyl complexes.8 The deprotonation of vinylidene ligands
(MdCdCHR), traditionally formed by a metal-mediated tau-
tomerization of terminal alkynes,11 provides an important com-
plementary method to the transmetalation approach to alkynyl
complexes.
Given that metalꢀalkynyl complexes typically possess strong
metalꢀcarbon bonds and their properties may be easily modu-
lated by the substituent on the alkynyl ligands, complexes con-
taining carbonyl co-ligands might find application as potential
therapeutic carbon monoxide-releasing molecules (CO-RMs).12
A number of different structural motifs have been explored as
CO-RMs (Figure 1). For example, simple metal carbonyl com-
pounds [MX(CO)5]ꢀ (M = Cr, Mo, W) have been investi-
gated,13 as have the rhenium(II) complexes [ReBr2(CO)2L2],14
tetrachlorocarbonyliridates,15 manganese thiocarboxylates,16 and
tricarbonyl group 7 compounds with imidazole-based phosphines.17
Transition metal alkynyl complexes (M-CtCR) have proven
to be versatile and robust synthons for a range of applications.1
From a frontier molecular orbital perspective, the alkynyl anion is
isoelectronic with carbon monoxide; however in the case of the
alkynyl group the nature of the metalꢀligand interaction may be
influenced by the effect of the different substituents on the
β-carbon.2 The synthetic routes available to these species using
terminal alkynes as precursors have ensured that a library of metal
alkynyl complexes based on different metals with a host of
different substituents is now known.3 Given this ability to tune
the nature of the metalꢀligand interaction, it is unsurprising that
metalꢀalkynyl complexes have been exploited, among other
applications, as materials for nonlinear optics3 and colorimetric
sensors.4
A number of synthetic methods have been developed to pre-
pare metalꢀalkynyl complexes. These include the transmetala-
tion of metal halide complexes with alkynyl nucleophiles such as
organo-tin, organo-lithium,5 and organo-copper6 and, more
recently, the use of alkynyl-substituted gold complexes as effec-
tive reagents for transmetalation.7 In the majority of cases the
alkynyl nucleophiles are prepared by deprotonation of an ap-
propriate terminal alkyne. The copper(I)-catalyzed coupling of
metal halides to terminal alkynes using amines as solvents is also
Received: June 8, 2011
Published: August 05, 2011
r
2011 American Chemical Society
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dx.doi.org/10.1021/om200495h Organometallics 2011, 30, 4643–4654
|

Organometallics
ARTICLE
Scheme 1a
a (i) + HCtCCR1R2(OH), CuI, NH2Me 1 M solution in THF (2a) or
NHEt2 (2bꢀe), 20 min.
’ RESULTS AND DISCUSSION
Synthesis of Propargyl Alcohol Complexes. Reaction of
[MoCl(η5-C5H5)(CO)3], 1, with propargyl alcohols HCtCC-
(OH)R1R2 in the presence of CuI for ca. 20 min results in the
formation of alkynyl-substituted complexes [Mo(CtCC{OH}-
R1R2)(η5-C5H5)(CO)3] (2a, R1 = R2 = H; 2b, R1 = R2 = Ph; 2c,
R1 = R2 = Me; 2d, R1 = Ph, R2 = Me; 2e, R1 = Ph, R2 = H),
Scheme 1. In the case of complex 2a, the reaction was performed
in a 1 M solution of NH2Me in THF in order to minimize the
subsequent formation of η3-allyl complexes (see text): in the
other instances the reaction was performed using NHEt2 as
solvent. The complexes proved to be photosensitive and decom-
posed on exposure to ambient light.26
Figure 1. Structures of selected CO-RMs.
Complex 2a exhibited a number of spectroscopic features that
are typical for this series of compounds. For example, a band was
observed at 2114 cmꢀ1 in the IR spectrum, which was assigned to
the CtC stretch of the alkynyl ligand, as were the expected two
bands at 2044 and 1963 cmꢀ1 in the terminal metal carbonyl
region. In addition to the resonances of the cyclopentadienyl and
carbonyl ligands, the 13C{1H} NMR spectrum displayed reso-
nances at δ 127.4, δ 82.4, and δ 53.4 for the R-, β-, and γ-carbon
of the alkynyl ligand, respectively. The structures of complexes 2c
and 2d were confirmed by single-crystal X-ray diffraction studies.
Selected bond angles and lengths for complexes 2c and 2d are
presented in Table 1, details of the data collection and structure
refinement for all complexes are reported in Table 2, and the
molecular structures of 2c and 2d are illustrated in Figures 2 and
3, respectively. The structural determinations demonstrated that
the features predicted on the basis of the spectroscopic data were
indeed present. The complexes adopt four-legged piano-stool
geometries with MoꢀC and CtC bond lengths of 2.1494(16)
and 1.203(2) Å, respectively, for complex 2c; in 2d the corre-
sponding distances were 2.1536(12) and 1.2096(17) Å. In both
cases the alkynyl ligands are essentially linear. (For 2c Mo(1)ꢀ
C(9)ꢀC(10) 178.44(15)°, C(9)ꢀC(10)ꢀC(11A) 172.0(4)°,
C(9)ꢀC(10)ꢀC(11B) 174.2(3)°; for 2d Mo(1)ꢀC(9)ꢀC-
(10) 177.67(10)°, C(9)ꢀC(10)ꢀC(11) 178.88(13)°.) These
metrical parameters are typical for molybdenum alkynyl com-
plexes.27
More elaborate structures based on iron18 as well as dicobalt
alkyne complexes19 and photochemically activated systems (Photo-
CORMs) have also been reported.18d,20,21 Very recently, oxo-
butadiene iron tricarbonyl compounds have been shown to act as
enzyme-triggered CO-releasing molecules (ET-CORMs).22
One particular focus of the development of CO-RMs has been
to incorporate biologically compatible ligands into the coordina-
tion sphere of the metal. For example, complexes containing
amino acid derivatives have been investigated such as the ex-
tensively studied ruthenium glycinate complex, CO-RM-3,23 and
the series of compounds M(NH2CHRCO2R0)(CO)5 (M = Cr,
Mo, W), where dissociation of the amino acid esters is crucial to
CO release.24 We have shown that iron tricarbonyl, cyclopenta-
dienyl iron, and molybdenum complexes containing the 2-pyr-
one motif may form an effective class of CO-RMs.25 Notably,
complex CO-RM-F10 (Figure 1) was shown to release CO and
act as an effective vasorelaxing agent at a concentration where the
complex exhibited little toxicity.
With these factors in mind, complexes based on the [Mo
(CtCR)(η5-C5H5)(CO)3] framework were considered to have
potential as an effective class of CO-RM, where the sub-
stituent on the alkynyl ligand may be selected to alter solubility
and potential uptake of the complex. Given the ease with which
substituted propargyl compounds HCtCCH2OR may be pre-
pared from the reaction of HCtCCH2Br with appropriate
nucleophilies, the development of a synthetic route to complexes
[Mo(CtCCH2OR)(η5-C5H5)(CO)3] was sought. The meth-
odology to prepare these complexes is herein described, along
with the observation of an unusual condensation reaction be-
tween an alkynyl group, a carbonyl ligand, and the amine solvent.
In addition, the CO-releasing properties of a number of selec-
ted compounds are described, which demonstrate that a sugar-
substituted complex is an effective photochemically activated
CO-RM.
The structural determination of 2d also demonstrated that, in
the solid state, an OH-π hydrogen bond is present between the
OH group on the alkynyl ligand and the CtC on a neighbor
(Figure 3b). The bond lengths (C(9)ꢀO(4) 3.214(2) Å; C(10)ꢀ
O(4) 3.234(2) Å; C(9)ꢀH(4) 2.46(2) Å; C(10)ꢀH(4) 2.46(2)
Å; π-CtC centroidꢀH(4) 2.39(3) Å, π-CtC centroidꢀO(4)
3.167(3) Å) indicate that this a relatively strong interaction of
this type.28 The hydrogen-bonding network within the structure
of 2c proved to be somewhat more complex. The CMe2OH
group was disordered over two positions. In one position the OH
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Organometallics
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Table 1. Selected Bond Lengths (Å) for Complexes 2c, 2d, 5a, 5b, 5c, and 6
2c
2d
5a
5b
5c
6b
MoꢀC(1)
MoꢀC(2)
MoꢀC(3)
MoꢀC(4)
MoꢀC(5)
MoꢀC(6)
MoꢀC(7)
MoꢀC(8)
MoꢀC(9)
MoꢀC(10)
C(6)ꢀO(1)
C(7)ꢀO(2)
C(8)ꢀO(3)
C(8)ꢀC(9)
C(9)ꢀC(10)
C(10)ꢀC(11)
2.3455(16)
2.3048(16)
2.3005(16)
2.3439(16)
2.3724(16)
2.0050(16)
1.9998(16)
2.0085(16)
2.1494(16)
2.3390(13)
2.3655(13)
2.3484(13)
2.3105(13)
2.3079(13)
2.0062(14)
2.0121(14)
2.0024(15)
2.1536(12)
2.3229(17)
2.3204(17)
2.3577(16)
2.3890(16)
2.3677(17)
1.9501(16)
1.9501(17)
2.3065(15)
2.4851(15)
2.3195(15)
1.159(2)
2.3790(14)
2.3890(14)
2.3490(14)
2.3201(14)
2.3311(14)
1.9546(14)
1.9534(14)
2.3162(14)
2.4602(13)
2.3330(13)
1.1595(18)
1.1596(18)
2.387(3)
2.357(3)
2.311(3)
2.310(3)
2.347(3)
1.956(3)
1.950(4)
2.315(3)
2.411(3)
2.318(3)
1.156(4)
1.158(4)
2.321(3)
2.377(3)
2.374(3)
2.316(3)
2.296(3)
1.953(3)
2.003(3)
2.181(3)
1.169(3)
1.145(4)
1.438(4)
1.493(4)
1.337(4)
1.407(4)
1.138(2)
1.1459(19)
1.137(2)
1.1412(17)
1.1408(17)
1.1471(18)
1.162(2)
1.423(2)
1.447(2)
1.493(2)
1.4227(19)
1.4446(18)
1.4946(18)
1.407(4)
1.446(4)
1.501(4)
1.203(2)
1.557(15)a
1.469(6)
1.2096(17)
1.4855(16)
C(11)ꢀC(13)
1.418(4)
a Data for both positions. b Data of one of the two independent molecules in the asymmetric unit.
group is engaged in hydrogen bonding with the CtC π-system
of a neighbor, although the interaction is not as strong as in 2d
(C(9)ꢀO(4B) 3.3224(1) Å, C(10)ꢀO(4B) 3.3672(2) Å). In
the second position, the OH group acts as a hydrogen bond
donor to the oxygen atom of the OH group (intermolecular contact
5.12 and also showed evidence for the two NEt2 groups. In one
instance the ethyl groups were equivalent (one resonance ob-
served for the methyl group and two for the diasterotopic methylene
protons); in the other case, the ethyl groups were found to be
nonequivalent (two resonances for the methyl groups were
observed and four signals for the methylene protons). In addition
to these peaks, three further resonances were observed for the
allyl group at δ 2.99 (apparent t, 1H, 4JHH = 3.0 Hz), 3.50 (d, 1H,
H(4A) O(4B) 2.4045(1) Å), which is in close proximity to
3 3 3
the CtC π-system. These two interactions are shown in Figure 2b.
The corresponding reactions between 1 and alkynes HCtC-
(CH2)nOH (n = 2, 3, 4) resulted in the formation of complexes
[Mo(CtC{CH2}nOH)(η5-C5H5)(CO)3] (n = 2, 3a; n = 3, 3b;
n = 4, 3c). In this context, it should be noted that Liu and co-
workers have described the synthesis of related complexes
[W(CtCCH2{CR2}nOH)(η5-C5H5)(CO)3] (n = 1, 2) via a
similar route.29 Reaction of 1 with a range of substituted
propargyl ethers HCtCCH2OR (R = OAc, CH2Ph, salicylate,
asprin, and fructopyranose) afforded the corresponding com-
plexes [Mo(CtCCH2OR)(η5-C5H5)(CO)3] (R = OAc, 4a;
R = CH2Ph, 4b; R = salicylate, 4c; R = asprin, 4d; and R =
fructopyranose, 4e) (Scheme 2). In each case, the products could
be isolated following chromatography on silica gel and were
characterized by both NMR and IR spectroscopy as well as high-
resolution mass spectrometry. These results demonstrated that
the coupling method was tolerant to a range of different func-
tional groups on the alkyne and represents the desired method to
prepare potential CO-RMs based on the [Mo(η5-C5H5)(CO)3]
fragment from terminal alkynes.
4
4JHH = 3.5 Hz), and 4.09 (d, 1H, JHH = 2.5 Hz). A COSY
experiment demonstrated that the resonance at δ 2.99 was
coupled to those at δ 3.50 and 4.09, but the latter two peaks did
not exhibit a mutual coupling. A HMQC experiment demon-
strated that the resonance at δ 4.09 was coupled to a CH re-
sonance in the 13C{1H} NMR spectrum at δ 37.7, whereas the
two other proton resonances for the allyl group showed a
coupling to a CH2 resonance at δ 23.4. The 13C{1H} NMR
spectrum of 5a also exhibited a resonance at δ 140.9, which was
assigned to the central carbon atom of the allyl ligand. Two
resonances for the carbonyl groups attached to the metal were
observed at δ 250.9 and 246.4, and a peak at δ 175.0 was assigned
to the carbon atom of the amide group.
In a similar manner, prolonged reaction of 1 with HCtCCH2-
(OH) in the presence of CuI in pyrrolidine and piperidine as
solvents afforded complexes 5b and 5c, respectively. In the case
of the reaction with piperidine an additional product, 6, was
isolated (see text). Complexes 5aꢀc exhibited a similar series of
spectroscopic features, and, in addition, their structures were
confirmed by single-crystal X-ray diffraction experiments. The
molecular structures of the complexes are shown in Figure 4, with
selected bond lengths in Table 1. The structural determinations
demonstrated that, as predicted on the basis of the spectroscopic
data, the complexes all possessed analogous structures. The
molybdenum is coordinated by an η5-cyclopentadienyl and
two carbonyl ligands, and the bond lengths within these groups
are essentially as expected. The remaining coordination sites at
the metal are occupied by a single ligand formed by the con-
densation of the propargyl alcohol with two equivalents of the
Formation of Allyl Complexes. Performing the reaction of 1
with HCtCCH2OH in the presence of CuI in NEt2H for 20 min
did not allow for the alkynyl complex 2a to be isolated. In this
case a new product, which was shown to be the substituted-allyl
complex 5a (Scheme 3), was isolated. The IR spectrum of 5a
recorded in CH2Cl2 solution exhibited two sharp bands in the
metalꢀcarbonyl stretching region at 1931 and 1843 cmꢀ1, con-
sistent with the presence of two mutually cis carbonyl ligands. In
addition a further band in the spectrum was observed at 1602 cmꢀ1
,
which was assigned to the amide group. The 1H NMR spectrum
of 5a displayed a resonance for an η5-cyclopentadienyl group at δ
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Organometallics
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Table 2. Data Collection and Structural Refinements Details for Single-Crystal X-ray Diffraction Studies of Complexes 2c, 2d, 5a,
5b, 5c, and 6
2c
2d
5a CH2Cl2
5b
5c
6
3
empirical formula
fw
C13H12MoO4
328.17
C18H14MoO4
390.23
C19.50H29ClMoN2O3 C19H24MoN2O3
C21H28MoN2O3
452.39
C19H23MoNO5
441.32
470.84
424.34
temperature/K
wavelength/Å
cryst syst
110.0
110(2)
110(2)
0.71073
monoclinic
C2/c
110(2)
110(2)
110(2)
0.71073
triclinic
0.71073
monoclinic
P2(1)/n
9.4514(16)
12.599(2)
13.711(2)
90
0.71073
triclinic
P1
0.71073
monoclinic
C2/c
0.71073
orthorhombic
Pna2(1)
17.023(3)
8.5476(13)
25.323(4)
90
space group
a/Å
P1
6.5791(4)
8.2078(5)
12.1346(8)
90.3600(10)
95.5800(10)
92.2120(10)
651.64(7)
2
30.691(3)
9.9703(10)
15.1389(15)
90
8.2474(11)
10.4284(14)
10.9979(15)
75.001(2)
74.407(2)
83.552(2)
879.1(2)
2
22.297(11)
7.938(4)
23.925(12)
90
b/Å
c/Å
R/deg
β/deg
90.867(3)
90
111.134(2)
90
108.277(11)
90
90
γ/deg
volume/Å3
90
1632.6(5)
4
4321.0(7)
8
4021(3)
8
3684.7(10)
8
Z
density (calculated)/
Mg mꢀ3
1.672
1.588
1.448
1.603
1.495
1.591
absorp coeff/mmꢀ1
1.009
328
0.820
784
0.751
1944
0.767
436
0.676
1872
0.741
1808
F(000)
cryst size/mm3
ϕ range for data
collection/deg
index ranges
0.37 ꢁ 0.11 ꢁ 0.10 0.20 ꢁ 0.20 ꢁ 0.08 0.35 ꢁ 0.19 ꢁ 0.19 0.35 ꢁ 0.22 ꢁ 0.16 0.22 ꢁ 0.21 ꢁ 0.18 0.26 ꢁ 0.06 ꢁ 0.04
1.69 to 28.25
2.20 to 30.04
2.16 to 28.30
1.98 to 28.38
1.79 to 28.42
1.61 to 28.30
ꢀ8 e h e 8
ꢀ10 e k e 10
ꢀ16 e l e 16
6723
ꢀ13 e h e 13
ꢀ17 e k e 17
ꢀ19 e l e 19
18 156
ꢀ40 e h e 40,
ꢀ13 e k e 13,
ꢀ20 e l e 20
29 065
ꢀ11 e h e 11
ꢀ13 e k e 13
ꢀ14 e l e 14
9054
ꢀ29 e h e 29
ꢀ10 e k e 10
ꢀ31 e l e 31
19 781
ꢀ22 e h e 22
ꢀ11 e k e 11
ꢀ33 e l e 33
36 194
reflns collected
indep reflns
3181[R(int)
= 0.0157]
4706 [R(int)
= 0.0156]
5374 [R(int)
= 0.0218]
4322 [R(int)
= 0.0119]
4968 [R(int)
= 0.0753]
9139 [R(int)
= 0.0387]
completeness to θ
absorp correction
max. and min. transmn
refinement method
data/restraints/params
goodness-of-fit on F2
final R indices
98.7% (to 28.25)
98.4% (to 30.04) 100% (to 28.30)
98.2% (to 28.38)
98.2% (to 28.42)
99.9% (28.30)
semiempirical from equivalents
1.000 and 0.830
0.937 and 0.836
0.867 and 0.782
0.885 and 0.791
0.885 and 0.062
0.971 and 0.844
full-matrix least-squares on F2
3181/6/200
1.054
4706/0/213
1.044
5374/0/260
4322/0/238
1.065
4968/0/253
1.031
9139/13/500
1.009
1.046
R1 = 0.0187
wR2 = 0.0464
R1 = 0.0194
wR2 = 0.0469
R1 = 0.0195
wR2 = 0.0511
R1 = 0.0215
wR2 = 0.0525
R1 = 0.0243
wR2 = 0.0598
R1 = 0.0266
wR2 = 0.0612
R1 = 0.0189
wR2 = 0.0473
R1 = 0.0197
wR2 = 0.0478
0.650 and ꢀ0.371
R1 = 0.0431
wR2 = 0.0897
R1 = 0.0600
wR2 = 0.0983
R1 = 0.0291
wR2 = 0.0628
R1 = 0.0375
wR2 = 0.0663
[I > 2σ(I)]
R indices (all data)
largest diff. peak and hole/e Åꢀ3 0.495 and ꢀ0.548
0.574 and ꢀ0.478 1.025 and ꢀ0.757
1.194 and ꢀ0.629 0.905 and ꢀ0.357
amine solvent and a further carbonyl group that was presumably
initially coordinated to the metal. This has resulted in the ge-
neration of an amide group attached to one terminus of the allyl
ligand, whereas the second NEt2 group is attached to the central
atom: the allyl group adopts an endo configuration. An examina-
tion of the bond lengths between the C3 framework and the
molybdenum indicates that the allyl ligand is asymmetrically
coordinated to the metal. In all cases, the MoꢀC bonds between
the two terminal carbon atoms are within the range typically
observed for this type of complex (e.g., for 5a MoꢀC(8)
2.3065(15) Å, MoꢀC(10) 2.3195(15) Å); however the distance
to the central carbon atom is considerably longer (for 5a
MoꢀC(9) 2.4851(15) Å). This suggests that the metal has an
extremely weak interaction with this carbon atom and the CꢀC
bonds within the allyl ligand are also somewhat longer than
expected (for 5a C(8)ꢀC(9) 1.423(2) Å and C(9)ꢀC(10)
1.447(2) Å). Furthermore, the carbonꢀnitrogen distance to
the central carbon atom suggests the presence of some CꢀN
multiple-bonding character (for 5a, C(9)ꢀN(2) 1.356(2) Å),
and the sum of the bond angles around the nitrogen atom are
359.82° (5a), 357.95° (5b), and 349.59° (5c), suggesting a lack
of pyramidalization. One possible interpretation of these data is
that the lone pair of the nitrogen atom is involved in significant π-
bonding with the allyl group and that the bonding within com-
plexes 5 is best described by a combination of two resonances
forms, Aand B(Figure5). TheallylligandinstructureAmay simply
be viewed as acting in a classical η3-fashion. In structure B the C3
ligandmaybeconsideredtobeactingasametallocyclopropanewith
no interaction between the central carbon atom and the metal.
Here, a formal double bond between the central carbon atom and
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Scheme 2a
a (i) + HCtCCCH2OR, CuI, NHEt2 (2bꢀe), 20 min.
the remarkably low stretching frequency for the metal carbonyl
bands in the IR spectrum. For comparisons, the endo isomer of
[Mo(η3-C3H5)(η5-C5H5)(CO)2] exhibits bands at 1970 and
1903 cmꢀ1 in cyclohexane solution,30 whereas the analogous
bands in 5a occur at 1931 and 1843 cmꢀ1, consistent with the
metal center being far more electron rich. This type of asymmetry
in the binding of the allyl ligand may be contrasted with, for
example, complexes based on the [M(η3-allyl)(L)(CO)(NO)]
(L = η5-C5H5 or Tp), in which a shift from η3ꢀη2 type binding is
observed due to the different π-acidities of the NO+ and CO
ligands.31
Figure 2. (a) Molecular structure of 2c. Thermal ellipsoids are shown at
the 50% probability level, and hydrogen atoms (except for H(4A))
omitted for clarity. The second disordered conformer of the CMe2OH
group is shown with dashed bonds. (b) Hydrogen-bonding arrange-
ments in the solid state.
As indicated above, the reaction of 1 with HCtCCH2(OH) in
the presence of CuI employing piperidine as solvent gave, in
addition to 5c, a further product, 6, which could be isolated
following column chromatography on silica gel. The IR spectrum
of 6 exhibited two bands in the metal carbonyl stretching region
at 1990 and 1931 cmꢀ1, which would appear to indicate that the
metal in 6 is somewhat less electron rich than in 5c. A further
CꢀO stretching band was observed at 1596 cmꢀ1, which was
assigned to the presence of an amide group. A high-resolution
mass spectrum of 6 indicated that the product had arisen from
the condensation of two molecules of HCtCCH2(OH) with a
molecule of the amine solvent. The structure of 6 was determined
by a single-crystal X-ray diffraction study, which demonstrated
that 6 crystallized in the orthorhombic space group Pna21 and
that the asymmetric unit contained both enantiomers of 6
(Figure 6). The structural determination showed that the molyb-
denum atom in 6 was coordinated by a η5-bound cyclopenta-
dienyl ring and two metal carbonyl groups. The remaining
coordination sites at the metal were shown to be occupied by a
single ligand, formed (as expected on the basis of the data from
mass spectrometry) from two molecules of HCtCCH2(OH)
and a piperidine group as part of an amide group. As in the case
of complexes 5, the CO group of this amide is assumed to
have arisen from coupling of a metal carbonyl with the amine
solvent. The alkynes have coupled in such a manner to create an
η3-butadienyl ligand, and the bond lengths within this group
demonstrate that the ligand is asymmetrically bound to the metal
with Mo(1)ꢀC(10) (2.181(3) Å) being shorter that the remain-
ing molybdenum carbon bonds (Mo(1)ꢀC(11) 2.300(3) Å;
Mo(1)ꢀC(13) 2.352(3) Å). This has been observed in other
molybdenum butadienyl ligands,32,33 although in some other ex-
amples of Group 6 metals the binding is more symmetric.34
Figure 3. (a) Molecular structure of 2d. Thermal ellipsoids are shown
at the 50% probability level, and hydrogen atoms (except for H(4A))
omitted for clarity. (b) Packing diagram showing OH-π hydrogen-
bonding motif.
the metal is present with a formal negative charge being placed on
the molybdenum. Resonance form B not only provides a con-
venient explanation for the unusually long MoꢀC bond lengths
observed in the structures of 5 but also provides a rationale for
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Scheme 3a
a (i) + HCtCCH2(OH), CuI, NHEt2; (ii) + HCtCCH2(OH), CuI, pyrrolidine; (iii) + HCtCCH2(OH), CuI, piperidine.
The NMR spectra of 6 exhibit a number of pertinent features
that would be expected on the basis of the structure determined
by X-ray crystallography. For example in the 1H NMR spectrum a
resonance at 6.71 (dd, J = 6.0 Hz, 8.0 Hz, 1H) for the proton
attached to the C-terminus of the alkene ligand was observed.
Furthermore the 13C{1H} NMR spectrum exhibited diagnostic
resonances at δ 170.1, 92.0, and 86.9 for the three molybdenum-
bound atoms of the butadienyl ligand:33 a resonance for the un-
coordinated carbon atom of this ligand was observed at δ 116.0.
A number of further experiments were undertaken in order to
gain insight into the mechanism by which complexes 5 and 6
were formed. In the first instance, a sample of 2a was simply
dissolved in NHEt2. This resulted in the rapid (ca. 20 min)
formation of 5a as the only product from the reaction, indicating
that CuI was required only for the formation of the alkynyl com-
plexes and was not necessary for the subsequent generation of the
allyl complexes. In addition, it was observed that dissolution of
4a, [Mo(CtCCH2OAc)(η5-C5H5)(CO)3], in NHEt2 also re-
sulted in the formation of 5a.
These results demonstrated that, at least in the case of the
unsubstituted alkynes, coupling between the alkynyl ligand, a
carbonyl ligand, and the amine solvent may occur. Similar coupling
reactions between carbonyl ligands and amines have also been
observed in the case of Group 6 tricrabonyl complexes contain-
ing η1-propargyl ligands35 and related species with an η2-bound
tritylallene.36 In the latter case, as in the chemistry reported here,
an allyl ligand with a terminal amido group was prepared. However,
in contrast to the chemistry reported by Lin, the reaction of com-
plexes 2 with the amine is a condensation reaction and also leads in
the incorporation of an additional amino group in the backbone of
the resulting allyl ligand. This additional amino group does appear to
be responsible for the asymmetric binding of the allyl ligand.
CO-Release Tests. The ability of selected complexes to release
CO (as potential CO-RMs) was assessed using an assay based
on the conversion of deoxymyoglobin (deoxy-Mb) to carbon
monoxymyoglobin (MbCO).37ꢀ39 Here a solution of deoxy-Mb
of known concentration is treated with the appropriate metal
carbonyl compound, and any CO released from the coordination
sphere of the metal is subsequently captured by the protein to form
MbCO. This conversion is monitored effectively by observing the
changes in the Q-bands of the protein between 500 and 600 nm,
thus allowing the rate and extent of CO to be quantified.
The abilities of complexes 1, 4b, and 4e were all evaluated in
this fashion, as was [Mo(CtCPh)(η5-C5H5)(CO)3], 7, prepared
by the method of Bruce.8 Complex 1 exhibited fast and con-
trolled CO release. A typical series of spectra for the conversion
of deoxy-Mb to MbCO by this complex are shown in Figure 7.
Solutions of 1 with concentrations of 60, 40, and 20 μM were
evaluated, which exhibited half-lives for CO release of 644, 615,
and 863 s, respectively. Complexes 4b and 7 proved to be
insoluble in the aqueous medium used for the assay, and an
upshift in the baseline was immediately observed: no CO release
was subsequently detected. In contrast 4e proved to be soluble in
the assay medium and released CO very slowly. An experiment
with a 60 μM solution of 4e resulted, after two hours, in the
generation of an MbCO solution with a concentration of 2.2 μM.
The potential for the photochemical promotion of CO release
from transition metal complexes has been reported.40 Dimeric
[Mn2(CO)10] was the first compound where photochemically
induced CO release was observed,37 and this has found applica-
tion in a number of animal studies.41 Also, Mn(CO)3 complexes
supported by tris(pyrazolyl)methane20 and imidazole-based
phosphine ligands17 release CO only on exposure to UV light,
as does [W(CO)5(TPPTS)]3ꢀ (TPPTS3ꢀ = tris(sulfonatophe-
nyl)phosphine trianion).21 Similarly the CO release from 4e
could also be promoted by exposure to UV light. Solutions of 4e
with concentrations of 60, 40, and 20 μM were prepared and
exposed to light of wavelength 325 nm from a 6 W hand-held
lamp. This resulted in a far more rapid release of CO when
compared to the thermal reaction, with the 60, 40, and 20 μM
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Figure 5. Proposed resonance forms for the bonding between the allyl
ligand and the molybdenum in complexes 5.
Figure 6. Structure of the two independent molecules in the asym-
metric unit of complex 6. Thermal ellipsoids are shown at the 50%
probability level, and hydrogen atoms (except for those attached to the
butadienyl ligand and OH groups) omitted for clarity. The bond lengths
and angles within the two independent molecules are generally statis-
tically identical: disorder in one CH2OH group is shown with dotted
lines.
solutions exhibiting half-lives of 962, 966, and 778 s, respec-
tively. Furthermore, the solution of 4e with a concentration of
20 μM resulted in the formation of an MbCO concentration of
44.8 μM over the course of 2.5 h, indicating that each complex
was releasing ca. 2.2 molecules of CO. These data show that
complex 4e has the potential to act as a light-activated water-
soluble CO-RM, capable of releasing multiple molecules
of CO.
In conclusion, we have shown that the copper-promoted
coupling of propargyl-substituted alkynes, HCtCCR1R2(OR3),
to [Mo(η5-C5H5)Cl(CO)3] is a versatile method for the in-
corporation of a range of different functional groups into the
coordination sphere of the metal. In the case of the parent
propargyl alcohol, the resulting alkynyl complex [Mo(CtCC-
H2{OH})(η5-C5H5)(CO)3] undergoes a rapid reaction with the
secondary amine solvent to give substituted allyl complexes. The
fructopyranose-substitued alkynyl complex is a water-soluble
CO-release molecule where release may be stimulated by ex-
posure to UV light.
Figure 4. Molecular structure of complex 5a (top), 5b (middle), and 5c
(bottom). Thermal ellipsoids are shown at the 50% probability level, and
hydrogen atoms (except for those attached to the allyl group) omitted
for clarity. A CH2Cl2 of crystallization is also omitted from the structural
representation of 5a.
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Figure 7. CO release profile for 1. (a) UVꢀvis spectrum showing the Q-bands during the conversion of deoxy-Mb to MbCO with time for a 60 μM
solution. (b) Plot of [Mb-CO] against time: (red [) [1] = 60 μM, (green 2) [1] = 40 μM, and (blue 9) [1] = 20 μM.
’ EXPERIMENTAL SECTION
added. HCtCCH2(OH) (69 μL, 1.2 mmol) was added, and the re-
action stirred for 15 min. The solvent was removed under vacuum, and
the product isolated by column chromatography. Yield: 180 mg (59%)
of an orange-red solid. IR ν (cmꢀ1): 2114 (w) (CtC), 2044 (s)
(CtO), 1963 (vs) (CtO). 1H NMR: δ 1.63 (br, 1H, OH), 4.28 (s, 2H,
CH2), 5.50 (s, 5H, η5-C5H5). 13C{1H} NMR: δ 53.4 (CH2OH), 82.4
(Mo-CtC), 92.9 (η5-C5H5), 127.4 (Mo-CtC), 222.8 (cis-CtO),
238.5 (trans-CtO). HRMS: [M + Na]+ 324.9364 (324.9371 expected
for C11H8MoNaO4).
Preparation of Complexes 2bꢀe, 3aꢀc, and 4aꢀe. These
species were all prepared according to a general procedure. A Schlenk
tube was charged with 281 mg (1.0 mmol) of [MoCl(η5-C5H5)(CO)3],
and the appropriate amine (3 mL) was added followed by the propargyl
alcohol (1.2 equivalents) and a catalytic amount of CuI. The reaction
mixture was stirred for 15ꢀ20 min, during which time a color change
from red to yellow occurred. After this time, the volatile materials were
removed under vacuum. Column chromatography on silica gel with a
mixture of CH2Cl2 and hexane afforded photosensitive yellow products.
[Mo(C;CCPh2{OH})(η5-C5H5)(CO)3], 2b. Yield: 280 mg (61%)
of a yellow solid. IR ν (cmꢀ1): 2114 (w) (CtC), 2040 (s) (CtO),
1963 (vs) (CtO). 1H NMR: δ 2.68 (s, 1H, OH), 5.44 (s, 5H, η5-C5H5),
7.22 (5H, C6H5), 7.61 (5H, C6H5). 13C{1H} NMR: δ 75.6 (CPh2OH),
All manipulations were conveniently accomplished by using standard
Schlenk line and glovebox apparatus. [Mo(η5-C5H5)Cl(CO)3], 1, was
prepared according to a modified literature procedure.42 Mo(CO)6 was
purchased from Strem Chemicals Inc. and propargylic alcohols were
obtained from Aldrich. 2-Propinyl salicylate,43 (2-propinyl)-2-acetyl
salicylate,43 and 1,2:4,5-di-O-isopropylidene-3-O-(2-propinyl)-β-D-fructo-
pyranose44 were prepared according to the literature methods. IR spectra
were acquired on a Mattson Research Series FT-IR spectrometer using
CsCl solution cells. NMR spectra were recorded using CDCl3 as solvent
on either a Bruker AMX300 (operating frequencies 1H 300.13 MHz, 13
C
1
76.98 MHz), Bruker AV500 (operating frequencies H 500.13 MHz,
13C 125.77 MHz), Bruker AV700 (operating frequencies H 700.13
1
MHz, 13C 176.05 MHz), or JEOL EX400 (operating frequencies H
1
400.13 MHz, 13C spectroscopic 100.60 MHz) spectrometer. For 13C
NMR data, “cis” and “trans” carbonyl resonances refer to orientation
relative to the alkynyl ligand. Mass spectra were obtained using the ESI
technique on a Bruker microTOF instrument. CO-release tests were
performed as described previously.13,19,24,39
Preparation of [Mo(C;CCH2OH)(η5-C5H5)(CO)3], 2a. A
Schlenk tube was charged with 281 mg (1.0 mmol) of [MoCl(η5-
C5H5)(CO)3], and 5 mL of a 1 M solution of NH2Me in THF was
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Figure 8. CO release profile for 4e. Plot of [Mb-CO] against time under exposure to UV light: (red [) [1] = 60 μM, (green 2) [1] = 40 μM, and
(blue 9) [1] = 20 μM.
84.1 (Mo-CtC), 92.9 (η5-C5H5), 126.1 (C6H5), 127.0 (C6H5), 128.0
(C6H5), 147.0 (C6H5), 131.8 (Mo-CtC), 222.6 (cis-CtO), 238.6
(trans-CtO). HRMS: [M ꢀ OH]+ 437.0 (437.0 expected for C23H16-
MoO4).
32.0 (tCCH2), 63.5 (CH2OH), 72.6 (Mo-CtC), 92.8 (η5-C5H5),
129.3 (Mo-CtC), 222.8 (cis-CtO), 239.4 (trans-CtO). HRMS:
[M + H]+ 330.9875 (330.9865 expected for C13H13MoO4).
[Mo(C;CC4H8OH)(η5-C5H5)(CO)3], 3c. Yield: 190 mg (55%) of
an orange solid. IR ν (cmꢀ1): 2115 (w) (CtC), 2044 (s) (CtO), 1964
(vs) (CtO). 1H NMR: δ 1.55 (m, 2H, CH2), 1.65 (m, 2H, CH2), 1.87
(br, 1H, OH), 2.34 (t, 2H, 3JHH = 6.6 Hz, CH2), 3.65 (t, 2H, 3JHH = 6.4
Hz, CH2OH), 5.47 (s, 5H, η5-C5H5). 13C NMR: δ 14.2 (CH2), 22.2
(CH2), 32.1 (CCH2), 62.5 (CH2OH), 70.5 (Mo-CtC), 92.9 (η5-
C5H5), 129.8 (Mo-CtC), 222.8 (cis-CtO), 239.8 (trans-CtO).
HRMS: [M + H]+ 330.9875 (343.9946 expected for C13H15MoO4).
[Mo(C;CCH2OAc)(η5-C5H5)(CO)3], 4a. Yield: 170 mg (49%) of
a yellow solid. IR ν (cmꢀ1): 2125(w) (CtC), 2045 (s), 1965 (vs)
(CtO), 1732 (m) (CdO). 1H NMR: δ 2.06 (s, 3H, CH3), 4.71 (s, 2H,
CH2), 5.50 (s, 5H, η5-C5H5). 13C{1H} NMR: δ 21.1 (CH3), 55.0
(CH2OAc), 85.4 (CtCCH2), 92.9 (η5-C5H5), 121.7 (Mo-CtC),
170.7 (CdO), 222.8 (cis-CtO), 238.5 (trans-CtO). HRMS: [M +
Na]+ 366.9467 (366.9477 expected for C13H10MoNaO5).
[Mo(C;CCMe2{OH})(η5-C5H5)(CO)3], 2c. Yield: 150 mg (45%)
of an orange solid. IR ν (cmꢀ1): 2113 (w) (CtC), 2044 (s) (CtO),
1961 (vs) (CtO). 1H NMR: δ 1.45 (s, 6H, CH3), 1.94 (br, 1H, OH),
5.47 (s, 5H, η5-C5H5). 13C{1H} NMR: δ 32.3 (CH3), 66.7
(CMe2{OH}), 75.9 (Mo-CtC), 92.8 (η5-C5H5), 134.4 (Mo-CtC),
222.8 (cis-CtO), 239.2 (trans-CtO). Anal. Found (expected)/%: C
47.60 (47.58), H 3.66 (3.69). HRMS: [M + Na]+ 352.9675 (352.9687
expected for C13H12MoO4Na).
[Mo(C;CCPhMe{OH})(η5-C5H5)(CO)3], 2d. Yield: 250 mg
(63%) of a yellow solid. IR ν (cmꢀ1): 2110 (w) (CtC), 2044 (s)
(CtO), 1963 (vs) (CtO). 1H NMR: δ 1.70 (s, 3H, CH3), 2.30 (br,
1H, OH), 5.49 (s, 5H, η5-C5H5), 7.29 (3H, C6H5), 7.69 (m, 2H, C6H5).
13C{1H} NMR: δ 34.3 (CH3), 71.3 (C(Ph)MeOH), 80.4 (Mo-CtC),
92.8 (η5-C5H5), 125.3 (C6H5), 127.9 (C6H5), 128.7 (Mo-CtC), 132.0
(C6H5), 147.7 (C6H5), 222.7 (cis-CtO), 238.8 (trans-CtO). Anal.
Found (expected)/%: C 55.40 (55.35), H 3.62 (3.62). HRMS:
[M + Na]+ 414.9822 (414.9842 expected for C18H14MoNaO4).
[Mo(C;CCHPh{OH})(η5-C5H5)(CO)3], 2e. Yield: 87 mg (26%)
of an orange solid. IR ν (cmꢀ1): 2114 (w) (CtC), 2043 (s) (CtO),
1962 (vs) (CtO). 1H NMR δ 2.15 (s, 1H, OH), 2.72 (s, CH), 5.48 (s,
5H, η5-C5H5), 7.07ꢀ7.13 (5H, C6H5). 13C NMR: δ 66.4 (CH), 83.9
(Mo-CtC), 92.9 (η5-C5H5), 126.9 (C6H5), 127.7 (C6H5), 128.3
(C6H5), 128.7 (C6H5), 142.6 (Mo-CtC), 222.7 (cis-CtO), 238.6
(trans-CtO). HRMS: [M + Na]+ 400.9678 (400.9685 expected for
C17H12MoO4Na).
[Mo(C;CCH2OCH2Ph)(η5-C5H5)(CO)3], 4b. Yield: 205 mg
(49%) of an orange solid. IR ν (cmꢀ1): 2125 (w) (CtC), 2044 (s)
(CtO), 1963 (vs) (CtO). 1H NMR: δ 4.23 (s, 2H, tCCH2), 4.62 (s,
2H, OCH2), 5.52 (s, 5H, η5-C5H5), 7.33ꢀ7.36 (5H, C6H5). 13C{1H}
NMR: δ 59.7 (tCCH2), 70.7 (OCH2), 82.7 (Mo-CtC), 92.9 (η5-
C5H5), 124.9 (Mo-CtC), 127.5 (C6H5), 128.2 (C6H5), 128.3 (C6H5),
128.5 (C6H5), 222.8 (cis-CtO), 238.8 (trans-CtO). HRMS: [M +
Na]+ 414.9835 (414.9842 expected for C18H14MoNaO4).
[Mo(C;CCH2OC(O){C6H4-2-OCOMe})(η5-C5H5)(CO)3], 4c.
Yield: 80 mg (17%) of an orange oil. IR ν (cmꢀ1): 2124 (w) (CtC),
2045 (s) (CtO), 1965 (vs) (CtO). 1H NMR: δ 2.39 (s, 3H, CH3),
[Mo(C;CC2H4{OH})(η5-C5H5)(CO)3], 3a. Yield: 168 mg (44%)
4.92 (s, 2H, CH2), 5.52 (s, 5H, η5-C5H5), 7.09ꢀ8.05 (4H, C6H4). 13
C
of a yellow solid. IR ν (cmꢀ1): 2116(w) (CtC), 2040 (s) (CtO), 1964
NMR: δ 21.2 (CH3),55.8 (CH2), 86.3 (CtC), 93.1 (η5-C5H5), 121.5
(Mo-CtC), 123.6 (C6H5), 123.7 (C6H5), 132.1 (C6H5), 123.6 (C6H5),
133.8 (C6H5), 150.6 (C6H5), 164.3 (CdO), 170.0 (CdO), 222.8 (cis-
CtO), 238.4 (trans-CtO). HRMS: [M + H]+ 464.9863 (464.9871
expected for C20H15MoO7).
3
(vs) (CtO). 1H NMR: δ 2.00 (br, 1H, OH), 2.55 (t, JHH = 8.0 Hz,
tCCH2), 3.58 (br, 2H, CH2OH), 5.46 (s, 5H, η5-C5H5). 13C NMR: δ
26.9 (tCCH2), 61.8 (CH2OH), 75.1 (Mo-CtC), 93.0 (η5-C5H5),
124.8 (Mo-CtC), 223.1 (cis-CtO), 239.2 (trans-CtO). HRMS: [M +
H]+ 316.9707 (316.9708 expected for C12H11MoO4).
[Mo(C;CCH2OC(O){C6H4-2-OH})(η5-C5H5)(CO)3], 4d, . Yield:
[Mo(C;CC3H6{OH})(η5-C5H5)(CO)3], 3b. Yield: 107 mg (32%)
38 mg (9%) of a yellow solid. IR ν (cmꢀ1): 2123 (w) (CtC), 2046
of an orange oil. IR ν (cmꢀ1): 2110 (w) (CtC), 2042 (s) (CtO), 1960
(s) (CtO), 1965 (vs) (CtO). H NMR: δ 4.99 (s, 2H, CH2), 5.52
1
1
3
(vs) (CtO). H NMR: δ 1.71 (apparent sextet, JHH = 6.0 Hz, 2H,
CH2), 2.43 (t, 3JHH = 6.6 Hz, tCCH2), 2.54 (br, 1H, OH), 3.78 (t, 3JHH
5.6 Hz, 2H, CH2OH), 5.47 (s, 5H, η5-C5H5). 13C NMR: δ 19.9 (CH2),
(s, 5H, η5-C5H5), 6.88ꢀ7.90 (4H, C6H4), 10.7 (s, 1H, OH). 13C NMR:
δ 55.8 (CH2), 87.5 (Mo-CtC), 93.1 (η5-C5H5), 112.7 (C6H4), 117.6
(C6H4), 119.4 (C6H4), 121.1 (Mo-CtC), 130.3 (C6H4), 136.1 (C6H4),
=
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161.6 (C6H4), 169.8 (CdO), 222.7 (cis-CtO), 238.3 (trans-CtO).
OdC-NCH2), 3.75 (m, 1H, OdC-NCH2), 4.20 (d, 1H, 4JHH = 2.8 Hz,
HCdC-CH2), 5.07 (s, 5H, η5-C5H5). 13C{1H} NMR: 23.6 (CH2), 24.8
(CH2), 25.4 (CH2), 25.9 (CH2), 26.0 (CH2), 26.6 (CH2), 36.3 (HC-
CdCH2), 42.5 (CH2), 46.5 (CH2), 93.2 (η5-C5H5), 137.1 (HC-
CdCH2), 174.8 (CdO), 245.7 (CtO), 249.3 (CtO). Anal. Found
(expected)/%: C 55.75 (55.21), H 6.24 (5.95), N 6.19 (5.84). HRMS:
[M + H]+ 455.1231 (455.1231 expected for C21H29MoN2O3).
[Mo(η3-C{dCHCH2OH}CdCHC{dO}NC5H10)(η5-C5H5)(CO)2],
6. Yield: 141 mg (31%). IR ν (cmꢀ1): 1990 (s) (CtO), 1931 (s) (CtO),
1596 (m) (CdO). 1H NMR: δ 1.59 (br, 10H, CH2), 3.45 (br, 2H, OCH2),
3.77 (br, 1H, OH), 3.90 (dd, 4JHH = 3.8 Hz, 3JHH = 10.6 Hz, 2H, OCH2), 4.30
(dd, 4JHH = 6.0 Hz, 3JHH = 13.2 Hz, 1H, CH), 4.41 (d, 3JHH = 12.4 Hz, 1H,
CH), 5.38 (s, 5H, η5-C5H5), 5.67 (br, 1H, OH), 6.71 (dd, 4JHH = 6.0 Hz,
8.0 Hz, 1H, CH). 13C{1H} NMR: δ 24.6 (CH2), 25.8 (CH2), 26.8 (CH2),
43.4 (CH2), 47.4 (CH2), 31.8 (HCd), 64.9 (OCH2), 65.2 (OCH2), 86.9
(Cq), 90.6 (η5-C5H5), 92.0 (CH), 116.0 (dCH), 170.1 (Cq), 172.4
(NCdO), 232.0 (CtO), 232.1 (CtO). Anal. Found (calculated)/%: C
51.71 (50.75), H 5.25 (5.21), N 3.17 (3.01). HRMS: [M + H]+ 444.0688
(444.0707 expected for C19H24MoNO5).
Details of X-ray Diffraction Experiments. Details of the col-
lection and refinement are presented in Table 2. Diffraction data were
collected at 110 K on a Bruker Smart Apex diffractometer with Mo KR
radiation (λ = 0.71073 Å) using a SMART CCD camera. Diffractometer
control, data collection, and initial unit cell determination were per-
formed using SMART.45 Frame integration and unit-cell refinement
were carried out with SAINT+.46 Absorption corrections were applied
by SADABS (v2.03, Sheldrick).47 Structures were solved by direct me-
thods using SHELXS-97 and refined by full-matrix least-squares using
SHELXL-97.48 All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were placed using a “riding model” and included in the
refinement at calculated positions. CCDC 827195 (2c), 827196 (2d),
827197 (5a), 827198 (5b), 827199 (5c), and 827200 (6) contain the
supplementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
HRMS: [M + H]+ 422.9761 (422.9764 expected for C18H13
MoO6).
-
[Mo(C;CCH2O-β-D-fructopyranose)(η5-C5H5)(CO)3], 4e.
Yield: 170 mg (40%) of a yellow powder. IR ν (cmꢀ1): 2113 (w)
1
(CtC), 2044 (s) (CtO), 1964 (vs) (CtO). H NMR: δ 1.24 (3H
CH3), 1.34 (3H CH3), 1.46 (3H CH3), 1.58 (3H CH3), 3.91 (m, 2H,
CH2), 4.10 (m, 3H, CH), 4.30 (dd, 1H, J = 5.6 Hz, 8.8 Hz, H1), 4.36 (d,
1
1
0
1H, J = 8.8 Hz, H ), 4.46 (d, 1H, J = 15.6 Hz, H ), 4.57 (d, 1H, J = 15.6
Hz, H ), 5.40 (s, 5H, η -C5H5). 13C NMR: δ 26.2 (CH3), 26.6 (CH3),
1
5
0
6
1
1
5
0
27.0 (CH3), 28.3 (CH3), 60.2 (C ), 61.2 (C ), 72.1 (C ), 72.8 (C ), 74.1
(C4), 78.1 (C3), 83.0 (Mo-CtC), 92.9 (η5-C5H5), 104.8 (C2), 109.1
(C{CH3}2), 112.0 (C{CH3}2), 125.0 (Mo-CtC), 222.7 (cis-CtO),
238.5 (trans-CtO). HRMS: [M + H]+ 545.0714 (545.0709 expected
for C23H27MoO9).
General Procedure for the Preparation of Complexes 5.
[(η5-C5H5)Mo(CO)3Cl] (281 mg, 1 mmol) was dissolved in the
appropriate amine (3 mL), and HCtCCH2OH (125 μL, 1.2 mmol)
was added followed by a catalytic amount of CuI. The reaction was
stirred at 25 °C for 10 to 15 min, and the solvent was then removed
under reduced pressure. The residue was purified by column chroma-
tography by elution with hexane and acetone. Crystals were obtained by
slow evaporation of a saturated hexane solution of complex with a trace
of dry CH2Cl2 at ꢀ30 or 25 °C.
[Mo(η3-H2CCN{C2H5}2CHC{dO}N{C2H5}2)(η5-C5H5)(CO)2],
5a. Yield: 130 mg (41%) of an orange solid. IR ν (cmꢀ1): 1931 (s)
(CtO), 1843 (s) (CtO), 1602 (m) (CdO). 1H NMR: δ 1.11 (t, 6H,
7.2 Hz, 2CH3), 1.14 (t, 3H, 7.2 Hz, CH3), 1.36 (t, 3H, 7.2 Hz, CH3), 2.93
(m, 2H, CH2), 2.99 (apparent t, 1H, JHH = 3.0 Hz, CdC-CH2), 3.13 (m,
2H, CH2), 3.21 (apparent sextet, 1H, 7.5 Hz), 3.50 (d, 1H, 2JHH = 3.5
Hz, HCdC-CH2), 3.56 (apparent sextet, 1H, 7.0 Hz), 4.01 (apparent
sextet, 1H, 7.0 Hz), 4.09 (d, 1H, 4JHH = 2.5 Hz, HCdC-C), 5.12 (s, 5H).
13C{1H} NMR: δ 12.89 (2 ꢁ CH3), 13.9 (CH3), 14.0 (CH3), 23.4 (CH-
CdCH2), 37.7 (CH-CdCH2), 40.1 (CH2), 41.8 (CH2), 42.9 (2 ꢁ
CH2), 93.5 (η5-C5H5), 140.9 (CH-CdCH2), 175.0 (OdC), 246.4
(CtO), 250.9 (CtO). Anal. Found (expected)/%: C 53.01 (53.27),
H 6.53 (6.59), N 6.39 (6.54). HRMS: [M + H]+ 431.1235 (431.1231
expected for C19H29MoN2O3).
’ ASSOCIATED CONTENT
S
Supporting Information. Details of the X-ray structure
b
determination of compounds 2c, 2d, 5a, 5b, 5c, and 6 in CIF
format. This material is available free of charge via the Internet at
http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: jason.lynam@york.ac.uk. Fax: (+44) 1904 322516. Tel:
(+44) 1904 322534.
[Mo(η3-CH2CN{C4H8}CHC{dO}N{C4H8})(η5-C5H5)(CO)2], 5b.
Yield: 81 mg (19%). IR ν (cmꢀ1): 1932 (s) (CtO), 1845 (s) (CtO),
1600 (m) (CdO). 1H NMR: δ 1.60 (br, 4H, CH2), 1.73 (m, 4H, CH2),
2.16 (br, 2H, CH2), 2.62 (br, 2H, CH2), 3.05 (apparent t, JHH = 2.6 Hz,
’ ACKNOWLEDGMENT
2
1H, HCdC-CH2), 3.10 (br, 2H, NCH2), 3.35 (d, JHH = 2.8 Hz,
HCdC-CH2), 3.72 (br, 2H, NCH2), 3.98 (d, 4JHH = 2.4 Hz, HCdC-
CH2), 5.07(s, 5H, η5-C5H5). 13C{1H} NMR: δ 24.6 (CH2), 24.8
(CH2), 26.4 (CH2), 26.6 (CH2), 29.3 (CH2), 31.8 (H2CdC-CH),
45.7 (CH2), 46.5 (CH2), 93.3 (η5-C5H5), 135.8 (H2CdC-CH), 174.0
(CdO), 245.9 (CtO), 250.5 (CtO). Anal. Found (expected)/%: C
55.72 (55.75), H 6.20 (6.21), N 6.09 (6.19). HRMS: [M + H]+ 427.0910
(427.0918 expected for C19H25MoN2O3).
We are grateful to the Leverhulme Trust (F/00 2244/AA),
EPSRC (EP/E005152/1), and The Royal Society (Fellowship to
I.J.S.F.) for funding
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