Photochemically reactive polymers; The synthesis and photochemistry of amide polymers and model compounds containing metal-metal bonds and internal radical traps

Article abstract of DOI:10.1016/S0022-328X(97)00598-6

The synthesis and photochemistry of a photochemically reactive polymer that has internal metal-radical traps (chlorine atoms) along its backbone is reported. Reaction of the organometallic 'diamine' (CpCH₂CH₂NH₂)₂Mo ₂(CO)₆ with an activated mixed anhydride derivative of 3,4-dichlorohexanedioic acid gave the polymer [-CHClCH₂C(O)NHCH₂CH₂(η⁵-C ₅H₄)(CO)₃Mo-Mo(CO)₃(η ⁵-C₅H₄)CH₂CH₂NHCOCH ₂CHCl-]_n. The difunctional activated mixed anhydride was used because the Mo-Mo bond reacts with acyl chlorides to form oligomeric amides containing -Mo(CO)₃Cl units. As an aid to the spectroscopic characterization of the polymers, model complexes were synthesized by reacting (CpCH₂CH₂NH₂)₂Mo ₂(CO)₆ with activated mixed anhydrides of chloroacetic acid and 5-chlorovaleric acid. Thus, (η⁵-C₅H₄R)₂Mo ₂(CO)₆ (R=-CH₂CH₂NHCOCH₂Cl and -CH₂CH₂NHCO(CH₂)₃CH₂Cl) were synthesized by reacting (CpCH₂CH₂NH₂)₂Mo ₂(CO)₆ with CH₃CH₂OC(O)OC(O)CH₂Cl and CH₃CH₂OC(O)OC(O)(CH₂)₃CH ₂Cl, respectively. Because of the metal-metal bonds along the backbone, the polyamide is photochemically reactive (as are the model complexes), undergoing metal-metal bond photolysis reactions similar to the Cp₂Mo₂(CO)₆ dimer. The products contain CpMo(CO)₃Cl units, indicative of 'self-trapping' by the chlorine atoms built into the polymer and model complexes. Photochemical decomposition also occurred in the solid state without external metal-radical traps.

Full text of DOI:10.1016/S0022-328X(97)00598-6

Journal of Organometallic Chemistry 554 Ž1998. 19–28
Photochemically reactive polymers; the synthesis and photochemistry of
amide polymers and model compounds containing metal–metal bonds
and internal radical traps
Gregory F. Nieckarz, John J. Litty, David R. Tyler )
Department of Chemistry, UniÕersity of Oregon, Eugene, OR 97403-1253, USA
Received 3 December 1996; received in revised form 11 April 1997
Abstract
The synthesis and photochemistry of a photochemically reactive polymer that has internal metal-radical traps Žchlorine atoms. along
its backbone is reported. Reaction of the organometallic ‘diamine’ ŽCpCH CH NH . Mo ŽCO. with an activated mixed anhydride
2
2
2
2
2
6
5
5
derivative of 3,4-dichlorohexanedioic acid gave the polymer w–CHClCH CŽO.NHCH CH Žh -C H .ŽCO. Mo–MoŽCO. Žh -
2
2
2
5
4
3
3
C H .CH CH NHCOCH CHCl–x . The difunctional activated mixed anhydride was used because the Mo–Mo bond reacts with acyl
5
4
2
2
2
n
chlorides to form oligomeric amides containing –MoŽCO. Cl units. As an aid to the spectroscopic characterization of the polymers,
3
model complexes were synthesized by reacting ŽCpCH CH NH . Mo ŽCO. with activated mixed anhydrides of chloroacetic acid and
2
2
2
2
2
6
5
5
-chlorovaleric acid. Thus, Žh -C H R. Mo ŽCO. ŽRs –CH CH NHCOCH Cl and –CH CH NHCOŽCH . CH Cl. were synthe-
5
4
2
2
6
2
2
2
2
2
2
3
2
sized by reacting ŽCpCH CH NH . Mo ŽCO. with CH CH OCŽO.OCŽO.CH Cl and CH CH OCŽO.OCŽO.ŽCH . CH Cl, respec-
2
2
2
2
2
6
3
2
2
3
2
2
3
2
tively. Because of the metal–metal bonds along the backbone, the polyamide is photochemically reactive Žas are the model complexes.,
undergoing metal–metal bond photolysis reactions similar to the Cp Mo ŽCO. dimer. The products contain CpMoŽCO. Cl units,
2
2
6
3
indicative of ‘self-trapping’ by the chlorine atoms built into the polymer and model complexes. Photochemical decomposition also
occurred in the solid state without external metal-radical traps. q 1998 Elsevier Science S.A.
Keywords: Amide polymers; Metal–metal bonds; Photochemical decomposition
1
. Introduction
Our syntheses of metal–metal bond-containing poly-
mers use metal–metal bonded dimers with functionally
substituted cyclopentadienyl ligands, a synthetic
methodology borrowed from earlier work on polyfer-
rocenes w21–30x. An example of a polyurethane synthe-
Photochemically reactive polymers w1–4x are of con-
siderable interest because they are useful as degradable
plastics w5x, photoresists w6–10x, biomedical materials,
and as precursors to ceramic materials w6–8,11–14x. In
sis is shown in Eq. 2
Ž . w15x.
previous papers, we described the synthesis of a new
class of photodegradable polymers that have metal–
metal bonds along the polymer backbone w15–18x. These
polymers are photochemically active because metal–
metal bonds can be cleaved with visible light w19,20x.
2
Ž .
1
Ž .
)
Corresponding author.
0
022-328Xr98r$19.00 q 1998 Elsevier Science S.A. All rights reserved.

2
0
G.F. Nieckarz et al.rJournal of Organometallic Chemistry 554 (1998) 19–28
Thus far, polyurethanes, polyureas, polyethers, poly-
2. Results and discussion
vinyls, polyamides and several types of copolymers
with metal–metal bonds along the backbone have been
synthesized w15–18x. As predicted, all of these polymers
2
.1. Synthetic strategy
are photodegradable, both in solution and in the solid
state, provided that a metal radical trap is present to
capture the metal radicals and prevent reformation of
the metal–metal bond by radical recombination w15–18x.
Selected organic halides are excellent traps for metal
radicals. It was decided therefore to substitute the poly-
mer backbones with halogens to test the feasibility of
synthesizing a polymer with a built-in radical trap.
These polymers would then be used to test the hypothe-
sis that a built-in radical trap can enhance the rate of
photodegradation. Although these premises could be
investigated with numerous types of polymers, our re-
cent studies of photodegradable polymers have focused
on polyamides w18x; therefore, polyamides were also
In solution, CCl or other organic halides are excellent
4
traps, while ambient oxygen serves that purpose in the
solid state reactions.
Our long-range goal is to develop ways to control the
rate of photodegradation of these polymers. Two meth-
ods are being investigated. One approach is to vary the
number of metal–metal bonds along the polymer back-
bone, and the other is to control the efficiency with
which the photogenerated metal radicals are captured.
used in this study. Polyamides with metal–metal bonds
along the backbone are synthesized by the reaction of
Ž
The capture efficiency will affect the rate of degrada-
tion because the metal radicals can back-react to reform
the metal–metal bond . To control and enhance the
Ž
CpCH CH NH .2 Mo2
hydride derivatives of carboxylic acids
Ž
CO.6 with activated mixed an-
e.g., Eq.
..
As in our previous study of polyamides with metal–
2
2
2
Ž
Ž
3 .
.
Ž
.
Ž
rate of radical trapping, we are designing polymers with
radical traps built into the backbone. It is our hypothesis
that it should be possible to control more easily the
degradation of polymers with built-in radical traps be-
cause the concentration of the trap can be manipulated.
This paper reports on our synthesis of a polymer and
metal bonds w18x,
Ž
CpCH CH NH .2 Mo2
Ž
CO.6 was
2
2
2
generated in situ by deprotonation of
Ž
CpCH CH
2
2
q
NH .2 Mo2ŽCO.6 using triethylamine. The dimer is
3
prepared and stored as the ammonium salt to prevent
reaction of the free amine with the metal–metal bond
w31x..
For this study, the plan was to incorporate halo-
gens along the backbone by using halogen-containing
activated mixed anhydride derivatives of carboxylic
acids.
several model complexes that have radical traps
rine atoms attached to the polymer backbone. The
photochemistry of these species is also reported.
Ž
chlo-
.
Ž
3
.
q
2
.2. A new synthesis of [(CpCH CH NH ) Mo
2 2 3 2
2
y
(
CO) ][NO ]
6 3 2
Our previously reported synthesis of w
Ž
CpCH CH
2
2
q
y
NH
. Ž . xwNO x was long and tedious w18x. It
Mo CO
3
2 2 6
3 2
involved five steps and required nearly 10 days of
intensive labor in order to obtain analytically pure mate-
rial. To expedite this investigation, and improved syn-
thesis was developed that has fewer steps, requires
much less time about 6 days , and gave the dimer in
Ž .
1
higher yield Scheme 1 .
Ž .
1
This new preparation of the amine ligand is a modification of the
one mentioned in a personal communication from Camil Joubran
and Professor Douglas Grotjahn, Department of Chemistry, Arizona
State University, Tempe, AZ, USA 85287-1604.
q
Scheme 1. Improved synthesis of wŽCpCH CH NH . Mo ŽCO. x
2
2
3
2
2
6
y
wNO x .
3
2

G.F. Nieckarz et al.rJournal of Organometallic Chemistry 554 (1998) 19–28
21
The new synthesis utilized the reaction of two equiv-
alents of cyclopentadienyl anion generated in situ with
n-butyl lithium in THF with 1 mol of 2-bromoethyla-
Ž
.
mine hydrobromide in THF. After drying, the amine
ligand was isolated as a pure, clear, yellow oil in 78%
yield. This new route resulted in the isolation of the
amine ligand in fewer steps and without need for purifi-
cation.
Ž
A difficult distillation was required in the origi-
q
nal synthesis.
.
The w
Ž
CpCH CH NH
.
Mo2
Ž
CO.6
x
2
2
3 2
y
wNO x dimer was then synthesized using Mo
Ž
CO
.
as
3
2
6
previously described
Ž
26% yield
.
w17x. As previously
noted, the dimer is air sensitive in solution, but rela-
tively stable in the solid state if it is kept in the dark.
Spectroscopic data are reported in Table 1.
2
.3. Synthesis of model compounds
Scheme 3. Synthesis of model compound 2 from chloroacetic acid
q
and ŽCpCH CH NH . Mo ŽCO. .
2
2
3
2
2
6
To facilitate the synthesis and characterization of the
new polymers, model compounds were synthesized first
using halogen-containing activated mixed anhydride
derivatives of monocarboxylic acids. These syntheses
and other exploratory experiments revealed that
bromine-containing carboxylic acids were not satisfac-
tory because the resulting products were too reactive.
For example, in the reaction with a-bromovaleric acid
bonds and form CpMo
ŽCO.3Cl-containing species w18x.
However, activated mixed anhydride derivatives of the
acids were reactive and gave good yields of the amide
products without degrading the metal–metal bonds.
Similar results were obtained using 5-chlorovaleric
Ž
CH3
Ž
CH2 .2CH BrCOOH
.
, the product was an elas-
acid. Thus, the direct reaction with
Ž
CpCH 2
2
tomeric solid, vaguely characterized to be an a-amino
cross-linked bis-amide network polymer formed by nu-
cleophilic attack of the amine on the a carbon. Other
experiments showed that, with the exception of
chloroacetic acid, chlorine atoms could not be in the
a-position relative to the amide linkage; the resulting
products were again too reactive to isolate and charac-
terize. For these reasons, 5-chlorovaleric acid, CH2
CH NH .2 Mo2 CO.6 gave no amide product. How-
Ž
2
2
ever, the activated mixed anhydride of 5-chlorovaleric
acid in THF gave model complex, 1, as shown in
Scheme 2. The product was isolated by precipitation
from THFrhexanes as an air stable
light red powder. This color is similar to the many
other model compounds and polymers containing Mo–
The presence of the amide linkage
Ž
in the absence of
.
Ž
Mo bonds w15–18x.
.
1
Cl
Ž
CH2 .3COOH, was used in this study.
Previous work showed that carboxylic acids do not
react readily with
CpCH CH NH .2 Mo2 CO.6 and
was indicated by an amide resonance in the H NMR at
7.04 ppm, and the Cp Mo2ŽCO.6 structural unit was
2
y1
Ž
Ž
indicated by y
Ž
C[O
.
at 2006, 1950, and 1906 cm
CO has bands at 2006,
6
.
2
2
2
that acid chlorides react to cleave the metal–metal
Ž
For comparison, Cp Mo
Ž
.
2
2
y1
1
950, and 1906 cm in THF w15x..
Amide bands were
y1
seen at 3431, 2919, 2850, 1644, 1469, and 1244 cm
and the electronic absorption spectrum had peaks at 508
,
)
and 393 nm
s™s
Ž
Table 1
.
, assigned to the dp™s and
)
transitions of the Mo–Mo chromophore, re-
spectively w19,20x.
Another model complex, 2, was synthesized by a
similar procedure using chloroacetic acid
Again, the product was isolated by precipitation from
THFrhexanes as an air stable in the dark red powder.
An amide resonance was observed in the H NMR at
Scheme 3 .
Ž .
Ž
.
1
7
1
.08 ppm and y
950, and 1906 cm . Amide stretches were observed
C[O bands were observed at 2013,
Ž .
y1
y1
at 3444, 3081, 2850, 1644, 1469, and 1256 cm . The
electronic spectrum has peaks at 509 and 392 nm,
which confirm the presence of Mo–Mo bonds. Elemen-
tal analysis also confirmed the proposed empirical for-
mula.
Scheme 2. Synthesis of model compound 1 from 5-chlorovaleric acid
q
and ŽCpCH CH NH . Mo ŽCO. .
2
2
3
2
2
6

Table 1
Selected spectroscopic data
1
a
b
IR y Žin cmy1.
c
Compound
H NMR d Žin ppm.
UV–Vis l Žin nm.
Reference
Cp Mo ŽCO.
6
5.60 Žbr., 5.44 Žbr.c
2012 Žsh, w., 1954 Žs., 1925 Žm.,
508, 388
w18x
2
2
d
2
011 Žm., 1959 Žs., 1913 Žs.
5.70e
b
CpMoŽCO. Cl
2051 Žs., 1972 Žvs.
2009 Žm., 1958 Žs., 1908Žs.
w16x
w31x
3
q
g
503,388g
508, 393
wŽCpCH CH NH .2
5.49–5.38 Žm,8H., 3.14 Žt,2H.,
2
2
3
f
Mo ŽCO. x–wNO x
2.78 Žt, 2H.
2
6
3 2
1
7.04 Žs, br, 2H., 5.39 Žs, br, 4H.,
3431 Žm., 2919 Žvs., 2850 Žs.,
2006 Žs., 1950 Žvs., 1906 Žvs.,
1644 Žm., 1469 Žw., 1244 Žw.
1644 Žm., 1469 Žw., 1244 Žw.
3444 Žm., 3081 Žw., 2850 Žm.,
2013 Žm., 1950 Žvs., 1906 Žvs.,
1644 Žm., 1469 Žw., 1256 Žw.
w18x
5
2
1
.20 Žs, br, 4H., 3.28 Žm, 4H.,
.56 Žt, 4H., 2.05 Žt, 4H., 1.58 Žm, 4H.,
h
.29 Žs, br, 64H., 0.89 Žt, 6H.
7.08 Žs, br, 2H., 5.39 Žs, br, 4H.,
2
509,392
505,392
This work
5
2
1
0
.20 Žs, br, 4H., 3.28 Žm, 4H.,
.56 Žt, 4H., 2.06 Žt, 4H.,
.58 Žm, 4H., 1.29 Žs, br, 44H.,
h
.89 Žt, 6H.
3
7.00 Žs, br, 2H., 5.400 Žs, br, 4H.,
3107 Žw., 2016 Žm., 1955 Žvs.,
1900 Žvs., 1641 Žm., 1471 Žm.,
1266 Žm., 823 Žm.
This work
5
3
3
.206 Žs, br 4H., 4.034, 4.010, 3.986,
.963 Žm, 2H., 3.236, 3.214,
.193, 3.170 Žm, 4H., 2.589, 2.565, 2.542
h
Žt, 4H., 2.492, 2.452 Žd, 4H.
a
KBr.
THF.
b
c
Acetone-d6.
d
Acetone.
CD Cl .
e
f
2
2
D O.
2
g
h
H O, pH 7 buffer.
2
THF– d8.

G.F. Nieckarz et al.rJournal of Organometallic Chemistry 554 (1998) 19–28
23
cmy1, amide infrared bands at 3107, 1641, 1471, 1266,
and 823 cm , and peaks at 505 and 392 nm in the
2
.4. Synthesis of a polymer with chlorine atoms along
y1
the backbone
electronic spectrum. Elemental analyses showed the in-
corporation of approximately 1.5 chlorine atoms per
repeat unit of the polymer backbone. Attempts to deter-
mine the molecular weight of the polymer by gel per-
meation chromatography were unsuccessful because the
polymer decomposed on the column. However, previous
work with other metal–metal bond-containing polymers
would suggest a molecular weight in the range of
10,000–20,000 w15–18x.
As was the case with the model complexes, the
reactions of
boxylic acids
Ž
CpCH CH NH .2 Mo2
Ž
CO.6 with dicar-
2
2
2
Ž
or their derivatives that have chlorine
.
atoms in the a position failed to yield stable products.
For that reason, 3,4-dichlorohexanedioic acid was syn-
thesized by chlorinating trans-b-hydromuconic acid.
The synthesis was a modification of a literature proce-
dure for chlorination of an alkene using thionyl chloride
4 .
w32x. The synthesis is outlined in Eq. Ž .
2
.5. Photochemistry in solution
The photochemistry l)540 nm
plexes 1 and 2 and of polymer 3 in degassed THF
solutions with no added radical trap is similar. Spec-
Ž
.
of model com-
4
Ž .
Ž
.
troscopic monitoring of the photoreactions showed the
disappearance of the Mo–Mo chromophore bands at
1
The chlorinated material was characterized by H
C[O bands at
Ž .
1
3
f390 and f505 nm and of the y
and C NMR and by infrared spectroscopy
. Complete incorporation of chlorine atoms was not
Ž
see Section
y1
f2010, 1950, and 1910 cm . In each case, new
3
.
y1
1
3
infrared bands appeared at 2046 and 1963 cm , indica-
achieved; C NMR and elemental analysis indicated
about 1.5 Cl atoms were incorporated per molecule.
However, this was not a concern as even partial incor-
poration of chlorine should affect the rate of polymer
degradation.
tive of the CpMo
CpMo
ŽCO.3Cl unit. Ž
For comparison,
y1
Ž
CO.3Cl has bands at 2046 and 1963 cm w33x..
These experiments demonstrated that we had indeed
synthesized a ‘self-trapping’ polymer. The quantum
yields for the reactions of the model complexes in THF
The 3,4-dichlorohexanedioic acid was used in the
synthesis of a polyamide by converting it to the acti-
vated mixed anhydride of the dicarboxylic acid and then
y4
are 0.06 for compound 1
for compound 2
Ž
w1xs4.7=10
M and 0.05
.
y4
Ž
w2xs2.6=10
M . The quantum
.
y4
yield for disappearance of the polymer
is 0.02.
Ž
9.3=10
M
.
reacting it in situ with
as shown in Scheme 4.
ŽCpCH CH NH .2 Mo2ŽCO.6
,
2 2 2
The polymer product was isolated as a THF-soluble,
air- and light-sensitive, tacky, red solid, similar in ap-
pearance to other polymers containing Mo–Mo bonds
w15–18x. The polymer was spectroscopically similar to
2.6. Photochemistry of polyamide films in the solid state
In previous studies with polyurethanes, polyureas,
polyvinyls and polyethers containing metal–metal bonds
w15–18x, it was established that both light and oxygen
are required for degradation to occur in the solid state.
Air oxygen is necessary for the degradation to occur
Ž .
the model compounds. There was an amide resonance at
7
.00 ppm, y C[O bands at 2016, 1955, and 1900
Ž .
because oxygen traps the metal radicals produced by
irradiation. In the absence of oxygen, the metal–metal
bonds recombine and no net photolysis takes place. To
test the hypothesis that the chlorine atoms in 3 can act
as built-in metal-radical traps in solid state photoreac-
tions
films of 3 were exposed to ambient light in the absence
of oxygen. The films were kept under nitrogen. For
and that oxygen is therefore not necessary , thin
Ž .
Ž
.
each film and its dark reaction control, the absorbance
)
of the dp™s transition was monitored periodically
over a period of 50 days. In fact, when exposed to light,
the films kept under nitrogen did decompose over the
course of about 5 days
the dp™s
Ž
as indicated by the decrease in
transition . In addition, infrared spec-
troscopy showed the appearance of new bands at 2048
)
.
y1
and 1965 cm , indicative of the CpMo
ŽCO.3Cl unit.
Other changes included a noticeable transformation in
the surface appearance from smooth to fissured. From
this data, we conclude that the photochemical decompo-
Scheme 4. Synthesis of a polyamide Ž3. with Mo–Mo bonds in the
backbone and chlorine atoms along the backbone.

2
4
G.F. Nieckarz et al.rJournal of Organometallic Chemistry 554 (1998) 19–28
sition of polymer 3 does not require oxygen, as is
required by all of the other metal–metal bond-contain-
ing polymers synthesized thus far. Control experiments
showed that films stored in the dark in air or under
purchased from Kodak Chemical and deoxygenated with
a nitrogen purge prior to use. Thionyl chloride was
purchased from J.T. Baker and used as received.
)
nitrogen showed no loss of absorbance in their dp™s
3
.2. Instrumentation and photochemistry
bands over 50 days. It is noteworthy that the rate of
polymer 3 photodegradation could be increased by ex-
posing it to oxygen. Comparison of samples irradiated
in air to those kept under nitrogen showed that the
Electronic spectra were recorded on a Perkin-Elmer
Lambda 6 spectrophotometer. Infrared spectra were ob-
tained on either a Nicolet 5DBX FT-IR, a Nicolet DX
FT-IR, or on a Nicolet 550 Magna FT-IR controlled by
a Gateway 2000 4DX-33V computer running OMNIC
2
photodegradation was about twice as fast in air. This
may simply be a result of having a higher concentration
of trap present in the samples exposed to air. It is also
interesting to note that diffusion in the polymer must be
sufficiently large to allow the metal radicals and chlo-
rine substituents to react.
In conclusion, the chlorine atoms along the backbone
of polymer 3 can act as internal radical traps for the
metal radicals produced by photolysis of the metal–
metal bonds. Future work in our laboratory is directed
at controlling the rate of polymer degradation by study-
ing how the concentration of internal trap affects the
rate of degradation.
1
13
software. All H and C NMR spectra were recorded
on either a General Electric QE-300 or a Varian Unity
Inova-300 spectrometer. The photochemical reactions in
both solution and the solid-state were carried out as
previously described w16–18x. Polymer molecular
weights were determined as previously described w18x.
5
3
.3. Synthesis of (h -C H CH CH NH )
5
5
2
2
2
This ligand was synthesized using a modification of
3
a procedure described by Joubran and Grotjahn. 2-
Bromoethylamine hydrobromide 6.20 g, 0.0303 mol
Ž
.
was added to an oven-dried 250 ml round-bottom flask
already charged with a stirbar and 80 ml of freshly
distilled THF, fit with a septum, and under nitrogen.
This resulted in a clear and white heterogeneous solu-
tion. Freshly distilled THF with the volume of 120 ml
of was syringed into a second 250 ml round-bottom
flask in an ice bath at 08C, already charged with a stir
bar and under nitrogen. To this second round-bottom
3
. Experimental
All air-sensitive manipulations were carried out un-
der nitrogen using standard Schlenk line techniques or a
Vacuum Atmospheres glovebox.
flask, freshly distilled cyclopentadiene
mol at 08C and under nitrogen was also added via
Ž
8.0 ml, 0.0968
3
.1. Materials
.
syringe. This solution was then cooled to y788C in an
Tetrahydrofuran was purchased from Baxter Chemi-
acetonerdry ice bath. To this solution, n-butyl lithium
cal and distilled under nitrogen from potassiumrbenzo-
phenone ketyl. Hexanes was purchased from Baxter
Chemical and distilled under nitrogen from
Ž
0.4 ml, 0.0646 mol was added via syringe. This
.
4
reaction mixture was then stirred for 20 min, at which
time it was added via cannula to the solution of 2-
bromoethylamine hydrobromide in THF. The combined
reaction solution was then stirred at 48C for 48 h, during
which time the reaction color turned from clear and
white to dark orange-brown. Next, the reaction solution
was added via cannula to an 800 ml separatory funnel
and diluted with 200 ml deoxygenated diethyl ether.
sodiumrbenzophenone ketyl or deoxygenated
Ž
by bub-
bling with nitrogen for at least 20 min prior to use.
.
Deionized water was taken directly from the tap and
deoxygenated by a nitrogen purge prior to use.
Chloroacetic acid, 5-chlorovaleric acid, and trans-b-hy-
dromuconic acid were purchased from Aldrich Chemi-
cal and were deoxygenated
Ž
either in vacuo or by
Ž
.
The ether was deoxygenated by a nitrogen purge. The
purging with nitrogen prior to use. Triethylamine was
.
organic reaction mixture was then washed with 2=
2
purchased from Aldrich Chemical, distilled from P O5
100-ml deoxygenated H O and then dried over MgSO .
2
4
under nitrogen, deoxygenated by three freeze–pump–
thaw cycles, and stored under nitrogen in a Teflon
sealed Schlenk storage flask. Ethyl chloroformate was
The product was isolated in vacuo as a clear-yellow oil
1
Ž
6
2
.56 g, 78% . H NMR CDCl : d 6.44, 6.29, 6.23,
. Ž
.
3
.08 m br , 3H, CpCH CH NH ; 2.98 d, 2H, CpC
Ž .
Ž
.
Ž
2
2
2
2
3
Note that oxo complexes form in the solution phase reactions of
C. Joubran, D. Grotjahn, Department of Chemistry, Arizona
State University, Tempe, AZ 85287-1604, personal communication.
Cp Mo ŽCO. with O . See Refs. w34,35x.
2
2
6
2

G.F. Nieckarz et al.rJournal of Organometallic Chemistry 554 (1998) 19–28
25
H CH NH
.
; 2.90, 2.88
Ž
t, 2H, CpCH C H C H NH ;
.
2
stir bar. The flask was fit with a septum and purged
2
2
2
2
2
2
.
2
s
.57, 2.55, 2.53, 2.51
br , 2H, CpCH CH NH .
.
2
Ž
m, 2H, CpC H CH NH
; 1.25
with N for 40 min while stirring. Freshly distilled THF
2
2
2
2
Ž
Ž
.
with a volume of 10 ml was then added via syringe. To
2
2
this clear and colorless solution, Et N
Ž
50 ml, 0.359
was added via syringe. The solution was then
cooled to 08C in an ice bath for 5 min, at which time
ethyl chloroformate 25 ml, 0.261 mmol was added via
3
q
3
.4. Synthesis of [(CpCH CH NH ) Mo (CO) ]
2
2
3
2
2
6
mmol
.
y
[
NO ]
3 2
Ž
.
q
The synthesis of w
Ž
CpCH CH NH
.
Mo
Ž
CO
.
x
2
2
3
3 2
syringe. The reaction mixture immediately turned from
clear and colorless to cloudy and white. The solution
was stirred for 40 min before it was allowed to react in
y
wNO x has been previously described w17x. Described
3
2
here is a modified synthesis, somewhat easier, which
gave the product with a similar yield and purity. All of
the following manipulations were performed in the dark
and under nitrogen, unless otherwise noted. A 500 ml
three-neck round-bottom flask, already charged with a
5
q
situ with
w
Ž
h -C H CH CH NH .2 Mo2
Ž
CO.6
x
5
4
2
2
3
y
wNO x .
3
2
stir bar and cyclopentadienylethylamine
mmol , was charged with 100 ml of freshly distilled
THF, and cooled to y788C in an acetonerliquid nitro-
gen bath. To this solution, n-butyl lithium 6.0 ml, 8.4
mmol was added via syringe, after which the reaction
Ž
2.56 g, 23.45
[(
CpCH CH N H C O CH Cl
( ) ( )
)
3
.6. Synthesis of 2,
) ]
2
2
2
.
Mo CO
(
3
2
Ž
All of the following manipulations were performed
in the dark, and under nitrogen, unless otherwise noted.
.
mixture changed color to pinkish-brown while being
stirred for 30 min. The reaction mixture was then
5
q
In the drybox,
wŽh -C H CH CH NH .2 Mo2
5 4 2 2 3
y
Ž
CO.6 xwNO x Ž .
48.8 mg, 0.069 mmol was placed into
3
2
allowed to warm to y208C, after which Mo
g, 27.2 mmol was added to the deprotonated-ligand
solution. The reaction mixture was then heated to 558C
reflux for 48 h, after which it was cannulaed into a
deoxygenated aqueous solution of Fe
NO3.3 P9 H O
made by dissolving Fe
NO3.3 P9 H O
mmol in 170 ml distilled water in a 300 ml round-bot-
tom flask and degassed by purging with nitrogen for 20
min resulting in the formation of a deep-red, heteroge-
ŽCO.6 Ž7.18
an oven dried Schlenk flask, already charged with a stir
bar and fitted with a septum. The flask was then
brought out of the drybox. The Schlenk flask was put
.
Ž
.
under N , and 20 ml of freshly distilled THF were
2
Ž
2
added via syringe. The heterogeneous, red solution was
Ž
Ž
Ž
7.8 g, 19.3
2
stirred for 5 min, at which time Et N
mmol
Ž
50 ml, 0.359
3
.
.
was added via syringe, which resulted in the
formation of a homogenous, red solution. The dimer
solution was then stirred for 15 min, after which it was
cooled to 08C, in an ice bath. After 35 min, the bis-mixed
anhydride was added in situ via cannula to the amine
dimer. The Schlenk flask which had contained the
mixed anhydride was rinsed with 10 ml THF which was
cannulaed into the reaction mixture. The reaction mix-
ture was stirred for 5 min at 08C, after which the ice
bath was removed. The reaction was then stirred for
.
neous solution. The reaction mixture was cooled to 08C
in an ice bath and kept under N for 48 h. The reaction
mixture was then filtered in air
2
but in the dark
Ž .
through a 150 ml glass filter-frit, resulting in the isola-
tion of a deep-red solid material. The product was then
dried in air for 48 h before being brought into the
drybox. In the drybox, the product in the frit was
extracted with approximately 5=20-ml MeOH, after
which the combined extracts were concentrated in vacuo
to approximately 20 ml. Next, approximately 80 ml of
diethyl ether was layered on top of the MeOH, the flask
was fitted with a septum and placed into the drybox
freezer for 48 h. The product was isolated as a fine red
precipitate via suction–filtration in a 60 ml medium
2
2.3 h, after which it was concentrated in vacuo to 5 ml
of a clear-red solution, put under N , and cannulaed into
2
1
00 ml de-ionized, deoxygenated
Ž
by bubbling with N2
for 90 min water at 08C, resulting in the immediate
.
formation of a cloudy-red solution. The cloudy-red solu-
tion was filtered in air through a fine porosity glass
filter-frit to separate a red solid from a clear and
colorless filtrate. The red solid was dried in air for 18.4
h then transferred into the drybox. The red product was
dissolved with 2=20-ml and 1=10-ml THF and fil-
tered through the glass filter-frit it was contained in.
This resulted in a clear-red solution, which was concen-
trated in vacuo to 2 ml and transferred to a round-bot-
tom flask. Hexanes was then layered atop the THF and
the round-bottom flask was stoppered and placed into
the drybox freezer at y408C for 48.6 h. The product
porosity frit then dried in vacuo for 2 h. Analytically
pure product was obtained
1
Ž
br
0.777 mg, 7%
.
. H NMR
Ž
DMSO-d6
.
: d 7.79
.72, 5.61, 5.29
.94, 2.91
Ž
br
s
Ž
.
, 6H, CpCH CH NH3.
;
2
2
5
2
Ž
m
Ž
.
, 4H, CpCH CH NH3.; 2.96,
2
2
Ž
t, 4H, CpCH C H NH
.
; 2.67, 2.64
Ž
t, 4H,
, 2923,
, 1914 vs
. Žamine
2
2
3
y1
CpC H CH NH3.. IR
Ž
KBr
; 2016
C[O..; 1389
.
cm : 3107
, 1961 vs
, 1348
m
Ž .
2
2
Ž
1
m
886
. Ž18 amine salt
.
Ž
m
.
.
Ž
.
Ž .
,
Ž
vs. Ž
y
Ž
Ž
s
Ž
s
.
.
3
.5. Synthesis of CH CH OC(O)OC(O)CH Cl
3
2
2
was isolated by suction–filtration as a fine red precipi-
1
Chloroacetic acid
into an oven-dried Schlenk flask already charged with a
Ž
13.3 mg, 0.141 mmol
.
was placed
tate
Ž
9.4 mg, 20%; mp 1668C
br
Ž
dec... H NMR
Ž
C
THF-d8
CH2
.
:
d 7.60y7.56
Ž
m
Ž
.
, 2H, CpCH CH N
Ž
H
.
Ž
O
.
2
2

2
6
G.F. Nieckarz et al.rJournal of Organometallic Chemistry 554 (1998) 19–28
Cl
5
Ž
3
2
Ž
Ž
1
Ž
Ž
.
; 5.41
.21
s, 4H, CpCH CH N
Ž
br
s
Ž
br
.
, 4H, CpCH CH N
Ž
H
.
C
Ž
O
.
CH Cl
.
;
min at 08C, after which the ice bath was removed and
the solution was allowed to warm to room temperature.
The reaction mixture was stirred for 18.5 h, after which
it was concentrated in vacuo to 10 ml resulting in a
clear-red solution. The reaction mixture was then cannu-
2
2
.
2
Ž
s
Ž
.
, 4H, CpCH CH N
Ž
H
C
Ž
O
.
CH Cl
.
; 3.96
; 3.37, 3.35, 3.33,
CH Cl ; 2.63, 2.61,
CH Cl . IR
; 2016
C[O..
, 1266
UV –Vis
15,038
2
2
2
Ž
H
.
C
Ž
O
.
H
C H Cl
.
2
2
2
.31
.59, 2.57
Ž
m, 2H, CpCH C H N
Ž
.
C
Ž
O
.
.
.
2
2
2
C
Ž
m, 4H, CpC H CH N
Ž
H
.
Ž
O
.
2
2
2
.
y1
KBr
, 1948
689 , 1655
amide II 830
THF
.
cm : 3305
Ž
m
.
, 3093
sho, vs
Ž
.
w
. Žfree N–H
, 1907
vs.Ž
; 1539
C –N str.
1548 ; 391
laed into 100 ml de-ionized, deoxygenated
ble for 18.6 h water at 08C, resulting in the immediate
Ž
by N -bub-
2
m
.
Ž
.
vs , 1921
Ž
Ž
m
.
y
Ž
;
.
Ž
m
.
Ž
m
. Žamide I
.
Ž
.
Ž
m
.
formation of a cloudy-red solution. The reaction mix-
.
;
Ž
m
.
Ž
.
ture was allowed to set, initially at 08C, under N , for
2
y1
y1
.
: l nm, ´ M cm ; 505
Ž
.
Ž
.
.
47.9 h. The product, observed as a red floculent solid in
a clear yellow-pink solution, was then isolated, in air,
via suction–filtration through a medium porosity filter-
frit. The product was then dried in air for 27.5 h, at
which time it was brought into the drybox. In the
drybox, the product was dissolved with 3=10-ml THF
and drawn through the filter-frit. The resulting clear-red
solution was then concentrated to 10 ml in vacuo and
transferred to a round-bottom flask. Hexanes was then
layered on top of the THF. The round-bottom flask was
then fit with a septum and placed into the drybox
freezer at y408C for 45.7 h. The product was isolated
Anal. Calc. for C H N O Mo Cl :C, 39.53; H, 3.04;
Found: C, 39.83;H, 3.19.
2
4
22
2
8
2
2
3
.7. Synthesis of CH CH OC(O)OC(O)(CH ) CH Cl,
an actiÕated mixed anhydride deriÕatiÕe of 5-chloro-
Õaleric acid
3
2
2
3
2
A mixed anhydride of HOC O
Ž .ŽCH2 .3CH Cl was
2
synthesized in an analogous manner to other mixed
anhydride compounds. Deoxygenated chlorovaleric acid
.
15.5 ml, 0.152 mmol was added via syringe to an
Ž
oven dried Schlenk flask, under N , already charged
as a bright-red solid via suction–filtration through a fine
2
1
with a stir bar and 20 ml freshly distilled THF, and fit
with a septum. The solution was stirred for 5 min and
cooled in an ice bath to 08C for 5 min. Deoxygenated
porosity filter-frit
Ž
28.2 mg, 47%
.
H
H
H
. H NMR
Ž
THF-d :d
8
7.10
5.40
5.21
Ž
s
Ž
br
br
br
.
, 2H, CpCH CH N
, 4H, CpCH CH N
Ž
.
.
.
C
C
C
Ž
Ž
Ž
O
O
O
.ŽCH2
.ŽCH2
.ŽCH2
.
CH Cl
.
.
.
;
;
;
2
2
3
3
3
2
Ž
s
Ž
.
Ž
Ž
.
.
.
CH Cl
2
2
2
Et N
Ž
30 ml, 0.215 mmol
reaction solution. The solution was stirred for 5 min,
after which deoxygenated by N -bubble)20 min ethyl
chloroformate 15 ml, 0.157 mmol was added via
.
was then syringed into the
Ž
s
Ž
.
, 4H, CpCH CH N
CH Cl
3
2
2
2
3.56, 3.54, 3.52
CH2 .2C H Cl
; 3.31, 3.29, 3.27, 3.25
.ŽCH2 .3CH Cl
; 2.59, 2.56, 2.54
.ŽCH2 .3CH Cl
; 2.12, 2.10, 2.06
Ž
m, 8H, CpCH CH N
Ž
H
C
Ž
O
.
CH2
m, 2H, CpCH2
t, 4H,
2
2
Ž
Ž
.
Ž
.
2
2
Ž
.
C H N
CpC H CH N
Ž
Ž
IR
2
Ž
Ž
Ž
Ž
H
.
C
Ž
O
.
Ž
2
2
syringe, resulting in the immediate formation of a turbid
solution. The activated mixed anhydride was stirred at
8C for 110 min before it was reacted in situ with the
Ž
H
.
C
Ž
O
.
2
2
2
t, 8H, CpCH CH N
Ž
H
.
C
Ž
O
H
.
.
.
C H2
Ž
CH2 .2CH Cl
.
; 1.73
2
2
2
0
s
Ž
br
KBr
009
amide I
C–N str.
1951 ; 392
.
8H, CpCH CH N
Ž
C
Ž
O
.
CH2
Ž
w
C H2 .2CH Cl
.
.
;
.
2
2
2
y1
amine dimer to form 1.
Ž
.
.
cm : 3271
Ž
m
, 3093
vs. Ž
Ž
. Žfree N–H
.
Ž
m
, 1941
; 1559
. UV–Vis
19,032
Ž
vs
m
.
, 1893
Ž
y
Ž
C[O..; 1641
Ž
m
m
3
.8. Synthesis of 1, [(CpCH CH N(H)C(O)(CH )
2 3
CH Cl)Mo(CO) ]
.
Ž
.
, 1239 m , amide II ; 836
Ž . Ž .
Ž
.
2
2
y1
y1
.
Ž
THF : l nm, ´ M cm ; 506
. Anal. Calc. for C H N O Mo
2
.
2
3
2
.
Ž
.
3
0
34
2
8
All of the following manipulations were performed
in the dark under nitrogen unless otherwise noted. In the
drybox, a Schlenk flask already containing a stir bar
Cl : C, 44.30; H, 4.21; Found: C, 44.47; H, 4.16.
2
3.9. Synthesis of 3,4-dichlorohexanedioic acid;
HOC(O)CH CH(Cl)CH(Cl)CH C(O)OH
5
q
was charged with w
Ž
h -C H CH CH NH .2 Mo2
5
4
2
2
3
2
2
y
Ž
CO
.
xwNO x
Ž
52.1 mg, 0.074 mmol
.
. The flask was
6
3
2
fit with a septum and brought out of the drybox. The
flask was charged by syringe with 20 ml freshly
The synthesis of 3,4-dichlorohexanedioic acid was
carried out by using a modification of a literature
procedure w32x. An oven-dried 250 ml round-bottom
flask already deoxygenated and charged with a stir bar
was fit with a reflux condenser. trans-b-Hydromuconic
Ž .
acid 973.6 mg, 6.755 mmol was then added to the
round bottom under a nitrogen counter-flow, after which
the set-up was evacuated for 2 min with stirring. The
reaction apparatus was then put under nitrogen and
2=50-ml freshly distilled THF was added via syringe,
at which time all of the white solid diacid dissolved. To
this solution, thionyl chloride 500 ml, 6.855 mmol
Ž .
was added via syringe. The clear and colorless reaction
mixture was heated to reflux for 9.3 h resulting in a
Ž
.
distilled THF resulting in the formation of a heteroge-
neous-red solution. This solution was stirred for 15 min
at which time deoxygenated Et N
Ž
30 ml, 0.215 mmol
.
3
was added via syringe resulting in the formation of a
clear-red solution. This solution was stirred for 45 min
at which time it was cooled to 08C in an ice bath. After
stirring for an additional 5 min the activated mixed
anhydride of 5-chlorovaleric acid was added in situ to
the amine dimer 2 via a cannula. The flask which had
contained the mixed anhydride was rinsed with 1=10-
ml freshly distilled THF which was then cannulaed to
the reaction mixture. The reaction was stirred for 30

G.F. Nieckarz et al.rJournal of Organometallic Chemistry 554 (1998) 19–28
27
clear-yellow solution, which was subsequently stirred
for 15.5 h at room temperature. The solution was con-
centrated in vacuo to yield a yellow oil which was then
All of the following manipulations were performed
in the dark, and under nitrogen, unless otherwise noted.
In the drybox, an oven round-bottom flask, already
5
partially dissolved in 50 ml Et O to give a heteroge-
containing a stir bar, was charged with w
Ž
h -C H CH
2
5
4
2
q
y
58.1 mg, 0.083 mmol .
xwNO x Ž .
3 2
neous yellow solution. This solution was then extracted
CH NH
.
Mo
Ž
CO
.
2
3
2
2
6
with 3=30-ml saturated NaHCO and allowed to dry
The flask was fitted with a septum, removed from the
drybox, and purged with nitrogen, for 2 h. Freshly
distilled THF with a volume of 20 ml of was syringed
into the reaction round-bottom flask, while the contents
was stirred in the dark, resulting in a heterogeneous-red
3
in air for 70.3 h resulting in a clear-yellow liquid. Next,
the product was completely dissolved in THF, dried
over MgSO, and filtered through a a4 Whatman filter
paper into an oven-dried 100 ml round-bottom flask
already charged with a stir bar. The solution was con-
centrated in vacuo resulting in a yellow solid. The solid
was dissolved in 2=5-ml THF and transferred to a
tarred, oven-dried 50 ml round-bottom flask charged
with a stir bar. Volatiles were removed in vacuo to yield
solution. Deoxygenated triethylamine
mmol was then added via syringe, resulting in a ho-
Ž
40 ml, 0.287
.
mogenous-red solution. The reaction solution was then
stirred for 15 min while it was cooled to 08C in an ice
bath. Next, the bis-mixed anhydride was added to the
amine dimer via cannula in one aliquot. The ice bath
was removed from under the reaction flask and allowed
to warm to room temperature. The reaction was stirred,
in the dark, under nitrogen for 2.5 h at which time it
was concentrated in vacuo. Seventy milliliters of ice
cold deoxygenated water was added via cannula to the
red oil left in the round-bottom flask. This solution was
kept under nitrogen, in the dark for 49 h, at which time
it was isolated in air in a 60 ml course porosity filter-frit.
The product remaining in the round-bottom and con-
tained in the filter-frit were dried in air for 16.5 days,
then brought into the drybox. In the drybox, the oily red
material both in the round-bottom and in the frit were
dissolved in THF and drawn through the frit which
contained part of the material. The resulting clear-red
solution was transferred to an Erlenmeyer flask and
concentrated in vacuo to 2 ml. Hexanes were layered
atop and the Erlenmeyer flask containing solution was
stoppered and placed into the drybox freezer at y408C
for 26 h. The product was isolated as a dark red oily
a yellowish-white pasty solid
Ž
164.1 mg, 11.3% mass
1
recovery
.
. H NMR
Ž
MeOH-d4
CH C HCl. .; 3.56, 3.55, 3.54
.
: d 4.08
Ž
m, 2H,
Ž
HO
O
Ž
s,
C
Ž
O
.
Ž
m, 4H,
Ž
HOC
Ž
.
2
2
1
3
C H CHCl. .
.
C NMR
Ž
MeOH-d4
.
s,
: d 128.26
HOC CH 2
CH CHCl. .
2
2
Ž
HOC
Ž
O
.
CH CHCl. .; 127.44
Ž
Ž
O
Ž .
2
2
CHCl. .; 39.10
Ž
s,
Ž
HOC
Ž
O
.
.
2
2
2
3
.10. Synthesis of (CH CH OC(O)OC(O)CH CHCl) ,
3 2 2 2
an actiÕated mixed anhydride deriÕatiÕe of 3,4-dichlo-
rohexanedioic acid
The activated mixed anhydride
OC OC
CH CHCl.2 was synthesized in an analo-
Ž
CH CH
3 2
Ž
O
.
O
Ž .
2
gous manner to other mixed anhydride compounds. An
oven-dried 50 ml round-bottom flask, already contain-
ing a stir bar, was charged with the yellow–tan solid
3
,4-dichlorohexanedioic acid 164 mg, 0.763 mmol .
Ž .
The flask containing the solid diacid was then fit with a
septum and evacuated for 1 min to deoxygenate the
flask. The flask was then put under nitrogen and 20 ml
of freshly distilled THF was added via syringe, resulting
in a clear-yellow solution. The reaction mixture was
then allowed to cool to 08C in an ice bath for 10 min,
solid after filtration through a 60 ml medium porosity
1
filter-frit.
THF-d8
Ž
137.1 mg, 73.8% mass recovery
: 7.00 br
.
H NMR
Ž
.
Ž
s
Ž
Ž
.
Ž
, 2H, CpCH CH N
Ž
H
.
.
.
C
Ž
C
Ž
C
Ž
O
.
O
.
O
.
2
2
with stirring. Deoxygenated triethylamine
mmol was then syringed into the mixture, while stir-
ring at 08C, and under nitrogen, for 40 min. Deoxy-
genated ethyl chloroformate 150 ml, 1.55 mmol was
Ž
250 ml, 1.79
CH CHCl–
CH CHCl–
CH CHCl–
.
.
.
; 5.400
; 5.21
s
s
br
br
.
, 4H, CpCH CH N
Ž
H
H
2
2
2
.
Ž
Ž
.
, 4H, CpCH CH N
Ž
2
2
2
; 4.03, 4.01, 3.99, 3.96
Ž
m, 2H, CpCH2
m,
; 2.59, 2.56,
CH CHCl– ; 2.49,
C H CHCl– . IR
2
Ž
.
CH N
Ž
H
.
C
Ž
O
.
CH C HCl– ; 3.24, 3.21, 3.19, 3.17
.
Ž
2
2
then added via syringe to the reaction flask at which
time the reaction mixture turned from clear-yellow to
cloudy and yellow. The reaction mixture was then
stirred for 60 min during which time the solution con-
tinued to change color from cloudy yellow–green to
cloudy green–brown. The activated mixed anhydride
was not characterized, but rather its formation inferred
by the formation of a cloudy solution, which was then
reacted in situ with the deprotonated ammonium dimer
to form 3.
4H, CpCH2CH N
Ž
H
.
C
Ž
O
.
CH CHCl–
.
2
2
2.54
2.45
Ž
t, 4H, CpC H CH N
Ž
H
.
H
C
Ž
C
O
.
O
.
2
2
2
Ž
d, 4H, CpCH CH N
Ž
.
Ž
.
.
2
2
2
y1
Ž
Ž
Ž
Ž
KBr
vs , 1900
, 1266
THF : l nm; 505, 392. Anal. Calc. for C H N O
.
cm : 3107
Ž
w
. Žfree N–H
.
; 2016
. Žamide I
. ŽC–N str..
. UV–Vis
Ž
m
.
.
, 1955
; 1471
.
.
Ž
vs. Ž
y
Ž
C[O..; 1641
Ž
m
m
Ž
m
.
,
Ž
amide II
.
; 823
Ž
m
.
2
6
24
2
8
Mo Cl : Cl, 7.21 Found: Cl, 6.72.
2
1.5
Acknowledgements
3
.11. Synthesis of polyamide 3, [–C(O)N(H)CH2
CH Cp)Mo(CO) Mo(CO) -(CpCH CH N(H)C(O)CH
Acknowledgement is made to the donors of the
Petroleum Research Fund, administered by the Ameri-
2
3
3
2
2
2
(
CHCl) CH –]
2
2
n

2
8
G.F. Nieckarz et al.rJournal of Organometallic Chemistry 554 (1998) 19–28
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Redpath ŽEds.., Degradable Materials, CRC Press, Boston, 1990,
can Chemical Society, for the support of this research.
B. Lindfors is acknowledged for the help with the
photochemical experiments.
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