Synthesis of alkynyl(tricarbonyl)rhenium complexes containing a lightly coordinated diamine ligand

Article abstract of DOI:10.1016/j.ica.2008.07.031

Several alkynyl(tricarbonyl)diaminerhenium complexes were prepared from corresponding halo complexes and silver acetylides. With the diamine N,N′-dimethylpiperazine the compounds were found to be sufficiently stable to allow synthetic transformations on t

Full text of DOI:10.1016/j.ica.2008.07.031

Inorganica Chimica Acta 362 (2009) 1571–1576
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Inorganica Chimica Acta
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Synthesis of alkynyl(tricarbonyl)rhenium complexes containing a lightly
coordinated diamine ligand
*
Natalie St. Fleur, J. Craig Hili, Andreas Mayr
Department of Chemistry, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Several alkynyl(tricarbonyl)diaminerhenium complexes were prepared from corresponding halo com-
plexes and silver acetylides. With the diamine N,N0-dimethylpiperazine the compounds were found to
be sufficiently stable to allow synthetic transformations on the acetylide ligand as well as purification
by chromatography and subsequent substitution of the diamine ligand by stronger ligands such as phen-
anthrolines or isocyanides.
Received 30 July 2008
Accepted 31 July 2008
Available online 7 August 2008
Keywords:
Ó 2008 Elsevier B.V. All rights reserved.
Alkynylrhenium complex
Diamine rhenium complex
Phenanthroline rhenium complex
Bis(isocyanide)rhenium complex
1. Introduction
each other in a predetermined manner the task may become man-
ageable [2].
Polyhedral molecular frameworks consisting of extended linear
ligands and connecting metal complex fragments are potentially
useful for applications in separations, gas storage, or as support
structures for the spatial organization of functional groups in cat-
alytically active sites or in electron-active devices. A variety of such
structures have been obtained by molecular self-assembly of suit-
able metal ions or metal complex fragments and extended linear
ligands [1]. Molecular self-assembly is an attractive procedure
since the final structures can be obtained in a single step from suit-
able components. However, it also imposes limitations on the
types of structures that can be obtained. Since molecular self-
assembly is a reversible process, the metal–ligand bonds need to
be kinetically labile and therefore tend to be weak. This negatively
affects the robustness of the structural frameworks. As a conse-
quence of the relatively weak structural links, it is also difficult
to predict the precise outcome of molecular self-assembly pro-
cesses. With regard to the design of complex molecular devices
an overwhelming problem is that symmetry-related sites cannot
be distinguished, i.e., functionalized independently. Thus if specific
molecular polyhedral frameworks are to be developed as support
structures for setting up complex functional sites, it is almost man-
datory to apply irreversible stepwise construction procedures.
Although the stepwise construction of even simple 3D frameworks
inevitably requires multiple steps, with building blocks that pre-
cisely define the geometry of the corner units and connect with
We have previously synthesized a variety of metal isocyanide
and diimine complexes for this type of molecular construction
[3]. Metal–isocyanide and metal–diimine fragments are held to-
gether by strong links and establish very well defined coordination
angles. Among the tested metal complexes rhenium isocyanide
and diimine complexes proved to be the most robust units. We
now seek to develop alkynyl(tricarbonyl)diisocyanide- and alky-
nyl(tricarbonyl)diiminerhenium complexes as building blocks for
the construction of molecular cubes, trigonal prisms, and related
structures. These compounds define the requisite geometries and
feature chemically robust and kinetically inert metal–ligand bonds
[4]. The acetylide ligand in these compounds is structurally equiv-
alent to an isocyanide ligand, yet compensates for the charge of the
rhenium(I) center.
As we considered various strategies for the construction of
molecular 3D frameworks, we realized that it would be helpful,
if the metal–ligand bonds constituting the polyhedral corners
could be formed in any desired sequence. In particular, we
needed procedures to make the rhenium–acetylide bonds either
before or after the rhenium-isocyanide or rhenium–diimine
bonds. While a variety of methods have been described for the
formation of rhenium–acetylide linkages [5] with other ligands
already in place, in particular diimine ligands, no suitable proce-
dures appear to be known for the selective substitution of ligands
on alkynylrhenium systems. The lack of such procedures
prompted us to develop alkynyl(tricarbonyl)rhenium complexes
containing a lightly coordinated diamine ligand and to demon-
strate the substitution of the diamine ligand under mild condi-
tions. In addition, it was also important that the acetylide
* Corresponding author. Tel.: +1 631 632 7951; fax: +1 631 632 7960.
E-mail address: amayr@notes.cc.sunysb.edu (A. Mayr).
0020-1693/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2008.07.031

1572
N. St. Fleur et al. / Inorganica Chimica Acta 362 (2009) 1571–1576
ligand could be subjected to structural modifications before the
introduction of the other ligands.
rhenium-coordinated acetylide group have been assigned unam-
biguously for complexes 13 and 21, for which samples with a
C-13 label in the Re-CCPh position were prepared. The resonances
for the metal-bound Re-CCPh carbon atom of 13 and 21 occur at d
132.3 and 124.1, while those for the Re-CCPh carbon atom are
found at d 102.9 and 105.6, respectively.
2. Results and discussion
The tricarbonyl(chloro)diamine- and bromo(tricarbonyl)-
diaminerhenium complexes 3–7 were prepared from the respec-
tive diamines and the pentacarbonylhalorhenium complexes 1
and 2 [6]. The iodo-derivative 8 was obtained by halogen exchange
in either 3 or 4. Test reactions established that the N,N0-dimethyl-
piperazine ligand imparts a favorable balance of stability and labil-
ity, as far as its binding to the metal center is concerned. In
contrast, the N,N0-diethylpiperazine and bis(diethylamino)meth-
ane ligands were too loosely coordinated, while the 1,2-
bis(diethylamino)ethane ligand was too tightly coordinated. The
N,N0-dimethylpiperazine complex 4 reacts with silver phenylacety-
lide and the silver acetylides 9–12 to afford the complexes 13–17
in 49–59% yield. The relative performance of the chloro-, bromo-,
and iodo complexes 3, 4, and 8 in these transformations was tested
with silver phenylacetylide. The respective yields of 13 were 50%,
55%, and 65%. Thus the iodo complex 8 gives a slightly higher yield
than the bromo complex 4, and the chloro complex 3 a marginally
lower yield. Since the synthesis of 8 requires an additional step
from 4 (or 3), we used the bromo complex 4 as the starting mate-
rial in the other reactions. The N,N0-dimethylpiperazinerhenium
acetylide complexes have all been purified by chromatography
on silica gel at room temperature. In contrast, the N,N0-diethylpip-
erazine complex 18 decomposed upon attempted chromatography.
The silver acetylides 9–12 were obtained by adapting published
procedures [7]. These compounds were used as obtained and not
fully characterized.
3. Summary
Several alkynyl(tricarbonyl)diaminerhenium complexes have
been prepared. The N,N0-dimethylpiperazine-substituted com-
plexes have the desirable combination of thermal stability and ease
of substitution of the diamine ligand that allows the convenient
manipulation of the alkynyl ligand before the introduction of
strongly coordinating ligands such as isocyanides or phenanthro-
lines. These properties make the new compounds promising as
building blocks for the stepwise construction of 3D polyhedral
frameworks. We expect that rhenium acetylide complexes with
lightly coordinated diamine ligands will also be versatile starting
materials in the exploration of other aspects of rhenium acetylide
chemistry.
4. Experimental
4.1. General information
Silver phenylacetylide [7], and some of the acetylenes used [11]
were prepared by adopting literature procedures. 3,8-Dihexyl-4,7-
dibromophenanthroline was prepared as described in the litera-
ture [12]. Other reagents and solvents were obtained from
commercial sources. The solvents toluene, triethylamine, CH2Cl2
and THF were dried using appropriate drying agents under an
atmosphere of nitrogen. All other solvents and reagents were used
as received. All reactions were performed under an atmosphere of
nitrogen gas. The IR spectra were recorded on a Mattson Galaxy
FTIR 3000 instrument. NMR samples were dissolved in CDCl3.
The 1H NMR spectra were recorded using a Varian Gemini 2300
spectrometer at 300 MHz, unless indicated otherwise, and 13C
NMR spectra were recorded using a Varian Inova 400 spectrome-
For potential applications as building blocks for 3D molecular
frameworks it is important that the acetylide ligand can be ex-
tended without affecting the N,N0-dimethylpiperazinerhenium
unit. This can indeed be accomplished. The 4-iodophenylacetylide
complex 16 underwent palladium-catalyzed coupling [8] with
trimethylsilylacetylene to afford complex 19 in 91% yield, and
the triisopropylsilyl group of 15 was replaced by hydrogen to give
complex 20 in 62% yield by treatment with fluoride in non-dried
THF.
ter. Silica gel (45–60 lm) was used for the chromatographic proce-
The final test of the new N,N0-dimethylpiperazinerhenium
acetylide complexes was the replacement of the diamine ligand.
Substitution of the N,N0-dimethylpiperazine ligand of 13 by 3,8-di-
hexyl-4,7-dibromophenanthroline to afford 21 proceeded essen-
tially quantitatively in hot toluene in just a few hours. Complex
21 was also obtained in 50% yield by reaction of complex 22 with
silver phenylacetylide. The reaction of the N,N0-dimethylpiperazine
complex 16 with 4-bromo-2,6-diisopropylphenylisocyanide was
allowed to proceed at room temperature. After 2 days, the alky-
nyl(diisocyanide)rhenium complex 23 was isolated in 74% yield.
For the tricarbonylrhenium complex fragment three strong IR
absorptions are expected for the carbonyl ligands [9]. The frequen-
cies of these bands are sensitive to the nature of the remaining li-
gands. For example, the carbonyl bands of the bromorhenium
complex 4 at 2028, 1924, and 1881 cmꢀ1 shift to 2009, 1904, and
1883 cmꢀ1 in 13, reflecting the replacement of bromide by phenyl-
acetylide. In the diisocyanide complex 23 these bands are at 2026,
1981, and 1943 cmꢀ1. The IR spectra of the alkynylrhenium com-
plexes also feature a weak band between 2075 and 2099 cmꢀ1
for the stretching vibration of the CC triple bond [10]. The IR spec-
tra of the silver acetylides 9–12 exhibit a weak band in the range of
2018–2033 cmꢀ1, which may be assigned to the silver acetylide
unit [7]. Complex 23 features two stretching frequencies at 2134
and 2175 cmꢀ1 for the isocyanide ligands. The C-13 NMR signals
for the carbonyl ligands of the Re(CO)3 fragment are found in the
range between 185 and 198 ppm. The C-13 NMR signals for the
dures. Elemental analyses were performed by Quantitative
Technologies Inc.
Caution: Silver acetylides are known to be potentially explosive.
We advise to handle the new silver acetylides described in this
work with the appropriate caution.
4.2. Synthetic procedures
4.2.1. ReCl(CO)3(N,N0-dimethylpiperazine), 3
A solution of ReCl(CO)5 (0.399 g, 1.10 mmol) and dimethyl
piperazine (0.256 g, 2.24 mmol) in toluene (70 mL) was stirred in
a flask equipped with a gas outlet at 85 °C for 2 h. The reaction
mixture was stirred for an additional 2 h at 65 °C before cooling
to room temperature. The white solid was filtered off, washed with
toluene and hexane, and dried under vacuum. Yield: 0.308 g (67%).
1H NMR: d 4.10–4.03 (m, 2H), 3.72–3.61 (m, 2H), 3.15–3.09 (m,
2H), 2.97 (s, 6H), 2.38–2.32 (m, 2H). 13C NMR: d 194.9, 190.9,
63.1, 56.8, 49.7. IR (CH2Cl2, cmꢀ1): 2027 (s), 1922 (s), 1879 (s). Anal.
Calc. for C9H14ClN2O3Re: C, 25.74; H, 3.36; N, 6.67. Found: C, 25.49;
H, 3.12; N, 6.56%.
4.2.2. General procedure for the synthesis of complexes 4–7.
ReBr(CO)3(N,N0-dimethylpiperazine), 4
A mixture of ReBr(CO)5 (4.5 g, 11 mmol), N,N0-dimethyl pipera-
zine (3 mL, 18 mmol), and toluene (200 mL) was stirred in a flask

N. St. Fleur et al. / Inorganica Chimica Acta 362 (2009) 1571–1576
1573
equipped with a gas outlet and heated to 65 °C for 20 h. After slow
cooling to 0 °C the solvent was decanted, and the off-white crystals
were washed with cold toluene and dried under vacuum. Yield:
4.1 g (96%). 1H NMR: d 4.17–4.14 (m, 2H), 3.69–3.66 (m, 2H),
3.22–3.18 (m, 2H), 2.99 (s, 6H), 2.54–2.49 (m, 2H). 13C NMR: d
194.5, 190.7, 63.3, 57.9, 49.8. IR (CH2Cl2, cmꢀ1): 2028 (s), 1924
(s), 1881 (s). Anal. Calc. for C9H14BrN2O3Re: C, 23.28; H, 3.04; N,
6.03. Found: C, 23.35; H, 2.74; N, 5.93%.
4.2.8. Ag(CC-4-i-Pr3SiCC-C6H2), 10
This compound was synthesized in a procedure analogous to
that for 9 from a solution of 2.545 g (9.01 mmol) of 4-(triisopropy-
lethynyl)phenylacetylene and 3.5 mL (2.55 g, 25.2 mmol) of trieth-
ylamine in 110 mL of acetonitrile and a solution of 1.559 g
(9.18 mmol) of silver nitrate in 40 mL of acetonitrile. Pale yellow
solid. Yield: 3.329 g (8.55 mmol), 95%. IR (KBr, cmꢀ1): 2152 (m),
2019 (w).
4.2.3. ReBr(CO)3(N,N0-diethylpiperazine), 5
4.2.9. Ag(CC-2,5-di-n-hexyl-4-I-C6H2), 11
Light yellow crystals (87%). 1H NMR: d 4.24–4.21 (m, 2H), 3.70–
3.67 (m, 2H), 3.13–3.00 (m, 6H), 2.51–2.45 (m, 2H), 1.42 (t, 6H,
J = 7.2 Hz). 13C NMR: (signals for carbonyl carbon atoms not found)
d 60.0, 56.3, 55.1, 11.9. IR (CH2Cl2, cmꢀ1): 2026 (s), 1922 (s), 1881
(s). Anal. Calc. for C11H18BrN2O3Re: C, 26.83; H, 3.68; N, 5.69.
Found: C, 25.39; H, 3.07; N, 4.92%.
A solution of 1.222 g (3.31 mmol) of 2,5-dihexyl-4-iodophenyl-
acetylene and 5 mL (3.64 g, 36.0 mmol) of triethylamine in 50 mL
of dichloromethane and 75 mL of ethanol is added to a stirred solu-
tion of 0.620 g (3.65 mmol) of AgNO3 in 50 mL of acetonitrile and
50 mL of ethanol. The mixture is stirred for 20 h in darkness. The
light yellow precipitate is filtered from the solution and washed
three times with 25 mL of acetonitrile followed by two rinsings
with 25 mL ethanol. Yield: 1.325 g (2.63 mmol), 78%. IR (KBr,
cmꢀ1): 2020 (w).
4.2.4. ReBr(CO)3(bis(diethylamino)methane), 6
Light yellow powder (46%). 1H NMR: d 4.83 (d, 1H, J = 12.1 Hz),
4.36 (d, 1H, J = 12.1 Hz), 3.58–3.33 (m, 8H), 1.17 (t, 6H, J = 7.1 Hz),
0.96 (t, 6H, J = 7.2 Hz). 13C NMR: d 194.7, 191.6, 84.5, 56.7, 49.0,
10.7, 9.7. IR (CH2Cl2, cmꢀ1): 2027 (s), 1921 (s), 1885 (s). Anal. Calc.
for C12H22BrN2O3Re: C, 28.35; H, 4.36; N, 5.51. Found: C, 28.33; H,
4.22; N, 5.41%.
4.2.10. Ag(CC-2,5-di-n-hexyl-4-i-Pr3SiCC-C6H2), 12
This compound was synthesized in a procedure analogous to
that described for 11 from a solution of 1.236 g (2.74 mmol) of
2,5-dihexyl-4-(triisopropylethynyl)phenylacetylene and 5 mL
(3.64 g, 36.0 mmol) of triethylamine in 50 mL of dichloromethane
and 100 mL of ethanol, and a solution 0.512 g (3.01 mmol) of
AgNO3 in 50 mL of acetonitrile and 50 mL of ethanol. Yellow solid.
Yield: 59%. IR (KBr, cmꢀ1): 2145 (m), 2018 (w).
4.2.5. ReBr(CO)3(1,2-bis(diethylamino)ethane), 7
Colorless crystals (60%). 1H NMR: d 3.63–3.48 (m, 4H), 3.26–
3.14 (m, 4H), 3.04–2.91 (m, 4H), 1.24–1.11 (m, 12H). 13C NMR: d
194.4, 191.9, 56.7, 56.1, 50.0, 9.8. IR (CH2Cl2, cmꢀ1): 2025 (s),
1915 (s), 1881 (s). Anal. Calc. for C13H24BrN2O3Re: C, 29.88; H,
4.63; N, 5.36. Found: C, 30.06; H, 4.53; N, 5.31%.
4.2.11. Re(CCPh)(CO)3(N,N0-dimethylpiperazine), 13
Method A: To a solution of 4 (0.205 g, 0.441 mmol) and N,N0-
dimethylpiperazine (0.235 g, 2.06 mmol) in toluene (25 mL) silver
phenylacetylide (0.111 g, 0.531 mmol) was added. The mixture
was stirred in darkness at 70 °C for 3 h. After cooling to room tem-
perature the suspension was filtered through a cellulose plug on a
fritted disk. The solvent was removed from the filtrate under vac-
uum. The product was purified by column chromatography on sil-
ica gel using hexane/ethyl acetate (1:1, v/v) as the eluent.
Crystallization from methylene chloride/hexane afforded off-white
crystals. Yield: 0.117 g (55%). 1H NMR: d 7.35–7.32 m, 2H), 7.22–
7.16 m, 2H), 7.13–7.10 m, 1H), 4.35–4.32 (m, 2H), 3.60–3.56 (m,
2H), 3.17–3.11 (m, 2H), 3.01 (s, 6H), 2.55–2.50 (m, 2H). 13C NMR:
d 196.4, 195.4, 132.3 (ReCCPh), 131.4, 127.9, 127.8, 125.2, 102.9
(ReCCPh), 64.2, 59.8, 50.0. IR (CH2Cl2, cmꢀ1): 2087 (w), 2009 (s),
1904 (s), 1883 (s). Anal. Calc. for C17H19N2O3Re: C, 42.05; H, 3.94;
N, 5.77. Found: C, 42.20; H, 3.85; N, 5.73%.
4.2.6. ReI(CO)3(N,N0-dimethylpiperazine), 8
Method A: A mixture of 0.382 g (0.910 mmol) of compound 3,
0.285 g (1.90 mmol) of sodium iodide, and 0.1 mL (0.117 g,
1.03 mmol) of N,N0-dimethylpiperazine was refluxed in 50 mL
THF for 1.5 h. The solvent was removed under vacuum. The prod-
uct was extracted with methylene chloride. The combined extracts
were filtered, and the solvent was removed under vacuum. Crystal-
lization from methylene chloride/hexane afforded a colorless solid.
Yield: 0.459 g (99%).
Method B: A mixture of 1.2 g (2.5 mmol) of 4, 2 g (6.2 mmol) of
zinc iodide, 0.5 mL (0.6 g, 5 mmol) of N,N0-dimethylpiperazine
and 60 mL of toluene was heated to 65 °C for 4 h. The solvent
was removed under vacuum. The residue was extracted with
dichloromethane. The combined extracts were filtered. The sol-
vent was removed and the residue washed with cold hexane. Col-
orless crystalline solid. Yield: 1.2 g (92%). 1H NMR: d 4.30–4.23
(m, 2H), 3.77–3.70 (m, 2H), 3.34–3.26 (m, 2H), 3.04 (s, 6H),
2.80–2.71 (m, 2H). 13C NMR: d 194.0, 190.2, 63.2, 60.4, 49.8. IR
(CH2Cl2, cmꢀ1): 2026 (s), 1924 (s), 1883 (s). Anal. Calc. for C9H14I-
N2O3Re: C, 21.14; H, 2.76; N, 5.48. Found: C, 21.17; H, 2.61; N,
5.45%.
Method B: This procedure is analogous to method A except that
3 (0.185 g, 0.441 mmol) was used instead of 4. Yield 0.107 g (50%).
Method C: This procedure is analogous to method A except that
8 (0.225 g, 0.440 mmol) was used instead of 4. Yield 0.140 g (65%).
4.2.12. Re(CC-4-I-C6H4)(CO)3(N,N0-dimethylpiperazine), 14
A
solution containing 0.564 g (1.68 mmol) of 9, 0.874 g
(1.88 mmol) of 4, and 0.1 mL (0.085 g, 0.75 mmol) of N,N0-dimeth-
ylpiperazine in 25 mL of toluene was stirred in darkness for 3 h at
70 °C. The solution was allowed to cool to room temperature and
filtered. The solvent was evaporated under vacuum. The residue
was purified by column chromatography, using a mixture of hex-
ane and ethyl acetate (3/2, v/v) as the eluent. Recrystallization
from ethyl acetate/hexane afforded pale yellow crystals. Yield:
0.538 g (0.880 mmol), 52%. 1H NMR: d 7.50 (d, 2H, J = 9 Hz, C6H4),
7.06 (d, 2H, J = 9 Hz, C6H4), 4.28 (m, 2H, CH2), 3.59 (m, 2H, CH2),
3.15 (m, 2H, CH2), 3.01 (s, 6H, CH3), 2.55 (m, 2H, CH2). 13C NMR:
d 196.0, 195.4, 136.9, 134.8, 133.2, 127.3, 102.1, 89.8, 64.2, 60.0,
50.1. IR (CH2Cl2, cmꢀ1): 2086 (w), 2009 (s), 1906 (s), 1885 (s). Anal.
4.2.7. Ag(CC-4-I-C6H4), 9
To a solution containing 0.420 g (2.47 mmol) of silver nitrate in
30 mL of acetonitrile was added under low-light conditions a solu-
tion containing 0.515 g (2.26 mmol) of 4-iodophenylacetylene and
5 mL (3.64 g, 36.0 mmol) of triethylamine in 30 mL of acetonitrile.
The contents were stirred under the exclusion of light for 24 h at
room temperature. The white precipitate was filtered off, washed
four times with ethanol, and dried under vacuum. Yield: 0.657 g
(1.96 mmol), 87%. IR (KBr, cmꢀ1): 2033 (w).

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N. St. Fleur et al. / Inorganica Chimica Acta 362 (2009) 1571–1576
Calc. for C17H18IN2O3Re: C, 33.39; H, 2.97; N, 4.58. Found: C, 33.13;
H, 2.86; N, 4.52%.
OC
OC
CO
CO
N
N
+
NN
OC
Re
X
OC
Re
X
4.2.13. Re(CC-4-i-Pr3SiCC-C6H4)(CO)3(N,N0-dimethylpiperazine), 15
This compound was synthesized following a procedure analo-
gous to that for compound 14, starting from 0.948 g (2.43 mmol)
of 10, 1.231 g (2.651 mmol) of 4, and 0.1 mL (0.0852 g,
0.746 mmol) of N,N0-dimethylpiperazine in 50 mL of toluene. Pale
yellow solid. Yield: 0.867 g (1.30 mmol), 54%. 1H NMR: d 7.30 (d,
2H, J = 8 Hz, C6H4), 7.23 (d, 2H, J = 8 Hz, C6H4), 4.28 (m, 2H, CH2),
3.57 (m, 2H, CH2), 3.13 (m, 2H, CH2), 3.01 (s, 6H, CH3), 2.53 (m,
2H, CH2), 1.12 (s, 21H, Si(i-Pr)3). 13C NMR: d 196.0, 195.4, 135.9,
131.6, 131.1, 127.9, 119.9, 107.5, 103.2, 90.8, 64.2, 59.9, 50.1,
18.6, 11.3. IR (CH2Cl2, cmꢀ1): 2150 (m), 2084 (w), 2010 (s), 1910
(s), 1883 (s). Anal. Calc. for C28H39N2O3ReSi: C, 50.50; H, 5.90; N,
4.21. Found: C, 50.24; H, 5.74; N, 4.21%.
OC
CO
1: X = Cl
2: X = Br
3: X = Cl; NN = N,N'-dimethylpiperazine
4: X = Br; NN = N,N'-dimethylpiperazine
5: X = Br; NN = N,N'-diethylpiperazine
6: X = Br; NN = bis(diethylamino)methane
7: X = Br; NN = 1,2-bis(diethylamino)ethane
NaI/THF
N
N
3
OC
Re
I
ZnI2/toluene
4
OC
CO
8
4.2.14. Re(CC-2,5-di-n-hexyl-4-I-C6H2)(CO)3(N,N0-
dimethylpiperazine), 16
This compound was prepared following the procedure de-
scribed for 13, using 0.434 g of 4 (0.935 mmol), 0.2 mL of N,N0-
dimethylpiperazine (0.235 g, 2.06 mmol), 50 mL of toluene, and
0.383 g of 11 (0.801 mmol). The product was purified by column
chromatography on silica gel using methylene chloride/hexane
(1:1, v/v) as the eluent. This afforded a pale yellow solid. Yield:
0.369 g (59%). 1H NMR: d 7.53 (s, 1H), 7.12 (s, 1H), 4.31 (m, 2H),
3.59 (m, 2H), 3.13 (m, 2H), 3.02 (s, 6H), 2.72 (t, 2H), 2.56 (m,
4H), 1.64 (m, 2H), 1.50 (m, 2H), 1.32 (m, 12H), 0.88 (m, 6H). 13C
NMR: d 196.1, 195.6, 143.8, 142.0, 138.8, 137.0, 132.3, 127.2,
101.0, 96.5, 64.1, 60.0, 50.1, 40.2, 34.4, 31.8, 31.7, 30.6, 30.4, 29.4,
29.1, 22.7, 22.6, 14.1, 14.1. IR (CH2Cl2, cmꢀ1): 2078 (w), 2008 (s),
1906 (s), 1883 (s). Anal. Calc. for C29H42IN2O3Re: C, 44.67; H,
5.43; N, 3.59. Found: C, 44.88; H, 5.42; N, 3.53%.
AgNO3
NEt3
Ag
C
C
R
H
C
C
R
9: R = 4-I-C6H4
10: R = 4-i-Pr3SiCC-C6H4
11: R = 4-I-2,5-di-n-hexyl-C6H2
12: R = 4-i-Pr3SiCC-2,5-di-n-hexyl-C6H2
N
N
+
AgCCR
OC
Re
C
C
R
3, 4, 5, or 8
OC
CO
13: NN = dimethylpiperazine; R = C6H5
14: NN = dimethylpiperazine; R = 4-I-C6H4
15: NN = dimethylpiperazine; R = 4-i-Pr3SiCC-C6H4
16: NN = dimethylpiperazine; R = 2,5-di-n-hexyl-4-I-C6H2
17: NN = dimethylpiperazine; R = 2,5-di-n-hexyl-4-i-Pr3SiCC-C6H2
18: NN = diethylpiperazine; R = C6H5
4.2.15. Re(CC-2,5-di-n-hexyl-4-i-Pr3SiCC-C6H2)(CO)3(N,N0-
dimethylpiperazine), 17
This compound was synthesized following a procedure analo-
gous to that for compound 13, using 0.251 g of 4 (0.541 mmol),
0.1 mL of N,N0-dimethylpiperazine (0.117 g, 1.03 mmol), 40 mL of
toluene, and 0.262 g of 12 (0.470 mmol). Column chromatography
with methylene chloride/hexane (1:1, v/v) afforded an off-white
solid. Yield: 0.392 g (57%). 1H NMR: d 7.19 (s, 1H), 7.11 (s, 1H),
4.30 (m, 2H), 3.56 (m, 2H), 3.10 (m, 2H), 3.01 (s, 6H), 2.75 (m,
2H), 2.51 (m, 2H), 1.64 (m, 4H), 1.32 (m, 12H), 1.14 (s, 21H), 0.88
(m, 6H). 13C NMR: d 196.2, 195.6, 142.1, 141.5, 138.0, 132.5,
131.9, 127.3, 119.3, 106.6, 102.0, 93.2, 64.1, 60.0, 50.1, 34.7, 34.5,
31.9, 31.8, 31.1 30.8, 29.5, 29.5, 22.7, 22.6, 18.7, 14.1, 14.1, 11.3.
IR (CH2Cl2, cmꢀ1): 2143 (m), 2081 (w), 2008 (s), 1906 (s), 1882
(s). Anal. Calc. for C40H63N2O3ReSi: C, 57.59; H, 7.61; N, 3.36.
Found: C, 57.48; H, 7.62; N, 3.38%.
4.2.17. Re(CC-2,5-di-n-hexyl-4-Me3SiCC-C6H2)(CO)3(N,N0-
dimethylpiperazine), 19
Compound 14 (0.341 g, 0.437 mmol) was dissolved in a mixture
of toluene (100 mL) and triethylamine (15 mL). Then Pd(PPh3)4
(0.050 g), trimethylsilylacetylene (0.15 mL), and CuI (0.025 g) were
added. After stirring for 3 h the reaction mixture was filtered, and
the solvent was removed under vacuum. The product was purified
by column chromatography on silica gel, using hexane/ethyl ace-
tate (1:1, v/v) as the eluent. Light-brown oil. Yield: 0.298 g (91%).
1H NMR: d 7.18 (s, 1H), 7.10 (s, 1H), 4.33–4.31 (m, 2H), 3.60–3.56
(m, 2H), 3.15–3.12 (m, 2H), 3.02 (s, 6H), 2.77–2.74 (m, 2H), 2.71–
2.63 (m, 2H), 2.56–2.52 (m, 2H), 1.67–1.57 (m, 4H), 1.36–1.26
(m, 12H), 0.91–0.85 (m, 6H), 0.26–0.21 (s, 9H). 13C NMR: d 196.1,
195.7, 142.4, 141.6, 138.1, 132.2, 132.00, 127.4, 118.9, 105.0,
102.1, 97.1, 64.2, 60.1, 50.2, 34.7, 34.3, 31.9, 31.8, 30.8, 30.6, 29.5,
29.4, 22.7, 14.1, 0.1. IR (CH2Cl2, cmꢀ1): 2143 (m), 2080 (w), 2008
(s), 1906 (s), 1883 (s).
4.2.16. Re(CCPh)(CO)3(N,N0-diethylpiperazine), 18
A mixture of 5 (0.364 g, 0.739 mmol), silver phenylacetylide
(0.178 g, 0.852 mmol), and toluene (100 mL) was heated to 65 °C
and stirred in darkness for 24 h. The resulting mixture was allowed
to cool to room temperature and filtered through a plug of cellu-
lose on a fritted disk. After removal of the solvent the residue
was recrystallized from methylene chloride and hexane. Off-white
crystals. Yield: 0.202 g (53%). 1H NMR: d 7.32–7.30 (m, 2H), 7.20–
7.16 (m, 2H), 7.12–7.08 (m, 1H) 4.38–4.36 (m, 2H), 3.61–3.59 (m,
2H), 3.61–2.99 (m, 6H), 2.47–2.43 (m, 2H), 1.46–1.42 (t, 6H). 13C
NMR: d 196.2, 195.3, 132.2, 131.2, 128.1, 127.9, 125.1, 103.7,
60.9, 56.8, 56.4, 12.1. IR (CH2Cl2, cmꢀ1): 2087 (w), 2008 (s), 1901
(s), 1884 (s).
4.2.18. Re(CC-4-ethynyl-C6H4)(CO)3(N,N0-dimethylpiperazine), 20
A solution containing 2.560 g (8.11 mmol) of tetrabutylammo-
nium floride in 30 mL of non-dried THF was added to a solution
of 0.987 g (1.482 mmol) of 15 and 0.1 mL (0.0852 g, 0.746 mmol)
of N,N0-dimethylpiperazine in 50 mL of THF. The contents were
stirred for 20 min, then diluted with 150 mL of dichloromethane

N. St. Fleur et al. / Inorganica Chimica Acta 362 (2009) 1571–1576
1575
and washed with 350 mL of a saturated solution of sodium bicar-
Me3SiCCH
bonate. The organic fraction was removed, and the aqueous layer
was extracted with 40 mL of dichloromethane. The combined or-
ganic solutions were dried over magnesium sulfate, and the sol-
vent was removed under vacuum. The product was purified by
column chromatography, utilizing a 4:1 (v/v) mixture of toluene
and ethyl acetate as the eluant. Light yellow solid. Yield: 0.469 g
(0.920 mmol), 62%. 1H NMR: d 7.31 (d, 2H, J = 8 Hz, C6H4), 7.24
(d, 2H, J = 8 Hz, C6H4), 4.26 (m, 2H, CH2), 3.56 (m, 2H, CH2), 3.17
(m, 2H, CH2), 3.08 (s, 1H, CH), 3.01 (s, 6H, CH3), 2.53 (m, 2H,
CH2). 13C NMR: d 195.9, 195.5, 136.2, 131.7, 131.3, 128.5, 118.4,
103.0, 84.1, 64.2, 60.0, 50.2. IR (CH2Cl2, cmꢀ1): 2105 (vw), 2084
(w), 2008 (s), 1906 (s), 1885 (s). Anal. Calc. for C19H19N2O3Re: C,
44.78; H, 3.76; N, 5.50. Found: C, 44.65; H, 3.72; N, 5.46%.
Hex
N
N
Pd(PPh3)4/CuI
NEt3/toluene
16
OC
Re
C
C
C
C
SiMe3
OC
CO
Hex
19
N
N
NBu F/H O
4
2
THF
C
C
C
C
H
OC
Re
15
OC
CO
20
4.2.19. Re(CCPh)(CO)3(4,7-dibromo-3,8-di-n-hexyl-1,10-
phenanthroline), 21
Br
Br
3,8-dihexyl-
4,7-dibromo-
phenanthroline
A mixture of 13 (0.100 g, 0.21 mmol) and 4,7-dibromo-3,8-di-n-
hexyl-1,10-phenanthroline (0.140 g, 0.28 mmol) in toluene
(15 mL) was heated to 100 °C for 2 h. After cooling to room temper-
ature, the solvent was removed under vacuum. The product was
purified by column chromatography on silica gel, using hexane/
dichloromethane (1:2, v/v) as the eluent. Yield: 0.175 g (97%). Crys-
tallization from methylene chloride/hexane afforded red-orange
crystals. 1H NMR (400 MHz): d 9.16 (s, 2H, phenanthroline), 8.42
(s, 2H, phenanthroline), 6.94–6.87 (m, 3H, C6H5), 6.79–6.76 (m,
2H, C6H5), 3.10 (m, 4H, CH2), 1.82 (m, 4H, CH2), 1.52 (m, 4H,
CH2), 1.39 (m, 8H, CH2), 0.93 (m, 6H, CH3). 13C NMR: d 197.9,
192.3, 153.5, 145.8, 141.4, 136.2, 131.4, 130.2, 127.5, 127.4,
127.4, 124.7, 124.1 (ReCCPh), 105.6 (ReCCPh), 34.7, 31.4, 29.5,
29.1, 22.5, 14.0. IR (CH2Cl2, cmꢀ1): 2094 (w), 2009 (s), 1906 (s).
Anal. Calc. for C35H35Br2N2O3Re: C, 47.90; H, 4.02; N, 3.19. Found:
C, 47.34; H, 3.79; N, 3.16%.
Hex
Hex
N
N
13
C
C
C6H5
21
OC
Re
OC
CO
AgCCC
H
6
5
Br
Br
Hex
Hex
3,8-dihexyl-
4,7-dibromo-
phenanthroline
N
N
OC
Re
Br
2
22
This compound was also prepared in 50% yield by reaction of 22
(0.214 g, 0.25 mmol) and AgCCPh (0.105 g, 0.50 mmol) in toluene
(25 mL) at 90 °C for 24 h.
OC
CO
4.2.20. ReBr(CO)3(4,7-dibromo-3,8-di-n-hexyl-1,10-phenanthroline),
22
A mixture of 2 (5.06 g, 10 mmol) and 4,7-dibromo-3,8-di-n-hex-
yl-1,10-phenanthroline (4.06 g, 10 mmol) in toluene (200 mL) was
heated to 80 °C for 2 h. The solvent was removed under vacuum.
The residue was redissolved in warm dichloromethane (150 mL).
Hexane (250 mL) was carefully layered on top of this solution. This
mixture was allowed to stand at room temperature for 24 h and
then cooled to ꢀ10 °C for several days to afford 7.86 g of yellow
crystals. A second crop of 0.35 g was obtained from the mother li-
quor. Combined yield: 8.21 g (96%). 1H NMR (400 MHz: d 9.11 (s,
2H), 8.44 (s, 2H), 3.12–3.07 (m, 4H), 1.84–1.80 (m, 4H), 1.55–1.51
(m, 4H), 1.43–1.37 (m, 8H), 0.95–0.92 (t, 6H). 13C NMR: d 196.4,
188.6, 153.5, 145.6, 141.8, 137.3, 130.5, 127.8, 34.8, 31.4, 29.5,
29.2, 22.6, 14.0. IR (CH2Cl2, cmꢀ1): 2024 (s), 1923 (s), 1902 (s). Anal.
Calc. for C27H30Br3N2O3Re: C, 37.86; H, 3.53; N, 3.27. Found: C,
38.06; H, 3.19; N, 3.27%.
Br
Br
N
N
4-bromo-
2,6-diisopropyl-
isocyanobenzene
Hex
C
C
16
C
C
I
OC
Re
OC
CO
Hex
23
4.2.21. Re(CC-2,5-di-n-hexyl-4-I-C6H2)(CN-2,6-diisopropyl-4-bromo-
C6H2)2(CO)3, 23
A solution of 0.264 g (0.339 mmol) 16 and 0.302 g (1.135 mmol)
2,6-diisopropyl-4-bromo-isocyanobenzene in 25 mL THF was al-
lowed to stand at room temperature for 3 days. After removal of
the solvent, the product was purified by column chromatography
on silica gel, using a 1:1 (v/v) mixture of hexane and dichlorometh-
ane. Light yellow oil. Yield: 0.299 g (74%). 1H NMR: d 7.53 (s, 1H),
7.31 (s, 4H), 7.09 (s, 1H), 3.42–3.32 (m, 4H), 2.74–2.69 (m, 2H),
2.59–2.53 (m, 2H), 1.63–1.48 (m, 4H), 1.36–1.17 (m, 36H), 0.95–
0.79 (m, 6H). 13C NMR: d 148.2, 147.6, 143.8, 141.5, 138.5, 132.1,
127.8, 127.1, 124.3, 123.7, 108.0, 99.3, 96.2, 40.3, 34.2, 31.8, 31.7,
30.4, 30.2, 29.3, 29.1, 22.6, 22.3, 22.3, 14.1, 14.1. IR (CH2Cl2,
cmꢀ1): 2177 (w), 2137 (m), 2099 (w), 2026 (s), 1981 (s), 1943 (s).
Acknowledgement
This work was supported by the National Science Foundation
(DMR-0304127).

1576
N. St. Fleur et al. / Inorganica Chimica Acta 362 (2009) 1571–1576
(i) J. Pérez, L. Riera, S. García-Granda, E. García-Rodríguez, D. Miguel,
References
Chem. Commun. (2002) 384;
(j) E. Hevia, J. Pérez, V. Miguel, S. Kassel, A. Rheingold, Inorg. Chem. 41
(2002) 4673;
(k) G. Albertin, S. Antoniutti, E. Bordignon, D. Bresolin, J. Organomet.
Chem. 609 (2000) 10;
(l) W.A. Herrmann, F.E. Kühn, C. Romão, J. Organomet. Chem. 495 (1995)
209;
(m) M. Ferrer, L. Rodríguez, O. Rossell, J.C. Lima, P. Gómez-Sal, A. Martín,
Organometallics 23 (2004) 5096;
(o) O. Seewald, U. Flörke, H. Egold, H.-J. Haupt, M. Schwefer, Z. Anorg.
Allg. Chem. 632 (2006) 204;
(p) B.J. Liddle, S.V. Lindeman, D.L. Reger, J.R. Gardinier, Inorg. Chem. 46
(2007) 8484.
[1] (a) M. Yoshizawa, T. Kusukawa, M. Fujita, S. Sakamoto, K. Yamaguchi, J. Am.
Chem. Soc. 123 (2001) 10454;
(b) Y.K. Kryschenko, S.R. Seidel, D.C. Muddiman, A.I. Nepomuceno, P.J. Stang, J.
Am. Chem. Soc. 125 (2003) 9647;
(c) P.N.W. Baxter, J.-M. Lehn, G. Baum, D. Fenske, Chem. Eur. J. 5 (1999)
102;
(d) J.L.C. Rowsell, O.M. Yaghi, Micropor. Mesopor. Mater. 73 (2004) 3;
(e) A.V. Davis, K.N. Raymond, J. Am. Chem. Soc. 127 (2005) 7912.
[2] P. Manini, W. Amrein, V. Gramlich, F. Diederich, Angew. Chem., Int. Ed. 41
(2002) 4339.
[3] (a) L. Yang, K.-K. Cheung, A. Mayr, J. Organomet. Chem. 585 (1999) 26;
(b) Y.-B. Dong, L. Yang, K.-K. Cheung, A. Mayr, J. Organomet. Chem. 598 (2000)
55.
[4] N.J. Long, C.K. Williams, Angew. Chem., Int. Ed. 42 (2003) 2586.
[5] (a) M.I. Bruce, D.A. Harbourne, F. Waugh, F.G.A. Stone, J. Chem. Soc. A (1968)
356;
[6] (a) P. Heard, P. Sroisuwan, R.A. Tocher, Polyhedron 22 (2003) 1321;
(b) F. Zingales, M. Graziani, F. Faraone, U. Belluco, Inorg. Chim. Acta 1 (1967)
172.
[7] (a) B.K. Teo, Y.H. Xu, B.Y. Zhong, Y.K. He, H.Y. Chen, W. Qian, Y.J. Deng, Y.H. Zou,
Inorg. Chem. 40 (2001) 6794;
(b) R.B. Davis, D.H. Schreiber, J. Am. Chem. Soc. 78 (1956) 1675.
[8] (a) L.J. Cassar, Organomet. Chem. 93 (1975) 253;
(b) H.A. Dieck, R.F. Heck, J. Organomet. Chem. 93 (1975) 259;
(c) K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett. (1975) 4467;
(d) J. Zhang, D.J. Pesak, J.L. Ludwick, J.S. Moore, J. Am. Chem. Soc. 116 (1994)
4227.
[9] E.W. Abel, S.P. Tyfield, Canad. J. Chem. 47 (1969) 4627.
[10] J. Manna, K.D. John, M.D. Hopkins, Adv. Organomet. Chem. 38 (1995) 87.
[11] (a) H. Kukula, S. Veit, A. Godt, Eur. J. Org. Chem. (1999) 277;
(b) L. Kloppenburg, D. Jones, U.H.F. Bunz, Macromolecules 32 (1999) 4194;
(c) U. Ziener, A. Godt, J. Org. Chem. 62 (1997) 6137.
[12] M. Schmittel, H. Ammond, Synlett (1997) 1096.
(b) A.A. Koridze, V.I. Zdanovich, O.A. Kizas, A.I. Yanovsky, Y.T. Struchkov, J.
Organomet. Chem. 464 (1994) 197;
(c) V.W.-W. Yam, V.C.-Y. Lau, K.-K. Cheung, Organometallics 14 (1995)
2749;
(d) V.W.-W. Yam, K.M.-C. Wong, S.H.-F. Chong, V.C.-Y. Lau, S.C.-F. Lam, L.
Zhang, K.-K. Cheung, J. Organomet. Chem. 670 (2003) 205;
(e) M. Appel, J. Heidrich, W. Beck, Chem. Ber. 120 (1987) 1087;
(f) S. Mihan, T. Weidmann, V. Weinrich, D. Fenske, W. Beck, J. Organomet.
Chem. 541 (1997) 423;
(g) D.R. Senn, A. Wong, A.T. Patton, M. Marsi, C.E. Strouse, J.A. Gladysz, J.
Am. Chem. Soc. 110 (1988) 6096;
(h) J.A. Ramsden, W. Weng, J.A. Gladysz, Organometallics 11 (1992)
3635;