Carboxylate and dicarboxylate derivatives of [Et4N][Re 2(CO)6(OR)3] (R = H or Me)

Article abstract of DOI:10.1016/j.ica.2004.11.016

The ligand exchange reaction of the anionic binuclear rhenium complexes Re₂(CO)₆(OR)₃^- (R = H (1) or Me (2)) has been studied with the carboxylic acids; benzoic acid (3, 4, and 5), fumaric acid (6), and terephth

Full text of DOI:10.1016/j.ica.2004.11.016

Inorganica Chimica Acta 358 (2005) 1041–1049
www.elsevier.com/locate/ica
Carboxylate and dicarboxylate derivatives of
[Et4N][Re2(CO)6(OR)3] (R = H or Me)
*
Kevin K. Klausmeyer , Franklin R. Beckles
Department of Chemistry and Biochemistry, Baylor University, Waco, TX 76798-7348, USA
Received 12 August 2004; accepted 10 November 2004
Abstract
ꢀ
The ligand exchange reaction of the anionic binuclear rhenium complexes Re2ðCOÞ ðORÞ (R = H (1) or Me (2)) has been stud-
6
3
ied with the carboxylic acids; benzoic acid (3, 4, and 5), fumaric acid (6), and terephthalic acid (7). The exchange with benzoic acid
can be controlled by stoichiometry to one, two, or three substitutions. The doubly (4) and triply (5) substituted complexes represent
new structural motifs for the triply bridged Re2(CO)6 unit. The dicarboxylic acids fumaric and terephthalic bridge two dirhenium
centers. Crystal structure determinations have been carried out for the new complexes synthesized.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Rhenium carbonyl; Carboxylate compounds; Ligand exchange
1. Introduction
with formic acid, various alcohols, and esters as well
as sulfur, selenium, phosphorus and nitrogen donors
[9,10].
Carboxylate ions ligated to higher valent rhenium
species have been of interest for many years. They are
known to employ several different binding modes and
to possess numerous structural motifs [1–6]. Previously,
in the literature only two examples of the relatively low
valent Re1+ carbonyl dimer which is triply bridged have
been structurally characterized, Re2(CO)6(OR)2
(O2CR0)ꢀ1. The earliest is that of Schubiger and co-
workers in 1997 [7], which features a triply bridged
dirhenium hexacarbonyl core containing two l-ethoxy
groups and an g1,g1-acetate group. The second reported
example is that of Brand and Shapley in 2000 [8], where
the dirhenium core is bridged by two l-methoxy ligands
and one g1,g1-bridging acetate (Scheme 1). Addition-
ally, there has been considerable work done through
electrospray mass spectrometry studying the exchange
In our previous paper we explored the ligand ex-
change reaction of aryloxides and alkoxides [11]. This
report extends the study of the carboxylate derivates
of the triply bridged dirhenium hexacarbonyl to multiple
substitutions using benzoic acid (Scheme 2) and to
linked dimeric derivatives using the dicarboxylic acids
fumaric acid and terephthalic acid. For benzoic acid
two new structural types have been found when the
starting complex is substituted two or three times.
2. Experimental
2.1. General considerations
All reactions were carried out under air free condi-
tions in an argon filled glove box, or using standard
Schlenk techniques. THF, diethyl ether, and hexanes
were freshly distilled from sodium/benzophenone ketyl,
*
Corresponding author. Tel.: +1 254 710 2665; fax: +1 254 710
4272.
E-mail address: kevin_klausmeyer@baylor.edu (K.K. Klausmeyer).
0020-1693/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.11.016

1042
K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1041–1049
(O2CC6H5), 53.13 (CH3CH2)4N and 7.75 ppm
(CH3CH2)4N.
H3C
C
-1
O
O
O
O
C
CH3
C
2.2.2. Synthesis of [Et4N][Re2(CO)6(OH)(O2C6H5)2]
(4)
O
C
Re
O
Re
C
O
O
C
Complex 1 (0.100 g, 0.138 mmol) was dissolved in
15 mL of CH2Cl2 and a benzoic acid (HO2C6H5) solu-
tion (2 equiv.) was added. The mixture was stirred at
room temperature for 14 h; the solvent was then re-
moved under reduced pressure to approximately 4 mL.
The resulting solution was precipitated with 40 mL of
diethyl ether. The white solid obtained was dried under
vacuum overnight; yield: 0.088 g (63%). Anal. Calc. for
C23H31NO10Re2: C, 38.28, H, 4.12, N, 1.40. Found: C,
38.57, H, 4.12, N, 1.59% IR (cmꢀ1): CH3CN, m(C–O)
C
CH3
O
O
Scheme 1. Representation of Re2(CO)6(OCH3)2(O2CCH3)ꢀ1
.
acetonitrile was freshly distilled from calcium hydride.
Infrared spectra were recorded on a ThermoMattson
1
IR300 spectrometer. H and 13C NMR spectra were re-
corded on a Bruker 300 MHz NMR spectrometer and
referenced to the residual solvent peaks.
1
2010 (m), 1898 (vs). H NMR (acetone-d6): d 7.98, and
7.41 ppm (m, m, 10H, O2CC6H5), 3.47 ppm (q, 4H,
(CH3CH2)2O), 3.40 ppm (q, 8H, (CH3CH2)4N), 1.35
ppm (tt, 12H, (CH3CH2)4N), 1.13 ppm (t, 6H,
(CH3CH2)2O). 13C NMR (acetone-d6): d 200.94 ppm
(CO), 174.39 ppm (O2CC6H5), 137.67, 133.66, 130.24,
and 128.59 ppm (O2CC6H5), 66.03 ppm (CH3CH2)2O,
52.96 ppm (CH3CH2)4N, 15.53 ppm (CH3CH2)2O and
7.56 ppm (CH3CH2)4N.
2.2. Syntheses
The compounds [Et4N][Re2(CO)6(OH)3] (1) and
[Et4N][Re2(CO)6(OCH3)3] (2) were synthesized follow-
ing published procedures [12]. Re2(CO)10 was purchased
from Pressure Chemical. All other reagents were pur-
chased from Aldrich Chemical or Alfa Chemical and
used as received. The synthesis of complexes 3 and 4
can be accomplished in THF, CH3CN, or CH2Cl2.
Complexes 5, 6, and 7 can be synthesized in THF or
CH3CN.
2.2.3. Synthesis of [Et4N][Re2(CO)6(O2C6H5)3] (5)
Complex 1 (0.100 g, 0.138 mmol) was dissolved in
15 mL of THF and a benzoic acid (HO2C6H5) solution
(3 equiv.) was added. The mixture was stirred at 60 ꢁC
for 14 h, the solvent then was removed under reduced
pressure to approximately 4 mL. The resulting solution
was precipitated with 40 mL of hexanes. The white solid
obtained was dried under vacuum overnight; yield: 0.090
g (63%). IR (cmꢀ1): CH3CN, m(C–O) 2010 (m), 1898
2.2.1. Synthesis of [Et4N][Re2(CO)6(OH)2(O2C6H5)]
(3)
Complex 1 (0.100 g, 0.138 mmol) was dissolved in 15
mL of acetonitrile and a benzoic acid (HO2C6H5) solu-
tion (1 equiv.) was added. The mixture was stirred at
room temperature for 12 h and then the solvent was re-
moved in vacuo. The solid was dissolved in a minimum
amount of solvent (2–3 mL) and precipitated by the
addition of 40 mL of hexane. The white solid obtained
was dried under vacuum overnight; yield: 0.082 g
(72%). Anal. Calc. for C23H31NO10Re2: C, 32.35, H,
3.67, N, 1.64. Found: C, 32.83, H, 3.62, N, 1.69%. IR
1
(vs). H NMR (acetone-d6): d 8.03, 7.56, 7.45 ppm (m,
m, m, 15H, O2CC6H5), 3.45 ppm (q, 8H, (CH3CH2)4N),
1.38 ppm (tt, 12H, (CH3CH2)4N). 13C NMR (acetone-
d6):
d
199.70 ppm (CO), 174.53 ppm (g1,g1-
O2CC6H5), 166.13 ppm (l-O2CC6H5), 136.40, 131.92,
129.90, and 128.12 ppm (g1,g1-O2CC6H5), 137.50,
132.11, 130.30 and 128.61 ppm (l-O2CC6H5), 53.13
(CH3CH2)4N and 7.75 ppm (CH3CH2)4N.
(cmꢀ1): THF, m(C–O) 2010 (m), 1898 (vs). H NMR
1
(acetone-d6): d 8.03, 7.49, 7.39 ppm (m, m, m, 5H,
OOCC6H5), 3.44 ppm (q, 8H, (CH3CH2)4N), 2.38 ppm
(br, 2H, (OH)), 1.34 ppm (tt, 12H, (CH3CH2)4N). 13C
NMR (acetone-d6): d 202.03 ppm (CO), 174.53 ppm
(O2CC6H5), 137.90, 131.93, 130.40, and 128.50 ppm
2.2.4. Synthesis of [Et4N]2[Re2(CO)6(OCH3)2
(O2CCH@CHCO2)Re2(CO)6(OCH3)2] (6)
Complex 2 (0.100 g, 0.131 mmol) was dissolved in
25 mL of THF and a fumaric acid (HO2CC2H2CO2H)
-1
Re2(CO)6(OH)3 + C6H5CO2H
3 eq.
1 eq.
2 eq.
-1
Re2(CO)6(OH)2(O2CC6H5)-1
Re2(CO)6(OH)(O2CC6H5)2
Re2(CO)6(O2CC6H5)3
-1
Scheme 2. Stoichiometric control of exchange with benzoic acid.

K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1041–1049
1043
solution (0.5 equiv.) was added. The mixture was stirred
at room temperature for 10 h, the solvent then was re-
moved under reduced pressure to approximately 4 mL.
The resulting solution was precipitated with 40 mL of
hexanes. The yellow solid obtained was dried under vac-
uum overnight; yield: 0.087 g (84%). Anal. Calc. for
C36H54N2O20Re4: C, 27.37, H, 3.45, N, 1.77. Found:
C, 27.03, H, 3.68, N, 1.69%. IR (cmꢀ1): THF, m(C–O)
2004 (m), 1886 (vs). 1H NMR (acetone-d6): d 6.79
ppm (s, 2H, O2CCH@CHCO2), 4.14 ppm (s, 12H,
(OCH3)), 3.45 ppm (q, 16H, (CH3CH2)4N), 1.41 ppm
(tt, 24H, (CH3CH2)4N). 13C NMR (acetone-d6): d
202.46 ppm (CO), 174.89 ppm (O2CCH@CHCO2),
137.71 ppm (O2CCH@CHCO2), 71.05 ppm (OCH3),
53.17 (CH3CH2)4N and 7.78 ppm (CH3CH2)4N.
of complexes 5, 6, and 7 were grown by vapor diffusion
of hexane into a THF solution at 5 ꢁC. For complex 7 a
few drops of methanol were added to aid in dissolving
the complex. Colorless block crystals 3, 4, 5, and 7
and yellow block for 6 were fixed to a cryo-loop in par-
atone-N oil and immediately placed in a nitrogen cold
stream (110 K). Data were collected on a Bruker
SMART 1000 X-ray diffractometer for 5 and a Bru-
ker-Nonius X8 APEX diffractometer for 3, 4, 6, and 7.
Data reduction was accomplished using SAINT-
PLUS [13] (Bruker) for 3–7. All structures were solved
by direct methods using the SHELX program suite, which
provided the positions of the rhenium atoms and some
of the atoms of the ligands. Subsequent least square
refinements revealed the positions of the remaining
atoms in the structure. Unless noted otherwise, all
non-hydrogen atoms were refined anisotropically.
2.2.5. Synthesis of [Et4N]2[Re2(CO)6(OCH2CH3)2
(O2CC6H4CO2)Re (CO)6(OCH2CH3)2] (7)
2
A mixture of 2 (0.100 g, 0.131 mmol) and terephthalic
acid (0.5 equiv.) was refluxed in ethanol for 18 h. The
solvent then was removed under vacuum to 4 mL and
60 ml of diethyl ether was added to precipitate white
3. Results and discussion
3.1. General characterizations
crystals; yield: 0.080
C44H68N2O20Re4: C, 31.34, H, 3.83, N, 1.66. Found:
g (75%). Anal. Calc. for
C, 31.78, H, 3.80, N, 1.65%. IR (cmꢀ1): ethanol, m(C–
O) 2009 (m), 1997 (s), and 1886 (vs). H NMR (metha-
3.1.1. Synthesis and IR spectra
1
The reaction of 1 with 1 equiv. of benzoic acid, with
0.5 equiv. of fumaric acid in THF, or 0.5 equiv. of tere-
phthalic acid in refluxing ethanol, yields a singly substi-
tuted rhenium complex. In the case of fumaric acid and
the terephthalic acid two rhenium centers are bridged by
the fumarate (6) and terephthalate (7). For 6 it is neces-
sary to add a few drops of methanol to the reaction mix-
ture to dissolve all of the reactants, when this is done
there is exchange for the hydroxy ligand by the metha-
nol. Complex 1 can be substituted twice with benzoic
acid by adding 2 equiv. of the acid and stirring for 14
h resulting in 4. The reaction of 1 with 3 equiv. of ben-
zoic acid results in complete substitution within 6 h at
60 ꢁC as witnessed in the infrared spectrum. Compounds
3–5 are soluble in acetone, THF, acetonitrile, and
CH2Cl2. Complex 6 is soluble in THF and acetonitrile,
while 7 is soluble only upon addition of a few drops of
methanol (see Scheme 3).
nol-d4): d 7.95 ppm (s, 4H, O2CC6H4CO2), 4.20 ppm (s,
12H, (OCH2CH3)), 3.48 ppm (q, 8H, (CH3CH2O)), 3.17
ppm (q, 12H, (CH3CH2)4N), 1.13 ppm (tt, 24H,
(CH3CH2)4N), and 1.06 ppm (t, 12H, (CH3CH2O)).
13C NMR (methanol-d4): d 201.5 ppm (CO), 173.4
ppm (O2CC6H4CO2), 139.5 and 128.3 ppm
(O2CC6H4CO2), 72.80 ppm (OCH2CH3), 53.17 ppm
(CH3CH2)4N, 17.69 ppm (OCH2CH3) and 7.78 ppm
(CH3CH2)4N.
2.3. X-ray crystallography
Details of data collection and refinement are given in
Table 2. Crystals of complex 3 were grown by vapor
diffusion of hexane into a 1,2-dichloroethane solution
at 5 ꢁC. Crystals of complex 4 were grown by vapor dif-
fusion of ether into a CH2Cl2 solution at 5 ꢁC. Crystals
O
O
-1
+
O
O
-1
O
O
C
C
C
C
C
C
Re
Re
O
HO
O
C
R
H2O
HO OH OH
Re
C
R
HO OH
+
O
Re
C
O
C
C
C
C
O
C
O
O
O
O
ꢀ1
3
Scheme 3. General reaction for exchange of Re2ðCOÞ ðOHÞ
.
6

1044
K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1041–1049
As expected, all complexes, 3–7 presented strong
1H NMR spectrum. For the complex 3, a benzoic acid
binding syn–syn to the Re2 core, the ring protons res-
bands in the region of 2030–1860 cmꢀ1 indicating the
presence of the {Re(CO)3} core. These data are pre-
sented in Table 1. Compounds 3 and 6 have two band
patterns suggesting a C3v local symmetry about the
rhenium atoms. Complexes 4 and 7 exhibit a splitting
of the higher wavenumber band suggesting a departure
from idealized symmetry. Compound 5 shows the high-
est degree of departure from idealized symmetry with a
splitting of both the higher wavenumber and lower
wavenumber bands.
1+
onance appears as multiplets at 8.03, and 7.43 ppm. The
protons corresponding to the hydroxy groups show as a
broad singlet at 2.38 ppm. The 13C NMR spectrum
shows that the carbonyl group resonance is at 202.03
ppm. The carboxylate carbon resonance is at 174.53
ppm and the ring carbons are as expected four signals
at 137.90, 131.93, 130.40, and 128.50 ppm.
For the complex 4, the two benzoic acid ligands are
1+
binding syn–syn to the Re2 core as in 3, the aromatic
The reaction of 1 with benzoic acid can be stoichoi-
metrically controlled. The substitution reaction for the
complexes 3–5 is interesting; each of the three forms a
bidentate bridging rhenium benzoate complex. In the
case of 3 the benzoic acid is bridging the rhenium centers
in a syn–syn geometry [5]. Complex 4 has two bridging
benzoates in a syn–syn geometry, however, in the case
of the triply substituted complex 5, two carboxylates
are bridging the metal centers through one oxygen
(unidentate) and the remaining ligand is bridging in a
syn–syn fashion.
In the case of complexes 6 and 7, we observed that the
reaction of 1 or 2 with fumaric acid and terephthalic
acid yields as a product a dimer-of-dimers. These com-
plexes confirm that dicarboxylic acids are able to link
two dirhenium centers together. For complex 7 the reac-
tion was carried out in refluxing solution of ethanol due
to the limited solubility of the terephthalic acid. For
complex 7 it is observed that if the starting material is
1 the substitution of the hydroxy group by the ethoxy
group take place, this is probably due to the harsh con-
ditions of the reaction. When redissolved in another sol-
vent (THF or CH3CN) with a few drops of methanol,
the ethoxy groups are replaced by methoxy. We have
yet to see additional reaction with dicarboxylic acids be-
yond the single exchange.
protons resonance shows as multiplet at 7.98 and 7.41
ppm. In this complex we noticed the presence of one
molecule of diethyl ether; the protons corresponding
to it appear at 3.47 and 1.13 ppm. The 13C NMR spec-
trum shows the carbonyl group resonance at 200.94
ppm. The carboxylate peak is very similar to the one
found in complex 3, 174.39 ppm. For the complex 5,
the different binding mode of the carboxylate ligand is
difficult to detect in the 1H NMR spectrum, the ring pro-
tons show at 8.03 and 7.45 as multiplets. By comparison
of this signal with the analogous protons in the complex
3, it is noticed the appearance of an extra set of peaks
but this signal is overlapped by the other signal. How-
ever, in the 13C NMR the difference of binding mode
is clearly displayed due to the presence of two signals
for each carbon in the ring as well as for the C–O reso-
nance of the carboxylate ligand. The set of peaks for the
ring carbons are between 137.50 and 128.12 ppm. The
carboxylate peak is at 174.36 ppm for the g1,g1-
OOCC6H5 and 166.13 ppm for the unidentate (l-
OOCC6H5) binding mode.
The 1H NMR of 6 shows one singlet at 6.79 ppm cor-
responding to the vinylic protons of the fumarate ligand.
The methoxy groups are at 4.14 ppm as a singlet. In the
13C NMR spectrum the carbonyl groups display a signal
at 202.46 ppm, just slightly downfield from those in
complex 3. The 1H NMR of 7 shows one singlet at
7.95 ppm corresponding to the ring protons of the tere-
phthalate ligand. The ethoxy groups signals show at 3.48
and 1.06 ppm.
3.1.2. NMR spectra
For each of the compounds 3–7 a proper integration
versus the protons of the Et4N cation was attained in the
Table 1
Infrared spectra for complexes 1–7
Compound
m(CO)
[Et4N][Re2(CO)6(OH)3] (1)a
1990 (s), 1870 (vs) [12]
1993 (s), 1876 (vs) [12]
2010 (s), 1898 (vs)
[Et4N][Re2(CO)6(OCH3)3] (2)b
[Et4N][Re2(CO)6(OH)2(O2CC6H5)] (3)b
[Et4N][Re2(CO)6(OH)(O2CC6H5)2] (4)a
[Et4N][Re2(CO)6(OOCC6H5)3] (5)a
[Et4N]2[Re4(CO)12(OMe)4(O4C4H2)] (6)a
[Et4N]2[Re4(CO)12(OMe)4(O2CC6H4CO2)]c (7)
2012 (s), 1998 (s), 1877 (vs)
2008 (s),1994 (s), 1877 (vs), 1868 (vs)
2004 (s), 1896 (vs)
2009 (m), 1997 (s), 1886 (vs)
a
CH3CN solution.
THF solution.
Ethanol solution.
b
c

K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1041–1049
1045
3.2. Description of the crystal structures
the acetate derivative. The non-bonding Re1–Re2 dis-
˚
˚
tance is 3.372 A about 0.2 A longer than that observed
for the bridging alkoxide ligands and slightly longer
than the acetate derivative. The hydroxide ligands are
flattened out to nearly planar with respect to the rhe-
X-ray crystal structure determinations were carried
out for the five derivatives synthesized and details of
data collection and refinement are given in Table 2.
All of the complexes contain an Re2(CO)6 core with
varying ligation around this core. All Re–C and C–O(car-
˚
nium atoms with a maximum deviation of 0.037 A from
a plane drawn through Re1, Re2, O9 and O10. The
bond angle at the benzoate carbon is 127.0(5)ꢁ, nearly
the same as that observed in the acetate derivative of
ꢁ126.5ꢁ [7,8]. One half of a molecule of 1,2-dichloroeth-
ane is present in the asymmetric unit.
bond lengths and Re–C–O angles fall well within
normally observed values and each rhenium has approx-
imate octahedral geometry.
bonyl)
3.2.1. Structure of complex 3
An ellipsoid plot of the singly substituted benzoate
complex 3 is shown in Fig. 1 and selected bond lengths
and angles are in Table 3. For 3 the benzoate bridges the
dimetal core in an analogous fashion to that seen for the
acetate derivative [8]. The Re–O bond lengths for the
hydroxide ligands are quite symmetric averaging
3.2.2. Structure of complex 4
A thermal ellipsoid plot of the anion of complex 4 is
shown in Fig. 2, and the selected bond distances and an-
gles are presented in Table 4. In this structure we ob-
serve that the binding of the two carboxylates ligands
is syn–syn in geometry which increases the non-bonding
˚
˚
2.13 A and the Re–O for the carboxylate shows a slight
distance between the rhenium centers by ꢁ0.5 A with re-
˚
asymmetry at 2.1692(18) A for Re1–O7 and 2.1518(18)
˚
A for Re2–O8. A similar asymmetry has been seen in
˚
spect to complex 3, 3.852 versus 3.372 A. The increase in
the distance between Re–Re forces a concomitant
Table 2
Crystal data, data collection, and structure refinement for 3–7
Compound
3
4
5
6
7
Empirical formula
Formula weight
Temperature (K)
C22H29ClNO10Re2
875.31
C32H41NO12Re2
1004.06
C35H35NO12Re2
1034.04
110
C18H27NO10Re2
789.81
C40H56N2O20Re4
1629.67
˚
Wavelength (A)
0.71073
monoclinic
P21/n
Crystal system
Space group
Unit cell dimensions
triclinic
ꢀ
monoclinic
P21/c
monoclinic
C2/c
monoclinic
C2/c
P1
˚
a (A)
11.3681(6)
11.3751(5)
11.6956(6)
82.5040(10)
78.8540(10)
68.9580(10)
1381.84(12)
2
16.2433(7)
11.1001(4)
19.5326(8)
10.9997(8)
27.221(2)
12.8999(9)
20.089(2)
12.4620(14)
19.871(2)
32.1202(11)
12.7935(4)
12.4046(4)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
94.350(2)
113.009(1)
104.049(6)
93.372(2)
3
˚
Volume (A )
3511.6(2)
4
1.899
3555.2(5)
4
1.932
4825.8(9)
8
2.174
5088.6(3)
4
2.127
Z
Dcalc. (Mg/m3)
Absorption coefficient (mmꢀ1
Crystal size (mm)
2.104
8.900
)
6.949
6.867
10.074
9.557
0.22 · 0.21 · 0.14
2.84–33.28
ꢀ17 6 h 6 17
ꢀ17 6 k 6 17
ꢀ17 6 l 6 17
35473
0.39 · 0.21 · 0.18
2.09–30.52
ꢀ23 6 h 6 23
ꢀ15 6 k 6 15
ꢀ27 6 l 6 27
67984
0.26 · 0.28 · 0.21
1.87–25.00
ꢀ13 6 h 6 13
ꢀ25 6 k 6 32
ꢀ14 6 l 6 15
23790
0.27 · 0.15 · 0.14
2.59–30.77
ꢀ28 6 h 6 24
ꢀ15 6 k 6 17
ꢀ28 6 l 6 26
28390
0.22 · 0.17 · 0.11
3.18–28.30
ꢀ38 6 h 6 42
ꢀ17 6 k 6 17
ꢀ16 6 l 6 16
27821
h Range for data collection (ꢁ)
Limiting indices
Reflections collected
Independent reflections (Rint
Absorption correction
Refinement method
Goodness-of-fit on F2
)
10503 (0.0331)
10706 (0.0317)
6244 (0.0278)
7446 (0.0242)
6301 (0.0369)
SADABS
Full-matrix least squares on F2
1.070
1.054
1.127
1.103
1.075
Final R indices (observed data)
R1
wR2
0.0244
0.0614
0.167
0.0365
0.0314
0.0767
0.0306
0.0724
0.0242
0.0588
R indices (all data)
R1
0.0333
0.0638
0.0214
0.0383
0.0335
0.0782
0.0349
0.0737
0.0309
0.0608
wR2
Largest difference peak and hole (e/A )
3
˚
2.302 and ꢀ1.411
1.112 and ꢀ0.626
3.041 and ꢀ1.289
3.696 and ꢀ2.123
2.417 and ꢀ1.603

1046
K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1041–1049
Fig. 1. Thermal ellipsoid plot of 3 with atomic numbering scheme. Ellipsoids are shown at the 40% level.
Table 3
increase in Re–O–Re angle to 131.64(8)ꢁ at O11, this is
˚
Selected bond lengths (A) and angles (ꢁ) for 3
significantly larger than the angles observed for the alk-
oxide, and the benzoate examples 3 and 5. In the crystal
structure one molecule of diethyl ether is H-bonded to
the hydroxy ligand with an O–O distance of
Re(1)–O(10)
Re(1)–O(7)
Re(2)–O(9)
O(7)–C(7)
C(7)–C(8)
2.135(2)
2.1692(18)
2.136(2)
1.265(3)
1.488(3)
Re(1)–O(9)
Re(2)–O(10)
Re(2)–O(8)
O(8)–C(7)
2.139(2)
2.134(2)
2.1518(18)
1.265(3)
˚
2.799(3)A. Complex 4 represents the first example of
two carboxylate ligands bridging a Re2(CO)6 core
structure.
O(10)–Re(1)–O(9)
O(9)–Re(1)–O(7)
O(10)–Re(2)–O(8)
C(7)–O(7)–Re(1)
Re(2)–O(9)–Re(1)
75.60(8)
79.42(7)
80.55(8)
130.93(17)
104.11(8)
O(10)–Re(1)–O(7)
O(10)–Re(2)–O(9)
O(9)–Re(2)–O(8)
C(7)–O(8)–Re(2)
Re(2)–O(10)–Re(1)
81.11(8)
75.69(8)
80.07(7)
131.67(17)
104.32(9)
3.2.3. Structure of complex 5
The anion of complex 5 is shown as a thermal ellip-
soid plot in Fig. 3, selected bond lengths and angles
are presented in Table 5. This structure differs from
the others presented here in that the Re2(CO)6 core is
bridged by three carboxylate ions using two different
bridging modes. Two of the benzoate ligands bridge
the two Re ions in a unidentate l fashion, and the other
benzoate bridges through both oxygens as seen in com-
plexes 3 and 4. This structural motif has been seen for
Cu, [14–17] Mn [18], and Mo [19–21]. Compound 5 is
the first example of a metal carbonyl compound bridged
in this manner. Previous examples containing a carbox-
ylate ligand bound to the Re2(CO)6 core contained only
one carboxylate with two bridging alkoxides [7,8]. By
bridging the Re core through both oxygens of the benzo-
˚
ate, the Re–Re distance is widened to 3.47 A and in-
˚
crease of about 0.3 A from the alkoxide bridged
˚
examples above and about 0.1 A longer than the 3.36–
˚
3.37 A observed in the mixed carboxylate/alkoxide li-
gand complexes (vide supra) [7,8]. The widening of the
Re–Re distance also leads to a significant widening of
the Re–O–Re bond angles to 105.5(1)ꢁ at O9 and
106.1(1)ꢁ at O11, this compares well to the mixed alkox-
ide derivatives where the angles are near 105ꢁ [7,8], and
is significantly larger than the normally observed 94ꢁ
Fig. 2. Thermal ellipsoid plot of 4 with atomic numbering scheme.
Ellipsoids are shown at the 40% level.
ꢀ
seen in the Re2(CO)6(OR)3 derivatives [12,22–25].

K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1041–1049
1047
Table 4
Selected bond lengths (A) and angles (ꢁ) for 4
˚
Re(1)–O(11)
Re(1)–O(7)
Re(2)–O(8)
O(7)–C(7)
O(9)–C(14)
C(7)–C(8)
2.1041(15)
Re(1)–O(9)
Re(2)–O(11)
Re(2)–O(10)
O(8)–C(7)
2.1485(14)
2.1182(15)
2.1806(14)
1.266(2)
2.1709(14)
2.1576(14)
1.271(2)
1.268(2)
1.498(3)
O(10)–C(14)
C(14)–C(15)
1.262(2)
1.502(3)
O(11)–Re(1)–O(9)
O(9)–Re(1)–O(7)
O(11)–Re(2)–O(10)
C(7)–O(7)–Re(1)
C(14)–O(9)–Re(1)
Re(1)–O(11)–Re(2)
O(8)–C(7)–C(8)
83.43(6)
84.25(5)
87.20(6)
O(11)–Re(1)–O(7)
O(11)–Re(2)–O(8)
O(8)–Re(2)–O(10)
C(7)–O(8)–Re(2)
C(14)–O(10)–Re(2)
O(8)–C(7)–O(7)
83.12(6)
82.00(6)
84.58(6)
133.71(13)
130.66(13)
131.64(8)
116.20(17)
127.34(18)
115.33(17)
131.60(13)
135.18(13)
126.90(18)
116.90(17)
117.33(17)
O(7)–C(7)–C(8)
O(10)–C(14)–C(15)
O(10)–C(14)–O(9)
O(9)–C(14)–C(15)
D–Hꢂ ꢂ ꢂA
d(D–H)
0.72(3)
d(Hꢂ ꢂ ꢂA)
d(Dꢂ ꢂ ꢂA)
\(DHA)
177(3)
O(11)–H(1)ꢂ ꢂ ꢂO(12)
2.08(3)
2.799(3)
Table 5
˚
Selected bond lengths (A) and angles (ꢁ) for 5
Re(1)–O(7)
Re(1)–O(9)
Re(2)–O(9)
O(7)–C(7)
2.134(3)
2.184(3)
2.177(3)
1.255(6)
1.332(6)
1.320(6)
1.498(7)
1.507(7)
Re(1)–O(11)
Re(2)–O(8)
Re(2)–O(11)
O(8)–C(7)
2.161(3)
2.138(3)
2.183(3)
1.272(6)
1.212(6)
1.217(6)
1.501(7)
O(9)–C(21)
O(11)–C(14)
C(7)–C(8)
O(10)–C(21)
O(12)–C(14)
C(14)–C(15)
C(21)–C(22)
O(7)–Re(1)–O(11)
O(11)–Re(1)–O(9)
O(8)–Re(2)–O(11)
Re(2)–O(9)–Re(1)
O(7)–C(7)–O(8)
84.39(13)
72.96(12)
80.79(13)
105.55(13)
127.0(5)
O(7)–Re(1)–O(9)
O(8)–Re(2)–O(9)
O(9)–Re(2)–O(11)
Re(1)–O(11)–Re(2)
O(7)–C(7)–C(8)
C(9)–C(8)–C(7)
81.06(13)
84.62(13)
72.68(12)
106.13(14)
117.5(4)
C(13)–C(8)–C(7)
O(12)–C(14)–O(11)
120.0(4)
122.6(5)
119.9(4)
122.7(5)
O(10)–C(21)–O(9)
bond lengths to the hydroxide ligand in 3 are all longer
˚
than 2.13 A and the same bond length in 4 is about 2.105
˚
A, i.e. the more substituted complex has the hydroxide
pulled closer to the metals. By switching to a l-bridging
mode the carboxylate is able to act as a better donor to
the metal centers in 5.
Fig. 3. Thermal ellipsoid plot of 5 with atomic numbering scheme.
Ellipsoids are shown at the 40% level.
3.2.4. Structure of complex 6
For the unique g1,g1 bridging benzoate the Re–O dis-
A thermal ellipsoid plot of complex 6 is shown in
Fig. 4 and selected bond lengths and angles are pre-
sented in Table 6. The structure of 6 features a fumarate
bridging two dimeric rhenium centers with a crystallo-
graphic center of symmetry located between the two car-
bons with the double bond. The local structure about
the dimeric rhenium center is analogous to that of com-
plex 3, with methoxides replacing the hydroxide ligands.
˚
tances are nearly identical at 2.134(3) A for Re1–O7
˚
and 2.138(3) A for Re2–O8. For the l-benzoate ligands
˚
˚
the Re–O distances average 2.17 A, which is 0.04 A
longer than for the unique benzoate. The C–O bond
lengths for the bridging oxygen are 1.332(6) for O9
and 1.320(6) for O11, which is to be expected for a lower
bond order in the C–O bond. The preference of 5 for its
observed binding mode rather than all g1,g1 bridging is
likely electronic in nature. It is noticed that the Re–O
˚
The Re–Re non-bonding distance is 3.372 A as in 3 and
the Re–O bond lengths for the methoxide ligands are

1048
K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1041–1049
Fig. 4. Thermal ellipsoid plot of 6 with atomic numbering scheme. Ellipsoids are shown at the 40% level.
Table 6
The C–O bond lengths for the carboxylate are symmet-
˚
Selected bond lengths (A) and angles (ꢁ) for 6
˚
ric at 1.259(3) and 1.265(3) A indicating substantial mul-
tiple bond character, while the C7–C8 bond length is of
˚
single bond order at 1.495(3) A. Ligation of the carbox-
ylate has removed the conjugation with the double bond
O(7)–Re(1)
O(9)–Re(1)
O(10)–Re(1)
C(7)–O(8)
C(7)–C(8)
C(9)–O(9)
2.175(3)
2.122(3)
2.123(3)
1.259(6)
1.495(6)
1.408(5)
O(8)–Re(2)
O(9)–Re(2)
O(10)–Re(2)
C(7)–O(7)
2.156(3)
2.123(3)
2.123(3)
1.265(6)
1.338(9)
1.393(7)
˚
of the fumarate which is 1.338(9) A.
C(8)–C(8)#1
C(10)–O(10)
3.2.5. Structure of complex 7
O(8)–C(7)–O(7)
O(7)–C(7)–C(8)
128.4(4)
115.0(4)
128.8(3)
119.8(3)
105.19(13)
122.9(4)
82.21(12)
74.62(12)
79.68(14)
O(8)–C(7)–C(8)
116.6(4)
113.8(8)
131.3(3)
121.5(3)
124.5(4)
105.13(14)
80.07(13)
80.93(12)
A thermal ellipsoid plot of the linked dimers of com-
plex 7 is presented in Fig. 5 and the corresponding bond
distances and angles are presented in Table 7. This com-
plex connects two dirhenium units through a terephthal-
ate ligand (dicarboxylate ion). The symmetry observed
for this compound is similar to the fumarate complex
in that there is an inversion center in the middle of the
ring. The distance corresponding to the interaction with
C(11)-N(1)–C(13)
C(7)–O(8)–Re(2)
C(9)–O(9)–Re(2)
C(10)–O(10)–Re(1)
Re(1)–O(10)–Re(2)
O(10)–Re(1)–O(7)
O(9)–Re(2)–O(8)
C(7)–O(7)–Re(1)
C(9)–O(9)–Re(1)
Re(1)–O(9)–Re(2)
C(10)–O(10)–Re(2)
O(9)–Re(1)–O(7)
O(9)–Re(2)–O(10)
O(10)–Re(2)–O(8)
˚
carboxylate ligands are 2.173(3) A for Re1–O9 and
˚
2.162(3) A for Re2–O10 which are comparable to the
˚
ones observed in complex 3. The angles between the rhe-
nium and the methoxides are 104.56(12)ꢁ for Re1–O7–
Re2 and 104.86(11)ꢁ for Re1–O8–Re2 which are slightly
2.123(3)
Re–O(carboxy) bond lengths are again slightly asymmetric
A
which compares closely to 3. The
˚
at 2.175(3) A for Re1–O7 and 2.156(3) A for Re2–O8.
˚
Fig. 5. Thermal ellipsoid plot of 7 with atomic numbering scheme. Ellipsoids are shown at the 30% level.

K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1041–1049
1049
Table 7
Selected bond lengths (A) and angles (ꢁ) for 7
Acknowledgements
˚
Re(1)–O(8)
Re(1)–O(9)
Re(2)–O(8)
O(7)–C(7)
O(9)–C(9)
2.123(2)
2.173(3)
2.118(3)
1.391(6)
1.264(4)
Re(1)–O(7)
Re(2)–O(7)
Re(2)–O(10)
O(8)–C(8)
2.132(3)
2.118(3)
2.162(3)
1.427(5)
1.277(4)
This research was funded by a grant from the Robert
A. Welch Foundation (AA-1508). The Bruker X8
APEX diffractometer was purchased with funds received
from the National Science Foundation Major Research
Instrumentation Program Grant CHE-0321214.
O(10)–C(9)
O(8)–Re(1)–O(7)
O(7)–Re(1)–O(9)
O(7)–Re(2)–O(10)
C(7)–O(7)–Re(2)
Re(2)–O(7)–Re(1)
C(8)–O(8)–Re(1)
C(9)–O(9)–Re(1)
O(9)–C(9)–O(10)
74.91(10)
81.64(11)
80.16(10)
121.8(3)
104.56(12)
121.1(2)
129.6(2)
127.7(4)
O(8)–Re(1)–O(9)
O(7)–Re(2)–O(8)
O(8)–Re(2)–O(10)
C(7)–O(7)–Re(1)
C(8)–O(8)–Re(2)
Re(2)–O(8)–Re(1)
C(9)–O(10)–Re(2)
80.99(10)
75.30(10)
80.68(10)
122.5(3)
References
121.1(2)
104.86(11)
131.6(2)
[1] W.A. Herrmann, W.R. Thiel, F.E. Kuehn, R.W. Fischer, M.
Kleine, E. Herdtweck, W. Scherer, J. Mink, Inorg. Chem. 32
(1993) 5188.
[2] K.-L. Lu, H.-H. Lee, C.-M. Wang, Y.-S. Wen, Organometallics
13 (1994) 593.
different for the ones observed in the fumarate complex
of 105.15(2)ꢁ.
[3] S. Feracin, T. Buergi, V.I. Bakhmutov, I. Eremenko, E.V.
Vorontsov, A.B. Vimenits, H. Berke, Organometallics 13 (1994)
4194.
[4] F. Tisato, F. Refosco, A. Moresco, G. Bandoli, A. Dolmella, C.
Bolzati, Inorg. Chem (1995) 34.
4. Conclusion
[5] F.A. Cotton, E.V. Dikarev, M.A. Petrukhina, Inorg. Chim. Acta
284 (1999) 304.
This work extends the number of examples of carbox-
ylate containing triply bridged anion Re2(CO)6(OR)2
(O2CR0)ꢀ1. Presented here are the first examples of
derivatives that have been substituted two and three
times. For the doubly substituted the binding mode
for both benzoates is the same, an g1,g1 fashion forcing
[6] C.J. Cameron, P.E. Fanwick, M. Leeaphon, R.A. Walton, Inorg.
Chem. 28 (1989) 1101.
[7] R. Alberto, R. Schibli, D. Angst, P.A. Schubiger, U. Abram, S.
Abram, T.A. Kaden, Transition Met. Chem. 22 (1997) 597.
[8] U. Brand, J.R. Shapley, Inorg. Chem. 39 (2000) 32.
[9] C. Jiang, T.S.A. Hor, Y.K. Yan, W. Henderson, L.J. McCaffrey,
JCS Dalton Trans. (2000) 3197.
˚
the rhenium atoms apart to a very wide 3.852 A. For the
[10] C. Jiang, W. Henderson, T.S.A. Hor, L.J. McCaffrey, Y.K. Yan,
Chem. Commun. (1998) 2029.
triply substituted derivative there is a combination of
coordinating modes. One benzoate has the common
g1,g1 mode and the other two are simply bridging
through one oxygen atom.
[11] K.K. Klausmeyer, F.R. Beckles, Inorg. Chim. Acta, doi: 10.1016/
j.ica.2004.11.017.
[12] C. Jiang, Y.-S. Wen, L.-K. Liu, T.S.A. Hor, Y.K. Yan, Organo-
met 17 (1998) 173.
The fumarate and terephthalate examples show that
it is possible to link these dimeric units together. It is
of interest now that we have connected metal centers
with still labile methoxy groups, to see if it will be pos-
sible to further substitute these complexes and link them
together to form anionic polymers or extended struc-
tures. Currently attempts are being made towards this.
[13] SAINT-Plus, version 6.02 ed., Bruker, Madison, WI, USA, 1999.
[14] H. Matsushima, M. Koikawa, R. Nukada, M. Mikuriya, T.
Tokii, Bull. Chem. Soc. Jpn. 72 (1999) 1025.
[15] H. Matsushima, M. Koikawa, M. Nakashima, T. Tokii, Chem.
Lett. (1995) 869.
[16] X.-Y. Le, X.-H. Zhou, K.-B. Yu, L.-N. Ji, Chin. J. Chem. 18
(2000) 638.
[17] Y.-P. Tian, Z.-J. Zhang, J.-Y. Wu, H.-K. Fun, M.-H. Jiang, X.-
Q. Xu, A. Usman, S. Chantrapomma, L.K. Thompson, New J.
Chem. 26 (2002) 1468.
[18] Z.J. Zhong, X.-Z. You, T.C.W. Mak, Polyhedron 13 (1994) 2157.
[19] F.A. Cotton, J. Su, Z. Yao, Inorg. Chem. Acta 266 (1997) 65.
[20] F.A. Cotton, J.J. Su, Cluster Sci. 6 (1995) 39.
[21] K. Jansen, K. Dehnicke, D.Z. Fenske, Naturforsch. Teil B 42
(1987) 1097.
5. Supplementary material
Crystallographic data (excluding structure factors)
for the structural analysis have been deposited with
the Cambridge Crystallographic Data Centre as Deposit
Nos. 247283 for 3, 247284 for 4, 247281 for 5, 247282
for 6, and 247285 for 7. Copies of the data can be ob-
tained free of charge from The Director, CCDC, 12 Un-
ion Road, Cambridge CB21EZ, UK (fax: +44 1223 336
033; e-mail: deposit@ccdc.cam.ac.uk).
[22] R. Alberto, A. Egli, U. Abram, K. Hegetschweiler, V. Gramlich,
P.A. Schubiger, JCS Dalton Trans. (1994) 2815.
¨
[23] W. Herrmann, D. Mihalios, K. Ofele, P. Kiprof, F. Belmedjahed,
Chem. Ber. 125 (1992) 1795.
[24] G. Ciani, A. Sironi, A. Albinati, Gazz. Chim. Ital. 109 (1979) 615.
[25] T. Beringhelli, G. Ciani, G. DÕAlfonso, A. Sironi, M. Freni, JCS
Dalton Trans. (1985) 1507.