Synthesis and characterization of ruthenium, rhenium and titanium formate, acetate and trifluoroacetate complexes. Correlation of IR spectral properties and bonding types

Article abstract of DOI:10.1016/S0277-5387(98)00414-8

New formate (1-3; 4b, 6 and 7), acetate (8, 9) and trifluoroacetate (12, 13 and 15) complexes have been synthesized and characterized by elemental analysis and by IR and ¹H and ¹³C NMR spectroscopies. New data or new synthetic proced

Full text of DOI:10.1016/S0277-5387(98)00414-8

Polyhedron 18 (1999) 1189–1200
Synthesis and characterization of ruthenium, rhenium and titanium formate,
acetate and trifluoroacetate complexes. Correlation of IR spectral properties
and bonding types
*
Dorothy H. Gibson , Yan Ding, Rebecca L. Miller, Bradley A. Sleadd, Mark S. Mashuta,
John F. Richardson
Department of Chemistry and Center for Chemical Catalysis, University of Louisville, Louisville, KY 40292, USA
Received 10 July 1998; accepted 12 October 1998
Abstract
New formate (1–3; 4b, 6 and 7), acetate (8, 9) and trifluoroacetate (12, 13 and 15) complexes have been synthesized and characterized
by elemental analysis and by IR and 1H and 13C NMR spectroscopies. New data or new synthetic procedures are provided for several
known complexes (4a, 5, 19, 11 and 14). X-ray structural data for cis-Ru(bpy)2(CO)(OCHO)(PO2F2) (4b) clearly identify the h1-bound
formate ligand bound to an octahedral ruthenium center and the data for fac-Re(CO)3(PPh3(OCOMe) (9) show an h2-bound acetate
ligand bound to an octahedral rhenium center. Infrared spectral data for four types of formate complexes, three bonding types of acetates
and the two known types of trifluoroacetate ligands are discussed. Comparisons of the vOCO bands for the carboxylate ligands in all of the
complexes show that these bands are useful in identifying the bonding type of each carboxylate ligand.
All rights reserved.
1999 Elsevier Science Ltd.
Keywords: Infrared spectra; Crystal structures; Spectra/structure correlations; Synthetic methods
Interest in the catalytic hydrogenation of CO2 to formate
or formic acid by metal complexes as well as in the
decomposition of formic acid on metal surfaces has
resulted in increased interest in metal complexes with
formate ligands [1–6]. In particular, the vibrational spec-
tral bands of the carboxylate groups in such model
compounds can be of assistance in the characterization of
surface-bound formate [7–10]. However, the utility of this
approach has been somewhat limited in the past by the
lack of structurally characterized compounds for which
both vOCO bands have been reported. In particular, the
lower-frequency nsym band has frequently not been iden-
tified in compounds which were structurally characterized.
Efforts to correlate carboxylate IR spectral bands with
structural types have been made earlier [11–13]; thus, the
general region where the bands will be found is well
known. However, the previous work was done without the
benefit of as much structural data to support the assign-
ments of bonding types as is available now. Furthermore, a
few new bonding types have been identified since the
earlier efforts to correlate spectra and structural data.
We describe herein the synthesis and characterization of
several new formate, acetate and trifluoroacetate complex-
es and discuss the relationships between their bonding
types and IR spectral characteristics together with the
structural characterizations of two of the new compounds.
With all of the compounds which we have prepared, the IR
spectral data have been obtained by solid-state techniques
(see Section 3) in order to compare the IR data with X-ray
structural data wherever possible. Also, representative
spectra are provided for a number of compounds which
illustrate intensity differences in the carboxylate bands for
differing structural types.
1. Results and discussion
1.1. Synthesis of new compounds
New formate complexes prepared for the present study
are of three types: h1 (bound to the metal by a single
carboxylate oxygen), h2 (bound to a single metal through
*
Corresponding author. Tel.: 11-502-8525977; fax: 11-502-8525977;
e-mail: dhgibs01@athena.louisville.edu
0277-5387/99/$ – see front matter
PII: S0277-5387(98)00414-8
1999 Elsevier Science Ltd. All rights reserved.

1190
D.H. Gibson et al. / Polyhedron 18 (1999) 1189–1200
both carboxylate oxygens) and m2 –h2 (bound through both
carboxylate oxygens to two different metal centers). In all
cases, the h1-type complexes have been used as precursors
to the other two types.
The new monodentate acetate complex, cis-
Ru(bpy)2(CO)(h1-OCOCH3) (8), was prepared by heating
the corresponding hydride complex with acetic acid. The
product was characterized by elemental analysis and
spectral data.
We prepared the h1-coordinated formates by reactions of
the corresponding methyl or hydrido complexes with
formic acid; the compounds are cis-Re(CO)4(PPh3)(h1-
OCHO) (1), Cp2Ti(CH3)(h1OCHO) (2) and CP2Ti(h1-
OCHO)2 (3) and cis-Ru(bpy)2(CO)(h1-OCHO)2PF6- (4a;
bpy52,29-bipyridyl). Compound 4a has been reported
previously [14], but full characterization data was not
provided. The PO2F2 salt of the same cation (4b) is new
and was formed as the result of hydrolysis of the PF6 salt
during synthesis (as observed previously with this anion
[15]); structural data for 4b are discussed below. The new
compounds have also been characterized by elemental
analysis and spectral data. We reported structural data for 3
previously [16]; spectral and analytical data for it are
provided in Section 3. Also, a new synthesis of the known
[17,18] compound, mer, trans-Re(CO)3(PPh3)2(h1-
OCHO) (5), was accomplished by treating the corre-
sponding hydride complex with formic acid; the spectral
properties of the product were identical to those reported
previously.
The bidentate acetate complex, fac-Re(Co)3(PPh3) (h2-
OCOCH3) (9), was obtained after prolonged heating of
cis-Re(CO)4(PPh3)(CH3) with acetic acid. The compound
was characterized by elemental analysis, spectral data and
by X-ray crystallography (see below) which established the
facial geometry of the carbonyl ligands and the h2 nature
of the acetate ligand with certainty.
An alternate method was used for the preparation of the
known [17] complex, cis, trans-Re(CO)2(PPh3)2-
(h2-OCOCH3) (10); in our procedure, mer, trans-Re-
(CO)3(PPh3)2(H) [21] was heated with acetic acid for
several hours to obtain the bidentate acetate complex. The
compound was obtained in high yield and had spectral
properties which were in agreement with those reported
previously.
A sample of fac-Mn(CO)3(PPh3)(h2-OCOCH3) (11)
was available from previous work [22]. The assignment of
facial geometry was made on the basis of characteristic IR
spectral bands for the terminal carbonyls in the compound
which are closely related to those of the analogous
rhenium complex, 9, that has been fully characterized.
The new trifluoroacetate complexes, Cp2Ti(CH3)(h1-
OCOCF3) (12) and cis-Re(CO)4(PPh3)(h1-OCOCF3) (13)
were made by treating the corresponding methyl complex-
es with trifluoroacetic acid. Samples of the known [17,23]
mer, trans-Re(CO)3(PPh3)2(h1-OCOCF3) (14) and the
new cis-[Ru(bpy)2(CO)(h1-OCOCF3)]PF6 (15), were ob-
tained by treating the corresponding hydride complexes
with the acid. The greater acidity of CF3COOH allows
much milder conditions to be used in this procedure than
with the preparations of formate and acetate complexes.
The new compounds were characterized by elemental
analysis and spectral data.
The known [18] h2-coordinated formate, cis, trans-
Re(CO)2(PPh3)2(h2-OCHO) (6), was prepared for the
present study by thermolysis of the corresponding h1-
complex, 5. The product had IR spectral properties which
were identical to those reported earlier.
As noted previously [11–13], carboxylate anions
bridged between two identical metal centers, and via both
oxygen atoms in m2 –h2 fashion, can assume any of the
geometries shown in Fig. 1 for formate ion unless the
metal atoms are bound together or connected by other
bridging ligands; in the latter cases, only the syn, syn
isomers are possible. Also, if the metal centers are
different, two isomers of the anti, syn type are possible.
The structurally characterized formate complexes of the
m2 –h2 type which are discussed below are all metallacy-
cles where the formate is constrained to be in the syn, syn
mode; several have more than one such formate bridge
[19]. The new complex, cis, cis-Re(CO)4(PPh3)(m2-h2-
OCHO)1BF24 (7), was prepared by reaction between the
monodentate complex 1 and cis-Re(CO)4(PPh3)(F-BF3)
[20]; it has been characterized by elemental analysis and
spectral data. The geometry about the formate ion in 7 is
not known and, in fact, samples of 7 may contain a
mixture of isomers.
1.2. Structural characterizations
The solid state structures of 4b and 9 have been
established by X-ray crystallography. The ORTEP diagram
for 4b is shown in Fig. 2; the diagram for 9 is shown in
Fig. 3. The crystal data for both compounds are summa-
rized in Table 1. Selected bond distances and bond angles
are shown in Table 2. The formate ligand is clearly
monodentate, with unequal O–C bond lengths of 1.151(7)
˚
˚
A and 1.224(8) A and a carboxyl O–C–O angle of
˚
127.0(7) A; the coordination geometry about the
ruthenium atom is distorted octahedral. The Ru–N bond
that is trans to the terminal carbonyl ligand is longer, at
˚
2.112(5) A than the Ru–N bonds which are cis to this
˚
ligand (both approximately 2.06 A) as is commonly seen
Fig. 1. Coordination geometries for m2 –h2–type formate complexes.
for cations of the general type cis-Ru(bpy)2(CO)(X)1

D.H. Gibson et al. / Polyhedron 18 (1999) 1189–1200
1191
giving rise to a symmetrically chelated acetate ligand. The
structure is closely similar to that for cis, trans-Re-
(CO)2(PPh3)2(h2-OCOCH3) reported by La Monica, et al.
[18].
Crystallographic data for Cp2Ti(OCHO)2 with two
monodentate formate ligands, have been reported by us
previously [16]. The O–C–O bond angles, 126.7(3)8 and
127.2(3)8, are slightly larger than for the ruthenium
complex 4b; however, the carboxylate O–C bond lengths
˚
˚
are similar to those of 4b at 1.188(4) A and 1.275(4) A.
1.3. IR spectral data
The region from 1800 to 950 cm21 of the DRIFTS (see
Section 3) spectra for the h1-type formate complexes 1 and
5 are shown in Fig. 4 together with that of the m2 –h2-
coordinated formate 7; spectral data for another h1 com-
plex, 4a, is shown in Fig. 5. All of the complexes in Fig. 4
contain triphenylphosphine ligands and thus show the
characteristic pair of weak bands at approximately 1430
and 1480 cm21; typically, the lower frequency band is
more intense. Compounds with this phosphine ligand also
show a low frequency band, of similar intensity, at
approximately 1100 cm21. The nOCO bands for the formate
ligand in each of these complexes (see Table 4 for
assignments) are weak to medium in intensity, but are
clearly more intense than the pair of bands for the
phosphine ligand in the 1450 cm21 region in each com-
pound. The nsym band in the m2 –h2-type complex 7 is
broad and has several shoulders on it as does the weaker
nasym band. These features were reproduced for several
different samples of the compound; since spectral data for
other complexes of this type have not been reproduced, it
is unclear whether this pattern is characteristic of com-
pounds with bridging formate ligands of this type or
whether it is due to the presence of multiple geometric
forms of the bridging formate ligands (as discussed above)
in the sample. Partial spectra for an h2 complex, 6, are
shown in Fig. 6. Note that the carboxylate bands have both
moved relative to those of the h1 complexes: the nasym
band is now at 1547 cm21 and the nsym band is at 1358
cm21 also, both bands are greatly diminished in intensity
as compared with the corresponding bands in the h1
complex.
Fig. 2. ORTEP drawing of 4b (cation only) with thermal ellipsoids shown
at the 50% probability level.
[24–27]. Selected bond distances and bond angles are
shown in Table 3. The geometry about the rhenium atom
in 9 is also best described as distorted octahedral. The
bidentate carboxyl O–C–O angle is 121.2(4)8 and is
substantially larger (112.7(7)8) than in the complex having
a chelated CO2 ligand, from a metallocarboxylate moiety,
bound through both oxygen atoms to this metal fragment
as the result of m2 –h3 bridging [28]. The Re–C bond
length for the carbonyl ligand trans to triphenylphosphine
˚
in 9 is slightly longer, at 1.957(4) A, than for those cis to
˚
this ligand (1.889(4) and 1.892(4) A). The O–Re bond
˚
lengths are similar in length (2.182(2) and 2.210(3) A),
The nOCO bands for formate complexes in four distinct
bonding modes are collected in Table 4 and include data
from our new complexes as well as data from well-
chararacterized compounds prepared by other groups pre-
viously. In addition to the three general types described
above, one recently characterized compound has a single
carboxylate oxygen bridged between two titanium centers,
providing a m2 –h1 bridging formate ligand [29]. Although
not the first structural report of a compound with this
bonding mode [30–33], it is the first for which the
carboxylate bands in IR spectral data can be readily
identified.
Fig. 3. ORTEP drawing of 9 with thermal ellipsoids shown at the 50%
probability level.

1192
D.H. Gibson et al. / Polyhedron 18 (1999) 1189–1200
Table 1
Summary of crystallographic data for [Ru(bpy)2(CO)(OCHO)]PF2O2 (4b) and Re(CO)3(PPh3)(OCOCH3) (9)
4b
9
Formula
C22H17F2N4O5PRu
587.44
C23H18O5PRe
591.57
0.4030.3630.33
colorless block
monoclinic
P21 /n
13.229 (3)
10.523 (2)
15.683 (2)
Formula weight
Cryst dimens, mm
Cryst descripn
Crystal system
Space group
0.4330.2530.17
yellow block
triclinic
¯
P1
˚
a, A
11.018 (3)
13.819 (3)
7.949 (3)
99.79 (2)
98.90 (2)
76.25 (2)
1150.2 (6)
2
1.696
8.10
Enraf-Nonius CAD4
graphite crystal
MoKa (l50.71073)
23 (1)
˚
b, A
˚
c, A
a, deg
b, deg
g, deg
93.69 (1)
3
˚
Vol. A
2178.7 (6)
4
1.803
Z
Dc, g cm23
m(Mo Ka) cm21
Diffractometer
Monochromator
56.84
Enraf-Nonius CAD4
graphite crystal
MoKa (l50.71073)
23 (1)
˚
Radiation (l, A)
Temp, 8C
Scan range, deg
Scan speed, deg/min
Maximum 2u, deg
0.8510.35 tan u
1–5
50.0
0.7510.35 tan u
1–5
55.0
Abs. corr.
PSI Scans
0.9110/1.0000
4042
3266
344
PSI Scans
0.8592/1.0000
53/2
3808
272
Transmission factors: min/max
No. unique reflns collected
No. reflns included (I0.3s (I0))
No. of params
Computer hardware
Computer software
Residuals: R; Rw
Silicon Graphics
teXsan (msc)
0.055; 0.055
3.27
Silicon Graphics
teXsan (msc)
0.022; 0.022
1.38
GOF
Least squares weights
Maximum peak in final diff. map
Minimum peak in final diff. map
[s2(F0)]21
[s2(F0)]21
3
3
1.71 e2 /A
0.65 e2 /A
˚
˚
3
3
21.03 e2 /A
20.60 e2 /A
˚
˚
aR5o iF0u2uFci/o uF0u; Rw5[o w(uF0u2uFcu)2]/o wF20]1 / 2
.
Table 3
2
˚
Selected bond distances (A) and angles (8) for Re(CO)3(PPh3)(h -
OCOCH3) (9)
Bond distances
Re–P
Table 2
Selected
2.4951(9)
2.182(2)
1.889(4)
1.280(5)
1.123(4)
1.148(4)
Re–O(1)
Re–C(3)
Re–C(5)
O(2)–C(1)
O(4)–C(4)
C(1)–C(2)
2.210(3)
1.957(4)
1.892(4)
1.266(5)
1.152(5)
1.491(6)
˚
bond
distances
(A)
and
Angles
(8)
for
Re–O(2)
Re–C(4)
O(1)–C(1)
O(3)–C(3)
O(5)–C(5)
[Ru(bpy)2(CO)(OCHO)]PF2O2 (4b)
Bond distances
Ru–O(2)
Ru–N(2)
Ru–N(4)
O(1)–C(1)
O(3)–C(2)
2.060(4)
2.061(5)
2.072(5)
1.151(7)
1.224(8)
Ru–N(1)
Ru–N(3)
Ru–C(1)
O(2)–C(2)
2.057(5)
2.112(5)
1.838(8)
1.253(8)
Bond angles
P–Re–O(1)
84.58(7)
176.6(1)
89.5(1)
94.7(1)
109.2(1)
104.6(1)
87.7(2)
86.8(2)
92.4(2)
121.2(4)
176.2(4)
178.7(3)
P–Re–O(2)
P–Re–C(4)
89.88(7)
93.9(1)
59.42(9)
163.9(1)
92.6(1)
168.6(1)
87.6(2)
90.7(2)
P–Re–C(3)
P–Re–C(5)
Bond angles
O(1)–Re–O(2)
O(1)–Re–C(4)
O(2)–Re–C(3)
O(2)–Re–C(5)
C(3)–Re–C(5)
Re–O(1)–C(1)
O(1)–C1–O(2)
O(2)–C(1)–C(2)
Re–C(4)–O(4)
O(2)–Ru–N(1)
O(2)–Ru–N(3)
O(2)–Ru–C(1)
N(1)–Ru–N(3)
N(1)–Ru–C(1)
N(2)–Ru–N(4)
N(3)–Ru–N(4)
N(4)–Ru–C(1)
Ru–C(1)–O(1)
93.5(2)
81.9(2)
96.2(2)
96.7(2)
89.4(2)
101.5(2)
78.1(2)
95.8(2)
178.8(6)
O(2)–Ru–N(2)
O(2)–Ru–N(4)
N(1)–Ru–N(2)
N(1)–Ru–N(4)
N(2)–Ru–N(3)
N(2)–Ru–C(1)
N(3)–Ru–C(1)
Ru–O(2)–C(2)
O(2)–C(2)–O(3)
167.4(2)
85.6(2)
78.5(2)
174.7(2)
89.3(2)
93.5(2)
173.7(2)
125.4(5)
127.0(7)
O(1)–Re–C(3)
O(1)–Re–C(5)
O(2)–Re–C(4)
C(3)–Re–C(4)
C(4)–Re–C(5)
Re–O(2)–C(1)
O(1)–C(1)–C(2)
Re–C(3)–O(3)
Re–C(5)–O(5)
117.5(4)
121.1(4)
178.5(4)

D.H. Gibson et al. / Polyhedron 18 (1999) 1189–1200
1193
Fig. 4. DRIFTS spectra (1800–950 cm21) for complexes 1, 5, and 7.
Fig. 5. DRIFTS spectra (1800–950 cm21) for complexes 4a, 8, and 15.
In the example compounds, those with h1-coordinated
formate ligands show the carboxyl nasym band in the region
value of Dn for the bridging type of 225 cm21 while Dn
for the h2-type is 216 cm21 for the available examples;
clearly, it is not a large enough difference to be definitive.
Although the compounds in Table 4 vary from metal-
locenes with pseudotetrahedral geometry at the metal to
square planar and octahedral complexes, there is not yet
any discernible pattern of dependence of the band positions
in these compounds on structural factors or geometry at the
metal center.
1603–1652 cm21 and the nsym band at 1253–1329 cm21
;
the median value of Dn is 337 cm21. In some cases,
isotopic labeling has been done to provide further con-
firmation of carboxylate band assignments. For example,
the IR spectrum of the structurally characterized trans-
Ru(dmpe)2(h1-OCHO)(H) shows bands for the carbox-
ylate at 1603 and 1329 cm21; use of 13CO2 in the
preparation of the compound gives a product with these
bands lowered to 1564 and 1309 cm21, respectively [34].
This technique is certainly necessary when there is severe
overlapping of bands from other ligands with those of the
carboxylate group. Usually, however, it is not necessary
now because the general position of these bands is well
known [11–13] and comparisons with spectra from other
closely related compounds in a series (e.g., those with a
halide instead of a carboxylate ligand, but otherwise the
same) will usually allow the identification of the nOCO
bands to be done.
The single example compound with a m2-h1-coordinated
formate ligand shows the carboxyl nasym band at 1664
cm21, well above the analogous band in simple h1-type
complexes. Also, the nsym band is at much lower frequency
(1205 cm21) than in the h1 complexes, leading to a large
Dn of 459 cm21 which easily identifies the bonding type
as distinct from the others.
Examination of the DRIFTS spectra in the region 1800–
950 cm21 for an h1 acetate, as illustrated by 8 in Fig. 5,
shows the problem which attends the assignment of bands
for the carboxylate stretching vibrations in acetate com-
plexes. There are three vibrations for the acetate ligand in
this region: nasym and nsym for the carboxylate and dC–H for
the methyl group. For 8, the band at 1605 cm21 and the
series of weak bands centered at approximately 1470 cm21
are due to the bipyridine ligand; the bands at 1621, 1380
and 1317 cm21 are due to the acetate ligand. By analogy
The h2- and m2 –h2-types of chelated complexes, for
which data is shown in Table 4, exhibit the nasym band well
below 1600 cm21 and the nsym band appears above 1300
cm21. The asymmetric stretching band in the compounds
with bridging ligands appears at slightly higher frequency
than the nasym band in compounds having both carboxyl
oxygens bound to a single metal. This results in a median

1194
D.H. Gibson et al. / Polyhedron 18 (1999) 1189–1200
Table 4
Carboxylate stretching frequencies of formate complexes
Compound
Structure assignment
Bonding
nasym (CO2)
nsym (CO2)
Dn
Ref
a
Cp2Ti(CH3)(OCHO) (2)
Cp2Ti(OCHO)2 (3)
trans-(PCy3)2Pt(H)(OCHO)
CpFe(CO)2(OCHO)
spectroscopy
X-ray
X-ray
X-ray
X-ray
spectroscopy
spectroscopy
spectroscopy
X-ray
X-ray
X-ray
h1
h1
h1
h1
h1
h1
h1
h1
h1
h1
h2
h2
h2
h2
h2
1652, 1636
1644
1620
1620
1630
1625
1616
1621
1621
1603
1585
1547
1553
1555
1570
1270, 1253
1290 (1273)
1310
1293
1280
1278
1289
1282
1282
1329
1350
1358
1310
1358
1360
366–399
354 (371)
310
327
350
347
327
339
339
274
235
189
243
197
210
a, [15]
[41]
[3]
fac-Re(bpy)(CO)3(OCHO)b
cis-Re(CO)4(PPh3)(OCHO) (1)
mer, trans-Re(CO)3(PPh3)2(OCHO) (5)
cis-[Ru(bpy)2(CO)(OCHO)]1PF6- b (4a)
cis-[Ru(bpy)2(CO)(OCHO)]1PO2F2 (4b)
trans-Ru(dmpe)(OCHO)(H)c
(PPh3)2Cu(OCHO)
[42,43]
a
a
a
a
[44]
[10,45]
a
cis, trans-Re(CO)2(PPh3)2(OCHO) (6)
mer-Ru(H)(PPh3)3(OCHO)
trans-Ru(CO)(PPh3)2(HC5CHPh)(OCHO)
Mo(H)(PMe3)4(OCHO) (trans H and
formate)
spectroscopy
X-ray
X-ray
[46,47]
[5]
[48]
X-ray
[CpTi(OCHO)]2(C10H8)
X-ray
X-ray
X-ray
spectroscopy
spectroscopy
spectroscopy
spectroscopy
m2 –h1
m2 –h2
m2 –h2
m2 –h2
m2 –h2
m2 –h2
m2 –h2
1664
1595
1590
1590
1570
1560
1563
1205
1349
1354
1358
1345
1315
1395
459
246
236
232
225
245
168
[49]
[50]
[51]
[51]
[51]
[Pd(PPh3)(Me)(OCHO)]2
[Rh(cod)(OCHO)]2d
[Rh(cod)(OCHO)Rh(CO)2d
[Rh(CO)2(OCHO)]2
[CpRe(NO)(CO)]2(OCHO)
cis, cis–[Re(CO)4(PPh3)]2(OCHO)1PF62
(7)
[52]
a
a
IR data from this work.
bpy52, 29-bipyridine.
dmpe5bis(1,2-dimethylphosphino)ethane.
cod51, 5-cyclooctadiene.
b
c
d
with organic acetates [11–13], the band at 1380 cm21 is
assigned to the symmetric scissoring vibration of the
acetate methyl group; the other two bands are assigned to
nasym and nsym of the carboxylate ligand, respectively. This
particular problem may not be resolved readily by prepar-
ing the isotopically substituted compound since all three
bands will sometimes move [11–13].
All of the compounds in Fig. 6 have triphenylphosphine
ligands which show a pair of bands in this region, typically
at 1430 and 1480 cm21, in addition to those of the
carboxylates. For the h2-coordinated acetate complexes,
only the manganese complex 11 clearly shows all of the
expected bands; in the other acetate complexes, there is
overlapping of one of the bands of the phosphine ligand
with one of the nOCO bands of the acetate ligand. As is the
case with h2-coordinated formate complexes (spectra of
compound 6 shown in Fig. 6 for comparison), the car-
boxylate nasym band in the acetates moves to lower
frequency; however, both of the other acetate bands in the
compound move to higher frequency. The bands for the
acetate ligand, in this region, in 11 are assigned as follows:
nasym at 1521 cm21, nsym at 1425 cm21 and dC–H at 1460
shown in Fig. 6 (compare the intensities of the carboxylate
bands against those for the phosphine ligands, in the 1430
and 1480 cm21 region, in these two compounds and the
same bands in any of the complexes illustrated in Fig. 4).
The reduction in intensities of the carboxylate bands is a
characteristic of h2-type formates and acetates as com-
pared to their h1-type counterparts. The bands due to the
triphenylphosphine ligands in 11 are thus identified as the
ones at 1471 cm21 and 1435 cm21, band positions which
are typical of these ligands in this region. The Dn for the
h2-type acetate complex, 11, is 106 cm21 and is much
smaller than the value for monodentate acetate complexes
(as is observed in comparisons of these two types of
formates).
Summary data for the nOCO bands for three bonding
types of acetate complexes are listed in Table 5. For the
h1-type complexes, the nasym band position is similar to
that for the related formate complexes; a range of 1612 to
1646 cm21 is observed. However, the nsym band is at
higher frequency (1300–1323 cm21) than in the formate
complexes giving a median value for Dn of 316 cm21. For
the h2-type acetates (Table 5) the nasym bands vary from
1515 to 1562 cm21 and the nsym band position varies from
1411 to 1425 cm21. However, there are some structural
differences among the example compounds; X-ray data
have been obtained recently for In(tpp)(OCOCH3) (tpp5
meso-tetraphenylporphyrin) which show differences in the
cm21. For comparison, the structurally characterized ben-
zoate complex, mer-Ir[P(CH3)3](H)(h2-O2CPh), shows the
carboxylate bands at 1510 and 1428 cm21 [35]. Note that
the intensities of the bands assigned to the carboxylate in
11 are very low as are the ones in the h2-type formate 6

D.H. Gibson et al. / Polyhedron 18 (1999) 1189–1200
1195
the carboxylate nOCO bands is in the formate complex, (339
cm21); the trifluoroacetate shows Dn5298 cm21 and the
acetate shows a separation of 304 cm21 for these bands.
Also, the acetate methyl C–H bending vibration is readily
seen at 1360 cm21. Particularly noteworthy is the vastly
reduced intensity of the nsym band (1403 cm21) in the
trifluoroacetate complex relative to the nasym band; this
appears to be a characteristic of the h1-type of trifluoroace-
tate complex. Strong bands in the 1200 cm21 region are
assigned to vibrations of the CF3 group [11–13,37–40].
Examples of complexes demonstrating just two bonding
types for the trifluoroacetate ligand are available and are
shown in Table 5. Because the electron-withdrawing
characteristics of the CF3 group reduces the nucleophilicity
of the carbonyl oxygen in the h1 complexes, ligand
displacement reactions which are used to prepare h2-type
formates and acetates will not proceed with trifluoroace-
tates. Only the h1 and m2 –h2-types are available for
comparison. The electron-withdrawing characteristics of
the trifluoromethyl group are also responsible for moving
the nasym band in both classes of compounds to higher
frequency values (1685–1713 cm21 in the h1-type and at
1682 cm21 in the one example bridging type); the band in
the h1 trifluoroacetate complexes is highest for this type,
but does not change very much for the bridging complexes.
The Dn for the h1 type of trifluoroacetate is relatively large
at a median value of 293 cm21 and much less, 228 cm21
for the bridging type.
,
2. Conclusions
Spectral data for four distinct classes of formate com-
plexes and three classes of acetates are now available, but
the low donor characteristics of the trifluoroacetoxy oxy-
gen atoms make the CF3CO2 group a much less versatile
ligand and limits its complexes to those in which this
ligand is monodentate at each metal center. In addition to
the bonding type, the nature of the R group in the
carboxylate ligand, OC(O)R, has a large impact on the IR
band positions for nOCO in all classes of compounds. The
electron-withdrawing CF3 group has the greatest impact,
moving both carboxylate bands to higher frequencies than
those in the corresponding formate and acetate complexes.
For formate and acetate complexes, the intensities of both
nOCO bands in compounds with h2-coordinated ligands are
much reduced as compared to their h1-bound analogs. For
example, compare the spectra for formate 5 (h1) in Fig. 4
to that for formate 6 (h2) in Fig. 6; both compounds have
two triphenylphosphine ligands.
Fig. 6. DRIFTS spectra (1800–950 cm21) for complexes 6, 9, 10, and 11.
˚
In–O bond lengths: 2.322(4) and 2.215(4) A [36]. The
investigators described the bonding as ‘‘asymmetric bi-
dentate’’ and noted that Dn for the compound is sig-
nificantly larger (141 cm21) than is typical for complexes
with symmetrically-bound h2-type acetate groups.
As with formate complexes, compounds having m2 –h2-
bound acetate ligands can exist in several different geomet-
ric forms. The compounds listed in Table 5 are ones that
are structurally constrained to be of the syn, syn type. Both
carboxyl C–O stretching bands are moved to higher
frequencies in comparison to the h2-bound types; the Dn
for the examples shown has an average value of 111 cm21
.
This value is very similar to the median of 104 cm21 for
the symmetrically bonded h2 complexes of this type (first
three entries of the h2 type in Table 5).
Fig. 5 shows DRIFTS spectra of h1-type formate,
acetate and trifluoroacetate complexes derived from the
cis-Ru(bpy)2(CO)1 fragment. All of the compounds show
three weak bands in the 1450 cm21 region which are due
to the bipyridine ligands; they differ slightly in intensity
from one compound to another. The widest separation of
The Dn values, within each ligand type, vary regularly
with the nature of bonding to the metal centers. Com-
pounds with chelated carboxyl oxygens have much smaller
Dn values than their monodentate counterparts, although
the type of chelation (h2 or m2 –h2) doesn’t appear to have
further impact. Additionally, with the complexes having

1196
D.H. Gibson et al. / Polyhedron 18 (1999) 1189–1200
Table 5
Carboxylate stretching frequencies of acetate and trifluoroacetate complexes
Compound
Structure
Bonding
nasym (CO2)
nsym (CO2 )
Dn
Ref
assignment
Cp2Ti(CH3)(OCOCH3)
spectroscopy
spectroscopy
spectroscopy
X-ray
h1
h1
h1
h1
1646
1612
1621
1625 (1595)
1300
1323
1317
1308
346
289
304
317
(287)
103
105
106
141
98
125
279
287
273
298
307
(292)
228
[53]
mer, trans-Re(CO)3(PPh3)2(OCOCH3)
cis-[Ru(bpy)2(CO)(OCOCH3)]1PF62 (8)
Pt(dppf)(OCOCH3)2c
a, [17]
a
[54]
a
fac-Re(CO)3(PPh3)(OCOCH3) (9)
cis, trans-Re(CO)2(PPh3)2(OCOCH3) (10)
fac-Mn(CO)3(PPh3)(OCOCH3) (11)
In(tpp)(OCOCH3)
[Rh(CO)(PCy3)]2(OCOCH3)(m-s, s-C5C5CPh2)
[Rh(CO)(PCy3)]2(OCOCH3)(m-h1:h2-C2Ph)
Cp2Ti(CH3)(OCOCF3) (12)
cis-Re(CO)4(PPh3)(OCOCF3) (13)
mer, trans-Re(CO)3(PPh3)2(OCOCF3) (14)
cis-[Ru(bpy)2(CO)(OCOCF3)]1PF62 (15)
Pt(dppm)(OCOCF3)2b
X-ray
X-ray
spectroscopy
X-ray
X-ray
h2
1515
1516
1521
1562
1538
1575
1701
1698
1412
1411
1425
1421
1440
1450
1422
1411
1412
1403
1406
h2
,
a
a
17
h2
h2
[36]
[55]
m2 –h2
m2h2
h1
X-ray
[56]
a
spectroscopy
spectroscopy
spectroscopy
spectroscopy
X-ray
h1
a
a
a
h1
1685
1701
1713 (1698)
h1
h1
[54]
[57]
Re2(NBut)4(m-O)(m-OSiMe3)3(OCOCF3)
X-ray
m22h2
1682
1454
a
IR data from this work.
dppm5bis(diphenylphosphino)methane.
dppf51, 19-bis(diphenylphosphino)ferrocene.
b
c
chelated carboxyl ligands, the nOCO bands shift their
positions greatly, with the nasym band moving to lower
frequency and the nsym band moving to higher frequency,
as compared to the monodentate complexes.
Mattson RS-1 FTIR Spectrometer using a Minidiff
DRIFTS accessory (Graseby Specac. Inc.). Melting points
were determined on a Thomas-Hoover capillary melting
point apparatus and are uncorrected. Elemental analyses
were performed by Midwest Microlab, Indianapolis, IN.
3. Experimental
3.2. Synthesis of cis-Re(CO)4(PPh3 )(h1-OCHO) (1)
3.1. General procedures.
Cis-Re(CO)4(PPh3)(CH3) (0.20 g, 0.35 mmol) was
placed in a flask, followed by excess formic acid (5 ml).
The mixture was heated to 508C with stirring for 2 h, then
cooled to room temperature and evaporated to dryness. The
residue was triturated with hexane, then the hexane
extracts were evaporated under vacuum to leave a white
solid (quantitative yield), mp 1098C.
All reactions were carried out under a nitrogen atmos-
phere either in Schlenkware or in a Vacuum Atmospheres
glovebox. The solvents used in the glovebox were distilled
under N2 from the following drying agents: CH2Cl2 with
P2O5 hexanes and toluene with Na/benzophenone. Re-
agent grade acetonitrile, ethanol, and diethyl ether were
used as received without further purification. Formic acid
(95%, aqueous), acetic acid, and trifluoroacetic acid were
purchased from Aldrich Chemical Co. and used as re-
ceived. cis-Re(CO)4(PPh3)(CH3) [58], cis-Re(CO)4-
(PPh3)(FBF3) [20], mer, trans-Re(CO)3(PPh3)2H [21],
mer, trans-Re(CO)3(PPh3)2(h1-OCOCH3) [17], cis-
Anal. calcd for C23H16O6PRe: C, 45.62; H, 2.66.
Found: C, 45.54; H, 2.70. IR (DRIFTS, KCl): nCO 2101,
2018, 1983, and 1960 cm21; nOCO 1626 and 1277 cm21
.
1H NMR (CDCl3): d 7.64 (s, OCHO); 7.45 (m, Ph). 13C
NMR (CDCl3): d 187.45 (s, CO); 187.38 (s, CO); 184.32
(d, JCP553.7 Hz, CO); 168.22 (d, JCP51.2 Hz, OCHO);
133.39 (d, JCP511.7 Hz, Ph); 131.28 (d, JCP547.8 Hz,
Ph); 131.14 (d, JCP51.2 Hz, Ph); 128.86 (d, JCP510.1 Hz,
Ph). 31P NMR (CDCl3): d 12.11.
[Ru(bpy)2(CO)H]PF6
[59],
and
Cp2Ti(CH3)(h1-
OCOCH3) [53] were prepared according to literature
1
methods. The H, 13C, and 31P NMR spectra were recorded
on a Bruker AMX-500 spectrometer; the 1H and 13C
chemical shifts were referenced to residual protons and
carbons in the deuterated solvents, respectively. The 31P
chemical shifts were determined using H3PO4(85%) as the
external standard. Infrared spectra were obtained by the
DRIFTS technique (diffuse reflectance infrared Fourier
transform spectroscopy [60]) and were recorded on an ATI
3.3. Synthesis of Cp2Ti(CH3 )(h1-OCHO) (2)
Cp2Ti(CH3)2 [61], 0.52 g (2.50 mmol), was dissolved
in CH2Cl2 (20 ml), formic acid (0.10 ml, 95%, 2.5 mmol)
was added and the mixture was stirred for 30 min. The
mixture was evaporated to dryness under vacuum and the

D.H. Gibson et al. / Polyhedron 18 (1999) 1189–1200
1197
residue was recrystallized from CH2Cl2 /hexanes to yield a
red solid, 0.55 g (92%), mp 117–1188C (dec).
mixture was heated at reflux for 30 min. The solvent was
removed under vacuum to yield a white solid, 0.105 g
(quantitative yield).
Anal. calcd for C12H14O2Ti: C, 60.53; H, 5.93. Found:
C, 60.72; H, 6.20. IR (DRIFTS, KCl): nOCO 1652, 1636,
IR (DRIFTS, KCl): nCO 2045, 1943, and 1902 cm21
;
1
1270, and 1258 cm21. H NMR (CD2Cl2): d 8.07 (s, 1,
nOCO 1616 and 1289 cm21 (lit. [17]: nCO 2040, 1950, and
1900 cm21; nOCO 1620 and 1300 cm21). 1H NMR
(CDCl3): d 7.54–7.34 (m, Ph); 7.07 (s, OCHO). 13C NMR
(CDCl3): d6 195.08 (t, JCP56.1 Hz, CO); 194.41 ((t,
JCP59.2 Hz, CO); 167.89 (s, OCHO); 133.70 (t, JCP55.6
Hz, Ph); 133.28 (t, JCP523.9 Hz, Ph); 130.22 (s, Ph);
128.25 (t, JCP55.1 Hz, Ph). 31P NMR (CDCl3): d 18.38.
OCHO); 6.19 (s, 10, Cp); 0.70 (s, 3, CH3). 13C NMR
(CD2Cl2): d 166.23 (OCHO); 115.07 (Cp); 45.99 (CH3).
3.4. Characterization data for Cp2Ti(h1-OCHO)2 (3)
[16]
Anal. calcd for C12H12O4Ti: C, 53.76; H, 4.51. Found:
C, 53.68; H, 4.47. IR (DRIFTS, KCl): nOCO 1644, 1290,
and 1273 cm21. 1H NMR (CD2Cl2): d 8.46 (s, 2, OCHO);
6.55 (s, 10, Cp). 13C NMR (CD2Cl2): d 167.05 (OCHO);
119.10 (Cp).
3.8. Synthesis of cis, trans-Re(CO)2(PPh3 )2(h2-OCHO)
(6)
Mer, trans-Re(CO)3(PPh3)2(h1-OCHO) (0.05 g, 0.06
mmol) was dissolved in toluene (10 ml) and the solution
was heated at reflux for 1 h. After cooling to room
temperature, the solvent was removed under vacuum
leaving a white residue which was washed with ethanol
(435 ml) then dried under vacuum, 0.04 g (81%).
3.5. Synthesis of cis-[Ru(bpy)2(CO)(h1-OCHO)]PF6 (4a)
Cis-[Ru(bpy)2(CO)(H)]PF6 (0.100 g, 0.17 mmol) was
placed in a flask, formic acid (5 ml) was added and the
mixture was stirred for 1 hr. The mixture was evaporated
to dryness under vacuum, then dissolved in CH3CN (10
ml) and treated with excess NH4PF6 (aq, 10 ml) to afford
anion-exchange. The resulting solution was concentrated to
half of its original volume and a yellow solid which
precipitated was collected by filtration and dried under
vacuum, 0.095 g (88%), mp.2508C.
IR (DRIFTS, KCl): nCO 1925 and 1849 cm21; nOCO
1547 and 1358 cm21 (lit. [17]: nCO, 1930 and 1850 cm21
;
nOCO, 1550 and 1360 cm21). 1H NMR (CDCl3): d 7.83 (t,
J
HP53.6 Hz, OCHO); 7.44–7.37 (m, Ph). 13C NMR
(CDCl3): d 201.46 (t, JCP57.1 Hz, CO); 173.86 (t, JCP5
2.0 Hz, OCHO); 134.17 (t, JCP56.1 Hz, Ph); 132.47 (t,
JCP522.9 Hz, Ph); 130.05 (s, Ph); 128.28 (t, JCP55.1 Hz,
Ph). 31P NMR (CDCl3): d 33.65.
IR (DRIFTS, KCl): nCO 1972 cm21; nOCO 1621
1
and 1281 cm21 (lit. [16] (CH2Cl2): nCO 1984 cm21). H
NMR (CD3CN): d 9.54 (d, J55.7 Hz, bpy); 8.85 (d,
J55.7 Hz, bpy); 7.83 (s, OCHO); 8.52–7.27 (m, bpy). 13
C
3.9. Synthesis of cis, cis-([Re(CO)4(PPh3 )]2(m2 –h2-
OCHO)]BF4 (7)
NMR (CD3CN): d 201.67 (CO); 169.04 (OCHO);
158.05–124.54 (20 resonances, bpy).
Cis-Re(CO)4(PPh3)(h1-OCHO) (1; 0.07 g, 0.12 mmol)
and cis-Re(CO)4(PPh3)(FBF3) (0.08 g, 0.12 mmol) were
combined in a flask. CH2Cl2 (10 ml) was added. The
mixture was stirred for 1 h and then solvent was removed
under vacuum to afford a white solid, 0.150 g (quantitative
yield), mp 1148C.
Anal. calcd for C45H31BF4O10P2Re2: C, 43.14; H, 2.49.
Found: C, 42.83; H, 2.62. IR (DRIFTS, KCl): nCO 2114,
2012, and 1955 cm21 nOCO 1562 and 1359 cm21. 1H NMR
(CD2Cl2): d, 7.58–7.38 (m, Ph); 6.94 (s, OCHO);. 13C
NMR (CD2Cl2): d 186.90 (d, JCP58.8 Hz, CO); 185.64
(d, JCP56.3 Hz, CO); 183.73 (d, JCP552.5 Hz, CO);
177.84 (s, OCHO); 135.55 (d, JCP510.1 Hz, Ph); 132.40
(d, JCP51.2 Hz, Ph); 129.85 (d, JCP549.0 Hz, Ph); 129.45
(d, JCP510.1 Hz, Ph). 31P NMR (CD2Cl2): d 13.31.
3.6. Synthesis of cis-[Ru(bpy)2(CO)(h1-OCHO)]PF2O2
(4b)
Cis-[Ru(bpy)2(CO)(H)]PF6 (0.12 g, 0.20 mmol) was
placed in a flask, formic acid (5 ml) was added. The
mixture was heated to reflux for 1 hr, then formic acid was
removed under vacuum. The residue was extracted with
CH3CN (20 ml) and the extract filtered. Ether (60 ml) was
added to precipitate a yellow solid; the solid was re-
crystallized from CH3CN/ether to yield yellow crystals,
0.043 g (36%).
Anal. calcd for C22H17F2N4O5PRu: C, 44.98; H, 2.92.
1
Found: C, 45.39; H, 3.06. The H and 13C NMR spectral
properties are identical to those of cis-[Ru(bpy)2(CO)(h1-
OCHO)]PF6 (4a). 31P NMR (CD3CN): d 212.93 (t, JPF5
948.0 Hz).
3.10. Synthesis of cis-[Ru(bpy)2(CO)(h1-OCOCH3 )]PF6
(8)
3.7. Synthesis of mer, trans-Re(CO)3(PPh3 )2(h1-OCHO)
(5)
Cis-[Ru(bpy)2(CO)(H)]PF6 (0.05 g, 0.08 mmol) was
placed in a flask together with acetic acid (5 ml). The
mixture was heated at 608C for 2.5 h, then acetic acid was
Mer, trans-Re(CO)3(PPh3)2(H) (0.10 g, 0.13 mmol)
was placed in a flask. Formic acid (10 ml) was added. The

1198
D.H. Gibson et al. / Polyhedron 18 (1999) 1189–1200
removed under vacuum. The residue was dissolved in
CH3CN (10 ml) and treated with NH4PF6 (aq, 10 ml) to
afford anion-exchange. The resulting solution was concen-
trated to half of its original volume, resulting in precipi-
tation of a yellow solid which was collected by filtration
and dried under vacuum, 0.04 g (76%), mp.2508C.
Anal. calcd for C23H19F6N4O3PRu: C, 42.80; H, 2.97.
Found: C, 42.50; H, 3.04. IR (DRIFTS, KCl): nCO 1964
work [22]. It showed IR(DRIFTS, KCl) nCO 2030, 1949,
1913 cm21; nOCO 1521 and 1415 cm21. 1H NMR (CDCl3):
d 7.41 (m, 15H, Ph); 1.02 (s, 3H, CH3). 13C NMR
(CDCl3) d 222.63 (CO); 212.67 (CO); 185.84 (OCO);
134.27 (d, JPC58.1 Hz, Ph); 136.63 (s, Ph); 130.17 (d,
JPC538.1 Hz, Ph); 128.56 (d, JPC56.1 Hz, Ph), 22.92 (s,
CH3).
1
cm21 nOCO 1621 and 1317 cm21. H NMR (CD3CN): d
3.14. Synthesis of Cp2Ti(CH3 )(h1-OCOCF3 ) (12)
9.55 (d, J55.7 Hz, bpy); 8.88 (d, J55.7 Hz, bpy); 8.49–
7.25 (m, bpy) 1.70 (s, CH3). 13C NMR (CD3CN): d 201.95
(CO); 177.78 (OCO); 158.21–124.44 (20 resonances,
bpy); 23.21 (CH3).
Cp2Ti(CH3)2 (1.60 g, 7.69 mmol) was dissolved in
CH2Cl2 (20 ml) and cooled to 08C. Trifluoroacetic acid
(0.60 ml, 99%, 7.7 mmol) was added dropwise. The
mixture was stirred for 30 min. The solvent was removed
under vacuum. The residue was recrystallized from
toluene/hexanes to yield a red solid, 2.12 g (90%), mp
117–1188C (dec).
Anal. calcd for C13H13F3O2Ti: C, 51.00; H, 4.28.
Found: C, 51.14; H, 4.38. IR (DRIFTS, KCl): nOCO 1700
and 1240 cm21. 1H NMR (C6D6): d 5.62 (s, 10, Cp); 0.97
(s, 3, CH3). 13C NMR (C6D6): d 160.06 (q, JCF539.1 Hz,
OCO); 115.41 (Cp); 51.06 (CH3).
3.11. Synthesis of fac-Re(CO)3(PPh3 )(h2-OCOCH3 ) (9)
Cis-Re(CO)4(PPh3)(CH3) (0.103 g, 0.18 mmol) was
placed in a flask together with acetic acid (5 ml). The
mixture was stirred at 608C for 6 h, then acetic acid was
removed under vacuum. The residue was recrystallized
from CH2Cl2 /hexane to yield colorless crystals, 0.079 g
(73%), mp 195–1968C.
Anal. calcd for C23H18O5PRe: C, 46.70; H, 3.07.
Found: C, 46.60; H, 3.14. IR (DRIFTS, KCl): nCO 2030,
1937, and 1901 cm21 nOCO 1515 and 1412 cm21. 1H NMR
(CDCl3): d, 7.50–7.33 (m, Ph); 1.10 (s, CH3). 13C NMR
(CDCl3): d 195.18 (d, JCP57.1 Hz, CO); 190.47 ((d,
JCP572.7 Hz, CO); 189.18 (d, JCP52.5 Hz, OCO); 134.24
(d, JCP511.2 Hz, Ph); 130.91 (d, JCP52.0 Hz, Ph); 129.33
(d, JCP545.3 Hz, Ph); 128.74 (d, JCP59.7 Hz, Ph); 24.09
(s, CH3). 31P NMR (CDCl3): d 29.33.
3.15. Synthesis of cis-Re(CO)4(PPh3 )(h1-OCOCF3 ) (13)
Cis-Re(CO)4(PPh3)(CH3) (0.20 g, 0.35 mmol) was
dissolved in CH2Cl2 (10 ml) and trifluoroacetic acid
(0.030 ml) was added. The mixture was stirred for 30 min.
Then the mixture was evaporated to dryness under vac-
uum. The gummy residue was treated with hexane. The
hexane was removed under vacuum to leave a white solid,
0.23 g (quantitative yield), mp 928C.
3.12. Synthesis of cis, trans-Re(Co)2(PPh3 )2(h2-
OCOCH3 ) (10)
Anal. calcd for C24H15F3O6PRe: C, 42.79; H, 2.24.
Found: C, 42.70; H, 2.25. IR (DRIFTS, KCl): nCO 2105,
1
2003, and 1958 cm21; nOCO 1698 and 1410 cm21. H
This compound was prepared by a modification of the
previous method [16]. Mer, trans-Re(CO)3(PPh3)2(H)
(0.10 g, 0.13 mmol) was placed in a flask together with
acetic acid (10 ml). The mixture was heated to 858C for 5
h, then acetic acid was removed under vacuum. The white
residue was washed with ethanol (435 ml) and dried
under vacuum, 0.08 g (91%).
NMR (CDCl3): d, 7.50–7.45 (m, Ph). 13C NMR (CDCl3):
d, 186.94 (d, JCP55.6 Hz, CO); 186.83 (d, JCP59.2 Hz,
CO); 183.86 (d, JCP556.0 Hz, CO); 162.25 (d of q,
JCP52.0 Hz, JCF537.6 Hz, OCO); 133.23 (d, JCP511.2
Hz, Ph); 131.34 (d, JCP52.5 Hz, Ph); 130.73 (d, JCP548.8
Hz, Ph); 129.02 (d, JCP510.2 Hz, Ph); 114.23 (q, JCF5
289.4 Hz, CF3). 31P NMR (CDCl3): d 11.88.
IR (DRIFTS, KCl): nCO 1925 and 1851 cm21; nOCO
1516 and 1411 cm21 (lit. [17]: nCO 1930 and 1850 cm21
3.16. Synthesis of mer, trans-Re(CO)3(PPh3 )2(h1-
OCOCF3 ) (14)
1
nOCO, 1515 cm21). H NMR (CDCl3): d 7.43–7.38 (m,
Ph); 0.42 (s, CH3). 13C NMR (CDCl3): d 201.88 (t,
JCP57.1 Hz, CO); 185.59 (t, JCP54.0 Hz, OCO); 134.24
(t, JCP55.6 Hz, Ph); 132.56 (t, JCP522.4 Hz, Ph); 129.87
(s, Ph); 128.20 (t, JCP54.6 Hz, Ph); 23.49 (s, CH3). 31P
NMR (CDCl3): d 33.14.
This compound was prepared by a modification of the
literature method [23]. Mer, trans-Re(CO)3(PPh3)2(H)
[21] (0.20 g, 0.25 mmol) was dissolved in CH2Cl2 (20
ml). The solution was then heated to reflux and CF3COOH
(1 ml) was added. The mixture was kept at reflux for 30
min then evaporated to dryness under vacuum. The residue
was washed with ethanol (4315 ml) and dried under
vacuum (0.20 g (90%).
3.13. Spectral properties of fac-Mn(CO)3(PPh3 )(h2-
OCOCH3 ) (11)
A sample of this compound was available from previous
IR (DRIFTS, KCl): nCO 2053, 1952, and 1901 cm21

D.H. Gibson et al. / Polyhedron 18 (1999) 1189–1200
1199
nOCO 1685 and 1412 cm21 (lit. [17]: nCO 2040, 1950, and
1895 cm21; nOCO 1680 and 1410 cm21). 1H NMR
(CD2Cl2): d 7.59–7.36 (m, Ph). 13C NMR (CD2Cl2): d
194.85 (t, JCP55.6 Hz, CO); 194.37 (t, JCP58.8 Hz, CO);
162.60 (q, JCF536.3 Hz OCO); 133.84 (t, JCP55.6 Hz,
Ph); 133.16 (t, JCP524.1 Hz, Ph); 130.94 (s, Ph); 128.92 (t,
JCP55.0 Hz, Ph); 114.32 (q, JCF5283.8 Hz, CF3). 31P
NMR (CD2Cl2): d 17.67.
variables. All calculations were performed using the
teXsan package (Molecular Structure Corporation) [62].
3.19. X-ray crystal structure of fac-Re(CO)3(PPh3 )(h2-
OCOCH3 ) (9)
A
colorless crystal of fac-Re(CO)3(PPh3)(h2-
OCOCH3), grown from CH2Cl2 /hexanes at 2308C, was
mounted on a glass fiber with epoxy cement. Data were
collected on an Enraf-Nonius CAD-4 diffractometor
equipped with a graphite monochromator. Crystal data,
data collection, and refinement parameters are listed in
Table 1. Of 5312 unique reflections, 3808 were considered
observed (I.3s(I)). The structure was solved by direct
methods. An empirical correction for absorption (C scans)
was applied. All non-hydrogen atoms were refined with
anisotropic thermal parameters. The hydrogen atoms were
located by difference maps and included as fixed contribu-
tions (B51.2 B of attached atom). A final R index of 0.022
was obtained for 272 variables. All calculations were
performed using the teXsan package (Molecular Structure
Corporation) [62].
3.17. Synthesis of cis-[Ru(bpy)2(CO)(h1-OCOCF3 )]PF6
(15)
Cis-[Ru(bpy)2(CO)(H)]PF6 (0.05 g, 0.08 mmol) was
dissolved in CH2Cl2 (10 ml) then trifluoroacetic acid (1
ml) was added. The mixture was stirred for 20 min then
evaporated to dryness under vacuum. The residue was
dissolved in CH2Cl2 (5 ml); diethyl ether (20 ml) was then
added to precipitate a yellow solid. The solid was collected
by filtration and dissolved in CH3CN (10 ml) and treated
with NH4PF6 (aq, 10 ml) to afford anion-exchange. The
resulting solution was concentrated to half of its original
volume and the yellow solid which precipitated was
collected by filtration and dried under vacuum, 0.04 g
(60%), mp.2508C.
3.20. Supplementary materials
Anal. calcd for C23H,6F9N4O3PRu: C, 39.49; H, 2.31.
Found: C, 39.58; H, 2.55. IR (DRIFTS, KCl): nCO 1990
cm21; nOCO 1701 and 1403 cm21. 1H NMR (CD3CN): d
9.55 (d, J55.7 Hz, bpy); 8.76 (d, J55.7 Hz, bpy); 8.56–
7.28 (m, bpy). 13C NMR (CD3CN): d 200.48 (CO); 163.66
(q, JCF535.6 Hz, OCO); 158.22–124.68 (20 resonances,
bpy); 114.70 (q, JCF5289.9 Hz, CF3).
Tables of bond lengths, bond distances, positional and
isotropic thermal parameters and general displacement
parameters for 4b and 9 are provided in the Supplementary
Materials which have been deposited at the Cambridge
Crystallographic Data Base.
Acknowledgements
3.18. X-ray crystal structure of [cis-
Ru(bpy)2(CO)(OCHO)]PF2O2 (4b)
Support of this work by the National Science Founda-
tion (CHE-9112872) and NSF/KY EPSCoR Program
(EHR-9108764) is gratefully acknowledged; also, the X-
ray equipment was purchased with assistance from NSF
(CHE-9016978). Partial support of the work by the United
States Department of Energy, Division of Chemical Sci-
ences (Office of Basic Energy Sciences), Office of Energy
Research, is also gratefully acknowledged.
A yellow crystal of [cis-Ru(bpy)2(CO)(OCHO)]PF202,
grown by diffusing diethyl ether over a CH3CN solution,
was mounted on a glass fiber with epoxy cement. Data
were collected on an Enraf-Nonius CAD-4 diffractometor
at room temperature. Crystal data, data collection, and
refinement parameters are summarized in Table 1. The
structure was solved by direct methods and completed by a
series of least-squares and difference Fourier synthesis. An
empirical correction for absorption (C scans) was applied.
All non-hydrogen atoms were refined with anisotropic
thermal parameters except for the partial occupancy F and
O atoms of the disordered PF2O22 anion. The disorder
consists of a P atom with four sets of F2O2 atoms, each at
25% occupancy. These atoms were refined with isotropic
thermal parameters. The hydrogen atoms were located by
difference maps and included as fixed isotropic contribu-
tions (B51.2 B of attached atom). Full-matrix least-squares
refinements were carried out for 3266 reflections with
(I.3s(I)). A final R index of 0.055 was obtained for 344
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