Synthesis and characterization of rhenium carbonyltrifluoroacetate complexes with phosphites, phosphonites and phosphinites

Article abstract of DOI:10.1016/j.poly.2009.04.045

The rhenium(I) complexes [Re(O₂CCF₃)(CO)₃(L)] (1) and [Re(O₂CCF₃)(CO)₂LL′] (L = Ph₂POCH₂CH₂OPPh₂; L′ = PPh_n(OR)_3-n; R = Me, Et; n = 0-2) (2a-f) have been synthesised by the reaction of the parent bromo derivatives with AgO₂CCF₃. These compounds have been characterized by microanalysis, IR, NMR, mass spectrometry and, in the cases of 1 and 2a, by X-ray diffraction. The metal is in a distorted octahedral environment with the trifluoroacetate ligand acting in a monodentate manner.

Full text of DOI:10.1016/j.poly.2009.04.045

Polyhedron 28 (2009) 2431–2435
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis and characterization of rhenium carbonyltrifluoroacetate complexes
with phosphites, phosphonites and phosphinites
*
Sandra Bolaño, Jorge Bravo , Jesús Castro, Soledad García-Fontán, María C. Rodríguez
Departamento de Química Inorgánica, Universidade de Vigo, Campus Universitario, E-36310 Vigo, Spain
a r t i c l e i n f o
a b s t r a c t
The rhenium(I) complexes [Re(O2CCF3)(CO)3(L)] (1) and [Re(O2CCF3)(CO)2LL0] (L = Ph2POCH2CH2OPPh2;
L0 = PPhn(OR)3ꢀn; R = Me, Et; n = 0–2) (2a–f) have been synthesised by the reaction of the parent bromo
derivatives with AgO2CCF3. These compounds have been characterized by microanalysis, IR, NMR, mass
spectrometry and, in the cases of 1 and 2a, by X-ray diffraction. The metal is in a distorted octahedral
environment with the trifluoroacetate ligand acting in a monodentate manner.
Article history:
Received 26 February 2009
Accepted 19 April 2009
Available online 12 May 2009
Keywords:
Carbonyls
Ó 2009 Elsevier Ltd. All rights reserved.
Rhenium
Phosphites
Phosphonites
Phosphinites
1. Introduction
2. Experimental
Transition metal carbonyl complexes are widely studied in
chemistry because they have many different applications ranging
from catalysts [1] to biochemistry [2]. Many properties of the com-
plexes, such as redox potential of the metal centre, lability of the
2.1. General methods and instrumentation
All experimental manipulations were carried out under an ar-
gon atmosphere using Schlenk techniques. Solvents were purified
by conventional procedures [7] and distilled prior to use. The com-
plexes [ReBr(CO)3(L)] and [ReBr(CO)2LL0] (L = Ph2POCH2CH2OPPh2;
L0 = PPhn(OR)3ꢀn, R = Me, Et; n = 0–2) were prepared by previously
described methods [6].
ligands, etc., are related to the synergistic effects of
r and p bonds
between the metal centre and the CO ligands [3]. On the other
hand, phosphines are also very common ligands with tuneable
electronic properties that allow them to mimic those of CO ligands.
Moreover, the possibility of modifying their steric properties ex-
plains their wide use in many coordination compounds. Replace-
ment of the R groups from PR3 compounds by OR groups to form
mixed phosphites (PRn(OR)3ꢀn; n = 0–2) modifies the electronic
The 1H, 31P{1H}, 13C{1H} and 19F{1H} NMR (d in ppm) spectra
were obtained on a Bruker ARX-400 spectrometer operating at fre-
quencies of 400, 161, 100 and 376 MHz, respectively. 1H and
13C{1H} chemical shifts are referred to internal TMS. 19F{1H}
and 31P{1H} chemical shifts are reported with respect to CFCl3
and 85% H3PO4, respectively, with downfield shifts considered
positive. Infrared spectra were recorded as KBr discs on a Bruker
VECTOR IFS28 FT spectrophotometer. Mass spectra were recorded
in the LSIMS (FAB+), Cs+ mode on a Micromass Autospec M
instrument, using 3-nitrobenzyl alcohol as the matrix material.
The conductivity values of 10ꢀ3 mol dmꢀ3 solutions of the
complexes in MeNO2 at 25 °C were measured with a Crison GLP
32 conductimeter. Elemental analyses (C, H) were performed using
a Fisons EA-1108 microanalyzer. Melting points were determined
on a GallenKamp MFB-595 and are uncorrected.
character of the ligand, enhancing its
p-acceptor character and
reducing its -donor behaviour [4]. These changes, in turn, modify
r
the properties of the metal complex. We are interested in analysing
the properties of carbonyl complexes that bear mono- and biden-
tate mixed phosphites and we have previously reported on the
properties of [ReX(CO)3L] [5] and [ReBr(CO)2LL0] [6] (X = Br, OTf;
L = diphosphinite; L0 = mixed phosphite). Substitution of the bromo
ligand by the potentially bidentate OTf ligand, did not produce rel-
evant differences on the properties of the complex. Thus, we report
here the carbonyl rhenium complexes [Re(O2CCF3)(CO)3(L)] and
[Re(O2CCF3)(CO)2LL0] (L = Ph2POCH2CH2OPPh2; L0 = PPhn(OR)3ꢀn
;
R = Me, Et; n = 0–2) bearing the more basic trifluoroacetate ligand
to investigate its influence on the properties of the new complexes.
2.2. Synthesis of the complexes
AgO2CCF3 was added to a dichloromethane solution of the pre-
cursor complex [ReBr(CO)2(X)(L)] (X = CO or L0) in a 1.5:1 molar
* Corresponding author. Tel.: +34 986 812 275; fax: +34 986 813 798.
E-mail address: jbravo@uvigo.es (J. Bravo).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.04.045

2432
S. Bolaño et al. / Polyhedron 28 (2009) 2431–2435
ratio. The mixture was heated under reflux for 2–3 h and the AgBr
formed was removed from the resulting grey suspension by filtra-
tion through Celite. In the case of complex 1, the concentration of
the resulting solution afforded an oil, which was triturated with
diethyl ether (5 mL) to give a beige solid. This solid was filtered
off, washed with diethyl ether (2 ꢁ 3 mL), dried under vacuum
and recrystallised from a mixture of CH2Cl2/diethyl ether. In the
case of compounds 2, white solids were obtained and these were
recrystallised from a mixture of CH2Cl2/hexane.
C38H35O8P3F3Re: C, 47.7; H, 3.7. Found: C, 48.1; H, 3.7%. FAB MS:
m/z (referred to the most abundant isotopes): 956 (42.0%) [M];
928 (45.9%) [MꢀCO]; 843 (88.7%) [MꢀO2CCF3]; 758 (100%)
[MꢀCOꢀL0]; 645 (5.0%) [MꢀCOꢀL0ꢀO2CCF3]. IR (cmꢀ1
) mCO: 1974,
1877; masym(OCO): 1697; m
sym(OCO): 1403. 1H NMR (CDCl3, ppm): d
7.64–7.26 [m, 25H, Ph (L+L0)], 4.54 [m, 1H, –CH2CH2–(L)], 4.06
[m, 2H, –CH2CH2–(L)], 3.94 [m, 1H, –CH2CH2–(L)], 3.40 [d, 3H,
JHP = 11 Hz, –CH3(L0)], 3.31 [d, 3H, JHP = 11 Hz, –CH3 (L0)]. 31P{1H}
NMR (CDCl3, ppm) (see Scheme 1 for labelling): d 116.3 (dd,
JAB = 34 Hz, JBC = 251 Hz, PB), 117.8 (dd, JAC = 33 Hz, PA), 143.9 (dd,
PC). 19F{1H} NMR (CDCl3, ppm): d ꢀ74.8 (s).
2.2.1. [Re(O2CCF3)(CO)3(L)] (1)
AgO2CCF3 (42.4 mg, 0.192 mmol) was added to a solution of
[ReBr(CO)3(L)] (100 mg, 0.128 mmol) in dichloromethane
Compound 2d, L0 = PPh(OEt)2: Yield P 59%. M.p. 177 °C.
KM(nitromethane) = 4.1
X
ꢀ1 cm2 molꢀ1
.
Anal. Calc. for C40H39O8
(20 mL).
3.5
ꢀ1 cm2 molꢀ1. Anal. Calc. for C31H24O7P2F3Re: C, 45.7; H, 3.0.
Found: C, 46.0; H, 3.1%. IR (cmꢀ1
CO: 2041, 1967, 1932; masym(OCO)
1692,
sym(OCO): 1420. 1H NMR (CDCl3, ppm): d 7.56–7.21 (m, 20H,
Yield P 58%.
M.p.
211 °C.
KM(nitromethane)
=
P3F3Re: C, 48.8; H, 4.00. Found: C, 48.7; H, 3.95%. FAB MS: m/z
(referred to the most abundant isotopes): 984 (43.9%) [M]; 956
(46.2%) [MꢀCO]; 871 (82.6%) [MꢀO2CCF3]; 758 (100%) [MꢀCOꢀL0];
X
)
m
:
m
645 (3.9%) [MꢀCOꢀL0ꢀO2CCF3]. IR (cmꢀ1
) mCO: 1993, 1888;
Ph), 4.33–4.07 (m, 4H, –CH2CH2–). 31P{1H} NMR (CDCl3, ppm): d
116.5 (s). 19F{1H} NMR (CDCl3, ppm): d ꢀ74.8 (s). 13C{1H} NMR
(CD2Cl2, ppm): d 66.5 (s, br, –CH2–), 114.7 (q, JCF = 288 Hz, CF3),
128.8–138.3 (Ph), 162.2 (qt, JCF = 37 Hz, JCP = 2 Hz, O2CCF3), 191.2
(m, 2CO cis to O2CCF3), 191.5 (t, JCP = 7 Hz, CO trans to O2CCF3).
masym(OCO): 1694; m
sym(OCO): 1406. 1H NMR (CDCl3, ppm): d 7.76–
7.16 [m, 25H, Ph (L+L0)), 4.55 [m, 1H, –CH2CH2–(L)], 4.05 [m, 1H,
–CH2CH2–(L)], 3.88 [m, 2H, –CH2CH2–(L)], 3.40–3.70 [m,
4H, –CH2–(L0)], 1.07 [t, 3H, JHH = 7 Hz, –CH3 (L0)], 1.00 [t, 3H,
JHH = 7 Hz, –CH3 (L0)]. 31P{1H} NMR (CDCl3, ppm) (see Scheme 1
for labelling): d 115.4 (dd, JAB = 37 Hz, JBC = 269 Hz, PB), 118.6 (dd,
JAC = 33 Hz, PA), 138.2 (dd, PC). 19F{1H} NMR (CDCl3, ppm):
d ꢀ74.8 (s).
2.2.2. [Re(O2CCF3)(CO)2(L)(L0)] (2)
AgO2CCF3 (33 mg, 0.15 mmol) was added to [ReBr(CO)2LL0]
(0.1 mmol) in CH2Cl2 (20 mL).
Compound 2e, L0 = PPh2(OMe): Yield P 40%. M.p. 174 °C.
Compound 2a, L0 = P(OMe)3: Yield P 37%. M.p. 202 °C.
KM(nitromethane) = 3.5 X
ꢀ1 cm2 molꢀ1. Anal. Calc. for C43H37O7P3F3Re:
KM(nitromethane) = 3.0
X
ꢀ1 cm2 molꢀ1. Anal. Calc. for C33H33O9P3F3Re:
C, 51.5; H, 3.7. Found: C, 51.4; H, 3.7%. FAB MS: m/z (referred to the
most abundant isotopes): 1003 (11.7%) [M+1]; 974 (7.7%) [MꢀCO];
889 (32.2%) [MꢀO2CCF3]; 758 (100%) [MꢀCOꢀL0]; 645 (7.6%)
C, 43.6; H, 3.7. Found: C, 43.4; H, 3.7%. FAB MS: m/z (referred to the
most abundant isotopes): 910 (48.5%) [M]; 882 (35.7%) [MꢀCO];
797 (100%) [MꢀO2CCF3]; 758 (95.6%) [MꢀCOꢀL0]; 645 (6.0%)
[MꢀCOꢀL0ꢀO2CCF3]. IR (cmꢀ1
) mCO: 1973, 1872; masym(OCO): 1695;
[MꢀCOꢀL0ꢀO2CCF3]. IR (cmꢀ1
)
m
CO: 1962, 1882;
m
asym(OCO): 1697;
m
sym(OCO): 1406. 1H NMR (CDCl3, ppm): d 7.65–7.19 [m, 30H, Ph
m
sym(OCO): 1418. 1H NMR (CDCl3, ppm): d 7.64–7.19 [m, 20H, Ph
(L+L0)], 4.31 [m, 1H, –CH2CH2–(L)], 3.91 [m, 3H, –CH2CH2–(L)],
2.88 [t, 3H, JHP = 6 Hz, –CH3(L0)]. 31P{1H} NMR (CDCl3, ppm) (see
Scheme 1 for labelling): d 115.2 (dapp, Japp = 33 Hz, PB+PC), 117.2
(tapp, PA). 19F{1H} NMR (CDCl3, ppm): d ꢀ75.0 (s).
(L)], 4.50 (m, 1H, –CH2CH2–), 4.00 (m, 3H, –CH2CH2–), 3.39 [d,
9H, JHP = 10 Hz, –CH3 (L0)]. 31P{1H} NMR (CDCl3, ppm) (see Scheme
1 for labelling): d 115.2 (dd, JAB = 33 Hz, JBC = 299 Hz, PB), 118.2 (dd,
JAC = 32 Hz, PA), 124.3 (dd, PC). 19F{1H} NMR (CDCl3, ppm): d ꢀ75.1
(s).
Compound 2f, L0 = PPh2(OEt): Yield P 44%. M.p. 170 °C.
KM(nitromethane) = 3.2
X
ꢀ1 cm2 molꢀ1. Anal. Calc. for C44H39O7P3F3Re:
Compound 2b, L0 = P(OEt)3: Yield P 36%. M.p. 190 °C.
C, 52.0; H, 3.97. Found: C, 49.2; H, 3.97%. FAB MS: m/z (referred to
the most abundant isotopes): 1017 (31.5%) [M+1]; 988 (11.1%)
[MꢀCO]; 903 (65.3%) [MꢀO2CCF3]; 758 (100%) [MꢀCOꢀL0]; 645
KM(nitromethane) = 2.9
X
ꢀ1 cm2 molꢀ1. Anal. Calc. for C36H39O9P3F3Re:
C, 45.4; H, 4.2. Found: C, 45.2; H, 4.1%. FAB MS: m/z (referred to the
most abundant isotopes): 952 (58.5%) [M]; 924 (52.7%) [MꢀCO];
839 (99.9%) [MꢀO2CCF3]; 758 (100%) [MꢀCOꢀL0]; 645 (6.2%)
(3.8%) [MꢀCOꢀL0ꢀO2CCF3]. IR (cmꢀ1
) mCO: 1979, 1881; msym(OCO):
1693;
m
asym(OCO): 1408. 1H NMR (CDCl3, ppm): d 7.75–7.16 [m,
[MꢀCOꢀL0ꢀO2CCF3]. IR (cmꢀ1
)
m
CO: 1975, 1876;
m
asym(OCO): 1696;
30H, Ph (L+L0)], 4.46 [m, 1H, –CH2CH2–(L)], 4.03–3.89 [m, 3H,
–CH2CH2–(L)], 3.23 [m, 2H, –CH2–(L0)], 0.81 [t, 3H, JHH = 7 Hz,
–CH3 (L0)]. 31P{1H} NMR (CDCl3, ppm) (see Scheme 1 for labelling):
d 113.8 (m, PB+PC), 117.5 (tapp, Japp = 32 Hz, PA). 19F{1H} NMR
(CDCl3, ppm): d ꢀ75.0 (s).
m
sym(OCO): 1410. 1H NMR (CDCl3, ppm): d 7.66–7.19 [m, 20H, Ph
(L)], 4.50 (m, 1H, –CH2CH2–), 4.20–3.80 [m, 3H, –CH2CH2–(L)],
3.76 [m, 6H, –CH2–(L0)], 1.01 [t, 9H, JHH = 7 Hz, –CH3(L0)]. 31P{1H}
NMR (CDCl3, ppm) (see Scheme 1 for labelling): d 114.6 (dd,
JAB = 49 Hz, JBC = 308 Hz, PB), 119.1 (dd, JAC = 32 Hz, PA), 119.9 (dd,
PC). 19F{1H} NMR (CDCl3, ppm): d ꢀ74.9 (s).
2.3. X-ray crystallography
Compound 2c, L0 = PPh(OMe)2: Yield P 28%. M.p. 182 °C.
KM(nitromethane) = 3.2
X
ꢀ1 cm2 molꢀꢀ1
.
Anal.
Calc.
for
Single crystals of compounds 1 and 2a were mounted on a
glass fibre and studied on a Bruker Smart CCD area-detector dif-
fractometer using graphite-monochromated Mo
Ka radiation
(K
= 0.71073 Å). The crystal parameters and experimental details
O
O
for data collection are summarized in Table 1. Absorption correc-
tions were carried out using SADABS [8]. The structures were solved
with the OSCAIL program [9] by the Patterson method and refined
by full-matrix least-squares based on F2 [10]. All non-hydrogen
atoms were refined with anisotropic displacement parameters.
The hydrogen atoms were included in idealised positions and re-
fined with isotropic displacement parameters. Atomic scattering
factors and anomalous dispersion corrections for all atoms were
taken from the International Tables for X-ray Crystallography
[11]. Details of crystal data and structural refinement are given
in Table 1.
F3CC
X
Br
Ph2
PA
Ph2
PA
X
O
O
AgOOCCF
- AgBr
+
3
(CH2)2
Re
(CH2)2
Re
O
PB
PB
O
OC
OC
Ph2
Ph2
CO
CO
1
X = CO ( )
P Ph (OR)
3-n
n = 0; R = Me (2a), Et (2b)
n = 1; R = Me (2c), Et (2d)
X =
C
n
2e
n = 2; R = Me ( ), Et (2f)
Scheme 1.

S. Bolaño et al. / Polyhedron 28 (2009) 2431–2435
2433
Table 1
Crystal data and structure refinement for compounds 1 and 2a.
1
2a
Empirical formula
Formula weight
Crystal size (mm)
T (K)
C62H48F6O14P4Re2
1627.28
C33H33F3O9P3Re
909.70
0.67 ꢁ 0.39 ꢁ 0.12
0.22 ꢁ 0.08 ꢁ 0.07
293(2)
293(2)
Wavelength (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
0.71073
0.71073
monoclinic
P21/c
12.0956(10)
17.4771(15)
17.1160(14)
90
triclinic
ꢀ
P1
10.1231(5)
17.9762(9)
18.5233(9)
67.5350(10)
a
(°)
b (°)
87.8420(10)
89.5730(10)
3112.7(3)
2
1.736
4.070
90.309(2)
90
3618.2(5)
4
1.670
3.557
c
(°)
V (Å3)
Z
Density (calc.) (Mg/m3)
l
(mmꢀ1
)
F(0 0 0)
1592
1800
h Range for data collection (°)
Index ranges
Reflections collected
2.01–28.01
1.67–17.99
ꢀ13 6 h 6 11, ꢀ23 6 k 6 23, ꢀ20 6 l 6 24
ꢀ10 6 h 6 10, ꢀ11 6 k 6 15, ꢀ13 6 l 6 14
18 666
8412
Independent reflections (Rint
)
13 127(0.0762)
9663
0.871
2468(0.0660)
1767
0.990
Reflections observed (>2
Data completeness
r)
Max. and min. transmission
Data/restraints/parameters
Goodness-of-fit on F2
1.000 and 0.234
13 127/0/793
0.961
1.000 and 0.719
2468/0/445
0.771
Final R indices [I>2
R indices (all data)
r
(I)]
R1 = 0.0681, wR2 = 0.1721
R1 = 0.0853, wR2 = 0.1819
4.241 and ꢀ3.922
R1 = 0.0282, wR2 = 0.0435
R1 = 0.0551, wR2 = 0.0480
0.309 and ꢀ0.355
Largest difference in peak and hole (e Åꢀ3
)
that are more distorted from the ideal octahedral geometry than
those for molecule 2; (iv) the orientation of the carboxylate moiety
[C–CO2] is different in the two molecules, being directed towards
the bisector of the two CO ligands in molecule 1 [torsion angles
38.3(4) and 52.8(4)°] and almost parallel to one of them [torsion
angle 1.3(6)°] and perpendicular to the other in molecule 2.
The Re–P bond lengths span from 2.431(2) to 2.456(2) Å, a nar-
rower range than that found in the closely related triflato complex
[Re(OSO2CF3)(CO)3(L)] [5b]. The Re–C bond lengths range from
1.87(1) to 2.00(1) Å, and they are similar to those of the triflato
complex [5b]. The Re–C bond distances trans to the phosphorus
atoms are, on average, 0.08 Å longer than that trans to the oxygen
atom, a greater but comparable difference, than that observed for
the triflato complex (0.06 Å) [5b]. Those values are also in a com-
parable range to that found for other fac-tricarbonyl Re(I) com-
plexes bearing related diphosphinite ligands [5c].
The trifluoroacetate group acts as a monodentate ligand in a
similar way to other rhenium(I) compounds bearing this group
as a ligand [14]. The OCO angle (ꢂ129°) and the O–C bond lengths
of the carboxylate moiety (1.20–1.23 Å), which are near to the ionic
limit (1.250 Å) as defined by Hocking and Hambley [15], are indic-
ative of a high ionic character (>90%) for the carboxylate–rhenium
interaction.
3. Results and discussion
3.1. Synthesis
The bromo complexes [ReBr(CO)3(L)] [5a] and [ReBr(CO)2LL0] [6]
[L = Ph2POCH2CH2OPPh2, L0 = PPhn(OR)3ꢀn n = 0–2] reacted with
an excess of AgO2CCF3 in refluxing dichloromethane to give
[Re(O2CCF3)(CO)3L] (1) and [Re(O2CCF3)(CO)2LL0] (2), respectively,
as beige (1) or white (2) solids (Scheme 1). The new complexes
are air-stable in the solid state and in solution at room temperature,
and were characterized by elemental analysis, IR spectroscopy, mass
spectrometry and, in the cases of compounds 1 and 2a, by X-ray
diffraction. Conductivity measurements on nitromethane solutions
of the compounds show values that are consistent with non-
electrolyte behaviour, in agreement with the coordination of the
trifluoroacetate anion to the rhenium atom. The compounds were
also studied in solution by NMR spectroscopy.
3.2. Description of the structures
3.2.1. [Re(O2CCF3)(CO)3(L)] (1)
An ORTEP [12] drawing of the two molecules in the asymmetric
unit, along with the numbering scheme adopted, is shown in Fig. 1.
Selected bond lengths and bond angles are listed in Table 2. The
asymmetric unit contains two different molecules with identical
formulae. Both consist of a rhenium(I) atom coordinated in an
octahedral arrangement by three facially disposed carbonyl li-
gands, two phosphorus atoms of the chelating phosphinite ligand
Ph2POCH2CH2OPPh2, and an oxygen atom of a trifluoroacetate ion
acting as a monodentate ligand. The main differences between
the two molecules in the asymmetric unit are: (i) the seven-mem-
bered chelate ring adopts a twisted boat conformation [13] in mol-
ecule 1 whereas it adopts a twisted chair conformation [13] in
molecule 2; (ii) the chelate angles are 86.5(1)° [Re(1)] and
90.0(1)° [Re(2)]; (iii) molecule 1 has surrounding Re(1) parameters
3.2.2. [Re(O2CCF3)(CO)2(L){P(OMe)3}] (2a)
An ORTEP [12] drawing of the molecule, along with the num-
bering scheme adopted, is shown in Fig. 2. Selected bond lengths
and bond angles are listed in Table 3. The compound consists of
a rhenium(I) atom coordinated by two cis carbonyl ligands, two
phosphorus atoms of the chelating bidentate phosphinite ligand
Ph2POCH2CH2OPPh2, another phosphorus atom from
a trim-
ethylphosphite ligand and an oxygen atom of a trifluoroacetate
group, which acts as a monodentate ligand. This arrangement re-
sults in an octahedral arrangement around the metal atom. The
three phosphorus atoms are in meridional positions. The Re–C

2434
S. Bolaño et al. / Polyhedron 28 (2009) 2431–2435
Fig. 1. Molecular structure of molecules 1 (left) and 2 (right) of compound 1.
bond distances are 1.864(12) and 1.914(13) Å, with the shorter one
corresponding to that trans to the trifluoroacetate ion. The biden-
tate phosphinite ligand shows two different Re–P bond lengths,
2.402(3) and 2.467(3) Å, with the shorter one corresponding to
that trans to the phosphite ligand. The geometrical parameters
for the trifluoroacetate ligand are similar to those observed for 1
and are consistent with its monodentate behaviour. The cis angles
range from 82.2(2) to 95.9(4)°. It is noteworthy that the most dis-
torted values are those of the trifluoroacetate ligand, probably due
to the steric requirements of the phenyl groups of the bidentate
phosphinite ligand in the direction of the position occupied by
the trifluoromethyl group. In fact, the carboxylate moiety of the tri-
fluoroacetate ligand is not parallel to any other ligand, but is direc-
ted towards the free space between a carbonyl and the phosphite
ligand with very different torsion angles: 21.8(4)° with the
carbonyl ligand and 69.9(3)° with the phosphite ligand [vectors
defined as O(4)–O(3) versus Re–O(2) and Re–P(3)]. The seven-
membered chelate ring adopts a twisted boat conformation [13]
with a chelate P(1)–Re–P(2) angle of 87.8(1)°.
3.3. Spectroscopic studies
The IR spectrum of compound 1 shows three strong m(CO) bands
that are characteristic of the fac-ReI(CO)3 fragment [16] at 2041,
1967 and 1932 cmꢀ1. These bands are displaced to higher wave-
numbers with respect to the precursor complex [ReBr(CO)3(L)]
[5a], in agreement with a minor electronic back-donation of the
Table 2
Selected bond lengths [Å] and angles [°] for compound 1.
Re(1)–C(3)
Re(1)–C(4)
Re(1)–C(5)
Re(1)–P(1)
Re(1)–P(2)
Re(1)–O(3)
C(3)–O(4)
C(5)–O(6)
C(4)–O(5)
O(3)–C(6)
O(7)–C(6)
1.874(10)
1.981(11)
1.954(11)
2.456(2)
2.433(2)
2.175(6)
1.179(11)
1.150(12)
1.106(12)
1.214(11)
1.230(12)
Re(2)–C(103)
Re(2)–C(104)
Re(2)–C(105)
Re(2)–P(101)
Re(2)–P(102)
Re(2)–O(103)
C(103)–O(104)
C(105)–O(106)
C(104)–O(105)
O(103)–C(106)
O(107)–C(106)
1.909(10)
1.937(10)
1.999(11)
2.449(2)
2.431(2)
2.185(7)
1.123(12)
1.115(12)
1.137(12)
1.218(13)
1.205(16)
Fig. 2. Molecular structure of compound 2a.
Table 3
Selected bond lengths [Å] and angles [°] for compound 2a.
C(3)–Re(1)–C(5)
C(3)–Re(1)–C(4)
C(3)–Re(1)–P(1)
C(5)–Re(1)–C(4)
C(5)–Re(1)–O(3)
C(4)–Re(1)–O(3)
C(3)–Re(1)–P(2)
C(5)–Re(1)–P(2)
O(3)–Re(1)–P(1)
O(3)–Re(1)–P(2)
C(4)–Re(1)–P(1)
P(2)–Re(1)–P(1)
C(4)–Re(1)–P(2)
C(3)–Re(1)–O(3)
C(5)–Re(1)–P(1)
89.6(4)
87.1(4)
96.5(3)
90.5(4)
91.2(3)
91.7(3)
88.5(3)
92.3(3)
82.76(17)
92.64(19)
91.2(3)
86.50(8)
174.8(3)
178.6(3)
173.7(3)
C(103)–Re(2)–C(105)
C(103)–Re(2)–C(104)
C(103)–Re(2)–P(102)
C(104)–Re(2)–C(105)
C(105)–Re(2)–O(103)
C(104)–Re(2)–O(103)
C(103)–Re(2)–P(101)
C(105)–Re(2)–P(101)
O(103)–Re(2)–P(102)
O(103)–Re(2)–P(101)
C(104)–Re(2)–P(102)
P(102)–Re(2)–P(101)
C(104)–Re(2)–P(101)
C(103)–Re(2)–O(103)
C(105)–Re(2)–P(102)
88.1(5)
91.9(4)
92.5(3)
88.6(4)
93.5(4)
89.4(4)
86.5(3)
89.7(3)
85.81(19)
92.3(2)
91.7(3)
90.00(8)
177.7(3)
178.0(3)
179.2(3)
Re(1)–C(1)
Re(1)–O(3)
Re(1)–P(1)
C(1)–O(1)
O(3)–C(3)
1.864(12)
2.175(8)
2.402(3)
1.174(11)
1.264(13)
Re(1)–C(2)
Re(1)–P(3)
Re(1)–P(2)
C(2)–O(2)
O(4)–C(3)
1.914(13)
2.362(3)
2.467(3)
1.164(12)
1.218(13)
C(1)–Re(1)–C(2)
C(2)–Re(1)–O(3)
C(2)–Re(1)–P(3)
C(1)–Re(1)–P(1)
O(3)–Re(1)–P(1)
C(1)–Re(1)–P(2)
O(3)–Re(1)–P(2)
P(1)–Re(1)–P(2)
86.7(5)
95.9(4)
91.2(3)
88.8(3)
95.4(2)
95.4(4)
82.2(2)
87.79(11)
C(1)–Re(1)–O(3)
C(1)–Re(1)–P(3)
O(3)–Re(1)–P(3)
C(2)–Re(1)–P(1)
P(3)–Re(1)–P(1)
C(2)–Re(1)–P(2)
P(3)–Re(1)–P(2)
175.0(4)
87.2(3)
88.5(2)
90.2(3)
175.71(11)
177.1(4)
90.95(11)

S. Bolaño et al. / Polyhedron 28 (2009) 2431–2435
2435
-L'
bidentate mixed-phosphite ligands are described. The new com-
plexes were prepared by the reaction of the parent bromo-com-
plexes with silver trifluoroacetate. All the complexes were
studied by spectroscopic techniques and, in the cases of complexes
1 and 2a, structures in the solid state were determined by X-ray
diffraction. In all cases the trifluoroacetate ligand behaves in a
monodentate manner.
Re(O2CCF3)(CO)(L)(L')
Re(O2CCF3)(CO)(L)
-O2CCF3
-CO
Re(O2CCF3)(CO)2(L)(L')
-O2CCF3
-{CO, L'}
Re(CO)2(L)(L')
Re(CO)(L)
Scheme 2. Fragmentation pathways for compounds 2a–f.
Supplementary data
CCDC 719369 and 719370 contains the supplementary crystal-
lographic data for compounds 1 and 2a, respectively. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/con-
ts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033; or e-mail: deposit@ccdc.cam.ac.uk.
rhenium atom to the CO ligands due to the replacement of Br by
the trifluoroacetate ligand. Similarly, the IR spectra of compounds
2 display two strong m(CO) bands, characteristic of cis-dicarbonyl
compounds [6,17], and these are also displaced to higher energy
with respect to the [ReBr(CO)2(L)(L0)] compounds [6]. On the other
hand, compounds 1 and 2 display a strong band at 1692–
1697 cmꢀ1 and a medium band at 1403–1418 cmꢀ1 due to the
asymmetric and symmetric modes of the carboxylate group of
the O2CCF3 ligand [18]. The energy difference between the two
bands is related to the coordination type of the carboxylate ligand
and, in our case, this is in accordance (ꢂ290 cmꢀ1) with a
monodentate behaviour of the ligand in all the complexes [19].
The X-ray diffraction studies of complexes 1 and 2a confirm this
behaviour.
Acknowledgements
Financial support from the Xunta de Galicia (Project PGIDT04P-
XIC31401PN) and the Spanish Ministry of Education (Project
BQU2003-06783) is gratefully acknowledged. We thank the Uni-
versity of Vigo CACTI services for collecting X-ray data and record-
ing NMR spectra.
The 1H NMR spectrum of compound 1 does not show any rele-
vant differences compared with that of the precursor. However,
the 31P{1H} NMR spectrum of 1 shows a singlet at a lower field
(d = 116.5 ppm) than that of the precursor (d = 105.3 ppm), as
expected because of the electron-withdrawing characteristics of
the trifluoromethyl group. In the case of compounds 2, the 1H
NMR signals of the –CH2CH2– group of the bidentate phosphinite li-
gand (which appear as three multiplets with intensities 1:1:2 in the
spectra of the parent bromide complexes), are two multiplets with
intensities 1:3, except for compounds 2c and 2d in which they ap-
pear as three 1:2:1 and 1:1:2 multiplets, respectively. In all cases,
these multiplets span in a similar but narrower region than those
of the bromide precursors. On the other hand, the signals of the
OR groups of the monodentate mixed-phosphite ligands, are similar
to those of the parent bromide complexes but slightly upfield
shifted. Compounds 2a–d display 31P{1H} NMR spectra that are
consistent with an ABM spin system (three double doublets), but
compounds 2e–f show signals corresponding to ABC and A2B spin
systems [20], respectively, reflecting the similarity between the P
nuclei of both bidentate and monodentate phosphinite ligands. In
all cases the signals are shifted downfield when compared to their
bromide analogues. These shifts are consistent with the IR data dis-
cussed above and are in accordance with the presence of the more
electron-withdrawing trifluoroacetate group, which reduces the
References
[1] T.G. Spiro, M.Z. Zgierski, P.M. Kozlowski, Coord. Chem. Rev. 219–221 (2001)
923.
[2] T.G. Spiro, I.H. Wasbotten, J. Inorg. Biochem. 99 (2005) 34.
[3] C. Elschenbroich, in: Organometallics, third ed., Wiley-VCH, Weinheim, 2006.
[4] (a) C.A. Tolman, Chem. Rev. 77 (1977) 313;
(b) M.M. Rahaman, H.Y. Liu, K. Eriks, A. Prock, W.P. Giering, Organometallics 8
(1981) 1.
[5] (a) S. Bolaño, J. Bravo, R. Carballo, S. García-Fontán, U. Abram, E.M. Vázquez-
López, Polyhedron 18 (1999) 1431;
(b) M.C. Rodríguez, J. Bravo, E. Freijanes, E. Oñate, S. García-Fontán, P.
Rodríguez-Seoane, Polyhedron 23 (2004) 1045;
(c) S. Bolaño, J. Bravo, J. Castro, S. García-Fontán, M.C. Marín, P. Rodríguez-
Seoane, J. Organomet. Chem. 690 (2005) 4945.
[6] F. Fernández-García, S. Bolaño, R. Carballo, S. García-Fontán, J. Bravo,
Polyhedron 20 (2001) 2675.
[7] D.D. Perrin, W.L.F. Armarego, Purification of Laboratory Chemicals, third ed.,
Butterworth and Heinemann, Oxford, 1988.
[8] G.M. Sheldrick, SADABS. An Empirical Absorption Correction Program for Area
Detector Data, University of Göttingen, Germany, 1996.
[9] P. McArdle, J. Appl. Cryst. 28 (1995) 65.
[10] G.M. Sheldrick, SHELX-97, Program for the Solution and Refinement of Crystal
Structures, University of Göttingen, Germany, 1997.
[11] International Tables for X-ray Crystallography, vol. C, Kluwer, Dordrecht, 1992.
[12] L.J. Farrugia, J. Appl. Cryst. 30 (1997) 565.
[13] E.L. Eliel, S.H. Wilen, Stereochemistry of Organic Compounds, Wiley, New York,
1994. p. 764.
[14] (a) A. Egli, K. Hegetschweiler, R. Alberto, U. Abram, R. Schibli, R. Hedinger, V.
Gramlich, R. Kissner, P.A. Schubiger, Organometallics 16 (1997) 1833;
(b) S.J. Dossett, M. Green, M.F. Mahon, J.M. McInnes, C. Vaughan, J. Chem. Soc.,
Dalton Trans. (1997) 3671;
rhenium
p-back-donation to the phosphorus ligands. The mass
spectra of compounds 2a–f show, in all cases, five sets of peaks
(see Section 2) displaying the rhenium isotope pattern. This allows
us to propose possible fragmentation pathways for these com-
pounds that would give rise to the identified fragments (Scheme 2).
The most abundant peak is, in all cases (except for 2a – although
in this case its abundance is also very high, 95.6%), that at m/
z = 758, corresponding to loss of a carbonyl and the monodentate
L0 ligand.
(c) F. Tisato, F. Refosco, A. Moresco, G. Bandoli, A. Dolmella, C. Bolzati, Inorg.
Chem. 34 (1995) 1779;
(d) S. Feracin, T. Buergi, V.I. Bakhmutov, I. Eremenko, E.V. Vorontsov, A.B.
Vimenits, H. Berke, Organometallics 13 (1994) 4194.
[15] R.K. Hocking, T.W. Hambley, Inorg. Chem. 42 (2003) 2833.
[16] L.H. Staal, A. Oskam, K. Vrieze, J. Organomet. Chem. 170 (1979) 235.
[17] G. Albertin, S. Antoniutti, S. Garcia-Fontán, R. Carballo, F. Padoan, J. Chem. Soc.,
Dalton Trans. (1998) 2071.
[18] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compounds, fifth ed., John Wiley and Sons, 1997.
[19] (a) D.H. Gibson, Y. Ding, R.L. Miller, B.A. Sleadd, M.S. Mashuta, J.F. Richardson,
Polyhedron 18 (1999) 1189;
(b) G.B. Deacon, R.J. Phillips, Coord. Chem. Rev. 33 (1980) 227.
[20] P.H.M. Budzelaar, gNMR Version 4.1, Cherwell Scientific Limited, Oxford, 1999.
4. Conclusions
The synthesis and structural characterization of trifluoroacetat-
ecarbonylrhenium(I) complexes bearing different mono- and