Synthesis and characterization of new chlorocarbonylrhenium(I) complexes with P-donor chelate ligands

Article abstract of DOI:10.1002/zaac.200900390

Chlorocarbonylrhenium(I) complexes fac,cis-[ReCl(CO)₃L ^1-3] [L¹ = Ph₂PO(CH₂) ₂OPPh₂ (1); L² = Ph₂PO(CH ₂J₃OPPh₂ (2); L

Full text of DOI:10.1002/zaac.200900390

ARTICLE
DOI: 10.1002/zaac.200900390
Synthesis and Characterization of New Chlorocarbonylrhenium(I)
Complexes with P-Donor Chelate Ligands
Sandra Bolaño,[a] Jorge Bravo,*[a] Jesús Castro,[a] Soledad García-Fontán,*[a] and
M. Carmen Marín[a]
Keywords: Carbonyl ligands; Chlorine; P ligands; Rhenium; NMR spectroscopy
Abstract. Chlorocarbonylrhenium(I) complexes fac,cis-[ReCl(CO)3L1–3
]
=
[ReH(CO)3L2] with HCl affords an isomer of compound 2, the complex
mer,cis-[ReCl(CO)3L2] (4). The new complexes were characterized by IR,
[L1 = Ph2PO(CH2)2OPPh2 (1); L2 = Ph2PO(CH2)3OPPh2 (2); L3
iPr2PO(CH2)2OPiPr2 (3)] were synthesized by reaction of [ReCl(CO)5] 1H, 13C{1H} and 31P{1H} NMR spectroscopy and in the case of complexes
with the appropriate diphosphinite ligands L1–3. Reaction of mer,cis- 2 and 4 by single-crystal X-ray structure determination.
Introduction
Experimental Section
Materials and Instrumentation
Organorhenium chemistry has expanded markedly in recent
decades and phosphorus-containing co-ligands are widely em-
ployed to stabilize organorhenium compounds [1]. Electronic
and steric properties of phosphanes can be easily modified and
allow the modulation of the properties of transition metal com-
plexes. Moreover, the transition metal chemistry of chelating
P-donor ligands is interesting, because of the variable electro-
negativity of spacer atoms, which greatly influences the donor-
acceptor properties of the phosphorus atoms. Phosphinites dis-
play a weaker σ-donor and stronger π-acceptor nature than
phosphanes [2] and this fact is expected to have an important
influence on the properties of the metal atom, and hence on
those of the complex. However, few rhenium complexes, with
chelating diphosphinite ligands, were reported [3].
We previously reported on the synthesis and properties of
halide and hydrido rhenium complexes with mono- and biden-
tate phosphinites, phosphonites or phosphites, and found sig-
nificant dependence of the properties of the complexes on the
nature of the phosphorus-bearing ligands [4]. In this paper, we
report the synthesis and properties of chlororhenium(I) tricar-
bonyl complexes with three diphosphinite ligands, which differ
in the nature of the R groups bound to the phosphorus atom
and in the length (two or three carbons) of the alkyl chain,
which links the two R2PO groups.
All synthetic work was carried out in an inert atmosphere by using
standard Schlenk techniques. All solvents were purified by conven-
tional procedures [5] and distilled prior to use. The ligands, 1,2-bis(di-
phenylphosphinoxy)ethane (L1) [4d, 1,3-bis(diphenylphosphin-
oxy)propane (L2) 4c, 1,2-bis(diisopropylphosphinoxy)ethane (L3) 4c],
and the precursors [ReCl(CO)5] [6] and mer,cis-[ReH(CO)3L2] [4c]
were prepared according to published methods. The H, 31P and 13C
1
NMR spectra were obtained with a Bruker ARX-400 spectrometer,
operating at frequencies of 400, 161 and 100 MHz, respectively. The
spectra were recorded in CDCl3 solutions, using the solvent as internal
lock. 1H and 13C{1H} NMR spectroscopic signals are referred to TMS
and those of 31P{1H} to 85 % H3PO4 as internal standard; the down-
field shifts were considered positive. IR spectra (KBr discs) were ob-
tained with a Bruker VECTOR IFS 28 FT apparatus and mass spectra
were recorded with a Micromass Autospec M LSIMS (FAB+) system.
Microanalyses were carried out with a Fisons Model EA 1108 elemen-
tal analyzer.
Preparation of fac-[ReCl(CO)3L] [L = L1 (1), L2 (2), L3 (3)]
[ReCl(CO)5] (0.1 g, 0.28 mmol) was suspended in toluene (10 mL)
and an equimolar amount of L was added (1.0 mL of a 0.29 m solution
of L1, 1.3 mL of a 0.22 m solution of L2, or 1.0 mL of a 0.29 m solu-
tion of L3). The mixture was heated to reflux for 4–5 h, cooled to
room temperature and stirred for further 4 h. The solvent was removed
in vacuo and the residue was treated with ethanol (2 mL) and afforded
a colorless product, which was filtered off, washed with ethanol and
dried in vacuo.
* Prof. Dr. J. Bravo
Compound 1: Yield: 82 % (0.17 g). C29H24ClO5P2Re (736.11): calcd.
C 47.32, H 3.29; found C 47.25, H 3.26. MS: m/z (referred to the most
abundant isotopes) = 736 [M], 700 [M –Cl], 673 [M –Cl –CO]. IR
Fax: +34-986813798
E-Mail: jbravo@uvigo.es
* Dr. S. García-Fontán
E-Mail: sgarcia@uvigo.es
[a] Departamento de Química Inorgánica
Facultade de Química
(KBr): ν
= 2037 (vs), 1957 (vs), 1922 (vs) cm–1. 1H NMR
˜
CO
(400 MHz, CDCl3): δ = 4.01 (m, 2 H, OCH2), 4.68 (m, 2 H, OCH2),
7.42–7.89 (m, 20 H, Ph) ppm. 31P{1H} NMR (161 MHz, CDCl3): δ =
107.6 (s) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ = 66.3 (s, OCH2),
Universidade de Vigo
36310 Vigo, Spain
506
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2010, 636, 506–510

New Chlorocarbonylrhenium(I) Complexes with P-Donor Chelate Ligands
128.1–138.7 (m, Ph), 187.1 (t, 2J(C,P) = 7 Hz, cis CO), 190.0 (m, Crystallographic data (excluding structure factors) have been deposited
trans CO).
with the Cambridge Crystallographic Centre as Supplementary Publi-
cation No. CCDC-738986, -738987 for compounds 2 and 4, respec-
tively. Copies of the data can be obtained free of charge on application
to The Director, CCDC, 12 Union Road, Cambridge CB21EZ, UK
Compound 2: Yield: 86 % (0.18 g). C30H26ClO5P2Re (750.13): calcd.
C 48.03, H 3.49; found C 48.10, H 3.40. MS: m/z (referred to the most
abundant isotopes) = 750, [M], 715 [M –Cl], 694 [M –2CO], 685 [M –
(Fax: +44 1223
3
36
0
33; E-Mail for inquiry: files-
Cl –CO]. IR (KBr): ν = 2031 (vs), 1946 (vs), 1916 (vs) cm–1. H
1
˜
CO
erv@ccdc.cam.ac.uk).
NMR (400 MHz, CDCl3): δ = 1.63 (m, 1 H, CH2), 2.25 (m, 1 H,
CH2), 3.36 (m, 2 H, OCH2), 4.50 (m, 2 H, OCH2), 7.14–7.96 (m, 20
H, Ph). 31P{1H} NMR (161 MHz, CDCl3): δ = 101.0 (s). 13C{1H}
Results and Discussion
NMR (100 MHz, CDCl3): δ = 45.7 (s, CH2), 65.5 (s, OCH2), 127.8–
2
139.0 (m, Ph), 186.6 (t, JC,P = 7.3 Hz, cis CO), 190.3 (m, trans CO). Synthesis and Spectroscopic Studies
Crystals suitable for X-ray structure analysis were obtained from a
Reactions of ligands L1–3 (see Scheme 1) with [ReCl(CO)5]
solution in 2:10 (v/v) CH2Cl2/EtOH by slow evaporation of the sol-
vent.
in 1:1 mol ratio in toluene under reflux afford the new chlorot-
ricarbonyl complexes fac-[ReCl(CO)3L] (1–3; Scheme 2) by
replacing two CO ligands by the corresponding bidentate li-
gand
Compound 3: Yield: 71 % (0.12 g). C17H32ClO5P2Re (600.04): calcd.
C 34.03, H 5.38; found C 34.01, H 5.29. MS: m/z (referred to the most
abundant isotopes) = 600 [M], 572 [M –CO], 565 [M –Cl], 544 [M –
The new complexes are stable in solid state and in solution
at room temperature, and were characterized by the usual spec-
troscopic techniques. The IR spectra show three strong ν(CO)
bands, which are characteristic for the fac configuration [12]
at 2037, 1957 and 1922 cm–1 for 1; 2031, 1946 and 1916 cm–1
for 2; 2026, 1947 and 1898 cm–1 for 3. These values are very
similar to those reported for the analogous complexes, which
bear bromide or hydride ligands instead of chloride [4c, 4d].
The 31P{1H} NMR spectra of complexes 1–3 show single reso-
nances, which indicate the magnetic equivalence of the two
2CO]. IR (KBr): νCO = 2026 (vs), 1947 (vs), 1898 (m) cm–1. 1H NMR
˜
(400 MHz, CDCl3): δ = 1.05–1.39 (m, 24 H, CH3), 2.50 (m, 2 H, CH),
2.75 (m, 2 H, CH), 3.84 (m, 2 H, OCH2), 4.44 (m, 2 H, OCH2).
31P{1H} NMR (161 MHz, CDCl3): δ = 138.8 (s). 13C{1H} NMR
(100 MHz, CDCl3): δ = 17.6 (m, CH3), 30.1 (m, CH), 65.6 (s, OCH2),
189.3–190.7 (m, CO).
Preparation of mer-[ReCl(CO)3L2] (4)
To a suspension of mer-[ReH(CO)3L2] (0.15 mg, 0.2 mmol) in CH2Cl2
(5 mL) cooled to –80 °C, an equimolar amount of HCl (37 %) was phosphorus nuclei of each ligand. These signals appear consid-
added and the reaction mixture was brought to room temperature and
stirred for 2 h. The obtained colorless solid was filtered off and recrys-
tallized from a CH2Cl2/EtOH solution by slow evaporation of the sol-
vent. Crystals suitable for X-ray structure analysis were obtained.
erably shielded relative to those of the corresponding free li-
gands and to those of the hydrido complexes [4c, 4d]. In the
1H NMR spectra, the signals that correspond to the methylene
protons of the bidentate ligand appear as two multiplets in
compounds 1 and 3 (2:2 intensity ratio) and as four multiplets
in compound 2 (1:1:2:2 intensity ratio), which indicate their
diastereotopic nature.
In keeping with the fac arrangement of the CO ligands, the
13C{1H} NMR spectra show two low field signals, which are
assignable to the CO groups: a triplet, corresponding to the
CO group located cis to both phosphorus nuclei (~ 187 ppm;
2JC,P ~ 7 Hz), and a multiplet (~ 190 ppm), corresponding to
the other two CO ligands.
Yield: 80 % (0.12 g). C30H26ClO5P2Re (750.13): calcd. C 48.03, H
3.49; found C 48.07, H 3.54. MS; m/z (referred to the most abundant
isotopes): 750, [M]; 715, [M –Cl]; 694, [M –2CO]. IR (KBr): ν
=
˜
CO
2059 (w), 1958 (vs), 1932 (vs) cm–1. 1H NMR (400 MHz, CDCl3):
δ = 1.97 (m, 2 H, CH2), 3.78 (m, 4 H, OCH2), 7.28–7.75 (m, 20 H,
2
Ph). 31P{1H} NMR (161 MHz, CDCl3): δ = 105.1 (d, JP,P = 16 Hz),
2
110.2 (d, JP,P = 16 Hz). 13C{1H} NMR (100 MHz, CDCl3): δ = 31.5
(s, CH2), 62.7 (s, OCH2), 127.8–142.4 (m, Ph), 192.0 (dd, 2JC,P = 56.3,
2
2JC,P = 6 Hz, trans, CO), 191.5 (t, JC,P = 9.2 Hz, cis, CO).
In previous investigations we observed that the reaction of
[ReH(CO)5] with the ligand L2 afforded the mer,cis-
[ReH(CO)3L2] compound instead of the more usual fac,cis iso-
mer, which is observed for the other two ligands. Taking ad-
vantage of this fact, we performed a protonation reaction with
HCl to obtain the mer isomer of compound 2. Thus, the treat-
ment of a suspension of mer-[ReH(CO)3L2] in CH2Cl2 with an
equimolar amount of HCl afforded mer-[ReCl(CO)3L2] (4) in
80 % yield (Scheme 3). During the reaction the release of a
gas (presumably H2) was observed. When the reaction mixture
is stirred for several days at room temperature, noticeably
isomerization to the facial isomer 2 is observed.
Complex 4 is stable in solid state and it was characterized
by the usual spectroscopic techniques. The IR spectrum shows
the CO vibrations as two strong bands at 1932 and 1958 cm–1
and a weak band at 2059 cm–1, which is characteristic of the
mer configuration [13]. The 31P{1H} NMR spectrum of 4
X-ray Crystallographic Analysis
Crystallographic data were collected with a Bruker Smart 1000 CCD
diffractometer using graphite monochromated Mo-Kα radiation (λ =
0.71073 Å), and were corrected for Lorentz and polarization effects.
The software SMART [7] was used for collecting frames of data, in-
dexing reflections and the determination of lattice parameters, SAINT
[8] for integration of intensity of reflections and scaling. The software
SADABS [9] was used for empirical absorption correction.
The structure was solved and refined with the Oscail program [10] by
direct methods and refined by full-matrix least-squares based on F2
[11]. Non-hydrogen atoms were refined with anisotropic displacement
parameters. Hydrogen atoms were included in idealized positions and
refined with isotropic displacement parameters. In the case of the mer
isomer, the distance between the atoms labeled as C(3) and O(3) was
fixed to chemically accepted values. Details of crystal data and struc-
tural refinement are given in Table 1.
Z. Anorg. Allg. Chem. 2010, 506–510
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
507

S. Bolaño, J. Bravo, J. Castro, S. García-Fontán, M. C. Marín
ARTICLE
Table 1. Crystal data and structure refinement for compounds 2 and 4.
Compound
2
4
Empirical formula
Formula weight
C30H26ClO5P2Re
750.10
C30H26ClO5P2Re
750.10
Temperature /K
293(2)
293(2)
Wavelength /Å
0.71073
0.71073
Monoclinic
P21
Crystal system
Triclinic
¯
Space group
P1
Unit cell dimensions /Å and /°
a = 10.4268(8)
b = 11.0596(8)
c = 12.964(1)
α = 90.344(1)
β = 101.659(1)
γ = 94.458(1)
1459.3(2)
a = 10.372(1)
b = 14.357(2)
c = 10.402(1)
α = 90
β = 108.589(2)
γ = 90
Volume /Å3
1468.2(3)
2
Z
2
Density (calculated) / g·cm–3
Absorption coefficient /mm–1
F(000)
1.707
1.697
4.402
4.376
736
736
Crystal size /mm
Theta range for data collection
Index ranges
0.57 × 0.43 × 0.04
1.85 to 28.04°
–13 ≤ h ≤ 13
–14 ≤ k ≤ 14
–17 ≤ l ≤ 14
9266
0.54 × 0.36 × 0.05
2.07 to 28.05°
–13 ≤ h ≤ 13
–18 ≤ k ≤ 16
–13 ≤ l ≤ 10
9492
Reflections collected
Independent reflections
Reflections observed (>2σ)
Data Completeness
6470 [R(int) = 0.0564]
5377
0.915
6229 [R(int) = 0.0782]
5543
0.972
Absorption correction
Max. and min. transmission
Refinement method
Semi-empirical from equivalents
1.0000 and 0.356964
Full-matrix least-squares on F2
6470/0/352
1.00000 and 0.272668
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I>2σ (I)]
6229/1/352
1.026
0.996
R1 = 0.0588
R1 = 0.0568
wR2 = 0.1429
R1 = 0.0615
wR2 = 0.1456
0.005(14)
wR2 = 0.1481
R indices (all data)
R1 = 0.0672
wR2 = 0.1524
Absolute structure parameter
Largest diff. peak and hole /e·Å–3
2.506 and –4.129
2.298 and –2.463
Scheme 3.
Scheme 1.
Scheme 2.
at 1.97 ppm (2H) and 3.78 ppm (4H) that may be assigned to
the methylene protons of the diphosphinite ligand. In agree-
ment with these results, the 13C{1H} NMR spectrum shows a
2
doublet of doublets at 192.0 ppm (2JC,P = 56.3, JC,P = 6 Hz)
at low fields, which corresponds to the CO group trans to the
phosphorus atom, and one triplet at 191.5 ppm (2JC,P
=
9.2 Hz), which corresponds to the mutually trans CO groups
(the intensity of this signal is approximately twice as the previ-
ous one).
Description of the Structures
shows two doublets, which are expected for two non-equiva-
2
lent phosphorus nuclei (at 105.1 and 110.2 ppm; JP,P
=
Perspective views of the molecular structures of compounds
16 Hz). The H NMR spectrum shows two multiplets located 2 and 4 are shown in Figure 1, Figure 2 and Figure 3, respec-
1
508
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© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2010, 506–510

New Chlorocarbonylrhenium(I) Complexes with P-Donor Chelate Ligands
Table 2. Selected bond lengths /Å and angles /° for compounds 2 and
4.
tively, along with the atom numbering scheme. Selected bond
lengths and bond angles are listed in Table 2.
Compound
2
4
Bond lenghts
Re–Cl
2.511(2)
1.951(10)
1.887(9)
1.979(9)
2.449(2)
2.470(2)
2.463(4)
1.981(13)
2.061(14)
2.036(18)
2.454(3)
2.386(2)
Re–C(1)
Re–C(2)
Re–C(3)
Re–P(1)
Re–P(2)
Bond angles
C(1)–Re–C(2)
C(1)–Re–C(3)
C(1)–Re–Cl
86.9(4)
89.8(4)
90.0(3)
89.7(3)
177.4(3)
90.5(4)
176.8(3)
89.6(3)
91.0(3)
88.9(3)
179.5(3)
88.7(3)
91.03(7)
92.11(7)
91.78(6)
174.6(9)
178.3(9)
178.3(9)
177.1(6)
89.9(6)
87.7(5)
C(1)–Re–P(1)
C(1)–Re–P(2)
C(2)–Re–C(3)
C(2)–Re–Cl
89.2(4)
90.9(5)
90.6(4)
95.2(4)
C(2)–Re–P(1)
C(2)–Re–P(2)
C(3)–Re–Cl
91.1(4)
86.3(4)
83.7(4)
C(3)–Re–P(1)
C(3)–Re–P(2)
P(1)–Re–Cl
165.6(4)
87.5(4)
Figure 1. Molecular structure of 2. Ellipsoids were drawn at 20 %
probability.
81.83(12)
171.12(13)
106.92(10)
176.4(13)
176.3(14)
174.8(19)
P(2)–Re–Cl
P(1)–Re–P(2)
O(1)–C(1)–Re
O(2)–C(2)–Re
O(3)–C(3)–Re
bidentate phosphinite ligand and a chloride ligand. The three
carbonyl ligands are facially disposed in compound 2 and me-
ridionally disposed in compound 4. In the case of the fac com-
pound 2, the octahedron is regular with angle deviations less
than 4° from the theoretically expected angles of 90° or 180°.
The bond lengths around the rhenium atom are in good agree-
ment with those found in the literature for similar systems [14].
Thus, the Re–P bond lengths are, in average, 2.459(9) Å, with
a difference less than 0.02 Å between them. The Re–C bond
lengths corresponding to the CO ligands trans to the phospho-
rus atoms are slightly longer [1.965(9) Å in average] than that
trans to the chloride ligand [1.887(9) Å], reflecting the π-ac-
ceptor character of the phosphinite ligand in contrast with the
π-donor character of the chloride. On the other hand, the eight
membered chelate ring adopts a typical chair conformation
[15] with the eight atoms located in two parallel planes [dihe-
dral angle 3.6(1)°]. P(1), P(2), O(51) and O(52) atoms define
one plane (rms: 0.045) with the rhenium atom situated at
0.650(5) Å below this plane. The C(51), C(52) and C(53) at-
oms conform the second plane (see Figure 2).
Figure 2. Chelate ring of compound 2.
Although some X-ray structurally resolved mer,trans-
[ReCl(CO)3P2] compounds are found in the literature, mainly
with monodentate phosphanes [13, 16], the mer,cis-
[ReCl(CO)3P2] compounds are scarce [4c, 4d, 13, 16c, 17–19].
In the case of compound 4, the cis configuration is required
by the nature of the diphosphinite ligand (Figure 3) and the
Figure 3. Molecular structure of 4. Ellipsoids were drawn at 20 %
probability.
In both complexes, the metal atom is octahedrally coordi- location of the chloride ligand in the same plane that contains
nated by three carbonyl ligands, two phosphorus atoms of the this ligand, seems to be the main steric reason for the distor-
Z. Anorg. Allg. Chem. 2010, 506–510
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
509

S. Bolaño, J. Bravo, J. Castro, S. García-Fontán, M. C. Marín
ARTICLE
Acknowledgement
Financial support from the Xunta de Galicia (Project
PGIDT04PXIC31401PN) and the Ministerio de Educación y Ciencia
(Project BQU2003-06783) is gratefully acknowledged. We thank the
University of Vigo CACTI services for collecting X-ray data and re-
cording NMR spectra.
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Figure 4. Chelate ring of compound 4.
tions, which are observed in the octahedral arrangement of the
compound.
Thus, the bond angles around the metal atom are more dis-
torted than in the fac isomer, which is the most important
source of distortion the chelating angle P(1)–Re–P(2)
[106.9(1)° in contrast with 91.78(6) for compound 2]. The dis-
tortion affects mainly to the position of phosphorus atom la-
beled as P(1), being the C(3)–Re–P(1) axis [165.6(4)°] the
most distorted in the molecule. The Re–Cl bond length,
2.463(4) Å, is shorter than that found in the fac isomer (vide
supra) and it is also in the low limit of the values found in the
literature [14]. As it was found in compound 2, the different
nature of chloride and phosphinite ligands is reflected on the
bond lengths trans to them: the Re–P bond trans to a carbonyl
ligand [2.454(3) Å] is significantly longer than that trans to
the chloride [2.386(2) Å]. The Re–C bond lengths do not show
important differences among them [2.026(18) Å, average]. Fi-
nally, the eight-membered ring of compound 4 also presents a
different conformation than that of the compound 2 (Figure 4).
Thus, it shows a twisted boat conformation with six atoms [Re,
P(1), P(2), O(51), O(52), and C(52)] virtually coplanar (rms:
0.0593 Å), the C(53) atom situated at 0.862(14) Å above this
plane, and the C(51) atom situated at 0.803(14) Å below it.
This configuration was already observed in other complexes
with this ligand [4b, 4c, 17].
Conclusions
The chloro complexes fac-[ReCl(CO)3L1–3] (1, 2, 3) [L1 =
[17] G. Albertin, S. Antoniutti, J. Castro, S. Carniato, S. García-Fon-
tán, J. Organomet. Chem. 2006, 691, 5592.
[18] G. Albertin, S. Antoniutti, J. Bravo, J. Castro, S. García-Fontán,
M. C. Marín, M. Noè, Eur. J. Inorg. Chem. 2006, 3451.
[19] S. Bucknor, F. A. Cotton, L. R. Falvello, A. H. Reid Jr., C. D.
Schmulbach, Inorg. Chem. 1986, 25, 1021.
1,2-bis(diphenylphosphinoxy)ethane; L2 = 1,3-bis(diphenyl-
phosphinoxy)propane; L3
=
1,2-bis(diisopropylphosphin-
oxy)ethane], and mer-[ReCl(CO)3L2] (4), were synthesized
and characterized. Compounds 2 and 4 were structurally char-
acterized by X-ray diffraction analysis. Compound 4 slowly
isomerizes in solution at room temperature to compound 2. All
complexes are mononuclear compounds.
Received: August 17, 2009
Published Online: December 3, 2009
510
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Z. Anorg. Allg. Chem. 2010, 506–510