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Rhenium(I) carbonyl complexes bearing the alkenylphosphinite ligand Ph2POCH2CHCH2
Journal Pre-proofs Rhenium(I) Carbonyl Complexes bearing theAlkenylphosphiniteligandPh2POCH2CH=CH2 Nuria Álvarez-Pazos, Jorge Bravo, Ana M. Graña, Soledad García-Fontán PII: DOI: Reference:
S0277-5387(19)30733-8 https://doi.org/10.1016/j.poly.2019.114288 POLY 114288
To appear in:
Polyhedron
Received Date: Revised Date: Accepted Date:
30 September 2019 5 December 2019 6 December 2019
Please cite this article as: N. Álvarez-Pazos, J. Bravo, A.M. Graña, S. García-Fontán, Rhenium(I) Carbonyl Complexes bearing theAlkenylphosphiniteligandPh2POCH2CH=CH2, Polyhedron (2019), doi: https://doi.org/ 10.1016/j.poly.2019.114288
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Rhenium(I) Carbonyl Complexes bearing theAlkenylphosphiniteligandPh2POCH2CH=CH2
Nuria Álvarez-Pazosa,b, Jorge Bravoa, Ana M. Grañac and Soledad García-Fontána,b [a] Departamento de Química Inorgánica, Universidade de Vigo, Campus Universitario, E-36310 Vigo, Galicia –Spain. [b] Metallosupramolecular Chemistry Group
Galicia
South
Health
Research
Institute
(IIS
Galicia
Sur)
SERGAS-UVIGO. Galicia – Spain. [c] Departamento de Química Física, Universidade de Vigo, Campus Universitario, E-36310 Vigo, Galicia –Spain.
Abstract New bromo- and chloro- tricarbonylrhenium(I) complexes [ReX(CO)3)L2] [X=Cl (1);
Br(2)]
containing
the
bifunctional
phosphinite/
alkene
ligand
Ph2POCH2CH=CH2(L), have been prepared by reaction of the complexes[ReX(CO)5] (X= Cl, Br) with L, in refluxing toluene. Both mer, trans (a) and fac, cis (b) isomers were obtained and the structures of derivatives 1a, 1b and 2a have been determined by single crystal X-ray diffraction analysis.
Keywords: Rhenium carbonyl, bromide, chloride, alkenylphosphinite ligand.
1. Introduction Transition metal carbonyl complexes have been extensively investigated due to the fact that they have many applications ranging from catalysts for CO2 reduction in CO [1], electron transfer processes [1c], non-linear optical properties [2] to biochemistry.[3] Some properties of these compounds are related to the synergistic effects of the σ and π bonds between the metal center and the CO ligands. [4] On the other hand, ligands containing phosphorus atoms are widely used in homogeneous catalysis, coordination and organometallic chemistry. [5] Their electronic and steric characteristics can be easily and predictably modified which allows to use them in many metal complexes. Substitution of the R groups
from PR3 by OR groups to form mixed phosphites (PRn(OR)3-n; n = 0–2) are being used as auxiliary ligands because their higher acceptor and lower donor character (compared with phosphines [3]) allows the design of new Lewis acid centers. These changes, in turn, modify the properties of the metal complex. We have previously reported the synthesis and characterization of rhenium and manganese carbonyl complexes containing phosphites, phosphinites and phosphonites (mono and bidentate) as supporting ligands. [6] Now, we have extended these studies to complexes containing the bifunctional ligand, L= Ph2POCH2CH=CH2, because this type of ligands can stabilize reactive intermediates thanks to its ability to generate/occupy a vacant coordination site at the metal center. [7] Although several transition metal complexes with alkenylphosphanes (R2P(CH2)nCH=CH2 n=0-2) have been reported [7, 8], to the best of our knowledge, there are no examples of rhenium(I) complexes with alkenylphosphite ligands, probably due to the low stability and difficulty of isolating these ligands. Therefore, is important to understand the coordination behavior of those ligand with a transition metal as it provides basic information about the reactivity, stability, steric and electronic situation around the metal center.
2. Experimental section 2.1. General considerations All experiments were carried out under an atmosphere of argon by Schlenk techniques. Solvents were dried by the usual procedures [9] and, prior use, distilled under argon. The starting material [ReCl(CO)5] was purchased from commercial source while [ReBr(CO)5] [10] and PPh2OCH2CH=CH2(L) [11] were prepared as described in the literature. All other reagents were obtained from commercial sources. NMR spectra were recorded at room temperature on Bruker ARX-400 and Bruker DPX-600 instruments, with resonating frequencies 400 MHz (1H), 161 MHz (31P{1H}) and 100 MHz (13C{1H}) using the solvents as the internal lock. 1H and
13C{1H}
signals are referred to internal TMS and
31P{1H}
to 85%
H3PO4; downfield shifts (expressed in ppm) are considered positive. 1H and 13C{1H} NMR signal assignments were confirmed by {1H, 1H} COSY and {1H,
13C}
HSQC.
Coupling constants are given in hertz. Infrared spectra were run on a Jasco FT/IR (ATR) spectrometer. C, H analyses were carried out with a Carlo Erba 1108 analyzer.
2.2. Synthesis of complexes mer, trans- and fac, cis- [ReX(CO3)L2] (X= Cl, Br; L= PPh2OCH2CH=CH2) (1a-b,2 a-b) An excess of the ligand L (1.0mmol) was added to a solution of [ReX(CO)5] (X= Cl, Br) (0.4mmol) in toluene (10 mL). The reaction mixture was refluxed for 4 hours. The solvent was removed under reduced pressure giving an oil. The oil was redissolved in 5ml of diethylether. This solution was purified by passing it through silica gel using dichloromethane as the eluent. Then the solvent was removed under reduced pressure giving an oil, which was treated with ethanol (4 mL) until a white solid separated. This solid was a mixture of mer, trans and fac, cis isomers (1a-b, 2a-b) in a 25:75 and 90:10 mole ratio, respectively (based on NMR integration data). These isomers were separated by column chromatography (silica gel and dichloromethane as the eluent). Recrystallization of the mixtures with CH2Cl2/ethanol (2:5) gave colorless crystals of 1a,b and 2aby slow evaporation of the solvent. mer, trans- [ReCl(CO3)L2] (1a). Anal. Calc. for C33H30ClO5P2Re (790.08 g/mol): C, 50.12; H, 3.83. Found: C, 50.20; H, 3.80. FT- IR (ATR): CO 2052 (w), 1938 (s), 1891 (s) cm-1. 1H NMR (CDCl3, 25 °C) δ: 7.86- 7.36 (m, 20H, Ph), 5.88 (m, 2H, CH L), 5.34 (dd, 3JHH= 17.2, 2JHH= 1.6 Hz, 2H, =CH2 L), 5.15 (dd, 3JHH= 10.5, 2JHH=1.4 Hz, 2H, =CH2 L), 4.31 (m, 4H, OCH2 L) ppm; 13C NMR (CDCl3, 25 °C) δ: 191.6 (t, 2JCP= 9.3 Hz, CO), 187.9 (t, 2JCP= 6.8 Hz, CO), 137.8- 128.1 (Ph), 133.6 (t, 3JCP= 3.6 Hz, CH L), 117.0 (s, =CH2 L), 67.5 (s br, OCH2 L) ppm; 31P NMR (CDCl3, 25 °C) δ: 102.2 (s) ppm. fac, cis-[ReCl(CO3)L2] (1b). Anal. Calc. for C33H30ClO5P2Re (790.08 g/mol): C, 50.12; H, 3.83. Found: C, 50.05; H, 3.86. FT- IR (ATR): CO 2029 (m), 1949 (s), 1886 (s) cm-1. 1H NMR (CDCl3, 25 °C) δ: 7.86- 7.36 (m, 20H, Ph), 5.70 (m, 2H, CH L), 5.18
(dd, 3JHH=17.2,2JHH= 1.6 Hz, 2H, =CH2 L), 5.08 (dd, 3JHH=10.5, 2JHH=1.3 Hz, 2H, =CH2 L), 4.06 (m, 4H, OCH2 L) ppm;
13C
NMR (CDCl3, 25 °C) δ: 190.1 (m, CO), 188,6
(t,2JCP= 8.5 Hz CO), 137.8 - 128.1 (Ph), 133.5 (t, 3JCP= 3.6 Hz, CH L), 117.1 (s, =CH2 L), 68.4 (t, 2JCP= 4.5 Hz, OCH2 L) ppm; 31P NMR (CDCl3, 25 °C) δ: 101.4 (s) ppm. mer, trans- [ReBr(CO3)L2] (2a). Anal. Calc. for C33H30BrO5P2Re (834.03 g/mol): C, 47.48; H, 3.63 Found: C, 47.50; H, 3.60. FT- IR (ATR): CO 2065 (w), 1946 (s), 1913 (s) cm-1. 1H NMR (CDCl3, 25 °C) δ: 7.86- 7.37 (m, 20H, Ph), 5.87 (m, 2H, CH L), 5.34 (dd, 3JHH= 17.2, 2JHH= 1.6 Hz, 2H, =CH2 L), 5.14 (dd, 3JHH= 10.5,2JHH= 1.2 Hz, 2H, =CH2 L), 4.26 (m, 4H, OCH2 L) ppm; 13C NMR (CDCl3, 25 °C) δ: 190.8 (t, 2JCP= 9.9 Hz, CO), 187.4 (t, 2JCP= 7.3 Hz, CO), 137.7- 128.3 (Ph), 133.5 (t, 3JCP= 4.2 Hz, CH L), 117.0 (s br, =CH2 L), 67.5 (t, 2JCP= 1.9 Hz, OCH2 L) ppm; 31P NMR (CDCl3, 25 °C) δ: 99.5 (s) ppm. fac, cis- [ReBr(CO3)L2](2b). Anal. Calc. for C33H30BrO5P2Re (834.03 g/mol): C, 47.48; H, 3.63 Found: C, 47.62; H, 3.58.FT- IR (ATR): CO 2030 (m), 1952 (s), 1890 (s) cm-1. 1H NMR (CDCl3, 25 °C) δ: 7.86- 7.37 (m, 20H, Ph), 5.98 (m, 2H, CH L), 5.20 (dd, 3JHH= 17.2, 2JHH= 1.4 Hz, 2H, =CH2 L), 5.09 (dd, 3JHH= 10.5,2JHH= 1.2 Hz, 2H, =CH2 L), 4.00 (m, 4H, OCH2 L) ppm; 13C NMR (CDCl3, 25 °C) δ: 189.1 (m, 2JCP = 9.9 Hz, CO), 188.0 (t, 2JCP= 8.4 Hz, CO), 135.7- 127.5 (Ph), 133.3 (t, 3JCP = 3.6 Hz, CH L), 117.0 (s, =CH2 L), 68.4 (t, 2JCP = 4.9 Hz, OCH2 L) ppm; 31P NMR (CDCl3, 25 °C) δ: 98.4 (s) ppm.
2.3. Crystal structure determination ofmer, trans- ReCl(CO3)L2] (1a), fac, cis[ReCl(CO3)L2] (1b) and mer, trans- [ReBr(CO3)L2] (2a). Crystallographic data were collected on Bruker D8 Venture diffractometer at CACTI (Universidade de Vigo) with graphite monochromated Mo K radiation (= 0.71073 Å) and were corrected for Lorentz and polarization effects. APEX 3 [12] software was used for collecting data frames, indexing reflections, and determining lattice parameters, SAINT [13] for integration of intensity of reflections and scaling, and SABADS [14] for empirical absorption correction. The crystallographic treatment of the compounds 1a, 1b and 2a was performed with the SHELXL97 program [15]. The structures were solved by direct methods. Non-hydrogen atoms
were refined with anisotropic displacement parameters by full-matrix leastsquares calculations on F2 using the program SHELXL with OLEX2 [16]. Hydrogen atoms were calculated in idealized positions and refined with isotropic displacement parameters. Details of crystal data and structural refinement are given in Table 1. Table 1. Crystal data and structure refinement details for the 1a, 1b and 2a compounds. 1a
1b
2a
Empirical formula
C33H30ClO5P2Re
C33H30ClO5P2Re
C33H30BrO5P2Re
Formula weight
790.16
790.16
834.62
Temperature (K)
105.46
99.95
100.0
Wavelength (Å)
0.71073
0.71073
0.71073
Crystal system
Monoclinic
Monoclinic
Monoclinic
Space group
P21/n
P21/n
P21/n
a (Å)
16.1776 (11)
17.0238 (6)
10.2859(4)
b (Å)
11.5441 (8)
9.8920 (4)
26.2030(8)
c (Å)
16.7889 (12)
18.8450 (7)
12.0318(4)
(°)
90
90
90
β (°)
96.992 (2)
103.292 (2)
99.1850 (10)
(°)
90
90
90
Volume (Å3)
3112.1 (4)
3088.5 (2)
3201.25 (19)
Z
4
4
4
Density (calculated) (Mg/m3)
1.686
1.699
1.732
Absorption coefficient (mm-1)
4.133
4.165
5.183
F(000)
1560
1560
1632
Crystal size (mm)
0.2330.0770.065 0.0730.0660.061
0.2190.1730.093
θ range for data collection (°)
2.444- 28.348
2.398-28.368
2.314- 28.345
Index ranges
−21 ≤ h ≤ 21
−22 ≤ h ≤ 22
−13 ≤ h ≤ 13
−15 ≤ k ≤ 15
−13 ≤ k ≤ 13
−34 ≤ k ≤ 34
−22 ≤ l ≤ 22
−25 ≤ l ≤ 23
−16 ≤ l ≤ 16
Reflections collected
58999
57028
63644
Independent reflections
7767
7721
7970
[R(int)= 0.0330]
[R(int) = 0.0593]
[R(int) = 0.0463]
Data completeness
0.999
0.999
0.999
Abs. Correc.
Semi-empirical
Semi-empirical from
from equivalents
equivalents
Max. and min. transmission
0.7457 and 0.4525
0.7457 and 0.6592
0.0962 and 0.0530
Refinement method
Full-matrix least-
Full-matrix least-
Full-matrix least-
squares on F2
squares on F2
7767/0/426
7721/0/407
7970/5/385
1.076
1.057
1.118
Unit cell dimensions
squares on Data/restraints/parameters Goodness-of-fit on
F2
F2
Semi-empirical from equivalents
Final R indices [I>2σ(I)] R indices (all data)
R1= 0.0189
R1= 0.0292
R1= 0.0500
wR2= 0.0399
wR2= 0.0429
wR2= 0.1071
R1= 0.0219
R1= 0.0437
R1= 0.0641
wR2= 0.0407
wR2= 0.0455
wR2= 0.1129
0.588 and −1.051
2.464 and −1.863
Largest diff. peak and hole, e.Å-3 0.864 and −0.826
3. Results and Discussion CO OC
Re
CO X
OC
L
PPh2 O
Toluene 4 h reflux
OC
Re
L CO X
OC
CO
L
X= Br, Cl
mer, trans X= Cl (1a); Br (2a)
OC
Re
L X
OC CO fac, cis
X= Cl (1b); Br (2b)
Scheme 1: Synthesis of the complexes 1a- b and 2a- b.
The reaction of [ReX(CO)5] (X = Cl, Br) with an excess of ligand [17] L=PPh2OCH2CH= CH2 in refluxed toluene replaced two CO ligands, resulting in a mixture of the mer, trans and fac, cis [ReX(CO)3L2] (X = Cl, Br) 1-2 isomers but in a different product distribution (25:75 1a-b and 90:10 2a-b mole ratio, respectively) (Scheme1). Similar fac, cis and mer, trans- complexes ([ReBr(CO)3L2] (L= PPh2-x(OR)X+1; X=0,1; R=Me, Et)) have been previously prepared by thermal displacement of CO ligand, being the fac, cis- isomers obtained in a lower yield than the corresponding mer, trans- ones. [6c] In our case, the isomer that is formed with higher yield depends on the nature of the halogen atom, being the major isomers fac, cis [ReCl(CO)3L2] 1b and mer, trans [ReBr(CO)3L2] 2a. We have performed preliminary computational studies of complexes 1 and 2. These studies show there are small differences of energy [18] between cis- and trans- dispositions suggesting that the reasons for the abovementioned isomer distribution should be due to the kinetic mechanism more than thermodynamic factors. The new complexes are stable in solid state and in halogenated solvents for, at least, a month at room temperature (tested by NMR spectroscopy). Analytical and spectroscopic (IR and NMR) data of compounds 1 and 2 support the proposed formulation. The three strong bands at ν(CO) 2029, 1949 and 1886 cm-1 for [ReCl(CO)3L2] (1b) and at 2030 (m), 1952 (s), 1890 (s) [ReBr(CO)3L2] (2b) are consistent with a fac- CO arrangement. [6b] The IR spectrum of the mer, trans
compounds shows a weak band at 2052 cm-1 (1a) and at 2065 cm-1 (2a), and two strong bands at 1938, 1891 cm-1(1a) and 1946, 1913 cm-1 (2a), respectively (See Supporting Information). The 31P{1H} NMR spectra in CDCl3 display a single resonance showing the magnetic equivalence of the phosphorous nuclei of both phosphinite ligands. The
1H
and
13C{1H}
NMR spectra confirm the κ1-P coordination mode of
alkenylphospinite, displaying resonances of the uncoordinated allylic group: the 1H NMR spectra shows two doublets of doublets at δ =5.34 and 5.15ppm (1a) δ=5.18 and 5.08 ppm (1b) δ=5.34 and 5.14 ppm (2a) δ=5.36 and 5.24 ppm (2b) corresponding to the diastereotopic =CH2 protons; and one multiplet (=CH resonance) at δ 5.88ppm (1a), δ= 5.70ppm (1b), δ= 5.87 ppm (2a) and δ= 5.98ppm (2b) (see Figure 1).
CH
=CH2
OCH2
Figure 1: 1H NMR spectrum of 2a (top) and 2b (bottom).
The 13C{1H} NMR spectra in CDCl3 shows two isomers clearly differentiated by the multiplicities of the low field signals assignable to the CO groups. Two triplets at δ: 191.6 ppm (2JCP=9.3 Hz) and 187.9 ppm (2JCP=6.8 Hz) (1a); 190.8 ppm (2JCP=9.9 Hz) and 187.4 (2JCP= 7.3 Hz) (2a) belonging the mer, trans isomers correspond to the two CO ligands trans to each other and the CO trans to the halide ligand, respectively (see figure 2). On the other hand, the spectra of the fac, cis isomers show a triplet at δ=188.6 ppm (2JCP= 8.5 Hz) (1b); 189.1 ppm (2JCP= 8.4 Hz)
(2b), corresponding to CO located cis to both phosphorous nuclei, and a multiplet at 190.1 ppm (1b) and 189.1 ppm (2b) corresponding to the other CO ligands. Simulation of these multiplets by gNMR [19] confirms the presence of an AA'X system
with
a
strong
coupling
between
both
phosphorous
nuclei
(δx=189.1 ppm; JAX= -11.91 Hz, JA´X= 71.49Hz, JAA´= -32.00 Hz) (See figure 3). This pattern was already observed for similar compounds. [6]
L L OC
CO
Re
OC CO
L Br
OC
Br
OC
Re CO
L
CO CO
CO
Figure 2: low field region 13C{1H} NMR spectra of the compounds 2a (left) and 2b (right).
189.900
189.600
189.300
189.000
188.700
188.400
189.900
189.600
189.300
189.000
188.700
188.400
Figure 3: Experimental (top) and simulated (bottom) 13C{1H} NMR spectra of the carbonyl ligand of the compound 2b.
In addition to the spectroscopic characterization of the complexes, the molecular structures of compounds 1a, 1b and 2a were determined by X-ray crystallography. ORTEP drawings of these structures (Figures 4 and 5) and selected bond lengths and angles (Table 2) are shown.
C(4)
C(5) C(6)
C(7) O(4)
O(4) C(5) C(4)
P(1) O(2)
C(2)
C(1)
P(1)
O(1) O(1)
Re
O(5)
C(1)
O(3)
O(2)
C(3)
C(2)
Re
C(9) P(2)
Cl
C(8) C(7)
P(2) Cl
C(7) C(3)
O(5) C(8) C(9)
O(3)
Figure 4: ORTEP drawing of complexes 1a (left) and 1b (right). Thermal ellipsoids are shown at 50% probability. Hydrogen atoms are omitted for clarity.
The complex 1b, adopt a slightly distorted octahedral geometry around the rhenium center. The rhenium atom is located on a twofold axis perpendicular to Cl-Re-C(1)-O(1) axis. A 180° rotation generates two equivalent carbonyl and two cis- phospinite ligands, and results in an orientational disorder between the Cl and C(1)-O(1) groups. Within the accuracy allowed by the disorder note above, the Re(I) is coordinated to three carbonyl in fac (1b) and mer (1a) arrangement, an halogen atom and two phosphorous atoms from the phosphinite ligands. The average Re-C and Re-P distances (1.928 (2) Å and 2.4588 (5) Å, respectively) are similar to the corresponding distances reported for analogous complexes. [6c] Besides the CO ligand trans to Cl is close to the Re atom as expected from the πdonor character of the halogen (1.873(17) Å vs. 1.960(3) Å). The bond angle P(1)Re-P(2) (91.61(2)°) is almost ideal, which seems to indicate that the ligand PPh2OCH2CH=CH2 does not originate any steric hindrance. [6a, 6b]
C(8)
C(7)
C(9)
O(5) P(2)
O(2) C(2)
O(1)
Re C(1) Br
C(3) O(3)
P(1) O(4)
C(6) C(5)
C(4)
Figure 5: ORTEP drawing of complex 2a. Thermal ellipsoids are shown at 50% probability. Hydrogen atoms are omitted for clarity.
Like in 1b the structures of compounds 1a and 2a are disordered. The rhenium atom lies in an octahedral coordination environment formed by two mutually trans phophinite ligands, three mer carbonyl groups and the halogen atom (Cl or Br). The length of the Re-P bonds is shorter in the mer, trans [ReBr(CO)3L2] isomer (2a) (2.3870 (16) Å) than in mer, trans [ReCl(CO)3L2] (1a) (2.4165 (6)) as found in other similar compounds. The replacement of Cl by Br ligand affects the geometry of the coordination polyhedron around rhenium being the P(1)-Re-P(2) angle in 1a 172.679(18)° is smaller than in 2a 177.29(7)°, suggesting a steric influence of these ligands.
Table2: Selected bond lengths (Å) and angles ( ° ) for 1a, 1b and 2a.
Re- P(1) Re- P(2) Re- C(1A) Re- C(1B) Re- C(2) Re- C(3) Re- Cl, Br(1A) Re- Cl, Br(1B) P(1)- Re- P(2) P(1)- Re- Cl(1A)
1a 2.4165(6) 2.4183(5) 1.966(9) 1.975(10) 1.979(3) 1.949(2) 2.479(2) 2.487(3) 172.679(18) 93.38(5)
1b 2.4623(7) 2.4553(7) 1.921(10) 1.873(17) 1.959(3) 1.960(3) 2.509(2) 2.500(4) 91.61(2) 89.38(5)
2a 2.3870(16) 2.3944(18) 2.20(2) 1.937(13) 1.893(8) 1.975(6) 2.566(8) 2.6435(9) 177.29(7) 90.95(15)
P(1)- Re- Cl(1B) P(2)- Re- Cl(1A) P(2)- Re- Cl(1B) P(1)- Re- C(1A) P(1)- Re- C(1B) P(1)- Re- C(2) P(1)- Re- C(3) P(2)- Re- C(1A) P(2)- Re- C(1B) P(2)- Re- C(2) P(2)- Re- C(3) C(1A)- Re- Cl(1A) C(1B)- Re- Cl(1B) C(2)- Re- Cl(1A) C(2)- Re- Cl(1B) C(3)- Re- Cl(1A) C(3)- Re- Cl(1B) C(1A)- Re- C(2) C(1B)- Re- C(2) C(1A)- Re- C(3) C(1B)- Re- C(3) C(2)- Re- C(3)
86.15(6) 88.63(5) 86.59(6) 86.5(3) 93.9(3) 91.16(7) 89.69(7) 86.3(3) 87.7(3) 96.01(7) 89.34(7) 95.9(3) 94.8(3) 85.86(9) 174.90(9) 171.36(9) 89.64(10) 177.2(3) 89.7(3) 92.3(3) 174.5(3) 86.01(10)
91.87(10) 92.87(5) 88.62(10) 90.9(3) 90.6(4) 178.33(9) 87.47(9) 87.7(3) 91.2(4) 88.61(9) 177.40(9) 179.3(3) 177.6(4) 92.27(10) 86.48(13) 89.56(10) 88.97(13) 87.5(3) 91.1(4) 89.8(3) 91.3(4) 92.24(12)
90.13(5) 88.04(15) 87.62(6) 93.2(17) 89.8(4) 89.9(3) 90.4(2) 84.6(17) 89.1(4) 92.5(3) 90.8(2) 101.6(17) 97.7(4) 85.6(3) 172.8(3) 175.3(3) 82.8(2) 172.1(17) 89.5(5) 82.7(17) 179.4(5) 90.0(3)
In the three complexes 1a, 1b and 2a the nature of ligands allows the formation of supramolecular assemblies based on edge-to-face CH··· interactions and nonclassic hydrogen bonds CH···O. In the complex 1a, chains along the b axis are formed by C-H···π interactions between an aromatic CH group and a phenyl ring[C21- H21··Cg(1)i i: x, -1+y, z; Cg(1): C22-C23-C24-C25-C26-C27, d(H···Cg) 3.00 Å; d(C···Cg) 3.8653(3)Å; (CH···Cg) 153° ] (see Figure 1). Two adjacent chains are further linked to each other by a weak non-classic hydrogen bond C-H···O being a terminal allylic CH the donor and a carbonyl ligand the acceptor [C9A-H9AA···O1Bii ii: ½-x, -½+y, ½-z; d(D···H) 0.95Å; d(H···A)2.57Å; d(D···A)3.4806(2)Å; (DHA)162°], generating a doublechain along the b axis (see Figure 6). In 1b, dimeric units are formed by C-H···π interactions between a terminal allylic CH and a phenyl ring [C6-H6A···Cg(1)i i: 1-x, 1-y, 1-z; Cg(1): C22-C23-C24-C25-C26C27, d(H···Cg) 2.89 Å; d(C···Cg) 3.8155(2)Å; (C-H···Cg) 166°]. The association of this dimeric units by additional C-H···π interactions involving an aromatic CH group and another phenyl ring [C12-H12···Cg(2)ii ii: -½+x, ½ -y, -½ +z; Cg(2): C28-
C29- C30- C31- C32- C33, d(H···Cg) 2.85 Å; d(C···Cg) 3.6504(1)Å; (C-H···Cg) 142°] permits the formation of a tridimensional network (see Figure 7). In the compound 2a, a single chain is generated due to the CH···π interaction also involving an aromatic CH group and another phenyl ring [C14-H14···Cg(1)i i: -½ +x, ½-y, ½+z; Cg(1): C28- C29- C30- C31- C32- C33, d(H···Cg) 2.99 Å; d(C···Cg) 3.7580(1)Å; (C-H···Cg) 139°]. The combination of the CH···π interactions and weak non-classic hydrogen bond involving carbonyl ligands [C11-H11···O2ii ii: –x, 1-y, 1-z; d(D···H) 0.95Å; d(H···A) 2.44 Å; d(D···A)3.2068(1)Å; (DHA) 138°; C12H12···O1Biii iii: -1+x, y, z; d(D···H) 0.95Å; d(H···A) 2.48 Å; d(D···A) 3.4255(1)Å; (DHA) 173°] generates a tridimensional architecture (see Figure 8).
Figure 6: Double chain along the b axis of the complex 1a formed by the CH···π interactions (blue) and non-classic hydrogen bonds (green).
Figure 7: 3D network of the compound 1b. CHallylic···π interactions in blue and CH···πinteractions in green.
Figure 8: Tridimensional architecture of the compound 2a (CH···π interactions in blue and hydrogen bonds in green).
4. Conclusions In this paper we report the synthesis and characterization of the first mer, transand fac, cis- [ReX(CO3)L] (X= Cl, Br) complexes containing the alkenylphosphinite ligand Ph2POCH2CH=CH2 (L). In all cases L is coordinated in a κ1-P mode. The nature of the halogen atom has an important role on the ratio of the fac, cis versus mer, trans- isomers, being the fac, cis- isomer more abundant when the halogen is Cl. Reasons for this difference should be kinetic because the energies of both isomers in each case are very similar.
Acknowledgements We thank PhD. Berta Covelo for making the supramolecular study and Professor Luis Muñoz for the NMR simulation. Financial support from Xunta de Galicia (Spain) (research ProjectED431D 2017/0) is gratefully acknowledged. We thank the Structural Determination Service of the Universidade de Vigo–CACTI for X-ray diffraction measurements and the collections of NMR data. Supplementary material CCDC1952317, 1952337 and 1952339 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystalographic Data Center via www.ccdc.cam.ac.uk/data_request/cif.
References All the autors contributed to the design and implementation of the research, to the analysis of the results and to the writting of the manuscript.
The autors declare no competing financial interests.
CO OC
Re
CO X
OC
L
PPh2 O
Toluene 4 h reflux
OC
Re
L CO X
OC
CO
L
X= Br, Cl
mer, trans X= Cl (1a); Br (2a)
OC
Re
L X
OC CO fac, cis
X= Cl (1b); Br (2b)
New complexes [ReX(CO)3)L2] [X=Cl, Br] containing a phosphinite ligand have been prepared. In all cases the bifunctional ligand is coordinated in a κ1-P mode and both mer-trans and fac-cis isomers were obtained.
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S0277-5387(19)30733-8 https://doi.org/10.1016/j.poly.2019.114288 POLY 114288
To appear in:
Polyhedron
Received Date: Revised Date: Accepted Date:
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Please cite this article as: N. Álvarez-Pazos, J. Bravo, A.M. Graña, S. García-Fontán, Rhenium(I) Carbonyl Complexes bearing theAlkenylphosphiniteligandPh2POCH2CH=CH2, Polyhedron (2019), doi: https://doi.org/ 10.1016/j.poly.2019.114288
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Rhenium(I) Carbonyl Complexes bearing theAlkenylphosphiniteligandPh2POCH2CH=CH2
Nuria Álvarez-Pazosa,b, Jorge Bravoa, Ana M. Grañac and Soledad García-Fontána,b [a] Departamento de Química Inorgánica, Universidade de Vigo, Campus Universitario, E-36310 Vigo, Galicia –Spain. [b] Metallosupramolecular Chemistry Group
Galicia
South
Health
Research
Institute
(IIS
Galicia
Sur)
SERGAS-UVIGO. Galicia – Spain. [c] Departamento de Química Física, Universidade de Vigo, Campus Universitario, E-36310 Vigo, Galicia –Spain.
Abstract New bromo- and chloro- tricarbonylrhenium(I) complexes [ReX(CO)3)L2] [X=Cl (1);
Br(2)]
containing
the
bifunctional
phosphinite/
alkene
ligand
Ph2POCH2CH=CH2(L), have been prepared by reaction of the complexes[ReX(CO)5] (X= Cl, Br) with L, in refluxing toluene. Both mer, trans (a) and fac, cis (b) isomers were obtained and the structures of derivatives 1a, 1b and 2a have been determined by single crystal X-ray diffraction analysis.
Keywords: Rhenium carbonyl, bromide, chloride, alkenylphosphinite ligand.
1. Introduction Transition metal carbonyl complexes have been extensively investigated due to the fact that they have many applications ranging from catalysts for CO2 reduction in CO [1], electron transfer processes [1c], non-linear optical properties [2] to biochemistry.[3] Some properties of these compounds are related to the synergistic effects of the σ and π bonds between the metal center and the CO ligands. [4] On the other hand, ligands containing phosphorus atoms are widely used in homogeneous catalysis, coordination and organometallic chemistry. [5] Their electronic and steric characteristics can be easily and predictably modified which allows to use them in many metal complexes. Substitution of the R groups
from PR3 by OR groups to form mixed phosphites (PRn(OR)3-n; n = 0–2) are being used as auxiliary ligands because their higher acceptor and lower donor character (compared with phosphines [3]) allows the design of new Lewis acid centers. These changes, in turn, modify the properties of the metal complex. We have previously reported the synthesis and characterization of rhenium and manganese carbonyl complexes containing phosphites, phosphinites and phosphonites (mono and bidentate) as supporting ligands. [6] Now, we have extended these studies to complexes containing the bifunctional ligand, L= Ph2POCH2CH=CH2, because this type of ligands can stabilize reactive intermediates thanks to its ability to generate/occupy a vacant coordination site at the metal center. [7] Although several transition metal complexes with alkenylphosphanes (R2P(CH2)nCH=CH2 n=0-2) have been reported [7, 8], to the best of our knowledge, there are no examples of rhenium(I) complexes with alkenylphosphite ligands, probably due to the low stability and difficulty of isolating these ligands. Therefore, is important to understand the coordination behavior of those ligand with a transition metal as it provides basic information about the reactivity, stability, steric and electronic situation around the metal center.
2. Experimental section 2.1. General considerations All experiments were carried out under an atmosphere of argon by Schlenk techniques. Solvents were dried by the usual procedures [9] and, prior use, distilled under argon. The starting material [ReCl(CO)5] was purchased from commercial source while [ReBr(CO)5] [10] and PPh2OCH2CH=CH2(L) [11] were prepared as described in the literature. All other reagents were obtained from commercial sources. NMR spectra were recorded at room temperature on Bruker ARX-400 and Bruker DPX-600 instruments, with resonating frequencies 400 MHz (1H), 161 MHz (31P{1H}) and 100 MHz (13C{1H}) using the solvents as the internal lock. 1H and
13C{1H}
signals are referred to internal TMS and
31P{1H}
to 85%
H3PO4; downfield shifts (expressed in ppm) are considered positive. 1H and 13C{1H} NMR signal assignments were confirmed by {1H, 1H} COSY and {1H,
13C}
HSQC.
Coupling constants are given in hertz. Infrared spectra were run on a Jasco FT/IR (ATR) spectrometer. C, H analyses were carried out with a Carlo Erba 1108 analyzer.
2.2. Synthesis of complexes mer, trans- and fac, cis- [ReX(CO3)L2] (X= Cl, Br; L= PPh2OCH2CH=CH2) (1a-b,2 a-b) An excess of the ligand L (1.0mmol) was added to a solution of [ReX(CO)5] (X= Cl, Br) (0.4mmol) in toluene (10 mL). The reaction mixture was refluxed for 4 hours. The solvent was removed under reduced pressure giving an oil. The oil was redissolved in 5ml of diethylether. This solution was purified by passing it through silica gel using dichloromethane as the eluent. Then the solvent was removed under reduced pressure giving an oil, which was treated with ethanol (4 mL) until a white solid separated. This solid was a mixture of mer, trans and fac, cis isomers (1a-b, 2a-b) in a 25:75 and 90:10 mole ratio, respectively (based on NMR integration data). These isomers were separated by column chromatography (silica gel and dichloromethane as the eluent). Recrystallization of the mixtures with CH2Cl2/ethanol (2:5) gave colorless crystals of 1a,b and 2aby slow evaporation of the solvent. mer, trans- [ReCl(CO3)L2] (1a). Anal. Calc. for C33H30ClO5P2Re (790.08 g/mol): C, 50.12; H, 3.83. Found: C, 50.20; H, 3.80. FT- IR (ATR): CO 2052 (w), 1938 (s), 1891 (s) cm-1. 1H NMR (CDCl3, 25 °C) δ: 7.86- 7.36 (m, 20H, Ph), 5.88 (m, 2H, CH L), 5.34 (dd, 3JHH= 17.2, 2JHH= 1.6 Hz, 2H, =CH2 L), 5.15 (dd, 3JHH= 10.5, 2JHH=1.4 Hz, 2H, =CH2 L), 4.31 (m, 4H, OCH2 L) ppm; 13C NMR (CDCl3, 25 °C) δ: 191.6 (t, 2JCP= 9.3 Hz, CO), 187.9 (t, 2JCP= 6.8 Hz, CO), 137.8- 128.1 (Ph), 133.6 (t, 3JCP= 3.6 Hz, CH L), 117.0 (s, =CH2 L), 67.5 (s br, OCH2 L) ppm; 31P NMR (CDCl3, 25 °C) δ: 102.2 (s) ppm. fac, cis-[ReCl(CO3)L2] (1b). Anal. Calc. for C33H30ClO5P2Re (790.08 g/mol): C, 50.12; H, 3.83. Found: C, 50.05; H, 3.86. FT- IR (ATR): CO 2029 (m), 1949 (s), 1886 (s) cm-1. 1H NMR (CDCl3, 25 °C) δ: 7.86- 7.36 (m, 20H, Ph), 5.70 (m, 2H, CH L), 5.18
(dd, 3JHH=17.2,2JHH= 1.6 Hz, 2H, =CH2 L), 5.08 (dd, 3JHH=10.5, 2JHH=1.3 Hz, 2H, =CH2 L), 4.06 (m, 4H, OCH2 L) ppm;
13C
NMR (CDCl3, 25 °C) δ: 190.1 (m, CO), 188,6
(t,2JCP= 8.5 Hz CO), 137.8 - 128.1 (Ph), 133.5 (t, 3JCP= 3.6 Hz, CH L), 117.1 (s, =CH2 L), 68.4 (t, 2JCP= 4.5 Hz, OCH2 L) ppm; 31P NMR (CDCl3, 25 °C) δ: 101.4 (s) ppm. mer, trans- [ReBr(CO3)L2] (2a). Anal. Calc. for C33H30BrO5P2Re (834.03 g/mol): C, 47.48; H, 3.63 Found: C, 47.50; H, 3.60. FT- IR (ATR): CO 2065 (w), 1946 (s), 1913 (s) cm-1. 1H NMR (CDCl3, 25 °C) δ: 7.86- 7.37 (m, 20H, Ph), 5.87 (m, 2H, CH L), 5.34 (dd, 3JHH= 17.2, 2JHH= 1.6 Hz, 2H, =CH2 L), 5.14 (dd, 3JHH= 10.5,2JHH= 1.2 Hz, 2H, =CH2 L), 4.26 (m, 4H, OCH2 L) ppm; 13C NMR (CDCl3, 25 °C) δ: 190.8 (t, 2JCP= 9.9 Hz, CO), 187.4 (t, 2JCP= 7.3 Hz, CO), 137.7- 128.3 (Ph), 133.5 (t, 3JCP= 4.2 Hz, CH L), 117.0 (s br, =CH2 L), 67.5 (t, 2JCP= 1.9 Hz, OCH2 L) ppm; 31P NMR (CDCl3, 25 °C) δ: 99.5 (s) ppm. fac, cis- [ReBr(CO3)L2](2b). Anal. Calc. for C33H30BrO5P2Re (834.03 g/mol): C, 47.48; H, 3.63 Found: C, 47.62; H, 3.58.FT- IR (ATR): CO 2030 (m), 1952 (s), 1890 (s) cm-1. 1H NMR (CDCl3, 25 °C) δ: 7.86- 7.37 (m, 20H, Ph), 5.98 (m, 2H, CH L), 5.20 (dd, 3JHH= 17.2, 2JHH= 1.4 Hz, 2H, =CH2 L), 5.09 (dd, 3JHH= 10.5,2JHH= 1.2 Hz, 2H, =CH2 L), 4.00 (m, 4H, OCH2 L) ppm; 13C NMR (CDCl3, 25 °C) δ: 189.1 (m, 2JCP = 9.9 Hz, CO), 188.0 (t, 2JCP= 8.4 Hz, CO), 135.7- 127.5 (Ph), 133.3 (t, 3JCP = 3.6 Hz, CH L), 117.0 (s, =CH2 L), 68.4 (t, 2JCP = 4.9 Hz, OCH2 L) ppm; 31P NMR (CDCl3, 25 °C) δ: 98.4 (s) ppm.
2.3. Crystal structure determination ofmer, trans- ReCl(CO3)L2] (1a), fac, cis[ReCl(CO3)L2] (1b) and mer, trans- [ReBr(CO3)L2] (2a). Crystallographic data were collected on Bruker D8 Venture diffractometer at CACTI (Universidade de Vigo) with graphite monochromated Mo K radiation (= 0.71073 Å) and were corrected for Lorentz and polarization effects. APEX 3 [12] software was used for collecting data frames, indexing reflections, and determining lattice parameters, SAINT [13] for integration of intensity of reflections and scaling, and SABADS [14] for empirical absorption correction. The crystallographic treatment of the compounds 1a, 1b and 2a was performed with the SHELXL97 program [15]. The structures were solved by direct methods. Non-hydrogen atoms
were refined with anisotropic displacement parameters by full-matrix leastsquares calculations on F2 using the program SHELXL with OLEX2 [16]. Hydrogen atoms were calculated in idealized positions and refined with isotropic displacement parameters. Details of crystal data and structural refinement are given in Table 1. Table 1. Crystal data and structure refinement details for the 1a, 1b and 2a compounds. 1a
1b
2a
Empirical formula
C33H30ClO5P2Re
C33H30ClO5P2Re
C33H30BrO5P2Re
Formula weight
790.16
790.16
834.62
Temperature (K)
105.46
99.95
100.0
Wavelength (Å)
0.71073
0.71073
0.71073
Crystal system
Monoclinic
Monoclinic
Monoclinic
Space group
P21/n
P21/n
P21/n
a (Å)
16.1776 (11)
17.0238 (6)
10.2859(4)
b (Å)
11.5441 (8)
9.8920 (4)
26.2030(8)
c (Å)
16.7889 (12)
18.8450 (7)
12.0318(4)
(°)
90
90
90
β (°)
96.992 (2)
103.292 (2)
99.1850 (10)
(°)
90
90
90
Volume (Å3)
3112.1 (4)
3088.5 (2)
3201.25 (19)
Z
4
4
4
Density (calculated) (Mg/m3)
1.686
1.699
1.732
Absorption coefficient (mm-1)
4.133
4.165
5.183
F(000)
1560
1560
1632
Crystal size (mm)
0.2330.0770.065 0.0730.0660.061
0.2190.1730.093
θ range for data collection (°)
2.444- 28.348
2.398-28.368
2.314- 28.345
Index ranges
−21 ≤ h ≤ 21
−22 ≤ h ≤ 22
−13 ≤ h ≤ 13
−15 ≤ k ≤ 15
−13 ≤ k ≤ 13
−34 ≤ k ≤ 34
−22 ≤ l ≤ 22
−25 ≤ l ≤ 23
−16 ≤ l ≤ 16
Reflections collected
58999
57028
63644
Independent reflections
7767
7721
7970
[R(int)= 0.0330]
[R(int) = 0.0593]
[R(int) = 0.0463]
Data completeness
0.999
0.999
0.999
Abs. Correc.
Semi-empirical
Semi-empirical from
from equivalents
equivalents
Max. and min. transmission
0.7457 and 0.4525
0.7457 and 0.6592
0.0962 and 0.0530
Refinement method
Full-matrix least-
Full-matrix least-
Full-matrix least-
squares on F2
squares on F2
7767/0/426
7721/0/407
7970/5/385
1.076
1.057
1.118
Unit cell dimensions
squares on Data/restraints/parameters Goodness-of-fit on
F2
F2
Semi-empirical from equivalents
Final R indices [I>2σ(I)] R indices (all data)
R1= 0.0189
R1= 0.0292
R1= 0.0500
wR2= 0.0399
wR2= 0.0429
wR2= 0.1071
R1= 0.0219
R1= 0.0437
R1= 0.0641
wR2= 0.0407
wR2= 0.0455
wR2= 0.1129
0.588 and −1.051
2.464 and −1.863
Largest diff. peak and hole, e.Å-3 0.864 and −0.826
3. Results and Discussion CO OC
Re
CO X
OC
L
PPh2 O
Toluene 4 h reflux
OC
Re
L CO X
OC
CO
L
X= Br, Cl
mer, trans X= Cl (1a); Br (2a)
OC
Re
L X
OC CO fac, cis
X= Cl (1b); Br (2b)
Scheme 1: Synthesis of the complexes 1a- b and 2a- b.
The reaction of [ReX(CO)5] (X = Cl, Br) with an excess of ligand [17] L=PPh2OCH2CH= CH2 in refluxed toluene replaced two CO ligands, resulting in a mixture of the mer, trans and fac, cis [ReX(CO)3L2] (X = Cl, Br) 1-2 isomers but in a different product distribution (25:75 1a-b and 90:10 2a-b mole ratio, respectively) (Scheme1). Similar fac, cis and mer, trans- complexes ([ReBr(CO)3L2] (L= PPh2-x(OR)X+1; X=0,1; R=Me, Et)) have been previously prepared by thermal displacement of CO ligand, being the fac, cis- isomers obtained in a lower yield than the corresponding mer, trans- ones. [6c] In our case, the isomer that is formed with higher yield depends on the nature of the halogen atom, being the major isomers fac, cis [ReCl(CO)3L2] 1b and mer, trans [ReBr(CO)3L2] 2a. We have performed preliminary computational studies of complexes 1 and 2. These studies show there are small differences of energy [18] between cis- and trans- dispositions suggesting that the reasons for the abovementioned isomer distribution should be due to the kinetic mechanism more than thermodynamic factors. The new complexes are stable in solid state and in halogenated solvents for, at least, a month at room temperature (tested by NMR spectroscopy). Analytical and spectroscopic (IR and NMR) data of compounds 1 and 2 support the proposed formulation. The three strong bands at ν(CO) 2029, 1949 and 1886 cm-1 for [ReCl(CO)3L2] (1b) and at 2030 (m), 1952 (s), 1890 (s) [ReBr(CO)3L2] (2b) are consistent with a fac- CO arrangement. [6b] The IR spectrum of the mer, trans
compounds shows a weak band at 2052 cm-1 (1a) and at 2065 cm-1 (2a), and two strong bands at 1938, 1891 cm-1(1a) and 1946, 1913 cm-1 (2a), respectively (See Supporting Information). The 31P{1H} NMR spectra in CDCl3 display a single resonance showing the magnetic equivalence of the phosphorous nuclei of both phosphinite ligands. The
1H
and
13C{1H}
NMR spectra confirm the κ1-P coordination mode of
alkenylphospinite, displaying resonances of the uncoordinated allylic group: the 1H NMR spectra shows two doublets of doublets at δ =5.34 and 5.15ppm (1a) δ=5.18 and 5.08 ppm (1b) δ=5.34 and 5.14 ppm (2a) δ=5.36 and 5.24 ppm (2b) corresponding to the diastereotopic =CH2 protons; and one multiplet (=CH resonance) at δ 5.88ppm (1a), δ= 5.70ppm (1b), δ= 5.87 ppm (2a) and δ= 5.98ppm (2b) (see Figure 1).
CH
=CH2
OCH2
Figure 1: 1H NMR spectrum of 2a (top) and 2b (bottom).
The 13C{1H} NMR spectra in CDCl3 shows two isomers clearly differentiated by the multiplicities of the low field signals assignable to the CO groups. Two triplets at δ: 191.6 ppm (2JCP=9.3 Hz) and 187.9 ppm (2JCP=6.8 Hz) (1a); 190.8 ppm (2JCP=9.9 Hz) and 187.4 (2JCP= 7.3 Hz) (2a) belonging the mer, trans isomers correspond to the two CO ligands trans to each other and the CO trans to the halide ligand, respectively (see figure 2). On the other hand, the spectra of the fac, cis isomers show a triplet at δ=188.6 ppm (2JCP= 8.5 Hz) (1b); 189.1 ppm (2JCP= 8.4 Hz)
(2b), corresponding to CO located cis to both phosphorous nuclei, and a multiplet at 190.1 ppm (1b) and 189.1 ppm (2b) corresponding to the other CO ligands. Simulation of these multiplets by gNMR [19] confirms the presence of an AA'X system
with
a
strong
coupling
between
both
phosphorous
nuclei
(δx=189.1 ppm; JAX= -11.91 Hz, JA´X= 71.49Hz, JAA´= -32.00 Hz) (See figure 3). This pattern was already observed for similar compounds. [6]
L L OC
CO
Re
OC CO
L Br
OC
Br
OC
Re CO
L
CO CO
CO
Figure 2: low field region 13C{1H} NMR spectra of the compounds 2a (left) and 2b (right).
189.900
189.600
189.300
189.000
188.700
188.400
189.900
189.600
189.300
189.000
188.700
188.400
Figure 3: Experimental (top) and simulated (bottom) 13C{1H} NMR spectra of the carbonyl ligand of the compound 2b.
In addition to the spectroscopic characterization of the complexes, the molecular structures of compounds 1a, 1b and 2a were determined by X-ray crystallography. ORTEP drawings of these structures (Figures 4 and 5) and selected bond lengths and angles (Table 2) are shown.
C(4)
C(5) C(6)
C(7) O(4)
O(4) C(5) C(4)
P(1) O(2)
C(2)
C(1)
P(1)
O(1) O(1)
Re
O(5)
C(1)
O(3)
O(2)
C(3)
C(2)
Re
C(9) P(2)
Cl
C(8) C(7)
P(2) Cl
C(7) C(3)
O(5) C(8) C(9)
O(3)
Figure 4: ORTEP drawing of complexes 1a (left) and 1b (right). Thermal ellipsoids are shown at 50% probability. Hydrogen atoms are omitted for clarity.
The complex 1b, adopt a slightly distorted octahedral geometry around the rhenium center. The rhenium atom is located on a twofold axis perpendicular to Cl-Re-C(1)-O(1) axis. A 180° rotation generates two equivalent carbonyl and two cis- phospinite ligands, and results in an orientational disorder between the Cl and C(1)-O(1) groups. Within the accuracy allowed by the disorder note above, the Re(I) is coordinated to three carbonyl in fac (1b) and mer (1a) arrangement, an halogen atom and two phosphorous atoms from the phosphinite ligands. The average Re-C and Re-P distances (1.928 (2) Å and 2.4588 (5) Å, respectively) are similar to the corresponding distances reported for analogous complexes. [6c] Besides the CO ligand trans to Cl is close to the Re atom as expected from the πdonor character of the halogen (1.873(17) Å vs. 1.960(3) Å). The bond angle P(1)Re-P(2) (91.61(2)°) is almost ideal, which seems to indicate that the ligand PPh2OCH2CH=CH2 does not originate any steric hindrance. [6a, 6b]
C(8)
C(7)
C(9)
O(5) P(2)
O(2) C(2)
O(1)
Re C(1) Br
C(3) O(3)
P(1) O(4)
C(6) C(5)
C(4)
Figure 5: ORTEP drawing of complex 2a. Thermal ellipsoids are shown at 50% probability. Hydrogen atoms are omitted for clarity.
Like in 1b the structures of compounds 1a and 2a are disordered. The rhenium atom lies in an octahedral coordination environment formed by two mutually trans phophinite ligands, three mer carbonyl groups and the halogen atom (Cl or Br). The length of the Re-P bonds is shorter in the mer, trans [ReBr(CO)3L2] isomer (2a) (2.3870 (16) Å) than in mer, trans [ReCl(CO)3L2] (1a) (2.4165 (6)) as found in other similar compounds. The replacement of Cl by Br ligand affects the geometry of the coordination polyhedron around rhenium being the P(1)-Re-P(2) angle in 1a 172.679(18)° is smaller than in 2a 177.29(7)°, suggesting a steric influence of these ligands.
Table2: Selected bond lengths (Å) and angles ( ° ) for 1a, 1b and 2a.
Re- P(1) Re- P(2) Re- C(1A) Re- C(1B) Re- C(2) Re- C(3) Re- Cl, Br(1A) Re- Cl, Br(1B) P(1)- Re- P(2) P(1)- Re- Cl(1A)
1a 2.4165(6) 2.4183(5) 1.966(9) 1.975(10) 1.979(3) 1.949(2) 2.479(2) 2.487(3) 172.679(18) 93.38(5)
1b 2.4623(7) 2.4553(7) 1.921(10) 1.873(17) 1.959(3) 1.960(3) 2.509(2) 2.500(4) 91.61(2) 89.38(5)
2a 2.3870(16) 2.3944(18) 2.20(2) 1.937(13) 1.893(8) 1.975(6) 2.566(8) 2.6435(9) 177.29(7) 90.95(15)
P(1)- Re- Cl(1B) P(2)- Re- Cl(1A) P(2)- Re- Cl(1B) P(1)- Re- C(1A) P(1)- Re- C(1B) P(1)- Re- C(2) P(1)- Re- C(3) P(2)- Re- C(1A) P(2)- Re- C(1B) P(2)- Re- C(2) P(2)- Re- C(3) C(1A)- Re- Cl(1A) C(1B)- Re- Cl(1B) C(2)- Re- Cl(1A) C(2)- Re- Cl(1B) C(3)- Re- Cl(1A) C(3)- Re- Cl(1B) C(1A)- Re- C(2) C(1B)- Re- C(2) C(1A)- Re- C(3) C(1B)- Re- C(3) C(2)- Re- C(3)
86.15(6) 88.63(5) 86.59(6) 86.5(3) 93.9(3) 91.16(7) 89.69(7) 86.3(3) 87.7(3) 96.01(7) 89.34(7) 95.9(3) 94.8(3) 85.86(9) 174.90(9) 171.36(9) 89.64(10) 177.2(3) 89.7(3) 92.3(3) 174.5(3) 86.01(10)
91.87(10) 92.87(5) 88.62(10) 90.9(3) 90.6(4) 178.33(9) 87.47(9) 87.7(3) 91.2(4) 88.61(9) 177.40(9) 179.3(3) 177.6(4) 92.27(10) 86.48(13) 89.56(10) 88.97(13) 87.5(3) 91.1(4) 89.8(3) 91.3(4) 92.24(12)
90.13(5) 88.04(15) 87.62(6) 93.2(17) 89.8(4) 89.9(3) 90.4(2) 84.6(17) 89.1(4) 92.5(3) 90.8(2) 101.6(17) 97.7(4) 85.6(3) 172.8(3) 175.3(3) 82.8(2) 172.1(17) 89.5(5) 82.7(17) 179.4(5) 90.0(3)
In the three complexes 1a, 1b and 2a the nature of ligands allows the formation of supramolecular assemblies based on edge-to-face CH··· interactions and nonclassic hydrogen bonds CH···O. In the complex 1a, chains along the b axis are formed by C-H···π interactions between an aromatic CH group and a phenyl ring[C21- H21··Cg(1)i i: x, -1+y, z; Cg(1): C22-C23-C24-C25-C26-C27, d(H···Cg) 3.00 Å; d(C···Cg) 3.8653(3)Å; (CH···Cg) 153° ] (see Figure 1). Two adjacent chains are further linked to each other by a weak non-classic hydrogen bond C-H···O being a terminal allylic CH the donor and a carbonyl ligand the acceptor [C9A-H9AA···O1Bii ii: ½-x, -½+y, ½-z; d(D···H) 0.95Å; d(H···A)2.57Å; d(D···A)3.4806(2)Å; (DHA)162°], generating a doublechain along the b axis (see Figure 6). In 1b, dimeric units are formed by C-H···π interactions between a terminal allylic CH and a phenyl ring [C6-H6A···Cg(1)i i: 1-x, 1-y, 1-z; Cg(1): C22-C23-C24-C25-C26C27, d(H···Cg) 2.89 Å; d(C···Cg) 3.8155(2)Å; (C-H···Cg) 166°]. The association of this dimeric units by additional C-H···π interactions involving an aromatic CH group and another phenyl ring [C12-H12···Cg(2)ii ii: -½+x, ½ -y, -½ +z; Cg(2): C28-
C29- C30- C31- C32- C33, d(H···Cg) 2.85 Å; d(C···Cg) 3.6504(1)Å; (C-H···Cg) 142°] permits the formation of a tridimensional network (see Figure 7). In the compound 2a, a single chain is generated due to the CH···π interaction also involving an aromatic CH group and another phenyl ring [C14-H14···Cg(1)i i: -½ +x, ½-y, ½+z; Cg(1): C28- C29- C30- C31- C32- C33, d(H···Cg) 2.99 Å; d(C···Cg) 3.7580(1)Å; (C-H···Cg) 139°]. The combination of the CH···π interactions and weak non-classic hydrogen bond involving carbonyl ligands [C11-H11···O2ii ii: –x, 1-y, 1-z; d(D···H) 0.95Å; d(H···A) 2.44 Å; d(D···A)3.2068(1)Å; (DHA) 138°; C12H12···O1Biii iii: -1+x, y, z; d(D···H) 0.95Å; d(H···A) 2.48 Å; d(D···A) 3.4255(1)Å; (DHA) 173°] generates a tridimensional architecture (see Figure 8).
Figure 6: Double chain along the b axis of the complex 1a formed by the CH···π interactions (blue) and non-classic hydrogen bonds (green).
Figure 7: 3D network of the compound 1b. CHallylic···π interactions in blue and CH···πinteractions in green.
Figure 8: Tridimensional architecture of the compound 2a (CH···π interactions in blue and hydrogen bonds in green).
4. Conclusions In this paper we report the synthesis and characterization of the first mer, transand fac, cis- [ReX(CO3)L] (X= Cl, Br) complexes containing the alkenylphosphinite ligand Ph2POCH2CH=CH2 (L). In all cases L is coordinated in a κ1-P mode. The nature of the halogen atom has an important role on the ratio of the fac, cis versus mer, trans- isomers, being the fac, cis- isomer more abundant when the halogen is Cl. Reasons for this difference should be kinetic because the energies of both isomers in each case are very similar.
Acknowledgements We thank PhD. Berta Covelo for making the supramolecular study and Professor Luis Muñoz for the NMR simulation. Financial support from Xunta de Galicia (Spain) (research ProjectED431D 2017/0) is gratefully acknowledged. We thank the Structural Determination Service of the Universidade de Vigo–CACTI for X-ray diffraction measurements and the collections of NMR data. Supplementary material CCDC1952317, 1952337 and 1952339 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystalographic Data Center via www.ccdc.cam.ac.uk/data_request/cif.
References All the autors contributed to the design and implementation of the research, to the analysis of the results and to the writting of the manuscript.
The autors declare no competing financial interests.
CO OC
Re
CO X
OC
L
PPh2 O
Toluene 4 h reflux
OC
Re
L CO X
OC
CO
L
X= Br, Cl
mer, trans X= Cl (1a); Br (2a)
OC
Re
L X
OC CO fac, cis
X= Cl (1b); Br (2b)
New complexes [ReX(CO)3)L2] [X=Cl, Br] containing a phosphinite ligand have been prepared. In all cases the bifunctional ligand is coordinated in a κ1-P mode and both mer-trans and fac-cis isomers were obtained.
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