Novel phospholyl(diphenylphosphino)methane-ruthenium complexes: Unexpected non-assisted cis to trans isomerization of [RuCl2(κ 2-P-P′)2]

Article abstract of DOI:10.1039/c2dt32032k

Using the unsymmetrical P-P′ phospholyl(phosphino)methane ligand, complex cis-[RuCl₂(κ²-P-P′)₂] is easily prepared from [RuCl₂(DMSO)₄]. The two phosphole-phosphorus atoms lie in the trans position to the two cis-chloro ligands. This complex slowly isomerizes spontaneously at 20 °C to the trans-[RuCl₂(κ²-P-P′)₂] diastereoisomer where the two phosphole moieties are mutually trans, as well as the two chloro ligands and the two Ph₂P moieties. DFT calculations show that this non-classical cis-trans isomerisation process requires a 3 kcal mol^-1 energy and involves the decoordination of a phosphole arm. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c2dt32032k

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An international journal of inorganic chemistry
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Volume 42 | Number 1 | 7 January 2013 | Pages 1–300
ISSN 1477-9226
COVER ARTICLE
Kalck, Gouygou et al.
Novel phospholyl(diphenylphosphino)methane-ruthenium complexes:
unexpected non-assisted cis to trans isomerization of [RuCl2(κ2-P–P')2]
1477-9226(2013)42:1;1-F

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PAPER
Novel phospholyl(diphenylphosphino)methane-
ruthenium complexes: unexpected non-assisted cis to
trans isomerization of [RuCl2(κ2-P–P’)2]†‡
Cite this: Dalton Trans., 2013, 42, 75
Duc Hanh Nguyen,a,b Jean-Claude Daran,a,b Sonia Mallet-Ladeira,a,b Thomas Davin,b,c
Laurent Maron,b,c Martine Urrutigoïty,a,b Philippe Kalck*a,b and Maryse Gouygou*a,b
Using the unsymmetrical P–P’ phospholyl(phosphino)methane ligand, complex cis-[RuCl2(κ2-P–P’)2] is
easily prepared from [RuCl2(DMSO)4]. The two phosphole-phosphorus atoms lie in the trans position to
the two cis-chloro ligands. This complex slowly isomerizes spontaneously at 20 °C to the trans-[RuCl2(κ2-
P–P’)2] diastereoisomer where the two phosphole moieties are mutually trans, as well as the two chloro
ligands and the two Ph2P moieties. DFT calculations show that this non-classical cis–trans isomerisation
process requires a 3 kcal mol−1 energy and involves the decoordination of a phosphole arm.
Received 3rd September 2012,
Accepted 15th October 2012
DOI: 10.1039/c2dt32032k
www.rsc.org/dalton
150–200 °C in the absence of solvent.3 Thermal conversion of
trans-[RuCl2(κ2-Ph2PCH2PPh2)2] into the cis-isomer was shown
Introduction
Small-bite angle diphosphines in which the two phosphorus to be quantitative in refluxing dichloroethane (83.3 °C).3 In
centers are separated only by a single atom linker unit, such as addition, the presence of catalytic amounts of CuCl or CuI
1,1-bis(diphenylphosphino)methane (dppm),1 give various allows the trans–cis isomerization at room temperature, in the
coordination modes being monodentate, or bi-coordinated in absence of light.5 This catalysis is supposed to involve two
either chelating- (resulting in highly strained 4-membered Ru(μ-Cl)Cu
metallocycles) or bridging-geometries (including A-frame and thus to labilize the ruthenium–chloro bond(s).
complexes). Inversely, photolysis or oxidative isomerization can convert
and
Ru(μ-Cl)2Cu
containing-intermediates
In the coordination sphere of ruthenium(II), dppm can act the cis to the trans-isomer through a ruthenium(III) intermedi-
as a chelating ligand leading to cis- and/or trans-isomers of ate.3 Cyclic voltammetry of the cis-[RuCl2(κ2-Ph2PCH2PPh2)2]
[RuX2(P–P)2].2,3 The trans-[RuCl2(κ2-Ph2PCH2PPh2)2] complex showed the presence of a free Cl− ion in nonaqueous
containing the dppm constrained ligand was prepared very solvents providing for instance in acetonitrile the cis-[RuCl-
early on by Chatt and Hayter.2
(CH3CN)(κ2-Ph2PCH2PPh2)2]Cl species.3 Thus, the cis–trans iso-
Two X-ray crystal structures of the methanol solvate or the merization can be promoted by photo- or electro-chemical
dichloromethane disolvate have been solved and show a dis- activation.
torted octahedral geometry.4 The cis-isomer has been prepared
Unsymmetrical
diphosphinomethane
ligands,
from [RuCl2(PPh3)4] by reaction of the Ph2PCH2PPh2 ligand at R1 PCH2PR2 , which are appropriate ligands for geometrical
2
2
isomerism studies in six-coordinate complexes, have attracted
less attention and to the best of our knowledge no ruthenium
complexes have been reported. As part of our continuing inter-
est in the design and coordination chemistry of hybrid phos-
pholyl(phosphino)methane ligands,6 we were interested in
introducing the unsymmetric dibenzophospholyl(diphenyl-
phosphino)methane ligand in the coordination sphere
of ruthenium(II). In the present study, we report the
selective synthesis of the cis-[RuCl2(κ2-P–P′)2] complex and its
unexpected isomerisation into the trans-[RuCl2(κ2-P–P′)2]
complex. The structures of both complexes were determined
by single crystal X-ray diffraction analyses. DFT calculations
have been carried out to study the cis–trans isomerisation
mechanism.
aCNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne,
F-31077 Toulouse, France. E-mail: philippe.kalck@ensiacet.fr,
maryse.gouygou@lcc-toulouse.fr
bUniversite de Toulouse, UPS, INPT, LCC, F-31077 Toulouse, France
cLPCNO, UMR 5215, Université de Toulouse-CNRS, INSA, UPS, 135 avenue de
Rangueil, 31077 Toulouse Cedex 4, France
†This paper is dedicated to our colleague Professor David J. Cole-Hamilton, on
the occasion of his 65th birthday. David, an outstanding scientist, was very crea-
tive in coordination catalysis to develop new concepts, to expand them to indus-
trial catalysis and to analyze in depth how the catalyst is working under
operating conditions.
‡Electronic supplementary information (ESI) available. CCDC 899803 and
899804. For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c2dt32032k
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Scheme 1
Results and discussion
[RuCl2(DMSO)4] (1) is a versatile starting precursor for the
preparation of numerous [RuCl2(L–L′)2] complexes such as
dichlorobis(diphosphine)ruthenium(II) complexes.7 The reac-
tion of 2 molar equiv. of dibenzophospholyl(diphenylphos-
phino)methane ligand 2, prepared according to the previously
described method,6a with 1 equiv. of complex 1 in dichloro-
methane at room temperature selectively leads to the for-
mation of a bis(phosphole–phosphine)ruthenium complex 3
(Scheme 1), as supported by elemental analysis, mass spec-
trometry and NMR spectroscopy.
Fig. 1 Molecular view of complex 3 with the atom-labelling scheme. Ellipsoids
are drawn at the 30% probability level. H atoms as well as the labels for the
phenyl groups have been omitted for clarity. Selected bond lengths (Å) and
angles (°): Ru(1)–P(1) 2.2924(13), Ru(1)–P(3) 2.2690(13), Ru(1)–P(2) 2.3573(14),
Ru(1)–P(4) 2.3491(14), Ru(1)–Cl(1) 2.4502(13), Ru(1)–Cl(2) 2.4671(12), P(1)–
Ru(1)–P(2) 70.53(4), P(1)–Ru1–P(3) 101.43(5), P(1)–Ru(1)–P(4) 109.63(5), P(1)–
Ru(1)–Cl(1) 165.80(5), P(1)–Ru(1)–Cl(2) 85.79(4)(5), P(2)–Ru(1)–P(3) 108.54(5),
P(2)–Ru(1)–P(4) 179.63 (5), P(2)–Ru(1)–Cl(1) 95.46(5), P(2)–Ru(1)–Cl2) 86.78(5),
P(3)–Ru(1)–P(4) 71.12(5), P(3)–Ru(1)–Cl(1) 84.88(5), P(3)–Ru(1)–Cl(2) 164.47(5),
P(4)–Ru(1)–Cl(1) 84.39(5), P(4)–Ru(1)–Cl(2) 93.55(5), Cl(1)–Ru(1)–Cl(2) 91.30(4),
P(1)–C(1)–P(2) 93.7(2), P(3)–C(2)–P(4) 93.5(2).
In addition, crystals of complex 3, suitable for X-ray ana-
lysis, were obtained by slow diffusion of diethyl ether into a con-
centrated dichloromethane solution at −20 °C. X-ray structural
analysis confirms the formation of the dichlorobis{dibenzo-
phospholyl(diphenylphosphino)methane}ruthenium complex
3. The molecular structure determined represented in Fig. 1
shows a near octahedral geometry for ruthenium. Indeed, this
complex is deformed in the equatorial plane of the octahedron
as shown by the Cl1–Ru1–P1 and the Cl2–Ru1–P3 angles
(165.80 (5)°, 164.47 (5)° respectively) whereas the P2–Ru1–P4
angle in the axial position is 179.63 (5)°. Thus P1, P3, Cl1 and
Cl2 are not rigorously in the same plane, since by considering
the average plane passing by Cl1, Cl2 and Ru1, the two P3 and
P1 atoms lie 0.588 Å above the plane for P3 and 0.550 Å below
the plane for P1. In addition, the crystal structure reveals the
arrangement around the Ru centre. The two Cl atoms are in cis
configuration, the two phosphorus atoms Pa of the phosphole
ring are trans to the chloro ligands whereas the two phos-
phorus atoms of the phosphino groups Pb are in the trans posi-
tion (Fig. 1).
observed in related complexes.8 We analyzed the possibilities
of some interactions within the complex which could explain
the relative stability of this configuration; however, although
the 3.652 Å distance between the two centroids of two phenyl
rings could be favourable to a π–π stacking, the 3.21 Å distance
of the normal vector to the plane leads to a 2.25 Å slippage
between the two planes, which prevents any interaction. More-
over, a 10° dihedral angle between the two ligands is consist-
ent with the absence of any interaction.
For such
a cis-complex containing an unsymmetric
ligand, three diastereoisomers could be formed: two C2 com-
plexes corresponding to Pa trans and Pb trans to the chloro
ligands (A and B forms) and one C1 complex in which Pa and
Pb are trans to the chloro ligands (C form) as represented in
Fig. 2.
1H and 31P NMR data are consistent with the A or B forms
of complex 3. Indeed, the two doublets of doublets observed in
31P NMR at 3.39 (dd, Pb, JPbPa = 40.5, JPbPa′ = 41.2 Hz) and at
−16.36 (dd, Pa, JPaPb = 40.5, JPaPb′ = 41.2 Hz) can be interpreted
as an AA′XX′ spin system. The higher field doublet of doublets
pattern is assigned to the Pa atom of the phospholyl group and
the lower field signal to the Pb atom of the diphenylphosphino
The two Ru–P bond lengths corresponding to the Pb atoms
trans to each other, Ru(1)–P(2) 2.3573(14) Å, Ru(1)–P(4) 2.3491(14)
Å, are significantly longer than those for the two Pa atoms
trans to the chloro atoms, Ru(1)–P(3) 2.2690(13) Å and Ru(1)–
P(1) 2.2924(13) Å. This difference could be the consequence of
the trans influence of the chloro ligands due to the π-donation
from the Cl through the Ru to the trans P1 and P3 as also
1
group via H–31P{1H} HMQC experiments. This spin system is
inconsistent with the C form which could display an ABCD
spin system corresponding to the four nonequivalent phos-
phorus nuclei.
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Fig. 2 The 3 possible diastereoisomers for complex 3.
Fig. 3 1H NMR spectra of complex 3 in CD2Cl2.
Fig. 5 Molecular view of complex 4 with the atom-labelling scheme. Ellipsoids
are drawn at the 30% probability level. H atoms have been omitted for clarity.
Selected bond lengths (Å) and bond angles (°): Ru(1)–P(1) 2.3282(4), Ru(1)–P(2)
2.3339(4), Ru(1)–Cl(1) 2.4149(4), P(1)–Ru(1)–P(2) 71.613(14), P(1)–Ru(1)–P(2)i
108.387(13), P(1)–Ru(1)–Cl(1) 85.753(14), P(1)–Ru(1)–Cl(1)i 94.247(13), P(2)–
Ru(1)–Cl(1) 84.131(14), P(2)–Ru(1)–Cl(1)i 95.869(14), P(1)–C(5)–P(2) 94.69(7)
[symmetry code (i) −x + 1, −y + 1, −z + 1].
Fig. 4 31P{1H} NMR isomerisation monitoring in CD2Cl2 at RT.
after 19 days was observed leading to the formation of a new
complex 4 (Scheme 1). Monitoring the course of this conver-
sion by 31P NMR spectroscopy (Fig. 4), we observed the dis-
appearance of the AA′XX′ system of the complex 3 concomitant
with the appearance of a new AA′XX′ system at higher field
relative to 3 (δ −0.49 (dd, Pb, JPaPb = 27.0, 30.4 Hz) and
−17.82 ppm (dd, Pa, JPaPb = 27.0, 30.4 Hz).
In 1H NMR, the spin system observed for the methylene
bridging protons also indicates the formation of the A or B
forms. The two CH2 groups are equivalent and resonate as two
sets of broad multiplets centered at δ 4.81 and 3.85 ppm in a
1 : 1 ratio, which indicates that two protons of CH2 are
diastereotopic (AB spin system), as confirmed by deeper NMR
1H- selective decoupling 31P measurements (Fig. 3).
Complex 4 is obtained as a pure isomer which could be iso-
lated in good yield (60%). Elemental analysis, mass spec-
In addition, the 1H NMR spectrum at room temperature
indicates the hindrance to rotation of the dibenzophospholyl
ring since the eight protons are inequivalent. Consequently,
we assume that the privileged formation of the C2-complex 3
(A form) is probably controlled by steric factors.
1
trometry, and H NMR spectroscopy confirmed the formation
of a bis(diphosphine)ruthenium complex 4. The molecular
structure, determined by X-ray analysis and represented in
Fig. 5, shows the trans positions for the two chloro, the two P1
and the two P2 atoms. The four Ru–P bond distances lie in the
range 2.3282–2.3338 Å as observed for related ruthenium(II)
bisphosphine trans-disubstituted complexes.9,10
The cis-complex 3 slowly evolves in dichloromethane solu-
tion at room temperature since its complete transformation
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We observed again the formation of only one diastereo- phosphino-Pb, respectively. In contrast to complex 3, the two
isomer among the two possible for complex 4 (Fig. 6).
equivalent methylene bridging protons resonate in 1H NMR as
31P NMR supports the formation of the D form. The AA′XX′ only one set of multiplets centered at 4.93 ppm leading to a
spin system observed in 31P NMR exhibits low JPP coupling single signal by 31P broadband decoupling which indicates
constants consistent with the D form but not with the E form that two protons of the CH2 are equivalent. In addition, the
which could display a higher JPP coupling constant for the two four distinct protons observed for the dibenzophospholyl ring
Pa and Pb phosphorus atoms in the trans-position. Interest- indicate the free rotation of this group in this case.
ingly, the 31P chemical shifts of 4 lie systematically upfield
To explain the isomerization of the cis-3 into the thermo-
relative to 3: 3.88 and 1.46 ppm away for phospholyl-Pa and dynamic product trans-4, we have examined the possible intra-
molecular rearrangement of the ligands in six-coordinate
complexes which can occur by twisting or dissociative pro-
cesses (Fig. 7).
According to this analysis, an intramolecular twist mechan-
ism can only lead to a new cis-complex. In addition, the iso-
merization of the cis-3 into the thermodynamic product trans-4
is inconsistent with a Pb bond-breaking/bond-making mechan-
ism as the two Pb atoms stay in the trans position in complex
4. According to these considerations, the isomerization cis-3 →
trans-4 could occur either via a Cl− decoordination or via a
Fig. 6 The two possible diastereoisomers for complex 4.
Pa-decoordination.
Fig. 7 Possible intramolecular rearrangements of complex 3 by twisting or dissociative processes.
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Fig. 8 Structures of the five possible isomers for the Ru complex (4-D, 4-E, 3-B, 3-A, 3-C).
In order to gain more insights into the relative stability of
the cis- and trans-Ru complexes and on the isomerisation
process, DFT calculations have been carried out. The five
isomers are depicted in Fig. 8 (Cl in trans, phosphole in trans,
complex 4-form D; Cl in trans, phosphole in cis, complex
4-form E; Cl in cis, phosphole in trans, complex 3-form B; Cl in
cis, phosphine in trans, complex 3-form A; Cl in cis, phosphole
in cis, complex 3-form C).
The five isomers were optimized and their relative stability
can be compared. The complex 4-D is the most stable, followed
by the complex 3-A (less stable by 2.13 kcal mol−1), then the
complex 4-E (with a difference of 2.95 compared to the
complex 4-D), then the complex 3-B (with a difference of
8.91 kcal mol−1). Finally, the complex 3-C is the least stable,
with a difference of 10.54 kcal mol−1 compared to the complex
4-D.
To further understand the stability of the complex, NMR
parameters of the two most stable complexes 4-D and 3-A have
been computed. Comparing the shielding for the P atoms of
the phospholes of the two complexes, we observe that the
screening is bigger for 4-D than for 3-A (Δδ = +26 ppm). This
trend is in agreement with what has been obtained experimen-
tally through phosphorus NMR analysis. This indicates an
increase of the electron density on the P atom of the phosp-
hole in 4-D and thus in the vicinity of the Ru atom. This will
strengthen the Ru–P bonds thus leading to the stabilization of
4-D. This bond strengthening is confirmed by the Wiberg
bond indexes obtained through the use of the Natural Bond
Orbital study (Ru–P(phosphole) bond indexes: 0.69 for 4-D and
0.78 for 3-A). The result shows stronger bond indexes for the
Ru–P(phosphole) of 4-D than those of 3-A.
Finally, the cis–trans isomerization process has been investi-
gated. Despite our effort, it has not been possible to locate any
transition state for this isomerization. This might be explained
by the fact that the decoordination of one phosphole arm from
Ru in 3-A leads to the rearrangement of the Cl atom from the
cis- to trans-position (see Fig. 9). This complex has been opti-
mized and is found to be a minimum on the Potential Energy
Surface that is less stable than 3-A by 16 kcal mol−1. This
complex is thus an intermediate in the reaction process and
gives a rough estimate of the activation barrier of isomeriza-
tion from complex 3-A into the complex 4-D. Isomerization
involving the decoordination of a chloride rather than a
Fig. 9 Optimized structure of the complex with Cl in cis and a decoordinated
phosphole arm.
phosphole arm has been computed to be much higher in
energy (roughly 53.0 kcal mol−1).
In conclusion, addition of two equivalents of the unsym-
metric phosphole–phosphine ligand to the ruthenium(II)
[RuCl2(DMSO)4] precursor leads to cis-[RuCl2(Pa–Pb)2]. A slow
isomerization process has been analyzed by NMR experiments
showing the exclusive formation of trans-[RuCl2(Pa–Pb)2]. DFT
calculations are consistent with a slightly lower (3 kcal mol−1
)
energy for the trans-isomer and with a cis-/trans-isomerization
mechanism involving the decoordination of a phosphole arm.
Further studies will be dedicated to the reactivity of these com-
plexes and more particularly to explore their potential in
catalysis.
Experimental section
General procedures
All reactions were carried out under an argon atmosphere in
dried glassware. Solvents were dried and freshly distilled
under an argon atmosphere over sodium–benzophenone for
diethyl ether and P2O5 for CH2Cl2. Thin-layer chromatography
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1
was performed on alumina. All NMR spectra data were CH2Cl2–MeOH (95 : 5)). Yield (60%). H NMR (298 K, CD2Cl2,
recorded on Bruker DRX 300 or Advance 300–500 spectro- 300.13 MHz, ppm): δ 8.34 (dt, 4H,vCH–, JHH = 7.8 Hz, JHP
=
1
meters with TMS as an internal reference for H and 13C, 85% 3.3 Hz, phosphole), 8.07 (d, 4H,vCH–, JHH = 7.5 Hz, phosp-
phosphoric acid as an external reference for 31P. Spectral hole), 7.65 (t, 4H,vCH–, JHH = 7.5 Hz, phosphole), 7.38 (t,
assignments were made by means of routine one and two 6H,vCH–, JHH = 7.2 Hz), 7.23 (m, 10H,vCH–, JHH = 7.2 Hz,
dimensional NMR experiments where appropriate. Mass spec- PPh2), 7.08 (t, 8H,vCH–, JHH = 7.5 Hz), 4.93 (qt, 4H, >CH2,
tral analyses were performed on a TSQ 7000 Thermoquest JHP = 4.5 Hz, PaCH2Pb). 31P{1H} NMR (298 K, CD2Cl2,
instrument (DCI). The major peak m/z was mentioned with the 121.495 MHz, ppm): δ −0.49 (t, Pa, JPaPb = 27.0, 30.4 Hz),
intensity as a percentage of the base peak in brackets. Elemen- −17.82 (t, Pb, JPaPb = 27.0, 30.4 Hz). 13C{1H} NMR data were not
tal analyses were measured with a precision superior to 0.3% recorded due to the slow solubility of this compound in the
at the Microanalysis Laboratory of the LCC at Toulouse. Com- usual organic solvents. MS (DCI, CH4) m/z: (%) = 936.05 (50%)
mercially available [RuCl2(DMSO)4] was used as received and [M]+, 901.09 (50%) [M − Cl]+. Anal. calcd for C50H40Cl2P4Ru:
ligand 1 was prepared according to the literature.5
C 64.11; H 4.30. Found: C 64.04; H 4.25.
SYNTHESIS
OF
CIS-[DICHLOROBIS{DIBENZOPHOSPHOLYL(DIPHENYLPHO-
X-ray structure determinations
SPHINO)METHANE}-RUTHENIUM(II)], 3. To
a
solution of [RuCl2-
(DMSO)4] (0.043 g, 0.087 mmol) in CH2Cl2 (20 mL) was added A single crystal of each compound was mounted under inert
a solution of dibenzophospholyl(diphenylphosphino)methane perfluoropolyether at the tip of a glass fiber and cooled in the
2 (0.068 g, 0.178 mmol) in CH2Cl2 (20 mL) at −60 °C. The cryostream of either a Bruker APEX2 diffractometer for 3 or an
reaction mixture was allowed to warm to RT and stirred further Agilent Technologies GEMINI EOS diffractometer for 4. The
for 20 h. The resulting orange solution was evaporated to structures were solved by direct methods (SIR97)11 and refined
dryness. Purification by alumina column chromatography by least-squares procedures on F2 using SHELXL-97.12 All H
(eluent: CH2Cl2 and CH2Cl2–MeOH (95 : 5)) yielded 0.055 g atoms attached to carbon atoms were introduced in the calcu-
(67%) of the cis-complex as a yellow solid and <5% of the lation at idealised positions and treated as riding models. One
trans-isomer as an off-white solid. 1H NMR (298 K, CD2Cl2, of the phenyls attached to P(2) in compound 3 is disordered
400.13 MHz, ppm): δ 9.33 (m, 2H,vCH–, JHH = 7.6 Hz, phosp- over two positions with a ratio of 3 to 1. The refinement of this
hole), 8.06 (m, 4H,vCH–, JHH = 2.8, 7.6 Hz, PPh2), 7.71 (d, disordered phenyl group has been carried out using restraints
2H,vCH–, JHH = 7.6 Hz, phosphole), 7.62 (dt, 2H,vCH–, JHH
=
available in SHELXL-97.13 Moreover, in compound 3, there are
1.2, 7.2 Hz, phosphole), 7.53 (t, 2H,vCH–, JHH = 7.2 Hz, some solvents included but only the dichloromethane could
phosphole), 7.52 (d, 2H,vCH–, JHH = 8.0 Hz, phosphole), 7.32 be located and treated as a disordered molecule. However,
(m, 10H,vCH–, JHH = 1.6, 4.8 Hz, PPh2), 7.02 (t, 2H,vCH–, owing to the poor quality of the data, some residual electron
JHH = 7.6 Hz, PPh2), 6.97 (t, 2H,vCH–, JHH = 7.6 Hz, phosp- density was difficult to model. Therefore, the SQUEEZE func-
hole), 6.71 (t, 4H,vCH–, JHH = 7.6 Hz, PPh2), 5.87 (td, 2H,v tion of PLATON13 was used to eliminate the contribution of
CH–, JHH = 1.6, 7.2 Hz, phosphole), 5.17 (m, 2H,vCH–, JHH
=
the electron density in the solvent region from the intensity
7.6 Hz, phosphole), 4.81 (m, 2H, >CH2, JHH = 13.6 Hz, data, and the solvent-free model was employed for the final
PaCHHPb), 3.85 (m, 2H, >CH2, JHH = 14.0 Hz, PaCHHPb). 31P refinement. The drawing of the molecules was realised with
{1H} NMR (298 K, CD2Cl2, 161.976 MHz, ppm): δ 3.39 (t, Pa, the help of ORTEP32.14 Crystal data and refinement para-
JPaPb = 40.5, 41.2 Hz), −16.36 (t, P2, JPaPb = 40.5, 41.2 Hz). 13C meters are shown in Table S1.‡ Crystallographic data (exclud-
{1H} NMR (298 K, CD2Cl2, 75.468 MHz, ppm): δ 142.78 (t, ing structure factors) for the structures reported in this paper
>Cv, JCP = 4.91 Hz), 141.74 (t, >Cv, JCP = 5.1 Hz), 135.84 (t, have been deposited with the Cambridge Crystallographic
>Cv, JCP = 18.4 Hz), 134.45 (t,vCH–, JCP = 5.6 Hz), 132.95 (t,v Data Centre as supplementary publication no. CCDC-899803
CH–, JCPb = 5.8 Hz, PPh2), 131.72 (t,vCH–, JCPb = 7.0 Hz, and 899804.
PPh2), 131.35 (vCH–, phosphole), 130.02 (t,vCH–, JCPb = 6.4
Hz, PPh2), 129.64 (d,vCH–, JCPa = 3.40 Hz, phosphole), 129.40
Computational details
(vCH–, phosphole), 128.79 (t,vCH–, JCPa = 4.8 Hz, phosp- Ruthenium and chlorine were treated with a Stuttgart–Dresden
hole), 127.85 (t,vCH–, JCPb = 5.1 Hz, PPh2), 127.68 (t,vCH–, pseudopotential in combination with the appropriate basis
JCPb = 5.0 Hz, PPh2), 126.78 (t,vCH–, JCPa = 5.0 Hz, phosphole), sets.15,16 The basis sets were augmented by a set of polariza-
120.80 (t,vCH–, JCPa = 2.8 Hz, phosphole), 120.55 (t,vCH–, tion functions (f for Ru and d for Cl).17 Carbon, phosphorus
JCPa = 2.87 Hz, phosphole), 44.53 (t, >CH2, JCP = 9.9 Hz, and hydrogen atoms were described with a 6-31G(d) polarized
PaCH2Pb). MS (DCI, CH4) m/z: (%) = 936.05 (50%) [M]+, 901.09 double-ζ basis set.18 Calculations were carried out at the DFT
(50%) [M − Cl]+. Anal. calcd for: C50H40Cl2P4Ru: C 64.11; level of theory using the hybrid functional B3PW91.19,20 Geo-
H 4.30. Found: C 64.06; H 4.42.
metry optimizations were carried out without any symmetry
SYNTHESIS OF TRANS-[DICHLOROBIS{DIBENZOPHOSPHOLYL(DIPHENYLPHOSP- restrictions and the nature of the extremer (minima) was veri-
HINO)METHANE}-RUTHENIUM(II)], 4. The trans-isomer complex has fied with analytical frequency calculations. For all transition
been formed by slow isomerization of the corresponding cis- states, the intrinsic reaction coordinate was followed to verify
isomer in CH2Cl2 at 20 °C. After 19 days, complex 4 was iso- the direct connection between the transition state and the
lated by alumina column chromatography (eluent: CH2Cl2 and adducts. All these computations were performed with the
80 | Dalton Trans., 2013, 42, 75–81
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Gaussian 0321 [7] suite of programs. Gibbs free energies were
obtained at 298.15 K within the harmonic approximation.
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