Photo- and Thermal Isomerization of (TP)Fe(CO)Cl2 [TP = Bis(2-diphenylphosphinophenyl)phenylphosphine]

Article abstract of DOI:10.1021/acs.organomet.5b00644

The title complex displayed structural flexibility via photo- and thermal-isomerization reactions between three isomers: (mer-TP)Fe(CO)Cl₂ (A), unsym-(fac-TP)Fe(CO)Cl₂ (B), and sym-(fac-TP)Fe(CO)Cl₂ (C). Irradiation of A a

Full text of DOI:10.1021/acs.organomet.5b00644

Article
pubs.acs.org/Organometallics
Photo- and Thermal Isomerization of (TP)Fe(CO)Cl [TP = Bis(2-
2
diphenylphosphinophenyl)phenylphosphine]
Ping Li, Bas de Bruin, Joost N. H. Reek, and Wojciech I. Dzik*
Homogeneous, Supramolecular and Bio-Inspired Catalysis, van’t Hoff Institute for Molecular Sciences, University of Amsterdam,
Science Park 904, 1098 XH Amsterdam, The Netherlands
*
S Supporting Information
ABSTRACT: The title complex displayed structural flexibility
via photo- and thermal-isomerization reactions between three
isomers: (mer-TP)Fe(CO)Cl (A), unsym-(fac-TP)Fe(CO)-
2
Cl (B), and sym-(fac-TP)Fe(CO)Cl (C). Irradiation of A at
2
2
RT with 525 nm light selectively produces B, while at 0 °C
isomer C is formed with the intermediacy of B. UV−vis
spectroscopy combined with TD-DFT calculations revealed
the nature of the photoisomerization process. Kinetics of the
thermal isomerization of C to B and B to A have been studied
31
with P NMR spectroscopy in CD Cl , and activation
2
2
parameters were determined. Isomers A and B have been
isolated and crystallographically characterized.
INTRODUCTION
synthesis and structural characterization of the title complex,
photoisomerization, and kinetic studies of the thermal-isomer-
ization reactions.
■
The ability of molecules to change their shape upon external
stimuli opens a variety of potential applications as molecular
1
switches or machines. In particular, the use of light as the
RESULTS AND DISCUSSION
switching factor has recently gained much interest in broad
contexts spanning from biological applications to material
■
Synthesis and Characterization of (TP)Fe(CO)Cl2
Complexes. (mer-TP)Fe(CO)Cl2 (A) was synthesized in
2
science.
In coordination chemistry, much attention has been focused
on steering the properties of the transition metal by switching
the conformation of a photoactive substituent appended to the
ligand. In this way properties such as spin state of the metal can
9
2% yield by treating FeCl ·4H O with a stoichiometric
2 2
amount of TP in a mixture of CH Cl and MeOH under an
2
2
atmosphere of carbon monoxide in the dark. Spectroscopic
analysis of A revealed the presence of a single carbonyl ligand,
3
be tuned. The opposite situation in which the photoevent
−1
as evidenced by the IR absorption band at 1972 cm , and a C
s
within the coordination sphere of the metal dictates the
conformational change of the ligand is much less common.
Examples are the reversible phototriggered change of denticity
of polyamine ligands accompanied by (de)coordination of an
31
symmetric orientation of the TP ligand evidenced by two
P
2
NMR resonances in CD Cl : a triplet at 115.64 ( J = 32.4
2
2
PP
2
Hz) and a doublet at 65.11 ppm ( J = 32.4 Hz), with an
PP
4
integral ratio of 1:2.
auxiliary ligand and mer-fac-isomerization of octahedral
5
When a solution of A in CH
Cl was brought into ambient
2 2
complexes with tridentate ligands. In the latter case the
light, a slow color change from orange to dark red was
denticity of the isomerized ligand does not change; that is,
there is no net formation or breaking of bonds, which can be
beneficial when rigidity of photoswitches is desired. It is
noteworthy that so far all the examples of photochemical metal-
dictated conformational change of the ligand proceeded on
noble metal centers. As such, the discovery of base-metal
complexes that reveal such behavior would enable the
development of a new class of low-cost photoswitches.
3
1
observed. This is accompanied by changes in the P NMR
spectrum, which displayed a set of three resonances: a doublet
2
2
of doublets at 111.55 ( J = 32.4 Hz, J = 47.0 Hz); a
PP
PP
2
2
doublet of doublets at 77.60 ( J = 32.0 Hz, J = 47.0 Hz);
and a triplet at 53.60 ppm ( J = 47.0 Hz), with an integral
PP
PP
2
PP
ratio of 1:1:1. The spectrum represents the formation of new
species B with a C symmetry indicative of an unsym-(fac-
1
TP)Fe(CO)Cl structure. The IR carbonyl stretch of 2008
2
In the context of our studies on photochemical proton
−1
6
,7
cm is indicative of weakening of π-back-donation from the
reduction, we discovered that the iron complex (TP)Fe-
CO)Cl2 (TP = bis[2-(diphenylphosphino)phenyl]-
iron center.
(
phenylphosphine) undergoes light-induced isomerization from
the mer- to fac-coordination mode of the tridentate TP ligand,
followed by a slow thermal reisomerization. Here, we report the
Received: July 9, 2015
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.5b00644
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Article
Solid-state structures of species A and B were obtained by
single-crystal X-ray diffraction (Figure 1). In both structures,
isomer B (1.790(2) Å), reflecting stronger back-donating ability
from Fe to CO in isomer A. The UV−vis spectra displayed
three clear isosbestic points at 419, 447, and 532 nm. The
intense visible absorption shifted from 566 nm in B to 482 nm
in A, which is in agreement with the color change from dark red
to orange.
The ability of iron(II) carbonyl compounds to undergo
photochemical isomerization followed by thermal rearrange-
11
ment to the initial state is well established. Depending on the
wavelength the photorearrangement can proceed via either CO
12
loss or halide dissociation, and in principle both pathways
could also be operational during the isomerization of A to B
triggered by visible light. The UV−vis spectrum of A reveals
two separate bands with peak maxima at λ = 366 and 482 nm.
In most cases, the lowest (singlet) excited state is most relevant
to explain the photoreactivity of a compound, and indeed
selective irradiation of the lowest energy band of A using a 525
nm LED lamp leads to clean formation of B in CD Cl with a
Figure 1. X-ray structures of isomers A (left) and B (right). Hydrogen
atoms and cocrystallized CH Cl solvent molecules are omitted for
2
2
clarity. Selected bond lengths (Å) and angles (deg) for A: Fe1−P1
2
2
1
.1852(10), Fe1−P2 2.2547(9), Fe1−P3 2.2422(9), Fe1−Cl1
.3410(10), Fe1−Cl2 2.3523(9), Fe1−C1 1.743(4), C1−O1
.141(4); P1−Fe1−P2 84.15(4), P1−Fe1−P3 86.49(4), P2−Fe1−
2
2
P3 169.17(4). For B: Fe1−P1 2.1639(6), Fe1−P2 2.2212(6), Fe1−P3
13
quantum yield of Φ = 0.72.
2.3369(6), Fe1−Cl1 2.3308(6), Fe1−Cl2 2.3499(6), Fe1−C1
1.790(2), C1−O1 1.139(3); P1−Fe1−P2 88.13(2) P1−Fe1−P3
83.91(2) P2−Fe1−P3 101.08(2).
TD-DFT calculations reveal that the 482 nm band of A (484
nm in DFT) is a mixed excitation consisting of HOMO →
LUMO and HOMO → LUMO+1 transitions. Excitation of this
band is associated with a Fe−Cl → TP-ligand charge transfer
process, with a small contribution of Fe in the two acceptor
orbitals (see the SI). Since the HOMO of A is essentially an
Fe−Cl π*-antibonding orbital, the photochemical reaction of A
to B mostly seems to involve photodissociation of a chlorine
atom. Complex B can only be selectively converted back to A
thermally. Attempts to convert B back to A in a photochemical
reaction were only partly successful. When the 566 nm band of
B was irradiated with 590 nm LED light, a steady-state mixture
of A and B was obtained (presumably due to overlap of the
bands of A and B).
each iron center is coordinated to a TP ligand, one carbonyl
ligand, and two chlorides and adopts a slightly distorted
octahedral configuration. The TP ligand coordinates to the Fe
center in a meridional fashion in isomer A and a facial fashion
in isomer B. The meridional coordination mode of the TP
ligand in A is remarkable, as none of the previously reported
8
mononuclear complexes of TP reveal such a binding mode. As
such, isomer A is the first metal complex that features TP as a
9
PPP pincer-type ligand. This behavior is, however, in accord
with the expected binding mode of three phosphine donors to
10
an octahedral monocarbonyl iron(II) species. The two
Kinetic Studies. To get insight on the thermal back-
isomerization of B to A, we conducted kinetic measurements
using variable-temperature 31P NMR spectroscopy (Figure 3).
terminal phosphorus atoms P2 and P3 in isomer A (Figure
1) are trans to each other with similar bond distances to the
iron center (2.2547(9) Å for Fe1−P2 and 2.2422(9) Å for
Fe1−P3), while the Fe1−P1 bond distance 2.1852(10) Å) is
significantly shorter. In contrast, the bond distance for Fe1−P3
(
2.3369(6) Å) in isomer B is significantly longer than that for
Fe1−P2 (2.2212(6) Å) due to the stronger trans influence of
the carbonyl ligand compared to the chloride.
When a solution of B in CH Cl was kept in the dark, isomer
2
2
31
A was fully recovered within 2 days, as indicated by P NMR.
The isomerization of B to A in CH Cl was also monitored
2
2
using IR and UV−vis spectroscopy, as shown in Figure 2. The
stretching frequency of the carbonyl ν(CO) displayed a red
−1
−1
shift from 2008 cm in B to 1972 cm in A. This observation
is consistent with the single-crystal structures showing
significantly shorter bond distance of Fe−C1 (trans to a π-
donating chloride) in isomer A (1.743(4) Å) than that in
Figure 3. Thermal isomerization of B to A in CD Cl in the dark. (a)
2
2
3
3
1
1
1
P{ H} NMR spectra at 298 K. (b) Kinetic curves obtained from
P{ H} NMR integrations for B (green) and A (blue) at 298 K. k =
2.91 ± 0.02) × 10 s . (c) Eyring plot of the thermal isomerization
of B to A: ΔH = 16.23 ± 0.73 kcal mol , ΔS = −24.74 ± 2.70 cal
1
−5 −1
(
⧧
−1
⧧
Figure 2. IR (left) and UV−vis (right) spectral change during the
thermal isomerization of B to A in CH Cl in the dark at 298 K.
−1 −1 ⧧ −1
mol K , ΔG (298 K) = 23.60 kcal mol .
2
2
B
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Over the period of of 20 h, the conversion of B to A reached
more than 90% in CD Cl at 298 K. The kinetic profile in
2
2
Figure 2b could be fitted with a first-order reaction (d[B]/dt =
k[B]), giving the reaction rate constant k = (2.91 ± 0.02) ×
−
−5 −1
1
0
s . The reaction rate constant for isomerization of B to A
was measured at various temperatures in the range between 288
and 308 K (Scheme S1 and Figures S8−S12). Plotting ln(k/T)
as a function of 1/T gave a linear Eyring profile (Figure 3c).
The linear fitting parameters afforded the activation parameters
⧧
for the thermal isomerization of B to A in CD Cl as ΔH =
2
2
−1
⧧
−1 −1
1
6.23 ± 0.73 kcal mol , ΔS = −24.74 ± 2.70 cal mol K ,
⧧
−1
and ΔG (298 K) = 23.60 kcal mol .
Interestingly, when irradiation of A was conducted at 0 °C, a
third species in addition to isomers A and B was detected. IR
spectroscopy revealed a monocarbonyl species with νCO =
Figure 5. DFT (BP86/def2-TZVP)-calculated energy levels for all
possible octahedral isomers of (TP)Fe(CO)Cl2.
1
31
1
1
988 cm− (Figure S1). The P{ H} spectrum of this species
isomer A has the lowest energy. Isomer B is 6.7 kcal/mol
higher in energy. The configuration of sym-(fac-TP)Fe(CO)Cl2
(
bottom curve in Figure 4a) displayed a triplet at 108.07 ppm
(
(
C) that was proposed as the species formed at 0 °C has higher
5 kcal mol ) energy than isomer B, which is consistent with
14
−1
the thermal decay of C to B in solution, as discussed below.
Species D and E are both calculated to be higher in energy than
species B and are thus not expected to re-form thermally to B.
The assignment of isomer C was also supported by the DFT-
calculated IR spectra. In accord with the experiments, the
carbonyl stretching frequency of structure C lies in between the
values of A and B (Figure 5 and Table S3). The TD-DFT-
calculated UV−vis spectrum of C reveals only a weak
absorption in the visible region, in accordance with the
experimental spectrum (one main band at 366 nm; see the SI).
The 31P{ H} NMR spectra shown in Figure 4a display the
spectral changes during the decay of C in solution in the dark at
1
2
70 K. The isomerization reaction of C to B was accompanied
by the formation of some A. The global fit (Scheme S2 and
equations S3−5) of the reaction profile in Figure 4b suggested
that the decay of C afforded only B, while a small amount of A
was formed by subsequent thermal decay of B. Activation
parameters for the isomerization of C to B were obtained from
Figure 4. Thermal isomerization of C to B in CD Cl in the dark. (a)
2
2
3
3
1
1
1
P{ H} NMR spectra at 270 K. (b) Kinetic curves obtained from
⧧
−1
1
the Eyring plot (Figure 4b) as ΔH = 26.85 ± 0.86 kcal mol ,
P{ H} NMR integrations for isomers C (red), B (green), and A
⧧
−1 −1
⧧
⧧
(
2
blue) at 270 K. (c) Eyring plot of the isomerization of C to B: ΔH =
ΔS = 21.90 ± 0.99 cal mol K , and ΔG (270 K) = 20.94
−1
⧧
−1 −1
⧧
−1
6.85 ± 0.86 kcal mol , ΔS = 21.90 ± 0.99 cal mol K , ΔG (270
kcal mol . The decay of C to B is much faster than the decay
−1
K) = 20.94 kcal mol .
of B to A at the same temperature (Figure 6). The half-life
(2
JPP = 43.7 Hz) and a doublet at 77.41 ppm (2JPP = 43.7 Hz)
with the integral ratio of 1:2, indicating a C symmetric
s
environment of iron. Three of such isomers can be considered:
fac-complex C in which the chlorides are trans to the P2 and P3
donors and the carbonyl ligand is trans to the P1 donor; a mer-
complex D in which the carbonyl ligand is trans to the P1
donor; and a mer-complex E, which is the conformational
isomer of A in which the phenyl ring is pointing toward the
chloride instead of the carbonyl (Figure 5). For a mer-
coordination mode of the species formed at low temperature
3
1
one would expect the P chemical shift of phosphines P2 and
P3 to be close to 65 ppm as it is in A. The value of 77.41
suggests that both phosphines are coordinated trans to
chlorides, thus rendering isomer C the most plausible structure
for this intermediate. Unfortunately, all attempts to crystallize
this species under irradiation failed, preventing us from
establishing the structure of C in the solid state. DFT
Figure 6. Reaction rate constant of thermal isomerization reactions of
31
C to B and B to A in CD Cl measured by P NMR.
2
2
(τ1/2) of photoproduct C can be extended from 90 s at 298 K
to 1.74 h at 273 K (Figure S18), which enabled us to study the
photoisomerization process in a relatively short time with little
interference from the decay of C to B (Figure S19). Following
the irradiation at 273 K in time with 31P NMR revealed full
conversion of A to a mixture of B and C within 3 min, followed
(
BP86/def2-TZVP) was used to calculate the relative energies
of all the possible octahedral isomers of (TP)Fe(CO)Cl (A−
E, Figure 5). In agreement with the experiment, the dark
2
C
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Article
by full conversion of residual B to C within the next 7 min.
Isomer B can thus be regarded as a structural intermediate
during both the light-induced isomerization of A to C and also
the backward decay from C to A, as shown in Scheme 1.
Scheme 2. Thermal Isomerization of B to A Proceeding via
Chloride Dissociation
Scheme 1. Stepwise Photo- and Thermal Isomerization
Reactions
of the phosphine arm. Quantum chemical modeling of possible
dissociative thermal-isomerization pathways would require a
detailed treatment of both singlet and triplet surfaces, which is
beyond the scope of this study.
Mechanistic Considerations. As discussed above, based
on TD-DFT calculations the proposed photoisomerization
mechanism involved photoinduced dissociation of a chlorine
atom, followed by TP ligand rearrangement and recapture of
the chlorine atom. In regard to the mechanisms of the thermal
isomerization reactions, the dissociation of one of the
coordinating groups (P, Cl, or CO) might be the initial step
before the rearrangement of the geometry around the iron
center. Thermal decay from B to A is significantly slowed
down in the presence of 1 atm of CO, which had little effect on
the isomerization from C to B (see the SI, Figures S20 and S21,
respectively). Carbonyl dissociation could thus be proposed as
the initial step for the thermal isomerization of B to A but not
for C to B. However, the highly negative entropy of activation
for the thermal isomerization of B to A is not in accord with a
dissociative process of an L-type ligand. A similar negative
entropy of activation value has been reported for mer-to-fac
CONCLUSION
■
In conclusion, we show that a tridentate phosphine ligand
coordinated to an iron(II) carbonyl center can undergo
photoinduced mer- to fac-isomerization with the reverse process
occurring thermally. This is a rare example of a photoswitch
operating via the change of geometry of a coordinated ligand
triggered by a photoevent within the coordination sphere of a
first-row transition metal.
1
5
EXPERIMENTAL SECTION
■
General Considerations. All experiments and manipulations were
carried out under a dry and oxygen-free atmosphere of nitrogen or
argon using standard Schlenk techniques unless otherwise specified.
Solvents were dried and distilled over an appropriate drying agent
under an atmosphere of nitrogen. All commercially available reagents
were used as received. Bis(2-diphenylphosphinophenyl)-
isomerization of MnBr(CO) (bpy′) in THF (bpy′ = 4,4′-
3
dimethyl-2,2′-bipyridine), and an ionic mechanism (halide
16
dissociation) was proposed. In that case the decrease of
entropy would be caused by electrostriction of the solvent
resulting from formation of charged species. This appears to be
the case here as well. Addition of methanol, which can stabilize
8a
phenylphosphine] was prepared according to a modified procedure
1
13
31
based on a literature report. The H, C, and P NMR spectra were
collected with a Varian Mercury 300 MHz or Bruker AVANCE 400
MHz spectrometer. Infrared spectra were recorded with a Nicolet
Nexus FT-IR spectrometer. UV−vis absorption spectra were recorded
with an HP G1103A spectrometer. trans-4-(Dicyanomethylene)-2-
methyl-6-(4-dimethylaminostyryl)-4H-pyran was used as a reference
−
the dissociated Cl ion to the freshly prepared solution of B in
3
1
DCM, led to instant disappearance of the P signals of B,
17
accompanied by clean formation of A within 1 h.
We used DFT to investigate whether the initial dissociation
of the chlorido ligand from B could lead to the formation of
species A. On the singlet surface, dissociation of a chlorido
ligand leads to the formation of a square pyramidal species
1
8
to determine the quantum yield. High-resolution mass spectra
HRMS) were recorded with an AccuTOF GC v 4g, JMS-T100GCV
mass spectrometer. Elemental analyses were performed by Mikroana-
lytisches Labor Kolbe, Mulheim, Germany.
(
̈
1
+
−
B (-Cl ), in which CO and the remaining chlorido ligand are
Synthesis of Bis[2-(diphenylphosphino)phenyl]-
phenylphosphine]. To a solution of (2-bromophenyl)-
diphenylphosphine (2.60 g, 7.62 mmol) in ether (30 mL) cooled at
coordinated in the basal positions. This species easily
isomerizes over a transition state that has an energy 2.6 kcal/
1
+
−
−
40 °C was added dropwise a solution of nBuLi (1.6 M in hexane, 5
mol higher than B (-Cl ) to a lower energy (ΔE
= −1.5
SCF
1
+
−
mL, 8.0 mmol) under stirring. The cold solution was stirred for 10 min
kcal/mol) square pyramidal A (-Cl ) species with the CO
ligand coordinated at the apical position. Recoordination of the
chlorido ligand to the latter species would lead to the formation
of species A. Remarkably, on the triplet surface, only A (-Cl )
could be located as a minimum (ΔE = +1.2 kcal/mol vs
B (-Cl )). These calculations show that dissociation of a
at −40 °C and anther 2 h from −40 °C to room temperature. A
solution of PhPCl (682 mg, 3.81 mmol) in ether (10 mL) was added
2
dropwise under stirring. After being stirred overnight at room
temperature, the solution was filtered. The thus-obtained white solid
was washed with ether (10 mL × 2) and dried in vacuo. The white
powder was extracted with CH Cl (60 mL × 3). The crude product
3
+
−
SCF
1
+
−
2
2
chloride from B should lead to facile formation of A regardless
of the spin state of the putative five-coordinate intermediate
was obtained by solvent evaporation under reduced pressure.
Analytically pure product was obtained after flash column chromatog-
raphy on silica gel (60−200 μm) using a mixture of CH Cl and
2
2
(
Scheme 2), which is in accord with the observed acceleration
1
hexane (1:1, v/v) as eluent. Yield: 0.86 g, 36%. H NMR (400 MHz,
of isomerization in the presence of methanol.
3
1
CD Cl , 298 K): δ 7.26−6.86 (m, 33H) ppm. P (162 MHz, CD Cl ,
2
2
2
2
The positive activation entropy of the thermal isomerization
of C to B points to a transition state with a dissociated
phosphine arm. The thus formed high-spin pentacoordinate
intermediate could subsequently isomerize, for example, via a
Berry-pseudorotation pathway and yield B after recoordination
2
2
2
98 K): δ 14.87 (d[AB] J = 175 Hz, 1P), 14.95 (d[AB] J = 125
PP PP
2
2
13
Hz, 1P), 17.89 (dd[AB] J = 175 Hz, J = 123 Hz, 1P) ppm.
C
PP
PP
NMR (101 MHz, CD Cl , 298 K): δ 137.57 (s), 137.45 (s), 137.34
2
2
(s), 137.12 (m), 134.30 (s), 134.24 (s), 134.18 (s), 134.12 (s), 134.04
(s), 133.64 (s), 133.54 (s), 133.44 (s), 133.34 (s), 128.89 (s), 128.60
D
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Article
(
s), 128.07 (m) ppm. Anal. Calcd (C H P ): C, 79.99; H, 5.27.
positions using a riding model. Details of the X-ray crystal structures
are listed in the SI (Table S1).
42
33 3
Found: C, 80.07; H, 5.23
Synthesis of (mer-TP)Fe(CO)Cl2 (A). Under an atmosphere of
Computational Methods. Density functional theory (DFT)
calculations were carried out with the Turbomole 6.5 program
carbon monoxide, a solution of TP (473 mg, 0.75 mmol) in CH Cl2
2
2
2
23
24
(
30 mL) was added to a solution of FeCl ·2H O (150 mg 0.75 mmol)
package using the BP86 functional with def2-TZVP basis sets
25
2
2
in MeOH (5 mL) under stirring at room temperature. A red solution
was formed immediately and turned to bright red after being stirred
for another 30 min in the dark under an atmosphere of carbon
monoxide. Solvent was removed under reduced pressure, and the
resulting orange powder was washed with MeOH (10 mL × 2) and
ether (10 mL × 2), respectively. The isomer A·1.2CH Cl was isolated
and resolution of identity approximation. Vibrational analysis of
calculated stationary points revealed no negative eigenvalues for
minima and one negative eigenvalue for the transition state. The UV−
vis transitions of complexes A, B, and C were calculated with TD-DFT
(nroots = 50; maxdim = 600; triplets = false) as implemented in the
ORCA package at the b3-lyp level (RIJCOSX ) using the def2-
TZVP basis set. ZORA scalar relativistic Hamiltonians (Special-
GridAtoms = 27, SpecialGridIntAcc = 7) and COSMO dielectric
solvent corrections (ε = 8.93; CH Cl ) were included. The
2
6
27
28
2
2
2
9
as an orange powder. Yield: 540 mg (0.61 mmol, 81%). Single crystals
suitable for X-ray diffraction were grown as orange needles by the
diffusion of THF to a solution of A in CH Cl in the dark at room
30
2
2
2
2
1
temperature. H NMR (400 MHz, CD Cl , 298 K): δ 8.28 (t, J = 7.2
coordinates from the structures optimized in Turbomole were used
as input for these ORCA TD-DFT calculations.
2
2
Hz, 2H), 7.94 (m, 4H), 7.83 (m, 2H), 7.73 (m, 4H), 7.66 (m, 4H),
.44 (m, 3H), 7.36 (m, 8H), 7.03 (t, J = 7.2 Hz, 2H) 6.82 (dt, J = 2.4
7
13
Hz, J = 7.2 Hz, 2H) 6.39 (m, 2H) ppm. C (101 MHz, CD Cl , 298
ASSOCIATED CONTENT
Supporting Information
2
2
■
K): δ 136.62 (t, J = 4.44 Hz) 135.88 (s), 135.73 (s), 133.05 (t, J = 5.15
Hz), 132.42 (t, J = 6.16) 131.76 (s), 131.65 (s), 131.40 (m), 130.60
*
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.5b00644.
(
=
1
1
7
1
s), 130.53 (s), 128.55 (t, 4.44 Hz), 128.33 (s), 128.23 (s), 127.75 (t, J
4.80) ppm. 3 P (162 MHz, CD Cl , 298 K): δ 115.64 (t, J = 32.4,
1
2
2
2
PP
2
−1
P), 65.11 (d, J = 32.4 Hz, 2P) ppm. IR (CH Cl , cm ): ν(CO)
PP
2
2
+
972 (s). HRMS (FD+) m/z: [M − CO] calcd for C H Cl Fe P
42 33 2 1 3
DFT structures, TD-DFT calculations, UV−vis spectra,
and kinetic curves (PDF)
Crystallographic data (CIF)
Crystallographic data (CIF)
Molecular structure (XYZ)
56.05216, found 756.05831. Anal. Calcd (C H Cl FeOP ·
4
3
33
2
3
.2CH Cl ): C, 59.83; H, 4.02. Found: C, 59.83; H, 4.14
2
2
Synthesis of unsym-(fac-TP)Fe(CO)Cl2 (B). A Schlenk tube
containing a solution of (mer-TP)Fe(CO)Cl2 (A)·1.2CH Cl2 (50
2
mg, 0.056 mmol) in CH Cl (4 mL) was placed in a fume hood with
2
2
the light on. The color of the solution changed from bright to dark red
in several hours. Single crystals suitable for X-ray diffraction were
AUTHOR INFORMATION
Corresponding Author
*E-mail: w.i.dzik@uva.nl.
■
collected after the slow evaporation of solvent as the isomer B·
1
0
.5CH Cl . Yield: 43 mg (0.052 mmol, 93%). H NMR (400 MHz,
2
2
CD Cl , 298 K): δ 8.14 (t, J = 8.5 Hz, 2H), 7.91 (dt, J = 15.7, 7.5 Hz,
2
2
2
7
6
2
1
1
1
1
3
1
2
7
0
H), 7.69−7.61 (m, 3H), 7.60−7.51 (m, 4H), 7.50−7.37 (m, 10H),
.33 (d, J = 9.1 Hz, 4H), 7.22−7.16 (m, 1H), 6.99 (t, J = 7.3 Hz, 2H),
.89 (t, J = 7.5 Hz, 1H), 6.57 (t, J = 7.6 Hz, 2H), 6.46 (t, J = 8.6 Hz,
H). 13C NMR (101 MHz, CD Cl , 223 K): δ 134.33 (d, J = 8.48 Hz),
Notes
The authors declare no competing financial interest.
2
2
ACKNOWLEDGMENTS
31.64 (s), 131.54 (s), 130.92 (s), 130.27 (s), 130.18 (s), 130.06 (s),
29.71 (s), 129.59 (s), 129.32 (s), 128.24 (s), 128.14 (s), 128.05 (s),
27.65 (s), 127.53 (s), 127.44 (s), 127.22 (s), 127.14 (s), 126.63 (s),
■
We thank the NRSC-C and The Netherlands Organization for
Scientific Research (NWO-CW, VENI grant 722.013.002) for
funding. Helpful assistance from Fei Wu and Tatu Kumpulai-
nen (Molecular Photonics, University of Amsterdam) with
mathematics and global fit is acknowledged.
3
1
2
26.53 ppm (s). P (162 MHz, CD Cl , 298 K): δ 111.55 (dd, J =
2
2
PP
2
2
2
2.4 Hz, J = 47.0 Hz, 1P), 77.60 (dd, J = 32.4 Hz, J = 47.0 Hz,
PP
PP
PP
−1
2
P), 53.60 (t, J = 47.0 Hz, 1P) ppm. IR (CH Cl , cm ): ν(CO)
PP
2
2
+
008 (s). HRMS (FD+) m/z: [M − CO] calcd for C H Cl Fe P
42
33
2
1 3
56.05216, found 756.06375. Anal. Calcd (C H Cl FeOP ·
4
3
33
2
3
REFERENCES
.5CH Cl ): C, 63.11; H, 4.14. Found: C, 63.34; H, 4.55. Note:
■
2
2
Absolutely pure NMR spectra of isomer B are not available due to its
decay to isomer A. The 13C NMR spectrum was recorded at −50 °C
to slow down the decay process.
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19
software. Absorption correction and scaling was performed with
SADABS. The structures were solved with SHELXS-97. Least-
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displacement parameters. Hydrogen atoms were located at calculated
20
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E
DOI: 10.1021/acs.organomet.5b00644
Organometallics XXXX, XXX, XXX−XXX

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2
(
(
Formation of D would require dissociation of the central PPh-donor
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high energy barrier. We speculate that the fact that E does not form
has a steric reason; recoordination of Cl to the (photogenerated) five-
F
DOI: 10.1021/acs.organomet.5b00644
Organometallics XXXX, XXX, XXX−XXX