(Cycloheptadienyl)diphenylphosphine: A versatile hybrid ligand

Article abstract of DOI:10.1021/om200999n

(3,5-Cycloheptadienyl)diphenylphosphine is easily synthesized from the reaction of diphenylphosphine with 1,3,5-cycloheptatriene. This new phosphine-diene has been coordinated as a monodentate P ligand with Pt, Pd, Au, Ni, and Ru; as a bidentate (P, olefin) ligand with Pt and Pd; and as a tridentate (P, diene) ligand with Rh. Fluxional properties of several complexes have been studied via NMR experiments and theoretical consideration.

Full text of DOI:10.1021/om200999n

Article
pubs.acs.org/Organometallics
(Cycloheptadienyl)diphenylphosphine: A Versatile Hybrid Ligand†
Alexandre Massard, Vincent Rampazzi, Arnaud Perrier, Ewen Bodio, Michel Picquet, Philippe Richard,
Jean-Cyrille Hierso, and Pierre Le Gendre*
́ ́ ́
Institut de Chimie Moleculaire de l’Universite de Bourgogne, ICMUB-UMR CNRS 6302, Universite de Bourgogne,
9 avenue Alain Savary, BP 47870, 21078 Dijon Cedex, France
S
* Supporting Information
ABSTRACT: (3,5-Cycloheptadienyl)diphenylphosphine is
easily synthesized from the reaction of diphenylphosphine
with 1,3,5-cycloheptatriene. This new phosphine-diene has
been coordinated as a monodentate P ligand with Pt, Pd, Au,
Ni, and Ru; as a bidentate (P, olefin) ligand with Pt and Pd;
and as a tridentate (P, diene) ligand with Rh. Fluxional
properties of several complexes have been studied via NMR
experiments and theoretical consideration.
drastically different from that of related (tropylidenyl)phos-
phines 1 and 2. Herein, we present and compare the coordina-
tion chemistry of this new hybrid ligand toward groups 8, 9,
and 10 transition metals and gold as a coinage metal.
INTRODUCTION
■
In recent years, the synthesis of mixed P-olefin ligands, includ-
ing chiral ones, has generated increasing interest.1,2 Indeed,
these ligands can lead to stable, but nonetheless highly active,
catalytic systems thanks to the combination of properties of the
two electronically different binding sites in a single ligand
framework: the σ-donor strength of a phosphorus center with
the good π-accepting capability of an olefin. Thus, the olefin,
which can readily and reversibly dissociate from the active
metal center, is able to open a coordination site, to stabilize
reactive intermediates and to facilitate a catalytic step.3,4 The
presence of the CC double bond in the immediate vicinity of
the transition metal may also create an asymmetric environment.5
(Tropylidenyl)phosphines 1 and 2 (Figure 1) have emerged as
RESULTS AND DISCUSSION
■
(3,5-Cycloheptadienyl)diphenylphosphine 3 has been obtained
in several grams scale via the one-step n-BuLi-mediated hydro-
phosphination of 1,3,5-cycloheptatriene with diphenylphosphine.
This phosphine is an easy to handle non-air-sensitive solid and
is soluble in most of the common organic solvents, such as toluene,
ether, THF, dichloromethane, and methanol. The phosphine-
diene 3 was reacted with miscellaneous metal-containing pre-
cursors, including platinum, palladium, gold, nickel, ruthenium,
or rhodium compounds. Three different coordination modes of
3 were observed depending on the metal/phosphine stoichio-
metry and on the nature of the precursor used: a monodentate
fashion (κP-coordination), a bidentate fashion (κP:η2-coordi-
nation), and a tridentate fashion (κP:η4-coordination).
κP-Coordination of 3 in Pd, Pt, Ni, Ru, and Au Com-
plexes. The reaction of [PtCl2(cod)] with 3 in a molar ratio of
1:2 afforded the complex [PtCl2{P(C7H9)Ph2}2] 4 as an off-
white powder (97%) after evaporation of cyclooctadiene (Scheme 1).
The ESI mass spectrum of 4 shows the expected parent ion
and fragmentation pattern. The complex displays a single reso-
nance in the 31P{1H} NMR spectrum downfield-shifted with
respect to the (cycloheptadienyl)phosphine (δP = 14.7 ppm vs
−4.7 ppm for 3) with platinum satellites separated by a
Figure 1. Tropylidenyl and cycloheptadienyl phosphines.
one of the most fruitful ligands of this class, allowing the
synthesis of a wide range of transition-metal complexes.6,7
These phosphines generally behave as chelating ligands in
which the phosphorus atom and the central CC bond of the
tropylidenyl ring, the latter adopting a boatlike conformation, serve
as preferred binding sites. As a part of our ongoing program on
the hydrophosphination reaction, we recently described the
synthesis of the (3,5-cycloheptadienyl)diphenylphosphine 3.8
In view of the conformational flexibility of the cycloheptadienyl
ring and of the relative position of the two double bonds in
regard to the phosphorus atom, we felt that the coordina-
tion chemistry of this new ligand should be diversified and
1
coupling constant J(195Pt−P) of 3690 Hz, which indicates the
presence of the chlorine atoms trans to the phosphorus ones
9
1
and thus the cis geometry. The H NMR spectra of 4 and of
the (cycloheptadienyl)phosphine are very similar, showing one
broad and complex signal for the four protons of the dienyl
Received: October 17, 2011
Published: January 20, 2012
© 2012 American Chemical Society
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a
Scheme 1. Synthesis of Platinum and Palladium Complexes
4 and 5
Table 1. Different κP Complexes Synthesized
system centered at δ = 5.75 ppm, which is consistent with the
κP-coordination of 3. A crystallization of the complex by dif-
fusion of pentane in dichloromethane allowed us to obtain
single crystals suitable for X-ray diffraction analysis (Figure 2).
a
Conditions: (cycloheptadienyl)phosphine (3), metal salt, CH2Cl2, 20 °C.
with [NiBr2(dme)] led to the bis(phosphine) complex 7 in
excellent yield (entry 2). The compound was silent for
1H NMR, suggesting a paramagnetic tetrahedral Ni(II)
complex and gives in the 31P NMR at 190 K a broad singlet
at 20.8 ppm. The ESI mass spectrum of 7 shows the expected
parent ion and fragmentation pattern. Equimolar reaction of
[AuCl(tht)] with 3 provided complex 8 in very good yield,
whereas a similar reaction with [Ru(η6-C10H16)Cl]2 led to
complex 9 (entries 3 and 4). In both cases, the spectroscopic
data show the κP-coordination of 3 with a pendant cyclo-
heptadienyl ring. The 31P NMR spectra of 8 and 9 show a
singlet at δ = 41.9 and 22.7 ppm, respectively. The olefinic
protons of the cycloheptadienyl moiety in the 1H NMR spectra
of 8 and 9 resonate as a broadened multiplet more complex
than the analogous signal in 3 or in complexes 4, 5, and 6. We
cannot undertake a meaningful analysis of this difference, but
simply note that the coordination of the (cycloheptadienyl)-
phosphine 3 to Au or Ru destroys the fortuitous isochrony of
the olefinic protons.
Figure 2. Crystal structure of 4 (ORTEP plot, 30% probability
ellipsoids). Dichloromethane solvent molecule omitted for clarity.
Selected distances (Å) and angles (deg): Pt−P1 2.254(2), Pt−P2
2.272(3), Pt−Cl1 2.350(2), Pt−Cl2 2.360(2), C3−C4 1.323(18),
C4−C5 1.473(19), C5−C6 1.333(17), C22−C23 1.35(2), C23−C24
1.40(2), C24−C25 1.312(19); P1−Pt−P2 98.21(9), P1−Pt−Cl1
91.31(9), P2−Pt−Cl1 170.42(9), P1−Pt−Cl2 176.26(9), P2−Pt−
Cl2 84.09(9), Cl1−Pt−Cl2 86.35(9), C3−C4−C5−C6 21(2), C22−
C23−C24−C25 21(3).
The crystal structure of 4 shows a square-planar environment
around the Pt center. The angles P2−Pt−P1 (98.20(9)°) and
Cl1−Pt−Cl2 (86.34(9)°) are significantly distorted from the
ideal 90° due to the steric hindrance of the phosphine groups.
The Pt−P bond lengths [Pt−P1 2.254(2) Å and Pt−P2
2.272(3) Å] range in classical values.10 The cycloheptadienyl
ring adopts a half-chair-like conformation with the diphenyl-
phosphino group in an exo position as in the phosphine 3.
The palladium analogue [PdCl2{P(C7H9)Ph2}2] (5) was
synthesized following the same way (Scheme 1). This complex
was quantitatively obtained (98%) as a yellow powder. The ESI
mass spectrum of 5 shows the expected parent ion and frag-
κP:η2-Coordination of 3 in Pt and Pd Complexes. With
the aim to involve the cycloheptadienyl ring in the coordination
sphere of the metal, we next reacted 1 equiv of [PtCl2(cod)]
with only 1 equiv of 3 (Scheme 2). Interestingly, no trace of 4
Scheme 2. Synthesis of Platinum Complex 10 and Palladium
Complex 12
1
mentation pattern. The H NMR spectrum of 5 is comparable
to the one of 4, giving evidence of the κP-coordination of 3.
The reaction of 2 equiv of 3 with [Pd(η3-C4H7)Cl]2 gave
complex 6 in good yield (Table 1, entry 1). Both H and 13C
1
was observed in this case. The expected complex 10 was
formed in 30 min in very good yield and was isolated as an off-
white solid.
NMR of 6 show the expected loss of symmetry of the methallyl
ligand, when compared to the dimeric precursor.11 Hence, the
1H NMR leads to four separate signals for the allylic anti and
syn protons (Δδ 1Hanti = 0.96 ppm and Δδ 1Hsyn = 1.44 ppm),
whereas two different chemical shifts are found in the 13C
NMR spectrum for the methylenic carbons cis and trans to the
phosphorus atom at δ = 59.5 and 78.2 ppm, respectively.
Moving up in the periodic table, the reaction of 2 equiv of 3
The 31P{1H} NMR spectrum of 10 displays one peak at
33.3 ppm with platinum satellites (1J(195Pt−P) = 3459 Hz).
This coupling constant indicates the presence of one chlorine
atom trans to the phosphorus one.9 The 1H NMR signal of the
olefinic protons, which resonates as a broad multiplet centered
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Figure 3. Partial H NMR spectra of 4 (a) and 10 (b), signals corresponding to the dienic system.
Figure 4. (a) Crystal structure of 10 (ORTEP plot, 30% probability ellipsoids). Selected distances (Å) and angles (deg) (Ct is the C1C2
centroid): Pt−P 2.2305(10), Pt−Cl1 2.3609(10), Pt−Cl2 2.3228(11), Pt−C1 2.187(4), Pt−C2 2.170(4), Pt−Ct 2.064(3), C1−C2 1.394(5), C6−
C7 1.336(6), C1−C7 1.475(5); Cl1−Pt−Cl2 90.85(4), Cl2−Pt−P 89.91(4), Ct−Pt−P 89.56(8), Ct−Pt−Cl1 89.98(8). (b) Overlay structures of 10
and of the free (cycloheptadienyl)phosphine 3 (in red; the P atom of the nonbonded ligand is located in the exo position).
at δ = 5.72 ppm in 4, is now split into four multiplets centered
at δ = 5.31, 5.40, 5.86, and 6.18 ppm (Figure 3). Two of
these signals at δ = 5.31 and 5.86 ppm have satellites with
2J(195Pt−H) = 68 and 73 Hz and can thus be assigned to
the olefinic protons of the coordinated olefin. The signal
at δ = 5.86 ppm appears as a pseudotriplet and can be attri-
buted to the proton farthest away from the P atom (Hδ). In
COSY experiment, Hδ shows two cross peaks with the other
olefinic protons, whereas the proton (Hγ) giving the signal at
δ = 5.31 ppm is connected to only one (see the Supporting
Information). The remaining two signals at δ = 5.40 and
6.18 ppm can be attributed to the protons of noncoordinated
olefin, the most upfield-shifted signal being due to the second
Hδ, as attested by the COSY spectrum of 10. These data
unequivocally demonstrate that the (cycloheptadienyl)-
phosphine chelates the Pt atom in solution, the binding sites
being the phosphorus atom and one of the two olefins. The
nature of complex 10 was further confirmed from the ESI mass
spectrum. Noteworthy, an analogue complex 11, bearing methyl
groups instead of chlorides, was synthesized from [PtMe2(cod)]
in moderate yield (48%).
A slow diffusion of heptane in a dichloromethane solution
of 10 afforded yellow needles suitable for a crystallographic
structure determination of this complex. The platinum atom
occupies the center of a square-planar arrangement defined by
the phosphorus atom, the centroid of one of the two CC
double bonds and the two chlorine atoms (Figure 4a). The
conformational flexibility of the ligand allows the phosphorus
atom to lie in an endo position of the cycloheptadienyl ring,
thus forming a Pt chelate. The flip of the ligand to the endo
conformation does not affect significantly the shape of the
cycloheptadienyl ring, as it can be seen in the overlay structures
of 10 and of the free ligand (the best overlay fit between the
two rings leads to a residual rms distance between equivalent
atoms equal to 7.8 × 10−2 Å, Figure 4b). Expectedly, the
coordinated C1C2 bond distances (1.394(5) Å) are slightly
elongated when compared with that of the free ligand or to the
noncoordinated CC bond of the cycle (1.336(6) Å). The
Pt−C(olefin) bond and Pt−P bond distances (Pt−C1,
2.187(4) Å; Pt−C2, 2.170(4) Å; Pt−P, 2.2305(10) Å) are in
the ranges of those observed for related complexes.12 The
difference in the Pt−Cl bond lengths (Pt−Cl1, 2.3609(10) Å vs
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Pt−Cl2, 2.3228(11) Å) reflects the stronger trans influence of
the phosphorus atom as compared to the olefin.
raised back, the H NMR spectrum again exhibits two broad
signals. The NMR behavior of 12 is consistent with the coordina-
tion of one of the two olefins to the Pd center with an accom-
panying dynamic exchange process. A low-energy activation
barrier ΔG⧧ = 12.15 0.06 or 12.0 0.3 kcal·mol−1 can be
estimated using the coalescence temperature Tc = 264 or 270 K
and the respective maximum peak separation in the slow-exchange
limit Δν190 K = 216 or 474 Hz, depending on the spin systems
taken into account (see the Supporting Information).13,14
The same synthetic way was applied to the formation of
[{(η2-C7H9)PPh2-κP}PdCl2] (12) (Scheme 2). The complex
was obtained in 16 h in excellent yield. The 31P NMR spectrum
of 12 displays one singlet at δ = 57.4 ppm, attesting the
coordination of the phosphorus atom to the Pd center. The
1H NMR spectrum of 12 appears much simpler than the
spectrum of 10 acquired under similar conditions (solvent,
temperature, and NMR field). It displays only two broad signals
at δ = 5.91 and 6.48 ppm in the chemical shift area of the dienic
system (instead of four signals for 10) with identical relative
intensities and one multiplet between 2.80 and 2.90 ppm
(instead of four signals split from 2.25 to 3.46 ppm for 10). All
these data are consistent with a symmetric chelate structure.
Single crystals of 12 suitable for X-ray diffraction analysis were
obtained by recrystallization in acetonitrile at −18 °C.
Surprisingly, the solid-state structures of 12 and 10 are very
It is worth noting that, upon heating until 393 K, there is no
sign of such a dynamic exchange in the case of the platinum
complex. The coordination shifts Δδ = (δcomplex − δfree ligand
observed for the olefinic carbons of 10 (mean Δδ = −40.1 ppm)
and of 12 (Δ
δ = −21.1 ppm) in the corresponding 13C NMR
spectra indicate a higher degree of back-donation from the Pt
center to the CC unit and may partly account for a more
rigid Pt structure.5
At this stage, a range of related questions arise about the
relative stability of the 16-electron complexes (κP:η2-coordina-
tion) versus 18-electron complexes (κP:η4-coordination), about
the mechanism of the dynamic exchange process, and on the
difference in the dynamic behaviors of the Pd and Pt com-
plexes. Simple orbital interaction considerations may first clarify
the electronic environment at the pseudo-square-planar
complexes 10 and 12. For the 16-electron system, in which
the metal is bonded to only one double bond, the σ-donor
interaction occurs mainly with the φ2 orbital of the dienyl π
system, whereas the π interaction takes place between a filled
dπ metal orbital with the empty φ3 orbital, giving rise to a net
back-donation stabilization effect (Figure 7).
)
̅
̅
Differently, in the 18-electron system, it is the occupied φ1
orbital that is involved in the stabilizing σ-donation system for
symmetrical reasons. The second occupied φ2 orbital interacts
then with a filled dπ metal orbital. This 4-electron/2-orbital π
interaction leads to a net repulsive polarization effect. Con-
sequently, a higher energy is expected for the 18-electron
species and such a complex would rather be an intermediate, or
a transition state, in the dynamic exchange process of the two
olefins connecting the two 16-electron complexes. DFT
calculations confirm that these 18-electron structures are
transition states and give a ΔG⧧ (298 K) for the Pd transition
state A⧧ equal to 10.5 kcal·mol−1 and a substantially higher
value of 20.1 kcal·mol−1 for the Pt TS (Figure 8). A dissociative
mechanism has been also considered for the dynamic exchange
process in both complexes (10 and 12). It involves the
decoordination of the olefin that generates low-coordinate
complexes that relax to T-shaped geometries with both chloride
atoms in the trans position (B in Figure 8).15 As expected,
these 14-electron intermediates lie higher in energy than the
16-electron complexes with a ΔG (298 K) equal to 10.9 kcal·mol−1
for the Pd complex and 18.9 kcal·mol−1 for the Pt one. These
energy values give a good indication of the difference in the
metal−olefin bond strength.16,17 Although the energy values
involved in the dissociative and associative processes seem
rather similar, they refer to two different types of entities, an
intermediate B for the dissociative process and a transition state
A⧧ for the associative route. Despite that we did not determine
the transition states for this dissociative process, it is clear that
the associative mechanism requires less energy and thus takes
preference over the dissociative one, with the energy of its
transition state lying in the range of one of the intermediates in
this dissociative mechanism.18 Concerning the difference in the
dynamic behavior of both complexes, DFT calculations of the
Figure 5. Crystal structure of 12 (ORTEP plot, 30% probability
ellipsoids). Selected distances (Å) and angles (deg) (Ct is the C1C2
centroid): Pd−P 2.2334(5), Pd−Cl1 2.3659(5), Pt−Cl2 2.3240(6),
Pd−C1 2.233(2), Pd−C2 2.219(2), Pd−Ct 2.1164(16), C1−C2
1.382(3), C6−C7 1.339(3), C1−C7 1.467(3); Cl1−Pd−Cl2 92.89(2),
Cl2−Pd−P 87.99(2), Ct−Pd−P 89.26(4), Ct−Pd−Cl1 90.35(4).
similar (Figure 5). The geometry around the Pd is square-
planar with the (cycloheptadienyl)phosphine ligand coordi-
nated in a bidentate mode. Remarkably, switching from Pt to
Pd does not cause significant changes in the metal−phosphorus
and metal−chlorine distances (Pd−P, 2.2334(5) Å; Pd−Cl1,
2.3659(5) Å; and Pd−Cl2, 2.3240(6) Å). Conversely, while
coordinated CC bond lengths are similar in both complexes,
the Pd−C1 and Pd−C2 distances (2.233(2) and 2.219(2) Å,
respectively) are longer than those observed in the Pt complex
10. These data suggest a stronger metal−olefin interaction in
the platinum complex.
Because the ability of the (cycloheptadienyl)phosphine to
adopt a bidentate coordination mode in the solid state was thus
established, it appeared clearly that the environment around the
Pd should be asymmetric. Nevertheless, as already mentioned,
NMR data collected at room temperature are consistent with a
symmetric chelate structure. To elucidate this apparent
1
discrepancy, we measured H NMR spectra of 12 at lower
temperatures. By decreasing the temperature, a decoalescence
phenomenon was observed (Figure 6). At 190 K, the two broad
signals of the olefinic protons are split into four signals
consistent with the solid-state conformation. The VT-NMR
shows a reversible behavior, since, when the temperature is
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Figure 6. (a) Dynamic exchange of the two olefin environments. (b) H NMR spectra of 12 at selected temperatures (CD2Cl2, 600.13 MHz).
Figure 7. Top view of the 16-electron and of the 18-electron complexes as well as a schematic representation of the dienyl π system.
κP:η4-Coordination of 3 in Rh Complexes. [Rh(cod)2]-
BF4 was reacted with an equimolar quantity of 3 and furnished
complex 13 in good yield (Scheme 3). The 31P{1H} NMR
spectrum of 13 reveals a doublet at δ = 78.6 ppm with a
rhodium coupling constant of 151 Hz, consistent with the
coordination of the phosphorus atom to the rhodium center.
The 1H NMR spectrum of 13 shows two signals at δ = 4.03 and
6.47 ppm due to the olefinic protons of the (cycloheptadienyl)-
phosphine, which provides evidence of the η4-coordination of
Figure 8. (A⧧) Transition state of the Pd complex in square-planar
geometry calculated at the DFT level. (B) Tricoordinated Pd complex
in T-shaped geometry calculated at the DFT level (same geometries
are obtained in the Pt series).
the cycloheptadienyl moiety.20 The variable-temperature NMR
experiment did not reveal significant changes and led to the
conclusion that the structure of 13 is rigid in solution at the
NMR time scale.
activation barriers in the associative mechanism give a
lower energy level for the Pd vs Pt complexes (Δ(ΔG⧧) =
9.6 kcal·mol−1). These results account for the higher fluxionality
of the Pd complex and can be related to the higher lability of
olefinic ligands generally observed for Pd−alkene complexes.19
As shown in Figure 9, the X-ray structure reveals a tridentate
coordination of the (cycloheptadienyl)diphenylphosphine. The
structure was solved in the noncentrosymmetric group Pc with
the result that two independent complexes are present in the
asymmetric unit as well as two BF4− counteranions and two
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Scheme 3. Synthesis of Rhodium Complex 13
The addition of a second equivalent of the hybrid ligand 3 to
13 led to the formation of the bis[(cycloheptadienyl)-
diphenylphosphine] cationic Rh complex 14 in good yield
(Scheme 4). The 31P{1H} NMR spectrum of 14 shows a
doublet at δ = 66.8 ppm with a rhodium coupling constant of
143 Hz. The 1H NMR spectrum of complex 14 shows only two
sharp signals at δ = 4.29 and 5.32 ppm for the olefinic protons.
These data are consistent with the coordination of each (cyclo-
heptadienyl)phosphine ligand to the rhodium center in a sym-
metric chelating fashion. Because the tridentate coordination of
both ligands would lead to a 20-electron Rh(I) species, which
is rather less than likely, this apparent symmetry can more
probably be achieved under dynamical conditions (Figure 10).
The fluxional properties of 14 were probed by a variable-
temperature 31P{1H} NMR experiment in CD2Cl2 from 300 K
down to 165 K (Figure 10, upper traces). At 218 K, the signal is
broad and merges almost with the baseline. At 214 K, two
broad resonances appear and become clearly visible at 190 K at
δ = 56.9 and 80.1 ppm, which indicates that the metal is
chelated in a different manner by the two (cycloheptadienyl)-
phosphines. Down to 165 K, the two broad signals give rise to
sharp doublets centered at δ = 56.5 and 79.0 ppm with typical
rhodium coupling constants of 151 and 134 Hz, respectively. It
is noteworthy that the 31P−31P coupling is not observed at low
temperature, although it might be expected to be seen. The
dynamic properties of 14 in solution could be explained by a
slippage of the diene moiety on the Rh center, as described for
the Pd complex 12, but extended to both cycloheptadienyl
rings at a concerted tempo (Figure 10).
Figure 9. Crystal structure of the cation complex 13 (ORTEP plot,
30% probability ellipsoids). Only one molecule is represented;
dichlomethane solvent molecules and the BF4− counteranion are
omitted for clarity. Selected distances (Å) and angles (deg) (Ctnm
represents the centroid of the Cn−Cm bond): Rh1−P1 2.3435(13),
Rh1−C1 2.251(5), Rh1−C2 2.220(6), Rh1−C5 2.244(5), Rh1−C6
2.247(4), Rh1−C11 2.183(5), Rh1−C12 2.184(6), Rh1−C13
2.185(6), Rh1−C14 2.192(5), C11−C12 1.408(8), C12−C13
1.425(9), C13−C14 1.428(7), Rh1−Ct12 2.126(4), Rh1−Ct56
2.139(4), Rh1−Ct1112 2.067(4), Rh1−Ct1314 2.069(4); Ct12−
Rh1−Ct56 84.63(14), Ct12−Rh1−P1 110.09(15), Ct12−Rh1−
Ct1112 150.49(16), Ct12−Rh1−Ct1314 100.09(15), Ct56−Rh1−
Ct1314 146.01(15), Ct56−Rh1−Ct1112 97.44(15), Ct56−Rh1−P1
113.46(11), Ct1112−Rh1−P1 96.11(12), Ct1112−Rh1−Ct1314
62.51(15), Ct1314−Rh1−P1 96.61(12).
By comparing selected experimental 31P{1H} NMR spectra
from this coalescence phenomenon with computer simulated
ones (Figure 10, lower traces), on the basis of an interchange in
the coordination mode of the two noncoupled phosphines,
exchange rates (k) can be calculated for each temperature. A
standard Eyring plot of ln(k/T) against 1/T gives the following
thermodynamic values at 298 K: ΔS⧧ = 1.0 2.7 cal·K−1·mol−1,
ΔH⧧ = 8.8 0.6 kcal·mol−1, and ΔG⧧ = ΔH⧧ − TΔS⧧ = 8.5
1.0 kcal·mol−1 (see the Supporting Information).22 The low
activation barrier is consistent with the observed dynamic
behavior of 14, and the value of the entropy (equal to zero
within the uncertainty) is consistent with the above-described
concerted slippage of the diene moieties on the Rh center in
which the transition state does not exhibit any loss or gain of
degrees of freedom.
dichloromethane solvent molecules. Nevertheless, due to a
pseudoinversion center, both molecules have almost identical
geometrical parameters. The best overlay fit between the two
molecules leads to a residual rms distance between equivalent
atoms (excluding the phenyl groups) equal only to 0.048 Å. For
the sake of clarity, the geometrical parameters are given for only
one molecule. The geometry around the rhodium center is a
distorted square-based pyramid with P atom deviating from the
ideal apical position. The basal positions are occupied by the
two olefins of the cyclooctadiene ligand and the dienyl part of
the hybrid ligand. As expected, the bond lengths C11−C12,
C12−C13, and C13−C14 (1.408(8), 1.425(9), and 1.428(7) Å,
respectively) of the coordinated cycloheptadienyl ring are
similar and range between those of single and double bonds
found in the (cycloheptadienyl)phosphine 3. The flexibility of
the cycloheptadienyl ring in the endo chairlike conformation allows
minimizing the steric congestion in complex 13, as attested by
the normal Rh−P (2.3435(13) Å) and Rh−C(olefin) bond
lengths (mean: 2.186(6) Å).21
A diffraction study on a single crystal of 14 confirmed the
two different coordination modes (κP:η2, κP:η4) of ligand 3
within the same metal complex (Figure 11a). The structure of
14 is very similar to the one of 13, but with two of the basal
positions of the square-planar pyramid around the rhodium
atom being occupied by the phosphorus atom and one olefin of
952
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Organometallics
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Scheme 4. Synthesis of Rhodium Complex 14
Figure 10. Dynamic exchange of the two phosphorus environments. Upper traces: 31P{1H} NMR spectra of 14 at selected absolute temperatures T
(CD2Cl2, 242.92 MHz). Lower traces: computer-simulated spectra using gNMR (calculated exchange rates k shown in parentheses if given).
the bidentate (cycloheptadienyl)phosphine in place of the
cyclooctadiene ligand (Figure 11b). Ligand 3 in its bidentate
coordination mode adopts a conformation comparable to that
observed in the Pd and Pt complexes (10 and 12, respectively).
The η2-coordinated cycloheptadienyl ring displays distinct C
C−CC bond lengths (C22−C23 1.397(2) Å, C23−C24
953
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Organometallics
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Figure 11. (a) Crystal structure of the cationic complex 14 (ORTEP plot, 30% probability ellipsoids). H atoms, dichloromethane solvent molecules,
and the BF4− counteranion are omitted for clarity. Selected distances (Å) and angles (deg) (Ctnm represents the centroid of the Cn−Cm bond):
Rh−P1 2.3449(4), Rh−P2 2.3398(4), Rh−C3 2.2152(16), Rh−C4 2.1880(16), Rh−C5 2.1866(16), Rh−C6 2.2111(16), Rh−C22 2.2165(16), Rh−
C23 2.2703(16), Rh−Ct34 2.0826(12), Rh−Ct56 2.0807(12), Rh−Ct2223 2.1320(12), C3−C4 1.428(3), C4−C5 1.412(3), C5−C6 1.423(2),
C22−C23 1.397(2), C23−C24 1.469(2), C24−C25 1.333(3); Ct34−Rh−Ct56 62.20(5), Ct34−Rh−P1 96.95(4), Ct34−Rh−P2 143.10(4), Ct34−
Rh−Ct2223 94.63, Ct56−Rh−P1 94.66(4), Ct56−Rh−P2 97.40(4), Ct56−Rh−Ct2223 143.61(5), Ct2223−Rh−P1 116.94, Ct2223−Rh−P2
85.02(3), P1−Rh−P2 116.105(14). (b) Overlay structures of 13 and 14 (in red).
1
on a Bruker micrOTOF-Q ESI-MS. H (300.13, 500.13, or 600.13
1.469(2) Å, C24−C25 1.333(3) Å), whereas these distances in
MHz), 13C (75.5, 125.8, or 150.9 MHz), and 31P (121.5, 202.5, or
242.9 MHz) NMR spectra were recorded on a Bruker 300 Avance, a
Bruker 500 Avance DRX spectrometer, or on a Bruker 600 Avance II
its tridentate counterpart are nearly the same (C3−C4 1.428(3)
Å, C4−C5 1.412(3) Å, C5−C6 1.423(2) Å). Both Rh−P bond
distances are similar and fall in the usual range (Rh−P1
spectrometer. Chemical shifts are quoted in parts per million (δ)
2.3449(4) Å, Rh−P2 2.3398(4) Å).
relative to TMS (1H), using the residual protonated solvent as an
internal standard, or external 85% H3PO4 (31P). Coupling constants
are reported in hertz.
CONCLUSION
■
Synthetic Procedures. (3,5-Cycloheptadienyl)diphenyl-
phosphine (3). In a Schlenk tube, an n-BuLi solution (0.19 mmol,
1.6 M in hexanes) was added to a solution of diphenylphosphine
(1.25 mmol) in freshly distilled toluene (2 mL). The solution was
stirred for 30 min at room temperature, and then 3,5-cycloheptatriene
(3.75 mmol) was added. The reaction mixture was stirred until full
consumption of diphenylphosphine (monitored by GC), around 18 h
at 70 °C. The reaction was then quenched with a small amount of
water, and MgSO4 was added. The mixture was filtered, and the filtrate
was evaporated under reduced pressure. The obtained slurry was
triturated with pentane to afford a white solid. The solid was dissolved
in a small amount of dichloromethane and crystallized by diffusion of
The coordination chemistry of (3,5-cycloheptadienyl)diphenyl-
phosphine 3 toward groups 8, 9, and 10 transition metals and
gold as a coinage metal has been studied. This hybrid ligand is
conformationally flexible and can thus behave as a mono-, bi-,
or tridentate ligand, depending on metals and experimental
conditions. Illustrative coordination complexes have been
prepared and fully characterized. The structure of a Pd(II)
complex containing the bidentate (cycloheptadienyl)phosphine
was found to be fluxional in solution, as illustrated by its NMR
dynamic behavior. This NMR behavior is consistent with the
coordination of one of the two olefins to the palladium center
with an accompanying dynamic exchange process. DFT
calculations gave insight into this mechanism and account
for the relative stability of the 16-electron complexes (κP:η2-
coordination) versus the 18-electron complexes (κP:η4-
coordination) and of the lower fluxionality of the parent
platinum complex. A fluxional Rh(I) complex bearing two
(cycloheptadienyl)phosphine ligands in a bi- and tridentate
fashion has also been described. The rhodium center is then
surrounded by two phosphines and four olefins, which should
considerably improve the stability of low oxidation states.23 All
these observations and the variety of complexes described
herein make this type of phosphine-diene promising for
organometallic chemistry and catalysis.
1
pentane (316 mg, 91%). H NMR (CDCl3, 300.13 MHz, 298 K): δ
(ppm) 2.23−2.48 (m, 4H, cycloheptadiene CH2), 2.71−2.81 (m, 1H,
cycloheptadiene CH), 5.79−5.89 (m, 4H, cycloheptadiene CH),
7.32−7.37 (m, 6H, Ph), 7.49−7.55 (m, 4H, Ph). 13C NMR (CDCl3,
75.47 MHz, 298 K): δ (ppm) 34.3 (d, JC−P = 18.1 Hz, cyclo-
heptadiene CH2), 34.7 (d, JC−P = 11.0 Hz, cycloheptadiene CH),
2
1
2
126.0 (s, cycloheptadiene CH), 128.5 (d, JP−C = 7.1 Hz, Ph Cortho),
129.0 (s, cycloheptadiene CH), 132.8 (d, JC−P = 13.8 Hz, Ph Cpara),
4
133.6 (d, 3JC−P = 19.3 Hz, Cmeta), 137.3 (d, 1JC−P = 14.4 Hz, Ph Cipso).
31P{1H} NMR (CDCl3, 202.45 MHz, 298 K): δ (ppm) −4.7 (s).
cis-Bis{(3,5-cycloheptadienyl)diphenylphosphine}PtCl2 (4). 3 (83 mg,
0.30 mmol, 2.5 equiv) was dissolved in 2 mL of dichloromethane. This
solution was cannulated over 5 min to a solution of [PtCl2(cod)]
(45 mg, 0.12 mmol, 1 equiv) in 2 mL of dichloromethane. When the
addition was completed, the solution was stirred for 18 h at room
temperature. The solution was then evaporated under reduced
pressure and triturated with pentane to afford a white solid. The
solid was dissolved in dichloromethane and crystallized by diffusion of
EXPERIMENTAL SECTION
■
All reactions were carried out under an atmosphere of purified argon
using vacuum line techniques. Solvents were dried and distilled under
argon before use. All other reagents were commercially available and
used as received. All the analyses were performed at the “Plateforme
1
pentane (96 mg, 97%). H NMR (CD2Cl2, 300.13 MHz, 298 K): δ
(ppm) 1.98 (m, 4H, cycloheptadiene CH2), 2.72 (m, 4H, cyclo-
heptadiene CH2), 3.23 (m, 2H, cycloheptadiene CH), 5.72 (m, 8H,
cycloheptadiene CH), 7.22−7.32 (m, 12H, Ph), 7.39−7.47 (m, 8H,
Ph). 13C NMR (CD2Cl2, 75.47 MHz, 298 K): δ (ppm) 34.6 (s,
cycloheptadiene CH2), 35.9 (d, 1JC−P = 40.7 Hz, cycloheptadiene CH),
̀ ́ ́
d’Analyses Chimiques et de Synthese Moleculaire de l’Universite de
Bourgogne”. The identity and purity (≥95%) of the complexes were
unambiguously established using high-resolution mass spectrometry
and multinuclear NMR. The exact mass of the complexes was obtained
1
125.7 (s, cycloheptadiene CH), 127.6 (d, JP−C = 56.6 Hz, Ph Cipso),
954
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2
128.5 (t, JC−P = 5.3 Hz, Ph Cortho), 131.4 (s, Ph Cpara), 132.1
75.47 MHz, 298 K): δ (ppm) 33.4 (d, 2JC−P = 6.6 Hz, cycloheptadiene
3
3
1
(t, JC−P = 8.3 Hz, cycloheptadiene CH), 134.0 (t, JC−P = 4.5 Hz, Ph
Cmeta). 31P{1H} NMR (CD2Cl2, 121.49 MHz, 298 K): δ (ppm) 14.2
(s, +d, 1JP−Pt195 = 3681.1 Hz). Several attempts at high-resolution mass
spectrometry failed to give a signal for C38H38P2PtCl+, but an exchange
between one chloride and one methoxy group has been observed.
CH2), 36.0 (d, JC−P = 35.7 Hz, cycloheptadiene CH), 126.8
1
(s, cycloheptadiene CH), 128.7 (d, JC−P = 57.9 Hz, Ph Cipso), 129.5
2
3
(d, JC−P = 11.4 Hz, Ph Cortho), 130.9 (d, JC−P = 19.0 Hz, cyclo-
heptadiene CH), 132.3 (d, 4JC−P = 2.6 Hz, Ph Cpara), 134.0 (d, 3JC−P
=
12.8 Hz, Ph Cmeta). 31P{1H} NMR (CDCl3, 121.49 MHz, 298 K): δ
(ppm) 41.9. HR-MS (ESIpos, methanol/dichloromethane; m/z): calcd
C19H19PAuClNa+ [M + Na]+ 533.04907. Found 533.04706.
HR-MS (ESIpos
, methanol/dichloromethane; m/z): calcd
C39H41O1P2Pt+ [M − 2Cl + OMe]+ 782.22749. Found 782.22839.
cis-Bis{(3,5-cycloheptadienyl)diphenylphosphine}PdCl2 (5). 3
(170 mg, 0.61 mmol, 2 equiv) was dissolved in 3 mL of dichloro-
methane. This solution was cannulated over 5 min to a solution of
PdCl2 (54 mg, 0.30 mmol, 1 equiv) in 2 mL of dichloromethane.
When the addition was completed, the solution was stirred for 18 h at
room temperature. The solution was then filtered over Celite,
evaporated under reduced pressure, and triturated with pentane to
afford a yellow solid. The solid was rinsed with pentane (220 mg,
98%). 1H NMR (CDCl3, 300.13 MHz, 298 K): δ (ppm) 1.98 (m, 4H,
cycloheptadiene CH2), 2.83 (m, 4H, cycloheptadiene CH2), 3.45
(m, 2H, cycloheptadiene CH), 5.79 (m, 8H, cycloheptadiene CH),
7.41−7.50 (m, 12H, Ph), 7.60−7.66 (m, 8H, Ph). 13C NMR (CDCl3,
75.47 MHz, 298 K): δ (ppm) 31.0 (t, 2JP−C = 12.0 Hz, cycloheptadiene
CH), 33.5 (s, cycloheptadiene CH2), 125.6 (s, cycloheptadiene CH),
{ (3 , 5 - C y c l o h e p t ad i e n y l )d i ph e n y l ph os p h i n e }( 2 , 7 -
dimethyloctadienediyl)RuCl2 (9). 3 (111 mg, 0.4 mmol, 2.2 equiv)
was dissolved in 2 mL of dichloromethane. This solution was can-
nulated over 5 min to a solution of [Ru(η6-C10H16)Cl]2 (112 mg,
0.18 mmol, 1 equiv) in 2 mL of dichloromethane (dichloro-bis-μ-
chloro-bis[(1−3η:6−8η)-2,7-dimethyloctadienediyl]diruthenium(II) is
commercially available, but we preferred synthesizing it according to
Salzer and co-workers’ method).24 When the addition was completed,
the solution was stirred for 15 min, evaporated under reduced
pressure, and triturated with pentane to afford a yellow solid. The solid
1
was rinsed with pentane (200 mg, 94%). H NMR (CDCl3, 600.13
MHz, 298 K): δ (ppm) 1.72 (m, 1H, CH2), 1.97 (m, 1H, CH2), 2.15
(s, 6H, CH3), 2.58 (m, 2H, CH2), 3.11−3.20 (m, 2H, CH2), 3.35
2
(m, 2H, CH2), 3.39 (m, 1H, cycloheptadiene CH), 3.42 (d, JH−H
=
2
1
2
3.3 Hz, 2H, allyl CH), 4.51 (d, JH−H = 9.2 Hz, 2H, allyl CH), 5.20
(m, 2H, allyl CH), 5.79−5.92 (m, 4H, cycloheptadiene CH), 7.34−
7.43 (m, 6H, Ph), 7.74 (t, 3JH−H = 8.6 Hz, 2H, Ph), 7.83 (t, 3JH−H = 8.6
Hz, 2H, Ph). 31P{1H} NMR (CDCl3, 242.97 MHz, 298 K): δ (ppm)
22.7. HR-MS (ESIpos, acetonitrile/dichloromethane; m/z): calcd
C29H35PRuCl+ [M − Cl]+ 551.12029. Found 551.12082.
127.9 (t, JC−P = 21.5 Hz, Ph Cipso), 128.3 (t, JC−P = 4.9 Hz, Ph
3
Cortho), 130.6 (s, Ph Cpara), 132.4 (t, JC−P = 8.3 Hz, cycloheptadiene
CH), 134.2 (t, JC−P = 5.7 Hz, Ph Cmeta). 31P{1H} NMR (CDCl3,
3
121.49 MHz, 298 K): δ (ppm) 28.7. HR-MS (ESIpos, methanol/
dichloromethane; m/z): calcd C38H38P2ClPd+ [M − Cl]+ 697.11666.
Found 697.12201.
{(η2-3,5-Cycloheptadienyl)diphenylphosphine-κP}PtCl2 (10). 3
(49 mg, 0.18 mmol, 1.2 equiv) was dissolved in 2 mL of dichloromethane.
This solution was cannulated over 5 min to a solution of [PtCl2(cod)]
(53 mg, 0.14 mmol, 1 equiv) in 3 mL of dichloromethane. When the
addition was completed, the solution was stirred for 30 min at room
temperature. The solution was then evaporated under reduced pres-
sure and triturated with pentane to afford an off-white solid. The solid
was dissolved in dichloromethane and crystallized by diffusion of
{(3,5-Cycloheptadienyl)diphenylphosphine}(2-methylallyl)PdCl
(6). 3 (181 mg, 0.65 mmol, 2 equiv) was dissolved in 2 mL of dichloro-
methane. This solution was cannulated over 5 min to a solution of
[Pd(η3-C4H8)Cl]2 (115 mg, 0.33 mmol, 1 equiv) in 3 mL of dichloro-
methane. When the addition was completed, the solution was stirred
for 30 min, evaporated under reduced pressure, and triturated with
hexane to afford a yellow solid. The solid was rinsed with hexane
(250 mg, 81%). 1H NMR (CDCl3, 300.13 MHz, 298 K): δ (ppm) 1.89
(s, 3H, CH3), 2.23−2.35 (m, 2H, cycloheptadiene CH2), 2.53 (m, 1H,
1
heptane to afford yellow needles (70 mg, 92%). H NMR (CDCl3,
300.13 MHz, 298 K): δ (ppm) 2.25−2.34 (m, 1H, cycloheptadiene
allyl CHanti), 2.67−2.75 (m, 2H, cycloheptadiene CH2), 3.01 (m, 1H,
2
3
1
CH2), 2.55 (dd, JH−H = 16.3 Hz, JH−P = 45.7 Hz, 1H, cyclo-
heptadiene CH2), 2.74−3.13 (m, 1H, cycloheptadiene CH2), 3.23−
3.46 (m, 1H, cycloheptadiene CH2), 3.44 (m, 1H, cycloheptadiene
allyl CHsyn), 3.11−3.19 (m, 1H, cycloheptadiene CH), 3.49 (d, JH−H
=
1
9.8 Hz, allyl CHanti), 4.45 (d, JH−H = 6.1 Hz, allyl CHsyn), 5.81
(m, 4H, cycloheptadiene CH), 7.40−7.44 (m, 6H, Ph), 7.59−764
(m, 4H, Ph). 13C NMR (CDCl3, 75.47 MHz, 298 K): δ (ppm) 23.4
CH), 5.31 (m, +dm, JH−Pt195 = 72.5 Hz, 1H, cycloheptadiene CH),
2
3
2
5.40 (m, 1H, cycloheptadiene CH), 5.86 (t, +dt, JH−P = 8.1 Hz,
(s, allyl CH3), 33.6 (d, JC−P = 4.6 Hz, cycloheptadiene CH2), 33.8
195
2JH−Pt = 67.7 Hz, 1H, cycloheptadiene CH), 6.18 (m, 1H, cyclo-
(d, 1JC−P = 19.6 Hz, cycloheptadiene CH), 59.5 (s, allyl CH2), 78.2 (s,
2
heptadiene CH), 7.40−7.60 (m, 6H, Ph), 7.75−7.90 (m, 4H, Ph). 13C
NMR (CDCl3, 75.47 MHz, 298 K): δ (ppm) 35.0 (s, cycloheptadiene
allyl CH2), 125.8 (s, cycloheptadiene CH), 128.7 (d, JC−P = 9.6 Hz,
Ph Cortho), 130.5 (d, 4JC−P = 2.2 Hz, Ph Cpara), 131.5 (d, 1JC−P = 36.7 Hz,
3
CH2), 38.1 (d, 2JC−P = 6.1 Hz, cycloheptadiene CH2), 38.1 (d, 1JC−P
=
Ph Cipso), 132.3 (s, cycloheptadiene CH), 133.3 (d, JC−P = 11.5 Hz,
Ph Cmeta). 31P{1H} NMR (CDCl3, 121.49 MHz, 298 K): δ (ppm) 31.9.
HR-MS (ESIpos, methanol/dichloromethane; m/z): calcd C23H26PPd+
[M − Cl]+ 439.08106. Found 439.08415.
1
195
36.8 Hz, cycloheptadiene CH), 83.0 (s, +d, JC−Pt = 126.1 Hz,
2
cycloheptadiene CH), 90.8 (d, JC−P = 7.2 Hz, cycloheptadiene CH),
1
1
122.9 (d, JC−P = 62.6 Hz, Ph Cipso), 128.1 (d, JC−P = 63.3 Hz, Ph
Cipso), 128.8 (d, 2JC−P = 11.2 Hz, Ph Cortho), 128.9 (s, cycloheptadiene
Bis{(3,5-cycloheptadienyl)diphenylphosphine}NiBr2 (7). 3 (50 mg,
0.18 mmol, 2.2 equiv) was dissolved in 2 mL of dichloromethane. This
solution was cannulated to a solution of [NiBr2(dme)] (25 mg,
0.08 mmol, 1 equiv) in 2 mL of dichloromethane. The solution quickly
turned to green and was stirred for 30 min at room temperature. The
solution was then evaporated under reduced pressure and triturated
with pentane to afford a brown solid (60 mg, 95%). 31P{1H} NMR
2
4
CH), 129.0 (d, JC−P = 11.2 Hz, Ph Cortho), 132.0 (d, JC−P = 2.9 Hz,
Ph Cpara), 132.7 (d, 4JC−3P = 2.8 Hz, Ph Cpara), 133.1 (d, 3JC−P = 9.1 Hz,
Ph Cmeta), 133.4 (d, JC−P = 4.0 Hz, cycloheptadiene CH), 135.4
(d, JC−P = 10.9 Hz, Ph Cmeta). 31P{1H} NMR (CDCl3, 121.49 MHz,
3
1
195
298 K): δ (ppm) 33.3 (s, +d, JP−Pt = 3458.8 Hz). HR-MS (ESIpos
,
methanol/dichloromethane; m/z): calcd C19H19ClPPt+ [M − Cl]+
508.05552. Found 508.05788.
(CD2Cl2, 242.97 MHz, 190 K): δ (ppm) 20.8 (br s). HR-MS (ESIpos
,
methanol/dichloromethane; m/z): calcd C38H38BrP2Ni+ 695.0959.
Found 695.0963.
{(η2-3,5-Cycloheptadienyl)diphenylphosphine-κP}PtMe2 (11). 3
(106 mg, 0.37 mmol, 1 equiv) was dissolved in 3 mL of dichloro-
methane. This solution was cannulated over 5 min to a solution of
[PtMe2(cod)] (124 mg, 0.37 mmol, 1 equiv) in 2 mL of dichloro-
methane. When the addition was completed, the solution was stirred
for 30 min at room temperature. The solution was then evaporated
under reduced pressure and triturated with pentane to afford an off-
white solid. The solid was dissolved in dichloromethane and precipi-
tated by diffusion of pentane (90 mg, 48%). 1H NMR (CD2Cl2, 300.13 MHz,
298 K): δ (ppm) 0.47 (d, +dd, 3JH−P = 7.5 Hz, 2JH−Pt195 = 65.6 Hz, 3H,
{(3,5-Cycloheptadienyl)diphenylphosphine}AuCl (8). 3 (54 mg,
0.19 mmol, 1.1 equiv) was dissolved in 2 mL of dichloromethane. This
solution was cannulated to a solution of [AuCl(tht)] (56 mg,
0.17 mmol, 1 equiv) in 2 mL of dichloromethane. The solution was
stirred for 1 h at room temperature. The solution was then evaporated
under reduced pressure and triturated with pentane to afford a white
solid (82 mg, 95%). 1H NMR (CDCl3, 300.13 MHz, 298 K): δ (ppm)
2.33−2.61 (m, 4H, cycloheptadiene CH2), 3.03−3.15 (m, 1H,
cycloheptadiene CH), 5.74−5.89 (m, 4H, cycloheptadiene CH),
7.43−7.56 (m, 6H, Ph), 7.72−7.70 (m, 4H, Ph). 13C NMR (CDCl3,
3
2
195
CH3), 1.00 (d, +dd, JH−P = 7.1 Hz, JH−Pt = 87.3 Hz, 3H, CH3),
2.30−2.71 (br s, 4H, cycloheptadiene CH2), 3.44−3.52 (m, 1H,
955
dx.doi.org/10.1021/om200999n | Organometallics 2012, 31, 947−958

Organometallics
Article
Table 2. Crystal and Structure Refinement Data for 4, 10, 12, 13, and 14
compounds
12
4
10
13
14
empirical formula
fw
C38H38Cl2P2Pt, CH2Cl2
907.53
C19H19Cl2PPt
544.30
C19H19Cl2PPd
455.61
C27H31PRh, CHCl3, BF4
695.58
C38H38P2Rh, CHCl3, BF4
865.71
temperature (K)
cryst syst
space group
a (Å)
115(2)
115(2)
115(2)
115(2)
115(2)
orthorhombic
P212121
orthorhombic
Pna21
orthorhombic
Pna21
monoclinic
Pc
monoclinic
C2/c
10.4161(2)
16.7564(4)
21.2276(6)
90
8.2954(3)
14.9017(5)
14.3336(5)
90
8.2534(3)
14.8778(5)
14.3698(5)
90
15.4399(7)
10.7640(4)
22.4708(8)
90
34.3066(8)
11.7956(3)
18.6351(4)
90
b (Å)
c (Å)
α (deg)
β (deg)
90
90
90
129.564(2)
90
105.3250(10)
90
γ (deg)
volume (Å3)
90
90
90
3704.99(15)
4
1771.86(11)
4
1764.50(11)
4
2879.0(2)
4
7272.9(3)
8
Z
ρ
calc
(g/cm3)
1.627
2.040
1.715
1.605
1.581
−1
μ (mm )
size (mm3)
F(000)
4.190
8.307
1.441
0.971
0.828
0.12 × 0.05 × 0.05
1800
0.20 × 0.15 × 0.07
1040
0.25 × 0.20 × 0.12
912
0.25 × 0.20 × 0.15
1408
0.25 × 0.20 × 0.10
3520
λ
0.71073
0.71073
2.06−27.51
h: −10; 10
k: −19; 19
l: −18; 10
15978
0.71073
2.88−27.47
h: −10; 10
k: −19; 19
l: −18; 18
12765
0.71073
0.71073
θ Range (°)
index ranges
1.91−27.46
h: −13; 13
k: −21; 21
l: −27; 27
8341
1.71−27.58
h: −19; 20
k: −13; 9
l: −29; 29
22354
2.56−27.59
h: −44; 44
k: −15; 13
l: −24; 24
15076
reflns collected
Rint
0.059
0.031
0.038
0.036
0.013
reflections with I ≥ 2σ(I)
data/restraints/param
final R indices [I ≥ 2σ(I)]
7752
3200
3777
11004
7828
8341/1/399
3238/3/215
3814/3/215
11612/18/734
8321/6/469
a
a
a
a
a
R1 = 0.0557
R1 = 0.0167
R1 = 0.0169
R1 = 0.0370
R1 = 0.0248
b
b
b
b
b
wR2 = 0.1116
wR2 = 0.0421
wR2 = 0.0395
wR2 = 0.0786
wR2 = 0.0552
a
a
a
a
a
R indices (all data)
R1 = 0.0637
R1 = 0.0172
R1 = 0.0173
R1 = 0.0404
R1 = 0.0272
b
b
b
b
b
wR2 = 0.1179
wR2 = 0.0425
wR2 = 0.0399
wR2 = 0.0812
wR2 = 0.0566
c
goodness-of-fit on F2
1.129
1.112
1.081
1.073
1.067
Flack param
0.082(11)
0.000(6)
0.563(18)
0.46(3)
abs correction
max and min trans
semiempirical
0.46 and 0.25
0.73 and −1.33
semiempirical
0.81 and 0.73
0.24 and −0.32
834838
semiempirical
0.84 and 0.78
0.77 and −0.63
834839
−3
Δρ (e Å )
CCDC deposition no.
2.02 and −0.93
834836
0.79 and −0.57
834840
834837
a
b
2
R1 = ∑(∥Fo| − |Fc∥)/∑|Fo|. wR2 = [∑w(Fo2 − Fc2)2/∑[w(Fo )2]1/2, where w = 1/[σ2(Fo2 + (0.00P)2 + 50.87P] for 4, w = 1/[σ2(Fo2 + (0.021P)2
+ 2.00P] for 10, w = 1/[σ2(Fo2 + (0.00P)2 + 1.51P] for 12, w = 1/[σ2(Fo2 + (0.00P)2 + 7.91P] for 13, and w = 1/[σ2(Fo2 + (0.01P)2 + 17.66P] for 14,
c
where P = (max(Fo ,0) + 2*Fc2)/3. S = [∑w(Fo − Fc2)2/(n − p)]1/2 (n = number of reflections, p = number of parameters).
2
2
cycloheptadiene CH), 4.08 (br s, 2H, cycloheptadiene CH), 6.11 (br s,
(br s, 2H, cycloheptadiene CH), 6.48 (br s, 2H, cycloheptadiene CH),
2H, cycloheptadiene CH), 7.44 (m, 6H, Ph), 7.64−7.71 (m, 4H, Ph).
7.49−7.52 (m, 4H, Ph), 7.59−7.62 (m, 2H, Ph), 7.86−7.90 (m, 4H, Ph).
13C NMR (CD2Cl2, 75.47 MHz, 298 K): δ (ppm) 0.3 (d, +dd, 2JC−P
=
1H NMR (CD2Cl2, 600.13 MHz, 190 K): δ (ppm) 2.14 (d, JH−H
=
≈
=
2
1
195
3
2
3
5.8 Hz, JC−Pt = 748.2 Hz, CH3), 8.1 (d, +dd, JC−P = 109.5 Hz,
19.7 Hz, 1H, cycloheptadiene CH2), 2.78 (pseudo t, JH−H ≈ JC−P
1JC−Pt = 624.0 Hz, CH3), 35.7 (br s, cycloheptadiene CH2), 39.3
23.5 Hz, 1H, cycloheptadiene CH2), 2.93 (dd, 2JH−H = 16.9 Hz, 3JH−P
195
(d, 1JC−P = 26.3 Hz, cycloheptadiene CH), 87.1 (br s, cycloheptadiene
55.0 Hz, 1H, cycloheptadiene CH2), 3.44 (br m, 1H, cycloheptadiene
CH2), 3.58 (br s, 1H, cycloheptadiene CH), 5.47 (br s, 1H, cyclo-
heptadiene CH), 6.20 (br s, 1H, cycloheptadiene CH), 6.26 (br s, 1H,
cycloheptadiene CH), 6.56 (br s, 1H, cycloheptadiene CH), 7.46 (br s,
4H, Ph), 7.58 (br s, 2H, Ph), 7.74 (br s, 4H, Ph). 13C NMR (CD2Cl2,
125.76 MHz, 298 K): δ (ppm) 36.2 (bs, cycloheptadiene CH2), 41.0
CH), 97.1 (br s, cycloheptadiene CH), 127.8−137.0 (m, Ph). 31P{1H}
1
195
NMR (CDCl3, 121.49 MHz, 298 K): δ (ppm) 42.9 (s, +d, JP−Pt
=
1894.0 Hz). HR-MS (ESIpos, methanol/dichloromethane; m/z): calcd
C20H22PPt+ [M − CH3]+ 488.11014. Found 488.11130.
{(η2-3,5-Cycloheptadienyl)diphenylphosphine-κP}PdCl2 (12). 3
(54 mg, 0.19 mmol, 1 equiv) was dissolved in 3 mL of dichloro-
methane. This solution was cannulated over 5 min to a solution of
[PdCl2(cod)] (56 mg, 0.19 mmol, 1 equiv) in 1 mL of dichloro-
methane. When the addition was completed, the solution was stirred
for 16 h at room temperature. The solution was then evaporated under
reduced pressure and triturated with pentane to afford a yellow solid.
The solid was dissolved in dichloromethane and precipitated by
1
1
(d, JC−P = 29.4 Hz, cycloheptadiene CH), 126.2 (d, JC−P = 42.7 Hz,
2
4
Ph Cipso), 128.8 (d, JC−P = 11.3 Hz, Ph Cortho), 132.5 (d, JC−P
=
2.5 Hz, Ph Cpara), 134.2 (d, 3JC−P = 8.8 Hz, Ph Cmeta), (cycloheptadiene
CH not observed). 13C NMR (CD2Cl2, 150.92 MHz, 190 K): δ (ppm)
2
34.6 (s, cycloheptadiene CH2), 37.6 (d, JC−P = 4.0 Hz, cyclo-
heptadiene CH2), 39.4 (d, JC−P = 29.0 Hz, cycloheptadiene CH),
1
2
101.7 (s, cycloheptadiene CH), 110.1 (d, JC−P = 6.9 Hz, cyclo-
diffusion of pentane. The collected mass was 81 mg (92%). H NMR
heptadiene CH), 123.2 (d, 1JC−P = 56.6 Hz, Ph Cipso), 126.7 (s, cyclo-
1
(CD2Cl2, 600.13 MHz, 298 K): δ (ppm) 2.80−2.90 (br m, 4H,
cycloheptadiene CH2), 3.55 (m, 1H, cycloheptadiene CH), 5.91
heptadiene CH), 127.6 (d, 1JC−P = 56.0 Hz, Ph Cipso), 128.3 (d, 2JC−P
=
2
10.8 Hz, Ph Cortho), 128.4 (d, JC−P = 11.6 Hz, Ph Cortho), 132.1
956
dx.doi.org/10.1021/om200999n | Organometallics 2012, 31, 947−958

Organometallics
Article
3
(s, Ph Cpara), 132.4 (s, Ph Cpara), 132.6 (d, JC−P = 8.3 Hz, Ph Cmeta),
was solved in the Pc noncentrosymmetric group. If two independent
complexes present in the asymmetric unit seem to be related by an
inversion center, this is not the case of the solvent, and a refinement of
the structure in the P21/c space group, at the cost of a disordered
solvent, results in numbers of non-positive definite thermal parameters
and in worse R values (R1 = 0.17 and wR2 = 0.42). The non-
centrosymmetric group was then favored. All non-hydrogen atoms
were refined with anisotropic thermal parameters. Except for
hydrogen atoms belonging to the coordinated double bonds, which
were refined using just a restraint on the C−H distance, all other
hydrogen atoms were included in their calculated positions and refined
with a riding model. Compound 14 was refined in the C2/c space
group. All non-hydrogen atoms were refined with anisotropic thermal
parameters. Except for hydrogen atoms belonging to the coordinated
double bonds, which were refined using just a restraint on the C−H
distance, all other hydrogen atoms were included in their calculated
positions and refined with a riding model.
3
134.9 (d, JC−P = 10.4 Hz, Ph Cmeta), 137.1 (s, cycloheptadiene CH).
31P{1H} NMR (CD2Cl2, 242.97 MHz, 298 K): δ (ppm) 57.4. HR-MS
(ESIpos, acetonitrile/dichloromethane; m/z): calcd C19H19Cl2PPdNa+
[M + Na]+ 476.95285. Found 476.95533.
[(1, 5-Cyclooctadiene){(η4 -3, 5-c ycloheptadienyl)-
diphenylphosphine-κP}Rh][BF4] (13). 3 (117 mg, 0.42 mmol, 1 equiv)
was dissolved in 2 mL of dichloromethane. This solution was can-
nulated over 5 min to a solution of freshly prepared [Rh(cod)2]BF4
(170 mg, 0.42 mmol, 1 equiv) in 2 mL of dichloromethane. When the
addition was completed, the solution was stirred for 90 min at room
temperature. The solution was then concentrated, and the product was
precipitated by addition of diethyl ether to afford a pale yellow powder
1
(193 mg, 80%). H NMR (CD2Cl2, 600.13 MHz, 298 K): δ (ppm)
2
3
1.11 (dd, JH−H = 14.3 Hz, JH−P = 60.3 Hz, 2H, cycloheptadiene
CH2), 2.29 (m, 2H, cycloheptadiene CH2), 2.39 (m, 2H, COD CH2),
2.52 (m, 2H, COD CH2), 3.24 (m, 1H, cycloheptadiene CH), 4.03
(br s, 2H, cycloheptadiene CH), 4.41 (br s, 4H, COD CH), 6.47 (br s,
Crystallographic data are reported in Table 2.
2H, cycloheptadiene CH), 7.50 (m, 4H, Ph), 7.61 (m, 6H, Ph). 13C
Theoretical Calculations. Calculations were performed using
Jaguar v. 5.528 at the DFT B3LYP/6-31G** level using the LANL2DZ
effective core basis set for the metals. The transition structures were
first located by a scan of the surface using a pertinent internal
coordinate and then by the quadratic synchronous transit method
(QST). The frequencies were checked, and the visualization of the
mode with a negative eigenvalue clearly corresponds to the expected
atomic displacements. DFT calculations were performed using HPC
2
NMR (CD2Cl2, 75.47 MHz, 298 K): δ (ppm) 29.8 (d, JC−P
=
14.1 Hz, cycloheptadiene CH2), 32.0 (d, 2JC−Rh = 2.1 Hz, COD CH2),
1
2
54.5 (d, JC−P = 33.2 Hz, cycloheptadiene CH), 77.0 (dd, JC−P
=
9.0 Hz, 1JC−Rh = 3.3 Hz, cycloheptadiene CH), 93.2 (d, 1JC−Rh = 6.4 Hz,
2
COD CH), 102.1 (s, cycloheptadiene CH), 129.9 (d, JC−P = 9.3 Hz,
Ph Cortho), 130.3 (dd, 1JC−P = 30.4 Hz, 2JC−Rh = 1.8 Hz, Ph Cipso), 131.9
4
3
(d, JC−P = 2.4 Hz, Ph Cpara), 132.9 (d, JC−P = 9.7 Hz, Ph Cmeta).
31P{1H} NMR (CDCl3, 121.49 MHz, 298 K): δ (ppm) 78.6 (d, 1JP−Rh
=
́
resources from DSI-CCUB (Universite de Bourgogne).
150.6 Hz). HR-MS (ESIpos, methanol/dichloromethane; m/z): calcd
C27H31PRh+ [M]+ 489.12129. Found 489.12302.
ASSOCIATED CONTENT
* Supporting Information
Spectroscopic data, estimation of thermodynamic data, geo-
metries of DFT molecular structures, and CIF files. This
material is available free of charge via the Internet at http://
pubs.acs.org.
■
[{(η4-3,5-Cycloheptadienyl)diphenylphosphine-κP}{(η2-3,5-
cycloheptadienyl)diphenylphosphine-κP}Rh][BF4] (14). 3 (33 mg,
0.12 mmol, 1 equiv) was dissolved in 1 mL of dichloromethane. This
solution was cannulated over 5 min to a solution of 13 (69 mg,
0.12 mmol, 1 equiv) in 1 mL of dichloromethane. The initially yellow
solution turned to orange, and the solution was stirred overnight at
room temperature. The solution was then concentrated, and the
product was precipitated by addition of pentane to afford an orange
powder (79 mg, 88%). 1H NMR (CDCl3, 600.13 MHz, 298 K):
S
AUTHOR INFORMATION
Corresponding Author
*E-mail: pierre.le-gendre@u-bourgogne.fr. Fax: +33-380396098.
■
2
3
δ (ppm) 1.83 (dd, JH−H = 15.0 Hz, JH−P = 50.4 Hz, 4H, cyclo-
heptadiene CH2), 2.27 (m, 4H, cycloheptadiene CH2), 3.21 (m, 2H,
cycloheptadiene CH), 4.29 (m, 4H, cycloheptadiene CH), 5.32 (m,
ACKNOWLEDGMENTS
4H, cycloheptadiene CH), 7.35 (m, 8H, Ph), 7.45−7.51 (m, 12H, Ph).
■
2
13C NMR (CD2Cl2, 125.76 MHz, 298 K): δ (ppm) 33.8 (d, JC−P
=
We thank the Conseil Reg
SMT08 program), the Minister
́
ional de Bourgogne (PARI IME
e de l’Enseignement Superieur
1
10.1 Hz, cycloheptadiene CH2), 49.5 (d, JC−P = 31.4 Hz, cyclo-
̀
́
heptadiene CH), 94.5 (m, cycloheptadiene CH), 100.4 (m, cyclo-
et de la Recherche, and the Centre National de la Recherche
Scientifique (CNRS, CP2D program “Chimie et Procedes pour
le Developpement Durable″) for financial support. We thank
Miss Marie-Jose Penouilh and Dr. Fanny Chaux for mass
heptadiene CH), 129.1 (d, 2JC−P = 8.8 Hz, Ph Cortho), 131.3 (d, 1JC−P
=
́
́
3
35.2 Hz, Ph Cipso), 131.5 (s, Ph Cpara), 132.9 (d, JC−P = 10.1 Hz,
́
Ph Cmeta). 31P{1H} NMR (CD2Cl2, 242.97 MHz, 298 K): δ (ppm)
́
1
66.8 (d, JP−Rh = 143.2 Hz). 31P{1H} NMR (CD2Cl2, 242.97 MHz,
165 K): δ (ppm) 56.5 (d, 1JP−Rh = 133.8 Hz), 79.0 (d, 1JP−Rh = 151.1 Hz).
HR-MS (ESIpos, methanol/dichloromethane; m/z): calcd C38H38P2Rh+
[M]+ 659.14983. Found 659.14929.
spectrometry analyses.
DEDICATION
■
†Dedicated to Doctor Christian Bruneau on the occasion of his
60th birthday.
X-ray Crystallography Procedures. X-ray Analysis of Com-
pounds 4, 10, 12, 13, and 14. Intensity data were collected on a
Bruker-Nonius APEX II diffractometer equipped with an Oxford
Cryosystem low-temperature device operating at 115 K. The
structures were solved by direct methods (SIR92)25 and refined
with full-matrix least-squares methods based on F2 (SHELXL-97)26
with the aid of the WINGX program.27 Compound 4 was solved in the
P212121 space group. Except for the solvent, all non-hydrogen atoms
were refined with anisotropic thermal parameters. Hydrogen atoms
were included in their calculated positions and refined with a riding
model. The CH2Cl2 solvent molecule is badly disordered and was
modeled as a rigid group over three positions using an overall isotropic
temperature factor. Compounds 10 and 12 were solved in the Pna21
space group. All non-hydrogen atoms were refined with anisotropic
thermal parameters. Except for the two hydrogen atoms belonging to
the coordinated double bond, which were refined using just a restraint
on the C−H distance, all other hydrogen atoms were included in their
calculated positions and refined with a riding model. Compound 13
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