Exploring (Ph2PCH2CH2)2E ligand space (E = O, S, PPh) in RhI alkene complexes as potential hydroacylation catalysts

Article abstract of DOI:10.1002/ejic.201100958

The ligands (Ph₂PCH₂CH₂)₂E (E = O, S, PPh) have been used to form a variety of Rh^I cations [Rh{(Ph₂PCH₂CH₂)₂E}(alkene)] ⁺ (alkene = methyl acrylate, trimethylvinylsilane). Variable-temperature NMR spectroscopy shows that the methyl acrylate ligands undergo a fluxional process on the metal, via a ¹-carbonyl intermediate, while the trimethylvinylsilane complexes cannot access this intermediate and do not undergo the same process. Their reactivity in hydroacylation reactions with 1-pentanal have been investigated, and these studies further suggest the important role that a chelating substituent next to the aldehyde might play in productive hydroacylation. A variety of Rh ^I cations [Rh{(Ph₂PCH₂CH₂) ₂E}(alkene)]⁺ (E = PPh, S, O; alkene = methyl acrylate and trimethylvinylsilane) have been prepared and their fluxional behaviour investigated by variable-temperature NMR spectroscopy. Copyright

Full text of DOI:10.1002/ejic.201100958

FULL PAPER
DOI: 10.1002/ejic.201100958
Exploring (Ph2PCH2CH2)2E Ligand Space (E = O, S, PPh) in RhI Alkene
Complexes as Potential Hydroacylation Catalysts
Sebastian D. Pike,[a] Rebekah J. Pawley,[a] Adrian B. Chaplin,[a] Amber L. Thompson,[a]
Joel A. Hooper,[a] Michael C. Willis,[a] and Andrew S. Weller*[a]
Keywords: Rhodium / NMR spectroscopy / Phosphanes / Decarbonylation / Alkenes
The ligands (Ph2PCH2CH2)2E (E = O, S, PPh) have been used
to form a variety of RhI cations [Rh{(Ph2PCH2CH2)2E}-
(alkene)]+ (alkene = methyl acrylate, trimethylvinylsilane).
Variable-temperature NMR spectroscopy shows that the
methyl acrylate ligands undergo a fluxional process on the
metal, via a κ1-carbonyl intermediate, while the trimethylvin-
ylsilane complexes cannot access this intermediate and do
not undergo the same process. Their reactivity in hydroacyl-
ation reactions with 1-pentanal have been investigated, and
these studies further suggest the important role that a chelat-
ing substituent next to the aldehyde might play in productive
hydroacylation.
tral oxygen on the ligand can move away to allow for both
olefin coordination and reductive elimination of the prod-
uct.[19,20] With a ligand that does not act in a hemilabile
manner, such as Xantphos or (Ph2PCH2CH2)2O, e.g. com-
plex B, Scheme 1, β-S-substituted aldehydes undergo oxi-
dative addition to give a six-coordinate complex that does
not proceed to bind an olefin, as the central oxygen remains
tightly bound. This stable six-coordinate configuration,
however, does lead to complexes that are stable to decar-
bonylation.[21]
Introduction
The transition-metal-catalysed hydroacylation reaction is
one that couples alkenes (or alkynes) with aldehydes, in an
atom-efficient way, to produce ketones [Equation (1),
Scheme 1].[1–4] It has attracted significant attention in recent
years, and a variety of, mainly rhodium-based, catalysts
have been described. The mechanism proceeds through oxi-
dative addition of aldehyde to a RhI centre to give an acyl–
hydride, olefin binding, and migratory insertion followed by
reductive elimination – which is accepted to be the turn-
over limiting step.[1,5–7] A significant obstacle barring the
way to the wider implementation of this potentially power-
ful methodology is the competitive reductive decarbon-
ylation reaction,[8,9] which produces an inactive metal car-
bonyl. This occurs from a low-coordinate acyl–hydride in-
termediate by (reversible) migratory deinsertion of CO to a
cis-vacant site, followed by irreversible reductive elimination
of a saturated product (R–H). Both productive (olefin coor-
dination, product reductive elimination[10,11]) and unpro-
ductive (carbonyl deinsertion,[12,13] reductive elimination of
R–H) steps require a low-coordinate transition-metal com-
plex, and a number of strategies have been employed to
promote the hydroacylation reaction over decarbonylation.
In view of this, chelation control from the substrate,[2,3,14–16]
by using, for example, β-S-substituted aldehydes such as A
(Scheme 1),[17] is one of the strategies used to deliver suc-
cessful intermolecular hydroacylation. Combined with this,
we have also reported the use of a hemilabile[18] diphos-
phanylether ligand, DPEphos, to protect the vacant site on
the metal centre towards decarbonylation, in which the cen-
Scheme 1.
Milstein and co-workers have shown the stability of five-
coordinate RhIII–hydrido–acyl complexes towards decar-
bonylation can be controlled by the π-donor nature of the
supporting ligands, which place the acyl group either cis or
trans to a vacant site,[13] depending on the geometry of the
five-coordinate intermediate. Similar observations have
been made by Nolan and Goldman,[22] which also under-
score computational work by Eisenstein on the relative geo-
metries of d6 ML5 species.[23] We were thus particularly in-
terested in exploring the reactivity of simple, non-chelating,
[a] Department of Chemistry, Inorganic Chemistry Laboratory,
University of Oxford,
South Parks Road, Oxford, OX1 3QR, UK
E-mail: andrew.weller@chem.ox.ac.uk
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Exploring (Ph2PCH2CH2)2E Ligand Space in RhI Alkene Complexes
aliphatic aldehydes with RhI complexes with tridentate li- H2C=CHC(O)OMe}][BArF4] (3a) by a different route,[21]
gands (Ph2PCH2CH2)2E (E = S, O, PPh), in which the cen- but did not describe the solid-state structure. For compari-
tral donor atom changes from being a potential π-donor (E son with 2a, we also report that here. We were unable to
= O, S) to one that is not (E = PPh) (Scheme 2). Such com- prepare the vinyltrimethylsilane complex analogue of 3a as
plexes would give five-coordinate acyl–hydride intermedi- in our hands, the complex [Rh{(κ3-Ph2PCH2CH2)2O}Cl]
ates on oxidative addition of simple aldehydes. To do this, could not be prepared by a route similar to those for
RhI precursors that are set up for oxidative addition reac- [Rh{(κ3-Ph2PCH2CH2)2PPh}Cl]or[Rh{(κ3-Ph2PCH2CH2)2-
tions are required, and we report cationic, alkene adducts S}Cl], while alternative routes also did not work.[21]
[Rh{(Ph2PCH2CH2)2E}(alkene)]+, as such complexes are
also likely to be compatible with the overall catalytic cycle
in which alkene is present in excess. We further describe the
reactivity of these complexes with pentanal in the hydro-
acylation reaction with methyl acrylate. Related RhI com-
plexes have been reported as aldehyde decarbonylation cata-
lysts, albeit operating at elevated temperatures to facilitate
turnover.[8,24,25]
Solid-State Structures
The solid-state structures of 2a and 3a (Figures 1 and 2)
are broadly similar, both have pseudo-square-planar envi-
ronments around the rhodium atom with similar Rh–P dis-
tances and a η2-bound alkene. The structural refinement for
3a was not as high quality as that for 2a because of the
nature of the crystals (see Experimental Section). For 3a,
the alkene is disordered over two positions in a 70:30 ratio,
related to each other by an approximate reflection, to afford
an enantiomeric pair of cations. The major difference be-
tween 2a and 3a comes from structural metrics associated
with the bound methyl acrylate, which is orientated approx-
imately in plane with respect to the RhP3 plane in 2a and
upright for both components in 3a. The C–C distance in
the alkene in 2a [1.381(3) Å] appears slightly shorter than
those in 3a [1.405(7) Å, major; 1.411(9) Å minor], although
within error they are equivalent. These distances lie in the
range found for later transition metals bound with methyl
acrylate (≈1.3–1.43 Å).[29–31] The corresponding Rh–C dis-
tances are, however, statistically longer for 2a than for 3a
[viz. 2.221(2), 2.219(2) vs. 2.074(16)–2.148(17) Å, respec-
tively], which might suggest more back-donation from the
metal to the alkene in 3a. The orientation of alkene ligands
in d8 ML3 fragments has received much attention, and stud-
ies indicate that steric factors tend to outweigh electronic
factors associated with the back-donation from a suitable
metal orbital to the alkene π* orbital,[32] which leads to
upright alkene orientations and a small barrier to rotation
of the alkene around the metal–alkene-axis. In-plane orien-
Scheme 2.
Results and Discussion
Synthesis
Our preparative route to the target complexes starts
from simple halide precursors (Scheme 3). [Rh{(κ3-
Ph2PCH2CH2)2PPh}Cl][26] was prepared by slight modifica-
tions to a known preparation, while [Rh{(κ3-Ph2PCH2-
CH2)2S}Cl] is a new complex prepared in good isolated
yield by addition of free ligand[27] to [Rh(cod)Cl]2. Addition
of the alkenes, methyl acrylate or vinyltrimethylsilane, to
CH2Cl2 solutions of these complexes in the presence of
Na[BArF4], to abstract chloride, resulted in the rapid
(30 min) and clean formation of the new complexes
[Rh{(κ3-Ph2PCH2CH2)2E}(η2-H2C=CHR)][BArF4] {E = S
1, PPh 2; R = C(O)OMe a, SiMe3 b; ArF = C6H3-3,5-
(CF3)2}. These were characterised by NMR spectroscopy,
and for 2a also by single-crystal X-ray diffraction as the
[B(3,5-Cl2C6H3)4]– salt.[28] We have recently reported the
in situ formation of [Rh{(κ3-Ph2PCH2CH2)2O}{η2-
Figure 1. Solid-state structure of 2a. Hydrogen atoms and anions
omitted. Thermal ellipsoids at the 30% probability level. Selected
bond lengths [Å] and angles [°]: 2a: Rh–P1 2.2942(6), Rh–P2
2.2328(6), Rh–P3 2.3300(6), C1–C2 1.381(3), Rh–C1 2.221(2), Rh–
C2 2.219(2);
P3Rh1P1P2/Rh1C1C2 28.78(11).
Є
(torsion) C1C2/O1C3 –22.8(4);
Є
(planes)
Scheme 3. ([BArF4]– anions omitted for clarity).
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assign individual signals for 2a, and by analogy those for
1a. For 1a, only two methylene environments (4 H relative
integral each) are observed in contrast to the four observed
for 2a (and 3a[21]).
These data suggest fluxional processes are occurring in
solution to give time-averaged C2v symmetry to the
{Rh(PEP)}+ fragment for 1a and Cs symmetry for 2a and
3a. A simple rotation of the alkene around the Rh–C1/C2
vector would make the phosphanes equivalent, and give
time-averaged C2v symmetry, only if associated with a low-
energy inversion of stereochemistry at the central E
group.[37,38] The NMR spectroscopic data suggest that this
occurs for 1a (E = S) but not for 2a or 3a, which show only
Cs symmetry. For 2a, inversion at the central PPh is likely
to be a high-energy process, while inversion at O in 3a is
also clearly not a low-energy process. Thus, in order to ob-
tain the observed equivalence of the phosphanes in 2a and
3a, some other fluxional process must be occurring other
than simple alkene rotation. The cooling of a sample of 1a
from room temperature to 200 K (CD2Cl2) results in NMR
spectra that are consistent with a static structure, i.e. a
tightly coupled AB doublet with inequivalent phosphorus
environments in the 31P{1H} NMR spectrum. The outer
lines of the second-order multiplet are of very low intensity
and could not be resolved. At this temperature, the methyl-
ene signals are broad and do not offer any additional struc-
tural information. For 2a, significant broadening is ob-
served at 190 K in the 31P{1H} NMR spectrum, which sug-
gests that the low-temperature limit is being approached.
Figure 2. Solid-state structure of 3a (minor component shown at
bottom, ratio 70:30, respectively). Selected bond lengths [Å] and
angles [°]: 3a: Rh1–P2 2.2917(16), Rh1–P8 2.2982(16), Rh1–O5
22.100(3), C33–C34 1.405(7), Rh1–C33 2.074(16), Rh1–C34
2.144(7), C330–C340 1.411(9), Rh1–C330 2.11(4), Rh1–C340
2.148(17); Є (torsion) C33/C34/C35/O36 12.4(11)°, C330/C340/
C350/O360 –11(3)°; Є (planes) O5Rh1P8P2/Rh1C33C34 76.9(5)°,
O5Rh1P8P2/Rh1C330C340 69.6(12)°.
1
As for 1a, the methylene signals are very broad in the H
NMR spectrum at low temperature and offer no extra in-
formation. For 3a, however, progressive cooling results in a
31P{1H} NMR spectrum at 200 K that shows a clearly re-
solved AB doublet with a 31P–31P coupling constant of
tations of the alkene are also known where subtle steric ef-
fects favour this conformation.[33] It would seem that these
electronic and steric contributions are finely balanced in the
systems here, with both orientations observed in the solid
state (but likely share the same orientation in solution vide
infra). However, it does appear that the upright orientation
in 3a allows for slightly better back-donation from the RhI
centre to the alkene, which would be in line with a suitable
high-lying, filled metal orbital that also has a contribution
from the π-donor oxygen atom, similar to that calculated
for analogous {Rh(PR3)2Cl} fragments.[34] Surprisingly,
there are only a handful of κ3-(Ph2PCH2CH2)2O[21,35] or
κ3-(Ph2PCH2CH2)2PPh[8,26,36] structures reported with Rh,
and none with (Ph2PCH2CH2)2S.
1
384 Hz (Figure 3). In the H NMR spectrum at this lowest
temperature, the three alkene peaks all shift ca. 0.7 ppm to
a lower frequency, and at least six broad environments are
observed for the methylene protons of the POP ligand.
These data are fully consistent with the static solid-state
structure. The variable-temperature 31P NMR spectroscopic
Solution NMR Spectroscopic Data
In solution at 298 K for complexes 1a and 2a, the
31P{1H} NMR spectroscopic data indicate one phosphorus
environment for the two trans-related phosphanes (e.g. P1/
P3 in 2a) that also show coupling to 103Rh, and for 2a, an
additional environment is observed that mutually couples
to the two other cis phosphanes (P2). In the 1H NMR spec-
trum, peaks assigned to the bound alkene are observed,
which are similar to those reported for 3a,[21] e.g. 2a δ =
Figure 3. Variable-temperature 31P{1H} NMR spectra of 3a. The
3.07 ppm (1 H), δ = 4.04 ppm (1 H + 1 H coincidence).
1
COSY and H/13C HSQC experiments were used to fully signal at δ ≈ 42 is an unidentified minor impurity.
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Exploring (Ph2PCH2CH2)2E Ligand Space in RhI Alkene Complexes
data are of sufficient quality to allow a line–shape analysis free alkene is slow, at best, for 1a–3a, we suggest an intra-
and an Eyring plot, from which the activation parameters molecular mechanism that involves the alkene coordinating
of ΔH‡ = +48Ϯ2 kJmol–1 and ΔS‡ = +37Ϯ9 JK–1mol–1 through the oxygen (intermediate A, Scheme 4), alkene flip
were calculated [ΔG‡(298) = +37Ϯ5 kJmol–1]. Given that around a nominal mirror plane, and re-coordination of the
inversion of the phosphane ligand backbone is proposed to alkene. We discount alternative coordination modes of the
not be occurring in 3a, these data indicate the barrier to the alkene in the intermediate species A, such as η2-CO:η2-CC
fluxional process of the alkene only. In the presence of ex- or a metallocyclic structure[39,40] as this would neither ac-
cess alkene, no exchange was observed on the NMR times- count for the positive entropy of activation nor the ob-
cale for 1a or 2a, with sharp peaks observed for both free served inequivalence of the geminal alkene protons. The
and bound alkene. By contrast, 3a, when prepared in situ, two η2-CC structures shown in Scheme 4 represent the two
has been reported to show slow exchange with excess components of disorder observed in the solid state for 3a.
methyl acrylate.[21] Its isolation in the pure form here shows
1
that it displays sharp H NMR resonances for the bound
alkene in the absence of excess methyl acrylate.
To explore this fluxional process in more detail, we pre-
pared the vinyltrimethylsilane complexes [Rh{(κ3-
Ph2PCH2CH2)2E}(η2-H2C=CHSiMe3)][BArF4] 1b and 2b
by a similar route to that for 1a and 2a. We have not been
able to prepare 3b. The incorporation of a SiMe3 group
has a significant effect on the fluxional process. At room
temperature, the 31P{1H} NMR spectrum for 1b shows a
1
Scheme 4. Suggested mechanism for the fluxional process in com-
plexes 1a, 2a and 3a.
very broad, almost featureless spectrum, and the H NMR
spectrum shows broad peaks for the methylene groups, but
very sharp peaks for the coordinated vinyl trimethylsilane.
No exchange is observed on addition of free alkene. On
cooling (200 K), the alkene peaks do not change in posi-
tion, but the methylene signals sharpen to give eight envi-
ronments, and the 31P{1H} NMR spectrum shows a tightly
Reaction with Aldehydes
Having established the synthesis and structures of the
coupled AB doublet [J(P,P) = 280 Hz]. The variable-tem- RhI alkene precursors, we investigated the reactivity with
perature 31P NMR spectroscopic data are of sufficient qual- pentanal. To our surprise, none of the complexes reacted
ity to allow an Eyring plot, from which the activation pa- with the aldehyde over an appreciable timeframe, with the
rameters of ΔH‡
+10Ϯ5 JK–1mol–1
=
+58Ϯ2 kJmol–1 and ΔS‡
were calculated
[ΔG‡(298)
=
=
unreacted alkene complex returned instead. Likewise, under
catalytic conditions (10 mol-%), 1a, 2a and 3a did not turn-
+55Ϯ4 kJmol–1]. This is the upper limit for alkene rota- over methyl acrylate and pentanal, with only the alkene
tion/inversion at sulfur, and the measured activation param- complexes observed. This lack of reactivity is in contrast
eters are consistent with those reported for other systems.[38] with that of β-S-substituted aldehyde A with 3a, which
In contrast, 2b shows sharp signals at room temperature, rapidly reacts by oxidative addition to give B (Scheme 1).
with eight methylene environments observed in the 1H Presumably, this reflects the requirement for an intermedi-
NMR spectrum. Three 31P environments are observed, ate with a coordinated σ-aldehyde to form prior to oxidat-
which all couple to one another, with two showing charac- ive addition,[41] and the alkenes are too tightly bound to be
teristic trans 31P–31P coupling [J(P,P) = 331 Hz]. These data easily displaced by pentanal, while the sulfur tether in A is
are consistent with a high barrier to inversion at phos- able to. Similar comments have been made with regard to
phorus.
the role of alkene in the intramolecular hydroacylation of
The observation of broad signals for the methylene 4-pentenal.[42] However, over extended time (2 d) solutions
groups in 1b suggests inversion at S is a higher barrier pro- of 1a and 3a do react with pentanal and are converted
cess than that in 1a; but perhaps, most importantly, the ob- smoothly to give the products of decarbonylation, 1c and
servation of three sharp environments for the phosphanes 3c (Scheme 5).[35] Interestingly, 2c was only observed as a
in 2b shows that there is no fluxional process operating to minor product after a longer period of time, with 2a still
make two of them equivalent, unlike for 2a. Pulling all these present as the major component, which suggests an even
data together, we suggest two fluxional processes are occur- slower reaction with the aldehyde. Compound 2c has pre-
ring: (i) the inversion at S, which is rapid in 1a but slower viously been prepared as the [SbF6]– salt by Crabtree.[8]
in 1b; while for 2a and 2b, no such inversion is possible; (ii) Compound 1c can be alternatively prepared in the absence
a process that effectively flips the alkene in 2a, but not 2b, of olefin by the rapid reaction of [Rh{(κ3-Ph2PCH2-
which is probably also operating in 3a. This second process CH2)2S}Cl] with Na[BArF4] as a halide abstracting reagent
must be mediated by the acrylate group, as the SiMe3 group in the presence of pentanal at room temperature. This dem-
effectively halts the process in 2b. Given the small, but posi- onstrates that under suitable conditions (i.e. no alkene) oxi-
tive, entropy of activation measured for the fluxional pro- dative addition of the aldehdye, followed by rapid reductive
cess in 1a and 3a, coupled with the fact that exchange with decarbonylation, can occur. Pertinently, 2c is formed much
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A. S. Weller et al.
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more slowly by the analogous preparation from [Rh{(κ3- served at room temperature. This might be due to less avail-
Ph2PCH2CH2)2PPh}Cl] (50% conversion after 11 d), with able electron density on the metal centre [cf. ν(CO) 1c
a hydride species initially formed: δ1H = –19.70 ppm [ddt, 2021 cm–1 vs. 2c 2029 cm–1], although we currently only
J(P2H) = 37, J(P1,3H) = 12, J(RhH) = 22 Hz]; δ31P{1H} speculate upon this.
48.20 ppm [app. dt J(HP1,3) = 12, J(P2P1,3) = 10, J(RhP1,3
)
= 100 Hz, P1 and P3], 101.25 ppm [ddt J(HP2) = 36.5,
J(P1,3P2) = 10 Hz J(Rh) = 110 Hz, P2]. These data suggest
that oxidative addition of pentanal has occurred at the RhI
centre. Unfortunately, this species has eluded definitive
characterisation. It is tempting to speculate that whatever
the underlying reasons behind the sluggish reactivity of 2a
with pentanal are, they are related to the formation of this
stable hydride species.
Conclusions
The RhI complexes [Rh{(Ph2PCH2CH2)2E}(alkene)]-
[BArF4] (alkene = methyl acrylate and trimethylvinylsilane)
have been synthesised with the intention of studying their
reactivity with simple aldehydes. The methyl acrylate li-
gands undergo a fluxional process on the metal, suggested
to be via a κ1-carbonyl intermediate, whereas the trimethyl-
vinylsilane complexes cannot access this intermediate. Sur-
prisingly, these complexes do not undergo reaction with
pentanal at a reasonable rate, which is in contrast to reac-
tions with chelating aldehydes containing a sulfur tether
such as A. Presumably, this reflects the requirement for an
intermediate with a coordinated σ-aldehyde to form prior
to oxidative addition, and the alkene methylacrylate is too
tightly bound to be displaced by pentanal. Irrespective of
whether or not pentanal could be induced to undergo oxi-
dative addition given the appropriate precursor complex,
under catalytic conditions, the excess alkene will bind
strongly to the metal centre thus attenuating reactivity with
the aldehyde. Such sluggish reactivity has to be designed-
out of future catalyst systems if non-chelating aldehydes are
to be used in the hydroacylation reaction. We are currently
exploring opportunities to do this.
Scheme 5. ([BArF4]– anions omitted for clarity).
The carbonyl species 1c, 2c and 3c display CO stretches
in their infrared spectra (CH2Cl2) characteristic of a single
terminal CO ligand: 1c 2021 cm–1, 2c 2029 cm–1,[8] 3c
1995 cm–1. The lower energy stretch seen in 3c could be
attributed to greater back-bonding to the CO π* orbital,
mediated by stronger π donation by the O in the ligand to
the metal centre. This is consistent with the upright geome-
try and observed bond lengths in 3a in the solid state.
Reaction with Dichloromethane
[Rh{(κ3-Ph2PCH2CH2)2S}Cl] reacts with CH2Cl2 over
18 h to give [Rh{(κ3-Ph2PCH2CH2)2S}Cl2CH2Cl] (1d)
(Scheme 6) in essentially quantitative yield, which was char-
acterised by NMR spectroscopy and microanalysis. No in-
termediates were observed by 31P{1H} NMR spectroscopy.
The 31P{1H} NMR spectrum of 1d shows a doublet with a
Rh–P coupling constant of 102 Hz, consistent with a RhIII
species. The 1H NMR spectrum of the reaction with
Experimental Section
General: All procedures, unless otherwise stated, were carried out
under an argon atmosphere, by using standard Schlenk-line and
glove-box techniques. All glassware was dried at 130 °C overnight
and flame-dried under vacuum before use. Dichloromethane, pen-
tane and toluene were dried by using a Grubbs-type solvent purifi-
cation system (MBraun SPS-800) and degassed by successive
CD2Cl2 shows four methylene environments for the phos- freeze-pump-thaw cycles before use.[44] CD2Cl2, fluorobenzene and
benzene were dried with CaH2, distilled under vacuum and stored
phane ligand, while the reaction with CH2Cl2 reveals an
extra methylene environment (doublet of triplets) attributed
to a CH2Cl group. A trans chloride structure is proposed
over 3-Å molecular sieves. (Ph2PCH2CH2)2S,[27] Na[BArF4],[45]
[46]
[Rh(COD)Cl]2
and 3a[21] were prepared according to literature
methods. Methyl acrylate was distilled before use and degassed. All
other chemicals were used as received by the supplier. NMR spec-
tra were recorded on Bruker AVC 500, Varian Mercury 300 or Var-
ian Unity 500 spectrometers at room temperature unless otherwise
stated. Chemical shifts are quoted in ppm and coupling constants
(J) in Hz. Residual protio solvent (e.g. CD2Cl2: δ = 5.32 ppm) was
used as a reference for 1H NMR spectroscopy. ESI-MS was carried
1
as the H NMR spectrum shows only three phenyl proton
environments, and a greater number of environments would
be expected for isomers with lower symmetry (by assuming
free rotation around the Rh–C bond). Oxidative addition of
dichloromethane to RhI complexes is well documented.[43]
Interestingly the analogous reaction with [Rh{(κ3-
Ph2PCH2CH2)2PPh}Cl] and dichloromethane was not ob- out on a Bruker microTOF-Q connected to a glovebox (60 °C,
4.5 kV).[47] Infrared spectra were collected on a Nicolet Magna-
I.R. 560 spectrometer. Elemental microanalysis was carried out by
Stephen Boyer at London Metropolitan University. Elemental mi-
croanalysis was completed only on the crystalline samples of 2a {as
the [B(3,5-Cl2C6H3)4]– salt} and 1d. The noncrystalline nature of
the other samples inhibited accurate microanalysis. ESI mass spec-
trometry was attempted for all cationic complexes; however, in
Scheme 6.
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Exploring (Ph2PCH2CH2)2E Ligand Space in RhI Alkene Complexes
X-ray crystallography data for 2a (Table 1) were collected on an
and -841413 (for 3a). These data can be obtained free of charge
Enraf Nonius Kappa CCD diffractometer using graphite mono- from The Cambridge Crystallographic Data Centre via
chromated Mo-Kα radiation (λ = 0.71073 Å) and a low-temperature
device [150(2) K];[48] data were collected using COLLECT, re-
duction and cell refinement were performed with DENZO/SCALE-
PACK.[49] The structure was solved by direct methods with
SIR2004[50] and refined full-matrix least-squares on F2 by using
SHELXL-97.[51] All non-hydrogen atoms were refined with aniso-
tropic displacement parameters. Alkene protons were located in the
Fourier difference map; their isotropic displacement parameters
were fixed to ride on the parent atoms. All other hydrogen atoms
were placed in calculated positions by using the riding model. Dis-
order of the solvent molecule was treated by modelling it over two
sites and restraining its geometry. Restraints to thermal parameters
were applied where necessary in order to maintain sensible values.
Because of the size of the crystals, data for 3a (Table 1) were col-
lected on I19 (EH1) at Diamond Light Source, Didcot. Data were
collected at 150 K[48] with CrystalClear[52] and reduced using Crys-
AlisPro.[53] The structure was solved using SuperFlip[54] and refined
with CRYSTALS.[55] On refinement, peaks were visible in the dif-
ference map close to the methyl acrylate, thus the occupancy was
refined, and the peaks became more pronounced and clearly an
alternative orientation was obtained with about 30% occupancy.
Given the close proximity of the two components and their relative
occupancies, free refinement was unstable, so “same-distance” re-
straints were used for the disordered components, and vibrational/
thermal similarity restraints were used throughout. One phenyl ring
of the anion had extremely prolate ellipsoids and was similarly
modelled as disordered. Hydrogen atoms were generally visible in
the difference map and were treated in the usual fashion,[56] posi-
tioned geometrically prior to refinement with soft restraints to give
coordinates for use in a riding model with re-refinement as re-
quired. Torsion/dihedral angles were calculated with PLATON.[57]
Crystallographic data have been deposited with the Cambridge
Crystallographic Data Centre under CCDC-841412 (for 2a)
www.ccdc.cam.ac.uk/data_request/cif.
[Rh{(κ3-Ph2PCH2CH2)2S}Cl]: [Rh(COD)Cl]2 (50 mg, 0.101 mmol)
was dissolved in toluene (6 mL) and heated to 60 °C in an oil bath.
(Ph2PCH2CH2)2S (93 mg, 0.203 mmol) was dissolved (using an ul-
trasound bath) separately in toluene (6 mL) and then slowly added
dropwise to the hot stirring [Rh(COD)Cl]2 solution. The solution
changed colour to bright yellow/orange, followed by product pre-
cipitation. The solution was then cooled to –18 °C, and the re-
sulting precipitate was filtered and washed with pentane. The pre-
cipitate was dried under vacuum to yield a very bright orange/yel-
low powder in 74% yield which was insoluble in benzene, fluoro-
benzene and acetone, and cleanly reacted with dichloromethane to
give the C–Cl activated products 1d (vide infra). NMR spectro-
scopic data were collected on a freshly prepared solution. 1H NMR
(300 MHz CD2Cl2): δ = 1.97 (td, J = 14, J = 5 Hz, 2 H, CH2), 2.16
(t, J = 14 Hz, 2 H, CH2), 3.00 (br. d, J = 13 Hz, 2 H, CH2), 3.42
(br. t, J = 22 Hz, 2 H, CH2), 7.28–7.45 (m, 12 H, Ph), 7.86–8.04
(m, 8 H, Ph) ppm. 31P{1H} NMR (122 MHz CD2Cl2): δ = 39.2 [d,
J(RhP) = 147 Hz, 2 P] ppm.
[Rh{(κ3-Ph2PCH2CH2)2PPh}Cl]: The synthesis was adapted from
that of Marder and co-workers,[26] by following an analogous pro-
cedure as for the preparation of [Rh{(κ3-Ph2PCH2CH2)2S}Cl]
(above) to give a bright yellow micro-crystalline material (72%
yield). The NMR spectroscopic data are in agreement with the pub-
lished results.
[Rh{(κ3-Ph2PCH2CH2)S}(η2-H2C=CHCOOCH3)][BArF
]
(1a):
4
[Rh{(κ3-Ph2PCH2CH2)2S}Cl] (9 mg, 0.015 mmol) was added to
Na[BArF4] (13.4 mg, 0.015 mmol) in a Young’s NMR tube. To this
was added methyl acrylate (13.5 μL, 0.150 mmol, 10 equiv.) and
then CD2Cl2 (0.45 mL). A bright orange solution formed, which
was concentrated to dryness under vacuum and washed with pen-
tane (with sonication) three times. This was then dried under vac-
uum to yield an oily solid, which was characterised in situ by NMR
1
spectroscopy. H NMR (500 MHz CD2Cl2, 293 K): δ = 2.87 (m, 4
Table 1. Crystallographic data for 2a and 3a.
H, CH2), 2.97–3.13 [m, 5 H, alkene(1 H) and CH2 (4 H)], 3.23 (s,
3 H, CH3), 3.83 (m, 1 H, alkene), 4.21 (m, 1 H, alkene), 7.46–7.69
(m, 20 H, Ph), 7.56 (s, 4 H, BArF4), 7.73 (s, 8 H, BArF4) ppm.
31P{1H} NMR (202 MHz CD2Cl2, 293 K): δ = 56.68 [d, J(RhP) =
126 Hz, 2 P] ppm. 31P{1H} NMR (202 MHz CD2Cl2, 200 K):
tightly coupled AB double doublet, outer lines of very low intensity
and could not be resolved. Inner lines: δ = 59.34 [d, J(RhP) =
129 Hz], 59.69 [d, J(RhP) = 129 Hz] ppm.
2a·CH2Cl2
3a
Formula
C63H53BCl10O2P3Rh C64H46BF24O3P2Rh
Mr
1403.18
triclinic
P1
1494.68
monoclinic
P21/c
Crystal system
Space group
T [K]
¯
150(2)
150(2)
a [Å]
b [Å]
c [Å]
α [°]
11.85470(10)
16.2792(2)
16.6793(2)
105.5233(5)
94.1208(4)
94.5998(5)
3076.82(6)
2
1.515
0.834
5.15 Յ θ Յ 27.88
24620
0.0228
13.8681(5)
28.8045(9)
16.6233(6)
90
106.893(3)
90
6353.9(4)
4
1.562
[Rh{(κ3-Ph2PCH2CH2)S}{η2-H2C=CHSi(CH3)3}][BArF
]
(1b):
4
[Rh{(κ3-Ph2PCH2CH2)2S}Cl] (9 mg, 0.015 mmol) was added to
Na[BArF4] (13.4 mg, 0.015 mmol) in a small Schlenk flask with a
stirrer bar. To this was added vinyltrimethylsilane (22 μL,
0.150 mmol, 10 equiv.) and then CH2Cl2 (1 mL). The solution
stirred for half an hour. The solvent was removed by vacuum, and
the remaining yellow/brown oily solid was washed with pentane
(with sonication) three times. After drying under vacuum, the com-
plex was characterised in situ by NMR spectroscopy. 1H NMR
(500 MHz CD2Cl2, 293 K): δ = –0.41 (s, 9 H, SiMe3), 1.85–3.75
(br., 8 H, CH2), 3.10 [d, J(H,H)cis = 12 Hz, 1 H, alkene(CH2)], 3.88
[dd, J(H,H)trans = 15 Hz, J(H,H)cis = 6 Hz, 1 H, alkene(CHR)],
4.59 [m, 1 H, alkene (CH2)], 7.33–7.61 (m, 20 H, Ph), 7.55 (s, 4 H,
BArF4), 7.73 (s, 8 H, BArF4) ppm. 31P{1H} NMR (122 MHz
CD2Cl2, 293 K): tightly coupled AB double doublet, outer lines of
very low intensity and could not be resolved. Inner lines: δ = 54.97
[d, J(RhP) = 137 Hz], 57.72 [d, J(RhP) = 127 Hz] ppm. 31P{1H}
NMR (202 MHz CD2Cl2, 200 K): δ = 55.21 [dd, J(P,P) = 282 Hz,
β [°]
γ [°]
V [Å3]
Z
Density [gcm–3]
μ [mm–1]
θ range [°]
Reflections collected
Rint
0.435
1.49 Յ θ Յ 32.15
85103
0.135
Completeness
No. of data/restraints/
parameters
R1 [IϾ2σ(I)]
wR2 [all data]
GoF
99.2%
14578/73/753
96.0%
13243/1026/1578
0.0357
0.0868
1.039
0.0643
0.1509
0.9308
Largest diff. peak and
0.652, –0.658
1.25, –1.76
hole [eÅ–3]
Eur. J. Inorg. Chem. 2011, 5558–5565
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5563

A. S. Weller et al.
FULL PAPER
J(RhP) = 132 Hz, 1 P] 61.40 [dd, J(P,P) = 282 Hz, J(RhP) =
136 Hz, 1 P] ppm.
J(P,P)cis = 34 Hz, J(P,P)trans = 240 Hz, 1 P], 63.05 [ddd, J(RhP) =
132 Hz, J(P,P)cis = 37 Hz, J(P,P)trans = 240 Hz, 1 P], 115.18 [dt,
J(RhP) = 142 Hz, J(P,P) = 35 Hz, 1 P] ppm.
[Rh{(κ3-Ph2PCH2CH2)S}CO][BArF
]
4
(1c): [Rh{(κ3-Ph2PCH2-
[Rh{(κ3-Ph2PCH2CH2)O}CO][BArF4] (3c): To the best of our
knowledge, no NMR or IR data has been reported for this known
species, hence we report it here.[35] (NMR tube scale) Compound
3a (10 mg, 0.015 mmol) was dissolved in [D6]acetone and to this
was added pentanal (7.1 μL, 0.067 mmol). The sealed tube was hy-
drogenated under H2 (4 atm). After 48 h, the carbonyl species
forms as the sole product and was characterised in situ by NMR
and IR spectroscopy and ESI mass spectrometry. 31P{1H} NMR
(122 MHz [D6]acetone): δ = 49.67 [d, J(RhP) = 129 Hz, 2 P] ppm.
CH2)2S}Cl] (9 mg, 0.015 mmol) was added to Na[BArF4] (13.4 mg,
0.015 mmol) in a Young’s NMR tube. To this was added pentanal
(13.4 μL, 0.126 mmol) and then CD2Cl2 (0.45 mL). The tube was
shaken to encourage mixing to form a bright yellow solution. The
resulting solution was then concentrated to dryness under vacuum
and washed with pentane (with sonication) three times. After dry-
ing under vacuum, the product was characterised in situ by NMR
spectroscopy. 1H NMR (500 MHz CD2Cl2): δ = 2.58–3.79 (br., 8
H, CH2), 7.47–7.69 (m, 20 H, Ph), 7.56 (s, 4 H, BArF4), 7.73 (s, 8
H, BArF4) ppm. 31P{1H} NMR (122 MHz CD2Cl2): δ = 53.34 [d,
IR ([D ]acetone): ν = 1995 cm–1. ESI-MS: calcd. for [M+] 573.06;
˜
6
J(RhP) = 131 Hz, 2 P] ppm. IR (CH Cl ): ν = 2021 cm–1. ESI-MS:
found 573.06.
˜
2
2
calcd. for [M+] 589.04; found 589.04.
[Rh{(κ3-Ph2PCH2CH2)S}Cl2CH2Cl]
(1d):
[Rh{(κ3-Ph2PCH2-
Acknowledgments
CH2)2S}Cl] (15 mg) was dissolved in CH2Cl2 and left for 18 h at
298 K. The complex was characterised in situ before the solution
was layered with pentane to form a microcrystalline solid appropri-
The EPSRC and the University of Oxford are acknowledged for
support.
1
ate for microanalysis H NMR (500 MHz CD2Cl2): δ = 2.85 (m, 2
H, CH2), 3.27 (m, 2 H, CH2), 3.40 (m, 2 H, CH2), 3.82 (m, 4 H,
CH2 and CH2Cl) 7.38–7.44 (m, 12 H, Ph), 7.74 (m, 4 H, Ph), 8.13
(m, 4 H, Ph) ppm. 31P{1H} NMR (122 MHz CD2Cl2): δ = 33.85 [d,
J(RhP) = 102 Hz, 2 P] ppm.C29H30Cl3P2SRh·1/3CH2Cl2 (710.14):
calcd. C 49.61, H 4.35; found C 49.49, H 4.12.
[1] D. P. Fairlie, B. Bosnich, Organometallics 1988, 7, 946–954.
[2] J. W. Suggs, J. Am. Chem. Soc. 1978, 100, 640–641.
[3] M. C. Willis, Chem. Rev. 2010, 110, 725–748 .
[4] T. B. Marder, D. C. Roe, D. Milstein, Organometallics 1988, 7,
1451–1453.
[5] Z. Shen, P. K. Dornan, H. A. Khan, T. K. Woo, V. M. Dong,
J. Am. Chem. Soc. 2009, 131, 1077–1091.
[6] A. H. Roy, C. P. Lenges, M. Brookhart, J. Am. Chem. Soc.
2007, 129, 2082–2093.
[7] I. F. D. Hyatt, H. K. Anderson, A. T. Morehead, A. L.
Sargent, Organometallics 2008, 27, 135–147.
[8] C. M. Beck, S. E. Rathmill, Y. J. Park, J. Chen, R. H. Crabtree,
L. M. Liable-Sands, A. L. Rheingold, Organometallics 1999,
18, 5311–5317.
[9] P. Fristrup, M. Kreis, A. Palmelund, P.-O. Norrby, R. Madsen,
J. Am. Chem. Soc. 2008, 130, 5206–5215.
[10] A. T. Luedtke, K. I. Goldberg, Inorg. Chem. 2007, 46, 8496–
8498.
[11] M. P. Lanci, M. S. Remy, D. B. Lao, M. S. Sanford, J. M.
Mayer, Organometallics 2011, 30, 3704–3707.
[12] D. Milstein, Acc. Chem. Res. 1984, 17, 221–226.
[13] R. Goikhman, D. Milstein, Angew. Chem. 2001, 113, 1153; An-
gew. Chem. Int. Ed. 2001, 40, 1119–1122.
[14] C. H. Jun, E. A. Jo, J. W. Park, Eur. J. Org. Chem. 2007, 1869–
1881.
[Rh{(κ3-Ph2PCH2CH2)2PPh}(η2-H2C=CHCOOCH3)][BArF4] (2a):
[Rh{(κ3-Ph2PCH2CH2)2PPh}Cl] (30 mg, 0.045 mmol) was added
to Na[BArF4] (39.6 mg, 0.045 mmol) in a small Schlenk flask. To
this was added methyl acrylate (40 μL, 0.444 mmol, 10 equiv.) and
then CH2Cl2 (1.5 mL). The solution was stirred for 1 h and filtered
to remove NaCl. The resulting solution was concentrated to dry-
ness under vacuum and washed with pentane (with sonication)
three times before the resulting oil was dried under vacuum to form
a yellow solid (yield = 52%). The solid-state structure was obtained
by using the [B(3,5-Cl2C6H3)4]– salt, which was prepared by a sim-
ilar method.[28] 1H NMR (500 MHz CD2Cl2): δ = 2.10 (br., 2 H,
CH2), 2.27 (br., 2 H, CH2), 2.60 (br., 2 H, CH2), 2.91 [double mul-
tiplet, J(P,H) = 42 Hz, CH2], 3.07 [d, J(H,H) = 6 Hz, 1 H, al-
kene(CH2)], 3.13 (s, 3 H, CH3), 4.04 [br., 2 H, alkene (coincident
protons; CH2 and CHCOOCH3)], 7.3–7.65 (m, 25 H, Ph), 7.55 (s,
4 H, BArF4), 7.73 (s, 8 H, BArF4) ppm. 13C{1H} NMR (126 MHz
CD2Cl2): δ = 27.48 (br., 2 C, CH2), 32.75 (br., 2 C, CH2), 52.01 (s,
1 C, CH3), 71.74 (s, 1 C, alkene CH2), 72.67 (s, 1 C, alkene CHR),
128–134.5 (phenyl region + [BArF4] resonances {118.16–117.94
(m), 125.16 [q, 1J(F,C) = 272 Hz], 129.42 [qq, 2J(F,C) = 31 Hz,
[15] K. Tanaka, Y. Shibata, T. Suda, Y. Hagiwara, M. Hirano, Org.
Lett. 2007, 9, 1215–1218.
[16] M. M. Coulter, K. G. M. Kou, B. Galligan, V. M. Dong, J. Am.
Chem. Soc. 2010, 132, 16330–16333.
1
4J(BC) = 3 Hz], 135.36 (s), 162.31 [q, J(BC) = 50 Hz]}), 169.61 (s,
1 C, CO2Me) ppm. 31P{1H} NMR (202 MHz CD2Cl2): δ = 66.49
[dd, J(P,P) = 38 Hz, J(RhP) = 132 Hz, 2 P], 123.29 [dt, J(P,P) =
38 Hz, J(RhP) = 134 Hz, 1 P] ppm. C63H53BCl10O2P3Rh·CH2Cl2
(1403.26) {as the [B(3,5-Cl2C6H3)4]– salt}: calcd. C 53.92, H 3.81;
found C 54.45, H 3.96.
[17] M. C. Willis, S. J. McNally, P. J. Beswick, Angew. Chem. 2004,
116, 344; Angew. Chem. Int. Ed. 2004, 43, 340–343.
[18] J. C. Jeffrey, T. B. Rauchfuss, Inorg. Chem. 1979, 18, 2658–
2666.
[19] G. L. Moxham, H. E. Randell-Sly, S. K. Brayshaw, R. L.
Woodward, A. S. Weller, M. C. Willis, Angew. Chem. 2006, 118,
7780; Angew. Chem. Int. Ed. 2006, 45, 7618–7622.
[20] G. L. Moxham, H. Randell-Sly, S. K. Brayshaw, A. S. Weller,
M. C. Willis, Chem. Eur. J. 2008, 14, 8383–8397.
[21] R. J. Pawley, G. L. Moxham, R. Dallanegra, A. B. Chaplin,
S. K. Brayshaw, A. S. Weller, M. C. Willis, Organometallics
2010, 29, 1717–1728.
[22] K. Wang, T. J. Emge, A. S. Goldman, C. Li, S. P. Nolan, Orga-
nometallics 1995, 14, 4929–4936.
[23] J. F. Riehl, Y. Jean, O. Eisenstein, M. Pelissier, Organometallics
1992, 11, 729–737.
[24] M. Kreis, A. Palmelund, L. Bunch, R. Madsen, Adv. Synth.
Catal. 2006, 348, 2148–2154.
[Rh{(κ3-Ph2PCH2CH2)2PPh}{η2-H2C=CHSi(CH3)3}][BArF4] (2b):
To [Rh{(κ3-Ph2PCH2CH2)2PPh}Cl] (10 mg, 0.015 mmol) was
added Na[BArF4] (13.2 mg, 0.015 mmol) and vinyltrimethylsilane
(21.8 μL, 0.149 mmol) in CD2Cl2 (0.5 mL). This was agitated in an
ultrasound bath for 1 h before in situ characterisation by NMR
spectroscopy. 1H NMR (500 MHz CD2Cl2): δ = –0.54 (s, 9 H,
SiMe3), 1.77–3.10 (br., 8 H, CH2), 3.54 [d, J(H,H) = 12 Hz, 1 H,
alkene (CH2)], 4.55 [dd, J(H,H)trans = 16 Hz, J(H,H)cis = 10 Hz, 1
H, alkene(CHR)], 5.04 [br., 1 H, alkene (CH2)], 7.35–7.69 (m, 25
H, Ph), 7.56 (s, 4 H, BArF4), 7.74 (s, 8 H, BArF4) ppm. 31P{1H}
NMR (202 MHz CD2Cl2): δ = 55.03 [ddd, J(RhP) = 138 Hz,
5564
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Eur. J. Inorg. Chem. 2011, 5558–5565

Exploring (Ph2PCH2CH2)2E Ligand Space in RhI Alkene Complexes
[25]
[26]
[41] B. K. Corkey, F. L. Taw, R. G. Bergman, M. Brookhart, Poly-
hedron 2004, 23, 2943–2954.
M. A. Garralda, Dalton Trans. 2009, 3635–3645.
S. A. Westcott, G. Stringer, S. Anderson, N. J. Taylor, T. B.
Marder, Inorg. Chem. 1994, 33, 4589–4594.
G. Degischer, G. Schwarzenbach, Helv. Chim. Acta 1966, 49,
1927–1931.
A. B. Chaplin, A. S. Weller, Eur. J. Inorg. Chem. 2010, 5124–
5128.
E. Hauptman, S. Sabo-Etienne, P. S. White, M. Brookhart,
J. M. Garner, P. J. Fagan, J. C. Calabrese, J. Am. Chem. Soc.
1994, 116, 8038–8060.
R. Bender, C. Okio, R. Welter, P. Braunstein, Dalton Trans.
2009, 4901–4907.
A. J. Edwards, S. Elipe, M. A. Esteruelas, F. J. Lahoz, L. A.
Oro, C. Valero, Organometallics 1997, 16, 3828–3836.
T. A. Albright, R. Hoffmann, J. C. Thibeault, D. L. Thorn, J.
Am. Chem. Soc. 1979, 101, 3801–3812.
[42] D. P. Fairlie, B. Bosnich, Organometallics 1988, 7, 936–945.
[43] A. J. Vetter, R. D. Rieth, W. W. Brennessel, W. D. Jones, J. Am.
Chem. Soc. 2009, 131, 10742–10752 and references therin.
[44] A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen,
F. J. Timmers, Organometallics 1996, 15, 1518–1520.
[45] W. E. Buschmann, J. S. Miller, K. Bowman-James, C. N. Miller,
Inorg. Synth. 2002, 33, 83–85.
[46] G. Giordano, R. H. Crabtree, Inorg. Synth. 1990, 28, 88–90.
[47] A. T. Lubben, J. S. McIndoe, A. S. Weller, Organometallics
2008, 27, 3303–3306.
[48] J. Cosier, A. M. Glazer, J. Appl. Crystallogr. 1986, 19, 105–107.
[49] Z. Otwinowski and W. Minor in Processing of X-Ray Diffrac-
tion Data Collected in Oscillation Mode, Vol. 276 1997, pp. 307–
326.
[50] M. C. Burla, R. Caliandro, M. Camalli, B. Carrozzini, G. L.
Cascarano, L. De Caro, C. Giacovazzo, G. Polidori, R.
Spagna, J. Appl. Crystallogr. 2005, 38, 381–388.
[27]
[28]
[29]
[30]
[31]
[32]
[33] M. Rubio, A. Suarez, D. del Río, A. Galindo, E. Ålvarez, A.
Pizzano, Organometallics 2009, 28, 547–560.
[34] C. Daniel, N. Koga, J. Han, X. Y. Fu, K. Morokuma, J. Am.
Chem. Soc. 1988, 110, 3773–3787.
[35] N. W. Alcock, J. M. Brown, J. C. Jeffery, J. Chem. Soc., Dalton
Trans. 1976, 583–588.
[36] U. Helmstedt, P. Lönnecke, E. Hey-Hawkins, Inorg. Chem.
2006, 45, 10300–10308.
[37] X. Shan, J. H. Espenson, Organometallics 2003, 22, 1250–1254.
[51] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
[52] CrystalClear, Rigaku Americas and Rigaku Corporation, 2009.
[53] CrysAlisPro, Oxford Diffraction/Agilent Technologies, 2010.
[54] L. Palatinus, G. Chapuis, J. Appl. Crystallogr. 2007, 40, 786–
790.
[55] P. W. Betteridge, J. R. Carruthers, R. I. Cooper, K. Prout, D. J.
Watkin, J. Appl. Crystallogr. 2003, 36, 1487.
[38] E. W. Abel, M. Booth, K. G. Orrell, G. M. Pring, J. Chem. [56] R. I. Cooper, A. L. Thompson, D. J. Watkin, J. Appl. Crys-
Soc., Dalton Trans. 1981, 1944–1950.
[39] R. Sustmann, B. Patzke, R. Boese, J. Organomet. Chem. 1994,
470, 191–197.
tallogr. 2010, 43, 1100–1107.
[57] A. L. Spek, J. Appl. Crystallogr. 2003, 36, 7–13.
Received: September 8, 2011
Published Online: November 14, 2011
[40] D. Kwon, M. D. Curtis, Organometallics 1990, 9, 1–5.
Eur. J. Inorg. Chem. 2011, 5558–5565
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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