CuI complexes containing a multidentate and conformationally flexible dibenzylidene acetone ligand (dbathiophos): Application in catalytic alkene cyclopropanation

Article abstract of DOI:10.1039/c0dt01612h

The synthesis and characterisation of a multidentate conformationally flexible ligand based on the dibenzylidene acetone core structure, dbathiophos (1), is described. Ligand 1 has a high affinity for cationic and neutral Cu ^I species. Three unique Cu^I complexes (4-6) are reported showing that the ligand backbone of dbathiophos is hemilabile, and able to adopt different 1,4-dien-3-one conformational geometries around Cu^I. Complexes 4 and 6 both effectively catalyse the cyclopropanation of styrene with ethyl diazoacetate at low catalyst loadings (1 mol% Cu). The Royal Society of Chemistry 2011.

Full text of DOI:10.1039/c0dt01612h

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PAPER
I
Cu complexes containing a multidentate and conformationally flexible
dibenzylidene acetone ligand (dbathiophos): Application in catalytic alkene
cyclopropanation†
Amanda G. Jarvis, Adrian C. Whitwood and Ian J. S. Fairlamb*
Received 19th November 2010, Accepted 24th January 2011
DOI: 10.1039/c0dt01612h
The synthesis and characterisation of a multidentate conformationally flexible ligand based on the
dibenzylidene acetone core structure, dbathiophos (1), is described. Ligand 1 has a high affinity for
I
I
cationic and neutral Cu species. Three unique Cu complexes (4–6) are reported showing that the
ligand backbone of dbathiophos is hemilabile, and able to adopt different 1,4-dien-3-one
I
conformational geometries around Cu . Complexes 4 and 6 both effectively catalyse the
cyclopropanation of styrene with ethyl diazoacetate at low catalyst loadings (1 mol% Cu).
Introduction
to metals has been, in our view, fairly neglected when compared
to their phosphine counterparts. Specifically, it was anticipated
that the combination of a soft phosphine sulfide donor group
with an alkene component would provide a unique coordination
The coordination of E,E-dibenzylidene acetone (dba-H) to
transition metals has attracted significant attention over the
1
last 30 years. Electron-deficient dba-H acts as a 1,4-diene
I
12
environment for the soft Cu centre.
5
2
2
2
4
ligand in [Rh(h -C
5
Me
5
)(h ,h -dba-H)] and [Fe(CO)
3
[h -{(CO)
3
(
CH CHPh)
2
5
}]; a range of coordination modes are seen in
4
6
Results and Discussion
other Fe, Ru and U complexes. Arguably the most well known
0
metal complexes possessing dba-type ligands are Pd
2
(dba-H)
3
Ligand 1 was prepared in 84% yield by Horner–Wadsworth–
Emmons reaction of bisphosphonate 2 (see ESI† for the prepa-
ration of this compound) with phosphine sulfide benzaldehyde 3
in the presence of NaOH at reflux for 48 h (Scheme 1). Gram-scale
quantities of 1 can be produced using this efficient transformation,
0
0
and Pd
2
(dba-Z)
3
, which are widely used Pd precursors in
synthetic chemistry, catalysis and organometallic coordination
chemistry (dba-Z = E,E-dibenzylidene acetone with different Z-
7
substituents). Intramolecular dba-H ‘alkene’ (olefin) exchange at
0
Pd , via C O coordination, occurs freely in solution, for which
and single crystals could be grown from CH
layered with diethyl ether which were analysed by X-ray diffraction
Fig. 1).
2
Cl
2
solutions of 1
8
several 1,4-dien-3-one conformations are readily accessible. We
hypothesised that one could control and enhance ‘dba-metal’
interactions if suitable 2-electron donor groups could be incor-
porated into the dba sub-structure. Recent catalytic applications
(
9
exploiting related chalcone-phosphino ligands reported by Lei
I
10
and co-workers, and dba effects with Cu reported by Buchwald,
have encouraged us to study more elaborate dba structures.
I
11
Moreover, Cu complexes of dienes/polyenes are relatively rare,
and hence the synthesis of a novel phosphine sulfide dba ligand
I
1, which we refer to as ‘dbathiophos’, and its Cu coordination
I
chemistry, is the main subject of this paper. Two Cu complexes
of 1 have been evaluated as catalysts in alkene cyclopropanation
reactions.
Ligand 1 was identified as a target which could be accessed
quickly and efficiently from readily available starting materials.
On a general note, the coordination of phosphine sulfide ligands
Scheme 1 Synthesis of dbathiophos 1.
I
The Cu coordination chemistry of ligand 1 is intriguing. For
example, reaction of 1 with Cu(CH CN) PF in CH Cl at ambient
temperature gave a new product which shows broad proton signals
3
4
6
2
2
1
by H NMR spectroscopy (in CD
2
2
Cl ) vide infra (Scheme 2).
Mass spectrometry (ESI-MS and LIFIDI) showed the presence
I
+
of one ion (m/z 729) which is [Cu (1)] . Crystals suitable for X-ray
diffraction were grown from CH Cl solutions of this material
carefully layered with diethyl ether. Microscopic inspection of
these crystals showed that both pale yellow (the majority) and
Department of Chemistry, University of York, Heslington, York, UK, YO10
2
2
5
DD. E-mail: ijsf1@york.ac.uk
†
CCDC reference numbers 801872–801875. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c0dt01612h
This journal is © The Royal Society of Chemistry 2011
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Fig. 1 X-ray structure of dbathiophos 1. Thermal ellipsoids at 50% prob-
ability; (disordered CH
clarity). Selected bond angles ( ): O(1)–C(1)–C(2) 122.2(2), C(9)–P(1)–S(1)
2
Cl
2
molecules and selected hydrogens omitted for
◦
1
12.80(10), C(10)–P(1)–S(1) 113.18(11), C(16)–P(1)–S(1) 111.36(11). See
Table 1 for selected bond lengths. The complex has crystallographically
imposed two-fold symmetry with the central C O bond on the two-fold
axis.
I
Fig. 2 X-ray structure of dinuclear Cu complex 4. Thermal elipsoids
shown at 50% probability; 2 ¥ PF
6
molecules and hydrogens (except
◦
H
2
O) omitted for clarity. Selected bond angles ( ): S(3)–Cu(1)–S(1) =
1
17.91(6), C(60)–Cu(1)–O(3) = 99.84(19), C(61)–Cu(1)–O(3) = 92.1(2),
S(3)–Cu(1)–O(3) = 96.22(13), S(1)–Cu(1)–O(3) = 98.62(13), S(4)–Cu(2)–
S(2)
O(4)
=
=
119.84(7), C(23)–Cu(2)–O(4)
94.1(2), S(4)–Cu(2)–O(4)
=
98.5(2), C(22)–Cu(2)–
=
96.42(13), S(2)–Cu(2)–O(4) =
9
5.52(14).
I
I
Fig. 3 X-ray structure of tetrameric Cu complex 5. Thermal elipsoids
Scheme 2 Synthesis of novel Cu complexes (2–4) of dbathiophos 1.
6
shown at 50% probability; 2 ¥ PF , hydrogens and disordered ether
and CH
bond angles ( ): C(7)–Cu(1)–S(2)
139.68(8), C(7)–Cu(1)–Cl(1)
102.56(8), S(2)–Cu(1)–Cl(1)
115.78(8), C(8)–Cu(1)–S(1) = 93.14(8), S(2)–Cu(1)–S(1) = 112.26(3),
Cl(1)–Cu(1)–S(1) = 96.37(2). The complex lies about an inversion centre.
2
Cl
2
solvent molecules are omitted for clarity. Selected
◦
bright yellow types were present. A pale yellow crystal was
=
102.24(8), C(8)–Cu(1)–S(2)
=
=
=
I
identified as dinuclear Cu complex 4, whereas a bright yellow
=
=
125.06(8), C(8)–Cu(1)–Cl(1)
104.95(3), C(7)–Cu(1)–S(1)
I
crystal was found to be tetranuclear Cu complex 5 (see Fig. 2 and
13
3
4
). The source of the chloride in 5 is unclear. On other occasions
was the only isolatable complex (~65% yield).
The reaction of CuCl with 1 in CH
gave complex 6 in 73% yield. Complex 6 was crystallised from
CH Cl solutions layered with pentane, which allowed a single
2
Cl
2
at ambient temperature
trans conformation, which is identical to Pd
C C bonds are coordinated to Pd ).
Each ligand in complex 5 bridges two Cu centres, which are
capped by the phosphine sulfide moieties. Two chloride ligands are
found embedded within the structure, forming a ‘pleated ladder’;
the inner step is a rhombus whereas the two outside steps possess
different bond angles and are twisted as a consequence. As this
exact structure is only supported by X-ray diffraction data we
were keen to check that the bridging ligands were chloride and
not hydroxide. First of all the Cu–Cl bond distances are similar
2
(dba-H) (where both
3
0
14
2
2
I
crystal X-ray structure to be determined (Fig. 4).
I
The Cu centre in complex 4 exhibits a distorted tetrahedral
arrangement; the sulfur atoms and the alkene form an almost
planar triangle with the water arranged perpendicularly to the
others. On comparison with the bond lengths for 1 the C C (s-
I
cis) and P S bonds lengthen on coordination to Cu (Table 1),
whereas the non-coordinated C C bonds (s-trans) share similar
bond lengths with 1 (note that the C C bonds in 1 adopt a
s-cis conformation relative to the carbonyl moiety due to steric
reasons). The P–S bonds, which are in similar environments, have
bond lengths which are identical (within error). The 1,4-dien-3-
one backbones in both bridging ‘dba’ ligands adopts a s-cis,s-
15
to recently reported Cu–Cl ladder complexes. Furthermore, the
bond lengths in related Cu–OH complexes are ca. 1.9–2.3 A. In
Cu–Cl complexes the bond lengths are typically 2.3–2.8 A, which
16
˚
14
˚
˚
matches our data (ca. 2.3–2.6 A) more closely.
3
696 | Dalton Trans., 2011, 40, 3695–3702
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Table 1 Comparison of key bond lengths ( A˚ ) in compounds 1–4
Key bonds and lengths ( A˚ )
Cpd.
C
C
C
O
P
S
Cu–S
—
Cu–C
—
Cu–Cl
—
1
4
C(2)–C(3)
.324(5)
C(22)–C(23)
.360(9)
C(19)–C(20)
.346(8)
C(60)–C(61)
.384(8)
C(63)–C(64)
.319(8)
C(8)–C(7)
.373(4)
C(10)–C(11)
.373(4)
C(1)–O(1)
1.221(6)
C(21)–O(1)
1.224(7)
C(62)–O(2)
1.225(7)
P(1)–S(1)
1.9619(11)
P(1)–S(1)
1.993(2)
P(2)–S(2)
1.987(3)
P(3)–S(3)
2.002(2)
P(4)–S(4)
1.995(2)
P(1)–S(1)
2.0221(10)
P(2)–S(2)
1.9936(10)
1
Cu(1)–S(1)
2.2826(18)
Cu(1)–S(3)
2.2488(16)
Cu(2)–S(2)
2.2619(18)
Cu(2)–S(4)
2.2585(18)
Cu(1)–S(1)
2.4872(8)
Cu(1)–C(60)
2.091(6)
Cu(1)–C(61)
2.125(6)
Cu(2)–C(22)
2.089(6)
Cu(2)–C(23)
2.087(7)
C(7)–Cu(1)
2.112(3)
C(8)–Cu(1)
2.164(3)
C(10)–Cu(2)
2.108(3)
C(11)–Cu(2)
—
1
1
1
1
5
6
C(9)–O(1)
1.224(4)
Cu(1)–Cl(1)
2.4155(7)
Cu(2)–Cl(1)
2.3330(7)
Cu(2)#1–Cl(1)
2.5906(7)
Cu(2)–Cl(1)#1
2.5907(7)
1
Cu(1)–S(2)
2.2767(8)
Cu(2)–S(1)
1
2
.2948(8)
2
.089(3)
C(2)–C(3)
.375(4)
C(1)–O(1)
1.228(5)
P(1)–S(1)
2.0072(12)
Cu(1)–S(1)
2.2546(9)
C(2)–Cu(1)
2.060(3)
Cu(1)–Cl(1)
2.1908(9)
1
C(3)–Cu(1)
2
.053(3)
I
6
are consistent with a reported neutral Cu complex possessing a
17
phosphine sulfide ligand.
NMR spectroscopic analysis
1
The H NMR spectrum of 4 exhibits fluxional behaviour at
3
00 K. We suspected that the free and coordinated alkenes
were undergoing exchange on the NMR timescale. A variable
1
18
temperature H NMR experiment confirmed that the very broad
signals recorded at 300 K were indeed those of the free and
coordinated alkenyl protons. The proton chemical shifts of the
3
I
coordinated alkene (d 5.94 and 5.99) possess a JHH coupling
Fig.
4
X-ray structure of dinuclear Cu complex 6. Thermal
◦
constant of 13.3 Hz, whereas the non-coordinated alkene (d 6.60
and 7.82), has a JHH coupling constant of 16.4 Hz (confirmed by
a low temperature 2D H- H COSY experiment, see ESI†). The
larger coupling constant and chemical shift difference is consistent
with a free alkene moiety.
elipsoids shown at 50% probability; Selected bond angles ( ):
C(3)–C(2)–Cu(1) 70.22(18), C(1)–C(2)–Cu(1) 105.11(17), P(1)–S(1)–Cu(1)
8.81(4), C(3)–Cu(1)–S(1) 104.51(9), C(2)–Cu(1)–S(1) 143.46(10),
Cl(1)–Cu(1)–S(1), 111.34(4). The complex has crystallographically im-
posed two-fold symmetry with the central C O bond on the two-fold
axis.
3
1
1
9
31
The P NMR spectrum of 4 exhibits two broad singlets,
indicating two phosphine sulfide chemical environments (d 46.4
1
and 40.6, and one septet at -143.80 ( JPF = 711 Hz), which is
I
The Cu environment in 5 is closer to a classic tetrahedral
attributed to the PF
6
anion). The two singlets sharpen on lowering
1
-31
arrangement than in 4, but it can still be considered as distorted.
The 1,4-dien-3-one backbone in both bridging ‘dba’ ligands
adopts a s-cis,s-cis conformation. The Cu–C bond lengths are
longer than those found in 4, with the Cu–C bonds a to the
carbonyl group longer than the b Cu–C bonds (see Table 1).
The P–S bonds in 5 also exhibit marked differences in their bond
lengths. For example, P(1)–S(1) is 2.0221(10), which forms part of
the outer step, whereas P(2)–S(2) is only 1.9936(10), being located
on the outside edge of the pleated ladder. The Cu–Cl bond which
forms part of the inner step is significantly shorter {Cu(2)–Cl(1) =
the temperature to 230 K. A 2D H P HMQC experiment shows
3
1
that the P signal at d 40.6 couples with the proton at d 5.94,
3
1
whereas the P signal at d 46.4 couples with d 7.82. Unfortunately,
1
3
we were unable to get complete C NMR spectroscopic data for
complex 4 (see ESI†).
Interestingly, a related cationic Cu complex, [(2,6-(Ph
I
2
P(o-
C
6
H
4
)CH N)
2
C
5
H
3
N)
2
Cu
2
](BF
4
) (7) was reported by Yeh and
2
19
Chen very recently (Scheme 3). They noted dynamic exchange
between the coordinated and the non-coordinated imine groups
‡
-1
-1
in solution {DG = 8.8 kcal mol (36.8 kJ mol ), estimated}.
2
0
2
.3330(7)} than the Cu–Cl bond located in the outer step {Cu(1)–
Using gNMR software, we were able to simulate the line
shape of the experimentally observed spectra to gain the rate
constants for the exchange process at a number of temperatures.
An Arrhenius plot of 1/T against ln k gives a straight line with
Cl(1) = 2.4155(7)}. Complex 6 exhibits a trigonal planar geometry
I
around Cu . The C–Cu bond lengths are much shorter than those
found in 4 and 5, but both the C–Cu and Cu–Cl bond lengths in
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1
Fig. 6 Variable temperature H NMR spectra of complex 6 in CD
2 2
Cl at
7
00 Hz.
I
Scheme 3 Dynamic exchange in dinuclear cationic Cu complex 4
(
I
19
bottom) and a related reported dinuclear cationic Cu complex 7 (top).
The two anions for each complex are omitted for clarity.
constant relative to the free ligand 1 (15.8 Hz). The broadness of
the a-proton is attributed to a partial restricted rotation about the
C–C bonds connecting the C O moiety. C NMR spectroscopic
1
3
slope -E /R, allowing the activation energy to be estimated (58.23
a
-
1
analysis (in CD Cl ) confirmed coordinated C C bonds with
kJ mol ). In addition, an Eyring plot of ln(k/T) against 1/T
2
2
2
broad signals observed at d 95.3 and 94.4.
afforded a straight line plot (R = 0.9995) from which the enthalpy
‡
-1
‡
-1
(
DH = 56.0 ±6.4 kJ mol ) and entropy (DS = 0.43 ±6.9 J mol
1 ‡
-
K ) of activation were determined. The small DS value is in
On the interconversion of 4↔5↔6
keeping with the exchange being intramolecularly independent of
‡
water dissociation. The DH value indicates that the barrier to
We hypothesised that it ought to be possible to interconvert
‡
rotation is primarily enthalpic. The free energy of activation (DG )
complexes 4↔5↔6, by either chloride addition, or chloride
-
1
-1
at 300 K is 55.9 ±9.7 kJ mol (13.4 ±2.3 kcal mol ).
metathesis by the PF anion. This was assessed by the addition of
6
1
The H NMR spectrum of complex 6 shows all of the expected
proton signals (Fig. 6). The P NMR spectrum shows one
a soluble chloride source (n-Bu NCl). Thus, to a CD Cl solution
4
2
2
3
1
of complex 4 (15 mg, 0.01 mmol, 0.015 M) was added aliquots of
a CD Cl solution containing n-Bu NCl (see Fig. 7).
phosphorus singlet (d 40.8). Whilst the alkenyl protons {d 6.07
2
2
4
(
Dd = 2.1) and 5.83 (Dd = 0.65)} become shielded on coordination
I
to Cu , unusually the signal at d 5.83 (a-proton) appears broad at
2
93 K, whereas the neighbouring b-proton appears as a doublet
1
signal (13.9 Hz). A variable temperature H NMR experiment
showed that the broad signal sharpens to give a doublet with a
matching JHH coupling constant (13.9 Hz), confirming that both
3
proton environments are associated with the alkene moiety. Cu
3
coordination also causes a small decrease in the JHH coupling
Fig. 7 Addition of chloride (n-Bu
monitored by H NMR spectroscopy at 500 MHz (at 298 K). (a) Complex
4
2 2
NCl) to complex 4 in CD Cl
1
4
4
; (b) 0.3 eq. n-Bu NCl; (c) 0.6 eq.; (d) 0.9 eq.; (e) 1.2 eq.; (f) 1.5 eq.; (g)
1
Fig. 5 Variable temperature H NMR spectra of complex 4 in CD
2
Cl
2
at
1.8 eq.; (h) 2.1 eq.; (i) 2.4 eq.; (j) 3 eq.; (k) 3.6 eq.; (l) ligand 1; (m) Complex
6.
5
00 Hz (* trace toluene).
3
698 | Dalton Trans., 2011, 40, 3695–3702
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1
31
I
Both H and P NMR spectra were recorded after each aliquot
Table 2 Cu -catalysed alkene cyclopropanation
3
1
was added (see ESI† for P NMR spectra). Spectroscopic analysis
shows that no observable ‘intermediate’ complex (e.g. 5) is formed
in this reaction upon the addition of 0.5 equiv. of chloride per
Cu. Increasing the chloride concentration leads to a new proton
signal (broad) at d 6.2–6.4. Following the addition of over 3 equiv.
of chloride per Cu, only the free ligand 1 is observed and not
complex 6. Ligand 1 was identified by comparison {spectra (k)
and (l) in Fig. 7} of the proton signals at d 6.48 appearing as a
doublet (15.6 Hz). A similar experiment by UV-Vis spectroscopic
analysis revealed the presence of several Cu species in solution, for
which further deductions could not be made.
Catalyst
Diastereomeric ratio
(cis-10/trans-10)
a
(
1 mol%)
Conversion (%)
No catalyst
CuBr
4
6
0
—
24
85
91
40 : 60
32 : 68
30 : 70
The reaction of complex 6 with AgPF
6
(varying equivalents,
shares a similar H NMR spectrum with
complex 4. On cooling, solutions of complex 6 with AgPF (ca.
.5 equiv.), the broad signals at d 5.85–6.15 do not sharpen up akin
1
see Fig. 8) in CD
2
Cl
2
a
1
6
%
Conversion to diastereomeric cyclopropane products by H NMR
2
spectroscopy (by-products include diethyl maleate and diethyl fumarate
(see ESI† for details).
I
to complex 4 (Fig. 5). Ag complexation to 1 is likely competing
I
with Cu coordination, which could account for the incomplete
conversion to 4 from 6.
1
and diethyl maleate (ratio: 60 : 40) was recorded by H NMR
spectroscopic analysis.
Conclusion
In summary, the synthesis and characterisation of dbathiophos 1,
I
and cationic and neutral Cu complexes derived thereof, have been
I
reported. In three structurally unique Cu complexes (4–6) it was
shown that the ligand backbone of 1 is hemilabile, multidentate
and able to adopt different 1,4-dien-3-one conformations around
I
Cu . We have further established that complexes 4 and 6 effectively
catalyse the cyclopropanation of styrene using ethyl diazoacetate
9
at low catalyst loadings (1 mol% Cu). Indeed, catalytic efficacy
22a
was commensurate with a recently reported catalyst system.
It is interesting to note that complex 7 acts as a Cu model for
19
the catalytic conversion of nitrite to nitrate. The similar dynamic
behaviour and coordination chemistry implies that 4 could also
act as a Cu model. Our findings concerning further applications
1
Fig. 8 Addition of AgPF
6
to complex 4 in CD
2
Cl
2
monitored by
H
6
;
NMR spectroscopy at 500 MHz (at 298 K). a) Complex 4; b) 2 eq. AgPF
c) 1 eq. AgPF ; d) 0.5 eq. AgPF ; e) Complex 6; f) ligand 1.
I
6
6
of 1, and the Cu complexes thereof, will be reported in due course.
Experimental section
Catalytic alkene cyclopropanation
The reactivity of complex 4 as a catalyst was investigated in a
General details
I
III
benchmark alkene cyclopropanation reaction, where Cu /Cu
NMR spectra were obtained in the solvent indicated, using a
21
1
species are believed to play an important role. With adequate con-
trols in place (entries 1 and 2, Table 2), heating ethyl diazoacetate
JEOL ECX400 or JEOL ECS400 spectrometer (400 MHz for H,
1
3
31
100 MHz for C and 162 MHz for P, respectively), a Bruker
1
13
31
9
6
in styrene (reagent and solvent) in the presence of 1 mol% of 4 at
0 C for 45 min afforded the cyclopropane 10 in a diastereomeric
500 (500 MHz, 126 MHz and 202 MHz for H, C and P,
respectively) and low temperature NMR studies were carried
◦
1
ratio of 32 : 68 and 85% overall conversion (entry 3). This compares
out on a Bruker AV700 (700 MHz and 283 MHz for H and
I
III
31
well with a recently reported Cu /Cu catalyst system for this
P respectively). Chemical shifts were referenced to the residual
22
cyclopropanation reaction. Complex 6 is a marginally superior
catalyst to 4 for this reaction (entry 4). The minor by-products of
the alkene cyclopropanation reaction, diethyl fumarate and diethyl
maleate, are formed by a well established competing reaction
undeuterated solvent of the deuterated solvent used (CHCl
3
d =
1
13
7.26 and 77.16, CDHCl
2
d = 5.31 and 53.80, H and C respec-
tively). NMR spectra were processed using MestrNova software.
We estimate that the error on the variable temperature NMR
22
◦
pathway. A stoichiometric reaction of 4 with 9 (9 : Cu, 1 : 1) in
CD Cl at ambient temperature showed no observable formation
measurements is ±1.5 C (determined by a methanol calibration
2
2
at 500 MHz). Melting points were recorded using a Stuart digital
SMP3 machine. TLC analysis was carried out on Merck TLC
aluminium sheets (silica gel 60 F254) and flash chromatography
run on silica gel 60. IR spectroscopy was undertaken using
a Jasco/MIRacle FT/IR-4100typeA spectrometer on the neat
1
of either diethyl maleate or diethyl fumarate after 1 h (by H NMR
spectroscopy). After 24 h a small amount of these products was
observable. However, under ‘catalytic’ conditions (4 : 9, 1 : 100), in
the absence of styrene, an 80% conversion to diethyl fumarate
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Table 3 Single crystal XRD data
2
9
30
31
Compound reference
Chemical formula
Formula Mass
ijf0821m (1)
ijf0829a (4)
ijf0825m (5)
ijf1015m (6)
C
41
H
32OP
2
S
2
·2(CH
2
Cl
2
)
C
82
H
64Cu
2
O
4
P
4
S
4
·2(PF
6
)
C
82
H
64Cl
2
Cu
4
O
2
P
4
S
4
·2(PF )·
6
41 2 2 2 2
C H32Cl Cu OP S
1
.58(C
4
H
10O)·0.41(CH
2
2
Cl )
836.58
1782.47
2117.11
Triclinic
864.71
Crystal system
Monoclinic
24.539(3)
9.8002(10)
17.1991(17)
90.00
90.768(2)
90.00
4135.8(8)
110(2)
C2/c
4
15724
3666
0.0302
0.0569
0.1612
0.0679
0.1732
Monoclinic
25.838(3)
25.365(3)
14.7220(15)
90.00
Monoclinic
29.431(3)
8.9496(10)
16.2751(18)
90.00
115.307(2)
90.00
3875.4(7)
110(2)
C2/c
4
18084
4810
0.0640
0.0423
0.0954
0.0880
0.1134
a/A˚
12.0204(7)
14.5437(9)
15.1233(9)
71.942(1)
71.271(1)
66.585(1)
2246.5(2)
110(2)
b/A˚
c/A˚
◦
a/
◦
b/
97.563(2)
90.00
9564.7(17)
110(2)
P2(1)/c
4
16818
16818
0.0000
0.0828
0.1993
◦
g /
Unit cell volume/A˚
3
Temperature/K
Space group
No. of formula units per unit cell, Z
No. of reflections measured
No. of independent reflections
¯
P1
1
23138
11056
0.0218
0.0452
0.1207
0.0614
0.1305
R
int
Final R
Final wR(F ) values (I > 2s(I))
Final R values (all data)
Final wR(F ) values (all data)
1
values (I > 2s(I))
2
1
0.1422
0.2117
2
2
7
compounds, or solution IR spectra were obtained on a Nicolet
Avatar 370 FT-IR spectrometer in the solvent stated. MS spectra
were measured using a Bruker Daltronics micrOTOF machine
with electrospray ionisation (ESI) or on a Thermo LCQ using
electrospray ionisation. UV-visible spectra were recorded using a
JASCO V-560. Elemental analysis was carried out on an Exeter
Analytical CE-440 Elemental Analyser. Dry and degassed toluene,
DCM and hexane were obtained from a Pure Solv MD-7 solvent
purification system. THF and ether were either obtained from a
Pure Solv MD-7 solvent purification system and degassed by the
freeze–pump–thaw method, or dried over sodium-benzophenone
ketyl and collected by distillation. Benzene was dried over sodium-
benzophenone ketyl, and ethanol was dried and distilled from
magnesium-iodine. Nitrogen gas was oxygen free and was dried
immediately prior to use by passage through a column containing
sodium hydroxide pellets and silica. Commercial chemicals were
purchased from Sigma–Aldrich or Alfa Aesar.
solution of 2-(diphenylthiophosphino)benzaldehyde, (500 mg,
2 eq., 1.56 mmol) in THF (3 mL). To this NaOH (124 mg, 4 eq.,
3.11 mmol) dissolved in H
dropwise. The mixture was refluxed for 48 h. After cooling, the
solution was washed with saturated NH Cl(aq) (5 mL), extracted
with ethyl acetate (5 ¥ 5 mL), dried over Na SO and filtered. After
2
O (0.5 mL) and THF (1 mL) was added
4
2
3
removing the solvent in vacuo the product was recrystallised from
DCM/Hexane (1 : 3 v/v) to afford the title compound as a yellow
◦
1
solid (435 mg, 84%). M.p. 133–138 C(dec); H NMR (400 MHz,
CD Cl ) d 8.17 (d, J = 16.0 Hz, 2H, H ), 7.84–7.69 (m, 10H, H
and o-Ar), 7.64–7.57 (m, 2H, H ), 7.56–7.49 (m, 4H, p-Ar), 7.49–
7.41 (m, 8H, m-Ar), 7.34 (tdd, J = 7.5, 2.3, 1.3 Hz, 2H, H ), 7.09
(ddd, J = 14.5, 8.0, 1.0 Hz, 2H, H ), 6.48 (d, J = 16.0 Hz, 2H, H );
) d 188.6 (C O), 141.5 (d, J = 8 Hz,
), 133.9 (d, J = 83 Hz, ipso-C), 133.4 (d,
), 132.7 (d, J = 11 Hz, o-Ar), 132.5 (d, J = 85, ipso-C),
132.4 (d, J = 3 Hz, C ), 132.2 (d, J = 3 Hz, p-Ar), 129.6 (d, J =
12 Hz, C ), 129.0 (d, J = 13 Hz, m-Ar), 128.8 (d, J = 10 Hz, C ),
126.8 (C ) d 42.07 (s); HRMS (ESI)
2
2
c
e
f
g
h
b
1
3
C NMR (100 MHz, CD
), 138.9 (d, J = 7 Hz, C
J = 11 Hz, C
2
Cl
2
C
c
d
h
f
Diffraction data were collected at 110 K on a Bruker Smart
g
e
3
1
˚
Apex diffractometer with Mo-Ka radiation (l = 0.71073 A)
b
); P NMR (162 MHz, CDCl
3
+
using a SMART CCD camera. Diffractometer control, data
collection and initial unit cell determination was performed using
m/z [MNa] 689.1266 (calculated for C41
H
32NaOP
2
S : 689.1262);
2
+
+
LRMS (ESI) m/z (rel.%) 689.1 [MNa] (100), 667.1 [MH] (3);
IR (solid, n cm ): 3053 (w), 1656 (w), 1619 (w), 1602 (w), 1460
(w), 1436 (m), 1184 (w), 1098 (m), 753 (m), 711 (s), 692 (s), 636
) lmax nm: 318 (e = 19513
.1/10CH Cl (675)
C 73.10, H 4.81; Observed C 73.32, H 4.83. Elemental analysis
was conducted on crystals used for the XRD analysis.
2
3
-1
“
SMART”. Frame integration and unit-cell refinement software
24
was carried out with “SAINT+”. Absorption corrections were
applied by SADABS (v2.10, Sheldrick). Structures were solved
by direct methods using SHELXS-97 and refined by full-matrix
least squares using SHELXL-97. All non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were placed using a
(s), 614 (m), 575 (m); UV-vis (CH
mol dm cm ); Anal. Calcd. for C41
2
Cl
H
2
25
-1
3
-1
32OP
2
S
2
2
2
“
riding model” and included in the refinement at calculated
positions, except for the alkene hydrogens in 5 and 6 which were
located by difference map. Important X-ray details are collated in
Table 3.
Cu(1)PF
6
(solvent) (4)
28
A solution of Cu(MeCN)
dry, degassed CH Cl (5 mL) was added by cannula to a solution
of ligand 1 (300 mg, 1 eq., 0.45 mmol) in dry, degassed CH Cl
4
PF
6
,
(168 mg, 1 eq., 0.45 mmol) in
2
2
2
2
◦
(
1E,4E)-1,5-bis(2-(diphenylphosphorothioyl)phenyl)pent-an-1,4-
(10 mL).‡ The resulting solution was stirred for 2 h at 20 C.
dien-3-one (1)
‡
The reaction was also carried out in THF. The product precipitated
[
3-(Diethoxy-phosphoryl)-2-oxo-propyl]-phosphonic acid diethyl
overnight and the resulting yellow crystals were collected by filtration
(48%).
26
ester (256 mg, 1 eq., 0.776 mmol) was added to a stirring
3
700 | Dalton Trans., 2011, 40, 3695–3702
This journal is © The Royal Society of Chemistry 2011

View Article Online
CH
2
Cl
2
was removed in vacuo to give a concentrated solution
for supporting a University Research Fellowship (I.J.S.F), and
EPSRC for a DTA award (A.G.J.). We thank Astra-Zeneca for
unrestricted research funding 2007–10 (Dr David Hollinshead).
(
4 mL) and layered with dry, degassed toluene (5 mL) to afford
yellow crystals (270 mg, 69%) separated by filtration. M.p. 200
◦
1
C(dec); H NMR (400 MHz, CD
2
Cl ) d 8.20–7.26 (br m, ~56H),
2
6
2
-
.98 (dd, J = 15.0, 7.5 Hz, 4H), 6.52 (br s, 2H), 6.21 (br s,
Notes and references
3
1
H); P NMR (162 MHz, CD
143.80 (hept, JPF = 711 Hz); C NMR (126 MHz, CD
2
Cl ) d 46.43 (br s), 40.59 (br s),
2
1
For an excellent review detailing various transition metal complexes
bearing a dba-H ligand(s), see: A. Z. Rubezhov, Russ. Chem. Rev.,
1988, 57, 1194–1207.
1
3
2
Cl )
2
observed signals – C O not observed d 137.8 (d, J = 8 Hz), 136.4,
1
1
36.1, 134.8–134.3 (m), 134.0–132.1 (m), 131.1 (d, J = 14 Hz),
31.0–130.8 (m), 130.6–129.9 (m); HRMS (ESI) m/z 729.0708
2 (a) H. B. Lee and P. M. Maitlis, J. Organomet. Chem., 1973, 57, C87–
C89; (b) J. A. Ibers, J. Organomet. Chem., 1974, 73, 389–400.
3
S. Bern e` s, R. A. Toscano, A. C. Cano, O. G. Mellado, C. Alvarez-
Toledano, H. Rudler and J.-C. Daran, J. Organomet. Chem., 1995, 498,
15–24.
-
1
(
(
(
calculated for C41
m), 1457 (m), 1438 (m), 1312 (w), 1170 (w), 1103 (m), 836 (s), 691
H
32OP
2
S Cu: 729.0660); IR (solid, n cm ): 1652
2
-
1
3
-1
4 (a) C. Alvarez-Toledano, E. Delgado, B. Donnadieu, E. Hernandez,
G. Martin and F. Zamora, Inorg. Chim. Acta, 2003, 351, 119–122;
s); UV-vis (CH
2
Cl
2
) lmax nm: 320 (e = 18345 mol dm cm );
(Cu (1) PF ) C 56.26, H 3.69, N
.00; Observed C 56.61, H 4.02, N 0.20.
Crystals of [Cu (1) (m-OH ]2PF (4) suitable for XRD analysis
were obtained by layering CH Cl with Et O, along with crystals
of [Cu Cl (1) ]2PF (5) presumably formed in the presence of trace
HCl or chloride abstraction of CH
Anal. Calcd. for C82
0
H
64Cu
4
F
12
P
6
2
2
6
(
b) F. Ortega-Jimenez, M. C. Ortega-Alfaro, J. G. Lopez-Cortes, R.
Gutierrez-Perez, R. A. Toscano, L. Velasco-Ibarra, E. Pena-Cabrera
and C. Alvarez-Toledano, Organometallics, 2000, 19, 4127–4133; (c) S.
Rivomanana, C. Mongin and G. Lavigne, Organometallics, 1996, 15,
2
2
2
)
2
6
2
2
2
1
195–1207.
4
2
2
6
´
5
6
S. V. Osintseva, F. M. Dolgushin, N. A. Shteltser, P. V. Petrovskii, A. Z.
13
2
Cl
2
.
Kreindlin, L. V. Rybin and M. Y. Antipin, Organometallics, 2005, 24,
2
279–2288.
(a) N. W. Alcock, N. Herron, T. J. Kemp and C. W. Shoppee, Chem.
Commun., 1975, 785–786; (b) N. W. Alcock, P. Meester and T. J.
Kemp, J. Chem. Soc., Perkin Trans. 2, 1979, 921–926; (c) N. W. Alcock
and P. Meester, Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst.
Chem., 1979, B35, 609–611; (d) M. Alagar, S. Kannan, K. Rajagopal, V.
Venugopal, R. V. Krishnakumar, M. Subha Nandhini and S. Natarajan,
Acta Crystallogr., Sect. E: Struct. Rep. Online, 2004, E60, m773–m775.
(a) I. J. S. Fairlamb, Org. Biomol. Chem., 2008, 6, 3645–3656; (b) I.
J. S. Fairlamb and A. F. Lee, Organometallics, 2007, 26, 4087–4089;
(c) I. J. S. Fairlamb, A. R. Kapdi and A. F. Lee, Org. Lett., 2004, 6,
Cu
2
Cl
2
(1) (6)
In a glove box, ligand 1 (125 mg, 1 eq., 0.188 mmol) was
dissolved in dry, degassed CH
2
Cl
2
(7 mL) and CuCl (37 mg, 2 eq.,
◦
0
.375 mmol) was added. After stirring for 1 h at 23 C, more
CH
2
2
Cl (2 mL) was added to dissolve the last traces of CuCl
7
and the reaction stirred overnight, until no solid remained. Half
the solvent was removed in vacuo, and the concentrated solution
left overnight. The precipitate was filtered, washed with pentane
4
435–4438; (d) Y. Mac e´ , A. R. Kapdi, I. J. S. Fairlamb and A. Jutand,
Organometallics, 2006, 25, 1785–1800; (e) I. J. S. Fairlamb, A. R. Kapdi,
A. F. Lee, G. P. McGlacken, F. Weissburger, A. H. M. de Vries and L.
Schmieder-van de Vondervoort, Chem.–Eur. J., 2006, 12, 8750–8761;
(f) P. Sehnal, H. Taghzouti, I. J. S. Fairlamb, A. Jutand, A. F. Lee and
A. C. Whitwood, Organometallics, 2009, 28, 824–829.
(
(
5 mL) and dried in vacuo to give a yellow crystalline product
119 mg, 73%). The solid was stored in a glove-box. M.p. 223
◦
1
C
(dec); H NMR (400 MHz, CD
2
Cl
2
) d 7.83–7.79 (m, 2H, H
and Ar), 7.37–7.31
), 6.92 (ddd, J = 14.5, 7.5, 1.0 Hz, 2H, H ), 6.07 (d,
J = 14.0 Hz, 2H, H ), 5.83 (d (br), J = 14.0 Hz, 2H, H
NMR (100 MHz, CD Cl ) d 184.2 (C O), 139.8 (d, J = 8 Hz,
), 134.4 (d, J = 2 Hz, C ), 133.9 (d, J = 3 Hz, p-Ar), 133.1 (d,
J = 11 Hz, Ar), 132.9 (d, J = 11 Hz, C ), 131.8 (d, J = 85 Hz,
ipso-C), 131.6 (d, J = 9 Hz, C ), 129.6 (d, J = 13 Hz, Ar), 128.6
d, J = 13 Hz, C ), 127.2 (d, J = 86 Hz, ipso-C), 95.3 (br, C C),
e
),
7
(
.79–7.67 (m, 12H, Ar), 7.66–7.54 (m, 10H, H
m, 2H, H
f
8
9
F. A. Jal o´ n, B. R. Manzano, F. G o´ mez-de, la Torre, A. M. L o´ pez-
g
h
Agenjo, A. M. Rodrıguez, W. Weissensteiner, T. Sturm, J. Mahıa and
´
´
1
3
);
C
M. Maestro, J. Chem. Soc., Dalton Trans., 2001, 2417–2424.
c
b
(a) Y. Zhao, H. Wang, X. Hou, Y. Hu, A. Lei, H. Zhang and L. Zhu, J.
Am. Chem. Soc., 2006, 128, 15048–15049; (b) For related ligand effects,
see: Q. Liu, H. Duan, X. Luo, Y. Tang, G. Li, R. Huang and A. Lei, Adv.
Synth. Catal., 2008, 350, 1349–1354; (c) X. Luo, H. Zhang, H. Duan,
Q. Liu, L. Zhu, T. Zhang and A. Lei, Org. Lett., 2007, 9, 4571–4574;
2
2
C
d
f
h
e
(
d) W. Shi, Y. Luo, X. Luo, L. Chao, H. Zhang, J. Wang and A. Lei,
(
g
J. Am. Chem. Soc., 2008, 130, 14713–14720; (e) H. Zhang, X. Luo, K.
Wongkhan, H. Duan, Q. Li, L. Zhu, J. Wang, A. S. Batsanov, J. A. K.
Howard, T. B. Marder and A. Lei, Chem.–Eur. J., 2009, 15, 3823–3829.
3
1
9
4.4 (br, C C); P NMR (162 MHz, CD
2
Cl
2
) d 40.78 (s); LRMS
+
+
(
ESI) m/z (rel.%) 1397.2 [Cu(1)
2
+
] (29), 829.0 [M-Cl] (100), 729.1
+
10 A. Kiyomori, J.-F. Marcoux and S. L. Buchwald, Tetrahedron Lett.,
999, 40, 2657–2660.
[M-CuCl
2
] (87), 667.1 [1+H] (4); HRMS (ESI) m/z 826.9623
1
-
1
(
calculated for C41
H
32Cl Cu
2
OP
2
S
2
= 826.9645); IR (solid, n cm ):
I
2
2
4
1
1 For Cu complexes containing h -isoprene, other h -dienes and h -
isoprene, see: (a) M. J. Bainbridge, J. R. Lindsay Smith and P.
H. Walton, Dalton Trans., 2009, 3143–3152; (b) M. Hakansson, S.
Jagner and D. Walther, Organometallics, 1991, 10, 1317–1319; (c) M.
Hakansson, K. Brantin and S. Jagner, J. Organomet. Chem., 2000, 602,
1
(
653 (w), 1537 (w), 1455 (w), 1433 (m), 1312 (m), 1247 (w), 1103
m), 1084 (m), 1064 (m), 967 (m), 756 (s), 691 (s); IR (CH Cl
n cm ): 3046 (w), 1653 (w), 1539 (w), 1457 (w), 1439 (m), 1314
w), 1271 (m), 1265 (m), 1261 (m), 1106 (w); UV-vis (CH Cl
nm: 396 (e = 12199 mol dm cm ) shoulders at 326 (e = 10213
2
2
,
-
1
(
2
2
) lmax
5
–14; (d) A. Camus, N. Marish, G. Nardin and L. Randaccio, Inorg.
-
1
3
-1
Chim. Acta, 1977, 23, 131–144. There are only a handful of complexes
where crystallographic evidence shows a single Cu centre bound to two
or more alkenes from the same polyene, see: (e) B. J. Bellott and G. S.
Girolami, Organometallics, 2009, 28, 2046–2052. Several coordination
mol- dm cm ) and 258 (e = 34 000 mol dm cm ); Anal. Calcd.
for C41Cl Cu .CH Cl (949) C 53.12, H 3.61; Observed
C 53.17, H 3.58.
1
3
-1
-1
3
-1
2
2
H
32OP
2
S
2
2
2
I
polymers utilise Cu -alkene binding to stabilize large supramolecular
networks, see; (f) Q. Ye, X.-S. Wang, H. Zhao and R.-G. Xiong, Chem.
Soc. Rev., 2005, 34, 208–225; (g) For a series of HPYA (4-pyridylacrylic
acid) and 3-HPYA (3-pyridylacrylic acid) of 1D and 2D copper(I)-
alkene coordination polymers with high thermal stability, see; (h) J.
Zhang, R.-G. Xiong, X.-T. Chen, C.-M. Che, Z. Xue and X.-Z. You,
Organometallics, 2001, 20, 4118–4121.
2 B. J. Hathaway, In Comprehensive coordination chemistry (Eds) G.
Wilkinson, R. D. Gillard and J. A. McCleverty, Oxford: Pergamon,
1987, vol. 5, p. 534.
Acknowledgements
Dr Petr Sehnal is thanked for assistance with the preparation of
compound 2 and scientific discussion. Prof. P. H. Walton, Dr A.
K. Duhme-Klair and Dr J. M. Lynam are all thanked for scien-
tific discussion. The Royal Society are gratefully acknowledged
1
This journal is © The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 3695–3702 | 3701

View Article Online
I
1
3 Halide activation of CH
example, [Cu(dppm-)] reacts with both CH
E. Anson, L. Ponikiewski and A. Rothenberger, Z. Anorg. Allg. Chem.,
2
Cl
2
by Cu complexes has been reported. For
22 (a) J. Garc ´ı a-L o´ pez, V. Ya n˜ ez-Rodr ´ı guez, L. Roces, S. Garc ´ı a-Granda,
A. Mart ´ı nez, A. Guevara-Garc ´ı a, G. R. Castro, F. Jim e´ nez-Villacorta,
M. J. Iglesias and F. L o´ pez Ortiz, J. Am. Chem. Soc., 2010, 132, 10665–
10667; (b) Also see: I. V. Shishkov, F. Rominger and P. Hofmann,
Organometallics, 2009, 28, 1049–1059; (c) J. I. Garc ´ı a, G. Jim e´ nez-Os e´ s,
V. M a r t ´ı nez-Merino, J. A. Mayoral, E. Pires and I. Villalba, Chem. Eur.
J., 2007, 13, 4064–4073; (d) W. Kirmse, Angew. Chem., Int. Ed., 2003,
42, 1088–1093.
2
Cl and CH Br , see: (a) C.
2
2
2
I
2
006, 632, 2402–2404. Lui reported a series of Cu complexes with
dithiophosphates and bis(diphenylphosphino) alkane ligands, where
Cu clusters were found to react with both CH Cl or CHCl (dependant
on ligand to metal ratio), see; (b) B.-J. Liaw, T. S. Lobena, Y.-W.
Lin, J.-C. Wang and C. W. Liu, Inorg. Chem., 2005, 44, 9921–9929.
We suspect that the source of chloride is most likely trace HCl in
2
2
3
23 Smart diffractometer control software (v5,625), Bruker-AXS, Bruker
CH
4 (a) C. G. Pierpont and M. C. Mazza, J. Chem. Soc. Chem. Commun.,
973, 207; (b) M. Ogasawara, K. Yoshida, H. Kamei, K. Kato, Y.
Uozumi and T. Hayashi, Tetrahedron: Asymmetry, 1998, 9, 1779–
2 2
Cl .
AXS GmbH, Karlsruhe, Germany.
1
24 Saint+ (v6.22) Bruker AXS, Bruker AXS GmbH, Karlsruhr, Germany.
25 G. M. Sheldrick, SHELXS-97, Program for solution of crystal struc-
tures, University of G o¨ ttingen, Germany, 1997.
26 B. Corbel, L. Medinger, J. P. Haelters and G. Strutz, Synthesis, 1985,
1048–1051.
27 A. Maraval, G. Magro, V. Maraval, L. Vendier, A. M. Caminde and J.
–P. Majoral, J. Organomet. Chem., 2006, 691, 1333–1340.
28 G. J. Kubas, Inorg. Synth., 1979, 19, 90–92.
29 The crystals contained disordered solvents, presumably a mixture of
dichloromethane and diethyl ether which could not be modelled as
1
1
787; (c) K. Selvakumar, M. Valentini, M. W o¨ rle and P. S. Pregosin,
Organometallics, 1999, 18, 1207–1215.
1
1
5 Y. Takemura, T. Nakajima and T. Tanase, Dalton Trans., 2009, 10231–
1
0243.
6 (a) G. A. van Albada, I. Mutikainen, O. Roubeau, U. Turpeinen and
J. Reedijk, Inorg. Chim. Acta, 2002, 331, 208–215; (b) S. Balboa, R.
Carballo, A. Casti n˜ eiras, J. M. Gonz a´ lez-P e´ rez and J. Nicl o´ s-Guti e´ rrez,
Polyhedron, 2008, 27, 2921–2930; (c) Y.-Q. Zheng and J.-L. Lin, Z.
Anorg. Allg. Chem., 2002, 628, 203–208.
discrete atoms. Therefore the SQUEEZE algorithm was used to account
for the solvent. The solvent void was measured to be 1469 A˚ 3 and 776
1
1
7 E. W. Ainscough, H. A. Bergen, A. M. Brodie and K. A. Brown, J.
Chem. Soc., Dalton Trans., 1976, 1649–1656.
electrons were attributed to the solvent. Since this is due to a mixture
of solvents, it is not possible to determine the overall formula, formula
weight or density for the crystals. It is assumed that the oxygen ligands
bound to the copper are water molecules, but suitable locations for the
hydrogens could not be determined and so these were omitted.
1
8 The variable temperature H NMR spectra of complex 4 reveal sharp
signals for the alkene protons. However, we suspect that another
unidentifiable species is present as the proton integrals are not perfect.
Further spectroscopic analysis is also complicated by the phosphorus
phenyl groups moving toward inequivalence at lower temperatures (also
see ESI†).
30 The crystals contained a mixture of disordered solvents. Relative
occupancy of each solvent was allowed to refine; overall occupancy
was restrained to be 1.0. The solvents were modelled as a diethyl
ether (79.4%) [with one terminal carbon disordered over two sites (C42
and C42a)] and a dichloromethane disordered over two sites (7.2%
1
2
9 C.-S. Chen and W.-Y. Yeh, Chem. Commun., 2010, 46,
3
098–3100.
0 gNMR software package (version 5.1, P. H. M. Budze-
laar, Department of Chemistry, University of Manitoba), see:
http://home.cc.umanitoba.ca/~budzelaa/gNMR/gNMR.html (last
accessed 19/11/2010).
and 13.4%). All solvent atoms were modelled isotropically. Within the
solvents, C–C bonds were restrained to be 1.51 A˚ , C–O bonds to 1.425
A˚ and C–Cl to 1.728 A˚ .
31 There is a small void in the model (volume 31 A˚ ). However, the largest
3
peak in the difference map in the void is only 0.62 e A˚ - , so the space is
1
2
1 H. Lebel, J.-F. Marcoux, C. Molinaro and A. B. Charette, Chem. Rev.,
2
003, 103, 977–1050.
assumed to be empty.
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702 | Dalton Trans., 2011, 40, 3695–3702
This journal is © The Royal Society of Chemistry 2011