Binaphthol-based diphosphite ligands in asymmetric nickel-catalyzed hydrocyanation of styrene and 1,3-cyclohexadiene: Influence of steric properties

Article abstract of DOI:10.1002/adsc.200600315

A series of chiral (R)-binaphthol-based diphosphite ligands with different substituents was prepared and applied in the asymmetric nickel-catalyzed hydrocyanation of styrene and 1,3-cyclohexadiene to investigate the influence of their steric properties. The optimum steric properties for the hydrocyanation reaction lie within a narrow window. With the optimized ligand, hydrocyanation of styrene gave full conversion (Subs/Ni = 100) with 49% ee, the TON was determined to be 600. Hydrocyanation of 1,3-cyclohexadiene gave 50% conversion (Subs/Ni = 500) with an excellent ee of 86 %. This demonstrates that high ees are not only accessible for vinylarenes but also for conjugated dienes in the asymmetric nickelcatalyzed hydrocyanation.

Full text of DOI:10.1002/adsc.200600315

FULL PAPERS
DOI: 10.1002/adsc.200600315
Binaphthol-Based Diphosphite Ligands in Asymmetric Nickel-
Catalyzed Hydrocyanation of Styrene and 1,3-Cyclohexadiene:
Influence of Steric Properties
a
a
a
b
b
Jos Wilting, Mich›le Janssen, Christian Müller, Martin Lutz, Anthony L. Spek,
a,
and Dieter Vogt *
a
Laboratory of Homogeneous Catalysis, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
Fax : (+31)-40-245-5054; e-mail: D.Vogt@tue.nl
Crystal and Structural Chemistry, Utrecht University, 3584 CH Utrecht, The Netherlands
b
Received: June 29, 2006; Published online: January 8, 2007
Supporting information for this article is available on the WWW under http://asc.wiley-vch.de/home/.
Abstract: A series of chiral (R)-binaphthol-based di- clohexadiene gave 50% conversion (Subs/Ni=500)
phosphite ligands with different substituents was pre- with an excellent ee of 86%. This demonstrates that
pared and applied in the asymmetric nickel-catalyzed high ees are not only accessible for vinylarenes but
hydrocyanation of styrene and 1,3-cyclohexadiene to also for conjugated dienes in the asymmetric nickel-
investigate the influence of their steric properties. catalyzed hydrocyanation.
The optimum steric properties for the hydrocyana-
tion reaction lie within a narrow window. With the
optimized ligand, hydrocyanation of styrene gave full Keywords: conjugated dienes; diphosphite ligands;
conversion (Subs/Ni=100) with 49% ee, the TON hydrocyanation; hydrogen cyanide; nickel; vinylar-
was determined to be 600. Hydrocyanation of 1,3-cy- enes
Introduction
Table 1. Literature overview of the asymmetric hydrocyana-
tion of vinylarenes.
The production of adiponitrile from butadiene and
hydrogen cyanide is an important homogeneous
Entry Substrate
Temp [8C] Yield [%] ee [%] Ref.
[
1]
[4]
nickel-catalyzed process in industry. Since the first
report on asymmetric hydrocyanation of norborn-
1
2
3
4
5
6
7
8
9
1
1
Styrene
Styrene
Styrene
Styrene
4-MeStyrene 100
4-MeStyrene 25
4-i-BuStyrene 60
25
60
100
20
nd
22
100
5
100
nd
65
42
51
65
41
70
63 (S)
57 (S)
30 (S)
91 (S)
95 (R)
[5]
[
2]
[6]
A
C
H
T
R
E
U
N
G
(adi)ene by Elmes and Jackson in 1979, accounts on
[
[
[
[
6]
6]
7]
5]
asymmetric hydrocyanation of carbon-carbon double
bonds have occasionally appeared in literature.
Table 1 shows an overview regarding the asymmetric
40
[
3]
hydrocyanation of vinylarenes (Scheme 1).
[7]
[5]
[7]
[8]
4-i-BuStyrene 25
100
100
100
100
RajanBabu and Casalnuovo discussed the impor-
tance of the electronic properties of the ligand in the
[a]
MV
N
60
0
0
[a]
0
1
MVN[
[
7]
a]
asymmetric hydrocyanation of MVN. It was shown
earlier that chelating p-acceptor ligands with a high
binding affinity to Ni(0) can lead to very stable nickel
bis-chelate complexes, decreasing the catalytic activi-
MVN
[a]
MVN=6-methoxy-2-vinylnaphthalene.
[9]
ty. All studies show that finding a suitable ligand
system is rather tedious and ꢀfine tuningꢁ is necessary
in order to obtain both high conversion and high enan-
tioselectivity. Thus, we investigated a modular ligand
suitable for modification on several positions. In this
report we focus on chiral (R)-binaphthol-derived di-
phosphite ligands with sterically different substituents Scheme 1. Asymmetric hydrocyanation of vinylarenes.
350
ꢂ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2007, 349, 350 – 356

Asymmetric Nickel-Catalyzed Hydrocyanation of Styrene and 1,3-Cyclohexadiene
FULL PAPERS
in order to prevent the formation of inactive bis-che-
lates but maintain at the same time catalytic activity.
Results and Discussion
Ligand Synthesis and Catalysis
Binaphthol is a common and relatively cheap chiral
building block, and therefore attractive for the syn-
thesis of chiral ligands. (R)-[1,1’]-Binaphthalenyl-2,2’-
bis(diaryl phosphite) is a modular ligand, which has
been applied in the asymmetric hydroformylation of
[10]
[11]
vinyl acetate
and aryl vinyl ethers.
Reaction of
2
2
equivalents of ortho-substituted phenols (phenol,
-methylphenol, 2-isopropylphenol, 2-([1,3]-dioxan-2-
yl)-phenol, 2-tert-butylphenol) with PCl in the pres-
3
ence of NEt and subsequently with 0.5 equivalents of
3
(
R)- [1,1’]-binaphthalenyl-2,2’-diol gave a set of the 5
diphosphite ligands L1–L5 (Figure 1).
The complexes L3Ni
Figure 2. Molecular structure of L3PtCl (ORTEP represen-
tation at 50% probability level, solvent molecules and hy-
(cod) and L3PtCl were stud- drogen atoms have been omitted for clarity).
2
A
H
R
U
G
2
ied in order to gain insight into the three-dimensional
structure of the ligand. In solution these complexes
1
show C symmetry as can be seen from the H NMR
2
31
(
Figure 3) and P NMR spectra. L3Ni(cod) displays a
A
H
R
U
G
singlet at 147.8 ppm and L3PtCl a singlet at 57.2 ppm
2
1
with platinum satellites ( J =5782 Hz), which indi-
Pt,P
cates high symmetry. Crystals suitable for X-ray dif-
fraction were obtained by slow recrystallization of
L3PtCl from CH CN/CH Cl at À308C. Figure 2 il-
2
3
2
2
lustrates the molecular structure of L3PtCl in the
2
solid state and indicates a distorted C symmetry in
2
contrast to the structure in solution (for bond distan-
ces and angles see Supporting Information).
Hydrocyanation of styrene with 1.1 equivalents of
1
ligand and nickel(0)bis(1,5-cyclooctadiene) [Ni
A
H
R
U
G
2
2
3
in toluene at 608C with HCN, reveals a difference in
conversion of 100% among these 5 catalyst systems.
It was found that Ni/L3 and Ni/L4 perform best in
terms of conversion and enantioselectivity (Table 2).
The reaction is completely selective towards the
A
H
R
U
Table 2. Asymmetric hydrocyanation of styrene with ligands
L1–L5.
[a]
branched product, a-methylbenzyl nitrile. However, Ligand
L1
L2
L3
L4
L5
the mass balance shows that some polymerization (up
to 5%) of styrene occurs as well.
1
R
H
<1
nd
Me
6
3
i-Pr
90
12
C H O
100
43
t-Bu
<1
nd
4
7
2
Conv. [%]
ee [%]
[a]
Conditions: Ni/L/styrene/HCN=1/1.1/100/200 in 1.2 mL
toluene at 608C for 4 h. nd=not determined.
Electronic and Steric Effects
It has been shown that the relative rate of reductive
elimination over b-hydride elimination increases
when the electron density on phosphorus is reduced
[7]
by electron-withdrawing groups on the ligand.
Moreover, the diphosphinite ligand containing elec-
Figure 1. Ligands L1–L5.
Adv. Synth. Catal. 2007, 349, 350 – 356
ꢂ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.asc.wiley-vch.de
351

Jos Wilting et al.
FULL PAPERS
tron-withdrawing CF groups in the meta positions is Table 3. ATR IR frequencies of the A
and B vibrations of
1
3
1
[a]
CO in (L)Ni(CO)2.
electronically comparable to diphosphite ligands,
based on the infrared frequencies of the A1
1
2
2
À1
À1
Ligand
R
R , Rꢁ
A [cm ]
B [cm ]
À1
À1
1
1
(
(
2038 cm ) and B (1987 cm ) vibrations of CO in
1
L)Ni(CO)2 complexes. This CF -diphosphinite L1
H
Me
H, H
H, H
H, H
H, H
H, H
2042
2040
2041
2044
2049
1990
1986
1987
1990
2001
3
system, reported by RajanBabu et al., performed best L2
L3
L4
L5
i-Pr
C H O
2
in the hydrocyanation of 6-methoxy-2-vinylnaphtha-
lene in terms of activity and enantioselectivity.
4
7
t-Bu
Ligands L1 to L5 show only a small difference in
[
12,13]
[a]
the Tolman electronic parameter (u)
(Table 3),
10 mg (0.036 mmol) Ni
A
H
R
U
G
2
which provides evidence that the differentiation in
catalysis should be solely attributed to the steric bulk
on the ortho positions of the ligands. The 5 ligands co-
ordinate in a bidentate fashion, as monodentate coor-
were dissolved in 2 mL toluene. The slightly yellow solu-
tion was bubbled with CO for 30 s, during which the solu-
tion turned colorless. All volatiles were removed under
vacuum and the remaining solid was used in the ATR IR
measurement.
dination would form the complex (L)Ni(CO) , which
3
À1 [12]
would give an IR CO vibration at ~2085 cm .
Furthermore, nickel bis-chelates have been identi-
fied as inactive systems in hydrocyanation reac-
3
1
1
Table 4. P{ H} NMR data of (L)Ni
C D
A
H
R
U
G
[7,9,14,15]
6
6
tions;
the formation of bis-chelates is likely to
be dependent on the steric bulk of the ligand. NMR Ligand
L1
L2
L3
L4
L5
experiments were carried out in which 1 and 3 equiva-
1
R
(
(
H
Me
i-Pr
C H O
2
t-Bu
145.4 (br)
-
4
7
lents of ligand L1–L5 were mixed with Ni
A
H
R
U
G
[a]
L)Ni
L) Ni
A
H
R
U
G
148.0 147.9 147.8 148.0
137.7 133.8
258C (Table 4). The bis-chelate complex was only ob-
[b]
-
-
2
served for ligands L1 and L2. It should be mentioned
here that not all bis-chelates are inactive in hydrocya-
nation reactions; possible ligand exchange for a sub-
strate molecule would give a catalytically active spe-
cies. We therefore decided to test ligands L2, L3 and
L5 in a closely related reaction, the isomerization of
[
a]
5
mg (0.018 mmol) Ni
A
H
R
U
G
were dissolved in 0.75 mL C D .
5
were dissolved in 0.75 mL C D .
6
6
[b]
mg (0.018 mmol) Ni
A
H
R
U
G
6
6
2
-methyl-3-butenenitrile to 3-pentenenitrile with 1
To stay within the active window but change the
[
16]
and 3 equivalents of ligand.
showed comparable rates (TOF=78 and 74 h , re- para position of the phenol or in the 3 and 3’ position
spectively) with 1 equiv. of ligand, whereas L5 gave of the BINOL fragment. As the binaphthol unit bears
Ligands L2 and L3 ligand significantly, modifications can be made in the
À1
À1
no activity. With 3 equivs., L2 is slower (36 h ) while the stereogenic element (atropisomeric axis) of the li-2
À1
the rate of L3 increased slightly (85 h ). Thus, forma- gands we decided to change the 3 and 3’ positions, R
2
’
tion of bis-chelates alone cannot explain the striking and R (Figure 4). Consecutive protection, lithiation,
difference observed in the hydrocyanation of styrene. methylation and deprotection steps were performed
Recent studies on the steric and electronic effect in order to obtain the substituted binaphthol deriva-
on the reductive elimination from palladium com- tives, similar to the route reported by Dennis and
[
20]
plexes show a small steric effect as compared to the Woodward. These two substituted binaphthols were
[17–19]
electronic effect.
We believe that the steric bulk converted into the diphosphites L6–L9 by reaction
not only prevents the formation of bis-chelates with with the phosphochloridites, which were derived in
ligands L3–L5 but also has an effect on either the rate situ from PCl3 and 2-isopropylphenol or 2-[1,3]-
of reductive elimination or on the rate of deactiva-
tion. This would explain the fact that these systems
become more efficient in the hydrocyanation of sty-
rene (in conversion and enantioselectivity) with in-
creasing steric bulk. However, this system also shows
that there is only a small window in steric bulk, as too
1
bulky ligands such as L5 (R =t-Bu) are inactive in
the hydrocyanation of styrene. We found no evidence
of different coordination behavior of L5, which could
have explained why the catalytic system Ni/L5 is not
active. In fact, all complexes (L)Ni
corresponding species (L)Ni(styrene) on addition of
A
H
R
U
G
AHCTREUNG
an excess of styrene, as indicated by NMR spectrosco-
py.
Figure 4. Ligands L6–L9.
352
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ꢂ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2007, 349, 350 – 356

Asymmetric Nickel-Catalyzed Hydrocyanation of Styrene and 1,3-Cyclohexadiene
FULL PAPERS
Table 5. Asymmetric hydrocyanation of styrene with Ni/
ACHTUNG-
[a]
T
R
E
U
N
G
(L6–L8).
Ligand
L5
L7
L8
L9
1
R
i-Pr
H, Me
19
i-Pr
Me, Me
86
0
C H O
H, Me
100
C H O
2
Me, Me
100
4
7
2
4
7
1
2’
R , R
Conv. [%]
ee [%]
33
34
13
Scheme 2.
[
a]
Conditions: Ni/L/styrene/HCN=1/1.1/100/200 in 1.2 mL
toluene at 608C for 4 h.
identical. Hydrocyanation of 1,3-cyclohexadiene is se-
lective towards 2-cyclohexene-1-carbonitrile
Scheme 2), some isomerization towards 3-cyclohex-
ene-1-carbonitrile is observed after full conversion
(
Table 6. Asymmetric hydrocyanation experiments with li-
gands L4 and L8.
[a]
[
23]
but no dinitriles were observed. Ligand L8 gives an
Entry Substrate
T [8C] L4
L8
excellent enantioselectivity of 86% in the hydrocya-
[
24,25]
(
Conv. [ee]) (Conv. [ee]) nation of 1,3-cyclohexadiene at 08C.
Not all cyclic
dienes react with high selectivity, though. When 1,3-
cyclooctadiene was applied as substrate three prod-
ucts were observed in the GC chromatogram, which
were identified by GC-MS and COSY NMR as 1-, 2-
and 3-cyclooctene-1-carbonitrile (Scheme 2).
In all hydrocyanation experiments, in which the cat-
alyst was active, cyclooctenenitriles were observed as
hydrocyanation products from 1,5-cyclooctadiene
1
2
3
4
5
6
7
8
9
Styrene
Styrene
Styrene
4-MeStyrene
trans-b-MeStyrene 60
60
0
100 [43]
69 [47]
nd
100 [54]
nd
nd
100 [43]
nd
100 [34]
100 [49]
9 [53]
100 [50]
24 [30]
100 [33]
100 [63]
53 [71]
45 [86]
À30
0
Piperylene
60
80
60
0
[
[
[
b]
c]
c]
Cyclohexadiene
Cyclohexadiene
Cyclohexadiene
nd
using Ni(cod) as metal precursor. This observation is
A
H
R
U
G
2
[
a]
different from the report by Casalnuovo and Rajan-
Babu, in which no cyclooctenenitriles were detected.
Based on this observation and the fact that their sub-
strate, 6-methoxy-2-vinylnaphthalene, does not ex-
Conditions:
.2 mL toluene for 4 h.
Acetone cyanohydrin was used as HCN source.
Ni/substrate=1/500.
Ni/L/substrate/HCN=1/1.1/100/200
in
1
[
[
b]
b]
change with 1,5-cyclooctadiene in (L)Ni
argue that the catalysis proceeds via (L)Ni(CN)H
stage V in Figure 5). In the catalytic system with
dioxan-2-yl-phenol in the presence of NEt . Ligands ligand L8 we first see formation of (L)Ni(cod), show-
L6–L9 (Figure 4) were applied in the nickel-catalyzed ing two doublets in the P NMR at 149.1 and 145.5
hydrocyanation of styrene (Table 5). with J =27.8 Hz. (L)Ni(styrene) is formed upon ad-
A
H
R
U
G
(
AHCTREUNG
3
3
1
AHCTREUNG
PP
All ligands (L1–L9) are C symmetric while ligands dition of 50 equivalents of styrene but (L)Ni
A
H
R
U
G
2
L6 and L8 have C -symmetry. Because ligands L4 and
1
L8 performed best, they were further investigated in
additional hydrocyanation experiments, in which tem-
perature and substrate were varied (Table 6).
With the best system (L8) we managed to run hy-
drocyanation experiments at 08C with full conversion
of the substrate styrene and 4-methylstyrene, the
enantioselectivity is promising but needs to be im-
proved. At 608C the TON was determined to be 603
from an experiment with a styrene to nickel ratio of
1000. trans-b-Methylstyrene also reacts with excellent
regioselectivity (>99%) towards a-ethylbenzyl ni-
trile.
Hydrocyanation of dienes like butadiene give dif-
ferent products for the 1,2- and 1,4-addition; hydro-
cyanation of butadiene results in formation of
2
-methyl-3-butenenitrile (1,2 product) and 3-pentene-
[
21,22]
nitrile (1,4 product). However, piperylene
and
[
23]
1,3-cyclohexadiene
react via a symmetrical allyl Figure 5. Catalytic cycle for Ni(0)-catalyzed hydrocyanation
system which causes the 1,2- and 1,4-products to be of styrene.
Adv. Synth. Catal. 2007, 349, 350 – 356
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www.asc.wiley-vch.de
353

Jos Wilting et al.
FULL PAPERS
31
1
Figure 6. P{ H}VT NMR of L8Ni(cod) and 50 equivs. styrene in toluene-d .
A
H
R
U
G
8
still present, even at elevated temperatures. Figure 6 PerSeptive Biosystems Voyager-DE PRO spectrometer. Ele-
3
1
1
mental analysis was performed on a Perkin–Elmer 2400 ap-
paratus. IR spectra were recorded on an Avatar 360 FT-IR
instrument in ATR mode.
shows the variable temperature (25-908C) P{ H}-
NMR spectra in which (L8)Ni(cod) with two doublets
at 149.1 and 145.5 ppm can be detected together with
the diastereoisomers of (L8)Ni(styrene) around
42 ppm, which show an increase in exchange at
AHCTREUNG
Caution! HCN is a highly toxic, volatile liquid (bp 278C)
that is also susceptible to explosive polymerization in the
presence of base catalysts. It should be handled only in a
well-ventilated fume hood and by teams of at least two tech-
nically qualified persons who have received appropriate
medical training for treating HCN poisoning. Sensible pre-
cautions include having available proper first aid equipment
as well as HCN monitors. Uninhibited HCN should be
stored at a temperature lower than its melting point
AHCTREUNG
1
higher temperatures. These two observations, the hy-
drocyanation of cyclooctadiene and the presence of
(
L)Ni
via stage II, an h -coordinated substrate complex
Figure 5).
A
C
H
T
R
E
U
N
G
(styrene), suggests that this reaction proceeds
2
(
(
À138C). Excess of HCN may be disposed by addition to
aqueous sodium hypochlorite, which converts the cyanide to
cyanate.
Conclusions
The steric parameter is equally important as the elec-
tronic effect in the hydrocyanation of vinylarenes. By
controlling the steric properties, the ligand can be
tuned not to form bis-chelates, while maintaining ac-
General Procedure for Ligands L1–L9
The appropriate phenol (14.0 mmol) and Et N (6 mL,
3
4
3.00 mmol) were added dropwise at À108C to a solution of
tivity in the hydrocyanation of vinylarenes and PCl (0.95 g, 6.99 mmol) in 200 mL of toluene and the mix-
3
(
cyclic)-1,3-dienes. Moderate enantioselectivities were ture was stirred for 30 min. The (R)-binaphthol derivative
obtained for styrene (53%) and 4-methylstyrene (1.00 g, 3.50 mmol) dissolved in 10 mL of THF was added
˚
dropwise to the mixture at À10 C. The mixture was stirred
(
54%). Hydrocyanation of 1,3-cyclohexadiene proved
to be selective to 2-cyclohexene-1-carbonitrile with
6% ee. In this ligand system the catalytic active
for 1 h at room temperature. Salts were filtered off over a
short pad of basic alumina (4 cm) and all volatiles were
evaporated.
8
steric window seems to be narrow. Several modifica-
tions to the ligand are possible which ultimately can
lead to high enantioselectivities.
General Procedure for the Hydrocyanation
Experiments
A solution of 1.1 equivs. (0.020 mmol) of ligand in 500 mL of
toluene was added to 5 mg (0.018 mmol) Ni(cod) in a glove-
A
H
R
U
G
2
Experimental Section
box (N atmosphere). From this stock solution 200 mL were
2
added with an Eppendorf pipette to a 15 mL reaction
Schlenk tube equipped with a Teflon coated stirring bar fol-
lowed by 500 equivs. (350 mL, 3.65 mmol) of 1,3-cyclohexa-
diene. A round-bottom Schlenk flask was filled with 1 mL
toluene and 100 mL hydrogen cyanide, which was taken up
in a 5 mL syringe and added to the reaction mixture by sy-
ringe pump in 2 h (closed system). The mixture was stirred
Chemicals were purchased from Aldrich, Acros or Merck
and used as received. Styrene and 4-methylstyrene were dis-
tilled over CaH prior to use. All preparations were carried
2
out under an argon atmosphere using standard Schlenk
[26]
[27]
[28]
techniques. Ni
A
C
H
T
R
E
U
N
G
(cod) , PtCl (cod) and HCN were syn-
A
T
E
N
2
2
thesized according to literature procedures. NMR spectra
were recorded on a Varian Unity Inova 500 (VT NMR), for another 2 h, after which it was cooled to 08C and flushed
1
13
1
Mercury 400 and Mercury 200 spectrometer ( H, C{ H},
with a gentle stream of argon for 1 min to remove traces of
HCN. The reaction product was then analyzed by GC. The
31
1
P{ H}). Maldi-TOF mass spectroscopy was performed on a
354
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ꢂ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2007, 349, 350 – 356

Asymmetric Nickel-Catalyzed Hydrocyanation of Styrene and 1,3-Cyclohexadiene
FULL PAPERS
second enantiomer on the chiral GC trace, for all products,
is the enantiomer in excess.
(Ed.: G. Dyker), Wiley-VCH, Weinheim, 2005, Vol. 1,
pp 87–96.
[
4] J. E. Babin, G. T. Whiteker, Asymmetricsyntheses using
optically active metal-ligand complex catalysts. US
Patent 5,360,938, 1994.
Isomerization of 2-Methyl-3-butenenitrile to 3-Pen-
tenenitrile
[
[
[
[
[
5] W. Goertz, P. C. J. Kamer, P. W. N. M. Van Leeuwen, D.
A
(
(
solution of 1 equiv. (0.018 mmol) or 3 equivs.
0.054 mmol) of L in 2.0 mL of toluene was added to 5 mg
0.018 mmol) Ni(cod) in a Schlenk tube and the mixture
Vogt Chem. Eur. J. 2001, 7, 1614–1618.
6] M. Yan, Q. Y. Xu, A. S. C. Chan, Tetrahedron: Asym-
metry 2000, 11, 845–849.
7] A. L. Casalnuovo, T. V. RajanBabu, T. A. Ayers, T. H.
Warren, J. Am. Chem. Soc. 1994, 116, 9869–9882.
8] T. V. Rajanbabu, A. L. Casalnuovo J. Am. Chem. Soc.
ACHTREUNG
2
was stirred for 5 min. To this solution 0.5 mL (5.20 mmol)
-methyl-3-butenenitrile was added and the Schlenk tube
2
was placed in an oil bath at 1008C. Samples for GC analysis
À1
were taken over time to determine the TOF (h ).
1
996, 118, 6325–6326.
9] W. Goertz, W. Keim, D. Vogt, U. Englert, M. D. K.
Boele, L. A. Van der Veen, P. C. J. Kamer, P. W. N. M.
Van Leeuwen, J. Chem. Soc., Dalton Trans. 1998,
L3PtCl2
A solution of 119 mg (13.40 mmol) L3 in 3 mL CH Cl and
2
2
2
981–2988.
2
mL CH CN was added to 50 mg (13.40 mmol) Pt(cod)Cl
A
H
R
U
G
3
2
[
10] N. Sakai, K. Nozaki, K. Mashima, H. Takaya, Tetrahe-
dron: Asymmetry 1992, 3, 583–586.
[11] C. Botteghi, G. Delogu, M. Marchetti, S. Paganelli, B.
and stirred for 1 hour at 258C. After 7 days at À308C crys-
tals were formed suitable for X-ray analysis. Filtration and
evaporation of all volatiles gave a white crystalline product;
yield:123 mg (10.64 mmol, 79%).
Sechi, J. Mol. Cat. A: Chem. 1999, 143, 311–323.
[
[
12] C. A. Tolman, Chem. Rev. 1977, 77, 313–348.
13] G. R. Van Hecke, W. D. Horrocks, Inorg. Chem. 1966,
X-Ray Crystal Structure Determination of L3PtCl2
5
, 1960–1968.
C H Cl O P Pt·2.3CH CN·0.35CH Cl , Fw=1277.09, color-
5
6
56
2
6
2
3
2
2
[14] M. J. Baker, K. N. Harrison, A. G. Orpen, P. G. Pringle,
3
less needle, 0.36”0.12”0.12 mm , triclinic, P1 (no. 1), a=
1.8303(5), b=11.9100(3), c=12.1728(3) Š, a=114.822(1),
b=95.154(4), g=98.106(2)8, V=1519.79(9) Š , Z=1, D =
G. Shaw, J. Chem. Soc., Chem. Commun. 1991, 803–
1
8
04.
3
x
[
15] M. J. Baker, P. G. Pringle, J. Chem. Soc., Chem.
À3
À1
1
.395 gcm , m=2.529 mm . 31162 reflections were mea-
Commun. 1991, 1292–1293.
16] J. Wilting, C. Müller, A. C. Hewat, D. D. Ellis, D. M.
Tooke, A. L. Spek, D. Vogt, Organometallics 2005, 24,
sured on a Nonius Kappa CCD diffractometer (sealed tube,
[
graphite monochromator, l=0.71073 Š) up to a resolution
À1
of (sin q/l)max =0.65 Š at a temperature of 125(2) K. An
1
3–15.
absorption correction based on multiple measured reflec-
tions was applied (0.35–0.74 correction range). 13968 reflec-
tions were unique (Rint =0.0254). The structure was solved
with direct methods [29] and refined with SHELXL-97 [30]
[
[
[
17] E. Zuidema, P. W. N. M. Van Leeuwen, C. Bo, Organo-
metallics 2005, 24, 3703–3710.
18] D. A. Culkin, J. F. Hartwig Organometallics 2004, 23,
3398–3416.
19] M. Caporali, C. Müller, B. B. P. Staal, D. M. Tooke,
A. L. Spek, P. W. N. M. Van Leeuwen, Chem. Commun.
2
against F of all reflections. Non-hydrogen atoms were re-
fined with anisotropic displacement parameters. Hydrogen
atoms were introduced in geometrically idealized positions
and refined with a riding model. The acetonitrile and di-
chloromethane solvent molecules were refined with partial
occupancies, respectively. 724 parameters were refined with
2
005, 3478–3480.
[
[
[
[
20] M. R. Dennis, S. Woodward, J. Chem. Soc., Perkin
Trans. 1 1998, 1081–1086.
21] W. Keim, A. Behr, H. O. Lühr, J. Weisser, J. Catal.
189 restraints. R1/wR2 [I>2s(I)]: 0.0287/0.0792. R1/wR2
1
982, 78, 209–216.
[all refl.]: 0.0289/0.0793. S=1.135. Refined Flack parameter
22] E. M. Campi, P. S. Elmes, W. R. Jackson, C. G. Lovel,
M. K. S. Probert, Aust. J. Chem. 1987, 40, 1053–1061.
23] J. E. Bäckvall, O. S. Andell, Organometallics 1986, 5,
2350–2355.
[
31] x=À0.010(4); 99.9% Friedel pair coverage. Residual
3
electron density between À0.41 and 1.69 eŠ . Geometry cal-
culations and checking for higher symmetry was performed
with the PLATON program [32]. CCDC 610629 contains
the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data request/cif.
[24] After submission of this manuscript, a paper was pub-
lished on the asymmetric nickel-catalyzed hydrocyana-
tion of several dienes: B. Saha, T. V. RajanBabu, Org.
Lett. 2006, 8, 4657–4659.
[
25] More information regarding the mechanism of the
asymmetric hydrocyanation of 1,3-cyclohexadiene has
been published recently: J. Wilting, M. Janssen, C.
Müller, D. Vogt, J. Am. Chem. Soc. 2006, 128, 11374–
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