A new set of nickelacyclic carboxylates ( nickelalactones ) containing pyridine as supporting ligand: Synthesis, structures and application in C-C- and C-S- linkage reactions

Article abstract of DOI:10.1016/j.jorganchem.2004.04.047

Nickelacycles of the type [(py)₂Ni(CH₂ COO)](1a), [(py) ₂Ni(C(Et) C(Et)=COO)] (2a), and [(py)Ni (CH₂)-CH₂-COO)] (3a) were synthesized and structurally investigated by NMR, IR spectroscopy and in case of 1a and 2a by X-ray diffraction analysis. In 1a and 2a the Ni(II) ion has square-planar geometry, in contrast to the η³ allyl compound [(bipy)Ni(CH₂)-CH₂-COO)] (3b), in which nickel center adopts square-pyramidal geometry. 1a reacts with di(2-pyridyl)dimethylsilane (Me₂(2-py)₂Si) under exchange of the pyridine ligands to give 1c. 1a-3a and their bipy derivatives react with di-p-tolyldisulfide to form β-thioesters upon workup. Furthermore, reaction of 2-bromopropiophenone with nickelacycles of the type 2 results in the formation of 3,4-diethyl-6-hydroxy-5-methyl-6-phenyl-5,6-dihydro-2H-pyrane-2-one in good yields (64-75%). These reactions offer attractive new preparative routes for functionalized organic compounds.

Full text of DOI:10.1016/j.jorganchem.2004.04.047

Journal of Organometallic Chemistry 689 (2004) 2952–2962
www.elsevier.com/locate/jorganchem
A new set of nickelacyclic carboxylates (‘‘nickelalactones’’)
containing pyridine as supporting ligand: synthesis, structures and
application in C–C– and C–S– linkage reactions
*
Jens Langer, Reinald Fischer, Helmar Gorls, Dirk Walther
¨
Institut fu¨r Anorganische und Analytische Chemie der Friedrich-Schiller-Universita¨t Jena, August-Bebel-Strasse 2, 07743 Jena, Germany
Received 23 January 2004; accepted 19 April 2004
Available online 30 July 2004
Abstract
Nickelacycles of the type [(py)2Ni(CH2CH2COO)] (1a), [(py)2Ni(C(Et)‚C(Et)–COO)] (2a), and [(py)Ni(CH2
(CH3) C(CH3)–CH2–COO)] (3a) were synthesized and structurally investigated by NMR, IR spectroscopy and in case of 1a
…
C
…
and 2a by X-ray diffraction analysis. In 1a and 2a the Ni(II) ion has square-planar geometry, in contrast to the g3allyl compound
…
…
[(bipy)Ni(CH2 C(CH3) C(CH3)–CH2–COO)] (3b), in which nickel center adopts square-pyramidal geometry. 1a reacts with di(2-
pyridyl)dimethylsilane (Me2(2-py)2Si) under exchange of the pyridine ligands to give 1c. 1a–3a and their bipy derivatives react with
di-p-tolyldisulfide to form b-thioesters upon workup. Furthermore, reaction of 2-bromopropiophenone with nickelacycles of the
type 2 results in the formation of 3,4-diethyl-6-hydroxy-5-methyl-6-phenyl-5,6-dihydro-2H-pyrane-2-one in good yields (64–75%).
These reactions offer attractive new preparative routes for functionalized organic compounds.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Nickelacyclic compounds; N ligands; Disulfides; Bromopropiophenone; Organic synthesis
1. Introduction
carboxylic acids or their derivatives, for example by al-
kylation with alkyl halides [4,5,18–21], insertion of un-
saturated compounds (CO [10,14,16,20], CO2
[16,20,22,23], RNC [24,25], alkenes [12,26], alkynes
[18,27–32]) or transmetalation reaction with ZnR2 [33–
35]. Furthermore, nickelacyclic carboxylates are also
found to be useful reagents for the construction of func-
tionalized steroid side chains [36–38]. Additionally,
complexes with an olefin or allyl group in the organic
ring system are considered to act as intermediate in cat-
alytic reactions of unsaturated substrates with CO2
[18,27–32,34,39–41].
However, some limitations prevent a broader scope
of the known organometallic compounds, such as the
low selectivity of some formation reactions of the met-
allacycles and their low solubility in organic solvents of-
ten resulting in long reaction times with organic
Nickelacyclic
carboxylates
(‘‘nickelalactones’’)
(Scheme 1) consisting of a Ni–C–C–COO- framework
and N–N chelating ligands or phosphines as supporting
ligands are well-known compounds which have been
synthesized by different synthetic approaches [1–17].
Of special interest is the oxidative coupling between car-
bon dioxide, unsaturated substrates and Ni(0) complexes
which may open new ways for using CO2 as building
block in organic synthesis.
Some of these nickelacycles are interesting starting
products for the syntheses of saturated or unsaturated
*
Corresponding author. Tel.: +49-3641-9-48110; fax: +49-3641-9-
48102.
E-mail address: cdw@uni-jena.de (D. Walther).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.04.047

J. Langer et al. / Journal of Organometallic Chemistry 689 (2004) 2952–2962
2953
Reaction of the tmeda complexes with an excess of
pyridine followed by evaporating tmeda and pyridine
under reduced pressure results in almost quantitative
yields of the pyridine complexes. Both 1a and 2a were
obtained as green single crystals upon recrystallization
from pyridine.
N
N
N
N
Ni
Ni
Ni
O
O
O
O
O
O
excess py
- tmeda
excess py
- tmeda
excess py
- tmeda
1
The H NMR spectrum of 1a in [D7]DMF displays
two triplets for the CH2 groups at d=0.69 (Ni–CH2)
and 1.85 ppm (CH2–COO) and four resonances of the
pyridine ligand protons between 7.47 and 9.0 ppm. A
similar simple pattern was observed in the 13C NMR
spectrum. As expected, six signals for the carbon atoms
were observed. Furthermore, the IR spectrum shows the
N
N
N
Ni
Ni
O
Ni
O
N
N
O
O
O
O
1a
2a
3a
C‚O stretching frequency at 1617 cmꢀ1
.
Scheme 1. Synthesis of the complexes 1a–3a.
The molecular structure determined by an X-ray dif-
fraction analysis clearly shows the essentially planar ge-
ometry of Ni (Fig. 1). The bond lengths and bond angles
are quite normal and are comparable with those of sim-
ilar complexes [12,42,43].
substrates. Furthermore, in many cases the supporting
ligands do not efficiently control the reactions with the
organic substrate.
In view of these facts, it would be highly desirable to
have a set of soluble metal complexes of the above type,
consisting of different metallacyclic units and simple
neutral ligands which could be easily displaced by a
great variety of other ligands. This would allow elucidat-
ing the influence of steric and electronic properties of
these ligands on the reactivity of the metallacyclic unit.
Consequently, these studies should result in developing
new efficient synthons for the synthesis of organic fine
chemicals and drugs.
In this initial paper we describe the hitherto unknown
reactive pyridine complexes 1a–3a containing three dif-
ferent types of metallacyclic moieties. These complexes
can indeed serve as useful starting compounds for sub-
stitution reactions with other neutral ligands resulting
in new metallacycles with very different reactivity. Addi-
tionally, 1a–3a can themselves act as synthons for reac-
tions with organic substrates. To proof this point, we
have examined their reactions with di-p-tolyldisulfide
and 2-bromopropiophenone resulting in new functional-
ized carboxylic acids or their derivatives. For compari-
son, analogous experiments were carried out with the
known bipy stabilized derivatives 1b–3b [1,7,28] to study
the influence of different ligands on the organometallic
reactivity. Interestingly, some of these reactions offer in-
teresting alternative synthetic methods for preparing
functionalized organic compounds.
Analogously to 1a, complex 2a forms well-shaped
green single crystals from pyridine. Its solid-state
structure has been also fully characterized by X-ray dif-
fraction. Fig. 2 shows the structure of 2a with the atom-
numbering scheme and selected bond distances and
angles.
1
The H and 13C NMR spectra of 2a in [D6]DMSO
confirm, that the solid-state structure is also maintained
in solution. Two triplets for the CH3 protons, two quar-
tets for the CH2 protons of the different ethyl groups
and four signals for the pyridine protons were found –
in agreement with the structure according Fig. 2. In
2. Results and discussion
2.1. Synthesis and structures of the complexes 1–3
˚
Fig. 1. Molecular structure of complex 1a. Selected bond distances (A)
Although for the complexes 1a–3a different prepara-
tive methods may exist, the best way of synthesizing
these complexes starts from the corresponding tmeda
stabilized complexes according to Scheme 1.
and bond angles (ꢁ): Ni–O1 1.8655(13), Ni–C1 1.917(2), Ni–N1
1.9884(17), Ni–N2 1.8814(15), O1–C3 1.292(2), O2–C3 1.237(2), C1–
C2 1.521(3), C2–C3 1.511(3), N1–Ni–N2 92.07(/), N1–Ni–O1 89.96(6),
N2–Ni–C1 92.06(8), C1–Ni–O1 85.97(8).

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J. Langer et al. / Journal of Organometallic Chemistry 689 (2004) 2952–2962
*
Fig. 3. Molecular structure of complex 3b DMF. (DMF and H-atoms
bond to C6 and C7 are omitted for clairity). Selected bond distances
˚
Fig. 2. Molecular structure of complex 2a. Selected bond distances (A)
and bond angles (ꢁ): Ni–O1 1.864(3), Ni–C1 1.909(4), Ni–N1 1.895(4),
Ni–N2 1.997(4), O1–C3 1,315(5), O2–C3 1.239(5), C1–C2 1.344(6),
C2–C3 1,468(6), N1–Ni–N2 92.08(15), N2–Ni–O1 89.30(14), N1–Ni–
C1 93.51(17), C1–Ni–O1 85.01(16).
˚
(A) and bond angles (ꢁ): Ni–O1 1.971(4), Ni–C5 2.003(7), Ni–C4
1.915(6), Ni–C3 1.955 (6), Ni–N1 1.999(4), Ni–N2 2.097(4), O1–C1
1.269(6), O2–C1 1.234(7), C1–C2 1.536(9), C2–C3 1.582(10), C3–C4
1.383(9), C4–C5 1.458(10), N1–Ni–N2 79.54(18), N1–Ni–O1
98.13(17), N2–Ni–O1 92.95(17), N1–Ni–C5 96.1(3), N1–Ni–C3
161.9(2), N2–Ni–C5 116.7(3), N2–Ni–C3 117.5(2), C3–Ni–O1
87.3(2), C5–Ni–O1 149.0(2).
the 13C NMR spectrum, besides the resonances for the
pyridine carbon atoms, the expected seven signals for
the carbons of the metallacyclic ring appeared, assigned
to two signals of the CH3 groups, two resonances of the
CH2 groups, two resonances of the C‚C carbons and
one signal belonging to the carboxylate carbon.
the nickel center, since bipy acts as chelating ligand.
The atoms N1, O, C1 and C3 are in an essentially planar
arrangement and N2 assumes the apical position. In the
known complex [(tmeda)Ni(CH2ꢁ ꢁ ꢁC(CH3)ꢁ ꢁ ꢁC(CH3)–
CH2COO)] the chelating ligand tmeda strongly coordi-
nates only with one nitrogen atom, the second is only
Complex 3a forms yellow crystals which were ob-
tained in excellent yield (86%). It contains only one py-
ridine ligand, as shown by elemental analysis and NMR
measurement, and its NMR spectra in [D8]THF at am-
bient temperature give evidence for the g3-arrangement
of the allyl group. Besides the proton signals for the
CH2COO group at d=2.17 and 2.97 ppm, one terminal
proton of the allyl group appears at 2.00 ppm. The other
terminal proton resonates at 2.39 ppm; however, this
signal overlaps with the signal of a methyl group giving
rise to a multiplet of the relative intensity of four. Fur-
thermore, the singlet for the second methyl group was
observed at 1.08 ppm. In addition, the three signals
for the protons of the coordinated pyridine ligand com-
plete the 1H NMR spectrum. These data clearly demon-
strate the presence of only one isomer in solution. The
very simple 13C NMR spectrum supports this finding:
Only 10 13C signals were observed, additionally indicat-
ing that there is no detectable equilibrium between
g3- and g1-coordination of the allyl group in [D8]THF
solution.
˚
weakly associated (Ni–N(2) 2,314(7) A) [9]. So the mo-
lecular structure of 3b in the solid-state is the first exam-
ple of a nickelacyclic carboxylate with square-pyramidal
coordination sphere.
The pyridine ligands in 1a can easily be substituted by
a number of other ligands. For example, reaction with
di(2-pyridyl)dimethylsilane (Me2(2-py)2Si) results in
the formation of the corresponding di(2-pyridyl)dimeth-
ylsilane complex 1c which was isolated in good yields
(70%). In contrast, the corresponding tmeda complex,
which is so far the most suitable starting compound
for exchange reactions of the neutral ligand, is unreac-
tive toward di(2-pyridyl)dimethylsilane. This compari-
son underlines the importance of the pyridine
complexes as starting products for the formation of
new nickelacyclic carboxylates with variable reactivity
of the organometallic framework.
Suitable crystals for the X-ray diffraction analysis
of 1c were grown from a solution in DMF. Under
these conditions the racemic mixture of both enantio-
meric forms (planar chirality) crystallized. Fig. 4
shows the solid-state structure of one enantiomer of
1c and displays selected bond lengths and angles in
the caption. The 1H NMR spectrum of 1c in
[D7]DMF displays two signals for the Ni–CH2-group
Several attempts to obtain single crystals failed so far.
However, the related, diamagnetic bipy complex 3b
could be obtained in single crystals.
An X-ray diffraction study of this compound (Fig. 3)
showed its molecular structure with the g3-allyl coordi-
nation and a square-pyramidal coordination sphere of

J. Langer et al. / Journal of Organometallic Chemistry 689 (2004) 2952–2962
2955
2.2. Reactions of the complexes 1a–3a and their bipy
derivatives 1b–3b
2.2.1. Reactions with di-p-tolyldisulfide
Reaction with di-p-tolyldisulfide with the pyridine
and bipyridine complexes resulted in the formation of
b-thiocarboxylic acids which were identified in some
cases as methyl esters according to Scheme 2.
Whereas with complex 1a 3-(p-tolylmercapto)-propi-
onic acid (4) [44] could be detected only in low yield
(22%), the bipy derivative 1b afforded high yield
(70%). This clearly demonstrates the influence of the
neutral ligand on the reaction. In this case bipy tunes
the reaction more efficiently than the pyridine ligands.
Although the preparative value of this reaction starting
from 1a or 1b is relatively low, by using substituted de-
rivatives the organometallic route may be an interesting
alternative to established methods and should open up
an easy entry to substituted thiachroman-4-ones [44].
Of particular interest is the reaction of the organic
sulfide with the bipy containing unsaturated metallacy-
cle 2b. In this reaction the unsaturated b-thioester
(Z)-2-ethyl-3-(p-tolylmercapto)-pent-2-enoic acid methyl
ester (5) bearing two alkyl substituents in a (Z)-arrange-
ment was isolated in moderate yields (53%) upon workup
with dimethyl sulfate.
Fig. 4. Molecular structure of complex 1c. (only one enantiomer
˚
shown) Selected bond distances (A) and bond angles (ꢁ): Ni–O1
1.856(2), Ni–C1 1.922(3), Ni–N1 1.891(3), Ni–N2 1.986(3), O1–C3
1.310(4), O2–C3 1.226(4), C1–C2 1,512(5), C2–C3 1,503(5), N1–Ni–N2
93.28(11), N2–Ni–O1 88.19(10), N1–Ni–C1 91.62(13), C1–Ni–O1
86.91(13).
at 0.72 and 0.82 ppm with the relative intensity 1:1.
This clearly shows the diasteriotopic character of the
CH2 groups in the CH2CH2COO fragment. In other
words, the conversion of one enantiomeric form into
the other in solution is slow, compared with the
NMR time scale.
To the best of our knowledge this compound has
never been described before. Generally, this reaction
1. di-p-tolyldisulfide,
DMF
2. HCl, water
LnNi
S
COOH
O
O
1a: L= py, n= 2
4
1b: L= bipy, n= 1
1. di-p-tolyldisulfide,
THF
2. (MeO)2SO2, Na2CO3
bipyNi
S
COOCH3
O
O
2b
5
1. di-p-tolyldisulfide,
DMF
2. HCl, water
S
bipyNi
O
O
COOH
3b
(Z) 6
S
COOH
+
(E) 6
Scheme 2. Formation of ß-thio-carboxylic acids from complexes of the type 1–3.

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J. Langer et al. / Journal of Organometallic Chemistry 689 (2004) 2952–2962
opens a simple and attractive general route for the
preparation of unsaturated b-thioesters starting from
CO2, an alkyne and an organic disulfide in the presence
of Ni(0) complexes. In contrast to a known method for
A very simple one-pot reaction to 8, starting directly
from CO2, 3-hexyne and in situ generated (bipy)Ni(cod)
without isolating the nickelacyclic carboxylate, is also
possible (yield: 60%) and increases the preparative value
of this synthesis.
synthesizing
a
similar b-thioester (predominantly
the (E)-isomer) starting from an allenic ester [45], the
organometallic way results in the formation of the
(Z)-isomer using only commercial available starting
products. Another advantage of the organometallic
route is the possibility to vary the alkyl substituents
in a wide range, whereas the known procedure needs
a defined substitution pattern.
Single crystals of 8, suitable for an X-ray diffraction
study were grown from a solution of heptane/THF.
Fig. 5 shows the molecular structure of the crystallizing
pair of diastereomers and contains relevant bond lengths
and bond angles in the figure caption.
As can be seen from the figure the two ethyl groups
on the olefinic bond assume Z-positions and two mole-
cules are linked via hydrogen bonds between the OH
groups and the carbonyl group of the neighboring
molecule.
When 3b was used in this C–S-linkage reaction, two
isomers of 3,4-dimethyl-5-(p-tolylmercapto)-pent-3-
enoic acid (6) were formed besides some minor byprod-
ucts. 6 was characterized by GC–MS, GC–IR and NMR
The 1H NMR spectrum in CDCl3 at ambient temper-
ature clearly demonstrates, that two pairs of diastereo-
isomers (in a ratio of about 5:1) are present in
solution. The equilibrium between both forms may pro-
ceed via a ring-opening reaction [49,50], however; this
intermediate could not be detected in the solution.
Generally, the organometallic reaction from three
simple organic compounds (alkynes, CO2 and a 2-halo-
genoketone or -aldehyde) may open an easy access to
functionalized 6-hydroxy-5,6-dihydro-2H-pyrane-2-ones
and, after dehydratization, to substituted pyran-2-ones.
Substituted 5,6-dihydro-2H-pyran-2-ones should also
be accessible through reduction with NaBH4 [51] These
compounds are of interest because they are part of natu-
ral products and drugs such as withaferin A and kaiwan
[52]. Furthermore, some 5,6-dihydro-2H-pyrane-2-one
derivatives show antitumoral or antibiotic abilities or in-
hibit HIV-protease [52].
Established methods to substituted 6-hydroxy-5,6-
dihydro-2H-pyrane-2-ones, such as the reaction of
substituted cyclohexenones with superoxide radicals,
generated by KO2/18-crown-6, [51,53] are often limited
to a special substitution pattern. In contrast, the or-
ganometallic reaction described here, should allow pre-
paring a much larger group of substituted pyranones
in a very simple reaction by using different alkynes
and 2-bromoketones.
1
experiments. In H NMR (NOESY) experiments a cou-
pling through space between the two methyl groups of
the main product was observed, assigned to be the
(Z)-isomer. Generally, this synthesis is an interesting
preparative route to new thioether substituted pent-
3-enoic acids [46,47], since an overall yield of 60% was
found. Mechanistical investigations of the reaction of
organic disulfides with nickelacyclic carboxylates are
subject of ongoing studies.
2.2.2. Reaction with 2-bromopropiophenone
The reaction of 1a or 1b with 2-bromopropiophenone
followed by hydrolysis results in the formation of 4-ben-
zoyl valeric acid (7) [48] in relatively low yields. In other
words, both complexes are not useful for the selective
synthesis of such types of carboxylic acids. Similarly,
the corresponding reaction with 3b yielded various carb-
oxylic acid. Among these, the desired unsaturated carb-
oxylic acid is only present as minor product, according
1
to H NMR- and MS analysis.
In contrast, the unsaturated complexes 2a and 2b
reacts with 2-bromopropiophenone in good yields to 3,
4-diethyl-6-hydroxy-5-methyl-6-phenyl-5,6-dihydro-2H-
pyrane-2-one (8), which was never synthesized before
(Scheme 3). The product was isolated in yields up to
75%, if the reaction with 2a was carried out in THF.
O
1. DMF or THF
2. HCl, water
Br
Ar
LnNi
Ar
+
O
O
- LnNiBrCl
OH
O
O
8
2a: L= py, n=2
2b: L= bipy, n=1
Scheme 3. Reaction of complexes of the type 2 with 2-bromopropiophenone.

J. Langer et al. / Journal of Organometallic Chemistry 689 (2004) 2952–2962
2957
(a)
(b)
Fig. 5. (a) Molecular structure of compound 8 (only one diastereomer shown) (left); (b) dimeric unit (H–atoms except the one bond to O3 are
˚
omitted for clairity) (right). Selected bond distances (A) and bond angles (ꢁ): O1–C1 1.3500(17), O1–C5 1.4648(16), O2–C1 1.2208(17), O3–C5
1.3938(16), C1–C2 1.474(2), C2–C3 1.341(2), C3–C4 1.509(2), C4–C5 1.527(2), O1–C1–O2 117.23(13), O1–C1–C2 119.99(12), O1–C5–O3 108.90(10),
O1–C5–C4 109.10(11), O2–C1–C2 122.72(13), O3–C5–C4 107.15(12), C1–C2–C3 119.21(13), C2–C3–C4 120.22(14), C3–C4–C5 110.12(12).
3. Conclusions
idyl)dimethylsilane [55] were prepared according to
known procedures. The nickelacycles [(L)Ni(C2H4-
The new pyridine complexes 1a–3a are easily accessi-
ble and can be used as valuable starting products for the
synthesis of many other nickelacycles with different neu-
tral ligands opening the possibility to tune the reactivity
of the organometallic moiety towards organic sub-
strates. Initial investigations have shown that some of
the nickelacyclic lactones are useful building blocks for
synthesizing organic fine chemicals. Especially unsatu-
rated b-thioesters and 3,4-diethyl-6-hydroxy-5-methyl-
6-phenyl-5,6-dihydro-2H-pyrane-2-one can be prepared
by simple routes in good yields. Scope and limitation
of these and similar reactions are subject of ongoing
studies.
COO)],
[(L)Ni(C(C2H5)‚C(C2H5)COO)],
[(L)Ni
…
…
(CH2 C(CH3) C(CH3)–CH2COO)] (L: tmeda, bipy)
and Ni(cod)2 were prepared by using literature proce-
dures [1,4,7,28,31,56].
4.2. Synthesis of [py2Ni(C2H4COO)] (1a)
To [(tmeda)Ni(C2H4COO)] (0.32 g, 1.3 mmol) pyri-
dine (10 ml) was added, the resulting suspension was
stirred for 20 min and the solvent was removed in vacu-
um (2·). The resulting residue was the desired product
as green solid in quantitative yield (0.38 g, 1.3 mmol).
C13H14N2NiO2 (288.96) Calc.: C 54.04, H 4.88, N
9.69; Found C 54.20, H 4.93, N 9.65. IR (nujol,
cmꢀ1): m(C‚O) 1617 (s). 1H NMR (200 MHz,
3
4. Experimental
[D7]DMF, 25 ꢁC): d=0.69 (t, JH,H =7.5 Hz, 2H, Ni–
CH2), 1.85 (t, JH,H =7.5 Hz, 2H, CH2–COO), 7.43 (t,
3
4.1. General procedures
4H, m-CH py), 7.89 (t, 2H, p-CH py), 8.42 (br, 2H, o-
CH py), 9.0 (d, 2H, o-CH py) ppm. 13C{1H}NMR (50
MHz, [D7]DMF, 25 ꢁC): d=3.6 (br, Ni–CH2), 38.1
(CH2–COO), 125.8 (4·m-CH, py), 137.9 (2·p-CH,
py), 152.7 (4·o-CH, py), 186.8 (COO) ppm.
1H NMR and 13C NMR spectra were recorded at
ambient temperature on a Bruker AC 200 MHz spec-
trometer. All spectra were referenced to TMS or deuter-
ated solvent as an internal standard. FAB-mass spectra
were obtained on a Finnigan MAT SSQ 710 system (2,4-
dimethoxybenzylalcohol as matrix), IR measurements
were carried out on a Perkin–Elmer System 2000 FT-IR.
All manipulations were carried out by using Schlenk
techniques under an atmosphere of argon. Prior to use,
tetrahydrofurane and diethyl ether were dried over po-
tassium hydroxide and distilled over Na/benzophenone.
Pyridine and DMF were distilled over CaH2. Di-p-
tolyldisulfide, 3-hexyne and 2,3-dimethylbutadiene was
purchased from Aldrich and used without further puri-
fication. 2-bromopropiophenone [54] and di(2-pyr-
Single crystals suitable for the X-ray diffraction were
obtained from a solution of pyridine.
4.3. Synthesis of [(Me2(2-py)2Si)Ni(C2H4COO)] (1c)
A solution of Me2(2-py)2Si (0.44 g, 2.08 mmol) in
THF (10 ml) was added to green [py2Ni(C2H4COO)]
(1a) (0.6 g, 2.08 mmol) at r.t. The resulting suspension
was stirred for 2 h and turned slowly to yellow. The yel-
low solid was removed by filtration, washed with ether
and dried in vacuum. This THF-containing product
was dissolved in DMF and evaporated to dryness under

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J. Langer et al. / Journal of Organometallic Chemistry 689 (2004) 2952–2962
reduced pressure to yield solvent free product. Yield:
0.50 g (70%). C15H18N2NiO2Si (345.1) Calc.: C 52.21,
H 5.26, N 8.12; Found C 52.10, H 5.22, N 8.41%.
IR (nujol, cmꢀ1): m(C‚O) 1617 (s),1H NMR (400
MHZ, [D7]DMF, 25 ꢁC): d=0.72 (m, 1H, Ni–CH H0),
0.82 (m, 1H, Ni–CHH0), 1.00 (s, 3H, Si–CH3), 1.82
(m, 1H, CH H0–COO), 1.86 (s, 3H, Si–CH3), 2.02 (m,
1H, CHH0–COO), 7.38 (m, 1H, CH py), 7.45 (m, 1H,
CH py), 7.70 (d, 1H, CH py), 7.82–7.92 (m, 3H, CH
py), 8.94 (d, 1H, CH py), 9.03 (d, 1H, CH py) ppm.
13CNMR (100 MHz, [D7]DMF, 25 ꢁC): d=ꢀ5.9 (Si–
CH3),ꢀ0.8 (Si–CH3), 7.9 (Ni–CH2), 38.4 (CH2–COO),
124.6 (CH py), 125.4 (CH py), 130.8 (CH py), 131.2
(CH py), 135.7 (CH py), 136.4 (CH py), 152.4 (CH
py), 153.8 (CH py), 164.9 (Si–C py), 186.6 (COO) ppm
(1 signal (Si–C py) overlaps with the signal of the
C‚O group from DMF).
NMR (200 MHz, [D8]THF, 25 ꢁC): d=1.08 (s, 3H,
2
CH3), 2.00 (br, 1H, H H0Cꢁ ꢁ ꢁ), 2.17 (d, JH,H =16.1
Hz, 1H,–CH H0–COO), 2.39 (s, 4H, CH3 +HH0 Cꢁ ꢁ ꢁ),
2
2.97 (d, JH,H =15.4 Hz, 1H,–CHH0–COO), 7.39 (br,
2H, m-CH py), 7.86 (br, 1H, p-CH py), 8.56 (br, 2H,
o-CH py) ppm. 13C{1H} NMR (100 MHz, [D6]DMSO,
25 ꢁC): d=19.7 (CH3), 21.4 (CH3), 43.6 (CH2–COO),
45.8 (CH2 allyl), 73.8 (C allyl), 116.4 (C allyl), 124.8
(m-CH py), 138.2 (p-CH py), 151.1 (o-CH py), 181.0
(COO) ppm.
4.6. Coupling reactions with organic substrates
4.6.1. Standard work up
The reaction mixture was evaporated to dryness in
vacuum. The residue was stirred for 1 h with diluted,
aqueous HCl solution (20 ml) and extracted with chloro-
form (2·20 ml). The organic phases were extracted with
saturated, aqueous sodium carbonate solution (2 ·20
ml). Then the combined aqueous phases were acidified
(HCl) and extracted with chloroform (3·20 ml). These
organic layers were dried with anhydrous sodium sulfate
and the solvent was removed in vacuum to give the
crude product.
Single crystals suitable for the X-ray diffraction were
obtained from a solution of DMF.
4.4. Synthesis of [py2NiC(C2H5)‚C(C2H5)–COO]
(2a)
Orange [(tmeda)NiC(C2H5)‚C(C2H5)–COO] (0.30
g, 1.0 mmol) was suspended in pyridine (10 ml) and stir-
red for 20 min. The suspension turned from initial or-
ange to green. The solvent was removed under reduced
pressure and the solid formed was dried in vacuum. 2
was obtained as a green solid in quantitative yield
(0.34 g, 1.0 mmol). C17H20N2NiO2 (343.05) Calc.: C
59.52, H 5.88, N 8.17; Found: C 59.15, H 5.95, N
8.51; IR (nujol, cmꢀ1): m(C‚O) 1619 (s). 1H NMR
4.7. Synthesis of 3-(p-tolylmercapto)-propionic acid (4)
[44]
4.7.1. (a) From [py2Ni(C2H4COO]) (1a)
Di-p-tolyldisulfide (0.64 g, 2.60 mmol) was added to a
stirred solution of green [py2Ni(C2H4COO)] (0.75 g,
2.60 mmol) in DMF (30 ml) and a slow color change
to brown was observed. Stirring was continued over
night, followed by standard work up. Yield: 110 mg
3
(200 MHz, [D6]DMSO, 25 ꢁC): d=0.46 (t, JH,H =7.0
3
Hz, 3H, Ni–C–CH2–CH ), 0.76 (t, JH,H =7.3 Hz, 3H,
3
3
CH3), 0.92 (q, JH,H =7.0 Hz, 2H, Ni–C–CH2–), 1.80
1
(22%). H NMR (200 MHz, CDCl3, 25 ꢁC): d=2.25 (s,
3
(q, JH,H =7.3 Hz, 2H, CH2), 7.37 (pseudo-t, 4H, m-
3
3H, CH3), 2.57 (t, JH,H =7.4 Hz, 2H, CH2), 3.05 (t,
CH py), 7.80 (br, 2H, p-CH py), 8.55 (br, 2H, o-CH
py), 9.08 (br, 2H, o-CH py) ppm. 13C{1H} NMR (100
MHz, [D6]DMSO, 25 ꢁC): d=14.1 (CH3), 14.8 (CH3),
20.5 (CH2), 24.6 (CH2), 124.8 (4·m-CH py), 137.8
(2·p-CH py), 139.0 (‚C–COO), 152.2 (4·o-CH py),
159.0 (Ni–C‚), 178.9 (COO) ppm.
3JH,H =7.4 Hz, 2H, CH2), 7.04 (AA0BB0, 2H, CH tolyl),
7.22 (AA0BB0, 2H, CH tolyl), 8.65 (br, 1H, COOH)
ppm. MS (DEI): m/z (%)=196 [M+] (100), 179 [M+–
OH] (12), 137 [M+–CH2–COOH] (58), 123 [p-tolyl-S+]
(19), 91 [p-tolyl+] (40).
Single crystals suitable for the X-ray diffraction were
obtained from a solution of pyridine.
4.7.2. (b) From [(bipy)Ni(C2H4COO)] (1b)
[(bipy)Ni(C2H4COO)] (0.94 g, 3.28 mmol) and di-p-
tolyldisulfide (0.81 g, 3.29 mmol) in DMF (40 ml) were
reacted as described in Section 4.7.1. Reaction was com-
pleted after 30 h. Yield: 450 mg (70%).
…
…
4.5. Synthesis of [pyNi(CH2 C(CH3) C(CH3)–
CH2–COO)] (3a)
[(tmeda)Ni(CH2ꢁ ꢁ ꢁC(CH3)ꢁ ꢁ ꢁC(CH3)–CH2COO)]
(0.99 g, 3.29 mmol) was dissolved in 10 ml pyridine, stir-
red for 20 min and evaporated to dryness (2·). To the
resulting orange oil diethyl ether (20 ml) was added. Af-
ter 30 min of stirring, 3 was isolated as yellow solid by
filtration. Yield: 0.75 g (86%). C12H15NNiO2(263.94)
Calc.: C 54.61, H 5.73, N 5.31; Found: C 54.64, H
4.7.3. (Z)-2-ethyl-3-(p-tolylmercapto)-pent-2-enoic acid
methylester (5)
To a suspension of orange [(bipy)Ni(C (C2H5)‚
C(C2H5)–COO)] (0.96 g, 2.81 mmol) in THF (40 ml)
di-p-tolyldisulfide (0.70 g, 2.84 mmol) was added. The
mixture was stirred for 36 h, after which dimethyl sulfate
(1.07 g, 8.48 mmol) was added. Upon stirring for 24 h
the excess of dimethyl sulfate was hydrolyzed by
1
5.55, N 5.56. IR (nujol, cmꢀ1): m(C‚O) 1636 (s). H

J. Langer et al. / Journal of Organometallic Chemistry 689 (2004) 2952–2962
2959
1
addition of an aqueous solution of sodium carbonate
(20 ml) and rapid stirring of the resulting mixture for
2 h. Then THF was removed in vacuum and the aque-
ous phase was extracted with heptane (3·20 ml). The
collected organic layers were concentrated and the 5
was separated by column chromatography on silica gel
(heptane/ethyl acetate 10:1) as nearly colorless oil. Yield:
tained 7 together with DMF. Yield: 100 mg (14%). H
NMR (400 MHz, CDCl3, 25 ꢁC): d=1.17 (d,
3JH,H =6.9 Hz, 3H, CH3), 1.73 (m, 1H, CH H0), 2.13
(m, 1H, CHH0), 2.35 (m, 2H, CHH0–COO), 3.56 (m,
1H, CH–CH3), 7.42 (m, 2H, m-CH Ph), 7.51 (m, 1H,
p-CH Ph), 7.93 (m, 2H, o-CH Ph) 8.2-9.5 (br, 1H,
COOH) ppm. 13C{1H} NMR (50 MHz, CDCl3, 25
ꢁC): d=17.3 (CH3), 28.1 (CH2), 31.6 (CH2–COO), 43.6
(CH), 128.4 (2·o-CH Ph), 128.7 (2·m-CH Ph), 133.0
(p-CH Ph), 136.3 (i-C Ph), 177.1 (COO), 203.7 (C‚O)
ppm. MS (DEI): m/z (%)=207 [M+ +1] (18), 206 [M+]
(34), 189 [M+–OH] (100), 105 [Ph–CO+] (100).
1
400 mg (53%). IR (nujol, cmꢀ1): m(C‚O) 1731 (s). H
NMR (400 MHz, CDCl3, 25 ꢁC): d=0.95 (t,
3
3JH,H =7.4 Hz, 3H, CH3), 1.05 (t, JH,H =7.4 Hz, 3H,
3
CH3), 2.16 (q, JH,H =7.4 Hz, 2H, CH2), 2.31 (s, 3H,
3
CH3 p-tolyl), 2.38 (q, JH,H =7.4 Hz, 2H, CH2), 3.75
(s, 3H, COOCH3), 7.09 (AA0BB0, 2H, CH tolyl), 7.30
(AA0BB0, 2H, CH tolyl) ppm. 13C{1H} NMR (100
MHz, CDCl3, 25 ꢁC): d=13.6 (CH3), 13.7 (CH3), 21.1
(CH3 tolyl), 23.8 (CH2), 24.8 (CH2), 51.5 (CH3–O),
129.6 (2 ·CH tolyl), 130.0 (i-C–S tolyl), 132.9 (‚C<),
133.2 (2·CH tolyl), 137.9 (i-C–CH3 tolyl), 145.3
(>C‚), 169.2 (COO) ppm. MS (DEI): m/z (%)=265
[M+ +1] (21), 264 [M+] (100), 233 [M+–OCH3] (51),
141 [M+–S-tolyl] (12), 109 (12).
4.8.2. (b) From [(bipy)Ni(C2H4COO)]
Starting from (2.79 mmol) [(bipy)Ni(C2H4COO)]
(0.80 g, 2.79 mmol) and 2-bromopropiophenone (0.42
ml, 2.76 mmol) in DMF (40 ml) reaction was carried
out analogously to (a). Yield: 40 mg (7%) of 7.
4.9. Synthesis of 3,4-diethyl-6-hydroxy-5-methyl-6-phe-
nyl-5,6-dihydro-2H-pyran-2-one (8)
4.7.4. Dimethyl-5-(p-tolylmercapto)-pent-3-enoic acid
(6)
4.9.1. (a) In DMF
…
…
[(bipy)Ni(C(C2H5)‚C(C2H5)–COO)] (0.64 g, 1.88
mmol) was dissolved in DMF (30 ml) and 2-brompro-
piophenone (0.42 g, 1.97 mmol) was added. The solution
was stirred at ambient temperature overnight and
turned from initial red to green. Following standard
procedure, 5,6-dihydro-2H-pyran-2-one 5 was obtained
as a white solid. Yield: 230 mg (47%). C16H20O3
(260.33) Calc.: C 73.82, H 7.74; Found: C 73.88, H
7.76. IR (KBr, cmꢀ1): m(OH) 3290 (br, s), m(C‚O)
1686(s). 1H NMR (400 MHz, CDCl3, 25 ꢁC): major pair
A solution of [(bipy)Ni(CH2 C(CH3) C(CH3)–
CH2COO)] 3b (0.46 g, 1.35 mmol) and di-p-tolyldisulfide
(0.34 g, 1.38 mmol) in DMF (30 ml) was stirred at am-
bient temperature over night. Usual work up yielded
sticky oil (260 mg). GC/IR, GC/MS analysis (after este-
rification with diazomethane) and 1HNMR (NOESY) of
the crude product showed the presence of (Z)-6 and (E)-
6 beside further minor products. (Z)-6: yield (155 mg,
1
46%). H NMR (200 MHz, CDCl3, 25 ꢁC): d=1.73 (s,
3H, CH3), 1.82 (s, 3H, CH3), 2.30 (s, 3H, CH3 tolyl),
2.89 (s, 2H, CH2), 3.51 (s, 2H, CH2), 7.06 (AA0BB0,
2H, CH tolyl), 7.25 (AA0BB0, 2H, CH tolyl), 8.50–9.50
(br, 1H, COOH) ppm. IR (as methyl ester) (pure, gas
phase, cmꢀ1): 3025, 2959, 2932, m(C‚O) 1756 (s),
1492, 1437, 1251, 1162 (s), 1018, 807. MS (DEI, as me-
thyl ester): m/z (%)=264 [M+] (62), 233 [M+–OCH3] (4),
141 [M+–S-tolyl] (100), 109 (4), 99 (6). (E)-6: yield (45
mg, 13%). IR (as methyl ester) (pure, gas phase,
cmꢀ1): 3024, 2960, 2932, m(C‚O) 1756 (s), 1492, 1438,
1246, 1197, 1151 (s),1018, 805. MS (DEI, as methyl es-
ter): m/z (%)=264 [M+] (51), 233 [M+–OCH3] (4), 205
[M+–COOCH3] (7), 141 [M+–S-tolyl] (100), 123 [tolyl-
S+] (23), 109 (14), 99 (10).
3
of diastereomers (ratio 5:1): d=0.74 (d, JH,H =7.2 Hz,
3H, CH3), 1.08 (t, JH,H =7.5 Hz, 3H, CH3), 1.21 (t,
3
3JH,H =7.6 Hz, 3H, CH3), 2.09 (m, 1H, CH H0), 2.40
(m, 2H, CHH0), 2.54 (m, 1H, CHH0), 2.66 (q,
3JH,H =7.2 Hz, 1H, CH), 3.50 (br, 1H, OH), 7.32–7.45
(m, 3H, m-CH+p-CH Ph), 7.58–7.63 (m, 2H, o-CH
Ph) ppm, minor pair of diastereomers: d=0.73 (t,
3JH,H =7.7 Hz, 3H, CH3), 0.92 (t, JH,H =7.4 Hz, 3H,
3
3
CH3), 1.29 (d, JH,H =7.0 Hz, 3H, CH3), 1,.9 (m, 1H,
CH H0), 2.19–2.40 (m, 3H, CHH0 +CHH0), 2.90 (q,
3JH,H =6.9 Hz, 1H, CH), 3.67 (br, 1H, OH), 7.32–7.45
(m, 3H, m-CH+p-CH Ph), 7.58–7.63 (m, 2H, o-CH
Ph) ppm. 13C{1H} NMR (100 MHz, CDCl3, 25 ꢁC): ma-
jor pair of diastereomers: d=12.3 (CH3), 13.9 (CH3),
16.5 (CH3), 19.9 (CH2), 25.1 (CH2), 42.5 (CH), 102.8
(C–OH), 125.6 (2·m-CH Ph), 125.7 (>C‚), 128.4
(2·o-CH Ph), 128.8 (p-CH Ph), 140.7 (i-C Ph), 157.7
(‚C<), 164.7 (COO) ppm. MS (DEI): m/z (%)]=261
[M+ +1] (21), 243 [M+–OH] (86), 138 [M+–OH–Ph–
CO] (100), 105 [Ph–CO+] (36).
4.8. Benzoylvaleric acid (7) [47]
4.8.1. (a) From [py2Ni(C2H4COO)] (1)
To a solution of 1 (0.98 g, 3.4mmol) in DMF (40 ml)
2-bromopropiophenone (0.52 ml, 3.4 mmol) was added
at r.t. The resulting solution was stirred overnight and
than the reaction mixture was worked up according to
the above standard procedure. The crude product con-
Single crystals suitable for the X-ray diffraction were
obtained from a heptane/THF mixture.

2960
J. Langer et al. / Journal of Organometallic Chemistry 689 (2004) 2952–2962
3
˚
4.9.2. (b) In THF
103.154(4)ꢁ, V=777.39(9) A , T=ꢀ90 ꢁC, Z=2,
Reaction was carried out as described above using
[(bipy)Ni(C(C2H5)‚C(C2H5)–COO)] (1.05 g, 3.08
mmol) and 2-bromopropiophenone (0.66 g, 3.09 mmol)
in THF (40 ml). Yield: 510 mg (64%) of 8.
q
calc =1.474 gcmꢀ3, l(Mo Ka)=13.3 cmꢀ1, F(000)=
360, 5458 reflections in h(ꢀ10/10), k(ꢀ11/12), l(ꢀ13/
12), measured in the range 4.20ꢁ 6H627.47ꢁ, complete-
ness
Hmax =98%, 3490 independent reflections,
Rint =0.046, 2854 reflections with Fo >4r(Fo), 190 pa-
rameters, 0 restraints, R1 obs =0.051, wR2 obs =0.123,
R1 all =0.066, wR2 all =0.135, Goodness-of-fit=1.049,
4.9.3. (c) From [py 2 Ni(C(C 2H5)‚C(C2H5)–COO)]
(2a)
Instead of the bipy-complex, 2 (0.47 g, 1.37 mmol)
was treated with 2-bromopropiophenone (0.21 ml, 1.37
mmol) in THF (20 ml). Yield: 270 mg (75%) of 8.
ꢀ3
˚
largest difference peak and hole: 0.663/ꢀ0.861 eA
.
Crystal data for 2a: C17H20N2NiO2, Mr =343.06
gmolꢀ1, yellow prism, size 0.04·0.04·0.03 mm3, triclin-
ꢀ
ic, space group P1, a=8.9580(7), b=9.6555(8), c=
˚
4.9.4. (d) One-pot reaction
10.2078(9) A, a=93.242(5), b=97.040(5), c=
3
˚
To a solution of Ni(cod)2 (0.97 g, 3.5 mmol) and bipy
(0.54 g, 3.5 mmol) in THF (20 ml), 3-hexyne (0.8 ml, 7.0
mmol) was added. The solution was saturated with CO2 at
ꢀ20 ꢁC and stirred for 24 h at r.t. Then 2-bromopropiophe-
none (0.53 ml, 3.5 mmol) was added and stirring was contin-
ued for additional 16 h. The isolation of the product was
performed as described above. Yield: 550 mg (60%) of 8.
114.918(7)ꢁ, V=788.92(11) A , T=ꢀ90 ꢁC, Z=2,
q
calc =1.444
gcmꢀ3
,
l(Mo
Ka)=12.38
cmꢀ1
,
F(000)=360, 4853 reflections in h(ꢀ11/11), k(ꢀ12/9),
l(ꢀ10/13), measured in the range 2.54ꢁ 6H627.51ꢁ,
completeness Hmax =92.5%, 3358 independent reflec-
tions, Rint =0.043, 2433 reflections with Fo >4r(Fo),
199
wR2 obs =0.135, R1 all =0.093, wR2 all =0.153, Goodness-
parameters,
0
restraints,
R1 obs =0.061,
of-fit=1.02ꢀ2,3 largest difference peak and hole: 0.668/
˚
5. Crystal structure determination
ꢀ0.806 eA
.
Crystal data for 3b: C17H18N2NiO2 C3H7NO,
*
The intensity data for the compounds were collected
on a Nonius KappaCCD diffractometer, using graphite-
monochromated Mo Ka radiation. Data were corrected
for Lorentz and polarization effects, but not for absorp-
tion effects [57,58].
Mr =414.14 gmolꢀ1
,
brown prism, size 0.03·
0.02·0.01 mm3, orthorhombic, space group Pbca,
˚
a=11.0372(3),
b=12.9813(5),
c=27.0149(9)
A,
,
3
V=3870.6(2) A , T=ꢀ90 ꢁC, Z=8, qcalc =1.421 gcmꢀ3
˚
l(Mo Ka)=10.28 cmꢀ1, F(000)=1744, 11889 reflec-
tions in h(ꢀ14/14), k(ꢀ16/11), l(ꢀ34/33), measured in
The structures were solved by direct methods (SHELXS
[1]) and refined by full-matrix least squares techniques
the range 4.61ꢁ6H627.45ꢁ, completeness Hmax
=
against Fo2
(
SHELXL-97 [59]). For the compound 1a
97.3%, 4310 independent reflections, Rint = 0.082,
2699 reflections with Fo >4r(Fo), 244 parameters, 0 re-
straints, R1 obs =0.074, wR2 obs =0.178, R1 all =0.132,
wR2 all =0.209, Goodness-of-fit=1.075, largest differ-
and 8 the hydrogen atoms were located by difference Fou-
rier synthesis and refined isotropically. For the other
compounds the hydrogen atoms were included at calcu-
lated positions with fixed thermal parameters. All nonhy-
drogen atoms were refined anisotropically [60]. XP
(SIEMENS Analytical X-ray Instruments, Inc.) was used
for structure representations.
Crystal data for 1a: C13H14N2NiO2, Mr =288.97
gmolꢀ1, yellow prism, size 0.12·0.10·0.08 mm3, mono-
clinic, space group P21/n, a=8.3785(3), b=19.4013(8),
ence peak and hole: 0.895/ꢀ0.557 eAꢀ3
.
Crystal data for 8: C16H20O3, Mr =260.32 gmolꢀ1
,
colorless prism, size 0.04·0.04·0.03 mm3, monoclinic,
space group P21/n, a=11.7228(4), b=10.5521(3),
3
˚
˚
c=11.7563(5) A, b=101.220(1)ꢁ, V=1426.46(9) A ,
T=ꢀ90 ꢁC, Z=4, qcalc =1.212 gcmꢀ3, l(Mo Ka)=.82
cmꢀ1, F(000)=560, 5449 reflections in h(ꢀ14/15),
k(ꢀ12/13), l(ꢀ15/15), measured in the range
2.24ꢁ6H627.48ꢁ, completeness Hmax =99.3%, 3257 in-
dependent reflections, Rint =0.027, 2318 reflections with
Fo >4r(Fo), 252 parameters, 0 restraints, R1 obs =0.046,
wR2 obs =0.106, R1 all =0.075, wR2 all == 0.122, Good-
3
˚
˚
c=8.6247(3) A, b=114.505(2)ꢁ, V=1275.69(8) A ,
T=ꢀ90 ꢁC, Z=4, qcalc =1.505 gcmꢀ3, l(Mo Ka)=
15.15 cmꢀ1, F(000)=600, 4849 reflections in h(ꢀ10/
10), k(ꢀ25/22), l(ꢀ10/11), measured in the range
2.85ꢁ6H627.47ꢁ, completeness Hmax =99.1%, 2894 in-
dependent reflections, Rint =0.028, 2248 reflections with
Fo >4r(Fo), 219 parameters, 0 restraints, R1 obs =0.033,
wR2 obs =0.0806, R1 all =0.042, wR2 all =0.082, Good-
ness-of-fit=0.996ꢀ, 3 largest difference peak and hole:
˚
0.185/ꢀ0.234 eA
.
ness-of-fit=0.979ꢀ, 3 largest difference peak and hole:
˚
0.536/ꢀ0.454 eA
.
6. Supplementary material
Crystal data for 1c: C15H18N2NiO2Si, Mr =345.11
gmolꢀ1, green prism, size 0.10·0.08·0.03 mm3, triclin-
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Nos. 229215 (1a), 229216 (1c),
ꢀ
ic, space group P1, a=8.3983(6), b=9.8490(7), c=
˚
10.2195(6) A, a=102.391(4), b=101.163(4), c=

J. Langer et al. / Journal of Organometallic Chemistry 689 (2004) 2952–2962
2961
[22] H. Hoberg, B. Apotecher, J. Organomet. Chem. 270 (1984) C15–
C17.
229217(2a), 229218 (3b), and 22919 (8). Copies of this
information may be obtained free of charge from The
Director, CCDC, 12, Cambridge CB2 IEZ, UK (fax:
+44-1223-336033; e-mail deposit@ccdc.cam.ac.uk or
www://www.ccdc.cam.ac.uk).
[23] A. Behr, U. Kanne, J. Organomet. Chem. 317 (1986) C41–
C44.
[24] A.M. Castan˜o, A.M. Echavarren, Tetrahedron Lett. 34 (1993)
4361–4362.
[25] A.M. Echavarren, A.M. Castan˜o, Tetrahedron 51 (1995) 2369–
2378.
[26] H. Hoberg, Y. Peres, A. Milchereit, J. Organomet. Chem. 307
(1986) C41–C43.
Acknowledgement
[27] H. Hoberg, D. Schaefer, J. Organomet. Chem. 238 (1982) 383–
387.
We are grateful to the Scholarship Program of the
German Federal Environmental Foundation (Deutsche
Bundesstiftung Umwelt DBU) and the Deutsche Fors-
chungsgemeinschaft for support of this research.
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