Nickelalactones with an allyl subunit-the effect of penta-coordination on structures and stability

Article abstract of DOI:10.1039/c4dt01863j

A series of allyl modified nickelalactone derivatives of the general formula [(L)_nNi{CH₂C(CH₃)C(CH ₃)CH₂COO}] was synthesized via ligand exchange reactions in order to investigate the influence of the neutral ligand L on the structure and stability of these complexes. While the square planar 1,8-diazabicyclo[5,4, 0]undec-7-ene ligated derivative 1 is stable in the solid state and in solution at ambient temperature, the use of the chelating ligands 6-diphenylphosphino-1, 8-diazabicyclo[5.4.0]undec-7-ene, 1,1-bis(dicyclohexylphosphino)methane and 1,2-bis(dicyclohexylphosphino)ethane (dcpe) led to square pyramidal derivatives 2, 4, and 5 with a novel ligand arrangement. In solution, these derivatives are fluxional and show increasing tendencies in the order 2 < 4 < 5 to decouple the nickelalactone moiety to 2,3-dimethylbutadiene (dmbd), CO ₂ and zero-valent nickel complexes. During the investigation of 5, the tetrahedral complex [(dcpe)₂Ni] (6) and the trigonal planar derivative [(dcpe)Ni(dmbd)] (7) were observed as predominant decomposition products. In the case of the application of 1,1-bis(diphenylphosphino)methane as a neutral ligand, a dinuclear nickelalactone species [(μ-dppm)(Ni{CH ₂C(CH₃)C(CH₃)CH₂COO})₂] (3) was isolated in which the two nickel atoms realize different coordination geometries (SP-4 and SPY-5) in the solid state. The complexes were characterized by NMR techniques, single crystal X-ray diffraction measurements and infrared spectroscopy.

Full text of DOI:10.1039/c4dt01863j

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Nickelalactones with an allyl subunit – the effect
of penta-coordination on structures and stability†
Cite this: Dalton Trans., 2014, 43,
13988
Robert R. A. Freund, Helmar Görls and Jens Langer*
A series of allyl modified nickelalactone derivatives of the general formula [(L)
n 2 3 3
Ni{CH C(CH )C(CH )-
CH COO}] was synthesized via ligand exchange reactions in order to investigate the influence of the
2
neutral ligand L on the structure and stability of these complexes. While the square planar 1,8-diazabi-
cyclo[5,4,0]undec-7-ene ligated derivative 1 is stable in the solid state and in solution at ambient tempera-
ture, the use of the chelating ligands 6-diphenylphosphino-1,8-diazabicyclo[5.4.0]undec-7-ene, 1,1-bis-
(dicyclohexylphosphino)methane and 1,2-bis(dicyclohexylphosphino)ethane (dcpe) led to square pyrami-
dal derivatives 2, 4, and 5 with a novel ligand arrangement. In solution, these derivatives are fluxional and
show increasing tendencies in the order 2 < 4 < 5 to decouple the nickelalactone moiety to 2,3-dimethyl-
2
butadiene (dmbd), CO and zero-valent nickel complexes. During the investigation of 5, the tetrahedral
complex [(dcpe) Ni] (6) and the trigonal planar derivative [(dcpe)Ni(dmbd)] (7) were observed as predomi-
2
nant decomposition products. In the case of the application of 1,1-bis(diphenylphosphino)methane as a
Received 22nd June 2014,
Accepted 23rd July 2014
neutral ligand, a dinuclear nickelalactone species [(µ-dppm)(Ni{CH C(CH )C(CH )CH COO}) ] (3) was iso-
2
3
3
2
2
lated in which the two nickel atoms realize different coordination geometries (SP-4 and SPY-5) in the
solid state. The complexes were characterized by NMR techniques, single crystal X-ray diffraction
measurements and infrared spectroscopy.
DOI: 10.1039/c4dt01863j
www.rsc.org/dalton
lactones, are interesting synthons for the synthesis of a
number of carboxylic acid derivatives in subsequent reactions.
Introduction
5
Metal mediated reactions of unsaturated hydrocarbons and Depending on the neutral ligand present, allyl modified
6
CO offer a straightforward strategy to use CO as a cheap and nickelalactones with a square planar (SP-4, type A, Chart 1) or
nontoxic carbon source in organic synthesis. In this context, square pyramidal (SPY-5, type C)
2
2
1
4b,7
coordination sphere were
the palladium catalyzed co-oligomerization of 1,3-butadiene isolated, while related derivatives which are formally derived
7
,8
7,8a,9
and carbon dioxide to 3-ethylidene-6-vinyltetrahydro-2H-pyran- by coupling of simple alkenes and alkynes
exclusively
2
-one, as one of the few examples of a selective and atom-econ- show square planar geometries. In this type of reaction, the
omical catalysis in which carbon dioxide is utilized as a C1 formation of penta-coordinated nickel derivatives seems
building block in C–C carbon bond formation, might be con- unique to 1,3-diene substrates in the presence of chelating
2
sidered a chemist’s dream reaction. Consequently, this system ligands. So far, only two structurally characterized derivatives
2
,3
has received considerable attention over decades, although have been known, containing the nitrogen donor ligands 2,2′-
7
the reaction seems unfortunately limited to 1,3-butadiene as bipyridine (bipy) and N,N,N′,N′-tetramethylethylenediamine
the substrate. In contrast, CO fixation via coupling with other
2
1
,3-dienes is possible in the presence of low-valent nickel
4
complexes. Although the latter reaction is not a catalytic
transformation, the isolable products, allyl modified nickela-
Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University Jena,
Am Steiger 3 Haus 4, D-07743 Jena, Germany. E-mail: j.langer@uni-jena.de;
Fax: +4936419132; Tel: +493641948126
†
Electronic supplementary information (ESI) available: NMR spectra of 1, 6 and
3
1
8
,
P NMR spectra of 7 used for the determination of the coalescence tempera-
ture and ORTEP plots of 6 and 8. CCDC 1002896–1002903 for 1, 2, 3, 4, 6, 7,
·0.5THF and 8 respectively. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/c4dt01863j
7
Chart 1 Known structural SP-4 and SPY-5 isomers of nickelalactones
with an allyl subunit.
13988 | Dalton Trans., 2014, 43, 13988–14000
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4
b
(
tmeda). In contrast, the utilization of the chelating ligand employed for the ligand exchange. Two equivalents of this
-[(diisopropylphosphino)methyl]pyridine led to a rearrange- base, which normally acts as a monodentate ligand, were used
ment from a π-allyl to a σ-allyl structure and consequently to a for this purpose per nickel centre, since this stoichiometry was
2
1
0
8a,9d
square planar complex (type B, Chart 1) while the introduc- found in related dbu-ligated nickelalactones
derived by
tion of 1,2-bis(diphenylphosphino)ethane (dppe) resulted in nickel mediated coupling of alkenes or alkynes and CO and
2
6
a
decomposition of the nickelalactone.
was also used in the in situ generation of diene derived deriva-
Obviously the nature of the neutral ligand strongly affects tives via route I. However, the isolated product [(dbu)Ni-
the structure, stability and reactivity of allyl modified nickel- {CH C(CH )C(CH )CH COO}] (1) contained only one equi-
5
d
2
3
3
2
alactones but due to the limited data available the ligand influ- valent of the ligand and underlined that a further uptake of
ence is not fully understood. Since such information is crucial neutral ligands which might lead to penta-coordination at
for the development of further applications of allyl-modified nickel is unfavorable under the applied conditions.
1
nickelalactones in organic synthesis, the effect of a series of
In the H NMR spectrum of 1, two signals each were
neutral ligands, including 1,8-diazabicyclo[5,4,0]undec-7-ene observed for the CH
2 H
group of the allyl subunit (δ = 1.34 and
(
dbu) and 1,2-bis(dicyclohexylphosphino)ethane (dcpe) as two 1.99) and the neighboring diastereotopic CH group (δH = 2.42
2
ligands previously used to achieve the oxidative coupling of and 3.01) in addition to the expected eight signals of the CH
substituted 1,3-dienes and CO at the zero-valent nickel center, groups of the dbu ligand. The two singlets of the methyl
2
2
4
c,5d
was investigated.
groups at δ = 0.92 and 2.12 complete the spectrum. In the
H
1
3
1
C{ H} spectrum, the allyl group shows resonances typical of
3
a unsymmetrical η -coordination mode at δ
C
= 41.1, 73.8 and
1
11.8 (see ESI, Fig. S1†).
A π-allyl structure was also confirmed in the solid state by
Different strategies for the synthesis of allyl modified nickel- X-ray diffraction experiments (see Fig. 1). While the application
alactones of the formal composition [(L)
Ni(RCHCR′CR″- of chelating nitrogen donor ligands such as tmeda and bipy
CH COO)] have been reported (see Scheme 1). Beside the resulted in derivatives with a more or less distorted square
Results and discussion
n
2
4
b,7
above mentioned route via oxidative coupling of 1,3-dienes pyramidal coordination sphere around the nickel center,
and CO
in the presence of the desired ligand L at the zero- compound 1, as the first structurally characterized complex of
2
valent nickel center, the reaction of a 2,4-dienecarboxylic acid this type with a monodentate nitrogen donor ligand, contains
with appropriate nickel(0) complexes is an alternative pathway the divalent nickel cation in a distorted square planar environ-
6
b
at least in the presence of some selected neutral ligands.
ment formed by the nitrogen atom N1 of dbu, the carboxylic
Additionally, ligand exchange reactions offer a third strategy oxygen atom O1 and the carbon atoms C3 and C5 of the π-allyl
with tmeda ligated complexes as suitable starting materi- group. A trans-arrangement of N1 and C3 is observed while O1
6
a,7,11
als.
Its simplicity makes this last route very appealing for is positioned trans relative to C5. The CH COO group as the
2
the study of the effect of different neutral ligands. Since most substituent with the highest priority attached to the allyl group
of the structurally characterized derivatives are formally shows a syn orientation, while the methyl group at C3 is conse-
derived from 2,3-dimethyl-1,3-butadiene (dmbd), the well- quently found in the anti position. Similar arrangements were
4
a,b
known complex [(tmeda)Ni{CH C(CH )C(CH )CH COO}]
found for related derivatives containing the monodentate
2
3
3
2
6
a
was prepared via route I (see Scheme 1) and used as the phosphanes Ph
staring material in subsequent ligand exchange reactions dimesitylimidazol-2-ylidene (IMes) as neutral ligands (see
route III) to allow a simple comparison with known deriva- Table 1). As judged by comparison of the NMR data (see ESI,
3
P, Cy
3
P
or the N-heterocyclic carbene 1,3-
6
c
(
tives. In an initial investigation the bicyclic amidine dbu was Table S1†), the structurally not characterized pyridine complex
Scheme 1 Routes to nickelalactones with an allyl subunit.
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tion of a ligand with a P,N donor set was obvious, not only
because of the overwhelming number of known nickel-
alactones containing ligands with at least one of these two donor
atoms, but also because ligands with this donor set are known
1
0
to trigger subsequent reactions like π–σ rearrangements or
1
2
even initiate cascade reactions in related complexes. Appli-
cation of the dbu-derived racemic chelating ligand 6-diphenyl-
phosphino-1,8-diazabicyclo[5.4.0]undec-7-ene (dbuP), recently
1
3
developed by Braunstein and co-workers,
in a ligand
exchange reaction additionally ensured a high degree of com-
parability to complex 1. The isolated red product of this reac-
tion is sparingly soluble in THF, toluene and benzene, but the
addition of small amounts of methanol enhanced its solubility
and allowed recrystallization of the product from toluene. Sub-
sequent removal of methanol induced crystallization and
2 3 3
resulted in red crystals of [(dbuP)Ni{CH C(CH )C(CH )-
CH COO}] (2) as judged by single crystal X-ray diffraction
2
2
Fig. 1 Molecular structure and numbering scheme of [(dbu)Ni{CH C-
experiments and elemental analysis. The solid state structure
(
CH
3 3 2 6 6
)C(CH )CH COO}]·0.5 C H (1). The ellipsoids represent a prob-
a
a′
of a racemic crystal containing the enantiomeric pair 2 /2
clarity. Selected bond lengths (Å): Ni1–C3 2.003(7), Ni1–C4 1.961(7), (see Chart 2) was determined and the molecular structure of 2
ability of 40%. H atoms and co-crystallized benzene are omitted for
a
Ni1–C5 1.992(7), Ni1–O1 1.935(5), Ni1–N1 1.944(5), O1–C1 1.282(8), O2–
C1 1.229(8), C1–C2 1.539(10), C2–C3 1.536(11), C3–C4 1.400(11), C3–
C6 1.518(10), C4–C5 1.430(12), C4–C7 1.537(12); angles (°): N1–Ni1–O1
is shown in Fig. 2.
a
In compound 2 , the central nickel atom is penta-co-
ordinated (assuming that the allyl ligand occupies two coordi-
nation sites). The coordination sphere is formed by the oxygen
9
9.4(2), N1–Ni1–C3 161.1(3), N1–Ni1–C4 143.1(3), N1–Ni1–C5 102.5(3),
O1–Ni1–C3 84.9(3), O1–Ni1–C4 116.5(3), O1–Ni1–C5 158.0(3), C3–
Ni1–C4 41.3(3), C3–Ni1–C5 73.7(3), C4–Ni1–C5 42.4(3), C3–C4–C5 atom of the carboxylate function, the nitrogen and phosphorus
15.8(7).
1
donor atoms of the dbuP ligand and the carbon atoms C3 and
C5 of the allyl subunit. The angular parameter τ, derived
from the two largest angles α and β observed around nickel
14
7
[(py)Ni{CH
2
C(CH
3
)C(CH
3
)CH
2
COO}] has a comparable struc- (N1–Ni–C5 168.7° and P1–Ni–C3 151.8°), was calculated [τ =
(α − β)/60°] in order to distinguish between a square pyramidal
ture too.
As mentioned above, complexes such as 1 show little ten- (SPY-5; τ = 0) and a trigonal bipyramidal (TBPY-5; τ = 1) ligand
dency to take up an additional monodentate neutral donor arrangement. The observed value of 0.28 allows a description
a
ligand. Therefore, the employment of chelating ligands is of 2 as a distorted square pyramidal complex. However, the
a
necessary to study the effect of an enhancement of the coordi- ligand arrangement in 2 is strikingly different from the one
nation number at nickel. In order to elucidate how the observed in the closely related tmeda and bipy ligated com-
4
b,7
enforced introduction of such a second neutral donor alters plexes.
While the chelating nitrogen donor ligands adopt
the structure and reactivity of the resulting nickelalactone, one basal and apical position of the pyramid, the dbuP ligand
ligands with two different donor atoms seemed preferable, blocks two basal coordination sites. The apical position is
since they might allow additional conclusions about preferred taken by the oxygen atom O1 of the carboxylate group. The
donor atoms and arrangements at the nickel center. The selec- resulting distance Ni1–O1 of 2.106(3) Å is longer than that
5
4
3
2
1
Table 1 Comparison of selected structural parameters of the nickelalactone moieties of [(L)Ni{C H
2
C (CH
3
)C (CH
3
)C H
2
C OO}]
Bond lengths [Å]
Coordination
3
4
5
3
4
4
5
L
geometry
Ni–C
Ni–C
Ni–C
Ni–O
C –C
C –C
Ref.
tmeda SPY-5
1.978(10)
1.955(6)
2.003(7)
2.045(6)
2.012(5)
2.025(3)
2.215(5)
2.096(6)
1.940(9)
1.915(6)
1.961(7)
1.948(6)
1.970(6)
1.968(3)
2.031(5)
2.001(5)
2.018(12)
2.003(7)
1.992(7)
1.981(5)
2.010(6)
1.994(3)
1.991(5)
2.099(8)
1.966(6)
1.971(4)
1.935(5)
1.917(3)
1.898(3)
1.889(2)
2.106(3)
2.114(4)
1.41(1)
1.44(1)
4b
7
bipy
dbu
IMes
SPY-5
SP-4
SP-4
SP-4
SP-4
1.383(9)
1.400(11)
1.465(8)
1.323(9)
1.401(4)
1.377(7)
1.360(7)
1.458(10)
1.430(12)
1.492(7)
1.436(9)
1.412(5)
1.441(7)
1.460(9)
—
6c
6a
6a
—
—
—
a
Ph
Cy
3
P
P
3
dbuP b SPY-5
dcpm SPY-5
c
dppm SP-4/SPY-5
2.008(8)/2.020(8) 1.983(8)/1.953(8) 1.999(9)/2.004(8) 1.919(6)/1.927(6) 1.416(13)/1.424(12) 1.400(13)/1.405(12)
a
b
Data suffer from a disorder of the allyl subunit. Data suffer from a positional disorder of the nickel atom. The data related to the dominantly
c
occupied position are listed. The dinuclear compound 3 contains a bridging dppm ligand.
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While the crystalline appearance, the elemental analysis
and the observation of a single absorption for the asymmetric
−
1
stretching mode of the carboxylate group at 1579 cm in the
infrared spectrum of solid 2 suggest a uniform compound in
3
1
the solid state, the P NMR data of a crystalline sample of 2 in
a mixture of C and CD OD clearly indicate that a mixture of
6
D
6
3
substances is present in solution. Beside a rather sharp singlet
at δ = 40.7 as the dominating signal of the spectrum, another
P
P
small singlet was observed at δ = 41.0 and tentatively assigned
to another diastereomer of 2 (see Chart 2).
Additionally, very broad signals at δ = 25.7, 38.3 and 44.0
P
are also present. Two possible explanations for this obser-
vation are (i) the formation of different species in equilibrium
in solution from a uniform crystalline batch due to the well-
known fluxionality of penta-coordinated species and/or a π–σ
(and reverse) rearrangement of the allyl group or (ii) the for-
mation of different aggregates in solution due to hydrogen
Chart 2 Two enantiomeric pairs of 2 forming diastereomers.
1
5
3
bond formation between the nickelalactones and CD OD.
Although we tend to option (i), we were not able to clearly rule
one of them out as the absence of methanol makes compound
2
insoluble in commonly used solvents such as toluene,
benzene or THF. The utilization of more polar solvents like
CD Cl enhanced the solubility of 2 but led to its subsequent
2
2
decomposition in solution. Additionally, temperature depen-
dent NMR measurements were performed to gain further
information about the system but were uninformative. Never-
theless, the dominant species present in solution clearly is a
1
3
1
nickelalactone with typical signals in the C{ H} NMR spec-
trum (see ESI, Table S1†).
In order to evaluate whether such fluxional behavior in
solution is typical of the penta-coordinated compounds under
investigation, we additionally included chelating phosphane
ligands in subsequent experiments, although the widely used
1,2-bis(diphenylphosphino)ethane (dppe) was reported to
trigger the decomposition of allyl modified nickelalactones
6
a
and led to formation of [Ni(dppe)
2
]. A chelating phosphane
Fig. 2 Molecular structure and numbering scheme of [(dbuP)Ni{CH
2
C-
a
ligand which is known to result in unique reactivity and struc-
(
CH
3
)C(CH
3
)CH
2
COO}] (2 ). The ellipsoids represent a probability of
8
c,16e
4
0%. H atoms are omitted for clarity. Selected bond lengths (Å): Ni1–C3 tures
when introduced as a neutral ligand in nickel-
2
2
.215(5), Ni1–C4 2.031(5), Ni1–C5 1.991(5), Ni1–O1 2.106(3), Ni1–P1
.0968(12), Ni1–N1 1.977(4), O1–C1 1.266(5), O2–C1 1.248(5), C1–C2
alactones and therefore might spare the nickelalactone under
investigation the fate of the dppe ligated derivative, is the
closely related 1,1-bis(diphenylphosphino)methane (dppm).
The initial experiments performed with equimolar amounts
1.532(7), C2–C3 1.527(7), C3–C4 1.377(7), C3–C6 1.526(8), C4–C5 1.441(7),
C4–C7 1.507(7); angles (°): P1–Ni1–N1 84.27(11), P1–Ni1–O1 122.47(10),
P1–Ni1–C3 151.78(14), P1–Ni1–C4 115.58(15), P1–Ni1–C5 94.28(16),
N1–Ni1–O1 92.90(14), N1–Ni1–C3 107.25(19), N1–Ni1–C4 129.19(19), of dppm and [(tmeda)Ni{CH
N1–Ni1–C5 168.7(2), O1–Ni1–C3 84.41(16), O1–Ni1–C4 110.14(17), O1–
3 3 2
C(CH )C(CH )CH COO}] led to
2
complicated product mixtures from which considerable
amounts of dppm were regained even after complete removal
of the liberated tmeda ligand from the system. The reason
therefore was sought in the weak chelating ability of dppm due
to the almost parallel alignment of the lone pairs of the two
Ni1–C5 97.29(18), C3–Ni1–C4 37.5(2), C3–Ni1–C5 69.3(2), C4–Ni1–C5
2.0(2), C3–C4–C5 116.7(5).
4
observed in related derivatives with deviating geometry (see phosphorus atoms which often leads to bridging or even
Table 1). In contrast to compound 1, the nitrogen donor atom monodentate coordination modes of dppm in related zero-
8
c,16
is now found in the trans position to the carbon atom C5. valent and divalent nickel compounds.
When dppm was
Within the nickelalactone, the orientation of the substituents consequently considered as an assembly of two independent
of the allyl subunit changed and an anti alignment of the monodentate phosphanes rather than a chelating ligand and
CH COO group is now observed. The finding indicates that a consequently a stoichiometry of 0.5 dppm per nickel center
2
π–σ–π rearrangement of the allyl group is part of the occurring was applied, an orange solid was obtained. This solid con-
rearrangement induced by the ligand exchange.
sisted mainly of [(µ-dppm)(Ni{CH C(CH )C(CH )CH COO}) ]
2 3 3 2 2
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(
3). A few well-shaped crystals of 3 were obtained of the ethe- nickel oxygen bond Ni2–O1 of 2.372(6) Å points to a rather
real mother liquor of the reaction at −20 °C. The molecular weak interaction. Similarly, the bonding of the tmeda ligand
structure of 3·Et O is shown in Fig. 3 along with selected bond in [(tmeda)Ni{CH C(CH )C(CH )CH COO}] is strongly asym-
lengths and angles of the molecule. metric with a much longer bond between the nickel center and
In 3, two crystallographically independent nickel atoms Ni1 the nitrogen atom in the apical position [Ni–N2 2.314(8) Å] than
2
2
3
3
2
4b
and Ni2 were observed, both incorporated in nickelalactone in the basal position [Ni–N1 2.064(7) Å].
moieties in which the CH COO groups occupy the syn posi- Although the formation of oligomeric nickelalactones via
2
tions at the allylic carbon atoms C3 and C10, respectively. bridging carboxylate groups is not without precedence and for
While the nickel atom Ni1 is found in a square planar coordi- instance derivatives of the general formula [(L)Ni-
1
7
2 2 n
nation environment closely related to the situation in 1 and (CH CH COO)] (n = 2, 4, 6) with monodentate phosphane
6
c
known derivatives containing monodentate phosphane and N-heterocyclic carbene donor ligands L are known, these
ligands, the coordination number of Ni2 is enhanced to five derivatives usually contain the nickel cation in the square
and a square pyramidal coordination sphere is formed due to planar coordination sphere. To the best of our knowledge, the
an additional contact between this nickel center and the endo- formation of oligonuclear square pyramidal nickelalactones
cyclic oxygen atom of the carboxylate moiety of the neighbor- such as 3, interconnected via the carboxylate group, was not
ing nickelalactone. The additional oxygen donor occupies the observed before. The isolation of such a compound is rather
apical position of the resulting pyramid. The extremely long surprising given the unwillingness of compound 1 to take up
an additional ligand. Its formation is clearly linked to the use
of dppm which acts as a bridging ligand and enforces close
proximity of neighboring nickelalactones. The formation of a
central six-membered ring, consisting of the methylene carbon
atom and the two phosphorus atoms of dppm, the two nickel
atoms and the bridging oxygen atom of one carboxylate group,
stabilizes the emerging molecule. The bond lengths and
angles within the two nickelalactone moieties of 3 are very
similar despite the deviating coordination number of the
nickel atoms comparable to those observed in related deriva-
tives with a syn orientation of the CH COO group (see Table 1).
2
The presence of two different carboxylate groups in solid
3
is also observable by infrared spectroscopy where two dis-
−
1
tinct vibrational bands at ˜ν = 1656 and 1634 cm for the asym-
metric carboxylate stretching vibration were observed (see
Table 2). In solution, the solid state structure is not preserved.
Here, the dominating species which contains 0.5 equivalent of
dppm per nickelalactone is a symmetric species with a single
3
1
1
signal in the P{ H} NMR spectrum at δ
P
= 13.0. The
1
3
1
C{ H} NMR data obtained are unremarkable and show
typical chemical shifts for the carbon atoms of the nickelalac-
tone moiety (see ESI, Table S1†).
Fig. 3 Molecular structure and numbering scheme of [(µ-dppm-
3
1
CH
4
κP;2κP’)Ni
2
2
{CH
2
C(CH
COO-2κ C;2κO}]·Et
0%. H atoms and the co-crystallized diethyl ether are omitted for
3
)C(CH
3 2 2 3 3
)CH COO-1κ C;1:2κO}{CH C(CH )C(CH )-
3
2
O (3). The ellipsoids represent a probability of
Table 2 Comparison of the asymmetric carboxylate stretching bands
5
4
3
2
1
of [(L)Ni{C H
2
C (CH
3
)C (CH
3
)C H
2
C OO}] in the solid state
clarity. Selected bond lengths (Å): Ni1–C3 2.008(8), Ni1–C4 1.983(8),
Ni1–C5 1.999(9), Ni1–O1 1.919(6), Ni1–P1 2.212(2), O1–C1 1.319(10),
O2–C1 1.228(11), C1–C2 1.522(12), C2–C3 1.522(13), C3–C4 1.416(13),
C3–C6 1.512(14), C4–C5 1.400(13), C4–C7 1.518(14), Ni2–C10 2.020(8),
Ni2–C11 1.953(8), Ni2–C12 2.004(8), Ni2–O1 2.372(6), Ni2–O3 1.927(6),
Ni2–P2 2.205(2), O3–C8 1.303(10), O4–C8 1.231(10), C8–C9 1.521(11),
Coordination
geometry
Alignment of
L
CH
2
COO
ν
as(COO)
Ref.
py
dbu
SP-4
SP-4
SP-4
SP-4
syn
syn
syn
syn
syn
syn
syn
anti
anti
anti
1636
1626
1639
1648
1650
1656/1634
1618
1579
1599
7
—
6c
6a
6a
—
4b
—
—
—
C9–C10 1.541(12), C10–C11 1.424(12), C10–C13 1.505(13), C11–C12 IMes
1
.405(12), C11–C14 1.517(13); angles (°): P1–Ni1–O1 107.53(18), P1–Ni1– Cy
C3 168.6(3), P1–Ni1–C4 128.0(3), P1–Ni1–C5 95.6(3), O1–Ni1–C3 Ph
/2 dppm
3
P
3
P
SP-4
1
SP-4/SPY-5
SPY-5
SPY-5
SPY-5
SPY-5
83.8(3), O1–Ni1–C4 119.1(3), O1–Ni1–C5 156.8(3), C3–Ni1–C4 41.6(4),
tmeda
dbuP
dcpm
C3–Ni1–C5 73.0(4), C4–Ni1–C5 41.2(4), C3–C4–C5 115.7(9), P2–Ni2–
O1 88.84(15), P2–Ni2–O3 97.33(18), P2–Ni2–C10 162.7(3), P2–Ni2–C11
1
23.5(3), P2–Ni2–C12 100.5(3), O1–Ni2–O3 87.8(2), O1–Ni2–C10
a
dcpe
1584
108.4(3), O1–Ni2–C11 133.1(3), O1–Ni2–C12 105.8(3), O3–Ni2–C10 85.7(3),
a
The appearance of a weaker second band at 1607 cm−1 indicates the
presence of another isomer.
O3–Ni2–C11 116.5(3), O3–Ni2–C12 157.7(3), C10–Ni2–C11 42.0(4), C10–
Ni2–C12 73.3(4), C11–Ni2–C12 41.6(4), C10–C11–C12 116.3(8).
13992 | Dalton Trans., 2014, 43, 13988–14000
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2
Only a slight downfield shift of the CH groups of the allyl
subunit to δC = 48.1 was detected. Additionally, the signal of
the allylic carbon atom in the trans position to phosphorus at
δ
C
= 83.0 as well as the signal of the carboxylate carbon at δ
C
=
1
83.7 were observed as pseudo-triplets, most likely due to
virtual coupling in an AA′X (or ABX) spin system (A, A′, B =
phosphorus, X = carbon). These observations indicate that the
solution structure of 3 is dominantly those of a SP-4 complex
and penta-coordinated species play a minor role under these
conditions. Nevertheless, such interactions do exist as high-
lighted by the solid state structure of 3. However, a second
weaker and incomplete signal set of another nickelalactone
13
1
1
was observed in both the C{ H} and H NMR spectra. Attempts
to remove this impurity by recrystallization were unsuccessful.
The too high carbon content determined by elemental analysis
points towards the initially envisioned nickelalactone [(dppm)-
Ni{CH C(CH )C(CH )CH COO}] as the impurity, while the
2
3
3
2
unreacted tmeda-containing starting material could be excluded
because the product contained no nitrogen.
Unfortunately, the inability to obtain a pure derivative of
2 3 3 2
the type [(L)Ni{CH C(CH )C(CH )CH COO}] which contains
dppm as a chelating ligand leaves the initial question concern-
ing the stability and structure of such chelate phosphane Fig. 4 Molecular structure and numbering scheme of [(dcpm)Ni{CH
2
C-
(
CH )C(CH )CH COO}]·CH OH (4). The ellipsoids represent a probability
3 3 2 3
ligated nickelalactones unanswered. In the second attempt,
the closely related 1,1-bis(dicyclohexylphosphino)methane
of 40%. H atoms (except the one at O3) and a disorder of the nickel
atom are omitted for clarity. Selected bond lengths (Å): Ni–C3 2.096(6),
Ni1–C4 2.001(5), Ni1–C5 2.099(8), Ni1–O1 2.114(4), Ni1–P1 2.134(4),
(dcpm) was employed. The ligand exchange reaction between
[
(tmeda)Ni{CH C(CH )C(CH )CH COO}] and dcpm takes Ni1–P2 2.305(6), O1–C1 1.226(5), O2–C1 1.248(5), C1–C2 1.502(7), C2–
2
3
3
2
another course than in the case of dppm and it was possible C3 1.564(8), C3–C4 1.360(7), C3–C6 1.453(8), C4–C5 1.460(9), C4–C7
1
1
.588(8), O2⋯O3 2.702(9); angles (°): P1–Ni1–P2 75.79(7), P1–Ni1–O1
02.3(2), P1–Ni1–C3 171.6(2), P1–Ni1–C4 133.1(3), P1–Ni1–C5 102.7(3),
to isolate a 1 to 1 adduct. Since the ligand that was used shows
superior σ-donor capacity relative to dppm, a stable product
was expected. However, the crude product, obtained at
P2–Ni1–O1 99.35(16), P2–Ni1–C3 108.5(4), P2–Ni1–C4 129.1(4), P2–
Ni1–C5 164.2(2), O1–Ni1–C3 84.3(2), O1–Ni1–C4 109.6(2), O1–Ni1–C5
ambient temperature, was observed to be a mixture which 96.3(3), C3–Ni1–C4 38.7(2), C3–Ni1–C5 71.2(2), C4–Ni1–C5 41.6(2),
already contained decomposition products beside the desired C3–C4–C5 119.9(6).
nickelalactone [(dcpm)Ni{CH C(CH )C(CH )CH COO}] (4).
2 3 3 2
Therefore recrystallization and meanwhile handling and
storage of the solutions at low temperatures (–40 °C) were
necessary to isolate a pure substance (see the Experimental
section). Nevertheless, only the addition of small portions of
methanol and further recrystallization yielded suitable crystals
for X-ray diffraction analysis. In the solid state, compound
the pyramid. Comparison of its properties with previously
investigated derivatives allowed the identification of the asym-
metric stretching vibration of the carboxylate group as a valid
criterion to simply distinguish this isomeric form from others.
Both known examples, compounds 2 and 4, show this band at
−1
−1
remarkably low wavenumbers (2: 1579 cm ; 4: 1599 cm
)
4
·MeOH resembles the dbuP ligated derivate 2 with respect to
while for all other derivatives higher values were found (see
Table 2). The observed values indicate an increased degree of
charge delocalization within the carboxylate group and
increased contribution of resonance form b (see Scheme 2) to
the overall structure of the molecule. Expectedly, hydrogen
bond formation to the exocyclic oxygen atom fortified this
the general conformation of the molecule, but in this case one
molecule of methanol per nickelalactone, which forms a
hydrogen bond to the exocyclic oxygen atom of the nickel
complex, was found within the crystal. This finding underlines
that the derivatives under investigation are rather stable
against protolysis in agreement with the results obtained for
related derivatives of the type [(L)
n 2 2
Ni(CH CH COO)] which also
8
c,15,17
form stable hydrogen bonds with alcohols
and
1
8
amines. The molecular structure of 4·MeOH is shown in
Fig. 4.
The preference of the less basic exocyclic oxygen atom of 4
for adduct formation results from steric shielding of the endo-
cyclic oxygen atom by the dcpm ligand. With compound 4, a
second square pyramidal nickelalactone derivative is available
in which the carboxylate group occupies the apical position of Scheme 2 Resonance forms a and b of 4.
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effect and measurement of crystals of 4·MeOH gave a value of asymmetric carboxylate stretching vibrations in the infrared
577 cm−
1
.
spectrum, a stronger one at ˜ν = 1584 and a weaker one at ˜ν =
1
In solution, compound 4 is neither uniform nor stable at 1607 cm− , as an indication that two slightly different isomers
ambient temperature. H and C{ H} spectra show the pres- or conformers of 5 are present in the solid state (Table 2). For
ence of at least two different nickelalactones as indicated for the major form, a structure in analogy to the complexes 2 and
instance by the presence of two different signals of the carboxy- 4 was confirmed by X-ray diffraction analysis. Due to the rather
1
1
13
1
C
late group at δ = 183.7 (major isomer) and 175.8. Additionally, low quality of the obtained crystals only a structural motif of 5
the isomers as penta-coordinated molecules can be fluxional (see Fig. 5) is available which was sufficient to establish the
themselves as observed for the major isomer in solution. In connectivity of the atoms but precludes further discussion of
3
1
1
the P{ H} spectrum this compound gave rise to a broadened bond lengths and angles. Despite several attempts, no suitable
singlet at δ = 10.6 due to rapid exchange of the positions of crystals of the other form of 5 were found and therefore its
P
the two non-equivalent phosphorus nuclei. The situation is conformation remains uncertain although the IR data might
further complicated by slow decomposition of 4 to unknown point to a square pyramidal complex with a ligand alignment
4
b
nickel containing products. The simultaneous occurrence of in analogy to the known tmeda derivative. Limited NMR data
typical signals of liberated 2,3-dimethylbutadiene at δ = 20.6, of 5 were obtained in THF-d under a CO atmosphere, applied
13.1 and 144.1 is an indication that decoupling of the nickel- to suppress decomposition via decoupling of the nickel-
alactone subunit occurred as one of the decomposition path- alactone to CO2 and 2,3-dimethylbutadiene. Unfortunately,
C
8
2
1
3
1
1
ways. Nevertheless, with the help of two-dimensional HMBC under these conditions, only a useful P{ H} spectrum of 5,
and HSQC NMR experiments it was possible to identify and consisting of two singlets at δ = 63.8 and 74.0 of equal inten-
assign all C{ H} NMR signals of the nickelalactone subunit sity, is accessible while the H NMR spectrum is uninformative
P
1
3
1
1
1
3
1
of the dominant species in solution (see ESI, Table S1†).
due to broad overlapping signals. A meaningful C{ H} NMR
The unexpected destabilization of the investigated nickel spectrum is prevented by the very limited solubility of 5 under
derivative upon utilization of dcpm needed some additional these conditions.
considerations. The use of highly basic chelate phosphanes
If compound 5 is kept in contact with the tmeda containing
like dcpm, dcpe and 1,2-bis(dicyclopentylphosphino)ethane as mother liquor of the reaction for an enhanced time span at
ligands usually led to stable, structurally characterized satura- low temperature, the solid product becomes more and more
8
c,19
9d
ted
moiety) which do not decouple spontaneously into CO
the parent hydrocarbon (alkene, alkyne) at ambient THF at ambient temperature without a CO atmosphere, but
and unsaturated nickelalactones (without the allyl contaminated with the above mentioned [(dcpe)
2
Ni] in the
2
and crystalline form. In contrast, isolated 5 dissolves readily in
2
temperature.
Additionally, dcpe is a ligand which is commonly used in valent nickel derivative [(dcpe)Ni{η -CH
the synthesis of such nickel derivatives via oxidative coupling (7) besides minor amounts of 6 were observed. Related com-
rapid decoupling and predominant formation of the zero-
2
2
3 3 2
C(CH )C(CH )CH }]
8
a,19
4c
of CO
2
and unsaturated substrates
including 1,3-dienes.
plexes of nickel with 1,3-butadiene ligands are known and
2
The observed instability of the dcpm ligated derivative 4 does different coordination modes of the diene ligand including η -;
not seem to fit the reactivity scheme although it is in line with
6
a
the reported behavior of the dppe derivative. Clearly, the
dcpe stabilized compound [(dcpe)Ni{CH C(CH )C(CH )-
2
3
3
CH COO}] (5) would be the perfect candidate to decide
2
whether chelate phosphane ligands per se have a destabilizing
effect on the investigated nickelalactones or dcpm is an excep-
tion due to the formation of an unfavorable four membered
chelate ring at nickel which already led to the isolation of the
unusual derivative 3 in the case of dppm. The initial ligand
exchange reactions at ambient temperature using dcpe led to a
slow color change from red to yellow and the precipitation of a
pale yellow substance which was identified as the well-known
2
0
zero-valent nickel complex [(dcpe) Ni] (6) by comparison of
2
the NMR data and additional X-ray diffraction analysis (see
ESI, Fig. S4†). The isolation of 6 underlines that chelating
diphosphane ligands indeed have a destabilizing effect on the
allyl modified nickelalactones under investigation. Neverthe-
less the isolation of the dcpe ligated nickelalactone 5 is poss-
ible due to its low solubility in THF via crystallization, when
the initial reaction mixture was rapidly cooled to −10 °C in
order to avoid the decoupling of the nickelalactone. The red
Fig. 5 Structural motif of [(dcpe)Ni{CH
THF (5). The H atoms, co-crystallized THF and a disorder of C2, C3, C5,
2 3 3 2
C(CH )C(CH )CH COO}]·0.5
crystalline product obtained in this manner showed two C6, O1 and O2 are omitted for clarity.
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4
2
2
21
η - and μ
2
–η :η -coordination were reported. While in the system dcpe/[Ni(cod)
2
] in analogy to the reactions with 1,3-
4
c
case of the closely related 1,3-butadiene complex [(dcpe)Ni- butadiene and isoprene. Additionally, their formation in the
CH
solid state,
tron-rich and sterically demanding ligand prefers η -coordi- their utilization. First of all, substitution of the cod ligand by
nation in 7 as confirmed by X-ray analysis. As depicted in electron rich diene derivatives is unfavorable and therefore
Fig. 6, the diene ligand adopts an s-trans conformation in this often an excess of the diene component is necessary to achieve
4
{
2 2
CHCHCH }] a η -coodination mode was found in the above described experiments underlines the obstacles on this
2
1b
2,3-dimethylbutadiene as a slightly more elec- known pathway to allyl modified nickelalactones and during
2
distorted trigonal planar nickel complex. Coordination to satisfying reaction rates. Furthermore, an excess of CO is not
2
nickel leads to a lengthening of the double bond between C1 only beneficial to shift the equilibrium between complexes like
2
and C2 [1.437(4)] by 0.086 Å relative to the undisturbed double 7 and CO towards the desired products but might also help in
bond between C3 and C4 [1.351(4) Å]. preventing the reversion of their formation in subsequent reac-
The presence of 6 as an impurity and its ongoing slow for- tions in order to make these derivatives utilizable in organic
mation besides liberated 2,3-dimethylbutadiene and other un- synthesis. The investigation especially of the dcpm and dcpe
identified products in solution indicate that compound 7 has ligated derivatives 4 and 5 indicates that this decoupling reac-
a lower stability than the related 1,3-butadiene derivative. The tion is a serious threat in solution.
straightforward synthesis of pure 7 was attempted by the reac-
tion of equimolar amounts of dcpe and [Ni(cod) ] (cod = cis,
2
cis-1,5-cyclooctadiene) in the presence of a tenfold excess of
Conclusion and perspective
2
,3-dimethylbutadiene but only led to isolation of [(dcpe)Ni-
2
2
(cod)] (8) in good yield. (The same product was obtained in In contrast to the nickelalactones derived via coupling of CO2
the absence of 2,3-dimethylbutadiene; see the Experimental and alkenes or alkynes, the stability of allyl modified nickel-
section and ESI, Fig. S6.†) Nevertheless, the formation of alactones derived from dienes does not benefit from the appli-
minor amounts of 7 in equilibrium was detected via NMR cation of chelating ligands. Particularly the use of widely
investigation of the reaction mixture.
applied bidentate chelate phosphane ligands has a destabiliz-
The structurally characterized derivatives 7 and 8 are two ing effect on these species. This deviating reactivity is closely
potential intermediates on route to the nickelalactone deriva- related to the penta-coordinated nature of derivatives such as
tive 5 via coupling of 2,3-dimethylbutadiene and CO
2
by the [(dcpm)Ni{CH
2
C(CH
3
3 2
)C(CH )CH COO}] (4) and [(dcpe)Ni-
{
CH C(CH )C(CH
2
3
3
)CH
2
COO}] (5) which seems to significantly
lower the activation barriers for decoupling reactions. This
activating effect of penta-coordination, although in context of
other reactions, is well-documented in the chemistry of related
8
23
d -systems of iridium(I) and ascribed to the formation of
highly distorted tetra-coordinated intermediates from the pre-
ferred penta-coordinated species which leads to a significant
lowering of the overall activation energies of the investigated
processes. However, the assumption that the observed destabi-
lization in the case of the investigated nickelalactones is
closely related to the hitherto unknown conformation of the
derivatives 4 and 5 and is not the result of the enhanced
coordination number alone can be ruled out. The starting
material
[(tmeda)Ni{CH C(CH )C(CH )CH COO}],
which
2
3
3
2
shares the coordination number of the compounds 4 and 5
but has another alignment of the ligands around the nickel
center, also showed slow decomposition when handled in a
solution without additional CO
dinuclear [(µ-dppm)(Ni{CH C(CH
2
present. The stability of
)C(CH )CH COO}) (3)
2
3
3
2
2
]
exceeds those of the dcpm and dcpe ligated derivatives, most
likely because this compound is a predominantly tetra-co-
ordinated species in solution although penta-coordination of
one of the two nickel centers was observed in the solid state.
Fig. 6 Molecular structure and numbering scheme of [(dcpe)Ni{CH
CH )C(CH )CH }] (7). The ellipsoids represent a probability of 40%.
H atoms are omitted for clarity. Selected bond lengths (Å) [values of
·0.5THF added in square brackets]: Ni1–C1 1.954(3) [1.954(3)], Ni1–C2
2
C-
(
3
3
2
7
1
.997(3) [2.009(3)], Ni1–P1 2.1361(7) [2.1420(7)], Ni1–P2 2.1565(7) [2.1571(7)], Among the penta-coordinated derivates investigated, the dbuP
C1–C2 1.437(4) [1.440(4)], C2–C3 1.476(4) [1.481(4)], C2–C5 1.515(4)
.508(4)], C3–C4 1.351(4) [1.341(5)], C3–C6 1.495(5) [1.504(5)]; angles (°):
2 3 3 2
ligated compound [(dbuP)Ni{CH C(CH )C(CH )CH COO}] (2)
1
shows the lowest tendency for the decoupling of the nickel-
alactone moiety and might indicate that chelating ligands with
P,N donor set are superior for the stabilization of these deriva-
tives. However, subsequent investigations with additional
P1–Ni1–P2 91.92(3) [92.25(3)], P1–Ni1–C1 108.47(9) [108.11(9)], P1–Ni1–
C2 150.23(9) [150.30(9)], P2–Ni1–C1 159.35(9) [158.87(10)], P2–Ni1–C2
1
16.70(9) [116.52(9)], C1–C2–C3 121.0(3) [119.5(3)], C1–C2–C5 117.8(3)
[
118.4(3)].
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ligands of this type are necessary to clarify this point. In con- Calcd for C16
H
26
N
2
NiO
2
(337.08): C, 57.01; H, 7.77; N, 8.31;
trast to the penta-coordinated derivatives, the square planar found: C, 57.07; H, 7.82; N, 8.23%; selected IR (ATR): ˜ν = 1626
−
1 1
compound [(dbu)Ni{CH
fectly stable in solution at ambient temperature.
2
C(CH
3
)C(CH
3
)CH
2
COO}] (1) is per- (s, νas,COO), 1592(s, νCvN) cm ; H NMR (600.1 MHz, C
6
D
C–
6
):
2
2 2
δ 3.24 (br s, 2H, CvN–CH ), 3.01 (d, 1H, JH,H = 15.9 Hz, O
It can be concluded from the obtained results that tetra-co- C(H )H ), 2.91 (br s, 2H, NvC–CH ), 2.70 (br s, 2H, NvC–
eq ax
2
ordinated allyl modified nickelalactones containing a single (CH
2
)
4
CH
2
2 2 2
), 2.65 (br s, 2H, CvN–(CH ) CH ), 2.42 (d, 1H,
2
highly basic monodentate neutral ligand show superior long
2
JH,H = 15.9 Hz, O C–C(Heq)Hax), 2.12 (s, 3H, CH3(meso)), 1.99 (s,
term stability in solution and therefore are the systems of 1H, C(Hanti)Hsyn), 1.47 (br s, 2H, NvC–CH CH ), 1.35–1.36
2
2
choice for the exploration of these derivatives as organometal- (m, 3H, CvN–CH
lic reagents in organic synthesis. Since it is commonly (CH CH ), 1.10 (br s, 2H, NvC–(CH
accepted that for the coupling process of a diene and CO at CH3(anti)). C{ H} NMR (150.9 MHz, C D ): δ 182.4 (COO),
2
CH
2
+ C(Hanti)Hsyn), 1.29 (br s, 2H, NvC–
2
)
2
2
2
)
3
CH ), 0.92 (s, 3H,
2
1
3
1
2
6 6
the nickel center itself, the presence of two monodentate 163.9 (CvN), 111.8 (C–CH3(meso)), 73.9 (C–CH3(anti)), 53.1
ligands or of a bidentate chelate ligand per nickel center is (NvC–(CH CH ), 47.7 (CvN–(CH CH ), 47.2 (CvN–CH ),
2
)
4
2
2
)
2
2
2
required, isolation of the product (in the case of monodentate 44.4 (O C–CH ), 41.1 (CH ), 38.9 (NvC–CH ), 29.2 (NvC–
2
2
2
2
ligands) and the subsequent exchange of the chelate ligand by (CH
2
)
2
CH
2
), 28.0 (NvC–(CH
2
)
3
CH
2
2 2
), 25.3 (NvC–CH CH ),
a monodentate one are further measures to ensure the stability 22.1 (CvN–CH
2
CH ), 21.7 (CH3(anti)), 20.1 (CH3(meso)). Crystals
2
of the complexes in following reactions. It should be noted of 1·0.5 benzene suitable for X-ray diffraction experiments
that even the presence of a second non-coordinated ligand in were obtained by cooling a saturated solution of 1 in a mixture
2
4
solution was proven counterproductive in related systems.
of n-heptane and benzene from ambient temperature to 0 °C.
Synthesis of [(dbuP)Ni{CH C(CH )C(CH )CH COO}]
order to further suppress the impending decoupling of the (2). Solid dbuP (400 mg, 1.17 mmol) was added in one portion
Additionally, a CO atmosphere might be beneficial as well in
2
2
3
3
2
nickelalactone in succeeding transformations.
to
a
2 3 3
stirred solution of [(tmeda)Ni{CH C(CH )C(CH )-
CH COO}] (341 mg, 1.14 mmol) in THF (26 mL) at ambient
2
temperature. After dissolution of the dbuP the red reaction
mixture was cooled to 5 °C and stored at this temperature.
After three days at this temperature the precipitated orange red
crude product (336 mg, 56%) was collected by filtration and
Experimental
General comments
All manipulations were carried out under an inert argon dried in a vacuum. Thereafter the compound was suspended
atmosphere using standard Schlenk techniques. THF, THP, in toluene (8 mL) and methanol was added dropwise with
toluene, diethyl ether and heptanes (mixture of isomers) were rapid stirring until a clear red solution was obtained. After-
dried over KOH and distilled over sodium/benzophenone wards the added methanol was slowly removed in a vacuum
under an argon atmosphere; deuterated THF and benzene until the crystallization of the product started. Then the
were dried over sodium, degassed, and saturated with argon. mixture was allowed to stand at −10 °C for 24 hours to com-
Acetone was dried over B
2
O
3
. The yields given are not opti- plete crystallization. The red crystals formed were separated by
mized. H and C{ H} NMR spectra were recorded on Bruker decantation, washed with toluene (3 mL) and dried in a
AC 400 or AC 600 spectrometers. Chemical shifts are reported vacuum. Yield: 214 mg (36%). Anal. Calcd for C28 NiO
in parts per million relative to Me Si as an external standard. (521.27): C, 64.52; H, 6.77; N, 5.37; found: C, 64.85; H, 6.66; N,
The residual signals of THF-d or C D were used as an 5.34; selected IR (ATR): ˜ν = 1579 cm− (s, νas,COO); H NMR
1
13
1
H
35
N
2
2
P
4
1
1
8
13
6 6
1
1
internal standard in the H and C{ H} NMR spectra. The fol- (400.1 MHz, C
lowing abbreviations are used for the NMR data: s = singlet; d (m, 2H, CH Ph), 7.4–7.1 (m, 8H, CH Ph), 3.4–2.3 (m, 7H, 3 ×
doublet; t = triplet; m = multiplet; br = broad and IR data: s = CH + CH dbuP), 2.51 (m, 1H, O C–CHH′), 2.40 (m, 1H, O C–
6 6 3
D + CD OD): major species in solution: δ 7.52
=
2
2
2
strong, m = medium. The pseudo-triplets observed are most CHH′), 1.87 (br, 1H, CHH′), 1.80 (m, 1H, CHH′), 1.5–0.9 (m,
2
5
likely the result of virtual coupling phenomena. [Ni(cod)
2
]
8H, 4 × CH
2
dbuP), 1.49 (s, 3H, CH
3
), 1.36 (d, 3H, J = 7.8 Hz,
4
a
13
1
and [(tmeda)Ni{CH C(CH )C(CH )CH COO}] were prepared CH3); C{ H} NMR (150.9 MHz, C D + CD OD): incomplete
according to known procedures. Dppm, dcpm and dcpe were signal set of the major species in solution: δ 179.2 (d, JC,P
2
3
3
2
6
6
3
3
=
=
2
2
purchased from Strem Chemical, Inc. and used as received.
9.8 Hz, COO), 166.4 (d, JC,P = 18.7 Hz, CvN), 116.5 (d, JC,P
2
Synthesis of [(dbu)Ni{CH C(CH )C(CH )CH COO}] (1). Dbu 2.4 Hz, C–CH3(meso)), 94.9 (d, J = 22.9 Hz, C–CH3(syn)), 54.0
C,P
0.44 mL, 448 mg, 2.94 mmol) was added dropwise to a stirred (s, CH
solution of [(tmeda)Ni{CH C(CH )C(CH )CH COO}] (440 mg, dbuP), 48.3 (s, CH
.47 mmol) in toluene (10 mL) at ambient temperature via a 39.2 (d, J = 5.0 Hz, CH allyl), 29.0 (s, CH dbuP), 28.2 (d,
2
3
3
2
1
(
2
dbuP), 53.8 (s, CH
2
dbuP), 48.5 (d, JC,P = 2.1 Hz, CH
3
2
3
3
2
2
dbuP), 46.2 (d, JC,P = 3.4 Hz, O
2
C–CH
2
),
2
1
C,P
2
2
2
3
syringe. The red reaction mixture was stirred for two hours fol-
JC,P = 8.7 Hz, CH
2
dbuP), 26.5 (s, CH
2
dbuP), 23.9 (d, JC,P
=
lowed by removal of the solvent under reduced pressure at 2.7 Hz, CH
3
), 22.4 (s, CH
2
3
dbuP), 21.1 (s, CH ), the assignment
ambient temperature. The resulting viscous red oil was dis- of the signals of the Ph groups is uncertain and therefore not
3
1
1
6 6 3
persed in diethyl ether (15 mL) whereupon the product precipi- given. P{ H} NMR (162.0 MHz, C D + CD OD): major
tated as an orange yellow solid. The compound was isolated by species: δ 40.7 (s). The crystals, obtained as described above,
filtration and dried in a vacuum. Yield: 249 mg (50%). Anal. are suitable for X-ray diffraction analysis.
13996 | Dalton Trans., 2014, 43, 13988–14000
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Paper
Synthesis of [(µ-dppm)(Ni{CH
2
C(CH
3
)C(CH
3
)CH
2
COO})
2
]
2
C–CH3(meso)), 88.7 (pseudo-t, 1C, C–CH3(syn)), 43.8 (s, 1C, CH ),
(
3). Solid dppm (180 mg, 0.48 mmol) was added in one 42.2 (s, 1C, CH allyl), 22.2 (s, 1C, CH ), 20.5 (s, 1C, CH ). Suit-
2 3 3
portion to a stirred red solution of [(tmeda)Ni{CH
2 3
C(CH )- able crystals of 4·MeOH for X-ray diffraction analysis were
C(CH )CH COO}] (280 mg, 0.93 mmol) in THF (10 mL) at obtained by cooling a solution of 4 in a mixture of heptanes,
3
2
ambient temperature. The resulting orange red reaction THF and a few drops of methanol from ambient temperature
mixture was stirred for 15 min and then toluene (10 mL) was to −20 °C.
added. Thereafter, the solvents were slowly removed by distilla-
tion in a vacuum. The remaining orange residue was taken up Solid dcpe (561 mg, 1.33 mmol) was added in one portion to a
in diethyl ether (10 mL) resulting in the precipitation of the stirred red solution of [(tmeda)Ni{CH C(CH )C(CH )CH COO}]
2 3 3 2
Synthesis of [(dcpe)Ni{CH C(CH )C(CH )CH COO}] (5).
2
3
3
2
orange product. The solid was isolated by filtration, washed (380 mg, 1.27 mmol) in THF (30 mL) at ambient temperature.
with diethylether (3 mL) and thoroughly dried in a vacuum. Immediately after dissolution of all solids, the resulting dark
Yield: 272 mg (78%, crude product). Anal. Calcd for red reaction mixture was cooled to 0 °C and stored for twelve
39 2 4 2
C H42Ni O P (754.095): C, 62.11; H, 5.61; found: C, 64.37; H, hours at this temperature. The red crystals of 5·0.5THF formed
1
5
.53; selected IR (ATR): ˜ν = 1656 (m, νas,COO), 1634 cm− (s, were isolated by filtration and dried in a vacuum. The com-
1
νas,COO); H NMR (400.1 MHz, THF-d
8
): major species in solu- pound slowly lost the co-crystallized THF upon prolonged
58NiO
= 10.9 Hz, PCH P), 3.11 (br. (607.47): C, 65.25; H, 9.62; found: C, 64.71; H, 9.73; selected IR
tion: δ 7.86 (br, 4H, CH Ph), 7.38 (br, 4H, CH Ph), 7.35–7.05 drying. Yield: 366 mg (47%). Anal. Calcd for C33
H
2 2
P
2
(m, 12H, CH Ph), 3.39 (t, 2H, J
H,P
2
2
2
−1
31
1
d, 2H,
1
1
(
(
J
H,H = 16.3 Hz, O
6.3 Hz, O C–CHH′), 2.05 (br, 2H, CHH′), 1.97 (br, 2H, CHH′), NMR (242.9 MHz, THF-d
.73 (br, 6H, CH3(meso)), 1.14 (br, 6H, CH3(anti)); C{ H} NMR 63.8 (s, 1P). The crystals obtained directly from the reaction
): major species in solution: δ 183.7 mixture were used to determine the structural motif of 5 via
2
C–CHH′), 2.53 (br. d, 2H,
J
H,H
=
(ATR): ˜ν = 1607 (m, νas,COO), 1584 cm (s, νas,COO); P{ H}
2
8
, CO atmosphere): δ 74.0 (s, 1P),
2
1
3
1
100.6 MHz, THF-d
pseudo-t, 2C, COO), 135.5 (br, 4C, i-C Ph), 134.6 (pseudo-t, X-ray diffraction experiments.
8
2
4
C, CH Ph), 133.3 (pseudo-t, 4C, CH Ph), 130.1 (br s, 4C, CH
Formation of [(dcpe) Ni] (6) and [(dcpe)Ni{η -CH C(CH )-
2
2
3
Ph), 128.9 (pseudo-t, 4C, CH Ph), 128.8 (br, 4C, CH Ph), 128.5 C(CH
3
)CH
2
}] (7). Complex 5 (274 mg, 0.45 mmol) was dis-
(
pseudo-t, 4C, CH Ph), 115.5 (s, 2C, C–CH3(meso)), 83.0 (pseudo- solved in THF (12 mL). The resulting solution was heated to
t, 2C, C–CH3
), 48.1 (s, 2C, CH2 allyl), 44.6 (s, 2C, O C– 40 °C for 30 minutes. Afterwards, the solvent was removed
2
(anti)
1
CH
2
), 28.1 (t, JC,P = 6.5 Hz, 1C, PCH
2
P), 23.4 (s, 2C, CH
3
), 20.2 in vacuo leaving a solidifying foam behind. This residue was
3
1
1
(
s, 2C, CH
3
); P{ H} NMR (162.0 MHz, THF-d ): major species: taken up in acetone (10 mL) leading to precipitation of a
8
δ 13.0 (s). Suitable crystals for X-ray diffraction analysis were yellow substance. The solid was isolated by filtration and dried
obtained by cooling the mother liquor of the reaction from in a vacuum. Yield: 133 mg [crude product, mixture of 6
ambient temperature to −20 °C.
Synthesis of [(dcpm)Ni{CH C(CH )C(CH )CH COO}] of 6: H NMR (600.1 MHz, THF-d , 298 K): δ 2.21 (br, 8H, CH
4). Solid dcpm (264 mg, 0.65 mmol) was added in one Cy), 1.90–1.05 (m, 88H, CH
portion to a stirred red solution of [(tmeda)Ni{CH C(CH )- THF-d , 298 K): δ 38.8 (br, 8C, CH Cy), 30.9 (br, 8C, CH
(minor component) und 7 (major component)]. Analytical data
1
2
3
3
2
8
1
3
1
(
2
dcpe); C{ H} NMR (150.9 MHz,
Cy),
2
3
8
2
C(CH )CH COO}] (193 mg, 0.64 mmol) in THF (15 mL) at 29.1 (s, 8C, CH Cy), 28.8 (s, 8C, CH Cy), 28.6 (s, 8C, CH Cy),
3
2
2
2
2
3
1
1
ambient temperature. After 5 min of stirring, the resulting 27.5 (s, 8C, CH
brownish red reaction mixture was reduced to half of its orig- (242.9 MHz, THF-d
inal volume and stored for 3 days at −20 °C. Thereafter, a NMR (600.0 MHz, THF-d , 298 K): δ 3.00 (s, 2H, vCHH′), 2.97
2
Cy), 22.5 (m, 4C, P–CH
, 298 K): δ 43.7(s). Analytical data of 7: H
2
); P{ H} NMR
1
8
8
compact layer of a red solid had formed at the wall of the (s, 2H, vCHH′), 1.60–1.90 (m, 32H, CH Cy + CH
Schlenk tube. This crude product (237 mg) was isolated by dmbd), 1.53 (m, 4H, P-CH ), 1.35–1.15 (m, 18H, CH
C{ H} NMR (150.9 MHz, THF-d , 298 K): δ 105.7 (br, 2C,
2
Cy + CH
3
2
2
Cy);
1
3
1
decantation and dried in a vacuum. Afterwards it was sus-
pended in heptanes (5 mL) and THP was slowly added until a vC<), 66.4 (br, 2C, vCH
clear solution was observed (the amount of THP necessary 4.6 Hz, 4C, P–CH), 29.9 (d, JC,P = 4.6 Hz, 4C, CH
slightly varies from batch to batch). Storage of the resulting 4C, CH2 Cy), 28.03 (d, JC,P = 8.3 Hz, 4C, CH2 Cy), 27.97 (d,
solution at −40 °C for one week resulted in the formation of C,P = 5.7 Hz, 4C, CH Cy), 27.2 (s, 4C, CH Cy), 24.6 (s, 2C, CH
·THP as an amorphous orange red solid. The compound was dmbd), 22.4 (pseudo-t, 2C, P–CH
isolated by filtration and dried in a vacuum. Prolonged drying THF-d , 298 K): δ 65 (very br, 1P), 50 (very br, 1P); P{ H} NMR
8
1
4
2
), 36.0 (dd, JC,P = 13.8 Hz, JC,P
=
2
Cy), 29.7 (s,
J
2
2
3
3
1
1
4
2
); P{ H} NMR (162.0 MHz,
3
1
1
8
2
was necessary to remove the co-crystallized THP. Yield: 169 mg (162.0 MHz, THF-d
8
, 253 K): δ 67.8 (br d, JP,P = 61.2 Hz, 1P),
(593.407): C, 64.77; H, 47.9 (d, JP,P = 63.2 Hz, 1P). Suitable crystals of 6 for X-ray diffr-
.51; found: C, 64.83; H, 9.74; selected IR (ATR): ˜ν = 1599 (s, action experiments were obtained during the attempted syn-
as,COO); compound 4 decomposes in THF-d at ambient temp- thesis of 5 at ambient temperature directly from the reaction
): δ −11.5 (s, *), 10.6 mixture. In the case of 7, crystals were obtained by recrystalli-
br s, compound 4, major species), 15.1 (s, *), 31.0 (s, *), 31.3 zation (ambient temperature to −20°) of the crude product in
s, *) + further minor signals (* = unidentified product). THF (7·0.5THF) or THP.
2
2 2
(44%). Anal. Calcd for C32H56NiO P
9
ν
8
3
1
1
erature; P{ H} NMR (162.0 MHz, THF-d
(
(
8
1
3
1
Selected C{ H} NMR data (100.6 MHz, THF-d
8
): nickel-
Synthesis of [(dcpe)Ni(cod)] (8). Solid dcpe (406 mg,
alactone moiety of 4: δ 183.7 (pseudo-t, 1C, COO), 115.6 (s, 1C, 0.96 mmol) was added in one portion to a stirred yellow solu-
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tion of [Ni(cod)
2
] (264 mg, 0.96 mmol) in THF (10 mL) at (150.9 MHz, THF-d
8
): δ 79.3 (pseudo-t, 4C, CH cod), 68.0 (s,
ambient temperature. After dissolution of the dcpe the yellow 2C, OCH2 THF), 36.1 (pseudo-t, 4C, CH Cy), 32.8 (pseudo-t,
reaction mixture was stored for two days at −10 °C. Afterwards, 4C, CH cod), 29.9 (pseudo-t, 4C, CH Cy), 28.4 (s, 4C, CH
the formed big bright yellow crystals of 8·THF were isolated by Cy), 28.2 (pseudo-t, 4C, CH Cy), 28.1 (pseudo-t, 4C, CH Cy),
decantation, washed with heptanes (5 mL) and briefly dried in 27.5 (s, 4C, CH Cy), 26.2 (s, 2C, CH THF), 21.4 (pseudo-t, 2C,
2
2
2
2
2
2
2
3
1
1
a vacuum. Yield: 545 mg (86%). Anal. Calcd for C38
H
68NiOP
2
2 8
P–CH ); P{ H} NMR (162.0 MHz, THF-d ): δ 59.9 (s).
1
(661.60): C, 68.99; H, 10.36; found: C, 69.06; H, 10.40; H NMR
600.1 MHz, THF-d ): δ 4.07 (br, 4H, CH cod), 3.62 (m, 4H,
(
8
Structure determination
OCH
.89–1.64 (m, 28H, CH
P–CH2), 1.33–1.16 (m, 20H, CH2 Cy);
2
THF), 2.36 (m, 4H, CHH′ cod), 2.12 (m, 4H, CHH′ cod),
1
2
THF + CH/CH
2
Cy), 1.41 (m, 4H, The intensity data for the compounds were collected on a
1
3
1
C{ H} NMR Nonius KappaCCD diffractometer using graphite-monochro-
Table 3 Crystal data and refinement details for the X-ray structure determination of compounds 1–8
Compound
Formula
fw/g mol
T/°C
Crystal system
Space group
1
2
3
4
5
C
16
H N NiO
26
2
2
C
28
H
35
N
2
2
NiO P
C
39
H
42Ni
2 4
O P
2 4 10
, C H O
C
32
H
56NiO
2 2
P , CH
4
O
C
33 2 2 4 8
H58NiO P , 0.5 C H O
−1
a
337.10
−140(2)
Orthorhombic
521.26
−140(2)
Monoclinic
P2 /n
828.21
625.46
−140(2)
Monoclinic
643.50
−140(2)
Monoclinic
−140(2)
Triclinic
Pˉ1
Ima2
1
P2
1
/n
1
P2 /c
a/Å
b/Å
c/Å
α/°
β/°
γ/°
V/Å
Z
ρ/g cm
µ/cm
28.090(2)
13.7216(9)
10.9264(7)
90
90
90
13.8132(5)
12.2553(4)
14.9680(4)
90
97.186(2)
90
2513.95(14)
4
1.377
10.9306(3)
11.3308(3)
18.4592(5)
72.221(1)
76.133(1)
67.433(1)
1990.74(9)
2
9.6594(4)
32.5695(15)
10.9054(5)
90
101.745(1)
90
3359.0(3)
4
1.237
11.1546(11)
34.917(3)
9.3693(8)
90
95.371(3)
90
3633.2(6)
4
1.176
3
4211.4(5)
8
−
3
a
1.063
9.33
1.382
10.70
−
1
a
8.64
7.03
6.51
Measured data
Data with I > 2σ(I)
4286
3643
24526
4441
7238
6342
16775
5704
11475
4494
Unique data (Rint
)
4286/0.0491
0.2185
0.0802
5761/0.0426
0.1194
0.0516
1.047
0.656/−0.413
—
7238/0.0626
0.2196
0.0971
1.231
1.315/−1.127
—
6726/0.0492
0.1642
0.0774
1.130
1.371/−0.680
—
6681/0.0765
0.4215
0.1601
1.110
1.667/−0.790
—
2
b
wR
2
(all data, on F )
b
R
S
1
(I > 2σ(I))
c
1.045
−3
Res. dens./e Å
1.104/−1.199
0.097(15)
1002896
Flack-parameter
CCDC No.
1002897
1002898
1002899
Motif
Compound
6
7
7·0.5THF
58NiP
8
Formula
C
52
H
96aNiP
4
C
32
H
58NiP
2
C
32
H
2
, 0.5 C
4 8
H O
34 2 4 8
C H60NiP , C H O
661.57
−1
fw/g mol
903.88
563.43
599.49
T/°C
Crystal system
Space group
−140(2)
Monoclinic
P2/n
−140(2)
−140(2)
−140(2)
Triclinic
Triclinic
Monoclinic
Pˉ1
Pˉ1
1
P2 /n
a/Å
b/Å
c/Å
α/°
β/°
γ/°
V/Å
Z
ρ/g cm
µ/cm
13.2538(3)
9.9914(2)
21.0848(3)
90
103.144(1)
90
10.1055(3)
11.0712(3)
14.8446(4)
104.247(2)
92.999(1)
103.896(2)
1551.63(8)
2
10.5810(2)
12.3040(2)
13.7385(2)
97.923(1)
106.776(1)
101.793(1)
1638.94(5)
2
11.7198(2)
20.4120(3)
15.3870(2)
90
100.370(1)
90
3620.75(9)
4
1.214
3
2718.98(9)
2
−
3
a
1.104
5.05
1.206
7.47
1.215
7.12
−
1
a
6.52
Measured data
Data with I > 2σ(I)
6212
5382
9680
6124
11318
6759
27930
7490
Unique data (Rint
)
6212/0.0305
0.1793
0.0640
1.052
2.156/−0.802
1002900
6983/0.0221
0.1065
0.0505
1.135
0.950/−0.607
1002901
7307/0.0214
0.1873
0.0606
1.097
1.777/−1.161
1002902
8240/0.0271
0.0801
0.0318
1.053
0.461/−0.699
1002903
2
b
wR
2
(all data, on F )
b
R
S
1
(I > 2σ(I))
c
−3
Res. dens./e Å
CCDC No.
a
b
Derived parameters do not contain the contribution of the disordered solvent. Definition of the R indices: R
1
)}
= (∑||F
o
| − |F
c o
||)/∑|F |.
2
2 2
2 2 1/2
−1
2
2
2
2
2
c
2
2 2
1/2
wR
2
= {∑[w(F
o
− F
c
) ]/∑[w(F
o
) ]} with w = σ (F
o
) + (aP) + bP; P = [2F
c
+ Max(F
o
)]/3. S = {∑[w(F
o
− F
c
) ]/(N
o
− N
p
.
13998 | Dalton Trans., 2014, 43, 13988–14000
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Dalton Transactions
Paper
mated Mo-K
polarization effects but not for absorption effects.
The structures were solved by direct methods (SHELXS)
and refined by full-matrix least squares techniques against F
α
radiation. Data were corrected for Lorentz and
Chem. Soc., 1988, 110, 3207–3212; (c) E. Dinjus and
W. Leitner, Appl. Organomet. Chem., 1995, 9, 43–50;
(d) N. Holzhey, S. Pitter and E. Dinjus, J. Organomet. Chem.,
1997, 541, 243–248; (e) A. Behr and M. Becker, Dalton
Trans., 2006, 4607–4613; (f) Y. Dai, X. Feng, B. Wang, R. He
and M. Bao, J. Organomet. Chem., 2012, 696, 4309–4314.
4 (a) D. Walther and E. Dinjus, Z. Chem., 1982, 22, 228–229;
(b) D. Walther, E. Dinjus, J. Sieler, N. N. Thanh, W. Schade
and I. Leban, Z. Naturforsch., B: Anorg. Chem. Org. Chem.,
1983, 38, 835–840; (c) H. Hoberg, D. Schaefer and
B. W. Oster, J. Organomet. Chem., 1984, 266, 313–320.
5 (a) H. Hoberg and B. Apotecher, J. Organomet. Chem., 1984,
270, C15–C17; (b) R. Fischer, D. Walther, G. Bräunlich,
B. Undeutsch, W. Ludwig and H. Bandmann, J. Organomet.
Chem., 1992, 427, 395–407; (c) G. Bräunlich, D. Walther,
H. Eibisch and B. Schönecker, J. Organomet. Chem., 1993,
453, 295–298; (d) M. Takimoto and M. Mori, J. Am. Chem.
Soc., 2001, 123, 2895–2896.
6 (a) D. Walther, E. Dinjus, H. Görls, J. Sieler, O. Lindqvist
and L. Andersen, J. Organomet. Chem., 1985, 286, 103–113;
(b) P. S. Schulz, O. Walter and E. Dinjus, Appl. Organomet.
Chem., 2005, 19, 1176–1179; (c) J. Langer, D. Walther and
H. Görls, J. Organomet. Chem., 2006, 691, 4874–4881.
7 J. Langer, R. Fischer, H. Görls and D. Walther, J. Organo-
met. Chem., 2004, 689, 2952–2962.
8 (a) H. Hoberg, D. Schaefer, G. Burkhart, C. Krüger and
M. J. Romão, J. Organomet. Chem., 1984, 266, 203–224;
(b) H. Hoberg, Y. Peres, C. Krüger and Y.-H. Tsay, Angew.
Chem., Int. Ed. Engl., 1987, 26, 771–773; (c) R. Fischer,
J. Langer, A. Malassa, D. Walther, H. Görls and
G. Vaughan, Chem. Commun., 2006, 2510–2512.
2
6,27
2
8
2
o
2
8
(SHELXL-97). The hydrogen atoms of compound 7 (except
for the methyl group at C6) and 8 (except for the hydrogen
atoms of the co-crystallized thf molecule) as well as the hydro-
gen atoms bound to C1 and C4 of 7·0.5THF were located by
difference Fourier synthesis and refined isotropically. All other
hydrogen atoms were included at calculated positions with
fixed thermal parameters. The crystal of 3 was a non-mero-
2
9
hedral twin. The twin law was determined by PLATON to
−1.0/0.0/0.0) (0.0/−1.0/0.0) (−0.485/−0.815/1.0). The contri-
(
bution of the main component was refined to 0.302(3). The
crystals of 1 and 6 contain large voids, filled with disordered
solvent molecules. The size of the voids is 615 Å per unit cell
3
3
(
1) and 161 Å per unit cell (6), respectively. Their contribution
to the structure factors was secured by back-Fourier transform-
ation using the SQUEEZE routine of the program PLATON,
resulting in 97 electrons per unit cell (1) and 20 electrons per
unit cell (6), respectively.
The crystals of 5 were extremely thin and of low quality,
resulting in a substandard dataset. However, the structure is
sufficient to show connectivities and geometry despite the
high final R value. We will only publish the conformation of
compound 5 and its crystallographic data. We will not deposit
the data of 5 in the Cambridge Crystallographic Data Centre.
All non-disordered, non-hydrogen atoms were refined an-
2
9
2
8
isotropically. Crystallographic data as well as structure solu-
tion and refinement details are summarized in Table 3. XP
(SIEMENS Analytical X-ray Instruments, Inc.) was used for
structure representation.
9 (a) G. Burkhart and H. Hoberg, Angew. Chem., Int. Ed. Engl.,
1
982, 94, 75; (b) D. Walther, G. Bräunlich, R. Kempe and
J. Sieler, J. Organomet. Chem., 1992, 436, 109–119;
c) J. Langer, M. Gärtner, H. Görls and D. Walther, Syn-
(
Acknowledgements
thesis, 2006, 2697–2706; (d) J. Langer, H. Görls and
D. Walther, Polyhedron, 2012, 32, 60–67.
Infrastructure of our institute was provided by the EU (Euro-
pean Regional Development Fund, EFRE) and the Friedrich 10 P. Schulz, Wiss. Ber. – Forschungszent. Karlsruhe, 2002, 6785,
Schiller University Jena. We thank Prof. M. Westerhausen for
his support.
1–146.
11 D. Walther and E. Dinjus, Z. Chem., 1984, 24, 63.
12 J. Langer, H. Görls, G. Gillies and D. Walther, Z. Anorg. Allg.
Chem., 2005, 631, 2719–2726.
1
3 M. O’Reilly, R. Pattacini and P. Braunstein, Dalton Trans.,
References
2009, 6092–6095.
1
For a review see: (a) W. Leitner, Coord. Chem. Rev., 1996, 14 A. W. Addison, T. N. Rao, J. Reedijk, J. van Rijn and
1
53, 257–284; (b) X. Yin and J. R. Moss, Coord. Chem. Rev.,
G. C. Verschoor, J. Chem. Soc., Dalton Trans., 1984,
1349–1356.
1
999, 181, 27–59; (c) M. Aresta and A. Dibenedetto, Dalton
Trans., 2007, 2975–2992; (d) M. Cokoja, C. Bruckmeier, 15 (a) B. Hipler, M. Döring, C. Dubs, H. Görls, T. Hübler and
B. Rieger, W. A. Herrmann and F. E. Kühn, Angew. Chem., E. Uhlig, Z. Anorg. Allg. Chem., 1998, 624, 1329–1335.
Int. Ed., 2011, 50, 8510–8537; (e) K. Huang, C.-L. Sun and 16 (a) X. L. R. Fontaine, S. J. Higgins, B. L. Shaw,
Z.-J. Shi, Chem. Soc. Rev., 2011, 40, 2435–2452.
(a) A. Behr and K.-D. Juszak, J. Organomet. Chem., 1983,
M. Thornton-Pett and W. Yichang, J. Chem. Soc., Dalton
Trans., 1987, 1501–1507; (b) L. Manojlovic-Muir,
H. A. Mirza, N. Sadiq and R. J. Puddephatt, Inorg. Chem.,
1993, 32, 117–119; (c) J. D. Heise, J. J. Nash, P. E. Fanwick
and C. P. Kubiak, Organometallics, 1996, 15, 1690–1696;
(d) J. Langer, R. Fischer, H. Görls and D. Walther, Acta
2
3
2
55, 263–268; (b) A. Behr, K.-D. Juszak and W. Keim,
Synthesis, 1983, 574.
(a) A. Behr and U. Kanne, J. Organomet. Chem., 1986, 309,
2
15–223; (b) P. Braunstein, D. Matt and D. Nobel, J. Am.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 13988–14000 | 13999

View Article Online
Paper
Dalton Transactions
Crystallogr., Sect. E: Struct. Rep. Online, 2008, 64, m412;
e) J. Langer, H. Görls and M. Westerhausen, Inorg. Chem.
A. Limberg and R. Mynott, Organometallics, 1995, 14, 1893–
1900.
(
Commun., 2010, 13, 488–490; (f) A. Sousa-Pedrares, 22 This compound was mentioned earlier, but no analytical
J. A. Viqueira, J. Antelo, E. Labisbal, J. Romero, A. Sousa,
O. R. Nascimento and J. A. García-Vázquez, Eur. J. Inorg.
Chem., 2011, 2273–2287; (g) T. S. Lobana, P. Kumari,
G. Hundal, R. J. Butcher, A. Castineiras and T. Akitsu,
Inorg. Chim. Acta, 2013, 394, 605–615.
data was reported: (a) H. Schwager, C. Krueger, R. Neidlein
and G. Wilke, Angew. Chem., Int. Ed. Engl., 1987, 99, 72–73;
(b) R. Benn, P. W. Jolly, T. Joswig, R. Mynott and
K. P. Schick, Z. Naturforsch., B: Anorg. Chem. Org. Chem.,
1986, 41, 680–691.
17 J. Langer, H. Görls, R. Fischer and D. Walther, Organo- 23 M. Martín, O. Torres, E. Oñate, E. Sola and L. A. Oro, J. Am.
metallics, 2005, 24, 272–279. Chem. Soc., 2005, 127, 18074–18084.
18 J. Langer, D. Walther, A. Malassa, M. Westerhausen and 24 S. Ogoshi, K.-I. Tonomori, M.-A. Oka and H. Kurosawa,
H. Görls, Eur. J. Inorg. Chem., 2010, 275–281. J. Am. Chem. Soc., 2006, 128, 7077–7086.
19 D. Jin, P. G. Williard, N. Hazari and W. H. Bernskoetter, 25 B. Bogdanović, M. Kröner and G. Wilke, Justus Liebigs Ann.
Chem. – Eur. J., 2014, 20, 3205–3211. Chem., 1966, 699, 1–23.
20 (a) P. Mastrorilli, G. Moro, C. F. Nobile and M. Latronico, 26 R. Hooft, COLLECT DataCollection Software for Nonius
Inorg. Chim. Acta, 1992, 192, 183–187; (b) A. Sacco and
P. Mastrorilli, J. Chem. Soc., Dalton Trans., 1994, 2761–2764.
KappaCCD, Nonius B. V., Delft, The Netherlands,
1998.
2
1 (a) W. Schröder and K.-R. Pörschke, J. Organomet. Chem., 27 Z. Otwinowski and W. Minor, in Methods in Enzymology, ed.
1
987, 322, 385–392; (b) R. Benn, P. Betz, R. Goddard,
P. W. Jolly, N. Kokel, C. Krüger and I. Topalović, Z. Natur-
forsch., B: Chem. Sci., 1991, 46,
c) K.-R. Pörschke, C. Pluta, B. Proft, F. Lutz and C. Krüger,
Z. Naturforsch., B: Chem. Sci., 1993, 48, 608–626; 29 A. L. Spek, Acta Crystallogr., Sect. D: Biol. Crystallogr., 2009,
d) E. Dreher, B. Gabor, P. W. Jolly, C. Kopiske, C. Krüger, 65, 148–155.
C. W. Carter and R. M. Sweet, Academic Press, 1997,
vol. 276, pp. 307–326.
1395–1405; 28 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystal-
logr., 2008, 64, 112–122.
(
(
14000 | Dalton Trans., 2014, 43, 13988–14000
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