Nickel(0) complexes of acyclic polyunsaturated aza ligands

Article abstract of DOI:10.1021/om301160m

The acyclic 4,9-bis(4-tolylsulfonyl)-4,9-diazadodeca-1,11-dien-6-yne (1) and 4,9-bis(4-tolylsulfonyl)-4,9-diazatrideca-1,(E)-6-dien-11-yne (2), which differ in the sequence of the two ene and one yne functions in the chain, have been reacted with 1 and 2 equiv of Ni(cod)₂. The reaction with 1 equiv of Ni(cod)₂ affords the mononuclear trigonal-planar nickel(0) complexes 3 and 5. These react with a further 1 equiv of Ni(cod)₂ by addition of a Ni(cod) entity to give the dinuclear derivatives 4 and 6. While 3 forms a mixture of isomers C₂-3 and C_s-3 in solution, C₂-3 is exclusively present in the crystal, where it is packed in parallel columns. Complex 6 crystallizes as a spherulite. Complexes 3-6 have been characterized by NMR and single-crystal X-ray structure analysis, and a detailed conformational analysis is given.

Full text of DOI:10.1021/om301160m

Article
pubs.acs.org/Organometallics
Nickel(0) Complexes of Acyclic Polyunsaturated Aza Ligands
̀
Sandra Brun, Oscar Torres, Anna Pla-Quintana, and Anna Roglans*
Department of Chemistry, Universitat de Girona, Campus de Montilivi s/n, E-17071 Girona, Spain
Richard Goddard and Klaus-Richard Porschke*
̈
Max-Planck-Institut fur Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mulheim an der Ruhr, Germany
̈
̈
S
* Supporting Information
ABSTRACT: The acyclic 4,9-bis(4-tolylsulfonyl)-4,9-diazadodeca-1,11-
dien-6-yne (1) and 4,9-bis(4-tolylsulfonyl)-4,9-diazatrideca-1,(E)-6-dien-
11-yne (2), which differ in the sequence of the two ene and one yne
functions in the chain, have been reacted with 1 and 2 equiv of Ni(cod)2.
The reaction with 1 equiv of Ni(cod)2 affords the mononuclear trigonal-
planar nickel(0) complexes 3 and 5. These react with a further 1 equiv of
Ni(cod)2 by addition of a Ni(cod) entity to give the dinuclear
derivatives 4 and 6. While 3 forms a mixture of isomers C2-3 and
Cs-3 in solution, C2-3 is exclusively present in the crystal, where it is
packed in parallel columns. Complex 6 crystallizes as a spherulite.
Complexes 3−6 have been characterized by NMR and single-crystal X-ray structure analysis, and a detailed conformational
analysis is given.
systematically studied the coordination behavior of acyclic
1,5-dienes, 1,6-dienes, 1,6-diynes, and 1,6,11-trienes on Ni(0),
Pd(0), and Pt(0). An important finding of these investigations
is that ligands having 1,6- or 1,6,11-sequences of the olefinic
functions are much better suited for coordination to these
trigonal-planar metal centers than the corresponding acyclic or
cyclic 1,5-dienes and 1,5,9-trienes. A typical metal(0) complex
having an acyclic 4,9-diazadodeca-1,6,11-triene ligand is
represented by III.6h In trigonal-planar complexes a chair-
type, formally Cs-symmetrical conformation of (1,6-diene)M0
substructures seems particularly stable. Nevertheless, some
tetrahedral (1,6-diene)Ni0 complexes showing a twist-type,
formally C2-symmetrical conformation have also been re-
ported.7
INTRODUCTION
■
It is well established that cyclic polyene or polyyne or mixed
polyene/-yne ligands can stabilize transition metals in their zero
oxidation state. Classical examples of such complexes are Wilke’s
trigonal-planar Ni(t,t,t-cdt) (I; t,t,t-cdt = trans,trans,trans-1,5,9-
cyclododecatriene) and tetrahedral Ni(cod)2 (cod = cis,cis-1,5-
cyclooctadiene).1 Ni(c,c,c-cdt) and other c,c,c-cdt−metal
complexes (c,c,c-cdt = cis,cis,cis-1,5,9-cyclododecatriene) have
also been studied in detail.2 Given that symmetrically structured
cod and t,t,t-cdt are conveniently obtained by the catalytic
cyclodi-3 and cyclotrimerization4 of butadiene and that c,c,c-cdt
can be prepared from t,t,t-cdt, the ene functions in these
cycloalkenes are congenitally positioned in 1,5-sequences
separated by ethano links, and the numbers of ring atoms are
multiples of 4. Nickel(0) is also known to be stabilized inside a
macrocyclic scaffold of three alkyne moieties, such as planar
tribenzocyclyne, as a similar 12-membered ring (II), or by
dibenzoheterocyclotriynes containing silicon, germanium, or
titanium as linking elements between two yne functions, as a
predominantly 11-membered or again 12-membered ring.5
The Roglans group, following the unexpected discovery of a
Pd(0)−(E,E,E)-1,6,11-triazacyclopentadeca-3,8,13-triene com-
plex,8 has worked intensively on the synthesis of a series of
azamacrocycles with various ring sizes and numbers of CC
and CC bonds.9 These macrocycles have been coordinated
to Pd(0), Pt(0), and Ag(I) to afford complexes such as IV−VI,
which contain a 15-membered ring ligand with the ene/yne
groups in 1,6,11-sequences.
Cyclicity and C2 bridges between the unsaturated functions
are not necessary prerequisites for stabilization of zerovalent
Received: November 30, 2012
Published: February 18, 2013
metals by such ligands. Porschke and co-workers6 have
̈
© 2013 American Chemical Society
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midpoints. The central azanickelacyclohexanic ring, which in
addition to Ni1 involves half of each of the two CC bonds
and their inner ligand section including N2, adopts a chair
conformation, with the dihedral angles within the ring ranging
between 55 and 69°. The remaining two pseudo-azanick-
elacyclohexanic rings involving ring sections around N1 (N1*),
half of one CC bond, and half the CC bond are equivalent
in the crystal and adopt “half-chair” conformations, with
dihedral angles in half of the ring being normal at 44−71° and
in the other merely 15−37°, due to the fact that C2 (C2*) is
constrained to lie in the Ni1,C1,C1* plane.
In the case of the cyclo-1,6,11-triene complex IV,9d the
observed isomers have two azapalladacyclohexanic rings in a
chair conformation and one ring in a twist conformation,
whereas the Pd(0)−cyclo-1,6,11-dienyne V and the Pd(0)−
cyclo-1,6,11-endiyne VI show only chair-type conformations.9e
These Pd(0) complexes display unprecedented thermal
stability, only partially decomposing above 250 °C, which is
in sharp contrast to the fact that Pd(t,t,t-cdt) and Pd(c,c,c-cdt)
are unknown compounds.
In a recent collaboration we succeeded in synthesizing the
Ni(0)−triazacyclopentadeca-3,8,13-triene VII and the Ni(0)−
triazacyclopentadeca-3,8-dien-13-yne VIII, which respectively
represent derivatives of IV and V. Complex VIII reacted further
with Ni(cod)2 to give dinuclear IX.10 The structure of VIII is
Cs-symmetrical and resembles a chair, with the 15-membered
ring providing the seat, the two SO2-tolyl (tosyl, Ts) groups at
NCH2CCCH2N representing the front legs, and the other
tosyl group forming the back rest (Figure 1). The coordination
The structure of IX is derived from that of VIII by
coordination of a Ni(cod) moiety to the triple bond. In the
crystal studied the refined occupancy was only 83.4%. The
coordination planes of the two Ni atoms, which each contain
the two carbon atoms of the shared CC bond, make an angle
of 92° to one another, and the metals are at a distance of
2.684(2) Å, indicating a marked d10−d10 interaction.10 The
Ni(0) derivative of the cyclopentadeca-1,6,11-endiyne complex
VI remains hitherto inaccessible.
We subsequently were interested to investigate how the
structure and properties of the Ni(0) complexes are affected by
replacing the 15-membered 1,6,11-triazacyclopentadeca-(E,E)-
3,8-dien-13-yne ligand in VIII and IX by acyclic analogues. Formal
excision of a CH2−N(Ts)−CH2 unit from this ligand can occur at
two different sites, affording after saturation of the chain ends by H
or Me either 4,9-bis(tosyl)-4,9-diazadodeca-1,11-dien-6-yne (1) or
4,9-bis(tosyl)-4,9-diazatrideca-1,(E)-6-dien-11-yne (2).
We report here the reaction of 1 and 2 with 1 or 2 equiv of
Ni(cod)2 to give the acyclic analogues 3−6 of the macrocyclic
mono- and dinuclear complexes VIII and IX. The new Ni(0)
complexes have been characterized in detail by NMR and X-ray
diffraction analysis, revealing interesting structural properties.
Figure 1. Molecular structure of the Ni(0)−1,6,11-triazacyclopenta-
deca-(E,E)-3,8-dien-13-yne complex VIII (at the 50% probability
level).10
RESULTS AND DISCUSSION
■
Synthesis of the Ligands. While 4,9-bis(tosyl)-4,9-
diazadodeca-1,11-dien-6-yne (1) is known,11 4,9-bis(tosyl)-4,9-
diazatrideca-1,(E)-6-dien-11-yne (2) is new. For the synthesis
of 2 (Scheme 1), the aminoallylbutenyl bromide A12 can be
geometry at Ni is trigonal planar with the CC bond and
the midpoints of both CC bonds lying in the plane, but the
CC bonds are twisted by 21° out of the plane about their
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azametallacyclohexanic ring, involving the ring section between
the two CC bonds, in the chair conformation, the equatorial
protons He of the geminal NCHeHa protons resonate at low
field (δ(H) 4.66), whereas the axial protons Ha resonate at
characteristically higher field (VIII: δ(H) 1.32). When the ring
adopts the C2-symmetrical twist conformation, as in Ni(0)−
triazacyclopentadeca-3,8,13-triene VII, the high-field shift of the
axial protons Ha is less (VII: δ(H) 2.84).10 For the asymmetric
pseudo-azametallacyclohexanic rings involving an alkene and an
alkyne function in a “half-chair” conformation, the Ha high-field
shift for NCHeHa connected to the alkene function in the
chairlike region is again large (VIII: δ(H) 2.00), while that for
NCHeHa connected to the alkyne function in the flat part is
small (VIII: δ(H) 4.13). The equatorial protons He (δ(H)
4.52−4.66) appear little affected by the conformation of the
chelate. These findings are helpful for the discussion of the
spectra of 3, 5, and 6.
Scheme 1. Synthesis of the 4,9-Diazatrideca-1,(E)-6-dien-
11-yne 2
coupled with the Boc-protected sulfonamide B13 to give C
(Boc = tert-butyloxycarbonyl). After elimination of the Boc
group, compound D can be coupled with 1-bromo-2-butyne
(E) to yield colorless microcrystals of 2 in 70% overall yield.
NMR spectroscopic data of 1 and 2 are contained in Tables 1
and 2. Compounds 1 and 2 are moderately soluble in THF,
which appears to be the best solvent.
1
The H and 13C NMR spectra of a solution of 3 in THF-d8
show two sets of signals in the ratio 1.7:1. Each component
1
gives rise to 10 H and 10 13C NMR signals (Table 1). The
signals of the major component can presumably be attributed
to the presence of the C2-symmetrical isomer C2-3 (as present
in the crystal) and the signals of the minor component to the
Cs-symmetrical isomer Cs-3, both components undergoing slow
exchange (eq 1). The isomers result from the fact that, on
coordination to the metal, the substituted alkene C atoms of the
N-allyl groups are stereogenic centers (marked with asterisks).
Thus, in C2-3, the possible diastereomeric forms are either R,R or
S,S, giving rise of a pair of spectroscopically indistinguishable
enantiomers, and in the Cs-3 conformation the diastereomeric
form is R,S, corresponding to the meso form. An exchange
between these isomers necessarily requires cleavage of one
Ni−alkene bond and recoordination of the alkene by its reverse
side. The exchange in solution is consequently slow.
Synthesis of the Nickel(0) Complexes 3 and 4. A yellow
solution of Ni(cod)2 in THF reacts with an equimolar amount
of 1 by displacement of the cod ligands and formation of com-
plex 3, in which the Ni atom is coordinated by the acyclic and
symmetric 4,9-diazadodeca-1,11-dien-6-yne ligand. The reac-
tion, which involves a slow color change via amber to light
yellow, takes about 12 h for completion. Over the course of
1−3 days well-formed yellow crystals of 3 separate from the
undisturbed solution in ≥80% yield. When 2 equiv of Ni(cod)2
is used, the color changes to amber, and red crystals of the
dinuclear complex 4 are obtained in about 60% yield, again over
the course of several days (Scheme 2). This reaction proceeds
via 3 as an intermediate, which reacts with the excess of
Ni(cod)2 by only partial displacement of cod. These reactions
are similar to the formation of the mono- and dinuclear Ni(0)−
triazacyclopentadeca-3,8,13-dienyne complexes VIII and IX.
The formation of the dinuclear complex 4 appears to be favored
for the acyclic ligand, since occupancy of the second Ni atom in
the crystalline solid is 100%. Crystallization of both 3 and 4 is
often delayed. While 3 is soluble in THF, 4 once crystallized is
insoluble in THF and other solvents, which precludes recording
of the NMR spectra of the pure compound.
NMR Spectra of 3. We have learned from the spectra of
the M(0)−triazacyclopentadeca-3,8-dien-13-yne complexes V
(M = Pd)9e and VIII (M = Ni)10 that for the Cs-symmetrical
In agreement with the previous findings, the presumed Cs-3
shows for the two pseudo-azanickelacyclohexanic rings involv-
ing alkene and alkyne functions in “half-chair” conformation a
marked high-field shift of H3a (δ(H) 2.11) in the chairlike
alkene part of the ring and only a small high-field shift of H4a
(δ(H) 4.02) in the flat alkyne part of the ring. For C2-3 the
high-field chemical shift of H3a (δ(H) 2.19) in the alkene part
of the chelate ring is also normal, and the coupling 3J(H2,H3a)
= 10.4 Hz appears. For the alkyne part of the ring the chemical
shift difference between H4e and H4a is larger than is typical
(δ(H) 4.70 (H4e) and 3.78 (H4a)). These observations can be
attributed to the unusual boat conformation of the two rings
seen in the X-ray structure. Clearly, the boat conformation of
the chelate rings in C2-3 and the “half-chair” conformation of
the chelate rings in Cs-3 are of similar stability, since both are
present in solution corresponding to the equilibrium of eq 1.
For the alkyne function of the main acyclic isomer, assumed
to be C2-3, the 13C coordination shift14 (Δδ(C) = 21.3 ppm)
is less than that of the minor isomer assumed to be Cs-3
Scheme 2. Synthesis of Complexes 3 and 4
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a
1
Table 1. H and 13C NMR Data of the 4,9-Diazadodeca-1,11-dien-6-yne 1 and the Isomers of Nickel(0) Complex 3
1H NMR
H1Z
H1E
H2
H3e
H3a
3.62 (d, 6.4)
H4e
H4a
H7 H8 H10
7.65 7.29 2.42
b
1
5.11 (dd, 16.8, 1.2) 5.18 (dd, 10.4, 1.2) 5.61 (qt, 16.8, 10.4, 6.4)
3.85 (s)
c
C2-3
3.35 (m), 2.55 (m)
3.47 (m), 2.95 (m)
3.75 (m)
3.48 (m)
4.60 (d, 13.2) 2.19 (dd, 13.2, 10.4) 4.70 (d, 13.2) 3.78 (d, 13.2) 7.63 7.29 2.38
c
Cs-3
4.60 (d, 13.2) 2.11 (m)
13C NMR
4.62 (d, 13.6) 4.02 (d, 13.6) 7.63 7.25 2.35
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
b
1
119.8
58.5
59.3
131.9
79.3
79.0
49.0
48.9
48.5
35.8
37.6
37.4
78.4
99.7
136.1
134.6
134.4
127.7
127.8
127.8
129.6
130.0
130.0
143.8
144.2
144.1
21.6
21.6
21.5
c
C2-3
c
Cs-3
101.3
a
Solvent CD2Cl2. J(H,H) couplings (in hertz) are given in parentheses. Assignment:
b
c
Solvent CDCl3. Tentative assignment.
(Δδ(C) = 22.9 ppm), which is explained by the out-of-plane
twist of the triple bond of the former (see the X-ray structure)
and hence hindered back-donation from Ni(0). Interestingly,
the 13C coordination shift of both isomers is larger than that of
the cyclic VIII (Δδ(C) = 20.1 ppm), suggesting that for both
isomers of 3, containing the flexible acyclic 1, the Ni(0)−alkyne
orbital overlap is better than that in the cyclic VIII.
Molecular Structures of 3 and 4. The molecular struc-
tures of the mono- and dinuclear complexes 3 and 4, containing
the 4,9-diazadodeca-1,11-dien-6-yne ligand, have been deter-
mined by single-crystal X-ray crystallography (Table S1; see the
Supporting Information). Both compounds crystallize in the
orthorhombic crystal system.
The molecules of complex 3 (space group Pbcn, No. 60) lie
on a crystallographic C2 axis which passes through the Ni atom
and the midpoint of the CC bond (Figure 2). Thus, whereas
a mixture of the C2 and the Cs isomers appears in solution,
the crystal contains only the C2 isomer. Individual molecules in
the crystal are chiral, but the crystal as a whole is a racemate. In
the solid the Ni atom has trigonal-planar coordination, with the
metal, the two terminal CC bonds, including both C atoms,
and the midpoint of the CC bond lying in the coordination
plane. The in-plane location of the CC bonds is a notable
feature of the structure. The Ni atom, the central CC bond,
and its two CH2 substituents also lie in an approximate plane
(C4−C5−C5*−C4* torsional angle 1.8(1)°), within which the
CH2 substituents are bent away from Ni, giving a CC−CH2
angle of 158.9(1)°. The CH2CCCH2 entity is twisted out of
the coordination plane by 22°, as a result of the geometrical
constraint of the chain.
Figure 2. Molecular structure of 3 (at the 50% probability level). Selected
bond distances (Å) and bond angles (deg): C1−C2 = 1.3901(12), C5−
C5* = 1.2499(15), Ni(1)−C(1) = 2.0296(8), Ni(1)−C(2) = 2.0379(8),
Ni(1)−C(5) = 1.9755(8); C5*−C5−C4 = 158.9(4), (midpoint C1−
C2)−Ni1−(midpoint C1*−C2*) = 124.3(5), (midpoint C1−C2)−
Ni1−(midpoint C5−C5*) = 117.9(4).
The lengths of the coordinated CC bonds C1−C2 at
1.390(12) Å and the Ni1−C bonds to the terminal (2.0296(8) Å)
and internal alkene C atoms (2.0379(8) Å) are as expected,
which is also the case for the lengths of the CC bond
C5−C5* (1.2499(15) Å) and the Ni1−C5/5* bonds
(1.9755(8) Å).
The Ni atom and the chain sections from the substituted
C atom of one CC bond to the corresponding inner C
atom of the CC bond give rise to two identical pseudo-
azanickelacyclohexanic rings. The conformation of these rings can
best be described as twist-boat, with Ni and N at the tips of the
boat. The dihedral angles within the six-membered rings range
from a low 21.9(1)° to a normal 60.5(1)°. The geometry at N is a
flattened pyramid (the sum of the three angles is 350.4(2)°), and
the SO2-tolyl substituents occupy formal axial positions in the
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pseudo-azanickelacyclohexanic rings. The orientation of the tolyl
groups is antiperiplanar to the N lone pairs; thus, the two groups
bend over the Ni atom and sandwich it (closest Ni−arene contacts
are Ni1−C7 at 3.608 Å and Ni1−C6 at 3.617 Å). As a result, the
molecules take up a relatively compact S-shaped conformation.
In the crystal molecules of 3 pack in parallel columns which
run parallel to the a axis. Each column is made up of identical
C2-symmetrical molecules having the same chirality and orientation.
In each column the molecules are stacked such that the phenyl
groups of adjacent molecules lie almost parallel to one another (the
interplanar angle is 8°), with the midpoints of the phenyl rings
separated by 3.75(1) Å, suggestive of a weak π-electron interaction
(the distance of the layers in graphite is 3.354 Å). Each column is
surrounded by six nearest neighbors. Along the b axis the molecules
are related by a glide plane and along the c axis by inversion centers.
Molecules of dinuclear 4 (space group P212121, No. 19) can
be thought of as being derived from 3 by coordination of a
Ni(cod) moiety to the CC bond. The C2 symmetry of 3 in
the crystal is thereby changed to approximate Cs in the crystal
of 4 (Figure 3). Whereas in 3 it is the two CC bonds that lie
in 3, the geometry at N1 and N2 is that of a flattened pyramid
(sums of angles at N are respectively 346.3(5) and 346.5(5)°),
but in contrast to 3, the tosyl substituents take up equatorial
positions in the chair conformations of the azanickelacyclohex-
anic rings and are directed away from Ni1. As in 3, the tolyl
groups adopt conformations about the S−N bonds antiperi-
planar to the N lone pairs. As a result both groups take up
positions on the opposite side of the coordination plane of Ni1
from the Ni(cod) entity. In 4 the CC bonds (1.388(8) Å,
mean) are slightly shorter and the Ni1−C bonds to the
terminal (2.035 Å, mean) and internal (2.064 Å, mean) alkene
C atoms longer than in the mononuclear 3. For the 2-fold Ni
coordinated alkyne ligand both the CC bond C5−C6 at
1.329(3) Å and the Ni1−C5/6 distances at 2.005 Å (mean) are
longer than in 3.
The second Ni atom (Ni2) in 4 makes an angle of 96° to the
Ni1 coordination plane at midpoint of the CC bond (for the
related IX the corresponding value is 92°). The Ni2−C5/6
bonds to the alkyne (1.905(11) Å, mean) are markedly shorter
than the Ni1−C5/6 bonds, reflecting stronger back-bonding of
Ni2 to the alkyne than for Ni1. For Ni1 the two CC bonds
are only slightly twisted out of the metal coordination plane,
thus effectively withdrawing electron density from Ni1. For Ni2
the CC bonds are perpendicular to the plane, rendering Ni2
more basic.
The Ni1···Ni2 distance at 2.7352(5) Å is somewhat longer
than the corresponding distance in the likewise dinuclear IX
(2.684(2) Å), and for both compounds some d10−d10
interaction between the metal centers cannot be ruled out.
Indeed, the midpoint of the CC bond and the midpoint of
the four C atoms of the cod make an angle of 171(1)° at Ni2,
whereas a similar distortion is not found for the coordination
plane of Ni1. Attachment of Ni2 to 3 causes the CH2−CC
angles to decrease from 158.9(4)° in 3 to 138(3)° (mean) in 4,
which is comparable to that in IX (140°). The CH2−CC−
CH2 entity remains approximately planar (C4−C5−C6−C7
torsional angle at 1.7°), but both Ni atoms lie out of this plane
on either side so that the plane appears to bisect the Ni1···Ni2
bond. These geometrical features induce the pronounced chair
conformation of the azanickelacyclohexanic rings.
The Ni(cod) moiety is unspectacular (mean CC bond
lengths 1.365(7) Å, mean Ni2−C bond lengths 2.10(2) Å).
Complex 4 represents a hitherto rare example of a structurally
characterized (L2Ni)2(μ-RCCR′)-type complex (L = alkene)
in which two CC bonds lie in one CC−Ni plane and two
others perpendicular to the second plane.10
The principal features of the structure of acyclic dinuclear 4
correspond to those of the cyclic dinuclear IX and, neglecting
the Ni2(cod) moiety, also to those of the cyclic mononuclear
VIII. Without the Ni2(cod) group, 4 can also be viewed as a
rough model for structure of the acyclic mononuclear Cs-3
which seems to be present in solution (eq 1). A similar con-
formation of the carbon skeleton would also be expected for
a so far uninvestigated M(0)−4,9-diazadodeca-1,(Z)-6,11-
triene complex.
Synthesis of the Nickel(0) Complexes 5 and 6. Similar
to the synthesis of 3 and 4, a THF solution of 1 or 2 equiv of
Ni(cod)2 reacts with the acyclic 4,9-diazatrideca-1,(E)-6-dien-
11-yne 2, with its unsymmetrical distribution of the two CC
and one CC multiple bonds. Using 1 equiv of Ni(cod)2, the
displacement of the cod ligands by 2 can be followed by the
color change from yellow via amber to light yellow at ambient
temperature over the course of 12 h, and after 1−3 days yellow
Figure 3. Molecular structure of 4 (at the 50% probability level). Selected
bond distances (Å) and bond angles (deg): C1−C2 = 1.382(4), C5−C6
= 1.329(3), C9−C10 = 1.393(4), C25−C26 = 1.370(4), C29−C30 =
1.360(5), Ni1−C1 = 2.033(2), Ni1−C2 = 2.073(3), Ni1−C5 = 2.001(2),
Ni1−C6 = 2.009(2), Ni1−C9 = 2.054(2), Ni1−C10 = 2.037(3), Ni2−C5
= 1.913(2), Ni2−C6 = 1.897(2), Ni2−C25 = 2.131(3), Ni2−C26 =
2.080(3), Ni2−C29 = 2.090(3), Ni2−C30 = 2.101(3), Ni1···Ni2 =
2.7352(5); C4−C5−C6 = 136.0(2), C5−C6−C7 = 139.9(2), (midpoint
C1−C2)−Ni1−(midpoint C9−C10) = 120.7(3), (midpoint C1−C2)−
Ni1−(midpoint C5−C6) = 119.4(2), (midpoint C9−C10)−Ni1−
(midpoint C5−C6) = 119.8(2).
in the metal coordination plane and the CC bond that is
twisted out of the plane, in 4 it is the CC bond that lies in
the Ni1 coordination plane, defined by the metal center and the
midpoints of the CC bond and the CC bonds, and the
two CC bonds that are twisted out of the plane (by 15
and 9°). Both azanickelacyclohexanic rings in 4 (assuming an
sp3-type hybridization of the 2-fold metal-coordinated alkyne
carbon atoms) adopt chair conformations. Dihedral angles
within the six-membered rings range from 45.6 to 70.0°, and
the two rings are approximate mirror images of one another. As
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cubes of mononuclear 5 are formed (Scheme 3). Isolated 5 is
only poorly soluble. When 2 equiv of Ni(cod)2 is used, partial
Scheme 3. Synthesis of Complexes 5 and 6
further cod displacement by the triple bond in 2 affords an
amber solution from which fine yellow felted needles of
dinuclear 6 precipitate in about 50% yield after a few days.
Interestingly, 6 is more soluble in THF than the
mononuclear 5, whereas the likewise dinuclear crystalline
(cyclic) IX and (acyclic) 4 are practically insoluble. By slowly
cooling a solution of 6 from ambient temperature to −20 °C
the complex can be recrystallized to form orange well-
formed spherulites (Figure 4). Since intermediate 5 is less
soluble than 6, it is essential that all 5 be converted into 6
before the crystallization starts.
Figure 4. Photo of the spherulites of 6.
6 are reshifted to higher field by 3.4−3.6 ppm and the signals of
C8 and the methyl C11 are shifted further to lower field. A
particularly strong high-field shift is found for the signal of H8a
at δ(H) 2.77 as compared to 5 (δ(H) 4.28), due to the chairlike
conformation of this part of the ligand as well. For the cod
ligand, 12 1H and 8 13C signals are observed, which proves the
asymmetric structure of the ligand and rules out rapid rotation
about the (cod)Ni−alkyne bond axis.
Ligand Exchange Reactions. Trial ligand exchange
reactions have shown that the cyclic ligand in VIII is not
displaced by either acyclic 1 or 2, and the unreacted VIII has
been recovered from such solutions. When the mononuclear
complexes 3 and 5 are treated with the corresponding 1,6,11-
triazacyclopentadeca-3,8-dien-13-yne in THF, both acyclic
ligands are displaced and VIII is formed. However, displace-
ment reactions between complex 3 and ligand 2 on the one
hand and complex 5 and ligand 1 on the other revealed the
presence of an equilibrium (eq 2) which is in favor of the left
side (about a 2:1 mixture), as shown by NMR. It follows from
these studies that (i) complexes 3 and 5 having the acyclic
ligands are more reactive than the cyclic VIII and that (ii) the
nickel atom is able to migrate from one acyclic ligand to the
other. This could be relevant for catalytic activity.
NMR Spectra of 5 and 6. In the 1H and 13C NMR spectra
of 5 and 6 all 13 protons (in addition to the methyl group) and
all 11 carbon atoms of the 4,9-diazatrideca-1,(E)-6-dien-11-yne
skeleton give rise to separate signals, on account of the
asymmetric structures. Diastereotopy of the geminal NCH2
protons proves that the structures are rigid. In addition, both
N-tosyl substituents are inequivalent. A conformational analysis
of the structures is based on the assignment of the signals of the
four NCHeHa methylene groups by 2D NMR techniques.
As expected (see introductory remarks in NMR Spectra of 3),
for the mononuclear 5 (Table 2) all signals of H3e, H4e,
H7e, and H8e are in the δ(H) 4.42−4.61 range. The protons
H3a and H4a at δ(H) 1.31 and 1.20 resonate at substantially
higher field, indicative of a chair conformation of the azanickela-
cyclohexanic structure involving the two CC bonds. Such a
structural entity is most stable and dictates the further conforma-
tion of the ligand. For the pseudo-azanickelacyclohexanic chelate
involving the central CC bond and the CC bond, the
expected “half-chair” conformation is evident from the lower high-
field shift of H7a at δ(H) 2.38 in the section between N and C
C and the inconspicuous signal of H8a at δ(H) 4.28 in the flat
section between N and CC. While the upfield (negative)
coordination chemical shift of all alkene C atoms at Δδ(C) = −57
to −59 ppm is uniform and relatively high, indicating good orbital
overlap, the alkyne C atom downfield shift at Δδ(C) = 14.0 and
17.3 ppm is lower than in 3 and VIII (≥20 ppm).
Molecular Structures of 5 and 6. The mono- and
dinuclear complexes 5 and 6, each containing the asymmetric
4,9-bis(4-tolylsulfonyl)-4,9-diazatrideca-1,6-dien-11-yne ligand,
both crystallize in the monoclinic crystal system in the space
group P21/c (No. 14) (Table S1; see the Supporting
Information). Both crystal structures include THF solute, but
in differing molar ratios. The central trans-substituted CC
It is fortunate that dinuclear 6 is quite soluble, so that
recording of the NMR spectra is possible, in contrast to the
situation for the insoluble IX and 4. Most 1H and 13C data of 6
(Table 2) vary only little from those of the mononuclear 5.
However, as a consequence of the altered hybridization of
C9/C10 as compared to 2 and 5, the alkyne C9/C10 signals of
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bond of the ligand appears to play as crucial a role in deter-
mining the mode of attachment of the ligand to the metal in 5
and 6 as the alkyne function does in 3 and 4. Whereas the
terminal functions of the chain in 3 and 4 are the same N-allyl,
in 5 and 6 they are N-allyl and N-but-2-yne groups.
As for 3, the geometry of mononuclear 5 is trigonal planar if
one defines the coordination plane by the metal center and the
midpoints of the CC and CC bonds (Figure 5). Whereas
the trans substitution of the central CC bond, together with
the requirement of an antiperiplanar arrangement of the tolyl
groups relative to the lone pairs of the N atoms, the tolyl
groups are forced to point away from the complex core in
opposite directions, thus giving rise to an additional structural
motif.
There are four equivalent complex molecules of 5 in the unit
cell (Z = 4), together with one THF solute molecule. Two
molecules each form a centrosymmetric pair in which the metal
coordination planes are perforce parallel (distance of planes
3.68(1) Å; Ni1···Ni1* distance 4.314(1) Å). The tolyl groups at
S2 and S2* align the partner molecules edgewise and point in
about the same directions as the tolyl groups at S1* and S1,
allowing for mating of the structures. The tolyl group at S2
appears also to undergo a π-electron interaction to one Ni1**
center of an adjacent pair (the shortest intermolecular distance
here is Ni1**···C19 at 3.974(1) Å). Voids around the tolyl
group at S1 are filled with THF.
The structure of the dinuclear 6 is derived from that of 5
by the attachment of a Ni(cod) moiety to the CC bond
(Figure 6). The major geometrical changes are in the region of
Figure 5. Molecular structure of 5 (at the 50% probability level),
without THF solute. Selected bond distances (Å) and bond angles
(deg): C1−C2 = 1.387(3), C5−C6 = 1.397(3), C9−C10 = 1.241(4),
Ni1−C1 = 2.032(2), Ni1−C2 = 2.060(2), Ni1−C5 = 2.031(2), Ni1−
C6 = 2.027(2), Ni1−C9 = 1.931(2), Ni1−C10 = 1.978(2); C8−C9−
C10 = 147.0(2), C9−C10−C11 = 153.0(3), (midpoint C1−C2)−
Ni1−(midpoint C5−C6) = 120.5(1), (midpoint C5−C6)−Ni1−
(midpoint C9−C10) = 119.6(1), (midpoint C1−C2)−Ni1−(mid-
point C9−C10) = 119.9(1).
the three CC bonds in complexes of type III, bearing an
acyclic 4,9-diazadodeca-1,6,11-triene ligand, are coplanar, the
three unsaturated moieties in 5 are twisted out of the
coordination plane by 8−12°. These distortions appear to be
induced by the terminal N-but-2-yne function, which restrains
C8 to a position close to the coordination plane of the metal.
The azanickelacyclohexanic ring in 5, involving N1 and two
α-C atoms of the metal-bound CC bonds, adopts a
pronounced chair conformation (dihedral angles within the
ring range from 58 to 73°), whereas the conformation of the
pseudo-azanickelacyclohexanic ring, involving N2 and one α-C
atom of a CC bond and the other of a CC bond, appears
to prefer that of a “flattened half-chair” (dihedral angles range
from 20 to 78°).
Figure 6. Molecular structure of 6 (at the 50% probability level),
without THF solute. Selected bond distances (Å) and bond angles
(deg): C1−C2 = 1.388(4), C5−C6 = 1.392(5), C9−C10 = 1.316(5),
C26−C27 = 1.371(6), C30−C31 = 1.374(5), Ni1−C1 = 2.022(3),
Ni1−C2 = 2.039(3), Ni1−C5 = 2.038(3), Ni1−C6 = 2.038(3), Ni1−
C9 = 2.009(3), Ni1−C10 = 2.029(3), Ni2−C9 = 1.903(3), Ni2−C10
= 1.917(4), Ni2−C26 = 2.113(4), Ni2−C27 = 2.080(4), Ni2−C30 =
2.061(3), Ni2−C31 = 2.094(3), Ni1···Ni1* = 2.6834(7); C8−C9−
C10 = 139.4(3), C9−C10−C11 = 140.9(3), (midpoint C1−C2)−
Ni1−(midpoint C5−C6) = 119.8(1), (midpoint C5−C6)−Ni1−
(midpoint C9−C10) = 120.5(1), (midpoint C1−C2)−Ni1−(mid-
point C9−C10) = 119.7(1).
The geometry at N is somewhat more pyramidal in 5 (sum
of angles is 343.3(3)° at N1 and 344.6(3)° at N2) than in both
3 and 4. The two tosyl SO2 substituents occupy equatorial
positions at N, similar to the case for dinuclear 4. As a result of
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this bond. Thus, the angle C8−C9−C10 is reduced to
139.4(3)° (5, 147.0(2)°) and C9−C10−C11 to 140.9(3)° (5,
153.0(3)°) and the bond lengths of C9−C10 at 1.316(5) Å (5,
1.241(4) Å) and Ni1−C9/10 at 2.020 Å (mean) (5, 1.954 Å,
mean) increase. As a consequence of the increase in the C8−
C9−C10 angle, the previously partially flat pseudo-azanick-
elacyclohexanic ring involving N2 is able to adopt a fuller chair
conformation, with the dihedral angles within the ring rang-
ing from 50.7 to 74.1°. The pyramidal geometry at N2 also
becomes more pronounced (sum of angles is 342.6(7)°). The
azanickelacyclohexanic ring involving N1 remains essentially
unchanged, with dihedral angles ranging from 58.3 to 73.2° and
sum of angles at N1 at 344.6(6)°. As in 5, both tosyl sub-
stituents occupy equatorial positions at N in the azanick-
elacyclohexanic rings, and the tosyl groups adopt again
conformations in which the tolyl groups are antiperiplanar to
the lone pairs of the N atoms to which they are attached.
One of the consequences of the geometrical changes at the
CC bond is that the C atoms of both CC bonds are now
able to take up positions in the coordination plane of Ni1 and
the CC bond is twisted out of it by only 5(1)°. The
Ni2(cod) moiety is bound to the CC entity via two short
bonds Ni2−C9/10 at 1.91(1) Å (mean), with an associated
Ni1,C9,C10/Ni2,C9,C10 interplanar angle of 93(1)°. This
leads to a Ni1···Ni2 distance of 2.6834(7) Å, which is just
slightly shorter than the Ni···Ni distance in 4. The CH2−C
C−CH3 entity lies largely in a plane (C8−C9−C10−C11
torsional angle is 8.5°) which bisects the Ni1···Ni2 bond. This
mirrors the relationship of the alkyne to the two Ni atoms
in 4. The geometry of the Ni2(cod) moiety is as expected.
Interestingly, since the geometrical features of a doubly co-
ordinated CC bond are similar to those of a single
coordinated CC bond, the conformation of the ligand
around Ni1 in 6 resembles that in III.
The packing of centrosymmetric pairs of complexes in the
crystal of 6 (Z = 4) is quite similar to that of 5, with the distinc-
tion that into each pair of complex molecules two Ni2(cod)
moieties have been inserted. The complexes appear to slide
away from one another, so that the Ni1···Ni1* distance is almost
doubled (8.616(1) Å), while maintaining parallel coordination
planes at Ni1 (interplanar distance 6.46(1) Å). In 6, the coordina-
tion planes of Ni1 are flanked by disordered THF solute
molecules. Each metal complex crystallizes with one THF solute
molecule, resulting in four THF molecules in the unit cell.
The similarities and differences in conformations of the
acyclic aza-dien-yne ligands in these complexes and their com-
parison with those of their cyclic analogues thus yield important
information about the conformational properties of the ligands
and the zerovalent metal complexes that are formed from them.
Particularly important are the conformations of the azanick-
elacyclohexanic rings and the ability of the unsaturated moieties
to adopt a favorable coplanar arrangement around the metals.
An ideal chair conformation of the azanickelacyclohexanic rings
appears to be best suited for coordination to Ni(0).
has previously been used as a ligand in the mono- and dinuclear
Ni(0) complexes VIII and IX.10 Whereas in M(0)−1,6,11-
triazacyclopentadeca-(E,E,E)-3,8,13-triene complexes such as IV
(M = e.g., Pd)8a,c,9e and VII (M = Ni)10 the three CC bonds
are twisted out of the coordination plane by structural
constraint of the cycle, in the related acyclic Ni(0)−dodeca-
1,6,11-triene-type complexes6h,15 such as III6h all CC bonds
lie in the coordination plane. The new mononuclear complexes
3 and 5 and their dinuclear derivatives 4 and 6 were synthesized
and their structure and solution properties studied.
(i) In the crystalline Ni(0)−4,9-diazadodeca-1,11-dien-6-yne
complex 3 the acyclic ligand adopts C2 point group symmetry,
thus giving C2-3, with the two terminal CC bonds lying in
the coordination plane of the Ni(0), which in turn causes an
out-of-plane twist of the central CC bond. In solution the
complex isomerizes, and the mirror-symmetric form Cs-3 is also
present, with which the C2 structure is in equilibrium. Cs sym-
metry is observed in M(0)−1,6,11-triazacyclopentadeca-(E,E)-
3,8-dien-13-yne complexes, such as VIII (M = Ni),10 containing
the cyclic ligand, but in this case, it is the CC bond that lies
in the coordination plane of the metal and the CC bonds
that are twisted out of the coordination plane.
(ii) In the structure of the acyclic and unsymmetrical Ni(0)−
4,9-diazadodeca-1,(E)-6-dien-11-yne 5, as a counterpart to 3,
both CC bonds and the CC bond are slightly twisted out
of the coordination plane. The structure is governed by the E
configuration of the diene and the associated chair
conformation of the 1,(E)-6-diene nickelacycle.
(iii) Mononuclear VIII,10 3, and 5 can coordinate a further
Ni(0) atom in the form of Ni(cod) at the CC bond, to form
alkyne-bridged dinuclear complexes IX,10 4, and 6. This goes
along with a change in hybridization of the alkyne C atoms
toward sp3 and formation of chairlike azanickelacyclohexanic
substructures. Hence, a similar bonding situation arises for the
cyclic dinuclear IX10 and the acyclic and symmetric dinuclear 4.
Since all carbons of the CC and CC bonds lie practically
in the coordination plane, the structures appear to favor de
facto (IX) or approximate (4) Cs symmetry. A similar geometry
can also be expected for M(0)−1,6,11-triazacyclopentadeca-
(E,E,Z)-3,8,13-triene16 and (so far unsought) acyclic M(0)−
4,9-diazadodeca-1,(Z)-6,11-triene complexes, where the (C
C)Ni(cod) is replaced by (Z)-CC.
(iv) In 6 the conformation of the ligand around Ni1
resembles that in III, considering that the geometrical features
of a doubly coordinated CC bond are similar to those of a
singly coordinated CC bond.
(v) While dinuclear IX and 4 are insoluble, precluding an
NMR characterization, for soluble 6 rotation of the Ni2(cod)
entity about the Ni2−alkyne bond has been ruled out by NMR.
The acyclic polyunsaturated aza ligands described here can
be used to stabilize Ni(0). These compounds appear more
reactive than those with the parent cyclic ligands due to the
absence of a macrocyclic effect. Thus, acyclic polyfunctional
ligands are particularly suited to confer on metal complexes
both thermal stability and reactivity.
CONCLUSIONS
■
The syntheses of mono- and dinuclear nickel(0) complexes
containing the open-chain ligands 4,9-bis(4-tolylsulfonyl)-4,9-
diazadodeca-1,11-dien-6-yne (1) and 4,9-bis(4-tolylsulfonyl)-
4,9-diazatrideca-1,(E)-6-dien-11-yne (2) are reported. These
ligands differ in their 1,6,11-sequences of the two ene and one
yne functions and may be viewed as distinct, acyclic sections of
cyclic 1,6,11-triazacyclopentadeca-(E,E)-3,8-dien-13-yne, which
EXPERIMENTAL SECTION
■
THF was dried by distillation from NaAlEt4. Ni(cod)21c and ligand 111
(C24H28N2O4S2, FW = 472.6) were prepared as reported. For the
synthesis of 2 (C25H30N2O4S2, FW = 486.6), see the Supporting
Information. Microanalyses were performed by Mikroanalytisches
Labor Kolbe, Mulheim, Germany. EI mass spectra were recorded at
̈
70 eV. 1H NMR spectra were measured at 300 and 400 MHz and 13
C
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1
NMR spectra at 75 and 100 MHz with Bruker instruments. H and
crystallographic data for 3−6. This material is available free of
charge via the Internet at http://pubs.acs.org. Supplementary
crystallographic data (3−6: CCDC 896849−896852) can also
be obtained free of charge via http://www.ccdc.cam.ac.uk/
deposit.
13C chemical shifts (δ) were referenced to internal solvent resonances
and are reported relative to SiMe4. DSC experiments were performed
using Mettler Toledo DSC820e and DSC822e instruments under
inert conditions (continuous flow of 40 mL/min of high-purity N2).
Aluminum crucibles (40 μL) were used; sample masses were between
4.5 and 7 mg. All handlings of nickel(0) complexes were done with
Schlenk-type glassware under an argon atmosphere.
(4,9-Bis(4-tolylsulfonyl)-4,9-diazadodeca-1,11-dien-6-yne)-
nickel(0) ((C24H28N2O4S2)Ni, 3). A solution of Ni(cod)2 (181 mg,
0.66 mmol) in anhydrous THF (20 mL) was combined with a solution
of the 4,9-diazadodeca-1,11-dien-6-yne 1 (312 mg, 0.66 mmol) in
THF (20 mL) at room temperature. After initial mixing, the solution
was left undisturbed. Over the course of 1−3 days yellow crystals of 3
were obtained. These were isolated by filtration, washed with diethyl
ether, and dried under vacuum: yield 292 mg (84%). Mp 161−163 °C
dec. For NMR data, see Table 1. Anal. Calcd for C24H28N2NiO4S2
(531.3): C, 54.25; H, 5.31; N, 5.27; Ni, 11.05. Found: C, 54.22; H,
5.51; N, 5.06; Ni, 11.34.
(4,9-Bis(4-tolylsulfonyl)-4,9-diazadodeca-1,11-dien-6-yne)-
dinickel(0) 1,5-Cyclooctadiene ((C24H28N2O4S2)Ni2(cod), 4). A
solution of Ni(cod)2 (394 mg, 1.43 mmol) in THF (30 mL) was
combined with a solution of 1 (338 mg, 0.71 mmol) in anhydrous
THF (20 mL) at room temperature. After initial mixing, the solution
was left undisturbed, and over the course of 3 days, red crystals of 4
were obtained. These were isolated by filtration, washed with diethyl
ether, and dried under vacuum: yield 283 mg (57%). Anal. Calcd for
C32H40N2Ni2O4S2 (698.2): C, 55.05; H, 5.77; N, 4.01; Ni, 16.81.
Found: C, 53.90; H, 5.54; N, 3.92; Ni, 16.81. Recording of the 1H and
13C NMR was prevented by the insolubility of the compound.
AUTHOR INFORMATION
Corresponding Author
*E-mail: anna.roglans@udg.edu (A.R.); poerschke@kofo.mpg.
de (K.-R.P.).
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank Mrs. D. Bartels for recording and evaluating the
NMR spectra of 2, 5, and 6 and Mrs. W. Gamrad for skillful
technical assistance. The project was funded by the program
Acciones Integradas Hispano-Alemanas between Germany
(DAAD, BMBF) and Spain (MICINN, Spanish Ministry of
Science and Innovation, project AIB2010DE-00262). Financial
support from the MICINN (project CTQ2011-23121) and the
Generalitat de Catalunya (project 2009SGR637) is also
gratefully acknowledged.
REFERENCES
■
(1) (a) Wilke, G. Angew. Chem. 1960, 72, 581. (b) Wilke, G. Angew.
Chem. 1963, 75, 10; Angew. Chem., Int. Ed. Engl. 1963, 2, 105.
(4,9-Bis(4-tolylsulfonyl)-4,9-diazatrideca-1,(E)-6-dien-11-
yne)nickel(0) ((C25H30N2O4S2)Ni·1/4THF, 5). The 4,9-diaza-trideca-
1,trans-6-dien-11-yne 2 (253 mg, 0.52 mmol) was dissolved in 10 mL
of THF by gentle heating. After it was recooled to ambient temper-
ature, the solution was briefly stirred with Ni(cod)2 (138 mg,
0.50 mmol) to obtain (via red) a clear amber solution. When the solu-
tion was left untouched for several days, the color faded over several
hours and eventually yellow cubes slowly crystallized. (Crystallization
appears to occur spontaneously and may be accelerated by seeding
in a subsequent preparation.) Crystallization was completed by
cooling in a refrigerator (−7 °C). After removal of the mother
liquor the product was washed with cold THF and dried under vacuum
at 0 °C: yield 280 mg (50%). For NMR data, see Table 2. Anal. Calcd for
C25H30N2NiO4S2·1/4C4H8O (563.4): C, 55.43; H, 5.73; N, 4.97; Ni, 10.42;
O, 12.07; S, 11.38. Found: C, 54.60; H, 5.74; N, 4.79; Ni, 10.11; S, 11.12.
(4,9-Bis(4-tolylsulfonyl)-4,9-diazatrideca-1,(E)-6-dien-11-
yne)dinickel(0) 1,5-Cyclooctadiene ((C25H30N2O4S2)-
Ni2(cod)·THF, 6). The reaction was carried out as for 5 by stirring
a solution of 2 (243 mg, 0.50 mmol) in 15 mL of THF with Ni(cod)2
(280 mg, 1.02 mmol) in slight excess at ambient temperature until
all Ni(cod)2 was dissolved (1 min). Henceforth the orange-red
(c) Bogdanovic, B.; Kroner, M.; Wilke, G. Liebigs. Ann. Chem. 1966,
699, 1.
̈
(2) Chernyshova, E. S.; Goddard, R.; Porschke, K.-R. Organometallics
̈
2007, 26, 4872 and references cited therein.
(3) Brenner, W.; Heimbach, P.; Hey, H.; Muller, E. W.; Wilke, G.
̈
Liebigs Ann. Chem. 1969, 727, 161.
(4) (a) Wilke, G. Angew. Chem. 1957, 69, 397. (b) Wilke, G.;
Bogdanovic, B.; Heimbach, P.; Kroner, M.; Muller, E. W. Adv. Chem.
̈
̈
Ser. 1962, 34, 137. (c) Breil, H.; Heimbach, P.; Kroner, M.; Muller, H.;
̈
̈
Wilke, G. Makromol. Chem. 1963, 69, 17.
(5) For a review, see: Youngs, W. J.; Tessier, C. A.; Bradshaw, J. D.
Chem. Rev. 1999, 99, 3153.
(6) (a) Bonrath, W.; Porschke, K.-R.; Michaelis, S. Angew. Chem.
̈
1990, 102, 295; Angew. Chem., Int. Ed. 1990, 29, 298. (b) Proft, B.;
Porschke, K.-R.; Lutz, F.; Kruger, C. Chem. Ber. 1991, 124, 2667.
̈
̈
(c) Krause, J.; Bonrath, W.; Porschke, K.-R. Organometallics 1992, 11,
̈
1158. (d) Porschke, K.-R.; Pluta, C.; Proft, B.; Lutz, F.; Kruger, C. Z.
Naturforsch., B 1993, 48, 608. (e) Proft, B.; Porschke, K.-R.; Lutz, F.;
Kruger, C. Chem. Ber. 1994, 127, 653. (f) Krause, J.; Haack, K.-J.;
Cestaric, G.; Goddard, R.; Porschke, K.-R. J. Chem. Soc., Chem.
̈
̈
̈
̈
̈
1
solution was left untouched for /2 day, avoiding precipitation of the
Commun. 1998, 1291. (g) Krause, J.; Cestaric, G.; Haack, K.-J.;
intermediately formed 5. After this time the solution was cooled
to −20 °C, where usually a yellow precipitate of 6 was formed. The
precipitate was redissolved by brief warming to 30−40 °C and addition
of just as much THF to allow for a saturated solution (the total
volume was about 25 mL). The solution was then recooled to −20 °C
for some days and eventually to −40 °C. This way 6 crystallized either
in the form of snowball-type clusters of felted fine yellow needles or
large orange spherulites; the typical yield was 200 mg (51%). The
spherulites were used for the X-ray structure analysis. For NMR data,
see Table 2. Anal. Calcd for C33H42N2Ni2O4S2·C4H8O (784.3): C,
56.66; H, 6.43; N, 3.57; Ni, 14.97; O, 10.20; S, 8.18. Found: C, 56.37;
H, 6.46; N, 3.68; Ni, 15.21; S, 8.27.
Seevogel, K.; Storm, W.; Porschke, K.-R. J. Am. Chem. Soc. 1999, 121,
9807. (h) Blum, K.; Chernyshova, E. S.; Goddard, R.; Jonas, K.;
̈
Porschke, K.-R. Organometallics 2007, 26, 5174.
̈
́
(7) Hratchian, H. P.; Chowdhury, S. K.; Gutierrez-García, V. M.;
Amarasinghe, K. K. D.; Heeg, M. J.; Schlegel, H. B.; Montgomery, J.
Organometallics 2004, 23, 4636.
(8) (a) Cerezo, S.; Cortes
M.; Parella, T.; Pleixats, R.; Roglans, A. Tetrahedron 1998, 54, 14885.
(b) Cortes, J.; Moreno-Manas, M.; Pleixats, R. Eur. J. Org. Chem. 2000,
239. (c) Cerezo, S.; Cortes
Molins, E.; Moreno-Manas, M.; Pleixats, R.; Torrejon
̀
, J.; Lopez-Romero, J.-M.; Moreno-Manas,
́
̃
̀
̃
̀
, J.; Galvan, D.; Lago, E.; Marchi, C.;
, J.; Vallribera, A.
Eur. J. Org. Chem. 2001, 329. (d) Cerezo, S.; Cortes, J.; Lago, E.;
́
̃
̀
Molins, E.; Moreno-Manas, M.; Parella, T.; Pleixats, R.; Torrejon
Vallribera, A. Eur. J. Inorg. Chem. 2001, 1999.
́
, J.;
̃
ASSOCIATED CONTENT
■
(9) (a) Moreno-Manas, M.; Pleixats, R.; Roglans, A.; Sebastian
́
, R.
̃
S
* Supporting Information
M.; Vallribera, A. Arkivoc 2004, iv, 109. (b) Moreno-Manas, M.;
̃
CIF files for complexes 3−6, synthesis protocol for 2, NMR
spectra of complexes 1, 2, 3, 5, and 6, and a table of X-ray
́
Pleixats, R.; Sebastian, R. M.; Vallribera, A.; Roglans, A. J. Organomet.
Chem. 2004, 689, 3669. (c) Pla-Quintana, A.; Roglans, A.; Torrent, A.;
1719
dx.doi.org/10.1021/om301160m | Organometallics 2013, 32, 1710−1720

Organometallics
Article
Moreno-Manas, M.; Benet-Buchholz, J. Organometallics 2004, 23,
̃
2762. (d) Pla-Quintana, A.; Roglans, A.; Julian
́
-Ortiz, J. V.; Moreno-
Manas, M.; Parella, T.; Benet-Buchholz, J.; Solans, X. Chem. Eur. J.
2005, 11, 2689. (e) Pla-Quintana, A.; Torrent, A.; Dachs, A.; Roglans,
̃
A.; Pleixats, R.; Moreno-Manas, M.; Parella, T.; Benet-Buchholz, J.
̃
Organometallics 2006, 25, 5612. (f) Dachs, A.; Masllorens, J.; Pla-
Quintana, A.; Roglans, A.; Farjas, J.; Parella, T. Organometallics 2008,
27, 5768.
(10) Brun, S.; Pla-Quintana, A.; Roglans, A.; Porschke, K.-R.;
̈
Goddard, R. Organometallics 2012, 31, 1983.
́
(11) Clavier, H.; Correa, A.; Escudero-Adan, E. C.; Benet-Buchholz,
J.; Cavallo, L.; Nolan, S. P. Chem. Eur. J. 2009, 15, 10244.
(12) Teichert, J. F.; Zhang, S.; van Zijl, A. W.; Slaa, J. W.; Minnaard,
A. J.; Feringa, B. L. Org. Lett. 2010, 12, 4658.
(13) Neustadt, B. R. Tetrahedron Lett. 1994, 35, 379.
(14) Jolly, P. W.; Mynott, R. Adv. Organomet. Chem. 1981, 19, 257.
(15) Cloke, F. G. N.; Hitchcock, P. B.; Lappert, M. F.; MacBeath, C.;
Mepsted, G. O. J. Chem. Soc., Chem. Commun. 1995, 87.
(16) Cortes
2001, 42, 4337.
̀
, J.; Moreno-Manas, M.; Pleixats, R. Tetrahedron Lett.
̃
1720
dx.doi.org/10.1021/om301160m | Organometallics 2013, 32, 1710−1720