Binuclear oxalamidinate complexes (MePd)2(oxam) and homoleptic complexes of the type [(THF)nLi4 (Me8)M2] and [(THF)4Li2 (Ph4)M] (M=Pd, Ni): Synthesis, structures and catalytic C-C linking reactions

Article abstract of DOI:10.1016/S0022-328X(03)00528-X

The dinuclear methyl complexes 1 and 2 of the type [CH₃ -Pd(oxam)Pd-CH₃] were obtained by reaction of (COD)PdCH₃(Cl) with the corresponding dilithium oxalic amidinates, prepared from LiBu and the oxalic amidines H₂Y or H₂Z (H₂Y= N,N′-bis(2-pyridylethyl)-1, 2-bis-(2,4,6-trimethylphenyl-imino)-ethane-1,2-diamine; H₂ Z = N,N ′-bis(diphenylphosphino-3-propyl)-1,2-bis-(2,4, 6-trimethylphenyl-imino)-ethane-1,2-diamine). Reaction of both 1 and 2 with an excess of LiCH₃ results in the formation of the dimeric compound [(THF)₄Li₄(CH₃) ₈Pd₂] (3). Similarly, monomeric phenyl complexes of the composition [(THF)₄Li₂M(C₆ H₅)₄] (M=Pd (4), Ni (5)) were prepared. The complexes were characterized by elemental analysis, mass spectroscopy, ¹H-NMR, ¹³C-NMR and ⁷Li-NMR spectroscopy, and by X-ray single-crystal diffraction analysis in the solid state. All complexes contain the metals in a planar-square environment. Compounds 1-3 and 4 are highly active, selective and long-living catalysts in the Heck reaction of 4-bromoacetophenone and n-butyl acrylate. Compound 5 and the related neutral ligand-free Ni complex [(THF)₄Li₄(CH₃)₈ Ni₂] (6) are active catalysts for the Kumada cross-coupling of MesitylMgBr with 4-bromotoluene and are even able to couple the corresponding aryl chloride or aryl fluoride with MesitylMgBr.

Full text of DOI:10.1016/S0022-328X(03)00528-X

Journal of Organometallic Chemistry 681 (2003) 24ꢁ36
/
www.elsevier.com/locate/jorganchem
Binuclear oxalamidinate complexes (MePd)2(oxam) and homoleptic
complexes of the type [(THF)nLi4(Me8)M2] and [(THF)4Li2(Ph4)M]
(Mꢀ
/
Pd, Ni): synthesis, structures and catalytic CÃ
/
C linking
reactions
Katja Lamm, Michael Stollenz, Mirko Meier, Helmar Gorls, Dirk Walther *
¨
Institut fur Anorganische und Analytische Chemie der Friedrich-Schiller-Universitat Jena, August-Bebel-Straße 2, D-07743 Jena, Germany
¨ ¨
Received 14 February 2003; received in revised form 12 May 2003; accepted 12 May 2003
Abstract
The dinuclear methyl complexes 1 and 2 of the type [CH3Ã
with the corresponding dilithium oxalic amidinates, prepared from LiBu and the oxalic amidines H2Y or H2Z (H2Yꢀ
pyridylethyl)-1,2-bis-(2,4,6-trimethylphenyl-imino)-ethane-1,2-diamine; H2ZꢀN,N?-bis(diphenylphosphino-3-propyl)-1,2-bis-
/
Pd(oxam)PdÃ
/
CH3] were obtained by reaction of (COD)PdCH3(Cl)
/
N,N?-bis(2-
/
(2,4,6-trimethylphenyl-imino)-ethane-1,2-diamine). Reaction of both 1 and 2 with an excess of LiCH3 results in the formation of
the dimeric compound [(THF)4Li4(CH3)8Pd2] (3). Similarly, monomeric phenyl complexes of the composition [(THF)4Li2M(C6H5)4]
1
(Mꢀ
/
Pd (4), Ni (5)) were prepared. The complexes were characterized by elemental analysis, mass spectroscopy, H-NMR, 13C-
7
NMR and Li-NMR spectroscopy, and by X-ray single-crystal diffraction analysis in the solid state. All complexes contain the
metals in a planar-square environment. Compounds 1ꢁ3 and 4 are highly active, selective and long-living catalysts in the Heck
/
reaction of 4-bromoacetophenone and n-butyl acrylate. Compound 5 and the related neutral ligand-free Ni complex
[(THF)4Li4(CH3)8Ni2] (6) are active catalysts for the Kumada cross-coupling of MesitylMgBr with 4-bromotoluene and are even
able to couple the corresponding aryl chloride or aryl fluoride with MesitylMgBr.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Palladium; Nickel; Heck reaction; Cross-coupling; Catalysts
1. Introduction
monomeric complexes of the composition [(solv)n-
Li2M(C6H5)4] (B) (Scheme 1) [10,11].
Homoleptic transition metal methyl complexes of the
type [M(CH3)n] are only known for d-electron-poor
metals in high oxidation states whereas such complexes
of d-electron-rich transition metals with ‘‘normal’’
oxidation states are unstable. However, stable com-
plexes with d-electron-rich metals can be obtained by
occupying additional coordination positions around the
metal by methyl groups resulting in the formation of
dimeric compounds of the type [(solv)nLi4(CH3)8M(II)2]
The first methyl complex of the type A containing
Cr(II) was isolated by Kurras and Otto [1] in the early
1960s. Recently, we have isolated and structurally
determined two methyl Ni(II) complexes of the type A
(nꢀ/2 or 4) [8]. Independently, Ihara et al. [9] prepared
the Ni complex with nꢀ/4. Surprisingly, Pd complexes
of the type A and B which would have been of particular
interest in catalysis are still unknown.
Due to their high reactivity, complexes of the type A
and B may act as starting material for the synthesis of
other organometallics. However, surprisingly less is
known about their potential as catalysts in homoge-
neous-catalytic reactions [9].
(A) (Scheme 1) [1ꢁ/10]. Similarly, phenyl complexes of
transition metals can be stabilized by the formation of
Wereportinthispublication,thesynthesisandstructure
of the new binuclear complex [(THF)4Li4(CH3)8Pd2] (3)
formed, for example, by reaction of the hitherto unknown
* Corresponding author. Tel.: ꢂ
948-102.
E-mail address: cdw@rz.uni-jena.de (D. Walther).
/
49-3641-948-119; fax: ꢂ49-3641-
/
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00528-X

K. Lamm et al. / Journal of Organometallic Chemistry 681 (2003) 24ꢁ
/
36
25
Scheme 1. Complex types A and B.
oxalic amidinate complexes 1 and 2 of the type [CH3Ã
/
bis(2,4,6-trimethylphenyl)-oxalamidinate) [12,13] in
THF at ꢃ78 8C resulted in the formation of a yellow
Pd(oxam)PdÃCH3] with an excess ofLiCH3 (oxam: three-
/
/
dentateoxalicamidinatescontainingN-orP-donoratoms
in the side chains). Furthermore, we describe the synthesis
and structure of the complexes [(THF)4Li2M(C6H5)4]
solution from which the pure dinuclear methyl palla-
dium(II) compound 1 could be isolated in 55% yield
(Scheme 2). Single crystals of 1 were grown from THF.
Similarly, complex 2, containing two phosphorous
donor atoms in the side arms, could be synthesized using
Li2Z (Scheme 2). Both complexes are readily soluble in
toluene or THF and are thermally stable even for several
hours in toluene solution at 100 8C. Elemental analysis
and mass spectrum confirmed their composition.
(Mꢀ/Pd(4),Ni(5)[11]).Additionally,weshowthatthePd
complexes 1ꢁ
/
3 and 4 are extremely active catalysts in the
Heck reaction, whereas (THF)4Li2NiPh4 and
[(THF)4Li4(CH3)8Ni(II)2] (6) are catalytically active in
theKumadaCÃ
fluoridewereusedascouplingcomponents.Itissomewhat
surprising that the complexes 3ꢁ6 are active, long-living
/
Ccouplingevenifanarylchlorideoranaryl
/
In the mass spectrum of 1, the binuclear complex ion
[CH3Pd(oxam)Pd]ꢂ (m/zꢀ
catalysts in these reactions, since the generally accepted
mechanismsofbothcatalyticcyclescontaintheredoxsteps
M(II)/M(0) and M(0)/M(II) which usually require addi-
tional neutral p-acceptor ligands for stabilizing the low
1
757) was detected. The H-
/
NMR spectrum of 1 at ambient temperature in THF-d8
is very similar to that of the corresponding Ni methyl
complex [8] with one singlet of the methyl protons of the
oxidationstateofthemetalinsolution.Thecomplexes3ꢁ6,
/
PdÃ
/
Me group at dꢀ
/
ꢃ
/
0.55 ppm and two singlets for
2.29 ppm (p-methyl)
however, do not contain such stabilizing ligands.
the methyl mesityl groups at dꢀ
/
and 2.18 ppm (o-methyl). The relative intensities of
these resonances were 1:1:2. In addition to the signals
corresponding to the protons of the aromatic rings
between 6.65 and 8.35 ppm, the 1H-NMR spectrum
showed two broad singlets at 2.26 and 2.86 ppm, which
are assigned to the CH2 groups.
2. Results
2.1. Synthesis and structures of the methyl palladium
complexes 1ꢁ3
/
The 13C-NMR spectrum in THF-d8 also showed a
very simple pattern. The resonance for the carbon of the
The reaction of (COD)PdCH3(Cl) with two equiva-
lents of Li2Y (H2Yꢀ
N1,N2-bis(2-pyridylethyl)-N3,N4-
/
PdÃ
/
CH3 groups was found at dꢀ4.9 ppm, and the
/

26
K. Lamm et al. / Journal of Organometallic Chemistry 681 (2003) 24ꢁ36
/
Scheme 2. Synthesis of the complexes 1ꢁ3.
/
signals of the mesitylÃ
/
Me carbons appeared at 19.4 and
fashion. Each metal ion is in a planar environment
created by three N atoms from the chelating ligand and
21.0 ppm, respectively. Furthermore, the resonances for
the CH2 carbons were observed at 43.4 and 44.6 ppm. In
addition, only nine resonances in the region of the sp2-
carbons between 123.1 and 167.3 ppm were observed.
This is typical for a symmetrical structure in solution
and corresponds to five signals for the inequivalent
aromatic CH groups, one signal at 167.3 ppm for the
equivalent oxalamidinate carbons and four signals for
the inequivalent quarternary C atoms of the aromatic
substituents. The expected number of the latter signals
was 5; possibly, one signal may be too weak or does
overlap with other signals in this region.
The solid-state structure of 1 determined by an X-ray
analysis is shown in Fig. 1. Relevant bond lengths and
angles are listed in the figure caption. The dinuclear
complex contains two Pd(II) centers connected via the
oxam ligand Y which acts in a bis-chelating tridentate
one carbon of the methyl group. The C1Ã
/
C2 bond
˚
distance in the chelating ligand (1.526(7) A) is that of a
single bond. Furthermore, bond angles around both
carbons are typical for sp2-hybridization. As expected,
the two methyl groups coordinated to the Pd centers of
the oxam bridge lie trans to each other. The PdÃ
/
C
˚
bonds (2.025(5) A) fall in a typical range. The solid-state
structure of 2, shown in Fig. 2, is similar to that of 1.
The coordination environment of the Pd atoms is also
˚
nearly planar (deviation 0.0356 A) and the CÃ
/N bonds
of the oxalamidinate bridge are almost equivalent,
indicating a high double-bond character due to a
complete electron delocalization over the two NCN
˚
˚
N2, 1.338(3) A).
NMR studies in THF-d8 confirm that 2 has a similar
units (1.317(3) A; C1Ã
/
1
structure in solution as in the solid state. In the H-

K. Lamm et al. / Journal of Organometallic Chemistry 681 (2003) 24ꢁ
/
36
27
˚
˚
˚
Pd2Ã
Pd2Ã
Pd2Ã
N4, 130.6(5) A.
Selected bond distances (A) and bond angles (8): PdÃ
C26, 2.077(2)8; PdÃP1, 2.2077(6)8; PdÃN1, 2.092(2)8;
PdÃN2A, 2.081(2)8; C1ÃN1, 1.317(3)8; C1ÃN2,
1.338(3)8; N1ÃC2, 1.468(3)8; C2ÃC3, 1.525(3)8; C3Ã
C4, 1.543(3)8; C4ÃP1, 1.821(2)8; C26ÃPdÃP1, 86.48(6)
PdÃN2A, 95.66(8)
N2A, 172.15(5) A;
/
N5, 174.2(2) A; C36Ã
/
Pd2Ã
Pd2ÃN6, 173.6(2) A; N5Ã
C1ÃN5, 131.0(5) A; N2Ã
/
N6, 91.2(2) A; N4Ã
/
˚
/
N5, 79.6(2) A; N4Ã
N6, 94.0(2) A; N1Ã
/
/
/
˚
˚
/
/
/
/
C2Ã
/
˚
˚
/
/
/
/
/
/
/
/
/
/
/
/
˚
˚
˚
A; C26Ã
/
PdÃ
PdÃN1, 99.68(5) A; P1Ã
PdÃN2A, 78.70(7) A; N1Ã
C1Ã
Symmetry transformations used to generated equiva-
lent atoms: A ꢃX, Y, ꢃZꢃ1/2.
/
N1, 172.90(8) A; C26Ã
/
/
˚
˚
A; P1Ã
N1Ã
N1Ã
/
/
/
PdÃ
C1Ã
C1ÃC1A, 113.8(2) A.
/
˚
˚
/
/
/
/
N2, 131.0(2) A;
˚
˚
/
/
C1A, 115.2(2) A; N2Ã
/
/
/
/
/
For the synthesis of the cluster complex 3, three
routes starting either from 1, 2 or from dinuclear
complexes of the type [(acac)Pd(oxam)Pd(acac)] [14]
could be used. Reaction of 1 or 2 with six equivalents of
Fig. 1. Molecular structure of complex 1.
NMR spectrum, the proton signals for the mesityl
LiMe in THF at ꢃ78 8C resulted in a yellow solution
/
methyl groups are observed at dꢀ
and the methylene protons give three broadened signals
in the ranges 1.44ꢁ1.51, 1.84ꢁ1.90 and 2.59ꢁ2.61 ppm.
Additionally, a doublet for the methylÃPd protons at
dꢀ 0.85 ppm was found.
Selected bond distances (A) and bond angles (8): Pd1Ã
N1, 2.029(4)8; Pd1ÃN2, 2.068(4)8; Pd1ÃN3, 2.061(4)8;
Pd1ÃC35, 2.025(5)8; Pd2ÃN4, 2.043(3)8; Pd2ÃN5,
2.086(4)8; Pd2ÃN6, 2.057(4)8; C1Ã
C2, 1.526(7)8; C1ÃN5, 1.291(6)8; C2Ã
C2ÃN4, 1.337(6)8; N2Ã
1.544(7)8; C4ÃC5, 1.504(8)8; C5Ã
C19, 1.447(6)8; C19ÃC20, 1.539(7)8; C20Ã
1.495(8)8; C21ÃN6, 1.373(7)8; C35ÃPd1ÃN1, 95.1(2)
Pd1ÃN3, 91.2(2)
Pd1ÃN3, 173.7(2) A;
Pd2ÃN4, 95.2(2) A; C36Ã
/2.15 and 2.31 ppm,
from which 3 could be isolated in 20% yield (Scheme 2).
Furthermore, [(acac)Pd(oxam)Pd(acac)] reacted with
/
/
/
eight equivalents of LiMe in THF at ꢃ78 8C to form
/
/
a brown suspension which turned to a yellow solution
by slowly warming to room temperature. Upon eva-
poration of most of the solvent and keeping the resulting
/
ꢃ
/
˚
/
/
/
solution at ꢃ258C, colorless crystals of 3 could be
/
/
/
/
isolated in 20% yield. The pyrophoric complex is
extremely sensitive towards traces of air or moisture.
It is soluble in THF, toluene and benzene.
Its 1H-NMR spectrum (in C6D6 at room temperature)
/
/
N1, 1.342(6)8; C1Ã
/
/
/
N2, 1.312(6)8;
/
/
C3, 1.463(7)8; C3Ã
N3, 1.350(7)8; N5Ã
C21,
/
C4,
showed only one singlet at ꢃ0.11 ppm besides the
/
/
/
/
proton resonances of the coordinated THF at 1.30 and
3.72 ppm indicating that the methyl groups are equiva-
lent. The symmetrical structure of the complex was
confirmed by the 13C-NMR spectrum showing only one
/
/
/
/
/
˚
˚
A; C35Ã
A; N1Ã
N2Ã
/
Pd1Ã
Pd1ÃN2, 79.7(2) A; N1Ã
Pd1ÃN3, 94.0(2) A; C36Ã
/
N2, 174.3(2) A; C35Ã
/
/
˚
˚
˚
/
/
/
/
signal for the methyl group at ꢃ7.6 ppm, and by the
/
˚
˚
/
/
/
/
/
7Li-NMR spectrum in which also only one signal at 9.3
ppm was observed.
Single crystals of 3 were obtained from THF suitable
for X-ray crystallographic determination. The crystal
structure confirmed the highly symmetrical structure in
solution indicated by NMR spectroscopy. Fig. 3 dis-
plays the dimeric molecular structure and selected bond
lengths and angles in the figure caption. The structure is
very similar to the corresponding dimeric Ni(II) com-
pound [8]. Each palladium ion in 3 is surrounded by
four methyl groups in a square-planar geometry. The
eight methyl groups of the dimer are situated at the
corners of a cube. The Pd centers are placed in the
middle of two squares lying on opposite sides. The
˚
PdÁ Á ÁPd separation is relatively long (3.279(2) A) con-
firming the absence of a metalÃ/metal bond between
those two metal centers. In the middle of the other four
squares of the Me8 cube, the four Li ions are situated.
Each Li atom coordinates one THF molecule and
Fig. 2. Molecular structure of complex 2.

28
K. Lamm et al. / Journal of Organometallic Chemistry 681 (2003) 24ꢁ36
/
2.2. Phenyl complexes (THF)4Li2PdPh4 (4) and
(THF)4Li2NiPh4 (5)
The so far unknown complex (THF)4Li2PdPh4 (4)
was synthesized starting with the dinuclear complex
[(acac)Pd(oxam)Pd(acac)] in a THF solution and eight
equivalents of Li(C6H5) at ꢃ
concentrating the brown reaction mixture, colorless
crystals could be grown at ꢃ25 8C. Like the above-
/
78 8C (Scheme 3). After
/
described homoleptic compound 3, they show an
extreme sensitivity towards air and moisture and a
comparable solubility. Therefore, only Li and Pd con-
tent could be determined by ICP-MS supporting the
above composition.
1
The H-NMR spectrum in C6D6 shows two singlets
for the CH2 groups of the coordinated THF molecules
at 1.38 and 3.51 ppm. The aromatic CH protons of the
phenyl groups give a doublet at 8.16 and three multiplets
Fig. 3. Molecular structure of complex 3.
at 6.95ꢁ
/
6.99, 7.11ꢁ
/
7.22 and 7.44ꢁ7.47 ppm which
/
cannot be integrated because of the overlapping with
the solvent signal. In the 13C-NMR spectrum, two
signals for the THF molecules at 25.9 and 68.0 ppm
appear, the signals for the phenyl groups are once more
difficult to separate from the solvent signals. At least
two signals can be found at 122.2 and 141.2 ppm. The
7Li-NMR spectrum shows only one signal at 7.1 ppm,
which supports the highly symmetrical structure of
compound 4.
interacts with the carbon atoms of four methyl groups
forming PdÃCH3ÃLi bonds. The CÃLi(THF) distances
(average 2.431 A) fall in a typical range. The PdÃCH3
distances range from 2.120 to 2.143 A (average 2.135 A),
which is slightly larger than the respective bond
/
/
/
˚
/
˚
˚
distances in comparable square-planar dimethylÃ
complexes that consist of additional P,P, P,N or N,N
CH3 bond distances are
/Pd
chelating ligands. Their PdÃ
/
˚
ranged from 2.016 to 2.097 A.
Fig. 4 displays the molecular structure and selected
bond lengths and angles in the figure caption for the Pd
complex 4 in the solid state determined by X-ray
˚
Selected bond distances (A) and bond angles (8): Pd1Ã
/
C1, 2.142(3)8; Pd1Ã
Pd1ÃC4, 2.139(3)8; Pd2Ã
2.126(3)8; Pd2ÃC7, 2.143(3)8; Pd2Ã
C1, 2.426(7)8; Li1ÃC4, 2.419(6)8; Li1Ã
Li1ÃC8, 2.440(7)8; Li1Ã
2.396(7)8; Li2ÃC2, 2.442(7)8; Li2Ã
C6, 2.444(7)8; Li2ÃO2, 2.006(6)8; Li3Ã
Li3ÃC3, 2.432(7)8; Li3ÃC6, 2.428(7)8; Li3Ã
2.447(7)8; Li3ÃO3, 2.032(6)8; Li4ÃC3, 2.464(7)8; Li4Ã
C4, 2.407(7)8; Li4ÃC7, 2.416(7)8; Li4ÃC8, 2.426(7)8;
Li4ÃO4, 2.000(6)8; C1Ã
C3, 169.4(1) A; C1Ã
/
C2, 2.134(3)8; Pd1Ã
/
C3, 2.120(3)8;
/
/
C5, 2.137(3)8; Pd2Ã
/
C6,
analysis of single crystals.
˚
/
/
C8, 2.137(3)8; Li1Ã
/
Selected bond distances (A) and bond angles (8): PdÃ
/
/
/
C5, 2.441(6)8;
C1, 2.095(5)8; PdÃ
PdÃC19, 2.091(5)8; Li1Ã
2.275(9)8; Li1ÃO1, 1.928(9)8; Li1Ã
C13, 2.368(9)8; Li2ÃC19, 2.258(9)8; Li2Ã
Li2ÃO4, 1.960(9)8; C1Ã
84.5(2) A; C1Ã
/
C7, 2.102(5)8; PdÃ
C1, 2.348(10)8; Li1Ã
O2, 1.930(9)8; Li2Ã
O3, 1.975(9)8;
/
C13, 2.090(5)8;
/
/
O1, 2.036(6)8; Li2Ã
C5, 2.433(7)8; Li2Ã
C2, 2.435(7)8;
C7,
/
C1,
/
/
/C7,
/
/
/
/
/
/
/
/
/
/
/
/
/
˚
/
/
PdÃ
/
C7, 95.4(2) A; C1Ã
/
PdÃ
PdÃ
PdÃ
/
C13,
C13,
C19,
/
/
/
˚
˚
/
PdÃ
/
C19, 178.8(2) A; C7Ã
C19, 85.5(2) A; C13Ã
/
/
/
/
˚
˚
178.5(2) A; C7ÃPdÃ
/
/
/
/
˚
˚
94.7(2) A.
/
/
Pd1Ã
Pd2ÃC4, 90.5(1) A; C5Ã
Pd2ÃC7, 169.5(1) A; C5Ã
/
C2, 89.7(1) A; C1Ã
/
Pd1Ã
Pd2ÃC6,
Pd2ÃC8,
/
˚
˚
/
/
/
/
Each Pd center is surrounded by four s-bounded
phenyl groups in a square-planar geometry. Further-
more, two Li ions are bound on opposite sides of the
˚
˚
88.7(1) A; C5Ã
/
/
/
/
˚
89.6(1) A.
According to these results, the solid-state structure of
3 is very similar to those of the corresponding Cr(II),
Mo(II) and Ni(II) compounds. The only remarkable
difference to the Cr(II) complex is the very large PdÁ Á ÁPd
separation found in 3, in contrast to the very short
PdC4 square, each forming two LiÃ
the ipso-carbons of the phenyl groups. Additionally,
each Li coordinates two THF molecules in a distorted
/
CÃ
/
Pd bridges with
tetrahedral geometry. The CÃ
coordinated side (average 958) are slightly larger than
the CÃPdÃC angles where no Li ion is placed (average
858). The LiÃC distances are in the range of typical
covalent bondings and the PdÃC distances (average
/
PdÃ
/
C angles at the Li-
˚
CrÁ Á ÁCr distance (1.968(2) A) in the corresponding Cr
/
/
complex [1]. It is, however, in agreement with the large
MÁ Á ÁM separations in the corresponding Ni and Pt
complexes [7,8]. In other words, a short MÁ Á ÁM contact
is no prerequisite for the stabilization of cluster com-
/
/
˚
2.095 A) fall also in the typical range. The phenyl groups
are distorted out of the plane of the ipso-carbon atoms
and are oriented towards the respective Li atom.
plexes of the type [M2(CH3)8]nꢃ
.

K. Lamm et al. / Journal of Organometallic Chemistry 681 (2003) 24ꢁ
/
36
29
Scheme 3. Formation reaction of the Pd complex 4.
overlapped by the signal for the solvent C6D6. This does
not allow an exact integration for determining the ratio
of bound phenyl groups to coordinated THF molecules.
However, Ni and Li analyses using ICP-MS analysis
suggested the composition to be (THF)4Li2NiPh4.
7
The Li-NMR spectrum displays only one signal for
the two Li atoms at 6.5 ppm which is in agreement with
a symmetrical structure in solution. The X-ray diffrac-
tion analysis of single crystals confirmed this structure in
the solid state. The molecular structure of the Ni
complex 5 (not depicted) is very similar to that of the
corresponding Pd complex 4 (Fig. 4) and need therefore
no further discussion.
2.3. Catalytic Heck reaction with 1ꢁ4
/
Fig. 4. Molecular structure of complex 4.
The Heck coupling is known to be a very useful
catalytic CÃC linking reaction for the formation of
substituted arylated olefins starting from ArÃX and
substituted olefins [15ꢁ18]. This reaction is catalyzed by
a variety of palladium complexes with different control-
ling ligands. Palladacycles with C, P coordination [19ꢁ
21] and carbene palladium complexes [22ꢁ25] belong to
the most active catalysts. Furthermore, various phos-
phines and phosphites are powerful ligands for the
activation of aryl chlorides [26,27].
Our synthetic route to obtain the corresponding Ni
complex 5, first prepared by Taube and Honymus [10],
was similar to that of the preparation of the methyl
complex (THF)4Li4Ni2Me8. Starting with the complex
[(acac)Ni(oxam)Ni(acac)] [14], the addition of eight
/
/
/
/
equivalents of Li(C6H5) at ꢃ78 8C in a THF solution
/
/
results in a dark brown solution by warming slowly to
room temperature. Complex (THF)4Li2NiPh4 (5) can
then be isolated by evaporating most of the solvent and
cooling the THF residue to ꢃ25 8C for 3 days. Yellow
/
To test the ability of 1, 2, 3 and 4 in catalyzing the
Heck reaction and to compare their catalytic activities,
we used in initial catalytic experiments the substrates 4-
bromoacetophenone and n-butyl acrylate which were
reacted in dimethylacetamide as solvent to give (E)-4-
acetylcinnamate as cross-coupling product (Eq. (1)):
crystals form, which are sensitive towards air and
moisture. The complex is soluble in THF, toluene and
benzene.
Its 1H-NMR spectrum (in C6D6 at room temperature)
shows two singlets for the CH2 groups of the coordi-
(1)
nated THF molecules at 1.36 and 3.41 ppm. For the
phenyl groups, various multiplets between 6.84 and 7.18,
7.46 and 7.50, and 8.28 and 8.31 ppm show, which are
Table 1 contains selected results which show that all
four complexes are highly active catalysts when the
catalyses were carried out in the presence of sodium

30
K. Lamm et al. / Journal of Organometallic Chemistry 681 (2003) 24ꢁ36
/
Table 1
Heck reaction catalyzed by the Pd complexes 1ꢁ4
/
Entry
Catalyst
Temperature (8C)
Complex (mol%)
Time (h)
Conversion (%)
Selectivity (%)
TON a
TOF b
1
2
3
4
5
6
1
2
3
3
3
4
120
120
120
100
120
120
0.02
0.02
0.02
0.02
0.0002
0.04
10
10
1
98
98
83
81
4900
4900
490
490
ꢀ/
99
90
87
98
94
98
5000
4500
5000
2900
29000
2450
1.5
15
1
100
91
435000
2450
Conditions: 6.25 mmolꢀone equivalent of 4-bromoacetophenone, 1.08 equivalents of n-butyl acrylate, 1.12 equivalents of Na-acetate as base,
/
10 ml DMA, yield: determination by GC analysis with diethyleneglycol-dibutylether as internal standard.
a
TON in units of mol converted substrate per mol catalyst.
TOFꢀ .
TON hꢃ1
b
/
acetate as base. No additives were required for a fast
and selective reaction to give the coupling product (E)-
4-acetylcinnamate. It is interesting to note that there is
no induction period in this catalytic reaction.
stabilizing ligands are involved in the catalytic cycle of
the homoleptic, s-organometallic Pd(II) compounds 3
and 4.
It is known that Pd(OAc)2 also shows high TON
(560 000 mol product per mol Pd) when used as
precatalyst in the Heck coupling between styrene and
4-bromoacetophenone [19b]. It could be possible that
the catalytically active species formed from Pd(OAc)2
has a structure similar to the active species generated by
our homoleptic Pd(II) compounds 3 and 4.
It is noteworthy that aryl chlorides were not activated
with these catalysts.
With complex 3, a turnover frequency (TOF) of
29 000 mol product per mol catalyst per hour and
turnover numbers of more than 400 000 mol product
per mol catalyst could be achieved in reactions which
were not optimized (Table 1, entry 5). Decreasing the
reaction temperature from 120 to 100 8C (Table 1, entry
3) does not lower the turnover number significantly.
However, at room temperature the complexes are
catalytically inactive. Furthermore, the formation of
catalytically inactive palladium black was not observed
when the catalysis was carried out between 100 and
120 8C even at long reaction times. Experiments with the
precatalysts 3 and 4 (entries 3 and 6, Table 1) show that
after all the substrates are consumed, more coupling can
be observed when adding additional 3.5 mmol substrates
to the reaction mixture. This increases the TON given in
Table 1 (entry 3: 7800 mol product per mol catalyst;
entry 6: 3900 mol product per mol catalyst) and leads to
2.4. Catalytic Kumada cross-coupling
The Ni complexes 5 and [(THF)4Li4(Me8)Ni2] (6)
were surprisingly active in the catalytic Kumada cross-
coupling [28ꢁ
/
33]. In contrast, the palladium complexes
1ꢁ4 were catalytically inactive in this reaction. Table 2
/
lists some selected results of the reaction between
MesitylMgBr and 4-methyl-aryl halides to form the
mixed substituted biaryl (Eq. (2)):
(2)
the conclusion that no decomposition of the active
catalyst takes place.
In comparison with 1 and 2, the catalysts 3 and 4 are
much more active. When using either complex 3 or 4 as
precatalyst in the Heck reaction, the aryl bromide is
coupled quantitatively in 1 h, whereas 1 and 2 require 10
It is noteworthy that not only the organic bromide
5) can be used in this reaction, but
10). In
(Table 2, entries 1ꢁ
also the chloride is active (Table 2, entries 6ꢁ
/
/
both cases, an induction period was not observed;
however, longer reaction times are required in the
reaction with the chloride, resulting in a maximum
TON of 120 upon 1 h (Table 2, entry 7), whereas the
h for the total conversion (Table 1, entries 1ꢁ
/3 and 6).
This is somewhat surprising, since no activating or
organic bromide reacted three times faster (TONꢀ360,
/

K. Lamm et al. / Journal of Organometallic Chemistry 681 (2003) 24ꢁ
/
36
31
Table 2, entry 1) in a much more selective reaction.
Furthermore, it is noteworthy that even the stable CÃ
bond of organic fluorides could be activated by using 6
as catalyst (Table 2, entries 11ꢁ13); however, the
/F
/
selectivity and the rate of this catalytic reaction were
found to be relatively low.
Compared with a new (carbene)Ni catalyst, recently
described by Herrmann et al. [34] to be active in the
cross-coupling of organic fluorides, compound 6 reacted
with a similar activity; however, the selectivity was
lower. In this case, the most selective reaction was
found at 0 8C (Table 2, entry 12). In a side reaction, the
product of the homocoupling 4,4?-dimethyl-diphenyl
(tolꢁtol) was observed. At 20 8C also the terphenylene
/
derivative was formed, indicating an additional radical
process at this temperature [35].
Table 2 does not represent the maximum TON for
optimized catalytic reactions. Adding more of the
substrates to the reaction mixture leads to more
coupling product after the original amount of substrates
is entirely converted by the active catalyst (Table 2).
This means that the catalyst is still active. For example,
the given TON for compound 6 can be increased to 690
mol converted substrate per mol catalyst by adding
more 4-bromotoluene and MesitylMgBr to the reaction
mixture (entry 3, Table 2).
5 is generally less active than 6, but reaches higher
selectivities (Table 2, entries 4, 5 and 10). Catalysts 5 and
6 are of interest for several reasons. According to the
generally accepted mechanism of this catalytic reaction
[28ꢁ33], the reductive elimination of the mixed biaryl is
/
an essential step closing the catalytic cycle and resulting
in the formation of low-valent nickel. Therefore, for
stabilizing the Ni(0) the addition of neutral ligands such
as phosphines or carbene-type ligands are required. In
case of the complexes 5 and 6, the presence of such a
ligand is no prerequisite for the long-living catalysts.
In order to get a deeper insight into the starting steps
of the catalytic cycle, the relatively slow reaction
between MesitylMgBr and 4-methyl-phenyl chloride,
using 1.5 mol% of complex 6 as precatalyst, was
monitored by GC (Table 3).
In the first period (Table 3, entries 1ꢁ3), three
/
reactions could be observed: the methyl transfer reaction
from compound 6 to the mesityl group of MesMgBr to
form 1,2,3,5-tetramethylbenzene, the cross-coupling re-
action, and the formation of products of the homocou-
pling (4,4?-dimethyl-diphenyl (tolꢁtol)). Furthermore,
/
small amounts of terphenylenes were yielded. After
about three of the four methyl groups at each Ni(II)
center were transferred to mesityl groups, this methyl
transfer stopped, whereas the catalyst was still active in
both the cross-coupling reaction and in the homocou-
pling reaction (Table 3, entries 4ꢁ6).
/
Additional stoichiometric experiments show that the
coupling between the methyl groups of complex 6 and 4-

32
K. Lamm et al. / Journal of Organometallic Chemistry 681 (2003) 24ꢁ36
/
Table 3
Product distribution of the reaction between 4-chlorotoluene and MesitylMgBr in the presence of 6 as catalyst
Entry Time (min) Conversion (%) a TON b mesꢁtol c TON b tolꢁtol c TON b terphenylene TON d tetramethylbenzene Methyl groups (%) e
/
/
1
2
3
4
5
6
10
30
32
45
56
69
81
96
13
17
20
24
28
31
6
9
2
4
5
6
7
9
4.3
4.9
5.6
5.7
5.7
5.7
60
68
78
80
80
80
90
12
15
19
24
210
390
1440
Conditions: 0.17 mmol 6, 11.3 mmolꢀ
/
one equivalent of 4-tolyl chloride, one equivalent of MesitylMgBr, 29 ml THF.
Amount of converted substrate 4-tolyl chloride.
In units of mol converted 4-tolyl chloride per mol catalyst.
mesꢁtolꢀmesityl-4-tolyl; tolꢁtolꢀ4,4?-dimethylphenyl.
In units of mol converted MesitylMgBr per mol catalyst.
Mol transferred methyl groups (tetramethylbenzene and p-xylene) per mol 6; the yield was determined by GC analysis with n-decane as internal
a
b
c
/
/
/
/
d
e
standard.
chlorotoluene in the absence of MesitylMgBr is a very
slow and subordinate reaction, yielding no coupling
products after 2 h. This corresponds with the above-
mentioned results of the catalysis (Table 3, entry 6),
where almost no p-xylene is formed (0.5%; 4% of the
transferred methyl groups).
When using the phenyl complex 5 as catalyst in the
cross-coupling reaction of 4-chlorotoluene and Mesi-
tylMgBr (Table 2, entry 10), also three of the four
organyl groups (76%) were removed from the Ni(II)
center during the catalytic cycle, analogous to complex
6. However, the pathway was found to be very different
from the above-mentioned reaction with 6. 43% of the
phenyl groups in 5 formed biphenyl (possibly formed by
reductive elimination of two phenyl groups from the
NiPh4 fragment) and 33% of the phenyl groups in 5
yielded 4-methyl-biphenyl as a result of the coupling
moacetophenone (Aldrich) were used as received; 4-
chlorotoluene, 4-fluorotoluene, n-decane and diethyle-
neglycol-dibutylether (Aldrich) were distilled and dried
over molecular sieve, and n-butyl acrylate (Aldrich) was
1
dried over molecular sieve. H- and 13C-NMR spectra
were recorded on a Bruker Avance 200 and on a Bruker
Avance 400 spectrometer. Mass spectra were recorded
on a Finnigan MAT SSQ 710. Values for m/z are for the
most intense peak of isotope envelope. The measured
isotopic patterns for the palladium-containing species
are in good agreement with the calculated isotopic
patterns using the program ICIS (version 8.2.1, Finni-
gan). Elemental analyses were performed with a Leco
CHNS-932 and an Elementar Vario EL III. Ni analyses
were obtained by titration of a solution in dilute
hydrochloric acid with 0.01 M EDTA using murexid
as indicator. Li and Pd analyses were performed by
between NiÃ
/
Ph groups and 4-chlorotoluene.
ETV-ICP-MS (Perkinꢁ
HGA 500).
/
Elmer Elan 6000, PerkinꢁElmer
/
In conclusion, both precatalysts 5 and 6 reacted in the
catalytic cycle under elimination of three organyl groups
from the metal. Therefore, we assume that in both cases
The ligands N,N?-bis(2-pyridylethyl)-1,2-bis-(2,4,6-
trimethylphenyl-imino)-ethane-1,2-diamine (H2Y) and
N,N?-bis(diphenylphosphino-3-propyl)-1,2-bis-(2,4,6-
trimethylphenyl-imino)-ethane-1,2-diamine (H2Z) were
prepared according to the described methods [12,13];
[(THF)4Li4(Me8)Ni2] (6) was prepared as described
recently [8]; (COD)Pd(CH3)Cl was obtained following
the procedure described in [36].
the species [NiÃ
in the catalytic cycle.
/
R] (RꢀCH3, Ph) play an essential role
/
3. Experimental
3.1. General procedures
3.2. Crystal structure determination
All manipulations were carried out by using modified
Schlenk techniques under an atmosphere of argon. Prior
to use, THF, diethyl ether, pentane and toluene were
dried over potassium hydroxide and distilled over
sodium/benzophenone. Methyllithium (1.6 M solution
in diethyl ether, Fluka), phenyllithium (1.8 M solution
in cyclohexane/diethyl ether, 70:30, Fluka), n-butyl-
lithium (1.6 M solution in hexane, Aldrich), Mesi-
tylMgBr (1.0 M solution in THF, Aldrich), 2-(2-
aminoethyl)-pyridine (Fluka), 4-bromotoluene, 4-bro-
The intensity data for the compounds were collected
on a Nonius KappaCCD diffractometer, using graphite-
monochromated MoꢁKa radiation. Data were corrected
/
for Lorentz and polarization effects, but not for
absorption effects [37,38].
The structures were solved by direct methods (SHELXS
[39]) and refined by full-matrix least-squares techniques
against Fo2 (SHELXL-97 [40]). All hydrogen atoms were
included at calculated positions with fixed thermal

K. Lamm et al. / Journal of Organometallic Chemistry 681 (2003) 24ꢁ
/
36
33
parameters. All non-hydrogen atoms were refined
anisotropically [40]. XP (SIEMENS Analytical X-ray
Instruments, Inc.) was used for structure representa-
tions.
cmꢃ3, m(Moꢁ
reflections in h (ꢃ
measured in the range 4.1085
Umax 98.4%, 8071 independent reflections, Rint
0.059, 6166 reflections with Foꢀ4s(Fo), 424 para-
meters, restraints, R1 0.065, wR2 0.155,
R1 0.093, wR2
/
Ka)ꢀ
/
5.57 cmꢃ1, F(0 0 0)ꢀ
11/11), k (ꢃ
U 527.458, completeness
/
752, 13 042
/
/
15/15), l (ꢃ19/22),
/
/
/
ꢀ
/
ꢀ
/
/
3.2.1. Crystal data for 1
0
ꢀ
/
ꢀ
/
obs
obs
C36H44N6Pd2×
orless prism, size 0.12ꢄ
space group Pbcn, aꢀ23.7807(9) A, bꢀ
/
1.25C4H8O, Mrꢀ
/
863.70 g molꢃ1, col-
ꢀ
/
ꢀ
/
0.174, GOOFꢀ
/
1.120, largest dif-
all
all
ꢃ3
0.08 mm3, orthorhombic,
ference peak and hole: 1.818/ꢃ
/
.
˚
1.433 e A
/
0.12ꢄ
/
˚
˚
/
/
15.0256(6) A,
90 8C, Zꢀ8,
8.88 cmꢃ1
3552, 17 940 reflections in h (ꢃ30/30), k (ꢃ
19/19), l (ꢃ30/30), measured in the range 1.6085U 5
27.468, completeness Umax 99.2%, 9609 independent
reflections, Rint 0.061, 3854 reflections with Foꢀ
4s(Fo), 451 parameters, five restraints, R1 0.052,
0.162, GOOFꢀ
0.944, largest difference peak and hole: 0.977/ꢃ0.563 e
3
˚
˚
cꢀ
rcalcd
F(0 0 0)ꢀ
/
23.6595(7) A, Vꢀ
/
8454.0(5) A , Tꢀ
/
ꢃ
/
/
3.2.5. Crystal data for 5
C40H52Li2NiO4, Mrꢀ
prism, size 0.20ꢄ0.18ꢄ
0.12 mm3, triclinic, space group
ꢀ
/
1.36
g
cmꢃ3
,
m(MoꢁKa)ꢀ
/
/
,
/
669.40 g , colorless
molꢃ1
/
/
/
/
/
˚
˚
˚
17.2180(8) A,
¯
/
/
/
P1; aꢀ
aꢀ90.648(3)8, bꢀ
1780.73(16) A , Tꢀ
cmꢃ3, m(Moꢁ 5.84 cmꢃ1, F(0 0 0)ꢀ
Ka)ꢀ
reflections in h (ꢃ11/11), k (ꢃ14/15), l (ꢃ
measured in the range 1.1985U 527.488, completeness
Umax 98.8%, 8049 independent reflections, Rint
0.051, 5495 reflections with Foꢀ4s(Fo), 503 para-
meters, restraints, R1 0.088, wR2 0.119,
R1 0.145, wR2
/
9.0874(5) A, bꢀ
95.572(3)8, gꢀ
90 8C, Zꢀ2, rcalcd
716, 12 229
22/22),
/
11.5830(6) A, cꢀ
99.042(3)8, Vꢀ
1.248 g
/
ꢀ
/
/
/
/
/
3
˚
ꢀ
/
/
/
ꢃ
/
/
ꢀ
/
ꢀ
/
/
/
/
obs
wR2
ꢀ/0.145, R1
ꢀ
/
0.134, wR2
all
ꢀ
/
/
/
/
/
obs
all
/
/
/
ꢃ3
˚
A
.
ꢀ
/
ꢀ
/
/
3.2.2. Crystal data for 2
C70H78N4P2Pd2, Mrꢀ
prism, size 0.22ꢄ0.20ꢄ
group C2/c, aꢀ
0
ꢀ
/
ꢀ
/
obs
obs
/
1250.10 g molꢃ1, colorless
0.10 mm3, monoclinic, space
ꢀ
/
ꢀ
/
0.134, GOOFꢀ
/
1.056, largest dif-
all
all
ꢃ3
˚
0.488 e A
/
/
ference peak and hole: 0.434/ꢃ
/
.
˚
˚
3
/
37.920(1) A, bꢀ
13.6274(5) A, bꢀ110.546(2)8, Vꢀ
90 8C, Zꢀ4, rcalcd
6.83 cmꢃ1, F(0 0 0)ꢀ
44/47), k (ꢃ15/16), l (ꢃ
2.3585U 527.478, completeness Umax
independent reflections, Rint 0.032, 4879 reflections
with Foꢀ4s(Fo), 352 parameters, 0 restraints, R1
0.033, wR2
/
12.6793(4) A, cꢀ
/
˚
˚
/
/
6135.3(3) A , Tꢀ
/
3.3. Complex 1
ꢃ
/
/
ꢀ
/
1.353 g cmꢃ3, m(Moꢁ
2592, 11 623 reflections in h (ꢃ
17/17), measured in the range
99.2%, 6961
/
Ka)ꢀ
/
/
/
A solution of H2Y (0.588 g, 1.11 mmol) in THF (40
ml) was stirred at ꢃ78 8C. n-Butyllithium, dissolved in
hexane (1.25 ml, 2.0 mmol), was added dropwise. After
/
/
/
/
/
ꢀ
/
ꢀ
/
stirring the solution at room temperature for 30 min and
of
/
ꢀ
/
cooling
down
to
ꢃ
/
78 8C,
a
solution
obs
ꢀ
/
0.072, R1
ꢀ
/
0.052, wR2
all
ꢀ/0.075,
(COD)Pd(CH3)Cl (0.530 g, 2.00 mmol) in THF (30
ml) was added. The solution was stirred for 18 h and
allowed to warm to room temperature. After removing
the solvents by oil pump vacuum, the obtained solid was
extracted with toluene (60 ml). The extract was filtered
and the residue was washed with toluene (10 ml). The
unified clear solution was concentrated by oil pump
vacuum to dryness and was diluted with diethyl ether
(10 ml). The precipitate was filtered, washed with diethyl
ether (20 ml) and dried by oil pump vacuum (4 h) at
room temperature. Yield: 0.508 g (55%) of the desired
product containing 0.8 equivalents of diethyl ether.
Complex 1 without non-coordinated solvent was ob-
tained by recrystallization from toluene in lower yields.
Single crystals suitable for X-ray determination were
isolated from THF-d8 at room temperature. Anal.
Calcd. for C36H44N6Pd2: C, 55.89; H, 5.73; N, 10.86.
Found: C, 54.23; H, 5.82; N, 10.07%. MS (DEI) m/z:
obs
all
GOOFꢀ
/
0.943, largest difference peak and hole:
ꢃ3
˚
0.592 e A
0.494/ꢃ
/
.
3.2.3. Crystal data for 3
C24H56Li4O4Pd2, Mrꢀ
prism, size 0.10ꢄ0.09ꢄ
group P21/c, aꢀ
/
649.25 g molꢃ1, colorless
0.04 mm3, monoclinic, space
/
/
˚
˚
/
10.5969(2) A, bꢀ
12.1083(3) A, bꢀ
Tꢀ 90 8C, Zꢀ4, rcalcd
Ka)ꢀ
12.14 cmꢃ1, F(0 0 0)ꢀ
in h (ꢃ13/13), k (ꢃ33/27), l (ꢃ
range 1.5685U 527.468, completeness Umax
6863 independent reflections, Rint 0.023, 5426 reflec-
tions with Foꢀ4s(Fo), 307 parameters, 0 restraints,
R1 0.035, wR2 0.089, R1 0.049, wR2
/
26.1649(4) A, cꢀ
/
3
˚
˚
/
115.8340(1)8, Vꢀ
/
3021.71(10) A ,
/
ꢃ
/
/
ꢀ
/
1.427 g cmꢃ3, m(Moꢁ
1344, 12 268 reflections
15/15), measured in the
99.2%,
/
/
/
/
/
/
/
/
ꢀ
/
ꢀ
/
/
ꢀ
/
ꢀ
/
ꢀ
/
ꢀ
/
obs
obs
all
all
0.096, GOOFꢀ
/
1.022, largest difference peak and
ꢃ3
˚
0.613 e A
hole: 0.525/ꢃ
/
.
757 [MÃ
[MÃ2CH3Ã
1H-NMR (200 MHz, THF-d8): d ꢃ
Pd ÃCH3), 2.18 (s, 12H, CH3, mes ortho), 2.29 (s, 6H,
CH3, mes para), 2.26 (m, 4H, CH2), 2.86 (m, 4H, CH2),
6.65 (s, 4H, mes meta), 7.09ꢁ7.18 (m, 4H, 3-, 5-pyridyl),
7.68 (t (3JHH
7.6 Hz), 2H, CH, 4-pyridyl), 8.35 (d
/
CH3]ꢂ (0.6%), 742 [MÃ
Pd]ꢂ (0.2%), 530 [MÃ
2CH3Ã
0.55 (s, 6H, CH3,
/
2CH3]ꢂ (0.2%), 636
3.2.4. Crystal data for 4
C40H52Li2O4Pd, Mrꢀ
prism, size 0.10ꢄ0.09ꢄ
0.05 mm3, triclinic, space group
/
/
/
/
2Pd]ꢂ (1.7%).
/
717.10 g molꢃ1, colorless
/
/
/
/
˚
˚
˚
17.2638(8) A,
¯
P1; aꢀ
aꢀ 92.371(3)8, bꢀ
1791.7(1) A , Tꢀ
/
9.0853(4) A, bꢀ
94.538(3)8, gꢀ
90 8C, Zꢀ2, rcalcd
/
11.5980(5) A, cꢀ
98.325(3)8, Vꢀ
1.329 g
/
/
/
/
/
/
3
˚
/
ꢃ
/
/
ꢀ
/
ꢀ
/

34
K. Lamm et al. / Journal of Organometallic Chemistry 681 (2003) 24ꢁ36
/
(3JHH
ꢀ
/
5.7 Hz), 2H, CH, 6-pyridyl) ppm. 13C-NMR
CH3), 19.4 (CH3,
3.6. Complex 4
(50 MHz, THF-d8): d 4.9 (CH3, Pd Ã
/
mes para), 21.0 (CH3, mes ortho), 43.4 (CH2), 44.6
(CH2), 123.1 (CH, 5-pyridyl), 125.4 (CH, 3-pyridyl),
127.7 (CH, mes meta), 132.1 (C), 138.0 (CH, 4-pyridyl),
146.8 (C), 152.4 (CH, 6-pyridyl), 162.2, 167.3 (C) ppm.
The compound was prepared as a colorless micro-
crystalline solid, using [(acac)Pd(oxam)Pd(acac)] (0.547
g, 0.64 mmol) in THF (80 ml) and eight equivalents of
phenyllithium, dissolved in cyclohexane/diethyl ether
(70:30) (2.9 ml, 5.2 mmol). Yield: 220 mg (24%). Single
crystals of 4 suitable for X-ray determination were
3.4. Complex 2
obtained from THF at ꢃ25 8C. The crystals contain
/
four THF molecules per Pd unit. Anal. Calcd. for
C40H52O4Li2Pd: Li, 1.94; Pd, 14.84. Found: Li, 2.16
The compound was prepared as a light yellow solid,
analogous to 1 using H2Z (0.882 g, 1.14 mmol). Yield:
0.400 g (33%) of 2 containing one equivalent of non-
coordinated THF. Single crystals of 2 which contain
three molecules of non-coordinated benzene-d6 per
dimeric unit suitable for an X-ray analysis were grown
from benzene-d6 at room temperature. Anal. Calcd. for
1
(ETV-ICP-MS), Pd, 14.55% (ETV-ICP-MS). H-NMR
(400 MHz, benzene-d6): d 1.38 (m, 16H, CH2), 3.51 (m,
16H, CH2), 6.95ꢁ
CH), 7.44ꢁ7.47 (m, 4H, CH), 8.16 (d, 2H, CH) ppm.
13C-NMR (100 MHz, benzene-d6): d 25.9 (s, CH2), 68.0
(s, CH2), 122.2 (s, CH), 126.7ꢁ129.2 (m, C, CH), 141.2
/
6.99 (m, 1H, CH), 7.11ꢁ
/
7.22 (m, 13H,
/
/
7
C52H60N4P2Pd2×
Found: C, 60.71; H, 6.29; N, 4.90%. MS (DEI): m/z: 999
[MÃ 2CH3ÃPdÃ
CH3]ꢂ (3%), 693 [MÃ PPh2]ꢂ (0.5%).
1H-NMR (400 MHz, THF-d8): d ꢃ0.85 (d (3JHP
3.2
Hz), 6H, CH3, Pd ÃCH3), 1.44ꢁ1.51 (m, 4H, CH2),
1.84ꢁ1.90 (m, 4H, CH2), 2.15 (s, 6H, CH3, mes para),
2.31 (s, 12H, CH3, mes ortho), 2.59ꢁ2.61 (m, 4H, CH2),
6.67 (s, 4H, CH, mes meta), 7.37ꢁ7.38 (m, 12H, CH,
Ph), 7.65ꢁ
7.69 (m, 8H, CH, Ph) ppm. 13C-NMR (100
MHz, THF-d8): d 2.3 (d (2JCP
13 Hz), CH3, Pd Ã
CH3), 19.8 (CH3, mes ortho), 20.9 (CH3, mes para),
27.3 (d (1JCP 27 Hz, CH2)), 28.3 (d (2JCP
8 Hz,
CH2)), 51.9 (CH2), 127.8 (CH, mes meta), 128.8ꢁ128.9,
134.3 (CH),
/C4H8O: C, 61.82; H, 6,30; N, 5.15.
(s, CH) ppm. Li-NMR (156 MHz, benzene-d6): d 7.1
ppm.
/
/
/
/
/
ꢀ
/
3.7. Complex 5
/
/
/
The compound was prepared as a light yellow
/
microcrystalline solid, analogous to
4
using
/
[(acac)Ni(oxam)Ni(acac)] (0.758 g, 0.86 mmol) in THF
(80 ml) and eight equivalents of phenyllithium, dissolved
in cyclohexane/diethyl ether (70:30) (3.8 ml, 6.88 mmol).
Yield: 250 mg (22%). Single crystals of 5 suitable for X-
/
ꢀ
/
/
ꢀ
/
ꢀ
/
ray determination were obtained from THF at ꢃ18 8C.
/
/
The crystals contain four THF molecules per Ni unit.
Anal. Calcd. for C40H52O4Li2Ni: Li, 2.07; Ni, 8.77.
Found: Li, 2.17 (ETV-ICP-MS); Ni, 8.75% (ETV-ICP-
130.6ꢁ
/
130.7 (CH), 131.2, 133.1 (C), 134.1ꢁ
/
134.5, 134.9, 146.3, 169.7 (C) ppm. 31P-NMR (162
1
MHz, THF-d8): d 36.7 ppm.
MS), 9.08% (titration). H-NMR (200 MHz, benzene-
d6): d 1.36 (m, 16H, CH2), 3.41 (m, 16H, CH2), 6.84ꢁ
7.18 (m, 14H, CH), 7.46ꢁ7.50 (m, 2H, CH), 8.28ꢁ8.31
(m, 4H, CH) ppm. 13C-NMR (50 MHz, benzene-d6): d
25.7 (s, CH2), 67.8 (s, CH2), 127.5ꢁ129.0 (m, C, CH)
/
/
/
3.5. Complex 3
/
7
A solution of 1 (0.155 g, 0.20 mmol) in THF (40 ml)
ppm. Li-NMR (156 MHz, benzene-d6): d 6.5 ppm.
was stirred at ꢃ78 8C. Methyllithium, dissolved in
/
diethyl ether (0.9 ml, 1.44 mmol), was added dropwise.
The solution was stirred for 18 h and allowed to warm
to room temperature. The reaction mixture was filtered
and the clear solution was concentrated in oil pump
3.8. Heck reaction
0.050 mmol of the catalyst were dissolved in 20 ml dry
THF containing 0.1 ml of a 1.6-M solution of methyl-
lithium. In a typical experiment, 6.25 mmol (1.244 g) 4-
bromoacetophenone and 7 mmol (0.547 g) anhydrous
sodium acetate as base were placed in a 25-ml two-
necked flask equipped with stirring bar, reflux conden-
ser and septum. The flask was degassed under vacuum
and purged with argon to ensure an inert reaction
atmosphere. Through the septum were added 10 ml of
N,N-dimethylacetamide as solvent, 0.5 g of diethylene-
glycol-dibutylether as GC standard and 6.75 mmol n-
butyl acrylate. The reaction mixture was thoroughly
stirred and heated to the appropriate reaction tempera-
ture at which it was held for 5 min. Either 0.5 ml of the
vacuum to 5 ml. Colorless crystals were formed at ꢃ
/
25 8C after 48 h. The solvent was removed and the solid
was washed with toluene (10 ml) and pentane (10 ml). It
was dried by overflowing argon for 5 min. A pyrophoric
colorless powder was obtained. Yield: ca. 20%. Single
crystals of 3 suitable for X-ray determination were
grown from THF at
C24H56O4Li4Pd2: Li, 4.28. Found: Li, 4.63% (ETV-
ꢃ18 8C. Anal. Calcd. for
/
1
ICP-MS); H-NMR (400 MHz, benzene-d6): d ꢃ
(s, 24H, CH3), 1.30 (m, 16H, CH2), 3.72 (m, 16H, CH2)
ppm. 13C-NMR (100 MHz, benzene-d6): d ꢃ
7.6 (s,
/
0.11
/
7
CH3), 25.5 (s, CH2), 68.7 (s, CH2) ppm. Li-NMR (156
MHz, benzene-d6): d 9.3 ppm.
catalyst solution for complexes 1ꢁ3 (1.25 mmol) or 1 ml
/

K. Lamm et al. / Journal of Organometallic Chemistry 681 (2003) 24ꢁ
/
36
35
(2.5 mmol) of the catalyst solution for complex 4 was
added. Samples of 0.5 ml were taken after the appro-
priate time intervals, hydrolyzed with 2 ml distilled
water and extracted with 2 ml CH2Cl2. The organic
Acknowledgements
Financial support for this work from the Deutsche
Forschungsgemeinschaft, the VW-Stiftung and the
Fonds der Chemischen Industrie is gratefully acknowl-
edged.
phase was dried over K2CO3 and stored at ꢃ25 8C until
/
GC analysis for the determination of yield and turnover
number could be performed.
References
3.9. Kumada cross-coupling reaction
[1] E. Kurras, J. Otto, J. Organomet. Chem. 4 (1965) 114.
[2] J. Krause, G. Marx, G. Schodl, J. Organomet. Chem. 21 (1970)
¨
159.
[3] S. Hao, S. Gambarotta, C. Bensimon, J. Am. Chem. Soc. 114
(1992) 3556.
For each catalytic reaction, a defined amount of
either complex 5 or 6 was weighed into a small glass tube
under an argon atmosphere and sealed by fusing the
open end, because of the extreme sensitivity of com-
plexes 5 and 6 towards air and moisture no standard
catalyst solution was prepared. Together with one
equivalent of the 4-methyl-benzyl halide, the sealed
catalyst was placed into a Schlenk tube and purged
with argon. One equivalent of a 1.0-M solution of
MesitylMgBr in THF, THF as solvent and 0.8 g n-
decane as internal GC standard were added to the
reaction mixture through a septum. The same concen-
tration of substrates was ensured for every amount of
[4] S. Hao, J.-I. Song, P. Berno, S. Gambarotta, Organometallics 13
(1994) 1326.
[5] F.A. Cotton, J.M. Troup, D.H. Webb, G. Williamson, J.
Wilkinson, J. Am. Chem. Soc. 96 (1974) 3824.
[6] F.A. Cotton, L.D. Gage, L.W. Mertis, G. Shive, J. Wilkinson, J.
Am. Chem. Soc. 98 (1976) 6922.
[7] R. Wyrwa, H. Gorls, Z. Anorg. Allg. Chem. 625 (1999) 1904.
¨
[8] D. Walther, M. Stollenz, H. Gorls, Organometallics 20 (2001)
¨
4221.
[9] E. Ihara, T. Fujimura, H. Yasuda, T. Maruo, N. Kanehisa, Y.
Kai, J. Polym. Sci. A38 (2000) 4764.
[10] R. Taube, G. Honymus, Angew. Chem. 87 (1975) 291.
[11] J.J.H. Edema, S. Gambarotta, F. van Bolhuis, W.J.J. Smeets,
A.L. Spekk, M.Y. Chiang, J. Organomet. Chem. 389 (1990) 47.
weighed in catalyst (Table 2: entries 1ꢁ
mmol 6, 3.9 mmol substrates, 10 ml THF; entries 4ꢁ
/
3 and 7ꢁ
/
9: 7.8
5:
[12] P. Langer, M. Doring, J. Wuckelt, H. Gorls, Eur. J. Inorg. Chem.
¨ ¨
(2001) 805.
[13] D. Walther, M. Stollenz, L. Bottcher, H. Gorls, Z. Anorg. Allg.
/
10.9 mmol 5, 5.5 mmol substrates, 14 ml THF; entry 6:
0.17 mmol 6, 11.3 mmol substrates, 29 ml THF; entry
10: 0.06 mmol 5, 3.0 mmol substrates, 7.7 ml THF; entry
11: 0.08 mmol 6, 3.4 mmol substrates, 8.7 ml THF;
¨
¨
Chem. 627 (2001) 1560.
[14] N. Theyssen, D. Walther, T. Dohler, H. Gorls, Eur. J. Inorg.
Chem. (2001) 2049.
¨
¨
[15] For a recent review see: (a) A.F. Littke, G.C. Fu, Angew. Chem.
114 (2002) 4351;
entries 12ꢁ13: 0.06 mmol 6, 2.3 mmol substrates, 6.0 ml
/
(b) A.F. Littke, G.C. Fu, Angew. Chem Int. Ed. 41 (2002) 4176
(and references therein).
THF). If necessary, the mixture was cooled to the
appropriate temperature; otherwise, it was held at
room temperature. The reaction started by breaking
the glass tube and dissolving the catalyst. Samples of 0.5
ml were taken after certain time intervals, hydrolyzed
with half concentrated hydrochloric acid (1.0 ml) and
extracted with toluene (1.0 ml). The organic phase was
dried over K2CO3 and transferred into vials. The yield
determination was done by gas chromatography.
[16] (a) A. de Meijere, F. Meyer, Angew. Chem. 106 (1994) 2473;
(b) A. de Meijere, F. Meyer, Angew. Chem Int. Ed. 33 (1994)
2379.
[17] V.V. Grushin, H. Alper, Chem. Rev. 106 (1994) 2473.
[18] W. Cabri, I. Caudiani, Acc. Chem. Res. 28 (1995) 2.
¨
[19] (a) W.A. Herrmann, C. Broßmer, K. .Ofele, C.-P. Reisinger, T.
Riermeier, M. Beller, H. Fischer, Angew. Chem. 107 (1995) 1989;
¨
(b) W.A. Herrmann, C. Broßmer, K. .Ofele, C.-P. Reisinger, T.
Riermeier, M. Beller, H. Fischer, Angew. Chem. Int. Ed. 28
(1995) 1844;
(c) W.A. Herrmann, C. Broßmer, C.-P. Reisinger, T. Riermeier,
¨
K. .Ofele, M. Beller, Chem. Eur. J. 3 (1997) 1357.
[20] W.A. Herrmann, V. Bohm, J. Organomet. Chem. 572 (1999) 141.
[21] W.A. Herrmann, V. Bohm, C.-P. Reisinger, J. Organomet. Chem.
¨
¨
4. Supplementary material
576 (1999) 23.
[22] (a) W.A. Herrmann, M. Elison, J. Fischer, C. Kocher, G.R.J.
¨
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Artus, Angew. Chem. 107 (1995) 2602;
(b) W.A. Herrmann, M. Elison, J. Fischer, C. Kocher, G.R.J.
¨
Artus, Angew. Chem. Int. Ed. 34 (1995) 2371;
(c) W.A. Herrmann, C.-P. Reisinger, M.J. Spiegler, J. Organomet.
Chem. 557 (1998) 93.
Data Centre, CCDC Nos. 202218ꢁ
pounds 1ꢁ5. Copies of this information may be
obtained free of charge from The Director, CCDC, 12
Union Road, Cambridge, CB2 1EZ, UK (Fax: ꢂ44-
/202222 for com-
/
[23] W.A. Herrmann, Th. Weskamp, V.P.W. Bohm, J. Organomet.
¨
Chem. 585 (1999) 348.
/
[24] W.A. Herrmann, V. Bohm, Chem. Eur. J. 6 (2000) 1017.
¨
[25] D.S. McGuiness, K.J. Cavell, Organometallics 19 (2000) 741.
1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
[26] M. Beller, A. Zapf, Synlett (1998) 792.

36
K. Lamm et al. / Journal of Organometallic Chemistry 681 (2003) 24ꢁ36
/
[27] A. Zapf, M. Beller, Chem. Eur. J. 7 (2001) 2908.
[28] E. Negishi, F. Liu, in: F. Diederich, P.J. Stang (Eds.), Metal-
catalyzed Cross-coupling Reactions, Wiley-VCH, New York,
1998, p. 34 (and references therein).
[34] W.A. Herrmann, V.P.W. Bohm, C.W.K. Gstottmayr, T. Wes-
¨ ¨
kamp, Angew. Chem. 18 (2001) 3500.
[35] G. Smith, J.K. Kochi, J. Organomet. Chem. 198 (1980) 199.
[36] R.E. Rulke, J.M. Ernsting, A.L. Spek, C.J. Elsevier, P.W.N.M.
¨
[29] (a) D.J. Ca´rdenas, Angew. Chem. 111 (1999) 3201;
(b) D.J. Ca´rdenas, Angew. Chem. Int. Ed. Engl. 38 (1999) 3018.
[30] E. Negishi, T. Takahashi, S. Baba, D.E. van Horn, N. Okukado,
J. Am. Chem. Soc. 109 (1987) 2393.
van Leeuwen, K. Vrieze, Inorg. Chem. 32 (1993) 5769.
[37] COLLECT, Data Collection Software, Nonius B.V., Netherlands,
1998.
[38] Z. Otwinowski, W. Minor, Processing of X-ray diffraction data
collected in oscillation mode, in: C.W. Carter, R.M. Sweet (Eds.),
Methods in Enzymology, Vol. 276, Macromolecular Crystal-
[31] E. Negishi, E.T. Takahashi, K. Akiyoshi, J. Organomet. Chem.
334 (1987) 181.
[32] C. Amatore, M. Azzabi, A. Jutand, J. Am. Chem. Soc. 113 (1991)
8375.
lography, Part A, Academic Press, New York, 1997, pp. 307ꢁ
[39] G.M. Sheldrick, Acta Crystallogr. Sect. A 46 (1990) 467.
[40] G.M. Sheldrick, SHELXL-97 (Release 97-2), University of Gottin-
/
326.
[33] J.F. Hartwig, F. Paul, J. Am. Chem. Soc. 117 (1995)
5373.
¨
gen, Gottingen, Germany, 1997.
¨