Stepwise deprotonation of a thiol-functionalized bis(1,2,4-triazolium) salt as a selective route to heterometallic NHC complexes

Article abstract of DOI:10.1021/om400143u

Heterometallic NHC complexes have been selectively prepared at room temperature directly from an azolium salt in a two-step procedure. In the unsymmetrically substituted bis(1,2,4-triazolium) ligand precursor, one of the m-xylylene-bridged triazolium units features an unprotected o-thiophenol substituent. This renders possible a selective deprotonation and in situ monopalladation at the NHC-thiolato unit. The obtained palladium(II) complex possesses two pendant triazolium units as vacant binding sites. After a second deprotonation/metalation step, a heterodinuclear palladium(II) gold(I) complex and a heterotrinuclear palladium(II) dicopper(I) complex were obtained. In the latter, two metal centers are connected via a thiolato bridge.

Full text of DOI:10.1021/om400143u

Article
pubs.acs.org/Organometallics
Stepwise Deprotonation of a Thiol-Functionalized Bis(1,2,4-
triazolium) Salt as a Selective Route to Heterometallic NHC
Complexes
Stefanie C. Seitz, Frank Rominger, and Bernd F. Straub*
Organisch-Chemisches Institut, Ruprecht-Karls-Universitat Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
̈
S
* Supporting Information
ABSTRACT: Heterometallic NHC complexes have been selectively prepared at room temperature directly from an azolium salt
in a two-step procedure. In the unsymmetrically substituted bis(1,2,4-triazolium) ligand precursor, one of the m-xylylene-bridged
triazolium units features an unprotected o-thiophenol substituent. This renders possible a selective deprotonation and in situ
monopalladation at the NHC−thiolato unit. The obtained palladium(II) complex possesses two pendant triazolium units as
vacant binding sites. After a second deprotonation/metalation step, a heterodinuclear palladium(II) gold(I) complex and a
heterotrinuclear palladium(II) dicopper(I) complex were obtained. In the latter, two metal centers are connected via a thiolato
bridge.
iridium to one binding site of the ligand and then rhodium,
palladium, or platinum to the other site of the triazolediylidene
(Figure 1, left). These mixed-metal complexes were successfully
employed in tandem reactions in which each metal carries out
one catalytic transformation in a one-pot procedure.
INTRODUCTION
■
Since the discovery of transition-metal complexes with N-
heterocyclic carbenes (NHCs) by Wanzlick1 and Ofele in
2
̈
1968, they became established ligands in organometallic
chemistry and homogeneous catalysis.3 NHCs can be easily
modified by attaching functional groups at their nitrogen atoms
which can act as additional donor ligands. While NHC ligands
with nitrogen, oxygen, or phosphorus as donor atoms are
commonly used,4 those with sulfur donors remain compara-
tively unexplored. Sulfur can occur in oxidation states from −II
to +VI, and so NHC ligands with different sulfur functionalities
such as thioether, thiolate, sulfoxide, sulfonate, and thiophene
exist.5 In this area thioether-functionalized NHCs are most
commonly used,6 whereas just a few NHC−thiolato ligands are
known so far.7 Herein, we present a thiol-functionalized
bis(1,2,4-triazolium) salt as an NHC ligand precursor for
heteronuclear complexes.
The use of a bis-NHC as ligand, in which two NHC groups
are linked by a variable spacer, is rare, due to the difficulty in
prohibiting a chelating instead of the desired bridging
coordination mode and in deprotonating the usually equal
carbene precursors selectively to introduce stepwise the desired
metals. Braunstein et al. prepared a stable free dicarbene by
deprotonation of the bis(imidazolium) precursor salt, which
was reacted with [IrCl(cod)]2 in ethanol to obtain a mixture of
the dinuclear Ir(I) complex and the mononuclear Ir(I) complex
with its second NHC unit reprotonated.13 After isolation of the
monometalated species, it was reacted with [RhCl(cod)]2 and
Cs2CO3 to generate a heterodinuclear Ir(I)−Rh(I) complex
(Figure 1, middle). Cowie et al. also used mono-NHC metal
complexes with a pendant imidazolium unit as precursors for
bis-NHC bridged mixed-metal complexes of Ir(I)−Rh(I),
Pd(II)−Ir(I), and Pd(II)−Rh(I) (Figure 1, right).14 Mono-
metallic precursors were obtained in good yields when the
bis(imidazolium) ligand precursor was reacted with (sub)-
In the literature, only a limited number of heterobimetallic
transition-metal complexes with NHC ligands have been
reported. In the majority of the cases, an NHC binding site
is mixed with an ancillary ligand, e.g. a phosphine,8
a
phenanthroline,9 a cyclopentadienyl,10 or a salen-type11 ligand,
to achieve binding of two different metal centers. Peris et al.
used a dicarbene ligand to connect two different metal centers
by stepwise deprotonation of the 1,2,4-trimethyl-1,2,4-triazo-
lium precursor salt.12 In this way, it was possible to bind at first
Received: February 19, 2013
© XXXX American Chemical Society
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Figure 1. Mixed-metal complexes with triazolediylidene or a bis(imidazolylidene) as bridging ligand.
a
Scheme 1. Synthesis of the Thiol-Functionalized Unsymmetrically Substituted Bis(1,2,4-triazolium) Salt 4
a
PMB = p-methoxybenzyl as protecting group.
Scheme 2. Oxidation of Thiophenol 4 in DMSO with Formation of Benzothiazole 5
15
stoichiometric metal acetates, e.g. Pd(OAc)2 and [Rh(cod)-
(OAc)]2,16 without additional base. The steric demand of the
employed tert-butyl substituents of the methylene-linked NHC
units appears to prevent a chelating coordination mode of the
bis-NHC ligand.17
solvents. In the last step, the p-methoxybenzyl protecting group
was removed under strongly acidic conditions (trifluorometha-
nesulfonic acid/trifluoroacetic acid in a molar ratio of 1/10) to
obtain the free thiophenol.20 Thereby the anion was exchanged
to obtain the bis(triazolium) bis(triflate) 4.
Usually thiols are prone to oxidation by changing the
oxidation state of the sulfur atom. For instance, mild oxidizing
agents such as iodine21 and dimethyl sulfoxide22 convert thiols
to disulfides. However, as described before,7g the thiol-
functionalized triazolium salt 4 reacts with DMSO with ring
closure, forming benzothiazole 5 instead of a disulfide (Scheme
2).
In this paper, we describe the selective deprotonation and
metalation of the herein presented bis(1,2,4-triazolium) ligand
precursor at its thiol-substituted triazolium fragment by
reaction with K2CO3 and PdCl2. The vacant triazolium unit
of the obtained palladium(II) complex was coordinated to
gold(I) or copper(I) to give mixed-metal complexes.
Formation of a benzothiazole was proved by slow oxidation
of the precursor salt 4 by air, whereupon crystals suitable for
single-crystal X-ray analysis were obtained (Figure 2). The
three rings of the benzothiazole system are planar, in contrast
to the observed torsion of the triazole and the phenyl ring of
the second triazolium unit caused by the methyl substituents in
ortho positions.
Synthesis of Heterometallic Complexes. The unsym-
metrically substituted bis(triazolium) salt 4 was deprotonated
selectively at the thiol-functionalized triazolium unit and bound
two times to palladium in a neutral square-planar complex. This
was achieved by reaction with palladium(II) chloride and
potassium carbonate as a mild base in pyridine at room
temperature over 3 days (Scheme 3). The second triazolium
fragment of the ligand system was preserved in each case. This
directed deprotonation of one triazolium unit is presumably
RESULTS AND DISCUSSION
■
Synthesis of the Ligand Precursor. The thiol-function-
alized unsymmetrically substituted bis(triazolium) salt 4, which
can act as a carbene ligand precursor, was synthesized in a
straightforward procedure. 4-(2,6-Dimethylphenyl)-1,2,4-4H-
triazole18 was reacted with an excess of α,α′-dichloro-m-xylene
at 120 °C without solvent to give the mono(triazolium) salt 1
(Scheme 1). This compound did not react with 4-[2-(4-
methoxybenzylthio)phenyl]-1,2,4-4H-triazole7g in a second
nucleophilic substitution by melting the two substrates together
accordingly in the first step. Thus, glacial acetic acid was used as
a polar, high-boiling solvent which facilitates as protic media the
disposal of the chloride anion.19 The obtained bis(triazolium)
salt 2 was objected to a counterion metathesis with
hexafluorophosphoric acid to improve its solubility in organic
B
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complex was objected to a salt metathesis with KPF6 to obtain
it as the hexafluorophosphate salt. Due to the small scale of
preparation and the expensive workup procedure the
compound was isolated in only moderate yields of 40%.
Attempts to crystallize complex 7 failed. The purity of the
obtained solid is sufficient, but small quantities of impurities
remained. However, it represents a rare example of a
heterobimetallic complex in which palladium is combined
with a coinage metal.
The ESI mass spectrum contains only one peak, which
corresponds to a monocationic complex containing one
palladium and one gold atom. As indicated in Scheme 3, the
gold(I) ion is presumably coordinated by two NHC ligands.
1
The H NMR spectrum shows again two isomers in a ratio of
2/1 (Figure 3), which could not be separated by column
chromatography or fractionated precipitation. For each isomer
there are two singlets for the remaining protons at the C3
positions of the triazol-5-ylidenes. The nonequivalent protons
of the methylene groups of the m-xylylene linker appear as four
doublets (for each isomer), and the nonequivalent methyl
groups of the dimethylphenyl substituent split into two singlets.
The 13C NMR spectrum depicts four signals of the carbene
carbons: at 172.1* and 176.0 ppm for the two Pd−Ccarbene
groups as well as at 186.4* and 186.9 ppm for the two Au−
Ccarbene groups. As the shifts of the carbon atoms bound to the
palladium center are almost identical with those of the
precursor complex 6, the diastereomeric ratio was apparently
conserved and the trans isomer dominates. Neither in the ESI
mass spectrum nor in the NMR spectra were found any signs
for the formation of a coordination polymer. The m-xylylene
linker is presumably flexible enough to enable the coordination
of a gold atom between the two NHC binding sites, even if
palladium is coordinated in a trans geometry.
Figure 2. Ball-and-stick model of the X-ray structure of benzothiazole
5. The counterions have been omitted for clarity. Both triflate anions
are partially replaced by hexafluorophosphate anions, which originate
from precursor salt 3. The anions have been modeled as a
superposition of both triflates using full local symmetry restraints.
This means that chemically equivalent distances and angles within one
anion as well as among the two independent copies were kept similar
within a standard deviation of 0.02. Selected bond lengths (Å) and
bond angles (deg): N(1)−N(2), 1.382(5); N(2)−C(3), 1.305(6);
C(3)−N(4), 1.361(6); N(4)−C(5), 1.349(5); C(5)−N(1), 1.326(6);
C(5)−S(1), 1.705(4); S(1)−C(12), 1.775(4); N(4)−C(11),
1.412(6); N(1)−N(2)−C(3), 104.7(4); N(2)−C(3)−N(4),
111.1(4); C(3)−N(4)−C(5), 106.9(4); N(4)−C(5)−N(1),
106.8(4); C(5)−N(1)−N(2), 110.5(3); S(1)−C(5)−N(4),
115.0(3); C(5)−N(4)−C(11), 113.6(3); N(4)−C(11)−C(12),
109.9(4); C(11)−C(12)−S(1), 112.9(3); C(12)−S(1)−C(5),
88.5(2); N(1)−C(5)−S(1)−C(12), 179.30; C(5)−N(1)−C(20)−
C(21), 13.73; C(35)−N(31)−C(30)−C(23), 109.64; C(35)−
N(34)−C(41)−C(42), 53.87.
In addition to gold(I), it was also possible to incorporate
copper(I) as the second metal into palladium(II) complex 6 by
reaction with 2 equiv of copper(I) acetate (Scheme 3). The
high acidity of 1,2,4-triazolium salts permits a facile
deprotonation without the need for an additional base. The
ESI mass spectra indicates the formation of a dicationic
complex in which one copper(I) center is bound to each vacant
NHC binding site. In contrast to palladium gold complex 7, a
heterotrinuclear palladium dicopper complex (8) was obtained.
The anions were exchanged with hexafluorophosphate by
reaction with KPF6 in a two-phase system of dichloromethane/
acetonitrile and water. Heteronuclear complex 8 crystallized
from the dichloromethane/acetonitrile solution upon addition
of diethyl ether. The single-crystal X-ray analysis confirms the
presence of a dicationic palladium dicopper complex (Figure
4). Each copper ion binds to one triazol-5-ylidene ligand and to
one sulfur atom of the NHC−thiolato unit attached to the
palladium atom. Rotation at the methylene units of the m-
xylylene linker enables this intramolecular coordination so that
two metals are connected via a thiolato bridge. Additionally,
acetonitrile is attached to each copper ion in a trigonal-planar
geometry with an angle S(1)−Cu(1)−C(25) of 117°. The
structure displays a square-planar coordination mode of two
NHC−thiolato fragments to palladium with a C(5)−Pd(1)−
S(1) angle of 88°. The planes of the triazole and the phenyl
ring are distorted by 33° to facilitate ligation and to avoid steric
hindrance induced by the substituents at the N1 position in the
apparent cis configuration. The bond lengths Cu(1)−C(25)
and Cu(1)−S(1) are, at 1.91 and 2.26 Å, slightly shorter than
the bond lengths of Pd(1)−C(5) (1.99 Å) and Pd(1)−S(1)
based on the chelating effect of the adjacent sulfur atom. The
precoordination of palladium to the thiolato donor facilitates
coordination of the triazol-5-ylidene ligand. The free carbene is
generated merely in small in situ concentrations through
deprotonation by the mildly basic carbonate.
1
The H NMR spectrum shows palladium complex 6 as a
mixture of its two diastereomers in a ratio of 2/1 (Figure 3).
For each isomer two singlets of the protons at the C3 and C5
positions of the triazolium unit and one singlet of the remaining
proton at the C3 position of the triazol-5-ylidene are observed.
The absence of a signal of the proton at the C5 position
indicates bonding to the metal center. In the case of the minor
diastereomer, the proton signals of the two methylene groups
of the m-xylylene linker split into two doublets. Each set can be
observed, whereas in the case of the dominating diastereomer
only two singlets are detected. The 13C NMR data exhibit two
signals for Pd−Ccarbene at 172.4* and 175.5 ppm (* being the
minor product). Since the signal of the carbene carbon of the
trans isomer is generally shifted more downfield than that of the
cis isomer at the same metal center,23 we assume that the trans
isomer is the dominating diastereomer due to steric hindrance.
The ESI mass spectrum confirms the presence of palladium
complex 6 as a dicationic species.
After monopalladation of the bis(carbene) precursor by
selective deprotonation, gold(I) was incorporated as the second
metal. The pendant triazolium unit of complex 6 was
deprotonated with sodium methoxide in DMSO and reacted
with gold(I) dimethyl sulfide chloride (Scheme 3). After
extraction from the DMSO solution and purification by column
chromatography the water- and air-stable palladium(II) gold(I)
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Scheme 3. Stepwise Deprotonation and Metalation of Thiol-Functionalized Unsymmetrically Substituted Bis-NHC Precursor 4
with Palladium(II) and Gold(I) or Copper(I) to Obtain Heteronuclear Complexes 7 and 8, Respectively
(2.33 Å). The Pd−Cu distance of 3.41 Å is too large for a direct
metal−metal interaction.
CONCLUSIONS
■
The high acidity of 1,2,4-triazolium salts leads to an in situ
deprotonation and metalation under mild conditions. This
synthetic advantage was successfully applied to the otherwise
challenging selective preparation of heterometallic NHC
complexes. The unsymmetrically substituted bis(1,2,4-triazo-
lium) salt with one thiophenol substituent is a rare ligand
precursor, because free thiol groups adjacent to azolium salts
are prone to oxidation under C−S bond formation. This was
structurally proven by a single-crystal X-ray analysis. Palladium-
(II) coordinated at the NHC−thiolato fragment, and then
gold(I) or copper(I) reacted with the pendant triazolium ligand
precursors in a second step to give water-stable heterodinuclear
and heterotrinuclear complexes, respectively. To the best of our
knowledge, these complexes are the first examples of bridged
bis-NHC complexes containing palladium and coinage metals.
In summary, we present a system that offers controlled
metalation based on a directed stepwise deprotonation as a
synthetic route to defined mixed-metal complexes.
1
The H NMR spectrum of palladium dicopper complex 8
represents only one species (Figure 3). The singlets of the
remaining protons at the C3 position of the triazol-5-ylidenes
coordinated to copper and palladium are visible at 8.19 and
8.82 ppm, respectively. The diastereotopic protons of the
methylene groups of the m-xylylene linker split up into four
doublets, and the methyl groups of the dimethylphenyl
substituent split into two singlets. In the 13C NMR spectrum
are depicted signals of Pd−Ccarbene at 168.9 ppm and Cu−
Ccarbene at 182.3 ppm. The relatively small downfield shift of
Pd−Ccarbene is consistent with the cis isomerism at the metal
center. After drying of the solid product in vacuo, no
acetonitrile was detected in the NMR spectra. The solvent
molecules are apparently only loosely bound to the copper
atoms. The elemental analysis is in agreement with a
composition of two coppers per palladium without additional
acetonitrile ligands in the isolated product.
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1
Figure 3. H NMR spectra of palladium dicopper complex 8 (green, top) and palladium gold complex 7 (red, middle) in comparison to that of
palladium complex 6 (blue, bottom). A prime (′) in the assignment of the signals signifies the triazole unit of the ligand with the 2,6-dimethylphenyl
substituent; an asterisk (*) denotes the minor diastereomer.
unless otherwise noted. Air- and moisture-sensitive reactions were
carried out by using standard Schlenk or drybox techniques under an
inert atmosphere (nitrogen or argon). NMR spectra were recorded by
using Bruker Avance 300 and Bruker Avance 500 spectrometers at 25
°C. Chemical shifts (δ) are reported in ppm relative to TMS and were
determined by reference to the residual 1H or 13C solvent peaks.24 ESI
mass spectra were obtained on a Finnigan MAT LCQ and Bruker ICR
Apex-Qe instruments. Melting points were determined using a
Gallenkamp hot-stage microscope and are uncorrected.
1-[1-(3-Chloromethyl)phenyl(methyl)]4-[2,6-dimethylphen-
yl]-1,2,4-4H-triazol-1-ium Chloride (1). 4-(2,6-Dimethylphenyl)-
1,2,4-4H-triazole18 (2.89 mmol, 500 mg) and α,α′-dichloro-m-xylene
(28.9 mmol, 5.05 g) were ground in a mortar and heated without
solvent to 120 °C for 2 h. The resulting melt was minced and stirred in
diethyl ether overnight. The colorless solid was filtered off, washed
with diethyl ether, and dried in vacuo to give chloride 1 (970 mg,
96%).
1H NMR (300 MHz, DMSO-d6): δ 2.15 (s, 6 H, CH3), 4.80 (s, 2 H,
3
CH2Cl), 5.85 (s, 2 H, NCH2), 7.37 (d, JHH = 7.5 Hz, 2 H, HXyl-3,
HXyl-5), 7.44−7.49 (m, 2 H, HXyl-4, HmXyl-5), 7.51−7.56 (m, 2 H,
Figure 4. Ball-and-stick model of the X-ray structure of dicationic
HmXyl-4, HmXyl-6), 7.64 (s, 1 H, HmXyl-2), 9.69 (s, 1 H, N2CHN4),
11.39 (s, 1 H, N1CHN4). 13C{1H} NMR (75 MHz, DMSO-d6): δ
palladium dicopper complex 8. The counterions have been omitted for
clarity. Selected bond lengths (Å) and bond angles (deg): Pd(1)−
17.3 (CH3), 45.6 (CH2Cl), 54.7 (NCH2), 128.7 (CmXyl-6), 129.0
(CXyl-3, CXyl-5), 129.2 (CmXyl-2), 129.2 (CmXyl-5), 129.3 (CmXyl-4),
130.4 (CXyl-1), 131.0 (CXyl-4), 133.6 (CmXyl-1), 134.6 (CXyl-2, CXyl-6),
C(5), 1.986(5); Pd(1)−C(35), 1.986(5); Pd(1)−S(1), 2.3265(14);
Pd(1)−S(2), 2.3266(14); Cu(1)−S(1), 2.2639(17); Cu(1)−C(25),
1.913(6); Cu(1)−N(10), 1.937(6); C(5)−Pd(1)−S(1), 87.73(15);
138.3 (CmXyl-3), 144.0 (N1CHN4), 145.5 (N2CHN4). MS (ESI+):
C(5)−Pd(1)−S(2), 170.13(15); S(1)−Cu(1)−C(25), 116.80(18);
m/z (%) 312.13 (100) [M − Cl]+, 659.22 (3) [2M − Cl]+. HRMS
N(10)−Cu(1)−S(1), 120.36(15); C(25)−Cu(1)−N(10), 122.6(2);
C(5)−N(4)−C(11)−C(12), 32.77.
(ESI+): m/z calculated for [C18H19ClN3]+ 312.1268, found 312.1262.
Anal. Calcd for C18H19Cl2N3: C, 62.08; H, 5.50; N 12.07. Found: C,
61.85; H, 5.48; N, 11.96. Mp: 220 °C.
1 , 1 ′ - [ 1 , 3 - P h e n y l e n e d i ( m e t h y l e n e ) ] [ 4 - [ 2 - ( 4 -
methoxybenzylthio)phenyl]-1,2,4-4H-triazol-1-ium][4-(2,6-di-
methylphenyl)-1,2,4-4H-triazol-1-ium] Dichloride (2). 4-[2-(4-
Methoxybenzylthio)phenyl]-1,2,4-4H-triazole7g (2.34 mmol, 695 mg)
and chloride 1 (1.56 mmol, 543 mg) were dissolved in glacial acetic
EXPERIMENTAL SECTION
General Information. All starting materials and solvents were
obtained from commercial suppliers (Sigma-Aldrich, Fisher Scientific,
Strem, Deutero, Eurisotop) and were used without further purification
■
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acid (15 mL) and heated to 120 °C for 3 days. The solvent was
removed under reduced pressure, and the obtained brown oil was
dissolved in dichloromethane. On addition of diethyl ether, a light
brown oil separated from the solution, which was washed with diethyl
ether and dried in vacuo to give a light brown foam. The foam was
dissolved again in dichloromethane, and on addition of diethyl ether
the product precipitated as a light brown solid. The precipitate was
filtered off, washed with diethyl ether, and dried in vacuo to give
dichloride 2 (860 mg, 85%).
1,1′-[1,3-Phenylenedi(methylene)][4-(2-thiophenyl)-1,2,4-
4H-triazol-1-ium][4-(2,6-dimethylphenyl)-1,2,4-4H-triazol-1-
ium] Bis(triflate) (4). The bis(hexafluorophosphate) 3 (0.400 mmol,
346 mg) was dissolved at 0 °C under an argon atmosphere in
trifluoroacetic acid (20.0 mmol, 1.54 mL). Anisole (2.0 mmol, 0.22
mL) and then trifluoromethanesulfonic acid (2.0 mmol, 0.18 mL)
were added. The mixture was stirred for 1 h at 0 °C before the solvent
was evaporated under reduced pressure. The obtained red oil was
suspended in diethyl ether/water. A yellow oil separated between the
two phases. The organic phase was pipetted off, and the aqueous phase
with the oil was washed two times with diethyl ether in this way. To
the aqueous phase were added dichloromethane and a small amount of
acetonitrile until the oil was dissolved. The organic phase was washed
twice with water and then dried over MgSO4 and filtered. The volume
of the solution was decreased under reduced pressure. On addition of
diethyl ether, the product precipitated, which was filtered off, washed
with diethyl ether, and dried in vacuo to give bis(triflate) 4 as a light
yellow solid (234 mg, 78%).
1H NMR (300 MHz, DMSO-d6): δ 2.15 (s, 6 H, CH3), 3.72 (s, 3 H,
OCH3), 4.18 (s, 2 H, SCH2), 5.87 (s, 2 H, NCH2), 5.88 (s, 2 H,
NCH2), 6.79 (d, 3JHH = 8.5 Hz, 2 H, HPMB-3, HPMB-5), 7.10 (d, 3JHH
=
3
8.5 Hz, 2 H, HPMB-2, HPMB-6), 7.36 (d, JHH = 7.7 Hz, 2 H, HXyl-3,
HXyl-5), 7.46−7.51 (m, 1 H, HXyl-4), 7.50−7.63 (m, 4 H, HmXyl-5, H-5,
3
HmXyl-4, HmXyl-6), 7.65−7.70 (m, 1 H, H-4), 7.81 (dd, JHH = 7.7 Hz,
4JHH = 1.0 Hz, 1 H, H-3), 7.86−7.89 (m, 2 H, H-6, HmXyl-2), 9.55 (s, 1
H, N2CHN4-TriPMB), 9.73 (s, 1 H, N2CHN4-TriXyl), 11.40 (s, 1 H,
N1CHN4-TriPMB), 11.57 (s, 1 H, N1CHN4-TriXyl). 13C{1H} NMR
(75 MHz, DMSO-d6): δ 17.4 (CH3), 38.1 (SCH2), 54.5 (NCH2), 54.7
(NCH2), 55.1 (OCH3), 113.9 (CPMB-3, CPMB-5), 127.5 (C-6), 128.0
(CPMB-1), 128.5 (C-5), 129.1 (CXyl-3, CXyl-5), 129.5 (CmXyl-4, CmXyl-5,
CmXyl-6), 129.7 (CmXyl-2), 130.0 (CPMB-2, CPMB-6), 130.5 (CXyl-1),
131.1 (CXyl-4), 131.9 (C-4), 132.0 (C-1), 132.3 (C-2), 133.1 (C-3),
133.9 (CmXyl-1, CmXyl-3), 134.7 (CXyl-2, CXyl-6), 143.8 (N1CHN4-
TriPMB), 144.3 (N1CHN4-TriXyl), 145.4 (N2CHN4-TriPMB), 145.5
(N2CHN4-TriXyl), 158.5 (CPMB-4). MS (ESI+): m/z (%) 287.13 (96)
[M − 2Cl]2+, 453.19 (91) [M − C8H9O − 2Cl]+, 573.24 (100) [M −
H − 2Cl]+, 609.22 (46) [M − Cl]+. HRMS (ESI+): m/z calculated for
[C34H33N6OS]+ 573.2431, found 573.2441; m/z calculated for
[C34H34ClN6OS]+ 609.2198, found 609.2208. Mp: 197 °C.
1H NMR (300 MHz, CD3CN): δ 2.09 (s, 6 H, CH3), 5.71 (s, 2 H,
3
NTriSHCH2), 5.73 (s, 2 H, NTriXylCH2), 7.32 (d, JHH = 7.4 Hz, 2 H,
HXyl-3, HXyl-5), 7.45−7.51 (m, 2 H, HXyl-4, H-4), 7.52−7.57 (m, 2 H,
HmXyl-5, H-5), 7.59−7.63 (m, 3 H, HmXyl-4, HmXyl-6, H-3), 7.69−7.73
(m, 1 H, H-6), 7.74 (br. s, 1 H, HmXyl-2), 8.80 (s, 1 H, N2CHN4-
TriXyl), 8.89 (s, 1 H, N2CHN4-TriSH), 9.71 (s, 1 H, N1CHN4-TriXyl),
9.79 (s, 1 H, N1CHN4-TriSH). 13C{1H} NMR (75 MHz, CD3CN): δ
17.9 (CH3), 56.9 (NTriSHCH2), 57.0 (NTriXylCH2), 122.0 (COTf, 1JCF
=
321 Hz), 128.6 (C-5), 129.1 (C-4), 129.7 (C-1), 130.3 (CXyl-3, CXyl
-
5), 131.2 (CmXyl-5), 131.6 (CmXyl-4, CmXyl-6), 131.7 (CmXyl-2), 131.8
(C-2), 132.8 (CXyl-4), 133.2 (C-3), 134.0 (CXyl-1), 134.1 (CmXyl-1,
CmXyl-3), 134.4 (C-6), 136.1 (CXyl-2, CXyl-6), 143.7 (N1CHN4-TriSH),
143.8 (N1CHN4-TriXyl), 146.0 (N2CHN4-TriSH), 146.3 (N2CHN4-
TriXyl). MS (ESI+): m/z (%) 453.19 (100) [M − H − 2OTf]+, 603.15
(15) [M − OTf]+. HRMS (ESI+): m/z calculated for [C26H25N6S]+
453.1856, found 453.1857; m/z calculated for [C27H26F3N6O3S2]+
603.1454, found 603.1459. Anal. Calcd for C28H26F6N6O6S3: C, 44.68;
H, 3.48; N, 11.16. Found: C, 44.41; H, 3.66; N, 11.15. Mp: 160 °C.
1,1′-[1,3-Phenylenedi(methylene)](1,2,4-triazol-1-ium[2,1-
b]benzothiazole)[4-(2,6-dimethylphenyl)-1,2,4-4H-triazol-1-
ium] Bis(triflate) (5). Under a nitrogen atmosphere, the bis(triflate) 4
(0.05 mmol, 38 mg) was dissolved in dry DMSO-d6 (0.5 mL) and
stirred at room temperature. After 48 h the conversion to
benzothiazole 5 was completed.
1 , 1 ′ - [ 1 , 3 - P h e n y l e n e d i ( m e t h y l e n e ) ] [ 4 - [ 2 - ( 4 -
methoxybenzylthio)phenyl]-1,2,4-4H-triazol-1-ium][4-(2,6-di-
m e t h y l p h e n y l ) - 1 , 2 , 4 - 4 H - t r i a z o l - 1 - i u m ] B i s -
(hexafluorophosphate) (3). To exchange the anions, dichloride 2
(1.26 mmol, 815 mg) was dissolved in dichloromethane and water was
added. Hexafluorophosphoric acid (3.8 mmol, 0.56 mL (60% aqueous
solution)) was added, and the two-phase system was vigorously stirred
for 2 h. Then the phases were separated and the aqueous phase was
extracted once with dichloromethane. The combined organic phases
were washed three times with water, dried over MgSO4, and filtered.
The solvent was removed under reduced pressure, and the obtained
residue was dissolved in dichloromethane. On addition of diethyl
ether, a light yellow oil separated from the solution, which was washed
with diethyl ether and dried in vacuo to give bish(exafluorophosphate)
3 as a light yellow solid (1.00 g, 92%).
1H NMR (300 MHz, DMSO-d6): δ 2.08 (s, 6 H, CH3), 5.79 (s, 2 H,
3
NTriXylCH2), 5.90 (s, 2 H, NTriSCH2), 7.37 (d, JHH = 7.7 Hz, 2 H,
HXyl-3, HXyl-5), 7.48−7.53 (m, 1 H, HXyl-4), 7.64 (br. s, 3 H, HmXyl-4,
HmXyl-5, HmXyl-6), 7.71−7.76 (m, 2 H, HmXyl-2, H-4), 7.81−7.87 (m, 1
1H NMR (300 MHz, acetone-d6): δ 2.19 (s, 6 H, CH3), 3.76 (s, 3
H, OCH3), 4.11 (s, 2 H, SCH2), 5.90 (s, 2 H, NTriPMBCH2), 5.98 (s, 2
H, NTriXylCH2), 6.76 (d, 3JHH = 8.7 Hz, 2 H, HPMB-3, HPMB-5), 7.00 (d,
3
3
H, H-5), 8.27 (d, JHH = 8.3 Hz, 1 H, H-3), 8.40 (d, JHH = 8.1 Hz, 1
H, H-6), 9.56 (s, 1 H, N2CHN4-TriXyl), 10.25 (s, 1 H, N2CHN4-
TriS), 10.60 (s, 1 H, N1CHN4-TriXyl). 13C{1H} NMR (75 MHz,
DMSO-d6): δ 17.2 (CH3), 54.8 (NTriSCH2), 55.1 (NTriXylCH2), 115.9
3
3JHH = 8.7 Hz, 2 H, HPMB-2, HPMB-6), 7.37 (d, JHH = 7.6 Hz, 2 H,
HXyl-3, HXyl-5), 7.47−7.52 (m, 1 H, HXyl-4), 7.59−7.66 (m, 2 H, H-5,
HmXyl-5), 7.70−7.76 (m, 4 H, HmXyl-4, HmXyl-6, H-4, H-6), 7.90−7.94
(m, 2 H, HmXyl-2, H-3), 9.02 (s, 1 H, N2CHN4-TriPMB), 9.36 (s, 1 H,
N2CHN4-TriXyl), 10.15 (s, 1 H, N1CHN4-TriPMB), 10.34 (s, 1 H,
N1CHN4-TriXyl). 13C{1H} NMR (75 MHz, acetone-d6): δ 17.6
(CH3), 40.3 (SCH2), 55.6 (OCH3), 56.6 (NTriPMBCH2), 56.9
(NTriXylCH2), 114.9 (CPMB-3, CPMB-5), 127.9 (C-6), 129.4 (CPMB-1),
130.1 (CXyl-3, CXyl-5), 130.1 (C-5), 130.7 (CPMB-2, CPMB-6), 131.0
1
(C-6), 120.7 (COTf, JCF = 323 Hz), 126.2 (C-3), 128.6 (C-1, C-5),
128.8 (C-4), 129.1 (CXyl-3, CXyl-5), 129.9 (CXyl-1), 130.1 (CmXyl-5),
130.2 (CmXyl-2), 130.5 (CmXyl-4, CmXyl-6), 131.3 (CXyl-4), 131.7 (C-2),
132.5 (CmXyl-1), 133.8 (CmXyl-3), 134.8 (CXyl-2, CXyl-6), 137.3
(N2CHN4-TriS), 143.8 (N1CHN4-TriXyl), 145.7 (N2CHN4-TriXyl),
154.3 (N1CN4-TriS). MS (ESI+): m/z (%) 226.09 (23) [M −
2OTf]2+, 451.17 (4) [M − H − 2OTf]+, 601.13 (100) [M − OTf]+.
HRMS (ESI+): m/z calculated for [C26H24N6S]2+ 226.0886, found
226.0887; m/z calculated for [C27H24F3N6O3S2]+ 601.1298, found
601.1295.
cis-/trans-Bis[1,1′-[1,3-phenylenedi(methylene)][4-(2,6-di-
methylphenyl)-1,2,4-4H-triazol-1-ium][4-(2-thiophenyl)-1,2,4-
4H-triazol-5-ylidene]]palladium(II) Bis(triflate) (6). Under an
argon atmosphere, pyridine (2 mL) was added to 4 (0.217 mmol,
163 mg), palladium(II) chloride (0.106 mmol, 18.7 mg), and
potassium carbonate (0.53 mmol, 73 mg). The mixture was stirred
at room temperature for 3 days until all palladium(II) chloride was
dissolved. The mixture was diluted with dichloromethane, the yellow
solution was filtered off, and the residue was washed with
dichloromethane. The solvent was removed under reduced pressure.
(CmXyl-5), 131.1, 131.2 (CmXyl-4, CmXyl-6), 131.3 (CmXyl-2), 131.4 (CXyl
-
1), 132.5 (CXyl-4), 133.1 (C-2), 133.2 (C-4), 133.7 (C-1), 134.4
(CmXyl-1, CmXyl-3), 135.5 (C-3), 136.0 (CXyl-2, CXyl-6), 143.8
(N1CHN4-TriPMB), 144.3 (N1CHN4-TriXyl), 146.1 (N2CHN4-
TriPMB), 146.5 (N2CHN4-TriXyl), 160.1 (CPMB-4). 31P{1H} NMR
1
(121 MHz, acetone-d6): −144.2 (sept, JPF = 709 Hz, PF6). MS (ESI
+): m/z (%) 287.13 (97) [M − 2PF6]2+, 453.19 (81) [M − C8H9O −
2PF6]+, 573.24 (8) [M − H − 2PF6]+, 719.22 (100) [M − PF6]+.
HRMS (ESI+): m/z calculated for [C34H34N6OS]2+ 287.1252, found
287.1252; m/z calculated for [C34H34F6N6OPS]+ 719.2151, found
719.2150. Anal. Calcd for C34H34F12N6OP2S: C, 47.23; H, 3.96; N,
9.72. Found: C, 47.38; H, 4.21; N, 10.01. Mp: 129 °C.
F
dx.doi.org/10.1021/om400143u | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
The obtained solid was dissolved in dichloromethane and the solution
filtered off again. The product precipitated on addition of diethyl ether,
which was filtered off, washed with diethyl ether, and dried in vacuo.
Palladium complex 6 was obtained as a yellow solid which is a mixture
of the two isomers in a 2/1 ratio (136 mg, 98%).
129.7 (CAr), 130.0 (CAr), 130.3 (CAr), 130.7 (CAr), 131.6 (CAr), 131.7
(CAr), 133.3 (CAr), 134.2 (CAr), 136.0 (CAr), 136.1 (CAr), 136.5 (CAr),
136.8 (CAr), 137.1 (CAr), 138.2 (CAr), 138.4 (CAr), 138.6 (CAr), 142.9
(N2CHN4Pd), 143.0 (N2CHN4Pd*), 145.1 (N2CHN4Au), 145.5
(N2CHN4Au*), 172.1 (N1CN4Pd*), 176.0 (N1CN4Pd), 186.4
(N1CN4Au*), 186.9 (N1CN4Au) (* denotes the minor product).
1H NMR (500 MHz, CD3CN): δ 1.98 (s, 6 H, CH3), 2.08 (s, 6 H,
CH3*), 5.00 (d, 2JHH = 15.5 Hz, 1 H, CH2NPd*), 5.12 (d, 2JHH = 15.5
Hz, 1 H, CH2NPd*), 5.31 (d, 2JHH = 14.6 Hz, 1 H, CH2NTri*), 5.44 (d,
2JHH = 14.6 Hz, 1 H, CH2NTri*), 5.55 (s, 2 H, CH2NTri), 5.98 (s, 2 H,
CH2NPd), 7.07−7.11 (m, 2 H, HAr), 7.13−7.25 (m, 6 H, HAr), 7.29−
7.31 (m, 4 H, HAr), 7.35−7.38 (m, 1 H, HAr), 7.41−7.53 (m, 8 H,
HAr), 7.58−7.60 (m, 1 H, HAr), 8.65 (s, 1 H, N2CHN4Pd), 8.71 (s, 1
H, N2CHN4Tri), 8.72 (s, 1 H, N2CHN4Pd*), 8.76 (s, 1 H,
N2CHN4Tri*), 9.63 (s, 1 H, N1CHN4Tri), 9.65 (s, 1 H, N1CHN4Tri*)
(* denotes the minor product). 13C{1H} NMR (125 MHz, CD3CN):
δ 17.9 (CH3), 18.1 (CH3*), 56.4 (CH2NPd), 57.2 (CH2NTri), 57.3
1
31P{1H} NMR (121 MHz, CD3CN): −144.5 (sept, JPF = 707 Hz,
1
PF6). 19F{1H} NMR (282 MHz, CD3CN): −72.7 (d, JPF = 707 Hz,
PF6). MS (ESI+): m/z (%) 1205.21 (100) [M − PF6]+. HRMS (ESI
+): m/z calculated for [C52H46AuN12PdS2]+ 1205.2121, found
1205.2125. Anal. Calcd for C52H46AuF6N12PPdS2: C, 46.21; H, 3.43;
N, 12.44; S, 4.75. Found: C, 45.67; H, 3.62; N, 11.91; S, 4.69. Mp: 285
°C dec.
cis-Bis[1,1′-[1,3-phenylenedi(methylene)][4-(2,6-dimethyl-
phenyl)-1,2,4-4H-triazol-5-ylidene][4-(2-thiophenyl)-1,2,4-4H-
triazol-5-ylidene]]dicopper(I)palladium(II) Bis-
(hexafluorophosphate) (8). Under an argon atmosphere, palladium-
(II) complex 6 (0.076 mmol, 100 mg) and copper(I) acetate (0.16
mmol, 20 mg) were dissolved in dry acetone (2 mL). After it was
stirred at room temperature overnight, the yellow solution was filtered
off the gray precipitate and the solvent was removed under reduced
pressure. The obtained yellow solid was subjected to a salt metathesis.
The product was dissolved under an argon atmosphere in dry
dichloromethane (2 mL) and a small amount of dry acetonitrile until
all solid was dissolved. A solution of potassium hexafluorophosphate
(1.52 mmol, 280 mg) in degassed water (2 mL) was added, and the
two-phase system was stirred vigorously for 2 h. The phases were
separated, and the aqueous phase was extracted three times with
dichloromethane. The combined organic phases were dried over
MgSO4 and filtered. The volume of the solution was decreased under
reduced pressure, and on addition of diethyl ether the product
precipitated. The yellow solid was filtered off, washed with diethyl
ether, and dried in vacuo to give the cis isomer of palladium dicopper
complex 8 as a yellow solid (56 mg, 52%).
(CH2NPd*/CH2NTri*), 122.1 (COTf,
1JCF = 321 Hz), 122.9 (CAr),
123.2 (CAr), 124.8 (CAr), 125.3 (CAr), 129.0 (CAr), 129.1 (CAr), 129.4
(CAr), 129.7 (CAr), 129.7 (CAr), 130.1 (CAr), 130.2 (CAr), 130.2 (CAr),
130.3 (CAr), 130.5 (CAr), 130.6 (CAr), 131.1 (CAr), 131.2 (CAr), 132.7
(CAr), 133.0 (CAr), 133.1 (CAr), 133.3 (CAr), 133.4 (CAr), 136.0 (CAr),
136.0 (CAr), 137.4 (CAr), 137.8 (CAr), 138.5 (CAr), 138.8 (CAr), 139.5
(CAr), 142.7 (N2CHN4Pd), 143.1 (N2CHN4Pd*), 143.4
(N1CHN4Tri*), 143.5 (N1CHN4Tri), 146.2 (N2CHN4Tri), 146.2
(N2CHN4Tri*), 172.4 (N1CN4Pd*), 175.5 (N1CN4Pd) (* denotes
the minor product). MS (ESI+): m/z (%) 505.3 (100) [M − 2OTf]2+,
1159.1 (47) [M − OTf]+. HRMS (ESI+): m/z calculated for
[C52H48N12PdS2]2+ 505.1303, found 505.1292; m/z calculated for
[C53H48F3N12O3PdS3]+ 1159.2121, found 1159.2127. Anal. Calcd for
C54H48F6N12O6PdS4: C, 49.52; H, 3.69; N, 12.83. Found: C, 49.73; H,
3.93; N, 12.61. Mp: 196 °C.
cis-/trans-Bis[1,1′-[1,3-phenylenedi(methylene)][4-(2,6-di-
methylphenyl)-1,2,4-4H-triazol-5-ylidene][4-(2-thiophenyl)-
1,2,4-4H-triazol-5-ylidene]]gold(I)palladium(II) Hexafluoro-
phosphate (7). Under an argon atmosphere, palladium(II) complex
6 (0.145 mmol, 190 mg), (dimethyl sulfide)gold(I) chloride (0.145
mmol, 42.7 mg), and sodium methoxide (0.29 mmol, 16 mg) were
dissolved in dry DMSO (3 mL). After it was stirred for 3 h at room
temperature, the brown solution was extracted with dichloromethane/
water. The organic phase was washed three times with water, dried
over MgSO4, and filtered. The solvent was removed under reduced
pressure, and the residue was purified by column chromatography
(silica gel, dichloromethane/2-propanol 30/1). The obtained yellow
solid was subjected to a salt metathesis. An excess of potassium
hexafluorophosphate (0.725 mmol, 133 mg) was dissolved in water (5
mL) and added to a solution of the product in dichloromethane (5
mL). The two-phase system was stirred vigorously for 2 h. The phases
were separated, and the aqueous phase was extracted once with
dichloromethane. The combined organic phases were washed three
times with water, dried over MgSO4, and filtered. The volume of the
solution was decreased under reduced pressure, and on addition of
diethyl ether the product precipitated. The yellow solid was filtered off,
washed with diethyl ether, and dried in vacuo. The obtained palladium
gold complex 7 is a mixture of the two isomers in a ratio of 2/1 (78
mg, 40%).
1H NMR (300 MHz, CD3CN): δ 1.70 (s, 3 H, CH3), 2.10 (s, 3 H,
CH3), 4.55 (d, 2JHH = 14.2 Hz, 1 H, CH2NCu), 4.89 (d, 2JHH = 15.1 Hz,
1 H, CH2NPd), 5.14 (d, 2JHH = 14.2 Hz, 1 H, CH2NCu), 5.35 (d, 2JHH
=
15.1 Hz, 1 H, CH2NPd), 7.07−7.12 (m, 2 H, HAr), 7.18−7.39 (m, 7 H,
HAr), 7.48 (br.s, 1 H, HAr), 7.62−7.65 (m, 1 H, HAr), 8.19 (s, 1 H,
N2CHN4Cu), 8.82 (s, 1 H, N2CHN4Pd). 13C{1H} NMR (75 MHz,
CD3CN): δ 17.7 (CH3), 18.8 (CH3), 56.8 (CH2NCu), 57.8 (CH2NPd),
124.1 (CAr), 127.5 (CAr), 129.2 (CAr), 129.5 (CAr), 129.6 (CAr), 129.8
(CAr), 130.7 (CAr), 130.8 (CAr), 133.3 (CAr), 135.9 (CAr), 136.4 (CAr),
136.9 (CAr), 137.1 (CAr), 137.3 (CAr), 137.5 (CAr), 143.2
(N2CHN4Cu), 143.7 (N2CHN4Pd), 168.9 (N1CN4Pd), 182.3
(N1CN4Cu). 31P{1H} NMR (121 MHz, CD3CN): −144.6 (sept,
1JPF = 707 Hz, PF6). 19F{1H} NMR (282 MHz, CD3CN): −72.7 (d,
1JPF = 707 Hz, PF6). MS (ESI+): m/z (%) 537.0 (15) [M + H − Cu −
2PF6]2+, 568.8 (60) [M − 2PF6]2+, 1073.0 (100) [M − Cu − 2PF6]+.
HRMS (ESI+): m/z calculated for [C52H46Cu2N12PdS2]2+ 567.0518,
found 567.0512; m/z calculated for [C52H46CuN12PdS2]+ 1071.1748.,
found 1071.1751. Anal. Calcd for C52H46Cu2F12N12P2PdS2: C, 43.78;
H, 3.25; N, 11.78; S, 4.50. Found: C, 43.83; H, 3.68; N, 11.46; S, 4.66.
Mp: >220 °C dec.
X-ray Diffraction Studies. The single-crystal X-ray diffraction
data sets were collected at 200(2) K on a Bruker APEX diffractometer
or a Bruker APEX II Quazar diffractometer equipped with a CCD area
detector and a standard sealed-tube Mo Kα (λ = 0.71073 Å) radiation
source. 0.3° ω scans covering a whole sphere in reciprocal space were
taken in each case, and an empirical absorption correction was applied
using SADABS25 on the basis of the Laue symmetry of the reciprocal
space. Structures were solved by direct methods and refined against F2
with a full-matrix least-squares algorithm using the SHELXTL-PLUS
(6.10) software package.26 For analysis and graphic representation, the
programs ORTEP27 and POV-Ray28 were used. CCDC 924413 (for
5) and 924414 (for 8) contain supplementary crystallographic data for
this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
1H NMR (300 MHz, CD3CN): δ 1.64 (s, 3 H, CH3*), 1.69 (s, 3 H,
2
CH3), 1.73 (s, 3 H, CH3), 1.84 (s, 3 H, CH3*), 4.33 (d, JHH = 14.8
Hz, 1 H, CH2NPd*), 5.14 (d, 2JHH = 14.8 Hz, 1 H, CH2NPd*), 5.18 (d,
2
2JHH = 15.5 Hz, 1 H, CH2NAu), 5.26 (d, JHH = 15.5 Hz, 1 H,
CH2NAu), 5.40 (d, 2JHH = 15.5 Hz, 1 H, CH2NPd), 5.60 (d, 2JHH = 15.3
Hz, 1 H, CH2NAu*), 5.66 (d, 2JHH = 15.3 Hz, 1 H, CH2NAu*), 6.08 (d,
2JHH = 15.5 Hz, 1 H, CH2NPd), 6.85−6.88 (m, 1 H, HAr), 6.91−6.93
(m, 1 H, HAr), 7.07−7.32 (m, 11 H, HAr), 7.35−7.51 (m, 8 H, HAr),
7.56−7.59 (m, 1 H, HAr), 7.69−7.72 (m, 1 H, HAr), 8.33 (s, 1 H,
N2CHN4Au), 8.40 (s, 1 H, N2CHN4Au*), 8.63 (s, 1 H, N2CHN4Pd*),
8.64 (s, 1 H, N2CHN4Pd) (* denotes the minor product). 13C{1H}
NMR (75 MHz, CD3CN): δ 17.8 (CH3*), 17.9 (CH3), 18.0 (CH3),
18.1 (CH3*), 56.3 (CH2NPd), 57.0 (CH2NAu), 57.1 (CH2NAu*), 57.4
(CH2NPd*), 122.8 (CAr), 122.9 (CAr), 124.5 (CAr), 125.2 (CAr), 127.3
(CAr), 127.4 (CAr), 127.6 (CAr), 128.4 (CAr), 128.9 (CAr), 129.0 (CAr),
G
dx.doi.org/10.1021/om400143u | Organometallics XXXX, XXX, XXX−XXX

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Article
(14) Zamora, M. T.; Ferguson, M. J.; McDonald, R.; Cowie, M.
Dalton Trans. 2009, 0, 7269.
(15) Herrmann, W. A.; Schwarz, J.; Gardiner, M. G. Organometallics
ASSOCIATED CONTENT
■
S
* Supporting Information
Figures, tables, and CIF files giving H and 13C NMR spectra
and crystal data for structures 5 and 8. This material is available
free of charge via the Internet at http://pubs.acs.org.
1
1999, 18, 4082.
(16) Wells, K. D.; Ferguson, M. J.; McDonald, R.; Cowie, M.
Organometallics 2008, 27, 691.
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(18) Holm, S. C.; Siegle, A. F.; Loos, C.; Rominger, F.; Straub, B. F.
Synthesis 2010, 2010, 2278.
(19) Berg, R.; Straub, J.; Schreiner, E.; Mader, S.; Rominger, F.;
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2525.
AUTHOR INFORMATION
Corresponding Author
*E-mail for B.F.S.: straub@oci.uni-heidelberg.de.
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
For financial support, we are indebted to the University of
Heidelberg, the Graduate College 850, the Fonds der
■
(22) Epstein, W. W.; Sweat, F. W. Chem. Rev. 1967, 67, 247.
(23) Huynh, H. V.; Ho, J. H. H.; Neo, T. C.; Koh, L. L. J. Organomet.
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(24) (a) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A. J. Org. Chem.
1997, 62, 7512. (b) Fulmer, G. R.; Miller, A. J. M.; Sherden, N. H.;
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K. I. Organometallics 2010, 29, 2176.
(25) Sheldrick, G. M. SADABS; Bruker Analytical X-ray Division,
Madison, WI, 2008.
(26) Sheldrick, G. M. Software Package SHELXTL 2008/4 for
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dx.doi.org/10.1021/om400143u | Organometallics XXXX, XXX, XXX−XXX