Synthesis of Complexes with Protic NH,NR-NHC Ligands by Oxidative Addition of N-Alkyl-2-iodoimidazoles to [M(PPh3)4] (M = Pd, Pt) Complexes

Article abstract of DOI:10.1002/ejic.201700403

The oxidative addition of N-methyl-2-iodoimidazole (1) or N-benzyl-2-iodoimidazole (2) to complexes [Pd(PPh₃)₄] or [Pt(PPh₃)₄] followed by the protonation of the unsubstituted imidazolato ring nitrogen atom yielded complexes trans-[M(NH,NMe-NHC)(PPh₃)₂I]PF₆ (M = Pd: trans-[3]PF₆; M = Pt: trans-[4]PF₆) and trans-[M(NH,NBz-NHC)(PPh₃)₂I]PF₆ (M = Pd: trans-[5]PF₆; M = Pt: trans-[6]PF₆) bearing imidazole-derived protic NH,NR-NHC (pNHC) ligands. In the absence of a proton source, the reaction of 1 with [Pd(PPh₃)₄] yielded the dinuclear dipalladium complex [7] featuring bridging imidazolato ligands metalated at the C2 ring-carbon atom and the N3 ring-nitrogen atom. Palladium complex trans-[3]PF₆ undergoes halogen abstraction with AgPF₆ to give acetonitrile complex trans-[Pd(NCCH₃)(NH,NMe-NHC)(PPh₃)₂](PF₆)₂ trans-[8](PF₆)₂. This complex reacts further with 1,10-phenanthroline (phen), affording complex [Pd(NH,NMe-NHC)(PPh₃)(phen)](PF₆)₂ [9](PF₆)₂.

Full text of DOI:10.1002/ejic.201700403

A Journal of
Accepted Article
Title: Synthesis of Complexes with Protic NH,NR-NHC Ligands by
Oxidative Addition of N-Alkyl-2-iodoimidazoles to [M(PPh3)4] (M
= Pd, Pt) Complexes
Authors: Ekkehardt Hahn, Hanpeng Jin, and Peter Kluth
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10.1002/ejic.201700403
European Journal of Inorganic Chemistry
FULL PAPER
DOI: 10.1002/chem.200((……))
Synthesis of Complexes with Protic NH,NR-NHC Ligands by Oxidative Addition of
N-Alkyl-2-iodoimidazoles to [M(PPh3)4] (M = Pd, Pt) Complexes
Hanpeng Jin, Peter Kluth and F. Ekkehardt Hahn*
Abstract: The oxidative addition of N-methyl-2-iodoimidazole 1 or N-benzyl-2-iodoimidazole 2 to complexes [Pd(PPh3)4] or [Pt(PPh3)4]
followed by the protonation of the unsubstituted imidazolato ring-nitrogen atom yielded complexes trans-[M(NH,NMe-NHC)(PPh3)2I]PF6
(M = Pd: trans-[3]PF6; M = Pt: trans-[4]PF6) and trans-[M(NH,NBz-NHC)(PPh3)2I]PF6 (M = Pd: trans-[5]PF6); M = Pt: trans-[6]PF6)
bearing imidazole derived protic NH,NR-NHC (pNHC) ligands. In the absence of a proton source, the reaction of 1 with [Pd(PPh3)4] yielded
the dinuclear dipalladium complex [7] featuring bridging imidazolato ligands metalated at the C2 ring-carbon atom and the N3 ring-nitrogen
atom. Palladium complex trans-[3]PF6 undergoes halogen abstraction with AgPF6 to give acetonitrile complex trans-[Pd(NCCH3)(NH,NMe-
NHC)(PPh3)2](PF6)2 trans-[8](PF6)2. This complex reacted further with 1,10-phenanthroline (phen), affording complex [Pd(NH,NMe-
NHC)(PPh3)(phen)](PF6)2 [9](PF6)2.
Introduction
Early on, complexes bearing protic NHC ligands have been
obtained by the template controlled cyclization of β-functionalized
isocyanides.[7],[10] More recently, the oxidative addition of N-alkyl-
2-halogenobenzimidazoles[5] or 2-halogenoazoles[6a,b] to complexes
of low-valent transition metal has been developed. These reactions
initially yield complexes bearing azolato ligands, which in the
presence of a proton source give the complexes with the protic NHC
ligands (types B or C Scheme 2). The initially formed azolato
complexes have occasionally been isolated.[5c,d]
The last two decades have experienced intensive research on stable
N-heterocyclic carbenes (NHCs) first described by Arduengo et
al.[1] Conventional NHCs bearing alkyl substituents at both ring-
nitrogen atoms (type A in Figure 1)[2] exhibit superb donor
properties and their complexes have consequently found multiple
applications in homogeneous catalysts[3] and diverse other areas.[4]
Recently, complexes of protic NHCs, i.e. of NHCs with an NH,NR
(type B)[5] or NH,NH substitution pattern (type C),[6] have attracted
attention. The N-H group found in these protic NHC ligands has
proven useful for the subsequent substitution (N-alkylation) of the
coordinated pNHC ligand,[7] as molecular recognition unit[8] and in
the activation of molecular hydrogen and catalytic hydrogenation
reactions.[9]
Scheme 1. Synthesis of complexes with pNHC ligands by oxidative addition
of the C2X bond of 2-halogenoazoles.
Since the C2I bond of azoles is the weakest one in the series of
C2X (X = Cl, Br, I) bonds, we intuitively assumed that the
oxidative addition of this bond to low-valent transition metals would
be most facile. This was, however, not observed. So far the C2−I
oxidative addition was only observed in two cases with Pd0 and
unsubstituted 2-iodoimidazole or 2-iodobenzimidazole to give
NH,NH-NHC complexes of type C. The oxidative addition of 2-
iodoimidazole to Pt0 yields only decomposition products while the
oxidative addition of N-alkyl-2-iodoazoles has not been studied yet.
Herein we describe the synthesis of two N-alkyl-2-
iodoimidazoles, their oxidative addition to complexes of type
[M(PPh3)4] (M = Pd, Pd) followed by protonation of the initially
formed azolato ligand and some ligand substitution reactions with
the complex of type [Pd(pNHC)(PPh3)2I].
Figure 1. Complexes with classical NHC (A) and protic NH,NR- (B) and
NH,NH-NHC ligands (C).
[a] Dr. Hanpeng Jin, Peter Kluth, Prof. Dr. F. Ekkehardt Hahn
Institut für Anorganische und Analytische Chemie
Westfälische Wilhelms-Universität Münster
Corrrensstraße 30, D-48149 Münster (Germany)
Fax: (+49) 251-833-3108
E-mail: fehahn@uni-muenster.de
http://www.uni-muenster.de/Chemie.ac/hahn/index.html
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic2017xxxxx
1
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10.1002/ejic.201700403
European Journal of Inorganic Chemistry
Results and Discussion
= 928.1040 (calcd 928.1049 for cation [4]+), both with the correct
isotope distribution for the respective cations.
Using previously described procedures,[11] we initially prepared the
N-methyl-2-iodoimidazole 1 and N-benzyl-2-iodoimidazole 2 by
iodation of the N-alkylimidazoles with elemental iodine (Scheme 2).
The composition and coordination geometry of complexes
trans-[3]PF6 and trans-[4]PF6 was unequivocally established by X-
ray diffraction studies (Figure 2). Crystals of the composition trans-
[3]PF6·CH2Cl2 and trans-[4]PF6·CH2Cl2 were obtained by slow
vapor diffusion of diethyl ether into saturated dichloromethane
solutions of the complexes at ambient temperature. The structure
analyses confirmed the trans-arrangement of the two phosphine
ligands in both complexes. A slightly distorted square-planar
coordination geometry around the metal atoms was observed for
both complexes with bond angles P1–M–P2 (M = Pd: 176.42(7)°; M
= Pt: 175.98(5)°) and I–Pd–C2 (M = Pd: 176.6(2)°; M = Pt:
177.03(13)°). In both complexes, the plane of the NHC ligand is
oriented almost perpendicular relative to the MCP2I plane. The
M−C2 bond length (M = Pd: 1.989(7) Å; M = Pt: 1.983(4) Å) fall in
the typical range for mononuclear palladium[5a] and platinum[5c]
complex cations of type trans-[M(NH,NR-NHC)(PPh3)2X]+ or
trans-[M(NH,NH-NHC)(PPh3)2X]+.[6b] The iodo ligand in trans-
position to the pNHC ligand does not lead to a significant change of
the MC2 bond lengths when compared to similar complexes
bearing an chlorido or bromo ligand in trans-position to the pNHC
ligand. The N1–C2–N3 bond angles of 104.7(6)° (M = Pd) and
104.5(4)° (M = Pt) fall in the typical range for classical NR,NR-
NHC ligands and the N1C2 and N3C2 bond lengths in both
cations are identical within experimental error. These observations
indicate that the pNHC ligands feature metric parameters and
bonding characteristics rather similar to those of classical NR,NR-
NHCs.[2]
Scheme 2. Synthesis of N-alkyl-2-iodomimidazoles 1 and 2.
Next, the oxidative addition of 1 to complexes [M(PPh3)4] (M =
Pd, Pt) in the presence of an excess of NH4PF6 as proton source was
studied. These reactions proceed smoothly in toluene at 100 °C over
6 hours to give complexes trans-[3]PF6 and trans-[4]PF6 in good
yields of 90% and 70%, respectively (Scheme 3). In both cases, only
the trans-complexes were obtained in contrast to the oxidative
addition of N-methyl-2-chlorobenzimidazole to [Pt(PPh3)4] which
always yielded some of the cis-complex.[5a,c] The reaction time for
the completion of the oxidative addition drops from 6 d for N-
methyl-2-chlorobenzimidazole[5a] to only 6 h for the N-methyl-2-
iodoimidazole.
Scheme 3. Synthesis of complexes trans-[3]PF6 and trans-[4]PF6.
Complexes trans-[3]PF6 and trans-[4]PF6, were completely
characterized by NMR spectroscopy and mass spectrometry. In the
1H NMR spectra, the characteristic resonances for the N-H ring
protons in these complexes were observed as singlets at  = 10.00
and  = 9.75 ppm, respectively. The chemical shifts for these
resonances fall in the range previously observed for the N-H
resonances of palladium and platinum complexes of types
[M(NH,NR-NHC)(PPh3)2X][5] and [M(NH,NH-NHC)(PPh3)2X].[6]
The protons on the triphenylphosphine ligands appeared in the range
of  = 7.64–7.57 ppm (m, 12H, Ph–Hortho), 7.50–7.45 ppm (m, 6H,
Ph–Hpara) and 7.45–7.38 ppm (m, 12H, Ph–Hmeta) for trans-[3]PF6
and at very similar chemical shifts for trans-[4]PF6. The 13C{1H}
NMR spectrum of trans-[3]PF6 spectrum exhibited a triplet at  =
161.7 ppm (2JC,P = 9.8 Hz) for the CpNHC carbon atom while the
equivalent resonance for platinum complex trans-[4]PF6 was
recorded upfield at  = 149.8 ppm (2JC,P = 9.7 Hz). The triplets for
the CpNHC resonances indicate coupling to two chemically equivalent
phosphorus atoms and this implies that the complexes possess the
trans-geometry. Consequently, only one signal for the two
equivalent PPh3 ligands was recorded in the 31P{1H} NMR spectra
of trans-[3]PF6 ( = 18.3 ppm) and trans-[4]PF6 ( = 13.5 ppm, Pt-
Figure 2. Molecular structures of trans-[3]+ in trans-[3]PF6·CH2Cl2 (left) and
trans-[4]+ in trans-[4]PF6·CH2Cl2 (right). Hydrogen atoms, except for the
NH protons, have been omitted for clarity. Selected bond lengths [Å] and
angles [°] for trans-[3]+ (M = Pd) and [trans-[4]+ (M = Pt)]: M–I 2.6170(6)
[2.6282(4)], M–P1 2.341(2) [2.3189(12)], M–P2 2.331(2) [2.3228(12)], M–
C2 1.989(7) [1.983(4)], N1–C2 1.361(10) [1.352(6)], N3–C2 1.353(9)
[1.337(6)]; I–M–P1 91.77(4) [87.75(3)], I–M–P2 88.16(5) [91.23(3)], I–M–
C2 176.6(2) [177.03(13)], P1–M–P2 176.42(7) [175.98(5)], P1–M–C2
91.3(2) [89.48(14)], P2–M–C2 88.9(2) [91.61(14)], N1–C2–N3 104.7(6)
[104.5(4)].
In order to demonstrate the general applicability of the oxidative
addition of the C2I bond of N-alkyl-2-iodoimidazoles for the
preparation of pNHC complexes, we have also prepared N-benzyl-2-
iodoimidazole 2 (Scheme 1). Ligand precursor 2 was reacted with
complexes [M(PPh3)4] (M = Pd, Pt) in the presence of an excess of
NH4PF6 in toluene to give, after a reaction time of 16 h (M = Pd) or
20
h (M = Pt), complexes trans-[5]PF6 and trans-[6]PF6,
respectively, in good yields (Scheme 4). Again, only the formation
of the trans-complexes was observed. The reaction time for
completion of the reaction was significantly longer than observed
for the oxidative addition of N-methyl-2-iodoimidazole, possibly
due to the larger steric demand of the pNHC resulting from ligand
precursor 2 and a slightly different electronic situation.
1
satellites, JPt,P = 2455 Hz), respectively. The high-resolution
electrospray ionization (HR-ESI) mass spectra for trans-[3]PF6 and
trans-[4]PF6 (positive ions) showed peaks with the highest intensity
peaks at m/z = 839.0453 (calcd 839.0448 for cation [3]+) and at m/z
2
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10.1002/ejic.201700403
European Journal of Inorganic Chemistry
[7] in the solid state. The complex is built from two Pd(PPh3)I-
moieties connected by two C,N-metalated imidazolato ligands
(Figure 3, right). The metric parameters measured for [7] fall in the
expected range. The palladium atoms are coordinated in a slightly
distorted square-planar geometry. Metalation of the ring-nitrogen
atom of the imidazolato ligand leads to inner-ring C−N−C angles
which are identical within experimental error (C2−N1−C5
109.1(2)°, C2−N3−C4 108.5(2)°; C42−N41−C45 109.0(2)°,
C42−N43−C44 108.3(2)), while azolato ligands with a “free” ring-
nitrogen atom (Scheme 5, D) feature small C−Nfree−C and larger
C−Nalkyl−C inner-ring angles.[5c,d,],[6c,d] The C,N-metalation of
azolato ligands has been observed before.[5c],[12]
Scheme 4. Synthesis of complexes trans-[5]PF6 and trans-[6]PF6.
Complexes trans-[5]PF6 and trans-[6]PF6 were also completely
characterized by NMR spectroscopy and mass spectrometry. The 1H
spectra of trans-[5]PF6 and trans-[6]PF6 resemble those of trans-
[3]PF6 and trans-[4]PF6, by featuring a strongly downfield shifted
N-H proton resonance at   9.8 ppm. The 13C{1H} spectra feature
triplets for the CpNHC carbon atom with coupling to two chemically
identical phosphorus atoms thereby indicating a trans-configuration
of the phosphine ligands. The chemical shift of the CpNHC resonance
is not significantly affected by the change of the N-substituent from
2
methyl to benzyl ( = 161.3 ppm, JC,P = 9.3 Hz for trans-[5]PF6; 
2
= 149.2 ppm, JC,P = 9.7 Hz) for trans-[6]PF6). The high-resolution
electrospray ionization (HR-ESI) mass spectrum (positive ions)
showed the highest intensity peaks at m/z = 915.0754 (calcd for [5]+
915.0763) and at m/z = 1004.1361 (calcd for [6]+ 1004.1363), both
with the correct isotope distribution for the respective cations.
At this point it appears that N-alkyl-2-iodoimidazoles behave
analogously to the other N-alkyl-2-halogenoazoles in oxidative
addition reactions. Since NH4PF6 is normally not acidic enough to
protonate N-alkylazoles, we assume that the formation of complexes
trans-[3]PF6trans-[6]PF6 proceeds by an initial oxidative addition
of the C2I bond of the imidazoles followed by protonation of the
ring-nitrogen atom of the formed azolato ligand. In order to
establish this reaction sequence, N-methyl-2-iodoimidazole was
reacted with an equimolar amount of [Pd(PPh3)4] in toluene in the
absence of a proton source (Scheme 5). This reaction yielded
complex [7] in an excellent yield of 95%.
Figure 3. Molecular structure of one molecule of [7] in [7]·2CH2Cl2. The
asymmetric unit contains two almost identical units of [7]·2CH2Cl2, only one
of which is depicted. Left: molecular structure of [7] with hydrogen atoms
omitted for clarity. Right: side view of [7] with P-phenyl groups and
hydrogen atoms omitted for clarity. Selected bond lengths [Å] and angles [°]:
Pd1–I1 2.6640(3), Pd1–P1 2.2687(6), Pd1–N43 2.061(2), Pd1–C2 2.002(3),
Pd2–I2 2.6695(3), Pd2–P2 2.2759(7), Pd2–N3 2.062(2), Pd2–C42 1.988(2),
N1−C2 1.362(3), N3−C2 1.341(3), N41−C42 1.366(3), N43−C42 1.339(3);
I1–Pd1–P1 92.92(2), I1–Pd1–N43 89.73(6), I1–Pd1–C2 175.37(7), P1–Pd1–
N43 174.79(6), P1–Pd1–C2 91.71(7), N43–Pd1–C2 85.64(9), I2–Pd2–P2
93.90(2), I2–Pd2–N3 90.15(6), I2–Pd2–C42 170.81(7), P2–Pd2–N3
171.32(6), P2–Pd2–C42 92.72(7), N3–Pd2–C42 84.17(9), C2–N1–C5
109.1(2), C2– N3–C4 108.5(2), C42–N41–N45 109.0(2), C42–N43–C44
108.3(2), N1–C2–N3 107.5(2), N41–C42–N43 107.7(2).
The isolation of trans-[3]PF6 in the presence of a proton source
and of [7] in the absence of a proton source indicates that complexes
of type D (Scheme 5) are indeed initially formed in the oxidative
addition of the C2−I bond of N-alkyl-2-iodoazoles to Pd0
complexes. The intermediate complex D features an imidazolato
ligand with a strongly nucleophilic ring-nitrogen atom which can
attack the metal atom of a second molecule of D. Such an attack,
after loss of two phosphine ligands, leads to dinuclear complex [7].
Next, the reactivity of pNHC complex trans-[3]PF6 was
investigated. Removal of the iodo ligand was achieved by reaction
of trans-[3]PF6 with an equimolar amount of AgPF6 in acetonitrile.
The vacant coordination site was then occupied by an acetonitrile
molecule to give complex trans-[8](PF6)2 in 96% yield (Scheme 6).
Complex trans-[8](PF6)2 was characterized by NMR spectroscopy.
The 13C{1H} NMR spectrum features the CpNHC resonance as a
triplet at  = 149.2 ppm upfield shifted from the equivalent
resonance observed for trans-[3]PF6 ( = 161.7 ppm). The
resonances for the carbon atoms of the acetonitrile ligand were
recorded at  = 127.2 and 1.8 ppm, clearly downfield from the
resonances of free acetonitrile.
Scheme 5. Synthesis of complex [7].
Complex [7] is highly symmetrical in solution and this leads to
rather simple NMR spectra. In the 1H NMR spectrum, the
resonances at  = 6.61 and 5.74 ppm were assigned to the protons
attached to the NHC backbone (H5 and H4, respectively). The
13C{1H} NMR spectrum exhibited a singlet at  = 159.5 ppm
assigned to the Cimidazolato carbon atom. Only one resonance at  =
24.6 ppm was detected in the 31P NMR spectrum for the
triphenylphosphine ligands. The high-resolution electrospray
ionization (HR-ESI) mass spectrum (positive ions) showed the peak
with the highest intensity at m/z = 1154.8995 (calcd for [[7]+H]+
1154.8988) with the correct isotope distribution.
The dinuclear nature of complex [7] was confirmed by an X-ray
diffraction study (Figure 3). Crystals of composition [7]·2CH2Cl2
were obtained by slow vapor diffusion of diethyl ether into a
saturated dichloromethane solution of complex [7] at ambient
temperature. While complex [7] exhibits C2-symmetry in solution as
demonstrated by NMR spectroscopy, Ci symmetry was observed for
Substitution of a phosphine ligand from trans-[8](PF6)2 was
achieved by reaction of with anhydrous 1,10-phenantroline in
dichloromethane. This reaction yielded complex [9](PF6)2 in 90%
yield (Scheme 6).
3
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10.1002/ejic.201700403
European Journal of Inorganic Chemistry
Conclusion
We have shown that N-alkyl-2-iodoimidazoles in the presence of
NH4PF6 react in an oxidative addition reaction with [M(PPh3)4] (M
= Pd, Pt) in a similar fashion as the previously studied N-alkyl-2-
chloro- and N-alkyl-2-bromoazoles. Only complexes of type trans-
[M(NH,NR-NHC)(PPh3)2I] were isolated with no cis-complexes
detectable. The oxidative addition of the C2−I bond proceeds faster
than that of the related C2−X (X = Cl, Br) bonds. In the absence of a
proton source, N-methyl-2-iodoimidazole reacts with [Pd(PPh3)4] to
give the dinuclear complex [7] containing two bridging C,N-
metalated imidazolato ligands. Ligand substitution reactions were
performed with palladium complex trans-[3]PF6 bearing a pNHC
ligand. Removal of the iodo ligand with AgPF6 led to the
acetonitrile adduct [8](PF6)2. Reaction of [8](PF6)2 with 1,10-
phenanthroline proceeded under substitution of one of the phosphine
ligands to give [9](PF6)2.
Scheme 6. Synthesis of complexes trans-[8](PF6)2 and [9](PF6)2 by ligand
exchange.
Formation of compound [9](PF6)2 was confirmed by NMR
1
spectroscopy. The H NMR spectrum features the resonance for the
N-H proton of the NH,NMe-NHC ligand at  = 10.93 ppm slightly
downfield shifted from the resonance for trans-[3]PF6 ( = 10.00
ppm). The 13C{1H} NMR spectrum exhibited a doublet at 152.5
ppm (2JC,P = 16.1 Hz) for the carbene carbon with coupling to the
phosphorus atom. This resonance is downfield shifted relative to the
equivalent resonance in the starting material trans-[3]PF6 ( = 161.7
ppm).[13] All resonances for the 1,10-phenanthroline ligand were
observed and assigned. The high-resolution electrospray ionization
(HR-ESI) mass spectrum (positive ions) featured the most intense
peak at m/z = 315.0579 (calcd for [9]2+ 315.0588) with the correct
isotope distribution.
The composition and coordination geometry of [9](PF6)2 was
established by an X- ray diffraction study (Figure 4). Crystals of
composition [9](PF6)2·2CH2Cl2 were obtained by slow vapor
diffusion of diethyl ether into a saturated dichloromethane solution
of [9](PF6)2. The structure analysis revealed a slightly distorted
square-planar coordination geometry around the palladium atom
with bond angles N4–Pd–C2 172.79(12)° and P– Pd–N5 178.14(8)°.
The 1,10-phenanthroline ligand maintains a planar structure in plane
with the palladium coordination plane. The pNHC ligand is oriented
roughly perpendicular to the coordination plane as was observed for
the other pNHC complexes described before. The metric parameters
of the NH,NMe-NHC ligand fall into the range observed previously
for protic NHC ligands. The Pd−P bond distance (2.2716(8) Å) is
shorter than in the trans-diphosphine complex trans-[3]PF6.
Experimental Section
General Procedures. All preparations were carried out under an argon
atmosphere using conventional Schlenk techniques or in a glovebox.
Solvents were dried and degassed by standard methods prior to use. NMR
spectra were recorded on a Bruker Avance I 400 or a Bruker Avance III 400
NMR spectrometer. Chemical shifts () are expressed in ppm downfield
from tetramethylsilane by using the residual protonated solvent signals as
internal standard. Coupling constants are expressed in Hertz. ESI-HRMS
spectra were obtained with an Orbitrap LTQ XL (Thermo Scientific)
spectrometer.
Imidazole,
N-methylimidazole,
1,10-phenanthroline,
[Pd(PPh3)4] and [Pt(PPh3)4] were purchased from commercial sources and
were used as received. For assignment of the NMR resonances see the
numbering at the molecular plots. Satisfactory elemental analyses of
compounds trans-[3]PF6 − [9](PF6)2 were difficult to obtain due to the
sensitivity of the compounds towards oxygen and moisture and the presence
of PF6 anions. A complete set of NMR spectra and ESI-HRMS mass spectra
is provided in the Supporting Information instead.
Synthesis of N-methyl-2-iodoimidazole 1.[11] Under an argon atmosphere,
N-methylimidazole (2.87 g, 2.8 mL, 35 mmol) was
dissolved in THF (150 mL) and the solution was cooled to
–78 °C. Over 1 h, a THF solution of n-butyl lithium (35
mmol, 21.9 mL of a 1.6 M solution) was added dropwise
and the mixture was stirred for
2 h at –78 °C.
Subsequently, a THF solution of iodine (10.7 g, 42 mmol in 40 mL of THF)
was added slowly and the reaction mixture was allowed to warm up to
ambient temperature over 3 h. The reaction was stopped by addition of a
saturated aqueous solution of Na2S2O3 (1 mL). The solvent was removed in
vacuo and the solid residue was extracted twice with chloroform (20 mL
each). The combined organic phase was washed twice with saturated
aqueous solutions of Na2S2O3 (30 mL each) and brine (20 mL each) and was
then dried over Na2SO4. Removal of the solvent in vacuo followed by
column chromatography (silica gel, CHCl3:MeOH = 10:1, v:v) gave 1 as an
off-white solid. Yield: 6.3 g (30.3 mmol, 87%). 1H NMR (400 MHz, CDCl3):
 = 7.02 (d, 3JH,H = 1.1 Hz, 1H, H4), 6.99 (d, 3JH,H = 1.1 Hz, 1H, H5), 3.58 (s,
3H, H6). 13C{1H} NMR (100 MHz, CDCl3):  = 132.3 (C4), 124.0 (C5), 90.8
(C2), 36.6 (C6). HRMS (ESI, positive ions): m/z = 230.9391 (calcd for
[1+Na]+ 230.9395).
Synthesis of N-benzyl-2-iodoimidazole 2.[11] To a solution of imidazole
(2.73 g, 41 mmol) in DMF (20 mL) was added
Figure 4. Molecular structure of [9]2+ in [9](PF6)2·2CH2Cl2. Hydrogen atoms,
except for the N-H proton, have been omitted for clarity. Selected bond
lengths [Å] and angles [°]: Pd–P 2.2716(8), Pd–N4 2.105(3), Pd–N5
2.090(3), Pd–C2 1.977(3), N1–C2 1.337(5), N3–C2 1.340(5); P–Pd–N4
99.26(7), P–Pd–N5 178.14(8), P–Pd–C2 87.60(9), N4–Pd–N5 80.13(10),
N4–Pd–C2 172.79(12), N5–Pd–C2 92.94(12), N1–C2–N3 105.5(3).
NaH (1.76 g, 60% in paraffin, 44 mmol) in small
portions at 0 °C. The mixture was stirred for 1 h at
0 °C. Then benzyl bromide (6.85 g, 4.76 mL, 40
mmol) was added to the mixture in one portion.
The solution was allowed to warm up ambient
temperature and was stirred at this temperature
stirred for 5 h. Removal of the solvent in vacuo gave a solid residue which
was isolated, dissolved in dichloromethane and washed with brine. Further
4
This article is protected by copyright. All rights reserved.

10.1002/ejic.201700403
European Journal of Inorganic Chemistry
purification was achieved by recrystallization from CH2Cl2/hexane. N-
benzylimidazole was obtained as white needles. Yield: 3.04 g (19.2 mmol,
48%). The N-benzylimidazole obtained from the previous reaction was used
for the iodation. Under an argon atmosphere, 3.04 g of N-benzylimidazole
were dissolved in THF (50 mL) and the solution was cooled to −78 °C. Over
1 h at −78 °C, a THF solution of n-butyl lithium (12.5 mL of a 1.6 M
solution, 20 mmol) was added dropwise and the mixture was stirred for 2 h
at −78 °C. Subsequently, a THF solution of iodine (5.1 g, 20 mmol in 40 mL
of THF) was added slowly and the reaction mixture was allowed to warm up
to ambient temperature and stirred for 3 h at this temperature. Then, a
saturated aqueous solution of Na2S2O3 (1 mL) was added to stop the reaction.
The solvent was removed in vacuo and the solid residue was extracted twice
with chloroform (20 mL each). The organic phase was washed twice with
saturated aqueous solutions of Na2S2O3 (30 mL each) and brine (20 mL each).
The organic phase was dried over Na2SO4 and the solvent was removed in
vacuo. Column chromatography (silica gel, CHCl3:MeOH = 50:1, v:v) gave
2 as off-white solid. Yield: 3.00 g (10.6 mmol, 55.2% relative to N-
benzylimidazole from the first reaction step. 1H NMR (400 MHz, CDCl3): 
Synthesis of complex trans-[5]PF6. Samples of N-benzyl-2-iodoimidazole 2
(28 mg, 0.1 mmol), [Pd(PPh3)4] (115 mg, 0.1
H
PF6
mmol) and NH4PF6 (49 mg, 0.3 mmol) were
suspended in toluene (10 mL). The reaction
mixture was heated at 100 °C for 16 h. Then
the solvent was removed in vacuo and the
solid residue was washed with hexane (3 ×
10 mL) and diethyl ether (3 × 10 mL). The
solid was suspended in dichloromethane (20
mL) and filtered to obtain a clear solution.
PPh3
Pd
N
4
5
2
I
N
PPh3
6
7
8
10
9
After removal of the solvent and drying in vacuo, complex trans-[5]PF6 was
1
obtained as yellow powder. Yield: 91 mg (0.09 mmol, 90%). H NMR (400
MHz, CD2Cl2):  = 9.85 (s, 1H, N-H), 7.58 (m, 12H, Ph-Hortho), 7.48 (m, 6H,
Ph-Hpara), 7.40 (m, 12H, Ph-Hmeta), 7.26 (m, 1H, H10), 7.13 (m, 2H, H9),
6.94 (m, 2H, H8), 6.43 (m, 1H, H4), 6.20 (m, 1H, H5), 4.75 (s, 2H, H6).
2
13C{1H} NMR (100 MHz, CD2Cl2):  = 161.3 (t, JC,P = 9.3 Hz, C2), 134.9
2/4
(v-t,
J
J
C,P
= 6.1 Hz, Ph-Cortho), 133.1 (s, C7), 131.5 (s, Ph-Cpara), 131.2 (t,
1/3
= 25.8 Hz, Ph-Cipso), 129,7 (s, C10), 129.5 (s, C8), 129.5 (s, C9), 129.1
C,P
= 7.34 (m, 3H, H9 and H10), 6.99 (d, JH,H = 7.2 Hz, 2H, H8), 7.11 (d, JH,H
=
(t, 3/5J C,P = 5.7 Hz, Ph-Hmeta), 122.5 (s, C4), 120.7 (s, C5), 55.3 (s, C6).
1.1 Hz, 1H, H4), 7.00 (d, JH,H = 1.1 Hz, 1H, H5), 5.09 (s, 2H, H6). 13C{1H}
NMR (100 MHz, CDCl3):  = 135.6 (C7), 132.9 (C4), 128.9 (C8), 128.2
(C10), 127.2 (C9), 123.3 (C5), 90.6 (C2), 53.0 (C6). HRMS (ESI, positive
ions): m/z = 306.9710 (calcd for [2+Na]+ 306.9708).
31P{1H} NMR (162 MHz, CD2Cl2):  = 18.3 (s, PPh3), –144.2 (sept, 1JF,P
=
712.4 Hz, PF6). 19F{H} NMR (376 MHz, CD2Cl2):  = –71.9 (d, 1JF,P = 712.4
Hz, PF6). HRMS (ESI, positive ions): m/z = 915.0754 (calcd for [5]+
915.0763).
Synthesis of complex trans-[3]PF6. A mixture of N-methyl-2-iodoimidazole
1 (208 mg, 1.0 mmol), [Pd(PPh3)4] (1155 mg, 1.0
Synthesis of complex trans-[6]PF6. A mixture of N-benzyl-2-iodoimidazole
2 (28 mg, 0.1 mmol), [Pt(PPh3)4] (125 mg, 0.1
mmol) and NH4PF6 (326 mg, 2.0 mmol) were
mmol) and NH4PF6 (49 mg, 0.3 mmol) were
suspended in toluene (50 mL). The reaction
suspended in toluene (10 mL). The reaction
mixture was heated at 100 °C for 6 h. The solvent
mixture was heated at 100 °C for 20 h. The
was then removed in vacuo and the residue was
solvent was then removed in vacuo and the
washed with pentane (3 × 20 mL) and diethyl
residue was washed with hexane (3 × 10 mL)
ether (3 × 20 mL). The obtained solid was suspended in dichloromethane (20
mL) and the mixture was filtered to obtain a clear solution. After removal of
the solvent in vacuo complex trans-[3]PF6 was obtained as pale yellow
powder. Yield: 887 mg (0.9 mmol, 90%). 1H NMR (400 MHz, CD2Cl2):  =
10.00 (s, 1H, N-H), 7.64−7.57 (m, 12H, Ph-Hortho), 7.50−7.45 (m, 6H, Ph-
and diethyl ether (3 × 10 mL). The solid was
then suspended in dichloromethane (20 mL)
and filtered to obtain a clear solution. After
removal of the solvent and drying in vacuo complex trans-[6]PF6 was
obtained as white powder. Further purification was achieved by
recrystallization from CH2Cl2/Et2O. Yield: 84 mg (0.07 mmol, 70%). 1H
NMR (400 MHz, CD2Cl2):  = 9.71 (s, 1H, N-H), 7.60 (m, 12H, Ph-Hortho),
7.48 (m, 6H, Ph-Hpara), 7.40 (m, 12H, Ph-Hmeta), 7.25 (m, 1H, H10), 7.11 (m,
2H, H9), 6.98 (m, 2H, H8), 6.29 (pseudo-t, 1H, H4), 6.15 (pseudo-t, 1H, H5),
4.75 (s, 2H, H6). 13C{1H} NMR (100 MHz, CD2Cl2):  = 149.2 (t, 2JC,P = 9.7
H
para), 7.45−7.38 (m, 12H, Ph-Hmeta), 6.47 (pseudo-t, 1H, H4), 6.19 (pseudo-t,
1H, H5), 3.25 (s, 3H, H6). 13C{1H} NMR (100 MHz, CD2Cl2):  = 161.7 (t,
2JC,P = 9.8 Hz, C2), 134.8 (v-t,
130.9 (v-t,
J
= 6.2 Hz, Ph-Cortho), 131.6 (Ph-Cpara),
2/4
C,P
1/3
3/5
J
C,P
= 25.9 Hz, Ph-Cipso), 129.1 (v-t,
J
C,P
= 5.4 Hz, Ph-Cmeta),
122.4 (C4, C5), 37.3 (C6). 31P{1H} NMR (162 MHz, CD2Cl2):  = 18.3 (s,
PPh3), –144.2 (sept, 1JF,P = 712.3 Hz, PF6). 19F NMR (376 MHz, CD2Cl2):  =
–72.1 (d, 1JF,P = 712.3 Hz, PF6). HRMS (ESI, positive ions): m/z = 839.0453
(calcd for [3]+ 839.0448).
Hz, C2), 135.0 (t, 2/3JC,P = 6.0 Hz, Ph-Cortho), 133.2 (s, C7), 131.6 (s, Ph-Cpara),
1/3
130.5 (t,
J
C,P
= 30.1 Hz, Ph-Cipso), 129.7 (s, C10), 129.6 (s, C8), 129.5 (s,
C9), 129.0 (t, 3/4JC,P = 5.4 Hz, Ph-Hmeta), 120.8 (s, C4), 119.8 (s, C5), 54.8 (s,
C6). 31P{1H} NMR (162 MHz, CD2Cl2):  = 13.5 (s, Pt satellites,
1JPt,P = 2464 Hz, PPh3), −144.2 (sept, 1JF,P = 712.2 Hz, PF6). 19F NMR (376
MHz, CD2Cl2):  = 72.0 (d, 1JF,P = 712.2 Hz, PF6). 195Pt{1H} NMR (376
MHz, CD2Cl2):  = –4797.1 (v-t, 1JPt,P = 2464 Hz). HRMS (ESI, positive
ions): m/z = 1004.1361 (calcd for [6]+ 1004.1363).
Synthesis of complex trans-[4]PF6. A mixture of N-methyl-2-iodoimidazole
1 (210 mg, 0.1 mmol), [Pt(PPh3)4] (125 mg, 0.1
mmol) and NH4PF6 (490 mg, 3.0 mmol) were
suspended in toluene (30 mL). The reaction
mixture was heated at 100 °C for 6 h.
Subsequently, the solvent was removed in vacuo
and the residue was washed with pentane (3 × 20
Synthesis of complex [7]. A mixture of N-methyl-2-iodoimidazole 1 (41 mg,
0.2 mmol) and [Pd(PPh3)4] (231 mg, 0.2
mL) and diethyl ether (3 × 20 mL). The obtained solid was suspended in
dichloromethane (20 mL) and filtered to give a clear solution. After removal
of the solvent in vacuo complex trans-[4]PF6 was obtained as colorless
powder. Further purification was achieved by recrystallization from
CH2Cl2/Et2O. Yield: 75 mg (0.07 mmol, 70%). 1H NMR (600 MHz,
CD2Cl2):  = 9.75 (s, 1H, N-H), 7.67−7.61 (m, 12H, Ph-Hortho), 7.52−7.47 (m,
6H, Ph-Hpara), 7.46-7.41 (m, 12H, Ph–Hmeta), 6.36 (m, 1H, H4), 6.16 (m, 1H,
mmol) were dissolved in toluene (10 mL).
The reaction mixture was heated at 100 °C
for 2 h and then cooled down to 0 °C. The
resulting suspension was filtered and the
solid was washed with hexane (2 × 10 mL)
and diethyl ether (2 × 10 mL). After drying
in vacuo complex [7] was obtained as a
H5), 3.24 (s, 3H, H6). 13C{1H} NMR (150 MHz, CD2Cl2):  = 149.8 (t, 2JC,P
yellow powder. Yield: 110 mg (0.095 mmol, 95%). 1H NMR (400 MHz,
CDCl3/DMSO-d6 (1:1, v:v)):  = 7.34−7.26 (m, 12H, Ph-Hortho), 6.96−6.89
(m, 6H, Ph-Hpara), 6.81−6.74 (m, 12H, Ph-Hmeta), 6.61 (s, 2H, H5), 5.74 (s,
2H, H4), 2.51 (s, 6H, H6). 13C{1H} NMR (100 MHz, CDCl3/DMSO-d6 (1:1,
2/4
= 9.7 Hz, C2), 134.4 (v-t,
J
= 6.0 Hz, Ph-Cortho), 131.2 (Ph-Cpara), 129.5
C,P
1/3
3/5
(v-t,
J
C,P
= 30.0 Hz, Ph-Cipso), 128.6 (v-t,
J
C,P
= 5.3 Hz, Ph-Cmeta), 121.1
(C5), 120.4 (C4), 36.6 (C6). 31P{1H} NMR (243 MHz, CD2Cl2):  = 13.5 (s,
Pt satellites, JPt,P = 2455 Hz, PPh3), –144.2 (sept, 1JF,P = 712.4 Hz, PF6). 19F
v:v)):  = 159.5 (C2), 134.3 (d, JC,P = 11.0 Hz, Ph-Cortho), 131.0 (d, JC,P =
4
1
2
1
NMR (564 MHz, CD2Cl2):  = –72.1 (d, 1JF,P = 712.4 Hz, PF6). HRMS (ESI,
positive ions): m/z = 928.1040 (calcd for [4]+ 928.1049).
50.9 Hz, Ph-Cipso), 130.1 (C4), 129.6 (d, JC,P = 2.2 Hz, Ph-Cpara), 12.4 (d,
3JC,P = 10.6 Hz, Ph-Cmeta), 119.3 (C5), 34.2 (C6). 31P NMR (162 MHz,
CDCl3/DMSO-d6 (1:1, v:v)):  = 24.6 (s, PPh3). HRMS (ESI, positive ions):
m/z = 1154.8995 (calcd for [7+H]+ 1154.8988).
5
This article is protected by copyright. All rights reserved.

10.1002/ejic.201700403
European Journal of Inorganic Chemistry
Synthesis of complex [8](PF6)2. Samples of complex trans-[3]PF6 (49 mg,
study were obtained by slow diffusion of diethyl ether into a solution of
[4]PF6 in dichloromethane. Formula C41H38N2Cl2F6IP3Pt, M = 1158.53,
colorless needle, 0.46 × 0.08 × 0.05 mm3, orthorhombic, space group P212121,
a = 10.3429(3), b = 18.1857(6), c = 22.9299(7) Å, V = 4313.0(2) Å3, Z = 4,
calcd = 1.784 g·cm3,  = 4.262 mm1, ω- and φ-scans, 78663 intensities
measured in the range 6.2° ≤ 2 ≤ 62.0°, semiempirical absorption
correction (0.244 ≤ T ≤ 0.815), 13663 independent intensities (Rint = 0.0654),
12145 observed intensities [I ≥ 2(I)], refinement of 506 parameters against
all F2 with anisotropic thermal parameters for all non-hydrogen atoms and
0.05 mmol)
and
AgPF6
(13 mg,
0.05 mmol) were suspended in acetonitrile
(10 mL). The reaction mixture was stirred
at ambient temperature for 10 h under
exclusion of light. The resulting
suspension was filtered through a short
pad of celite. The solvent was removed in vacuo to give complex trans-
[8](PF6)2 as a white powder. Yield: 50 mg (0.048 mmol, 96%). 1H NMR
(400 MHz, CD2Cl2):  = 10.22 (s, 1H, N-H), 7.65−7.46 (m, 30H, PPh3),
6.65−6.62 (m, 2H, H4 and H5), 3.23 (s, 3H, H6), 1.40 (s, 3H, H8). 13C{1H}
hydrogen atoms on calculated positions, R = 0.0296, wR = 0.0612, Rall
=
0.0377, wRall = 0.0635. The asymmetric unit contains one formula unit of
[3]PF6·CH2Cl2.
2
NMR (100 MHz, CD2Cl2):  = 149.2 (t, JC,P = 9.0 Hz, C2), 133.9 (v-t,
2/4
3/5
J
C,P
= 6.6 Hz, Ph-Cortho), 132.9 (Ph-Cpara), 130.2 (v-t,
J
C,P
= 5.5 Hz, Ph-
1/3
C
meta), 127.2 (C7), 126.6 (v-t,
J
C,P
= 26.3 Hz, Ph-Cipso), 124.3 (C5), 123.5
Crystal Data for [7]·2CH2Cl2. Crystals suitable for an X-ray diffraction
study were obtained by slow diffusion of diethyl ether into a solution of [7]
in dichloromethane. Formula C46H44N4Cl4I2P2Pd, M = 1323.19, yellow cube,
0.26 × 0.23 × 0.19 mm3, triclinic, space group P1, a = 10.0745(2), b =
20.6752(3), c = 25.2164(4) Å,  = 70.4510(10),  = 83.9120(10),  =
79.6640(10)°, V = 4863.29(15) Å3, Z = 4, calcd = 1.807 g·cm3,  = 2.331
mm1, ω- and φ-scans, 89372 intensities measured in the range 2.1° ≤ 2 ≤
64.0°, semiempirical absorption correction (0.506 ≤ T ≤ 0.746), 30361
independent intensities (Rint = 0.0309), 26081 observed intensities [I ≥ 2(I)],
refinement of 1085 parameters against all F2 with anisotropic thermal
parameters for all non-hydrogen atoms and hydrogen atoms on calculated
positions, R = 0.0316, wR = 0.0737, Rall = 0.0389, wRall = 0.0777. The
asymmetric unit contains two formula unit of [7]·2CH2Cl2.
(C4), 37.7 (C6), 1.8 (C8). 31P{1H} NMR (162 MHz, CD2Cl2):  = 20.5 (s,
PPh3), –144.2 (sept, 1JF,P = 711.1 Hz, PF6). 19F NMR (376 MHz, CD2Cl2):  =
–72.0 (d, 1JF,P = 711.1 Hz, PF6). HRMS (ESI, positive ions): m/z = 747.1082
(calcd for [8−CH3CN+Cl]+ 747.1088).
Synthesis of complex [9](PF6)2. Samples of complex trans-[8](PF6)2 (54 mg,
0.05 mmol) and 1,10-phenanthroline
(9 mg, 0.05 mmol) were dissolved in
dichloromethane (10 mL). The reaction
mixture was stirred at ambient
temperature for 12 h. The solvent was
then removed in vacuo and the solid
residue was washed with diethyl ether (3
×
20 mL). After drying in vacuo
white powder. Yield: 42 mg
Crystal Data for [9](PF6)2·2CH2Cl2. Crystals suitable for an X-ray
diffraction study were obtained by slow diffusion of diethyl ether into a
solution of [9](PF6)2 in dichloromethane. Formula C36H33N4Cl4F12P3Pd, M =
1090.77, colorless prism, 0.42 × 0.23 × 0.19 mm3, triclinic, space group P1,
a = 11.9801(3), b = 13.4209(3), c = 14.6680(3) Å,  = 73.9660(10),  =
85.8570(10),  = 82.1390(10)°, V = 2243.86(9) Å3, Z = 2, calcd = 1.614
g·cm3,  = 0.841 mm1, ω- and φ-scans, 25872 intensities measured in the
range 5.8° ≤ 2 ≤ 60.0°, semiempirical absorption correction (0.638 ≤ T ≤
0.746), 12999 independent intensities (Rint = 0.0228), 11171 observed
intensities [I ≥ 2(I)], refinement of 570 parameters against all F2 with
anisotropic thermal parameters for all non-hydrogen atoms and hydrogen
atoms on calculated positions, R = 0.0550, wR = 0.1576, Rall = 0.0634, wRall
= 0.1657. The asymmetric unit contains one formula unit of [9](PF6)2 one
CH2Cl2 molecule and two CH2Cl2 molecules with SOF = 0.5.
complex [9](PF6)2 was obtained as
a
1
(0.045 mmol, 90%). H NMR (400 MHz, CD2Cl2):  = 10.93 (s, 1H, N-H),
8.74 (dd, 3JH16,H17 = 8.3 Hz, JH16,H18 = 1.3 Hz, 1H, H16), 8.61 (dd, 3JH9,H8
4
4
3
= 8.2 Hz, JH9,H7 = 1.3 Hz, 1H, H9), 8.15 (d, JH14,H15 = 8.8 Hz, 1H, H14),
3
3
8.12 ppm (d, JH15,H14 = 8.8 Hz, 1H, H15), 7.86 (ddd, JH17,H16 = 8.3 Hz,
3JH17,18 = 5.2 Hz, JH17,P = 1.4 Hz, 1H, H17), 7.84−7.76 (m, 6H, Ph-Hortho),
5
7.75 (1H, detected by HMBC, H7), 7.68−7.60 (m, 3H, Ph-Hpara), 7.56−7.50
(m, 6H, Ph-Hmeta), 7.53 (1H, detected by HMBC, H18), 7.39 (dd, 3JH8,H9 = 8.2
3
Hz, JH8,H7 = 5.3 Hz, 1H, H8), 7.11 (m, 1H, H4), 6.96 (m, 1H, H5), 3.80 (s,
3H, H6). 13C{1H} NMR (100 MHz, CD2Cl2):  = 152.5 (d, JC,P = 16.1 Hz,
2
3
C2), 152.0 (d, JC,P = 3.4 Hz, C7), 151.5 (C18), 148.3 (C11), 146.9 (C12),
141.4 (C9), 141.3 (C16), 134.7 (d, JC,P = 11.7 Hz, Ph-Cortho), 133.6 (d,
2
4JC,P = 3.0 Hz, Ph-Cpara), 131.6 (d, 4JC,P = 2.3 Hz, C13), 131.5 (C10), 130.4 (d,
3JC,P = 11.7 Hz, Ph-Cmeta), 128.6 (C14), 128.3 (C15), 126.9 (d, 4JC,P = 3.0 Hz,
C17), 126.5 (d, 1JC,P = 56.8 Hz, Ph-Cipso), 125.5 (d, 4JC,P = 1.0 Hz, C8), 124.7
(C5), 123.2 (C4), 38.3 (C6). 31P NMR (162 MHz, CD2Cl2):  = 29.6 (s, PPh3),
–144.7 (sept, 1JF,P = 712.9 Hz, PF6). 19F NMR (376 MHz, CD2Cl2):  = −72.6
(d, 1JF,P = 712.9 Hz, PF6). HRMS (ESI, positive ions): m/z = 315.0579 (calcd
for [9]2+ 315.0588).
CCDC-1543704 ([3]PF6·CH2Cl2), CCDC-1543705 ([4]PF6·CH2Cl2),
CCDC-1543706 ([7]·2CH2Cl2) and CCDC-1543707 ([9](PF6)2·2CH2Cl2)
contain the 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.
X-Ray Diffraction Studies. X-Ray diffraction data were collected with a
Bruker APEX-II CCD diffractometer equipped with a micro source at
153(2) K using graphite monochromated Mo-K ( = 0.71073 Å) radiation.
Diffraction data were collected over the full sphere and were corrected for
absorption. Structure solutions were found with the SHELXS-97 package[14]
using the heavy-atom method and were refined with SHELXL-97[14] against
F2 using first isotropic and later anisotropic thermal parameters for all non-
hydrogen atoms. Hydrogen atoms were added to the structure models on
calculated positions.
Acknowledgements
This work was supported by the Deutsche Forschungsgemeinschaft (IRTG
2027, SFB 858).
Keywords: N-alkyl-2-iodoimidazoles, oxidative addition, palladium,
platinum, protic NHC ligands
[1] a) A. J. Arduengo, III, R. L. Harlow, M. Kline, J. Am. Chem. Soc. 1991,
113, 361–363.
Crystal Data for [3]PF6·CH2Cl2. Crystals suitable for an X-ray diffraction
study were obtained by slow diffusion of diethyl ether into a solution of [3]
in dichloromethane. Formula C41H38N2Cl2F6IP3Pd, M = 1069.84, yellow
needle, 0.37 × 0.08 × 0.05 mm3, orthorhombic, space group P212121, a =
10.3378(2), b = 18.1780(4), c = 22.9689(5) Å, V = 4316.3(2) Å3, Z = 4, calcd
= 1.646 g·cm3,  = 1.438 mm1, ω- and φ-scans, 78689 intensities measured
in the range 5.8° ≤ 2 ≤ 62.0°, semiempirical absorption correction (0.001 ≤
T ≤ 0.014), 13636 independent intensities (Rint = 0.0502), 11319 observed
intensities [I ≥ 2(I)], refinement of 506 parameters against all F2 with
anisotropic thermal parameters for all non-hydrogen atoms and hydrogen
atoms on calculated positions, R = 0.0674, wR = 0.1599, Rall = 0.0780, wRall
= 0.1687. The asymmetric unit contains one formula unit of [3]PF6·CH2Cl2.
[2] a) M. C. Jahnke, F. E. Hahn, Angew. Chem. 2008, 120, 3166–3216;
Angew. Chem. Int. Ed. 2008, 47, 3122–3172; b) M. Poyatos, J. Mata, E.
Peris, Chem. Rev. 2009, 109, 3677–3707; c) M. Melaimi, M.
Soleilhavoup, G. Bertrand, Angew. Chem. 2010, 122, 8992–9032;
Angew. Chem. Int. Ed. 2010, 49, 8810–8849; d) M. N. Hopkinson, C.
Richter, M. Schedler, F. Glorius, Nature 2014, 510, 485–496.
[3] a) W. A. Herrmann, Angew. Chem. 2002, 114, 1342–1363; Angew.
Chem. Int. Ed. 2002, 41, 1290–1309; b) N. Marion, S. Díez-González,
S. P. Nolan, Angew. Chem. 2007, 119, 3046–3058; Angew. Chem. Int.
Ed. 2007, 46, 2988–3000; c) S. Díez-González, N. Marion, S. P. Nolan,
Chem. Rev. 2009, 109, 3612–3676; d) E. Peris, Chem. Rev. in press,
DOI: 10.1021/acs.chemrev.6b00695.
[4] a) K. M. Hindi, M. J. Panzner, C.A. Tessier, C. L. Cannon, W. J.
Crystal Data for [4]PF6·CH2Cl2. Crystals suitable for an X-ray diffraction
Youngs, Chem. Rev. 2009, 109, 3859–3884; b) L. Mercs, M. Albrecht,
6
This article is protected by copyright. All rights reserved.

10.1002/ejic.201700403
European Journal of Inorganic Chemistry
Chem. Soc. Rev. 2010, 39, 1903–1912: c) W. Liu, R. Gust, Chem. Soc.
Rev. 2013, 42, 755–773; d) A. Rit, T. Pape, F. E. Hahn, J. Am. Chem.
Soc. 2010, 132, 4572–4573; e) A. Rit, T. Pape, A. Hepp, F. E. Hahn,
Organometallics 2011, 30, 334–347; f) F. M. Conrady, R. Fröhlich, C.
Schulte to Brinke, T. Pape, F. E. Hahn, J. Am. Chem. Soc. 2011, 133,
11496–11499; g) M. Schmidtendorf, T. Pape, F. E. Hahn, Dalton Trans.
2013, 42, 16128–16141; h) Y.-F. Han, G.-X. Jin, F. E. Hahn J. Am.
Chem. Soc. 2013, 135, 9263–9266; i) N. Sinha, L. Stegemann, T. T. Y.
Tan, N. L. Doltsinis, C. A. Strassert, F. E. Hahn, Angew. Chem. 2017,
129, 2829–2833; Angew. Chem. Int. Ed. 2017, 56, 2785–2789.
Inorg. Chem. 2007, 9, 1210–1214; b) F. E. Hahn, ChemCatChem 2013,
5, 419−430.
[9] a) V. Miranda-Soto, D. B. Grotjahn, A. G. DiPasquale, A. L.
Rheingold, J. Am. Chem. Soc. 2008, 130, 1320013201; b) V.
Miranda-Soto, D. B. Grotjahn, A. L. Cooksy, J. A. Golen, C. E.
Moore, A. E. Rheingold, Angew. Chem. 2011, 123, 657661; Angew.
Chem. Int. Ed. 2011, 50, 631635; c) S. Cepa, C. Schulte to Brinke, F.
Roelfes, F. E. Hahn, Organometallics 2015, 34, 5454–5460; d) F.
Aznarez, M. Iglesias, A. Hepp, B. Veit, P. J. Sanz Miguel, L. A. Oro,
G.-X. Jin, F. E. Hahn, Eur. J. Inorg. Chem. 2016, 4598–4603.
[5] a) T. Kösterke, T. Pape, F. E. Hahn, J. Am. Chem. Soc. 2011, 133,
21122115; b) T. Kösterke, T. Pape, F. E. Hahn, Chem. Commun.
2011, 47, 1077310775; c) T. Kösterke, J. Kösters, E.-U. Würthwein,
C. Mück-Lichtenfeld, C. Schulte to Brinke, F. Lahoz, F. E. Hahn,
Chem. Eur. J. 2012, 18, 1459414598; d) D. Brackemeyer, A. Hervé,
C. Schulte to Brinke, M. C. Jahnke, F. E. Hahn, J. Am. Chem. Soc.
2014, 136, 78417844.
[10] M. Tamm, F. E. Hahn, Coord. Chem. Rev. 1999, 182, 175209.
[11] a) W. He, Y.-C. Ge, C.-H. Tan, Org. Lett. 2014, 62, 32443247; b) R.
Marcia de Figueiredo, S. Thoret, C. Huet, J. Dubois, Synthesis 2007,
529540.
[12] S. E. Flowers, B. M. Cossairt, Organometallics 2014, 33, 4341–4344.
[13] H. V. Huynh, Y. Han, R. Jothibasu, J. A. Yang, Organometallics 2009,
28, 5395−5404.
[6] a) R. Das, C. G. Daniliuc, F. E. Hahn, Angew. Chem. 2014, 126, 1183–
1187; Angew. Chem. Int. Ed. 2014, 53, 1163–1166; b) R. Das, A. Hepp,
C. G. Daniliuc, F. E. Hahn, Organometallics 2014, 33, 6975–6987; for
reviews on complexes bearing protic NHCs see: c) M. C. Jahnke, F. E.
Hahn, Chem. Lett. 2015, 44, 226–237; d) M. C. Jahnke, F. E. Hahn,
Coord. Chem. Rev. 2015, 293−294, 95–115.
[14] SHELXS-97, SHELXL-97: G. M. Sheldrick, Acta Crystallogr., Sect. A
2008, 64, 112–122.
[7] a) F. E. Hahn, V. Langenhahn, T. Pape, Chem. Commun. 2005, 5390–
5392; b) F. E. Hahn, V. Langenhahn, N. Meier, T. Lügger, W. P.
Fehlhammer, Chem. Eur. J. 2003, 9, 704–712; c) P. G. Edwards, F. E.
Hahn, Dalton Trans. 2011, 40, 1027810288.
Received: ((will be filled in by the editorial staff))
Revised: ((will be filled in by the editorial staff))
Published online: ((will be filled in by the editorial staff))
[8] a) N. Meier, F. E. Hahn, T. Pape, C. Siering, S. R. Waldvogel, Eur. J.
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European Journal of Inorganic Chemistry
Entry for the Table of Contents (Please choose one layout)
FULL PAPER
Protic NHCs
Hanpeng Jin, Peter Kluth and F.
Ekkehardt Hahn*
Page No. – Page No.
N-Alkyl-2-iodoimidazoles react in the presence of NH4PF6 in an oxidative addition
with [M(PPh3)4] (M = Pd, Pt) to give complexes of type trans-[M(NH,NR-
NHC)(PPh3)2I]PF6 with a protic NH,NR-NHC ligand. Substitution reactions of only
the iodo or both the iodo and one of the phosphine ligands in such complexes have
been studied.
Synthesis of Complexes with Protic
NH,NR-NHC Ligands by Oxidative
Addition of N-Alkyl-2-iodoimidazole
to [M(PPh3)4] (M = Pd, Pt) Complexes
8
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