Heterobimetallic complexes containing an N-heterocyclic carbene based multidentate ligand and catalyzed tandem click/Sonogashira reactions

Article abstract of DOI:10.1039/c0dt01211d

Mono- and polynuclear complexes containing 3-(1,10-phenanthrolin-2-yl)-1- (pyridin-2-ylmethyl)imidazolylidene (L), [NiL₂](PF₆) ₂ (2), [CoL₂](PF₆)₃ (3), [PtLCl](PF₆) (4), [PdAgL

Full text of DOI:10.1039/c0dt01211d

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PAPER
Heterobimetallic complexes containing an N-heterocyclic carbene based
multidentate ligand and catalyzed tandem click/Sonogashira reactions†
Shaojin Gu,a Daichao Xua and Wanzhi Chen*a,b
Received 11th September 2010, Accepted 23rd November 2010
DOI: 10.1039/c0dt01211d
Mono- and polynuclear complexes containing 3-(1,10-phenanthrolin-2-yl)-1-(pyridin-2-ylmethyl)-
imidazolylidene (L), [NiL2](PF6)2 (2), [CoL2](PF6)3 (3), [PtLCl](PF6) (4), [PdAgL2](PF6)3 (5),
[PdCuL2](PF6)3 (6), [Pd2L2Cl2](PF6)2 (7), and [Pd3L2Cl4](PF6)2 (8) have been prepared and fully
characterized by NMR, ESI-MS spectroscopy, and X-ray crystallography. In complexes 2–4, the ligand
binds to metals in a pincer NNC fashion with the pyridine group uncoordinated. Complexes 5 and 6
are isostructural to each other in which the palladium ions are surrounded by two pyridines and two
imidazolylidenes and Ag(I) or Cu(I) is coordinated by two 1,10-phenanthroline moieties. In the
trinuclear palladium complex 8, one palladium ion has an identical coordination mode as in 5 and 6,
and the other two palladium ions are bonded to the 1,10-phenanthroline. Complex 6 exhibits excellent
catalytic activity for the tandem click/Sonogashira reaction of 1-(bromomethyl)-4-iodobenzene, NaN3,
and ethynylbenzene in which three C–N bonds and one C–C bond are formed in a single flask.
which are efficient cross-coupling catalysts.7 In this paper we
Introduction
report the synthesis and characterization of a few hetero- and
The study of heterobimetallic complexes is of great interest
homobimetallic complexes based on the 3-(1,10-phenanthrolin-2-
in the fields of materials science and homogeneous catalysis
yl)-1-(pyridin-2-ylmethyl)imidazolylidene.
mainly due to their unusual physical properties and reactivity
which homometallic complexes cannot have.1 Especially, the
Results and discussion
heterobimetallic structures are hoped to exhibit unusual cat-
alytic activity due to cooperative reactivity of the two different
metals.2 N-Heterocyclic carbenes (NHCs) have been receiving
increasing attention as strong donating ancillary ligands for
organometallic chemistry and homogeneous catalysis.3 Donor-
functionalised NHC ligands contain multiple donor atoms with
different electronic and steric properties offering opportunities
for the construction of bi- and polynuclear organometallic
complexes.4 A bimetallic complex supported by an NHC ligand
would be bifunctional and suitable for tandem reactions in which
the sequential reactions are typically catalyzed by two different
metal centers.5 These complexes may also work for reactions re-
quiring cooperative catalysts. For example, Sonogashira coupling
reactions are often performed with Pd/Cu systems.6 We have
reported that 1-butyl-3-(1,10-phenanthrolin-2-yl)imidazolylidene
as a pincer NNC ligand forms nickel and palladium complexes
As shown in Scheme 1, treatment of the in situ generated silver-
NHC complex from HL·PF6 (L = 3-(1,10-phenanthrolin-2-yl)-
1-(pyridin-2-ylmethyl)imidazolylidene) and Ag2O with 0.5 equiv.
of [NiCl2(PPh3)2] and [CoCl2(PPh3)2] in acetonitrile afforded
complexes [NiL2](PF6)2 (2) and [CoL2] (PF6)3 (3), respectively.
Reaction of the same silver-NHC complex with [PtCl2(COD)]
yielded [PtLCl](PF6) (4). However, the same reaction with
[PdCl2(CH3CN)2] gave [PdAgL2](PF6)3 (5) in 45% yield. Further
reaction of 5 with one equivalent of CuI in acetonitrile afforded
a red brown complex with the formulation of [PdCuL2](PF6)3 (6).
When one equivalent of [PdCl2(CH3CN)2] was allowed to react
with the in situ generated silver-NHC complex, the trinuclear
palladium complex [Pd3L2Cl4](PF6)2 (8) was obtained in 38% yield.
A higher yield of complex 8 could be obtained by treatment of the
acetonitrile solution of the silver-NHC complex with one and a
half equivalents of [PdCl2(CH3CN)2]. Complex 8 could also be
obtained by reacting 5 with one equivalent of [PdCl2(CH3CN)2] in
72% yield. Recrystallization of 8 in acetonitrile by slow diffusion
of diethyl ether did not give crystals of 8, only a small amount
of compound [Pd2L2Cl2](PF6)2 (7) was obtained as a pale yellow
crystalline solid.
aDepartment of Chemistry, Zhejiang University, Xixi Campus, Hangzhou
310028, People’s Republic of China. E-mail: chenwzz@zju.edu.cn; Fax: +86-
571-88273314; Tel: +86-571-88273314
bState Key Laboratory of Structural Chemistry, Fujian Institute of Research
on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian
350002, P. R. China
† Electronic supplementary information (ESI) available: Crystallographic
data for 2 and 4, and spectroscopic data of coupling products. CCDC
reference numbers 792158–792163. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/c0dt01211d
All the compounds are air stable and they were characterized by
elemental analyses, ESI-MS, and NMR spectroscopy. Complex 2
is paramagnetic preventing the collection of the fine structure of
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Scheme 1 Synthesis of NHC complexes 2–8.
its H NMR spectrum. The 13C NMR spectra of the palladium
complexes show their carbenic carbon resonances at ca. 160 ppm,
characteristic of carbenic carbons bonded to palladium. Normally
Pd–C resonances of Pd–NHC complexes are found in the wide
range of 139–178 ppm.8 The ESI-MS spectra of the mononuclear
complexes 2–4 show peaks at 877.04, 1023.14, and 568.21 amu
ascribed to their corresponding [M - PF6]+ ions. In the ESI-MS
spectra of 5 and 6, the peaks of [PdML2(PF6)2]+ (M = Ag and
Cu) were observed at 1178.64, and 1134.73 amu. In addition, the
fragmentation to [PdL2(PF6)]+ at 924.96 amu was also seen.
Crystals of 2–4 suitable for X-ray crystallography were easily
obtained by slow diffusion of diethyl ether into its acetonitrile
solution. The platinum complex has an usual square planar
structure.9 Complex 2 is a rare example of an octahedral nickel
compound containing NHC ligands in which the metal ion
is surrounded by two 3-(1,10-phenanthrolin-2-yl)-1-(pyridin-2-
ylmethyl)imidazolylidene ligands.7,10 Most of the known nickel(II)-
NHC complexes have square planar geometry.11 The nickel and
cobalt complexes have the same distorted octahedral geometry
although displaying different oxidation state, thus only 3 is
discussed and the structures of 2 and 4 are given in the supporting
information. The crystal structure of 3 is shown in Fig. 1. The
two phenanthroline moieties around the cobalt ion are nearly
perpendicular to each other with a dihedral angle of 89.37◦.
1
Fig. 1 ORTEP drawing of the cationic section of [CoL2](PF6)3 (3).
Thermal ellipsoids are drawn at the 30% probability level. Hydrogen
atoms and anions have been removed for clarity. Selected bond distances
◦
˚
(A) and angles ( ): Co(1)–N(8) 1.871(4), Co(1)–N(3) 1.874(4), Co(1)–C(1)
1.927(6), Co(1)–C(22)1.949(6), Co(1)–N(4) 2.016(5), Co(1)–N(9)
2.043(5); N(8)–Co(1)–N(3) 175.7(2), N(8)–Co(1)–C(1) 101.6(2),
N(3)–Co(1)–C(1) 80.4(2), N(8)–Co(1)–C(22) 80.3(2), N(3)–Co(1)–C(22)
103.5(2), C(1)–Co(1)–C(22) 92.0(2), N(8)–Co(1)–N(4) 96.25(19),
N(3)–Co(1)–N(4) 81.8(2), C(1)–Co(1)–N(4) 162.1(2), C(22)–Co(1)–N(4)
91.2(2), N(8)–Co(1)–N(9) 81.7(2), N(3)–Co(1)–N(9) 94.53(19),
C(1)–Co(1)–N(9) 90.4(2), C(22)–Co(1)–N(9) 162.0(2), N(4)–Co(1)–N(9)
91.94(1).
˚
The Co–C bond distances (1.927(6) and 1.949(6) A) are normal
as compared to those of the reported Co(III)–NHC complexes
12
˚
(1.93 to 1.96 A). Two Co–N distances trans to NHC donors
˚
are remarkably longer (0.14–0.17 A) than the other two Co–
N distances due to a large trans effect of the NHC groups and
geometry requirement.
As shown in Fig. 2, the structure of complex 5 consists of
one Pd(II) and one Ag(I) ion which are both tetracoordinated.
The coordination geometry of Pd is distorted square planar with
palladium coordinated to two carbenes and two pyridine groups.
˚
The Pd–C distances (1.945(10) and 1.972(10) A) are normal as
compared to those of known Pd(II)–NHC complexes (1.88 to
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Fig. 3 ORTEP drawing of the cationic section of [PdCuL2](PF6)3
(6). Thermal ellipsoids are drawn at the 30% probability level.
Hydrogen atoms and anions have bee◦n removed for clarity.
Fig. 2 ORTEP drawing of the cationic section of [PdAg(L)2](PF6)3 (5).
Thermal ellipsoids are drawn at the 30% probability level. Hydrogen
atoms and anions have been removed for clarity. Selected bond
˚
Selected bond distances (A) and angles ( ): Pd(1)–C(30) 1.962(4),
Pd(1)–C(15) 1.963(4), Pd(1)–N(2) 2.088(4), Pd(1)–N(1) 2.093(3),
Cu(1)–N(7) 1.985(4), Cu(1)–N(9) 1.989(4), Cu(1)–N(10) 2.071(3),
Cu(1)–N(8) 2.109(4); C(30)–Pd(1)–C(15) 92.74(18), C(30)–Pd(1)–N(2)
distances (A) and angles (◦): Pd(1)–C(22) 1.945(10), Pd(1)–C(1),
˚
1.972(10), Pd(1)–N(5) 2.073(8), Pd(1)–N(10) 2.074(8), Ag(1)–N(9)
2.244(10), Ag(1)–N(4) 2.262(11), Ag(1)–N(3) 2.411(9), Ag(1)–N(8)
2.469(9); C(22)–Pd(1)–C(1) 90.8(4), C(22)–Pd(1)–N(5) 176.1(4),
C(1)–Pd(1)–N(5) 86.1(4), C(22)–Pd(1)–N(10) 86.5(4), C(1)–Pd(1)–N(10)
176.5(4), N(5)–Pd(1)–N(10) 96.7(3), N(9)–Ag(1)–N(4) 139.7(4),
N(9)–Ag(1)–N(3) 140.6(3), N(4)–Ag(1)–N(3) 70.0(4), N(9)–Ag(1)–N(8)
70.6(3), N(4)–Ag(1)–N(8) 144.2(4), N(3)–Ag(1)–N(8) 96.9(3).
86.30(17),
C(15)–Pd(1)–N(2)
175.43(17),
C(30)–Pd(1)–N(1)
176.83(16), C(15)–Pd(1)–N(1) 84.80(16), N(2)–Pd(1)–N(1) 96.31(15),
N(7)–Cu(1)–N(9) 130.66(18), N(7)–Cu(1)–N(10) 131.06(15), N(9)–Cu(1)–
N(10) 82.06(15), N(7)–Cu(1)–N(8) 82.16(17), N(9)–Cu(1)–N(8)
132.66(15), N(10)–Cu(1)–N(8) 101.14(14).
13
˚
2.1 A). The silver ion is surrounded by two planar heterocycles.
˚
Two Ag–N distances (av. 2.44 A) neighboring to the NHC
moieties are remarkably longer than the other two Ag–N
˚
bonds (av. 2.25 A). For comparison, the Ag–N bond lengths of
[Ag(Phen)2]+ were reported to be 2.31–2.39 A.
In complex
14,15
˚
5, the silver atom was surrounded by two planar metallocycles
subtending an angle of 48◦ which is larger than those of
[Ag(Phen)2]+ complexes (32 to 40◦).14,15
Complex 6 is isostructural with 5 showing similar structural
˚
features (Fig. 3). Similar to 5, the two Cu–N distances (av. 2.09 A)
neighboring the NHC moieties are much longer than the other
˚
two Cu–N bonds (av. 1.98 A). The two rings around copper(I)
display a dihedral angle of 68◦, which are normal a◦s compared to
those of reported [Cu(Phen)2]+ complexes (44 to 77 ).16
The structure of 7 is shown in Fig. 4. The cation contains two
Pd(II) ions with different coordination modes. The coordination
geometry of Pd(1) is distorted square planar with palladium
coordinated to two carbenes and two pyridine groups. Pd(2) is
coordinated by a phenanthroline ring and two chloride ions. The
Fig. 4 ORTEP drawing of the cationic section of [Pd2Cl2L2](PF6)2
(7). Thermal ellipsoids are drawn at the 30% probability level.
Hydrogen atoms and anions hav◦e been removed for clarity. Selected
˚
bond distances (A) and angles ( ): Pd(1)–C(22) 1.966(9), Pd(1)–C(1)
1.993(9), Pd(1)–N(5) 2.094(8), Pd(1)–N(10) 2.109(8), Pd(2)–N(4)
2.060(8), Pd(2)–N(3) 2.102(8), Pd(2)–Cl(2) 2.260(3), Pd(2)–Cl(1) 2.275(3);
C(22)–Pd(1)–C(1) 92.7(4), C(22)–Pd(1)–N(5) 178.0(3), C(1)–Pd(1)–N(5)
85.4(3), C(22)–Pd(1)–N(10) 87.7(3), C(1)–Pd(1)–N(10) 179.6(3),
N(5)–Pd(1)–N(10) 94.2(3), N(4)–Pd(2)–N(3) 80.3(3), N(4)–Pd(2)–Cl(2)
93.6(2), N(3)–Pd(2)–Cl(2) 172.3(2), N(4)–Pd(2)–Cl(1) 169.2(3),
N(3)–Pd(2)–Cl(1) 96.7(2), Cl(2)–Pd(2)–Cl(1) 88.41(12).
˚
Pd–C distances (1.96–1.99 A) are normal.
Catalytic properties
All the carbene complexes 2–8 in their solid states and solutions
can be stored in air for months without observable decomposition.
This encourages us to examine their catalytic properties especially
the heterobimetallic complexes in some organic transformation
requiring bimetallic catalysts. Heterobimetallic PdCu complex
6 offers an opportunity to explore the tandem transformation
combining two reactions typically catalyzed by Pd and Cu
precatalyst.
Initially, we examined the efficiency in copper-catalyzed one-pot
synthesis of 1,2,3-triazole from 1-(bromomethyl)-4-iodobenzene,
NaN3, and ethynylbenzene. We noted that without catalyst and
in the presence of complex 5, the three-component reaction gave
a mixture of 1-(azidomethyl)-4-iodobenzene, and two cycload-
dition regioisomers (Table 1, entries 1–2). To our delight, the
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Table 1 One-flask “click”/Sonogashira reaction of 1-(bromomethyl)-4-iodobenzene
entry
1a
catalyst
—
substrate
product
yield (%)f
12 (2 : 1)
2a
5
11(1.6 : 1)
3a
4b
6
6
74
86
5c
6d
7d
6
74
81
68
6
CuI + 1
8d
8
71
78
52
9d
5
10g
8 + CuI
11h
12d
PdCl2(PPh3)2 + CuI
49
2
10 (2 : 1)
13d
3
15 (2 : 1)
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Table 1 (Contd.)
entry
14d
catalyst
substrate
product
yield (%)f
4
11
(1.6 : 1)
15d
16e
6
6
82
50
17d
6
53
a Reaction conditions: 1-(bromomethyl)-4-iodobenzene (0.5 mol), catalyst (0.01 mmol), NaN3 (0.6 mmol), ethynylbenzene (1 mmol), DMF (2 mL), 80 ◦C,
5 h. b 1-(4-Iodobenzyl)-4-phenyl-1H-1,2,3-triazole (0.5 mol), complex 6 (0.01 mmol), ethynylbenzene (1 mmol), pyrrolidine (1.0 mmol), DMF (2 mL),
80 ◦C, 2 h. c 1-(Bromomethyl)-4-iodobenzene (0.5 mol), complex 6 (0.01 mmol), NaN3 (0.6 mmol), ethynylbenzene (1.0 mmol), DMF (2 mL), 80 ◦C, 5
h. After 5 h, ethynylbenzene (1 mmol) and pyrrolidine (1 mmol) were added. d 1-(Bromomethyl)-4-iodobenzene (0.5 mol), catalyst (0.01 mmol), NaN3
(0.6 mmol), alkyne (2 mmol), pyrrolidine (1 mmol), DMF (2 mL), 80 ◦C, 5 h. e Reaction stopped after 24 h. f Isolated yield. g Complex 8 (0.01 mmol),
and CuI (0.01 mmol) as catalysts. h PdCl2(PPh3)2 (0.01 mmol), and CuI (0.01 mmol) as catalysts.
three-component reaction is very clean giving 1-(4-iodobenzyl)-
4-phenyl-1H-1,2,3-triazole in 74% isolated yield using 2 mol%
of complex 6 (Table 1, entry 3). These data show that the
PdCu complex 6 is active for the azide alkyne cycloaddition
(CuAAC) which is typically catalyzed by copper salts. The isolated
triazole compound bearing an additional iodo substituent was
subsequently submitted to Sonogashira reaction with another
molecule of alkyne. The alkynylation with ethynylbenzene was
successful by using 2 mol% of complex 6 in the presence of two
equivalents of pyrrolidine at 80 ◦C, offering the corresponding
coupling product in 86% yield (entry 4). Furthermore, we found
that the reaction could be achieved in a stepwise way, i.e.
after completion of the azide-alkyne cycloaddition, subsequent
addition of another portion of ethynylbenzene and pyrrolidine
afforded the alkynylation product in 74% yield (Table 1, entry
5). The success of both click and Sonogashira reaction promoted
us to explore the possibility of a real tandem click/Sonogashira
reaction in one flask. Actually, the three-component coupling of
1-(bromomethyl)-4-iodobenzene, NaN3, and two equivalents of
ethynylbenzene could be simply completed by mixing the three re-
actants with the catalyst at 80 ◦C under similar reaction conditions
as described for separate click and Sonogashira coupling. As seen
from Table 1, the reaction of 1-(bromomethyl)-4-iodobenzene with
1.2 equiv NaN3, 4.0 equiv ethynylbenzene in the presence of 2.0
equiv pyrrolidine and 2 mol% catalyst in DMF afforded the desired
product in 81% yield (entry 6). For comparison, the catalytic
efficiency of palladium complex 8 and palladium-silver complex
5 were also studied under the same conditions. When complex 8
itself was employed, only the Sonogashira reaction could proceed
affording 1-(azidomethyl)-4-(phenylethynyl)benzene in 71% yield
(entry 8), whereas CuI (2 mol%) could only accomplish the click
reaction in the presence of the ligand (entry 7). A similar result was
also observed using heterobimetallic PdAg complex 5 as catalyst
(entry 9). As we expected, the combination of complex 8 and CuI
can catalyze the tandem reaction affording the desired product in
52% yield (entry 10). In addition, PdCl2(PPh3)2 together with CuI
also gave the target product but in slightly lower yield (entry 11).
These results clearly indicate that the mixed Pd–Cu complex is
suitable for such Sonogashira and click reactions.
Under the optimal reaction conditions, we also tested the
tandem click/Sonogashira reaction using complexes 2–4 (entries
12–14). The three-component reaction in the presence of 2–5 and
8 gave mixtures of 1,4- and 1,5-cycloaddition regioisomers in the
ratio of 1.6 : 1 to 2.0 : 1 (entries 8, 9, and 12–14), which is consistent
with the reported results under catalyst-free conditions,17 indicat-
ing that these catalysts do not influence the azido-alkynylation
reaction.
In a similar manner, we continued our investigation of the
tandem reactions between different alkynes and different arenes.
The one-flask reaction could be expanded to p-tolyacetylene in
82% yield (entry 15). Aliphatic 1-hexyne is also applied to the
tandem click/Sonogashira reaction in a moderate yield (entry 16).
Unfortunately, only the click reaction occurred using 1-bromo-4-
(bromomethyl)benzene as substrate (entry 17).
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H, 3.13; N, 13.76%. ESI-MS m/z (%): 877.04 [M - PF6]+, 366.45
[M - 2PF6]2+.
Conclusions
In summary, a few mononuclear nickel, cobalt, platinum com-
plexes and heteropolynuclear palladium-silver and palladium-
copper complexes supported by 3-(1,10-phenanthrolin-2-yl)-1-
(pyridin-2-ylmethyl)imidazolylidene have been synthesized and
structurally characterized. The palladium-copper complex has
proved to be a good catalyst for tandem click/Sonogashira
reactions of 1-(bromomethyl)-4-iodobenzene, NaN3, and alkynes
which allows three C–N bonds and one C–C bond to be formed
in a single vessel selectively.
[CoL2](PF6)3 (3)
The compound was prepared similarly as for 2 from HL·(PF6)
(98 mg, 0.20 mmol), Ag2O (24 mg, 0.10 mmol), and CoCl2(PPh3)2
1
(66 mg, 0.10 mmol). Yellow solid. Yield: 91 mg, 73%. H NMR
(400 MHz, DMSO-d6): d 9.54 (d, J = 9.2 Hz, 2H), 8.96 (d, J =
8.8 Hz, 2H), 8.87 (d, J = 1.2 Hz, NCHCHN, 2H), 8.73 (d, J =
8.0 Hz, 2H), 8.39 (d, J = 8.8 Hz, 2H), 8.21 (d, J = 8.8 Hz, 2H),
7.70 (s, J = 1.2 Hz, NCHCHN, 2H), 7.64–7.62 (m, 4H), 7.58 (d,
J = 4.8 Hz, 2H), 7.38 (t, J = 8.0 Hz, 2H), 6.99 (t, J = 6.0 Hz, 2H),
6.52 (d, J = 8.8 Hz, 2H), 4.54 (d, J = 16.8 Hz, CH2, 2H), 4.30 (d,
J = 16.8 Hz, CH2, 2H). 13C NMR (100 MHz, DMSO-d6): d 153.0,
152.6, 152.5, 149.2, 145.3, 144.8, 144.7, 140.3, 137.5, 131.6, 129.6,
128.9, 128.7, 128.3, 127.6, 123.4, 122.3, 120.2, 116.3, 54.0. Anal.
Calcd for C42H30F18N10CoP3·2CH3CN·H2O: C, 43.55; H, 3.02; N,
13.25. Found: C, 43.49; H, 2.86; N, 13.02%. ESI-MS m/z (%):
1023.14 [M - PF6]+, 439.04 [M - 2PF6]2+.
Experimental section
All the chemicals were obtained from commercial sup-
pliers and used without further purification. 2-Iodo-1,10-
phenanthroline,18 NiCl2(PPh3)2,19 CoCl2(PPh3)2,20 PtCl2(COD),21
22
and PdCl2(CH3CN)2 were prepared according to the known
procedure. Elemental analyses were performed on a Flash EA1112
instrument. 1H and 13C NMR spectra were recorded on a Bruker
Avance-400 (400 MHz) spectrometer. Chemical shifts (d) are
expressed in ppm downfield to TMS at d = 0 ppm and coupling
constants (J) are expressed in Hz. Mass spectral data were
acquired using a Waters Micromass ZQ mass spectometer (positive
mode, ESI source).
[PtCl(L)](PF6) (4)
The compound was prepared similarly as for 2 from HL·(PF6)
(98 mg, 0.20 mmol), Ag2O (24 mg, 0.10 mmol), and PtCl2(COD)
1
(74 mg, 0.20 mmol). Yellow solid. Yield: 26 mg, 18%. H NMR
(400 MHz, DMSO-d6): d 9.11 (d, J = 8.4 Hz, 1H), 9.01 (d, J =
7.6 Hz, 1H), 8.90 (d, J = 5.2 Hz, 1H), 8.57–8.55 (m, 2H), 8.45 (d,
J = 8.4 Hz, 1H), 8.24–8.19 (m, 3H), 7.88–7.84 (m, 2H), 7.50 (d, J =
7.6 Hz, 1H), 7.39–7.36 (m, 1H), 5.87 (s, 2H).13C NMR (100 MHz,
DMSO-d6): d 154.8, 150.9, 149.9, 149.5 (Pt-C), 148.2, 144.4, 144.2,
142.8, 141.0, 137.8, 131.9, 128.1, 127.9, 127.7, 127.1, 125.2, 123.9,
122.4, 120.3, 111.8, 56.3. Anal. Calcd for C21H15ClF6N5PPt: C,
35.38; H, 2.12; N, 9.82. Found: C, 34.95; H, 2.16; N, 9.63%. ESI-
MS m/z (%): 568.21 [M - PF6]+.
HL·(PF6) (L = 3-(1,10-phenanthrolin-2-yl)-1-(pyridin-2-ylmethyl)-
imidazolylidene) (1)
A solution of 2-iodo-1,10-phenanthroline (3.1 g, 10 mmol) and
1-picolylimidazole (3.2 g, 20 mmol) in 50 mL of toluene and
5 mL DMF was refluxed for two days. The resulting solid was
filtered and washed with toluene (2 ¥ 10 mL) and diethyl ether
(2 ¥ 10 mL), and then it was dissolved in 20 mL of methanol. The
methanol solution was decolorized with activated charcoal and
filtered. Subsequent addition of an aqueous solution of NH4PF6
(2.0 g, 12.3 mmol) to the methanolic solution afforded a white
solid, which was collected by filtration and dried. Yield: 2.7 g, 56%.
1H NMR (400 MHz, DMSO-d6): d 10.47 (s, NCHN, 1H), 9.19
(d, J = 3.2 Hz, 1H), 8.95 (d, J = 8.4 Hz, 1H), 8.79 (s, NCHCHN,
1H), 8.60 (d, J = 7.6 Hz, 2H), 8.42 (d, J = 8.8 Hz, 1H), 8.16 (s,
2H), 8.13 (s, NCHCHN, 1H), 7.95–7.87 (m, 2H), 7.61 (d, J =
8.0 Hz, 1H), 7.44 (t, J = 6.0 Hz, 1H), 5.83 (s, CH2, 2H).13C NMR
(100 MHz, DMSO-d6): d 153.6, 150.8, 149.9, 145.7, 144.6, 144.2,
141.6, 137.9, 137.2, 136.5, 129.7, 129.2, 128.4, 126.4, 124.9, 124.2,
123.1, 120.2, 114.5, 54.0. Anal. Calcd for C21H16N5PF6: C, 52.18;
H, 3.34; N, 14.49. Found: C, 51.96; H, 3.31; N, 14.15%. ESI-MS
m/z (%): 338.25 [M - PF6]+.
[PdAg(L)2](PF6)3 (5)
The compound was prepared similarly as for 2 from HL·(PF6) (98
mg, 0.20 mmol), Ag2O (24 mg, 0.10 mmol), and PdCl2(CH3CN)2
1
(26 mg, 0.10 mmol). Yellow precipitate. Yield: 60 mg, 45%. H
NMR (400 MHz, DMSO-d6): d 9.58 (br, 2H), 9.05 (br, 2H), 8.95
(br, 2H), 8.52–8.27 (m, 12H), 7.91 (d, J = 7.6 Hz, 2H), 7.79 (t, J =
6.0 Hz, 4H), 6.93 (br, 2H), 5.52 (br, 4H).13C NMR (100 MHz,
DMSO-d6): d 160.1 (Pd-C), 153.9, 153.3, 152.9, 148.7, 142.1,
141.5, 139.8, 130.3, 129.4, 129.2, 127.1, 126.8, 126.5, 126.1, 124.4,
122.7, 54.7. Anal. Calcd for C42H30AgF18N10P3Pd: C, 38.10; H,
2.28; N, 10.58. Found: C, 38.09; H, 2.17; N, 10.47%. ESI-MS m/z
(%): 1178.64 [M - PF6]+, 924.96 [M - Ag - 2PF6]+, 390.32 [M -
Ag - 3PF6]2+.
[Ni(L)2](PF6)2 (2)
A solution of HL·(PF6) (98 mg, 0.20 mmol) in 6 mL of acetonitrile
[PdCu(L)2](PF6)3 (6)
◦
was treated with Ag2O (24 mg, 0.10 mmol) at 50 C. After 10 h,
Ag2O completely disappeared, NiCl2(PPh3)2 (66 mg, 0.10 mmol)
was added. After it was stirred for 12 h at room temperature,
the solution was filtered. The filtrate was then concentrated to
ca. 2.0 mL. Addition of Et2O (20 mL) to the filtrate afforded a
brown solid. The precipitate was collected and washed with Et2O
to obtain the brown solid. Yield: 64 mg, 63%. Anal. Calcd for
C42H30F12N10NiP2: C, 49.29; H, 2.95; N, 13.69. Found: C, 48.93;
A solution of 5 (66 mg, 0.050 mmol) in 3.0 mL of acetonitrile
was treated with CuI (9.6 mg, 0.050 mmol) at room temperature
for 6 h. The solution was filtered and concentrated to ca. 1 mL.
Addition of Et2O (5.0 mL) to the filtrate afforded a red brown
precipitate. Yield: 58 mg, 91%. 1H NMR (400 MHz, DMSO-d6):
d 9.33 (d, J = 4.4 Hz, 2H), 9.16 (d, J = 8.0 Hz, 2H), 9.02 (d, J =
7.6 Hz, 2H), 8.48 (d, J = 8.8 Hz, 2H), 8.44 (d, J = 8.8 Hz, 2H), 8.38
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Table 2 Summary of the crystallographic data for 3, and 5–7
3
5
6
7
Formula
Fw
C46H36CoN12P3F18
1250.71
C42H30AgPdN10P3F18
1323.94
C46H36PdCuN12P3F18
1361.72
C46H38N12OCl2Pd2P2F12
1348.52
Crystal system
Triclinic
P1
11.6398
13.6787(14)
16.929(2) A
81.067(2)
73.9700(10)
81.180(2)
2541.8(5)
2
1.634
12406
8655, 0.0483
1.001
0.0691, 0.1637
0.1497, 0.2115
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/c
¯
Space group
˚
a/A
20.7545(19)
8.1456(14)
28.866(3)
90
94.547(2)
90
4864.7(10)
4
1.808
23846
8573, 0.0852
1.134
0.0892, 0.1738
0.1376, 0.1872
21.9896(6)
13.9782(4)
17.6873(4)
90
100.695(2)
90
5342.2(2)
4
1.693
23861
9387, 0.0405
1.016
0.0460, 0.1021
0.0875, 0.1098
8.3080(11)
23.423(2)
26.169(3)
90
97.390(2)
90
5050.1(9)
4
1.774
25279
8870, 0.0389
1.074
0.0791, 0.2014
0.1166, 0.2360
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
V, A
Z
Dc/Mg m-3
Reflections collected
Reflections independent, Rint
Goodness-of-fit on F2
R1, wR2 (I > 2s(I))
R1, wR2 (all data)
(d, J = 7.2 Hz, 4H), 8.28–8.22 (m, 4H), 7.84 (d, J = 8.0 Hz, 2H), 7.74
(t, J = 6.0 Hz, 2H), 7.41 (s, 2H), 6.81 (s, 2H), 5.48 (d, J = 14.8 Hz,
2H), 5.42 (d, J = 15.2 Hz, 2H).13C NMR (100 MHz, DMSO-d6):
d 159.6 (Pd–C), 153.3, 153.0, 151.3, 147.2, 142.3, 142.2, 142.1,
140.5, 138.5, 130.3, 129.5, 129.1, 127.1, 126.8, 126.6, 124.8, 122.8,
122.5, 54.4. Anal. Calcd for C42H30CuF18N10P3Pd: C, 39.42; H,
2.36; N, 10.95. Found: C, 39.50; H, 2.55; N, 10.82%. ESI-MS m/z
(%): 1134.73 [M - PF6]+, 494.08 [M - 2PF6]2+, 924.90 [M - Cu -
2PF6]+.
chromatograph on silica gel (petroleum ether : ethyl acetate = 3 : 1,
v/v) to afford the desired product.
X-ray crystallography
Single-crystal X-ray diffraction data were collected at 298(2) K
on a Siemens Smart/CCD area-detector or Oxford Diffraction
Gemini A Ultra diffractometer with Mo-Ka radiation (l =
˚
0.71073 A) by using an w–2q scan mode. Unit-cell dimensions
were obtained with least-squares refinement. Data collection and
reduction were performed using the SMART and SAINT or
Oxford Diffraction CrysAlisPro software.23 The structures were
solved by direct methods, and the non-hydrogen atoms were
subjected to anisotropic refinement by full-matrix least squares
on F2 using SHELXTXL package.24 Hydrogen atom positions
for all of the structures were calculated and allowed to ride on
[Pd3L2Cl4](PF6)2 (8)
The compound was prepared similarly as for 2 from HL·(PF6) (98
mg, 0.20 mmol), Ag2O (24 mg, 0.10 mmol), and PdCl2(CH3CN)2
1
(78 mg, 0.30 mmol). Yield: 74 mg, 52%. H NMR (400 MHz,
CH3CN-d3): d 9.61 (d, J = 5.2 Hz, 2H), 9.11 (d, J = 8.4 Hz, 2H),
9.02–8.99 (m, 4H), 8.37 (d, J = 8.4 Hz, 2H), 8.26 (d, J = 8.8 Hz,
2H), 8.22–8.19 (m, 2H), 8.07 (td, J = 7.6, 1.2 Hz, 2 H), 7.69 (d, J =
8.4 Hz, 2H), 7.59–7.55 (m, 4H), 7.14 (s, 2H), 6.52 (s, 2H), 5.52 (d,
J = 14.4 Hz, 2H), 4.61 (d, J = 14.4 Hz, 2H).13C NMR (100 MHz,
CH3CN-d3): d 162.4 (Pd-C), 155.1, 152.3, 150.6, 150.2, 146.5,
145.5, 143.6, 141.3, 141.2, 132.1, 130.0, 129.4, 127.3, 126.7, 125.6,
123.4, 122.6, 55.2. Anal. Calcd for C42H30Cl4F12N10P2Pd3·H2O: C,
34.94; H, 2.23; N, 9.70. Found: C, 34.78; H, 2.19; N, 9.40%. ESI-
MS m/z (%): 1280.45 [M - PF6]+, 567.86 [M - 2PF6]2+.
˚
their respective C atoms with the C–H distances of 0.93–0.97 A
and Uiso(H) = 1.2 - 1.5Ueq(C). Further details of the structural
analysis are summarized in Table 2.
Acknowledgements
The authors thank the National Natural Science Foundation
of China (20872129 and 21072170), Key Project of Depart-
ment of Education of Zhejiang Province (Z200908265), and
the Fundamental Research Funds for the Central Universities
(2010QNA3004) for financial support.
General procedure for tandem click/Sonogashira reaction
A Schlenk tube was charged with the palladium-copper complex
6 (0.010 mmol), NaN3 (0.60 mmol), DMF (2.0 mL), and 1-
(bromomethyl)-4-iodobenzene (0.50 mmol) under an atmosphere
of N2. To the solution formed was added alkyne (2.0 mmol)
and pyrrolidine (1.0 mmol) via syringe at room temperature with
stirring. The resulting mixture was stirred at 80 ◦C for 5 h.
The reaction was ceased by addition of water. The mixture was
extracted with ethyl acetate (3 ¥ 10 mL). The combined organic
layers were washed with saturated brine (3 ¥ 10 mL) and dried
with anhydrous magnesium sulfate. The filtrate was concentrated
by rotary evaporation and the product was purified by column
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