Self-Assembled Cyclophane-Type Copper(I) Complexes of 2,4,6-Tris(diphenylphosphino)-1,3,5-triazine and Their Catalytic Application

Article abstract of DOI:10.1021/acs.inorgchem.5b02075

The triazine-based trisphosphine, 2,4,6-tris(diphenylphosphino)-1,3,5-triazine (1) was prepared in improved yield by reacting cyanuric chloride with 3 equiv of trimethylsilyldiphenylphosphine. The solid-state structure of 1 showed short intermolecular P··

Full text of DOI:10.1021/acs.inorgchem.5b02075

Article
pubs.acs.org/IC
Self-Assembled Cyclophane-Type Copper(I) Complexes of 2,4,6-
Tris(diphenylphosphino)-1,3,5-triazine and Their Catalytic
Application
Guddekoppa S. Ananthnag,† Joel T. Mague,‡ and Maravanji S. Balakrishna*,†
†Phosphorus Laboratory, Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
‡Department of Chemistry, Tulane University, New Orleans, Lousiana 70118, United States
S
* Supporting Information
ABSTRACT: The triazine-based trisphosphine, 2,4,6-tris-
(diphenylphosphino)-1,3,5-triazine (1) was prepared in
improved yield by reacting cyanuric chloride with 3 equiv of
trimethylsilyldiphenylphosphine. The solid-state structure of 1
showed short intermolecular P···P contacts of 3.362 Å, which
is significantly shorter than the sum of the van der Waals radii
of phosphorus atoms (3.6 Å). The reaction of 2,4,6-
tris(diphenylphosphino)-1,3,5-triazine (1) with copper(I)
salts in a 2:3 molar ratio yielded various cyclophane-type
complexes in quantitative yield. The solid-state structures of
these clusters have been found to depend on the size of the
halide ions, the solvent employed, and the reaction conditions. Copper(I) chloride formed a monomeric metallocyclophane,
whereas copper(I) bromide and copper(I) iodide derivatives preferred dimeric and 1D-polymeric structures, respectively. The
tricationic complexes derived from CuI ion and 2,4,6-tris(diphenylphosphino)-1,3,5-triazine also adopted monomeric
metallocyclophane structures. These complexes have been employed in the A3 coupling reaction under microwave irradiation.
The copper(I) iodide derivative showed excellent catalytic efficiency.
ligand 2,4,6-tris(diphenylphosphino)-1,3,5-triazine and related
C3 symmetrical tris(phosphine) ligands are ideally suited
candidates for this purpose.28−32 These ligands have been
extensively explored by James and others to form extended
networks through multiple ligand coordination to metal centers
or through additional bridging ligands to form chains,33
cyclophane,28,34,35 and tetrahedral27,30,36 clusters.31,36
Simple monomeric cyclophanes derived from tris-
(phosphine) ligands with copper(I) and platinum(II) metal
centers have been reported in the literature.28,34,35 Here, we
present a novel series of cyclophane-type copper(I) complexes
derived from 2,4,6-tris(diphenylphosphino)-1,3,5-triazine.
These are the first examples of di- and polymeric structures
consisting of cyclophane scaffolds as monomeric units. The
application of some of these copper(I) complexes in the A3
coupling reaction is also discussed.
INTRODUCTION
■
Metal-assisted self-assembly for the construction of supra-
molecular architectures with specific functions has become an
attractive approach in recent years.1−5 These supramolecular
systems find numerous applications in catalysis,6−8 photo-
voltaics,9,10 therapeutic agents,11−13 storage,14,15 and chemical
sensors.2,16,17 The most used building blocks for the
construction of transition-metal-based self-assemblies are
platinum group metals.18−20 Recently, extensive studies have
focused on group 11 metal complexes because of their rich
photophysical properties.21,22 Copper(I) halides readily form
complexes with soft donor ligands in which the coordination
number of the metal center can be varied between two to four.
Because of this geometrical flexibility, copper(I) ion adopts
various coordinating architectures.23
The ligating topologies of the organic ligands and highly
directional and predictable nature of the metal−ligand
coordination sphere determine the structural outcome and
properties of supramolecular systems.4,24,25 Therefore, ration-
alization of the ligand design for controlling the geometries and
properties of the resulting metal−ligand assemblies have been
given much attention in recent years. A large number of
supramolecular assemblies derived from rigid, multidentate
phosphine ligands have been reported in the literature.26,27 To
form a three-dimensional metal−ligand assembly, either metal
or ligand should possess a connectivity of at least three. The
RESULTS AND DISCUSSION
■
The tris(phosphine), 2,4,6-tris(diphenylphosphino)-1,3,5-tria-
zine (1) was prepared by the reaction of cyanuric chloride with
Ph2PSiMe3 in THF at 0 °C in 59% yield. Previously, 1 was
prepared by the reaction of cyanuric fluoride and KPPh2 in 41%
yield.36,37
Received: September 9, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.5b02075
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Chart 1. Copper Complexes of Trisphosphine 1
The addition of an acetonitrile solution of copper(I) halide
(CuCl, CuBr, or CuI) to a dichloromethane solution of 1 (L)
in a 3:2 molar ratio at room temperature resulted in the
formation of copper(I) complexes, [(CuCl)3(L)2(NCMe)2]
(2), [(CuBr)3(L)2]2 (3), and [(CuI)3(L)2(NCMe)]n (4)
(Chart 1). Similar reaction of 1 with [Cu(NCMe)4]BF4
afforded the tricationic metallocyclophane [{(Cu(NCMe)2)3-
(L)2}(BF4)3] (5) in quantitative yield. Addition of 1,10-
phenanthroline to a solution of 4 in dichloromethane resulted
initially in the formation of [{(Cu(Phen))3(L)2}(I)3] (6) in
quantitative yield, as confirmed by spectroscopic and analytical
data. Complex 6 consists of a cyclophane structure similar to
that of 5. The crystallization of complex 6 from a mixture of
dichloromethane and petroleum ether produced yellow crystals
of [(CuI(Phen))3(L)] (6a) along with 1. It is assumed that,
during the crystallization, complex 6 decomposed to form
crystals of 6a and the ligand 1. The complexes 2−6 are
moderately air-stable yellow solids, readily soluble in polar
organic solvents.
Figure 1. Molecular structure of [(CuCl)3(L)2(MeCN)2] (2). All
Slow diffusion of acetonitrile into a saturated solution of 2
(in 1,2-dichloroethane) and 4 (in dichloromethane) gave
crystals suitable for single-crystal X-ray diffraction studies. The
molecular structures of all complexes with atom numbering
schemes are shown in Figures 1−6. Selected bond lengths and
bond angles are given in Tables 1−5, while crystal data and the
details of the structure determinations are given in Table 6.
Single crystals of complex 3 were obtained by layering
petroleum ether over a saturated solution of 3 in 1,2-
dichloroethane. The core structures of 2−4 consist of two
triazine rings held together by three copper(I) atoms to form
metallocyclophanes. The size of the halide ions appears to
control the solid-state structure of these copper complexes. The
copper(I) chloride derivative 2 is a monomeric metal-
locyclophane, whereas the copper(I) bromide derivative 3 is
dimeric, formed by dimerization of two metallocyclophane
fragments bridged by a Cu2(μ-Br)2 unit (Chart 1). The copper
iodide derivative 4 is polymeric in nature. The larger size of the
iodide ion facilitates the formation of [Cu(μ-I)Cu] links to
form a 1D polymer. The two triazine rings in 2−4 are separated
by a distance of 4.01, 3.90, and 4.37 Å, respectively. The
separation between the two triazine rings in 2−4 is significantly
larger than that observed in the platinum complex of
hydrogen atoms and lattice solvents are omitted for clarity.
tris(diphenylphosphino)benzene (L), [(PtCl2)3L2] (3.12 Å),35
which is essentially due to the tetrahedral (∼109.5°) or trigonal
planar (∼120°) geometry adopted by copper compared to
square planar (∼90°) platinum centers. The separation
between the two triazine rings in 2−4 is also larger than the
corresponding distance in pure organic paracyclophane (3.25
Å), because of longer Cu−P bond distances (2.23−2.27 Å)
compared to a typical C−C bond distance of 1.54 Å.38 The two
triazine rings in 2−4 are inclined to each other at an angle of
2.66, 5.44, and 18.06°, respectively. The inclination in 4 is
significantly higher because of the intracyclophane [Cu(μ-
I)Cu] bridge. The intracyclophane [Cu(μ-I)Cu] bridge is
observed only in 4 due to the larger size of iodide. The P···P
separations in 2 [4.012−4.083 Å] are larger than those in both
3 [3.878−3.933 Å] and 4 [3.937−4.048 Å]. The geometry
around two of the copper atoms in 2 is tetrahedral, whereas the
third copper atom is trigonal planar and is surrounded by two
phosphorus atoms and a chloride ion. Crystallization of 2 in the
absence of acetonitrile led to the isolation of a symmetrical
cyclophane cluster with all the copper centers being
B
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Figure 2. Molecular structure of [(CuBr)3(L)2]2 (3). All hydrogen atoms and lattice solvents are omitted for clarity.
Figure 3. Molecular structure of [(CuI)3(L)2(MeCN)]n (4). All
hydrogen atoms and lattice solvents are omitted for clarity.
Figure 4. Molecular structure of [(CuI(Phen))3(L)] (6a). All
hydrogen atoms and lattice solvents are omitted for clarity.
tricoordinated (see Figure S1 in the Supporting Information).
All the copper centers in 4 are tetracoordinated and adopt a
distorted tetrahedral geometry. The P−Cu−P bond angles
around the copper atoms in 3 do not deviate much from ideal
trigonal planar geometry [118.32(6)−122.61(6)°], but signifi-
cant deviations from tetrahedral geometry are observed for 4
[121.62(3)−127.39(5)°]. The average metal−phosphorus
distances in 2−4 are 2.24, 2.25, and 2.26 Å, respectively, and
are in good agreement with those in [(R3P)2CuX].28,39,40 In 3,
the average Cu−Br bond distances for the tetrahedral copper
(2.566 Å) is larger than those in the tricoordinated centers
(2.335 Å). In the case of 4, all the four Cu−I bond distances
differ significantly from one another and fall in the range of
2.5821(8)−2.7297(7) Å.
On storing complex 6 in a mixture of dichloromethane and
petroleum ether at room temperature, X-ray quality crystals of
both 6a and ligand 1 were formed. The asymmetric unit in 1
contains two molecules with one of them showing strong
intermolecular π−π stacking and nonbonding P···P contacts.
The intermolecular π−π stacking is observed between the
central triazine rings of two molecules to form a dimeric
structure with an interplane distance of 3.44 Å. The centroids
of the two triazine rings exhibit a parallel displacement of
approximately 2.57 Å. Interestingly, two short intermolecular
P···P contacts of 3.362 Å between P1 and P3 atoms of two
independent molecules of 1 are observed. The P···P contact is
significantly shorter than the sum of the van der Waals radii of
phosphorus atoms (3.6 Å),41 but larger than that observed in
phospha[1]ferrocenophane derivatives.42,43 The average P−
C
triazine (1.842 Å) bond distance in 1 is longer than the average
P−Cphenyl (1.829 Å) bond distance. The structure of 6a consists
of a three tetracoordinated copper centers, being coordinated
by 1,10-phenanthroline, iodide, and one phosphorus atom
(Figure 4). The average Cu−I (2.606 Å) bond distance in 6a is
similar to that of [Ph3PCuI(1,10-phen)] (2.6157(6) Å),
whereas the average Cu−P (2.179 Å) bond distance is slightly
shorter than the same in [Ph3PCuI(1,10-phen)] (Cu−P =
2.1977(9) Å).44 To confirm the persistence of the solid-state
1
structures in solution, H, 31P{1H}, and ESI-MS spectra were
1
recorded for 2−6. The H NMR spectra of 2−6 in CDCl3
solution are similar to that of ligand 1 and showed multiplets in
C
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Figure 5. Core of 1D polymer [(CuI)3(L)2(MeCN)]n (4).
Figure 6. (a) Molecular structure of 2,4,6-tris(diphenylphosphino)-1,3,5-triazine (1). (b) Intermolecular P···P interaction in 1.
Table 1. Selected Bond Lengths [Å] and Bond Angles [deg]
for 1
Table 3. Selected Bond Lengths [Å] and Bond Angles [deg]
for 3
bond length [Å]
bond angle [deg]
bond length [Å]
Cu1−Br1
bond angle [deg]
P1−Cu1−P4
P1−C1
1.837(2)
1.839(3)
1.829(3)
1.844(2)
1.341(3)
1.340(3)
C1−P1−C4
103.43(11)
100.93(12)
99.99(12)
2.5720(11)
2.4597(11)
2.3322(12)
2.3389(11)
2.2669(19)
2.2718(18)
2.2391(18)
2.2465(19)
2.2304(18)
2.2528(18)
118.32(6)
119.67(7)
122.61(6)
97.65(5)
P1−C4
P1−C10
P2−C2
N1−C1
N1−C2
C4−P1−C10
C2−P2−C22
C2−P2−C16
C1−N1−C2
C2−N2−C3
Cu1i−Br1
Cu2−Br2
Cu3−Br3
Cu1−P1
Cu1−P4
Cu2−P2
Cu2−P5
Cu3−P3
Cu3−P6
P2−Cu2−P5
P3−Cu3−P6
P1−Cu1−Br1
P1−Cu1−Br1i
P2−Cu2−Br2
P5−Cu2−Br2
P3−Cu3−Br3
P6−Cu3−Br3
Br−Cu1−Br1i
103.22(12)
114.87(19)
115.05(19)
114.07(5)
120.72(6)
119.43(5)
120.61(5)
116.60(5)
93.41(3)
Table 2. Selected Bond Lengths [Å] and Bond Angles [deg]
for 2
bond length [Å]
Cu1−Cl1
bond angle [deg]
P1−Cu1−P1i
2.215(5)
2.253(3)
2.253(4)
2.228(3)
2.237(4)
2.258(4)
132.71(6)
126.39(1)
126.39(1)
113.63(5)
112.88(7)
116.87(3)
Table 4. Selected Bond Lengths [Å] and Bond Angles [deg]
for 4
Cu2−Cl2
Cu3−Cl3
Cu1−P1
Cu2−P2
Cu3−P3
P2−Cu2−P2i
P3−Cu3−P3i
P1−Cu1−Cl1
P2−Cu2−Cl2
P3−Cu3−Cl3
bond length [Å]
Cu1−I3
bond angle [deg]
P1−Cu1−P4
2.6509(7)
2.5821(8)
2.6386(7)
2.6727(8)
2.7297(7)
2.2616(13)
2.2538(12)
2.2736(13)
2.2631(13)
2.2724(13)
2.2376(13)
2.020(4)
127.39(5)
124.73(5)
121.62(5)
130.535(19)
100.04(4)
106.68(3)
103.93(4)
112.62(4)
102.209(19)
108.06(2)
Cu2−I2
Cu3−I3
Cu1−I1
Cu2−I1
Cu1−P1
Cu1−P4
Cu2−P2
Cu2−P5
Cu3−P3
Cu3−P6
Cu3−N7
P2−Cu2−P5
P3−Cu3−P6
Cu1−I1−Cu2
P1−Cu1−I3
P1−Cu1−I1
P2−Cu2−I1
P2−Cu2−I2
I1−Cu1−I3
I1−Cu2−I2
the region of 7.46−7.10 ppm. The 1H NMR spectrum of 5 and
6 showed additional signals from acetonitrile and 1,10-
phenthroline, respectively. The 31P{1H} NMR spectra of 2−6
consist of single resonances in the range of 1.7 to −3.3 ppm,
indicating the presence of single species in solution. The ESI-
MS spectra of 2 showed a base peak at 1527.06 corresponding
to the [M − Cl]+ ion. Surprisingly, the ESI-MS spectra of 3 and
4 also showed base peaks of monomeric units at 1616.85 and
1710.93 corresponding to [Mmonomer − X]+ fragments,
respectively. The mass spectrum of 5 showed a weak peak at
485.70 corresponding to the [M − (CH3CN)6 − (BF4)3]3+ ion.
The mass spectral data and solution NMR studies show that
the complexes adopt a monomeric structure in solution. The
weak halide bridges in 3 and 4 break down in solution to form
monomeric entities. However, the solid-state 31P NMR (CP-
MAS) spectrum of 4 showed a multiplet in the region of −24.0
D
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c
Table 5. Selected Bond Lengths [Å] and Bond Angles [deg]
for 6a
Table 7. Optimization of Reaction Conditions
bond length [Å]
bond angle [deg]
I1−Cu1−P1
a
Sl. no.
catalyst
solvent
conv (%)
Cu1−I1
2.5939(10)
2.6124(11)
2.6134(10)
2.070(5)
105.75(6)
103.02(16)
122.58(16)
80.72(19)
121.74(6)
101.83(16)
100.87(16)
109.51(6)
107.26(16)
1
2
2 (0.33 mol %)
3 (0.33 mol %)
4 (0.33 mol %)
4 (0.33 mol %)
no catalyst
MeCN (5% H2O)
MeCN (5% H2O)
MeCN (5% H2O)
MeCN
89
93
Cu2−I2
Cu3−I3
Cu3−N8
Cu1−N4
Cu2−N6
Cu1−P1
Cu2−P2
Cu3−P3
I1−Cu1−N4
P1−Cu1−N4
N4−Cu1−N5
I2−Cu2−P2
I2−Cu2−N6
I2−Cu2−N7
I3−Cu3−P3
I3−Cu3−N8
b
3
100 (95 )
4
83
32
31
56
72
78
2.075(5)
5
MeCN (5% H2O)
toluene
2.068(6)
6
4 (0.33 mol %)
4 (0.33 mol %)
4 (0.33 mol %)
4 (0.33 mol %)
4 (0.1 mol %)
4 (0.01 mol %)
2.1719(19)
2.1781(19)
2.1862(19)
7
neat
8
THF
9
H2O
b
10
11
MeCN (5% H2O)
MeCN (5% H2O)
99 (95 )
to 6.4 ppm, thus confirming the polymeric structure in the solid
state.
94
a
Conversion is based on amines by GC analysis using dodecane as
internal standard. Isolated yield. The reaction was carried at 100 °C,
b
c
Multicomponent coupling of an alkyne, an aldehyde, and an
amine leading to the formation of synthetically useful
propargylamines is referred as the A3 coupling reaction.45−48
Several transition-metal catalysts, including copper, silver, gold,
ruthenium, cobalt, and iridium, have been tested for the A3
coupling reaction.49−52 Copper salts, such as CuCl, CuCl2,
CuBr, and CuI, in the presence RuCl3 as cocatalyst have been
successfully utilized in the A3 coupling reaction.52 In order to
assess the catalytic utility of copper clusters 2−4, A3 coupling
reactions have been performed under microwave irradiation.
The desired propargylamines are obtained in excellent yields
by the reaction of aldehyde, amine, and alkyne in the presence
of copper catalysts (2−4). Initially, a mixture of phenyl
acetylene, formaldehyde, and N-benzylethanamine was used as
a model substrate to optimize the reaction conditions. The
conversions were excellent when 4 (0.33 mol %) was used as a
catalyst (Table 7, entry 3) under microwave irradiation in wet
acetonitrile. The yield was lowered considerably in other
solvents (Table 7, entries 5−8). A moderate conversion of 32%
under microwave irradiation (5 min) in a closed vessel.
was observed even in the absence of the catalyst (Table 7, entry
5). It was observed that the presence of water was necessary for
the higher yields (Table 7, entry 9). Further, catalyst loading
was decreased to 0.1 mol % without affecting the conversion
significantly (Table 7, entry 10). Under the optimized reaction
conditions, various combinations of substituted amines and
alkynes with para-formaldehyde were subjected to the coupling
reaction. For example, the reaction of pentyne with form-
aldehyde and N-benzylethanamine gave 87% yield (Chart 2,
entry b). Similarly, the reaction of morpholine or N-
methylpiperazine with formaldehyde and alkynes gave good
to excellent yield (Chart 2, entries c−g). The results of the
coupling reaction are summarized in Chart 2. In comparison to
the literature methods, the present protocol involves only 0.1
mol % catalyst loading without any additives.45 The
a
Table 6. Crystallographic Data of 1−4 and 6a
1
2
3
4
6a
formula
formula weight
crystal system
space group
a [Å]
C39H30N3P3
633.57
C82H66Cl3Cu3N8P6·C2H4Cl2
C78H60Br3Cu3N6P6·0.5(C2H4Cl2)
C80H63Cu3I3N7P6·C2H3N
1920.57
monoclinic
Cc (No. 9)
13.303(3)
27.703(7)
21.447(5)
90
C75H54Cu3I3N9P3
1745.50
1745.17
trigonal
P3121 (No. 152)
17.5311(3)
17.5311(3)
23.1240(4)
90
1746.94
monoclinic
P21/n (No. 14)
17.192(4)
18.254(4)
24.392(5)
90
triclinic
triclinic
P1 (No. 2)
̅
P1 (No. 2)
̅
10.2469(2)
13.8978(3)
23.3456(4)
89.790(1)
79.542(1)
84.910(1)
3256.25(11)
4
11.5209(12)
15.8765(17)
24.201(3)
75.258(1)
86.507(1)
74.065(1)
4116.3(8)
2
b [Å]
c [Å]
α [deg]
β [deg]
γ [deg]
V [Å3]
90
101.724(3)
90
98.274(3)
90
120
6154.77(18)
3
7495(3)
4
7822(3)
4
Z
ρcalc [g cm−3
]
1.292
1.413
1.548
1.631
1.408
μ[mm−1
F(000)
T (K)
]
1.927
3.893
2.654
2.165
1.994
1320
2676
3508
3800
1716
150
100
100
100
150
2θ range [deg]
3.2−72.4
25 575
5.82−133.2
40 344
7220
2.6−25.0
56 156
10 269
0.108
1.9−29.4
69 004
1.7−28.3
19 957
total no. of reflns
no. of indep reflns
12 205
18 868
10 476
Rint
R
0.051
0.047
0.043
0.144
0.0468
0.0417
0.1048
1.10
0.0662
0.1144
1.12
0.0282
0.0657
wR
S
0.1145
0.0662
0.1477
1.03
1.02
0.89
a
w = 1/[s2(Fo2) + (0.0241P)2 + 1.2733P], where P = (F2o + 2F2)/3.
E
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ac
,
Chart 2. Substrate Scope for A3 Coupling Reaction
a
b
c
Isolated yield. Conversion is based on amine by GC analysis. A3 coupling of alkyne, aldehyde, and amine using catalyst 4 (0.1 mol %) in wet
acetonitrile (4 mL) at 100 °C, under microwave irradiation (5 min).
reference (solid state 31P, δ 0). The microanalyses were performed
using a Carlo Erba Model 1112 elemental analyzer. The mass spectra
were recorded using a Waters Q-Tof micro (YA-105). The melting
points were observed in capillary tubes and are uncorrected.
experimental procedure was simple and produced good to
excellent yield within 5 min. However, similar coupling
reactions of N-benzylethanamine and morpholine in the
presence of 0.1 mol % of [Cu(PPh3)2I] also produced the
corresponding products in 86% and 79% yields. On increasing
the [Cu(PPh3)2I] loading to 0.2 mol %, the yields improved to
96% and 85%, respectively.
Synthesis of 2,4,6-Tris(diphenylphosphino)-1,3,5-triazine,
[C3N3(PPh2)3] (1).35 To a solution of cyanuric chloride (3.5 g,
19.14 mmol) in tetrahydrofuran (30 mL) was added a solution of
trimethylsilyldiphenylphosphine (16.3 g, 63.15 mmol) in the same
solvent (40 mL) at 0 °C. The reaction mixture was stirred for 2 h at
room temperature. The solvent and trimethylsilyl chloride formed
were removed under reduced pressure. The white sticky solid was
triturated with dry ethanol to obtain pure 1 as a white solid. Yield: 59%
CONCLUSIONS
■
In summary, self-assembled cyclophane-type metal−ligand
clusters based on tritopic tris(phosphine) and copper(I) salts
have been synthesized. The solid-state structures of these
complexes depend on the size of the halide ions. The copper(I)
chloride derivative is a monomeric metallocyclophane, whereas
the copper bromide derivative is dimeric. The large iodide ions
act as a bridge between individual metallocyclophane units to
form a 1D polymeric chain. The tricationic clusters, as
expected, adopt monomeric metallocyclophane structures.
The study suggests that the size of these cyclophane clusters
can be controlled by varying the size of the halide ions or by
making cationic complexes. Preliminary application of copper-
(I) metallocyclophanes toward catalytic A3 coupling reactions
suggests that they might serve as useful scaffolds for new
catalyst design. The work in this direction is in progress in our
laboratory.
1
(7.2 g). H NMR (400 MHz, CDCl3): δ 7.35−7.31 (m, Ar, 18H),
7.23−7.19 (m, Ar, 12H). 31P{1H} NMR (162 MHz, CDCl3): δ 0.7 (s).
Synthesis of {(C3N3(PPh2)3)2(CuCl)3} (2). To a dichloromethane
solution (10 mL) of CuCl (0.0141 g, 0.142 mmol) was added
dropwise a solution of 1 (0.06 g, 0.0947 mmol) in the same solvent
(10 mL) at room temperature with stirring. The clear yellow solution
was further stirred for 4 h, and the solvent was reduced to 3 mL under
reduced pressure and layered with petroleum ether (3 mL) to obtain a
yellow precipitate. The precipitate was isolated by filtration, washed
with diethyl ether (5 mL), and dried under reduced pressure. The X-
ray quality crystals were obtained by layering a concentrated solution
of 2 in 1,2-dichloroethane with acetonitrile. Yield: 90% (0.067 g). mp:
1
255 °C (dec.). H NMR (400 MHz, CDCl3): δ 7.40−7.11 (m, Ar,
60H). 31P{1H} NMR (162 MHz, CDCl3): δ −2.1 (s). CP-MAS
31P{1H} NMR (200 MHz): δ −1.0 (br s). MS (EI): m/z = 1527.06
[M − Cl]+. Anal. Calcd. for C82H66Cl3Cu3N8P6·C2H4Cl2: C, 57.80; H,
4.04; N, 6.42%. Found: C, 57.61; H, 3.79; N, 6.23%.
Synthesis of {(C3N3(PPh2)3)2(CuBr)3}2 (3). A solution of 1 (0.1 g,
0.1578 mmol) in dichloromethane (10 mL) was added dropwise to a
solution of CuBr (0.034 g, 0.2367 mmol) in acetonitrile (5 mL). The
yellow solution was stirred for 4 h, and the solvent was removed under
reduced pressure to afford a yellow solid. The crude product was
recrystallized from a mixture of dichloromethane and petroleum ether.
The X-ray quality crystals were obtained by layering a concentrated
solution of 3 in 1,2-dichloroethane with petroleum ether. Yield: 92%
EXPERIMENTAL SECTION
■
General Procedures. All manipulations were performed under
rigorously anaerobic conditions using Schlenk techniques. All the
solvents were purified by conventional methods53 and distilled prior to
use. The compounds, PPh2SiMe3,54 CuCl,55 CuBr,55 and [Cu-
56
(CH3CN)4]BF4 were prepared according to the published
procedures. Cyanuric chloride, CuI, and 1,10-phenthroline were
purchased from Aldrich Chemicals and used as such without further
purification. Other chemicals were obtained from commercial sources
and purified prior to use.
1
(0.124 g). mp: 246 °C (dec.). H NMR (400 MHz, CDCl3): δ 7.41−
7.10 (m, Ar, 60H). 31P{1H} NMR (162 MHz, CDCl3): δ −2.7 (s). MS
(EI): m/z = 1616.85 [Mmonomer − Br]+. Anal. Calcd. for C156H120
-
1
Instrumentation. The solution H, 13C, and 31P{1H} NMR (δ in
Br6Cu6N12P12·C2H4Cl2: C, 54.31; H, 3.58; N, 4.81%. Found: C, 54.16;
ppm) spectra were recorded using a Bruker AV 400 spectrometer
operating at frequencies of 400, 100, and 162 MHz, respectively. The
spectra were recorded in CDCl3 solutions with CDCl3 as internal lock.
Solid-state 31P NMR spectra were recorded on a Bruker AV 500 MHz
spectrometer operating at a frequency of 200 MHz with magic-angle
spinning (MAS) at 15 kHz. NMR shifts are given in δ with positive
values downfield of tetramethylsilane (1H and 13C{1H}), external
H3PO4 in D2O (31P), and external ammonium dihydrogen phosphate
H, 3.55; N, 4.59%.
Synthesis of {(C3N3(PPh2)3)2(CuI)3(NCCH3)}n (4). This was
synthesized by a procedure similar to that of 3, using 1 (0.056 g,
0.0884 mmol) and CuI (0.0253 g, 0.1326 mmol). The X-ray quality
crystals were obtained by layering a concentrated solution of 4 in
dichloromethane with acetonitrile. Yield: 94% (0.076 g). mp: 230 °C
(dec.). 1H NMR (400 MHz, CDCl3): δ 7.42−7.12 (m, Ar, 60H), 1.99
(s, CH3CN, 18H). 31P{1H} NMR (162 MHz, CDCl3): δ −3.3 (s).
F
DOI: 10.1021/acs.inorgchem.5b02075
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
CP-MAS 31P{1H} NMR (200 MHz): δ −24.0 to 6.4 (m). MS (EI):
m/z = 1710.93 [Mmonomer − (CH3CN) − I]+. Anal. Calcd. for
C80H63I3Cu3N7P6·CH3CN: C, 51.27; H, 3.46; N, 5.83%. Found: C,
51.14; H, 3.39; N, 5.72%.
Selected NMR and mass spectra, and crystal structures
(PDF)
Crystallographic data for 1 (CIF)
Crystallographic data for 2 (CIF)
Crystallographic data for 3 (CIF)
Crystallographic data for 4 (CIF)
Crystallographic data for 6a (CIF)
Synthesis of [{(C3N3(PPh2)3)2(Cu(NCCH3)2)3}(BF4)3] (5). A
solution of 1 (0.1 g, 0.1578 mmol) in dichloromethane (10 mL)
was added dropwise to a solution of [(Cu(NCMe)4)BF4] (0.075 g,
0.2367 mmol) in acetonitrile (5 mL). The yellow solution was stirred
for 4 h, and the solvent was reduced to 2 mL and layered with
petroleum ether (3 mL) to obtain a yellow precipitate. The precipitate
was isolated by filtration, washed with diethyl ether (5 mL), and dried
AUTHOR INFORMATION
Corresponding Author
*Phone: +91 22 2576 7181. E-mail: krishna@chem.iitb.ac.in,
msb_krishna@iitb.ac.in.
■
1
under reduced pressure. Yield: 81% (0.126 g). mp: 235 °C (dec.). H
NMR (400 MHz, CDCl3): δ 7.46 (t, J = 7.4 Hz, 12H), 7.30−7.20 (m,
Ar, 48H), 1.99 (s, CH3CN, 18H). 31P{1H} NMR (162 MHz, CDCl3):
δ 1.7 (s). MS (EI): m/z = 485.7 [M − (CH3CN)6 − BF4]3+. Anal.
Calcd. for C90H78N12B3Cu3F12P6: C, 55.02; H, 4.00; N, 8.56%. Found:
C, 55.11; H, 3.89; N, 8.12%.
Notes
The authors declare no competing financial interest.
Synthesis of [{(C3N3(PPh2)3)2(Cu(1,10-phen)3}(I)3] (6). To a
solution of 4 (0.048 g, 0.026 mmol) in dichloromethane (5 mL) was
added dropwise a solution of 1,10-phenanthroline (0.014 g, 0.078
mmol) in the same solvent (5 mL) at room temperature. The reaction
mixture was stirred for a further 2 h, concentrated to 2 mL, and layered
with petroleum ether (3 mL). The turbid yellow solution was stored at
room temperature for 24 h to obtain 6 as a yellow crystalline solid.
Yield: 92% (0.057 g). mp: 223 °C (dec.). 1H NMR (400 MHz,
CDCl3): δ 8.55 (br s, 6H), 8.24 (d, 6H, J = 8 Hz), 7.83 (m, 12H), 7.43
(m, 12H), 7.28−7.07 (m, 48H). 31P{1H} NMR (162 MHz, CDCl3): δ
1.3 (s). Anal. Calcd. for C75H54Cu3I3N9P3 C114H84N12Cu3I3P6: C,
57.80; H, 4.04; N, 6.42%. Found: C, 57.60; H, 3.79; N, 6.32%.
General Procedure for A3 Coupling Reactions. The reactions
were performed in a closed vessel containing a mixture of alkyne (1
equiv), amine (1.0 equiv), (CH2O)n (1.1 equiv), and catalyst (0.1 mol
%) in wet acetonitrile (4 mL). An initial microwave power of 80 W
was applied to reach 100 °C temperature. After a specified reaction
time, the reaction mixture was filtered and dried under reduced
pressure. The residual mixture was diluted with H2O (8 mL) and Et2O
(8 mL), followed by extraction twice with Et2O (6 mL). The
combined organic fractions were dried over MgSO4, and the solvent
was evaporated under vacuum. The crude products were purified by
silica gel column chromatography using petroleum ether/ethyl acetate
as the eluent. Yields were calculated against alkyne.
X-ray Crystallography. A crystal of each of the compounds 1, 2,
4, and 6a suitable for X-ray crystal analysis was mounted on a
Mitegenloop with a drop of Paratone oil and placed in a cold nitrogen
stream on the diffractometer. Hemispheres of data for 1 and 2 were
collected on a Bruker D8 Venture diffractometer using mirror-
monochromated Cu−Kα radiation (λ = 1.54178 Å), while full spheres
of data for 4 and 6a were collected on a Bruker Smart APEX
instrument with graphite-monochromated Mo−Kα radiation (λ =
0.71073 Å) using the APEX257 program suite. A crystal of 3 was
mounted on a glass fiber using epoxy glue and placed on a Rigaku
Saturn724 CCD diffractometer equipped with graphite-monochro-
mated Mo−Kα radiation (λ = 0.71073 Å). The raw data were reduced
to F2 values using the SAINT software. Multiple measurements of
equivalent reflections provided the basis for an empirical absorption
correction as well as a correction for any crystal deterioration during
the data collection (SADABS57). All the structures were solved by
direct methods (SHELXS58and SHELXT58) and refined by full-matrix
least-squares procedures on F2 using SHELXL58 (SHELXTL program
package57). Hydrogen atoms attached to carbon were placed in
calculated positions and included as riding contributions with isotropic
displacement parameters tied to those of the attached non-hydrogen
atoms.
ACKNOWLEDGMENTS
■
We are grateful to the Science & Engineering Research Board,
New Delhi, India, for financial support of this work through
grant No. SB/S1/IC-08/2014. G.S.A. thanks CSIR, New Delhi,
and IIT Bombay for the fellowship. We also thank the
Department of Chemistry Instrumentation Facilities, IIT
Bombay, for spectral and analytical data. J.T.M. thanks the
National Science Foundation under Grant NSF-MRI #1228232
for the purchase of the D8 Venture diffractometer and the
Chemistry Department of Tulane University for support of the
X-ray laboratory. We thank Mr. Vitthal K. for verifying some
catalytic data.
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ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.5b02075.
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