Using pyridinyl-substituted diaminotriazines to bind pd(II) and create metallotectons for engineering hydrogen-bonded crystals

Article abstract of DOI:10.1021/ic2003047

The pyridinyl groups of pyridinyl-substituted diaminotriazines 3a,b and 4a,b can bind metals, and the diaminotriazinyl (DAT) groups serve independently to ensure that the resulting complexes can participate in intercomplex hydrogen bonding according to ch

Full text of DOI:10.1021/ic2003047

ARTICLE
pubs.acs.org/IC
Using Pyridinyl-Substituted Diaminotriazines to Bind Pd(II) and Create
Metallotectons for Engineering Hydrogen-Bonded Crystals
Adam Duong, Thierry Maris, and James D. Wuest*
Dꢀepartement de Chimie, Universitꢀe de Montrꢀeal, Montrꢀeal, Quꢀebec H3C 3J7, Canada
S Supporting Information
b
ABSTRACT: The pyridinyl groups of pyridinyl-substituted diaminotriazines
3a,b and 4a,b can bind metals, and the diaminotriazinyl (DAT) groups serve
independently to ensure that the resulting complexes can participate in
intercomplex hydrogen bonding according to characteristic motifs. As planned,
ligands 3a,b and 4a,b form trans square-planar 2:1 complexes with PdCl2, and
further association of the complexes is directed in part by hydrogen bonding of
the DAT groups. Similarly, ligands 3a,b and 4a,b form cationic square-planar
4:1 complexes with Pd(BF4)2, Pd(PF6)2, and Pd(NO3)2, and the complexes
again typically associate by hydrogen bonding of the peripheral DAT groups. The observed complexes have predictable
constitutions and shared structural features that result logically from their characteristic topologies and the ability of DAT
groups to engage in hydrogen bonding. These results illustrate the potential of a hybrid inorganic/organic strategy for
constructing materials in which coordinative bonds to metals are used in conjunction with other interactions, both to build the
molecular components and to control their organization.
’ INTRODUCTION
consists of a covalently bonded molecular core, functionalized
by multiple peripheral groups (b) that engage in interactions
according to established patterns. Covalently bonded cores
are attractive because they are robust, but they must often be
made laboriously by multistep syntheses. An appealing alter-
native is the self-assembly of topologically related tetrahedral
or square-planar structures represented by metallotecton 2,
which is held together by coordinative bonds to a metal.5ꢀ7
Moreover, this alternative approach allows the geometry
of coordination to be altered systematically by varying the metal.
Despite the conspicuous advantages of this strategy, metallo-
tectons remain underexploited in the effort to engineer new
materials, possibly because their use requires a dual under-
standing of both organic and inorganic chemistry.
For nearly a century, X-ray diffraction has been used
to reveal the atomic structure of crystals.1 During that time,
more than 500 000 structures of molecular crystals have been
resolved and catalogued.2 Despite the imposing mass of col-
lected data, however, full understanding of the factors under-
lying structural preferences remains elusive.3 Each added
structure is unique, and its crystallographic parameters cannot
be predicted reliably. Designing new molecular crystals and
other ordered materials is a profoundly difficult enterprise, yet
it is essential for progress in many areas of science and
technology. Under these circumstances, qualitative guidelines
for controlling molecular organization are indispensable and
must be improved.
A widely used approach is based on the concept of building
ordered materials by the spontaneous association of tectons,
which are molecules with suitable topologies and an ability to
engage in multiple predictable interactions with neighbors.4
When properly exploited, this approach can yield materials
with predetermined organization and with collective proper-
ties that depend on those of the individual molecular compo-
nents, modified in a programmable way by the effect of their
neighbors. Even though structural parameters cannot be predic-
ted reliably in detail, this strategy allows gross features to be intro-
duced with confidence, and it will continue to be an important
source of new molecular materials.
This strategy must be further tested and refined by using it
to build materials from the widest possible range of molecular
components, held together by a full spectrum of interactions
that meet basic criteria of strength and reliability. Most tectons
that have been studied so far are typified by structure 1, which
Received: February 14, 2011
Published: May 18, 2011
r
2011 American Chemical Society
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Figure 1. Structure of complex PdCl2(3a)2 2DMSO in crystals grown from DMSO/H2O. Hydrogen bonds are represented by broken lines. Except
3
where noted otherwise, carbon atoms are shown in gray, hydrogen atoms in white, nitrogen atoms in blue, oxygen atoms in red, sulfur atoms in yellow,
chlorine atoms in green, and palladium atoms in rose. (a) Thermal atomic displacement ellipsoid plot, with ellipsoids of non-hydrogen atoms drawn at
the 50% probability level and hydrogen atoms represented by a sphere of arbitrary size. Key bond lengths include Pd1ꢀN1 = 2.012(18) Å and Pd1ꢀCl1 =
2.309(3) Å. Key bond angles include Cl1ꢀPd1ꢀCl1A = 177.0(6)°, N1ꢀPd1ꢀN1A = 180°, and N1ꢀPd1ꢀCl1 = 91.5(3)°. (b) View along the a axis
showing eight NꢀH N hydrogen bonds of modified type III (3.103(12) Å) formed by the central metallotecton and eight neighbors, four in an upper
3 3 3
plane (normal colors) and four in a lower plane (red). Guest molecules of DMSO are omitted for clarity. (c) Alternative view along the c axis showing the
relationship between the central metallotecton and its neighbors.
To further explore the potential of this approach, we elected to
study the behavior of metallic complexes of substituted pyridine
3a8 and its elongated derivative 3b,9 as well as their isomers
4a10 and 4b.11 The design of this set of ligands is based on the
well-established ability of pyridines to bind metals, combined
with the tendency of diaminotriazinyl (DAT) groups to engage
in multiple hydrogen bonds according to motifs IꢀIII.12 Pyri-
dines are typically stronger ligands than triazines, so we expec-
ted the two distinct parts of compounds 3a,b and 4a,b to
operate orthogonally, one to ensure formation of a metallotecton
by coordination and the other to direct intermolecular associa-
tion by hydrogen bonding. In initial work, we decided to examine
the ability of ligands 3a,b and 4a,b to bind Pd(II), which is known
to favor related complexes with a square-planar geometry.13,14 By
focusing on a single metal with a predictable geometry of coor-
dination, bound by a family of ligands that vary systematically, we
designed our study to produce a set of closely related structures
that can be compared to reveal basic principles of metallotectonic
assembly.
’ RESULTS AND DISCUSSION
Syntheses of Ligands 3a,b and 4a,b. 6-(Pyridin-4-yl)-1,3,
5-triazine-2,4-diamine (3a),8 6-[4-(pyridin-4-yl)phenyl]-1,3,
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Table 1. Crystallographic Data for 1:2 and 1:1 Complexes of PdCl2 with Pyridinyl-Substituted Diaminotriazines 3a,b, 4a,b, and 6
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complex
PdCl2(3a)2 2DMSO
PdCl2(3a)2 2DMSO dioxane
PdCl2(3b)2
PdCl2(4a)2 3DMSO
PdCl2(6)
3
3
3
3
crystallization medium
formula
cryst syst
space group
a (Å)
DMSO/H2O
C20H28Cl2N12O2PdS2
orthorhombic
I222
DMSO/dioxane
DMSO/EtOAc
C28H24Cl2N12Pd
monoclinic
P21/n
DMSO
C22H34Cl2N12O3PdS3
monoclinic
C2/c
DMSO/H2O
C8H8Cl2N5Pd
monoclinic
P21/n
C24H36Cl2N12O4PdS2
triclinic
P1
3.7721(10)
11.346(3)
28.990(7)
90
6.1250(8)
9.7568(13)
15.6448(18)
105.458(6)
96.393(6)
97.755(7)
882.19(19)
1
13.6163(10)
10.9178(9)
18.8566(15)
90
37.2003(9)
8.0105(2)
11.0946(3)
90
7.9908(3)
9.1500(4)
15.4450(16)
90
b (Å)
c (Å)
R (deg)
β (deg)
γ (deg)
V (Å3)
90
93.775(3)
90
93.530(1)
90
98.586(2)
90
90
1240.7(6)
2
2797.1(4)
4
3299.84(15)
4
1116.62(8)
4
Z
F
calc (g cmꢀ3
)
1.900
1.502
1.676
1.586
2.174
T (K)
100
150
150
100
150
μ (mmꢀ1
)
10.014
0.0734
0.0740
0.1754
0.1758
2699
7.152
7.477
8.192
17.711
R1, I > 2σ(I)
R1, all data
0.0491
0.0583
0.0235
0.0263
0.0533
0.0623
0.0248
0.0290
wR2, I > 2σ(I)
0.1340
0.1350
0.0659
0.0709
wR2, all data
0.1377
0.1355
0.0669
0.0721
measured reflns
12588
30310
25455
14799
independent reflns
observed reflns [I > 2σ(I)]
1091
3156
5280
2910
2213
1023
2882
3201
2761
2027
a. Structures of the 2:1 Complex of 6-(Pyridin-4-yl)-1,3,
5-triazine-2,4-diamine (3a) with PdCl2. Pyridine itself is known
to react with PdCl2 to give square-planar complex 5 with trans-
oriented pyridinyl ligands,13 so we expected ligand 3a to yield an
analogous 2:1 complex.
5-triazine-2,4-diamine (3b),9 6-(pyridin-3-yl)-1,3,5-triazine-2,4-
diamine (4a),10 and 6-[4-(pyridin-3-yl)phenyl]-1,3,5-triazine-
2,4-diamine (4b)11 were prepared by reported methods.
Structures of Unbound Ligands 3a,b and 4a,b. To provide
a basis for understanding the association of metallotectons de-
rived from compounds 3a,b and 4a,b, we examined the structures
of crystals of the unbound ligands themselves in a preliminary
study.11 A comparison of the structures identified three shared
features: (1) The compounds adopt flattened conformations typical
of aryl-substituted triazines;12 (2) they form approximately
coplanar hydrogen bonds according to characteristic motifs Iꢀ
III; and (3) these interactions play a major role in directing
molecular organization. Because compounds 3a,b and 4a,b have
similar flattened molecular shapes and incorporate DAT groups,
they crystallize similarly to give hydrogen-bonded structures built
from chains, tapes, and layers. The same factors can be expected
to help direct the association of metallotectons derived from
compounds 3a,b and 4a,b when they are used as ligands.
Syntheses and Structures of Complexes of Ligands 3a,b
and 4a,b with PdCl2. Complexes were prepared by mixing the
ligands (2 equiv) with PdCl2 (1 equiv) in MeCN. The pre-
cipitated solids were then crystallized, and the structures were
determined by X-ray crystallography.
Crystals grown from DMSO/H2O were found to have the
composition PdCl2(3a)2 2DMSO and to belong to the orthor-
3
hombic space group I222. Views of the structure are provided in
Figure 1, and other crystallographic data are presented in Table 1.
As anticipated, the pyridinyl groups of compound 3a are bound
in a trans orientation to give a square-planar Pd(II) complex
(Figure 1a), with normal PdꢀN and PdꢀCl distances.13 The
pyridinyl and triazinyl rings in each ligand are nearly coplanar, as
expected,12 and the torsional angle between the average planes is
only 4.8(6)°. The average planes of the two trans-oriented
ligands form an angle of 50.6(2)° with respect to each other,
and they lie at angles of 1.3(3)° and 49.4(1)° with respect to the
essentially planar PdN2Cl2 core of the metallotecton.
The resulting metallotecton predictably defines a linear struc-
ture with DAT groups at its two extremities. Each DAT group
participates in four NꢀH N hydrogen bonds according to a
3 3 3
modified version of motif III, and each metallotecton thereby
forms a total of eight hydrogen bonds with eight neighbors to give
a three-dimensional network (Figures 1b,c). Channels aligned with
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Figure 2. Structure of complex PdCl2(3a)2 2DMSO dioxane in crystals grown from DMSO/dioxane. Hydrogen bonds are represented by broken
3
3
lines. Carbon atoms are shown in gray, hydrogen atoms in white, nitrogen atoms in blue, oxygen atoms in red, sulfur atoms in yellow, chlorine atoms in
green, and palladium atoms in rose. (a) Thermal atomic displacement ellipsoid plot, with ellipsoids of non-hydrogen atoms drawn at the 50% probability
level and hydrogen atoms represented by a sphere of arbitrary size. Key bond lengths include Pd1ꢀN1 = 2.018(3) Å and Pd1ꢀCl1 = 2.3207(13) Å.
Representative bond angles include Cl1ꢀPd1ꢀCl1A = 180°, N1ꢀPd1ꢀN1A = 180°, and N1ꢀPd1ꢀCl1 = 90.20(12)°. (b) View showing how
NꢀH N hydrogen bonds of type I (2.980(5) Å), reinforced by NꢀH O hydrogen bonds involving bridging molecules of DMSO (average
3 3 3
3 3 3
distance = 2.959(5) Å), link the metallotectons into chains, which are further connected into sheets by NꢀH O hydrogen bonds (3.049(5) Å)
3 3 3
involving intervening molecules of dioxane. (c) View showing alternating layers of metallotectons and guests, with molecules of DMSO omitted for
clarity.
the a axis contain disordered molecules of DMSO, which form
hydrogen bonds with the DAT groups (Figure 1a) and thereby
prevent the metallotectons from associating end-to-end by
forming hydrogen bonds of type I. As planned, the observed struc-
ture is organized by a combination of coordinative interactions
and hydrogen bonds. Key features of the structure are a logical
result of (1) the tendency of PdCl2 to form trans square-planar
1:2 complexes with pyridines and (2) the creation of a metallo-
tecton with DAT groups at the ends of an elongated linear
structure, which favors a parallel alignment held together by
hydrogen bonds.
To probe the effect of solvent on the formation and association
of metallotectons derived from PdCl2 and ligand 3a, we also grew
crystals from DMSO/dioxane. They proved to have the composition
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Figure 3. Structure of complex PdCl2(3b)2 in crystals grown from DMSO/EtOAc. Hydrogen bonds are represented by broken lines. Carbon atoms are
shown in gray, hydrogen atoms in white, nitrogen atoms in blue, chlorine atoms in green, and palladium atoms in rose. (a) Thermal atomic displacement
ellipsoid plot, with ellipsoids of non-hydrogen atoms drawn at the 50% probability level and hydrogen atoms represented by a sphere of arbitrary size.
Key bond lengths include Pd1ꢀN1 = 2.026(4) Å, Pd1ꢀN7 = 2.033(4) Å, Pd1ꢀCl1 = 2.3079(15) Å, and Pd1ꢀCl2 = 2.2968(15) Å. Representative
bond angles include Cl1ꢀPd1ꢀCl2 = 177.21(5)°, N1ꢀPd1ꢀN7 = 179.4(2)°, and N1ꢀPd1ꢀCl1 = 88.33(15)°. (b) View showing how NꢀH
hydrogen bonds of type I (2.961(6) Å) link the metallotectons into chains, which are further connected into sheets by edge-to-face NꢀH
hydrogen bonds (3.081(6) Å).
N
N
3 3 3
3 3 3
PdCl2(3a)2 2DMSO dioxane and to belong to the triclinic
PdCl2(3b)2 and to belong to the monoclinic space group P21/n.
3
3
space group P1. Views of the structure are shown in Figure 2,
and other crystallographic data are summarized in Table 1. Again,
a square-planar complex with trans-oriented pyridinyl groups is
formed (Figure 2a), with normal PdꢀN and PdꢀCl distances.13
The pyridinyl and triazinyl rings in each ligand are essentially
coplanar, and both ligands lie in the same plane, which forms an
angle of 62.7(1)° with the PdN2Cl2 core of the metallotecton.
As shown in Figure 2b, the metallotectons are linked into
chains by hydrogen bonding of DAT groups according to motif I,
Figure 3 provides views of the structure, and Table 1 contains
other crystallographic data. As planned, a square-planar complex
with trans-oriented pyridinyl groups is produced (Figure 3a),
with normal PdꢀN and PdꢀCl distances.13 The bound ligands
adopt nearly planar conformations, and their average planes form
similar angles (44.4(1)° and 71.6(1)°) with the PdN2Cl2 core of
the metallotecton.
As shown in Figure 3b, the metallotectons are joined to form
chains through NꢀH N hydrogen bonds of type I involving
3 3 3
reinforced by NꢀH O hydrogen bonds involving bridging
DAT groups, and the chains are further connected to form sheets
3 3 3
molecules of DMSO. The chains are further joined to form sheets
through edge-to-face NꢀH N hydrogen bonds. Again, PdCl2
3 3 3
by NꢀH O hydrogen bonds with connecting molecules of
reacts predictably with ligand 3b to form a metallotecton that
crystallizes to generate a structure with expected features, dictated
in part by hydrogen bonding of the DAT groups and by the elon-
gated topology of the molecular constituents, which favors a parallel
arrangement.
3 3 3
dioxane (Figure 2b), and the sheets stack to give a structure that
consists of layers of metallotectons separated by intervening
layers of DMSO and dioxane (Figure 2c). Together, these results
confirm that the product of the reaction of PdCl2 with ligand 3a
can be crystallized under different conditions to give structures
built predictably from a metallotecton with a single well-defined
constitution. However, the conformation of the metallotecton
can vary, thereby allowing somewhat different structures to be
formed. Nevertheless, both observed structures predictably share
two key features: (1) The elongated linear metallotectons are
arranged in a parallel orientation, and (2) they are positioned by
multiple coplanar hydrogen bonds involving DAT groups.
b. Structure of the 2:1 Complex of 6-[4-(Pyridin-4-yl)phenyl]-
1,3,5-triazine-2,4-diamine (3b) with PdCl2. On the basis of the
observed behavior of 6-(pyridin-4-yl)-1,3,5-triazine-2,4-diamine
(3a), we expected elongated analogue 3b to behave in a similar
way. Crystals of the complex of PdCl2 with ligand 3b were grown
from DMSO/EtOAc. They were found to have the composition
c. Structure of the 2:1 Complex of 6-(Pyridin-3-yl)-1,3,
5-triazine-2,4-diamine (4a) with PdCl2. To probe the effect of
distorting the linear geometry of metallotectons derived from ligand
3a and its extended analogue 3b, we grew crystals of the complex of
PdCl2 with ligand 4a from DMSO. They proved to have the
composition PdCl2(4a)2 3DMSO and to belong to the monoclinic
3
space group C2/c. Views of the structure are shown in Figure 4, and
other crystallographic data are presented in Table 1. As expected,
complexation yields a square-planar complex with trans-oriented
pyridinyl groups (Figure 4a), and the PdꢀN and PdꢀCl distances
are normal.13 Each bound ligand adopts a flattened conformation,
and the two ligands lie in essentially the same plane, which forms an
angle of 66.8(1)° with the PdN2Cl2 core of the metallotecton. The
two DAT groups are oriented on opposite sides of the PdN2Cl2 core.
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Figure 4. Structure of complex PdCl2(4a)2 3DMSO in crystals grown from DMSO. Hydrogen bonds are represented by broken lines. Carbon atoms
3
are shown in gray, hydrogen atoms in white, nitrogen atoms in blue, oxygen atoms in red, sulfur atoms in yellow, chlorine atoms in green, and palladium
atoms in rose. (a) Thermal atomic displacement ellipsoid plot, with ellipsoids of non-hydrogen atoms drawn at the 50% probability level and hydrogen
atoms represented by a sphere of arbitrary size. Key bond lengths include Pd1ꢀN1 = 2.0150(16) Å and Pd1ꢀCl1 = 2.2981(5) Å. Representative bond
angles include Cl1ꢀPd1ꢀCl1A = 180°, N1ꢀPd1ꢀN1A = 180°, and N1ꢀPd1ꢀCl1 = 90.97(5)°. (b) View showing how NꢀH N hydrogen bonds
3 3 3
of type I (2.961(3) Å) link the metallotectons into chains, which interact with adjacent chains by NꢀH O hydrogen bonds involving bridging
3 3 3
molecules of DMSO.
Although the DAT groups of each metallotecton no longer
have a collinear orientation, as maintained in analogous com-
plexes of ligands 3a and 3b, association occurs in essentially the
Pd(II). To test this possibility, ligand 6 and PdCl2 were mixed in
a 1:1 ratio in MeCN. The precipitated solid was then crystallized
from DMSO/H2O, and the structure was determined by X-ray
crystallography.
The crystals were found to have the composition PdCl2(6)
and to belong to the monoclinic space group P21/n. Views of the
structure are presented in Figure 5, and other crystallographic
data are provided in Table 1. As expected, complexation yields a
square-planar chelate (Figure 5a) with normal PdꢀN and
PdꢀCl distances.13 The PdꢀNtriazine bond is longer than the
PdꢀNpyridine bond, reflecting the weaker coordination of tri-
azines. The bound ligand is essentially planar and lies close to the
average plane of the PdN2Cl2 core of the complex.
same way. Specifically, NꢀH N hydrogen bonding of type I
3 3 3
leads to the formation of zigzag chains, which engage in addi-
tional intra- and interchain NꢀH O hydrogen bonds invol-
3 3 3
ving bridging molecules of DMSO (Figure 4b). Again, complex-
ation of PdCl2 produces a metallotecton with a predictable cons-
titution; furthermore, its elongated geometry and the incorpo-
rated DAT groups ensure the formation of a structure in which
the components have an approximately parallel orientation and
engage in multiple intermolecular hydrogen bonds according to
reliable patterns.
The chelates are paired by NꢀH N hydrogen bonds of
Synthesis and Structure of the 1:1 Complex of 6-(Pyridin-
2-yl)-1,3,5-triazine-2,4-diamine (6) with PdCl2. Ligands 3a,
3b, and 4a all behave as expected by producing square-planar
trans 2:1 complexes with PdCl2 analogous to structure 5. In these
complexes, the pyridinyl and DAT groups operate orthogonally
to ensure coordination and intermolecular hydrogen bonding,
respectively, without mutual interference. In contrast, ligand 615
promises to allow the two groups to cooperate by chelating
3 3 3
type I to form dimers, which associate with adjacent dimers
in various ways, such as by forming NꢀH Cl interactions
3 3 3
(Figure 5b). The structure of the complex is noteworthy because
it establishes that compound 6 can serve as a bidentate ligand
analogous to 2,20-bipyridine. This suggests a potentially general
strategy in which heteroaromatic groups in other well-known
multidentate ligands are replaced with DAT groups to create
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Figure 5. Structure of complex PdCl2(6) in crystals grown from DMSO/H2O. Hydrogen bonds are represented by broken lines. Carbon atoms are
shown in gray, hydrogen atoms in white, nitrogen atoms in blue, chlorine atoms in green, and palladium atoms in rose. (a) Thermal atomic displacement
ellipsoid plot, with ellipsoids of non-hydrogen atoms drawn at the 50% probability level and hydrogen atoms represented by a sphere of arbitrary size.
Key bond lengths include Pd1ꢀN1 = 2.029(2) Å, Pd1ꢀN2 = 2.087(2) Å, Pd1ꢀCl1 = 2.2897(8) Å, and Pd1ꢀCl2 = 2.3041(7) Å. Representative bond
angles include Cl1ꢀPd1ꢀCl2 = 86.12(3)°, N1ꢀPd1ꢀN2 = 80.54(10)°, N1ꢀPd1ꢀCl1 = 93.06(8)°, and N2ꢀPd1ꢀCl2 = 173.35(7)°. (b) View
showing how NꢀH N hydrogen bonds of type I (3.023(4) Å) link the chelates into dimers, which associate with adjacent dimers in various ways, such
3 3 3
as by forming NꢀH Cl interactions.
3 3 3
surrogates with two characteristic properties: (1) They can
chelate metals in analogous ways, and (2) the resulting com-
plexes have similar topologies, but they are endowed with the
additional ability to engage in extensive hydrogen bonding
according to reliable patterns. However, metallotectons derived
from PdCl2 and bidentate ligand 6 have only one DAT group per
complex, so they are less able to engage in intermolecular hydro-
gen bonding than complexes derived from monodentate ligands
3a,b and 4a,b, which have two DAT groups. For this reason, we
elected to reserve further study of ligand 6 and bidentate ana-
logues for future work and to focus in the present study on the
behavior of monodentate ligands 3a,b and 4a,b.
Syntheses and Structures of 4:1 Complexes of Ligands 3a,
b and 4a,b with Pd(BF4)2, Pd(PF6)2, and Pd(NO3)2. Complexes
were prepared by mixing the ligands (4 equiv) with salts of Pd(II)
(1 equiv) in MeCN. The precipitated solids were then crystal-
lized, after exchange of anions if needed, and the structures were
determined by X-ray crystallography.
designed to create a robust open rectangular grid held together
by hydrogen bonding of four tetragonally directed DAT groups.
In fact, however, the observed structure is relatively compact and
can be considered to be built from the tetrameric units shown in
Figure 6b, in which face-to-face and edge-to-face aromatic inter-
actions of DAT groups are present but normal hydrogen bonds
are absent. Interpenetration of the resulting cationic grids (Figure 6c)
leads to a three-dimensional structure in which each molecule in
a grid forms a total of six NꢀH N hydrogen bonds with six
3 3 3
adjacent molecules in an interpenetrating grid (Figure 6d). In
addition, H2O and BF4ꢀ included within the structure engage in
extensive hydrogen bonding.
b. Structure of the 4:1 Complex of 6-[4-(Pyridin-4-yl)phenyl]-
1,3,5-triazine-2,4-diamine (3b) with Pd(NO3)2. To further as-
sess the potential of pyridinyl-substituted diaminotriazines to
form metallotectons related to complex 7, we examined the
product of the reaction of extended ligand 3b with Pd(NO3)2.
Crystals grown from DMSO/H2O/MeOH were found to have
the composition [Pd(3b)4](NO3)2 5DMSO 2H2O MeOH
a. Structure of the 4:1 Complex of 6-(Pyridin-4-yl)-1,3,
5-triazine-2,4-diamine (3a) with Pd(BF4)2. Pyridine reacts with
Pd(BF4)2 to give square-planar dication 7,14 so we expected
ligand 3a to yield an analogous 4:1 complex. Crystals grown from
DMSO/H2O/MeCN proved to have the composition [Pd(3a)4]-
3
3
3
and to belong to the triclinic space group P1. Views of the struc-
ture are presented in Figure 7, and other crystallographic data are
provided in Table 2. Again, the pyridinyl groups of the ligand
bind Pd(II) to give a square-planar complex (Figure 7a), with
normal PdꢀN distances.14 The ligands adopt a variety of non-
planar conformations, and their average planes lie at an average
angle of 36.0(3)° with respect to the PdN4 core of the metal-
lotecton.
(BF4)2 9H2O andtobelongtothemonoclinic spacegroup P21/n.
3
Figure 6 shows views of the structure, and Table 2 summarizes
other crystallographic data. As anticipated, the pyridinyl groups
of ligand 3a bind Pd(II) to give a square-planar complex (Figure 6a),
with normal PdꢀN distances.14 The pyridinyl and triazinyl rings
in each ligand are nearly coplanar, and the pyridinyl groups lie
essentially perpendicular to the PdN4 core of the metallotecton,
as observed in related structures.14
Two arms of each metallotecton participate in the formation of
a total of four NꢀH N hydrogen bonds of type II to form
3 3 3
characteristic dimers (Figure 7b), which associate with adjacent
dimers to form sheets held together by additional NꢀH
N
3 3 3
The resulting metallotecton has a molecular structure that
adheres closely to expectations; moreover, it appears to be properly
hydrogen bonds of type I, NꢀH O hydrogen bonds involv-
3 3 3
ing bridging molecules of DMSO, and aromatic interactions. All
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Figure 6. Structure of complex [Pd(3a)4](BF4)2 9H2O in crystals grown from DMSO/H2O/MeCN. Except where noted otherwise, carbon atoms
3
are shown in gray, hydrogen atoms in white, boron atoms in orange, nitrogen atoms in blue, fluorine atoms in green, and palladium atoms in rose.
(a) Thermal atomic displacement ellipsoid plot, with ellipsoids of non-hydrogen atoms drawn at the 50% probability level and hydrogen atoms
represented by a sphere of arbitrary size. Key bond lengths include Pd1ꢀN10 = 2.031(3) Å, Pd1ꢀN20 = 2.024(4) Å, Pd1ꢀN30 = 2.027(3) Å, and
Pd1ꢀN40 = 2.029(3) Å. Representative bond angles include N10ꢀPd1ꢀN20 = 89.42(13)°. (b) View showing the construction of cationic grids built
from tetrameric aggregates. Guest molecules of H2O and BF4ꢀ are omitted for clarity. (c) View illustrating the interpenetration of grids, with one drawn
in green and three independent grids in red. (d) View showing NꢀH N hydrogen bonds between molecules in the green and red grids.
3 3 3
hydrogen bonding between DAT groups is reinforced by bridg-
ing nitrate anions.
necessarily conducted in solvents that can compete with DAT
groups as participants in hydrogen bonding.
As planned, both ligand 3a and extended version 3b form
square-planar dicationic Pd(II) complexes analogous to structure
7. The resulting metallotectons have similar topologies and a
shared ability to engage in hydrogen bonding directed by peri-
pheral DAT groups, yet their patterns of association are distinctly
different. The observed differences may arise in part because the
counterions are not the same and because the crystallizations are
c. Structure of the 4:1 Complex of 6-(Pyridin-3-yl)-1,3,
5-triazine-2,4-diamine (4a) with Pd(PF6)2. The solid formed by
the reaction of Pd(BF4)2 with isomeric ligand 4a proved to have low
solubility, so it was subjected to metathesis by the addition of excess
NaPF6 in H2O/MeCN, and crystals of the ion-exchanged product
were grown from DMSO/H2O/EtOH. They were found to have
the composition [Pd(4a)4](PF6)(OH) 4H2O 2EtOH and to
3
3
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Table 2. Crystallographic Data for 1:4 Complexes of Pd(II) with Pyridinyl-Substituted Diaminotriazines 3a,b and 4a,b
[Pd(3b)4](NO3)2
[Pd(4a)4](PF6)(OH)
[Pd(4b)4](NO3)2
3
3
3
complex
[Pd(3a)4](BF4)2 9H2O
5DMSO 2H2O MeOH
4H2O 2EtOH
6DMSO 4H2O
3
3
3
3
3
crystallization medium
formula
cryst syst
space group
a (Å)
DMSO/H2O/MeCN
C32H50B2F8N24O9Pd
monoclinic
P21/n
DMSO/H2O/MeOH
C67H86N26O14PdS5
triclinic
DMSO/H2O/EtOH
C36H53F6N24O7PPd
monoclinic
C2/m
DMSO/H2O
C68H92N26O16PdS6
monoclinic
C2/m
P1
15.2752(3)
18.5707(4)
17.5545(4)
90
11.4019(17)
16.516(2)
24.136(3)
95.452(7)
91.174(6)
108.713(6)
4279.2(11)
2
12.914(3)
20.449(3)
11.744(4)
90
20.6228(6)
21.2334(6)
15.2728(5)
90
b (Å)
c (Å)
R (deg)
β (deg)
γ (deg)
V (Å3)
98.680(1)
90
101.709(6)
90
126.999(1)
90
4922.67(18)
4
3036.9(12)
2
5341.2(3)
2
Z
F
calc (g cmꢀ3
)
1.612
1.355
1.296
1.132
T (K)
200
150
150
150
μ (mmꢀ1
)
3.987
3.500
3.400
3.016
R1, I > 2σ(I)
R1, all data
0.0769
0.0709
0.0528
0.0620
0.0791
0.0901
0.0529
0.0623
wR2, I > 2σ(I)
0.1869
0.1536
0.1736
0.1579
wR2, all data
0.1884
0.1560
0.1739
0.1585
measured reflns
67694
60316
24003
41486
independent reflns
observed reflns [I > 2σ(I)]
8948
15194
2709
4841
7082
6471
2703
4337
belong to the monoclinic space group C2/m. Views of the structure
are shown in Figure 8, and other crystallographic data are presented
in Table 2. As expected, a square-planar complex is formed
(Figure 8a), with a normal PdꢀN distances.14 The ligands adopt
flattened conformations, and their average planes lie at an ave-
rage angle of 63.9(1)° with respect to the PdN4 core of the metal-
lotecton. The DAT groups of trans-disposed ligands have an
opposed orientation, with one DAT group above the PdN4 plane
and the other below it.
crystallographic data. As planned, coordination yields a square-
planar complex (Figure 9a), with a normal PdꢀN distances.14
The ligands adopt flattened conformations, and their average
planes form an average angle of 76.3(1)° with respect to the
PdN4 core of the metallotecton. The DAT groups of trans-
disposed ligands have an opposed orientation, with one DAT
group above the PdN4 plane and the other below it, giving the
metallotecton an elongated topology. As shown in Figure 9b, the
metallotectons associate to form sheets maintained by NꢀH
N
3 3 3
The structure can be considered to consist of cationic sheets in
the ab plane, in which the four DAT groups of each metallotecton
hydrogen bonds of type I. Other interactions help control the
overall molecular organization, including NꢀH O hydro-
3 3 3
participate in a total of 16 NꢀH N hydrogen bonds (Figure 8b).
gen bonds involving two types of bridging DMSO, one that
3 3 3
Each DAT group engages in two NꢀH N hydrogen bonds of
reinforces motif I (average NꢀH O distance = 2.888(6) Å)
3 3 3
3 3 3
type III, as well as two additional single NꢀH N hydrogen
and the other that helps orient adjacent arms of each metallo-
3 3 3
bonds. The extensively hydrogen-bonded structure is also re-
inforced by aromatic interactions. The cationic sheets are sepa-
rated by intervening anionic layers containing hydrogen-bonded
PF6ꢀ, disordered OHꢀ, H2O, and EtOH (Figure 8c). Again, the
complexation of ligand 4a with Pd(II) occurs predictably to give
a square planar metallotecton analogous to structure 7, and the
peripheral DAT groups play a key role in directing molecular
association by engaging in hydrogen bonds according to estab-
lished patterns.
tecton (NꢀH O distance = 3.038(3) Å).
3 3 3
’ CONCLUSIONS
Our results provide a deeper understanding of how coordina-
tive bonds to metals can be used in conjunction with other
interactions to direct molecular assembly. In particular, our work
illustrates how materials with predictable structural features can
be built from metallotectons, which are well-defined complexes
incorporating ligands that can bind metals and can simulta-
neously engage in multiple intercomplex interactions according
to reliable motifs. To further gauge the potential of this approach,
we have examined the behavior of Pd(II) complexes of ligands
3a,b, 4a,b, and 6, which incorporate pyridinyl groups to bind
metals and DAT groups to help ensure participation in reliable
intermolecular hydrogen bonds.
d. Structure of the 4:1 Complex of 6-[4-(Pyridin-3-yl)phenyl]-
1,3,5-triazine-2,4-diamine (4b) with Pd(NO3)2. To complete
our assessment of the ability of pyridinyl-substituted diamino-
triazines to form metallotectons related to complex 7, we exam-
ined the product of the reaction of extended ligand 4b with
Pd(NO3)2. Crystals grown from DMSO/H2O proved to have
the approximate composition [Pd(4b)4](NO3)2 6DMSO 4H2O
3
3
and to belong to the monoclinic space group C2/m. Figure 9
As planned, on the basis of established patterns of coordina-
tion involving pyridine and simple derivatives, ligands 3a,b, 4a,b,
provides views of the structure, and Table 2 summarizes other
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Figure 7. Structure of complex [Pd(3b)4](NO3)2 5DMSO 2H2O MeOH in crystals grown from DMSO/H2O/MeOH. Hydrogen bonds are
3
3
3
represented by broken lines. Carbon atoms are shown in gray, hydrogen atoms in white, nitrogen atoms in blue, oxygen atoms in red, sulfur atoms in
yellow, and palladium atoms in rose. (a) Thermal atomic displacement ellipsoid plot, with ellipsoids of non-hydrogen atoms drawn at the 50% probability level
and hydrogen atoms represented by a sphere of arbitrary size. Key bond lengths include Pd1ꢀN1 = 2.032(5) Å, Pd1ꢀN7 = 1.983(5) Å, Pd1ꢀN13 = 1.997(5) Å,
and Pd1ꢀN19 = 2.023(5) Å. Representative bond angles include N1ꢀPd1ꢀN7 = 90.07(19)°. (b) View showing how NꢀH N hydrogen bonds of type II
3 3 3
(average distance = 3.084(9) Å) join the metallotectons to form dimers, which interact with adjacent dimers by additional NꢀH N hydrogen bonds of type I
3 3 3
(3.054(7) Å), NꢀH O hydrogen bonds involving bridging molecules of DMSO (average distance = 2.936(8) Å), and aromatic interactions.
3 3 3
and 6 all bind Pd(II) to gave square-planar complexes with
predicted constitutions. Although the precise geometry of the
resulting metallotectons could not be foreseen with confidence,
in all cases, the ligands adopted normal flattened conformations
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and maintained expected orientations with respect to the PdL4
core. As anticipated, subsequent association of the resulting
metallotectons was found to be directed in part by their logical
topologies and by the ability of the peripheral DAT groups to
engage in intermolecular hydrogen bonding according to estab-
lished motifs IꢀIII. In only one case were such interactions not
present.
Complexes of ligands 3a,b, 4a,b, and 6 have shared structural
features that can be considered to be introduced reliably by
design. However, comparisons of molecular organization reveal
few striking analogies, and structural details vary widely, parti-
2þ
cularly in the ionic PdL4 complexes. These differences pre-
sumably reflect diverse factors, such as the contributions of ionic
interactions, the role of the specific anions, and competitive
hydrogen bonding involving molecules of solvent.
Despite the present lack of perfect control, our work never-
theless affirms the promise of designing new ordered materials
based on the hybrid inorganic/organic strategy of using metallo-
tectons. A conspicuous advantage of this strategy is that the
molecular core can be constructed spontaneously by coordina-
tion, and peripheral functionality can independently control how
the complexes are positioned with respect to their neighbors.
’ EXPERIMENTAL SECTION
General Notes. 6-(Pyridin-4-yl)-1,3,5-triazine-2,4-diamine (3a),8
6-[4-(pyridin-4-yl)phenyl]-1,3,5-triazine-2,4-diamine (3b),9 6-(pyridin-
3-yl)-1,3,5-triazine-2,4-diamine (4a),10 6-[4-(pyridin-3-yl)phenyl]-
1,3,5-triazine-2,4-diamine (4b),11 and 6-(pyridin-2-yl)-1,3,5-triazine-2,
4-diamine (6)15 were prepared by reported methods. Their complexes
with Pd(II) were made by the procedures summarized below. Other
chemicals were purchased from commercial sources and used without
further purification.
General Procedure for Preparing PdCl2 Complexes of
Ligands 3a,b, 4a,b, and 6. A stirred suspension of PdCl2 (1.0
equiv) and the ligand (2.0 equiv in the cases of compounds 3a,b and 4a,
b; 1.0 equiv in the case of compound 6) was heated at reflux in MeCN
(20 mL) for 12 h. The resulting mixture was cooled, and precipitated
solids were separated by filtration. The solids were washed thoroughly
with H2O, MeCN, and acetone. The product was then finally dried
under vacuum before being purified by crystallization.
2:1 Complex of 6-(Pyridin-4-yl)-1,3,5-triazine-2,4-diamine (3a) with
PdCl2 (Orthorhombic Form). The reaction of ligand 3a (51 mg, 0.27 mmol)
with PdCl2 (24 mg, 0.14 mmol) according to the general procedure yielded
the crude 2:1 complex (62 mg, 0.11 mmol, 81%). Pale yellow crystals of
Figure 8. Structure of complex [Pd(4a)4](PF6)(OH) 4H2O 2EtOH
composition PdCl2(3a)2 2DMSO were grown by allowing H2O to diffuse
3
3
3
in crystals grown from DMSO/H2O/EtOH. Except where noted
otherwise, carbon atoms are shown in gray, hydrogen atoms in white,
nitrogen atoms in blue, fluorine atoms in green, phosphorus atoms in
purple, and palladium atoms in rose. (a) Thermal atomic displacement
ellipsoid plot, with ellipsoids of non-hydrogen atoms drawn at the 50%
probability level and hydrogen atoms represented by a sphere of arbitrary
size. Key bond lengths include Pd1ꢀN1 = 2.023(4) Å. Representative bond
angles include N1ꢀPd1ꢀN1B = 90.95(19)°. (b) View showing the
formation of cationic sheets in the ab plane, in which the four DAT groups
slowly into a solution in DMSO. IR (ATR): 3429, 3330, 3202, 1651, 1614,
1529, 1445, 1421, 1398, 1061, 811 cmꢀ1. HRMS (ESI) calcd for [C16H16-
ClN12Pd]þ: m/e 517.03388. Found: 517.03406.
2:1 Complex of 6-(Pyridin-4-yl)-1,3,5-triazine-2,4-diamine (3a) with
PdCl2 (Triclinic Form). The crude 2:1 complex was prepared as described
above, and pale yellow crystals of composition PdCl2(3a)2 2DMSO
3
3
dioxane were grown by slow evaporation of a solution in DMSO/
dioxane. IR (ATR): 3429, 3330, 3202, 1651, 1614, 1529, 1445, 1421,
1398, 1061, 811 cmꢀ1. HRMS (ESI) calcd for [C16H16ClN12Pd]þ: m/e
517.03388. Found: 517.03406.
of a central metallotecton (red) engage in a total of 16 NꢀH N hydro-
3 3 3
gen bonds with six neighbors (blue and green). Each DAT group forms two
2:1 Complex of 6-[4-(Pyridin-4-yl)phenyl]-1,3,5-triazine-2,4-diamine
(3b) with PdCl2. The reaction of ligand 3b (80 mg, 0.30 mmol)
with PdCl2 (27 mg, 0.15 mmol) according to the general procedure
yielded the crude 2:1 complex (88 mg, 0.12 mmol, 80%). Pale yellow
crystals of composition PdCl2(3b)2 were grown by slow evaporation
of a solution in DMSO/EtOAc. IR (ATR): 3481, 3435, 3395, 3303,
3129, 1613, 1586, 1520, 1436, 1396, 808 cmꢀ1. HRMS (ESI) calcd for
NꢀH N hydrogen bonds of type III (3.091(6) Å) involving the two
3 3 3
neighbors shown in green, as well as two additional single NꢀH
N
3 3 3
hydrogen bonds (3.069(6) Å) with neighbors in red. In addition, the
structure is reinforced by aromatic interactions. Neutral guests and coun-
terions are omitted for clarity. (c) View along the a axis showing how catio-
nic sheets of the metallotecton are separated by intervening anionic layers
containing hydrogen-bonded PF6ꢀ, disordered OHꢀ, H2O, and EtOH.
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Figure 9. Structure of complex [Pd(4b)4](NO3)2 6DMSO 4H2O in crystals grown from DMSO/H2O. Hydrogen bonds are represented by broken
3
3
lines. Carbon atoms are shown in gray, hydrogen atoms in white, nitrogen atoms in blue, oxygen atoms in red, sulfur atoms in yellow, and palladium
atoms in rose. (a) Thermal atomic displacement ellipsoid plot, with ellipsoids of non-hydrogen atoms drawn at the 50% probability level and hydrogen
atoms represented by a sphere of arbitrary size. Key bond lengths include Pd1ꢀN1 = 2.046(2) Å. Representative bond angles include N1ꢀPd1ꢀN1B =
90.81(11)°. (b) View showing the formation of sheets held together by NꢀH N hydrogen bonds of type I (2.955(5) Å), reinforced by NꢀH
O
3 3 3
3 3 3
hydrogen bonds involving bridging molecules of DMSO.
[C28H24ClN12Pd]þ: m/e 669.09648. Found: 669.09845. Anal. Calcd for
C28H24Cl2N12Pd: C, 47.64; H, 3.43; N, 23.81. Found: C, 47.49; H, 3.27;
N, 23.32.
2:1 Complex of 6-(Pyridin-3-yl)-1,3,5-triazine-2,4-diamine (4a) with
PdCl2. The reaction of ligand 4a (74 mg, 0.39 mmol) with PdCl2 (35 mg,
0.20 mmol) according to the general procedure yielded the crude 2:1
complex (79 mg, 0.14 mmol, 72%). Pale yellow crystals of composition
PdCl2(6) were grown by slow evaporation of a solution in DMSO/H2O.
IR (ATR): 3448, 3400, 3188, 3119, 1659, 1634, 1581, 1518, 1489, 1397,
1262, 1058, 1031, 779 cmꢀ1. HRMS (ESI) calcd for [C8H8ClN6Pd]þ:
m/e 328.95283. Found: 328.95347. Anal. Calcd for C8H8Cl2N6Pd: C,
26.29; H, 2.21; N, 22.91. Found: C, 26.28; H, 2.26; N, 22.35.
General Procedures for Preparing Other Pd(II) Complexes
of Ligands 3a,b and 4a,b. A stirred suspension of Pd(BF4)2 or
Pd(NO3)2 (1.0 equiv) and the ligand (4.0 equiv) was heated at reflux in
MeCN (20 mL) for 12 h. The resulting mixture was cooled, and precip-
itated solids were separated by filtration. The solids were washed thoroughly
with H2O, MeCN, and acetone. The product was then finally dried under
vacuum before being purified by crystallization. In the case of the complex of
ligand 4a with Pd(BF4)2, the crude product was subjected to ion exchange
before crystallization by treatment with excess NaPF6 in H2O/MeCN.
4:1 Complex of 6-(Pyridin-4-yl)-1,3,5-triazine-2,4-diamine (3a)
with Pd(BF4)2. The reaction of ligand 3a (80 mg, 0.43 mmol) with
PdCl2(4a)2 3DMSO were grown by slow evaporation of a solution in
3
DMSO. IR (ATR): 3465, 3382, 3323, 3196, 3140, 1626, 1614, 1546,
1397, 805 cmꢀ1. HRMS (ESI) calcd for [C16H16ClN12Pd]þ m/e:
517.03388. Found: 517.03405. Anal. Calcd for C16H16Cl2N12Pd H2O:
3
C, 33.61; H, 3.17; N, 29.40. Found: C, 33.37; H, 3.06; N, 28.68.
1:1 Complex of 6-(Pyridin-2-yl)-1,3,5-triazine-2,4-diamine (6) with
PdCl2. The reaction of ligand 6 (67 mg, 0.36 mmol) with PdCl2 (63 mg,
0.36 mmol) according to the general procedure yielded the crude 1:1
complex (116 mg, 0.32 mmol, 89%). Yellow crystals of composition
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Pd(BF4)2 4MeCN (47 mg, 0.11 mmol) according to the general pro-
cedure yielded the crude 4:1 complex (87 mg, 0.084 mmol, 78%).
In the case of crystals of composition [Pd(4a)4](PF6)(OH) 4H2O 2-
3
3
3
EtOH, the structural solution led to the position of the Pd center with
one attached ligand 4a, half a PF6ꢀ counterion, three atoms from a guest
molecule of EtOH, and two isolated atoms of oxygen. After subsequent
cycles of least-squares refinement, the positions of two atoms of
hydrogen linked to one of the isolated atoms of oxygen were clearly
visible in the Fourier difference map, revealing a molecule of H2O that is
doubly hydrogen bonded. The second isolated atom of oxygen was
found to be disordered over four symmetry-related positions. The
closest peak of high electron density found in the difference Fourier
map was attributed to an atom of hydrogen, thereby defining an OHꢀ
and assuring charge balance in the crystal lattice.
Colorless crystals of composition [Pd(3a)4](BF4)2 9H2O were grown
3
by allowing H2O and MeCN to diffuse slowly into a solution in DMSO.
IR (ATR): 3500ꢀ3000 (b), 1615, 1425, 1392, 1301, 1217, 957,
821 cmꢀ1. HRMS (ESI) calcd for [C32H32N24Pd]2þ: m/e 429.11383.
Found: 429.11505. Anal. Calcd for C32H32B2F8N24Pd 2H2O: C, 35.96;
3
H, 3.40; N, 31.45. Found: C, 35.91; H, 3.10; N, 30.86.
4:1 Complex of 6-[4-(Pyridin-4-yl)phenyl]-1,3,5-triazine-2,4-diamine
(3b) with Pd(NO3)2. The reaction of ligand 3b (55 mg, 0.21 mmol)
with Pd(NO3)2 (12 mg, 0.052 mmol) according to the general proce-
dure yielded the crude 4:1 complex (57 mg, 0.044 mmol, 85%). Yellow
crystals of composition [Pd(3b)4](NO3)2 5DMSO 2H2O MeOH were
3
3
3
grown by allowing H2O and MeOH to diffuse slowly into a solution in
DMSO. IR (ATR): 3319, 3100 (b), 1612, 1526, 1438, 1394, 1324,
811 cmꢀ1. HRMS (ESI) calcd for [C56H48N24Pd]2þ: m/e 581.17588.
Found: 581.17864. Anal. Calcd for C56H48N26O6Pd: C, 52.24; H, 3.76;
N, 28.28. Found: C, 52.30; H, 3.71; N, 27.74.
’ ASSOCIATED CONTENT
S
Supporting Information. Tables of structural data in CIF
format. This material is available free of charge via the Internet at
http://pubs.acs.org.
b
4:1 Complex of 6-(Pyridin-3-yl)-1,3,5-triazine-2,4-diamine (4a) with
Pd(PF6)2. The reaction of ligand 4a (76 mg, 0.40 mmol) with Pd(BF4)2
(28 mg, 0.10 mmol) according to the general procedure yielded a solid,
which was then treated with NaPF6 (67 mg, 0.40 mmol) in a mixture
of H2O (10 mL) and MeCN (10 mL) to give the crude 4:1 complex
(82 mg, 0.071 mmol, 71%). Colorless crystals of composition [Pd(4a)4]-
(PF6)(OH) 4H2O 2EtOH were grown by allowing H2O and EtOH to
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: james.d.wuest@umontreal.ca.
3
3
diffuse slowly into a solution in DMSO. IR (ATR): 3469, 3349, 3100
(b), 1625, 1536, 1450, 1382, 1023, 807 cmꢀ1. HRMS (ESI) calcd for
[C32H32N24Pd]2þ: m/e 429.11383. Found: 429.11355.
’ ACKNOWLEDGMENT
We are grateful to the Natural Sciences and Engineering
4:1 Complex of 6-[4-(Pyridin-3-yl)phenyl]-1,3,5-triazine-2,4-diamine
(4b) with Pd(NO3)2. The reaction of ligand 4b (60 mg, 0.23 mmol)
with Pd(NO3)2 (14 mg, 0.061 mmol) according to the general proce-
dure yielded the crude 4:1 complex (65 mg, 0.050 mmol, 87%). Yellow
crystals of composition [Pd(4b)4](NO3)2 6DMSO 4H2O were grown
ꢀ
Research Council of Canada, the Ministꢁere de l’Education du
Quꢀebec, the Canada Foundation for Innovation, the Canada Re-
search Chairs Program, and Universitꢀe de Montrꢀeal for financial
support.
3
3
by allowing H2O to diffuse slowly into a solution in DMSO. IR (ATR):
3475, 3307, 3166, 1623, 1527, 1447, 1390, 789 cmꢀ1. HRMS (ESI) calcd
for [C56H48N24Pd]2þ: m/e 581.17588. Found: 581.17864. Anal. Calcd
for C56H48N26O6Pd: C, 52.24; H, 3.76; N, 28.28. Found: C, 52.21; H,
3.72; N, 27.35.
’ REFERENCES
(1) Bragg, W. L. Proc. R. Soc. London 1913, 89, 248–277.
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X-Ray Crystallographic Studies. Crystallographic data were
collected with Cu KR radiation at the temperatures indicated in Tables 1
and 2 using a Bruker Microstar diffractometer equipped with a rotating
anode. Intensity data were integrated using the SAINT program,16 and
semiempirical absorption corrections were applied using the SADABS
program.17 The structures were solved by direct methods, and non-
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from difference Fourier maps, recalculating their positions using stan-
dard values for distances and angles, and then refining them as riding
atoms. Hydrogen atoms from water molecules were located directly and
refined using restraints.
In complex PdCl2(3a)2 2DMSO, the complex and the included
3
molecules of DMSO lie on a 2-fold axis, which results in statistical
disorder over two positions with a half-occupancy factor for each atom
of chlorine and DMSO. Certain molecules of DMSO are also disor-
dered in crystals of composition PdCl2(3a)2 2DMSO dioxane, PdCl2-
3
3
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3
3
3
3
crystals of composition [Pd(4b)4](NO3)2 6DMSO 4H2O, DMSO lies
3
3
on a mirror plane, giving two alternative positions for one of the methyl
groups with a half-occupancy factor. In certain cases, guest molecules
proved to be significantly disordered and could not be modeled
properly; therefore, the SQUEEZE option in the PLATON software
package19 was used to calculate the region of solvent disorder and to
remove its contribution from the overall intensity data.
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