Dynamic ring-opening polymerization of silver(i) complexes with bis(amidopyridine) ligands

Article abstract of DOI:10.1039/b918615h

The factors which influence the formation of chelate, macrocycle or polymer in the reaction of silver(i) salts with bis(pyridine) ligands have been probed by studying structures in the solid state and cold spray ionization mass spectra in solution, with the ligands C₆H₄-1,3-[CONR(CH ₂)_n-3-C₅H₄N]₂, 1 (R = Me, n = 0) or 3 (R = H, n = 1) or 5-t-Bu-C₆H₃-1,3- [CONR(CH₂)_n-4-C₅H₄N]₂, 2 (R = Me, n = 0) or 4 (R = H, n = 1). In both the solid state and solution, the complex [Ag(1)₂]BF₄ exists as a chelate complex 5. The ligands NN = 2-4 form complexes in the solid state with either macrocyclic structures [Ag₂(μ-NN)₂]X₂ [6, NN = 2, X = BF₄; 9, NN = 3, X = NO₃] or polymeric structures [7, NN = 2, X = NO₃; 8, NN = 3, X = CF₃CO₂; 10, NN = 4, X = CF₃CO₂]. The ligands 2 and 3 gave both macrocyclic and polymeric complexes, depending on the anion. In solution, these complexes existed as mixtures of macrocycles and ring-opened oligomers. In the crystalline state, the complexes 6-10 underwent supramolecular association through combinations of hydrogen bonding, secondary bonding of the type Ag...X to anions, or argentophilic bonding of the type Ag...Ag. The Royal Society of Chemistry 2010.

Full text of DOI:10.1039/b918615h

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PAPER
www.rsc.org/dalton | Dalton Transactions
Dynamic ring-opening polymerization of silver(I) complexes
with bis(amidopyridine) ligands†
Nancy L. S. Yue, Michael C. Jennings and Richard J. Puddephatt*
Received 8th September 2009, Accepted 20th October 2009
First published as an Advance Article on the web 25th November 2009
DOI: 10.1039/b918615h
The factors which influence the formation of chelate, macrocycle or polymer in the reaction of silver(I)
salts with bis(pyridine) ligands have been probed by studying structures in the solid state and cold spray
ionization mass spectra in solution, with the ligands C6H4-1,3-[CONR(CH2)n-3-C5H4N]2, 1 (R = Me,
n = 0) or 3 (R = H, n = 1) or 5-t-Bu-C6H3-1,3-[CONR(CH2)n-4-C5H4N]2, 2 (R = Me, n = 0) or 4 (R =
H, n = 1). In both the solid state and solution, the complex [Ag(1)2]BF4 exists as a chelate complex 5.
The ligands NN = 2–4 form complexes in the solid state with either macrocyclic structures
[Ag2(m-NN)2]X2 [6, NN = 2, X = BF4; 9, NN = 3, X = NO3] or polymeric structures [7, NN = 2, X =
NO3; 8, NN = 3, X = CF3CO2; 10, NN = 4, X = CF3CO2]. The ligands 2 and 3 gave both macrocyclic
and polymeric complexes, depending on the anion. In solution, these complexes existed as mixtures of
macrocycles and ring-opened oligomers. In the crystalline state, the complexes 6–10 underwent
supramolecular association through combinations of hydrogen bonding, secondary bonding of the type
Ag ◊ ◊ ◊ X to anions, or argentophilic bonding of the type Ag ◊ ◊ ◊ Ag.
Introduction
There is much current interest in the self-assembly of coordination
polymers, whose topology may be controlled by the stereochem-
istry of the metal ion and the geometry of the ligand.1 The
chemistry of silver(I) has played a leading role in this field, in part
because silver(I) forms labile metal–ligand bonds which can take
part in dynamic coordination chemistry.1-3 In addition, silver(I)
can adopt several different coordination geometries, and so it has
yielded a particularly rich array of supramolecular structures.1-6
Coordination polymers containing amide functionality can give
higher order structures because hydrogen bonding through the
amide functionality can complement the dynamic coordination
chemistry in forming polymeric networks through self-assembly.4-6
If the ligands are flexible, it is sometimes possible to control the
ring-opening polymerization by either kinetic or thermodynamic
control,4-6 and an example from silver(I) chemistry is shown in
Scheme 1.6 The macrocycle A to polymer B equilibrium involves
reversible dissociation of Ag–N bonds and reversible changes in
conformation of the N-methylamide groups.
Characterization of the fascinating architectures of coordina-
tion polymers mainly depends on solid state characterization
Scheme 1
using X-ray crystallography. In the solution state, spectroscopic
analysis by IR, NMR and ESI-MS may be used, but it is often
very difficult to determine if the observed solid state polymeric
structure is maintained in solution.1-7 For example, the value of
NMR spectroscopy is limited because of dynamic effects if there
is an easy equilibrium between macrocyclic and linear units in
solution.7 The standard form of ESI-MS has proved to be a
useful method for identifying oligomeric or polymeric units in the
solution state but, for most silver(I) coordination polymers, only
dimeric or trimeric species have been observed.5-8 In this work,
the technique of cold-spray ionization mass spectrometry (CSI-
MS), which is a modified ESI-MS method that is carried out at
low temperature,8 has been used to probe the structures of silver(I)
compounds in solution. The low temperature slows decomposition
and so enables observation of higher molecular weight oligomers.
The ligands used are the flexible bis(amidopyridine) ligands
1–4 (Scheme 2), and the approach is to crystallize complexes with
silver(I), to determine the solid state structures, and then to probe
the structures in solution by using the CSI-MS technique. Amides
tend to adopt a roughly planar structure, though the barrier to
rotation about the RN–CO bond is modest, and N-methylamide
Department of Chemistry, University of Western Ontario, London, Canada
N6A 5B7. E-mail: pudd@uwo.ca; Fax: 519 661 3022; Tel: 519 661 2111
† CCDC reference numbers 747042–747047. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b918615h
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Fig. 1 Structure of the cationic bis(chelate) complex 5. The tetrafluorob-
orate anion is not shown. Selected bond parameters: Ag–N(1) 2.316(3);
˚
Ag–N(23) 2.312(3) A; N(1)–Ag–N(1A) 123.7(2); N(23)–Ag–N(23A)
135.0(1); N(1)–Ag–N(23) 104.1(1); N(1)–Ag–N(23A) 96.7(1)◦. Torsion
angles: C(8)–N(7)–C(9)–O(10) 4.2(6); O(18)–C(17)–N(19)–C(20) -5.3(6)◦.
1
2
Symmetry equivalent: -x, y, - z.
N–Ag–N angles ranging from 96.7(1)–135.0(1)◦. The angle as-
sociated with the chelate ligand, N(1)–Ag–N(23) = 104.1(1)◦, is
close to the natural tetrahedral angle. The MeNCO unit of the
N-methylamide group has the cis geometry as indicated by the
torsion angles C(8)–N(7)–C(9)–O(10) = 4.2(6) and O(18)–C(17)–
N(19)–C(20) = -5.3(6)◦. However, the aryl and pyridyl groups
twist out of this MeNCO plane. Some twist is needed to avoid
steric effects with the ortho hydrogen atoms of the aryl groups, but
the greater distortion is needed in order to attain the conformation
needed for chelation [for example, the plane N(7)C(8)C(9)O(10)
is twisted by 65◦ and 55◦ with respect to the neighboring aryl
and pyridyl groups respectively]. The silver(I) centers lie at a two-
fold symmetry site, and individual molecules have C2 symmetry.
Complex 5 is the only chelate derivative isolated from the group of
ligands 1–4. Evidently any strain arising from the twisting of the
aryl groups out of the MeNCO plane of the N-methylamide group
is more than compensated for by the chelate effect, with entropy
favoring formation of the mononuclear complex.
Scheme 2 The ligands 1–4.
derivatives 1 and 2 are expected to have the methyl group cis to
oxygen (termed the cis-stereochemistry of the MeNCO group),
while the simple amide derivatives 3 and 4 are expected to have
the trans-stereochemistry of the HNCO groups, and may take
part in hydrogen bonding.4,6,9 Complexes 1 and 3 have 3-pyridyl
substituents while 2 and 4 have 4-pyridyl units, and all ligands are
based on a central 1,3-C6H4 unit or its 5-t-butyl derivative.
Results
Synthesis and solid state structures of silver(I) complexes
The reaction of ligand 2 with silver tetrafluoroborate or nitrate
gave the macrocyclic complex [Ag2(m-2)2(BF4)][BF4], 6, or the
polymeric complex [{Ag(m-2)(NO3)}n], 7, respectively, as shown
in Scheme 4. The structure of complex 6 is similar to that reported
The reaction of AgBF4 with the ligand 1 in a 1 : 1 ratio unexpect-
edly gave crystals of the complex [Ag(1)2][BF4], 5. Complex 5 was
then prepared in high yield by carrying out the reaction in a 1 : 2
mole ratio (Scheme 3).
=
earlier with the ligand 1,3-C6H4[C( O)NMe-4-C5H4N]2, with one
tetrafluoroborate anion loosely bound within the cavity of the
˚
macrocycle [Ag ◊ ◊ ◊ F(52) 2.85(1); Ag(A) ◊ ◊ ◊ F(51) 2.62(1) A]. There
is an inversion centre in the centre of the macrocycle and so
the encapsulated tetrafluoroborate anion is disordered about this
position, though only one component is shown for clarity.
Complex 7, whose structure is shown in Fig. 3, exists in
the form of a polymeric, sinusoidal chain containing silver(I)
cations and bridging bis(pyridine) ligands 2. There are weaker
interactions between silver(I) cations and nitrate anions, which
are located between pairs of silver(I) cations at distances of
˚
Ag ◊ ◊ ◊ O(42) = 2.76 and Ag(1) ◊ ◊ ◊ O(42) = 2.68 A. The angle
N(11)–Ag–N(38A) = 165.5(2)◦ is significantly distorted from
linearity, presumably as a result of the secondary bonding to the
nitrate anions. The MeNCO N-methylamide units of the ligands
2 are in the cis geometry, with the torsion angles C(18)–N(17)–
C(19)–O(20) = 1.1(5) and O(32)–C(31)–N(33)–C(34) 8.8(6)◦.
The U-shaped structure of each Ag-2-Ag unit (Fig. 3) appears
equally well suited to formation of a macrocycle [Ag2(m-2)2]2+ as
the observed polymer [Agn(m-2)n]n+. Indeed, the similar ligand
Scheme 3 Reagent: (i) AgBF4.
The structure of complex 5 is shown in Fig. 1. It is an unusual
chelate complex [Ag(1)2][BF4] with 14-membered chelate rings.
The silver(I) ion has distorted tetrahedral stereochemistry, with
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Fig. 3 Structure of the polymeric complex 7. Selected bond parameters:
˚
Ag–N(11) 2.191(3); Ag–N(38A) 2.187(4) A; N(11)–Ag–N(38A)
165.5(2)◦.
Torsion
angles:
C(18)–N(17)–C(19)–O(20)
-1.1(5);
O(32)–C(31)–N(33)–C(34) 8.8(6)◦. Symmetry equivalents: A,
- x,
1
2
1
2
1
2
+ y, 2 - z; B, - x, -12 + y, 2 - z.
to Scheme 5. The polymeric and macrocyclic complexes require
different conformations of the ligand 3, illustrated as 3a and 3b
in Scheme 5. Thus, the ligands 2 and 3 have each yielded both
macrocyclic and polymeric forms of their silver(I) complexes.
Scheme 4 Reagents: (i) AgBF4; (ii) AgNO3.
=
NN = 1,3-C6H4[C( O)NMe-4-C5H4N]2, without the t-butyl
substituent in 2, does form the macrocyclic structure [Ag2(m-
NN)2]2+ with an encapsulated nitrate anion,6 and it is clear that
the ligand 2 adopts similar conformations in both the macrocyclic
and polymeric structures.
Scheme 5 Reagents: (i) AgO2CCF3; (ii) AgNO3.
The structure of polymer 8 is shown in Fig. 4. Fig. 4(a)
shows part of a single polymer chain and illustrates how both
trifluoroacetate anions form very weak secondary bonds to Ag(1)
Fig. 2 Structure of the macrocyclic complex 6. Selected bond parameter◦s:
˚
˚
[Ag(1) ◊ ◊ ◊ O(32) = 3.13 A] while also being “chelated” by hydrogen
Ag–N(11) 2.15(1); Ag–N(38A) 2.15(1) A; N(11)–Ag–N(38A) 177.4(4) .
bonding to the two NH groups of the ligand in conformation
Symmetry equivalent: 1-x, 1-y, -z.
˚
3a [N(8) ◊ ◊ ◊ O(31) 3.173(5); N(19) ◊ ◊ ◊ O(31) 2.993(6) A]. Both
The ligand 3 gave crystalline silver(I) complexes on reaction
with silver trifluoroacetate or silver nitrate, which were shown
to have the polymeric structure [{Ag(m-3)}n](CF3CO2)n, 8, or
macrocyclic structure [Ag2(m-3)2](NO3)2, 9, respectively, according
silver atoms are at centres of symmetry so the NAgN and
OAgO angles are strictly linear. Fig. 4(b) shows sections of
three neighboring polymer chains. The polymers are connected
by three types of secondary bonds to form a sheet structure.
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Fig. 4 Views of the structure of complex 8: (a) part of a polymer
chain, showing the interactions of the trifluoroacetate anions with NH
groups and with Ag(1); (b) part of a supramolecular sheet, showing
secondary bonding to Ag(2B) and p-stacking of phthalamide groups.
Fig. 5 The structure of complex 9, showing two macrocycles connected
through secondary Ag ◊ ◊ ◊ Ag and Ag ◊ ◊ ◊ O bonds. Selected bond para-
˚
meters: Ag–N(11) 2.158(4); Ag–N(33) 2.147(4); Ag ◊ ◊ ◊ Ag(1) 3.3629(8) A;
N(33)–Ag–N(11) 167.1(1)◦. Symmetry equivalents: A, 2-x, -y, 1-z; B,
1--x, -y, 1-z.
˚
Selected bond parameters: Ag(1)–N(1) 2.108(5); Ag(2)–N(23) 2.154(4) A;
N(1A)–Ag(1)–N(1) = N(23A)–Ag(2)–N(23) = 180◦. Hydrogen bond
˚
distances: N(8) ◊ ◊ ◊ O(31) 3.173(5); N(19) ◊ ◊ ◊ O(31) 2.993(6) A. Symmetry
equivalent: A, -x-1, -y-2; -z.
Firstly, the trifluoroacetate anions serve to link chains through
forming bridging (NH)2 ◊ ◊ ◊ OCO ◊ ◊ ◊ Ag(1) units, as described
above. Secondly, the Ag(2) atoms are linked through sec-
ondary bonding to carbonyl groups of neighboring chains to
=
=
form C O(10) ◊ ◊ ◊ Ag(2) ◊ ◊ ◊ O(10) C units with Ag(2) ◊ ◊ ◊ O(10) =
˚
2.82 A]. Thirdly, pairs of phthalamide groups from neighboring
˚
chains are parallel to each other, separated by 3.3 A and form a
p-stacking interaction. The phthalamide groups are twisted with
respect to the chain direction to allow this p-stacking and so
the chains are tightly intermeshed, with the helicity alternating
between P and M and with the p-stacking between PM pairs
(Fig. 4b).
The large macrocyclic structure of complex 9 [Ag ◊ ◊ ◊ Ag(B) =
˚
10.08 A] is shown in Fig. 5, which shows that the ligands
are in conformation 3b. There is an inversion centre at the
centre of each macrocycle, so all silver atoms are equiv-
alent. Each macrocycle is associated with the neighbouring
macrocycle through silver ◊ ◊ ◊ silver interactions [Ag ◊ ◊ ◊ Ag(1) =
Fig. 6 A view of part of the supramolecular sheet structure of complex
=
9, showing both the Ag ◊ ◊ ◊ Ag and NH ◊ ◊ ◊ O C bonding interactions.
The nitrate groups are omitted for clarity. Hydrogen bond distances:
˚
˚
3.3629(8) A], supported by secondary bonding to the nitrate
N(18) ◊ ◊ ◊ O(20) 2.842(4); N(29) ◊ ◊ ◊ O(28) 2.866(4) A.
anions [Ag(1) ◊ ◊ ◊ O(41)
=
2.85, Ag ◊ ◊ ◊ O(41)
=
2.62 and
˚
Ag ◊ ◊ ◊ O(42) = 2.91 A] to give a chain of metallocycles.
The asymmetric unit in the structure of complex 10 is
shown in Fig. 7. It illustrates the conformation of the phthala-
mide unit which allows “chelation” of the trifluoroacetate anion
by the two NH hydrogen bond donors [N(8) ◊ ◊ ◊ O(32A) 2.943(3);
N(19) ◊ ◊ ◊ O(32A) 3.012(4) A]. Propagation of this structure gives
rise to a coordination polymer.
The polymers and the association between polymer chains in
complex 10 are shown in Fig. 8. Within each polymer chain, the
helicity of the ligands 4 are all the same (P or M). The chains
The dimensionality of the supramolecular structure is further
increased because each macrocycle is hydrogen bonded inter-
molecularly to four other macrocycles by hydrogen bonding be-
˚
=
tween the amide groups of the type NH ◊ ◊ ◊ O C [N(29) ◊ ◊ ◊ O(28) =
˚
2.866(4); N(18) ◊ ◊ ◊ O(20) = 2.842(4) A] as shown in Fig. 6. The
hydrogen bonding links a given macrocycle to two macrocycles in
each of the polymer chains on either side to give a supramolecular
sheet of macrocycles (Fig. 6).
=
The reaction of ligand 4 with silver trifluoroacetate gave the
polymeric complex 10, as shown in Scheme 6.
are crosslinked through complementary C O ◊ ◊ ◊ Ag bonding and
there are two types of association. The stronger association is
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CSI-MS studies of complexes in solution
NMR studies of these complexes in solution were of limited value
because dynamic exchange occurred, so the degree of aggregation
was probed by using positive ion CSI-MS. The experiments
were carried out using solutions in acetonitrile at temperatures
ranging from 0 to -30 ◦C, and masses are given for the 107Ag
isotopomers. It should be noted that the solvents used for the
syntheses, NMR and CSI-MS are typically different. Thus, for
example, the crystals were usually grown from mixed solvents and
could not be grown from acetonitrile, while the mixed solvent
systems are unsuited to the NMR experiments and also, to a
lesser extent, the CSI-MS experiments. We have recorded both
NMR and CSI-MS experiments of complexes 8–10 in acetonitrile
and in dichloromethane–methanol, and shown that they are very
similar (Experimental section), but the quantitative aspects of the
equilibria are certainly expected to be solvent as well as anion
dependent.3 All complexes gave good CSI-MS data from CH3CN
solution and these are described below.
Scheme 6 Reagent: (i) AgO2CCF3.
The CSI-MS of the complex [Ag(1)2][BF4], 5, gave envelopes
of peaks at m/z = 799, 494, 453 and 347, assigned to [Ag(1)2]+,
[Ag(1)(MeCN)]+, [Ag(1)]+, and [(1)H]+, respectively. There were
no significant ions containing more than a single silver atom,
indicating that the chelate structure is maintained in solution,
albeit with some solvolysis. In contrast, the macrocyclic complex
[Ag2(2)2(BF4)][BF4], 6, gave envelopes of peaks at m/z = 1105, 550,
and 403, assigned to [Ag2(2)2(BF4)]+, [Ag(2)(MeCN)]+ and [(2)H]+,
respectively, indicating that the macrocyclic structure was largely
maintained in solution. The polymeric complex [{Ag(2)}n](NO3)n,
7, gave envelopes of peaks at m/z = 2053, 1809, 1482, 1080,
911, 550, and 403, assigned to [Ag3(2)4(NO3)]+, [Ag2(2)3(NO3)]+,
[Ag2(2)2(NO3)]+, [Ag(2)2]+, [Ag(2)(MeCN)]+ and [(2)H]+, respec-
tively. Some of these peaks are equivalent to those for complex
6, probably indicating the presence of some macrocyclic complex
[Ag2(m-2)2(NO3)]+ in solution. However, the observation of peaks
for [Ag3(2)4(NO3)]+ and [Ag2(2)3(NO3)]+ indicates that there are
also ring-opened oligomers present.
The CSI-MS of the polymeric complex [{Ag(3)}n](CF3CO2)n, 8,
revealed envelopes of peaks centered at m/z = 2025 [Ag5(3)3X4]+,
1805 [Ag4(3)3X3]+, 1459 [Ag4(3)2X3]+, 1239 [Ag3(3)2X2]+, 1019
[Ag2(3)2X]+, 799 [Ag(3)2]+, 453 [Ag(3)]+ and 347 [(3)H]+,
with X = CF3CO2. For comparison, the macrocyclic com-
plex [Ag2(3)2](NO3)2, 9, gave envelopes of peaks at m/z =
2167 [Ag5(3)4X4]+, 1998 [Ag4(3)4X3]+, 1652 [Ag4(3)3X3]+, 1483
[Ag3(3)3X2]+, 968 [Ag2(3)2X]+, 799 [Ag(3)2]+, 453 [Ag(3)]+ and 347
[(3)H]+, with X = NO3. In this case, there are many similarities,
suggesting that both exist in solution as a mixture of macrocyclic
and ring-opened oligomeric forms.
Fig. 7 The asymmetric unit in the structure of complex 10, showing
the “chelation” of the trifluoroacetate anion by two NH hydrogen bond
donors. Selected bond parameters: Ag–N(1) 2.177(3); Ag–N(24) 2.167(2),
N(1)–Ag–N(24A) 170.6(1). Hydrogen bond distances: N(8) ◊ ◊ ◊ O(32A)
˚
2.943(3); N(19) ◊ ◊ ◊ O(32A) 3.012(4) A.
˚
between units such as Ag ◊ ◊ ◊ O(10D) = 2.563(2) A in neighboring
chains, shown in red in Fig. 8, and this gives rise to a double
stranded polymer. These pairs of polymer chains have opposite
helicity, and are related by inversion symmetry. The double
stranded polymers are connected to polymers on each side (shown
in blue in Fig. 8) by weaker intermolecular interactions such
˚
as Ag ◊ ◊ ◊ O(18A) = 2.630(2) A. The overall result is to form
a supramolecular “sheet of polymers” structure in which the
polymer chains have alternating PMPM helicity (Fig. 8).
The CSI-MS of the polymeric complex [{Ag(4)}n](CF3CO2)n,
10, in acetonitrile showed envelopes of peaks centered at m/z =
1753 [Ag3(4)3X2]+, 1533 [Ag2(4)3X]+, 1355 [Ag3(4)2X2]+, 1313
[Ag(4)3]+, 1131 [Ag2(4)2X]+, 911 [Ag(4)2]+, 731 [Ag2(4)X]+, 550
[Ag(4)(MeCN)]+, 509 [Ag(4)]+ and 403 [(4)H]+. The peak at m/z =
1313, corresponding to [Ag(4)3]+, indicates the presence of some
three coordinate silver(I) ions in solution.
Fig. 8 The supramolecular “sheet of polymers” structure of complex
10, with anions and t-butyl groups omitted for clarity. The stronger
association is between polymers shown in red: Ag ◊ ◊ ◊ O(10D) 2.563 (2);
Discussion
˚
Ag ◊ ◊ ◊ O(18A) = 2.630(2) A; N(1)–Ag–O(10) 88.4(1); N(24)–Ag–O(10)
99.40(9)◦. Symmetry equivalents: A, -x, 1-y, -2-z; B, 1+x, -1+y, 1+z; C,
1-x, 1-y, -2-z.
Based on the structures of the crystalline complexes and on
the CSI-MS data, it can be argued that the ring-opening
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polymerization involves some of the compounds in Scheme 7.
When chelation to give complexes of type C (complex 5, Fig. 1)
cannot occur, the complexes tend to crystallize as either the
macrocycles of type D (complexes 6, Fig. 2; 9, Fig. 5) or the
polymers of type K, n = infinity (complexes 7, Fig. 3; 8, Fig. 4; 10,
Fig. 8). It is unusual, in studies of this kind, to be able to isolate
larger macrocycles such as E or ring-opened oligomers such as
G–K in Scheme 7.4,10 In the CSI-MS, only singly charged cations
have been observed, indicating tight ion-pairing with anions,
probably through either Ag+ ◊ ◊ ◊ X- or NH ◊ ◊ ◊ X- interactions. Only
the covalently linked anions are shown in Scheme 7, and the
likely folding of the oligomers arising from secondary bonding
interactions (see Fig. 3 for example) is ignored. As well as the
compounds in Scheme 7 that are proposed to be involved in
forming the polymers, the CSI-MS indicates the presence of
ions of general formula [Ag(NN)(MeCN)]+ and (Ag(NN)3]+,
indicating more extensive ligand exchange with involvement of
solvent acetonitrile molecules or silver(I) compounds with higher
coordination number. The dynamic ligand exchange is likely to
occur by an associative mechanism, involving reversible exchange
between pyridyl, anion and solvent molecules. The end groups in
Experimental
1
1H and 13C{ H} spectra were recorded using a Varian Mercury
400 spectrometer. The labeling scheme for the NMR spectra
is described in Scheme 8. CSI mass spectra were recorded
using a modified Micromass LCT spectrometer at a desolvation
temperature of -10 to -30 ◦C and were calibrated with CsI at
a concentration of 10mg ml-1 in acetonitrile. Solvents were dried
immediately before use in reactions with water sensitive reagents.
Scheme 8 Proton labeling scheme for ligands 1–4.
1
the ring opened oligomers can be k -bipyridine (F, G, K), anion
X- (I), or one of each group (J). By adding the number of anions
needed to give singly charged cations, these ions, as observed in the
CSI-MS, will have formulae [Agn(NN)n+1Xn-1]+, [Agn(NN)n-1Xn-1]+,
and [Agn(NN)nXn-1]+, respectively. The results of the CSI-MS
experiments are consistent with this picture, with the exception
of the observed ion [Ag5(3)3X4]+, X- = trifluoroacetate, in the
CSI-MS of complex 8. One possibility is that this ion may involve
association between a dimer [Ag2(O2CCF3)2]11 and an oligomer
=
5-tert-Butyl-C6H3-1,3-[C( O)NMe-4-C5H4N]2, 2
To a solution of 4-(aminomethyl)pyridine (1.0 g, 9.2 mmol) and
excess Et3N (1.4 mL, 13.9 mmol) in CH2Cl2 (50 mL), was added
a solution of 5-tert-butylisophthaloyl chloride (1.2 g, 4.6 mmol)
in CH2Cl2 (10 mL). The reaction mixture was stirred at room
temperature under nitrogen for 12 h, the solvent was evaporated
under vacuum, the product was extracted with benzene, and the
solvent was evaporated to give the product as a white solid. Yield:
1.56 g (98%). NMR in CDCl3: d(1H) = 8.43 [d, 4H, J(HH) = 5 Hz,
H2¢]; 7.83 [t, 1H, J(HH) = 2 Hz, H2]; 7.13 [d, 2H, J(HH) = 2 Hz,
[Ag3(3)3(O2CCF3)2]+, but the CSI-MS only gives the overall
+
formula. It should also be noted that the formula [Agn(NN)nXn-1
]
is consistent with either the oligomeric ring-opened structure (J)
or the macrocyclic structure (D, E).
H4]; 6.82 [d, 4H, J(HH) = 5 Hz, H3¢]; 3.46 [s, 6H, CH3]; 0.91
This work has shown the fine balance between formation of
macrocyclic and polymeric complexes which can be switched
by minor changes in the bipyridine ligand structure. The
higher order structures are dependent on hydrogen bonding,
when possible, or on secondary bonding effects which may
include both Ag ◊ ◊ ◊ X and Ag ◊ ◊ ◊ Ag bonding. The combina-
tion of crystallography and CSI-MS gives an insight into how
the complex structures are built up from the simple building
blocks.
13
=
[s, 9H, t-Bu]. d( C) = 169.8 (C O), 151.9, 150.9, 150.6, 150.5,
134.9, 122.0, 126.6, 120.5, 37.3 (CH3), 30.5 (t-Bu). Anal. Calcd.
for C24H26N4O2: C, 71.62; H, 6.51; N, 13.92. Found: C, 71.14; H,
6.85; N, 13.70%.
=
1,3-C6H4[C( O)NH-CH2-3-C5H4N]2, 3
To a solution of a mixture of 3-(aminomethyl)pyridine (3.0 g,
14.8 mmol) and excess triethylamine (6.2 mL, 44.3 mmol) in
Scheme 7 Some of the likely cations involved in the ring-opening polymerization.
1278 | Dalton Trans., 2010, 39, 1273–1281 This journal is The Royal Society of Chemistry 2010
©

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CH2Cl2 (80 mL), was added a solution of isophthaloyl chloride
(3.2 g; 29.6 mmol) in CH2Cl2 (20 mL). The reaction mixture
was stirred at room temperature under nitrogen overnight. The
solvent was evaporated under vacuum and the yellow residue was
redissolved in thf (20 mL) and filtered. The solvent was evaporated
under vacuum to give the product as a white solid. Yield: 3.72 g
(73%). NMR in CD2Cl2/dmf-d7: d(1H) = 8.58 [t, 2H, J(HH) =
6 Hz, CONH]; 8.48 [s, 2H, H2¢]; 8.39 [d, 2H, J(HH) = 6 Hz, H6¢];
8.25 [t, 1H, J(HH) = 2 Hz, H2]; 7.96 [d, 2H, J(HH) = 8 Hz, H4¢];
7.75 [dt, 2H, J(HH) = 8 Hz, 2 Hz, H4]; 7.48 [t, 1H, J(HH) =
8 Hz, H5]; 7.29 [dd, 2H, J(HH) = 6 Hz, 8 Hz, H5¢]; 4.57 [d, 4H,
J(HH) = 6 Hz, CH2]; NMR in (CD3)2SO: d(1H) = 9.26 [t, 2H,
J(HH) = 6 Hz, CONH]; 8.57 [d, 2H, J(HH) = 2 Hz, H2¢]; 8.46
[dd, 2H, J(HH) = 5 Hz, 2 Hz, H6¢]; 8.38 [s, 1H, H2]; 8.02 [dd, 2H,
J(HH) = 8 Hz, 2 Hz, H4¢]; 7.75 [d, 2H, J(HH) = 8 Hz, H4]; 7.58 [t,
1H, J(HH) = 8 Hz, H5]; 7.37 [dd, 2H, J(HH) = 5 Hz, 8 Hz, H5¢];
was added to precipitate the product as a white solid, which was
collected by filtration, washed with ether and dried under vacuum.
Yield: 0.104 g (84%). NMR in CDCl3/CD3OD: d(1H) = 8.47 [d,
4H, J(HH) = 6 Hz, H2¢]; 7.43 [s, 1H, H2]; 7.34 [s, 2H, H4]; 7.05
[d, 4H, J(HH) = 5 Hz, H3¢]; 3.51 [s, 6H, MeN]; 1.02 [s, 9H,
t-Bu]. Anal. Calcd. for C24H26AgBF4N4O2: C, 48.27; H, 4.39; N,
9.38. Found: C, 48.65; H, 4.28; N, 9.74%. Colourless plates of
6·4CH2Cl2 were grown by slow diffusion of solutions of AgBF4 in
thf and ligand 2 in CH2Cl2.
[{Ag(l-2)}n][NO3]n, 7
To [AgNO3] (0.04 g, 0.236 mmol) in thf/water (10 mL/2 mL) was
added a solution of ligand 2 (0.095 g, 0.236 mmol) in a mixture of
CH2Cl2 (10 mL) and methanol (2 mL). The mixture was stirred for
4 h, then pentane (20 mL) was added to precipitate the product
as a white solid, which was collected by filtration, washed with
acetone and dried under vacuum. Yield: 0.089 g (69%). NMR in
CDCl3/CD3OD: d(1H) = 8.33 [d, 4H, J(HH) = 6 Hz, H2¢]; 7.67
[d, 2H, J(HH) = 1 Hz, H4]; 6.78 [s, 1H, H2]; 6.72 [d, 4H, J(HH) =
6 Hz, H3¢]; 3.32 [s, 6H, MeN]; 1.22 [s, 9H, t-Bu]. Anal. Calcd. for
C24H26AgN5O5: C, 50.36; H, 4.58; N: 12.24%. Found: C, 49.96;
H, 4.23; N, 12.21%. Colourless plates of 7 were grown by slow
diffusion of solutions of AgNO3 in aqueous thf and ligand 2 in
CH2Cl2.
4.51 [d, 4H, J(HH) = 6 Hz, CH2]. NMR in CD2Cl2/CD3OD:
13
=
d( C) = 168.1 (C O), 149.0, 148.3, 136.9, 135.5, 134.9, 131.0,
129.4, 126.31, 124.43, 41.9 (CH2). Anal. Calcd for C20H18N4O2: C:
69.35; H: 5.24; N: 16.17. Found: C: 69.13; H: 5.36; N: 15.90%.
=
5-tert-Butyl-1,3-C6H3[C( O)NH-CH2-4-C5H4N]2, 4
To a solution of a mixture of 4-(aminomethyl)pyridine (0.4 g,
7.7 mmol) and excess triethylamine (1.61 mL, 11.5 mmol) in
thf (50 mL), was added a solution of 5-tert-butyl-isophthaloyl
chloride (1 g, 3.8 mmol) in thf (10 mL). The reaction mixture
was stirred at room temperature under nitrogen overnight. The
resulting mixture was filtered to obtain the yellow product. The
product was washed twice with water (30 mL) and a small amount
of thf, and then dried under vacuum overnight. Yield: 1.31 g (85%).
NMR in CD2Cl2/CD3OD: d(1H) = 8.40 [br d, 4H, J(HH) = 5 Hz,
H2¢], 8.12 [t, 1H, J(HH) = 2 Hz, H2]; 8.07 [d, 2H, J(HH) = 2 Hz,
[{Ag(l-3)}n][CF3CO2]n, 8
To a solution of [AgO2CCF3] (0.030 g, 0.136 mmol) in acetone
(10 mL) was added a solution of ligand 3 (0.047 g, 0.136 mmol) in
a mixture of CH2Cl2 (10 mL) and methanol (2 mL). The mixture
was stirred for 4 h, then pentane (20 mL) was added to precipitate
the product as a white solid, which was collected by filtration,
washed with acetone and dried under vacuum. Yield: 0.050 g
(65%). NMR in CD2Cl2/dmf-d7: d(1H) = 9.10 [t, 2H, J(HH) =
6 Hz, CONH]; 8.71 [br s, 2H, H2¢]; 8.53 [br s, 1H, H2]; 8.47 [d,
2H, J(HH) = 5 Hz, H6¢]; 8.02 [d, 2H, J(HH) = 8 Hz, H4¢]; 7.84
[d, 2H, J(HH) = 8 Hz, H4]; 7.47 [t, 1H, J(HH) = 8 Hz, H5];
7.35 [dd, 2H, J(HH) = 8 Hz, 5 Hz, H5¢]; 4.60 [d, 4H, J(HH) =
6 Hz, CH2]. NMR in CD3CN: d(1H) = 9.26 [t, 2H, J(HH) =
6 Hz, CONH]; 8.75 [br s, 2H, H2¢]; 8.47 [br s, 1H, H2]; 8.32 [d, 2H,
J(HH) = 5 Hz, H6¢]; 7.98 [d, 2H, J(HH) = 8 Hz, H4¢]; 7.76 [d, 2H,
J(HH) = 8 Hz, H4]; 7.47 [t, 1H, J(HH) = 8 Hz, H5]; 7.31 [dd, 2H,
J(HH) = 8 Hz, 5 Hz, H5¢]; 4.54 [d, 4H, J(HH) = 6 Hz, CH2].
CSI-MS in CH2Cl2–MeOH: m/z = 2025 [Ag5(3)3(CF3CO2)4]+,
1805 [Ag4(3)3(CF3CO2)3]+, 1459 [Ag4(3)2(CF3CO2)3]+, 1239
[Ag3(3)2(CF3CO2)2]+, 1019 [Ag2(3)2(CF3CO2)]+. Anal. Calcd. for
C22H18AgF3N4O4: C, 46.58; H, 3.20; N, 9.88. Found: C, 46.11; H,
2.82; N, 9.45%. Colourless crystals of 8 were obtained by slow
diffusion of an equal equivalent of [AgO2CCF3] in acetone into
a concentrated solution of ligand 3 in a mixture of CH2Cl2 and
methanol.
H4]; 7.26 [dd, 4H, J(HH) = 5 Hz, 2 Hz, H3¢]; 4.58 [d, 4H, J(HH) =
13
=
6 Hz, CH2]; 1.33 [s, 9H, t-Bu]. d( C) = 168.6 (C O), 153.1, 149.6,
149.4, 134.6, 128.4, 123.6, 123.1, 68.4 (CH2), 31.1 (CH3). Anal.
Calcd for C24H26N4O2: C: 71.62; H: 6.51; N: 13.92%. Found: C:
71.56; H: 6.87; N: 13.74%.
[Ag(1)2][BF4], 5
To a solution of AgBF4 (0.040 g, 0.205 mmol) in thf (10 mL)
was added a solution of ligand 1 (0.142 g, 0.41 mmol) in CH2Cl2
(10 mL). The mixture was stirred for 4 h, then pentane (20 mL)
was added to precipitate the product as a white solid, which
was collected by filtration, washed with ether and dried under
vacuum. Yield: 0.108 g (59%). NMR in dmf-d7: d(1H) = 8.43
[d, 2H, J(HH) = 5 Hz, H6¢]; 8.30 [m, 2H, H2¢]; 7.72 [dd, 2H,
J(HH) = 8 Hz, 5 Hz, H5¢]; 7.64 [m, 2H, H5]; 7.01 [m, 4H,
J(HH) = 8 Hz, H4, H6, H4¢]; 3.52 [2, 6H, MeN]. Anal. Calcd
for C40H36AgBF4N8O4: C, 54.14; H, 4.09; N, 12.63. Found: C,
53.68; H, 3.87; N, 12.24%. Colourless crystals of 5 were obtained
by slow diffusion of solutions of [AgBF4] in thf and ligand 1 in
CH2Cl2.
[{Ag(l-3)}n][NO3]n, 9
This was prepared in a similar way as for complex 8 except that
AgNO3 was used. Yield: 91%. NMR in dmso-d6: d(1H) = 9.25 [t,
2H, J(HH) = 5 Hz, CONH]; 8.56 [br s, 2H, H2¢]; 8.48 [d, 2H,
J(HH) = 5 Hz, H6¢]; 8.37 [s, 1H, H2]; 8.02 [d, 2H, J(HH) = 8 Hz,
H4¢]; 7.79 [d, 2H, J(HH) = 8 Hz, H4]; 7.58 [t, 1H, J(HH) = 8 Hz,
[Ag2(l-2)2][BF4]2, 6
To a solution of [AgBF4] (0.04 g, 0.206 mmol) in thf (10 mL) was
added a solution of ligand 2 (0.083 g, 0.206 mmol) in CH2Cl2
(10 mL). The mixture was stirred for 4 h, then pentane (20 mL)
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Table 1 X-ray data for the complexes
Complex
5
6·4CH2Cl2
7
8
9
10·CH2Cl2·solvent
Formula
FW
C40H36AgBF4N8O4 C52H60Ag2B2Cl8F8N8O4
C24H26AgN5O5
572.37
150(2)
0.71073
Monoclinic
C2
16.4077(6)
9.8095(4)
14.9862(5)
90
93.438(2)
90
C22H18AgF3N4O4
567.27
150(2)
0.71073
Monoclinic
P21/c
10.7454(3)
11.3948(4)
18.2357(8)
90
99.076(2)
90
2204.8(1)
4
1.709
0.977
C20H18AgN5O5
516.26
150(2)
0.71073
Orthorhombic
Pbca
13.2247(5)
9.6779(3)
30.769(1)
90
90
90
3938.0(2)
8
1.742
C27H28AgCl2F3N4O4
708.30
150(2)
0.71073
Triclinic
¯
P1
10.7192(4)
12.2831(7)
13.4164(7)
67.884(2)
77.113(3)
74.065(3)
1559.3(1)
2
887.45
150(2)
0.71073
Monoclinic
C2/c
1534.04
150(2)
0.71073
Monoclinic
P2/c
T (K)
˚
l (A)
Cryst. syst.
Space gp.
˚
a (A)
22.440(1)
15.230(1)
15.933(1)
90
134.747(3)
90
16.034(1)
10.4349(6)
20.490(1)
90
105.409(3)
90
˚
b (A)
˚
c (A)
a (◦)
b (◦)
g (◦)
3
˚
V (A )
3867.4(5)
4
1.524
3305.1(4)
2
1.541
2407.7(1)
4
1.579
Z
dc (Mg m-3)
Abs. coeff. (mm-1)
1.509
0.873
0.524
0.986
0.883
1.069
Data/restr./param. 3408/3/276
5670/14/449
1.041
0.108
4226/1/317
1.041
0.035
3888/0/310
1.051
0.055
3495/0/280
1.015
0.044
5443/4/415
1.123
0.038
Goof
1.087
0.043
0.105
R1, I > 2s(I)
wR2, all data
0.367
0.078
0.107
0.125
0.094
H5]; 7.42 [dd, 2H, J(HH) = 5 Hz, 8 Hz, H5¢]; 4.51 [d, 4H,
J(HH) = 6 Hz, CH2]. NMR in CD3CN: d(1H) = 9.19 [t, 2H,
J(HH) = 5 Hz, CONH]; 8.55 [br s, 2H, H2¢]; 8.43 [d, 2H, J(HH) =
5 Hz, H6¢]; 8.31 [s, 1H, H2]; 7.99 [d, 2H, J(HH) = 8 Hz, H4¢];
7.78 [d, 2H, J(HH) = 8 Hz, H4]; 7.51 [t, 1H, J(HH) = 8 Hz,
H5]; 7.40 [dd, 2H, J(HH) = 5 Hz, 8 Hz, H5¢]; 4.48 [d, 4H,
J(HH) = 6 Hz, CH2]. CSI-MS in CH2Cl2–MeOH: m/z = 2167
[Ag5(3)4(NO3)4]+, 1998 [Ag4(3)4(NO3)3]+, 1652 [Ag4(3)3(NO3)3]+,
1483 [Ag3(3)3(NO3)2]+, 968 [Ag2(3)2(NO3)]+, 799 [Ag(3)2]+. Anal.
Calcd for C20H18AgN5O5: C, 46.53; H, 3.51; N, 13.57. Found: C,
46.07; H, 3.32; N, 13.26%. Colourless needles of 9 were obtained
by slow diffusion of solutions of AgNO3 in aqueous acetone and
ligand 3 in a mixture of CH2Cl2 and methanol.
data reduction were carried out using the Nonius DENZO
package. The data were scaled using SCALEPACK (Nonius,
1998). The SHELXTL-NT V6.1 (Sheldrick, G. M., Madison,
WI) program package was used to solve and refine the structure
by direct methods. The hydrogen atom positions were calculated
geometrically and were included as riding on their respective
carbon atoms. Details of the data collection and refinement are
given in Table 1. Unusual features are discussed briefly below:
[Ag2(l-2)2][BF4]2·4CH2Cl2, 6
-
The B–F bond lengths of BF4 groups and the C–Cl distances of
˚
˚
solvent molecules were fixed at 1.388 A and 1.65 A, respectively.
One solvent molecule was modeled as a 50 : 50 disorder. The
parameters are imprecise because of solvent disorder, but the
connectivity is well-established.
{[Ag(l-4)][CF3CO2]}n, 10
This was prepared in a similar way as for complex 8 except that
ligand 4 was used. Yield: 92%. NMR in CD3OD: d(1H) = 8.56 [d,
4H, J(HH) = 5 Hz, H2¢]; 8.27 [t, 1H, J(HH) = 2 Hz, H2]; 8.15 (d,
2H, J(HH) = 2 Hz, H4]; 7.54 [d, 4H, J(HH) = 5 Hz, H3¢]; 4.68
[d, 4H, CH2]; 1.40 [s, 9H, t-Bu]. NMR in CD3CN: d(1H) = 8.53
[d, 4H, J(HH) = 5 Hz, H2¢]; 8.30 [t, 1H, J(HH) = 2 Hz, H2]; 8.11
(d, 2H, J(HH) = 2 Hz, H4]; 7.55 [d, 4H, J(HH) = 5 Hz, H3¢];
4.65 [d, 4H, CH2]; 1.34 [s, 9H, t-Bu]. CSI-MS in CH2Cl2–MeOH:
m/z = 1753 [Ag3(4)3(CF3CO2)2]+, 1533 [Ag2(4)3(CF3CO2)]+, 1355
[Ag3(4)2(CF3CO2)2]+, 1131 [Ag2(4)2(CF3CO2)]+, 911 [Ag(4)2]+, 731
[Ag2(4)(CF3CO2)]+. Anal. Calcd. for C26H26AgF3N4O4: C, 50.10;
H, 4.20; N, 8.99. Found: C, 49.84; H, 4.51; N, 8.86%. Colourless
plates of 10·CH2Cl2 were obtained by slow diffusion of solutions of
AgO2CCF3 in aqueous acetone and ligand 4 in CH2Cl2–methanol.
[Ag(l-4)][CF3CO2]·CH2Cl2, 10
The tert-butyl groups were disordered and were modeled at a 60/40
ratio. The solvent was modeled at a 45/55 ratio of two orientations
with the C–Cl bonds fixed at 1.72 A. There was some unaccounted
for electron density which could not be successfully modeled. It
was attributed to disordered solvent, and was removed by using
SQUEEZE.12
˚
Acknowledgements
We thank the NSERC (Canada) for financial support.
Notes and references
1 A. M. Spokoyny, D. Kim, A. Sumrein and C.A. Mirkin, Chem. Soc.
Rev., 2009, 38, 1218; S. Noro, S. Kitagawa, T. Akutagawa and T.
Nakamura, Prog. Polym. Sci., 2009, 34, 240; J. W. Steed, Chem. Soc.
Rev., 2009, 38, 506; R. J. Puddephatt, Chem. Soc. Rev., 2008, 37, 2012;
C. Janiak, Dalton Trans., 2003, 2781; D. Braga, Chem. Commun., 2003,
2751; J. A. R. Navarro and B. Lippert, Coord. Chem. Rev., 2001, 222,
219; R. Robson, J. Chem. Soc., Dalton Trans., 2000, 3735.
X-ray structure determination
Crystals were mounted on glass fibers, and data were collected
using a Nonius Kappa-CCD diffractometer with COLLECT
(Nonius, 1998) software. The unit cell parameters were calculated
and refined from the full data set. Crystal cell refinement and
1280 | Dalton Trans., 2010, 39, 1273–1281
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The Royal Society of Chemistry 2010
©

View Article Online
2 A. G. Young and L. R. Hanton, Coord. Chem. Rev., 2008, 252, 1346;
C. L. Chen, B. S. Kang and C. Y. Su, Aust. J. Chem., 2006, 59, 3; S.-L.
Zheng, M.-L. Tong and X.-M. Chen, Coord. Chem. Rev., 2003, 246, 185;
A. M. Beatty, Coord. Chem. Rev., 2003, 246, 131; A. N. Khlobystov,
A. J. Blake, N. R. Champness, D. A. Lemenovskii, A. G. Majouga, N.V.
Zyk and M. Schroder, Coord. Chem. Rev., 2001, 222, 155; C. Kaes, A.
Katz and M. W. Hosseini, Chem. Rev., 2000, 100, 3553.
3 X. J. Cui, A. N. Khlobystov, X. Y. Chen, D. H. Marsh, A. J. Blake,
W. Lewis, N. R. Champness, C. J. Roberts and M. Schroder, Chem.–
Eur. J., 2009, 15, 8861; J.-L. Du, T.-L. Hu, S.-M. Zhang, Y.-F. Zeng and
X. H. Bu, CrystEngComm, 2008, 10, 1866; Z. P. Deng, L. N. Zhu, S.
Gao, L. H. Huo and S. W. Ngu, Cryst. Growth Des., 2008, 8, 3277; S.
Muthu, J. H. K. Yip and J.J. Vittal, J. Chem. Soc., Dalton Trans., 2002,
4561; C. B. Aakeroy and A. M. Beatty, Aust. J. Chem., 2001, 54, 409; L.
Brammer, J. C. M. Rivas, R. Atencio, S. Fang and F. C. Pigge, J. Chem.
Soc., Dalton Trans., 2000, 3855.
2007, 360, 3741; H. Krishna and S.S. Krishnamurthy, Inorg. Chim.
Acta, 2007, 360, 3462; M.-C. Brandys and R. J. Puddephatt, J. Am.
Chem. Soc., 2001, 123, 4839; E. Lozano, M. Nieuwenhuyzen and S. L.
James, Chem.–Eur. J., 2001, 7, 2644; L. Carlucci, G. Ciani, D. M.
Proserpio and A. Sironi, Inorg. Chem., 1998, 37, 5941.
6 N. L. S. Yue, M. C. Jennings and R. J. Puddephatt, Eur. J. Inorg. Chem.,
2007, 1690; N. L. S. Yue, M. C. Jennings and R. J. Puddephatt, Dalton
Trans., 2006, 3886; N. L. S. Yue, M. C. Jennings and R. J. Puddephatt,
Inorg. Chem., 2005, 44, 1125; N. L. S. Yue, M. C. Jennings and R. J.
Puddephatt, Chem. Commun., 2005, 4792.
7 H.-F. Zhu, L.-Y. Kong, T.-A. Okamura, J. Fan, W.-Y. Sun and N.
Ueyama, Eur. J. Inorg. Chem., 2004, 1465Effendy,; F. Marchetti, C.
Pettinari, R. Pettinari, M. Ricciutelli, B. W. Skelton and A. H. White,
Inorg. Chem., 2004, 43, 2157.
8 S. Sakamoto, M. Fujita, K. Kim and K. Yamaguchi, Tetrahedron, 2000,
56, 955; K. Yamaguchi, J. Mass Spectrom., 2003, 38, 473.
4 T. J. Burchell and R. J. Puddephatt, Inorg. Chem., 2006, 45, 650; T. J.
Burchell, D. J. Eisler and R. J. Puddephatt, Chem. Commun., 2004, 944;
T. J. Burchell, D. J. Eisler, M. C. Jennings and R. J. Puddephatt, Chem.
Commun., 2003, 2228; Z. Qin, M. C. Jennings and R.J. Puddephatt,
Inorg. Chem., 2003, 42, 1956; Z. Qin, M. C. Jennings, R. J. Puddephatt
and K. W. Muir, Inorg. Chem., 2002, 41, 4590; Z. Qin, M. C. Jennings
and R. J. Puddephatt, Chem. Commun., 2001, 2676.
5 S. L. James, Chem. Soc. Rev., 2009, 38, 1744; G. R. Whittell, B. M.
Partridge, O. C. Presly, C. J. Adams and I. Manners, Angew. Chem.,
Int. Ed., 2008, 47, 4354; C.-L. Chen, Z.-Q. Yu, Q. Zhang, M. Pan, J.-Y.
Zhang, C.-Y. Zhao and C.-Y. Su, Cryst. Growth Des., 2008, 8, 897;
C.-X. Ren, L. Cheng, B.-H. Ye and X.-M. Chen, Inorg. Chim. Acta,
9 I. Azumaya, K. Yamaguchi, I. Okamoto, H. Kagechika and K. Shudo,
J. Am. Chem. Soc., 1995, 117, 9083; I. Okamoto, M. Nabeta, Y.
Hatakawa, N. Morita, T. Takeya, H. Masu, I. Azumaya and O. Tamura,
J. Am. Chem. Soc., 2007, 129, 1892; N. N. Adarsh, D. K. Kumar and
P. Dastidar, CrystEngComm, 2009, 11, 796; C. J. Sumby and L. R.
Hanton, Tetrahedron, 2009, 65, 4681.
10 C. A. Wheaton, D. J. Eisler, M. C. Jennings and R. J. Puddephatt,
J. Am. Chem. Soc., 2006, 128, 15370; C.P. McArdle, M. J. Irwin, M. C.
Jennings and R. J. Puddephatt, Angew. Chem., Int. Ed., 1999, 38, 3376.
11 Y. Sun, B. Ross, R. Y. Wang and S. Wang, Can. J. Chem., 2009, 87, 188.
12 A. L. Spek, “Platon–A Multipurpose Crystallographic Tool,” Utrecht
University, Utrecht, The Netherlands, 2006.
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 1273–1281 | 1281
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