Anion-dependent silver(I) coordination polymers of the tridentate pyridylphosphonite: PPh(3-OCH2C5H4N) 2

Article abstract of DOI:10.1021/ic0486365

Three new multidimensional coordination polymers have been constructed from the reaction of AgX, where X = OTf^-, BF₄^-, or tfa^-, with the novel phosphonite PhP(3-OCH₂C ₅H₄N)₂, PCP-32, 1. It is seen that regardless of the ratio of reactants mixed, polymeric growth of the compounds always reveals a ligand-to-metal ratio of 1:2 for PCP-32AgOTf, 2, 1:1 for PCP-32AgBF₄, 3, and 1:2 for PCP-32Ag(tfa), 4. The coordination number, metal environment, ligand conformation, and polymer dimensionality are found to vary greatly from 2 to 4 and are dependent upon the anion present. Coordination numbers from 2 to 4, representing linear, trigonal, and distorted tetrahedral environments are displayed. PCP-32AgOTf polymerizes as a linear chain containing both two- and four-coordinate silvers, PCP-32AgBF₄ repeats a single trigonal motif throughout its structure, and PCP-32Ag(tfa) shows two unique distorted tetrahedral silver centers. Ligand flexibility allows for cross-ligand Ag-Ag distances to range from 3.1918(8) to 14.015(2) A. The coordination polymers have been characterized by elemental analysis, variable-temperature multinuclear NMR spectroscopy, single-crystal X-ray diffraction, and fluorometric studies.

Full text of DOI:10.1021/ic0486365

Inorg. Chem. 2005, 44, 996−1005
Anion-Dependent Silver(I) Coordination Polymers of the Tridentate
Pyridylphosphonite: PPh(3-OCH2C5H4N)2
Rodney P. Feazell, Cody E. Carson, and Kevin K. Klausmeyer*
Department of Chemistry and Biochemistry, Baylor UniVersity, Waco, Texas 76798
Received September 28, 2004
Three new multidimensional coordination polymers have been constructed from the reaction of AgX, where X
)
OTf-, BF4-, or tfa-, with the novel phosphonite PhP(3-OCH2C5H4N)2, PCP-32, 1. It is seen that regardless of the
ratio of reactants mixed, polymeric growth of the compounds always reveals a ligand-to-metal ratio of 1:2 for
PCP-32AgOTf, 2, 1:1 for PCP-32AgBF4, 3, and 1:2 for PCP-32Ag(tfa), 4. The coordination number, metal
environment, ligand conformation, and polymer dimensionality are found to vary greatly from 2 to 4 and are dependent
upon the anion present. Coordination numbers from 2 to 4, representing linear, trigonal, and distorted tetrahedral
environments are displayed. PCP-32AgOTf polymerizes as a linear chain containing both two- and four-coordinate
silvers, PCP-32AgBF4 repeats a single trigonal motif throughout its structure, and PCP-32Ag(tfa) shows two unique
distorted tetrahedral silver centers. Ligand flexibility allows for cross-ligand Ag−Ag distances to range from 3.1918-
(8) to 14.015(2) Å. The coordination polymers have been characterized by elemental analysis, variable-temperature
multinuclear NMR spectroscopy, single-crystal X-ray diffraction, and fluorometric studies.
Introduction
number from 2 to 6 by merely changing the size or
concentration in solution of a ligating species makes it an
appealing candidate for use in deliberately designed or
The self-assembly of coordination polymers that offer a
variety of novel structural, electronic, optical, catalytic, and
medicinal properties is currently an intense area of study in
supramolecular chemistry.1-6 Specific attention has been
given to those structures based upon the coinage metals.1,3,7,8
In particular, coordination polymers involving the silver(I)
ion have made a large contribution to this field due in part
to the ease with which it varies its coordination number.9-29
The fact that silver(I) can readily vary its coordination
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* To whom correspondence should be addressed. E-mail:
Kevin_Klausmeyer@baylor.edu.
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996 Inorganic Chemistry, Vol. 44, No. 4, 2005
10.1021/ic0486365 CCC: $30.25
© 2005 American Chemical Society
Published on Web 01/11/2005

Polymers of the Tridentate Pyridylphosphonite
Scheme 1. Anion-Dependent Coordination Modes for PCP-31a
“tailored” polymeric coordination complexes.7,30,31 Other
options for controlling structural growth that have proven
useful include varying anions to achieve different degrees
of interaction or changing the bridging ligand itself to make
it more or less rigid.32,33
Silver(I) coordination polymers of pyridyl-substituted
phosphines are virtually unknown. This could be due to the
fact that the majority of work done with pyridyl-substituted
phosphines has involved 2-pyridyl substitution.34-44 The
small bite angle associated with the 2-pyridyl substitution
inherently limits such a ligand’s ability to bridge, and as a
result, most complexes of the 2-pyridyl-substituted phos-
phines are small, discrete structures.34-41,44 The few reported
3- and 4-pyridyl-substituted phosphines have been sparsely
explored in terms of their coordination chemistry and
polymer-forming abilities given, at least in part, the difficulty
by which these ligands are synthesized and handled.45-48 We
demonstrated recently with the report of the 3-pyridyl-
substituted phosphinite, Ph2P(3-OCH2C5H4N) or PCP-31,
that opening the bite angle of these heterobidentate ligands
to the point of minimal interaction between the hard and
soft binding sites allows the synthesis of some very interest-
ing coordination polymers of various silver(I) salts.29 The
PCP-nm naming convention that we have adopted allows
for ease in discussion of these pyridylmethylphosphinites as
there are many substitutions that can be made and systematic
nomenclature can be cumbersome. As such, PCP indicates
a (A) linear chain of ligand-bridged metal centers. (B) Head-to-tail
bimetallic cycles anion-bridged into a polymer. (C) Tridentate PCP-32
ligand.
the pyridylcarbinol class of phosphorus ligands, where n is
the position of substitution on the pyridyl ring and m is the
number of carbinol substitutions on the phosphorus. As
shown in our previous study, the flexibility imparted upon
the pyridyl phosphinite ligand by the addition of an -OCH2-
spacer as well as the outwardly oriented binding sites of the
meta- and para-nitrogen donors allow for amazing versatility
in the coordination modes achievable. A sample of the
coordination modes of PCP-31 that occur with various silver-
(I) salts is shown in Scheme 1. We have taken our inquiry
of the PCPs a step further by adding a second pyridyl
substitution, effecting a tridentate pyridyl/phosphine donor
ligand and expanding the dimensionality available to the
coordination polymers formed by ligation to silver(I) salts
of various anions. These polymers display a variety of
interesting structural and electronic characteristics. The
molecular structures and luminescence properties are dis-
cussed herein.
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Experimental Section
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General Procedures. All experiments were carried out under
an argon atmosphere using a Schlenk line and standard Schlenk
techniques. Glassware was dried at 120 °C for several hours prior
to use. All reagents were stored in an inert atmosphere glovebox;
solvents were distilled under nitrogen from the appropriate drying
agent immediately before use. Triethylamine was purchased from
Aldrich and purged with argon before use. 3-Pyridylcarbinol was
purchased from Aldrich and used as received. Dichlorophenylphos-
phine, silver(I) trifluoroacetate, silver(I) triflate, and silver(I)
tetrafluoroborate were purchased from Strem Chemicals Inc. and
used as received. Celite was purchased from Aldrich and dried at
120 °C prior to use. 1H and variable-temperature 31P NMR spectra
were recorded at 360.13 and 145.78 MHz, respectively, on a Bruker
Spectrospin 360 MHz Spectrometer. Elemental analyses were
performed by Atlantic Microlabs Inc., Norcross, GA. Excitation
and emission spectra were recorded on an Instruments S. A. Inc.
model Fluoromax-2 spectrometer using band pathways of 5 nm
for both excitation and emission and are presented uncorrected.
Synthesis of Phenylphosphino-bis-3-pyridylcarbinol, PPh(3-
OCH2C5H4N)2, PCP-32 (1). In an argon-purged addition funnel
degassed triethylamine (2.28 mL, 16.4 mmol) was added via syringe
to a stirred solution of 3-pyridylcarbinol (1.50 g, 13.8 mmol) in 20
mL of toluene at room temperature. The solution was stirred for
15 min, then cooled to 0 °C, and shielded from light with aluminum
foil. A solution of dichlorophenylphosphine (1.23 g, 6.87 mmol)
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Inorganic Chemistry, Vol. 44, No. 4, 2005 997

Feazell et al.
Table 1. Crystallographic Data for 2-4
2, PCP-32AgOTf
3, PCP-32AgBF4
4, PCP-32Ag(tfa)
formula
C20H17Ag2F6N2O8PS2‚(CH3CN)0.33
(CH2Cl2)0.66
914.92
C80H80Ag4B4F16N12O8P4
C40H34Ag2F6N4O8P2‚(C4H10O)0.5
fw
2240.16
1127.45
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
10.8716(9)
11.9998(9)
12.170(1)
94.502(5)
100.834(5)
93.599(4)
1549.7(2)
2
15.565(2)
20.999(3)
28.131(4)
9.343(1)
31.912(5)
15.157(3)
95.63(1)
9195(2)
4
4497(1)
4
space group
T (K)
P-1
110
1.961
1.671
62.40
20219
9442 (0.0400)
56/431
0.0459
0.1136
0.0755
0.1281
1.016
P212121
110
1.618
1.000
46.52
67540
13167(0.0836)
0/1147
0.0464
0.1126
0.0543
0.1177
1.112
P21/n
110
1.665
1.024
D
calcd(g cm-3
)
µ (mm-1
2θmax, deg
reflns measured
)
52.00
38630
8838(0.0809)
6/601
0.0497
0.1073
0.0797
0.1204
1.027
reflns used (Rint
restraints/params
R1, [I > 2σ(I)]
wR2, [I > 2σ(I)]
)
2
R(Fo ) (all data)
2
Rw(Fo ) (all data)
GOF on F2
in 15 mL of toluene was then added over 15 min. The solution
was stirred for 1 h and then allowed to warm to room temperature.
The resultant, thick cloudy mixture was reduced to three-fourths
of its original volume under vacuum and immediately filtered
through Celite and washed with 5 mL of cold toluene. The solvent
was removed from the yellow solution in vacuo to leave the crude
product as a pale yellow oil in 95% yield (2.12 g, 6.26 mmol).
The oil was then extracted with 180 mL of hexanes to leave the
final product, 1, as a colorless oil in 77% yield (1.71 g, 5.28 mmol).
1H NMR (CDCl3, 298 K) δ: 4.87 (d,m, 4 H, J(PH) ) 8.8 Hz),
7.34 (m, 2 H), 7.48 (m, 3 H), 7.681 (m, 4 H), 8.59 (m, 4 H). 31P
NMR (CDCl3, 298 K) δ: 160.4 (sep, J(PH) ) 7.3 Hz).
g, 0.308 mmol) in 5 mL of CH2Cl2. This was allowed to stir for 5
min until the solid Ag(tfa) was dissolved, after which time a brown
oil precipitated. The solution was dried in vacuo to leave a fluffy
brown powder. This was then dissolved in a small amount of CH3-
CN and precipitated with ether. This was repeated until the off-
white powder, 4, was obtained in 94% (0.22 g, 0.29 mmol) yield.
Colorless blocks of 4 were obtained by the vapor diffusion of ether
into a solution of 4 in CH3CN at 5 °C. 1H NMR (CD3CN, 298 K)
δ: 5.12 (d,m, 4H), 7.39 (m, 2H), 7.59 (m, 3H), 7.82 (m, 4H), 8.50
(d, 2H), 8.59 (s 2H). 31P NMR (238 K) δ: 152.2. Anal. Calcd for
C23.5H18.75N2.25O6.25PAg2F6: C, 35.58; H, 2.38; N, 3.97. Found: C,
35.86; H, 2.40; N, 3.78.
Synthesis of PCP-32AgOTf (2). To a stirred solution of AgOTf
(0.158 g, 0.615 mmol) in 3 mL of CH3CN was added 1 (0.100 g,
0.308 mmol) in 3 mL of CH3CN. The resulting solution was allowed
to stir for 3 min and then dried in vacuo to leave a fluffy, off-
white solid. The solid was then repeatedly redissolved in a small
amount of CH3CN and precipitated with ether until compound 2
was obtained as a white powder in 86% (0.22 g, 0.26 mmol) yield
upon drying. Colorless plates of 2 were obtained by slow diffusion
of ether into a solution of 2 in CH2Cl2 at 5 °C. 1H NMR (CD3CN,
298 K) δ: 5.11 (d,m, 4H), 7.47 (m, 2H), 7.65 (m, 3H), 7.85 (m,
4H), 8.12 (m, 4H). 31P NMR (238 K) δ: 146.4 (d, J(Ag-P) )
908.2 Hz). Anal. Calcd for C23H20.5N2.5O8.5PS2F6Ag2: C, 30.94;
H, 2.31; N, 3.92. Found: C, 30.66; H, 2.37; N, 3.61.
X-ray Crystallographic Analysis. Crystallographic data were
collected on crystals with dimensions 0.081 × 0.097 × 0.196 mm
for 2, 0.168 × 0.140 × 0.041 mm for 3, and 0.070 × 0.090 ×
0.100 mm for 4. Data were collected at 110 K on a Bruker X8
Apex using Mo KR radiation (λ )0.710 73 Å). All structures were
solved by direct methods after correction of the data using
SADABS.49 Crystal data are presented in Table 1, and selected
interatomic distances and angles and other important distances are
given in Table 2. All of the data were processed using the Bruker
AXS SHELXTL software, version 6.10.50 Unless otherwise noted,
all non-hydrogen atoms were refined anisotropically and hydrogen
atoms were placed in calculated positions. The crystal structure of
2 contains a disordered solvent position that is occupied in part by
a molecule of dichloromethane and in part by a molecule of
acetonitrile. The crystal structure of 3 contains four solvent
Synthesis of PCP-32AgBF4 (3). To a stirred solution of AgBF4
(0.120 g, 0.616 mmol) in 3 mL of CH3CN was added 1 (0.198 g,
0.610 mmol) in 3 mL of CH3CN. The resulting solution was allowed
to stir for 2 min and then dried in vacuo to leave an off-white
powder. This was then dissolved in a small amount of CH3CN and
precipitated with ether, repeating until compound 3 was obtained
as a white powder upon drying in 93% (0.29 g, 0.57 mmol) yield.
Colorless plates of 3 were obtained by slow diffusion of ether into
-
molecules of acetonitrile and four noncoordinating BF4 anions,
two of which are disordered over two positions. Compound 4’s
crystal structure contains an ether solvent molecule whose disorder
is linked to the disorder of the C32 phenyl ring.
Results and Discussion
1
a solution of 3 in CH3CN at 5 °C. H NMR (CD3CN, 298 K) δ:
Synthesis and NMR Spectroscopy. Compound 1 is made
by a procedure similar to that reported for the synthesis of
5.07 (d,m, 4H), 7.45 (m, 2H), 7.65 (m, 3H), 7.85 (m, 4H), 8.48 (d,
2H), 8.55 (s, 2H). 31P NMR (238 K) δ: 149.8 (d, J(Ag-P) ) 804.7
Hz). Anal. Calcd for C18H17N2O2PAgBF4: C, 41.66; H, 3.30; N,
5.40. Found: C, 41.15; H, 3.27; N, 5.30.
Synthesis of PCP-32Ag(tfa) (4). To a stirred suspension of Ag-
(tfa) (0.136 g, 0.615 mmol) in 5 mL of CH2Cl2 was added 1 (0.100
(49) Sheldrick, G. M. SADABS; University of Gottingen: Gottingen,
Germany, 1997.
(50) Sheldrick, G. M. SHELXTL, version 6.10; Bruker AXS, Inc.: Madison,
WI, 2000.
998 Inorganic Chemistry, Vol. 44, No. 4, 2005

Polymers of the Tridentate Pyridylphosphonite
Table 2. Selected Bond Lengths (Å) and Angles (deg) and Important
Distances for 2-4
substituted counterpart and decomposes at a more rapid rate
in solution at room temperature. After isolation as a colorless
oil, 1 is found to be readily hydrolyzed, oxidizes in air, and
decomposes with exposure to heat or light. The thermal
instability is such that storage at a temperature of -35 °C is
insufficient to halt the degradation of the fluid, colorless oil
into a thick, dark-yellow cloudy oil over time. Pure 1 can
be separated at any point, when necessary, from its decom-
position products by extraction into hexanes. The ligand is,
however, initially synthesized in sufficient purity to allow
2, PCP-32AgOTf
Ag1-O6
2.287(3)
2.434(3)
2.152(4)
3.1918(8)
5.487(4)
3.8137(7)
6.7435(7)
Ag1-P1
2.323(1)
2.456(3)
2.156(3)
5.161(3)
3.466(5)
6.5088(7)
Ag1-O3#1
Ag2-N2
Ag1-O3
Ag2-N1
P1-N1
Ag2-Ag2#2
P1-N2#2
Ag1-Ag1#1
Ag1-Ag2#2
N1-N2#2
Ag1-Ag2
O6-Ag1-P1
144.84(7)
O6-Ag1-O3#1
O6-Ag1-O3
O3#1-Ag1-O3
N2-Ag2-Ag2#2
84.0(1)
82.6(1)
77.5(1)
P1-Ag1-O3#1
P1-Ag1-O3
N2-Ag2-N1
N1-Ag2-Ag2#2
122.30(7)
122.99(7)
172.3(1)
75.2(1)
1
for further use without the final hexane extraction. H and
31P NMR spectra of 1 were obtained in CDCl3 and show the
pronounced three-bond coupling of phosphorus to the phenyl
and methylene protons; a well-defined phosphorus septet is
thus found centered at 159.9 ppm.
112.5(1)
3, PCP-32AgBF4
Ag1-N1
2.289(6)
Ag1-N2
2.296(6)
2.274(6)
2.348(2)
2.285(6)
2.268(6)
2.352(2)
5.906(7)
6.165(7)
8.541(9)
5.999(7)
6.061(6)
8.769(9)
9.024(1)
9.454(1)
8.763(1)
9.324(1)
9.263(1)
8.763(1)
2.92(1)
Ag1-P1
2.3363(19)
2.318(7)
2.265(6)
2.362(2)
2.295(6)
6.195(6)
8.743(8)
5.860(7)
6.145(6)
8.444(9)
5.956(7)
9.287(1)
8.648(1)
9.099(1)
9.597(1)
8.648(1)
9.208(1)
2.90(1)
Ag2-N3
Ag2-N4
Ag2-P2
The silver compounds 2-4 were made by reaction of 1
with silver salts of the respective anions under ambient
conditions and inert atmosphere. Solutions of the three
compounds readily decompose to leave metallic silver and
an unidentifiable black byproduct. However, the powders of
each complex have proven themselves to be quite robust,
withstanding long exposure to air and room temperatures
with little sign of decomposition. They demonstrate a
concomitant increase in photostability, showing only slight
signs of decomposition for days upon exposure to light as
opposed to hours for the analogous complexes of the
monosubstituted PPh2(3-OCH2C5H4N). This relative increase
in solid-state stability could be accredited to the extra
dimensionality that the second carbinol substitution imparts
on the coordination of the ligand. Compounds 2-4 appear
to be stable indefinitely in the solid state if stored in the
dark and refrigerated under inert atmosphere. Variable-
temperature 31P NMR spectra were recorded to -35 °C in
deuterated acetonitrile. At this temperature the dissociation
of the Ag-P bond is slowed to a time scale where significant
polymeric character is observed and the various Ag-P
couplings can be readily seen.
Compound 2 is made by the mixing of 2 equiv of AgOTf
with a solution of 1 in acetonitrile. A light brown color
appears almost immediately upon mixing and is indicative
of the reactions of 1 with the various silver salts. If left
stirring at room temperature, this color rapidly grows more
intense and eventually becomes cloudy, signifying decom-
position of the coordination complex. Drying of the solution
in vacuo yields a crude, oily brown powder that is purified
with acetonitrile and ether. Upon drying of the precipitate 2
is collected as a white powder. Solutions of 2 in various
solvents noticeably decompose within minutes at room
temperature. However, when dichloromethane solutions
layered with ether are kept at 5 °C, they are sufficiently stable
to allow the growth of diffraction-quality crystals. Over time,
oxidation of the ligand in solution results in precipitation of
metallic silver. At room temperature a very broad phosphorus
resonance is evident centered at 148.0 ppm in the 31P
spectrum, indicating at least some degree of Ag-P coupling
in solution. Upon cooling to -35 °C this broad signal splits
into a doublet of very sharp peaks centered slightly upfield
at 146.4 ppm.
Ag3-N5
Ag3-N6
Ag3-P3
Ag4-N7
Ag4-N8
Ag4-P4
P1-N3
P1-N8#4
P2-N5
N3-N8#4
P2-N2#1
P3-N7
N5-N2#1
P3-N4#11
P4-N1#6
N1#6-N6#3
Ag1-Ag4#5
Ag2-Ag3
Ag3-Ag1#1
Ag3-Ag2#2
Ag4-Ag1#6
Ag1#7-Ag3#4
Ag2-F7#9
Ag4-F15#11
N7-N4#11
P4-N6#3
Ag1-Ag2
Ag2-Ag4#5
Ag2-Ag1#1
Ag3-Ag4
Ag4-Ag2#2
Ag4-Ag3#4
Ag1-F16#8
Ag3-F8#10
2.87(2)
2.73(1)
N(1)-Ag(1)-N(2)
N(2)-Ag(1)-P(1)
N(3)-Ag(2)-P(2)
N(5)-Ag(3)-N(6)
N(6)-Ag(3)-P(3)
N(7)-Ag(4)-P(4)
93.1(2)
133.1(2)
134.4(2)
107.3(2)
124.1(2)
136.4(2)
N(1)-Ag(1)-P(1)
N(3)-Ag(2)-N(4)
N(4)-Ag(2)-P(2)
N(5)-Ag(3)-P(3)
N(7)-Ag(4)-N(8)
N(8)-Ag(4)-P(4)
132.4(2)
99.4(2)
125.6(2)
127.8(2)
98.3(2)
124.4(1)
4, PCP-32Ag(tfa)
Ag1-N2#1
Ag1-O3
Ag2-N3#3
Ag2-O7
P1-N1
2.297(4)
2.386(4)
2.322(4)
2.344(4)
6.203(4)
6.108(4)
10.774(6)
9.112(1)
14.015(2)
Ag1-P1
2.357(1)
2.509(4)
2.329(1)
2.355(4)
5.520(5)
5.651(5)
10.026(6)
6.466(1)
9.227(1)
Ag1-O3#2
Ag2-P2
Ag2-N1
P1-N2
P2-N4
N3-N4
Ag1-Ag1#1
Ag2-Ag2#3
P2-N3
N1-N2
Ag1-Ag2
Ag1#1-Ag2
N(2)#1-Ag(1)-P(1) 132.5(1)
126.8(1)
N(2)#1-Ag(1)-O(3)
94.1(1)
P(1)-Ag(1)-O(3)
N(2)#1-Ag(1)-O(3)#2 87.9(1)
P(1)-Ag(1)-O(3)#2 122.5(1)
N(3)#3-Ag(2)-P(2) 125.4(1)
O(3)-Ag(1)-O(3)#2
N(3)#3-Ag(2)-O(7)
N(3)#3-Ag(2)-N(1)
O(7)-Ag(2)-N(1)
74.4(1)
86.8(1)
98.2(1)
86.4(1)
P(2)-Ag(2)-O(7)
P(2)-Ag(2)-N(1)
133.3(1)
116.3(1)
a Symmetry transformations used to generate equivalent atoms: For 2:
#1 ) -x + 1, -y, -z + 2; #2 ) -x + 1, -y, -z + 1. For 3: #1 ) -x
+ 1, y + 1/2, -z + 1/2; #2 ) -x, y + 1/2, -z + 1/2; #3 ) -x + 1,
y-1/2, -z + 1/2; #4 ) -x - 1, y + 1/2, -z + 1/2; #5 ) -x, y - 1/2, -z
+ 1/2; #6 ) -x - 1, y - 1/2, -z + 1/2; #8 ) x - 2, y - 1, z; #9 ) x -
0.5, -y + 0.5, -z + 1; #10 ) x - 1, y, z - 1; #11 ) -x, y - 0.5, -z +
0.5. For 4: #1 ) -x + 1, -y + 1, -z + 1; #2 ) -x + 2, -y + 1, -z +
1; #3 ) x-1/2, -y + 3/2, z - 1/2.
the singly substituted derivative, diphenylphosphino-3-py-
ridylcarbinol, adjusting for the addition of a second equiva-
lent of carbinol to the phosphine. PCP-32 is seen to be quite
a bit more sensitive to reaction conditions than its singly
Inorganic Chemistry, Vol. 44, No. 4, 2005 999

Feazell et al.
Scheme 2. Binding Modes of PCP-32 with Silver Salts
Figure 1. Thermal ellipsoid plot of the unique portion of the PCP-
32AgOTf polymer. Ellipsoids are drawn at the 30% probability level.
The coordination polymer, 3, is obtained as an off-white
powder by the reaction of AgBF4 with a solution of 1 mol
equiv of 1 in acetonitrile. Solutions of 3 also quickly develop
a brown tint but do not undergo extensive decomposition in
such a short time as for 2. This increase in stability of the
portions of the ligand in each of the structures are quite
diverse. Silver geometries range from the near linear 172.3-
(1)° of Ag2 in 2 to the distorted tetrahedrons of the silvers
in 4. Scheme 2 gives a representation of the different binding
modes displayed by PCP-32. The two carbinol substitutions
of each ligand are, as expected, capable of a variety of
rotations and extensions allowing the py-Ag binding of the
two “arms”, in relation to one another, to go from nearly
parallel and co-directional in 2 to pointing in nearly opposite
directions in 3. The flexibility of the -OCH2- spacer groups
also allow for a broad range of metal-metal distances to be
had by the N-bound silvers of the ligand. This interval spans
from the very close Ag-Ag interaction of 2 at 3.1918(8) Å
to the outstretching reach of 14.015(2) Å in 4. With the 1:2
ratio of P to N in the ligand, a strict head-to-tail-type
coordination throughout the polymer analogous to those seen
in the PCP-31 structures is difficult to achieve and is
therefore not observed in any of the structures. There is
instead a mixture of Ag coordination environments within 2
and 4 and a repetitive head-to-tail-to-tail motif apparent in
3. All of these structural arrangements are spawned from
the varying degrees of interaction that are seen by the
different anions. With both of the structures containing
oxygen donor anions, at least partial oxide bridging is
apparent between some of the silver atoms. Conversely, in
the case of BF4- there is no anionic bridge and only a slight
M-anion interaction that merely serves to hold the BF4- in
position in the lattice.
-
BF4 complex is analogous to the behavior of the Ph2P(3-
OCH2C5H4N)AgBF4 coordination polymer; the reasoning
behind this has been previously theorized.29 Tiny, colorless
parallelepiped-shaped crystals of 3 were grown by slow
diffusion of ether into a solution of 3 in acetonitrile at 5 °C.
Room-temperature 31P NMR spectra of 3 reveal a shouldered
peak, due to Ph-H coupling, centered upfield from the free
ligand at 149.0 ppm. The Ag-P coupling is not readily
apparent in acetonitrile solution at 23 °C. Upon cooling to
-35 °C a silver-split phosphorus doublet is again noticed,
now centered at 149.8 ppm.
Complex 4 is seen to be highly prone to decomposition
in solution, rapidly precipitating metallic silver and an oily
black byproduct. To circumvent this difficulty the ligand was
added to a suspension of Ag(tfa) in CH2Cl2, in which 4 is
only sparingly soluble. In this manner, as the silver salt is
drawn into solution by the forming coordination polymer it
is immediately precipitated back out of solution, reducing
the chance for decomposition. Reaction is apparent from the
rapid replacement of the Ag(tfa) granules with a light-brown
oily precipitate along with a slight darkening of the solution.
Upon purification the compound is reclaimed as a finely
divided colorless powder that quickly deposits metallic silver
from solutions. Crystals of 4 were grown with some difficulty
by vapor diffusion of ether into dilute solutions of 4 in
acetonitrile at 5 °C. Solutions in high concentrations of 4
typically resulted in precipitation versus crystallization. 31P
NMR spectra of 4 show a single broadened phosphorus peak
approximately 8 ppm upfield of the free ligand at 152.0 ppm.
Lowering the NMR operating temperature to -35 °C shows
a slight broadening (∼1 ppm) of the 31P resonance, though
the Ag-P coupling can still not be discerned.
The molecular structure of compound 2 contains two
distinct silver environments representative of the coordination
extremes shown herein. Both a pseudo-two-coordinate and
a four-coordinate arrangement are displayed. A thermal
ellipsoid plot of the unique portion of this structure is shown
in Figure 1. The two unique metal centers are repeated in
one dimension, linked by bridging anions, to form the linear
coordination polymer as demonstrated in Figure 2. Ag1 is
bridged via one oxygen atom of each of two separate triflates
X-ray Crystal Structures. The silver coordination envi-
ronments as well as the twisted conformations of the carbinol
1000 Inorganic Chemistry, Vol. 44, No. 4, 2005

Polymers of the Tridentate Pyridylphosphonite
Figure 2. View of the 1-D chain of PCP-32AgOTf, 2. H atoms and the noncoordinating portion of the triflates have been removed for clarity.
Figure 3. Thermal ellipsoid plot of the cationic unique portion of the PCP-32AgBF4 polymer. The partial spiral of the pyridyl linkages through the linear
chain is apparent. Ellipsoids are drawn at the 50% probability level. H atoms have been removed for clarity.
to an opposing, symmetry-equivalent P-bound Ag. The
tetrahedron of P and O around Ag1 is completed by a
terminal triflate bound to each metal. This effectively
imposes a -2 charge on the Ag2OTf4 cluster that balances
the positive charge levied across the ligand at the N-bound
silvers. It is seen that the coordinating triflates are only
observed at the phosphorus-bound Ag centers. This enforces
a very prominent trans-ligand static charge separation. The
two pyridyl rings of each ligand are brought within close
proximity of one another at 3.466(5) Å, possibly by slight
π-π interactions of the adjacent aromatic rings. The planes
of these rings are seen to be nearly parallel though the N2
pyridyl is disordered over two positions as it hinges about
the N-Ag bond. This close positioning of pyridyl donors
allows for the N-bound silvers to come within 3.1918(8) Å
of each other, leading to a respectable Ag-Ag interaction
that likely has an influence on the luminescence of this
species. The average cross-ligand distance observed separat-
ing the P- and N-bound silvers is 6.626 Å, from which is
given some indication of the amount of charge separation
present. Intraligand P-N distances vary slightly from P1-
N1 to P1-N2A at 5.161(3) and 5.487(4) Å, respectively.
The Ag-P bonds display typical values at 2.323(1) Å, while
the N-Ag bonds are noticeably short with an average of
2.155 Å. This is undoubtedly due to the charge density
present on the N-bound silvers that is not balanced by a
closely associated anion. Ag(1)-O distances vary from
2.287(3) to 2.456(3) Å with the shorter value represented
by the terminal bound triflate. Ag1 is in a severely distorted
tetrahedral arrangement with its oxygen-only face being
constricted by the bridging trifluoroacetates and displaying
O-Ag-O angles from 77.5(1)° to 84.0(1)°. The O-Ag-P
angles are in turn widened from 122.30(7)° to 144.84(7)°.
The environment of Ag2 is nearly linear with respect to
pyridyl coordination with an N-Ag-N angle of 172.2(1)°.
This slight distortion results from the movement of the Ag
toward its symmetry equivalent, which is slightly askew from
Ag2. The N-Ag-Ag angles, at 75.2(1)° and 112.5(1)°, show
one silver to be oriented slightly above the other.
A thermal ellipsoid plot of the unique portion of 3 is shown
in Figure 3. In the structure of 3 we see four crystallographi-
cally inequivalent silver centers arranged linearly whose
differences arise from a slight twisting of the ligands through
the length of the unique portion. However, rather than a fully
spiraling polymer, only a partial helix is seen to repeat
throughout the lattice. This partial spiral is evident in either
of the two dimensions in which the polymer is perpetuated
and is demonstrated in Figure 4. This two-dimensional
growth of 3 gives rise to an infinite pleated sheet structure
with anions dispersed throughout the crevices of the layers.
A view of how these 2-D layers pack together is shown in
Figure 5. Opposing the trend of structures 2 and 4, all silvers
in 3 are identical in connectivity, being coordinated by two
pyridyls and one phosphorus donor in a doubly distorted
trigonal arrangement. The first distortion involves the angles
which for the N-Ag-N junction are all acute from 93.1-
(2)° to 107.3(2)°, while the other two N-Ag-P angles are
widened to values of 124.1(2)° to 136.4(2)°. The second
-
distortion stems from the long-distance interaction of a BF4
fluorine approaching at an average proximity of 2.8 Å to
Inorganic Chemistry, Vol. 44, No. 4, 2005 1001

Feazell et al.
Figure 4. View of the chain of PCP-32AgBF4, 3, perpetuated in one dimension. The partial spiral of the pyridyl linkages can be seen to abruptly restart
at the end of the unique portion. H atoms have been removed for clarity.
extension. Those silvers contained within the collinear
backbone of the structure have separations from 9.263(1) to
9.597(1) Å, while those arranged nearly perpendicular have
slightly smaller values from 9.024(1) to 9.324(1) Å. This
accompanies a substantial increase in cross-ligand metal-
metal separation of the N-bound silvers, whose distance in
3 averages at 8.7055 Å. 3 crystallizes in the noncentrosym-
metric space group P212121 with a refined Flack parameter
of 0.00(2).
Compound 4 forms a structurally complicated polymer that
displays a variety of interesting attributes. Figure 6 shows
the molecular structure of the unique portion of 4. This
winding 3-D growth is displayed in Figure 7. Growth of the
polymer occurs in three dimensions due to the bridging
actions of both the ligand and the trifluoroacetates. The ligand
in this case occupies two separate roles within the structure.
In the first instance the phosphonite is tridentate using all
three binding sites to coordinate to two different types of
metal centers. Using one pyridyl “arm” and the phosphorus,
two equivalent silvers, Ag1 and Ag1#1, are bound by two
symmetry-equivalent ligands in a head-to-tail fashion forming
a ring. Each of these silvers is subsequently bridged by two
η1,µ2-trifluoroacetates to yet another equivalent metal. The
remaining “arm” of the ligand extends from the ring and
acts as a bridge to the other unique silver of the polymer,
Ag2. It is as a result of this outstretching reach that we see
the greatest cross ligand metal-metal distance of the three
polymers. The N-bound silvers of these oppositely directed
donors are separated by a distance of 14.015(2) Å across
the breadth of the ligand. The P-bound to N-bound metal
distances across this ligand show separations of 9.112(1) and
6.466(1) Å for Ag1-Ag2 and Ag1-Ag1A, respectively. Ag2
is bound by the phosphorus and nitrogen of two separate
but equivalent ligands that are in a similar conformation to
that of the one P-bound to Ag1 and the pyridyl that bridges
to Ag1 to achieve a head-to-tail-to-tail motif. In this case,
however, the ligands are not involved in ring formation. The
attached ligands instead continue off via one pyridyl exten-
sion each in two separate polymeric strands that run parallel
to one another. The remaining “arm” of this ligand is a
curious feature in that it has a noncoordinating “dangling”
pyridyl that sits within the space between ligands. It is
believed that the steric packing that encapsulates this
particular pyridyl ring is responsible for its unsaturated
coordination state since even when an excess of Ag(tfa) is
used the noncoordinating nitrogen is present in the crystal
structure. The similar conformations of the two unique
ligands in the structure of 4 likewise display similar
intraligand N-N distances at 10.774(6) Å for the P1 ligand
and 10.026(6) Å for that of P2. Comparable P-N distances
Figure 5. View down the a axis of how the 2-D sheets of PCP-32AgBF4
stack together encompassing the BF4- anions. H atoms have been removed
for clarity.
the metal. As the metal centers are pulled out of their
N-N-P coordination planes, a resulting mean perturbance
of 0.121 Å is seen. All Ag-N and Ag-P bonds show typical
lengths with ranges of 2.265(6)-2.318(7) and 2.336(2)-
2.362(2) Å, respectively. Overall, intraligand P-N distances
show an increase in length of close to 1 Å from 2. Averages
are 5.932 Å on the outstretched pyridyl arms and 6.142 Å
on the collinear pyridyls. This results in an increase in
separation of P- and N-bound silvers; the magnitude of this
separation depends upon the orientation of the pyridyl
1002 Inorganic Chemistry, Vol. 44, No. 4, 2005

Polymers of the Tridentate Pyridylphosphonite
Figure 6. Thermal ellipsoid plot of the unique portion of PCP-32Ag(tfa), 4. Ellipsoids are drawn at the 30% probability level. As shown, N4 is seen to
be noncoordinating. All other pyridyl donors are metal bound.
Figure 7. Packing structure of complex 4 showing the 3-D growth of the polymer. H atoms, trifluoromethyls, and all but the ipso portion of the phenyl
rings have been removed for clarity.
are also noticed with each ligand having a short and long
stretch: P1-N2 and P1-N1 separations are 5.520(5) and
6.203(4) Å, respectively, while the analogous P2-N4 and
P2-N3 distances are 5.651(5) and 6.108(4) Å. The single
cross-ligand metal-metal distance of the P2 ligand is that
of the P2 to N3 silvers, which is slightly longer than that of
Inorganic Chemistry, Vol. 44, No. 4, 2005 1003

Feazell et al.
(1)° angle. The remaining angles around Ag1 are also
distorted from the ideal tetrahedral geometry and have values
interspersed between the aforementioned extremes. In the
absence of the bridging trifluoroacetates displayed by Ag1,
the distortions of the tetrahedral coordination sphere of Ag2
are not seen to be as severe. The environment of Ag2 is
displayed in Figure 9 and includes two pyridyl donors, the
phosphorus atom P2, and a terminal bound η1-trifluoroac-
etate. The silver-pyridyl linkages in this case are uncom-
monly lengthy at 2.355(4) and 2.322(4) Å for Ag2-N1 and
Ag2-N3#3, while the Ag2-P2 and Ag2-O7 bonds are in
the typical range at 2.329(1) and 2.344(4) Å, respectively.
The angles about Ag2 however are still shown to be rather
extreme from 86.4(1)° to 133.3(1)°.
Figure 8. Coordination environment of Ag1 in the polymer of 4. Ellipsoids
Luminescent Properties. Mixed inorganic-organic co-
ordination polymers have been recently explored as having
potential as new “organic” light-emitting devices, OLEDs.
The advantage of these hybrids over the strictly organic
luminescent materials is the ability to tune their absorption
and emission by altering the metal environment. This
variability stems from either metal-to-ligand or ligand-to-
metal charge transfer, which is obviously not an option with
the traditional organic LED.51 All excitation and emission
spectra were recorded at concentrations of 1 × 10-4 M in
acetonitrile glasses at 77 K. These spectra are demonstrated
in Figure 10. The resemblance of the excitation spectra of
compounds 2-4 with that of the free PhP(3-OCH2C5H4N)2
ligand are suggestive of a ligand-based absorption which then
decays by means of ligand-to-metal charge transfer. The
excitation spectrum of the free ligand 1 shows two maxima
at 298 and 352 nm. Excitation maxima for 2, 3, and 4 are
295, 297, and 305 nm, respectively. Emission spectra for
all compounds 1-4 show multiple maxima, illustrating the
complexity of the decay transitions associated with such a
complicated system. The ligand itself demonstrates several
emission maxima across a wide section of the spectrum.
Peaks are seen at 412, 442, 474, and 544 nm. A great deal
of free ligand character is seen in the spectrum of 3, which
is the weakest emitter of the silver complexes. Peaks are
seen at 412, 441, and 477, and a shoulder is noticed at ∼547
nm. This suggests that the emission is mainly a ligand-based
one intensified by metal coordination. The emission of the
silver triflate complex is much more intense and covers a
broader spectral range than either 1 or 3. Peaks are displayed
at 363, 404, 423, 438, 452, and 501 nm, and again a shoulder
are drawn at the 50% probability level.
Figure 9. Coordination environment of Ag2 in the polymer of 4. Ellipsoids
are drawn at the 50% probability level.
the P1 ligand at 9.227(1) Å. Both silver centers here are in
distorted tetrahedral arrangements. The coordination around
Ag1 is completed by one pyridyl and phosphorus donor as
well two bridging trifluoroacetate oxygens and is shown in
a close-up view in Figure 8. The Ag1-N2#1 bond is only
slightly stretched for a Ag-pyridyl distance at 2.297(4) Å,
while the Ag1-P1 bond is a typical 2.357(2) Å. Bonds to
the bridging trifluoroacetates are seen to be inequivalent with
Ag1-O3 at 2.386(4) Å and Ag1-O3#2 at 2.509(4) Å. It is
also noticed that the small bridging distance of the η1,µ2-
trifluoroacetates constrict the angle they create with the metal
to an acute 74.4(1)°. As a result, the P1-Ag1-N1 angle
has room to spread apart, which is apparent with a 132.5-
Figure 10. Normalized excitation and emission spectra of compounds 1-4 taken in acetonitrile glasses at 1 × 10-4 M at 77 K: (s) PCP-32, (- - -)
PCP-32AgBF4, (‚ ‚ ‚) PCP-32AgOTf, (- ‚ -) PCP-32Ag(tfa).
1004 Inorganic Chemistry, Vol. 44, No. 4, 2005

Polymers of the Tridentate Pyridylphosphonite
Figure 11. View of the cationic polymer formed in the reaction of PHP-31 with AgPF6. H atoms have been removed for clarity.
is noticed at 547 nm. The emission spectrum of complex 4
is noticeably more intense than the others, as expected from
visual observations, and is also slightly red shifted. The local
maxima for this complex are seen at 449, 465, 487, and 513
nm.
activity are noticed by altering the rigidity of these ligands
by addition or subtraction of atoms between the phosphorus
and pyridyl rings. Preliminary structural studies of the silver-
(I) coordination complexes formed by the PHP-31 ligand
(the hydroxypyridine-derived analogue of PCP-31) show
polymers much like those of the PCP ligands but are
obviously more restricted in their arrangements. An example
of this is shown in Figure 11, where the complex PHP-
31AgPF6 demonstrates its cationic 1-D polymer of two-
coordinate silver.
Conclusions
We demonstrated in this study the versatility of the
phosphonite PhP(3-OCH2C5H4N)2 in the formation of anion-
dependent, luminescent coordination polymers. The flex-
ibility of the pyridyl extensions allowed trans-ligand metal-
metal distances to span a range of over 10 Å from 3.1918(8)
to 14.015(2) Å. These pyridyl arms were seen to adopt
conformations ranging from parallel to opposed. The silver
coordination environment, dimensionality of the polymers,
and luminescence characteristics are all seen to be dependent
upon the anion present. We are currently exploring the
coordination and luminescence properties of silver complexes
of the trisubstituted analogue of the phosphonite as well as
their closely related 2- and 4-pyridyl-substituted isomers. We
are also studying the coordination properties of these ligands
with other metals that have more of a preference for
phosphorus versus nitrogen, or vice versa, in their coordina-
tion. It is also of interest to determine what changes in
Acknowledgment. This research was supported by funds
provided by the University Research Committee at Baylor
University (019-F00-URC and 011-N02-URC), a grant
provided by the Vice-Provost for Research at Baylor
University, and a grant from the Robert A. Welch Foundation
(AA-1508). The Bruker X8 APEX diffractometer was
purchased with funds received from the National Science
Foundation Major Research Instrumentation Program, Grant
CHE-0321214.
Supporting Information Available: Extra figures as well as a
listing of the final atomic coordinates, anisotropic thermal param-
eters, and complete bond lengths and angles in CIF format are
available for complexes 2-4. This material is available free of
charge via the Internet at http://pubs.acs.org.
(51) Bacher, A.; Erdelen, C. H.; Paulus, W.; Ringsdorf, H.; Schmidt, H.-
W.; Schuhmacher, P. Macromolecules 1999, 32, 4551-4557.
IC0486365
Inorganic Chemistry, Vol. 44, No. 4, 2005 1005