Two-, Three-, and Four-Coordinate Ag(I) Coordination Polymers Formed by the Novel Phosphinite PPh2(3-OCH2C5H 4N)

Article abstract of DOI:10.1021/ic035168a

The novel phosphinite PPh₂(3-OCH₂C₅H ₄N) (1) has been synthesized, and its coordination properties to Ag(I) have been studied. When reacted in a 1:1 ratio with Ag(I), coordination polymers with different coordination numbers about the Ag are found depending on the anion. For PPh₂(3-OCH₂C₅H ₄N)AgBF₄ (2), a two-coordinate Ag is observed with a P-Ag-N angle of 167°. Mixed three and four coordination about Ag is observed for PPh₂(3-OCH₂C₅H₄N)AgOTf (3), and for the trifluoroacetate derivative, PPh₂(3-OCH ₂C₅H₄N)Agtfa (4), only a four-coordinate Ag is produced. X-ray crystal-structure determinations for compounds 2-4 have been carried out. The X-ray structures show a wide range of Ag-Ag distances in the polymers, which are dependent on the conformation of the bridging ligand.

Full text of DOI:10.1021/ic035168a

Inorg. Chem. 2004, 43, 1130−1136
Two-, Three-, and Four-Coordinate Ag(I) Coordination Polymers Formed
by the Novel Phosphinite PPh2(3-OCH C H N)
2 5 4
,†
Kevin K. Klausmeyer,* Rodney P. Feazell,† and Joseph H. Reibenspies‡
Department of Chemistry and Biochemistry, Baylor UniVersity, Waco, Texas 76798, and
Department of Chemistry, Texas A&M UniVersity, College Station, Texas 77843-3255
Received October 8, 2003
The novel phosphinite PPh2(3-OCH C H N) (1) has been synthesized, and its coordination properties to Ag(I) have
2
5 4
been studied. When reacted in a 1:1 ratio with Ag(I), coordination polymers with different coordination numbers
about the Ag are found depending on the anion. For PPh2(3-OCH C H N)AgBF (2), a two-coordinate Ag is observed
2
5
4
4
with a P−Ag−N angle of 167°. Mixed three and four coordination about Ag is observed for PPh2(3-OCH C H N)-
2
5 4
AgOTf (3), and for the trifluoroacetate derivative, PPh (3-OCH C H N)Agtfa (4), only a four-coordinate Ag is produced.
2
2 5 4
X-ray crystal-structure determinations for compounds 2−4 have been carried out. The X-ray structures show a
wide range of Ag−Ag distances in the polymers, which are dependent on the conformation of the bridging ligand.
Introduction
what gives silver the ability to produce such intriguing
structural motifs is the ease with which it varies its
Silver-based coordination polymers have received great
attention lately.1-11 This is owed to the rich chemistry that
is available to this versatile metal. Silver phosphine/silver
pyridine complexes have repeatedly demonstrated interesting
electronic, medicinal, and structural properties.1-33 Part of
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* Author to whom correspondence should be addressed. E-mail:
Kevin_Klausmeyer@baylor.edu. Fax: 254-710-4272.
† Baylor University.
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‡ Texas A&M University.
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1130 Inorganic Chemistry, Vol. 43, No. 3, 2004
10.1021/ic035168a CCC: $27.50 © 2004 American Chemical Society
Published on Web 01/08/2004

Ag(I) Coordination Polymers
coordination number, generally from two to four.22 Thus far,
the vast majority of silver coordination polymers employ
ligands that are symmetric, very often using some isomer of
bipyridine.6
To provide an easier entry into new pyridyl-containing
phosphines and in an attempt to open a new area of
coordination-polymer chemistry using ligands with different
binding functionalities, an OCH2 “spacer” has been inserted
between the P and 3-pyridyl components, thereby achieving
the goal of P-N isolation with an added benefit of inherent
flexibility in the P-N distance. From this, several new
coordination compounds of silver that have been prepared
with a novel pyridylcarbinol-substituted phosphine ligand are
now reported.
Pyridyl-substituted phosphines, which were first reported
nearly 60 years ago, have become commonplace and have
been thoroughly explored since their introduction.9,23,25-30,32-53
They are an interesting family of ligands because they have
the potential to display both the hard- and soft-donating
abilities of the nitrogen and phosphorus, respectively, in a
single moiety. The majority of reports in this area have been
of 2-pyridylphosphines, with their chelating or bimetallic/
biligand ring-forming abilities.23,25-38,43-49,51-56 Relatively
little work has been reported for 3- and 4-pyridylphosphines,
most likely because of the difficulty with which they are
synthesized.34,37,49 Using only 2-pyridyl substituents, the
arrangement of the complexes formed is inherently limited
to those discrete structures that can be obtained with the acute
angles present. This excludes a vast array of complexes that
could be formed by separating the nitrogen and phosphorus
to the point of minimal interaction.
Experimental Section
General Procedures. All of the experiments were carried out
under an argon atmosphere, using a Schlenk line and standard
Schlenk techniques. All of the glassware was dried at 120 °C for
several hours prior to use. All of the reagents were stored in an
inert-atmosphere glovebox; solvents were distilled under nitrogen
from the appropriate drying agent immediately before use. Tri-
ethylamine was purchased from Aldrich and purged with argon
before use. 3-Pyridylcarbinol was purchased from Aldrich and used
as received. Chlorodiphenylphosphine, 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 room-
temperature 31P NMR spectra were recorded at 300.13 and 121.49
MHz, respectively, on a Bruker Spectrospin 300 MHz spectrometer.
Low-temperature 31P NMR spectra were recorded at 145.78 MHz
on a Bruker Spectrospin 360 MHz spectrometer. Elemental analyses
were performed by Atlantic Microlabs Inc., Norcross, GA.
(31) Inoguchi, Y.; Milewski-Mahrla, B.; Neugeauer, D.; Jones, P. G.;
Schmidbaur, H. Chem. Ber. 1983, 116, 1487-1493.
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Ed. Engl. 1996, 35, 739 and 740.
(33) Berners-Price, S. J.; Bowen, R. J.; Harvey, P. J.; Healy, P. C.;
Koutsantonis, G. A. J. Chem. Soc., Dalton Trans. 1998, 1743.
(34) Newkome, G. R. Chem. ReV. 1993, 93, 2067-2089.
(35) Barloy, L.; Malaise´, G.; Ramdeehul, S.; Newton, C.; Osborn, J. A.;
Kyritsakas, N. Inorg. Chem. 2003, 42, 2902-2907.
(36) Yam, V. W.-W.; Chan, L.-P.; Lai, T.-F. J. Chem. Soc., Dalton Trans.
1993, 2075-2077.
Synthesis of Diphenylphoshino-3-pyridylcarbinol, PPh2(3-
OCH2C5H4N) (1). In an argon-purged addition funnel, 1.3 mL of
degassed triethylamine (9.33 mmol) was added via a syringe to a
stirred solution of 1.00 g of 3-pyridylcarbinol (9.16 mmol) in 20
mL of toluene at room temperature. The solution was then cooled
to 0 °C and shielded from light with aluminum foil. A solution of
2.02 g (9.16 mmol) of chlorodiphenylphosphine in 20 mL of toluene
was then added dropwise over 10 min. The solution was stirred
for 1 h, then allowed to warm to room temperature, and stirred for
an additional 1 h. The resultant cloudy mixture was reduced to 3/4
of its original volume under vacuum and immediately filtered
through Celite. The triethylammonium chloride salts were washed
with an additional 5 mL of cold toluene, and the solvent was
removed from the yellow liquid at reduced pressure to leave a pale
yellow oil in 96% yield. The oil was then extracted several times
with hexanes. Drying of the hexane wash in vacuo yielded the clear,
colorless oil, 1, in 81% yield (2.18 g, 7.44 mmol). 1H NMR (CDCl3,
298 K) δ: 4.93 d, 2H, J(PH) ) 9.10 Hz; 7.28 m, 1H; 7.39 m, 6H;
7.53 m, 4H; 7.68 dt, 1H; 8.56 d, 1H; 8.63 s, 1H. 31P NMR δ: 116.2
m, J(PH) ) 8.1 Hz.
(37) Bowen, R. J.; Garner, A. C.; Berners-Price, S. J.; Jenkins, I. D.; Sue,
R. E. J. Organomet. Chem. 1998, 554, 181-184.
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Trans. 2000, 2559-2575.
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A. J. Am. Chem. Soc. 1984, 106, 1323-1332.
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Chem. 1988, 27, 2040-2045.
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G.; Springler, B.; Zehnder, M. Inorg. Chim. Acta 2000, 300-302,
49-55.
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Soc., Dalton Trans. 1996, 1845-1851.
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1996, 15, 79-81.
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A. J. Chem. Soc., Dalton Trans. 1989, 1499-1506.
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1193-1203.
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M. Angew. Chem., Int. Ed. 2001, 40, 4271-4274.
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2002, 5, 803 and 804.
(49) Kurtev, K.; Ribola, D.; Jones, R. A.; Cole-Hamilton, D. J.; Wilkinson,
G. J. Chem. Soc., Dalton Trans. 1980, 55-58.
Synthesis of PPh2(3-OCH2C5H4N)AgBF4 (2). To a stirred
solution of 0.300 g of AgBF4 (1.54 mmol) in 5 mL of CH2Cl2 was
added 0.452 g (1.54 mmol) of 1 in 5 mL of CH2Cl2. The resulting
solution remained clear and colorless, and the solvent was removed
by vacuum after 5 min of stirring. Upon drying, the white powder,
2, was reclaimed in 91% yield (0.686 g, 1.406 mmol). Crystals of
2 were obtained by vapor diffusion of ether into a CH2Cl2 solution
(50) Gregorzik, R.; Wirbser, J.; Vahrenkamp, H. Chem. Ber. 1992, 125,
1575-1581.
(51) Astley, T.; Headlam, H.; Hitchman, M. A.; Keene, F. R.; Pilbrow, J.;
Stratemeier, H.; Tiekink, E. R. T.; Zhong, Y. C. J. Chem. Soc., Dalton
Trans. 1995, 3809-3818.
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Trans. 1994, 3067-3068.
1
at 5 °C. H NMR (CD3CN, 298 K) δ: 5.05 d, 2H; 7.37 m, 7H;
(54) Olmstead, M. M.; Maisonhat, A.; Farr, J. P.; Balch, A. L. Inorg. Chem.
1981, 20, 4060-4064.
7.58 t, 4H; 7.78 d, 1H; 8.43 d, 1H; 8.69 s, 1H. 31P NMR (238 K)
δ: 111.9 dd, J(107Ag-P) ) 790.1 Hz, J(109Ag-P) ) 685.1 Hz.
Elem anal. Calcd: C, 44.31; H, 3.30; N, 2.87. Found: C, 45.11;
H, 3.39; N, 3.16.
(55) Maisonnet, A.; Farr, J. P.; Olmstead, M. M.; Hunt, C. T.; Balch, A.
L. Inorg. Chem. 1982, 21, 3961-3967.
(56) Keene, F. R.; Stephenson, P. J.; Tiekink, E. R. T. Inorg. Chim. Acta
1991, 187, 217-220.
Inorganic Chemistry, Vol. 43, No. 3, 2004 1131

Klausmeyer et al.
Table 1. Crystallographic Data for 2-4
2
3
4
formula
formula weight
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
C18H16AgBF4NOP(CH2Cl2)1.5
615.36
29.399(5)
11.204(2)
14.189(2)
C76H64Ag4F12N4O16P4S4(CH2Cl2)2
2370.76
17.972(5)
10.191(3)
27.936(8)
C40H32Ag2F6N2O6P2
1028.36
8.991(1)
9.103(1)
25.965(4)
96.721(2)
95.492(2)
105.485(2)
2015.9(5)
2
94.266(9)
115.441(4)
4660.7(11)
8
4620(2)
2
space group
T (K)
C2/c
110
Pc
110
P1h
110
λ (Å)
0.710 73
1.754
1.323
66
34 150
8789
0/285
0.0301
0.0812
0.0402
0.0834
1.073
X8 Apex
0.710 73
1.704
1.198
0.710 73
1.694
1.127
55
27 968
8965
125/546
0.0531
0.1260
0.0567
0.1278
1.105
D
calcd (g cm-3
)
µ (mm-1
2θmax (deg)
reflns measured
)
55
47 570
18 852
201/1106
0.0624
0.1531
0.0693
0.1531
1.088
reflns used (Rint
restraints/parameters
R1 [I > 2σ(I)]
)
wR2 [I > 2σ(I)]
2
R(Fo ) (all of the data)
2
Rw(Fo ) (all of the data)
GOF on F2
instrument
SMART 1000
Apex
Synthesis of PPh2(3-OCH2C5H4N)AgOTf (3). To a stirred
solution of 0.088 g (0.342 mmol) of AgOTf in 10 mL of THF was
added 0.100 g (0.341 mmol) of 1 in 5 mL of THF. This solution
was stirred for 5 min, and then the solvent was removed in vacuo
to leave a white solid, 3, in 92% yield (0.172 g, 0.312 mmol).
Crystals of 3 were grown by slow diffusion of diethyl ether into a
otherwise noted, all of the non-hydrogen atoms were refined
anisotropically, and hydrogen atoms were placed in calculated
positions. The structure of 3 is a racemic twin, which was refined
using the TWIN command in SHELX.
Results and Discussion
1
Synthesis and NMR Spectroscopy. Compound 1 is made
by the SN2-type substitution of a chlorophosphine with an
alkoxypyridine in a modified version of the phenol-derived
analogue reported by Bedford and Welch.59 Deprotonation
of the carbinol to make the -OCH2C5H4N nucleophile is
facile in toluene with the base triethylamine. Great care must
be taken for the synthesis of 1 as a result of the observations
that in the intermediate stages of the reaction all of the
reaction components are extremely sensitive to factors such
as temperature, light, addition rate, concentration, and
solvent. High temperatures, rapid or extremely slow addition
rates, and ion-stabilizing solvents, such as THF, tend to favor
the production of the well-known phosphorus/phosphine
oxide byproduct PPh2P(O)Ph2.60 Exposure to light at any
stage of the synthesis leads to the accelerated formation of
the yellow decomposition product. Once isolated, 1 is stable
to moisture but unstable to air, heat, or light. Decomposition
can be slowed, though not completely halted, by keeping it
shielded from light and refrigerated under an inert atmo-
sphere. 1H and 31P NMR spectra of 1 were obtained in CDCl3
and demonstrate the very pronounced three-bond coupling
of phosphorus to the phenyl and methylene protons. A
defined phosphorus septet is found centered at δ ) 116.3,
which is in the region expected for aromatic-substituted
phosphinites.35
solution of 3 in CH2Cl2 at 5 °C. H NMR (CD3CN, 298 K) δ:
5.07 d, 2H; 7.34 m, 7H; 7.57 t, 4H; 7.86 d, 1H; 8.46 d, 1H; 8.66
s, 1H. 31P NMR (238 K) δ: 112.1 dd, J(107Ag-P) ) 788.7 Hz,
J(109Ag-P) ) 688.1 Hz. Elem anal. Calcd: C, 41.47; H, 2.93; N,
2.55. Found: C, 40.90; H, 2.82; N, 2.69.
Synthesis of PPh2(3-OCH2C5H4N)Agtfa (4). To a stirred
suspension of 0.076 g (0.344 mmol) of Agtfa in 10 mL of CH2Cl2
was added 0.100 g (0.341 mmol) of 1 in 5 mL of CH2Cl2. The
solid Agtfa dissolved immediately upon introduction of the ligand.
After approximately 5 min of vigorous stirring, a precipitate formed.
The brown-yellow solvent was removed via cannula, and the solid
4 was washed with another 5 mL aliquot of CH2Cl2. The residual
solvent was then removed in vacuo to leave a white solid, 4, in
98% yield (0.172 g, 0.334 mmol). Crystals of 4 were obtained by
slow diffusion of diethyl ether into a solution of 4 in CH2Cl2 at 5
1
°C. H NMR (CDCl3, 298 K) δ: 5.05 d, 2H; 7.43 m, 7H; 7.58 t,
4H; 7.83 d, 1H; 8.51 d, 1H; 8.59 s, 1H. 31P NMR (219 K) δ: 117.5
d, J(Ag-P) ) 519.0 Hz. Elem anal. Calcd: C, 46.72; H, 3.14; N,
2.72. Found: C, 46.67; H, 3.10; N, 2.90.
X-ray Crystallographic Analysis. Crystallographic data were
collected on crystals with the dimensions 0.29 × 0.28 × 0.25 mm
for 2, 0.22 × 0.17 × 0.13 mm for 3, and 0.26 × 0.22 × 0.15 mm
for 4. Data for 3 and 4 were collected at 110 K on a SMART 1000
and Bruker Apex diffractometer, respectively. Data for 2 was
collected on a Bruker X8 Apex at 110 K. All of the structures were
solved by direct methods after the correction of the data using
SADABS.57 Crystal data are presented in Table 1, and selected
interatomic distances, angles, torsion angles, and other important
distances are given in Table 2. All of the data were processed using
the Bruker AXS SHELXTL software, version 6.10.58 Unless
The silver compounds 2-4 were synthesized by the
reaction with simple silver salts under ambient conditions
(58) Sheldrick, G. M. SHELXTL, version 6.10; Bruker AXS, Inc.: Madison,
WI, 2000.
(57) Sheldrick, G. M. SADABS; University of Go¨ttingen: Go¨ttingen,
(59) Bedford, R. B.; Welch, S. L. Chem. Commun. 2001, 1, 129 and 130.
(60) Rabinowitz, R.; Pellon, J. J. Org. Chem. 1961, 26, 4623-4626.
Germany, 1997.
1132 Inorganic Chemistry, Vol. 43, No. 3, 2004

Ag(I) Coordination Polymers
Scheme 1. General Synthetic Scheme for the Carbinol-Substituted Phosphine Coordination Complexes of Silver(I) Saltsa
a In a, X ) BF4 or Tfa, and in b, X ) OTf.
Table 2. Selected Bond Lengths (Å), Angles (deg), Torsion Angles
Compound 2 is the most robust of the coordination
(deg), and Important Distances for 2-4a
complexes presented. Though it still suffers from decomposi-
tion in solution, under conditions similar to those of 3 and
4, it is at a notably slower rate, while the rapid rate of
decomposition of 3 and 4 may be due to having a counterion
bound to the silver, which makes reduction of the metal more
facile. Compound 2 is prepared from the mixing of 1 equiv
of AgBF4 in CH2Cl2 with a solution of 1. The two-coordinate
coordination polymer is collected as a white solid by removal
of CH2Cl2 under vacuum after less than 5 min of reaction.
The precipitation of metallic silver from solutions of 2 is at
such a rate that after 24 h, layered in a crystallization tube
at 5 °C, there is only a slightly dark appearance to the tube,
whereas under similar conditions, compounds 3 and 4 would
have released the majority of their solute as a black
precipitate. 31P NMR spectra of 2 were recorded in CD3CN
down to 238 K. At room temperature, 31P NMR spectra show
a doublet of broad peaks centered at 114.0 ppm, owing to
the silver-phosphorus coupling. This indicates at least some
degree of coordination of the ligand to silver in room-
temperature solutions, though the process does appear to be
dynamic on the NMR time scale. Slowing of the dissociation
of the Ag-P bond by lowering the temperature causes the
doublet peaks to sharpen, move slightly upfield, and eventu-
ally split, revealing the coupling of the separate isotopes of
Ag.
Compound 2
Ag1-N1
2.171(1)
7.1914(9)
5.569(2)
Ag1-P1
2.3543(5)
2.785(1)
3.883(2)
Ag1-Ag1#1
P1#1-N1
Ag1#2-F2
P1#1-C2
P1#1-O1-C1-C2
N1-Ag1-P2
167.28(4)
-155.1(1)
Compound 3
Ag1-N2#1
Ag1-O5
2.232(7) Ag1-P1
2.494(8) Ag2-N1
2.341(2) Ag2-O8
2.255(7) Ag3-P3
2.490(6) Ag3-O9
2.241(7) Ag4-P4
2.515(6) Ag1-Ag2
10.678(3) Ag1-Ag4
4.806(1) Ag2-Ag4
9.265(2) P1-N1
6.119(7) P3-N3
6.014(7) P1-C2
3.866(9) P3-C40
3.865(8) N2#1-Ag1-P1
2.334(2)
2.217(7)
2.470(7)
2.355(2)
2.524(7)
2.359(2)
9.165(2)
4.460(1)
8.912(2)
5.933(7)
5.979(7)
3.902(8)
3.891(8)
142.8(2)
119.4(2)
83.8(3)
140.2(2)
119.9(2)
124.1(2)
146.9(2)
119.9(2)
Ag2-P2
Ag3-N4#2
Ag3-O11
Ag4-N3
Ag4-O14
Ag1-Ag3
Ag2-Ag3
Ag3-Ag4
P2-N2
P4-N4
P2-C21
P4-C59
N2#1-Ag1-O6
N1-Ag2-P2
P2-Ag2-O8
N4#2-Ag3-O11
N4#2-Ag3-O9
O11-Ag3-O9
N3-Ag4-O14
P1-O1-C1-C2
86.5(3)
145.5(2)
119.9(2)
86.7(2)
82.3(2)
88.2(2)
P1-Ag1-O6
N1-Ag2-O8
N4#2-Ag3-P3
P3-Ag3-O11
P3-Ag3-O9
N3-Ag4-P4
P4-Ag4-O14
83.3(2)
-169.4(5)
P3-O3-C39-C40 -169.6(5)
P2-O2-C20-C21 166.7(6)
P4-O4-C58-C59 167.3(5)
Compound 4
Ag1-N1#1
2.269(4)
2.375(4)
2.264(5)
2.419(4)
3.8686(9) Ag1-Ag1#2
3.9404(9) Ag2-Ag2#3
5.370(4)
5.337(4)
133.4(1)
119.7(1)
114.5(1)
136.3(1)
112.7(1)
113.91(9)
Ag1-P1
Ag1-O2
Ag2-P2
Ag2-O5
2.356(1)
2.549(4)
2.368(1)
2.576(4)
6.068(1)
5.937(1)
3.794(5)
3.784(5)
Ag1-O2#2
A solution of silver triflate in THF added to 1 equiv of 1
in THF yields the mixed coordination complex 3 as a white
powder upon drying. Stirring for longer than a few minutes,
however, results in a precipitate of metallic silver from an
unknown redox reaction. Saturated CH2Cl2 solutions of 3
turn dark, form a brown precipitate within hours, but still
manage to grow X-ray quality crystals over several days
when layered with diethyl ether at 5 °C. 31P NMR spectra
of this compound were obtained using CDCl3 and collected
to 238 K. Again, some degree of coordination of phosphorus
to silver is seen at room temperature, though dissociation is
rapid. After the cooling of the sample to 238 K, the isotopic
coupling of silver can be observed to form a doublet of
doublets that is centered slightly upfield of the original
doublet’s 114.6 ppm position.
Ag2-N2#3
Ag2-O5#4
Ag1-Ag1#1
Ag2-Ag2#4
P1-N1
P1-C2
P2-C22
P2-N2
N1#1-Ag1-P1
P1-Ag1-O2#2
P1-Ag1-O2
N2#3-Ag2-P2
P2-Ag2-O5#4
P2-Ag2-O5
N1#1-Ag1-O2#2
N1#1-Ag1-O2
O2#2-Ag1-O2
N2#3-Ag2-O5#4
N2#3-Ag2-O5
O5#4-Ag2-O5
103.1(2)
91.6(1)
76.5(1)
107.2(2)
92.2(1)
75.9(1)
P1-O1-C1-C2 -136.7(3)
P2-O2-C21-C22 -134.4(3)
a Symmetry transformations used to generate the equivalent atoms for
2: #1 ) x, -y + 2, z + 1/2; #2 ) x, y - 1, z. For 3: #1 ) x + 1, y, z; #2
) x - 1, y, z. For 4: #1 ) -x, -y + 2, -z; #2 ) -x, -y + 1, -z; #3 )
-x + 1, -y + 2, -z + 1; #4 ) -x + 2, -y + 2, -z + 1.
in an inert atmosphere as outlined in Scheme 1. Upon
coordination, all of the silver compounds reported herein are
white powders that noticeably decompose within several
hours upon exposure to light. Solutions of the metal
compounds 2-4 in organic solvents undergo reduction of
silver to precipitate metallic silver and an oily black
phosphorus byproduct. Compounds 2-4 appear to be stable
indefinitely in the solid state when kept in the absence of
light and refrigerated under an inert atmosphere.
All of the attempts to synthesize the coordination com-
pound 4 using the ligand 1 and completely dissolved silver
trifluoroacetate were unsuccessful; the results of such reac-
tions consistently are brown solutions with a rapid precipita-
tion of silver in the flask. It was found that the most
productive route to compound 4 was to allow the ligand 1
to solubilize the silver trifluoroacetate directly into a solution
from its solid state. The dissolved ligand, upon addition to
a CH2Cl2 suspension of the silver salt, immediately draws
Inorganic Chemistry, Vol. 43, No. 3, 2004 1133

Klausmeyer et al.
the silver salt into the solution. Following several minutes
of vigorous stirring, the slightly soluble complex 4 precipi-
tates from the solution. The precipitate is collected and
washed with several aliquots of CH2Cl2. The product is a
white solid that noticeably decomposes in solution within
minutes at room temperature. Single crystals of 4 were grown
with some difficulty from the saturated solutions of CH2Cl2,
layered with diethyl ether at 5 °C. 1H and 31P NMR spectra
were obtained in CDCl3 by keeping the sample in an ice
bath until the injection into the spectrometer. 31P NMR
spectra were recorded to 219 K. The 31P NMR spectrum of
4 indicates a P-Ag bond that is considerably more labile
than those of compounds 2 and 3, with the room-temperature
resonance showing no sign of Ag coupling. A single peak
is observed at 116.9 ppm that, upon cooling to 219 K, first
broadens and then splits to form a doublet centered at 117.5
ppm.
Figure 1. Thermal ellipsoid plot of the polymeric cation of 2 with an
atomic numbering scheme. Ellipsoids are shown at the 50% level.
X-ray Crystal Structure. The coordination of the silver
centers in each of the compounds 2-4 is notably different.
We were able to achieve compounds demonstrating each of
the common coordination numbers of silver, 2-4, by
changing only the counterion in each case. Variations in
coordination have also been observed by changing the
crystallization solvent; for instance, a different structural
isomer of compound 3, obtained by crystallization from THF,
has been observed that contains only three-coordinate silver
centers. The crystal structure data for this isomer are of very
poor quality and therefore are not included in this report;
there are continuing efforts to crystallize the compound from
THF. As the coordination number about the silver center
increases, there is a concomitant increase in the Ag-N and
Ag-P bond lengths; all of these bond lengths fall well within
the expected ranges.3,5 For compounds 2-4, varying only
the anion between the structures, we can see the N-Ag-P
bond angle increase from 133.4° in 4 to a nearly linear 167.3°
Figure 2. Thermal ellipsoid plot of 3 with an atomic numbering scheme.
Ellipsoids are shown at the 30% level. Hydrogen atoms and the CF3SO2
portion of three of the triflates have been removed for clarity.
bond length is 2.3543(5) Å, and the N-Ag distance is
2.171(1) Å. All of the other bond lengths and angles fall
well within the expected ranges. The Ag-Ag distance across
the bridging ligand is 7.1914(9) Å. One and a half molecules
of CH2Cl2 are present per asymmetric unit.
The X-ray crystal structure of compound 3 reveals the
triflate anion playing an integral part in deciding the
geometry of the silver ions. A thermal ellipsoid plot is shown
in Figure 2, and selected bond lengths and angles are given
in Table 2. The asymmetric unit of 3 contains four unique
silver centers, which upon further inspection reveals a cross-
linked polymer structure. Cross-linking is achieved by the
bridging of Ag2 and Ag3 through a triflate (S2). Each
phosphinite ligand acts as a bridge that connects two silver
cations as in 2. Ag1, Ag3, and Ag4 each have a terminal
triflate bound through a single sulfonate oxygen. The triflate
bound to Ag2 also forms a bridge to Ag3, resulting in four
coordination about Ag3. The other three silvers display a
distorted trigonal arrangement resulting from the single anion
and two ligands coordinating to each other, giving an O, P,
N environment. The cross-linked polymer structure contains
six repeating Ag-containing rings as shown in Figure 3. The
Ag-Ag distances range from 4.806(1) Å in the triflate-
bridged atoms, Ag2 and Ag3, to the more than doubled
distance of 10.678(3) Å in the diagonal silvers, Ag1 and Ag3.
While not bridged by triflate, the Ag1-Ag4 distance is only
4.460(1) Å, probably as a result of packing or a pseudo-π-
stacking interaction of the pyridine rings. The Ag-N bonds
range from 2.217(7) to 2.255(7) Å, slightly longer than that
observed in 2, and the Ag-P bonds average 2.34 Å, nearly
-
angle in the two-coordinate BF4 complex, 2. All of the
compounds have one structural feature in common in that
the phosphinite-ligand coordinates head-to-tail, P-Ag-N,
rather than in a head-to-head fashion, which would form
different P-Ag-P and N-Ag-N localities in the polymer.
In each of the structures, the phosphinite ligand is able to
adopt different conformations in the polymer. The P-N
distance across the ligand varies from 5.33 to 6.11 Å; this
ability to adapt the distance between the bonding moieties
in the ligand allows the Ag-Ag distances bridged by the
same ligand to vary from 5.93 to 9.26 Å.
Compound 2 makes use of the noncoordinating BF4 anion
to display nearly exclusive ligand-metal interactions. A
thermal ellipsoid plot of the one-dimensional polymeric
structure of the zigzag chains of 2 is presented in Figure 1,
and selected bond lengths and angles are given in Table 2.
Without a coordinating counterion, the silver centers take
on a near-linear geometry with respect to the head-to-tail
linking by 1. The N-Ag-P angle is slightly off linear at
167.3°; the distortion from 180° is likely caused by the long-
range interaction of BF4- with Ag+. The shortest contact is
Ag1-F2 with a distance of 2.785(1) Å, slightly longer than
the sum of the van der Waals radii for the ions. The Ag-P
1134 Inorganic Chemistry, Vol. 43, No. 3, 2004

Ag(I) Coordination Polymers
Figure 3. Ball and stick diagram of 3 showing the six Ag-containing rings.
Triflate oxygens that are bound to Ag are labeled. Phenyl rings and hydrogen
atoms are removed for clarity.
the same as that in 2. The intraligand P-N distances range
from 5.933(7) Å for P1-N1 to 6.119(7) Å for P2-N2, about
0.4 Å longer than that observed in 2. This observation helps
to account for the much longer Ag-Ag distances across the
same ligand, which range from 9.164(2) Å for Ag1-Ag2 to
9.265(2) Å for Ag3-Ag4. The N-Ag-O bond angles
around the Ag centers range from 82.3° to 86.5°, and the
P-Ag-O angles for Ag1, Ag2, and Ag4 are all near the
ideal trigonal-planar angle of 120°, ranging from 119.4(1)°
to 119.9(2)°; the exception is the P-Ag-O angle for Ag3,
which is a bit wider at 124.1(2)°. The N-Ag-P angle is
consistently the widest in the structure, from 140.1(2)° for
Ag3 to 146.9(2)° for Ag4. For the three-coordinate Ag
centers, the sum of the angles averages 349°, showing the
distortion from the trigonal-planar geometry. The polymer
chains are continued to the next unit by the pendent N2 and
N4 pyridine rings. The fluorine atoms of the triflate groups
are highly disordered about the C-S axis; because of this
disorder, they were refined isotropically, and each group was
restrained to have the same C-F bond lengths, angles, and
thermal parameters. There are two molecules of the CH2Cl2
solvent in the lattice, of which one (C78) is disordered. This
carbon was refined isotropically.
The crystal structure of compound 4 reveals a diamond-
like binuclear silver center with each Ag bridged by two
trifluoroacetate ions. There are two independent Ag centers
in the structure, with only minor differences between the
two; a thermal ellipsoid plot of one of the independent units
is shown in Figure 4. Each silver has near-tetrahedral
geometry with a Ag1-Ag1A distance of 3.8686(9) Å and
slightly longer for Ag2-Ag2A at 3.9404(9) Å. Each Ag is
also bound by two ligands with opposing ends facing each
other in a head-to-tail fashion. The pendent ends of the
ligands are bound to the Ag+ and then to another Ag+,
making a ring as shown in Figure 5. The Ag-Ag distance
across this ring is 6.068(1) Å for Ag1-Ag1B and 5.937(1)
Å for Ag2-Ag2B. Therefore, for 4, the coordination polymer
formed is not from the linkage through the phosphinite ligand
but through the trifluoroacetate-bridged Ag+ centers. The
coordination about the Ag ions in 4 is the most electron rich
of those presented here, being ligated by two O’s, a N, and
a P. The Ag-N bonds of 4 reflect the effect of increased
coordination by lengthening to 2.269(4) Å for Ag1-N1 and
2.264(5) Å for Ag2-N2, which is nearly a 0.1 Å increase
from 2. The Ag-P bond lengths are less impacted, being at
2.356(1) Å for Ag1-P1 and 2.368(1) Å for Ag2-P2. In the
adoption of the conformation for the ring structure, the P-N
Figure 4. Thermal ellipsoid plot of 4 with an atomic numbering scheme.
Hydrogen atoms have been removed for clarity, and ellipsoids are shown
at the 30% level.
Figure 5. Ball and stick diagram of the ring formed by 1 and Ag, which
is linked by the trifluoracetate ions forming an infinite chain. Phenyl groups
and hydrogens have been removed for clarity.
distance displays its shortest distance observed at 5.370(4)
Å for P1-N1 and 5.337(4) Å for P2-N2. The P-Ag-N
angles are the most acute of the examples presented here,
being 133.4(1)° for N1-Ag-P1 and 136.3(1)° for N2-
Ag2-P2. The fluorine atoms of the trifluoracetate groups
are disordered about the C-C axis, and the fluorine atoms
of each group are restrained to have the same C-F bond
lengths and thermal parameters.
Conclusions
We have reported the synthesis of a novel pyridyl-
containing phosphinite, which shows the ability to bind silver
ions through both the phosphorus and nitrogen moieties.
Several new coordination polymers of Ag(I) have been
characterized using X-ray crystallography, which reveals a
structure dependence on the anion used for crystallization.
The inherent flexibility of the ligand is manifested in the
wide-ranging difference in Ag-Ag distances across the
ligand from 5.937(1) to 9.265(2) Å. We are continuing to
study the coordination properties of 1 with other metals
and are also actively pursuing the bi- and trisubstituted
Inorganic Chemistry, Vol. 43, No. 3, 2004 1135

Klausmeyer et al.
3-pyridylcarbinol derivatives, which have initially shown
increased diversity of coordination to Ag(I). We are also
exploring the chemistry of the 4-pyridylcarbinol derivatives,
which thus far exhibit even more diverse coordination modes
to Ag(I) than the 3-pyridylcarbinol species. Competition
studies of these various ligands toward different metals are
also underway.
University, and a grant from the Robert A. Welch Foundation
(AA-1508). The Bruker X8 Apex diffractometer was pur-
chased with funds received from the National Science
Foundation Major Research Instrumentation Program Grant
CHE-0321214.
Supporting Information Available: A listing of the final
atomic coordinates, anisotropic thermal parameters, and com-
plete bond lengths and angles for complexes 2-4 is available.
This material is available free of charge via the Internet at
http://pubs.acs.org.
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
IC035168A
1136 Inorganic Chemistry, Vol. 43, No. 3, 2004