Luminescent tetranuclear silver(I) arylacetylide complexes bearing tricyclohexylphosphine ligands: Synthesis, molecular structures, and spectroscopic comparison with gold(I) and copper(I) arylacetylides

Article abstract of DOI:10.1021/om010835y

A series of luminescent tetranuclear silver(I) arylacetylides [Ag₄[μ(C≡C)_xC₆H₄R-p)₄ }-(PCy₃)_y (x = 1, y = 2, R = H (1), CH₃ (2), OCH₃ (3), Cx≡CPh (5); x = 2, y = 4, R = H (4)) were synthesized by treatment of tricyclohexylphosphine (PCy₃) with [Ag{(C≡C)_xC₆H₄R-p}]_∞ in dichloromethane in the absence of light, and their spectroscopic and photophysical properties have been investigated. The X-ray structure of 1 exhibits a planar parallelogram-like Ag₄core and consists of [Ag(C≡CPh)₂] and [Ag(PCy₃)] fragments with phenylacetylide σ-coordinated to silver atoms in a μ₂-bonding mode (mean asymmetric Ag-C(α) distances are 2.05 and 2.33 A?). For 2, 3, and 5, with different para substituents in the arylacetylide units, similar tetranuclear structures are observed. In contrast, the structure of 4 can be described as two interpenetrating tetrahedra of four silver atoms and four phenylbutadiynyl moieties forming a twisted cubane structure, with each silver atom further coordinated to a PCy₃ ligand. The electronic absorption spectra of 1-5 in CH₂Cl₂ are dominated by strong, vibronically structured absorptions at 250-332 nm (ε 10⁴-10⁵ dm³ mol^-1 cm^-1) with vibrational spacings of 1420-2160 cm^-1 which are attributed to v(C≡C) or admixtures of acetylenic and aryl stretching frequencies. The solid-state emission spectra of 1-3 at 298 and 77 K show intense vibronically structured bands at 422-607 nm which are attributed to ³(ππ*) excited states of the arylacetylide ligands. For 4, the solid-state emission is slightly red-shifted in energy from the ³(ππ*) emission of the corresponding mononuclear [Au(PCy₃)-(C≡C-C≡CPh)] congener, whereas for 5, a red-shift in its emission is observed from that of 1-4. A comparison between the emission of Cu(I), Ag(I), and Au(I) arylacetylides is made.

Full text of DOI:10.1021/om010835y

Organometallics 2002, 21, 2275-2282
2275
Lu m in escen t Tetr a n u clea r Silver (I) Ar yla cetylid e
Com p lexes Bea r in g Tr icycloh exylp h osp h in e Liga n d s:
Syn th esis, Molecu la r Str u ctu r es, a n d Sp ectr oscop ic
Com p a r ison w ith Gold (I) a n d Cop p er (I) Ar yla cetylid es
Yong-Yue Lin,† Siu-Wai Lai,*,† Chi-Ming Che,*,† Kung-Kai Cheung,† and
Zhong-Yuan Zhou‡
Department of Chemistry and the HKU-CAS J oint Laboratory on New Materials,
The University of Hong Kong, Pokfulam Road, Hong Kong,
and Department of Applied Biology and Chemical Technology,
The Hong Kong Polytechnic University, Hunghom, Hong Kong
Received September 19, 2001
A series of luminescent tetranuclear silver(I) arylacetylides [Ag4{µ-(CtC)xC6H4R-p)4}-
(PCy3)y] (x ) 1, y ) 2, R ) H (1), CH3 (2), OCH3 (3), CtCPh (5); x ) 2, y ) 4, R ) H (4)) were
synthesized by treatment of tricyclohexylphosphine (PCy3) with [Ag{(CtC)xC6H4R-p}]∞ in
dichloromethane in the absence of light, and their spectroscopic and photophysical properties
have been investigated. The X-ray structure of 1 exhibits a planar parallelogram-like Ag4
core and consists of [Ag(CtCPh)2] and [Ag(PCy3)] fragments with phenylacetylide σ-coor-
dinated to silver atoms in a µ2-bonding mode (mean asymmetric Ag-C(R) distances are 2.05
and 2.33 Å). For 2, 3, and 5, with different para substituents in the arylacetylide units,
similar tetranuclear structures are observed. In contrast, the structure of 4 can be described
as two interpenetrating tetrahedra of four silver atoms and four phenylbutadiynyl moieties
forming a twisted cubane structure, with each silver atom further coordinated to a PCy3
ligand. The electronic absorption spectra of 1-5 in CH2Cl2 are dominated by strong,
vibronically structured absorptions at 250-332 nm (ꢀ 104-105 dm3 mol-1 cm-1) with
vibrational spacings of 1420-2160 cm-1 which are attributed to ν(CtC) or admixtures of
acetylenic and aryl stretching frequencies. The solid-state emission spectra of 1-3 at 298
and 77 K show intense vibronically structured bands at 422-607 nm which are attributed
to 3(ππ*) excited states of the arylacetylide ligands. For 4, the solid-state emission is slightly
3
red-shifted in energy from the (ππ*) emission of the corresponding mononuclear [Au(PCy3)-
(CtC-CtCPh)] congener, whereas for 5, a red-shift in its emission is observed from that of
1-4. A comparison between the emission of Cu(I), Ag(I), and Au(I) arylacetylides is made.
In tr od u ction
clusters,1d,5 and silver(I) aggregates.1e,6 Among these
three classes of coinage metal acetylide compounds,
silver(I) derivatives are less studied in the literature.
Presumably this is due to their extreme instabilities
with regard to light-induced decomposition reactions.
The tendency of forming polymeric chains confers dif-
ficulties in obtaining species with well-defined stoichi-
ometry. Reports on the employment of N, P, O, and S
donor ligands yielding d10-metal aggregates with lower
nuclearity have recently appeared.5c-g,6d By varying the
The versatile coordination behavior of acetylide ligands
has been aptly demonstrated by recent studies on the
structural diversity of coinage metal derivatives.1 Con-
comitantly, d10-d10 closed-shell metallophilic interac-
tions2 and ligand functionality have resulted in the
formation and isolation of multinuclear aggregates and
three-dimensional networks with novel and diverse
structures; examples are some binuclear, polymeric, and
catenane-like gold(I) complexes,3,4 copper(I) alkynyl
(3) (a) J ia, G.; Puddephatt, R. J .; Scott, J . D.; Vittal, J . J . Organo-
metallics 1993, 12, 3565. (b) Schmidbaur, H. Chem. Soc. Rev. 1995,
391. (c) Irwin, M. J .; J ia, G.; Payne, N. C.; Puddephatt, R. J .
Organometallics 1996, 15, 51. (d) McArdle, C. P.; Irwin, M. J .;
J ennings, M. C.; Puddephatt, R. J . Angew. Chem., Int. Ed. 1999, 38,
3376. (e) McArdle, C. P.; Vittal, J . J .; Puddephatt, R. J . Angew. Chem.,
Int. Ed. 2000, 39, 3819.
(4) (a) Li, D.; Xiao, H.; Che, C. M.; Lo, W. C.; Peng, S. M. J . Chem.
Soc., Dalton Trans. 1993, 2929. (b) Shieh, S. J .; Xiao, H.; Peng, S. M.;
Che, C. M. J . Chem. Soc., Dalton Trans. 1994, 3067. (c) Yam, V. W.
W.; Choi, S. W. K.; Cheung, K. K. Organometallics 1996, 15, 1734. (d)
Xiao, H.; Cheung, K. K.; Che, C. M. J . Chem. Soc., Dalton Trans. 1996,
3699. (e) Irwin, M. J .; Vittal, J . J .; Puddephatt, R. J . Organometallics
1997, 16, 3541. (f) Hunks, W. J .; MacDonald, M. A.; J ennings, M. C.;
Puddephatt, R. J . Organometallics 2000, 19, 5063.
* Corresponding author. Fax: +852 2857 1586. E-mail: cmche@
hku.hk.
† The University of Hong Kong.
‡ The Hong Kong Polytechnic University.
(1) (a) van Koten, G.; J ames, S. L.; J astrzebski, J . T. B. H. In
Comprehensive Organometallic Chemistry II; Abel, E. W., Stone, F.
G. A., Wilkinson, G., Eds.; Pergamon: Oxford, 1995; Vol. 3, p 57. (b)
Lang, H.; Ko¨hler, K.; Blau, S. Coord. Chem. Rev. 1995, 143, 113. (c)
J anssen, M. D.; Ko¨hler, K.; Herres, M.; Dedieu, A.; Smeets, W. J . J .;
Spek, A. L.; Grove, D. M.; Lang, H.; van Koten, G. J . Am. Chem. Soc.
1996, 118, 4817. (d) Yam, V. W. W.; Fung, W. K. M.; Cheung, K. K.
Angew. Chem., Int. Ed. Engl. 1996, 35, 1100. (e) Guo, G. C.; Zhou, G.
D.; Mak, T. C. W. J . Am. Chem. Soc. 1999, 121, 3136.
(2) Pyykko¨, P. Chem. Rev. 1997, 97, 597.
10.1021/om010835y CCC: $22.00 © 2002 American Chemical Society
Publication on Web 05/02/2002

2276 Organometallics, Vol. 21, No. 11, 2002
Lin et al.
distilled over calcium hydride. All other solvents were of
analytical grade and purified according to conventional meth-
ods.13 All reactions were carried out in the absence of light
using standard Schlenk techniques.
electronic and steric demands of ancillary ligands, the
control over the generation of particular aggregates can
be elucidated.
Recent studies by various groups have highlighted the
rich photoluminescent properties and potential device
Fast atom bombardment (FAB) mass spectra were obtained
on a Finnigan Mat 95 mass spectrometer with a 3-nitrobenzyl
alcohol matrix. 1H (in MHz, 500), 13C (126), and 31P (202) NMR
measurements were performed on a Bruker DPX 500 FT-NMR
spectrometer with tetramethylsilane (1H and 13C) and H3PO4
(31P) as references. Elemental analysis was performed by the
Institute of Chemistry at the Chinese Academy of Sciences,
Beijing. Infrared spectra were recorded on a BIO RAD FT-IR
spectrophotometer. UV-vis spectra were recorded on a Perkin-
Elmer Lambda 19 UV/vis spectrophotometer.
Em ission a n d Lifetim e Mea su r em en ts. Steady-state
emission spectra were recorded on a SPEX 1681 Fluorolog-2
series F111AI spectrophotometer. Low-temperature (77 K)
emission spectra for glasses and solid-state samples were
recorded in 5 mm diameter quartz tubes, which were placed
in a liquid nitrogen Dewar equipped with quartz windows. The
emission spectra were corrected for monochromator and pho-
tomultiplier efficiency and for xenon lamp stability.
Emission lifetime measurements were performed with a
Quanta Ray DCR-3 pulsed Nd:YAG laser system (pulse output
355 nm, 8 ns). The emission signals were detected by a
Hamamatsu R928 photomultiplier tube and recorded on a
Tektronix model 2430 digital oscilloscope. Errors for λ values
((1 nm), τ ((10%), and φ ((10%) are estimated. Details of
emission quantum yield determinations using the method of
Demas and Crosby14 have been provided previously.15
applications
of
polynuclear
copper(I)7
aryl-
acetylide complexes which display long-lived and emis-
sive excited states in solution at room temperature.
Assignment of these electronic excited states remains
elusive in the literature,8 but the effect of metallophi-
3
licity in red-shifting the (ππ*) emissions of arylacetyl-
ides has been noted in several examples of polynuclear
Au(I) and Cu(I) arylacetylide complexes. On the other
hand, investigations on spectroscopic properties of poly-
nuclear [Ag(CtCR)]n aggregates remain sparse and the
question as to the effect of Ag(I)-Ag(I) and alkynyl-
Ag(I) interactions upon the spectroscopic and photo-
physical properties of the excited states derived from
[Ag(CtCR)]n aggregates remains to be addressed.
This present account reports the synthesis, crystal
structures, and photophysical properties of a series of
tetranuclear Ag(I) arylacetylide compounds bearing
tricyclohexylphosphine ligand (PCy3). Compared to
arylphosphines, PCy3 does not exhibit low-lying ligand-
localized excited states, and this will facilitate spectro-
scopic assignments of the [Ag(CtCR)]n aggregates. This
paper focuses on the effect of modifying (1) the nature
of substituents on the arylacetylide moiety and (2) the
steric demand from arylacetylide to phenylbutadiynyl,
upon the stoichiometry and structural conformation
adopted by the Ag(I) arylacetylide complexes. The
spectroscopic properties of Cu(I), Ag(I), and Au(I) ary-
lacetylides are compared and the involvement of ary-
lacetylide-to-metal charge transfer in the emissions of
d10 metal arylacetylides is discussed.
Syn th esis. [Ag4(µ-CtCP h )4(P Cy3)2], 1. To a stirred sus-
pension of [Ag(CtCPh)]∞ (0.10 g, 0.48 mmol) in dichlo-
romethane (30 mL) at room temperature was added tricyclo-
hexylphosphine, PCy3 (0.073 g, 0.26 mmol). Upon stirring for
2 h, the color of the mixture changed to light yellow and the
mixture was filtered and evaporated to dryness. Recrystalli-
zation by slow diffusion of diethyl ether into a dichloromethane
solution of the crude product afforded colorless crystals.
Yield: 0.11 g, 66%. Anal. Calcd for C68H86P2Ag4: C, 58.47; H,
6.21. Found: C, 58.41; H, 6.20. FAB-MS: m/z 1397 [M+], 1314
[M+ - Cy]. 1H NMR (CD2Cl2): 1.15-1.29 (m, 18H, Cy), 1.40-
1.45 (m, 12H, Cy), 1.65 (m, 6H, Cy), 1.75-1.77 (m, 12H, Cy),
1.86-1.93 (m, 18H, Cy), 7.09-7.17 (m, 12H, Ph), 7.31-7.33
Exp er im en ta l Section
Gen er a l P r oced u r es. All starting materials were used as
10
received. 4-Phenyl-1,3-butadiyne9 and [Ag(CtCPh)]∞ were
2
(m, 8H, Ph). 13C{1H} NMR (CD2Cl2): 26.4 (Cy), 27.7 (d, J PC
prepared by literature methods (Ca u tion : silver acetylides
in the dry state detonate easily by mechanical shock and
should be handled with care in small amounts). 4-(Phenyl-
ethynyl)phenylacetylene was synthesized via Pd/Cu-catalyzed
carbon-carbon coupling of (trimethylsilyl)(4-iodophenyl)acety-
lene11 and phenylacetylene followed by the desilylation reac-
tion.12 Dichloromethane for synthesis and photophysical stud-
ies was washed with concentrated sulfuric acid, 10% sodium
hydrogen carbonate, and water, dried by calcium chloride, and
3
1
) 11.5 Hz, Cy), 31.5 (d, J PC ) 4.0 Hz, Cy), 32.4 (d, J PC
)
13.5 Hz, Cy), 111.2 (Ag-CtC), 113.5 (Ag-CtC), 125.4, 127.2,
128.3, 132.5 (Ph). 31P{1H} NMR (CD2Cl2): 35.74 (br d). IR
(KBr): ν 2076 (CtC) cm-1
.
[Ag4(µ-CtCC6H4CH3-p)4(P Cy3)2], 2. [Ag(CtCC6H4CH3-
p)]∞ was prepared by a procedure similar to that described for
[Ag(CtCPh)]∞ except 4-ethynyltoluene was used. Reaction of
[Ag(CtCC6H4CH3-p)]∞ (0.11 g, 0.49 mmol) with PCy3 (0.070
g, 0.25 mmol) using the method described for 1 afforded
colorless crystals. Yield: 0.16 g, 89%. Anal. Calcd for C72H94P2-
Ag4: C, 59.52; H, 6.52. Found: C, 59.29; H, 6.74. FAB-MS:
m/z 1453 [M+]. 1H NMR (CD2Cl2): 1.20-1.30 (m, 18H, Cy),
1.41-1.43 (m, 12H, Cy), 1.67 (m, 6H, Cy), 1.76-1.78 (m, 12H,
Cy), 1.90-1.92 (m, 18H, Cy), 2.28 (s, 12H, CH3), 6.92 (d, 8H,
(5) (a) Corfield, P. W. R.; Shearer, H. M. M. Acta Crystallogr. 1966,
21, 957. (b) Naldini, L.; Demartin, F.; Manassero, M.; Sansoni, M.;
Rassu, G.; Zoroddu, M. A. J . Organomet. Chem. 1985, 279, C42. (c)
Knotter, D. M.; Spek, A. L.; van Koten, G. J . Chem. Soc., Chem.
Commun. 1989, 1738. (d) Reger, D. L.; Huff, M. F. Organometallics
1992, 11, 69. (e) Knotter, D. M.; Spek, A. L.; Grove, D. M.; van Koten,
G. Organometallics 1992, 11, 4083. (f) Munakata, M.; Kitagawa, S.;
Kawada, I.; Maekawa, M.; Shimono, H. J . Chem. Soc., Dalton Trans.
1992, 2225. (g) Diez, J .; Gamasa, M. P.; Gimeno, J .; Lastra, E.; Aguirre,
A.; Garc´ıa-Granda, S. Organometallics 1993, 12, 2213.
(6) (a) Wang, C. F.; Peng, S. M.; Chan, C. K.; Che, C. M. Polyhedron
1996, 15, 1853. (b) Yam, V. W. W.; Fung, W. K. M.; Cheung, K. K.
Organometallics 1997, 16, 2032. (c) Wang, Q. M.; Mak, T. C. W. J .
Am. Chem. Soc. 2001, 123, 7594. (d) Wang, Q. M.; Mak, T. C. W.
Angew. Chem., Int. Ed. 2001, 40, 1130.
3
3J HH ) 7.9 Hz, C6H4), 7.20 (d, 8H, J HH ) 8.0 Hz, C6H4). 13C-
{1H} NMR (CD2Cl2): 21.5 (CH3), 26.4 (Cy), 27.7 (d, 2J PC ) 11.4
3
1
Hz, Cy), 31.5 (d, J PC ) 3.6 Hz, Cy), 32.3 (d, J PC ) 14.1 Hz,
Cy), 109.5 (Ag-CtC), 114.1 (Ag-CtC), 122.3, 129.0, 132.4,
(11) Hsung, R. P.; Chidsey, C. E. D.; Sita, L. R. Organometallics
1995, 14, 4808.
(7) (a) Ma, Y. G.; Chan, W. H.; Zhou, X. M.; Che, C. M. New J . Chem.
1999, 23, 263. (b) Ma, Y.; Che, C. M.; Chao, H. Y.; Zhou, X.; Chan, W.
H.; Shen, J . Adv. Mater. 1999, 11, 852.
(8) Che, C. M.; Chao, H. Y.; Miskowski, V. M.; Li, Y. Q.; Cheung, K.
K. J . Am. Chem. Soc. 2001, 123, 4985.
(9) Kende, A. S.; Smith, C. A. J . Org. Chem. 1988, 53, 2655.
(10) Blake, D.; Calvin, G.; Coates, G. E. Proc. Chem. Soc. 1959, 396.
(12) Lavastre, O.; Cabioch, S.; Dixneuf, P. H.; Vohlidal, J . Tetrahe-
dron 1997, 53, 7595.
(13) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals, 2nd ed.; Pergamon: Oxford, 1980.
(14) Demas, J . N.; Crosby, G. A. J . Phys. Chem. 1971, 75, 991.
(15) Lai, S. W.; Chan, M. C. W.; Cheung, T. C.; Peng, S. M.; Che, C.
M. Inorg. Chem. 1999, 38, 4046.

Silver(I) Arylacetylide Complexes
Organometallics, Vol. 21, No. 11, 2002 2277
Ta ble 1. Cr ysta l Da ta
4‚0.5Et2O
C114H157O0.5P4Ag4
1
5
formula
fw
cryst size, mm
cryst syst
space group
a, Å
C
68H86P2Ag4
C100H102P2Ag4
1797.24
0.40 × 0.35 × 0.15
triclinic
P1h
10.149(2)
12.649(3)
16.909(3)
78.91(3)
82.26(3)
88.80(3)
2110.7(8)
1
1396.79
0.14 × 0.10 × 0.08
triclinic
P1h
2090.76
0.20 × 0.16 × 0.14
monoclinic
C2/c
27.750(6)
14.851(2)
55.998(9)
90
10.100(3)
13.455(4)
13.856(4)
62.796(5)
76.059(6)
72.428(7)
1584.7(8)
1
b, Å
c, Å
R, deg
â, deg
96.274(7)
90
22940(7)
8
γ, deg
V, Å3
Z
Dc, g cm-3
µ, cm-1
2θmax, deg
no. unique data
no. obsd data
no. variables
1.464
13.06
55.4
7212
3285 (I > 2σ(I))
335
0.043, 0.11
+0.50, -0.60
1.211
7.71
55.1
26126
12348 (I > 2σ(I))
1102
0.065, 0.20
+0.94, -1.05
1.414
9.98
50.7
6984
5263 (I g 2σ(I))
478
0.027, 0.065
+0.32, -0.64
R,a Rw
b
residual F, e Å-3
a
b
2
R ) ∑||Fo| - |Fc|| /∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2
.
137.3 (C6H4). 31P{1H} NMR (CD2Cl2): 36.72 (br d). IR (KBr):
ν 2064 (CtC) cm-1
18H, Cy), 7.31-7.52 (m, 36H, aryl H). 13C{1H} NMR (CD2-
Cl2): 26.4 (Cy), 27.6 (d, 2J PC ) 11.5 Hz, Cy), 31.6 (Cy), 32.2 (d,
1J PC ) 16.7 Hz, Cy), 89.9 (CtCPh), 90.4 (CtCPh), 120.8 (Ag-
CtC), 123.7 (Ag-CtC), 128.6, 128.8, 131.6, 131.9, 132.0 (aryl
C). 31P{1H} NMR (CD2Cl2): 38.97 (br d). IR (KBr): ν 2215,
.
[Ag4(µCtCC6H4OCH3-p)4(P Cy3)2], 3. [Ag(CtCC6H4OCH3-
p)]∞ was prepared by a procedure similar to that described for
[Ag(CtCPh)]∞ except 1-ethynyl-4-methoxybenzene was used.
Reaction of [Ag(CtCC6H4OCH3-p)]∞ (0.12 g, 0.50 mmol) with
PCy3 (0.070 g, 0.25 mmol) using the method described for 1
afforded colorless crystals. Yield: 0.14 g, 74%. Anal. Calcd for
C72H94O4P2Ag4: C, 57.01; H, 6.25. Found: C, 56.65; H, 6.56.
FAB-MS: m/z 1517 [M+]. 1H NMR (CD2Cl2): 1.22-1.31 (m,
18H, Cy), 1.39-1.44 (m, 12H, Cy), 1.66-1.67 (m, 6H, Cy),
1.77-1.79 (m, 12H, Cy), 1.86-1.93 (m, 18H, Cy), 3.74 (s, 12H,
2069 (CtC) cm-1
.
X-r a y Cr ysta llogr a p h y. Crystals of 1-3, 4‚0.5Et2O, and
5 were grown by slow diffusion of diethyl ether into dichlo-
romethane solutions. Crystal data and details of data collection
and refinement for 1, 4‚0.5Et2O, and 5 are summarized in
Table 1 (see Supporting Information for 2 and 3).
Data for complexes 1 and 4‚0.5Et2O were collected at 294
K on a Bruker CCD area detector diffractometer by the æ and
ω scan technique using graphite-monochromated Mo KR
radiation (λ ) 0.71073 Å). For both complexes, the coordinates
of the metal atoms were determined by direct methods, and
the remaining non-hydrogen atoms were located from succes-
sive Fourier difference syntheses. The structures were refined
by full-matrix least-squares techniques with an anisotropic
thermal parameter for all the non-hydrogen atoms. The
calculations were performed on a COMPUCON PC/586 com-
puter with the Bruker AXS SHELXTL/PC program package.16
For 1, a crystallographic asymmetric unit consists of half of
one molecule. For 4‚0.5Et2O, a crystallographic asymmetric
unit consists of one molecule, with half of one diethyl ether
molecule as solvent of crystallization.
Diffraction experiments for 2, 3, and 5 were performed at
301 K on a MAR diffractometer with graphite-monochroma-
tized Mo KR radiation (λ ) 0.71073 Å). The structures of 2
and 5 were solved by direct methods (SIR92 or SIR97),17
whereas that of 3 was done by Patterson methods and
expanded by Fourier methods (PATTY).18 Refinement of
structures was performed by full-matrix least-squares using
the software package TeXsan19 on a Silicon Graphics Indy
computer (for 2 and 3) or using the SHELXL-97 program
3
3
OCH3), 6.63 (d, 8H, J HH ) 8.6 Hz, C6H4), 7.24 (d, 8H, J HH
)
8.8 Hz, C6H4). 13C{1H} NMR (CD2Cl2): 26.4 (Cy), 27.7 (d, 2J PC
3
1
) 11.5 Hz, Cy), 31.5 (d, J PC ) 3.9 Hz, Cy), 32.4 (d, J PC
)
14.1 Hz, Cy), 55.6 (OCH3), 108.7 (Ag-CtC), 113.4 (Ag-Ct
C), 113.9, 117.8, 133.9, 159.1 (C6H4). 31P{1H} NMR (CD2Cl2):
36.03 (br s). IR (KBr): ν 2056 (CtC) cm-1
.
[Ag4(µ-CtC-CtC-P h )4(P Cy3)4], 4. [Ag(CtC-CtC-
Ph)]∞ was prepared by a procedure similar to that described
for [Ag(CtCPh)]∞ except 4-phenyl-1,3-butadiyne was used. To
a suspension of [Ag(CtC-CtC-Ph)]∞ (0.14 g, 0.60 mmol) in
dichloromethane (20 mL) was added PCy3 (0.17 g, 0.61 mmol).
The mixture was heated under reflux for 2 h, and the resultant
dark green mixture was filtered and evaporated to dryness to
give a yellow solid. Recrystallization by slow diffusion of
diethyl ether into a dichloromethane solution of the crude
product afforded yellow crystals. Yield: 0.16 g, 52%. Anal.
Calcd for C112H152P4Ag4: C, 65.50; H, 7.46. Found: C, 65.65;
H, 7.85. FAB-MS: m/z 2053 [M+]. 1H NMR (CD2Cl2): 1.22-
1.40 (m, 60H, Cy), 1.71-1.73 (m, 12H, Cy), 1.82-1.91 (m, 60H,
Cy), 7.26-7.29 (m, 12H, Ph), 7.40-7.43 (m, 8H, Ph). 13C{1H}
2
NMR (CD2Cl2): 26.4 (Cy), 27.7 (d, J PC ) 9.2 Hz, Cy), 31.6
(Cy), 32.2 (d, 1J PC ) 15.6 Hz, Cy), 68.2 (Ag-CtC-CtC), 77.2
(Ag-CtC-CtC), 88.8 (Ag-CtC), 123.9 (Ph), 125.7 (Ag-Ct
C), 128.2, 128.6, 132.7 (Ph). 31P{1H} NMR (CD2Cl2): 39.28 (br
s). IR (KBr): ν 2169, 2001 (CtC) cm-1
.
(16) Sheldrick, G. M. SHELXL 97, A Program for Crystal Structure
Determination; University of Go¨ttingen, 1997.
[Ag4(µ-CtC-C6H 4-CtC-P h )4(P Cy3)2], 5. [Ag(CtC-
C6H4-CtC-Ph)]∞ was prepared by a procedure similar to that
described for [Ag(CtCPh)]∞ except 4-(phenylethynyl)pheny-
lacetylene was used. Reaction of [Ag(CtC-C6H4-CtC-Ph)]∞
(0.15 g, 0.49 mmol) with PCy3 (0.070 g, 0.25 mmol) using the
method described for 1 afforded colorless crystals. Yield: 0.12
g, 55%. Anal. Calcd for C100H102P2Ag4: C, 66.83; H, 5.72.
(17) (a) SIR92: Altomare, A.; Cascarano, M.; Giacovazzo, C.; Gua-
gliardi, A.; Burla, M. C.; Polidori, G.; Camalli, M. J . Appl. Crystallogr.
1994, 27, 435. (b) SIR97: Altomare, A.; Burla, M. C.; Camalli, M.;
Cascarano, M.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.;
Polidori, G.; Spagna, R. J . Appl. Crystallogr. 1998, 32, 115.
(18) PATTY: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bos-
man, W. P.; Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla,
C. The DIRDIF program system; Technical Report of the Crystal-
lography Laboratory; University of Nijmegen: The Netherlands, 1992.
(19) TeXsan: Crystal Structure Analysis Package, Molecular Struc-
ture Corporation: The Woodlands, TX, 1985 and 1992.
1
Found: C, 67.05; H, 6.03. FAB-MS: m/z 1797 [M+]. H NMR
(CD2Cl2): 1.21-1.33 (m, 18H, Cy), 1.36-1.42 (m, 12H, Cy),
1.71-1.73 (m, 6H, Cy), 1.82-1.84 (m, 12H, Cy), 1.91-1.92 (m,

2278 Organometallics, Vol. 21, No. 11, 2002
Lin et al.
package (for 5) on PC. For 5, a crystallographic asymmetric
unit consists of half of a formula unit. All non-H atoms were
refined anisotropically and H atoms were generated by the
program SHELXL-97.
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion . Treatment of
PCy3 with 1 or 2 equiv of [Ag(CtCC6H4R-p)]∞ (R ) H,
CH3, OCH3, and CtCPh) in dichloromethane afforded
the colorless complexes [Ag4(µ-CtCC6H4R-p)4(PCy3)2]
(1-3 and 5, respectively) in moderate to high yields
(55-90%). Attempts to synthesize derivatives with
electron-withdrawing aryl substituents (R ) Cl, F)
resulted in extremely unstable complexes. The reaction
between equimolar amounts of PCy3 and [Ag(CtC-Ct
CPh)]∞ in dichloromethane gave the yellow complex 4,
[Ag4(µ-CtC-CtCPh)4(PCy3)4]. This class of compounds
is stable in solid state, but in solution, they are stable
only in the absence of light.
F igu r e 1. Perspective view of 1 (30% probability el-
lipsoids).
The parent molecular ions M+ of complexes 1-5 can
be located in their FAB mass spectra. The IR spectra of
1-3 reveal weak ν(CtC) absorption at 2056-2076 cm-1
;
similar ν(CtC) stretching frequencies were found in
[Cu6(C6H4NMe2-2)4(µ2-η1-CtCR)2] (R ) Ph, 2040 cm-1
;
R ) C6H4Me-4, 2042 cm-1 20 and [Cu3(µ3-η1-CtCPh)2-
)
(µ-Ph2PCH2PPh2)3]BF4 (2027 cm-1).21 In the IR spec-
trum of 4, the two observed frequencies at 2001 and
2169 cm-1 are similar to those found in the copper
analogue, [Cu(CtC-CtCPh)PMe3]n (1981 and 2161
cm-1).22 The IR spectrum of 5 shows two weak ν(CtC)
absorptions at 2069 and 2215 cm-1
.
The 1H NMR spectra of 1-5 show multiplets at δ
1.15-1.93 and 6.63-7.52 due to the cyclohexyl and aryl
1
protons, respectively. For 2 and 3, the H NMR spectra
show the methyl and methoxy resonances as a singlet
at δ 2.28 and 3.74, respectively. The integrated intensi-
ties for these signals are in good agreement with that
deduced from the chemical formulation.
The 13C{1H} NMR spectra of 1-5 display collections
of peaks at δ 26.4-32.4 and 113.9-159.1 corresponding
to the cyclohexyl carbons of the PCy3 and aryl ligands,
respectively. Two broad singlets at δ 113.4-114.1 and
108.7-111.2 in the 13C{1H} NMR spectra of 1-3 are
assigned to the R- and â-acetylide carbon atoms. The
broad nature of these peaks is due to unresolved
coupling with 107Ag and 109Ag nuclides. In the 13C{1H}
NMR spectra of 4, singlets at 125.7, 88.8, 77.2, and 68.2
ppm are assigned to the R, â, γ, and δ butadiynyl atoms.
The 31P{1H} NMR spectra of 1-5 show a broad doublet
centered at δ 35.74-39.28 with averaged coupling to
107Ag and 109Ag nuclides.
Cr ysta l Str u ctu r es. X-ray structural determinations
of 1-3, 4‚0.5Et2O, and 5 have been performed (Figures
1-3; perspective views for 2 and 3 are available in the
Supporting Information); selected bond lengths and
angles are listed in Table 2. The molecular structures
of 1-3 and 5 can be visualized as being constructed from
two trans-[Ag(CtCC6H4R-p)2] and [Ag(PCy3)] units (i.e.,
2:1 arylacetylide to PCy3 ratio). The core of each
F igu r e 2. Perspective view of 4 (40% probability el-
lipsoids).
molecule consists of four silver atoms arranged in a
parallelogram-like array forming a Ag4 plane. This
differs remarkably from the tetranuclear copper ana-
logue [Cu4(µ3-η1-CtCPh)4{P(C6H4Me-p)3}4],23 which bears
a 1:1 phenylacetylide to phosphine stoichiometry and
adopts a cubane structure. The observed silver-silver
distances are 2.9367(9) and 2.9819(9) Å for 1, 2.8670(4)
and 3.0707(5) Å for 2, and 2.9450(9) and 2.9891(9) Å
for 5. These Ag-Ag separations are longer than the sum
of van der Waals radii for silver (2.89 Å),24 and they
may be considered as weakly interacting.25 The Ag(1)-
Ag(2)-Ag(1A) and Ag(2)-Ag(1)-Ag(2A) angles in 1
(76.55(1)° and 103.45(1)°) deviate from 90°, like a
parallelogram (82.98(1) and 97.02(1)° for 2; 79.00(3) and
101.00(3)° for 5).
Each of the silver atoms in the trans-[Ag(CtCC6H4R-
p)2] fragments in 1-3 and 5 is σ-bonded to two aryl-
acetylide ligands, with Ag-C bond distances ranging
from 2.048(3) to 2.083(3) Å. An approximately linear
(20) ten Hoedt, R. W. M.; van Koten, G.; Noltes, J . G. J . Organomet.
Chem. 1977, 133, 113.
(21) Die´z, J .; Gamasa, M. P.; Gimeno, J .; Aguirre, A.; Garc´ıa-Granda,
S. Organometallics 1991, 10, 380.
(23) Yam, V. W. W.; Lee, W. K.; Cheung, K. K. J . Chem. Soc., Dalton
Trans. 1996, 2335.
(24) Emsley, J . The Elements; Clarendon: Oxford, 1998; p 192.
(25) J ansen, M. Angew. Chem., Int. Ed. Engl. 1987, 26, 1098.
(22) Coates, G. E.; Parkin, C. J . Inorg. Nucl. Chem. 1961, 22, 59.

Silver(I) Arylacetylide Complexes
Organometallics, Vol. 21, No. 11, 2002 2279
angle of ca. 50°. The acetylide groups further coordinate
to adjacent Ag atoms with average Ag-C(R) and Ag-
C(â) distances of 2.35 and 2.85 Å, respectively. Thus,
the bonding mode of the acetylide group is similar to
that previously reported for the arylphosphine congener,
[Ph3PAgCtCPh]4‚3.5THF (asymmetric Ag-C(R) dis-
tances: 2.05 and 2.45 Å, respectively).26 The CtC bond
distances (average 1.20 Å) are normal for a carbon-
carbon triple bond.
The Ag(I) in the [Ag(PCy3)] units of 1-3 and 5 are
covalently bonded to one PCy3 ligand, argentophilically
interacting with two adjacent silver centers, and asym-
metrically bonded to two arylacetylide units. The bond
angles around these Ag(I) range from 50.1° to 119.1°.
The two PCy3 ligands are orientated in a trans fashion
out of the Ag4 plane. The Ag-P bond distances (mean
2.43 Å) are typical of those reported for silver(I)-
phosphine complexes such as [(Ph3P)2Ag]BF4 (average
2.42 Å).27
F igu r e 3. Perspective view of 5 (30% probability el-
For 2, 3, and 5, in which different p-substituents at
the arylacetylide but the same phosphine ligand are
adopted, tetranuclear structures similar to that of 1 are
observed. It is evident that different p-substituents in
the arylacetylide units (CH3 in 2, OCH3 in 3, and Ct
CPh in 5) do not impose any significant influence on
the molecular structure of the complexes. The aryl C6H4
rings in the [Ag(CtCC6H4R-p)2] strands orientate in a
coplanar fashion, allowing intramolecular π-stacking
interaction with interplanar separations of ∼3.5 Å.
However, the phenyl rings at both ends of the [Ag(Ct
CC6H4CtCPh)2] units in 5 show no additional π-stack-
ing interaction. Replacing the arylacetylide by the
phenylbutadiynyl ligand has yielded a different ag-
gregate, complex 4, with a higher phosphine-to-aryl-
acetylide ratio than 1-3 and 5. The molecular structure
of 4 depicts two interpenetrating tetrahedra of four
silver atoms and four phenylbutadiynyl ligands situated
on alternate corners of a twisted cubane structure, with
each silver atom further coordinated to a PCy3 ligand.
Such a cubane-type structure is similar to those ob-
served for the tetrameric [Ag4(PPh3)4X4]28 complexes (X
) Cl, Br, I) and the copper analogues.29
The Ag-Ag distances in 4 range from 2.9295(6) to
3.2067(5) Å and are longer than those in the analogous
[Cu4(µ3-η1-CtCPh)4{P(C6H4Me-p)3}4] complex (2.567-
(2)-2.607(2) Å).23 The silver atoms cause a significant
expansion of the inner M4 tetrahedron when compared
to the structure of its Cu4 analogue. Other vertexes in
the cubane core of 4 are occupied by four C(R) atoms of
the phenylbutadiynyl ligands, which are σ-bonded to the
silver atoms. The asymmetric Ag-C(short) and Ag-
C(long) contacts lie in the 2.151(3)-2.194(3) Å and
2.421(3)-2.559(3) Å ranges, respectively, and are par-
tially longer than those observed in 1-3 and 5. The Ag-
C-Ag angles, ranging from 80.7(1)° to 85.8(1)°, and the
C-Ag-C angles, varying from 106.8(1)° to 111.3(1)°,
deviate from the ideal value of 90°. The mean of two
alternating CtC distances is 1.205 Å, while the carbon-
lipsoids).
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg)
Complex 1
Ag(1)-Ag(2)
Ag(2)-Ag(1A)
Ag(1)-Ag(2A)
Ag(1)-C(1)
Ag(1)-C(34)
Ag(2)-C(34)
Ag(2)-C(1A)
Ag(2A)-C(1)
2.9367(9) Ag(2)-P(1)
2.982(1) C(1)-C(2)
2.9819(9) C(2)-C(3)
2.048(3) C(5)-C(6)
2.055(3) C(33)-C(34)
2.285(3) C(27)-C(33)
2.377(4) P(1)-C(9)
2.377(4) C(11)-C(12)
2.4100(8)
1.203(4)
1.438(4)
1.364(7)
1.204(4)
1.437(4)
1.850(3)
1.494(6)
Ag(1)-Ag(2)-Ag(1A) 76.55(1) C(2)-C(1)-Ag(1)
Ag(2)-Ag(1)-Ag(2A) 103.45(1) C(34)-Ag(2)-C(1A) 109.2(1)
C(1)-Ag(1)-C(34)
Ag(1)-C(1)-Ag(2A) 84.4(1)
C(1)-Ag(1)-Ag(2A) 52.5(1)
173.5(3)
176.2(2) P(1)-Ag(2)-Ag(1A) 109.28(2)
C(34)-Ag(2)-Ag(1A) 106.77(8)
C(21)-P(1)-Ag(2)
110.0(1)
Complex 4‚0.5Et2O
3.0462(5) Ag(2)-C(93)
Ag(1)-Ag(2)
Ag(1)-Ag(3)
Ag(1)-Ag(4)
Ag(2)-Ag(3)
Ag(2)-Ag(4)
Ag(3)-Ag(4)
Ag(1)-C(73)
Ag(4)-C(73)
Ag(1)-C(83)
Ag(2)-C(83)
2.176(3)
2.521(3)
2.151(3)
2.559(3)
1.207(5)
1.388(6)
1.179(6)
1.387(5)
2.432(1)
1.854(3)
2.9295(6) Ag(3)-C(93)
2.9962(5) Ag(3)-C(103)
3.2067(5) Ag(4)-C(103)
2.9482(6) C(73)-C(74)
3.2005(5) C(74)-C(75)
2.444(3) C(75)-C(76)
2.175(4) C(76)-C(77)
2.194(3) Ag(1)-P(1)
2.421(3) P(2)-C(19)
Ag(1)-C(73)-Ag(4) 80.7(1)
Ag(2)-C(93)-Ag(3) 85.8(1)
Ag(1)-C(83)-Ag(2) 82.4(1)
Ag(3)-C(103)-Ag(4) 85.2(1)
C(73)-C(74)-C(75) 178.4(4) C(93)-C(94)-C(95) 176.4(4)
C(75)-C(76)-C(77) 173.4(5) C(95)-C(96)-C(97) 175.0(4)
C(73)-Ag(1)-C(83) 111.3(1)
C(83)-Ag(2)-C(93) 109.0(1)
C(93)-Ag(3)-C(103) 106.8(1)
C(73)-Ag(4)-C(103) 108.3(1)
Complex 5
Ag(1)-Ag(2)
Ag(1)-Ag(2*)
Ag(2)-C(1)
Ag(2)-C(17)
Ag(1)-C(1)
Ag(1*)-C(17)
2.9450(9) Ag(1)-P(1)
2.9891(9) C(1)-C(2)
2.061(4) C(2)-C(3)
2.057(3) C(25)-C(26)
2.335(4) C(26)-C(27)
2.414(3) P(1)-C(33)
2.427(1)
1.198(4)
1.443(5)
1.194(5)
1.435(5)
1.840(3)
Ag(2)-Ag(1)-Ag(2*) 79.00(3) C(2)-C(1)-Ag(2)
Ag(1)-Ag(2)-Ag(1*) 101.00(3) C(9)-C(10)-C(11) 177.4(4)
C(1)-Ag(2)-C(17)
Ag(1)-C(1)-Ag(2)
C(17)-Ag(2)-Ag(1*) 53.35(9)
169.5(3)
179.8(1) C(1)-Ag(1)-C(17*) 105.5(1)
83.9(1) P(1)-Ag(1)-Ag(2) 111.32(3)
(26) Brasse, C.; Raithby, P. R.; Rennie, M. A.; Russell, C. A.; Steiner,
A.; Wright, D. S. Organometallics 1996, 15, 639.
(27) Bachman, R. E.; Andretta, D. F. Inorg. Chem. 1998, 37, 5657.
(28) (a) Teo, B. K.; Calabrese, J . C. Inorg. Chem. 1976, 15, 2467. (b)
Teo, B. K.; Calabrese, J . C. J . Chem. Soc., Chem. Commun. 1976, 185.
(29) (a) Churchill, M. R.; Kalra, K. L. Inorg. Chem. 1974, 13, 1065.
(b) Barron, P. F.; Dyason, J . C.; Engelhardt, L. M.; Healy, P. C.; White,
A. H. Inorg. Chem. 1984, 23, 3766.
coordination geometry (C-Ag-C angles range from
176.2(2)° to 179.8(1)°) is therefore evident. These four
arylacetylide groups do not lie coplanar with the central
Ag4 plane, but are slanted in a parallel fashion at an

2280 Organometallics, Vol. 21, No. 11, 2002
Lin et al.
the copper analogues such as [Cu4(µ3-η1-CtCPh)4-
{P(C6H4R)3}4] (R ) H, F, Me, OMe),23 which contain
weak Cu-Cu interactions and arylacetylides π-coordi-
nated to the Cu(I) centers, exhibit a variety of excited
states (see below).
The electronic absorption spectrum of 2 exhibits
similar vibronically structured bands at 242-278 nm
with progressional spacings of 1765-1796 cm-1, at-
tributable to the ν(CtC) stretching frequencies of the
arylacetylide. In the absorption spectrum of 3, struc-
tured bands at 261-283 nm with progressional spacings
of 1429-1549 cm-1 are not as well resolved as those in
1 and 2. These spacings are significantly lowered from
that expected for ν(CtC) in the acetylenic excited state.
We suggest that the transition has both 1(ππ*) acety-
1
lenic and (ππ*) aryl characteristics. Complex 4 shows
F igu r e 4. UV-vis absorption spectrum of 4 in dichlo-
intense vibronically structured absorption at 259-309
nm with progressional spacings of 2114, 2013, and 2121
cm-1 respectively. These spacings are comparable to
those observed in the absorption spectrum of the free
HCtC-CtCPh in dichloromethane (ca. 2000 cm-1 at
243-285 nm). Only one vibrational progression at-
tributed to ν(CtC) is evident in the absorption of 4 at
259-309 nm, suggesting that the electronic transition
is localized on the acetylenic CtC-CtC unit and
assigned to the intraligand [1IL: π f π*(CtC-CtCPh)]
transition. The absorption spectrum of 5 shows two
peaks at 310 and 332 nm and two shoulders at 298 and
317 nm; these transitions are slightly red-shifted from
that observed in 1-4. This corresponds to lowering of
the π f π* transition energy resulting from the ex-
tended conjugation system of the arylacetylide moieties
in 5.
romethane at 298 K.
Ta ble 3. UV-Visible Absor p tion Da ta of
Com p lexes 1-5 in Dich lor om eth a n e
-1
complex
λ
max/nm (ꢀ/dm3 mol-1 cm
)
1
226 (58700), 237 (59100), 248 (66100), 262 (82000),
275 (83800), 291 (sh, 34400)
2
242 (28700), 253 (38800), 265 (49100), 278 (48200),
300 (sh, 14200)
3
4
261 (56200), 272 (54400), 283 (53000), 303 (sh, 24800)
240 (252000), 259 (39500), 274 (82800), 290 (135000),
309 (120000)
5
298 (sh, 113000), 310 (132000), 317 (sh, 127000), 332
(120000)
carbon bond distance between them is 1.386 Å, which
reflects partial multiple bond character. The phenylb-
utadiynyl ligands are not significantly distorted from
linearity, as indicated by the angles C(73)-C(74)-C(75)
(178.4(4)°), C(75)-C(76)-C(77) (173.4(5)°), C(93)-C(94)-
C(95) (176.4(4)°), and C(95)-C(96)-C(97) (175.0(4)°).
The four Ag-P bond distances (mean 2.43 Å) fall in the
same range as 1-3 and 5, whereas the P-Ag-C angles
vary from 103.98(8)° to 138.11(9)°.
Solid -Sta te a n d Solu tion Em ission Sp ectr os-
cop y. Excitation of complexes 1-5 at λ > 350 nm in
solid state at 298 and 77 K produces blue-white lumi-
nescence (Table 4). The room-temperature solid-state
emission spectra show well-resolved vibronic structures
at 415-623 nm with vibrational spacings of ca. 1100,
1600, and 2100 cm-1 (see Figure 5 for 1). Such spacings
are attributed to a combination of vibrational modes of
the CtC groups and aryl moieties. Upon cooling to 77
K, these emission bands are better resolved. Similar
observation for [Pt(PEt3)2(CtCPh)2]32 was reported by
Sacksteder et al. The large Stokes shift of these emis-
sions from the corresponding singlet intraligand transi-
tions is indicative of their triplet parentage, and they
are attributed to the 3(ππ*) excited states with an
admixture of phenyl and acetylenic character. Compari-
son has been made with the mononuclear gold(I) com-
plex [Au(PCy3)(CtCPh)],30 in which the [Au(PCy3)]+
unit is isolobal to H+ and does not have strong absorp-
tion at λ > 250 nm. The solid-state emission spectrum
of [Au(PCy3)(CtCPh)] at 298 K displays a vibronically
structured band at 421-511 nm (see Figure 5), which
is at similar energy to the emission of complex 1. This
reveals the solid-state emissions of 1-3 to be purely
intraligand in character, and the interaction(s) within
the Ag4 core together with the interaction(s) between
the Ag4 core and arylacetylides do not have any signifi-
Absor p tion Sp ectr oscop y. All complexes in solu-
tions are sensitive toward photodecomposition, and all
photophysical measurements have been taken using
freshly prepared samples. The UV-visible spectral data
of complexes 1-5 in dichloromethane (Table 3; see
Figure 4 for 4) show the intense, vibronically structured
absorptions at 250-332 nm (ꢀ 104-105 dm3 mol-1 cm-1),
which are attributed to ligand-localized transitions.
Since the aliphatic PCy3 ligands are optically transpar-
ent in the UV region λ g 250 nm, the high-energy
absorptions in 1-5 are assigned as singlet intraligand
π f π*(arylacetylide) transitions. For 1, the well-
resolved structured absorption bands at 226-291 nm
exhibit vibrational spacings of 1804-2155 cm-1, which
are typical for ν(CtC) stretching frequencies of the
phenylacetylide group. These spacings show disparity
to that of 1098-1865 cm-1 observed for [Au(CtCPh)-
(PCy3)]30 at 249-290 nm, which involve mixing between
1(ππ*) acetylenic and 1(ππ*) aryl states. Absorption
bands in a similar range have been reported for the
silver(I) [Ag3(CtCPh)2(dppm)3]Cl6a and gold(I) pheny-
lacetylide complexes, namely, [Au(L)(CtCPh)] (L )
PPh3,4a PMe331) and [{Au(CtCPh)}2(µ-dppe)] (dppe )
1,2-bis(diphenylphosphino)ethane).4a On the contrary,
3
cant perturbation on the (ππ*) emission energy of the
(31) Yam, V. W. W.; Choi, S. W. K. J . Chem. Soc., Dalton Trans.
1996, 4227.
(32) Sacksteder, L. A.; Baralt, E.; DeGraff, B. A.; Lukehart, C. M.;
Demas, J . N. Inorg. Chem. 1991, 30, 2468.
(30) Chao, H. Y. Ph.D. Thesis, The University of Hong Kong, 2001.

Silver(I) Arylacetylide Complexes
Organometallics, Vol. 21, No. 11, 2002 2281
Ta ble 4. Em ission Da ta of Com p lexes 1-5 (λex 350 n m )
solid state
fluid (concentration 5 × 10-5 M)
298 K: λmax/nm; τo/µs
77 K: λmax/nm
298 K:a λmax/nm; τo/µs; φo
77 K: λmax/nm
1
2
3
422 (max), 443, 460, 497,
514, 541; 7.52
424, 442 (max), 455, 465, 477,
480, 501, 515, 547, 559 (sh),
576 (sh), 592 (sh)
427, 438, 456, 478 (max), 498,
507, 518, 530, 551, 565, 579,
607 (sh)
425, 435, 451, 458, 471 (max),
496, 526, 539, 553, 575, 591,
606 (sh)
418 (max), 434, 455, 480 (sh);
0.31; 0.025
426 (max), 448, 465, 490 (sh)b
428, 479 (max), 509, 516, 532
(sh), 550 (sh), 565 (sh); 0.93
unstable
399, 413, 419, 426 (max), 434,
441, 449, 457, 466, 483 (sh),
495 (sh), 505 (sh)c
401, 414, 420, 428, 436, 442,
451, 459, 469, 486 (sh),
496 (sh)c
428, 448, 473, 496 (max), 523,
527, 542 (sh), 578 (sh); 0.88
399, 435 (max), 487 (sh), 540
(sh); 0.22; 5.13 × 10-3
4
5
489 (max), 547, 623 (sh); 0.30
515 (max), 547; 0.50
489 (max), 510, 528, 547,
620 (sh)
515, 544 (max), 570, 592, 612
464 (max), 491, 514, 543 (sh),
579 (sh); 0.29; 0.033
510 (very weak)
442 (max), 452, 462, 475, 490,
499, 514, 531, 548b
520, 542 (max), 567b
In dichloromethane; decomposition observed after data collection. In MeOH/EtOH (4:1). c In butyronitrile.
a
b
F igu r e 5. Solid-state emission spectra of 1 and [Au(PCy3)-
(CtCPh)] at 298 K (λex 350 nm).
F igu r e 6. Normalized excitation and emission spectra (λem
442 nm; λex 284 nm) of 4 in MeOH/EtOH (4:1) at 77 K.
arylacetylides. The room-temperature solid-state emis-
sion of 4 with peak maxima at 489 and 547 nm is
slightly red-shifted in energy from the emission of [Au-
(PCy3)(CtC-CtCPh)] with peak maxima at 466 and
519 nm;30 both emissions display similar progressional
spacings (2168 cm-1 in 4, 2191 cm-1 in [Au(PCy3)(Ct
C-CtCPh)]). The solid-state emission of 5 (λmax 515 nm
at 298 K; 544 nm at 77 K) is comparable in energy to
that of the mononuclear gold(I) congener [Au(PCy3)(Ct
CC6H4CtCPh)] (λmax 516 nm at 298 K; 541 nm at 77
K) but red-shifts from the emissions of 1-4. We tenta-
tively suggest that the decrease in energy is a conse-
quence of the extended π-conjugation in the [Ag(Ct
CC6H4CtCPh)2] units. Unlike gold(I) and silver(I)
arylacetylides, the copper(I) analogues such as [Cu4(µ3-
η1-CtCPh)4{P(C6H4R)3}4] (R ) H, F, Me, OMe)23 usually
display broad and unstructured emission with peak
maxima at 510-550 nm, which are at similar or lower
energy than the emissions of 1-3. This suggests that
the visible emission of polynuclear Cu(I) arylacetylide
is unlikely to have ligand-to-metal charge transfer
(LMCT) character since LMCT for Ag(I) should be at
lower energy than Cu(I). For polynuclear Cu(I) aryl-
acetylide complexes, π-coordination of arylacetylide
ligands to Cu(I), and weak intramolecular Cu-Cu
interactions are usually evident, and these structural
features are responsible for the red-shift in emission
energy from the 3(ππ*) emissions of arylacetylide ligands.
In this work, π-coordination of arylacetylides to Ag(I)
is not evident in the crystal structures of 1-5 and the
arylacetylides adopt a σ-µ2 coordination mode. Unlike
the copper(I) arylacetylide compounds, coordination of
[RCtC]- to Ag(I) has virtually little effect on the
intraligand 3(ππ*) emission energy. For those Au(I)
arylacetylides without Au-Au interaction, only σ-coor-
dination of arylacetylide to Au(I) dominates, and this
causes no significant perturbation on the intraligand π
f π* transition. For [{Au(CtCPh)}2(µ-dppe)],4a its solid-
state emission occurs at 550 nm and this was previously
attributed to arise from intramolecular Au-Au interac-
tion in the crystal lattice, which causes a red-shift in
3
emission energy from the intraligand (ππ*) emission.
Emission data for complexes 1-5 in dichloromethane
at 298 K and in glassy MeOH/EtOH (4:1) or butyroni-
trile solutions at 77 K are listed in Table 4. The room-
temperature emissions in dichloromethane solutions are
very weak (λmax 360-550 nm) and slowly change against
time of measurement. Weak emission observed in
dichloromethane solution of 1 at 418-480 nm is virtu-
ally at the same wavelength range as that in the
mononuclear [Au(PCy3)(CtCPh)]30 counterpart, sug-
3
gesting that the emissions are attributed to the (ππ*)
excited states of the phenylacetylide ligands. Compound
5 emits weakly in dichloromethane at 510 nm, which is
similarly attributed to come from the 3(ππ*) excited state
localized on the acetylenic unit.
Complexes 1-5 in 77 K glassy solutions display
intense vibronically structured emissions at 399-567
nm with progressional spacings of ∼1100-2000 cm-1
.
The excitation and emission spectra of 4 (Figure 6) in
77 K glassy MeOH/EtOH solution illustrate the large

2282 Organometallics, Vol. 21, No. 11, 2002
Lin et al.
5b
the tetrameric copper(I) complex [Ph3PCuCtCPh]4
and related derivatives.23 Compared to 1-3 and 5, the
extended butadiynyl ligand apparently alleviates steric
strain between the Cy and aryl groups and facilitates
coordination of a PCy3 ligand per Ag atom. In summary,
the structural variations in these tetranuclear silver(I)
complexes can be rationalized in terms of intramolecular
repulsion involving the bulky PCy3 and the arylacetylide
ligands. The adoption of differing structural motifs
appears to be controlled by the steric influence of both
phosphine and acetylide auxiliaries.
Employment of the aliphatic PCy3 ligand makes
spectroscopic assignments less complicated. The large
cone angle of PCy3 maintains its steric bulkiness as that
in PPh3. Absorption spectra of the complexes in this
work are dominated by the vibronically structured
singlet π f π* transition(s) of the arylacetylides in the
UV region; the metal-centered, Ag(I)-to-arylacetylide
and/or arylacetylide-to-Ag(I) charge-transfer transitions
have not been located at λ g 250 nm despite the
structural data revealing that both arylacetylide-to-Ag-
(I) and Ag(I)-Ag(I) interactions are evident in the
crystal structures of the complexes. When comparing
the emission data of these Ag(I) arylacetylides with that
of the mononuclear gold(I) counterparts, the emission
F igu r e 7. Examples of Ag(I) acetylide aggregates bearing
phosphine ligands: (a) polymeric chains of [Me3PAgCt
CR]∞ (R ) Ph,33 SiMe326) and (b) [Ph3PAgCtCPh]4.26
3
Stokes shift of the emission, and hence (ππ*) excited
states of the arylacetylide ligands are assigned.
Gen er a l Rem a r k s
An early example of silver(I) acetylide compounds
with phosphine ligands, namely, [Me3PAgCtCPh]∞,33
shows infinite polymeric chains of silver atoms. A
similar chain-like structure is also found for [Me3PAgCt
3
is characteristic of the triplet intraligand (ππ*) excited
26
CSiMe3]∞ (Figure 7a), showing that alternation of
state. Upon coordinating arylacetylide to Au(I) or Ag-
(I), the triplet intraligand emission is enhanced and
readily tuned by varying the π-conjugation along the
arylacetylide unit. Previously studied Cu(I) arylacetyl-
ides usually display long-lived, intense, and lower
energy emission which show significant disparity in
photophysical properties from that of Ag(I) and Au(I)
congeners. Since the LMCT excited states of Ag(I) are
expected to occur at lower energy than that of Cu(I),
the triplet emission from polynuclear Cu(I)-arylacetyl-
ides is unlikely to have LMCT character in view of the
present findings. For the Ag4 complexes studied in this
work, the Ag-Ag and arylacetylide-to-Ag(I) interactions
phenyl- to trimethylsilylacetylide does not influence the
structure of these polymeric chains. However, when the
PMe3 is replaced by the more bulky PPh3 unit, the
tetrameric [Ph3PAgCtCPh]4‚3.5THF26 with a “flat-
butterfly” geometry is observed (Figure 7b). Undoubt-
edly, the nature of the phosphine auxiliaries plays an
important role in the formation of the [Ag(CtCR)]n
aggregate. In this work, we have employed tricyclohexy-
lphosphine ligand, which has a large cone angle (170°).34
The molecular structures of [Ag4(µ-CtCC6H4R-p)4-
(PCy3)2] (R ) H (1), CH3 (2), OCH3 (3), and CtCPh (5))
reveal that these tetranuclear assemblies are con-
structed from [Ag(CtCC6H4R-p)2] and [Ag(PCy3)] units
with a phosphine-to-arylacetylide ratio of 1:2. This is
in contrast to the 1:1 ratio found for [Ph3PAgCtCPh]4‚
3.5THF and [Me3PAgCtCPh]∞. This decrease in ratio
originates from the bulkiness of the PCy3 ligand.
Furthermore, steric repulsion between the cyclohexyl
and aryl moieties in 1-3 and 5 results in two kinds of
Ag(I), one with σ-coordination to two arylacetylides and
the other with σ-coordination to a PCy3 group. The Ag-
(PCy3) and [Ag(CtCR)2] fragments are held together via
σ-coordination of arylacetylide to Ag(I) and weak Ag-
(I)-Ag(I) interactions.
3
have little effect upon the intraligand (ππ*) emission
energy. Whether this would mean that Ag(I) functions
merely as a Lewis acid like a monovalent cation within
the [Ag(CtCR)]n aggregates would require more studies
to validate.
Ack n ow led gm en t. We are grateful for financial
support from The University of Hong Kong, the HKU
Large Item Equipment Grant, and the Research Grants
Council of the Hong Kong SAR, China [HKU 7298/99P].
We thank Dr. N. Zhu for the structural determination.
The molecular structure of 4 bearing phenylbutadiy-
nyl ligands depicts a twisted cubane-type aggregate with
1:1 PCy3-to-[Ph-CtC-CtC] ratio, which is similar to
Su p p or tin g In for m a tion Ava ila ble: Listings of crystal
data, atomic coordinates, calculated coordinates, anisotropic
displacement parameters, and bond lengths and angles for
1-3, 4‚0.5Et2O, and 5. This material is available free of charge
via the Internet at http://pubs.acs.org.
(33) Corfield, P. W. R.; Shearer, H. M. M. Acta Crystallogr. 1966,
20, 502.
(34) Tolman, C. A. Chem. Rev. 1977, 77, 313.
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