Synthesis and design of novel tetranuclear and dinuclear gold(I) phosphine acetylide complexes. First X-ray crystal structures of a tetranuclear ([Au4(tppb)(C≡CPh)4]) and a related dinuclear ([Au2(dppb)(C≡CPh)2]) complex

Article abstract of DOI:10.1021/om950586b

Reaction of [Au(C≡CR)]_∞ with dppb and tppb in CH₂Cl₂ afforded the corresponding luminescent Au₂(dppb)(C≡CR)₂ and Au₄(tppb)(C≡CR)₄ (dppb = 1,4-bis(diphenylphosphino)-benzene; tppb = 1,2,4,5-tetrakis(diphenylphosphino)benzene; R = C₆H₁₃, Ph, 4-MeO-Ph); their photophysical properties have been studied, and the X-ray crystal structures of Au₂(dppb)(C≡CPh)₂ (2) and Au₄(tppb)(C≡CPh)₄ (5) have been determined. Close Au?Au contacts are present in 5, which twisted the six-membered ring that comprises the PAu₂PC₂ unit. Such a structure is reminiscent of a distorted anthracene-like unit containing Au atoms as part of the heterocycle, owing to the auriophilicity which brings the Au atoms into close contact.

Full text of DOI:10.1021/om950586b

1734
Organometallics 1996, 15, 1734-1739
Syn th esis a n d Design of Novel Tetr a n u clea r a n d
Din u clea r Gold (I) P h osp h in e Acetylid e Com p lexes. F ir st
X-r a y Cr ysta l Str u ctu r es of a Tetr a n u clea r
([Au 4(tp p b)(CtCP h )4]) a n d a Rela ted Din u clea r
([Au 2(d p p b)(CtCP h )2]) Com p lex
Vivian Wing-Wah Yam,* Sam Wing-Kin Choi, and Kung-Kai Cheung
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong
Received J uly 28, 1995X
Reaction of [Au(CtCR)]∞ with dppb and tppb in CH2Cl2 afforded the corresponding
luminescent Au2(dppb)(CtCR)2 and Au4(tppb)(CtCR)4 (dppb ) 1,4-bis(diphenylphosphino)-
benzene; tppb ) 1,2,4,5-tetrakis(diphenylphosphino)benzene; R ) C6H13, Ph, 4-MeO-Ph);
their photophysical properties have been studied, and the X-ray crystal structures of
Au2(dppb)(CtCPh)2 (2) and Au4(tppb)(CtCPh)4 (5) have been determined. Close Au‚‚‚Au
contacts are present in 5, which twisted the six-membered ring that comprises the PAu2PC2
unit. Such a structure is reminiscent of a distorted anthracene-like unit containing Au atoms
as part of the heterocycle, owing to the auriophilicity which brings the Au atoms into close
contact.
In tr od u ction
photophysics with long-lived emission. Their photo-
physics and spectroscopy together with those of other
related complexes Au2(dppb)(CtCR)2 (R ) Ph (2),
4-MeO-Ph (3)) and Au4(tppb)(CtCR)4 (R ) Ph (5),
4-MeO-Ph) (6)) will also be described. The X-ray crystal
structures of 2 and 5 have been determined.
Recently, the study and design of novel materials with
unique physical properties have become the focus of
much interest.1 In our recent efforts on the synthesis,
characterization, and luminescent properties of acetyl-
ide-bridged metal complexes,2 a series of related poly-
nuclear Au(I) acetylides have been explored. In view
of the preference of metal complexes with d10 electronic
configuration to form linear two-coordinate species, they
may serve as good and attractive candidates for the
design of rigid-rod materials which may find applica-
tions in areas of materials science such as liquid crystal
technology.3 However, to our surprise, the design of
liquid crystalline materials with d10 Au(I) is relatively
rare.4 In this paper, we report on the synthesis and
characterization of binuclear Au2(dppb)(CtCC6H13)2 (1)
and tetranuclear Au4(tppb)(CtCC6H13)4 (4) with short
Au‚‚‚Au contacts (dppb ) 1,4-bis(diphenylphosphino)-
benzene; tppb ) 1,2,4,5-tetrakis(diphenylphosphino)-
benzene). In 1, the oct-1-ynyl groups serve as the
flexible peripheral chains. This, together with the rigid
central phosphine backbone, is expected to give one-
dimensional compounds with potential calamitic meso-
genic properties. On the other hand, when the bridging
phosphine is changed from dppb to tppb, compound 4
is constructed with the acetylide groups extended in a
two-dimensional array. These organometallic Au(I)
phosphine acetylides have been shown to exhibit rich
Exp er im en ta l Section
Ma t er ia ls a n d R ea gen t s. Potassium tetrachloro-
aurate(III), phenylacetylene, and oct-1-yne were obtained from
Aldrich Chemical Co. (4-Methoxyphenyl)acetylene was ob-
tained from Maybridge Chemical Co. Ltd. [Au(CtCR)]∞,5a
dppb,5b and tppb5b were prepared by published methods. All
solvents were purified and distilled by standard procedures
before use. All other reagents were of analytical grade and
were used as received.
P r ep a r a tion of Com p lexes. All reactions were carried
out under a stream of dry nitrogen at room temperature.
[Au 2(d p p b)(CtCC6H13)2] (1). To a dichloromethane solu-
tion of [Au(CtCC6H13)]∞ (100 mg, 0.327 mmol) was added a
solid sample of dppb (73 mg, 0.164 mmol). After it was stirred
for 15 min, the solution was concentrated and white solid was
precipitated by addition of n-hexane. Recrystallization was
accomplished by the slow diffusion of n-hexane vapor into a
dichloromethane solution of the solid to give colorless crystals
(yield 130 mg, 75%). 1H NMR (270 MHz, CD2Cl2, 298 K,
relative to TMS): δ 0.88 (t, 6H, -CH3), 1.12-1.51 (m, 16H,
-CH2-), 2.24 (t, 4H, -CtCCH2-), 7.45-7.60 (m, 24H, dppb).
Positive FAB-MS: m/z 1058 (M)+, 951 (M - octynyl)+. IR
(Nujol): ν/cm-1 2133 (vw, CtC). Anal. Calcd for C46H50
-
Au2P2‚0.5CH2Cl2: C, 50.71; H, 4.63. Found: C, 50.93; H, 4.41.
[Au 2(d p p b)(CtCP h )2] (2). To a yellow suspension of
[Au(CtCPh)]∞ (100 mg, 0.336 mmol) in CH2Cl2 was added a
solid sample of dppb (75 mg, 0.168 mmol). A clear yellow
solution was obtained, and the mixture was stirred for 15 min.
The solution was then concentrated, and n-hexane was added
to precipitate the yellow products. Recrystallization was
accomplished by the slow diffusion of diethyl ether vapor into
a dichloromethane solution of the solid to give yellow crystals
X Abstract published in Advance ACS Abstracts, February 1, 1996.
(1) (a) Bruce, D. W.; O’Hare, D. Inorganic Materials; Wiley: New
York, 1992. (b) Bruce D. W.; Holbrey, J . D.; Tajbakhsh, A. R.; Tiddy,
G. J . T. J . Mater. Chem. 1993, 3, 905. (c) Bruce, D. W. Adv. Mater.
1994, 6, 699.
(2) (a) Yam, V. W.-W.; Lee, W. K.; Lai, T. F. Organometallics 1993,
12, 2383. (b) Yam, V. W.-W.; Chan, L. P.; Lai, T. F. Organometallics
1993, 12, 2197. (c) Mu¨ller, T. E.; Choi, S. W. K.; Mingos, D. M. P.;
Murphy, D.; Williams, D. J .; Yam, V. W.-W. J . Organomet. Chem. 1994,
484, 209.
(3) Collings, P. J . Liquid Crystals; Princeton University Press:
Princeton, NJ , 1990.
(4) Kaharu, T.; Ishii, R.; Adachi, T.; Yoshida, T.; Takahashi, S. J .
Mater. Chem. 1995, 5, 687.
(5) (a) Coates, G. E.; Parkin, C. J . Chem. Soc. 1962, 3220. (b)
Christina, H.; McFarlane, E.; McFarlane, W. Polyhedron 1988, 7, 1875.
0276-7333/96/2315-1734$12.00/0 © 1996 American Chemical Society

Gold(I) Phosphine Acetylide Complexes
Organometallics, Vol. 15, No. 6, 1996 1735
(yield 122 mg, 70%). 1H NMR (270 MHz, CD2Cl2, 298 K,
relative to TMS): δ 7.06-7.57 (m, 10H, -CtCPh; 24H, dppb).
Positive FAB-MS: m/z 941 (M - CtCPh)+. IR (Nujol): ν/cm-1
2125 (vw, CtC).
tions were rigorously degassed with no fewer than four freeze-
pump-thaw cycles.
Cr ysta l Str u ctu r e Deter m in a tion . Crystals of 2 and 5
were obtained by slow diffusion of diethyl ether vapor into a
dichloromethane solution of the compounds. Diffraction data
for 2 and 5 were measured at 25 °C on a Rigaku AFC7R
diffractometer and a Nonius-Enraf CAD4 diffractometer,
respectively, with graphite-monochromatized Mo KR radiation
(λ ) 0.710 73 Å). Three standard reflections measured after
every 300 reflections showed a decay of 16.64% for 2, while
for 5, no decay was observed when three standard reflections
were measured after every 2 h. The intensity data were
corrected for Lorentz, polarization, and absorption effects. The
empirical absorption corrections were based on azimuthal (ψ)
scans of four strong reflections. Crystal and structure deter-
mination data for 2 and 5 are summarized in Table 1. The
space group of 2 was uniquely determined from systematic
absences, and that of 5 was confirmed by the successful
refinement of the structure. Both structures were determined
by heavy-atom Patterson methods and expanded using Fourier
techniques6 and refinement by full-matrix least squares using
the MSC-Crystal Structure Package TEXSAN on a Silicon
Graphics Indy computer. The complex molecules of both 2 and
5 consist of halves related by a center of symmetry at (0, 0, 1)
and (0.5, 0.5, 0.5), respectively, at the center of the central
ring system. All non-hydrogen atoms were refined anisotro-
pically. Hydrogen atoms at calculated positions with thermal
parameters equal to 1.3 times that of the attached carbon
atoms were not refined. The final agreement factors for 2 and
5 are given in Table 1. The final atomic coordinates and
thermal parameters of the non-hydrogen atoms of 2 and 5 are
collected in Tables 2 and 3, respectively. The atomic coordi-
nates of the hydrogen atoms of 2 and 5 are given in Tables SI
and SII (Supporting Information), respectively.
[Au 2(d p p b)(CtC(4-MeO-P h ))2] (3). The procedures were
similar to those for 2, except [Au(CtC(4-MeO-Ph)]∞ (100 mg,
0.305 mmol) was used instead of [Au(CtCPh)]∞: yield 117 mg,
70%. 1H NMR (270 MHz, CD2Cl2, 298 K, relative to TMS): δ
3.78 (s, 6H, -OMe), 6.75-7.34 (m, 8H, -CtCPh), 7.48-7.64
(m, 24H, dppb). Positive FAB-MS: m/z 1103 (M + 1)+, 971 (M
- CtCPhOMe)+. IR (Nujol): ν/cm-1 2116 (vw, CtC). Anal.
Calcd for C48H38Au2O2P2: C, 52.27; H, 3.45. Found: C, 52.06;
H, 3.23.
[Au 4(tp p b)(CtCC6H13)4] (4). To a benzene solution of
[Au(CtCC6H13)]∞ (100 mg, 0.327 mmol) was added a solid
sample of tppb (67 mg, 0.082 mmol). After it was stirred for
30 min in the dark, the solution was concentrated and yellow
solid was precipitated by addition of n-hexane. Recrystalli-
zation was accomplished by the slow diffusion of n-hexane
vapor into a benzene solution of the solid to give a yellow solid
(yield 133 mg, 80%). The product should be kept in the
absence of light. 1H NMR (270 MHz, CD2Cl2, 298 K, relative
to TMS): δ 0.89 (t, 12H, -CH3), 1.12-1.51 (m, 32H, -CH2-),
2.28 (m, 8H, -CtCCH2-), 7.12-7.50 (m, 42H, tppb). Positive
FAB-MS: m/z 2037 (M - 1)+, 1730 (M - Au - octynyl - 2)+.
IR (Nujol): ν/cm-1 2130 (vw, CtC). Anal. Calcd for C86H94
-
Au4P4: C, 50.60; H, 4.61. Found: C, 50.30; H, 4.50.
[Au 4(tp p b)(CtCP h )4] (5). To a yellow suspension of
[Au(CtCPh)]∞ (100 mg, 0.336 mmol) in CH2Cl2 was added a
solid sample of tppb (68 mg, 0.084 mmol). A clear yellow
solution was obtained, which was stirred for 30 min. The
solution was then concentrated, and n-hexane was added to
precipitate the yellow products. Recrystallization was ac-
complished by the slow diffusion of diethyl ether vapor into a
dichloromethane solution of the solid to give yellow crystals
(yield 118 mg, 70%). 1H NMR (270 MHz, CD2Cl2, 298 K,
relative to TMS): δ 7.06-7.57 (m, 20H, -CtCPh; 42H, tppb).
Positive FAB-MS: m/z 2006 (M)+, 1905 (M - CtCPh)+. IR
(Nujol): ν/cm-1 2114 (vw, CtC). Anal. Calcd for C86H62Au4P4:
C, 51.45; H, 3.09. Found: C, 51.87; H, 2.98.
Resu lts a n d Discu ssion
Analogous to the preparation of monomeric gold
alkynyl phosphine complexes of the type [RCtCAu-
(PR3)],5a reaction of [Au(CtCR)]∞ with 0.5 equiv of the
dppb ligand and 0.25 equiv of tppb in CH2Cl2 afforded
the desired complexes [Au2(dppb)(CtCR)2] and [Au4-
(tppb)(CtCR)4], respectively, in greater than 70% yield.
Subsequent recrystallization from a dichloromethane-
diethyl ether mixture gave colorless to yellow crystals
of 1-6. Reaction of PhCtCH with [Au2(dppb)Cl2] in
the presence of KOH to give 2 has also been reported.7h
All the newly synthesized compounds gave satisfactory
elemental analyses and have been characterized by IR,
positive FAB-MS, and 1H NMR spectroscopy. Com-
pounds 2 and 5 have also been characterized by X-ray
crystallography.
[Au 4(tp p b)(CtC(4-MeO-P h ))4] (6). The procedures were
similar to those for 5, except [Au(CtC(4-MeO-Ph)]∞ (100 mg,
0.305 mmol) was used instead of [Au(CtCPh)]∞: yield 135 mg,
83%. 1H NMR (270 MHz, CD2Cl2, 298 K, relative to TMS): δ
3.79 (s, 12H, -OMe), 6.75-7.47 (m, 16H, -CtCPh-; 42H,
tppb). Positive FAB-MS: m/z 1995 (M - CtCPhOMe)+. IR
(Nujol): ν/cm-1 2101 (vw, CtC). Anal. Calcd for C90H70
-
Au4O4P4: C, 50.80; H, 3.29. Found: C, 51.00; H, 3.05.
P h ysica l Mea su r em en ts a n d In str u m en ta tion . UV-
visible spectra were obtained on a Hewlett-Packard 8452A
diode array spectrophotometer, IR spectra as Nujol mulls on
a Bio-Rad FTS-7 Fourier-transform infrared spectrophotom-
eter (4000-400 cm-1), and steady-state excitation and emission
spectra on a Spex Fluorolog 111 spectrofluorometer. Low-
temperature (77 K) spectra were recorded by using an optical
Dewar sample holder. 1H NMR spectra were recorded on a
J EOL J NM-GSX270 Fourier-transform NMR spectrometer
with chemical shifts reported relative to TMS. Positive ion
FAB mass spectra were recorded on a Finnigan MAT95 mass
spectrometer. Elemental analyses of the new complexes were
performed by Butterworth Laboratories Ltd.
The perspective drawings of 2 and 5 with atomic
numberings are shown in Figures 1 and 2, respectively.
Selected bond distances and angles are listed in Tables
4 and 5. In contrast to most Au(I) compounds, where
(6) PATTY & DIRDIF92: Beurskens, P. T.; Admiraal, G.; Beursken,
G.; Bosman, W. P.; Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.;
Smykalla, C. The DIRDIF Program System; Technical Report of the
Crystallography Laboratory; University of Nijmegen: Nijmegen, The
Netherlands, 1992.
(7) (a) Yam, V. W.-W.; Lai, T. F.; Che, C. M. J . Chem. Soc., Dalton
Trans. 1990, 3747. (b) Stu¨tzer, A.; Bissinger, P.; Schmidbaur, H. Chem.
Ber. 1992, 125, 367. (c) Da´vila, R. M.; Stables, R. J .; Fackler, J . P.,
J r. Organometallics 1994, 13, 418. (d) Angermaier, K.; Zeller, E.;
Schmidbaur, H. J . Organomet. Chem. 1994, 472, 371. (e) Lin, I. J . B.;
Hwang, J . M.; Feng, D. F.; Cheng, M. C.; Wang, Y. Inorg. Chem. 1994,
33, 3467. (f) Payne, N. C.; Ramachandran, R.; Puddephatt, R. J . Can.
J . Chem. 1995, 73, 6. (g) Assefa, Z.; McBurnett, B. G.; Stables, R. J .;
Fackler, J . P., J r.; Assmann, B.; Angermaier, K.; Schmidbaur, H. Inorg.
Chem. 1995, 34, 75. (h) J ia, G.; Puddephatt, R. J .; Scott, I. D.; Vittal,
J . J . Organometallics 1993, 12, 3565.
Emission-lifetime measurements were performed using a
conventional laser system. The excitation source was the 355-
nm output (third harmonic) of a Quanta-Ray Q-switched GCR-
150-10 pulsed Nd-YAG laser (10 Hz). Luminescence decay
signals were recorded on a Tektronix Model TDS 620A digital
oscilloscope and analyzed using a program for exponential fits.
All solutions for photophysical studies were prepared under
vacuum in a 10-cm3 round-bottomed flask equipped with a
side-arm 1-cm fluorescence cuvette and sealed from the
atmosphere by a Kontes quick-release Teflon stopper. Solu-

1736 Organometallics, Vol. 15, No. 6, 1996
Ta ble 1. Cr ysta l a n d Str u ctu r e Deter m in a tion Da ta for 2 a n d 5
Yam et al.
2
5
formula
fw
T, K
Au2P2C46H34
1042.66
298
Au4P4C86H62
2007.20
298
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
cryst syst
space group
Z
9.217(5)
17.596(2)
11.842(4)
90
94.82(4)
90
1913(1)
monoclinic
P21/c
12.332(2)
12.520(3)
13.277(2)
90.71(1)
90.59(1)
118.44(2)
1802.1(6)
triclinic
P1h (No. 2)
1
2
F(000)
F
cryst dimens, mm
996
1.809
954
1.849
calcd, g cm-3
0.15 × 0.10 × 0.25
0.10 × 0.07 × 0.25
λ, Å (graphite monochromated, Mo KR)
0.710 73
0.710 73
µ(Mo KR), cm-1
77.99
0.678-1.000
2θmax ) 48° (h, 0-10; k, 0-20;
82.78
0.809-1.000
2θmax ) 44° (h, 0-13; k, -13 to +13;
transmissn factors
collecn range
l, -13 to +13)
ω-2θ; 16.0
1.21 + 0.35 tan θ
3337
l, -14 to +14)
ω-2θ; 1.03-5.49
0.55 + 0.35 tan θ
4653
scan mode; scan speed, deg min-1
scan width, deg
no. of data collected
no. of unique data
3127
4400
Rint
0.023
0.015
no. of data used in refinement, m
no. of parameters refined, p
1887 (I > 3σ(I))
226
3405 (I > 3σ(I))
424
R(Fo)
Rw(Fo)
0.028
0.021
0.034a
0.021b
S
1.12
1.34
max shift, (shift/error)max
0.01
+0.44, -0.61
0.01
+0.53, -0.36
residual extrema in final diff map, e Å-3
a
b
w ) 4Fo2/σ2(Fo2), where σ2(Fo2) ) [σ2(I) + (0.031Fo2)2]. w ) 4Fo2/σ2(Fo2), where σ2(Fo2) ) [σ2(I) + (0.005Fo2)2].
Ta ble 2. F r a ction a l Coor d in a tes a n d Th er m a l
P a r a m eter sa for Non -Hyd r ogen Atom s a n d Th eir
Esd ’s for 2
between the phenyl planes of the phenylethynyl and the
central phenyl unit is 37.83° in 2. The Au-P bond
distance of 2.273(2) Å in 2 is comparable to those
observed in other alkynylgold phosphines2c,7f,h but longer
than those of the chlorogold phosphine complexes,7d,g
in line with the higher trans influence of the alkynyl
group. The angles P(1)-Au(1)-C(1) of 175.5(3)° and
Au(1)-C(1)-C(2) of 175.8(9)°, which are close to linear-
ity and typical of sp hybridization in Au(I) and acetyl-
enic carbon, are in the range found for other gold(I)
phosphine and acetylide complexes.2c,7f,h Furthermore,
the CtC bond distance of 1.18(1) Å is typical of terminal
acetylides. All other bond angles and bond lengths are
normal.
atom
x
y
z
Beq, Å2
Au(1)
P(1)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
0.10254(4)
-0.0231(3)
0.216(1)
0.287(1)
0.376(1)
0.348(1)
0.435(1)
0.546(2)
0.580(1)
-0.07083(2)
0.0241(1)
-0.1578(6)
-0.2094(5)
-0.2702(5)
-0.3043(5)
-0.3623(6)
-0.3894(7)
-0.3557(8)
-0.2974(7)
0.0117(5)
-0.0190(5)
-0.0312(5)
0.1189(5)
0.1807(5)
0.2510(6)
0.2612(6)
0.2030(7)
0.1303(6)
0.0230(5)
0.0880(5)
0.0832(7)
0.0130(8)
-0.0507(7)
-0.0467(5)
0.65074(3)
0.7289(2)
0.5941(8)
0.5676(8)
0.5311(9)
0.4259(9)
0.392(1)
4.382(9)
3.75(5)
5.3(3)
4.7(2)
5.0(3)
5.8(3)
6.7(3)
8.0(4)
8.5(4)
7.1(3)
3.7(2)
4.5(2)
4.6(2)
4.0(2)
6.0(3)
7.8(4)
8.1(4)
6.9(3)
5.1(3)
3.9(2)
5.0(3)
6.9(3)
6.5(3)
6.5(3)
5.0(2)
0.460(1)
0.564(1)
C(8)
C(9)
0.493(1)
0.5979(9)
0.8822(7)
0.9361(7)
1.0518(8)
0.7045(7)
0.7752(9)
0.748(1)
-0.0128(9)
0.1111(10)
0.1257(10)
0.0460(8)
0.020(1)
0.073(1)
0.150(1)
0.179(1)
0.125(1)
-0.2166(9)
-0.301(1)
-0.452(1)
-0.513(1)
-0.430(1)
-0.283(1)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
Similarly, the bond lengths of Au-P (2.266(2) and
2.275(2) Å) and Au-C (1.996(7) and 1.998(7) Å) in 5 are
normal. The bond angles of P-Au-C (174.3(2) and
174.2(2)°) and Au-C-C (175.6(7) and 171.9(6)°) are also
near linearity. However, unlike 2, short intramolecular
Au‚‚‚Au contacts of 3.1541(4) Å are found between
adjacent Au units. Such distances are shorter than the
sum of the van der Waals radii for Au and are compa-
rable to Au‚‚‚Au distances in other Au(I) phosphine
complexes,7 indicative of the presence of weak Au‚‚‚Au
interactions in the solid state. The dihedral angles
between the phenyl planes of the phenylethynyl and the
central phenyl unit are in the range 57.56-69.16°, with
the two phenyl planes of the phenylethynyl units on the
adjacent Au(1) and Au(2) at an angle of 12.76° to each
other. The arrangement of the two adjacent Au-
(CtCPh) groups is in a crossed geometry rather than a
radial one, with a P(1)-Au(1)-Au(2)-P(2) torsion angle
of 75.31(6)°. Consequently, the shape of the molecule
is that of a distorted anthracene-like structure consist-
0.657(1)
0.5888(10)
0.6109(8)
0.6872(7)
0.6795(8)
0.6531(10)
0.6397(9)
0.6448(9)
0.6687(8)
a
Beq
)
8/3π2(U11(aa*)2 + U22(bb*)2 + U33(cc*)2 + 2U12aa*bb*
cos γ + 2U13aa*cc* cos â + 2U23bb*cc* cos R).
there exist short Au‚‚‚Au intermolecular contacts,7a-g
no such short interactions are observed in 2 (Au‚‚‚Au
) 4.62 Å), as the bulky phenyl rings of the phosphine
probably prevent their close approach. The torsion
angle Au(1)-P(1)-C(9)-C(10), which defines the con-
formation of the alkynylgold unit with respect to the
central phenyl ring, is 33.05°, and the dihedral angle

Gold(I) Phosphine Acetylide Complexes
Organometallics, Vol. 15, No. 6, 1996 1737
Ta ble 3. F r a ction a l Coor d in a tes a n d Th er m a l
P a r a m eter sa for Non -Hyd r ogen Atom s a n d Th eir
Esd ’s for 5
atom
x
y
z
Beq, Å2
Au(1)
Au(2)
P(1)
P(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11) -0.0844(6)
C(12) -0.1458(8)
C(13) -0.2614(10)
C(14) -0.3161(9)
C(15) -0.2533(9)
C(16) -0.1396(7)
0.24500(2)
0.28739(2)
0.2484(2)
0.4741(2)
0.2332(6)
0.2347(7)
0.2389(8)
0.1540(8)
0.158(1)
0.249(1)
0.340(1)
0.332(1)
0.1296(7)
0.0337(7)
0.08004(2)
0.25662(2)
0.2410(1)
0.3373(1)
-0.0717(6)
-0.1576(7)
-0.2611(7)
-0.3355(8)
-0.4345(9)
-0.4584(10)
-0.383(1)
-0.2884(9)
0.2021(6)
0.1799(6)
0.1534(6)
0.2122(8)
0.184(1)
0.39822(2)
0.21790(2)
0.4810(1)
0.2986(1)
0.3371(5)
0.3007(5)
0.2549(6)
0.1873(8)
0.1434(8)
0.1722(9)
0.2397(9)
0.2796(7)
0.1402(5)
0.1007(5)
0.0556(5)
0.0881(6)
0.0450(8)
-0.0244(8)
-0.0575(7)
-0.0171(5)
0.4346(5)
0.4439(7)
0.4095(8)
0.3680(8)
0.3604(7)
0.3916(6)
0.6118(5)
0.6701(6)
0.7681(6)
0.8051(6)
0.7498(6)
0.6523(5)
0.3377(5)
0.2680(5)
0.2913(7)
0.3840(8)
0.4550(6)
0.4319(5)
0.2181(5)
0.1456(5)
0.0825(6)
0.0918(8)
0.1620(9)
0.2251(6)
0.4884(4)
0.4142(4)
0.4277(4)
3.361(7)
3.331(7)
2.96(4)
2.76(4)
3.8(2)
4.5(2)
4.9(2)
7.3(3)
9.0(4)
9.6(4)
10.1(4)
8.0(3)
3.8(2)
3.9(2)
3.8(2)
6.1(3)
7.7(3)
8.3(3)
6.9(3)
4.8(2)
3.3(2)
5.8(2)
8.0(3)
7.7(3)
7.3(3)
5.1(2)
3.0(2)
4.9(2)
5.8(3)
6.1(3)
5.6(2)
4.5(2)
2.8(2)
4.4(2)
5.7(2)
5.7(3)
6.0(3)
4.3(2)
3.3(2)
4.9(2)
6.9(3)
7.6(3)
7.7(3)
5.3(2)
2.4(1)
2.3(1)
2.7(2)
0.092(1)
0.0334(9)
0.0632(7)
0.2821(6)
0.3977(7)
0.4222(9)
0.331(1)
C(17)
C(18)
C(19)
C(20) -0.0494(9)
C(21) -0.0637(8)
0.1347(6)
0.1474(8)
0.0554(10)
0.216(1)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
C(40)
C(41)
C(42)
C(43)
0.0276(7)
0.2119(6)
0.2923(7)
0.2629(9)
0.1521(10)
0.0710(7)
0.1002(7)
0.5281(6)
0.5230(7)
0.5660(8)
0.6127(7)
0.6191(8)
0.5774(7)
0.5961(6)
0.5714(7)
0.664(1)
0.1917(7)
0.2011(5)
0.1797(7)
0.1392(8)
0.1213(7)
0.1422(7)
0.1815(6)
0.2321(5)
0.1480(7)
0.0681(7)
0.0721(7)
0.1542(8)
0.2363(6)
0.4406(6)
0.5040(7)
0.5813(8)
0.5915(9)
0.5291(9)
0.4538(7)
0.3860(5)
0.4264(5)
0.5398(5)
F igu r e 1. Perspective drawing of complex of 2 with the
atomic numbering scheme. Thermal ellipsoids are shown
at the 30% probability level. The starred atoms have
fractional coordinates at (-x, -y, 2 - z).
0.778(1)
0.8048(9)
0.7144(8)
0.3946(5)
0.4843(5)
0.5872(6)
a
See footnote a in Table 2.
ing of a central benzene ring with two fused Au2PC2P
six-membered rings at the two opposite sides, as com-
pared to the three fused benzene rings in anthracene.
This arises as a result of the presence of weak Au‚‚‚Au
interactions, which hold the two Au(CtCPh) units
together, although such a structure may also be favored
on steric grounds. In order to minimize the steric
repulsion between the phenyl rings on the neighboring
PPh2 groups, the rings may prefer to get rid of each
other by the rotation of the P-C σ bonds such that the
two Au atoms are forced to approach each other.
However, given the ability of the acetylenic moieties of
a related cis-PtMe2(Ph2PCtCPh)2 system to adopt a
noncrossed geometry,8 it is believed that auriophilicity
plays a crucial role in dictating the structure of 5.
F igu r e 2. Perspective drawing of the complex of 5 with
atomic numbering scheme. Thermal ellipsoids are shown
at the 25% probability level. The starred atoms have
fractional coordinates at (1 - x, 1 - y, 1 - z).
tion bands at ca. 250-300 nm. With reference to
previous work on ethynylgold(I) complexes2c and the
similarities of the absorption bands with the corre-
sponding ligands, the bands are assigned as the σ f π*
(Phbridge) transition. This type of transition involves the
promotion of an electron from the phosphorus lone-pair
orbital σ-bonded to an Au atom to the empty antibond-
ing orbital of π origin situated on the bridging phenyl
group of the phosphine. From the absorption spectra
of the ligands dppb and tppb, as compared to PPh3, it
is shown that the transition energy of their lowest lying
The electronic absorption spectra of the complexes
1-6 and the related Au(PPh3)(CtCPh) (7)2c in dichlo-
romethane at room temperature show intense absorp-
(8) J ohnson, D. K.; Rukachaisirikul, T.; Sun, Y.; Taylor, N. J .; Canty,
A. J .; Carty, A. J . Inorg. Chem. 1993, 32, 5544.

1738 Organometallics, Vol. 15, No. 6, 1996
Yam et al.
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) w ith Estim a ted Sta n d a r d Devia tion s (Esd ’s)
in P a r en th eses for 2
Bond Lengths
Au(1)-P(1)
Au(1)-C(1)
2.273(2)
2.00(1)
C(1)-C(2)
1.18(1)
Bond Angles
P(1)-Au(1)-C(1)
Au(1)-P(1)-C(9)
Au(1)-P(1)-C(12)
Au(1)-P(1)-C(18)
C(9)-P(1)-C(12)
175.5(3)
109.4(3)
114.3(3)
113.9(3)
106.2(4)
C(9)-P(1)-C(18)
C(12)-P(1)-C(18)
Au(1)-C(1)-C(2)
C(1)-C(2)-C(3)
103.8(4)
108.4(4)
175.8(9)
177.0(1)
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles
(d eg) w ith Estim a ted Sta n d a r d Devia tion s (Esd ’s)
in P a r en th eses for 5
F igu r e 3. Solid-state emission (solid line) and excitation
(dotted line) spectra of ground 5 at 25 °C.
Bond Lengths
Au(1)-Au(2)
Au(1)-P(1)
Au(1)-C(1)
Au(2)-P(2)
3.1541(4)
2.266(2)
1.996(7)
2.275(2)
Au(2)-C(9)
C(1)-C(2)
C(9)-C(10)
1.998(7)
1.182(9)
1.193(9)
Ta ble 6. Electr on ic Absor p tion a n d Em ission
Da ta for Com p ou n d s 1-7
emissnb
Bond Angles
79.31(4) Au(1)-P(1)-C(23) 108.3(2)
Au(2)-Au(1)-P(1)
absa
compd (ꢀ/dm3 mol-1 cm-1
λ
max/nm
medium
(T/K)
λ
max/nm
(τ0/µs)
Au(2)-Au(1)-C(1) 106.0(2)
Au(1)-P(1)-C(41) 118.9(2)
Au(2)-P(2)-C(29) 117.0(2)
Au(2)-P(2)-C(35) 111.1(2)
)
P(1)-Au(1)-C(1)
P(2)-Au(2)-C(9)
Au(1)-Au(2)-P(2)
174.3(2)
174.2(2)
75.86(4) Au(1)-C(1)-C(2)
1
256 (38 400)
solid (298)
510 (153.8)
427, 537
268 (sh) (26 870) solid (77)
175.6(7)
178.7(8)
275 (sh) (18 735) CH2Cl2 (298) 392 (0.67)
Au(1)-Au(2)-C(9) 109.7(2)
C(1)-C(2)-C(3)
284 (sh) (6 070)
587d (0.93)
P(2)-Au(2)-C(9)
Au(1)-P(1)-C(17)
174.2(2)
113.9(2)
Au(2)-C(9)-C(10) 171.9(6)
C(9)-C(10)-C(11) 178.3(8)
2
259 (53 440)
270 (63 470)
283 (57 060)
solid (298)
solid (298)c
507 (5.32)
505 (sh) (1.20), 590,
631d (4.44)
483
absorption bands is in the order PPh3 ≈ dppb > tppb.
This is understandable, since increasing the number of
PPh2 groups attached to the central phenyl ring would
render the ring more electron deficient, thus lowering
the corresponding π* level, which results in a red shift
in transition energy. A comparison of the electronic
absorption data with those for 7 shows that the absorp-
tion energy of 7 is similar to that for 2 but greater than
that for 5, similar to the trend observed for the corre-
sponding phosphines. It is also interesting to note that
the extinction coefficients of the low-energy absorption
bands of 5 are roughly twice that of 2 and four times
that of 7, which roughly parallel the number of
Au(PhCtC) units in the complexes, confirming their
assignment as σ f π* (Phbridge) transitions. Such
enhancements in the absorption coefficients when the
number of chromophoric units is increased may find
useful applications in the design of light harvesting
devices.
solid (77)
solid (77)c
507, 596, 617d
CH2Cl2 (298) 395, 411 (sh), 476 (sh),
601 (sh)
628d (0.27)
3
261 (48 070)
270 (50 335)
275 (49 710)
285 (47 880)
299 (40 590)
solid (298)
solid (77)
486, 563e (5.06)
483, 556e
CH2Cl2 (298) 395, 462 (sh),
541 (2.66)
4
5
289 (sh) (37 715) solid (298)
355 (sh) (5 620) solid (77)
405, 602 (1.28)
586
CH2Cl2 (298) 409, 577 (0.71)
241 (sh) (138 455) solid (298)
271 (sh) (102 320) solid (298)c
599, 611e (0.57)
529 (2.52)
584, 611e
365 (sh) (9 400)
solid (77)
solid (77)c
529, 569e
CH2Cl2 (298) 510, 538 (sh) (0.46)
6
262 (sh) (133 850) solid (298)
276 (133 895) solid (77)
415, 628e (1.85)
414, 618e
288 (sh) (126 185) CH2Cl2 (298) 447, 601 (0.47)
302 (sh) (103 260)
Excitation of the complexes at λ > 350 nm both in
the solid state and in dichloromethane solution results
in long-lived intense luminescence. Figure 3 shows the
solid-state excitation and emission spectra of 5, and the
photophysical data for 1-7 are summarized in Table 6.
The solid-state emission spectra of dppb, 1, and 2 are
very similar in energy, with an intense emission cen-
tered at ca. 500 nm, which is at higher energy than that
of 3. The long lifetime of the emission in the micro-
second range suggests that it is most likely associated
with a spin-forbidden transition. The emission of 3 is
red-shifted relative to 2. This can be rationalized by
the fact that the -OMe group on the acetylide is
electron-donating in nature, which reduces the extent
of metal to ligand back-π-donation (dπ(Au) f π*(-
CtCR)) to the acetylide, leading to an increased dπ(Au)-
3d(P) overlap and hence resulting in a reinforced Au-P
bond via the synergistic effect. The same is observed
for 5 and 6 (611 nm for 5 vs 628 nm for 6). Similarly,
370 (sh) (10 945)
7f
238 (32 000)
271 (19 400)
solid (298)
solid (77)
459 (33.4)
457
291 (sh) (11 400) CH2Cl2 (298) 410, 454 (sh) (6.6)
dppb
274 (18 640)
solid (298)
solid (77)
CH2Cl2 (298) 402, 510, 546 (sh)
409, 500 (sh)
443
tppb
245 (sh) (27 720) solid (298)
261 (22 770)
329 (sh) (4 965)
466, 495
502, 547
solid (77)
CH2Cl2 (298) 509, 544 (sh)
a
All absorption spectra are recorded using CH2Cl2 as solvent
b
at 298 K. Excitation wavelength is 350 nm. c Crystalline un-
d
ground samples were used for measurement. Excitation wave-
length is 500 nm. e Excitation wavelength is 450 nm. f From ref
2c.
the solution luminescence of 1 and 2 shows very similar
emission energy maxima and patterns with a high-
energy band at ca. 395 nm and a low-energy emission

Gold(I) Phosphine Acetylide Complexes
Organometallics, Vol. 15, No. 6, 1996 1739
at ca. 600 nm. The former is likely to be π f π*
an important role in governing the energy of the
emissive states.
(Phbridge) and the latter is likely to be σ f π* (Phbridge
)
in origin. An alternative assignment of the lowest lying
excited state as metal-to-ligand charge transfer (MLCT,
d(Au) f π*(CtCR)) in 1-3 and metal-metal-bond-to-
ligand charge transfer (MMLCT, dσ*(Au) or dδ*(Au) f
π*(CtCR)) in 4-6, which also gives rise to an observed
red shift in emission energy on going from 1-3 to 4-6
(Au‚‚‚Au for 5, 3.1541(4) Å), has been precluded, owing
to the fact that the emission energies did not comply
with the π*(CtCR) energy level of the acetylides, where
an order of orbital energies of π*(CtCC6H13) >
π*(CtCPhOMe) > π*(CtCPh) is expected. An assign-
ment of the origin of emission for 1-3 in the solid state
from a MMLCT is also unlikely, owing to the large
intermolecular Au‚‚‚Au separation (2, 4.62 Å).
Furthermore, it is interesting to note that the solid-
state emissions of 2 and 5, both at room temperature
and 77 K, show different emission maxima for the
crystalline unground and fully ground samples. Emis-
sion energy decreases for a ground sample of 2 as
compared to a crystalline unground sample, while the
reverse is observed for ground and crystalline unground
samples of 5. It is likely that the degree of solvent
incorporation in the crystalline samples of 2 and 5 plays
It should be mentioned that, unlike Au(I) phosphine
complexes such as [Au3(dmmp)2]3+ 7a
the origin of the
,
luminescence for complexes 1-6 is consistent with a σ
f π* (Phbridge) excited state and the presence of an
Au‚‚‚Au interaction in 5 would not be expected to
perturb the origin of the luminescent state.
Preparations of analogous complexes with longer
aliphatic acetylene derivatives and investigations of
their liquid crystalline properties are in progress.
Ack n ow led gm en t. V.W.-W.Y. acknowledges finan-
cial support from the Research Grants Council, the
Croucher Foundation, and The University of Hong
Kong. S.W.-K.C. acknowledges the receipt of a post-
graduate studentship and a Swire Scholarship, admin-
istered by The University of Hong Kong.
Su p p or tin g In for m a tion Ava ila ble: Text giving details
of the crystal structure solutions and tables giving fractional
coordinates and thermal parameters for hydrogen atoms,
general displacement parameter expressions U, and all bond
distances and bond angles for 2 and 5 (20 pages). Ordering
information is given on any current masthead page.
OM950586B