Synthesis, characterization, structure and luminescence studies of dinuclear gold(I) alkynyls of bis(diphenylphosphino)alkyl- and aryl-amines

Article abstract of DOI:10.1016/j.ica.2005.11.007

A series of alkynylgold(I) bis(diphenylphosphino)alkyl- and aryl-amine complexes, [{Ph₂PN(R)PPh₂}Au₂(C{triple bond, long}CR′)₂] [R = ⁿPr, R′ = Ph (1), C₆H₄OMe-p (2), C₆H₄Me-p (3), C₆H₄Cl-p (4); R = C₆H₄OMe-p, R′ = Ph (5)], has been synthesized. The X-ray crystal structures of 1 and 2 revealed the presence of short intramolecular Au?Au contacts with the distances of 2.8404(8) and 3.0708(7) ?. The luminescence behavior of the complexes were studied.

Full text of DOI:10.1016/j.ica.2005.11.007

Inorganica Chimica Acta 359 (2006) 3639–3648
www.elsevier.com/locate/ica
Synthesis, characterization, structure and luminescence studies of
dinuclear gold(I) alkynyls of bis(diphenylphosphino)alkyl- and
aryl-amines
*
Sung-Kong Yip, Wai Han Lam, Nianyong Zhu, Vivian Wing-Wah Yam
Centre for Carbon-Rich Molecular and Nano-Scale Metal-Based Materials Research, Department of Chemistry, The University of Hong Kong,
Pokfulam Road, Hong Kong SAR, PR China
Received 1 November 2005; accepted 12 November 2005
Available online 4 January 2006
Dedicated to Professor D.M.P. Mingos.
Abstract
A series of alkynylgold(I) bis(diphenylphosphino)alkyl- and aryl-amine complexes, [{Ph2PN(R)PPh2}Au2(C„CR0)2] [R = nPr,
R0 = Ph (1), C6H4OMe-p (2), C6H4Me-p (3), C6H4Cl-p (4); R = C6H4OMe-p, R0 = Ph (5)], has been synthesized. The X-ray crystal
˚
structures of 1 and 2 revealed the presence of short intramolecular Auꢀ ꢀ ꢀAu contacts with the distances of 2.8404(8) and 3.0708(7) A.
The luminescence behavior of the complexes were studied.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Gold(I); Alkynyl ligands; Luminescence; Phosphine ligands
1. Introduction
amine-type ligands have proved to be very versatile because
substituents on both phosphorus and nitrogen atoms could
be varied with attendant changes in the P–N–P bond angle
and the conformation around the phosphorus centers [4,5].
As an extension of our recent interest in d10 metal com-
plexes with bis(diphosphino)amine-type ligands [4d–g],
herein are reported the synthesis, characterization, structure
and luminescence studies of a series of alkynylgold(I)
bis(diphenylphosphino)alkyl- and aryl-amine complexes,
During the last decade, the synthesis, molecular struc-
tures and chemistry of gold(I) phosphine alkynyl complexes
have attracted much attention, in part due to the reports on
their rich luminescence properties and their ability to build
supramolecular structures based on the aurophilic nature of
gold [1]. There has also been a growing interest in the study
of dinuclear gold(I) alkynyl complexes with bidentate phos-
phine ligands, as it was believed that the presence of biden-
tate phosphines would bring the two gold atoms into close
proximity to have weak metal–metal interactions that con-
ferred them the rich luminescence properties. However, most
of the gold(I) complexes involved the use of phosphines
with P–(CH2)n–P unit [2,3], and examples with Ph2PN(R)-
PPh2 ligands were limited [4]. Recently, bis(diphosphino)-
n
[{Ph2PN(R)PPh2}Au2(C„CR0)2] [R = Pr, R0 = Ph (1),
C6H4OMe-p (2), C6H4Me-p (3), C6H4Cl-p (4); R = C6H4-
OMe-p, R0 = Ph (5)]. The X-ray crystal structures of 1
and 2 have been determined.
2. Results and discussion
2.1. Syntheses and characterization
*
The alkynylgold(I) bis(diphenylphosphino)alkyl- and
aryl-amine complexes were prepared by modification of
Corresponding author.
E-mail address: wwyam@hkucc.hku.hk (V.W.-W. Yam).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.11.007

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S.-K. Yip et al. / Inorganica Chimica Acta 359 (2006) 3639–3648
˚
the literature procedures [1e,3b]. Instead of reaction of
alkynes with (PR3)AuCl in the presence of a base such as
NaOEt or NaOMe [1b,3d,6], the complexes were synthe-
1.246(16) A in 1 and 2 were typical of terminal alkynyl-
gold(I) systems [1b,3b-d,6b,7]. The C„C bond distances
of complex 1 were slightly longer than that of 2, probably
C
sized by the depolymerization reaction of [Au(C„CR)]
1
resulted from the C H
contact found in the crystal pack-
C
with phosphine ligands. All the newly synthesized com-
ing, in which the aromatic proton of one molecule inter-
acted with one of ethynyl groups on the adjacent
molecule. The Au–C distances of complexes 1 and 2 were
1
plexes have been characterized by H NMR, 31P NMR,
and IR spectroscopy and positive-ion FAB-mass spectrom-
etry, and gave satisfactory elemental analyses. The struc-
tures of complex 1 and 2 were determined by X-ray
crystallography.
˚
in the range of 2.013(10)–2.134(14) A.
The intramolecular Auꢀ ꢀ ꢀAu distances of complexes 1
˚
and 2 were 2.8404(8) and 3.0708(7) A, respectively, indica-
The IR spectra of all the alkynylgold(I) complexes
showed weak intensity absorption bands at ca. 2081–
2122 cmꢁ1, typical of the m(C„C) stretch of the alkynyl
tive of the presence of Auꢀ ꢀ ꢀAu interactions. The intramo-
lecular Auꢀ ꢀ ꢀAu distances of complex 1 was short
compared to that of other dinuclear gold(I) phosphine
complexes, such as [(dppm)2Au2]Cl2 (2.962(1) A) [8], and
[(dmpm)2Au2](ClO4)2 (3.028(2) A) [9]. The arrangements
of the two adjacent Au(C„CPh) groups in 1 and
Au(C„CC6H4OMe-p) groups in 2 were found to be in a
crossed geometry, in which the C–Au–Au–C torsion angles
of complexes 1 and 2 were 32.5(8)ꢁ and 37.1(4)ꢁ,
respectively.
1
unit. The H NMR spectra of all the complexes showed
˚
resonance signals and coupling patterns that were consis-
tent with their chemical formulations. Complexes 1–5
showed a singlet in the 31P{1H} NMR spectra, indicating
that all the phosphine groups on the complexes were chem-
ically and magnetically equivalent.
˚
It was interesting to note that in the alkynylgold(I) com-
2.2. Crystal structure determination
plexes with P–(CH2)n–P moiety, reaction of [Au(C„CPh)]
1
with dppm gave the trinuclear complex, [Au3(dppm)2-
(C„CPh)2][Au(C„CPh)2], rather than a dinuclear com-
plex, in which the trinuclear cation with three gold atoms
adopted an isosceles triangular arrangement with intramo-
The perspective drawings of complexes 1 and 2 were
depicted in Figs. 1 and 2, respectively. The crystal structure
determination data of 1 and 2 were listed in Table 1.
Selected bond distances and angles for 1 and 2 were sum-
marized in Tables 2 and 3, respectively.
The X-ray crystal structures of 1 and 2 showed C–Au–P
angles of 173.3(2)–176.2(3)ꢁ, which deviated slightly from
the idealized geometry of 180ꢁ, probably as a result of
the steric demand of the ligand or crystal packing forces.
The C„C bond lengths in the range of 1.180(11)–
˚
lecular Auꢀ ꢀ ꢀAu distances of 3.083(2) and 3.167(2) A [3b],
while using the slightly longer P–(CH2)2–P moiety, the dinu-
clear alkynylgold(I) complex, [Au2(dppe)(C„CPh)2], was
obtained which was found to show an intermolecular
˚
Auꢀ ꢀ ꢀAu distance of 3.153(2) A [3a] in its X-ray crystal
structure.
Fig. 1. Perspective view of [{Ph2PN(nPr)PPh2}Au2(C„CPh)2] (1) with atomic numbering scheme. Hydrogen atoms have been omitted for clarity.
Thermal ellipsoids are shown at 30% probability level.

S.-K. Yip et al. / Inorganica Chimica Acta 359 (2006) 3639–3648
3641
Fig. 2. Perspective view of [{Ph2PN(nPr)PPh2}Au2(C„CC6H4OMe-p)2] (2) with atomic numbering scheme. Hydrogen atoms have been omitted for
clarity. Thermal ellipsoids are shown at 30% probability level.
Table 1
Table 2
˚
Crystal and structure determination data for 1 and 2
Selected bond distances (A) and angles (ꢁ) with estimated standard
deviations (esdꢀs) in parentheses for 1
Complex
1
2
˚
Bond distances (A)
Bond angles (ꢁ)
Formula weight
1023.61
253(2)
0.71073
orthorhombic
Pna21
1083.66
253(2)
0.71073
monoclinic
P21/n
T (K)
Au(1)–Au(2)
Au(1)–C(1)
Au(2)–C(9)
C(1)–C(2)
C(9)–C(10)
Au(1)–P(1)
Au(2)–P(2)
2.8404(8)
2.093(12)
2.134(14)
1.236(14)
1.246(16)
2.350(3)
C(1)–Au(1)–P(1)
C(2)–C(1)–Au(1)
C(1)–Au(1)–Au(2)
C(9)–Au(2)–P(2)
C(10)–C(9)–Au(2)
C(9)–Au(2)–Au(1)
175.0(3)
175.9(9)
102.2(3)
176.2(3)
172.5(10)
94.6(3)
˚
k (A)
Crystal system
Space group
Unit cell dimensions
˚
a (A)
19.283(4)
13.622(3)
14.504(3)
90
90
90
3809.8(14)
4
1.785
7.807
1960
0.3 · 0.2 · 0.2
ꢁ23 6 h 6 23,
ꢁ16 6 k 6 16,
ꢁ14 6 l 6 14
21933
12.965(3)
16.495(3)
20.167(4)
90
107.24(3)
90
4119.1(15)
4
1.747
˚
b (A)
2.396(3)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
Table 3
˚
Selected bond distances (A) and angles (ꢁ) with estimated standard
deviations (esdꢀs) in parentheses for 2
3
˚
V (A )
Z
˚
Bond distances (A)
Bond angles (ꢁ)
Dcalc (Mg mꢁ3
)
Absorption coefficient (mmꢁ1
F(000)
)
7.230
2088
Au(1)–Au(2)
Au(1)–C(1)
Au(2)–C(10)
C(1)–C(2)
C(10)–C(11)
Au(1)–P(1)
Au(2)–P(2)
3.0708(7)
2.013(10)
2.043(10)
1.180(11)
1.185(11)
2.264(2)
C(1)–Au(1)–P(1)
C(2)–C(1)–Au(1)
C(1)–Au(1)–Au(2)
C(10)–Au(2)–P(2)
C(11)–C(10)–Au(2)
C(10)–Au(2)–Au(1)
174.9(3)
174.8(8)
99.6(3)
173.3(2)
177.6(9)
106.2(2)
Crystal size (mm)
Index ranges
0.6 · 0.4 · 0.3
ꢁ14 6 h 6 14,
ꢁ19 6 k 6 19,
ꢁ24 6 l 6 24
24658
2.271(2)
Reflection collected
Independent reflections (Rint
Data/parameters
)
6319 (0.0467)
6319/1/434
0.972
R1 = 0.0311,
wR2 = 0.0836
0.863 and 1.438
7383 (0.0623)
7383/0/460
0.926
R1 = 0.0340,
wR2 = 0.0785
1.064 and 1.228
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
325–330 nm. Fig. 3 showed the electronic absorption spec-
trum of [{Ph2PN(nPr)PPh2}Au2(C„CC6H4Me-p)2] (3)
recorded in dichloromethane at 298 K. The electronic
absorption data for complexes 1–5 were summarized in
Table 4. The close resemblance of the electronic absorp-
tion energies of the high-energy bands at ca. 256–272
and ca. 287–297 nm to that of the free aminodiphosphine
ligands and gold(I) complexes containing aminodiphos-
phine ligands, such as [{Ph2PN(R)PPh2}Au2Cl2], and the
free alkynes suggested their assignments as intraligand
(IL) or metal-perturbed IL transitions characteristic of
Largest difference in peak
ꢁ3
˚
and hole (e A
)
2.3. Electronic absorption spectroscopy
The electronic absorption spectra of 1–5 in dichloro-
methane showed intense high-energy absorption bands at
ca. 256–297 nm, and low-energy absorption bands at ca.

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S.-K. Yip et al. / Inorganica Chimica Acta 359 (2006) 3639–3648
6
5
4
3
2
1
0
250
300
350
400
450
Wavelength / nm
Fig. 3. Electronic absorption spectrum of 3 in CH2Cl2 at 298 K.
the aminodiphosphine and the alkynyl ligands, while the
low-energy absorptions at ca. 325–330 nm, which were
absent in the related [{Ph2PN(R)PPh2}Au2Cl2], were ten-
tatively assigned to originate from ligand-to-ligand charge
transfer (LLCT) transitions from the p orbitals on the
alkynyl ligands to the p* orbitals on the Ph2PN(R)PPh2
ligands.
Fig. 4. Contour plots (contour value = 0.01) of the frontier molecular
orbitals for 1, with their orbital energy (eV) shown in parenthesis.
In order to examine the electronic structures and gain a
deeper insight into the nature of the frontier molecular
orbitals of the alkynylgold(I) aminodiphosphine com-
plexes, density functional theory calculation at the
B3LYP level was performed on 1 based on the experimen-
tal geometry obtained from the X-ray structural data (for
details, see Section 4). The selected frontier molecular orbi-
tals (the two highest occupied and two lowest unoccupied
orbitals) with the corresponding orbital energy were shown
in Fig. 4. The type of each molecular orbital was assigned
based on its orbital composition shown in Table 5, which
were expressed in terms of contributions from the two
Au metal centers (Au), phenylethynyl ligands (C„CPh)
and Ph2PN(nPr)PPh2 ligands (PNP).
As shown in Fig. 4, the HOMO and HOMO ꢁ 1 are
mainly composed of the p orbitals on the two phenylethynyl
ligands, while the LUMO and LUMO + 1 are predomi-
nantly located at the PNP ligand, in which they correspond
Table 4
Photophysical data for complexes 1–5
Complex
Absorption in CH2Cl2 at 298 K k/nm (e/dm3 molꢁ1 cmꢁ1
)
Medium (T/K)
Emission kem/nm (so/ls)b
1
256 sh (50810), 270 sh (45540), 290 (40990), 325 sh (17820)
258 sh (57510), 270 sh (49030), 297 (53500), 330 sh (23890)
256 sh (42440), 272 sh (37280), 293 (35650), 328 sh (16360)
256 sh (54870), 272 sh (51760), 292 (52420), 325 sh (23170)
258 sh (45550), 270 sh (40680), 287 (36170), 328 sh (13970)
Solid (298)
Solid (77)
Glass (77)a
530 (5.2)
535 (12.2)
495 (4.9)
2
3
4
Solid (298)
Solid (77)
Glass (77)a
493 (8.7)
485, 530 (16.1)
505 (6.5)
Solid (298)
Solid (77)
Glass (77)a
496 (7.4)
480, 524 (26.4)
500 (5.8)
Solid (298)
Solid (77)
Glass (77)a
503 (10.3)
501 (16.9)
497 (4.5)
5
Solid (298)
Solid (77)
Glass (77)a
615 (1.0)
629 (6.3)
510 (10.7)
a
In CH2Cl2–MeOH–EtOH (4:1:2 v/v).
Emission lifetimes recorded with 10% uncertainty.
b

S.-K. Yip et al. / Inorganica Chimica Acta 359 (2006) 3639–3648
3643
Table 5
Mulliken percentage compositions of the frontier molecular orbitals of 1
as shown in Fig. 4a
Au
C„CPh
PNP
LUMO + 1
LUMOb
HOMOc
HOMO ꢁ 1
a
2
10
12
6
0
2
87
93
97
89
2
1
The compositions were expressed in terms of contributions from the
two Au metal centers (Au), phenylethynyl ligand (C„CPh) and
Ph2PN(R)PPh2 ligand (PNP).
b
Total % contribution of the Au d and p orbitals (30% and 61%) in the
LUMO.
c
Total % contribution of the Au d and s orbitals (75% and 19%) in the
HOMO.
to the p* orbitals on the PPh2 units. It is worth mentioning
that small contributions from the d and p orbitals of the two
Au metal centers were also found in the HOMO and
LUMO, respectively. From Fig. 4, we can see that the
450
500
550
600
650
Wavelength /nm
Fig. 6. Emission spectrum of 2 in the solid state at 77 K.
ꢂ
HOMO has dr character, while the LUMO has pr charac-
ter (Here, we define the r-type d and p orbitals by viewing
the orbitals along the Auꢀ ꢀ ꢀAu axis). Based on the frontier
orbitals of 1, the low-energy absorptions of 1–5 probably
correspond to LLCT transitions from the p orbitals on
the phenylethynyl ligands to the p* orbitals on the
Ph2PN(nPr)PPh2 ligand, with some mixing of metal-cen-
tered dr ! pr transitions typical of d10 metal complexes
ꢂ
with metal–metal interactions [2a–d,10].
2.4. Photoluminescence properties
The alkynylgold(I) bis(diphenylphosphino)alkyl- and
aryl-amine complexes 1–5 displayed emission bands at
both room temperature and 77 K upon excitation at
350 nm. The photophysical data of the alkynylgold(I)
bis(diphenylphosphino)alkyl- and aryl-amines complexes
were summarized in Table 4. The emission spectra of 1,
2, and 3 were shown in Figs. 5–7. In 77 K glass, the bands
450
500
550
600
Wavelength / nm
Fig. 7. Emission spectrum of 3 in CH2Cl2–MeOH–EtOH (4:1:2 v/v) glass
at 77 K.
were centered at ca. 495–510 nm while in the solid state at
both 77 and 298 K, the bands occurred at 480–629 nm
upon excitation at ca. 350 nm. The higher energy of the
emission in 77 K glass relative to that in the solid state
was in line with the absence of short Auꢀ ꢀ ꢀAu contacts in
the 77 K glass. Similar findings have also been observed
in the related alkynylgold(I) phosphine systems, such as
in [(dppe)Au2(C„CPh)2] [3a] and [(dppe)Au2{C„CC
(@CH2)Me}2] [3d]. Luminescence lifetimes in the microsec-
ond range suggested an excited state of triplet parentage.
Previous studies showed that [(Ph3P)Au(C„CPh)]
[3a] exhibited well-resolved vibronic-structured emission
bands at ca. 420 nm, which were assigned as derived from
3[p–p*(alkynyl)] excited states. In view of the fact that the
emissions for 1–5 occurred at lower energies and were less
vibronic-structured compared to that of the alkynyl phos-
phorescence observed in [(Ph3P)Au(C„CPh)] [3a], an
450
500
550
600
650
700
Wavelength / nm
Fig. 5. Emission spectrum of 1 in the solid state at 298 K.

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S.-K. Yip et al. / Inorganica Chimica Acta 359 (2006) 3639–3648
assignment of the emissive state as derived from the intral-
igand [p ! p*(C„C)] origin was therefore unlikely. The
assignment appeared to be in good agreement with the nat-
ure of the frontier orbitals inferred from DFT calculations
of the ground state. The slight red shift in emission energy
of 1 relative to 2 in the solid state might be attributed to the
presence of a stronger intramolecular Auꢀ ꢀ ꢀAu interaction
in 1, as reflected by the shorter Auꢀ ꢀ ꢀAu contacts in the
X-ray structure.
3
slight red shift of emission energy observed upon increasing
the electron-donating ability of the alkynyl groups
appeared to be in line with an assignment with significant
p(C„C) character in the HOMO. It was also found that
a red shift in emission energy of 5 relative to 1 was
observed. Such a red shift was probably attributed to the
presence of the less electron-rich Ph2PN-(C6H4OMe-
p)PPh2 ligand compared to Ph2PN(nPr)PPh2, in 5 and 1,
respectively, as reflected from their 31P NMR spectral data,
3. Conclusion
A series of alkynylgold(I) bis(diphenylphosphino)alkyl-
and aryl-amine complexes was successfully synthesized
and spectroscopically characterized. The X-ray crystal
structures of 1 and 2 revealed the presence of short intra-
molecular Auꢀ ꢀ ꢀAu contacts with the distances of
in
line
with
an
excited
state
of
large
[p(ArC„C) ! p*(PNP)] LLCT character. Alternatively,
an assignment of an excited state of triplet
[p(ArC„C) ! 6s/6p(Au)] ligand-to-metal charge transfer
(LMCT) character was also possible since the less elec-
tron-rich Ph2PN(C6H4OMe-p)PPh2 ligand would render
the gold(I) center more electron-deficient, lowering the
metal acceptor-orbital energy. On the basis of studies of
the electronic structure and the nature of the frontier orbi-
tals, an assignment of the emission as derived from triplet
states of a p(ArC„C) ! p*(PNP) LLCT character was
favoured. The lack of an obvious dependence of transition
energies on the nature of the alkynyl and the aminophos-
phine ligands in the electronic absorption spectra of 1–5
was probably a result of the lack of features in the absorp-
tion spectra and the occurrence of the LLCT transition at
the low-energy region as shoulders that were obscured by
the high-energy IL bands. Complexes 1–5 were found to
undergo rapid photodecomposition upon excitation at ca.
350 nm in dichloromethane and acetone at room tempera-
ture, which hindered further photophysical studies in
solution.
˚
2.8404(8) and 3.0708(7) A, respectively. This class of dinu-
clear gold(I) phosphine complexes displayed photolumines-
cence in both 77 K glass and in the solid state. The
assignments of the emissive state was suggested to be
derived from triplet states of a [p(ArC„C) ! p*(PNP)]
LLCT character, with mixing of a [p(ArC„C) ! 6s/
6p(Au)] LMCT character. The emission of the complexes
in the solid state was believed to arise from the same origin
as in the 77 K glass, but with modifications by the intramo-
lecular Auꢀ ꢀ ꢀAu interaction.
4. Experimental
4.1. Materials and reagents
Potassium tetrachloroaurate(III) was obtained from
Strem Chemical Ltd. 2,20-Thiodiethanol, phenylacetylene,
and 1-chloro-4-ethynylbenzene were obtained from Aldrich
Chemical Company. 4-Methoxyphenylacetylene was
obtained from Maybridge Chemical Company Ltd., and
4-ethynyltoluene from GFS Chemical Co. Ltd.
Complexes 1–4 containing Ph2PN(nPr)PPh2 as the
bridging ligand showed emission bands at ca. 493–530 nm
and 480–535 nm in the solid state at room temperature
and at 77 K, respectively, upon excitation at k > 350 nm,
whereas complex 5 with Ph2PN(C6H4OMe-p)PPh2 showed
an emission band at 615 nm and 629 nm in the solid state at
room temperature and at 77 K, respectively. The lifetimes
of the emissive states of 1–5 in the microsecond range were
also suggestive of a triplet parentage. Given the presence of
short intramolecular Auꢀ ꢀ ꢀAu contacts observed in the
solid-state structures of 1 and 2, with Auꢀ ꢀ ꢀAu distances
[Au(C„CR)]
[11], bis(diphenylphosphino)-n-propyl-
1
amine (Ph2PN(nPr)PPh2) [4a] and bis(diphenylphosph-
ino)-4-methoxy-aniline (Ph2PN(C6H4OMe-p)PPh2) [4d]
were synthesized by modification of the literature methods.
Dichloromethane (Lab Scan, AR) was purified and dis-
tilled using standard procedures before use [12]. All other
solvents and reagents were of analytical grade and were
used as received.
˚
of 2.8404(8) and 3.0708(7) A, respectively, one might
All reactions were carried out under anhydrous and
anaerobic conditions using standard Schlenk technique.
expect that the origin would involve a triplet state of
1
1
3
1
3
1
ꢂ
ꢂ
metal-centered ½ðdd Þ ðprÞ ꢃ or ½ðdr Þ ðprÞ ꢃ character. In
view of the observation of vibronically structured emission
bands in the solid-state emission spectra of 2 and 3 at 77 K,
indicative of the involvement of the ligand character in the
emission origin, the assignment of an emissive state as
derived from a pure metal-centered origin was not favored.
Instead, an assignment of the origin as derived from states
of a LLCT [p(ArC„C) ! p*(PPh2)] character, probably
mixed with some LMCT [p(ArC„C) ! 6s/6p(Au)] and
metal-centered [5d(Au) ! 6s/6p(Au)] character, that was
modified by Auꢀ ꢀ ꢀAu interaction, was suggested. Such an
4.2. Physical measurements and instrumentation
1H and 31P{1H} NMR spectra were recorded on a Bru-
ker DPX-300 (300 MHz) and DRX-500 (202 MHz) FT
NMR spectrometers, with chemical shifts reported relative
to SiMe4 and H3PO4 (85%), respectively. Positive ion fast-
atom bombardment (FAB) mass spectra were recorded on
a Finnigan MAT95 mass spectrometer. Elemental analyses
of all newly synthesized metal complexes were performed on
a Carlo Erba 1106 elemental analyzer at the Institute of

S.-K. Yip et al. / Inorganica Chimica Acta 359 (2006) 3639–3648
3645
Chemistry of the Chinese Academy of Sciences in Beijing,
PR China. The electronic absorption spectra were recorded
on a Hewlett–Packard 8452A diode array spectrophotome-
ter. Steady-state emission and excitation spectra recorded at
room temperature and at 77 K were obtained on a Spex
Fluorolog-2 Model F111 spectrofluorometer with or with-
out Corning filters. All solutions for photophysical studies
were prepared under high-vacuum in a 10-cm3 round-bot-
tomed flask equipped with a side-arm 1-cm fluorescence
cuvette and sealed from the atmosphere by a Rotaflo
HP6/6 quick-release Teflon stopper. Solutions were rigor-
ously degassed on a high-vacuum line in a two-compartment
cell with no less than four successive freeze–pump–thaw
cycles. Solid-state photophysical measurements were car-
ried out with the solid sample loaded in a quartz tube inside
a quartz-walled Dewar flask. Liquid nitrogen was placed
into the Dewar flask for low temperature (77 K) measure-
ments. Luminescence lifetime measurements were per-
formed using a conventional laser system. The excitation
source was the 355 nm output (third harmonic) of a Spec-
tra-Physics Quanta-Ray Q-switched GCR-150-10 pulsed
Nd-YAG laser. Luminescence decay signals from a Ham-
amatsu R928 photomultiplier tube were converted to volt-
age changes by connecting to a 50 X load resistor and
were then recorded on a Tektronix Model TDS-620A digi-
tal oscilloscope. The lifetime s was determined by a single
exponential fitting of the luminescence decay trace with
the relationship I = I0 exp(ꢁt/s), where I and I0 are the
luminescence intensity at time = t and 0, respectively.
recrystallized from dichloromethane–n-hexane to give 2
as pale yellow crystals. Yield: 0.125 g, 76%. 1H NMR
(300 MHz, CDCl3, 298 K, relative to Me4Si): d 0.23 (t,
3H,
J = 7.2 Hz,
CH2CH2CH3),
0.78
(m,
2H,
CH2CH2CH3), 3.00 (m, 2H, CH2CH2CH3), 3.76 (s, 6H,
OCH3) 6.67 (d, 4H, J = 8.8 Hz, Ar), 7.36 (d, 4H,
J = 8.8 Hz, Ar), 7.51–7.78 (m, 20H, PPh2). 31P{1H}
NMR (202 MHz, CDCl3, 298 K, relative to 85% H3PO4):
d 96.84 (s, Ph2PN(nPr)PPh2). Positive FAB-MS: m/z 1083
[M]+. IR (KBr disk, m/cmꢁ1): 2109 (w), m(C„C). Elem.
Anal. Calc. for C45H41Au2NO2P2: C, 49.86; H, 3.81; N,
1.29. Found: C, 49.56; H, 3.88; N, 1.36%.
4.3.3. [{Ph2PN(nPr)PPh2}Au2(C„CC6H4Me-p)2] (3)
This was prepared according to the procedure for 1
except [Au(C„CC6H4Me-p)] (100 mg, 0.321 mmol) was
1
used instead of [Au(C„CPh)] . The product was recrys-
1
tallized from dichloromethane–n-hexane to give 3 as pale
yellow crystals. Yield: 0.126 mg, 74%. 1H NMR
(300 MHz, CDCl3, 298 K, relative to Me4Si): d 0.24 (t,
3H,
J = 7.2 Hz,
CH2CH2CH3),
0.79
(m,
2H,
CH2CH2CH3), 2.29 (s, 6H, CH3), 3.03 (m, 2H,
CH2CH2CH3), 6.94 (d, 4H, J = 8.0 Hz, Ar), 7.32 (d, 4H,
J = 8.0 Hz, Ar), 7.54–7.78 (m, 20H, PPh2). 31P{1H}
NMR (202 MHz, CDCl3, 298 K, relative to 85% H3PO4):
d 96.58 (s, Ph2PN(nPr)PPh2). Positive FAB-MS: m/z 1051
[M]+. IR (KBr disk, m/cmꢁ1): 2114 (w), m(C„C). Elem.
Anal. Calc. for C45H41Au2NP2 Æ 0.5H2O: C, 50.96; H,
3.99; N, 1.32. Found: C, 50.88; H, 3.97; N, 1.24%.
4.3. Synthesis of dinuclear alkynylgold(I)
bis(diphenylphosphino)alkyl- and aryl-amine complexes
4.3.4. [{Ph2PN(nPr)PPh2}Au2(C„CC6H4Cl-p)2] (4)
This was prepared according to the procedure for 1
except [Au(C„CC6H4Cl-p)] (100 mg, 0.301 mmol) was
1
4.3.1. [{Ph2PN(nPr)PPh2}Au2(C„CPh)2] (1)
used instead of [Au(C„CPh)] . The product was recrys-
1
To a dichloromethane solution of [Au(C„CPh)]
tallized from dichloromethane–n-hexane to give 4 as pale
1
1
(100 mg, 0.336 mmol) was added a solid sample of
Ph2PN(nPr)PPh2 (71.7 mg, 0.168 mmol) under a nitrogen
atmosphere. After it was stirred for 1 h, the solution was
concentrated and white solid was precipitated by addition
of n-hexane. Recrystallization was accomplished by the
slow evaporation of a dichloromethane–n-hexane solution
mixture of the product to give 1 as pale yellow crystals.
yellow crystals. Yield: 0.118 g, 72%. H NMR (300 MHz,
CDCl3, 298 K, relative to Me4Si):
d 0.20 (t, 3H,
J = 7.3 Hz, CH2CH2CH3), 0.73 (m, 2H, CH2CH2CH3),
2.88 (m, 2H, CH2CH2CH3), 7.07 (d, 4H, J = 8.8 Hz, Ar),
7.30 (d, 4H, J = 8.8 Hz, Ar), 7.54–7.77 (m, 20H, PPh2).
31P{1H} NMR (202 MHz, CDCl3, 298 K, relative to 85%
H3PO4): d 97.31 (s, Ph2PN(nPr)PPh2). Positive FAB-MS:
m/z 1091 [M]+. IR (KBr disk, m/cmꢁ1): 2122 (w),
m(C„C). Elem. Anal. Calc. for C43H35Au2Cl2NP2 Æ H2O:
C, 46.51; H, 3.36; N, 1.26. Found: C, 46.78; H, 3.25; N,
1.49%.
1
Yield: 0.127 g, 74%. H NMR (300 MHz, CDCl3, 298 K,
relative to Me4Si): d 0.21 (t, 3H, J = 7.2 Hz, CH2CH2CH3),
0.76 (m, 2H, CH2CH2CH3), 2.96 (m, 2H, CH2CH2CH3),
7.09–7.41 (m, 10H, C„CPh), 7.51–7.77 (m, 20H, PPh2).
31P{1H} NMR (202 MHz, CDCl3, 298 K, relative to 85%
H3PO4): d 97.14 (s, Ph2PN(nPr)PPh2). Positive FAB-MS:
m/z 1023 [M+H]+. IR (KBr disk, m/cmꢁ1): 2116 (w),
m(C„C). Elem. Anal. Calc. for C43H37Au2NP2 Æ 0.5H2O:
C, 50.01; H, 3.71; N, 1.36. Found: C, 49.95; H, 3.66; N,
1.37%.
4.3.5. [{Ph2PN(C6H4OMe-p)PPh2}Au2(C„CPh)2] (5)
This was prepared according to the procedure for 1
except Ph2PN(C6H4OMe-p)PPh2 (82.6 mg, 0.168 mmol)
was used instead of Ph2PN(nPr)PPh2. The product was
recrystallized from dichloromethane–n-hexane to give 5
as pale yellow crystals. Yield: 0.122 g, 67%. 1H NMR
(300 MHz, CDCl3, 298 K, relative to Me4Si): d 3.60 (s,
3H, OCH3), 6.10 (d, 4H, J = 8.9 Hz, NC6H4OMe), 6.27
(d, 4H, J = 8.9 Hz, NC6H4 OMe), 7.09–7.68 (m, 30H,
C„CPh, PPh2). 31P{1H} NMR (202 MHz, CDCl3,
4.3.2. [{Ph2PN(nPr)PPh2}Au2(C„CC6H4OMe-p)2] (2)
This was prepared according to the procedure for 1
except [Au(C„CC6H4OMe-p)]
was used instead of [Au(C„CPh)] . The product was
(100 mg, 0.305 mmol)
1
1

3646
S.-K. Yip et al. / Inorganica Chimica Acta 359 (2006) 3639–3648
P
2
298 K, relative to 85% H3PO4):
d
102.20 (s,
f
½wðF o2 ꢁ F c2Þ ꢃ=ðn ꢁ pÞg1=2, where n was the number of
Ph2PN(C6H4OMe-p)PPh2). Positive FAB-MS: m/z 1086
[M]+. IR (KBr disk, m/cmꢁ1): 2114 (w), m(C„C). Elem.
Anal. Calc. for C47H37Au2NOP2 Æ CHCl3 Æ 0.33C6H14: C,
48.59; H, 3.48; N, 1.13. Found: C, 48.62; H, 3.33; N, 1.31%.
reflections and p was the total number of parameters
refined. The weighting scheme was: w ¼ 1=½r2ðF o2Þþ
2
ðaPÞ þ bPꢃ, where P was ½2F 2c þ maxðF 2o; 0Þꢃ=3. Conver-
gence ((D/r)max = 0.001, av. 0.001) for 434 variable param-
eters by full-matrix least-squares refinement on F2 reached
to R1 = 0.0311 and wR2 = 0.0836 with a goodness-of-fit of
0.972, the parameters a and b for weighting scheme were
0.0477 and 0. The final difference Fourier map showed
maximum rest peaks and holes of 0.863 and
4.4. Crystal structure determination
Single crystals of 1 and 2 suitable for X-ray diffraction
studies were grown by layering n-hexane into a dichloro-
methane solution of the corresponding complexes in the
dark.
ꢁ1.438 e Aꢁ3, respectively.
4.4.2. [{Ph2PN(nPr)PPh2}Au2(C„CC6H4OMe-p)2] (2)
[C45H41Au2NO2P2], formula weight = 1083.66, mono-
clinic, space group P21/n, a = 12.965(3) A, b =
˚
4.4.1. [{Ph2PN(nPr)PPh2}Au2(C„CPh)2] (1)
˚
[C43H37Au2NP2], formula weight = 1023.61, ortho-
˚
˚
˚
rhombic, space group Pna21, a = 19.283(4) A, b =
16.495(3) A, c = 20.167(4) A, b = 107.24(3)ꢁ, V = 4119.1(15)
3
3
A , Z = 4, Dcalc = 1.747 g cmꢁ3, l(Mo Ka) = 7.230 mmꢁ1
,
˚
˚
˚
˚
13.622(3) A, c = 14.504(3) A, V = 3809.8(14) A , Z = 4,
Dcalc = 1.785 g cmꢁ3, l(Mo Ka) = 7.807 mmꢁ1, F(000) =
1960, T = 253 K. A crystal of dimensions 0.3 · 0.2 ·
0.2 mm mounted in a glass capillary was used for data col-
lection at ꢁ20 ꢁC on a MAR diffractometer with a 300 mm
image plate detector using graphite monochromatized Mo
F(000) = 2088, T = 253 K. A crystal of dimensions 0.6 ·
0.4 · 0.3 mm mounted in a glass capillary was used for
data collection at ꢁ20 ꢁC on a MAR diffractometer with a
300 mm image plate detector using graphite monochroma-
˚
tized Mo Ka radiation (k = 0.71073 A). Data collection
˚
Ka radiation (k = 0.71073 A). Data collection was made
was made with 3ꢁ oscillation step of u, 300 s exposure time
and scanner distance at 120 mm. 60 images were collected.
The images were interpreted and intensities integrated using
program DENZO [13]. The structure was solved by direct
methods employing SIR-97 program [14] on PC. Gold, phos-
phorus and many non-hydrogen atoms were located accord-
ing to the direct methods and the successive least-squares
Fourier cycles. The positions of the other non-hydrogen
atoms were found after successful refinement by full-matrix
least-squares using program SHELXL-97 [15] on PC. Accord-
ing to the SHELXL-97 program [15], all 7383 independent
reflections (Rint equal to 0.0623, 4767 reflections larger than
with 2ꢁ oscillation step of u, 420 s exposure time and scan-
ner distance at 120 mm. 90 images were collected. The
images were interpreted and intensities integrated using
program DENZO [13]. The structure was solved by direct
methods employing SIR-97 program [14] on PC. Gold,
phosphorus and many non-hydrogen atoms were located
according to the direct methods and the successive least-
squares Fourier cycles. The positions of the other non-
hydrogen atoms were found after successful refinement
by full-matrix least-squares using program SHELXL-97 [15]
on PC. The absolute structure was assisted by the Flack
absolute structure parameter equal to 0.009(10). According
to the SHELXL-97 program [15], all 6319 independent reflec-
tions (Rint equal to 0.0467, 4931 reflections larger than
P
P
4r(Fo) where Rint
¼
jF 2o ꢁ F 2oðmeanÞj= ðF 2oÞ from a
total 24658 reflections were participated in the full-matrix
least-squares refinement against F2. These reflections were
in the range ꢁ14 6 h 6 14, ꢁ19 6 k 6 19, ꢁ24 6 l 6 24
with 2hmax equal to 50.70ꢁ. One crystallographic asymmetric
unit consisted of one formula unit. In the final stage of
least-squares refinement, all non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were generated
by program SHELXL-97 [15]. The positions of hydrogen
atoms were calculated based on riding mode with thermal
parameters equal to 1.2 times that of the associated car-
bon atoms, and participated in the calculation of final
R-indices. Since the structure refinements were against F2,
R-indices based on F2 were larger than (more than double)
those based on F. For comparison with older refinements
based on F and an OMIT threshold, a conventional
index R1 based on observed F values larger than 4r(Fo)
was also given (corresponding to intensity P2r(I)).
P
P
4r(Fo) where Rint
¼
jF 2o ꢁ F 2oðmeanÞj= ðF 2oÞ) from a
total 21933 reflections were participated in the full-matrix
least-squares refinement against F2. These reflections were
in the range ꢁ23 6 h 6 23, ꢁ16 6 k 6 16, ꢁ14 6 l 6 14
with 2hmax equal to 51.34ꢁ. One crystallographic asymmet-
ric unit consisted of one formula unit. In the final stage of
least-squares refinement, all non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were generated
by program SHELXL-97 [15]. The positions of hydrogen
atoms were calculated based on riding mode with thermal
parameters equal to 1.2 times that of the associated carbon
atoms, and participated in the calculation of final R-indi-
ces. Since the structure refinements were against F2, R-indi-
ces based on F2 were larger than (more than double) those
based on F. For comparison with older refinements based
on F and an OMIT threshold, a conventional index R1 based
P
P
P
wR2 ¼ f ½wðF 2o ꢁ F c2Þ ꢃ= ½wðF 2oÞ ꢃg1=2, R1 = iFo| ꢁ |Fci
2
2
P
on observed F values larger than 4r(Fo) was also given
/
|Fo|, the goodness-of-fit was always based on F2:
P
P
2
(corresponding to intensity P2r(I)). wR2 ¼ f ½wðF 2oꢁ
GOF ¼ S ¼ f ½wðF o2 ꢁ F 2cÞ ꢃ=ðn ꢁ pÞg1=2, where n was the
number of reflections and p was the total number of param-
eters refined. The weighting scheme was: w ¼ 1=½r2ðF o2Þþ
P
P
P
2
2
F 2cÞ ꢃ= ½wðF o2Þ ꢃg1=2, R1 = iFo| ꢁ |Fci/ |Fo|, the good-
ness-of-fit was always based on F2: GOF ¼ S ¼

S.-K. Yip et al. / Inorganica Chimica Acta 359 (2006) 3639–3648
3647
2
ðaPÞ þ bPꢃ, where P was ½2F 2c þ maxðF 2o; 0Þꢃ=3. Conver-
(d) T. Muller, J.C. Green, D.M.P. Mingos, C.M. McPartlin, C.
¨
Whittingham, D.J. Williams, T.M. Woodroffe, J. Organomet. Chem.
551 (1998) 313;
(e) V.W.W. Yam, S.W.K. Choi, K.K. Cheung, Organometallics 15
(1996) 1734;
(f) S.K. Yip, E.C.C. Cheng, L.H. Yuan, N. Zhu, V.W.W. Yam,
Angew. Chem. Int. Ed. 43 (2004) 4954;
(g) R.J. Puddephatt, Coord. Chem. Rev. 216–217 (2001) 313;
(h) C.P. McArdle, S. Van, M.C. Jennings, R.J. Puddephatt, J. Am.
Chem. Soc. 124 (2002) 3959.
gence (D/r)max = 0.001, av. 0.001) for 460 variable parame-
ters by full-matrix least-squares refinement on F2 reached to
R1 = 0.0340 and wR2 = 0.0785 with a goodness-of-fit of
0.926, the parameters a and b for weighting scheme were
0.0424 and 0. The final difference Fourier map showed max-
ꢁ3
˚
imum rest peaks and holes of 1.064 and ꢁ1.228 e A
,
respectively.
[2] (a) C.M. Che, H.L. Kwong, V.W.W. Yam, K.C. Cho, J. Chem. Soc.,
Chem. Commun. (1989) 885;
4.5. Computational details
(b) C.M. Che, H.L. Kwong, C.K. Poon, V.W.W. Yam, J. Chem.
Soc., Dalton Trans. (1990) 3215;
(c) V.W.W. Yam, T.F. Lai, C.M. Che, J. Chem. Soc., Dalton Trans.
(1990) 3747;
(d) V.W.W. Yam, W.K. Lee, J. Chem. Soc., Dalton Trans. (1993)
2097;
(e) J.M. Forward, D. Bohmann, J.P. Fackler Jr., R.J. Staples, Inorg.
Chem. 34 (1995) 6330.
Using GAUSSIAN-03 [16], density functional theory (DFT)
calculation at the Becke3LYP (B3LYP) level [17] was used
to calculate the electronic structures of the ground state of
[{Ph2PN(nPr)PPh2}Au2(C„CPh)2] (1) on the basis of the
experimentally determined geometry obtained from crys-
tallographic data. In that geometry, all the C–H bond
[3] (a) D. Li, X. Hong, C.M. Che, W.C. Lo, S.M. Peng, J. Chem. Soc.,
Dalton Trans. (1993) 2929;
˚
lengths of 1 were set at 1.09 A. The Stuttgart/Dresden
effective core potentials (ECPs) [18] on Au replaced the
inner core electrons, while the SDD basis set [19] was
applied to describe the outer core [(5s)2(5p)6] and valence
5d electrons. Two f-type polarization functions were
employed for Au (the diffused one af = 0.2 and the com-
pact one af = 1.19) [20]. For all other atoms, the 6-
31G(d) basis set [21] was used. The molecular orbitals
obtained from the B3LYP calculation were plotted using
the GAUSSVIEW program [22].
(b) C.M. Che, H.K. Yip, W.C. Lo, S.M. Peng, Polyhedron 13 (1994)
887;
(c) V.W.W. Yam, S.W.K. Choi, J. Chem. Soc., Dalton Trans. (1996)
4227;
(d) V.W.W. Yam, K.L. Cheung, S.K. Yip, K.K. Cheung, J.
Organomet. Chem. 681 (2003) 196;
(e) C.P. McArdle, M.C. Jennings, J.J. Vittal, R.J. Puddephatt, Chem.
Eur. J. 7 (2001) 3572;
(f) F. Mohr, R.J. Puddephatt, J. Organomet. Chem. 689 (2004) 374.
[4] (a) G. Ewart, A.P. Lane, J. McKechnie, D.S. Payne, J. Chem. Soc.
(1964) 1543;
(b) H. Schmidbaur, F.E. Wagner, A. Wohlleben-Hammer, Chem.
Ber. 112 (1979) 496;
Acknowledgements
(c) J.S. Field, J. Grieve, R.J. Haines, N. May, M.M. Zulu, Polyhedron
17 (1998) 3021;
(d) V.W.W. Yam, C.L. Chan, K.K. Cheung, J. Chem. Soc., Dalton
Trans. (1996) 4019;
(e) V.W.W. Yam, E.C.C. Cheng, Z.Y. Zhou, Angew. Chem. Int. Ed.
39 (2000) 1683;
(f) V.W.W. Yam, E.C.C. Cheng, N. Zhu, Angew. Chem. Int. Ed. 40
(2001) 1763;
V.W.-W.Y. acknowledges support from the University
Development Fund of The University of Hong Kong
and the University of Hong Kong Foundation for Edu-
cation Development and Research Limited. S.-K.Y.
acknowledged the receipt of a Postgraduate Studentship,
and W.H.L. the receipt of a University Postdoctoral Fel-
lowship, both of which were administrated by the Uni-
versity of Hong Kong. The work has been supported
by a CERG Grant from the Research Grants Council
of the Hong Kong Special Administrative Region, China
(Project No. HKU 7049/05P). We also thank the Com-
puter Center at HKU for providing the computational
resources.
(g) V.W.W. Yam, C.L. Chan, C.K. Li, K.M.C. Wong, Coord. Chem.
Rev. 216–217 (2001) 173.
[5] (a) N. Kuhn, M. Winter, J. Organomet. Chem. 229 (1982) C33;
(b) T.J. Barder, F.A. Cotton, D. Lewis, W. Schwotzer, S.M. Tetrick,
R.A. Walton, J. Am. Chem. Soc. 106 (1984) 2882;
(c) R. Uson, J. Fornies, R. Navarro, J.I. Cebollada, J. Organomet.
Chem. 304 (1986) 381;
(d) R. Uson, J. Fornies, R. Navarro, M. Tomas, C. Fortuno, J.I.
Cebollada, Polyhedron 8 (1989) 1045;
(e) M.S. Balakrishna, V. Sreenivasa Reddy, S.S. Krishnamurthy,
Coord. Chem. Rev. 129 (1994) 1.
Appendix A. Supplementary data
[6] (a) H.Y. Chao, W. Lu, Y. Li, M.C.W. Chan, C.M. Che, K.K.
Cheung, N. Zhu, J. Am. Chem. Soc. 124 (2002) 14696;
(b) W. Lu, N. Zhu, C.M. Che, J. Am. Chem. Soc. 125 (2003) 16081.
[7] (a) C.M. Che, H.Y. Chao, V.M. Miskowski, Y. Li, K.K. Cheung, J.
Am. Chem. Soc. 123 (2001) 4985;
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.ica.2005.11.
007.
(b) W. Lu, H.F. Xiang, N. Zhu, C.M. Che, Organometallics 21
(2002) 2343.
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