Gold(i) and silver(i) complexes containing a tripodal tetraphosphine ligand: Influence of the halogen and stoichiometry on the properties. the X-ray crystal structure of two gold(i) dimeric aggregates

Article abstract of DOI:10.1039/b716736a

Complexes of the type [Au₂(μ-PP₃) ₂]X₂ [X = Cl (1), Br (2), I (3)], [Ag₂(μ- PP₃)₂](NO₃)₂ (4), Ag(PP ₃)Cl (5), M₃(μ-PP₃)X₃ [M = Au, X = Cl (10), Br (11), I (12); M = Ag, X = NO₃ (13)] and Au ₄(μ-PP₃)X₄ [X = Cl (14), Br (15), I (16)] have been prepared by interaction between gold(i) or silver(i) salts and the ligand tris[2-(diphenylphosphino)ethyl]phosphine (PP₃) in the appropriate molar ratio. Microanalysis, mass spectrometry, IR and NMR spectroscopies and conductivity measurements were used for characterization. 1-3 and 4 are ionic dinuclear species containing four-coordinate gold(i) and four/three coordinate silver(i), respectively. Solutions of 10-12 behave as mixtures of complexes in a 2:1 [Au₂(μ-PP₃)X ₂; X = Cl(6), Br(7), I(8)] and 4:1 (14-16) metal to ligand ratio. 13 and 15 react with free PP₃ in solution to generate the ionic compounds 4 and 2, respectively. Complexes 15 and 16, with four linear PAuX fragments per molecule, were shown by X-ray diffraction to consist of dimeric aggregates via close intermolecular gold(i)gold(i) contacts of 3.270 (15) and 3.184 (16). The resultant octanuclear systems have an inversion center with two symmetry-related gold(i) atoms being totally out of the aurophilic area and represent a new form of aggregation compared to that found in other halo complexes of gold(i) containing polyphosphines. The luminescence properties of the ligand and complexes, in the solid state, have been studied. Most of the gold systems display intense luminescent emission at room and low temperature. The influence of the halogen on the aurophilic contacts of compounds with a 4:1 metal to ligand ratio results in different photophysical properties, while 15 and 16 are luminescent complex 14 is nonemissive. The luminescence increases with increasing the phosphine/metal ratio affording for complexes 1-3, without aurophilic contacts, the stronger emissions. Silver complexes 4 and 5 are nonemissive at room temperature and show weaker emissions than gold(i) species at 77 K. The Royal Society of Chemistry.

Full text of DOI:10.1039/b716736a

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www.rsc.org/dalton | Dalton Transactions
Gold(I) and silver(I) complexes containing a tripodal tetraphosphine ligand:
influence of the halogen and stoichiometry on the properties. The X-ray
crystal structure of two gold(I) dimeric aggregates†
D. Ferna´ndez,a M. I. Garc´ıa-Seijo,a M. Bardaj´ı,b A. Lagunab and M. E. Garc´ıa-Ferna´ndez*a
Received 31st October 2007, Accepted 21st January 2008
First published as an Advance Article on the web 31st March 2008
DOI: 10.1039/b716736a
Complexes of the type [Au2(l-PP3)2]X2 [X = Cl (1), Br (2), I (3)], [Ag2(l-PP3)2](NO3)2 (4), Ag(PP3)Cl
(5), M3(l-PP3)X3 [M = Au, X = Cl (10), Br (11), I (12); M = Ag, X = NO3 (13)] and Au4(l-PP3)X4
[X = Cl (14), Br (15), I (16)] have been prepared by interaction between gold(I) or silver(I) salts and the
ligand tris[2-(diphenylphosphino)ethyl]phosphine (PP3) in the appropriate molar ratio. Microanalysis,
mass spectrometry, IR and NMR spectroscopies and conductivity measurements were used for
characterization. 1–3 and 4 are ionic dinuclear species containing four-coordinate gold(I) and
four/three coordinate silver(I), respectively. Solutions of 10–12 behave as mixtures of complexes in a 2:1
[Au2(l-PP3)X2; X = Cl(6), Br(7), I(8)] and 4:1 (14–16) metal to ligand ratio. 13 and 15 react with free
PP3 in solution to generate the ionic compounds 4 and 2, respectively. Complexes 15 and 16, with four
linear PAuX fragments per molecule, were shown by X-ray diffraction to consist of dimeric aggregates
˚
˚
via close intermolecular gold(I) · · · gold(I) contacts of 3.270 A (15) and 3.184 A (16). The resultant
octanuclear systems have an inversion center with two symmetry-related gold(I) atoms being totally out
of the aurophilic area and represent a new form of aggregation compared to that found in other halo
complexes of gold(I) containing polyphosphines. The luminescence properties of the ligand and
complexes, in the solid state, have been studied. Most of the gold systems display intense luminescent
emission at room and low temperature. The influence of the halogen on the aurophilic contacts of
compounds with a 4:1 metal to ligand ratio results in different photophysical properties, while 15 and
16 are luminescent complex 14 is nonemissive. The luminescence increases with increasing the
phosphine/metal ratio affording for complexes 1–3, without aurophilic contacts, the stronger
emissions. Silver complexes 4 and 5 are nonemissive at room temperature and show weaker emissions
than gold(I) species at 77 K.
two-coordinate (by using sterically bulky ligands) and tetrahedral
Introduction
four-coordinate geometries for gold and silver, respectively it is
possible to prepare and isolate both silver(I) and gold(I) complexes
with varying coordination geometries ranging from linear to
tetrahedral.7a,8–12 The five-coordination13 has been also reported
in a few cases.
The ability of the ligands to act as donors through various
coordination modes can give rise to species ranging from simple
mononuclear systems to multinuclear clusters and coordination
polymers,8–12 with the tendency of Cu(I), Ag(I) and Au(I) complexes
to form clusters and aggregates being a result of metal–metal
interactions.2b–d Furthermore, subtle modifications to the polymers
compositions, as an added methyl group in the 3-position on the
pyridyl fragment of an imidazolium N-heterocyclic carbene ligand
used in the preparation of Au(I)–Ag(I) coordination polymers,
lead to significant variations in structures and luminescence
properties.1e
The coordination chemistry of the coinage metals has been
subjected of investigation for decades due to the wide range of
applications of their metal complexes. These metals all display the
ability to form attractive nonbonding “metallophilic” interactions
that can strongly influence the structure and properties in the
resultant materials. Such interactions have been shown to play a
significant role in the origin of the luminescent activity, the use
of phosphine ligands favoring both the metal centres proximity
and the luminescence.1–6 The interactions are most likely the result
of relativistic and correlation effects particularly in the case of
gold for which these effects are especially pronounced,1c,6 leading
to compounds with gold–ligand bonds that are shorter than the
corresponding silver–ligand bonds.7 In spite of the preferred linear
aDepartamento de Qu´ımica Inorga´nica, Universidad de Santiago de Com-
postela, E-15782, Santiago de Compostela, Spain. E-mail: qiegfq@usc.es;
Fax: 34-981-597525; Tel: 34-981-563100/14241
An important number of emissive gold(I) systems arise from
species containing bridging ligands and aurophilic contacts,14–16
where the changes in the anionic ligands or neighboring
anions can dramatically influence the optical behaviour.4d,15a,16
Thus, the emission spectra of [Au3(l-dpmp)2X](PF6)2
bDepartamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales
de Arago´n, Universidad de Zaragoza-CSIC, E-50009, Zaragoza, Spain
† CCDC reference numbers 656179 [X = Br(15)] and 656180 [X = I(16)].
For crystallographic data in CIF or other electronic format see DOI:
10.1039/b716736a
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(dpmp = bis(diphenylphosphinomethyl)phenylphosphine; X =
Cl, Br, I), consisting of three Au(I) ions bridged by two dpmp
ligands, were entirely different depending on the halide anion with
the bromo complex being not luminescent.16a The interatomic
Owing to the scantiness of reports on Au(I) and Ag(I) complexes
containing tripodal polyphosphine ligands19 and with the aim of
exploring the role of the halogen (or other anionic ligands or
counterions) and the stoichiometry in the structure and photo-
physical properties of the resultant compounds, here we describe
the coordination of the potentially tetradentate tetraphosphine
tris[2-(diphenylphosphino)ethyl]phosphine (PP3) with Ag(I) and
Au(I).
distance usually observed in compounds with these aurophilic16b
16c
˚
interactions is on the order of 3.00–3.25 A and their strength
has been estimated to be in the range of 6 to 8 kcal mol−1.16d–f
However, using variable temperature31P-NMR spectroscopy and
simulations it was found an aurocarborane 1,1ꢀ-(AuPPh3)2-[2-
(1ꢀ,2ꢀ-C2B10H10)-1,2-C2B10H10] with an unusually strong aurophilic
interaction of 11 kcal mol−1. It seems that the electron deficiency
of the gold atoms caused by the strong negative inductive effect of
the carborane cages is responsible for the stronger interaction in
contradiction to other analyses of the nature of gold carboranyl
compounds. On the other hand, the complexes prepared by
treatment of [(CH2)n(Ph2PAuO2CCF3)2] with 4,4ꢀ-bipyridine
seem to exist in solution as an equilibrium mixture of linear
oligomers and cyclic complexes that when n = 1,3 or 5 consist
of luminescent 26-, 30- and 34-membered cationic rings and
trifluoroacetate counteranions. The X-ray crystal structure of the
weakly emissive solid with n = 1 confirms a macrocyclic structure
where the geometry about each gold(I) centre is approximately
Results and discussion
Syntheses
Treatment of a solution of Au(tdg)X (tdg = thiodiglycol = 2,2ꢀ-
thiodiethanol; X = Cl, Br) and AgNO3 in methanol or AuI and
AgCl as solids with dichloromethane solutions of PP3 in the ap-
propriate stoichiometric ratio gives solutions and/or precipitates
of complexes 1–5 and 10–16. By addition of diethylether and/or
water, air-stable solids were afforded in good (85%) or moderate
(30–45%) yields. The reaction of 15 and 13 with two equivalents
of PP3 gives 2 and 4, respectively in solution. Complexes 1, 4, 5
and 10 were isolated as dichloromethane solvates. Most of these
compounds (2–5, 10,11, 14–16) are white solids. 1 is yellow, 12
grey and 13 beige. Complex 12 was not soluble in DMF and 3 was
insoluble in both DMF and DMSO. For each stoichiometry the
solubilities in the common organic solvents increase from silver to
gold and from chlorides to bromides. With independence of the
metal the highest solubilities were found for compounds with a
1:1 stoichiometry.
linear and the transannular gold-gold distances are 3.106(1) and
16g
˚
3.084(1) A.
Another kind of emissive gold(I) compound containing phos-
phines was found in three or four coordinate systems without
aurophilic contacts. One example consists of Au(I)-based metal-
locryptates of the type [Au2M(l-dppn)3](PF6)3 (M = alkali metal
ion, dppn = 2,9-bis(diphenylphosphino)-1,8-naphthyridine), pre-
pared by a template reaction, with structures containing three-
coordinate gold(I) that are emissive species when M = Li,
Na, K, Cs and that convert into a nonluminescent com-
pound by replacement of gold and M by silver.17 Other exam-
ples correspond to three-coordinate dimeric, [Au2(NP3)2](BPh4)2
Characterization
The results of conductivity measurements, mass and far infrared
spectra for compounds 1–5 and 10–16 are given in Table 1 and 2
1
shows the 31
P{ H}NMR data.
Complexes 1, 4, 5, 13 and 14 were previously reported.19b,c
Solutions of complex 4 consist of [Ag2(l-PP3)2]2+ dications, bearing
AgP4 + AgP3 environments, and NO3− counteranions. Complex 5
contains silver(I) bound to three phosphorus atoms and the data
for 13 reveal the presence of both AgP2 + AgP environments with
the nitrates acting as ligands.19–22
(NP3
=
tris[2-(diphenylphosphino)ethyl]amine) and three-
coordinate monomeric, Au(NP3)X, X = PF6−,NO3−, species
with the geometries trigonal planar or distorted tetrahedral and
−
counteranions influencing the optical properties. Thus, the BPh4−
−
and PF6 salts exhibit yellow luminescence whereas the NO3
salt gives a blue luminescence. The luminescence disappears for
Au(NP3)X at room temperature when Au(I) is replaced by Ag(I).18a
Likewise, the first prepared sigma-bonded gold(I) polymers con-
taining only phosphorus-donor ligands correspond to strongly
luminescent three-coordinate gold(I) species with one-dimensional
and two-dimensional structures.18b However, the compound
[Au(dcpe)2](PF6) (dcpe = 1,2-Bis(dicylohexylphosphino)ethane)
with an approximately tetrahedral AuP4 structure is nonemissive
(solution or solid) while [Au2(dcpe)2](PF6)2 with AuP3 units shows
emission as a solid at 77 K but not at room temperature and
[Au2(dcpe)3](PF6)2, luminescent in the solid state, constituted the
first example of a gold complex, containing an isolated AuP3 unit,
that emits in solution at room temperature. These data indicate
that not only the geometry but also the Au–L bonding and
metal to ligand ratios are key factors in Au(I) photophysics.18c
Finally, Au(I) species of the type [Au(4-R-dppn)2]X (dppn =
1,8-bis(diphenylphosphino)naphthalene; R = H: X = PF6, Cl;
R = Me: X = PF6) are examples of tetrahedral four-coordinate
compounds with a photoluminescent and electroluminescent
behaviour.18d
Gold(I) complexes with a 1:1 metal to ligand ratio. Complexes
2 and 3 are isostructural with 1. These compounds are salts
containing a binuclear cation, [Au2(l-PP3)2]2+, in which each PP3
coordinates through three phosphorus atoms to one gold(I) and
is acting as a bridging ligand through a terminal phosphorus
to the other metal ion. The bridging arms of the PP3 ligands
produce a ten-membered ring that incorporates the two gold ions.
Both golds have nearly tetrahedral AuP4 geometry. The cation
retains its binuclear structure in solution. Two halides act as
counteranions.19,20 A comparable behaviour was observed for the
tripodal ligand CP3 (1,1,1-tris(diphenylphosphinomethyl)ethane),
by interaction with Au(tdg)Cl, giving not a mononuclear neutral
complex but a trinuclear cationic species, [Au3(l-CP3)2Cl2]Cl, with
the cation containing both tetrahedral and linear golds.19a
Gold(I) complexes with a 3:1 metal to ligand ratio. Complexes
10 and 11 are not conductors in DMF. The solids 10–12 decompose
(over 250 ◦C) without melting. The far infrared spectrum of
10 shows a very strong band in agreement with the presence
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Table 1 Conductivities, mass spectra and far infrared data for compounds 1–5 and 10–16
MS(L-SIMS)/ESI-MS(+)* m/z (%
Compound
K(DMF)/X−1 cm2 mol−1
abundance)
IR (M–X)# m max/cm−1
(1)·2CH2Cl2
131.8
132.6
1522a (8%), 867b(100%)
2
1522a(12%), 867b(100%)
1522a(12%), 867b(100%)
1344a(31%), 779*b(100%)
779 (12%)
3
(4) CH2Cl2
165.7
87.0
4.9
1383 vs
185 s
324 vs
233 s, 217 m, 206 m
174 vs, 165 sh
1488 m, 1360 s, 1384 vs, 1280 s, 1026 w, 992 w
324 vs
(5)·0.5CH2Cl2
(10)·3CH2Cl2
1331c(11.4%), 1134d(7.2%), 1099e(9%)
1695f(2%), 1419g(3%), 1143h(4%)
1839f(10%), 1515g(4%), 1191h(6%)
950e(26%), 888i(100%)
11
12
13
14
9.4
101.1
3.3
1563c(8%), 1331e(21.6%), 1134j(5.1%),
1099k (6.8%)
15
16
4.2
3.7
232 vs, 219 vs, 207 s
174 vs, 168 sh, 150 w
M+ = Molecular ion, #(M = Au, Ag; X = Cl, NO3):a (M+ − 2X − C2H4PPh2). b (M+− 2X − PP3 − M). c (M+ − X). d (M+ − X − M). e (M+ − 2X − M).
f (M+ − 3X − PP3− 2M). g (M+ − 4X − PP3 − 3M). h (M+ − 5X − PP3 − 4M). i (M+ − 3X − M). j (M+ − 2X − 2M). k (M+ − 3X − 2M).
1
Table 2 31P-{ H}NMR data (r.t.) for complexes 1–5, 10–16 and for titrations of 13 and 15 with PP3
Compound
dPa
J(P–P)
Solvent
(1)·2CH2Cl2
31.9(m)[2P], 24.6(m)[2P], 12.9(m)[4P]
34.0(m)[2P], 26.6(m)[2P], 15.0(m)[4P]
33.9(m)[2P], 25.7(m)[2P], 15.2(m)[4P]
15.2(br,d)[2P], 8.0(br,d)b [1P],−0.2(dm)[4P], −4.7(br,d)[1P]
14.6(dd)[2P], 8.2(br)[1P], −0.3(dm)[4P], −4.8(br)[1P]
15.1(dm)[2P], 0.6(dm)[4P]
−3.8(br)[4P]
132, 71, 61
132, 72, 60
132, 71, 62
CDCl3
CD2Cl2
CD2Cl2
CD2Cl2
CD2Cl2
CDCl3 + CD3OD
CDCl3
CD2Cl2
DMSO-d6
2
3
(4)·CH2Cl2
c
(4)·CH2Cl2
(4)·CH2Cl2
d
(5)·0.5CH2Cl2
c
(5)·0.5CH2Cl2
15.9(d)[1P], 10.0(d)[1P], −0.5(br)[2P]
6 + 14
(10)·3CH2Cl2
6
49.7(br)[1PA], 34.9(d)·[2PC], 33.0(br,d)[1PB]
36.9(q)*[1PA], 34.1(d)*[3PB]
7 + 15
152·
14
59*
11
CDCl3
CDCl3
7
50.5(br)[1PA], 40.0(br,d)·[2PC], 31.0(br)[1PB]
38.9(s)[3PB], 31.0(br,m)[1PA]
8 + 16
158·
15
12
8
50.0(br)[1PA], 43.9(br)[2PC], 34.1(br)[1PB]
38.2(d)*[3PB], 34.1(br)[1PA]
7.4(br)[4P]
16
55*
13
CDCl3 + DMF
CD2Cl2 + DMF
CDCl3 + DMF
DMSO-d6
CD2Cl2
CDCl3 + DMF
13c
10.4(br,d)[2P], 7.6(br,d)[2P]
31.5(m)[1PA], 29.3(m)[3PB]
36.8(q)[1PA], 35.7(d) [3PB]
35.3(d)[3PB], 33.8(m)[1PA]
4 + 9
53
58
48
43
14
15
16
13 + 1 eq. PP3
4
9
12.1(br)[2P], −2.7(br)[4P]
8.1(br)[4P]
d
13 + 2 eq. PP3
15 + 1 eq. PP3
12.5(dm)[2P], −3.0(dm)[4P] (4)
7 + 2
CDCl3 + DMF
CDCl3 + DMSO-d6
7
2
47.0(br)[1PA], 45.1(br,m)[2PC], 33.5(br)[1PB]
38.0(m)[2P], 28.5(m)[2P], 18.7(m)[4P]
37.9(m)[2P], 28.4(m)[2P], 18.6(m)[4P] (2)
169
131, 70, 61
132, 70, 60
15 + 2 eq. PP3
CDCl3 + DMSO-d6
a [nP] = relative intensities. b 1J(31P,107/109Ag) = 376/433 Hz. c 1J(31P,107/109Ag): 343/395 and 194/223 Hz (4, 253 K, d 14.6 dd and −0.3 dm, respectively),
402 (av.) and 395 (av.) Hz. (5, 233 K, d 15.9 d and 10.0 d, resp.), 752 (av.) and 512 (av.) Hz (13, 253K, d 10.4 br and 7.6, resp.). d 356/410 and 199/229 Hz
(4, 298 K, d 15.1 dm and 0.6 dm, resp.), 340/391 and 190/219 Hz (13 + 2 eq. PP3, d 12.5 dm and −3.0 dm, resp.).
of equivalent terminal Au–Cl bonds as expected for a struc-
ture containing three linear PAuCl fragments involving terminal
phosphorus.19a The most abundant peak at highest m/z of 10
can be assigned to a fragmentation of a monomeric species, by
loss of one halogen. The three and two bands assigned to the
m(Au–X) vibrations of 11 and 12, respectively are indicative of
non-equivalent terminal Au–X bonds. The peaks at highest m/z
for 11 and 12 correspond to tetranuclear fragments, Au4(PP3)X3.
On this basis, complex 10 is apparently a monomer while 11 and
1
12 could be dimers. However, the 31P{ H}NMR spectra of the
three complexes show a similar dissociative behaviour in solution
compatible with a dimeric structure as shown in Scheme 1. Indeed,
the high number of resonances found in the spectrum of 10,
recorded in a coordinating solvent as DMSO-d6, is in agreement
with a mixture of species. The quartet at d 36.9 and the resonance
at d 34.1 (Fig. 1), with approximately relative intensities 1:3 and
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1
31P{ H}NMR spectra of 11 and 12, recorded in CDCl3, are also
consistent with the presence of mixtures of 7 + 15 and 8 + 16,
respectively. The peaks assigned to the apical phosphorus of 15
and 16 appear now at higher field than those corresponding to the
terminal ones [d 38.9(11), 38.2 (12)] and are overlapped with the
signals at d 31.0 and 34.1 due to complexes 7 and 8, respectively.
The preparation of crystals of 15 starting from solutions of 11
in DMF/Et2O (eqn (1)) is another evidence of this dissociative
process in solution.
According to Scheme 1 the dissolution of 11 would involve
a ring-opening process that converts the two vulnerable three
coordinate golds into two linear P–Au–Br moieties leading to com-
plex 15 and leaving one (PP3)Au2Br2 fragment that contains two
uncoordinated phosphorus and two linear golds. This produces
the lone pair cession of the two uncoordinated phosphorus to one
linear gold affording complex 7. It seems that complexes 10–12
do not exist in solution as individual species and the differences
observed between 10 and 11–12 could arise from a different form
of supramolecular aggregation of the solids. If the solids are
formed by aggregates of compounds with 2:1 and 4:1 metal to
ligand ratios, we suppose for 10 a form of aggregation that retains
the shortest intermolecular contacts of 1419c and joins aurophilic
interactions involving the linear fragment of 6. Likewise, for
11–12 the supramolecular arrangement would include aurophilic
contacts due to 15 and 16 (vide infra) and those involving linear
PAuX fragments of complexes 7 and 8, respectively.
Scheme 1 Complexes 10–12 as precursors of compounds 6–8 and 14–16.
Gold(I) complexes with a 4:1 metal to ligand ratio. Complexes
14–16 are neutral species in DMF. The peak at highest m/z value in
the LSI mass spectrum of 14 corresponds to the loss of one halogen
from the molecular ion. The bands observed in the far infrared
spectrum of 14–16 are consistent with the presence of terminal M–
1
X bonds.23 The 31P{ H}NMR spectrum consisting of two signals
with relative intensities 1:3 (A:B) (vide infra) and the phosphorus
coupling constants JAB ranging from 58 to 43 Hz support the
structures shown in Scheme 1. It should be noted that solutions
in CD2Cl2 of the iodo derivative 16 exhibit an inversion of the
resonances due to the apical (d 33.8) and terminal phosphorus (d
35.3) compared to complexes 14 (CDCl3 + DMF) and 15 (DMSO-
d6) with the different coordination ability of the solvents being
probably the reason of this fact. This inversion (just found for
solutions of 11 and 12 in CDCl3) was also previously observed for
14 in CDCl3.19c
Crystallography of 14–16. The structure proposed in solution
for complex 14 coincides with that one found in the solid state by
X-ray diffraction.19c
In this work we afforded crystals of (15)·2H2O and (16)·2DMSO
that were studied by X-ray crystallography.† Single crystals of
(15)·2H2O were obtained by slow evaporation of a DMF/Et2O
solution of 11 (vide supra) while crystals of (16)·2DMSO appeared
by recrystallization from solutions of 16 in DMSO. Perspective
views of the molecular structures and numbering schemes are
shown in Fig. 2 and 3. Crystallographic data are given in Table 3
and selected bond lengths and angles are listed in Table 4.
In both cases the asymmetric units are made up of neutral
tetranuclear complexes where four Au–X moieties are bridged by
1
Fig. 1 31P-{ H} NMR spectrum at room temperature for (10)·3CH2Cl2
in DMSO-d6 affording a mixture of 6 (●) and 14 (*).
coupling constants between phosphorus JAB of 59 Hz (vide infra),
seem to correspond to complex 14 while the signals at d 34.9 and
33.0 with relative intensities 2:1 and JAC of 152 Hz are assigned to
complex 6. The broad signal of 6 at d 49.7 (Table 2) is not shown
in Fig. 1. Thus, solutions of complex 10 in DMSO appear to give
a mixture of compounds 14 and 6. The signals observed in the
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Table 3 Summary of crystal parameters, data collection and refinement for (15)·2H2O and (16)·2DMSO
Complex
(15)·2H2O
(16)·2DMSO
Empirical formula
Formula weight
Temperature/K
C42H46P4Br4O2Au4
1810.14
293(2)
C92H108P8I8O4S4Au8
4244.72
293(2)
˚
Wavelength/A
0.71073
0.71073
Crystal size/mm
Color/habit
0.28 × 0.09 × 0.08
Colorless/prisms
Monoclinic
C2/c
25.795(9)
24.108(9)
20.483(7)
90
0.24 × 0.07 × 0.06
Yellow/needles
Monoclinic
C2/c
25.449(5)
23.715(5)
20.506(5)
90
Crystal system
Space group
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
113.905(6)
90
11645(7)
112.735(5)
90
11414(4)
3
˚
Volume/A
Z
8
4
Calculated density/Mg m−3
Absorption coefficient/mm−1
F(000)
2.065
12.930
6608
1.21 to 22.32
−27 ≤ h ≤ 25
0 ≤ k ≤ 25
0 ≤ l ≤ 21
29264
2.470
12.633
7728
1.22 to 24.72
−29 ≤ h ≤ 27
0 ≤ k ≤ 27
0 ≤ l ≤ 24
30837
h range for data collection/◦
Index ranges
Reflections collected
Independent reflections
Max. and min. transmission
Data/restraints/parameters
Goodness of fit on F2
7282 [Rint = 0.0738]
0.4244 and 0.1225
7282/42/439
0.966
R1 = 0.0572
wR2 = 0.1940
1.903 and −2.623
9967 [Rint = 0.0715]
0.5178 and 0.1515
9711/0/520
1.018
R1 = 0.0812
wR2 = 0.2345
4.268 and −4.104
Final R indices [I > 2r(I)]
−3
˚
Largest diff. peak and hole/e A
nearly linear P–Au–fragments,10b,19a,24,25e very close to those found
for 1419c and shorter upon reduction of the coordination number
than the average Au–P distances found for 1.19 These Au–P
bond lenghts are also shorter, as expected,7 than the average of
the Ag–P distances observed for the infinite chain structures of
Table 4 Selected distances (A), aurophilic contacts (A) and angles (◦)
for complexes (15)·2H2O and (16)·2DMSO
a
˚
˚
Complex
(15)·2H2O
(16)·2DMSO
Au(1)–P(1)
Au(2)–P(2)
Au(22)–P(2)
Au(3)–P(3)
Au(4)–P(4)
Au(1)–X(1)
2.242(6)
2.152(2)
2.409(2)
2.223(8)
2.240(7)
2.418(3)
2.391(2)
2.378(9)
2.399(4)
2.412(3)
3.270(2)
172.4(2)
172.5(8)
177.1(5)
179.4(2)
175.4(2)
2.236(7)
2.242(8)
Ag2(CP3)X2 (CP3 = 1,1,1-tris(diohenylphosphinomethyl)ethane;
19b
˚
˚
˚
X = Cl: 2.443(3) A, X = Br: 2.458(11) A, X = I: 2.503(7) A)
2.236(7)
2.255(7)
2.427(3)
2.400(6)
˚
The shortest Au–P distance for 15 (2.152(2) A) corresponds to
Au(2)–P(2) while for 16 the Au(1)–P(1) and Au(3)–P(3) distances
˚
˚
Au(2)–X(2)
are slightly shorter (2.236(7) A) than Au(2)–P(2) (2.242(8) A) and
Au(22)–Br(22)b
Au(3)–X(3)
˚
Au(4)–P(4) (2.255(7) A).
The average for Au–Br distances in 15 (2.400(5) A) is within
2.294(3)
2.410(3)
3.184(2)
172.2(2)
171.4(4)
˚
Au(4)–X(4)
Au(1)–Au(4_7)a
P(1)–Au(1)–X(1)
P(2)–Au(2)–X(2)
P(2)–Au(22)–Br(22)
P(3)–Au(3)–X(3)
P(4)–Au(4)–X(4)
the expected values for this type of bonds in linear P–Au–Br
˚
moieties with the shortest bond lengths (2.391 A) corresponding
˚
to Au(2)–Br(2). However, the average for Au–I (2.408(4) A, 16)
bonds is smaller than in other trigold complexes containing
triphosphines19a,24,25a with the shortest distance (2.294(3) A) in-
˚
179.2(2)
174.7(2)
volving Au(3) and I(3). The close to linear X–Au–P arrange-
ments [av. 175.4(3)◦ (15), 174.4(2)◦ (16)] are◦in accordance with
those observed in Au3(l-CP3)Br3 (173.1(1) ),19a Au3(l-tppm)I3
[tppm = tris(diphenylphosphino)methane, 168.3(1)◦]24 or Au3(l-
CP3)I3 (174.5(3)◦).
a Aurophilic contacts (PA = apical phosphorus, PB = terminal phosphorus)
A
B
˚
for: (14)·2.8CH2Cl2·Et2O [Au(P )–Au(P ) = 3.061 A (intermolecular
B
B
˚
interaction involving one asymmetric unit), Au(P )–Au(P ) = 3.140 A
(intermolecular interaction involving two different asymmetric units)];
(15)·3H2O and (16)·2DMSO involving Au(PA)–Au(PB) between two
symmetry-related molecules. b Au(22) and Br(22) are disordered atoms.
An interesting feature of these structures is the presence of
pairs of symmetry-related molecules with each one belonging to
a different asymmetric unit. This contrast to the structure of 14
previously reported19c that showed an asymmetric unit containing
two molecules. The AuX moieties bridged by the apical and
one dangling phosphorus of each component [Au(1)–Au(4_7)
the tetraphosphine generating nearly linear P–Au–X arrangements
in agreement with the structures proposed in solution.
˚
˚
The averages of the Au–P [2.253(9) A (15); 2.242(7) A (16)]
bond lenghts are in the expected range for compounds containing
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Fig. 3 Perspective view of two symmetry-related molecules for complex
16 showing short Au(1)–Au(4_7) and Au(4)–Au(1_7) contacts. The
symmetry generations of atoms are labelled with _7s. Phenyl rings were
omitted for clarity.
Fig. 2 Perspective view of two symmetry-related molecules for complex
15 showing short Au(1)–Au(4_7) and Au(4)–Au(1_7) contacts. The
symmetry generations of atoms are labelled with _7s. Phenyl rings were
omitted for clarity.
25c
˚
for Au3(l-CP3)Cl3 (3.091 A) and [Au4(l-dpmp)2Cl2](CF3SO3)2
22b
˚
(3.103(2), 3.106(2) A).
Thus, the crystal structures of 15 and 16 constitute a new
example of supramolecular aggregation compared with 14 and
other gold(I) compounds containing tripodal ligands of the type
Au4(l-PP3)(SR)4 (RS = quinoline-2-thiolate) or Au3LX3 (L = NP3,
CP3; X = Cl, Br, I) reflecting the influence of the halogen. Crystals
of Au3(l-NP3)X3 (X = Cl, Br)25a are aggregated into layers with
the shortest intermolecular distances corresponding to Au · · · X
instead of Au · · · Au contacts while the molecules of Au3(l-NP3)I3
are linked up through close Au · · · Au interactions involving two
of the three P–Au–I linear fragments. However, complexes Au4(l-
PP3)(SR)4 and Au3(l-CP3)X3 (X = Cl, I) do not show aggregation,
exibiting only intramolecular gold-gold bonds, and the crystals
of Au3(l-CP3)Br3 are made up of dimeric aggregates with all
phosphorus atoms involved in aurophilic (one inter- and two intra-
molecular) contacts.19a,25c,d
and Au(1_7)–Au(4)] of these dimeric aggregates are crossed
˚
giving close intermolecular Au · · · Au contacts of 3.270(2) A for
˚
15 and 3.184(2) A for 16. A third PAuX fragment of each
molecule is relatively close to the aurophilic region without
˚
affording short contacts (3.914 A for 16). The fourth arm of
each phosphine attached to the Au(2)–X(2) or Au(2_7)–X(2_7)
fragment is totally out of the clustering pattern excluding any
participation in aurophilic interactions. The gold-gold contacts26
are slightly longer than those found between molecules for 1419c
involving gold atoms bound to one apical and one terminal
˚
phosphorus in the same dimeric asymmetric unit [3.061(5) A] and
to terminal phosphorus of molecules belonging to different asym-
˚
metric units [3.140(5) A] (Table 4). The interactions are also longer
˚
˚
than the intermolecular attractions of 3.048 A and 3.107(7) A
found for complexes Au3(l-tripod)Br3 and Au3(l-CP3)Br3,25a
19a
respectively although shorter than the intramolecular distances
observed in the trinuclear derivative [Au3(l-dpmp)Cl3] (dpmp =
Transition from high to low metal to ligand ratios
10b
˚
bis(diphenylphosphinomethyl)phenylphosphine) (3.3709(4) A)
or in [Au2(l-dppm)Cl2] [dppm = bis(diphenylphosphino)methane,
It is known that the binuclear cation of complex 1 is resistant
to reaction with the nucleofile azide and thiocyanate but reacts
readily with Me2SAuCl to form the neutral compound 14 via a
ring-opening process.19c
3.351(2) A].25b All intramolecular gold-gold separations for 14–16
˚
˚
(5–12 A) correspond to non-bonded Au · · · Au distances in con-
trast with the short intramolecular aurophilic contacts observed
2638 | Dalton Trans., 2008, 2633–2642
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In this work we report the reactivity versus PP3 of the complexes
1
15 and 13, followed by 31P{ H}NMR, to give the ionic species 2
and 4, respectively (Table 2).
When complex 15 reacts in CDCl3/DMSO-d6 with one equiv-
alent of PP3 there appear six resonances assigned to a mixture of
compounds 2 and 7. The signal at d 45.1 that allows a coupling
constant between phosphorus JAC of 169 Hz is attributable,
together with the resonances at d 47.0 and 33.5, to complex 7
while the remaining multiplets correspond to complex 2 (eqn (2)).
It should be noted that the reaction occurs in a 2:2 stoichiometric
ratio instead of the expected 1:1 ratio to give complex 7 (Au4(l-
PP3)Br4 + PP3 → 2 Au2(l-PP3)Br2). With the second addition of
ligand the signals due to 7 disappear (eqn (3)).
Fig. 4 77 K solid-state excitation and emission spectra of the tetraphos-
phine (-·--·-) and complexes 1 (---) and 2 ( · · · ) and 3 ( ), using a 1%
intensity atenuator.
Therefore, the conversion of the stoichiometry 4:1 into 1:1 by
interaction of 15 with PP3 takes place previous formation of 7
(2:1) seeming to confirm the non-existence of complex 11 (3:1
stoichiometry) in solution (vide supra). Subsequent additions of
phosphine lead to the presence of 2, as predominant species,
in coexistence with free and oxidized PP3 and a new complex
(detected by ESI-MS) corresponding to a 1:2 gold to phosphine
ratio.
A similar behaviour was observed for 13 in CDCl3/DMF. The
first equivalent of ligand seems to give a mixture of 4 and 9 (Ag2(l-
PP3)(NO3)2) and with the second addition of PP3 complex 4 is the
only species formed. Subsequent additions of PP3 give complex 4
in coexistence with free and oxidized phosphine.
Photoluminescence studies
In order to investigate the correlation between structures and
visible light emission upon UV excitation the solid-state, emission
and excitation spectra at 298 and 77 K for the isolated complexes
and the tetraphosphine have been determined, and the results are
summarized in Table 5 and Figs. 4 and 5. The emission of PP3
at room and low temperatures in the visible range, that occurs at
higher energies than in complexes, can be related to p–p* phenyl
Fig. 5 Solid-state excitation and emission spectra of the tetraphosphine
(-·--·-) and complexes 15 (---) and 16 ( ) at 77 K.
ring transitions as observed for the linear triphosphine bis(2-
diphenylphosphinoethyl)phenylphosphine (P3).22a For complexes
the luminescence arises from the ligands, the geometry to the metal
centre or the presence of intermetallic interactions.
Table 5 Emission and excitation maxima (in nm) measured for the tetraphosphine and complexes 1–5, 10–12 and 15–16 in the solid state at 298 and
77 K
Complex
Excitation 298 K
Emission 298 K
Excitation 77 K
Emission 77 K
PP3
275–300
385
280–340
342
—
—
352
379
324; 368
423
518
527
475 (sh); 513
—
—
250–300
354
280–325
280–325
310
280–322
333
354
423
504
495
455
482
444
469
495
(1)·2CH2Cl2
2
3
(4)·CH2Cl2
(5)·0.5CH2Cl2
(10)·3CH2Cl2
11
482; ∼530 (sh)
506
537
12
330; 375
341
362
563
460 (sh); 562
509
15
16
310–360; 380
—
521; ∼580 (sh)
—
354
473
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25f
While Au(I) complexes (excluding 16 that emits only at room
temperature) are luminescent both at room and low temperatures,
compounds containing Ag(I), harder than Au(I), only luminesce
at 77 K. The Au(I) compounds here reported are luminescent in
all stoichiometries studied, however the only Ag(I) luminescent
complexes were those corresponding to a 1:1 metal to ligand
ratio at 77 K. For gold(I) luminescence increases with increasing
the phosphine/metal ratio. On the contrary, the gold(I) com-
plexes containing isolated AuP3 units and the ligand dcpe =
1,2-Bis(dicyclohexylphosphino)ethane are emissive, in the solid
state, for a 1:1 ([Au2(dcpe)2](PF6)2) and 3:2 ([Au2(dcpe)3](PF6)2
phosphine/metal ratio and nonemissive in case of a 2:1 ra-
tio ([Au(dcpe)2](PF6).18c According to the structures shown in
Scheme 1 the only difference between complexes 1–3 seem to
come from the counteranions with the emission energy at 77 K
increasing from Cl to Br to I (Fig. 4). At room temperature
the emission energy decreases from Cl to Br, increases from Br
to I and is accompanied with a shoulder at 475 nm for 3. This
significant effect of the counterion on the solid state emission of
binuclear gold(I) phosphine complexes was previously reported.15a
It was found a correlation between emission and the distance
of the negative charge from the Au atoms, resulting that the
emission band red-shifts as the distance decreases. For 1–3 at
77 K it seems that the distance increases going down on the
halogens group. On the other hand, taking into account the large
Au · · · Au intermolecular distance found by X-ray diffraction for
containing gold(I) chains in [Au(S2CN(C5H11)2)]2 with complex
12 exhibiting two emission and excitation spectra at 77 K.
Conclusions
By synthetic control of the stoichiometry it was possible to prepare
the series of gold(I) complexes [Au2(l-PP3)2]X2, Aun(l-PP3)Xn (n =
3, 4) X = Cl, Br, I and silver(I) [Ag2(l-PP3)2](NO3)2, Ag(PP3)Cl,
Ag3(l-PP3)(NO3)3. The gold(I) complexes in a 1:1 stoichiometric
ratio are binuclear ionic systems with AuP4 tetrahedral arrange-
ments to the metal. The structural data for the silver(I) compound
in a 1:1 ratio indicate the existence as a ionic system that consists
of dications [Ag2(l-PP3)2]2+ with three- and four-coordination to
−
the metal and NO3 counterions. Complexes prepared in 3:1 and
4:1 metal to ligand ratios are neutral species. The solutions of
gold(I) complexes with a 3:1 stoichiometry behave as mixtures
of compounds with a 2:1 and 4:1 gold to phosphine ratio. The
complexes Au4(l-PP3)Br4 and Ag3(l-PP3)(NO3)3 react in solution
with two equivalents of PP3 to form the salts [Au2(l-PP3)2]Br2
and [Ag2(l-PP3)2](NO3)2, respectively. Gold(I) adopts a nearly
linear geometry in all complexes prepared with a 4:1 metal to
ligand ratio. The phosphine, the silver(I) complexes with 1:1
stoichiometry and most of the gold systems are luminescent in the
solid state. The luminescence found in Au4(l-PP3)X4 (X = Br, I)
whose X-ray crystal structure confirm the presence of linear PAuX
fragments is attributable to the type of metallophilic interactions.
The structures consists of an unusual type of dimeric aggregates,
via close aurophilic contacts, that differs from the supramolecular
architecture found for Au4(l-PP3)Cl4, a nonemissive complex.
However, the stronger emission observed for complexes [Au2(l-
PP3)2]X2 (X = Cl, Br, I) with tetrahedral gold(I) and without
aurophilic contacts seem to arise from the phosphine ligand
modified by the metal centre.
˚
complex 1 (6.175 A) the emission maxima of complexes 1–3 (with
AuP4 arrangements) could be attributed to a phosphine transition
modified by the gold(I) centre, as described for other tetrahedral
four-coordinate gold(I) complexes.3b Complex 4, containing three
and four-coordinate Ag(I) and nitrate as counterion, gives a
weaker emission compared to 1–3 and at higher energy than
complexes 1 and 2 with chloro and bromo counterions, respec-
tively. The silver chloro complex 5 emits at higher energy than the
nitrate, 4.
Likewise, systematic changes occur with variation of the halide
ligand X in gold(I) compounds showing metal/ligand ratios from
3 to 4. The emission energies decrease from Cl to Br to I in
complexes with 3:1 gold to phosphine ratios and increase in those
with a 4:1 ratio (Fig. 5). The only nonemissive gold(I) system was
the chloro complex Au4(l-PP3)Cl4 (14). Thus the supramolecular
arrangement of the solids (14–16), with important contribution
of the halides and giving different types of aurophilic interactions
(vide supra), seems to influence their properties.
Experimental
General procedures
Dichloromethane was redistilled under nitrogen over CaCl2.
Gold iodide was purchased from Strem Chemicals, tris[2-
(diphenylphosphino)ethyl]phosphine, silver chloride and 2,2ꢀ-
thiodiethanol from Aldrich, potassium bromide from Panreac,
silver nitrate from Analema and gold metal from S.E.M.P.S.A. Mi-
croanalyses were performed on a Fisons Instrument EA 1108
CHNS-O. Liquid Secondary-Ion Mass Spectra (LSI MS) were ob-
tained in a Micromass Autospec spectrometer using 3-nitrobenzyl
alcohol as the matrix. Infrared spectra were recorded at ambient
temperature as KBr pellets (4000–400 cm−1) and Nujol mulls (500–
100 cm−1) on a Nicolet IMPACT 400 with a DTGS detector
and a Mattson Cygnus 100 spectrophotometer. The bands are
reported as vs = very strong, s = strong, m = medium, sh =
shoulder, a = asymmetric vibration, s = symmetric vibration.
In complexes with a 4:1 metal to ligand ratio the type of
aurophilic Au · · · Au interactions is suggested as the source for
their visible emission that blue-shifts as the halide X is changed
from Br to I, in good agreement with other emitting mononuclear
gold(I) compounds.4d The luminescence disappears if gold(I) is
replaced by other metals as Pd(II) or Pt(II) affording heteronuclear
systems [MAu(PP3)X2]X and MAu2(PP3)X4 (M = Pd, Pt; X =
Cl, Br, I) with linear PAuX arrangements and distorted square-
planar M(II) centres.19d The opposite red-shifts observed for
emissions of complexes with a 3:1 gold to phosphine ratio
(10–12) could be attributed to the presence of not only linear
geometries for gold(I) according to the structures proposed. The
wavelength-dependent emission spectra observed for 10–12 at low
temperature are in agreement with those previously found for
31P { H} NMR spectra and the 109Ag NMR spectrum were
1
recorded on a Bruker AMX500 spectrometer at 202.46 MHz and
23.31 MHz, respectively. Chemical shifts are reported relative to
external standard 85% H3PO4 (31P) and a saturated solution of
AgNO3 in D2O (109Ag); d = chemical shift in ppm; s = singlet, d =
doublet, dd = doublet of doublets, dm = doublet of multiplets,
m = multiplet, br = broad signal; J = coupling constant in hertzs.
10b
[Au3(l-dpmp)(l-S2CN(CH2Ph)2)Cl]CF3SO3 and for aggregates
2640 | Dalton Trans., 2008, 2633–2642
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Conductivities were measured at 25 ◦C using 10−3 M solutions in
DMF on a WTW model LF-3 instrument. Emission and excitation
spectra were measured in the solid state as finely pulverized KBr
mixtures at room temperature and 77 K with a Perkin-Elmer LS-
50B spectrofluorometer and using a 1% intensity atenuator when
required.
Titrations of complexes 13 and 15 with PP3. To a solution of
13 and 15 in DMF and DMSO-d6, respectively, solutions of PP3 in
1
CDCl3 were added in different stoichiometric ratios. The 31P-{ H}
NMR spectra were recorded after each addition. The results are
given in Table 2.
Crystal structure determination of 15 and 16. Colorless prisms
of (15)·2H2O and yellow needles of (16)·2DMSO were mounted
on glass fibers and used for data collection. Crystals data were col-
lected at 293(2) K, using a BRUKER SMART CCD 1000 diffrac-
tometer. Graphite monochromated MoKa radiation was used
throughout. The data were processed with SAINT27 and empirical
absorption correction was made using SADABS.28 The structures
were solved by direct methods using the program SIR-9229 and
refined by full-matrix least-squares techniques against F2 using
SHELXL-97.30 Positional and anisotropic atomic displacement
parameters were refined for all non-hydrogen atoms. Hydrogen
atoms were placed geometrically and positional parameters were
refined using a riding model. Hydrogen atoms of water molecules
were not placed for (15)·2H2O and the oxygens were refined at
partial occupancy of 60/40% for O(1 W)/O(3 W) and 70/30%
for O(2 W)/O(4 W), respectively. One of the gold and one of the
bromine atoms of complex (15)·2H2O are subjected to a two-fold
disorder, the atoms Au(2), Au(22), Br(2) and Br(22) were refined
with a half occupancy factor. Moreover, in both structures some of
the phenyl rings were fitted as regular hexagons. Atomic scattering
factors were obtained with the use of International Tables for
X-ray Crystallography.31 Molecular graphics were obtained from
ORTEP-3 for Windows.32
Preparations and titrations. Preparation of Au(tdg)Cl
Solutions of Au(tdg)X were prepared in situ following the proce-
dures previously described.26
Preparation of [Au2(l-PP3)2]X2 [X = Br (2), I (3)]. Solutions of
Au(tdg)X (0.087 g, 0.443 mmol in Et2O, X = Br) or AuI as solid
(0.111 g, 0.347 mmol) were added to a solution of PP3 (0.297 g,
0.443 mmol for X = Br; 0.233 g, 0.347 mmol for X = I) in dry
CH2Cl2 (10–20 mL). The resultant mixtures were stirred for ∼24 h
at room temperature (when X = I in an ice bath). After that
solvents were partially removed in vacuo to leave precipitates that
were treated with H2O (X = Br) or Et2O (X = I). The final solids
were filtered off and dried in vacuo. K(DMF), MS and IR data are
1
shown in Table 1 and the 31P { H} NMR resonances are given in
Table 2. 2: Yield: 60%. Color: white, mp 160 ◦C. Found: C, 52.8;
H, 4.5. C84H84P8Au2Br2 requires: C, 53.2; H, 4.5. 3: Yield: 45%.
◦
Color: white, mp 271 C. Found: C, 50.3; H, 4.3. C84H84P8Au2I2
requires: C, 50.7; H, 4.2.
Preparation of Au3(l-PP3)X3 [X = Cl (10), Br(11), I(12)].
Solutions of Au(tdg)X (0.203 g, 1.029 mmol in MeOH, X = Cl;
0.149 g, 0.756 mmol in Et2O, X = Br) or AuI as solid (0.228 g,
0.703 mmol) were added to a solution of PP3 (0.230 g, 0.343 mmol
for X = Cl; 0.169 g, 0.252 mmol for X = Br; 0.157 g and 0.235 mmol
for X = I) in dry CH2Cl2 (12–15 mL). Precipitates were obtained
after stirring the reaction mixtures for 24 h at room temperature
(when X = I in an ice bath). Unreacted AuI was removed by
decantation and in this case Et2O was added for precipitation. The
solids were filtered off and 10 and 11 were stirred with H2O. Final
products were filtered off and dried in vacuo. K(DMF), MS and
Acknowledgements
We thank the Xunta de Galicia (Spain), the University of Santiago
de Compostela (grant for M.I.G.S.) and the Direccio´n General
de Investigacio´n Cient´ıfica y Te´cnica (project BQU2001-2409-
C02-01) for financial support, M. Garc´ıa Varela (University of
Santiago de Compostela) for her collaboration affording crystals
of one compound and the Unidade de Raios X (RIAIDT) of
the University of Santiago de Compostela for the performance of
intensity measurements of crystals for complexes 15 and 16.
1
IR data are shown in Table 1 and the 31P { H} NMR resonances
are given in Table 2. (10)·3CH2Cl2: Yield: 60%. Color: white, mp
265 ◦C (dec). Found: C, 33.6; H, 3.1. C45H48P4Au3Cl9 requires:
C, 33.3; H, 3.0. 11: Yield: 85%. Color: white, mp 253 ◦C (dec).
Found: C, 33.1; H, 2.9. C84H84P8Au6Br6 requires: C, 33.6; H, 2.8.
12: Yield: 77%. Color: grey, mp 285 ◦C (dec). Found: C, 30.6; H,
2.8. C84H84P8Au6I6 requires: C, 30.7; H, 2.6.
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Preparation of Au4(l-PP3)X4 [Br (15), I(16)]. Solutions of
Au(tdg)X (0.314 g, 1.596 mmol in Et2O, X = Br) or AuI as solid
(0.198 g, 0.612 mmol) were added to a solution of PP3 (0.268 g,
0.399 mmol, X = Br; 0.103 g, 0.153 mmol, X = I) in dry CH2Cl2
(10–15 mL). The reaction mixtures were stirred (for 24 h, X = Br;
30 min, X = I) at room temperature (when X = I in an ice bath).
The solvents were removed in vacuo for X = Br and Et2O was added
for precipitation when X = I. Solids were treated with H2O, filtered
off and dried in vacuo. K(DMF), MS and IR data are shown in
1
Table 1 and the 31P { H} NMR resonances are given in Table 2. 15:
Yield: 30%. Color: white, mp 257 ◦C (dec). Found: C, 28.8; H, 2.7.
C42H42P4Au4Br4 requires: C, 28.3; H, 2.4. 16: Yield: 60%. Color:
white, mp 280 ◦C (dec). Found: C, 26.0; H, 2.2. C42H42P4Au4I4
requires: C, 25.6; H, 2.1.
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2642 | Dalton Trans., 2008, 2633–2642
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