Synthesis, spectroscopy and crystal structures of [Au2{μ-Ph2PN(Et)PPh2}2][SbF 6]2 and [Au3Cl2{μ-Ph2PN(Et)PPh2} 2]PF6

Article abstract of DOI:10.1016/S0277-5387(98)00130-2

Treatment of [Au(MeCN)₂]SbF₆ in acetonitrile with bis(diphenylphosphino)ethylamine (dppa) afforded a colourless crystalline material characterised as [Au₂(μ-dppa)₂] [SbF₆]₂. An X-ray diffraction study confirmed that the two ligands bridge the two gold atoms with a Au...Au separation of 2.838(2) A. The electronic absorption spectrum exhibits a band at 298 nm (∈_max, ca. 17000 dm³mol^-1cm^-1) attributable to a p_σ?d_σ* transition. The compound luminesces strongly in acetonitrile (λ_max = 500 nm). Treatment of HAuCl₄.2H₂O with 2,2′-thioethanol in methanol followed by the ligand afforded a colourless crystalline material characterised as [Au₃Cl₂(μ-dppa)₂]PF₆. A crystal structure determination revealed a cation of C₂ symmetry, comprising a bent chain of three gold atoms (Au...Au...Au= 167.5(8)°, Au...Au = 3.037(1)A), with each pair of adjacent gold atoms bridged by a diphosphazane ligand and with the coordination at the outer gold atoms completed by a chloride ligand. This compound luminesces extremely weakly in acetonitrile but does emit strongly at 485 nm when irradiated in the solid state. The luminescence displayed by both compounds is attributed to the presence of a substantial intramolecular interaction between the gold atoms, but ligand effects appear to be more important in determining the emissive energies.

Full text of DOI:10.1016/S0277-5387(98)00130-2

Polyhedron Vol[ 06\ No[ 06\ pp[ 2910Ð2918\ 0887
Þ 0887 Elsevier Science Ltd
Pergamon
All rights reserved[ Printed in Great Britain
9166Ð4276:87 ,08[99¦9[99
\
PII] S9166Ð4276"87#99029Ð1
Synthesis\ spectroscopy and crystal structures
of ðAu1"m!Ph1PN"Et#PPh1#1ŁðSbF5Ł1 and
ðAu2Cl1"m!Ph1PN"Et#PPh1#1ŁPF5ꢀ
John S[ Field\a\$ Judith Grieve\a Raymond J[ Haines\a Noellene Maya and
Mthembeni M[ Zulub\%
a Department of Chemistry\ University of Natal\ Private Bag X90\ Scottsville\ Pietermaritzburg\
Republic of South Africa 2198
b Department of Chemistry\ University of Zululand\ Private Bag X0990\ Kwadlangezwa\
Republic of South Africa 2775
"Received 13 November 0886^ accepted 18 March 0887#
Abstract*Treatment of ðAu"MeCN#1ŁSbF5 in acetonitrile with bis"diphenylphosphino#ethylamine "dppa#
a}orded a colourless crystalline material characterised as ðAu1"m!dppa#1ŁðSbF5Ł1[ An X!ray di}raction study
Ä
con_rmed that the two ligands bridge the two gold atoms with a Au===Au separation of 1[727"1# A[ The
electronic absorption spectrum exhibits a band at 187 nm "emax\ ca[ 06999 dm2 mol−0 cm−0# attributable to a
psCdsꢀ transition[ The compound luminesces strongly in acetonitrile "lmaxꢁ499 nm#[ Treatment of
HAuCl3[1H1O with 1\1?!thioethanol in methanol followed by the ligand a}orded a colourless crystalline
material characterised as ðAu2Cl1"m!dppa#1ŁPF5[ A crystal structure determination revealed a cation of C1
Ä
symmetry\ comprising a bent chain of three gold atoms "Au===Au===Auꢁ056[4"7#>\ Au===Auꢁ2[926"0# A#\ with
each pair of adjacent gold atoms bridged by a diphosphazane ligand and with the coordination at the outer
gold atoms completed by a chloride ligand[ This compound luminesces extremely weakly in acetonitrile but
does emit strongly at 374 nm when irradiated in the solid state[ The luminescence displayed by both compounds
is attributed to the presence of a substantial intramolecular interaction between the gold atoms\ but ligand
e}ects appear to be more important in determining the emissive energies[ Þ 0887 Elsevier Science Ltd[ All
rights reserved
———————————————————————————————————————————————
Homoleptic digold"I# complexes\ in which the gold room temperature emission spectrum of the BH2CN−
atoms are bridged by two symmetric diphosphine salt has been recorded in the solid state\ since this
ligands and in which each gold atom is two!coor! species decomposes on irradiation in solution^ emis!
dinate\ have been shown to be photoluminescent ð0Ł[ sion occurs at 389 nm in this case ð1\ 4Ł[ In contrast\
mononuclear bisphosphine complexes such as ðAu"P!
Ph2#1ŁBPh3 are not luminescent ð5Ł[ This has led to the
conclusion that the loss of centrosymmetric structure\
brought about by the presence of an Au===Au inter!
action in the dinuclear species\ is in some way respon!
sible for the luminescence displayed by compounds of
this type ð5Ł[ However\ the intermetallic separation
does not appear to play a signi_cant role in deter!
mining the energy of the emission[ For instance\ Fack!
ler et al[ have shown that there is no direct correlation
between the Au===Au separation and the emission
wavelength "recorded in the solid state# for the
following series of luminescent ligand!bridged
digold"I# compounds] ðAu1"m!dppm#1ŁðBH2CNŁ1\
The best studied examples are salts of the dppm
"dppmꢁPh1PCH1PPh1# ligand!bridged digold"I#
cation\ ðAu1"m!dppm#1Ł1¦[ The BF−3 salt is strongly
phosphorescent in acetonitrile solution\ the emission
being observed at 482 nm at room temperature with a
lifetime of 10 ms and a quantum yield of 9[20 ð1Ł[ The
ClO−3 salt also exhibits phosphorescence at room tem!
perature in acetonitrile solution\ but at 469 nm with a
lifetime of 07 ms and a quantum yield of 9[04 ð2\ 3Ł[ The
ꢀ "Dedicated to our friend and colleague\ Jack Lewis\ on
the occasion of his 69th birthday#
$ Author to whom correspondence should be addressed[
% The late[
ðAu1"m!dppm#1ŁCl1\
ðAu"CH1#1PPh1Ł1\
ðn!Bu3NŁ1
2910

2911
J[ S[ Field et al[
ðAu"S1C1C"CN#1#Ł1\ ðAu"CH1P"S#Ph1#Ł1\ and ðAu is to be expected in view of the stronger electron!
"S1CNEt1#Ł1 ð1Ł[ It has been suggested that this lack withdrawing properties of the ethylamino as opposed
of correlation may be as a consequence of the HOMO to the methylene group[ The compound is stable in
having some ligand character and not being a purely the solid state but\ if left to stand in solution in the
metal orbital\ with ligand changes a}ecting the energy presence of oxygen\ it slowly degrades[
of the HOMO\ either directly or indirectly ð1Ł[ This
The procedure used for the preparation of
being the case\ the emissive properties of diphosphine ðAu2Cl1"m!dppa#1ŁPF5 is similar to one of two methods
ligand!bridged digold"I# complexes of the ðAu1"m! employed by Lin et al[ for the preparation of
dppm#1Ł1¦ type may be more the property of the ðAu2Cl1"m!dppm#1ŁCl ð7Ł[ Thus\ the compound is
diphosphine ligand and\ in particular\ of the AuP1 obtained in good yield by reacting HAuCl3[1H1O with
unit rather than of the intergold separation ð0Ł[ The 1\1?!thioethanol in methanol before treating it with a
diphosphazane ligand Ph1PN"Et#PPh1 "dppa# is slight excess of ligand[ Isolation of the compound as
closely related to the dppm ligand\ the only di}erence a colourless microcrystalline solid was achieved by
being the presence of an ethylamino\ rather than a addition of NH3PF5 and crystallisation from the meth!
methylene group\ between the two phosphorus atoms[ anol solution[ Elemental analysis\ the infrared spec!
It was therefore of interest to compare the structure trum recorded as a KBr pellet and the 0H NMR
and emissive properties of the diphosphazane ligand! spectrum are all consistent with the formulation of the
bridged chromophore\ ðAu1"m!dppa#1Ł1¦\ with those compound as ðAu2Cl1"m!dppa#1ŁPF5\ as subsequently
of the ðAu1"m!dppm#1Ł1¦ species[ Accordingly\ the con_rmed by means of a single crystal structure deter!
SbF−5 salt of the ðAu1"m!dppa#1Ł1¦ cation has been mination "see below#[ The 20P"0H# NMR spectrum
synthesised\ its structure determined by means of X! recorded in CD2CN exhibits a well!de_ned AA?BB?
ray di}raction\ and its absorption and emission spec! pattern with the multiplets centred at 092[50 and
tra in acetonitrile recorded[
72[00 ppm[ Such a pattern is also observed for the
Trigold"I# complexes stabilised by bidentate bridg! ðAu2Cl1"m!dppm#1Ł¦ cation in its ðAuCl"C5F4#2Ł− salt
ing ligands have received less attention\ especially with ð6Ł[ On the other hand the 20P"0H# spectrum for the
regard to their photophysical properties[ However\ chloride salt is complicated by an exchange process
the syntheses and crystal structures of the driven by the reaction of the chloride counterion with
ðAuCl"C5F4#2Ł− and chloride salts of the ðAu2Cl1"m! the trinuclear gold cation[ In this case\ a AA?BB?
dppm#1Ł¦ cation have been reported ð6\ 7Ł[ In contrast pattern is only observed in the presence of added
to ðAu1"m!dppm#1Ł1¦\ this cation does not appear to AgBF3\ i[e[\ when the potentially coordinating chlor!
luminesce in solution\ the authors only reporting the ide counterion is replaced by the non!coordinating
existence of an intense emission at 374 nm in the solid tetra~uoroborate anion ð7Ł[ As expected\ the phos!
state for the chloride salt ð7Ł[
phorus atoms in the diphosphazane ligand!bridged
To establish whether ðAu2Cl1"m!dppa#1Ł¦ has simi! trigold cation are deshielded relative to those in the
lar luminescent properties\ its synthesis as the hexa! analogous dppm ligand!bridged species^ Uson et al[
~uorophosphate salt was e}ected and its crystal report an AA?BB? pattern for ðAu2Cl1"m!dppm#1ŁðAu!
structure and emission properties determined[
Cl"C5F4#2Ł with the multiplets centred at 26[0 and
18[9 ppm ð6Ł[ As with the dinuclear diphosphazane
ligand!bridged species\ the trinuclear complex
ðAu2Cl1"m!dppa#1ŁPF5 is stable in the solid state but\
if left to stand in solution in the presence of oxygen\
RESULTS AND DISCUSSION
Treatment of an acetonitrile solution of it slowly degrades[
ðAu"MeCN#1Ł¦ with a molar equivalent of the solid
Ph1PN"Et#PPh1 "dppa# ligand a}orded a yellow solu!
tion from which ðAu1"m!dppa#1ŁðSbF5Ł1 could be iso! Crystal structure and photophysical properties of
lated in good yield as a colourless microcrystalline ðAu1"m!dppa#1ŁðSbF5Ł1
solid by precipitation with diethylether[ Elemental
analysis\ the infrared spectrum recorded as a KBr
Crystals of the compound consist of well!separated
pellet and the H NMR spectrum are all consistent ðAu1"m!dppa#1Ł1¦ cations and SbF5− anions\ there
with the formulation of the compound as ðAu1"m! being no unusual intermolecular contact distances[
dppa#1ŁðSbF5Ł1\ as subsequently con_rmed by means Figure 0 shows an ORTEP drawing of the cation\
of a single crystal structure determination "see below#[ while selected interatomic distances and angles for the
The 20P"0H# NMR spectrum recorded in CD2CN cation are given in Table 0[
0
exhibits a single sharp peak at 099[14 ppm\ indicative
of a phosphorus atom bonded to a gold atom^ the sphazane ligands such that there is
The two gold atoms are bridged by the two dipho!
crys!
a
phosphorus atoms of the free ligand resonate at tallographically imposed centre of symmetry midway
59[59 ppm[ Interestingly\ the phosphorus atoms of the between them[ The coordination at each gold atom is
diphosphazane ligand are considerably deshielded only approximately linear\ as evidenced by a P"0#Ð
relative to those of the dppm ligand\ the latter reson! AuÐP"1?# angle of 056[4"7#>[ As illustrated in Fig[ 0\
ating at ca[ 24 ppm in ðAu1"m!dppm#1ŁðClO3Ł1 ð3Ł[ This the deviation from linearity apparently results from

Synthesis\ spectroscopy and crystal structures
2912
Fig[ 0[ ORTEP drawing of the ðAu1"m!dppa#1Ł1¦ cation in ðAu1"m!dppa#1ŁðSbF5Ł1[ The carbon atoms are drawn as spheres of
arbitrary radius and the remaining atoms as 19) probability ellipsoids[
Ä
Table 0[ Selected interatomic distances "A# and angles "># for ðAu1"m!dppa#1ŁðSbF5Ł1
Au===Au?
AuÐP"1?#
P"0#ÐC"0#
P"1#ÐC"02#
P"1#ÐC"08#
1[727"1#
1[187"4#
0[64"2#
0[64"2#
0[71"2#
AuÐP"0#
P"0#ÐN
P"0#ÐC"6#
P"1#ÐC"6#
P"1#ÐC"08#
1[202"5#
0[69"1#
0[68"2#
0[68"2#
0[71"2#
P"0#ÐAuÐP"1?#
AuÐP"0#ÐC"0#
NÐP"0#ÐC"0#
C"0#ÐP"0#ÐC"6#
Au?ÐP"1#ÐC"02#
NÐP"1#ÐC"02#
056[4"6#
095[3"09#
009[0"02#
095"1#
004[4"8#
096[4"01#
000[1"03#
010[4"6#
AuÐP"0#ÐN
004[3"7#
AuÐP"0#ÐC"6#
NÐP"0#ÐC"6#
Au?ÐP"1#ÐN
Au?ÐP"1#ÐC"08#
NÐP"1#ÐC"08#
P"0#ÐNÐP"1#
P"1#ÐNÐC"14#
003[2"8#
093[6"01#
000[2"7#
094[5"8#
094[3"01#
006[9"00#
005[8"6#
C"02#ÐP"1#ÐC"08#
P"0#ÐNÐC"14#
the two gold atoms being pulled towards each other approach of the chloride anions ð02Ł[ In fact\ the core
by a substantial Au===Au interaction[ This is re~ected structure of the ðAu1"m!dppa#1Ł1¦ cation is very similar
Ä
in an Au===Au distance of 1[727"1# A that is sig! in all respects to that observed for the other digold"I#
ni_cantly shorter than the Au===Au distances in ligand bridged species listed above\ there being no
Ä
ðAu1"m!dppm#1ŁðBH2CNŁ1=1CH1Cl1 "1[871 A# ð8Ł\ evidence of a tendency for the gold atom to become
Ä
Ä
ðAu1"m!Me1PCH1PMe1#1ŁðClO3Ł1
"2[917 A#
ð09Ł\ three!coordinate by associating with the ~uoride of
ðAu1"m!Me1PCH1PMe1#1ŁBr1[H1O "2[912 A# ð09Ł\ the SbF−5 anion[ There is a slight twisting of the bridg!
Ä
ðAu1"m!Me1PCH1PMe1#1ŁCl1[H1O "2[909 A# ð00Ł and ing ligands about the Au==Au vector\ as re~ected by a
Ä
ðAu1"m!Cy1PCH1PCy1#1ŁðPF5Ł1 "1[824 A# ð01Ł[ It is also P"0#ÐAu===Au?ÐP"1# torsion angle of 01[3>[ The AuÐP
Ä
Ä
shorter than the Au===Au distance of 1[851 A reported bond lengths of 1[203"4# and 1[186"4# A are somewhat
Ä
for ðAu1"m!dppm#1ŁCl1\ but this comparison is not shorter than the value of 1[399 A given for eight com!
strictly valid since the gold atoms in the latter com! pounds of the closely related dppm ligand with gold
pound are formally three!coordinate\ due to the close ð03Ł\ but are very similar to the AuÐP distance of

2913
J[ S[ Field et al[
Fig[ 1[ Absorption and emission "239 nm excitation# spectra in CH2CN of ðAu1"m!dppa#1ŁðSbF5Ł1[
1¦
Ä
1[203"1# A in ðAu1"m!Cy1PCH1PCy1#1Ł ð01Ł and the
The emission maximum of 499 nm\ recorded at
Ä
AuÐP distances of 1[200"3# and 1[206"3# A in ðAu1 room temperature in acetonitrile for the ðAu1"m!
"m!dppm#1ŁðBH2CNŁ1=1CH1Cl1 ð8Ł[
dppa#1Ł1¦ cation\ occurs at a considerably lower wave!
The room temperature UV:vis absorption spectrum length\ compared to the wavelengths recorded for the
of ðAu1"m!dppa#1ŁðSbF5Ł1 in acetonitrile is shown in emission maxima observed under the same conditions
Fig[ 1[ A very intense absorption band is observed for the ðAu1"m!dppm#1Ł1¦ cation^ these occur at 469
as a shoulder at 115 nm which can be attributed to and 482 nm for the ClO−3 ð2\ 3Ł and BF3− salts ð1Ł
transitions within the phenyl rings ð1Ł[ Also observed respectively[ The di}erence of 12 nm in the emission
are bands at 156 nm "emax\ ca[ 12999 dm2 mol−0 cm−0
#
wavelengths for the latter two salts has been ascribed
and at 187 nm "emax\ ca[ 06999 dm2 mol−0 cm−0# while to medium e}ects ð0Ł\ but these seem unlikely to
some lower energy and weaker absorptions are account for the decrease in emission wavelength of
observed in the region 229Ð269 nm[ Thus\ the bands −69 nm observed for the dppa ligand!bridged species[
in the 149Ð399 nm region appear at positions very The emissive state for the dppm ligand!bridged cation
similar to those observed in the absorption spectrum is generally accepted as being phosphorescent ð1Ð3Ł\
of ðAu1"m!dppm#1ŁðClO3Ł1 recorded in acetonitrile ð3Ł\ with the excited state being assigned as either
but with di}erences in the relative intensities of the 2Au"dsꢀ#"ps# ð1Ð3Ł or B0u"ddꢀ#"ps# ð2\ 3Ł[ Assuming
2
bands and a generally lower resolution of the peaks that one of these two assignments also applies to the
in the absorption spectrum of ðAu1"m!dppa#1ŁðSbF5Ł1[ dppa ligand!bridged chromophore\ the expectation
On this basis\ we tentatively assign the absorption would be that a decrease in the Au===Au distance would
band at 187 nm to the spin!allowed psCdsꢀ transition\ lead to an increase in the interaction between the gold
the equivalent band in the dppm!bridged cation being atoms and\ hence\ an increase in the emission wave!
at 189 nm for the ClO−3 salt ð3Ł and at 182 nm for the length[ Exactly the opposite trend is observed when
BF−3 salt ð1Ł[ Figure 1 also shows the emission spec! the Au===Au distances of the two cations are
trum of the ðAu1"m!dppa#1Ł1¦ cation measured at compared[ Thus\ although the Au===Au distance of
1¦
Ä
room temperature in acetonitrile\ an intense and 1[727"1# A observed for ðAu1"m!dppa#1Ł
is sig!
Ä
asymmetric emission band being observed at 499 nm[ ni_cantly shorter than the value of 1[871"1# A
Thus\ the ðAu1"m!dppm#1Ł1¦ and ðAu1"m!dppa#1Ł1¦ reported for the BH2CN− salt of the ðAu1"m!
chromophores have in common the fact that they dppm#1Ł1¦ cation ð8Ł\ the wavelength of the emission
both emit strongly on irradiation in solution[ This is is substantially shorter[ It seems certain that e}ects
unusual\ as most ligand!bridged digold"I# species do intrinsic to the bridging ligands are responsible for the
not generally emit in solution\ only displaying lumi! large di}erence in emission energy observed for the
nescence in the solid state ð1Ł[ For example\ the ðAu1"m!dppm#1Ł1¦ and ðAu1"m!dppa#1Ł1¦ chromo!
diphosphine ligand!bridged species ðAu1"m!Cy1PCH1 phores[ Such an e}ect could be caused by replacing
PCy1#1Ł1¦ does not emit at room temperature\ only a CH1 group in the dppm ligand with an electron!
luminescing at 378 nm in the solid state at 66 K ð01Ł[
withdrawing N"Et# group to give the dppa ligand\

Synthesis\ spectroscopy and crystal structures
2914
resulting in less electron density on the donor phos! 04[3 and 15[6> in the ðAuCl"C5F4#2Ł− salt and 12[5> in
phorus atoms in the dppa as compared to the dppm
ligand[ However\ we are not in a position to quantify
such an e}ect on the relative energies of the HOMO
and LUMO in species of this type and\ hence\ to fully
explain the di}erences in emission energy[
the chloride salt[ It has been previously shown that
diphosphazane ligands are very ~exible in terms of
twisting about the metalÐmetal vector which they
bridge ð04Ł and it may be that this is\ in some way\
responsible for the adoption of a near linear arrange!
ment of gold atoms in the ðAu2Cl1"m!dppa#1Ł¦ cation[
The central gold atom is symmetrically coordinated
by the phosphorus atoms of trans disposed diphos!
phazane ligands with a P"0#ÐAu"0# P"0?# angle of
064[3"5#>[ The outer two gold atoms are asym!
metrically coordinated\ being bonded to the phos!
phorus atom of a diphosphazane ligand and to a
chloride ligand^ the P"1#ÐAu"1#ÐCl angle of 066[0"0#>
shows only a small deviation from linearity[ The
Crystal structure and photophysical properties of
ðAu2Cl1"m!dppa#1ŁPF5
Crystals of the compound consist of well!separated
ðAu2Cl1"m!dppa#1Ł¦ cations and PF5− anions\ there
being no unusual intermolecular contact distances[
Figure 2 shows an ORTEP drawing of the cation
while selected interatomic distances and angles for the
cation are given in Table 1[
The cation comprises a bent chain of three gold
atoms\ each pair of adjacent gold atoms being bridged
by a diphosphazane ligand and with the coordination
at the two outer gold atoms being completed by a
chloride ligand[ Overall\ the cation has C1 symmetry[
The deviation of the chain of gold atoms from linearity
is re~ected by a Au"1#===Au"0#===Au"1?# angle of
052[7"1#>[ This is in marked contrast to the arrange!
ment of gold atoms in ðAu2Cl1"m!dppm#1Ł¦\ where
the Au===Au===Au angles are 63[1 and 63[5> for the
ðAuCl"C5F4#2Ł− and Cl− salts respectively ð6\ 7Ł[ Each
diphosphazane ligand is considerably twisted\ as
re~ected by a P"0#ÐAu"0#===Au"1#ÐP"1# torsion angle
of 35[8>[ The equivalent torsion angles in the dppm!
Ä
Au"0#===Au"1# distance of 2[926"0# A is somewhat
shorter than the Au===Au distances observed for the
ðAu2Cl1"m!dppm#1Ł¦ cation\ these being 2[956 and
−
Ä
Ä
2[053 A for the ðAuCl"C5F4#2Ł salt and 2[965 A for
the chloride salt ð6\ 7Ł[ This trend is consistent with
the shorter Au===Au distance observed for the ðAu1"m!
dppa#1Ł1¦ cation as compared to that reported for the
ðAu1"m!dppm#1Ł1¦ cation "see above#[ The Au"0#ÐP"0#
Ä
bond length of 1[202"1# A is signi_cantly longer than
the Au"1#ÐP"1# bond length of 1[117"1# A\ pre!
Ä
sumably because of the greater trans in~uence of the
diphosphazane as opposed to the chloride ligand[ As
Ä
might be expected\ the AuÐP"0# distance of 1[202"1# A
Ä
agrees well with that of 1[205 A found for ðAu"P!
MePh1#1Ł¦ ð05Ł since\ in both cases\ the gold atom
bridged trigold"I# cation are somewhat smaller\ being is symmetrically coordinated by phosphorus donor
Fig[ 2[ ORTEP drawing of the ðAu2Cl1"m!dppa#1Ł1¦ cation in ðAu2Cl1"m!dppa#1ŁPF5[ The carbon atoms are drawn as spheres
of arbitrary radius and the remaining atoms as 49) probability thermal ellipsoids[

2915
J[ S[ Field et al[
Ä
Table 1[ Selected interatomic distances "A# and angles "># for ðAu2Cl1"m!dppa#1ŁPF5
Au"0#===Au"1#
Au"1#ÐCl
P"0#ÐN
P"0#ÐC"6#
P"1#ÐC"02#
NÐC"14#
2[926"0#
1[171"1#
0[698"5#
0[686"6#
0[679"02#
0[389"8#
Au"0#ÐP"0#
AuÐP"1#
P"0#ÐC"0#
P"1#ÐN
1[202"1#
1[117"1#
0[796"6#
0[572"5#
0[798"6#
P"1#ÐC"08#
Au"1#===Au"0#===Au"1?#
P"1#ÐAu"1#ÐCl
Au"0#ÐP"0#ÐC"0#
NÐP"0#ÐC"0#
C"0#ÐP"0#ÐC"6#
Au"1#ÐP"1#ÐC"02#
NÐP"1#ÐC02
052[7"1#
066[0"0#
001[7"1#
093[4"2#
097[6"2#
009[3"1#
096[6"2#
095[1"2#
012[2"4#
P"0#ÐAu"0#ÐP"0?#
Au"0#ÐP"0#ÐN
Au"0#ÐP"0#ÐC"6#
NÐP"0#ÐC"6#
Au"1#ÐP"1#ÐN
Au"1#ÐP"1#ÐC"08#
NÐP"1#ÐC"08#
P"0#ÐNÐP"1#
064[3"5#
098[3"1#
002[2"1#
096[5"2#
009[7"1#
005[6"1#
093[4"2#
006[4"2#
008[0"4#
C"02#ÐP"1#ÐC"08#
P"0#ÐNÐC"14#
P"1#ÐNÐC"14#
ligands[ Similarly\ the Au"1#ÐP"1# distance of
The room temperature UV:vis absorption spectrum
Ä
1[117"1# A corresponds closely with the AuÐP distance of ðAu2Cl1"m!dppa#1ŁPF5 in acetonitrile is shown in
Ä
of 1[127"4# A in ðClAu"dppm#AuClŁ ð06Ł since the Fig[ 3[ The band at 129 nm\ which is observed as a
coordination environments of the gold atoms are the shoulder on the very intense peak in the ultraviolet
Ä
same[ The Au"1#ÐCl bond length of 1[171"1# A is very region\ can be attributed to transitions within the phe!
similar to that observed in ðClAu"dppm#AuClŁ ð06Ł nyl rings ð1Ł[ Also observed are a band at 184 nm
"1[177 A# and those reported for the ðAu2Cl1"m! "emaxꢁca[ 19999 dm2 mol−0 cm−0# and a relatively
Ä
dppm#1Ł¦ cation of 1[177 and 1[290 A in the weak absorption centred at 246 nm[ The band at
Ä
ðAuCl"C5F4#2Ł− salt and 1[189 A in the chloride salt[ 184 nm is in a very similar position to that at 187 nm
Ä
In summary\ although the arrangements of the gold observed in the UV:vis spectrum of ðAu1"m!
atoms in ðAu2Cl1"m!dppm#1Ł¦ and ðAu2Cl1"m!dppa#1Ł¦ dppa#1ŁðSbF5Ł1 measured in acetonitrile Fig[ 1[ On this
cations are di}erent\ the immediate coordination basis\ and for the same reasons as those discussed
environments of the gold atoms are very similar[
above\ it is also tentatively assigned to a psCdsꢀ
Fig[ 3[ Absorption in CH2CN and solid state emission "239 nm excitation# spectra of ðAu2Cl1"m!dppa#1ŁPF5[

Synthesis\ spectroscopy and crystal structures
2916
transition[ Irradiation of an acetonitrile solution of Yield] ca[ 9[66 g "89)#[ Found] C\ 25[6^ H\ 1[8^ N\
ðAu2Cl1"m!dppa#1ŁPF5 at 239 nm only a}ords a very 0[6^ Calc[ for C41H49Au1F01N1P3Sb1] C\ 25[8^ H\ 2[9^
weak and indistinct emission band centred at about N\ 0[5)[ IR data "KBr pellet\ cm−0#] 547 "vs# "
0
459 nm[ On the other hand\ a powdered sample of the SbF−5 #[ H NMR "CD2CN#] d 6[53 "m\ 39H\ C5H4#^
compound exhibits an intense blue emission as shown 2[01 "q\ 3H\ CH1#^ 9[24 "t\ 5H\ CH2#[ 20P"0H# NMR
in Fig[ 3 "lmaxꢁ364 nm#[ This emission is slightly blue! "CD2CN#] d 099[14[
shifted compared to the emission maximum of 374 nm
recorded in the solid state for ðAu2Cl1"m!dppm#1ŁCl
ð7Ł[ The origin of the emission is uncertain[ However\
Synthesis of ðAu2Cl1"m!dppa#1ŁPF5
solid ðAuCl"PPh2#Ł has only a slight bluish!white emis!
Thiodiglycol "1\1?!thiodiethanol# "ca[ 9[1 cm2# was
sion\ due to pÐpꢀ transitions in the phenyl rings and
added\ with stirring\ to an orange!coloured solution
bis"phosphine#gold"I# complexes such as ðAu"P!
of HAuCl3[1H1O "9[100 g\ 9[459 mmol# in methanol
Ph2#1ŁBPh3 do not emit at all\ neither in solution nor
"ca[ 04 cm2# at room temperature[ A slight excess of
in the solid state ð5Ł[ It would therefore appear that
solid Ph1PN"Et#PPh1 "9[121 g\ 9[459 mmol# was then
the intramolecular goldÐgold interactions present in
added with stirring[ After a period of ca[ 29 min the
the trinuclear ðAu2Cl1"m!L!L#1Ł1¦ cations "L!
ligand had dissolved to a}ord a solution of red!brown
Lꢁdppm or dppa# are\ in some way\ responsible for
colour which subsequently turned yellow[ After stand!
the intense emission observed in the solid state for
ing overnight\ the solution became colourless[ An
these compounds[
excess of solid NH3PF5 "9[074 g\ 0[039 mmol# was
added and the solution stirred for 2Ð3 h[ During this
EXPERIMENTAL
General considerations
time\ the product precipitated from the solution as a
colourless microcrystalline solid[ This was isolated by
_ltration through glass micro_bre paper\ washed with
water followed by ether and _nally dried in vacuo[
All manipulations were performed under nitrogen Yield] ca[ 9[69 g "79)#[ Found] C\ 27[4^ H\ 2[1^ N\
using a combination of vacuum and Schlenk tech! 0[7^ Calc[ for C41H49Au2Cl1F5N1P4] C\ 27[2^ H\ 2[0^ N\
niques[ Solvents were puri_ed and degassed by stan! 0[6)[ IR data "KBr pellet\ cm−0#] 739 "vs# "PF5−#[ 0H
dard procedures ð07Ł[ Infrared data were recorded as NMR "CD2CN#] d 6[53 "m\ 39H\ C5H4#^ 2[01 "q\ 3H\
KBr pellets on a Shimadzu FTIR!3299 spectro! CH1#^ 9[24 "t\ 5H\ CH2#[ 20P"0H# NMR "CD2CN#] d
photometer[ 0H NMR spectra were recorded on a 092[50 and 72[00 "AA?BB? pattern#[
Varian Gemini!199 spectrometer with chemical shifts
referenced to SiMe3[ 20P"H# NMR spectra were rec!
X!ray structure determinations of ðAu1"m!dppa#1Ł
orded on a Varian FT79A spectrometer\ chemical
ðSbF5Ł1 and ðAu2Cl1"m!dppa#1ŁPF5
shifts being quoted relative to 74) H2PO3 "external\
20P#[ Absorption spectra were recorded on a Shimadzu
Crystal data\ data collection and re_nement par!
UV!1090PC UV!vis scanning spectrophotometer[
ameters for ðAu1"m!dppa#1ŁðSbF5Ł1 and ðAu2Cl1"m!
Emission spectra were obtained on a Shimadzu RF!
dppa#1ŁPF5 are given in Table 2[ Single crystals of the
4999 recording spectro~uorophotometer[ The C\ H\
former compound were grown by slow di}usion of
and N analyses were performed by Galbraith Lab!
diethylether into a solution of the compound in
oratories of Knoxville\ Tennessee[ The ligand
dichloromethane\ while single crystals of the latter
Ph1PN"Et#PPh1 was prepared by a slight modi_cation
compound were grown by slow di}usion of diethyl!
of the literature method ð08Ł[
ether into an acetonitrile solution of the compound[
Weissenberg photographs of the ðAu1"m!dppa#1Ł
Synthesis of ðAu1"m!dppa#1ŁðSbF5Ł1
ðSbF5Ł1 crystals showed that the re~ections were gen!
erally weak and rather di}use\ but repeated attempts
Excess gold powder "9[127 g\ 0[197 mmol# was to grow crystals which gave a better!de_ned di}rac!
added with stirring to a solution of NOSbF5 "9[023 g\ tion pattern were unsuccessful[ Di}ractometer data
9[493 mmol# in acetonitrile "ca[ 09 cm2# at room tem! were collected at 184 K with a Nonius CAD3
perature[ Stirring was continued overnight to allow di}ractometer using graphite monochromated MoÐ
Ä
oxidation of gold to gold"I#[ The excess gold powder Ka radiation "lꢁ9[60962 A#[ Lattice parameters were
was removed by _ltration through glass micro_bre obtained from the least!squares re_nement of the set!
_lter paper a}ording a clear colourless solution[ Solid ting angles of 14 re~ections with u×01>[ Re~ection
Ph1PN"Et#PPh1 "9[197 g\ 9[493 mmol# was added with intensities were measured by the variable!speed v!1u
stirring following which the ligand dissolved and the method in the range 2¾1u¾35>[ Examination of
solution turned yellow[ After ca 0 h\ the volume of the three standard re~ections\ monitored after every
solution was reduced in vacuo and diethylether added[ 59 min\ showed no evidence for crystal deterioration
The product\ which separated from the solution as for either compound[ Both data sets were corrected
a colourless microcrystalline solid\ was isolated by for Lorentz!polarisation e}ects and were also cor!
_ltration\ washed with diethylether and dried in vacuo[ rected for absorption using the psi!scan method ð19Ł

2917
J[ S[ Field et al[
Table 2[ Crystal and intensity collection data and details of re_nement for ðAu1"m!dppa#1ŁðSbF5Ł1 and
ðAu2Cl1"m!dppa#1ŁPF5
ðAu1"m!dppa#1ŁðSbF5Ł1
ðAu2Cl1"m!dppa#1ŁPF5
Formula
C41H49Au1F01N1P3Sb1
0535[26
C41H49Au2Cl1F5N1P4
0522[96
Formula weight
Crystal size "mm#
Crystal system
9[39×9[14×9[04
Monoclinic
01[059"3#
08[671"5#
00[284"3#
88[18"2#
1694"1#
9[17×9[14×9[11
Monoclinic
11[858"3#
04[670"2#
05[805"2#
006[75"1#
4319"1#
Ä
a "A#
Ä
b "A#
Ä
c "A#
b ">#
V "A #
2
Ä
Z
1
3
Ä
Radiation\ l "A#
9[60962
9[60962
Space group
P10:c
1[91
56[50
C1:c
1[99
75[15
r"calc[# "g cm−2
#
m"MoÐKa# "cm−0
#
Unique intensities
Weighting scheme
No[ of parameters
RꢁS"F9−Fc#:SF9
RWꢁSw0:1"F9−Fc#:Sw0:1F9
"D:s#max
1309 ðI×2s"I#Ł
0:ðs1"F#¦9[9917F1Ł
221
9[988
9[009
2146 ðI×2s"I#Ł
0:ðs1"F#¦9[9998F1Ł
210
9[917
9[923
9[944
9[946
0[09
−2
Ä
Ä
Drmax "eA
#
3[07 "ca[ 0 A from Au#
"maximum and minimum transmission factors are these compounds have in common Au===Au distances
9[8888\ 9[7825 and 9[8876\ 9[7305 for ðAu1"m!dppa#1Ł which are su.ciently short to indicate a substantial
ðSbF5Ł1 and ðAu2Cl1"m!dppa#1ŁPF5 respectively#[
interaction between the gold atoms[ This interaction
The structures of ðAu1"m!dppa#1ŁðSbF5Ł1 and is believed to be\ in some way\ responsible for the
ðAu2Cl1"m!dppa#1ŁPF5 were solved by standard Pat! luminescence exhibited by the compounds\ in solution
terson methods using the program SHELXS 75 ð10Ł for the dinuclear species and in the solid state for the
and subsequently completed by Fourier recycling and trinuclear complex[ However\ we have not been able
re_nement using the program SHELX 65 ð10Ł[ The to establish a correlation between the Au===Au sep!
full!matrix least!squares re_nements were based on aration and the energy of the emission and\ thus\
=F9=[ The ethyl groups of the diphosphazane ligands conclude that the emission wavelength is determined
in ðAu1"m!dppa#1ŁðSbF5Ł1 are disordered such that they more by the properties of the ligand[ This conclusion
are not precisely related by the centre of symmetry is borne!out by a comparison of the emission proper!
midway between the two gold atoms[ Various models ties of the diphosphazane ligand!bridged compounds
for the disorder were tested but none gave a sat! with those reported for salts of the bis"diphenyl!
isfactory solution[ In the end\ restrictions were placed phosphino#methane ligand!bridged cations\ ðAu1"m!
on the NÐC and CÐC bond lengths with the methylene Ph1PCH1PPh1#1Ł1¦ and ðAu2Cl1"m!Ph1PCH1PPh1#1Ł¦[
and methyl hydrogens not being included in the
re_nement[ All the non!H atoms were assigned aniso!
tropic temperature factors and the H!atoms a single
common isotropic temperature factor^ the latter were
placed in calculated positions\ except for the NEt
hydrogens as noted above[ Neutral!atom scattering
factors were used with corrections for anomalous dis!
persion ð11Ł[
Acknowled`ements*We thank the University of Natal and
the South African Foundation for Research Development
for _nancial support[ The assistance of Elena I[ Lakoba and
Campbell J[ Parry is gratefully acknowledged[
REFERENCES
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CONCLUSION
Two diphosphazane ligand!bridged complexes of
gold have been synthesised\ their crystal structures
determined and their spectroscopic properties inves!
tigated\ these being ðAu1"m!Ph1PN"Et#PPh1#1ŁðSbF5Ł1
and ðAu2Cl1"m!Ph1PN"Et#PPh1#1ŁPF5[ The cations of

Synthesis\ spectroscopy and crystal structures
2918
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