Effects of diphosphine structure on aurophilicity and luminescence in Au(I) complexes

Article abstract of DOI:10.1039/b410619a

The effects of diphosphine flexibility and bite angle on the structures and luminescence properties of Au(I) complexes have been investigated. A range of diphosphines based on heteroaromatic backbones [bis(2-diphenylphosphino) phenylether (dpephos), 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene (xantphos), and 4,6-bis(diphenylphosphino)dibenzofuran (dbfphos)] has been used to prepare mono- and digold derivatives. A clear relationship between the presence of aurophilic contacts and the emission properties of dinuclear complexes has been observed, with one of the complexes studied, [Au ₂Cl₂(μ-xantphos)], exhibiting luminescence thermochromism.

Full text of DOI:10.1039/b410619a

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F U L L P A P E R
Effects of diphosphine structure on aurophilicity and luminescence in
Au(I) complexes†‡
Aranzazu Pintado-Alba,a Héctor de la Riva,a Mark Nieuwhuyzen,a Delia Bautista,b
Paul R. Raithby,c,d Hazel A. Sparkes,c Simon J. Teat,d José M. López-de-Luzuriagae and
M. Cristina Lagunas*a
a
School of Chemistry, The Queen’s University of Belfast, Belfast, UK BT9 5AG.
E-mail: c.lagunas@qub.ac.uk; Fax: +44 (0)2890 382117; Tel: +44 (0)2890 974436
Servicio Universitario de Instrumentación Científica, Universidad de Murcia,
b
E-30100 Murcia, Spain
Department of Chemistry, University of Bath, Claverton Down, Bath, UK BA2 7AY.
c
E-mail: p.r.raithby@bath.ac.uk; Fax: +44 (0)1225 386231; Tel: +44 (0)1225 383183
CCLRC Daresbury Laboratory, Warrington, UK WA4 4AD
Departamento de Química, Universidad de La Rioja, UA-CSIC, E-26004 Logroño, Spain
d
e
Received 12th July 2004, Accepted 14th September 2004
First published as an Advance Article on the web 27th September 2004
The effects of diphosphine flexibility and bite angle on the structures and luminescence properties of Au(I)
complexes have been investigated. A range of diphosphines based on heteroaromatic backbones [bis(2-
diphenylphosphino)phenylether (dpephos), 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene (xantphos), and 4,6-
bis(diphenylphosphino)dibenzofuran (dbfphos)] has been used to prepare mono- and digold derivatives. A clear
relationship between the presence of aurophilic contacts and the emission properties of dinuclear complexes has
been observed, with one of the complexes studied, [Au2Cl2(l-xantphos)], exhibiting luminescence thermochromism.
Introduction
The rich photochemistry exhibited by many Au(I)
complexes and the potential applications derived therefrom
(e.g., development of molecular sensors and switches or energy
storage devices) has triggered numerous studies focused on
clarifying the relationships between the structures and the
optical properties of the compounds.1–6 Particularly interesting
are the connections found between the emission bands of the
complexes and the presence of weak interactions (2.7–3.5 Å)
between neighbouring Au atoms (aurophilicity).2 In some cases,
however, no clear relation between AuAu distances and
emission properties has been found.3 In this context, dinuclear
Au(I) complexes with bridging diphosphines of variable length
have been extensively studied.4–6 Most of these contain non-rigid
diphosphines [e.g., of the type R2P(CH2)nPR2] which do not
allow great control on the geometry adopted by the complexes.
The use of more rigid phosphines is therefore desirable.
In this work, three diphosphine ligands derived from rigid
heteroaromatic backbones [bis(2-diphenylphosphino)phenyl
ether (dpephos),7 4,6-bis(diphenylphosphino)dibenzofuran
(dbfphos),7–9 and 9,9-dimethyl-4,5-bis(diphenylphosphino)-
xanthene (xantphos),10 Chart 1] have been used to prepare mono-
anddigold(I)derivatives.Ithasbeenshownthatthesmallvariations
in the backbones of these ligands affect their bite angles, while
keeping electronic effects very similar (Chart 1).7 The influence
of the variable flexibility and bite angles of the diphosphines on
the structures of the new Au(I) complexes prepared has been
analysed. In addition, the relationship between aurophilic
interactions and optical properties of dinuclear [(AuCl)2(l-
diphos)] species has been studied. While preparing this paper,
the synthesis and optical properties at room temperature of one
of the compounds reported here, [(AuCl)2(l-xantphos)], were
published.11 However, low-temperature luminescence, NMR and
crystallographic data, which are included in the present work,
have not been previously reported.
Chart 1 Ligands used for the synthesis of Au(I) complexes. Bite angles
obtained from ref. 7
Results
Synthesis
Complexes [(AuCl)2(l-diphos)]·CH2Cl2 (diphos = dpephos, 1;
xantphos, 2; dbfphos, 3; Scheme 1) were readily prepared by
reacting the corresponding diphosphine with two equivalents of
[AuCl(tht)] (tht = tetrahydrothiophene) in dichloromethane.
Attempts to isolate annular species of the type [Au2(l-
diphos)2]X2 (X = OTf, ClO4) by reacting 1 or 2 with the
† Electronic supplementary information (ESI) available: UV-Vis spectra
of 1–6. See http://www.rsc.org/suppdata/dt/b4/b410619a/
‡ Dedicated to Prof. José Vicente on the occasion of his 60th birthday.
Scheme 1 Synthesis of complexes; adpephos or xantphos.
T h i s j o u r n a l i s
©
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
D a l t o n T r a n s . , 2 0 0 4 , 3 4 5 9 – 3 4 6 7
3 4 5 9

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corresponding free phosphine and AgOTf or NaClO4 in molar
ratio 1:1:2 failed. Various mixtures of products that could
not be separated resulted in all cases. In order to clarify these
processes, the reactions of the digold chloride complexes 1
or 2 with free ligand were studied by NMR spectroscopy, as
described in the next section.
Complexes [Au(diphos)2][SbF6] [diphos = dpephos (4),
xantphos (5), dbfphos (6)] were obtained by reacting 1, 2 or 3
with the corresponding free diphosphine and NaSbF6 in molar
ratio 1:3:2 (Scheme 1). Complex 6 gave partial decomposition
in solution, as shown by the presence of a small amount of
diphosphine oxide in its 31P{1H} NMR spectrum.
in solution to the formation of five- or six-membered chelate
rings, since no evidence of analogous species was found when
diphosphines leading to four- or seven-membered rings [i.e.,
Ph2P(CH2)nPPh2, n = 1 or 4] were used.13
An analogous behaviour has been found in the reaction
between complex 1 and free dpephos, performed in CDCl3 or
CD2Cl2. Upon addition of 0.5 equiv. of ligand, the initial singlet
corresponding to 1 (21.4 ppm) disappeared and two new very
broad resonances at 22.4 and 18.1 ppm appeared. The signal at
18.1 ppm increased in intensity at the expense of the other when
more dpephos (i.e., Au:dpephos ratio of 1:1) was added, and
has been tentatively assigned to a tri-coordinated 1:1 complex,
[(AuCl)2(l-dpephos)2] (A, Scheme 1). Further addition of
free phosphine resulted in a unique (sharper) intermediate
resonance at 21.9 ppm, which has been assigned to a bis-chelated
species (C, Scheme 1). Complex [Au(dpephos)2][SbF6] (4) was
later isolated, and its 31P{1H} NMR spectrum at r.t. showed a
singlet at 18.2 ppm which remained sharp at 213 K. The slightly
different chemical shift of this signal with respect to that found
during the titration (21.9 ppm) may be due to the influence of
the anion.
The addition of free xantphos to complex 2 was also
followed by 31P{1H} NMR spectroscopy in CDCl3, with
comparable results (Fig. 1). Upon addition of 0.5 equiv. of
free diphosphine, three signals at 27.7, 22.9, and 5.8 (br) ppm
appeared in the spectrum, in addition to that corresponding to
2 (24.7 ppm). The latter decreased gradually in intensity with
the subsequent addition of diphosphine (up to 1.5 equiv.),
while the singlets at 27.7 and 5.8 ppm increased, and the
smallest signal at 22.9 ppm remained almost unchanged. On
further addition of xantphos, the broad peak at 5.8 ppm was
virtually the only signal remaining, until a singlet at −17.2 ppm,
corresponding to the free ligand, appeared at a 2:xantphos
ratio of ca. 1:3. The signal at 5.8 ppm was assigned to a bis-
chelated species [Au(xantphos)2]+ (C), which was later isolated
as its [SbF6]− salt (5, Scheme 1) and characterised by X-ray
diffraction (Fig. 10). The singlets at 27.7 and 22.9 ppm have
been assigned to three-coordinated 1:1 Au:xantphos species
[(AuCl)2(xantphos)2] (A) and [AuCl(xantphos)] (B). At 213 K,
the signal at 5.8 ppm gave an AABB pattern (Fig. 2). The
two Me groups of the backbone also become inequivalent in
the 1H NMR spectrum at low temperature. This behaviour
is consistent with the solid-state structure of 5 (Fig. 10), in
which the two P atoms of each xantphos unit are in different
chemical environments. As represented in Fig. 3, P1 is opposite
to the aromatic backbone of the other xantphos unit, whereas P2
is opposite the phenyl groups. At higher temperatures, the four
P atoms become equivalent, indicating that a fluxional process
involving flipping of the xantphos conformation takes place
NMR spectroscopy
The NMR spectra of the complexes are consistent with the
proposed structures. The presence of one molecule of CH2Cl2
in solid samples of 1–3 was confirmed by their 1H and 13C{1H}
NMR spectra. In the aromatic regions of the 1H NMR spectra,
the signal at the lowest frequency (6.4–7.0 ppm), which appears
as a ddd (1, 2) or a dd (3), has been assigned to the ortho-H
atoms of the organic backbone, with 3J(PH) coupling constants
in the range 11.9–13.4 Hz.
In the 13C{1H} NMR spectrum of 3, the ipso-, ortho- and
meta-C atoms of the Ph2P groups each appears as a doublet
with J(PC) of 64, 15 or 12 Hz, respectively, whereas the para-
C atoms give a singlet. Three other signals corresponding to C
atoms of the diphenyl ether backbone also give doublets, with
that of highest coupling constant (58 Hz) being assigned to the
ipso-C atom.
Based on the assignment made for 3, the 13C{1H} NMR
spectra of 1 and 2, which are more complicated, were analysed.
The spectrum of complex 1 shows two types of Ph groups.
These could indicate that the rigid structure of 1 in the solid
state, with a AuAu interaction (see below), is retained in
solution. However, a locked conformation of the Ph groups
could also occur without the need for an aurophilic interaction.
The resonances of the Ph2P ortho-, meta- and ipso-C atoms in
the spectrum of 2 appear as multiplets or apparent triplets. The
13C{1H} NMR spectrum of free xantphos, which also shows
apparent triplets for some of its C atoms, has been analysed as
an AAX system (A = A = 31P, X = 13C) with a large coupling
between the two 31P nuclei, which results from the orientation
of the P lone pairs and the short PP distance.7,10 The observed
spectra of 2 can be rationalised in an analogous way, with a
large 31P31P coupling transmitted through the organic backbone
and/or the AuAu interaction. The latter mechanism requires
the assumption that the structure of 2 in solution is similar to
that of the crystal, with the aurophilic interaction remaining in
solution (see below).
The 31P{1H} NMR spectra of 1–3 showed a single resonance
in the range 21–26 ppm. Coordination to Au(I) produced the
expected downfield shift (ca. 40 ppm) with respect to the free
ligands.
As mentioned above, the stepwise addition of free dpephos
or xantphos to a solution of 1 or 2 was followed by 31P{1H}
NMR. This type of titration reaction has been used in
the past to investigate the formation of three- and four-
coordinated Au(I) species in solution.12–14 For example, the
spectra of complexes [(AuCl)2(l-diphosphine)] (diphosphine =
Ph2P(CH2)nPPh2, n = 2, 3 or cis-Ph2PCHCHPPh2)13 showed,
upon addition of less than 1 equiv. of free phosphine,
the formation of significant quantities of a bis-chelated
[Au(diphosphine)2]+ species, whose resonance was generally
broadened through exchange with other species in solution
(e.g., tri-coordinated [(AuCl)2(l-diphosphine)2]). The fact that
separate resonances for [Au(diphosphine)2]+ and free phosphine
could be seen in the spectra upon addition of 3 equivalents
of ligand, indicated that only slow exchange between free and
bound phosphine occurred in solution. The authors attributed
this exceptional stability of the bis-chelated Au(I) complexes
Fig. 1 31P{1H} NMR spectra of complex 2 in CDCl3 in the presence
of free xantphos.
3 4 6 0
D a l t o n T r a n s . , 2 0 0 4 , 3 4 5 9 – 3 4 6 7

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on the NMR timescale (Fig. 3). This may or may not involve
de-coordination from the metal. Analogous behaviour can be
assumed for complex 6, whose 31P{1H} NMR at r.t. shows a very
broad peak, which splits into two broad singlets at 213 K. The
fact that all P centers in complex 4 remain equivalent at 213 K
on the NMR timescale suggests that in this case the analogous
fluxional behaviour is faster. This is consistent with the higher
flexibility of dpephos with respect to xantphos or dbfphos.
Fig. 5 Crystal structure of 1 (solvent molecules and H atoms are
omitted for clarity).
Fig. 2 Observed (above) and simulated (below) 31P{1H} NMR spectra
of complex 5 at 213 K, showing AABB pattern [J(AA) = 22.2 Hz,
J(AB) = 24.2 Hz, J(AB) = 13.3 Hz, J(BB) = 18.5 Hz].
Fig. 6 Crystal structure of 2 (solvent molecules and H atoms are
omitted for clarity).
Fig. 3 Proposed fluxional behaviour for complexes 4–6 in solution.
Crystal structures
The crystal structures complexes 1–3, and 5 were determined, in
addition to that of free dpephos, which had not been previously
reported (Figs. 4–1015). Crystal data and selected bond lengths
and angles are included in Tables 1 and 2, repectively.
Dpephos. The crystal structure of the free phosphine is shown
in Fig. 4. The distance between the two P atoms (4.876 Å) is
shorter than that found in dbfphos [5.741(1) Å]9 and larger than
those of xantphos, for which three different crystal structures
have been reported [P–P = 4.045(1) Å,10 4.080 Å,7 or 4.155(1) Å
(xantphos·THF)10]. The two phenyl rings in the backbone of
dpephos form an angle of ca. 67°, with the lone pairs of the P
atoms pointing away from each other.
[(AuCl)2(l-dpephos)]·CH2Cl2 (1). Complex
1 shows a
AuAu interaction of 3.0038(6) Å (Fig. 5). This seems
to be easily accommodated within the bite angle of the
Fig. 7 Hydrogen bonding interactions in 2 (H atoms not involved in
the interactions are omitted for clarity); Cl1H15B: 2.726 Å, Cl1C15:
3.654 Å, Cl1H15B–C15: 158.4°; Cl1H55: 2.788 Å, Cl1C55:
3.554 Å, Cl1H55–C55: 138.3°; Cl2H99A: 2.646 Å, Cl2C99:
3.619 Å, Cl2H99A–C99: 168.0°; Cl4H53: 2.898 Å, Cl4C53:
3.746 Å, Cl4H53–C53: 149.4°.
phosphine, as the conformation of the dpephos backbone in
the complex is almost the same as in the free ligand (i.e., the
distance between the P atoms is 4.858 Å and the angle between
the phenyl rings is of ca. 61°). The aurophilic interaction forces
the Au coordination environments to deviate from linearity,
with P–Au–Cl angles of 170.57(9) and 174.26(9)°. The P–Au–Cl
fragments are almost perpendicular to each other [e.g., the Cl(1)–
Au(1)–Au(2)–Cl(2) torsion angle is 81°]. Short AuO contacts
in the range 3.04–3.25 Å have been shown to be important in
Fig. 4 Crystal structure of dpephos.
D a l t o n T r a n s . , 2 0 0 4 , 3 4 5 9 – 3 4 6 7
3 4 6 1

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Table 1 Crystal data for dpephos and complexes 1–3 and 5
dpephos
1
2
3
5
Formula
M
Crystal system
Space group
a/Å
C36H28OP2
538.52
Monoclinic
P21/c
13.8258(16)
11.9848(14)
17.725(2)
2830.5(6)
153(2)
C37H30Au2Cl4OP2
1088.28
Monoclinic
P21/c
8.9229(16)
20.269(4)
19.987(4)
3526.8(12)
150(2)
C40H34Au2Cl4OP2
1128.34
Monoclinic
Cc
10.4484(9)
24.8178(15)
15.0035(9)
3804.7(5)
173(2)
C40H36Au2Cl2O2P2
1075.46
Monoclinic
P21/c
12.6522(11)
10.8373(10)
26.931(2)
3689.5(5)
150(2)
C81H67AuCl9F6O2P4Sb
1947.99
Triclinic
P1
12.8424(11)
15.0214(13)
21.1198(18)
3967.0(6)
153(2)
b/Å
c/Å
U/Å3
T/K
Z
4
4
4
4
2
l(Mo-Ka)/mm−1
Refls. measured
Unique refls. (Rint)
R (I > 2r(I))
wR(F2) (all data)
0.181
30543
6594 (0.0557)
0.0441
0.1203
8.021
29760
10004 (0.0580)
0.0465
0.1185
8.100
6794
6527 (0.0203)
0.0241
0.0403
8.210
21155
8104 (0.0241)
0.0336
0.0793
2.421
44257
17665 (0.0734)
0.0657
0.1496
Table 2 Selected bond lengths (Å) and angles (°) for 1–3 and 5
1
2
3
Au(1)–Au(2)
Au(1)–Cl(1)
Au(2)–Cl(2)
Au(1)–P(1)
Au(2)–P(2)
3.0038(6)
2.300(2)
2.310(2)
2.234(2)
2.235(2)
2.9947(4)
—
2.3009(17)
2.3071(16)
2.2347(17)
2.2410(16)
2.2879(15)
2.3004(13)
2.2257(13)
2.2315(13)
P(1)–Au(1)–Cl(1)
P(2)–Au(2)–Cl(2)
170.57(9)
174.26(9)
173.07(6)
168.47(7)
179.24(6)
179.20(5)
5
Au(1)–P(2)
Au(1)–P(1)
2.474(2)
2.4771(19)
Au(1)–P(3)
Au(2)–P(4)
2.4691(19)
2.471(2)
P(2)–Au(1)–P(1)
P(2)–Au(1)–P(3)
P(1)–Au(1)–P(3)
109.55(7)
115.78(7)
108.01(7)
P(2)–Au(1)–P(4)
P(1)–Au(1)–P(4)
P(3)–Au(1)–P(4)
107.76(7)
109.02(7)
106.56(7)
Fig. 9 Intermolecular interactions in 3 [Au2Cl2: 3.377 Å;
Cl2H36: 2.779 Å, Cl2C36: 3.704 Å, Cl2H36–C36: 164.52°] (the
second molecule is related by the symmetry operation −x, −y, 1 − z;
most H atoms are omitted for clarity).
Fig. 10 Crystal structure of the cation in 5 (solvent molecules and H
atoms are omitted for clarity).
Fig. 8 Crystal structure of 3 (most H atoms are omitted for clarity);
O2H26: 2.685 Å, O2C26: 3.543 Å, O2H26–C26: 150.7°.
the structures of organogold derivatives of diphenyl ether,
[(AuPPh3)(C6H4OC6H5)] and [(AuPPh3)2((C6H4)2O)].16 In the
case of complex 1, the distances between the metals and O
are larger (ca. 3.5 Å), but may still have an influence on its
structure.
in 2 undergoes some distortion upon coordination. Thus, the
distance between the P atoms (4.735 Å) is significantly larger
in 2 than in the free xantphos (see above)7,10 and the xanthene
backbone is both folded and twisted along the central ring,
presumably to accommodate the two Au atoms at a close
distance. Such distortion is not present in the free diphosphine,
where the backbone is only slightly folded, with the two phenyl
rings forming and angle of ca. 160°. Another difference with
the structure of 1 resides in the distances between O and the Au
atoms, which in 2 are 3.097 and 3.992 Å. The former indicates
the presence of a weak AuO interaction (i.e., shorter than the
sum of their van der Waals radii of ca. 3.2 Å). Additionally,
[(AuCl)2(l-xantphos)]·CH2Cl2 (2). The crystal structure of
2 (Fig. 6) shows a similar aurophilic interaction [2.9947(4) Å]
and comparable P–Au–Cl angles [168.47(7) and 173.07(6)°]
to those of 1. The angle between the P–Au–Cl fragments
[Cl(1)–Au(1)–Au(2)–Cl(2) torsion angle: 90.7°] is slightly larger
in 2. However, unlike complex 1, the diphosphine backbone
3 4 6 2
D a l t o n T r a n s . , 2 0 0 4 , 3 4 5 9 – 3 4 6 7

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Table 3 Absorptiona and emissionb data for the free phosphines and complexes 1–6
kabs/nm (emax/dm3 mol−1 cm−1
)
kem/nm [s0/ls]
dpephos
xantphos
dbfphos
262 sh (3359), 267 (4400), 274 (5025), 289 (5688)
Solid
440 (r.t.)
441 (77 K)
499 (r.t.)
505 (77 K)
436 (r.t.)
447 (77 K)
510 (r.t.)
446 (77 K)
Cl2CH2
Solid
262 (23667), 305 sh (9216)
Cl2CH2
Solid
253 (44023), 297 (25368), 311 sh (14849), 322 sh (8306)
441 (r.t.)
438 (77 K)
Cl2CH2
Solid
521 (r.t.)
445 (77 K)
1
2
3
248 sh (7912), 269 (3058), 277 (2993), 286 (2642), 293 (2409)
261 (28548), 278 (25763)
450 sh, 620 [12] (r.t.)
628 (77 K)
431, 654 (77 K)
449 sh, 620 [76] (r.t.)
447, 621 (77 K)
429, 507 sh (77 K)
429, 458, 488 sh [11] (r.t.)
427, 456, 488 sh (77 K)
430, 450, 489 sh (r.t.)
430, 454, 486 sh (77 K)
485 [12] (r.t.)
458 (77 K)
Cl2CH2
Solid
Cl2CH2
Solid
245 sh (43802), 277 (8634), 298 (15389), 310 (11099)
Cl2CH2
Solid
4
5
264 sh (64092)
276 (72845)
Cl2CH2
Solid
448 (77 K)
491 [14] (r.t.)
488 (77 K)
Cl2CH2
Solid
505 (r.t.)
460 (77 K)
470 [8] (r.t.)
486 (77 K)
6
295 (92575)
Cl2CH2
515 (r.t.)
440 (77 K)
a In Cl2CH2 at r.t. b kex = 290–340 nm.
there is a network of hydrogen bonds in the crystal involving Cl
atoms both from the complex and the solvent (Fig. 7).
Au(I) four-coordinate complexes, such as [Au{o-phenylenebis-
(dimethylarsine)}]+,18 [Au(dppe)2]+,12,19,21 and [Au{4-methyl-1,8-
bis(diphenylphosphino)naphthalene}2]+,20 show wider ranges
of P–Au–P angles [86.7–121.8, 85.4(1)–129.6(1) and 86.9(2)–
133.3(2)°, respectively], indicating tetrahedral geometries
significantly more distorted than that of 5. The Au–P bond
distances [2.4691(19)–2.4771(19) Å] are slightly longer in 5 than
in [Au(dppe)2]+ [2.389(3)–2.416(3) Å]12 and [Au{4-methyl-1,8-
bis(diphenylphosphino)naphthalene}2]+ [2.379(6)–2.388(6) Å].20
These bonds are also longer that the Au–P distances in two-
coordinate derivatives 1–3.
The bite angles of the ligands, 106.56(7)° (P3–Au1–P4)
and 109.55(7)° (P2–Au1–P1), are smaller than the calculated
natural bite angle for free xantphos (111.7°),7 and the Au
atom is situated at ca. 3.4 Å from each of the O atoms of the
ligands. Each of the xantphos units in the complex is folded
along the OCMe2 imaginary line (i.e., the angle between the
two phenyl rings is ca. 145°), with the central ring adopting a
boat-like conformation. The P1–P2 and P3–P4 distances are of
4.043 and 3.962 Å, respectively. These features are analogous
to those found in the free ligand7,10 (see above), indicating that
only little distortion occurs upon coordination of the gold atom
in a chelating manner. This contrasts with the crystal structure
of 2, in which the xantphos unit undergoes a high distortion
when bridging between two metals. Finally, the C31C–C36C
and C11A–C16A rings lie almost parallel to each other at a
distance of ca. 3.8 Å, suggesting the presence of a phenyl–
phenyl interaction. Ring stacking has also been observed in the
structure of [Au(dppe)2]+ (inter-ring separation = 3.5 Å).21
[(AuCl)2(l-dbfphos)]. The crystal structures of [(AuCl)2(l-
dbfphos)]·CH2Cl2 (3) and of the diethyl ether solvate (3)
analogue were obtained. The structures of the two species
were similar, and only the latter was fully refined (Fig. 8). The
solid-state structure of [(AuCl)2(l-dbfphos)] is fundamentally
different to that of 1 or 2. The two Au–Cl units in the former
adopt an anti position that situates the metal atoms at a longer
distance (7.21 Å) from each other, preventing the formation
of an aurophilic contact. The geometry around the metals is
almost perfectly linear, with P–Au–Cl angles of 179.24(6) and
179.20(5)°, and the distances between O and the Au atoms
(4.116 and 3.990 Å) are too long to be considered as interactions.
The dibenzofuran backbone is almost coplanar and the distance
between the two P atoms (5.834 Å) is similar to that found in the
free ligand.9 As in complex 1, the diphosphine is not distorted
by coordination to the Au atoms. The O atom of the diethyl
ether molecule forms a H-bonded interaction with one of the Ph
groups, as represented in Fig. 8.
A close look at the way the molecules are packed in the
crystal shows the presence of intermolecular AuCl and
CHCl contacts (Fig. 9). Two Au–Cl units of adjacent
molecules are situated in an anti-paralell manner, forming a
rectangle through intermolecular AuCl contacts of 3.377 Å,
slightly shorter than the sum of the van der Waals radii
(3.41 Å). Analogous AuCl interactions have been previously
described.17 Each of the two Cl atoms in the rectangle also forms
an inter-molecular H-bond, as shown in Fig. 9.
Optical properties
[Au(xantphos)2][SbF6] (5). Complex 5 (Fig. 10) crystallises
with three molecules of chloroform. The geometry around
the metal is pseudo-tetrahedral with P–Au–P angles in the
range 106.56(7)–115.78(7)°. The crystal structures of related
The absorption and emission spectra of complexes 1–6 have
been studied and compared to those of the free ligands. The
photophysical data are summarised in Table 3.
D a l t o n T r a n s . , 2 0 0 4 , 3 4 5 9 – 3 4 6 7
3 4 6 3

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The absorption spectra of all compounds were obtained from
dichloromethane solutions (ESI†). The spectrum of dpephos
exhibits a structured band between 250 and 325 nm, while
xantphos presents a broad absorption band with a maximum
at 262 nm and a shoulder at ca. 305 nm. An intense absorption
at 253 nm and a broad band at 297 nm with tails into longer
wavelengths are observed in the spectrum of dbfphos. The shapes
of the electronic spectra for 1–3 resemble roughly that of the
corresponding parent phosphine, whereas the four-coordinate
complexes 4–6 exhibit broad more intense absorptions which
tail to ca. 350 nm.
particular in the case of 2, which presents the shortest AuO
distance (ca. 3.1 Å). A number of intermolecular hydrogen
bonds are also present in 2 (Fig. 7). The importance of the
cumulative contribution to the stabilisation energy of weak
interactions in a crystalline solid has been recently highlighted
in the literature.23 The competition between aurophilic and other
secondary interactions in the crystal packing of Au complexes
has also been analysed.24
It is interesting to note that the three diphosphines are able to
stabilise eight-membered chelate rings with Au(I) in a pseudo-
tetrahedral environment (complexes 4–6). This contrasts with
the behaviour of more flexible diphosphines, for which four-
coordinate chelated Au(I) complexes containing large rings
(i.e., >six-membered rings) have been found to be unstable.13 The
preference of xantphos to coordinate in a chelate manner has
been pointed out before as a result of the phosphine’s bite angle.7
The fact that this ligand adopts a less strained conformation in
complex 5 than in 2 agrees with its predicted preference for
chelating. The stability of unusually large chelated rings is more
surprising in the case of dbfphos, whose large bite angle has
been suggested to not favour ring closure.7 In fact, metal
complexes containing dbfphos in a chelating coordination mode
are scarce and only a few Re and Ru compounds in which the
metal also coordinates to the O atom of the diphosphine have
been described.25 As in complexes 1 and 2, the presence of weak
AuO interactions (of ca. 3.4 Å) in the structure of 5 could
contribute to the stabilisation energy of the crystal. Similar
contacts may also be present in 4 and 6.
When excited at 300–330 nm, the emission spectra of the free
phosphines at r.t. or 77 K consist of a broad emission band with
kmax in the 436–521 nm region.
The solid-state emission spectra of complexes 1 and 211 at r.t.
are similar to each other, exhibiting a broad band at 620 nm and
a shoulder at ca. 450 nm (Fig. 11) when excited at 300 nm. Their
spectra at 77 K, however, are quite different. While the spectrum
of 1 does not change with temperature, the relative intensities
of the two emissions of 2 change dramatically, with the high
energy (HE) emission favoured at 77 K (Fig. 11). The excitation
spectra monitored for both the HE and the LE emissions of 2 at
77 K are analogous. Complexes 1 and 2 are not luminescent in
dichloromethane solution at r.t. but they emit at 77 K. Thus, a
glassy solution of 1 gives two bands at 431 and 654 nm, whereas
the xantphos derivative 2 shows mainly one broad band at
430 nm.
Previous studies have established that the lowest energy
absorption for aryl phosphines is associated with a l → ap (or
n → p*) transition involving the promotion of an electron from
the lone pair orbital (l) on phosphorus to an empty antibonding
orbital of p origin on a phenyl ring.26,27 Such transition can be
buried under the tail of more intense p → p* bands.26 The l → ap
transition, which becomes a r → ap transition on coordination,
should shift to higher energy as the electron pair is stabilised by
the metal, but examples in which it remains unchanged or shifts
to lower energies have also been reported.27 In the latter cases, the
transition energy has been suggested to be modified by metal-
phosphorus p-backbonding or alterations on the angle between
the P l-orbital and the axis of the adjacent C 2pp-orbital upon
coordination.27 Luminescence arising from the l → ap state has
been described for a number of aryl mono- and di-phospines,26
whereas emission bands arising from r → ap transitions (often
label as ILCT transitions) are shown by some of their d10 metal
complexes, including four-coordinate Au(I) derivatives.27,28 In
some cases, this emission has been proposed to have a mixed
ILCT/MLCT [d (metal) → p* (phosphine)] character.
According to this interpretation, the intense absorptions
that the three diphosphines exhibit in the 250–300 nm region
have been assigned to p → p* transitions localised on the
aromatic groups, while the tails at longer wavelengths may
be associated with the l → ap transition. This transition shifts
slightly to higher energy upon coordination in 2 and 3, does
not change significantly in the case of 1, and it moves to lower
energy in 4–6. The emission observed for the free diphosphines
at 436–447 nm is suggested to arise from the l → ap transition.
The HE emissions in 1 and 2, which are similar in energy
and shape to those of the free ligands, may be associated
with an ILCT (r → ap) transition. The same origin can be
assumed for the emission of 3, which appears in the same
region. However, given the distinctive vibrational structure
of this band, a different origin cannot be ruled out. The
difference in energy between the two sharper vibrational peaks
in the emission spectrum of 3 (solid state at r.t.) is of 1476 cm−1,
which corresponds closely to a peak at 1478 cm−1 of medium
intensity found in its IR spectrum in Nujol. This band has been
assigned to an aromatic C–C stretching frequency, suggesting
a p → p* origin for the emission of 3. An emission of r →
ap origin should show the vibrational structure of the P–Ph
Fig. 11 Solid-state emission spectra (kexc = 300 nm) of complexes 1–3
at r.t. (left), and complex 2 at r.t. and 77 K (right).
The emission of 3 differs significantly from that of 1 or 2
(Fig. 11), and exhibits, both in the solid state and in dichloro-
methane, a structured band at 420–500 nm, which increases in
intensity at low temperature.
Four-coordinate complexes 4–6 show solid-state emission at
r.t. and 77 K, with a broad band in the region 458–491 nm when
exited at 300–335 nm. Luminescence has been observed for the
three complexes in degassed dichloromethane at 77 K, and in the
case of 5 and 6, also at room temperature.
Discussion
The lack of aurophilic interaction in [(AuCl)2(l-dbfphos)] (3, 3)
contrasts with the structures of complexes 1 and 2, and it may
be attributed to the rigid conformation of dbfphos, whose large
bite angle would not accommodate comfortably an AuAu
fragment. In fact, in two analogous complexes recently prepared
by us, [{Au(SC6H4Cl-4)}2(l-dbfphos)] and [{Au(CCPh)}2(l-
dbfphos)],22 it has been found that dbfphos only allows
very weak AuAu contacts (of ca. 3.4 Å). In the case of
[(AuCl)2(l-dbfphos)], such weak aurophilic interaction would
be in competition with intermolecular AuCl and CHCl
interactions (Fig. 9) which, as a whole, seem to have a greater
influence on the overall structure of the complex. In complexes
1 and 2, the shorter aurophilic contact (of ca. 3.0 Å) allowed
by the diphosphine ligands, is strong enough to prevail over
competing intermolecular interactions. In addition, weak
intramolecular AuO contacts may contribute to stabilise
the AuAu bonded conformation of these two compounds, in
3 4 6 4
D a l t o n T r a n s . , 2 0 0 4 , 3 4 5 9 – 3 4 6 7

View Article Online
stretching frequency, which normally appears as a strong very
sharp band at ca. 1440 cm−1 (a band with these characteristics
is found at 1435 cm−1 in the IR spectrum of 3). Mononuclear
Au(I) complexes {(R2PhP)AuX}n (R = Me, Ph, X = Cl, Br) also
exhibit a structured phosphorescence at ca. 360 nm that has
been proposed to originate from a phenyl-localised 3pp* state.29
The LE emission at 620 nm, which is not observed in
the spectrum of 3 or the free ligands, can be related to the
aurophilic interaction present in 1 and 2. The nature of
the lowest energy emissive state of polynuclear phosphine
Au(I) complexes in which AuAu interactions are present is
normally considered to originate from a metal-centered (MC)
transition modified by the aurophilic interaction (dr*/dd* →
shows no evidence of the interaction remaining in solution.
Finally, complex 3, with the more rigid dbfphos, adopts a
structure in the solid state in which intermolecular AuCl
contacts prevail over potentially very weak intramolecular
AuAu interactions.
The three phosphines are able to form stable four-coordinate
derivatives (4–6) which are highly luminescent both in the solid
state and in solution. These are notable in that only a few other
emissive tetrahedral Au(I) complexes have been described to
date, with only two showing emission at r.t. in solution.20
Experimental
General
2
pr/sr; where dr* or dd* is generated by overlap of Au 5dz or
2
2
5dx −y orbitals, respectively) or a metal–metal to ligand charge
transfer (MMLCT, dr*/dd* → p*) transition.
Literature methods were followed for the syntheses of the
diphosphine ligands.7 An alternative method to that described
below for the synthesis of [(AuCl)2(l-xantphos)] has recently
been published.11 31P{1H} NMR (referenced to external 85%
Thetemperaturedependenceof thesolid-stateluminescenceof
2 is indicative of a thermally activated energy transfer from the
HE to the LE excited state, which may be closer in energy than
the corresponding states in complex 1. Analogous luminescence
thermochromism has been found in other Au(I) complexes.5,29
Loss of the aurophilic contacts in solution and/or solvent
quenching may be responsible for the non-emissive nature of
1 and 2 at r.t. in dichloromethane. In the glassy state, however,
a LE emission at 654 nm can still be seen in the spectrum of
1, indicating that some aurophilic contacts are present. The
inequivalence of the Ph groups observed in the 13C NMR
spectrum of 1 also supports this proposal.
The emission of each of the tetrahedral compounds 4–6 is
closely related to that of the corresponding free phosphine,
with the solid-state bands in the complexes red-shifted 20–40
nm with respect to those in the ligands. The mechanism for the
emission in 4–6 is thus considered to involve r → ap transitions.
An analogous assignment has been done for the emission
of related bis(diphenylphosphino)naphthalene complexes.20
Luminescence of four-coordinated Au(I)–phosphine complexes
is rare, in particular in fluid solution, but it has been shown to be
enhanced when stacked P–phenyl groups are present, with low
energy transitions (i.e., 520–620 nm) associated with intra- and/
or inter-molecular Ph–Ph excited dimers.21 Although a weak
Ph–Ph interaction has been identified in the crystal structure of
5, evidence of excimer formation has not been found.
1
H3PO4), and H- and 13C{1H} NMR (standard SiMe4) spectra
were recorded on a Brüker Advance DPX 300 or DPX 500, at
r.t. using CDCl3 as solvent, unless otherwise stated. Elemental
analyses (CHN) were performed in ASEP (School of Chemistry,
Queen’s University Belfast). Electrospray mass spectra were
obtained on a VG Quattro spectrometer. Infrared spectra were
recorded on a Perkin Elmer Spectrum One FT-IR spectrometer.
The electronic absorption spectra were recorded on
a
Perkin Elmer UV/Vis spectrometer Lambda800. The emission
spectra were recorded on a Perkin Elmer LS55 luminescence
spectrometer equipped with a R928 photomultiplier and a low-
temperature accessory. For the luminescence measurements in
dichloromethane, the solvent was previously degassed and the
concentration of the solutions used was of ca. 10−3 M. Emission
lifetimes were recorded on a Jobin-Yvon Horiba Fluorolog
3-22 Tau-3 spectrofluorimeter equipped with a Fluoromax
phosphorimeter accessory containing a UV xenon flash tube
with a flash rate between 0.05 and 25 Hz. The data were fitted
using the Jobin-Yvon software package and the Origin 6.1
program.
Crystal structures
Single crystals of dpephos and complexes 1–3 and 5 were
obtained by slow diffusion of hexane or diethyl ether in dichloro-
methane solutions of the compounds.
The lifetime of complexes 1–6, measured in the solid state
at room temperature, are in the microsecond range (Table 3),
indicating that the emissions occur from excited states of triplet
parentage and probably phosphorescent. This is in agreement
with the assignments of the bands.
Crystals of 1 and 3 were mounted in inert oil on glass fibres,
and data were measured using a Bruker AXS SMART CCD
area detector, fitted with an Oxford Cryostream low-temperature
attachment, on Station 9.8 of the CCLRC Daresbury Laboratory
using an X-ray wavelength of k = 0.6892 Å (for 1) and
k = 0.6898 Å (for 3).30 The two structures were solved by direct
methods and subjected to full-matrix least-squares refinement
on F2 (program SHELXL-97).31 The structure of 1 was found
to be twinned and in order to obtain a satisfactory refinement
the twin matrix −1 0 0; 0 −1 0; 1 0 1, obtained using the ROTAX
program,32 was applied with a refined scale factor of 0.232 for the
two components. For both structures, all non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were included
using rigid methyl groups or a riding model. Weighting schemes
were introduced to give flat analyses of variance and refinement
continued until convergence was reached.
Crystals of 2 were mounted in inert oil on a glass fiber
and transferred to a Siemens P4 diffractometer with an LT2
low-temperature attachment. The unit cell parameters were
determined from a least-squares fit of 100 accurately centered
reflections (9.8 < 2h < 24.9). The structure was solved by
the heavy-atom method and refined anisotropically on F2.31
Hydrogen atoms were included using a riding method. The
absolute structure parameter33 is −0.022(5).
Conclusions
The use of three diphosphines with various bite angles and
flexibilities allows for some control over the structures of Au(I)
complexes, which, in turn, have a strong influence on the optical
properties of the compounds.
In the digold(I) derivatives, the aurophilic interactions
determine the emission of the complexes, with
a
distinctive low energy band clearly associated with the
presence of AuAu contacts. The more flexible dpephos
allows the establishment of such AuAu (and AuO) contacts
in the solid state while remaining relatively unconstrained,
as indicated by the crystallographic data of 1. This lack of
constraint may allow the structure of 1 to remain largely
unchanged in solution, as optical and 13C{1H} NMR studies
suggest. As the flexibility of the phosphine decreases (and the
bite angle increases), the aurophilic interaction becomes less
favoured. Thus, the xantphos ligands in complex 2 adopt a
distorted conformation with respect to that of the free ligand
or complex 5. Although an aurophilic interaction is observed
for 2 in the solid state, presumably also favoured by the presence
of AuO and hydrogen-bonding interactions, its luminescence
Crystallographic data for dpephos and complex 5 were
collected using a Bruker SMART diffractometer with graphite
D a l t o n T r a n s . , 2 0 0 4 , 3 4 5 9 – 3 4 6 7
3 4 6 5

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[Au(diphos)2][SbF6] [diphos = dpephos (4), xantphos (5),
monochromated Mo-Ka radiation. The crystal stability was
monitored and there was no significant decay (±1%). Data
were collected at low temperature (ca. 153 K). Omega–phi scans
were employed for data collection and Lorentz and polarisation
corrections were applied. The structures were solved by
direct methods and all non-hydrogen atoms were refined
with anisotropic atomic displacement parameters. Hydrogen
atom positions were located from a Fourier difference map
and refined with isotropic atomic displacement parameters
for dpephos. Hydrogen atoms for 5 were added at idealised
positions, subsequent refinement uses a riding model with
atomic displacement parameters fixed at 1.2Ueq of the atom to
which they are attached (1.5Ueq for methyl groups). The function
minimised for wR2 was ∑[w(|Fo|2 − |Fc|2)] with reflection weights
w−1 = [r2|Fo|2 + (g1P)2 + g2P] where P = [max |Fo|2 + 2|Fc|2]/3 for
all F2 and the function minimised for R1 was R[w(|Fo| − |Fc|)].
The SAINT34 and SHELXTL35 PC packages were used for data
collection, reduction, structure solution and refinement.
CCDC reference numbers 244462–244466.
dbfphos (6)]. To a suspension of 1, 2 or 3 (0.075 mmol) in
chloroform (15 cm3) was added the corresponding diphosphine
(0.250 mmol). After stirring the resulting mixture for 0.5 h, a
solution of NaSbF6 (0.039 g, 0.149 mmol) in acetone (ca. 1 cm3)
was added. After 0.5 h, the solvent was evaporated to dryness
and dichloromethane (ca. 5 cm3) added to the resulting white
residue. The suspension was filtered over Celite and the filtrate
concentrated to dryness to give the product as a white (4, 5) or
a yellow (6) solid. Complex 5 was washed with acetone–diethyl
ether (1:15, ca. 5 cm3).
4 (0.08 g, 72%) (Found: C, 57.62; H, 3.80. C72H56AuF6O2P4Sb
requires C, 57.27; H, 3.74%); dH (300 MHz) 7.91–6.65 (52 H, m,
Ph), 6.28 [4 H, d, J(HH or HP) = 8 Hz, H(3)]; dP (121.5 MHz)
18.2 (s); m/z 1274 (M+).
5 (0.07 g, 58%) (Found: C, 58.74; H, 4.09. C78H64AuF6O2P4Sb
requires C, 58.92; H, 4.06%); dH (500 MHz, 300 K) 7.51–6.73
(52 H, m, Ph), 1.59 (12 H, br s, 4 CH3), (213 K) 7.55–6.15 (52 H,
m, Ph), 1.83 (6 H, s, 2 CH3) 0.88 (6 H, s, 2 CH3); dP (202.5 MHz,
300 K) 5.8 (br s), (213 K) 5.5, 0.5 [4 P, AABB, J(AA) =
22.2 Hz, J(AB) = 24.2 Hz, J(AB) = 13.3 Hz, J(BB) = 18.5 Hz];
m/z 1354 (M+).
See http://www.rsc.org/suppdata/dt/b4/b410619a/ for crystal-
lographic data in CIF or other electronic format.
6 (0.11 g, 98%) (Found: C, 58.15; H, 3.87. C72H52AuF6O2P4Sb
requires C, 57.43; H, 3.48%); dH (500 MHz) 8.06 [4 H, d,
3J(HH) = 8 Hz, H(1,9)], 7.35–7.12 (44 H, m, Ph), 6.99 [4 H,
apparent t, J(HH or HP) = 8 Hz, H(3,7)]; dP (121.5 MHz,
300 K) 6.5 (br s), (202.5 MHz, 213 K) 34.1 (br s), −19.8 (br s);
m/z 1270 (M+).
Syntheses
[(AuCl)2(l-diphos)]·CH2Cl2 [diphos = dpephos (1), xantphos
(2), dbfphos (3)]. To
a solution of the corresponding
diphosphine [0.4 g, 0.742 mmol (1), 0.3 g, 0.519 mmol (2); 0.4 g,
0.743 mmol (3)] in 15 cm3 of dichloromethane, two equivalents
of [AuCl(tht)] were added. The resulting solution was stirred at
room temperature under an atmosphere of dinitrogen for 2 h,
and then concentrated to dryness. To the residue, a mixture of
acetone–ether (1:15, ca. 15 cm3) was added, and the resulting
suspension filtered. The resulting white solid was air-dried.
1 (0.58 g, 72%) (Found: C, 40.63; H, 2.40. C37H30Au2Cl4OP2
requires C, 40.83; H, 2.78%); mmax/cm−1 (AuCl) 320, 311
(Nujol); dH (300 MHz) 7.60–7.09 (26 H, m, Ph), 6.71 [2 H, ddd,
Acknowledgements
We are grateful to the EPSRC and the McClay Trust for their
financial support, including PhD grants for H. de la R. and
A. P.-A., respectively.
References
3J(HH) = 7.7 Hz, J(HH) = 1.5 Hz, J(HP) = 11.9 Hz, H(3)],
5.30 (2 H, s, CH2Cl2); dP (121.5 MHz) 21.7 (s); dC (75.4 MHz)
158.9 [2 C, d, J(CP) = 6 Hz, CO], 135.0 [4 C, d, J(CP) = 14 Hz,
o-C6H5P], 134.2 (2 C, s, C6H4OP), 133.9 [2 C, d, J(CP) = 6 Hz
C6H4OP], 133.1 [4 C, d, J(CP) = 14 Hz, o-C6H5P], 132.1 (2 C,
s, p-C6H5P), 131.1 (2 C, s, p-C6H5P), 129.7 [4 C, d, J(CP) =
12 Hz, m-C6H5P], 129.2 [4 C, d, J(CP) = 12 Hz, m-C6H5P],
128.3 [2 C, d, 1J(CP) = 64 Hz, i-C6H5P], 127.0 [2 C, d, 1J(CP) =
65 Hz, i-C6H5P], 125.1 [2 C, d, J(CP) = 9 Hz, C6H4OP], 120.2
[2 C, d, J(CP) = 5 Hz, C6H4OP], 119.1 [2 C, d, 1J(CP) = 62 Hz,
i-C6H4OP], 53.4 (s, CH2Cl2).
4
3
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and S.-M. Peng, Chem. Commun., 1997, 135.
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2 (0.46 g, 79%) (Found: C, 42.86; H, 3.02. C40H34Au2Cl4OP2
requires C, 42.58; H, 3.03%); mmax/cm−1 (AuCl) 318 (Nujol); dH
3
4
(300 MHz) 7.62 [2 H, dd, J(HH) = 7.7 Hz, J(HH) = 1.2 Hz,
H(1,8)], 7.44–7.25 (20 H, m, Ph), 7.06 [2 H, apparent t, 3J(HH) =
3
4
7.7 Hz, H(2,7)], 6.44 [2 H, ddd, J(HH) = 7.7 Hz, J(HH) =
3
1.3 Hz, J(HP) = 12.7 Hz, H(3,6)], 5.30 (2 H, s, CH2Cl2), 1.69
(6 H, s, 2 CH3); dP (121.5 MHz) 24.0 (s); dC (125.7 MHz) 152.6
(2 C, s, CO), 134.4 (8 C, m, o-C6H5P), 133.1 (2 C, s, C6H3OP),
131.5 (4 C, s, p-C6H5P), 131.3 (2 C, s, C6H3OP), 129.6 (2 C, s,
C6H3OP), 129.5 (2 C, s, C6H3OP), 128.9 (8 C, m, m-C6H5P),
124.4 (4 C, apparent t, i-C6H5P), 116.4 [2 C, d, 1J(CP) = 58 Hz,
i-C6H3OP], 34.6 (s, CMe2), 31.6 (2 C, s, 2 CH3), 53.4 (s, CH2Cl2).
3 (0.73 g, 91%) (Found: C, 40.79; H, 2.42. C37H28Au2Cl4OP2
requires C, 40.90; H, 2.59%); mmax/cm−1 (AuCl) 332, 321 (Nujol);
dH (300 MHz) 8.17 [2 H, d, 3J(HH) = 7.8 Hz, H(1,9)], 7.61–7.46
(20 H, m, Ph), 7.41 [2 H, apparent t, 3J(HH) = 7.7 Hz, H(2,8)],
11 V. Pawlowski, H. Kunkely and A. Vogler, Inorg. Chim. Acta, 2004,
357, 1309.
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13 S. J. Berners-Price and P. J. Sadler, Inorg. Chem., 1986, 25, 3822.
14 S. J. Berners-Price, R. J. Bowen, T. W. Hambley and P. C. Healy, J.
Chem. Soc., Dalton Trans., 1999, 1337.
15 Ortep representations have been done using Ortep-3 for Windows
(L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565). Ellipsoids are
drawn at 30% probability.
3
3
7.06 [2 H, dd, J(HH) = 7.7 Hz, J(HP) = 13.4, H(3,7)], 5.30
(2 H, s, CH2Cl2); dP (121.5 MHz) 25.2 (s); dC (125.7 MHz) 156.2
(2 C, s, CO), 134.3 [8 C, d, J(CP) = 15 Hz, o- C6H5P), 132.9 [2 C,
d, J(CP) = 8 Hz, C6H3OP], 132.7 (4 C, s, p-C6H5P), 129.7 [8 C,
1
d, J(CP) = 12 Hz, m-C6H5P), 127.2 [4 C, d, J(CP) = 64 Hz,
i-C6H5P), 124.8 (2 C, s, C6H3OP), 124.3 (2 C, s, C6H3OP), 124.2
[2 C, d, J(CP) = 17 Hz, C6H3OP], 113.6 [2 C, d, 1J(CP) = 58 Hz,
i-C6H3OP], 53.4 (s, CH2Cl2).
3 4 6 6
D a l t o n T r a n s . , 2 0 0 4 , 3 4 5 9 – 3 4 6 7

View Article Online
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D a l t o n T r a n s . , 2 0 0 4 , 3 4 5 9 – 3 4 6 7
3 4 6 7