Synthesis, characterization and bromination of bis(phosphinoferrocenyl) gold(I) compounds

Article abstract of DOI:10.1016/j.jorganchem.2007.11.057

Reaction of [(dppf)Au₂Br₂] (3) {dppf = 1,1′-bis(diphenylphosphino)ferrocene} and [(dippf)Au₂Br₂] (4) {dippf = 1,1′-bis(diisopropylphosphino)ferrocene} with excess bromine yields two new complexes [(C₅

Full text of DOI:10.1016/j.jorganchem.2007.11.057

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 701–708
www.elsevier.com/locate/jorganchem
Synthesis, characterization and bromination
of bis(phosphinoferrocenyl) gold(I) compounds
Tebogo V. Segapelo a, Ilia A. Guzei b, James Darkwa a,*
a Department of Chemistry, University of Johannesburg, Auckland Park Kingsway Campus, P.O. Box 524, Johannesburg 2006, South Africa
b Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, United States
Received 25 October 2007; accepted 29 November 2007
Available online 11 January 2008
Abstract
Reaction of [(dppf)Au2Br2] (3) {dppf = 1,10-bis(diphenylphosphino)ferrocene} and [(dippf)Au2Br2] (4) {dippf = 1,10-bis
(diisopropylphosphino)ferrocene} with excess bromine yields two new complexes [(C5H4Br3)(PR2)AuBr] (R = Ph, 5; R = i-Pr, 6).
Bromination of the free diphosphinoferrocene ligands produces the expected brominated cyclopentenes (C5H4Br3)(PR2) (R = Ph, 7;
R = i-Pr, 8) in good yields; however, these compounds could not be complexed to gold due to reduced basicity of 7 and 8. When the
bromination is performed under wet aerobic conditions the oxidized pseudo-centrosymmetric product, [doppf][FeBr4] (9)
{doppf = 1,10-bis(oxodiphenylphosphino)ferrocene, is formed as the major product. Solid-state structures of 1, 2, 4, 6, and 9 have been
established by means of single-crystal X-ray crystallography.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Diphenylphosphinoferrocene; Diisopropylphosphinoferrocene; Bromination; Phosphinocyclopentene; Ligands; Gold(I) complexes
1. Introduction
can absorb sulfur dioxide reversibly [6]. Ironically, dppf
has fewer gold complexes reported in the literature, and
only a few of these are Au(III) complexes [7].
Ferrocene has become a versatile building block for the
synthesis of compounds with tailor-made properties. This
has been made possible by well-established methods for
its incorporation into complex structures [1–4]. Com-
pounds with donor heteroatoms (e.g. P, N, S, O) substi-
tuted onto cyclopentadienyl rings dominate its chemistry
especially those featuring homo-substituents. One such
ligand, 1,10-bis(diphenylphosphino)ferrocene (dppf), has
been used for the past three decades due to the interesting
structural and redox properties of its metal compounds [1].
The popularity of the diphosphines stems from their ability
to modify their bite angle in order to adapt to different geo-
metric requirement. In particular, group 10 metal dppf
compounds are the most extensively studied [5]. For
instance, we observed that dppf palladium and platinum
complexes can be used to form thiolate complexes that
During our attempts to prepare Au(III) complexes with
dppf and its isopropyl analogue (dippf), we discovered that
the Au(III) starting materials are readily reduced to Au(I)
in the presence of these diphosphines. Attempts to oxidize
the reduced products by bromine resulted in bromination
of the cyclopentadienyl rings and subsequent demetallation
of the diphenylphosphinoferrocene ligand. Herein we pres-
ent the synthesis and reactivity of dppf and dippf Au(I)
complexes and their reactions that led to the bromination
of the cyclopentadienyl rings of dppf and dippf.
2. Results and discussion
2.1. Gold complexes of dppf and dippf
Complexes 1–4 were prepared from equimolar amounts
of either Na[AuCl4] or HAuCl4 and the appropriate diph-
osphino ligand (Scheme 1). Syntheses of the bromo
*
Corresponding author.
E-mail address: jdarkwa@uj.ac.za (J. Darkwa).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.11.057

702
T.V. Segapelo et al. / Journal of Organometallic Chemistry 693 (2008) 701–708
Whereas the reactions in Scheme 1 using dppf and dippf
R
R
P
P
with the gold starting materials produced the known com-
plexes 1–3 [9a,9b–12], only 1 has previously been structurally
characterized. In addition to spectroscopic characterization
of 1–4, single crystal X-ray determination confirmed the
structures deduced from our spectroscopic data. Table 1
gives crystallographic data for 1, 2 and 4 and Figs. 1–3 show
molecular drawing diagrams and selected metric parameters
for these three complexes.
Three (pseudo)polymorphs are known for 1: unsolvated
1 [9a] and 1a [9b], a chloroform solvate 1ꢀ2/3CHCl3, [10]
and a bis-dichloromethane solvate 1ꢀ2CH2Cl2 [11]. While
the interatomic bond distances and angles are similar in
all four structures the mutual orientation of the substituted
Cp rings is worth mentioning. The unsolvated 1, whose
structure is reported herein, crystallizes in the monoclinic
space group C2/c with Z0 = 0.5 at 100 K and the complex
resides on a crystallographic inversion centre. The P1–Cen-
troid1–Centroid2–P(1A) torsion angle is 180° with the anti-
periplanar arrangement and staggered the Cp rings (180°)
due to the imposed symmetry. In the polymorph 1a this
angle is 162.8° and the arrangement is antiperiplanar. In
pseudopolymorph 1ꢀ2/3CHCl3 there are two symmetry
independent complexes, the first one resides on a crystallo-
graphic inversion centre and exhibits features similar to
those in 1. The other molecule does not have any crystallo-
graphic symmetry and the P1–Centroid1–Centroid2–P(1A)
torsion angle spans 125.3° which corresponds to an anticli-
P
Au X
R
R
HAuCl4/ Na[AuCl4]
NaBr
Fe
Fe
R
R
Au P
R
X
R
R
X
Complex
1
Yield(%)
Ph
Cl
45
i-Pr
Ph
Cl
Br
Br
2
3
4
42
16
37
i-Pr
Scheme 1. Preparation of complexes 1–4.
analogues (3 and 4) were performed according to the reac-
tions in Scheme 1 in the presence of excess NaBr. The
yields obtained were generally low.
Addition of excess phosphine to Au(III) is known to
reduce it to Au(I) [8], hence the low yields obtained might
be due to some of the diphosphinoferrocene ligands acting
as a reducing agent and thus only small amounts of it are
available to react with the Au(I) produced. When a twofold
excess of the phosphines was used the yields improved only
slightly.
Table 1
Crystallographic data for 1, 2, 4, 6 and 9
1
2
4
6
9
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
C
34H28Au2Cl2FeP2
C22H36Au2Br2FeP2
972.05
100(2)
0.71073
Monoclinic
C2/c
25.9048(12)
7.8665(4)
14.3244(7)
90
C22H36Au2Cl2FeP2
883.13
100(2)
0.71073
Monoclinic
C2/c
25.9629(19)
7.5672(6)
14.2703(11)
90
C11H18AuBr4P
697.83
100(2)
0.71073
Monoclinic
P21/c
13.857(2)
10.1413(15)
13.3486(19)
90
C34H29Br4Fe2O2P2
962.85
105(2)
0.71073
Triclinic
1019.19
100(2)
0.71073
Monoclinic
C2/c
15.8958(18)
13.1673(15)
15.0236(17)
90
99.896(2)
90
˚
ꢀ
Space group
P1
˚
a (A)
10.9884(7)
12.7674(9)
13.6125(9)
84.4600(10)
67.0920(10)
80.5570(10)
1734.2(2)
2
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
110.7470(10)
90
2729.7(2)
4
110.3490(10)
90
2628.7(3)3
4
114.928(2)
90
1701.1(4)
4
3
˚
Volume (A )
3097.7(6)
4
2.185
Z
Dcalc (Mg/m3)
2.365
2.232
2.725
1.844
Absorption coefficient
10.211
14.300
12.012
18.117
5.567
(mmꢁ1
)
Crystal size (mm3)
0.41 ꢂ 0.35 ꢂ 0.33
12091
Multi-scan with
SADABS
0.37 ꢂ 0.33 ꢂ 0.24
10541
Multi-scan with
SADABS
0.45 ꢂ 0.31 ꢂ 0.16
10394
Multi-scan with
SADABS
0.24 ꢂ 0.21 ꢂ 0.12
18345
Multi-scan with
SADABS
0.28 ꢂ 0.14 ꢂ 0.14
30240
Empirical with
SADABS
Reflections collected
Absorption correction
Maximum and minimum
transmission
0.1336 and 0.1024
0.1307 and 0.0765
0.2495 and 0.0745
0.2198 and 0.0977
0.5095 and 0.3047
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
1.17
1.137
1.082
1.094
0.996
R1 = 0.0762,
wR2 = 0.2031
R1 = 0.0819,
wR2 = 0.2056
R1 = 0.0168,
wR2 = 0.0414
R1 = 0.0178,
wR2 = 0.0418
R1 = 0.0149,
wR2 = 0.0369
R1 = 0.0158,
wR2 = 0.0373
R1 = 0.0357,
wR2 = 0.0953
R1 = 0.0381,
wR2 = 0.0965
R1 = 0.0198,
wR2 = 0.0535
R1 = 0.0222,
wR2 = 0.0545
R indices (all data)

T.V. Segapelo et al. / Journal of Organometallic Chemistry 693 (2008) 701–708
703
˚
Fig. 1. Molecular drawing of 1 shown with 30% probability ellipsoids. The hydrogen atoms are omitted for clarity. Selected interatomic distances (A) and
angles (°) for 1: Au(1)—P(1) 2.238(4); Au(1)–Cl(1) 2.254(5); P(1)–C(1) 1.777(15); P(1)–C(6) 1.819(16); P(1)–C(12) 1.816(16); and P(1)–Au(1)–Cl(1)
171.83(17).
Fig. 2. Molecular drawing of 2 shown with 50% probability ellipsoids.
The hydrogen atoms are omitted for clarity. Selected interatomic distances
˚
(A) and angles (°) for 2: Au(1)–P(1) 2.2369(6); Au(1)–Cl(1) 2.2883(6);
Fig. 3. Molecular drawing of 4 shown with 50% probability ellipsoids.
P(1)–C(1) 1.837(3); P(1)–C(6) 1.852(3); P(1)–C(9) 1.797(3); P(1)–Au(1)–
Cl(1) 178.13(2).
The hydrogen atoms are omitted for clarity. Selected interatomic distances
˚
(A) and angles (°) for 4: Au(1)–P(1) 2.2408(7); Au(1)–X(1) 2.4031(3); P(1)–
C(1) 1.794(3); P(1)–C(6) 1.853(3); P(1)–C(9) 1.842(3); P(1)–Au(1)–X(1)
176.768(19).
nal arrangement with a mutual orientation of the Cp rings
intermediate between staggered (108°) and eclipsed (144°).
The complex in the other solvated pseudopolymorph
1ꢀ2CH2Cl2 also resides on an inversion centre and the
arrangement is therefore antiperiplanar staggered.
The P–Centroid1–Centroid2–P torsion angle in the isomor-
phous solid-state structures of 2 and 4 spans 147.1° corre-
sponding to an anticlinal arrangement.
Complexes 2 and 4 also contain two linearly coordi-
nated gold atoms bound to the diphosphinoferrocene
ligand and have linear geometries around the gold atoms.
The two cyclopentadienyl rings in the ferrocenyl groups
are essentially eclipsed which is expected behaviour of the
majority of monosubstituted ferrocenyl derivatives [13].
The Au-halide arrangement with phosphines are how-
ever different from 1. In complex 1 the Au–P–P–Au torsion
angle is 180.0° (antiperiplanar) due to the symmetry consid-
erations whereas in 2 and 4 the corresponding angles span
110.3° and 112.5° (anticlinal), respectively. The Au–P and
Au–Cl distances in 1 and 2 (and Au–P distance in 4 and

704
T.V. Segapelo et al. / Journal of Organometallic Chemistry 693 (2008) 701–708
6) are in excellent agreement with the average values of
˚
2.229(15) and 2.288(13) A, respectively, obtained by averag-
ing 346 relevant valued complexes reported to the Cam-
bridge Structural Database (CSD). The Au–Br bond
distances in 4 and 6 agree well with the average value of
˚
2.404(10) A computed for 41 relevant complexes reported
to the CSD. The P–Au–Halogen angles in 1, 2, 4, and 6
approach linearity as expected.
2.2. Demetallation of complexes and ligands by bromine
Of the three coinage metals, only gold is readily oxidized
to the +3 oxidation state. Schneider et al. [14] have shown
that when an oxidant such as bromine is added to
[(dppm)(AuBr)2] (dppm = diphenylphosphinomethane), it
first gives [(dppm)AuBr(AuBr3)] and subsequently
[(dppm)(AuBr3)2]. In an attempt to use this approach to
re-convert the Au(I) complexes 3 and 4 to Au(III), we
reacted these complexes with bromine (Scheme 2). We,
however, isolated complexes 5 and 6; showing that bromin-
ation of the cyclopentadienyl rings rather than oxidation of
the Au atom had occurred. Compound 5 was obtained in
64% yield as a red solid, while 6 was obtained in 44% yield
as gold-coloured crystals.
Fig. 4. Molecular drawing of 6 shown with 50% probability ellipsoids.
Selected interatomic distances (A) and angles (°) for 4: Au–P 2.2376(16);
Au–Br(1) 2.4046(7); P–C(7) 1.806(6); P–C(4) 1.840(7); P–C(1) 1.836(7);
C(7)–C(11) 1.335(9); P–Au–Br(1) 175.98(4).
˚
bered ring is in an envelope conformation with a 19.8°
dihedral flap angle.
We could readily brominate dppf and dippf to give the
tribromo substituted phosphinocyclopentenes 7 and 8
and were isolated as red oils, in good yields (Scheme 3).
However, attempts to complex these brominated phosphi-
nocyclopentenes with [AuCl(tht)] and [PdCl2(NCMe)2]
were unsuccessful. This could be due to the reduced donor
ability of the phosphorus atom by the bromide atoms on
the cyclopentene ring.
1
In the H NMR spectrum of 5, peaks due to the bromi-
nated cyclopentene ring appear at 6.76, 5.77, 5.38 and
5.05 ppm, while the phenyl peaks of the diphenylphosphine
1
appear as a multiplet centred at 7.65 ppm. The H NMR
spectrum of 6 also shows a similar chemical shift pattern
with peaks due to the brominated cyclopentene ring
appearing at 6.78, 5.25, 5.20, and 4.98 ppm, with the pro-
ton on the carbon of the double bond being the most
downfield peak and peaks due to the isopropyl moieties
appearing at approximately 2.62 and 1.56 ppm as
multiplets.
It is clear that demetallation resulted from addition of
bromine to the cyclopentadienyl moiety and that the coor-
dinated Au metal plays no role in promoting the demetal-
The structure for complex 6 was determined by single
X-ray crystallography. Crystallographic data are in Table
1 and molecular drawing diagram of 6 and bond
parameters are presented in Fig. 4. The structure of 6 bears
resemblance to the recently reported structure for E1-1-(i-
Pr)2P-2-Me2 N-indeneAuCl complex [15]. The five-mem-
R
P
R
Br
R
R
(i)
Fe
Br
P
R
R
P
Br
(ii)
R
R=Ph 7, i-Pr 8
P
Au Br
Br
R
R
R
Br2
CH2Cl2, 0 oC
Fe
Br
P
Au Br
Ph Ph
R
FeBr4
P
O
Br Au
P
Br
R
Fe
H
R
Yield (%)
R
P
O
9
60
67
5
6
Ph
i-Pr
Ph
i-Pr
3
4
Ph Ph
Scheme 3. (i) Bromination in an inert atmosphere and (ii) bromination in
air, using moist solvents.
Scheme 2. Bromination of bis(phosphino)ferrocene gold complexes.

T.V. Segapelo et al. / Journal of Organometallic Chemistry 693 (2008) 701–708
705
lation. In fact, the intrinsic high nucleophilic character of
the aromatic cyclopentadienyl ring makes them more sus-
ceptible to electrophilic addition by powerful oxidants such
as Br2 or Cl2. The halogenation of cyclopentadienyl rings
takes place following the same mechanism known for halo-
genation of alkenes. This SN2 like mechanism results in an
overall trans addition of the halides. The trans addition is
in good agreement with what is observed in the molecular
structure of 6, where bromines on adjacent carbons are
found to be trans to each other.
Fig. 5(a). A molecular drawing of 9. All H atoms except hydroxyl atom H are omitted.
Fig. 5(b). A top view of the structure of 9. The counterion and all H atoms except the hydroxyl H atom are omitted.

706
T.V. Segapelo et al. / Journal of Organometallic Chemistry 693 (2008) 701–708
Table 2
3. Conclusions
˚
Selected bond lengths [A] and angles [°] for 9
˚
Bond lengths [A]
It is clear that the conditions under which the bromina-
tion reactions are performed are crucial to the type of the
products obtained. When bromination and subsequent
demetallation occurs, the basicity of the phosphines is so
reduced that any attempts to use these brominated phos-
phines in synthesis should be preceded by the complexation
of the desired metal to the diphospinoferrocene before
addition of bromine.
P(1)–O(1)
P(1)–C(1)
P(1)–C(11)
P(1)–C(17)
P(2)–O(2)
P(2)–C(6)
P(2)–C(29)
P(2)–C(23)
O(1)–H
1.5229(11)
1.7697(15)
1.7899(15)
1.7935(15)
1.5257(11)
1.7701(15)
1.7864(14)
1.7969(15)
1.39(4)
O(2)–H
1.03(4)
4. Experimental
Bond angles [°]
O(1)–P(1)–C(1)
O(1)–P(1)–C(11)
C(1)–P(1)–C(11)
O(1)–P(1)–C(17)
C(1)–P(1)–C(17)
C(11)–P(1)–C(17)
O(2)–P(2)–C(6)
O(2)–P(2)–C(29)
C(6)–P(2)–C(29)
O(2)–P(2)–C(23)
C(6)–P(2)–C(23)
C(29)–P(2)–C(23)
P(1)–O(1)–H
112.60(6)
108.50(7)
105.79(7)
111.36(7)
109.17(7)
109.23(7)
111.05(6)
109.51(6)
106.96(7)
111.40(7)
110.70(7)
107.03(7)
123.5(15)
120(2)
4.1. General considerations
All reactions were carried out under an atmosphere of
pre-purified nitrogen unless otherwise indicated. Air- and/
or moisture-sensitive materials were handled using stan-
dard Schlenk techniques except in the preparation of 9.
Hexane, benzene, toluene, diethyl ether, and tetrahydrofu-
ran were purified by distillation from sodium benzophe-
none ketyl under a nitrogen atmosphere. All other
solvents were of reagent grade and were used without fur-
ther purification unless oxygen-free solvent was needed;
then the solvent was purged with nitrogen for ca.
15 min. Dppf and dippf were prepared using reported
procedures [19]. NMR spectra were recorded on a Gemini
2000 instrument (1H at 200 MHz, 13C at 50 MHz). The
chemical shifts are reported in d (ppm) referenced to
P(2)–O(2)–H
When bromination was performed using dppf in air it pro-
duces an oxidized diphosphine, [doppf][FeBr4] (doppf =
1,10-bis(oxodiphenylphosphino)ferrocene), product as the
major product (9), and its structure has been established by
single X-ray diffraction. Table 1 contains the crystallo-
graphic data and Fig. 5 and Table 2 show the molecular
structure and the bond parameters, respectively.
Fig. 5(b) is a top view of 9, which shows that the two cyclo-
pentadienyl rings are staggered as observed in similar
compounds [16]. However, this Fe complex is not pseudo-
centrosymmetric or anticlinal and the P–Centroid–
Centroid–P torsion angle measures 41.9° corresponding to
synclinal arrangement. The reason for this conformation is
the hydrogen bonding interaction between the oxygen atoms
O1 and O2. Neutral ferrocenephosphine oxides have P@O
units that are trans and centrosymmetric but it appears that
on oxidation of diphosphinoferrocene in moist solvent in the
presence of bromine, both phosphorus and iron get oxidized
and lose this symmetry. The distance between the two Oxy-
1
residual H and 13C signals of deuterated chloroform as
internal standard. Microanalyses were carried out at the
University of Cape Town (South Africa) using a Fisons
EA 1108 CHNS elemental analyzer. Mass spectrometry
was performed at the University of Stellenbosch (South
Africa) on a Waters API Quatro Micro at a cone voltage
of 15 kV.
4.2. Synthesis of dppfAu2Cl2 (1)
To
sodium
tetrachloroaurate(III)
dihydrate,
Na[AuCl4]ꢀ2H2O, (0.33 g, 0.90 mmol) dissolved in acetoni-
trile and 6 drops of water was added dppf (0.50 g,
0.90 mmol) in dichloromethane (20 mL). The orange solu-
tion was stirred until it turned yellow with formation of a
white precipitate after an hour. The solvent was removed
under vacuum to yield a yellow solid. Recrystallization of
the yellow solid by slow diffusion of acetonitrile into a
dichloromethane solution of 1 at ꢁ15 °C afforded X-ray
˚
gen atoms, O1 and O2, is 2.417 A, and is similar to the values
of 2.411 (4) reported by Razak et al. [17]. This would induce
significant steric conflict between these oxygen atoms, a big
conflict unless there is an H atom is present between the O
atoms which would result in a very strong O–Hꢀ ꢀ ꢀO bond.
The ferrocene Fe atom is in the +2 oxidation state in this
instance, with the overall positive charge of the cation com-
ing from a proton that hydrogen-bonds the oxygen atoms.
Further evidence is in the lengths of the P–O bond lengths,
1
quality single crystals (0.41 g, 45%). H NMR (CDCl3): d
7.45 (m, 20H, PPh2), 4.72 (s, 4H, C5H4), 4.31 (s, 4H,
C5H4). 31P{1H}: d 30.0.
4.3. Synthesis of dippfAu2Cl2 (2)
˚
which average to 1.523 A. Allen et al. [18] reported P–O with
a delocalized H atom to be 1.513 A while Razak et al. [17]
obtained values between 1.513 and 1.529 A.
A solution of dippf (0.25 g, 0.55 mmol) in MeOH
(15 mL) was added drop-wise for 25 min to a stirred solu-
tion containing Na[AuCl4]ꢀ2 H2O (0.22 g, 0.50 mmol) and
˚
˚

T.V. Segapelo et al. / Journal of Organometallic Chemistry 693 (2008) 701–708
707
sodium chloride (1.13 g, 4.00 mmol) in water (20 mL) at
0 °C. A green solid separated immediately. Stirring was
continued for 30 min and the solid was filtered, washed
with water (20 mL) and re-dissolved in dichloromethane.
Recrystallization by slow diffusion of diethyl ether into
a dichloromethane solution of 2 at ꢁ15 °C gave X-ray
solution was added a solution of Br2 (0.096 g, 0.60 mmol,
0.031 mL) in dichloromethane (10 mL), drop-wise via a
pressure-equalizing funnel. The resultant red solution
was stirred for an hour, filtered and the filtrate evapo-
rated to give a red oil (0.098 g, 64%), that solidified under
1
vacuum. H NMR (CDCl3): 7.65 (s, 1H, PPh2), 6.76 (s,
1
quality single crystals (0.15 g, 42%). H NMR (CDCl3):
1H, C5H4Br3), 5.77 (s, 1H, C5H4Br3), 5.38 (d, 1H,
C5H4Br3, 3JH–H = 16.6 Hz), 5.05 (s,1H, C5H4Br3).
31P{1H}: d 21.0.
d 4.75 (s, 4H, C5H4), 4.50 (s, 4H, C5H4), 3.59 (m, 4H,
P(i-Pr)2), 1.25 (m, 24H, P(i-Pr)2). 13C{1H} NMR: d 74.9
(d, C5H4, JP–C = 28.5 Hz), 73.4 (d, C5H4, JP–C
=
28.5 Hz), 25.6 (i-Pr), 25.1 (i-Pr), 19.3 (i-Pr). 31P{1H}: d
50.0. Anal. Calc. for C22H36Au2Cl2FeP2 ꢀ THF: C 28.63,
H 3.90. Found: C 28.78, H 3.86%. MS (ESI) m/z (%):
847 (M+ꢁCl, 100).
4.7. Synthesis of C5H4Br3P(iPr)2AuBr (6)
Complex 6 was prepared by a similar procedure as
described for 5 using 4 (0.097 g, 0.1 mmol) and Br2
(0.096 g, 0.60 mmol, 0.031 mL). The oil obtained was then
re-dissolved in dichloromethane and layered with an equiv-
alent amount of diethyl ether followed by a large excess of
hexane and allowed to stand for 3 days. The product was
obtained as golden crystals (0.061 g, 44%) suitable for
X-ray diffraction studies. 1H NMR (CDCl3): 6.78 (dd,
4.4. Synthesis of dppfAu2Br2 (3)
To a stirred red solution of Na[AuCl4]ꢀ2H2O (0.30 g,
0.75 mmol) and NaBr (0.23 g, 2.25 mmol) in a mixture of
water–ethanol (8:2 mL) was added drop-wise, over a per-
iod of 20 min a solution of dppf (0.42 g, 0.75 mmol) dis-
solved in dichloromethane (10 mL). The mixture was
stirred for 50 min, after which water was mopped from
the reaction by the addition of MgSO4. The green solution
was filtered and the filtrate evaporated under reduced pres-
sure. The remaining ethanol solution was decanted from
the solid that was then re-dissolved in chloroform and pre-
cipitated with hexane to yield a brown solid (0.134 g, 16%).
Recrystallization of the brown solid by slow diffusion of
THF into a dichloromethane solution of 3 at ꢁ15 °C affor-
ded X-ray quality single crystals. 1H NMR (CDCl3): d
7.47(s, 20H, PPh2), 4.74 (s, 4H, C5H4), 4.31 (s, 4H,
C5H4). 31P{1H}: d 32.0. Anal. Calc. for C34H28Au2Br2-
FeP2 ꢀ 0.5THF: C 37.76, H 2.90. Found: C 37.82, H 2.50.
MS (ESI) m/z (%): 1027 (M+ꢁBr, 10).
3
3
1H, C5H4Br3, JH–H = 0.8 Hz, JH–H = 5.8 Hz), 5.25
3
(d, 1H, C5H4Br3, JH–H = 3.0 Hz), 5.20 (d, 1H, C5H4Br3,
3JH–H = 2.2 Hz), 4.98 (t, 1H, C5H4 Br3, JH–H = 1.6 Hz),
3
2.62–2.41 (m, 2H, P(i-Pr)2), 1.56–1.18 (m, 12H, P(i-Pr)2).
13C {1H}NMR: d 148 (d, C5H4Br3, JP–C = 29.4 Hz),
131.3 (s, i-Pr) 129.2 (s, i-Pr), 57.8 (d, C5H4Br3, JP–C
=
44.4 Hz), 54.8 (d, C5H4Br3, JP–C = 20.7 Hz), 52.6 (d,
C5H4Br3, JP–C = 44.4 Hz), 19.5 (i-Pr). 18.7 (i-Pr). 31P{1H}
NMR: d 46.0. Anal. Calc. for C11H18AuBr4P: C 18.93, H
2.60. Found: C 19.05, H 2.55.
4.8. Synthesis of C5H4Br3PPh2 (7)
To an orange solution of dppf (0.20 g, 0.36 mmol) dis-
solved in dichloromethane (10 mL) and cooled to 0 °C, a
solution of Br2 (0.35 g, 2.16 mmol) dissolved in dichloro-
methane (15 mL) was added drop-wise via a pressure-
equalizing dropping funnel. The resulting deep red solution
was stirred for an hour, filtered and concentrated and ether
(10 mL) was added. The product was obtained as red wax
4.5. Synthesis of dippfAu2Br2 (4)
A solution of dippf (0.23 g, 0.55 mmol) in MeOH
(15 mL) was added drop-wise with stirring to a deep red
solution of Na[AuCl4] ꢀ 2H2O (0.20 g, 0.50 mmol) and
NaBr (0.34 g, 3 mmol) in water (15 mL). A brown solid
separated and was filtered after 25 min. Recrystallization
by slow diffusion of THF into a dichloromethane solution
of 3 at room temperature gave X-ray quality single crystals
1
(0.21 g, 60%). H NMR (CDCl3): 7.64 (s, 1H, C5H4Br3),
7.47 (m, 10H, PPh2), 4.27 (s, 1H, C5H4Br3), 4.25 (s, 1H,
C5H4Br3). 31P{1H} NMR: d 28.0.
4.9. Synthesis of C5H4Br3P(iPr)2 (8)
1
(0.20 g, 37%). H NMR (CDCl3): d 4.75 (s, 4H, C5H4),
4.50 (s, 4H, C5H4), 3.59 (m, 4H, P(i-Pr)2), 1.25 (m, 24H,
P(iPr)2). 13C{1H} NMR: d74.8 (d, C5H4, JP–C = 27.3 Hz),
73.4 (d, C5H4, JP–C = 27.6 Hz), 25.8 (i-Pr), 24.5 (s, i-Pr),
19.4 (i-Pr). 31P{1H} NMR: d 53.0. Anal. Calc. for
C22H36Au2Br2FeP2: C 27.18, H 3.73. Found: C 27.29, H
4.10. MS (ESI) m/z (%): 891 (M+ꢁBr, 70).
Compound 8 was prepared in a similar manner to 7
using dippf (0.20 g, 0.48 mmol) and Br2. The resulting
deep red solution was stirred for an hour, filtered and
evaporated. The crude product was then purified by col-
umn chromatography over silica using a mixture of
dichloromethane and hexane as eluent (1:2). The prod-
uct was obtained as red oil (0.27 g, 67%). 1H NMR
(CDCl3): 7.73 (s, 1H, C5H4Br3), 7.57 (s, 1H,
C5H4Br3), 4.25 (s,1H, C5H4Br3), 4.24 (s,1H, C5H4Br3),
3.02 (s, 2H, P(i-Pr2)2), 1.36 (s, 6H, P(i-Pr2)2). 31P{1H}:
d 35.0.
4.6. Synthesis of C5H4Br3PPh2AuBr (5)
Complex 3 (0.11 g, 0.1 mmol) was dissolved in dichlo-
romethane (10 mL) and solution cooled to 0 °C. To this

708
T.V. Segapelo et al. / Journal of Organometallic Chemistry 693 (2008) 701–708
4.10. Synthesis of doppfFeBr4 (9)
These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.a-
c.uk/data_request/cif. Supplementary data associated with
this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2007.11.057.
To an orange solution of dppf (0.28 g, 0.50 mmol) dis-
solved in dichloromethane (10 mL) and cooled to 0 °C, a
solution of Br2 (0.48 g, 3.0 mmol) dissolved in dichloro-
methane (15 mL) was added drop-wise via a pressure-
equalizing funnel. The resulting deep red solution was
stirred for an hour, filtered and evaporated to afford a
red solid. Recrystallization from chloroform gave red crys-
tals (0.27 g, 56%), suitable for X-ray diffraction studies.
31P{1H}: d 28.0. IR (nujol mull): t(P@O)1168 cmꢁ1. MS
(ESI): m/z (%) 587 (M+ꢁFeBr4, 100).
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Appendix A. Supplementary data
CCDC 665047, 665048, 665049, 665050 and 665051 con-
tain the supplementary crystallographic data for this paper.