Gold(I) and silver(I) complexes of a diphosphine analog of a half-calix[4]arene moiety

Article abstract of DOI:10.1016/j.poly.2012.11.036

The diphosphine ligand bis(5-(tert-butyl)-3-((diphenylphosphino)methyl)-2- methoxyphenyl)methane (BDMMphos) has been metallated with the transition metal complexes Ag(CH₃CN)₄BF₄ and Au(Me ₂S)Cl to yield the corresponding diphosphine metal complexes (BDMMphos)AgBF₄ (1), (BDMMphos)(AuCl)₂ (2) and (BDMMphos)AuClO₄ (3). All of the complexes were characterized by elemental analyses, ¹H, ³¹P and ¹³C NMR spectroscopies and X-ray structure determination. The diphosphine ligand BDMMphos displayed versatile coordination properties. In complexes 1 and 3, BDMMphos chelated metal ions to form stable 12-membered ring complexes with large bite angles, while in complex 2, BDMMphos simply coordinated to two AuCl units as a bridging ligand.

Full text of DOI:10.1016/j.poly.2012.11.036

Polyhedron 50 (2013) 502–506
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Polyhedron
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Gold(I) and silver(I) complexes of a diphosphine analog of a half-calix[4]arene
moiety
⇑
⇑
Xiang-Tai Meng, Rong-Hua Xu, Qing-Shan Li , Feng-Bo Xu
State Key Laboratory and Institute of Elemento-organic Chemistry, Department of Chemistry, Nankai University, Tanjin 300071, PR China
Department of Applied Chemistry, Tianjin University of Technology, Tianjin 300384, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
The diphosphine ligand bis(5-(tert-butyl)-3-((diphenylphosphino)methyl)-2-methoxyphenyl)methane
(BDMMphos) has been metallated with the transition metal complexes Ag(CH3CN)4BF4 and Au(Me2S)Cl
to yield the corresponding diphosphine metal complexes (BDMMphos)AgBF4 (1), (BDMMphos)(AuCl)2
(2) and (BDMMphos)AuClO4 (3). All of the complexes were characterized by elemental analyses, 1H,
31P and 13C NMR spectroscopies and X-ray structure determination. The diphosphine ligand BDMMphos
displayed versatile coordination properties. In complexes 1 and 3, BDMMphos chelated metal ions to
form stable 12-membered ring complexes with large bite angles, while in complex 2, BDMMphos simply
coordinated to two AuCl units as a bridging ligand.
Received 12 June 2012
Accepted 13 November 2012
Available online 5 December 2012
Keywords:
Ag(I) and Au(I) complexes
Diphosphine ligand
Crystal structure
Ó 2012 Elsevier Ltd. All rights reserved.
Large-bite angle
Weak AgÁ Á ÁO interaction
1. Introduction
sized some metal-mediated extended calixarenes with big cavities,
in which metal complexes can act as host molecules to recognize
There has been a continued interest in the design and synthesis
of diphosphine ligands due to the widespread application of their
metal complexes in many catalytic processes and wide uses in
coordination chemistry [1–4]. Moreover, transitional metal cata-
lysts containing bidentate P-donor ligands have received much
attention, because a definite correlation between the diphosphine
bite angle to the metal ions and the corresponding catalytic activ-
ities has been observed for numerous industrially important reac-
tions [5,6]. Therefore, the development of ligand scaffolds has
become more and more valuable when these scaffolds can afford
new catalytic activities. A lot of scaffolds have been developed to
support large bite angle diphosphines in catalysis, such as Xant-
phos, DPEphos and DBFphos (Fig. 1) [7–10]. Unfortunately, among
these large bite angle diphosphine ligands, ligands with versatile
coordination modes are limited. For example, Xantphos, DBEphos
have excessively rigid skeletons, they usually act as rigid scaffolds.
Whereas, DPEphos and other long alkyl chain diphosphine ligands
have more flexible frames, and usually form polymer metal com-
plex mixtures on coordinating with metal ions. In order to enrich
the variety of large bite angle diphosphine ligands, it is continu-
ously necessary to design new scaffolds with versatile coordination
modes. Our group has developed a new large bite angle ligand
based on the half-calix[4]arene moiety [11,12], and have synthe-
some ions and neutral molecules. On the other hand, it is also
important to synthesize some large bite angle transition metal cat-
alysts with special activities for catalytic processes. Thus, a new
diphosphine ligand and three N-heterocyclic carbene ligands based
on this type of scaffold were designed and some transition metal
complexes were synthesized. In these metal complexes, the half-
calix[4]arene fragment scaffold displayed a coordination ability
with two donor atoms in the ligand coordinated with two separate
metal ions (Fig. 2). As part of our continuous research on this
diphosphine ligand, we herein report the application of BDMM-
phos to the syntheses of some Ag(I) and Au(I) complexes. Struc-
tural characterization of the Ag(I) and Au(I) complexes
demonstrated that the BDMMphos ligand also shows a flexible
coordination ability with Ag(I) and Au(I) ions.
2. Results and discussion
The diphosphine ligand BDMMphos was treated with Ag(CH3-
CN)4BF4 in dichloromethane at room temperature for 30 min,
forming the Ag complex (BDMMphos)AgBF4 (1), (Scheme 1). The
31P NMR spectrum of 1 in CDCl3 solution showed a double doublet
signal centered at 10.9 ppm with coupling constants
1J(107Ag–31P) = 517.6 Hz and 1J(109Ag–31P) = 597.6 Hz, which was
in agreement with those reported for other molecular species
exhibiting a P–Ag(I)–P coordination mode [13,14]. In order to ob-
tain more insight into the structure of 1, its positive electrospray
ionization mass spectrum (ESI-MS) was measured. To our surprise,
⇑
Corresponding authors. Tel.: +86 22 23505927; fax: +86 22 23503710 (Q.-S. Li).
E-mail addresses: mengxiangtai23@mail.nankai.edu.cn (X.-T. Meng), qli@nan-
kai.edu.cn (Q.-S. Li).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.11.036

X.-T. Meng et al. / Polyhedron 50 (2013) 502–506
503
O
O
Ph2P
PPh2
PPh2
DPEphos
PPh2
PPh2
DBFphos
O
PPh2
PPh2 OMe
OMe PPh2
Xantphos
BDMMphos
Fig. 1. Selected diphosphine ligands with large-bite angle to metal ions.
the ESI-MS spectrum showed a signal at 844(m/z), which was as-
signed to a species corresponding to one ligand coordinated with
one Ag atom, and not to the extended calixarene-type complex.
To investigate in detail the structural characterization of 1, a single
crystal of 1 was grown by slow diffusion of pentane into its ClCH2-
CH2Cl solution. The crystal structure of 1Á2ClCH2CH2Cl was deter-
mined by X-ray crystallographic analysis. As shown in Fig. 3, in
contrast to the Cu(I) complexes, the diphosphine ligand BDMM-
phos acts as a chelated bidentate ligand, the two P atoms being
bonded to Ag with a P1–Ag–P2 angle of 161.04(4)°, which is larger
than that reported [15]. The P–P distance is 4.694 Å. The two Ag–P
bond lengths are nearly identical (Ag–P1 2.3791(16) and Ag–P2
2.3803(17) Å), and they falls within the range for common Ag–P
bond lengths [16,17]. It is noteworthy that the AgÁ Á ÁO distances
(AgÁ Á ÁO1 2.797 and AgÁ Á ÁO2 2.682 Å) in 1 are different to a normal
Ag–O bond length, being much longer than those reported [18] but
smaller than the sum of their van der Waals radius (3.12 Å), indi-
cating the existence of a weak AgÁ Á ÁO interaction in 1. Thus, the
coordination geometry of Ag(I) in complex 1 is best described as
an approximately linear two-coordinate Ag center with two PPh2
groups, and there are two additional weak, long-range AgÁ Á ÁO
interactions in the solid structure of 1. The dihedral angle of the
skeleton of the two benzene rings in the half-calix[4]arene frag-
ment is 64.6°. The C28–C36–C37, C26–C25–P1 and C39–C49–P2
angles are 120.67°, 108.21° and 107.87°, respectively.
Fig. 3. Crystal structure of 1. All hygrogen atoms, the anion and solvent are omitted
for clarity. Selected bond lengths (Å) and angles (°): Ag1–P1 2.3791(16), Ag1–P2
2.3803(17), Ag1–O1 2.7973(23), Ag1–O2 2.6820(28), P2–Ag1–P1 161.037(56).
Ag(CH3CN)4BF4
CH2Cl2, rt, 30 min
MeO
OMe
Ph2P
PPh2
PPh2OMe
OMe PPh2
Ag
1
-
BF4
BDMMphos
Scheme 1. Preparation of complex 1.
Au(Me2S)Cl
CH2Cl2, rt, 30 min
OMe PPh2
PPh2 OMe
Au
Cl
OMe PPh2
PPh2 OMe
Au
Cl
2
BDMMphos
Similarly, the reaction of the diphosphine ligand BDMMphos
with two equivalents of Au(Me2S)Cl in dichloromethane produced
the complex (BDMMphos)(AuCl)2 (2) (Scheme 2), using the simple
synthetic strategy of R3PAuCl (R = aryl or alkyl) in the literature
[19,20]. The 31P NMR spectrum of 2 showed a singlet at d
32.7 ppm, and the ESI-MS spectrum showed a signal at 1165 (m/
z), indicating the formation of a (BDMMphos)(AuCl)2 molecule. A
single crystal of 2 suitable for X-ray determination was grown by
slow diffusion of pentane into a ClCH2CH2Cl solution of 2. As
Scheme 2. Preparation of complex 2.
shown in Fig. 4, the diphosphine ligand BDMMphos acts as a bridg-
ing ligand coordinated through two phosphorus atoms to two AuCl
arms, which is in agreement with the results obtained in ESI-MS
spectrum. The two P–Au–Cl fragments in 2 are almost perpendicu-
lar to each other. The P1–Au1–Cl1 and P2–Au2–Cl2 bond angles are
N
N
R
R
R
R
N
N
N
N
Ph2P
OCH3
H
OCH3 PPh2
O Cu
OCH3
OCH3
OCH3
OCH3
H
H
X
Cu O
Ag
N
Ag
N
H
Ph2P H3CO
H3CO
PPh2
-
-
X = ClO4- or BF4
2PF6
Fig. 2. Extended calixarenes containing metal bridges.

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X.-T. Meng et al. / Polyhedron 50 (2013) 502–506
Fig. 4. Crystal structure of 2. All hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angles (°): Au1–P1 2.2276(28), Au1–Cl1 2.2776(41),
Au2–P2 2.2262(25), Au2–Cl2 2.2685(27), P1–Au1–Cl1 177.661(99), P2–Au2–Cl2
177.962(114).
Fig. 5. Crystal structure of 3. All hydrogen atoms and the anion are omitted for
clarity. Selected bond lengths (Å) and angles (°): P1–Au1 = P1A–Au1 2.2958(12),
O1–Au1 = O1A–Au1 3.1704(33), P1–Au1–P1A 177.596(42).
177.64(9)° and 177.94(11)°, respectively, and the Au–P and Au–Cl
bond lengths are as common as reported [21]. In addition, the dis-
tance between the two Au atoms is 12.534 Å, no intramolecular or
intermolecular Au–Au interaction is observed. The Au1Á Á ÁO1 and
Au2Á Á ÁO2 distances are 5.592 and 5.835 Å, respectively, indicating
that there are no AuÁ Á ÁO interactions in 2. The dihedral angle of
the skeleton of the two benzene rings in the half-calix[4]arene
fragment is 83.1°. The C16–C25–C26, C14–C13–P1 and C28–C37–
P2 angles are 116.49°, 113.28° and 116.58°, respectively.
Further investigation utilized complex 2 to synthesize an ex-
tended Au-calixarene bearing P–Au(I)–P moieties, and to compare
this with the former extended calixarene containing P–Cu(I)–P
bridges (Scheme 3). Thus, the reaction of 2 with two equivalents
of AgClO4, and with another one equivalent of the ligand BDMM-
phos added to the resultant solution of the dicationic gold com-
plex, should afford the corresponding dicationic gold complex 4,
according to the procedure for the Cu complex [11]. However,
the ESI-MS spectrum showed a molecular weight signal at 933.70
(m/z), corresponding to a complex containing one ligand and one
gold atom (complex 3). Thus, the structure should be similar to
the silver complex 1, but not to the extended calixarene 4. In the
31P NMR spectrum complex 3 displayed a single resonance at d
42.6 ppm in CDCl3. A single crystal of 3 was obtained by slow evap-
oration of a mixed ClCH2CH2Cl and CH3OH solution of 3. As shown
in Fig. 5, BDMMphos acts as a bidentate chelating ligand coordi-
nated to one gold(I) center which adopts an approximately linear
geometry (P1–Au1–P1A 177.59(6)°). The Au1–P1 and Au1–P1A
bond lengths are equal (2.2958(11) Å). Similar to those in complex
1, the AuÁ Á ÁO distance of 3.17 Å indicates a weak interaction be-
tween the Au and oxygen atoms in 3 [22]. No direct interactions
between the gold(I) center and the perchlorate anion are observed.
The P–P distance is 4.591 Å, which is shorter than that in the Ag(I)
complex. The dihedral angle of the two benzene rings in the half-
calix[4]arene fragment is 64.5°. The C16–C21–C16A and C14–
C13–P1 angles are 118.76° and 109.61°, respectively. Compared
with that in the silver complex 1, the C16–C21–C16A angle is smal-
ler. The formation of compound 3 instead of 4 in the reaction can
be explained as follows. The transannular Au(I)–Au(I) interaction
is important in stabilizing [Au2L2] macrocyclic complexes. To some
extent, the steric effects of the half-calix[4]arene scaffold with a
bulky group tBu prevents the formation of the transannular
Au(I)–Au(I) interaction. On the other hand, the P–Au bond length
(2.2958 Å) is longer than that of P–Cu (2.2306 Å), the rigidity of
the ligand permits the formation of the [AuL] complex, but for
the ligand and the Cu(I) ion, only the formation of the [Cu2L2]
metallocyclophane is observed.
3. Experimental
3.1. General procedures
AgClO4, CH2Cl2
rt, 30 min
PPh2OMe
OMe PPh2
PPh2 OMe
Au
OMe PPh2
Au
All manipulations were carried out under an inert atmosphere
of argon using Schlenk techniques. All the solvents were purified
according to standard procedures. 1H, 13C and 31P NMR spectra
were recorded on Bruker AC-300 and Varian-400 spectrometers.
1H, 13C NMR chemical shifts were calibrated to tetramethylsilane
as an external reference, and 31P NMR chemical shifts were cali-
brated to 85% H3PO4 as an external reference. Elemental analyses
were measured using a Yanaco MT-3 elemental analyzer.
Au
Cl
Au
Cl
-
-
ClO4
ClO4
2
BDMMphos
(1 equiv.)
rt, 30 min
PPh2 OMe
Au
OMe PPh2
Au
MeO MeO
Ph2P
PPh2
ClO4
PPh2 OMe
OMe PPh2
Au
3.2. Crystallography
-
3
Colorless crystals of complexes 1–3 were selected for the dif-
fraction analysis. Collection of intensity data was carried out on a
Bruker Smart-1000 CCD diffractometer, using graphite-monochro-
-
2ClO4
4
matized Mo Ka radiation (k = 0.71073 Å) at 298(2) K. The struc-
Scheme 3. Preparation of complex 3.
tures were solved by direct methods and expanded using Fourier

X.-T. Meng et al. / Polyhedron 50 (2013) 502–506
505
Table 1
Details of the crystal parameters, data collection and refinement for complexes 1–3.
1
2
3
Empirical formula
C
53H62AgBCl4F4O2P2
C49H54Au2Cl2O2P2
1201.70
293(2)
C49H54AuClO6P2
1033.31
293(2)
Formula weight (g molÀ1
)
1129.45
293(2)
Temperature (K)
Crystal system
Space group
triclinic
P1
triclinic
P1
monoclinic
C2/c
ꢀ
ꢀ
Unit cell dimensions
a (Å)
b (Å)
c (Å)
a
12.525(5)
14.852(11)
17.179(7)
109.582(6)
107.445(5)
95.134(7)
2807(2)
2
9.5998(18)
13.836(3)
19.409(4)
77.447(3)
82.787(3)
69.990(2)
2368.7(8)
2
23.2109(14)
17.1365(10)
12.0086(7)
90
90.1740(10)
90
4776.4(5)
4
1.463
b
c
V (Å3)
Z
Dcalc (g cmÀ3
)
1.336
0.657
1.691
6.425
Absorption coefficient (mmÀ1
)
3.251
F(000)
1164
1172
2132
h Range for data collection (°)
Reflections collected
2.04–25.03
9799
6576
1.052
1.75–25.03
12986
8253
2.25–25.03
12741
4226
Independent reflections
Goodness-of-fit on F2
1.080
1.082
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0825, wR2 = 0.1583
R1 = 0.0527, wR2 = 0.1433
R1 = 0.0462, wR2 = 0.1249
R1 = 0.0740, wR2 = 0.1372
R1 = 0.0301, wR2 = 0.0870
R1 = 0.0323, wR2 = 0.0880
difference techniques with the SHELXTL-97 program package. The
non-hydrogen atoms were refined anisotropically by full-matrix
least-squares calculations on F2. Hydrogen atoms were located
using the geometric method. Crystallographic data for the three
complexes are summarized in Table 1.
124.42 (Caromatic), 126.25 (Caromatic), 126.32 (Caromatic), 127.88
(2Caromatic), 129.09 (d, J = 11.5 Hz, 4CaromaticP), 129.10 (4Caromatic in
PPh2), 129.68 (4Caromatic in PPh2), 131.92 (4Caromatic in PPh2),
133.20 (2Caromatic), 133.54 (4Caromatic in PPh2), 133.67 (4Caromatic
in PPh2), 146.77 (CaromatictBu), 146.80 (CaromatictBu), 154.38
(CaromaticOCH3), 154.44 (CaromaticOCH3).
3.3. Preparation of complex 1Á2ClCH2CH2Cl
3.5. Synthesis of 3
Under an atmosphere of argon and in the absence of light, to a
dichloromethane (20 ml) solution of BDMMphos (150 mg,
0.20 mmol) was added a dichloromethane (10 ml) solution of
Ag(CH3CN)4BF4 (70 mg, 0.20 mmol) at room temperature. The mix-
ture was allowed to stir for 30 min. After filtration of any insoluble
materials, the solution was evaporated, and the resultant solid was
recrystallized from 1,2-dichloroethane and pentane, affording the
complex 1Á2ClCH2CH2Cl as a white powder (142 mg, 76%). Anal.
Calc. for C53H62AgBCl4F4O2P2: C, 56.36; H, 5.53. Found: C, 56.31;
To
a
dichloromethane (10 ml) solution of
2
(103 mg,
0.14 mmol) was added AgClO4 (60 mg, 0.28 mmol) in one portion
under an argon atmosphere in the absence of light. The resulting
mixture was stirred for 30 min and a white precipitate formed.
103 mg (0.14 mmol) of the ligand BDMMphos was added to the
resulting mixture and stirring was continued for another 30 min.
After filtration of any insoluble materials, the solution was evapo-
rated, and the resulted residue was recrystallized from dichloro-
methane and diethyl ether, affording a white solid, 3 (210 mg,
75%). Anal. Calc. for C49H54AuClO6P2: C, 56.95; H, 5.27. Found: C,
56.82; H, 5.38%. 1H NMR (400 MHz, CDCl3) d (ppm): 1.02 (s, 18H,
tBu), 3.63 (m, 1H, ArCH2Ar), 4.02 (s, 6H, OCH3), 4.17 (m, 1H, ArCH2-
Ar), 4.21 (d, 4H, CH2PPh2), 6.11 (s, 1H, ArH), 6.32 (s, 1H, ArH), 6.83–
6.87 (m, 1H, ArH), 7.20–7.23 (m, 4H, PPh2), 7.37–7.53 (m, 4H,
PPh2), 7.59–7.61 (m, 8H, PPh2), 7.72–7.78 (m, 1H, ArH), 7.84–7.89
(m, 4H, PPh2). 31P{1H} NMR (121 MHz, CDCl3) d (ppm): 42.61 (s).
13C{1H} NMR (100 MHz, CDCl3) d (ppm): 29.88 (d, J = 27.6 Hz,
2CH2P), 30.96 (CMe3), 31.23 (CMe3), 32.31 (ArCH2Ar), 33.76
(CMe3), 34.22 (CMe3), 63.94 (OCH3), 65.83 (OCH3), 126.15
(Caromatic), 126.35 (Caromatic), 126.45 (Caromatic), 126.50 (Caromatic),
128.97 (2Caromatic), 129.95 (4Caromatic in PPh2), 132.22 (d,
J = 20.0 Hz, 4CaromaticP), 132.75 (4Caromatic in PPh2), 132.88
(4Caromatic in PPh2), 133.79 (2Caromatic), 134.49 (4Caromatic in PPh2),
134.62 (4Caromatic in PPh2), 143.25 (2CaromatictBu), 149.41 (Caromatic-
OCH3), 150.34 (CaromaticOCH3).
t
H, 5.47%. 1H NMR (300 MHz, CDCl3) d (ppm): 1.02 (s, 18H, Bu),
3.53 (s, 6H, OCH3), 3.98 (d, 4H, CH2PPh2), 4.21 (s, 2H, ArCH2Ar),
6.19 (s, 2H, ArH), 7.19 (s, 2H, ArH), 7.23–7.69 (m, 20H, PPh2).
31P{1H} NMR (121 MHz, CDCl3) d (ppm): 10.9 (d). 13C{1H} NMR
(100 MHz, CDCl3) d (ppm): 30.03 (d, J = 30.8 Hz, 2CH2P), 31.30
(ArCH2Ar), 34.20 (2CMe3), 43.80 (2CMe3), 60.71 (2OCH3), 127.13
(4Caromatic), 128.02 (2Caromatic), 128.22 (d, J = 12.8 Hz, 4CaromaticP),
128.24 (4Caromatic in PPh2), 129.08 (4Caromatic in PPh2), 130.32
(4Caromatic in PPh2), 132.04 (2Caromatic), 133.11 (4Caromatic in PPh2),
133.23 (4Caromatic in PPh2), 147.62 (2CaromatictBu), 154.10
(2CaromaticOCH3).
3.4. Preparation of complex 2
Similarly, from 150 mg (0.20 mmol) of BDMMphos, 120 mg
(0.20 mmol) of Au(SMe2)Cl and 10 ml dichloromethane, 150 mg
(61%) of 2 were obtained as a white solid. Anal. Calc. for C49H54Au2-
Cl2O2P2: C, 48.97; H, 4.53. Found: C, 48.89; H, 4.48%. 1H NMR
t
(400 MHz, CDCl3) d (ppm): 1.07 (s, 18H, Bu), 3.56 (s, 6H, OCH3),
4. Conclusions
3.86 (d, 4H, CH2PPh2), 3.91 (s, 2H, ArCH2Ar), 6.87 (s, 2H, ArH),
7.06 (s, 2H, ArH), 7.43–7.72 (m, 20H, PPh2). 31P{1H} NMR
(121 MHz, CDCl3) d (ppm): 32.59 (s). 13C{1H} NMR (100 MHz,
CDCl3) d (ppm): 29.50 (d, J = 34.7 Hz, 2CH2P), 30.10 (ArCH2Ar),
31.20 (2CMe3), 34.27 (2CMe3), 61.47 (2OCH3), 124.38 (Caromatic),
In conclusion, three Ag(I) and Au(I) metal complexes (1–3) of
the diphosphine ligand BDMMphos, with a half-calix[4]arene frag-
ment scaffold, have been prepared. The characterization of these
complexes demonstrated a chelated coordination of the diphos-

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X.-T. Meng et al. / Polyhedron 50 (2013) 502–506
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