Synthesis, spectral, thermal, and a crystalline structure of complexes containing [MeC(CH2PPh2)3Cu(I)]

Article abstract of DOI:10.1007/s11164-012-0592-z

The preparation of new [MeC(CH₂PPh₂)₃CuCl] 1 and its derivatives was carried out directly by mixing of CuCl and MeC(CH₂PPh₂)₃ ligand in dry THF, the neutral precursor 1 served to prepare [MeC(CH₂PPh₂) ₃Cu(NCCH₃)]BF₄ 2 and [MeC(CH ₂PPh₂)₃Cu(PCH₂Ph) ₃]BF₄ 3. These complexes are characterized on the basis of elemental analysis, IR, EDS, ¹H, ¹³C and ³¹P{¹H}NMR, FAB-MS, TG/DTA and single-crystal X-ray diffraction studies. Complex 1 crystallizes in the Orthorhombic unit cells with the space group Pna2(1). The structural behavior of MeC(CH₂PPh ₂)₃ ligand in the formed complexes during the coordination reaction was monitored by ³¹P{¹H}NMR in CDCl₃ at room temperature for the first time.

Full text of DOI:10.1007/s11164-012-0592-z

Res Chem Intermed (2013) 39:721–732
DOI 10.1007/s11164-012-0592-z
Synthesis, spectral, thermal, and a crystalline structure
of complexes containing [MeC(CH2PPh2)3Cu(I)]
•
Ismail Warad Omar H Abd-Elkader
•
•
Ahmed Boshaala Nabil Al-Zaqri
•
•
Belkheir Hammouti Taibi Ben Hadda
Received: 22 April 2012 / Accepted: 3 May 2012 / Published online: 30 May 2012
Ó Springer Science+Business Media B.V. 2012
Abstract The preparation of new [MeC(CH2PPh2)3CuCl] 1 and its derivatives
was carried out directly by mixing of CuCl and MeC(CH2PPh2)3 ligand in dry THF,
the neutral precursor 1 served to prepare [MeC(CH2PPh2)3Cu(NCCH3)]BF4 2 and
[MeC(CH2PPh2)3Cu(PCH2Ph)3]BF4 3. These complexes are characterized on the
1
basis of elemental analysis, IR, EDS, H, 13C and 31P{1H}NMR, FAB-MS, TG/
DTA and single-crystal X-ray diffraction studies. Complex 1 crystallizes in the
Orthorhombic unit cells with the space group Pna2(1). The structural behavior of
MeC(CH2PPh2)3 ligand in the formed complexes during the coordination reaction
was monitored by 31P{1H}NMR in CDCl3 at room temperature for the first time.
Keywords Cu(I) complexes Á Tripodal phosphine ligands Á Crystal structure Á
NMR
I. Warad (&) Á N. Al-Zaqri
Department of Chemistry, Science College, King Saud University, PO Box 2455, Riyadh 11451,
Saudi Arabia
e-mail: warad@ksu.edu.sa
O. HAbd-Elkader
Electron Microscope Unit, Zoology Department, College of Science, King Saud University,
Riyadh 11451, Saudi Arabia
A. Boshaala
Chemistry Department, Faculty of Science, Benghazi University, PO Box 1308, Benghazi 130800,
Libya
B. Hammouti
LCAE-URAC18, Faculte des Sciences, Universite Mohammed 1er, 60000 Oujda, Morocco
´
´
T. Ben Hadda
Laboratoire Chimie Materiaux, FSO, Universite Mohammed 1er, 60000 Oujda, Morocco
´
´
123

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I. Warad et al.
Introduction
Over the years, tripodal phosphine ligands have played a very important role in the
design and development of metal complexes-mediated catalysis [1–10]. Bidentate
and tridentate phosphine ligands provide an important advantage over monodentate
phosphine ligands with respect to high control of the coordination number and
stereochemistry of their complexes [11]. Moreover, polyphosphine complexes
have two or more chelate rings usually minimized the unwanted isomers numbers,
and therefore, expected to reveal better stability and catalytic activities [3–11].
Among these ligands, the high C3-symmetric {3-(diphenylphosphino)-2-[(diphenyl-
phosphino)methyl]-2-methylpropyl}(diphenyl)phosphine, MeC(CH2PPh2)3 and its
derivatives are the most extensively investigated ligands to form a large verity of
transition metal complexes, which are found to have applications in several fields of
catalysis [7–11]. The way in which a given polyphosphine coordinates to transition
metal centers depends on the metal type, the counter ions, the ligand arrangement,
and the other ligands surrounding the metal center [12]. Due to the presence of
phosphine atoms in the backbone of the coordinated ligands, structural and fluxional
behavior of such complexes during reaction processes can be easily monitored by
31P{1H}-NMR [13].
In continuation to our ongoing interest in synthesis and characterization of a
variety of novel phosphine transition metal complexes [14–18], herein, we
synthesized and characterized three new neutral and cationic Cupper(I) complexes
using MeC(CH2PPh2)3 ligand. The structure of the MeC(CH2PPh2)3CuCl complex
was characterized by X-ray single crystal measurement.
Experimental
General remarks, materials, and physical measurements
All reactions were carried out in an inert atmosphere (argon) by using standard high
vacuum and Schlenk-line techniques. MeC(CH2PPh2)3, CuCl, and AgBF4 were
available from Merck and used as received. Elemental analyses were carried out on
1
an Elementar Varrio EL analyzer. High-resolution H, 13C{1H}, DEPT 135, and
31P{1H} NMR spectra were recorded on a Bruker DRX 250 spectrometer at 298 K.
FT-IR and FAB-MS data were obtained on a Bruker IFS 48 FT-IR spectrometer and
Finnigan 711A (8 kV), modified by AMD, and reported as mass/charge (m/z),
respectively.
Synthesis of the complex [MeC(CH2PPh2)3CuCl] 1
A mixture of MeC(CH2PPh2)3 (100 mg, 0.16 mmol) in 20 mL of dry dichloro-
methane and CuCl (16 mg, 0.16 mmol) in 40 mL of dry THF was placed in a
round-bottom flask and stirred at room temperature until the tepidity disappeared
(1 day). The solution was concentrated to about 4 mL under reduced pressure. The
addition of 50 mL of dry diethyl ether caused the precipitation of white powder,
123

Synthesis of complex [MeC(CH2PPh2)3Cu(I)]
723
which was filtered and then dried under vacuum to 105.3 mg (yield 90 % based on
Cu). (Scheme 1).
Cu(I)Cl (0.16 mmol) was treated with MeC(CH2PPh2)3 ligand (0.16 mmol), to
produce 1 as white crystal, m.p. = 253 °C. 1H-NMR (CDCl3): d (ppm) 1.57 (s, 3H,
CH3), 2.16 (m, 6H, PCH2), 7.10–7.80 (3 m, 30H, C6H5), 31P{1H}(CDCl3): d (ppm)
-30.2 ppm. 13C{1H}NMR (CDCl3): d (ppm) 35.78 (s, CH3), 43.63 (s, C), 49.19 (m,
CH2), 128.23–141.22 (4 m, C6H5). MS m/z 722.67 [M?] for C41H39ClCuP3.
Calculated: C, 68.05; H, 5.43; Cl, 4.90 %. Found C, 68.35; H, 5.32; Cl, 4.78 %.
PPh
2
24h stirring
THF
CuCl
+
PPh
2
Ph P
Ph P
PPh
2
2
2
PPh
2
Cu
Cl
AgBF4
CH3CN
1
BF4
BF4
P(CH2Ph)3
CH3CN
Ph P
Ph P
PPh
2
2
2
Ph P
Ph P
PPh
2
2
2
Cu
Cu
P(CH Ph)
NCPh
2
3
2
3
Scheme 1 Synthesis of new Cu(I) complexes 1–3
123

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I. Warad et al.
Synthesis of the [MeC(CH2PPh2)3CuNCCH3]BF4 2
A solution of MeC(CH2PPh2)3CuCl (50 mg, 0.07 mmol) in dry 20 mL of CH3CN
was treated with solid AgBF4 (14 mg, 0.08 mmol) directly. The reaction mixture
was stirred for 10 min at RT during which the white precipitate of AgCl was
formed, which was filtrated off (P4), the solution was concentrated to about *2 mL
under reduced pressure. The addition of 50 mL of dry n-hexane caused the
precipitation of white powder, which was filtered and then dried under vacuum to
43 mg (yield 72 % based on Cu). An equivalent amount of MeC(CH2PPh2)3CuCl
and AgBF4 was mixed together, to give 2 as light yellow crystal, m.p. = 270 °C.
1HNMR (CDCl3): d (ppm) 1.67 (s, 3H, CH3), 1.92 (s, 3H, CH3CN), 2.28 (m, 6H,
PCH2), 7.00–7.90 (3 m, 30H, C6H5), 31P{1H}(CDCl3): d (ppm) -20.2 ppm.
13C{1H}NMR (CDCl3): d (ppm) 1.21 (s, CH3CN), 37.82 (s, CH3), 43.83 (s, C),
50.96 (m, CH2), 117.95 (s, CH3CN), 129.00–142.00 (4 m, C6H5). MS m/z 991.2
[M?] for [C48H44CuP3]BF4. Calculated: C, 65.57; H, 5.02; F, 8.67 %. Found C,
65.35; H, 5.12; F, 8.48 %.
Synthesis of the [MeC(CH2PPh2)3CuP(CH2Ph)3]BF4 3
A solution of [MeC(CH2PPh2)3CuNCCH3]BF4 (27 mg, 0.03 mmol) in 20 mL of
dry CH3CN was treated with (10 mg, 0.032 mmol) P(CH2Ph)3 dissolved in 10 mL
of dry CH3CN. The reaction mixture was stirred for 2 h at RT, and then the solution
was concentrated to about 1 mL under reduced pressure. The addition of 50 mL of
dry diethyl ether caused the precipitation of white powder, which was filtered and
then dried under vacuum to 20 mg (yield 61 % based on Cu).
Equivalent amount of [MeC(CH2PPh2)3CuNCCH3]BF4 and AgBF4 was mixed to
give 3.
1
White crystal. m.p. = 220 °C. HNMR (CDCl3): d (ppm) 1.76 (s, 3H, CH3),
2.17 (m, 6H, PCH2Ph), 2.38 (m, 6H, PCH2), 7.00–7.80 (3 m, 45H, C6H5),
31P{1H}(CDCl3): d (ppm) -10.4. 13C{1H}NMR (CDCl3): d (ppm) 38.42 (s, CH3),
44.53 (s, C), 49.87 (m, CH2Ph), 51.88 (m, CH2), 128.00-142.00 (br, m, C6H5). MS
(FAB, m/z): 790.2 [M?] for [C62H60CuP4]BF4. Calculated: C, 69.09; H, 5.57; F,
7.06 %. Found C, 68.85; H, 5.45; F, 7.25 %.
X-ray structural analyses for the desired complex 1
The crystal was grown by slow diffusion of diethyl ether into a solution of the
complex in dichloromethane. Data were collected at 173(2) Siemens P4 diffrac-
tometer operating in the omega scan mode, using graphite monochromated Mo Ka
˚
radiation (k = 0.71073 A). Details of crystal data, data collection, and structure
refinement are given in Table 1. The structure was solved by direct methods using
the Bruker SHELXS-97 programme and refined by full matrix least-squares on F2
using the Bruker SHELXL-97 programme [19, 20].
123

Synthesis of complex [MeC(CH2PPh2)3Cu(I)]
725
Table 1 Crystal data and structure refinement for complex 1
Empirical formula
Formula weight
Temperature
C41H39ClCuP3
723.62
293(2) K
˚
0.71073 A
Wavelength
Crystal system
Space group
Orthorhombic
Pna2(1)
˚
Unit cell dimensions
a = 20.708(10) A a = 90°
˚
b = 10.273(5) A b = 90°
˚
c = 16.965(8) A c = 90°
3
˚
Volume
3609(3) A
Z
4
Density (calculated)
Absorption coefficient
F(000)
1.332 mg/m3
0.841 mm-1
1504
Crystal size
0.34 9 0.22 9 0.20 mm3
Theta range for data collection
Index ranges
1.97–25.90°
-25 \ = h \ = 25, -12 \ = k \ = 12, -20 \ = l \ = 20
Reflections collected
Completeness to theta = 25.90°
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I [ 2sigma(I)]
Absolute structure parameter
Largest diff. peak and hole
CCDC number:853698
29,457
99.1 %
Semi-empirical from equivalents
0.8499 and 0.7631
Full-matrix least-squares on F2
6,882/1/415
0.856
R1 = 0.0429, wR2 = 0.0708
-0.008(11)
-3
˚
0.726 and -0.224 e A
Results and discussion
Complex synthetic investigation
The reason for choosing the C3-symmetric MeC(CH2PPh2)3 ligand with the
equivalent P atoms was to reduce the number of possible isomeric metal complexes.
The reaction scheme for the synthesis of new [MeC(CH2PPh2)3Cu(I)] complexes is
depicted in Scheme 1.
The air-stable complex [MeC(CH2PPh2)3Cu(I)Cl] 1 was obtained in a very good
yield by mixing CuCl with equivalent of MeC(CH2PPh2)3 in dry THF. Treatment of
1 with equivalent amount of AgBF4 in CH3CN leads to monocation air-sensitive
[MeC(CH2PPh2)3Cu(I)(NCPh)]BF4 2 formation, which served to prepare air
unstable monocation [MeC(CH2PPh2)3Cu(I)(P(CH2Ph)3)]BF4 3. The structure of
the desired complexes have been deduced from elemental analysis, FAB-mass
123

726
I. Warad et al.
1
spectrometry, infrared spectroscopy, EDS, UV–visible, H, 13C{1H} and 31P{1H}
NMR, spectroscopy TG/DTA, and X-ray single crystal measurement.
Electronic absorption and IR spectral studies
The electronic absorption spectrum of desired complexes was acquired in
chloroform at room temperature. The complexes formed colorless solutions
(10-4 M). The complexes displayed intense transitions in the UV–Vis region.
”
Bands ( *104 mol-1 dm3 cm-1) in the high-energy side at 200–280 nm that is
referred to the ligand centered charge transitions. On the basis of its intensity and
”
position, the lowest energy transitions at *310–400 nm ( *103 mol-1 dm3 cm-1
)
have been tentatively assigned to Mdp–Lp* metal to ligand charge transfer
transitions (MLCT) [21]. As typical example absorption bands at 205, 212, and
310 nm are depicted in Fig. 1a.
Fig. 1 a UV–Vis spectrum of complex 1 in CHCl3 at RT. b IR-KBr disk spectra of (a) MeC(CH2PPh2)3
free ligand, (b) complex 1, (c) complex 2, (d) complex 3
123

Synthesis of complex [MeC(CH2PPh2)3Cu(I)]
727
The IR spectra of the complexes have been examined in comparison with the
spectra of the free ligands. IR spectra of the desired complexes in particular show
main three sets of characteristic absorptions in the range 3,480 cm-1 broad
(excepted complex 1), 3,120 cm-1 sharp and 2,920–2,800 cm-1 multiple, which
can be assigned to –H2O, Ph-CH, and alkyl-CH stretching vibrations, respectively.
All the other function group vibrations are appeared at their expected positions as in
Fig. 1b.
EDS measurements
To identify and differentiate the chemical composition of the desired complexes
1–3. The complexes were subjected to EDS measurement as in Fig. 2. All the
complexes were found to have signs belong their composition; they contain signs of
carbon at 0.2 eV, cupper signs at 0.8, 8.1 eV, and phosphine signs at 2 eV. The sign
at 2.6 eV in complex 1 was cited to chloride atom (Fig. 2a), this sign was
disappeared in complex 2 and 3 (Fig. 2b and c), because the chloride atom was
removed by AgBF4, the presence of fluoride sign at 1.7 eV in both complex 2 and 3
(Fig. 2b and c) confirmed chloride-abstraction from complex 1 to produce complex
2 and 3.
Thermal studies
The thermal decomposition studies of the complex 1 was investigated in the
0–1,000 °C temperature range under open atmosphere at a heating rate of 10 °C/
min. Typical thermal TG and DTA curves are given in Fig. 3.
There is no weight loss in the range 0–380 °C, which indicates the absence of
coordinated or uncoordinated water molecules. Such complexes undergo two-step
decomposition with weight loss experimentally 90 %, the coordinated chlorides and
MeC(CH2PPh2) ligands have been de-structured from the complex in between 380
and 450 °C and 450 and 840 °C with exothermic DTA peaks at 440, 475, 585, 675,
and 810 °C. The final residue was analyzed by IR spectra and identified as Cupper
oxide (Cu2O, 28 %).
NMR investigations
The 31P{1H} NMR spectra of the desired complexes 1–3 was recorded in CDCl3 at
RT, it revealed one broad singlet signal at -31.1, -20.2, and 10.4 (multi) ppm,
respectively. This is consistent with the formation of tetrahedral C3v symmetry
complexes with three equivalent phosphorus of the ligand coordinated to the
Cu(I) center atom. The broadening of the signal is indicative of fluxional behavior
inside these complexes, as in (Fig. 4).
1
In the H-NMR and 13C{1H}NMR, spectra of the desired complexes have been
recorded in CDCl3 solution to confirm the binding of the ligand to the Cu(I) and
their assignments are given in Sect. 2. Several characteristic set of signals are
observed attributed to the triphos ligand, CH3CN and P(CH2PH)3. The integration
1
of the H resonances confirms the desired complexes formation.
123

728
I. Warad et al.
Fig. 2 EDS sings of atomic content in of complex 1 (a), complex 2 (b), and complex 3 (c)
X-ray structural analyses for the complex 1
The molecular structure of the complex 1 has been determined by single crystal
X-ray diffraction and the ORTEP diagram is given in Fig. 5. Complex 1 is
crystallized as free solvated isomer with approximate C3v symmetry.
The Cu(I) atom in complex 1 has a distorted tetrahedral environment formed by
three P atoms from MeC(CH2PPh2)3 and one Cl atom. The average for Cu-P bond
˚
lengths in the complex (2.292 A) is very close to the value found (2.2953 A) in the
˚
chloro complex [22] and in both cases are in the expected range for four-coordinate
˚
˚
Cu(I) systems (2.304 A). However, the Cu–Cl distance (2.2587 A) [22].
A summary of crystal parameters, data collection, and refinement for the crystal
structure is given in Table 1, selected bond lengths and angles are listed in Table 2,
and atomic coordinates and equivalent isotropic displacement parameters for
complex 1 are listed in Table 3.
123

Synthesis of complex [MeC(CH2PPh2)3Cu(I)]
729
Fig. 3 TG and DTA thermal curves of complex 1
Fig. 4 31P{1H} NMR spectrum free ligand (a), 1 (b), 2 (c), and 3 (d), in CDCl3 at RT
123

730
I. Warad et al.
Fig. 5 Labeled ORTEP diagram of complex 1 with thermal probability
˚
Table 2 Bond lengths [A] and angles [°] for complex 1
P(1)–Cu(1)
P(2)–Cu(1)
P(3)–Cu(1)
Cl(2)–Cu(1)
2.2930(15)
2.2819(14)
2.2954(14)
2.2587(14)
Cl(2)–Cu(1)–P(2)
Cl(2)–Cu(1)–P(1)
P(2)–Cu(1)–P(1)
Cl(2)–Cu(1)–P(3)
P(2)–Cu(1)–P(3)
P(1)–Cu(1)–P(3)
125.84(5)
120.22(5)
92.08(4)
120.77(5)
95.92(5)
94.22(4)
Conclusions
The desired Cu(I) complexes were made available through direct synthesis using
equivalent tripodal triphosphine ligand in good yield. The structure of the
complexes was characterized by several physical measurements, EA, FAB-MS,
IR, UV–Vis, 1H, 13C and 31P{1H}NMR, TG/DTA and X-ray single crystal. In solid
state using X-ray single crystal structure of complex characterized as regular
tetrahedral, which was also confirmed by liquid 31P{1H}NMR.
123

Synthesis of complex [MeC(CH2PPh2)3Cu(I)]
731
4
2
Table 3 Atomic coordinates (910 ) and equivalent isotropic displacement parameters (A 9 103) for
˚
complex 1
X
Y
Z
U (eq)
C(1)
10324(2)
10020(2)
10589(2)
10680(2)
10296(2)
10501(3)
11069(4)
11443(3)
11247(3)
11023(2)
11634(2)
12078(2)
11922(3)
11319(3)
10861(2)
9584(2)
10032(2)
10364(2)
10816(3)
10944(3)
10630(2)
10171(2)
8705(2)
8641(2)
8114(3)
7646(2)
7705(2)
8229(2)
9633(2)
8265(2)
7842(2)
7306(2)
7191(3)
7597(2)
8121(2)
8856(2)
8534(2)
8398(2)
8586(2)
8909(2)
7197(4)
7825(3)
8317(4)
7271(4)
6869(4)
5850(6)
5225(5)
5599(5)
6614(4)
9869(3)
9921(3)
10816(4)
11670(4)
11641(4)
10748(4)
8952(3)
11482(4)
11650(5)
12600(6)
13424(5)
13261(4)
12285(4)
11072(3)
11169(4)
11784(5)
12321(5)
12255(5)
11618(4)
6736(3)
7157(4)
8185(4)
8101(6)
6987(6)
5963(5)
6044(5)
5914(3)
6160(4)
5171(5)
3923(5)
3667(4)
4171(2)
4914(2)
5419(2)
7011(2)
7635(3)
8113(3)
7961(4)
7343(4)
6864(3)
6736(2)
6434(3)
6683(3)
7267(3)
7584(3)
7330(2)
4616(2)
5173(2)
4472(3)
4402(3)
5028(4)
5723(4)
5793(3)
4829(2)
4025(2)
3696(3)
4161(4)
4948(4)
5299(3)
5343(2)
5387(2)
5338(3)
4825(4)
4405(3)
4469(3)
4948(2)
6673(2)
7365(2)
7884(2)
7728(3)
7044(3)
55(1)
43(1)
48(1)
55(1)
73(1)
100(2)
111(2)
101(2)
74(1)
47(1)
59(1)
69(1)
78(1)
76(1)
63(1)
46(1)
48(1)
80(2)
101(2)
92(2)
80(2)
60(1)
49(1)
66(1)
82(2)
87(2)
91(2)
65(1)
47(1)
49(1)
71(1)
94(2)
93(2)
81(1)
66(1)
45(1)
53(1)
65(1)
64(1)
66(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
C(40)
123

732
I. Warad et al.
Table 3 continued
X
Y
Z
U (eq)
C(41)
P(1)
9046(2)
10401(1)
9387(1)
8984(1)
8895(1)
9328(1)
4642(3)
8694(1)
10274(1)
7280(1)
10073(1)
9243(1)
6522(3)
6463(1)
5314(1)
6013(1)
7617(1)
6504(1)
56(1)
48(1)
44(1)
45(1)
88(1)
50(1)
P(2)
P(3)
Cl(2)
Cu(1)
Acknowledgments The project was supported by King Saud University, Deanship of Scientific
Research, College of Science Research Center.
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