Synthesis and characterization of lead(II) complexes with the 4-methoxybenzoyltrifluoroacetonate ligand

Article abstract of DOI:10.1515/znb-2009-0906

To investigate the intermolecular interactions of ligands in lead(II) complexes featuring stereo-chemical activity of the lone electron pair and noncovalent donor-acceptor interactions giving rise also to multidimensional networks, the compounds [Pb₂

Full text of DOI:10.1515/znb-2009-0906

Synthesis and Characterization of Lead(II) Complexes
with the 4-Methoxybenzoyltrifluoroacetonate Ligand
Farzin Marandia and Harald Krautscheidb
a Department of Science, Payame Noor University (PNU), Zanjan, Iran
b Institut fu¨r Anorganische Chemie, Universita¨t Leipzig, Johannisallee 29, 04103 Leipzig, Germany
Reprint requests to Dr. F. Marandi. Fax +98 241 4248542. E-mail: f.marandi@gmail.com
Z. Naturforsch. 2009, 64b, 1027 – 1031; received April 15, 2009
To investigate the intermolecular interactions of ligands in lead(II) complexes featuring stereo-
chemical activity of the lone electron pair and noncovalent donor-acceptor interactions giving
rise also to multidimensional networks, the compounds [Pb2(phen)2(mbtfa)4] (1) and [Pb2(dmp)2
(mbtfa)4] (2) (phen, dmp and mbtfa− for 1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline and
4-methoxybenzoyltrifluoroacetonate ligands, respectively) have been prepared and characterized by
elemental analysis and their crystal structures investigated. The structures show the coordination
number of Pb(II) to be seven and eight, respectively. Supramolecular structures of 1 and 2 are real-
ized by weak directional intermolecular interactions.
Key words: Lead(II), Crystal Structure, Intermolecular Interactions
Table 1. Crystal data and structure refinement for 1 and 2.
Introduction
Compound
Empirical formula
1
2
The Pb2+ cation has a [Xe]4 f145d106s2 electronic
configuration and exhibits an especially versatile char-
acter with respect to the HSAB theory [1] for which
it appears as a borderline acid, able to bind to wide
families of ligands [2] within very flexible coordina-
tion modes [3]. The coordination chemistry of Pb(II)
is mainly determined by two factors: (i) its large
C68H48F12
N4O12Pb2
1755.48
210(2)
-
C72H56F12
N4O12Pb2
1811.59
180(2)
-
Formula weight
Temperature, K
˚
Wavelength, A
0.71073
0.71073
Crystal size, mm3
Crystal system
Space group
0.23×0.19×0.16 0.49×0.11×0.014
triclinic
triclinic
P1 (no. 2)
¯
¯
P1 (no. 2)
˚
a, A
11.2342(9)
11.9459(8)
13.5133(10)
100.361(8)
109.481(9)
100.996(9)
1619.2(2)
1
10.9573(9)
12.2169(10)
14.8803(12)
98.411(6)
104.334(6)
114.111(6)
1691.2(2)
1
1.779
5.070
884
1.9 – 26.0
−13 ≤ h ≤ 13
−13 ≤ k ≤ 15
−18 ≤ l ≤ 18
14298 / 6551
0.058
˚
˚
size (ionic radius 1.32 A [4], covalent radius 1.54 A
˚
˚
b, A
˚
[4], van der Waals radius 2.00 A [5]), which per- c, A
α, deg
mits coordination numbers that range from quasi-
one [6] to twelve [7], and (ii) its 6s electron pair,
which may or may not play a role in the stereochem-
istry of lead(II) complexes [8]. The lone pair activ-
ity can depend on (1) hard or soft ligands, (2) at-
tractive or repulsive interactions among ligands, and
(3) the number of electrons (charge) transferred from
the ligands to the metal atom [3a]. It has been pro-
posed that holodirected structures do not necessar-
ily exclude an inactive lone pair [9]. Recently, in
an effort to explore the role of weak intermolec-
ular interactions among ligands in the stereochem-
ical activity of valence shell electron lone pairs,
the lead(II) complexes with fluorinated β-diketonate
and neutral aromatic diamine chelating ligands have
been synthesized and characterized by X-ray crystal
structure determination [10]. Fluorinated β-diketonate
β, deg
γ, deg
3
˚
Volume, A
Z
Density (calcd.), g cm−3 1.800
µ(MoKα ), mm−1
F(000), e
5.293
852
2.6 – 26.0
−13 ≤ h ≤ 13
−13 ≤ k ≤ 13
−16 ≤ l ≤ 16
θ range, deg
Index ranges
Reflections coll. / indep. 13210 / 5945
Rint
0.026
93.5%
5945 / 442
0.0209 / 0.0406
0.0300 / 0.0418
1.031
Completeness to θmax
Data / ref. parameters
R1 / wR2 [I ≥ 2σ(I)]
R1 / wR2 (all data)
Goodness-of-fit on F2
98.6%
6551 / 467
0.0338 / 0.0766
0.0433 / 0.0790
0.974
−3
˚
∆ρfin (max / min), e A
0.54 / −0.43
1.55 / −1.41
c
0932–0776 / 09 / 0900–1027 $ 06.00 ꢀ 2009 Verlag der Zeitschrift fu¨r Naturforschung, Tu¨bingen · http://znaturforsch.com
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1028
F. Marandi – H. Krautscheid · Lead(II) Complexes with the 4-Methoxybenzoyltrifluoroacetonate Ligand
Fig. 1. ORTEP view of 1 with displace-
ment ellipsoids shown at the 30 % proba-
bility level.
Fig. 2. ORTEP view of 2 (disordered fluorine
atoms omitted for clarity; displacement ellip-
soids 30 %).
ligands are very good probes because of their abil- Results and Discussion
ity for forming intermolecular C–F···π, C–H···π, C–
F···H–C, C–H···O, F···F and π···π interactions. In
The single-crystal X-ray analyses revealed that 1
this paper we report the synthesis and crystal struc-
tures of [Pb2(phen)2(mbtfa)4] (1) and [Pb2(dmp)2-
(mbtfa)4] (2), where phen, dmp and mbtfa− are the ab-
breviations of 1,10-phenanthroline, 2,9-dimethyl-1,10-
phenanthroline and 4-methoxybenzoyltrifluoroaceton-
ate ligands, respectively.
and 2 are dinuclear complexes, similar to other lead(II)
complexes with β-diketonate anions [10b, c]. Crystal
and structure refinement data are given in Table 1,
and selected bond lenghts and angles are listed in Ta-
ble 2. Each asymmetric unit contains one Pb(II) ion,
one phen ligand in 1, one dmp ligand in 2, and two
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F. Marandi – H. Krautscheid · Lead(II) Complexes with the 4-Methoxybenzoyltrifluoroacetonate Ligand
1029
Fig. 3. Packing diagram of 1 as viewed along the
crystallographic a axis showing the F···H, O···H
and F···O interactions and π-π stacking.
Fig. 4. Packing diagram of 2 as viewed along the
a axis showing the F···H and O···H interactions
and π-π stacking.
mbtfa− anions. The coordination number of the Pb(II) H–C interactions (in 1, O6···H11C–C11 2.573(5) A,
˚
atoms in 1 is seven (four nitrogen atoms of two phen ∠O6···H11C–C11 165.17◦, and in 2, O4···H28i–
i
i
i
◦
ligands and three oxygen atoms of two mbtfa− an- C28 2.705(5) A, ∠O4···H28 –C28 143.50 ) and
˚
˚
ions with an additional long Pb···O interaction) and F···O(methoxy) interactions in 1, F5···O3 2.914(4) A
eight in 2 (four nitrogen atoms of two dmp ligands (Figs. 3 and 4) [16 – 18]. The packing diagrams of the
and four oxygen atoms of two mbtfa− anions) (Figs. 1 complexes exhibit structural topologies via two differ-
i
˚
and 2). Three bond lenghts Pb1–O5 2.918(5) A in 1 ent types of π-π stacking (in 1, face-to-face of aromatic
˚
˚
˚
and Pb1–O2 2.829(5) A, Pb1–O1 2.874(3) A in 2 are rings with a distance of 3.289 A, edge-to-edge with a
˚
significantly longer than the sum of the ionic radii, but distance of 3.358 A (Fig. 3) and in 2, face-to-face with
˚
˚
shorter than the sum of the van der Waals radii (3.54 A) a distance of 3.447 A, edge-to-edge with a distance of
˚
[11]. The longer Pb–O bonds were largely overlooked 3.360 A (Fig. 4) [19 – 21].
in previous papers [12]. These long distances are in-
terpreted as a consequence of the position of the oxy-
A useful comparison for 1 and 2 is provided by
a recent structural study of the dinuclear complexes
gen atoms close to the sterically active Pb(II) lone pair of Pb(II) with other fluorinated β-diketonates [10b, c].
[3a, 13 – 15].
The gap in the coordination sphere in 1 is larger than
A search was made for weak directional inter- in 2 (Figs. 1 and 2, Table 2), therefore, the Pb(II) lone
molecular interactions in the crystal structure of pair in 1 is stereochemically more active than in 2.
these compounds. An interesting feature in 1 and 2
To investigate the thermal stability of the complexes,
is that there are C–H···F interactions (in 1, F2··· thermogravimetric analyses (TGA) were carried out on
i
i
i
i
˚
H25 –C25 2.492(4) A and in 2, F4A···H11b –C11
the crystalline samples. The results have shown that
2.417(9), F1A···H11A–C11 2.585(9), F5A···H32– compound 1 starts to decompose at 300 ◦C, while the
i
i
C32 2.622(1) and FA2···H17 –C17 2.648(1) A), O··· decomposition of complex 2 starts at 200 ◦C. It seems
˚
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1030
F. Marandi – H. Krautscheid · Lead(II) Complexes with the 4-Methoxybenzoyltrifluoroacetonate Ligand
˚
Table 2. Selected bond lengths (A) and angles (deg) for 1 and
throline (0.18 g, 1 mmol) or 2,9-dimethyl-1,10-phenanthrol-
ine (0.210 g, 1 mmol) in the other one. Methanol was then
carefully added to fill both arms, the tube was sealed and the
2 with estimated standard deviations in parenthesesa.
1
2
◦
Pb1–O1
Pb1–O2
Pb1–O4
Pb1–O5
2.364(3)
2.482(2)
2.554(3)
2.602(2)
2.664(3)
2.689(3)
2.927(2)
3.954(4)
74.89(8)
79.52(9)
128.69(9
92.94(9)
69.00(8)
68.77(7)
77.28(9)
80.19(9)
135.54(8)
149.16(8)
84.62(8)
140.11(8)
78.66(8)
147.21(8)
61.89(8)
Pb1–O4
Pb1–O5
Pb1–N1
Pb1–N2
Pb1–O2i
Pb1–O1i
Pb1–O2
Pb1–O1
Pb···Pb
2.471(4)
2.528(4)
2.662(4)
2.663(5)
2.720(4)
2.760(5)
2.829(4)
2.874(3)
3.778(5)
ligand-containing arm immersed in a bath at 60 C, while
the other was left at ambient temperature. After 4 d, crys-
tals deposited in the arm at ambient temperature, which were
then filtered off, wa◦shed with acetone and ether, and dried
Pb1–N2
◦
in air. 1: m. p. 210 C, yield: 65 %, 2: m. p. 190 C, yield:
Pb1–N1
Pb1–O5i
70 %. Elemental analysis: C68H48F12N4O12Pb2 (1): calcd.
C 46.48, H 2.73, N 3.19; found C 46.68, H 2.70, N 2.75, and
C72H56F12N4O12Pb2 (2): calcd. C 47.69, H 3.09, N 3.09;
found C 47.40, H 2.90, N 3.40.
Pb···Pb
O1–Pb1–O2
O1–Pb1–O4
O2–Pb1–O4
O1–Pb1–O5
O2–Pb1–O5
O4–Pb1–O5
O1–Pb1–N2
O2–Pb1–N2
O4–Pb1–N2
O5–Pb1–N2
O1–Pb1–N1
O2–Pb1–N1
O4–Pb1–N1
O5–Pb1–N1
O4–Pb1–O5
O4–Pb1–N1
O5–Pb1–N1
O4–Pb1–N2
O5–Pb1–N2
N1–Pb1–N2
O4–Pb1–O2i
O5–Pb1–O2i
N1–Pb1–O2i
N2–Pb1–O2i
69.86(12)
115.38(15)
84.16(14)
80.75(14)
120.00(14)
62.86(14)
116.26(13)
74.90(12)
111.62(12)
161.58(12)
X-Ray structure analyses of 1 and 2
The data collections were performed on imaging plate
diffractometers Stoe IPDS (1) and Stoe IPDS-2T (2) us-
˚
ing MoKα radiation (λ = 0.71073 A). All intensities were
corrected for Lorentz and polarization effects. A numeri-
cal absorption correction was applied to the data of 2. The
structures were solved by Direct Methods and refined by
full-matrix least-squares methods on F2 using all measured
unique reflections (SHELXS/L-97 [22]). The CF3 groups in
2 showed rotational disorder. Anisotropic displacement pa-
rameters were used for all Pb, C, N, O, and non-disordered
F atoms. Hydrogen atoms were included in calculated posi-
tions. The crystallographic data are summarized in Table 1.
Graphical presentations were drawn using ORTEP-3 [23].
CCDC 718040 (1) and 718041 (2) contain the supple-
mentary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data request/
cif.
N2–Pb1–N1
a
Symmetry operation: i: −x, −y, −z.
reasonable to assume that the enhancement of the solid
state stability in 1 is a result of stronger intermolecular
interactions.
Experimental Section
Preparation of [Pb2(phen)2(mbtfa)4] (1) and
[Pb2(dmp)2(mbtfa)4] (2)
The title complexes were prepared by the branched
tube method: 4-methoxybenzoyltrifluoroacetone, Hmbtfa,
(0.460 g, 2 mmol) was placed in one arm of the branched
tube and lead(II) nitrate (0.331 g, 1 mmol) with 1,10-phenan-
Acknowledgement
Support of this investigation by Payame Noor University
is gratefully acknowledged by F. M.
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