Synthesis and crystal structures of fluorinated β-diketonate metal (Al3+, Co2+, Ni2+, and Cu2+) complexes

Article abstract of DOI:10.1246/bcsj.82.96

Co²⁺, Ni²⁺, and Cu²⁺ complexes with bis(pentafluorobenzoyl)methanide (L, C₆F₅COCHCOC ₆F₅^-) were prepared from [Al(L)₃], which was directly synthesized from

Full text of DOI:10.1246/bcsj.82.96

96
Bull. Chem. Soc. Jpn. Vol. 82, No. 1, 96–98 (2009)
Short Articles
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Synthesis and Crystal Structures of
Fluorinated ¢-Diketonate Metal
(Al3+, Co2+, Ni2+, and Cu2+)
Complexes
O
O
F
F
F
F
pentafluorobenzoyl chloride
vinyl acetate
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F
F
F
F
F
AlCl3
Al
O
O
1,1,2,2-tetrachloroethane
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O
O
F
F
F
F
F
F
F
F
F
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[AlL3] (1)
Akiko Hori,* Ayaka Shinohe, Shohei Takatani,
and Takeshi K. Miyamoto
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O
CH3
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Department of Chemistry, School of Science,
1a
1b
Kitasato University, 1-15-1 Kitasato, Sagamihara 228-8555
Scheme 1. Synthesis of 1 and by-products 1a and 1b.
Received August 26, 2008; E-mail: hori@kitasato-u.ac.jp
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Co2+, Ni2+, and Cu2+ complexes with bis(pentafluoro-
benzoyl)methanide (L, C6F5COCHCOC6F5Õ) were prepared
from [Al(L)3], which was directly synthesized from AlCl3,
pentafluorobenzoyl chloride, and vinyl acetate under N2
atmosphere. The complexation of L with Co2+ and Ni2+
ions gave [M2(L)4(OH2)2] (M = Co and Ni) and that with
Cu2+ ion gave [Cu(L)2].
F
F
F
F
F
O
O
F
F
H2O
M
O
F
M(OAc)2·nH2O
F
F
O
M
O
1
F
F
F
O
OH2
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O
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O
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F
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F
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2: M = Co, 3: M = Ni
Cu(OAc)2·H2O
F
F
F
F
F
Fluorine-attached coordination complexes have been widely
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F
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F
F
investigated to control their spectroscopic and redox properties
due to their potentially unique properties; high electrophilicity
and polarization.1,2 Especially, fully fluorinated aromatic
substituents, e.g., ÍC6F5 or ÍC6F4Í, show unique interactions
with aromatic hydrocarbons because of the reversion of charge
orientation of the quadrupole moments;3 benzene and hexa-
fluorobenzene have alternately layered stacks.4 This is now
well known as the areneÍperfluoroarene interaction to develop
self-assembled supramolecular motifs.5,6 However, the syn-
thesis of perfluorinated ¢-diketones fundamentally shows poor
yields and instability because of the possibility of intra-
molecular cyclization reactions; e.g., bis(pentafluorobenzoyl)-
methane (HL) is transformed into 5,6,7,8-tetrafluoro-2-(penta-
fluorophenyl)-4H-chromen-4-one (1b).7 Thus, we attempted a
metal-exchange reaction to develop a synthesis of fluorinated
¢-diketonate metal complexes. In this paper we report the
unique synthesis and crystal structures of fluorinated com-
plexes, [Co2(L)4(OH2)2] 2, [Ni2(L)4(OH2)2] 3, and [Cu(L)2]8 4
from [Al(L)3] 1.
F
F
O
O
F
O
O
F
F
F
Cu
F
4
F
F
F
Scheme 2. Syntheses of 2, 3, and 4 from 1 with metal acetate
in CH2Cl2Íethanol solution at rt.
37%). 1H NMR spectrum gave only one singlet peak at ¤ 6.29,
showing clearly a highly symmetric structure. The result of
elemental analysis shows the isolation of 1 as a pure product:
Calcd for C45H3AlF30O6 (%): C, 43.71; H, 0.24. Found: C,
43.79; H, 0.34. The crystal structure of 1 was deposited in
CCDC 699193. The yield of 1 decreased in air and the
formation of by-product 1b increased when the reaction was
conducted at high temperature.
Al3+ complex 1 is useful as a starting material for the
complexation with valuable transition metals, in this case,
Co2+, Ni2+, and Cu2+ ions (Scheme 2).
Starting material of Al3+ complex 1 was directly prepared as
colorless block crystals during the preparation of its ligand,
bis(pentafluorobenzoyl)methane (HL), as previously reported
via the vinyl acetate.9 The reaction of pentafluorobenzoyl
chloride and vinyl acetate in 1,1,2,2-tetrachloroethane in
the presence of anhydrous AlCl3 gave 1 with two by-prod-
ucts: 1-(pentafluorophenyl)-1,3-butanedione (1a) and 5,6,7,8-
M(OAc)2¢4H2O (M = Co and Ni) and 1 were combined
in an ethanol/CH2Cl2 solution to give dinuclear complexes
[Co2(L)4(OH2)2] 2 and [Ni2(L)4(OH2)2] 3. The results of
elemental analyses showed the formation of 2 (Calcd for
C60H8Co2F40O10 (%): C, 40.79; H, 0.46. Found: C, 40.85; H,
0.56) and 3 (Calcd for C60H8F40Ni2O10 (%): C, 40.81; H, 0.46.
Found: C, 40.98; H, 0.47). These complexes were crystallized
from CH2Cl2 with the gas-phase diffusion of benzene to give red
block crystals of 2¢2C6H6 and green block crystals of 3¢2C6H6.
The same products 2 and 3 were obtained when 10% water was
added to the reaction mixture, irrespective of the polarity of the
solvents. This fact is in contrast to the general tendency that
tetrafluoro-2-(pentafluorophenyl)-4H-chromen-4-one
(1b)
(Scheme 1). In spite of the description in Ref. 9, the free
ligand HL was not obtained under these conditions. Typically,
the reaction was employed under N2 atmosphere and was
precisely kept at 35 °C to give the desired complex 1 (yield
Published on the web January 14, 2009; doi:10.1246/bcsj.82.96

A. Hori et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 1 (2009)
97
(a)
F7
F8
C12
F4
C4
C13
F5
F6
C11
C10
C9
C14
C5
C6
C1
F9
C15
O5
O1
O4i
Coi
F3
F10
O2
C8
C3
C2
C7
O2
benzene
Co
O1
F16
Co
O4
C25
C24
benzene
F17
C27
F2
C26
O3
O3
O4
F1
F11
C16
C28
C21
C22 C23
F15
F18
C17
C29
F19
F12
C30
C20
F14
C18
C19
F20
F13
(b)
Figure 2. A part of the structure around Co2+ ion of 2.
C29iÍC30i) in 2 have further intramolecular ³Í³ stacks with
a distance of nearly 3.3 ¡ and the closest atom£atom distance
is 2.949 ¡ (F5£F19i). Thus, the pentafluorophenyl rings have a
twisted conformation with the coordination plane, leading to
the efficient overlapping of the ligands for dinuclear com-
plexes. This feature is in contrast to the case of the complexes
of DBM,11 where phenyl rings and the coordination plane are
essentially planar due to the expanding ³-conjugation, which
causes a steric hindrance and hence mononucleation. Further-
more, both crystals of 2 and 3 were well grown in benzene
atmosphere and two benzenes behave as crystal solvents. The
benzenes are located close to the pentafluorophenyl groups and
the average C6H6£C6F5 intermolecular distance is around
3.4 ¡, showing the areneÍperfluoroarene interaction.4Í6
O1i
O2
benzene-2
Cu
benzene-2
O2i
O1
benzene-1
Figure 1. ORTEP drawings of the crystal structure of (a)
2¢2C6H6 and (b) 4¢3C6H6 at 100 K with 50% probability
thermal ellipsoids. For (a) and (b), symmetry transforma-
tions used to generate equivalent atoms show i (Õx + 1,
Õy, Õz) and i (Õx + 2, Õy + 1, z), respectively.
On the other hand, complex 1 and Cu(OAc)2¢H2O gave the
mononuclear complex [Cu(L)2] 4 as bluish green crystals of
4¢3C6H6 under the same conditions as those of 2 and 3.8
Complex 4 comprises one Cu2+ and two L to give the
mononuclear complex (Figure 1b). The geometry around the
metal is essentially planar. The average of the CuÍO(L) and
O=C bond distances are 1.92 and 1.27 ¡, respectively. The
pentafluorophenyl groups are also highly twisted with respect
to the coordination plane and the torsion angles C5ÍC6ÍC7ÍC8
and C8ÍC9ÍC10ÍC15 are 58.9(3) and 57.9(3)°, respectively.12
In the crystal of 4, three benzenes are sited in unique
positions in the crystal. Benzene-1 closely interacts with Cu2+
ion and two benzene-2 interact with pentafluorophenyl groups
of 4. Benzene-1 is observed at the axial position of Cu and the
intermolecular distance between 4 and benzene-1 is approx-
imately 3.4 ¡. Benzene-1 is stabilized by cationͳ interaction13
with Cu2+ and by the CH£F interaction14 with pentafluoro-
phenyl groups. The cavity effects surrounding pentafluoro-
phenyl rings of 4 also stabilized the position of benzene-1.
Benzene-2 is located close to the pentafluorophenyl group of 4
and the average C6H6£C6F5 intermolecular distance is 3.4 ¡.
All crystals show good affinity for benzene molecules and
sufficiently large crystals are grown in benzene atmosphere.
In conclusion, remarkably different complexes, dinuclear
complexes with the fluorinated ligand and mononuclear
complexes11 with DBM, have been obtained for Co2+ and
Ni2+ with octahedral geometry, while mononuclear complexes
have been obtained for Cu2+ with square-planar geometry.
These facts result from the steric hindrance due to fluorine
substitutions and electrostatic interactions.
mononuclear complexes are obtained with bulky diketonate
ligands or in polar media.10,11 For example, when M(OAc)2¢
4H2O (M = Co and Ni) and dibenzoylmethane (DBM, non-
fluorinated ligand) were combined in the same procedure,
mononuclear complexes were obtained and it was thought that
the large phenyl groups sterically hindered dinucleation and
two polar solvent molecules sited on axial positions.11 Thus,
structures of 2 and 3 are unique objects, being thought to result
from the influence of fluorine-substitutions.
The crystal structure of complex 2 is shown in Figure 1a and
the crystal structure of 3 resembles that of 2. Complex 2
comprises two Co2+ ions, four ligands (L), and two water
molecules to give the dinuclear complex. Complex 3 also
comprises two Ni2+ ions, four ligands (L), and two water
molecules. Both of the geometries around metal centers are
pseudo octahedral. The metal£metal separations are 3.182 ¡
(2) and 3.139 ¡ (3). The MÍO(L) distances are 2.0132(11),
2.0407(11), 2.0496(11), 2.0465(11), and 2.1628(11) ¡ for 2
and 1.9842(11), 2.0138(12), 2.0087(12), 2.0231(11), and
2.1224(12) ¡ for 3. The CoÍO5(water) and NiÍO5(water)
distances are 2.1127(13) and 2.0829(13) ¡, respectively. The
average of the O=C bond distances are the same, 1.27 ¡, for 2
and 3. The pentafluorophenyl groups of 2 are highly twisted
with respect to the coordination plane and the torsion angles
C5ÍC6ÍC7ÍC8, C8ÍC9ÍC10ÍC15, C20ÍC21ÍC22ÍC23, and
C23ÍC24ÍC25ÍC30 are 38.9(2), 63.6(2), 35.7(2), and 68.2(2)°,
respectively (Figure 2). Those of 3 are similarly twisted with
respect to the coordination plane. Two pentafluorophenyl
groups (C1ÍC2ÍC3ÍC4ÍC5ÍC6 and C25iÍC26iÍC27iÍC28iÍ

98
Bull. Chem. Soc. Jpn. Vol. 82, No. 1 (2009)
© 2009 The Chemical Society of Japan
¢ = 107.770(1)°, V = 2139.6(4) ¡3, Z = 2, µcalcd = 1.919 g cmÕ3
,
Experimental
2
GOF = 1.062, R((I) > 2·(I)) = 0.0399, wR(Fo ) = 0.1096, CCDC
699193; (b) 2¢2C6H6: C72H20Co2F40O10, MW 1922.74, mono-
clinic, P21/n, a = 11.5519(6) ¡, b = 16.1859(9) ¡, c =
18.0976(10) ¡, ¢ = 98.961(1)°, V = 3342.5(3) ¡3, Z = 2,
All chemicals were of reagent grade and used without further
purification. 1H NMR spectral data were recorded on a Bruker
DRX600 spectrometer. Infrared and electronic absorption spectra
were recorded on a Shimadzu IR 8400s and JASCO V-570
spectrometer, respectively. Cyclic voltammetry (CV) was per-
formed with a BAS CV-100W potentiostat using tetrabutylammo-
nium perchlorate (TBAP) solution. CV of fluorine-attached
compound 2Í4 was only irreversible. The results of elemental
analysis of C and H were collected by Perkin-Elmer PE2400
analyzer.
µ
calcd = 1.910 g cmÕ3
,
GOF = 1.066, R((I) > 2·(I)) = 0.0293,
2
wR(Fo ) = 0.0887, CCDC 699194; (c) 3¢2C6H6: C72H20F40Ni2O10,
MW 1922.30, monoclinic, P21/n, a = 11.5848(5) ¡, b =
16.1079(6) ¡, c = 18.0508(7) ¡, ¢ = 99.050(1)°, V = 3326.5(2)
¡3, Z = 2, µcalcd = 1.919 g cmÕ3, GOF = 1.086, R((I) > 2·(I)) =
2
0.0293, wR(Fo ) = 0.0866, CCDC 699196; (d) 4¢3C6H6: C48H20-
CuF20O4, MW 1104.18, orthorhombic, Fdd2, a = 26.7956(13) ¡,
b = 47.077(2) ¡, c = 6.7294(3) ¡, V = 8488.8(7) ¡3, Z = 8,
[Al(L)3] 1. Anhydrous AlCl3 (2.93 g, 22 mmol) and penta-
fluorobenzoyl chloride (5.00 g, 22 mmol) in 1,1,2,2-tetrachloro-
ethane (20 mL) was stirred at 45 °C for 1 h under N2. Vinyl acetate
(1.89 g, 0.022 mmol) was added dropwise into the reaction mixture
at 25 °C over 60 min. The mixture was stirred at 35 °C for 12 h and
was then poured into 10% hydrochloric acid (50 mL) at 0 °C. The
mixture was steam distilled to remove the solvent and the residue
was extracted with diethyl ether. The residue was distilled to
remove 1a at 80 °C under vacuum (around 1 mmHg). The residue
was purified by column chromatography (alumina, benzene); the
first product (Rf = 0.8) was complex 1 and the second product
(Rf = 0.5) was characterized as 1b. Complex 1 was further
purified by crystallization in benzene/hexane. Yield 37%. mp
194 °C. 1H NMR (600 MHz, CDCl3): ¤ 6.29 (s). 13C NMR (150
MHz, CDCl3): ¤ 178.4 (CO), 145.0 (d, J = 256 Hz, CF), 142.9 (d,
J = 256 Hz, CF), 137.8 (d, J = 256 Hz, CF), 113.5 (t, J = 14.8
Hz), 107.2 (CH). UVÍvis {CH2Cl2, - nm (¾ MÕ1 cmÕ1)}: 337
(74600), 254 (29000). IR (KBr disk, cmÕ1): 1653, 1591, 1501,
1437, 1397, 1342, 1116, 999, 938, 825.
[Co2(L)4(OH2)2] 2. A solution of 1 (1.00 g, 0.8 mmol) in 1:1
ethanolÍCH2Cl2 solution (20 mL) was added to a solution of
Co(OAc)2¢4H2O (0.30 g, 1.2 mmol) in ethanol (10 mL). The
mixture was stirred for 2 h at rt. The reaction mixture was
evaporated to give red powder. The powder was extracted with
CH2Cl2 and crystallized in CH2Cl2/benzene to give complex 2.
Yield 70%. mp 126 °C. UVÍvis {CH2Cl2, - nm (¾ MÕ1 cmÕ1)}:
546sh (100), 512sh (130), 319 (62200), 232 (40300). IR (KBr disk,
cmÕ1): 3675, 1653, 1589, 1498, 1436, 1412, 1330, 1212, 1111,
998, 819, 629. CV (0.1 M TBAP/CH2Cl2, V): Ep 1.194, Ep
µ
calcd = 1.728 g cmÕ3
,
GOF = 1.140, R((I) > 2·(I)) = 0.0246,
2
wR(Fo ) = 0.0829, CCDC 699195. These data can be obtained
free of charge from The Cambridge Crystallographic Data Center
via www.ccdc.cam.ac.uk/data_request/cif.
This work was supported by a Grant-in-Aid for Young
Scientists B (No. 19750052) of MEXT and a Kitasato
University Research Grant for Young Researchers. A.H thanks
the Hayashi Memorial Foundation for Female Natural Scien-
tists.
References
1
a) P. Kirsch, Modern Fluoroorganic Chemistry: Synthesis,
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C. J. Willis, Coord. Chem. Rev. 1988, 88, 133.
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R. J. Doerksen, A. J. Thakkar, J. Phys. Chem. A 1999, 103,
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J. H. Williams, Acc. Chem. Res. 1993, 26, 593.
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a1
a2
1.178, Ep 0.25.
c
7
8
E. Uhleman, H. Motzny, G. Wilke, Z. Chem. 1972, 12, 267.
The crystal structure of 4¢3C6H6 at rt was briefly com-
[Ni2(L)4(OH2)2] 3. This was obtained as green crystals by the
same procedure as 2 with Ni(OAc)2¢4H2O. Yield 75%. mp 153 °C.
UVÍvis {CH2Cl2, - nm (¾ MÕ1 cmÕ1)}: 631 (20), 331 (55100), 280
(21300), 230 (42300). IR (KBr disk, cmÕ1): 3671, 1653, 1589,
1500, 1411, 1331, 1216, 1113, 999, 821. CV (0.1 M TBAP/
CH2Cl2, V): Ep 1.50, Ep 1.75.
[Cu(L)2] 4. This was obtained as bluish green crystals by the
same procedure as 2 with Cu(OAc)2¢H2O. Yield 94%. mp 216 °C.
UVÍvis {CH2Cl2, - nm (¾ MÕ1 cmÕ1)}: 662 (40), 330 (36000),
258 (26400); [Cu(dbm)2]: 646 (50), 350 (47100), 266 (35400).12
IR (KBr disk, cmÕ1): 1652, 1568, 1510, 1502, 1426, 1406, 1342,
1228, 1117, 999, 934, 816, 648.
municated: A. Hori, T. Arii, CrystEngComm 2007, 9, 215.
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9
Beaucaire, J. Org. Chem. 1970, 35, 930.
10 F. A. Cotton, R. C. Elder, Inorg. Chem. 1966, 5, 423;
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a1
a2
11 D. V. Soldatov, J. A. Ripmeester, Chem.ÐEur. J. 2001, 7,
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Ratcliffe, J. A. Ripmeester, Inorg. Chem. 2001, 40, 1626.
12 ³Í³* transition energies of 4 are higher than those of
[Cu(dbm)2] because of increased ³ localization and very broad dÍd
bands of 4 are slightly red-shifted. Cf. L. David, C. Crăciun, O.
Cozar, V. Chiş, C. Agut, D. Rusu, M. Rusu, J. Mol. Struct. 2001,
563Ï564, 573.
Crystal Structure Determination.
Single-crystal X-ray
structures were determined on a Bruker SMART APEX CCD
diffractometer with graphite monochrometer Mo K¡ (- =
0.71073 ¡) generated at 50 kV and 35 mA. All crystals were
coated by paraton-N and were measured at 100 K.
Crystal data for (a) 1: C45H3AlF30O6, MW 1236.45, monoclinic,
P21, a = 12.9098(13) ¡, b = 12.3912(12) ¡, c = 14.0452(14) ¡,
13 J. C. Ma, D. A. Dougherty, Chem. Rev. 1997, 97, 1303.
14 V. R. Thalladi, H.-C. Weiss, D. Bläser, R. Boese, A.
Nangia, G. R. Desiraju, J. Am. Chem. Soc. 1998, 120, 8702.