Insertion reactions of organic anhydrides into the M-O bond of CuOtBu and Sb(OMe)3

Article abstract of DOI:10.1016/j.ica.2007.06.035

The synthesis and structural characterization of the copper salts [Cu₂(2-Boc-benzoate)₄(dme)₂] (1), [Cu(2-Boc-benzoate)₂(tmeda)] (2), [Cu₂(2-Boc-benzoate)₂(dppm)] (3), [Cu(2-Boc-nicotinate)

Full text of DOI:10.1016/j.ica.2007.06.035

Available online at www.sciencedirect.com
Inorganica Chimica Acta 361 (2008) 43–48
www.elsevier.com/locate/ica
Insertion reactions of organic anhydrides into the M–O bond of
CuOtBu and Sb(OMe)3
a
a,b,
*
Lukasz Ponikiewski , Alexander Rothenberger
a
Institut fu¨r Anorganische Chemie, Universita¨t Karlsruhe, Engesserstraße 15, 76131 Karlsruhe, Germany
Institut fu¨r Nanotechnologie, Forschungszentrum Karlsruhe GmbH, Postfach 3640, 76021 Karlsruhe, Germany
b
Received 24 March 2007; accepted 8 June 2007
Available online 30 June 2007
Abstract
The synthesis and structural characterization of the copper salts [Cu2(2-Boc-benzoate)4(dme)2] (1), [Cu(2-Boc-benzoate)2(tmeda)] (2),
[Cu2(2-Boc-benzoate)2(dppm)] (3), [Cu(2-Boc-nicotinate)(PPh3)2] (4), [Cu2{2-Boc-5,6-anhydride-naphthylcarboxylate}2(dppm)2] (5)
[dme = 1,2-dimethoxyethane, dppm = bis(diphenylphosphino)methane, tmeda = N,N0-tetramethylethylenediamine, Boc = tert-butoxy-
carbonyl] prove that cyclic organic anhydrides and dianhydrides readily insert into the Cu–O bond of [CuOtBu] forming carboxylate
ligands with ester functionalities in the ligand periphery. [Sb(CO2Ph-o-CO2Me)2(OMe)(tmeda)] (6) was synthesised by insertion reaction
of Sb(OMe)3 with phthalic anhydride.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Metal alkoxide; Organic anhydride; Insertion reactions
1. Introduction
reactions of organic anhydrides into the Cu–O bond of
[CuOtBu] [5–7]. These gave rise to a series of functionalised
copper carboxylates and further results are reported here.
This type of reaction, originally applied by Bergman and
coworkers to probe the reactivity of metal–oxygen bonds
in late transition metal alkoxides [8], can be extended to
the main group metal alkoxide Sb(OMe)3 and the first
compound resulting from these efforts is reported here.
Metal carboxylates have received a lot of attention due
to their use in inorganic/organic hybrid materials and par-
ticularly metal oxalates have proven to be useful starting
materials for the synthesis of ion-exchanging materials,
molecular magnets and catalysts [1,2]. Copper carboxylates
have also been used as catalysts for the decarboxylation of
organic acids and several synthetic methods have been
developed for the synthesis of copper(I) and copper(II) car-
boxylate complexes [3]. Syntheses of copper(I) and cop-
per(II) carboxylates under aprotic conditions were
achieved by the reaction of Cu(I) oxide and organic anhy-
drides as starting materials [4]. Having investigated the
reactivity of copper(I) tert-butoxide with trimethylsilyl
derivatives of the heavier group 15 elements, antimony
and bismuth, we have recently started looking at insertion
2. Experimental
General remarks. All operations were carried out in an
atmosphere of purified Argon. Solvents were dried over
sodium/benzophenone. Maleic anhydride was recrystal-
lized from diethylether. Dppm and phthalic anhydrid were
purchased from Aldrich. [CuOtBu] was prepared according
to a published procedure [9].
*
Corresponding author. Address: Institut fur Anorganische Chemie,
¨
1. To a solution of 137 mg (1 mmol) CuOtBu in 10 mL
THF was added a solution of 148 mg (1 mmol)
isobenzofuran-1,3-dione (in the following phthalic
Universita¨t Karlsruhe, Engesserstraße 15, 76131 Karlsruhe, Germany.
Tel.: +49 (0) 721 6082849; fax: +49 (0) 721 6088440.
E-mail address: ar252@chemie.uni-karlsruhe.de (A. Rothenberger).
0020-1693/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2007.06.035

44
L. Ponikiewski, A. Rothenberger / Inorganica Chimica Acta 361 (2008) 43–48
anhydride) in 15 mL THF. The resulting yellow solution
NMR (CDCl3, 25 °C, 161.975 MHz, 85%H3PO4):
1
was refluxed for 1 h and gradually a colour change to
blue-green was observed. A red precipitate of copper
was filtered off, the solvent was changed to DME and
1 ml toluene was added. Storage of the solution at
4 °C for 2 days yielded blue crystals of 1. Yield: 0.23 g
(71.5%), m.p. 240 °C. Anal. Calc. for C60H82Cu2O22
(with one DME): C, 56.20; H, 6.45. Found: C, 56.38;
H, 6.45%. UV/Vis (THF): kmax(e) 669 nm (184); IR
ꢀ2.28 (s, PPH3); H NMR (CDCl3, 25 °C, 300 MHz,
TMS): 8.6–7.24 (m, 33H, ar.), 3.8 (m, 4H, THF), 1.4
(s, 9H, OtBu); 13C{H} NMR (CDCl3, 25 °C,
400 MHz, TMS) 167.60 (COOꢀ), 138.29–128.69 (m, C.
ar.), 27.95 (s, Me) ppm.
5. 268 mg (1 mmol) of 1,4,5,8-naphthalenetetracarboxylic
dianhydride in 10 mL THF was suspended and a solu-
tion of 137 mg (1 mmol) [CuOtBu] was added. The reac-
tion was heated and refluxing for 1 h created an orange
coloured clear solution. After addition of 385 mg
(1 mmol) dppm in 10 mL THF a colour change to yel-
low was observed. The solution was filtered, reduced
to approximately 4 mL and 1 mL hexane was added.
Storage at 4 °C produced yellow-orange crystals of 5.
Yield: 0.64 g (82%); m.p. 205 °C. Anal. Calc. for
(CsJ, Nujol): m/cmꢀ1 = 1721, 1627, 1596 (COOꢀ,
~
C@O) cmꢀ1
.
2. To a solution of 148 mg (1 mmol) phthalic anhydride in
5 mL DME was added a solution of 137 mg (1 mmol)
[CuOtBu] in 10 mL DME and 0.15 mL (1 mmol)
TMEDA. After addition of TMEDA the colour changes
to dark green. A red precipitate of elemental copper was
filtered off. After filtration the solvent was reduced to
approximately 3 mL, and 1 mL hexane was added. Stor-
age of the solution at 0 °C for two days produced blue
crystals of 2. Yield: 0.52 g, 83%; m.p. 214 °C. Anal. Calc.
for C30H42CuN2O8: C, 57.91; H, 6.80; N, 4.50. Found:
C, 57.60; H, 6.90; N, 4.50%. UV/Vis (thf): kmax (e)
677 nm (118); IR (CsI, Nujol) ~m ¼ 1721, 1612, 1586,
C110H118Cu2O20P4 (with 5 THF): C, 65.69; H, 5.91.
~
Found: C, 65.22; H, 5.93%; IR (KBr) m ¼ 1712, 1593
(COOꢀ, C@O), 1434 (P–Ph3);
6. To a solution of 215 mg (1 mmol) [Sb(OMe)3] in 10 mL,
296 mg (2 mmol) phthalic anhydride in 5 mL THF was
added. The resulting white precipitate was stirred for
1 h at RT. The precipitate was dissolved upon addition
of 0.15 mL (1 mmol) TMEDA. After filtration the solu-
tion was reduced to approximately 3 mL and storage at
4 °C produced colourless crystals of 6. Yield: 0.53 g
(76%); m.p. 109 °C. Anal. Calc. for C29H41- N2O10Sb
(with one molecule of THF as lattice-bound solvent):
C, 49.80; H, 5.91; N, 4.01. Found: C, 49.43; H, 5.9ꢀ5;
1558 (COOꢀ, C@O) cmꢀ1
.
3. To a solution of 148 (1 mmol) phthalic anhydride in
5 mL THF was added a solution of 137 mg (1 mmol)
[CuOtBu] in 5 mL THF. The resulting yellow solution
was stirred for 1 h at RT and gradually a colour change
to blue-green was observed. After stirring, a solution of
193 mg (0.50 mmol) dppm in 5 mL THF was added. The
resulting yellow solution was filtered and the solvent was
reduced to approximately 5 mL and layered with 30 mL
hexane. Storage of the solution at RT for one week pro-
duced colourless crystals of 3. Yield: 0.41 g (86%); m.p.
220 °C. Anal. Calc. for C49H48Cu2O8P2: C, 61.69; H,
~
N, 4.38%; IR (CsI, Nujol) m ¼ 1722, 1643, 1570 (COO ,
C@O), 1373, 1332, 1294, 1256, 1112, 1076, 1029 (C–N)
cmꢀ1
.
2.1. X-ray crystallographic study
5.07. Found: C, 61.62; H, 4.89%. IR (CsI, Nujol)
ꢀ
~
m ¼ 1726, 1607, 1588, 1565, 1582 (COO , C@O), 1484,
Data for 2 were collected on a STOE STADI 4 diffrac-
tometer equipped with a CCD detector. Data for 1, 3–6
were collected on a STOE IPDS II diffractometer using
graphite-monochromated Mo Ka radiation (k = 0.71073
1436 (P–Ph) cmꢀ1
;
31P{1H} NMR ([D6]-DMSO, 25 °C,
161.975 MHz, 85%H3PO4): ꢀ6.6 (s); 1H NMR ([D6]-
DMSO, 25 °C, 400 MHz, TMS): 7.8–6.9 (m, 26H, ar.),
3.2 (m, 2H, Ph2PCH2PPh2), 1.4 (s, 18 H, OtBu);
13C{H} NMR ([D6]-DMSO, 25 °C, 400 MHz, TMS)
173.62 (COOꢀ), 168.28 (COOtBu), 133.9–127.7 (C ar.),
81.3 (s, O–CMe3), 28.1 (s, Me) ppm.
˚
A). The structures were solved by direct methods and
refined by full-matrix least-squares on F2 (all data) using
the SHELXTL program package [10]. Hydrogen atoms were
placed in calculated positions, non-hydrogen atoms were
assigned anisotropic thermal parameters. Disordered com-
ponents (lattice-bound solvent) were assigned isotropic
thermal parameters. Crystals of 3 were of poor quality
and all C atoms were refined with isotropic thermal param-
eters. The crystallographic data and structure refinement
parameters for the compounds are listed in Table 1.
4. To a solution of 137 mg (1 mmol) [CuOtBu] in 10 mL
THF was added a solution of 157 mg (1 mmol) pyri-
dine-2,3-dicarboxylic anhydride in 5 mL THF. The
resulting yellow solution with white precipitate was stir-
red for 1 h at RT and a solution of 524 mg (2 mmol)
PPh3 in 10 mL THF was added. The yellow solution
was filtered, reduced to approximately 5 mL and layered
with 30 mL hexane. Storage of the solution at RT for
one week produced colorless crystals of 4. Yield:
0.53 g (76%); m.p. 109 °C. Anal. Calc. for C47H42Cu-
NO4P2: C, 69.66; H, 5.22; N, 1.73. Found: C, 69.47;
3. Results and discussion
Reactions of phthalic anhydride with [CuOtBu] in a
variety of donor solvents afforded compounds 1–4 (Scheme
1). At RT, insertion of the anhydride into the Cu–O bond
of [CuOtBu] afforded in a disproportionation reaction 1
~
H, 5.07; N, 1.89%. IR (CsI, Nujol) m ¼ 1716, 1592
(COOꢀ, C@O), 1571, 1550 (C–N) cmꢀ1
;
31P{1H}

L. Ponikiewski, A. Rothenberger / Inorganica Chimica Acta 361 (2008) 43–48
45
Table 1
Details of the X-ray data collection and refinements
Compound
1
2
3
4
5
6
Formula
Formula weight
T (K)
C60H82Cu2O22
1282.35
200(2)
C30H42CuN2O8
622.20
200(2)
C49H48Cu2O8P2
953.89
100(2)
C47H42CuNO4P2
810.30
110(2)
C102H102Cu2O18P4
1866.80
120(2)
C29H41N2O10Sb
699.39
200(2)
Crystal system
triclinic
triclinic
monoclinic
P21/n
12.194(2)
21.224(4)
17.133(3)
90
92.14(4)
90
4431.0(15)
4
triclinic
monoclinic
P21/n
18.855(4)
23.594(5)
24.410(5)
90
107.42(3)
90
10361(4)
4
monoclinic
P21/c
14.199(2)
26.279(5)
8.522(3)
90
96.69(3)
90
3157.9(14)
4
ꢀ
ꢀ
ꢀ
Space group
P1
P1
P1
˚
a (A)
11.2269(9)
12.896(1)
12.998(1)
108.073(9)
108.358(8)
104.574(8)
1565.6(3)
1
9.058(1)
12.592(2)
14.247(2)
94.90(1)
97.45(1)
96.45(1)
1593.3(4)
2
10.386(2)
13.422(3)
14.809(6)
96.50(2)
101.62(2)
97.12(2)
1985.9(9)
2
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
3
˚
V (A )
Z
qcalc (Mg mꢀ3
F(000)
)
1.360
676
0.755
1.297
658
0.734
1.430
1976
1.086
1.335
844
0.676
1.197
3904
0.534
1.471
1440
0.930
l (mmꢀ1
)
h-range (°)
3.89–31.91
8290
6343
0.0284
387
3.71–31.91
11149
6944
0.0857
380
2.26–25.00
5709
4644
0.1078
233
1.54–27.05
4281
4015
0.0411
496
1.23–26.08
26175
15106
0.0889
1036
2.12–25.89
15104
5883
0.0412
386
Reflections collected
Unique date
Rint.
Parameters
wR2 (all data)
S (Goodness-of-fit)
R1 [I > 2r(I)]
0.0869
0.894
0.0425
0.503, ꢀ0.395
0.2101
0.908
0.0721
0.573, ꢀ1.027
0.1322
0.923
0.0938
0.431, ꢀ0.382
0.1474
0.879
0.0570
0.417, ꢀ0.386
0.1486
0.925
0.0705
0.386, ꢀ0.348
0.0825
1.042
0.0320
0.547, ꢀ0.749
ꢀ3
˚
Peak, hole (e A
)
a chelating ligand for the Cu(II) centre in 2 unlike dme in
the solid-state structure of 1 (Fig. 2).
DME
[Cu2(2-Boc-benzoate)4(dme)2] (1)
[Cu(2-Boc-benzoate)2(tmeda)] (2)
[Cu2(2-Boc-benzoate)2(dppm)] (3)
O
-Cu
The Cu atom in 2 is bonded to a bidentate tmeda ligand
CuOtBu +
CuOtBu +
TMEDA
O
-Cu
˚
[Cu–N 2.015(4) and 2.025(4) A] and two 2-Boc-benzoato
dppm
O
O
ligands. The carboxylate groups are essentially monoden-
˚
tate with Cu–O distances of 1.975(3) and 1.972(3) A
(Fig. 2). The oxygen atoms O(2) and O(6) [Cu–O ca.
2.4 A] complete the distorted octahedral coordination
PPh3
[Cu(2-Boc-nicotinate)(PPh3)2] (4)
O
˚
hexane,
THF
N
sphere of Cu(1) in 2. Similar Cu–O bond distances and
angles around the Cu(II) centre were observed in
[Cu(fum)(tmeda)] Æ 2H2O (fum = fumarate) and in an iso-
structural 2-Boc-maleato complex [6,7]. In the presence of
tertiary phosphines disproportionation can be suppressed,
e.g., in the presence of dppm, 3 was obtained (Fig. 3,
Scheme 1).
O
O
O
O
O
O
O
O
CO2Cu(dppm)
CuOtBu +
O
O
(5)
Boc
2
Scheme 1. Synthesis of 1–5 (dme = 1,2-dimethoxyethane; tmeda = N,N0-
tetramethylethylenediamine; dppm = bis(diphenylphosphino)methane,
In the solid-state, 3 consists of two three-coordinated
Cu(I) centres held together by two 2-Boc-benzoato and
one dppm ligand. Cu(1) and Cu(2) are each coordinated
by a P atom of a dppm ligand [Cu–P 2.166(4) and
py = C5H3N, Boc = tert-butoxycarbonyl).
˚
2.164(4) A] and two oxygen atoms of two 2-Boc-benzoato
together with elemental copper. The formation of 1 pro-
ceeds slowly overnight when carried out at RT and phthalic
anhydride is transformed into the 2-Boc-benzoate anion.
The solid-state structure of 1 consists of dicopper(II) tet-
racarboxylate ‘paddlewheel’ units (Fig. 1). The coordina-
tion geometry and bonding parameters of the copper
atoms found in 1 are common for Cu(II) carboxylates
and a wealth of structural and theoretical accounts for
these systems exist [3].
ligands. A similar reaction with maleic anhydride, pro-
duced one dimeric complex with central Cu2O2 four-mem-
bered ring [6]. Here, however, formation of larger
aggregates might be hindered by the steric requirements
of the generated ligands. By changing the nature of anhy-
drides involved in insertion reactions, the synthesis of lar-
ger aggregates is a possibility. Therefore, a number of
pyridyl-containing organic anhydrides were investigated
and it was hoped that additional N-donor centres will form
extended coordination oligomers or polymers. So far, how-
ever, this has either resulted in insoluble and amorphous
When the reaction was performed in the presence of
TMEDA, 2 was obtained (Scheme 1). Insertion of phthalic
anhydride into the Cu–O bond occurred and tmeda acts as

46
L. Ponikiewski, A. Rothenberger / Inorganica Chimica Acta 361 (2008) 43–48
Fig. 3. Molecular structure of 3 in the solid state (ellipsoids at 50%
probability level; hydrogen atoms are omitted for clarity). Selected bond
˚
lengths (A) and angles (°): Cu(1)–O(1) 2.015(12), Cu(1)–O(5) 1.958(10),
Cu(1)–P(1) 2.166(4), Cu(2)–O(2) 1.996(13), Cu(2)–O(6) 2.003(10), Cu(2)–
P(2) 2.164(4), O(5)–Cu(1)–O(1) 101.8(4), O(5)–Cu(1)–P(1) 138.9(3), O(1)–
Cu(1)–P(1) 118.9(3), O(2)–Cu(2)–O(6) 102.3(4), O(2)–Cu(2)–P(2) 123.3(3),
O(6)–Cu(2)–P(2) 134.4(4).
Fig. 1. Molecular structure of 1 in the solid state (ellipsoids at 50%
probability level; hydrogen atoms are omitted for clarity). Final label A
denotes symmetry operations: ꢀx + 1, ꢀy + 2, ꢀz + 1 and ꢀx, ꢀy + 1,
˚
compounds or as is demonstrated by the reaction of a solu-
tion of [CuOtBu] with pyridine-2,3-dicarboxylic anhydride
in the presence of the PPh3 has resulted in mononuclear
complexes like 4 (Scheme 1). The solid-state structure of
4 consists of a distorted-tetrahedrally surrounded Cu atom
(Fig. 4). The generated carboxylate group chelates Cu(1),
ꢀz + 1. Selected bond lengths (A) and angles (°): Cu(1)–O(1) 1.9519(19),
Cu(1)–O(5) 1.9540(18), Cu(1)–O(6A), 1.9573(18), Cu(1)–O(2A)
1.9599(18), Cu(1)–O(9) 2.1874(17), O(1)–Cu(1)–O(5) 90.19(8), O(1)–
Cu(1)–O(6A) 87.93(8), O(5)–Cu(1)–O(6A) 169.80(7), O(1)–Cu(1)–O(2A)
169.76(7), O(5)–Cu(1)–O(2A) 88.12(8), O(6A)–Cu(1)–O(2A) 91.96(8),
O(1)–Cu(1)–O(9) 95.18(7), O(5)–Cu(1)–O(9) 95.72(7), O(6A)–Cu(1)–O(9)
94.43(7), O(2A)–Cu(1)–O(9) 95.04(7).
˚
with Cu–O distances of 2.172(6) and 2.280(8) A. The tetra-
hedral coordination sphere is completed by two P atoms of
two PPh3.
Surprisingly, out of the two potential products (2-Boc-
nicotinato- or 3-Boc-picolinato-anions could be formed in
the course of the reaction) the Cu salt of 2-Boc-nicotinic
acid was formed, a fact which could be rationalised by
nitrogen pre-coordination of [CuOtBu] and ester formation
with the closest carbonyl group.
Previously, it was shown that insertion reactions of
organic dianhydrides and [CuOtBu] result in Cu(I) com-
plexes if the reactions are either kept at low temperature or
performed in the presence of phosphine donors [6,7]. The
stepwise opening, however, has not yet been achieved. In a
reaction of [CuOtBu] with the anhydride of naphthalene-
1,4,5,8-tertcarboxylic acid in the ratio 1:1, the phosphine-
stabilized copper salt of 5 was obtained. Solid samples of
5, are insoluble once isolated but the molecular structure
of 5 could be confirmed by X-ray crystallography (Fig. 5).
Compound
5 consists of one [Cu2(dppm)2] unit
˚
[Cu(1)ꢁ ꢁ ꢁCu(2) 2.980(2) and Cu–P av. 2.24 A]. Each copper
atom is coordinated by one oxygen atom O(1), O(8) of the
monodentate carboxylate group in the generated carboxy-
lato ligand, resulting in a distorted trigonal planar coordi-
nation environment for Cu(1) and Cu(2). Examples for
three-coordinated Cu atom in Cu(I) dicarboxylates are
found in Cu(I) perfluorosuccinate, copper(I) glutarate
and in the ion-separated complex [Cu(OAc)(BF4)(dppm)2]
Fig. 2. Molecular structure of 2 in the solid state (ellipsoids at 50%
probability level; hydrogen atoms are omitted for clarity). Selected bond
˚
lengths (A) and angles (°): Cu(1)–O(1) 1.975(3), Cu(1)–O(5) 1.972(3),
Cu(1)–N(1) 2.015(4), Cu(1)–N(2) 2.025(4), O(5)–Cu(1)–O(1) 95.61(14),
O(5)–Cu(1)–N(1) 91.77(16), O(1)–Cu(1)–N(1) 160.19(14), O(5)–Cu(1)–
N(2) 159.77(14), O(1)–Cu(1)–N(2) 91.88(16), N(1)–Cu(1)–N(2) 87.36(18).

L. Ponikiewski, A. Rothenberger / Inorganica Chimica Acta 361 (2008) 43–48
47
O
TMEDA
THF
O
O
Sb(OMe)3 + 2
[Sb(OMe)(CO2C6H4-o-CO2Me)2(tmeda)] (6)
Scheme 2. Synthesis of 6 (tmeda = N,N0-tetramethylethylenediamine).
Fig. 4. Molecular structure of 4 in the solid state (ellipsoids at 50%
probability level; hydrogen atoms are omitted for clarity). Selected bond
˚
lengths (A) and angles (°): Cu(1)–O(1) 2.172(6), Cu(1)–P(1) 2.234(3),
Cu(1)–P(2) 2.250(2), Cu(1)–O(2) 2.280(8), O(1)–Cu(1)–P(1) 113.3(2),
O(1)–Cu(1)–P(2) 116.6(2), P(1)–Cu(1)–P(2) 128.73(10), O(1)–Cu(1)–O(2)
59.8(3), P(1)–Cu(1)–O(2) 111.09(19), P(2)–Cu(1)–O(2) 103.3(2).
Fig. 6. Molecular structure of 6 in the solid state (ellipsoids at 50%
probability level). Selected bond lengths (A) and angles (°): Sb(1)–O(1)
˚
2.235(2), Sb(1)–O(5) 2.132(2), Sb(1)–O(9) 1.951(2), Sb(1)–N(1) 2.490(3),
Sb(1)–N(2) 2.595(3), O(9)–Sb(1)–O(5) 84.67(8), O(9)–Sb(1)–O(1) 86.38(9),
O(5)–Sb(1)–O(1) 82.48(9), O(9)–Sb(1)–N(1) 85.69(9), O(5)–Sb(1)–N(1)
79.94(9), O(1)–Sb(1)–N(1) 161.30(9), O(9)–Sb(1)–N(2) 75.75(8), O(5)–
Sb(1)–N(2) 146.62(9), O(1)–Sb(1)–N(2) 122.14(9), N(1)–Sb(1)–N(2)
71.96(9).
with phthalic anhydride giving rise to 6 in which one meth-
oxy group is retained (Scheme 2, Fig. 6).
Crystals of 6 could only be obtained in the presence of
the additional donor TMEDA and in the solid state, 6
consists of a pentacoordinated Sb centre in distorted
square-pyramidal coordination environment. The central
antimony atom is surrounded by a chelating TMEDA
ligand and two monodentate 2-Boc-benzoato ligands,
whilst the remaining methoxy group forms the top of the
square-pyramidal arrangement.
4. Conclusion
Fig. 5. Molecular structure of 5 in the solid state (ellipsoids at 50%
probability level; hydrogen atoms are omitted for clarity). Selected bond
The syntheses and structural characterisation of the cop-
per carboxylates 1–5 prove that cyclic organic anhydrides
readily insert into the Cu–O bond of [CuOtBu] forming
carboxylate ligands with ester functionalities in the ligand
periphery. These donor centres may be used in the con-
struction of complex aggregates with different dimensional-
ity either by stabilising other metal centres or suitable
organics, e.g., polyols, amines, etc. The experience gathered
in this area so far, however, indicates that possibly new
synthetic approaches are necessary to overcome solubility
problems. The incorporation of main group metals via
the anhydride/metal alkoxide route (here antimony) repre-
sents a new development in this area and more examples of
novel complexes can be expected.
˚
lengths (A) and angles (°): Cu(1)–O(1) 1.973(5), Cu(1)–P(3) 2.2305(18),
Cu(1)–P(1) 2.256(2), Cu(2)–O(8) 1.991(5), Cu(2)–P(2) 2.230(3), Cu(2)–P(4)
2.2449(19), O(1)–Cu(1)–P(3) 127.77(15), O(1)–Cu(1)–P(1) 115.01(16),
P(3)–Cu(1)–P(1) 116.61(8), O(8)–Cu(2)–P(2) 115.56(17), O(8)–Cu(2)–P(4)
118.58(18), P(2)–Cu(2)–P(4) 125.86(8).
[3b,11,12]. The investigation of stepwise opening reactions
of polyanhydrides is ongoing and further results are to be
expected.
Finally, a first result from efforts to apply insertion reac-
tions of organic anhydrides into the metal–O bond of metal
alkoxides in main group metal alkoxide chemistry is
described. As a model compound Sb(OMe)3 was reacted

48
L. Ponikiewski, A. Rothenberger / Inorganica Chimica Acta 361 (2008) 43–48
[2] C.N.R. Rao, S. Natarajan, R. Vaidhyanatan, Angew. Chem. 116
5. Supplementary material
(2004) 1490.
[3] (a) M. Melnik, Coord. Chem. Rev. 42 (1982) 259;
(b) D.J. Darensbourg, E.M. Longridge, B. Khandelwal, J.H.
Reibenspies, J. Coord. Chem. 32 (1994) 27;
(c) J. Bickley, R.P. Bonar-Law, M.A. Borrero Martinez, A. Steiner,
Inorg. Chim. Acta 357 (2004) 891.
[4] F.A. Cotton, E.V. Dikarev, M.A. Petrukhina, Inorg. Chem. 39 (2000)
6072, and references therein.
CCDC 641382, 641383, 641384, 641385, 641386 and
641387 contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033; or e-mail: deposit@ccdc.cam.ac.uk.
[5] (a) D. Fenske, A. Rothenberger, S. Wieber, Z. Anorg. Allg. Chem.
629 (2003) 929;
(b) R. Ahlrichs, C.E. Anson, R. Clerac, D. Fenske, A. Rothenberger,
M. Sierka, S. Wieber, Eur. J. Inorg. Chem. (2004) 2933.
[6] L. Ponikiewski, A. Rothenberger, Inorg. Chim. Acta 358 (2005) 1322.
[7] C.E. Anson, R.L. Langer, L. Ponikiewski, A. Rothenberger, Inorg.
Chim. Acta 358 (2005) 3967.
Acknowledgements
We thank the Forschungszentrum Karlsruhe and Prof.
Dieter Fenske for support.
[8] J.R. Fulton, A.W. Holland, D.J. Fox, R.G. Bergman, Acc. Chem.
Res. 35 (2002) 44.
[9] T. Greiser, E. Weiss, Chem. Ber. 109 (1976) 3142.
[10] G.M. Sheldrick, SHELXTL-97, University of Go¨ttingen 1997.
[11] P. Angaridis, F.A. Cotton, M.A. Petrukhina, Inorg. Chim. Acta 324
(2001) 318.
References
[1] R.D. Archer, Inorganic and Organometallic Polymers, Wiley VCH,
Weinheim, 2001.
[12] P.D. Harvey, M. Drouin, T. Zhang, Inorg. Chem. 36 (1997) 4998.