Synthesis, structures and reactivity of N-donor-functionalised Cu(I) aryloxides

Article abstract of DOI:10.1016/j.ica.2005.12.017

The preparation and characterisation of the Cu(I) aryloxides [Cu₁₆(3-pyO)₁₆(dppm)₈] (1), [{Cu₂(2-pyO)₂(dppm)}₂] (2) and [{Cu₃(μ₃-6-OQ)₂(dppm)₃}{(6-HOQ)₂(μ-6-OQ)}] (3) (dppm = 1,2-bis-diphenylphosphinomethane, 6-HOQ = 6-hydroxyquinoline, py = pyridine) are described. A first attempt to employ organic anhydrides in insertion reactions with Cu(I) aryloxides was made producing the one-dimensional coordination polymer 1/_∞[Cu₃(3-pyO)(CO₂C₂H₄Boc)(dppm^-)(dppm)]_∞ (4) (Boc = tert-butoxycarbonyl).

Full text of DOI:10.1016/j.ica.2005.12.017

Inorganica Chimica Acta 359 (2006) 2263–2267
www.elsevier.com/locate/ica
Synthesis, structures and reactivity of N-donor-functionalised
Cu(I) aryloxides
a
a
a,b,
*
Christopher E. Anson , Lukasz Ponikiewski , Alexander Rothenberger
a
Institut fu¨r Anorganische Chemie, Universita¨t Karlsruhe, Engesserstraße 15, Geb. 30.45, D-76131 Karlsruhe, Germany
b
Institut fu¨r Nanotechnologie, Forschungszentrum Karlsruhe GmbH, Postfach 3640, 76021 Karlsruhe, Germany
Received 4 November 2005; accepted 11 December 2005
Available online 27 March 2006
Abstract
The preparation and characterisation of the Cu(I) aryloxides [Cu16(3-pyO)16(dppm)8] (1), [{Cu2(2-pyO)2(dppm)}2] (2) and [{Cu3(l3-6-
OQ)2(dppm)3}{(6-HOQ)2(l-6-OQ)}] (3) (dppm = 1,2-bis-diphenylphosphinomethane, 6-HOQ = 6-hydroxyquinoline, py = pyridine) are
described. A first attempt to employ organic anhydrides in insertion reactions with Cu(I) aryloxides was made producing the one-dimen-
sional coordination polymer 1/ [Cu3(3-pyO)(CO2C2H4Boc)(dppmꢀ)(dppm)] (4) (Boc = tert-butoxycarbonyl).
1
1
Ó 2005 Elsevier B.V. All rights reserved.
Keywords: Metal alkoxide; Organic anhydride; Insertion reaction
1. Introduction
order to construct complex metal organic aggregates by
insertion reactions we therefore set out to synthesise a vari-
ety of Cu(I) aryloxides containing hydroxypyridines and
hydroxyquinolines as N-heterocyclic substituents and
probe their reactivity with organic anhydrides. These
efforts complement synthetic investigations of Cu(I) aryl-
oxides with nitrogen donor atoms centres similar to that
of copper(I) complexes of 6-methyl-2-hydroxypyridine
and 6-hydroxy-2,20-bipyridine [7–9] and represent a step
in the ongoing development of insertion reactions as a
new route to inorganic/organic hybrid materials. Here we
report the synthesis and structural characterisation of three
new Cu(I) aryloxides and the first results of subsequent
reactions with organic anhydrides.
Insertion reactions of organic anhydrides into the
metal–oxygen bond of late transition metal alkoxides could
provide a new route to inorganic/organic hybrid materials
with possible applications, e.g., as storage devices for gases
or matrices for catalytic transformations [1–4]. As a model
reaction we have recently described the insertion reaction
of various organic anhydrides into the Cu–O bond of
[CuOtBu], producing Cu(I) carboxylate complexes when
performed at low temperature or in the presence of tertiary
phosphine ligands (Scheme 1) [5,6].
Metathesis reactions of Cu(I) complexes obtained in
these reactions with transition metal halides offer access
to a large number of compounds [6] which can subse-
quently be tested for physical properties desirable for a spe-
cific inorganic/organic hybrid material (see Scheme 2).
In addition to the choice of anhydride and metal atom a
further modification of the synthetic approach represents
the use of a variety of Cu(I) alkoxides or aryloxides. In
2. Experimental
2.1. General remarks
All operations were carried out in an atmosphere of
purified argon. Solvents were dried over sodium/benzophe-
none. Maleic anhydride was recrystallised from diethyle-
ther. Chemicals were purchased from Aldrich. [CuOtBu]
was prepared according to a published procedure [10].
*
Corresponding author. Tel.: +49 0 721 6082849; fax: +49 0 721
6088440.
E-mail address: rothenberger@chemie.uni-karlsruhe.de (A. Rothen-
berger).
0020-1693/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.12.017

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C.E. Anson et al. / Inorganica Chimica Acta 359 (2006) 2263–2267
2. 2 was synthesised analogously to 1 with the exception
that 2-hydroxypyridine was used in place of 3-hydroxypyri-
dine. Storage of the solution for two days in RT produced
colourless crystals of 2. Yield 0.29 g, 68%; m.p. 275 °C;
Calc. for C70H60Cu4N4O4P4 (excluding lattice-bond
THF): C, 60.0; H, 4.3; N, 4.0. Found: C, 59.7; H, 4.3; N,
3.8%. IR (CsI, nujol) mmax/cmꢀ1 = 1586 (C–N), 1465 (P–
C); dP ([D6]DMSO, 25 °C, 161.96 MHz, 85% H3PO4),
ꢀ11.2 (br s, PPh); dH (400 MHz, [D6]DMSO, 25 °C,
TMS), 8.6–6.9 (m, 26H , H ar.), 3.6 (m, 4H, thf), 1.8 (m,
4H, thf), 3.3 (br. s, 2H, CH2PPh2); dC (400 MHz,
[D6]DMSO, 25 °C, TMS), 133.0–127.9 (C ar.), 67.0, 25.1
(s, thf), 27.8 (s, CH2PPh2).
O
O
O
O
Cu
R
+
+
CuOR
R'
O
R'
O
R'
O
R'
Scheme 1. Insertion reaction of organic anhydrides into the Cu–O bond
of Cu(I) alkoxides R,R0 = alkyl.
O
O
Cu
M
+ MX
+ CuX
O
R'
O
R'
Scheme 2. Metathesis reactions of Cu(I) complexes obtained from
insertion reactions (M = metal).
1. To a solution of 0.14 g of (1.00 mmol) [CuOtBu] in 10
mL THF was added a solution of 0.10 g (1.00 mmol) 3-
hydroxypyridine in 5 mL THF. After stirring the reaction
mixture for 30 min at RT, a colourless precipitate was
formed and dissolved upon addition of a solution of
0.20 g (0.50 mmol) dppm in 5 mL THF. The reaction was
filtered and the yellow filtrate concentrated to approxi-
mately 3 mL. Addition of 1 mL hexane and storage of
the solution at ꢀ20 °C for 2 days produced colourless crys-
tals of 1. Yield 0.38 g, 90%; m.p. 209 °C; Calc. for
3. To a solution of 0.14 g (1.00 mmol) [CuOtBu] in 5 mL
THF was added a solution of 0.15 g (1.00 mmol) 6-
hydroxyquinoline in 10 mL THF. The solution was stirred
for 2 h resulting in the formation of a colourless precipi-
tate. After addition of a solution of 0.40 g (1.00 mmol)
dppm in 5 mL THF the reaction was filtered and the brown
filtrate concentrated to approximately 5 mL. Addition of
1 mL hexane and storage of the solution at ꢀ40 °C for
one week produced colourless crystals of 3. Yield 0.45 g,
68%; m.p. 206 °C; Calc. for C471H385Cu12N19O19P24 (corre-
sponding to loss of lattice THF): C, 69.7; H, 4.8; N, 3.3.
C
280H240Cu16N16O16P16 (corresponding to loss of lattice
THF): C, 60.0; H, 4.3; N, 4.0. Found: C, 59.0; H, 4.3; N,
4.0%. IR (KBr) mmax/cmꢀ1 = 1564, 1544 (C–N), 1468 (P–
C); dP (CDCl3, 25 °C, 161.96 MHz, 85% H3PO4) ꢀ13,0
(br s, PPh); dH (400 MHz, CDCl3, 25 °C, TMS) 8.1–6.9
(m, 24 H ar., Ph and py), 3.8, 1.8 (m, 4H, thf), 3.2 (br s,
2H, CH2PPh2), dC (400 MHz, CDCl3, 25 °C, TMS),
132.9–128.5 (C ar.), 68.0, 25.6 (s, thf), 34.1 (s, CH2PPh2).
Found: C, 68.9; H, 4.8; N, 3.2. IR (KBr) mmax
/
cmꢀ1 = 3456 (OH), 1605, 1579 (C–N), 1462 (P–C); dP
([D6]DMSO, 25 °C, 161.96 MHz, 85% H3PO4) ꢀ13.0
(br s, PPh), dH (400 MHz, [D6]DMSO, 25 °C, TMS) 8.8–
6.8 (m, 26H, ar.), 3.6, 1.7 (m, 4H, thf), 3.4 (br. s, 2H,
CH2PPh2), dC (400 MHz, [D6]DMSO, 25 °C, TMS)
132.8–127.9 (C ar.), 67.0, 25.1 (s, thf), 30.9 (s, CH2PPh2).
Table 1
Details of the X-ray data collection and refinements
Compound
1
2
3
4
Formula
Formula weight
T (K)
C
422H526Cu16N16O50P16
C78H76Cu4N4O6P4
1543.47
173(2)
C591H625Cu12N19O49P24
10284.00
120(2)
C74H80Cu3NO7.5P4
1417.89
120(2)
8134.75
203(2)
Crystal system
Space group
triclinic
triclinic
triclinic
monoclinic
C2/c
44.249(3)
14.0383(7)
25.1116(15)
90
115.616(4)
90
14065.6(14)
8
ꢀ
ꢀ
ꢀ
P1
P1
P1
˚
a (A)
20.5768(10)
21.3764(9)
24.7779(11)
74.857(3)
79.860(4)
74.600(4)
10075.7(8)
1
11.0458(12)
12.6158(15)
12.8624(9)
92.870(8)
103.952(8)
91.570(9)
1735.9(3)
1
14.489(3)
28.050(3)
32.873(3)
101.811(6)
98.220(6)
95.810(6)
12825(3)
1
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
3
˚
U (A )
Z
qcalc (g/cm3)
1.341
0.958
4274
1.476
1.358
796
1.331
0.633
5404
1.339
1.043
5904
l (mmꢀ1
F(000)
)
2h Range (°)
Reflections collected
Unique data
Rint
1.61–27.11
80497
40850
3.82–31.75
8788
6912
1.28–27.15
103909
52591
1.54–26.00
49858
13840
0.0768
0.0301
0.0855
0.1860
Parameters
1911
433
2278
785
wR2 (all data)
S (Goodness-of-fit)
R1 [I > 2r(I)]
0.2478
0.986
0.0849
1.1685, ꢀ0.744
0.1506
1.104
0.0410
0.797, ꢀ0.952
0.2391
0.909
0.0831
1.233, ꢀ0.641
0.2886
1.028
0.0962
1.747, ꢀ0.771
ꢀ3
˚
Peak, hole (e Æ A
)

C.E. Anson et al. / Inorganica Chimica Acta 359 (2006) 2263–2267
2265
4. To a solution of 0.10 g (1.00 mmol) 3-hydroxypyridine
in 10 mL THF was added 1.00 mmol tBuLi (0.6 mL, 1.7 M
in pentane) and 0.14 g of (1.00 mmol) [CuOtBu]. After heat-
ing the solution to reflux for 1 h a grey precipitate was
formed. In a seperate Schlenk tube a solution of 0.28 g
(2.00 mmol) [CuOtBu] in 10 mL THF was added to 0.10 g
(1.00 mmol) maleic anhydride. The solution was stirred
for 1 h and 0.77 g (2.00 mmol) dppm was added. Combina-
tion of both reaction mixtures and heating to reflux for 1 h
resulted in a brown solution. Crystals of 4 and a colourless
precipitate were obtained by diffusion of pentane into the
reaction mixture within a double Schlenk tube. Repeated
elemental analysis of the solid residue showed large devia-
tions to calculated values for 4 and indicates the formation
of byproducts. The products are insoluble in organic sol-
vents once formed and prevented further characterisation.
2.2. X-ray crystallographic study
Data were measured on a STOE IPDS II (1, 3, 4) and a
STOE STADI-4 (2) diffractometer, using Mo Ka radiation.
The structures were solved by direct methods, and refined
by full-matrix least-squares against F2 using all data (see
Table 1 for details) [11]. Organic hydrogen atoms were
placed in idealised positions. Non-H atoms were refined
with anisotropic thermal parameters; crystals of 1–4 con-
tain large amounts of partially disordered solvent mole-
cules which were refined isotropically. The synthesis of 4
was repeated several times but the dataset presented was
the best we were able to obtain.
Fig. 1. Molecular structure of 1 in the solid-state (phenyl rings of dppm
ligands have been omitted; ellipsoids at 50% probability level). Selected
˚
ranges of bond lengths (A) and angles (°): Cu–O 1.990(5)–2.196(5), Cu–N
1.993(6)–2.104(6), Cu–P 2.153(2)–2.188(2), N–Cu–O 97.6(2)–115.7(2), O–
Cu–O 83.13(18)–88.34(19), N–Cu–P 107.32(17)–144.22(16), P–Cu–O
102.26(12)–113.33(13) (three-coordinated Cu) 103.4(2)–130.12(19).
and dppm ligands. 32 molecules of THF co-crystallise per
macrocycle as lattice solvent; upon the loss of THF, crys-
tals of 1 become amorphous. 1 represents the first Cu(I)
complex containing a [3-pyO]ꢀ ligand. Two Cu(II) com-
plexes containing 3-pyOH or [3-pyO]ꢀ ligands have been
reported which also show supramolecular aggregation via
hydrogen bonding and sidearm coordination of N atoms
3. Results and discussion
The acid–base reactions of CuOtBu with 3-hydroxypyri-
dine (3-pyOH), 2-hydroxypyridine (2-pyOH) and 6-hydroxy-
quinoline (6-HOQ) in THF at RT produced insoluble
grey precipitates. Upon addition of the auxiliary ligand
dppm, crystals of 1–3 were obtained from the solutions
(Scheme 3).
In the case of [Cu16(3-pyO)16(dppm)8] (1) (dppm = 1,2-
bis-diphenylphosphinomethane), NMR and infrared spec-
tra indicated the presence of phosphine ligands and the
pyridyl-group but the true nature only became apparent
when sensitive single crystals of 1 were analysed by X-ray
crystallography (Fig. 1).
In the solid-state, 1 consists of a macrocyclic arrange-
ment of 16 Cu atoms held together by bridging 3-pyO
3-pyOH
dppm
[Cu16(3-pyO)16(dppm)8] (1)
Fig. 2. Molecular structure of 2 in the solid-state (ellipsoids at 50%
˚
2-pyOH
dppm
probability level). Selected bond lengths (A) and angles (°): Cu(2)–N(1)
CuOtBu
[{Cu2(2-pyO)2(dppm)}2] (2)
1.985(3), Cu(2)–N(2) 1.988(4), Cu(1)–O(2) 1.991(3), Cu(1)–O(1) 2.098(3),
Cu(1)–O(10) 2.107(3), Cu(1)–P(1) 2.1472(11), Cu(2)–P(2) 2.1844(11), O(2)–
Cu(1)–O(1) 102.59(12), O(2)–Cu(1)–O(10) 96.46(12), O(1)–Cu(1)–O(10)
80.48(11), O(2)–Cu(1)–P(1) 131.75(9), O(1)–Cu(1)–P(1) 119.68(9), O(10)–
Cu(1)–P(1) 111.67(8), N(1)–Cu(2)–N(2) 112.30(14), N(1)–Cu(2)–P(2)
127.80(10), N(2)–Cu(2)–P(2) 118.06(11), Cu(1)–O(1)–Cu(10) 99.52(11).
6-HOQ
dppm
[{Cu3(µ-6-OQ)2(dppm)3}{(6-HOQ)2(µ-6-OQ)}] (3)
Scheme 3. Synthesis of 1–3.

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C.E. Anson et al. / Inorganica Chimica Acta 359 (2006) 2263–2267
to Cu atoms of adjacent units [12]. The bond distances
[Cu–O 1.990(5)–2.196(5) A, Cu–N 1.993(6)–2.104(6)] in 1
are in the range of commonly observed bond distances in
compounds with similar structural motifs [13].
each unit are chelated by two 2-pyO ligands and P atoms of
dppm ligands. Whilst Cu(2) is coordinated by two N and P
ligand atoms, Cu(1) is four-coordinated by bridging O(1)
and O(10), non-bridging O(2) and P(1) (Fig. 2).
˚
[{Cu2(2-pyO)2(dppm)}2] (2) was isolated in good yield
from the reaction of CuOtBu and 2-pyOH in the presence
of dppm. In the solid-state 2 consists of a centrosymmetric
dimer of [Cu2(2-pyO)2(dppm)] units. The two Cu atoms in
The synthetic route to 1 and 2, which were both isolated
in ca. 70% yield, indicates that reactions of CuOtBu with
arylhydroxides could provide easy access to a variety of
Cu(I) aryloxides. The lower pKa values of arylhydroxides
t
(4–8) in comparison to BuOH (ca. 17) favour the one-
pot-reactions of arylhydroxides with the strong base
CuOtBu over reactions of alkali-metallated aryloxides with
Cu(I) halides.
The outcome of the analogous reaction of CuOtBu with
6-HOQ and dppm is markedly different from the previ-
ously described acid–base reactions of arylhydroxides with
CuOtBu. Colourless crystals of [{Cu3(l3-6-OQ)2(dppm)3}-
{(6-HOQ)2(l-6-OQ)}] (3) were isolated in 68% yield and
the structure was determined by X-ray crystallography
(Fig. 3).
In the solid-state, 3 exists as solvent-separated ion-pairs
of [Cu3(l3-(6-OQ)2(dppm)2]+ cations and [(6-HOQ)2(l-6-
OQ)]ꢀ anions. In the cation three Cu atoms are unsymmet-
rically bridged by two O atoms of quinolineoxide ligands
forming a cage with three dppm ligands. It is the first time
that such a structural motif has been observed with Cu(I).
Similar cage architectures, however, are known for Cu(II)
and mixed-valent complex cations [14,15]. The anion con-
sists of two molecules of 6-HOQ and one [6-OQ]ꢀ anion
linked by hydrogen bonding. It was impossible to locate
H atoms in the Fourier map (all H atoms were added
and refined in idealised positions) but direct evidence for
Fig. 4. Solid-state structure of a monomeric unit in 4 (phenyl rings of
Fig. 3. Molecular structure in the solid-state of
a
[Cu3(l3-(6-
dppm ligands have been omitted; ellipsoids at 50% probability level).
Selected bond lengths (A) and angles (°): Cu(1)–O(1) 2.134(6), Cu(2)–O(2)
1.982(6), Cu(3)–O(5) 1.849(6), Cu(1)–P(1) 2.277(2), Cu(1)–P(3) 2.282(2),
Cu(2)–P(2) 2.220(2), Cu(2)–P(4) 2.223(2), Cu(3)–C(50) 1.916(8), O(5)–
Cu(3)–C(50) 179.0(3), O(1)–Cu(1)–P(1) 115.21(16), P(1)–Cu(1)–P(3)
128.40(9), O(1)–Cu(1)–P(1) 115.21(16), O(2)–Cu(2)–P(2) 115.92(18),
O(2)–Cu(2)–P(4) 119.90(18).
OQ)2(dppm)2]+ and a [(6-HOQ)2(l-6-OQ)]ꢀ ion present in 3 (ellipsoids
at 50% probability level; only a-C atoms of phenyl rings in dppm ligands
˚
˚
are displayed). Selected bond lengths (A) and angles (°): Cu–O 2.147(4)–
2.243(4), Cu–P 2.2413(18)–2.2585(19), O(5)ꢁ ꢁ ꢁHꢁ ꢁ ꢁO(7) 2.55(1), O(6)ꢁ ꢁ ꢁH
ꢁ ꢁ ꢁO(7) 2.53(1), O–Cu–O 71.39(17)–73.69(17), O–Cu–P 102.53(13)–
122.43(12), P–Cu–P 120.68(7)–122.39(7).
OLi
O
O
dppm
O
[Cu3(3-pyO)(CO2C2H4Boc)(dppm-)(dppm)]
3CuOtBu +
+
1/
tBu
-LiO
4
N
-tBuOH
Scheme 4. Synthesis of 4.

C.E. Anson et al. / Inorganica Chimica Acta 359 (2006) 2263–2267
2267
undissociated hydroxy protons was found in the infra-red
spectrum of 3 (mmax = 3456 cmꢀ1). The ‘partial deprotona-
tion approach’ used for the synthesis of 3 offers many pos-
sibilities for the syntheses of supramolecular assemblies of
metal alkoxides stabilised by hydrogen-bonded anions.
Current work is focusing on these aspects, and on insertion
reactions of organic anhydrides into the metal–oxygen
bond of the new Cu(I) alkoxides 1–3. So far these efforts
have led to the formation and characterisation of
1/ [Cu3(3-pyO)(CO2C2H4Boc)(dppmꢀ)(dppm)] (4) (Boc =
obtained free of charge at 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; e-mail: deposit@ccdc.cam.ac.uk].
Acknowledgements
A.R. thanks Prof. D. Fenske for his support and the
Forschungszentrum Karlsruhe for funding.
1
1
tert-butoxycarbonyl) (Scheme 4, Fig. 4).
References
In the solid-state, 4 exists as a one-dimensional coordi-
nation polymer of [Cu3(3-pyO)(CO2C2H4Boc)(dppmꢀ)-
(dppm)]-units linked by coordination of N(1) to Cu(1)
(Fig. 4). The formation of 4 could be rationalised by co-
complexation of [Cu(3-pyO)], [Cu(CO2C2H4Boc)] and
[Cu(dppmꢀ)] in the presence of an additional auxiliary
dppm ligand.
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4. Conclusion
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The work described here represents a part of our ongo-
ing efforts to establish the ‘anhydride-metal alkoxide
approach’ to metallo-organic open frameworks (MOF’s).
So far we have successfully described the insertion reac-
tions of a variety of organic anhydrides into the Cu–O
bond of the Cu(I) alkoxide [CuOtBu] and the subsequent
metal exchange by metathesis reactions with a variety of
transition metal halides. Here we have described the syn-
thesis of a range of novel Cu(I) alkoxides (1–3), which will
in future allow the facile construction of polydentate
ligands necessary for the formation of MOF’s. Future
work will focus on these aspects, but the synthesis of 4 illus-
trates that a number of obstacles are yet to be overcome.
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[13] A CCDC search on compounds containing both Cu–N(aromatic) and
Cu–O(alkoxide) bonds resulted in 1022 hits with average Cu–N
˚
˚
distances of 2.013 A and Cu–O distances of 1.995 A; F.H. Allen,
Acta Crystallogr., Sect. B 58 (2002) 380.
5. Supplementary material
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CCDC nos. 285877–285880 contain the supplementary
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