Aerial oxidation of primary alcohols and amines catalyzed by Cu(II) complexes of 2,2′-selenobis(4,6-di-tert-butylphenol) providing [O,Se,O]-donor atoms

Article abstract of DOI:10.1039/b403953j

Seven copper(II)-complexes 1-7 with the ligand 2,2′-selenobis(4,6-di- tert-butylphenol) providing [O,Se,O]-donor atoms have been isolated and characterized. Three of them 1,2 and 3 are mononuclear, two 4 and 7 dinuclear and 5, 6 are trinuclear. The crystal structures of the complexes were determined by X-ray diffraction and the electronic structures were established by various physical methods including EPR and variable temperature (2-290 K) susceptibility measurements. The magnetic behaviour of the compounds 4-6 exhibits antiferromagnetic exchange coupling resulting in well-isolated S_t = 1/2 ground state for 5 and 6 and a diamagnetic spin state for 4. Complexes 5 and 6 belong to the class of asymmetric trinuclear copper(II) complexes modelling the trinuclear copper site in multicopper oxidases. Complex 1 is a catalyst in the presence of a strong base for the aerial oxidation of primary alcohols to the corresponding aldehydes. A dinuclear complex, seemed to be 4, prepared in situ has been found to be a catalyst for the aerial oxidation of primary amines containing α-C -H atoms. Primary kinetic isotope effects show that H-abstraction from the α-carbon atom of a coordinated substrate (alcoholato or amine) is the rate-determining step in both cases. Two functional models for the metalloenzymes galactose oxidase and amine oxidases are thus described.

Full text of DOI:10.1039/b403953j

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F U L L P A P E R
Aerial oxidation of primary alcohols and amines catalyzed
by Cu(II) complexes of 2,2′-selenobis(4,6-di-tert-butylphenol)
providing [O,Se,O]-donor atoms†
Tapan K. Paine, Thomas Weyhermüller, Karl Wieghardt and Phalguni Chaudhuri*
Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36,
D-45470 Mülheim an der Ruhr, Germany. E-mail: chaudh@mpi-muelheim.mpg.de;
Fax: +49 (0)208 306 3951; Tel: +49 (0)208 306 3662
Received 18th March 2004, Accepted 13th May 2004
First published as an Advance Article on the web 21st June 2004
Seven copper(II)-complexes 1–7 with the ligand 2,2′-selenobis(4,6-di-tert-butylphenol) providing [O,Se,O]-donor atoms
have been isolated and characterized. Three of them 1, 2 and 3 are mononuclear, two 4 and 7 dinuclear and 5, 6 are
trinuclear. The crystal structures of the complexes were determined by X-ray diffraction and the electronic structures were
established by various physical methods including EPR and variable temperature (2–290 K) susceptibility measurements.
The magnetic behaviour of the compounds 4–6 exhibits antiferromagnetic exchange coupling resulting in well-isolated
St = 1/2 ground state for 5 and 6 and a diamagnetic spin state for 4. Complexes 5 and 6 belong to the class of asymmetric
trinuclear copper(II) complexes modelling the trinuclear copper site in multicopper oxidases. Complex 1 is a catalyst in the
presence of a strong base for the aerial oxidation of primary alcohols to the corresponding aldehydes. A dinuclear complex,
seemed to be 4, prepared in situ has been found to be a catalyst for the aerial oxidation of primary amines containing -
C–H atoms. Primary kinetic isotope effects show that H-abstraction from the -carbon atom of a coordinated substrate
(alcoholato or amine) is the rate-determining step in both cases. Two functional models for the metalloenzymes galactose
oxidase and amine oxidases are thus described.
2,2′-selenobis-(4,6-di-tert-butylphenol), H2LSe. Additionally,
a
Introduction
modified ligand dianion [LSe1 2− isolated as a dinuclear Cu(II) spe-
]
Phenol containing ligands1,2 have attracted considerable attention
in the bioinorganic chemical community because of the widespread
occurrence of the tyrosyl radicals3 in various metalloproteins
involved in oxygen-dependent enzymatic oxidations. One of the
widely studied tyrosyl-radical containing metalloproteins is galac-
tose oxidase (GO). GO is a fungal enzyme which catalyses the aero-
bic oxidation of primary alcohols to aldehydes with concomitant
formation of H2O2.4 The structure5 of this biomolecule and its reac-
tion mechanism6 are well established. In its catalytically active form
there is an ortho-S-modified tyrosyl radical (Tyr 272) coordinated
to a single copper(II) ion and a unique radical cofactor. The rate
determining step of this catalysis upon binding of the alcohol sub-
strate to the Cu(II) ion is the hydrogen abstraction (KH/KD = 6–8)7
from the alpha carbon atom of the alcohol with formation of a coor-
dinated ketyl radical anion. Rapid intramolecular electron transfer
with reduction of Cu(II) to Cu(I) then leads to the formation of the
unbound aldehydes. The reduced enzyme reacts with dioxygen with
formation of dihydrogen peroxide and regeneration of the active
radical cofactor.
This has led bioinorganic chemists to design and synthesize
structural and functional models of the biomolecules using a phe-
nol-containing ligand which has the potential ability to form one-
electron oxidized phenoxyl radical complexes. These phenoxyl
radical complexes can be used as bioinspired radical catalysts for
conversion of different organic substrates.2a–c,8
We have already reported a thiobisphenol ligand2a for generating
copper(II)-containing catalysts. Now we have substituted the sul-
fur-donor atom of the ligand by selenium as an obvious and natural
progression of our earlier work. This work deals with the study of
Cu(II) complexes of a selenobisphenol ligand and their possible use
as homogeneous catalysts. The selenobisphenolate ligand used is
cies 7 is also described.
A mononuclear Cu(II) complex in combination with a base
was found to oxidize catalytically primary alcohols to aldehydes,
aerobically. Moreover, a dinuclear Cu(II) complex catalyzes the
oxidative deamination reactions of primary amines in air. This is
a rare example for a functional model of the copper amine oxidase
enzymes.3b,3f,9 Two trinuclear Cu(II) complexes which can be consid-
ered as models for multicopper oxidases10–15 are also reported.
Results and discussion
The ligand H2LSe reacts with copper ions in the presence of differ-
ent amines giving rise to a variety of Cu(II) complexes as shown in
Scheme 1.
† Electronic supplementary information (ESI) available: Molecular struc-
tures of H2LSe (Fig. S1), complex 2 [CuLSe(Et2NH)] (Fig. S2), complex
5 [(LSe)2(HLSe)Cu3(2-OH)(CH3CN)] (Fig. S3) and EPR spectra for
complexes 1, 4 and 5 with their simulations (Figs. S4–S7). Tables S1 and
S2 list the bond lengths and angles for H2LSe and complex 5, respectively.
See http://www.rsc.org/suppdata/dt/b4/b403953j/
Scheme 1
2 0 9 2
D a l t o n T r a n s . , 2 0 0 4 , 2 0 9 2 – 2 1 0 1
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4

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Table 1 Selected bond distances (Å) and angles (°) for complexes 1 and 2
1
2
Cu(1)–O(1)
Cu(1)–O(2)
Cu(1)–Se(1)
Cu(1)–N(1)
C(2)–O(1)
1.898(2)
1.889(2)
2.3922(6)
2.052(2)
1.330(3)
1.336(3)
Cu(1)–O(1)
Cu(1)–O(2)
Cu(1)–Se(1)
Cu(1)–N(30)
C(2)–O(1)
1.879(2)
1.885(2)
2.3842(5)
2.029(3)
1.335(4)
1.335(4)
C(16)–O(2)
C(16)–O(2)
O(2)–Cu(1)–O(1)
O(2)–Cu(1)–N(1)
O(2)–Cu(1)–Se(1)
N(1)–Cu(1)–Se(1)
N(1)–Cu(1)–O(1)
Se(1)–Cu(1)–O(1)
150.25(8)
98.02(9)
89.05(6)
153.13(7)
96.80(8)
89.27(6)
O(2)–Cu(1)–O(1)
O(2)–Cu(1)–N(30)
O(2)–Cu(1)–Se(1)
N(30)–Cu(1)–Se(1)
N(30)–Cu(1)–O(1)
Se(1)–Cu(1)–O(1)
147.82(11)
98.41(13)
90.40(7)
147.00(10)
98.15(13)
90.53(7)
The ligand H2LSe reacts with Cu(I) or Cu(II) salt in methanolic
solvent in the presence of different amine bases of known ligating
properties to form four-coordinated square-planar Cu(II) com-
plexes, in which the fourth coordination site is occupied by the
corresponding amine base. Tertiary amines (e.g. Et3N), secondary
amines (e.g. Et2NH), and primary amines without any -H atom
(e.g. tBuNH2) do form such complexes in the presence of air as is
evidenced by isolation of 1, 2 and 3, respectively.
But, when the amine is a primary amine with at least one -H
atom a totally different reactivity is observed in air. If the reaction is
carried out in the presence of benzylamine under argon a dinuclear
Cu(II) complex 4 is isolated, where two benzylamine molecules
disposed in anti positions are attached to two Cu(II) centers. When
the same reaction is carried out in air no such Cu(II) complex could
be isolated. Instead an organic product, benzylidinebenzylamine
(PhCHNCH2Ph), is detected, which is a Schiff base condensation
product of benzaldehyde and benzylamine. Benzaldehyde is formed
by the aerial oxidation of benzylamine, catalyzed by a Cu(II) com-
plex, formed in situ in solution. This oxidative deamination reaction
is found to be catalytic in nature.
Fig. 1 UV-vis spectral change of 6 in CH2Cl2 during the aerial oxidation.
Single crystal X-ray diffraction studies
Molecular structure of the ligand H2LSe. Although the ligand
was unambiguously characterized by different spectroscopic tech-
niques,17 its structure was determined by a single crystal X-ray dif-
fraction study to ascertain the C–Se bond lengths and to determine
particularly the aromatic C–C bond distances. The crystal symmetry
is C2. Fig. S1 (see ESI†) displays the structure of the ligand in the
solid state. The bond parameters listed in Table S1 (see ESI†) are
comparable with those of GeLSe 17a and do not warrant any special
2
discussion.
Molecular structure of [CuLSe(Et3N)] (1). The ORTEP diagram
with the atom-labeling scheme is given in Fig. 2 and the selected
bond parameters are given in Table 1. There are two crystallographi-
cally independent molecules, whose metrical parameters are very
similar.
Bulky tertiary amines, e.g. (iPr)2NEt (also a weak base ), do not
coordinate to copper because of steric reasons but behave as bases
deprotonating the ligand and trinuclear Cu(II) complexes are formed
according to Scheme 1.
Treatment of the trinuclear complexes 5, 6 with respective
amines results in the mononuclear complexes 1, 2, 3 whereas with
benzylamine they form oxidized products under air. Interestingly,
complex 6 reacts with the oxygen of air in a solvent mixture of
CH2Cl2 and CH3CN (1:1) forming a small amount of dinuclear
2−
Cu(II) complex 7 with a modified ligand [LSe1
]
along with the
trinuclear species. GC-analysis after removal of copper ion from
the solution confirms the formation of the modified ligand H2LSe1
.
Isolation of the pure dinuclear species 7 was not possible because
of the presence of a trinuclear species as an impurity that remains
in the mixture. A mechanical separation under a microscope al-
lowed us to determine only the X-ray structure of 7 from a mixture
of 6 and 7.
The mononuclear amine complex 1, [CuLSe(Et3N)] in combina-
tion with a base (methanolic Bu4NOCH3 or BuLi) in CH3CN under
air reacts with primary alcohols to catalytically oxidize them to the
corresponding carbonyl compounds.
Fig. 2 Molecular structure of [(Et3N)CuLSe] 1. Thermal ellipsoids are
shown at 40% probability.
Cu(1) is coordinated to the O,Se,O donor set of the ligand and
to N(1) of the Et3N molecule, yielding a distorted square planar
geometry. Two phenolate oxygen atoms and selenium and nitrogen
atoms are bonded trans to each other, having an O(1)–Cu–O(2)
bond angle at 150.25(8)° and Se(1)–Cu–N(1) angle at 153.13(7)°.
The Cu–O(phenolate)[1.895Å] and Cu–N[2.052(2)Å] bonds are in
the normal range for Cu(II) complexes,2 which also conforms with
susceptibility measurements.
As IR and Mass spectrometric data used for initial characteriza-
tion of complexes 1–6 are unexceptional, and do not need any dis-
cussion, the results are given in the Experimental section.
The electronic spectra recorded in CH2Cl2 (see Experimental sec-
1
2
2
tion) are in agreement with a (dx −y ) electronic configuration of the
d9 copper(II) centers in the complexes.
Interestingly, the trinuclear species 6 shows two bands in the
visible region (630 nm and 480 nm). But, in CH2Cl2, over time
the nature of the spectrum changes dramatically and finally shows
only one band at 460 nm (Fig. 1). This seems to be due to a self-
decomposition of the complex in CH2Cl2 solvent under air. Isolation
of the dinuclear species 7 with the modified ligand supports this
proposal.
Molecular structure of [CuLSe(Et2NH)] (2). This complex is
isostructural with complex 1 as is exhibited by the ORTEP diagram
shown in Fig. S2 (see ESI†) and the bond parameters in Table 1. We
will refrain from discussing the structural details again.
D a l t o n T r a n s . , 2 0 0 4 , 2 0 9 2 – 2 1 0 1
2 0 9 3

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Table 2 Selected bond distances (Å) and angles (°) for complex 4
Table 3 Selected bond distances (Å) and angles (°) for complex 6
Cu(1)–O(1)
Cu(1)–N(1)
Cu(1)–Se(1)
Cu(2)–O(2)
Cu(2)–Se(2)
Cu(1)–Cu(2)
C(1)–O(1)
C(16)–O(2)
C(32)–O(3)
C(45)–O(4)
1.946(5)
2.024(7)
2.4503(14)
1.960(5)
2.4685(14)
3.122(5)
1.320(10)
1.346(9)
1.352(9)
1.333(9)
Cu(1)–O(3)
Cu(1)–O(2)
Cu(2)–O(4)
Cu(2)–N(2)
1.947(5)
2.220(5)
1.878(5)
2.017(6)
Cu(1)–O(1)
Cu(1)–O(3)
Cu(2)–O(6)
Cu(2)–O(3)
Cu(2)–Se(3)
Cu(3)–O(4)
Cu(3)–O(90)
C(2)–O(1)
1.859(2)
1.942(2)
1.895(2)
1.973(2)
2.4205(5)
1.871(2)
2.039(2)
1.323(4)
1.364(3)
1.340(3)
Cu(1)–O(95)
Cu(1)–Se(1)
Cu(2)–O(95)
Cu(2)–O(5)
Cu(3)–Se(2)
Cu(3)–O(5)
C(8)–O(2)
1.939(2)
2.4024(5)
1.969(2)
2.322(2)
2.4356(5)
1.915(2)
1.384(4)
1.328(4)
1.336(4)
C(38)–O(4)
C(62)–O(6)
C(32)–O(3)
C(68)–O(5)
O(1)–Cu(1)–O(3)
O(3)–Cu(1)–N(1)
O(3)–Cu(1)–O(2)
O(1)–Cu(1)–Se(1)
N(1)–Cu(1)–Se(1)
O(4)–Cu(2)–O(2)
O(2)–Cu(2)–N(2)
O(2)–Cu(2)–Se(2)
Cu(1)–O(2)–Cu(2)
94.9(2)
84.9(3)
110.3(2)
87.5(2)
92.6(2)
154.8(2)
96.2(2)
93.3(2)
96.4(2)
O(1)–Cu(1)–N(1)
O(1)–Cu(1)–O(2)
N(1)–Cu(1)–O(2)
O(3)–Cu(1)–Se(1)
O(2)–Cu(1)–Se(1)
O(4)–Cu(2)–N(2)
O(4)–Cu(2)–Se(2)
N(2)–Cu(2)–Se(2)
179.3(3)
93.4(2)
87.3(2)
164.8(2)
84.49(14)
88.5(2)
O(1)–Cu(1)–O(95)
O(95)–Cu(1)–O(3)
O(95)–Cu(1)–Se(1)
O(6)–Cu(2)–O(95)
O(95)–Cu(2)–O(3)
O(95)–Cu(2)–O(5)
O(6)–Cu(2)–Se(3)
O(3)–Cu(2)–Se(3)
O(4)–Cu(3)–O(5)
O(5)–Cu(3)–O(90)
O(5)–Cu(3)–Se(2)
Cu(1)–O(3)–Cu(2)
Cu(2)–O(5)–Cu(3)
Cu(1)Cu(2)
172.34(9)
78.48(8)
96.51(6)
170.26(8)
77.02(8)
92.47(8)
89.17(6)
165.78(6)
163.51(9)
91.18(9)
91.38(6)
100.83(9)
99.33(8)
3.018(1)
3.240(1)
4.933(1)
O(1)–Cu(1)–O(3)
O(1)–Cu(1)–Se(1)
O(3)–Cu(1)–Se(1)
O(6)–Cu(2)–O(3)
O(6)–Cu(2)–O(5)
O(3)–Cu(2)–O(5)
O(95)–Cu(2)–Se(3)
O(5)–Cu(2)–Se(3)
O(4)–Cu(3)–O(90)
O(4)–Cu(3)–Se(2)
O(90)–Cu(3)–Se(2)
Cu(1)–O(95)–Cu(2)
96.33(9)
90.05(7)
162.97(6)
93.59(8)
93.52(9)
112.41(8)
99.32(6)
81.29(5)
91.50(9)
88.10(7)
172.29(8)
101.09(9)
87.0(2)
166.4(2)
Molecular structure of [CuLSe(PhCH2NH2)]2 (4). The structure
analysis of this complex shows the presence of a dinuclear unit as
the smallest unit present in the crystal with one four-coordinated
and another five-coordinated copper center. The ORTEP drawing
of the molecule is displayed in Fig. 3, with selected bond distances
and angles provided in Table 2.
Cu(2)Cu(3)
Cu(3)Cu(1)
bond lengths and angles are listed in Table S2 (see ESI†). There
are two types of copper(II) ions in complex 5, two terminal four-
coordinated distorted square planar and a five-coordinated central
copper square-pyramidal in geometry, as has also been found for 6
(see Fig. 4). There is no monoatomic bridging between the terminal
square-planar copper centers. The poor quality of the data collection
precludes detailed discussion of the structure but it does appear to
have the same overall motif as that of its comparable complex 6.
Fig. 3 Molecular structure of [(PhCH2NH2)2Cu2LSe2] 4. Thermal ellip-
soids are at 40% probability.
The copper ion Cu(2) is in a distorted square-planar environ-
ment having a CuO2SeN coordination sphere. The ligand with the
O(1),Se(1),O(2) donor atoms coordinates to Cu(1) in a facial man-
ner to develop a distorted square pyramidal geometry with a CuNO4
environment. One phenolate oxygen O(2) acts as a bridging unit be-
tween Cu(1) and Cu(2) centers. Two phenolates, O(4) and bridging
O(2) from two different ligands, the selenium atom Se(2) and the
nitrogen atom N(2) form the basal plane for the Cu(2) center. The
Cu(2)–O(2) and Cu(2)–O(4) bonds are in a mutually trans position;
similarly Cu(2)–Se(2) and Cu(2)–N(2) are trans to each other. The
bond distances for the five-coordinated center Cu(1) is significantly
longer than those for the four-coordinated Cu(2) center [Cu(1)–O(1)
1.946(5)Å, Cu(2)–O(4) 1.878(5)Å]. The angle O(2)–Cu(2)–O(4) at
154.8(2)° deviates significantly from linearity, as well as the angle
Se(2)–Cu(2)–N(2) at 166.4(2)°. But the angle for five coordinated
Cu(1), O(1)–Cu(1)–N(1) at 179.3(3)° is linear. In solution it also
exists as a dimer, as established by solution EPR spectroscopy.
Fig. 4 An ORTEPrepresentation of [(LSe2)(HLSe)Cu3(2-OCH3)(CH3OH)]
6. Thermal ellipsoids are shown at 40% probability.
Molecular
structure
of
[LSe2(LSeH)Cu3(-OCH3)-
(CH3OH)]·CH2Cl2 (6). The structure of the complex consists of
a trinuclear unit containing the LSe2(HLSe)Cu3 core similar to com-
plex 5. The molecular geometry and the atom-labeling scheme is
shown in Fig. 4; selected bond lengths and angles for this complex
are presented in Table 3.
There are two types of copper bonded in the trinuclear unit, two
of them, Cu(1) and Cu(3), are four-coordinated distorted square
planar and the central copper Cu(2) is five-coordinated. The central
copper Cu(2) is facially coordinated to the ligand with O, Se, O
donor atoms at distances Cu(2)–O(5) [2.322 (2) Å], Cu(2)–Se(3)
[2.4205(5) Å] and Cu(2)–O(6) [1.895(2)Å]. The coordination ge-
ometry of a distorted square pyramidal is completed by two oxygen
atoms, O(95) [bridging OCH3 from solvent methanol between
Structure of [LSe2(LSeH)CuII (2-OH)(CH3CN)]·CH3CN (5).
3
Complex 5 contains a tricopper(II) unit in which a hydroxide ligand
bridges two copper centers shown in Fig. S3 (see ESI†) and selected
2 0 9 4
D a l t o n T r a n s . , 2 0 0 4 , 2 0 9 2 – 2 1 0 1

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Table 4 Selected bond distances (Å) and angles (°) for complex 7
Both copper centers are tetracoordinated by two ligands with
the O, Se, O donor atoms, resulting in two CuO3Se coordination
polyhedra, where both the Cu(II) are distorted square planar in ge-
ometry. The Cu(1)–O(1) distance at 1.860(4) Å and the Cu(2)–O(4)
distance at 1.861(4) Å are significantly shorter than the Cu(1)–O(6)
[1.962(4) Å] and Cu(2)–O(3)[1.964(4) Å]. The phenolate oxygens
O(1) and O(3) from one ligand coordinated to Cu(1) are trans to
each other making an O(1)–Cu(1)–O(3) angle at 173.5(2)°. Simi-
larly, the O(4)–Cu(2)–O(6) angle at 172.0(2)° clearly shows the co-
ordination geometry as distorted square-planar. Phenolate oxygen
O(1) and Se(1) are cis to each other. O(6) and O(3), two phenoxide
oxygens, form the bridging ligands between Cu(2) and Cu(1); thus
the coordination polyhedron can be described as a edge-shared
square planar. The Cu(1)Cu(2) distance is 2.859(11) Å.
Cu(1)–O(1)
Cu(1)–O(6)
Cu(2)–O(6)
Cu(2)–Se(2)
Cu(1)Cu(2)
C(1)–O(1)
1.860(4)
1.962(4)
1.936(4)
2.4265(10)
2.859(1)
1.320(7)
1.328(7)
Cu(1)–O(3)
Cu(2)–O(4)
Cu(2)–O(3)
Cu(1)–Se(1)
1.937(4)
1.861(4)
1.964(4)
2.4192(10)
C(14)–O(3)
C(64)–O(6)
1.362(7)
1.372(7)
C(51)–O(4)
O(1)–Cu(1)–O(3)
O(3)–Cu(1)–O(6)
O(3)–Cu(1)–Se(1)
O(4)–Cu(2)–O(6)
O(6)–Cu(2)–O(3)
O(6)–Cu(2)–Se(2)
Cu(1)–O(3)–Cu(2)
173.5(2)
76.7(2)
95.14(13)
172.0(2)
76.7(2)
O(1)–Cu(1)–O(6)
O(1)–Cu(1)–Se(1)
O(6)–Cu(1)–Se(1)
O(4)–Cu(2)–O(3)
O(4)–Cu(2)–Se(2)
O(3)–Cu(2)–Se(2)
Cu(1)–O(6)–Cu(2)
99.3(2)
89.27(13)
170.08(12)
96.4(2)
88.52(13)
174.11(12)
94.4(2)
98.62(12)
94.3(2)
Magnetic susceptibility and EPR measurements
Magnetic susceptibility data for polycrystalline samples of com-
plexes 1–6 were collected in the temperature range 2–290 K in an
Cu(1) and Cu(2)] and O(3) [from phenolate bridge between Cu(1)
and Cu(3)]. Thus phenolate oxygen O(6), Se(3),O(95) and O(3)
form the basal plane for Cu(2), in which O(6) and O(95) are trans
to each other with an O(6)–Cu(2)–O(95) angle at 170.26(8)°.
Cu(1) is surrounded by two bridging oxygen atoms and one phe-
nolate oxygen atom O(1) and Se(1), where O(95)–Cu(1)–O(1) and
O(3)–Cu(1)–Se(1) angles are at 172.34(9) and 162.97(6)°, respec-
tively, deviating considerably from ideal square-planar geometry.
The protonated phenolate oxygen O(2) remains non-coordinated,
making a hydrogen bond with O(95) of the bridging methoxide with
O(95)O(2) of 2.739(4) Å.
Similarly Cu(3) makes a distorted square-planar geometry by
bonding with two phenolates O(4) and O(5), which are trans to
each other with an angle of 163.51(9)°, and Se(2) and O(90) [trans
to each other at 172.29(8)°]. The unique coordination environment
makes the Cu3LSe3 unit asymmetric, with three copper atoms at the
corners of an isosceles triangle. Cu(1) and Cu(2) are bridged by one
phenolate and one methoxy oxygen resulting in a Cu(1)Cu(2)
distance of 3.0176(5) Å. On the other hand Cu(3) and Cu(2) are
bridged through only one phenolate oxygen O(5), whereas Cu(1)
and Cu(3) are not directly linked through such a monoatomic bridg-
ing mode. The structural parameters agreed well with magnetic
exchange between the paramagnetic Cu(II) centers.
applied magnetic field of 1 T. The Heisenberg spin Hamiltonian
 
in the form H = −2J ΣSiSj for an isotropic exchange coupling was
ij
used. The experimental magnetic data were simulated using a least-
squares fitting computer program with a full-matrix diagonalization
of exchange coupling, Zeeman splitting and axial single-ion zero-

2
field interactions (DSz ), if necessary. We start our discussion with
the magnetic properties of mononuclear complexes 1–3. Above
T ≈ 20 K complexes 1–3 exhibit essentially temperature indepen-
dent eff values of 1.76 ± 0.03, 1.83 ± 0.01 and 1.86 ± 0.04 B,
respectively, in accord with the monomeric nature of the complexes
in the solid state. Below ca. 20 K, the magnetic moment eff starts to
decrease monotonically reaching the values 1.30 B for 1, 1.41 B
for 2 and 1.73 B for 3 at 2 K. The experimental magnetic moments
were simulated by a least-squares fitting computer program with a
full-matrix diagonalization approach. The best fit parameters evalu-
ated are gCu = 2.06,  = −1.34 K for 1, gCu = 2.13,  = −0.97 K for 2
and gCu = 2.085,  = −0.10 K, TIP = 150 × 10−6 emu for 3, where 
is the Weiss constant and TIP represents the temperature-indepen-
dent contributions to the susceptibility, so called high-frequency
terms. Thus, magnetic measurements show unambiguously that
1–3 contain d9 Cu(II) ions in complete agreement with X-ray and
EPR results (see later).
Molecular structure of [LSe12Cu2] (7). A single crystal was ob-
tained during recrystallization of complex 6 from a solvent mixture
In contrast, the magnetic behaviour of complex 4 is characteristic
of an anti-ferromagnetically coupled dinuclear complex (Fig. 6). At
290 K the eff value of 2.67 B (MT = 0.8842 cm3 K mol−1) decreases
monotonically with decreasing temperature until it reaches a value
of 1.70 B (MT = 0.3579 cm3 K mol−1) at 2 K; this is a clear indica-
tion of a weak exchange coupling between two paramagnetic Cu(II)
centers. By using the isotropic Heisenberg spin–Hamiltonian in the
form H = −2JS1S2 (S1 = S2 = 1/2) the magnetic data have been fitted
satisfactorily, taking into account exchange coupling and Zeeman
splitting. A weak intramolecular antiferromagnetic exchange cou-
pling of J = −1.3 cm−1, gCu = 2.103 and TIP = 207 × 10−6 cm3 mol−1
for 4 has been established in accord with its dimeric structure in the
solid state (Fig. 3).
of CH2Cl2 and CH3CN. The dimeric unit Cu2LSe1 consists of two
2
2−
modified ligands [LSe1
] formed during recrystallization from li-
gand LSe as shown in Scheme 1 where two phenolates act as a bridg-
ing unit between two Cu(II) centers. The etheral oxygen atoms, O(5)
and O(2) do not coordinate to the metal ions. The modified ligand
thus also behaves as a tridentate ligand. The ball and stick diagram
with the atom-labeling scheme is shown in Fig. 5, and selected bond
parameters are given in Table 4.
The magnetic moments of 2.30 B (MT = 0.6591 cm3 K mol−1)
and 2.54 B (MT = 0.8088 cm3 K mol−1) at 290 K for complexes
5 and 6, respectively, are considerably smaller than the expected
spin-only value of 3.0 B for three uncoupled Cu(II) ions; the mag-
netic moments decrease upon cooling, reaching the values of 1.50
(MT = 0.2808 cm3 K mol−1) and 1.81 (MT = 0.4091 cm3 K mol−1)
B at 2 K for 5 and 6, respectively. A plateau is reached in the range
100–15 K with the eff value of 1.82 ± 0.02 B for 5 and 60–5 K
with the eff value of 1.92 ± 0.08 B for 6. The results indicate
a moderately strong antiferromagnetic interaction amongst the
neighbouring copper(II) ions within the trinuclear unit. As there
is no monoatomic bridging between the copper centers, Cu(2)
and Cu(3) with Cu(2)Cu(3) 4.722 Å for 5 and Cu(3) and Cu(1)
with Cu(3)Cu(1) 4.933 Å for 6, and to avoid overparametriza-
tion we have neglected the interactions Cu(2)Cu(3) in 5 and
Cu(3)Cu(1) in 6 and considered a “2J” model to fit the experi-
mental magnetic data. The best fits shown as solid lines in Fig. 6
Fig. 5 A perspective view of [Cu2LSe12] 7.
D a l t o n T r a n s . , 2 0 0 4 , 2 0 9 2 – 2 1 0 1
2 0 9 5

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Reactivity studies
It has already been discussed that the trinuclear species 6 forms a
modified ligand-containing dinuclear Cu(II) complex 7 in a solvent
mixture of CH2Cl2 and CH3CN in air. Formation of a new species
is also clearly seen from the time-dependent electronic spectral
changes passing through an isosbestic point for 6 in CH2Cl2
(Fig. 1). Formation of 7 from an aerial oxidation of 6 is an indica-
tion of a radical mediated reaction. In addition to that, complex 6
in CH2Cl2 reacts with 2,4-di-tert-butylphenol to oxidize it to the
C–C-coupled product, biphenol. Formation of biphenol indicates
clearly the generation of the phenoxyl radical in situ from 6 during
this transformation.
Catalytic oxidation of primary amines
Primary amines with at least one -H atom undergo an oxidative
deamination reaction in the presence of Cu(I) salt and H2LSe ligand.
It has been shown in Scheme 1 that Cu(II) complexes containing
such amines (e.g. benzylamine) are very reactive under air. Conver-
sion of primary amines to the corresponding carbonyl compounds
or their Schiff base condensation product under such conditions is
catalytic in nature.
2 RCH2NH2 + O2 Cat → RCH= NCH2R + NH3 + H2O2
CH3OH,RT
In a standardized experimental set-up the catalyst was generated
in the following fashion: to a mixture of CuCl and ligand H2LSe
(1:1; 2.5 mM) in dry CH3OH (50 cm3) under an argon atmosphere
were added the corresponding primary amines (125 mM) (ben-
zylamine or -methylbenzylamine or -phenylbenzylamine or
cyclohexylamine). The resulting solution was stirred at 22 ± 1°C
for 24 h in an open vessel in the presence of air. The products were
then quantitatively analyzed for organic products by GC-MS using
an internal standard, NH3 was detected qualitatively. H2O2 could not
be detected in the reaction solution, probably because of the decom-
position of H2O2 by the Cu(II) complex showing catalase activity.
The uptake of O2 was also measured volumetrically. The turnover
number (TON) was then determined as the number of moles of
product per mole of catalyst. When the substrate is benzylamine
only the organic product benzylidinebenzylamine was detected,
with 17 turnovers. Similar Schiff-base products were observed for
-phenylbenzylamine and cyclohexylamine. On the other hand,
acetophenone was detected as the only oxidation product of -
methylbenzylamine with 10 turnovers.
The kinetics of the catalytic oxidative deamination of primary
amines have been measured by variation of the total concentration
of [CuCl], H2LSe (1.25 mM–6.25 mM) and [amine] (125 mM–
750 mM) under 1 bar of air in CH3OH. Water does not coordinate
to any intermediate in the catalytic cycle, and has no influence on
the rate of the reaction. From all these data a rate law was deduced:
Rate = k[catalyst][amines]
From the UV-vis and EPR spectra of the catalytic solution
during benzylamine oxidation it became clear that the dinuclear
Cu(II) complex, 4 is formed in the solution. It is anticipated that the
complex does participate in the catalytic cycle after coordination
to another molecule of benzylamine. The observed first order de-
pendence on both the copper and amine concentrations implies that
the four-coordinated Cu(II) center of the dimer, 4, binds a substrate
amine molecule with formation of a five coordinate intermediate
(Scheme 2). Although higher amine concentrations were used, no
saturation kinetics was observed (Fig. 7). This implies that the bind-
ing constant for the substrate is small (Scheme 2).
Fig. 6 Plots of eff vs. T for 4–6. The solid lines represent the simulations
of the experimental data (see text).
yield J12 = −181 cm−1, J13 = −134 cm−1, J23 = 0 (fixed), g = 2.05,
TIP = 180 × 10−6 cm3 mol−1 (fixed) for 5 and J12 = −275 cm−1,
J23 = −182 cm−1, J13 = 0 (fixed), g = 2.086, TIP = 180 × 10−6 cm3
mol−1 (fixed) for 6. Considering a “3J” model, there was no im-
provement in the quality of the fits and the third coupling constant
was found to be substantially weak (|J| < 30 cm−1) in comparison
to the other two exchange coupling constants. So we consider the
“2J” model is more realistic in terms of bond connectivities and
exchange pathways (see X-ray structures, Fig. S3 (see ESI†) and
Fig. 4). Hence we conclude that 5 and 6 have a well-separated
ground state of St = 1/2 with moderately strong exchange couplings,
which are comparable, between neighbouring copper(II) centers.
To model the structure and physical properties of the trinuclear
copper site in multicopper oxidases, a number of symmetric and
asymmetric trinuclear copper(II) complexes have been reported in
the literature.10–15 Complexes 5 and 6 can thus be placed in the class
of asymmetric trinuclear copper(II) complexes with -OH and -
OCH3 bridging ligands.
EPR spectra
The X-band EPR spectra of complexes 1, 4 and 5 were recorded
at low temperature (2.6–10 K) both in solution and in solid state.
The spectra displays typical features of a tetragonally distorted
Cu(II) complex with a (dx2 2)1 electronic configuration. Simula-
−y
tion of the spectra yielded the following parameters: gx = 2.03,
gy = 2.11, gz = 2.23, Ax = 0.26 × 10−4, Ay = 19.18 × 10−4 and
Az = 136.73 × 10−4 cm−1 for 1 in CH2Cl2, gx = 2.05, gy = 2.10,
gz = 2.21, Axx = 18.6 × 10−4 cm−1, Ayy = 11.4 × 10−4 cm−1 and
Azz = 125.5 × 10−4 cm−1 for 5 (solid) and gx = 2.04, gy = 2.09,
gz = 2.24, Axx = 0.25 × 10−4 cm−1, Ayy = 12.7 × 10−4 cm−1 and
Azz = 140 × 10−4 cm−1 for 5 (in CH2Cl2). The spectra and their simu-
lations are given as ESI† (Figs. S4–S7).
2 0 9 6
D a l t o n T r a n s . , 2 0 0 4 , 2 0 9 2 – 2 1 0 1

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In a standardized experimental set-up the catalyst was generated
in the following fashion: to a mixture of alcohol (2M) and base
(40 mM Bu4NOCH3, 20% methanolic solution) in dry CH3CN
(10 cm3) under an argon atmosphere was added the complex
(2mM). The resulting green solution was then opened and stirred
at 22 ± 1°C for 24 h in an open vessel in the presence of air. The
formation of aldehyde product with time was determined by taking
samples at different times. For benzyl alcohol the oxidation process
continues up to 10 h and then the product formation saturates. The
final organic products were quantitatively analysed by GC-MS,
using an internal standard. The turnover number (TON) was then
determined as the number of moles of product per mole of complex.
When the substrate is benzyl alcohol the organic product benzal-
dehyde was detected with 95 turnovers. With cinnamyl alcohol as
substrate, cinnamaldehyde was detected with 27 turnovers under the
same reaction conditions.
The kinetics (Fig. 8) of the catalytic alcohol oxidation have
been measured by variation of total concentration of [complex]
(0.5–5 mM) and [alcohols] under 1 bar of air in CH3CN. From all
these data a rate law was deduced: Rate = k[catalyst][alcohols]
Scheme 2
Fig. 8 Production of benzaldehyde as a function of time for the aerial
oxidation of benzyl alcohol catalyzed by complex 1. Reaction conditions:
1 = 1.25 mM, Bu4NOCH3 = 40 mM, C6H5CH2OH = 1 M in CH3CN.
By using at the alpha-carbon selectively deuterated benzyl alco-
hol as substrate, C6H5CD2OH, a kinetic isotope effect (KIE) under
turnover conditions of 8.5 at 22 ± 1°C has been determined. This
implies that H-atom abstraction from the -carbon atom of the co-
ordinated benzyl alcohol represents the rate-determining step of the
oxidation reaction.
The mechanism for the alcohol oxidation (Scheme 3) is very
similar to that proposed for the enzyme galactose oxidase3,6 and
a number of functional model systems.2,8 It involves binding of an
alcoholato ligand to the complex with formation of the phenoxyl
radical species, and H-atom transfer from the -carbon atom of the
coordinated alcoholato ligand in the rate-determining step, with the
formation of a bound ketyl radical anion, which reduces in an in-
tramolecular one-electron transfer step the Cu(II) to Cu(I) ions and
formation of aldehydes. Reoxidation of the reduced catalyst with O2
regenerates the active catalyst.
Fig. 7 Turnover numbers (TON) as a function of benzylamine-concen-
tration for the aerial oxidation of amine catalyzed by [CuCl] = [H2LSe] =
2.5 mM in CH3OH.
By using the -carbon selectively deuterated benzylamine as sub-
strate, C6H5CD2NH2, a kinetic isotope effect (KIE) under turnover
conditions of 4 at 22 ± 1°C has been determined. This implies that
in the above five-coodinate intermediate H atom abstraction from
the -carbon atom of the coordinated benzylamine represents the
rate-determining step of the deamination reaction.
From all these results the mechanism for this oxidative deamina-
tion reaction can be proposed as follows (Scheme 2):
Thus, this is an example of a functional model for the metalloen-
zyme, copper amine oxidase.
Concluding remarks
We have prepared and characterized a new family of mononuclear,
dinuclear and trinuclear copper(II) complexes with an ancillary
selenobisphenol ligand contributing two phenolate and one sele-
noether donor groups. Emphasis has been given in this work not
only to establish the geometrical but also the electronic structures
of the compounds isolated. Thus, the compounds have been char-
acterized by the crystal structures, magnetic susceptibility and EPR
measurements. Furthermore, the potential for using the complexes
for aerial generation of phenoxyl radicals from coordinated pheno-
lates in order to mimic the function of metalloenzymes like amine
Catalytic oxidation of primary alcohols
Mononuclear Cu(II) complex 1 in combination with a base
(Bu4NOCH3) in CH3CN catalytically oxidizes primary alcohols
to the corresponding aldehydes with moderate to high turnover
numbers. This oxidation can also be performed in neat alcohol
(e.g., benzyl alcohol) with base (BuLi). The only organic product
observed is the aldehyde.
1, Bu4OCH3 , Air
RCH2OH → RCHO
RT, CH3CN
D a l t o n T r a n s . , 2 0 0 4 , 2 0 9 2 – 2 1 0 1
2 0 9 7

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program SADABS (G. M. Sheldrick, Universität Göttingen) and
that of 2 with the MulAbs, Platon 99 program suite.18 The Siemens
SHELXTL software package19 was used for solution, refinement,
and artwork of the structure, and neutral atom scattering factors of
the program were used. All structures were solved and refined by
direct methods and difference Fourier techniques. Unless otherwise
stated all non-hydrogen atoms were refined anisotropically, and
hydrogen atoms were placed at calculated positions and refined as
riding atoms with isotropic displacement parameters.
The molecule H2LSe belongs to the space group Pccn (No. 56)
with the Se atom on 2/3, 2/3, z and is disordered by 180° rotation
along the Se(1)–C(1) axis due to the crystallographic two-fold axis.
The two positions in a ~1:1 ratio were refined for O(1):O(1x) due
to the disorder. The O(1) split atoms were untied from the carbons
to geometrically attach the H-atoms. The coordinates with standard
deviations are given in the CIF file. The question of whether the
OH-groups are positioned side by side to form a weak hydrogen-
bond (distance OO 2.98 Å) resulting from the disorder due to the
crystallographic C2-symmetry or both conformers are present is yet
to be resolved.
In complex 2 the coordinated diethylamine is disordered over two
sites with an occupancy of 2:1. The carbon atoms, C(31), C(33),
C(34) and all atoms of the minor component were isotropically re-
fined. C(45) to C(48) of complex 4 were isotropically refined since
they were not positive-definite. Water molecule O(10) in 4 is dis-
ordered over two sites (80:20). The minor component O(10x) was
isotropically refined. The crystal of complex 5 diffracted weakly.
Only heavy atoms, Cu and Se, were anisotropically refined.Amulti-
scan (SADABS) absorption correction was applied for 5. Transmis-
sion factors obtained are 0.633 (min.) and 0.862 (max.).
In complex 6 the tert-butyl groups C(25) to C(28) and C(55) to
C(58) are disordered by rotation. Split models were refined. Atom
C(25) was found to be “non-positive-definite” and was therefore
isotroically refined. The solvate CH2Cl2 molecule was found to be
severely disordered. Three split positions (70:15:15) were refined.
The poorly defined carbon atom C(100) and minor components of
the chlorine atoms Cl(1x), Cl(2x) and Cl(2y) were isotropically
refined.
For complex 7, tert-butyl groups C(24), C(25) and C(26) are dis-
ordered by rotation and the split positions (1:1) were isotropically
refined. Two dichloromethane molecules of crystallization are also
disordered. For the first one two split positions for the Cl-atoms,
namely Cl(2)–C(98)–Cl(3) and Cl(2x)–C(98)–Cl(3x) were refined
with occupancies of 80:20. Minor Cl-positions were refined isotro-
pically. For the second, the split positions Cl(4)–C(99)–Cl(5) and
Cl(4x)–C(99x)–Cl(5x) were isotropically refined with occupation
factors of 2:1.
Scheme 3
oxidase and galactose oxidase was evaluated. A notable outcome
of this work is the observation that copper(II) complexes with the
selenobisphenol ligand prepared in situ can catalyze the aerial
oxidation of alcohols and amines, for which rate-laws have been
determined and probable mechanisms for the oxidations have been
proposed (Schemes 2 and 3). Our studies confirm the presence of a
primary kinetic isotope effect thus providing compelling evidence
that H-atom abstraction from the -C-atom of the substrates is the
rate-limiting step.
That under certain circumstances facile formation of phenoxyl
radicals can be achieved is exemplified by the oxidation of 2,4-di-
tert-butylphenol to its biphenol product using complex 6, and by
the isolation of complex 7, a dicopper(II) compound with a modi-
fied ligand produced in situ in the reaction solution. This provides
further credence to the proposed mechanisms involving phenoxyl
radicals.
Experimental
Materials and physical measurements. Commercial grade
chemicals were used for synthetic purposes and solvents were
distilled and dried before use. Fourier transform infrared spectros-
copy on KBr pellets was performed on a Perkin–Elmer 2000 FT-IR
instrument. Solution electronic spectra were measured on a Perkin-
Elmer Lambda 19 spectrophotometer. Mass spectra were recorded
either in the EI or ESI (in CH2Cl2) mode with a Finnigan MAT 95
or 8200 spectrometer. Magnetic susceptibilities of the polycrystal-
line samples were recorded on a SQUID magnetometer (MPMS,
Quantum Design) in the temperature range 2–290 K with an ap-
plied field of 1 T. Diamagnetic contributions were estimated for
each compound by using Pascal’s constants. X-band EPR spectra
were recorded on a Bruker ESP 300E spectrometer equipped with
a helium flow cryostat (Oxford Instruments ESR 910), an NMR
field probe (Bruker 035M), and a microwave frequency counter
HP5352B. Spin-Hamiltonian simulations of the EPR spectra were
performed with a program that was developed from the routines of
Gaffney and Silverstone16 and that specifically makes use of the
resonance-search procedure based on a Newton–Raphson algorithm
as described therein. GC of the organic products during catalysis
were performed either on HP 5890 II or HP 6890 instruments using
RTX-1701 15 m S-41 or RTX-5 Amine 13.5 S-63 columns, respec-
tively. GC-MS was performed using the above columns coupled
with a HP 5973 mass spectrometer with a mass selective detector.
NMR spectra were measured using a DRX 400 spectrometer.
Details of the data collection and structure refinements are sum-
marized in Tables 5 and 6.
CCDC reference numbers: 233443 (H2LSe), 233444 (1), 233445
(2), 233446 (4), 233447 (5), 233448 (6), 233449 (7).
See http://www.rsc.org/suppdata/dt/b4/b403953j/ for crystallo-
graphic data in CIF or other electronic format.
Ligand synthesis. The ligand H2LSe was synthesized accord-
ing to the method described in the literature.17 Crystals suitable
for X-ray crystallographic analysis were grown from a solution of
H2LSe in heptane/methanol (1:1).
General method of synthesis for complexes 1–3
1 mmol of ligand (0.49 g) was dissolved in dry CH3OH (50 cm3).
To that solution CuCl (0.1 g, 1 mmol) was added under argon. After
addition of 0.5 cm3 of the respective amine the solution was refluxed
under argon for 30 min. After cooling to room temperature it was
opened to the air. The color changed to deep green or blue imme-
diately and within 1 h greenish microcrystalline solid separated,
which was filtered and dried. Recrystallization was performed from
a solvent mixture of CH2Cl2 and CH3OH (1:1). The reaction can
also be performed with CuCl2 (1 mmol) in CH3OH under air at room
temperature to give the mononuclear complexes in high yield.
X-ray crystallographic data collection and refinement of the
structures. Single crystals of H2LSe, 1, 2, 4, 5, 6 and 7 were coated
with perfluoropolyether, picked up with glass fibers, and mounted
on a Nonius Kappa-CCD diffractometer (complex 2) or Siemens
SMART (1, 4, 5, 6 and 7) equipped with a cryogenic nitrogen
cold stream operating at 100(2) K. Graphite monochromated Mo
K radiation ( = 0.71073 Å) was used. Intensity data were cor-
rected for Lorentz and polarization effects. The intensity data set
of 1, 4, 5, 6 and 7 were corrected for absorption with use of the
2 0 9 8
D a l t o n T r a n s . , 2 0 0 4 , 2 0 9 2 – 2 1 0 1

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Table 5 Crystallographic data for H2LSe, 1, 2 and 4
H2LSe
1
2
4
Empirical formula
Formula weight
Temperature/K
C28H42O2Se
489.58
100(2)
C34H55CuSeNO2
652.32
100(2)
C32H51CuNO2Se
624.27
100(2)
C70H100Cu2N2Se2O5
1334.59
100(2)
Wavelength (Mo K)/ Å
Crystal system
Space group
Unit cell dimensions
0.71073
0.71073
Monoclinic
P2(1)/n
a = 14.1711(10) Å
b = 12.5356(9) Å
c = 39.248(3) Å
 = 94.96(2)°
0.71073
Monoclinic
P2(1)/n
a = 9.6208(12) Å
b = 12.399(2) Å
c = 27.000(3) Å
 = 95.35(2)°
0.71073
Triclinic
P-1
Orthorhombic
Pccn No. 56
a = 10.641(2) Å
b = 24.267(5) Å
c = 10.424(2) Å
 =  =  = 90°
a = 13.831(1) Å
b = 14.797(2) Å
c = 18.613(2) Å
 = 95.22(1)°
 = 90.96(1)°
 = 113.85(1)°
3463.5(6), 2
1.280
Volume/Å3, Z
2691.7(9), 4
1.208
1.415
6946.0(9), 8
1.248
1.705
3206.8(7), 4
1.293
1.843
Density (calc.)/Mg m−3
Absorption coeff./ mm−1
F(000)
1.712
1400
1040
2760
1316
Crystal size/mm
 range for data collect./°
Index range
0.58 × 0.10 × 0.10
1.68 to 23.16
−10 <= h <= 11,
−17 <= k <= 26,
−10 <= l <= 11
9436
0.23 × 0.20 × 0.08
1.71 to 30.00
−21 <= h <= 20,
−10 <= k <= 18,
−54 <= l <= 59
66185
0.43 × 0.34 × 0.05
2.23 to 30.00
−10 <= h <= 14,
−18 <= k <= 18,
−41 <= l <= 40
25278
0.25 × 0.19 × 0.14
1.61 to 22.50
−16 <= h <= 16,
−17 <= k <= 13,
−19 <= l <= 22
12614
Reflections collected
Independent reflect.
1918
19434
9193
8923
Absorption correction
Data/restraints/param.
Goodness-of-fit on F2
Final R indices [I > 2(I)]
SADABS
1918/0/151
0.949
R1 = 0.0474,
wR2 = 0.1169
R1 = 0.0651,
wR2 = 0.1216
0.653 and −1.156
SADABS
19317/0/703
0.997
R1 = 0.0490,
wR2 = 0.0891
R1 = 0.1015,
wR2 = 0.1044
0.650 and −0.615
MulAbs
9188/0/344
1.128
R1 = 0.0503,
wR2 = 0.1298
R1 = 0.0610,
wR2 = 0.1339
1.220 and −0.988
SADABS
8905/0/650
0.891
R1 = 0.0643,
wR2 = 0.1199
R1 = 0.1477,
wR2 = 0.1423
0.822 and −0.551
R indices (all data)
Largest diff. peak and hole/e.Å−3
Table 6 Crystallographic data for 5, 6 and 7
5
6
7
Empirical formula
Formula weight
Temperature/K
C86H125Cu3Se3NO7·CH3CN
1753.42
100(2)
C87H130Cu3Cl2O8Se3
1802.31
100(2)
C84H120Cu2Se2O6·2.5 CH2Cl2
1723.11
100(2)
Wavelength (MoK)/Å
Crystal system
0.71073
Triclinic
0.71073
Triclinic
0.71073
Monoclinic
Space group
P-1
P-1
C2/c
Unit cell dimensions
a = 15.263(4) Å
b = 17.498(5) Å
c = 18.419(6) Å
 = 76.04(2)°
 = 69.81(2)°
 = 88.14(2)°
4474(2), 2
1.302
1.977
1830
a = 14.0807(8) Å
b = 14.7358(8) Å
c = 22.7829(12) Å
 = 77.247(2)°
 = 80.203(2)°
 = 80.814(2)°
4506.6(4), 2
1.328
a = 18.466(2) Å
b = 21.457(3) Å
c = 44.773(5) Å
 = 100.57(2)°
Volume/Å3, Z
17439(4), 8
1.313
1.525
Density (calc.)/Mg m−3
Absorption coeff./mm−1
F(000)
2.022
1878
7224
Crystal size/mm
 range for data collect./°
Index range
0.18 × 0.18 × 0.10
1.48 to 19.00
−16 <= h <= 16,
−19 <= k <= 19,
−20 <= l <= 13
11483
0.38 × 0.20 × 0.18
1.85 to 30.00
−12 <= h <= 21,
−14 <= k <= 23,
−31 <= l <= 35
43624
0.20 × 0.14 × 0.08
1.62 to 25.00
−25 <= h <= 28,
−21 <= k <= 32,
−49 <= l <= 68
67266
Reflections collected
Independent reflect.
7191
23878
15324
Absorption correction
Data/restraints/param.
Goodness-of-fit on F2
Final R indices [I > 2(I)]
SADABS
7104/31/461
0.925
R1 = 0.0883,
wR2 = 0.1783
R1 = 0.2267,
wR2 = 0.2404
1.177 and −0.684
SADABS
23819/25/994
0.961
R1 = 0.0466,
wR2 = 0.1027
R1 = 0.0809,
wR2 = 0.1149
1.454 and −1.034
SADABS
15249/6/912
1.036
R1 = 0.0751,
wR2 = 0.1379
R1 = 0.1300,
wR2 = 0.1580
1.418 and −1.193
R indices (all data)
Largest diff. peak and hole/e.Å−3
Complex [CuLSe(Et3N)] (1). Yield: 0.33 g (51%). Anal. calcd.
for C34H55SeNCuO2 (652.32 g mol−1): C, 62.60; H, 8.50; N, 2.15;
Cu, 9.74. Found: C, 61.2; H, 8.4; N, 2.1; Cu, 9.4%. IR (cm−1):
3445 (br), 2952–2868 (s), 1432 (s), 1255 (s), 829, 724. Absorption
spectrum (CH2Cl2); max (nm),  (M−1cm−1): 595 (sh); 735, 590. MS
(ESI positive mode in CH2Cl2): [M + H]+ = 653 (100%).
Complex [CuLSe(Et2NH)] (2). Yield: 0.51 g (82%). Anal. calcd.
for C32H51SeNCuO2 (624.27 g mol−1): C, 61.57; H, 8.23; N, 2.24;
Cu, 10.18. Found: C, 61.2; H, 8.1; N, 1.9; Cu, 10.5%. IR (cm−1):
3443 (br), 3265, 2953–2866 (s), 1431 (s), 1254 (s), 995, 829, 725.
Absorption spectrum (CH2Cl2); max (nm),  (M−1cm−1): 570 (sh);
690, 470.
D a l t o n T r a n s . , 2 0 0 4 , 2 0 9 2 – 2 1 0 1
2 0 9 9

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Complex [CuLSe(tBuNH2)] (3). Yield: 0.40 g (64%).Anal. calcd.
for C32H51SeNCuO2 (624.27 g mol−1): C, 61.57; H, 8.23; N, 2.24;
Cu, 10.18. Found: C, 60.9; H, 8.1; N, 2.3; Cu, 10.1%. IR (cm−1):
3448 (br), 3336–3320, 2955–2866 (s), 1433 (s), 1254 (s), 1080,
829, 725. Absorption spectrum (CH2Cl2); max (nm),  (M−1cm−1):
485 (sh); 570(sh); 688, 390.
in air at room temperature for 10 h. After that the sample was taken,
passed through a short silica column, washed with CH2Cl2 and the
products were detected and quantified with respect to an internal
standard by GC. Benzaldehyde was quantified using dodecane and
cinnamaldehyde was quantified using hexadecane as internal stan-
dards. Aldehyde products were also isolated chemically by reacting
the solution with methanolic NaHSO3 solution (saturated) after
removal of Cu(II). The solution was then kept for 24 h to precipitate
the bisulfite adduct. The solid was then filtered and dried.
No oxidation of primary alcohol was observed in the absence of
the Cu(II) complex.
Complex [CuLSe(PhCH2NH2)]2·H2O (4)
1 mmol of Cu(ClO4)2, 6 H2O (0.37 g) was dissolved in dry CH3OH
(10 cm3). To that a CH2Cl2 (10 cm3) solution of 1 mmol ligand
(0.49 g) and 1 cm3 of PhCH2NH2, was added dropwise to make a
layer. It was then allowed to diffuse and kept under a slow sweep of
argon at room temperature. After 1 day deep brown crystals sepa-
rated out. Yield: 0.26 g (39%). Anal. calcd. for C70H100Se2N2Cu2O5
(1334.59 g mol−1): C, 63.00; H, 7.55; N, 2.10; Cu, 9.52. Found: C,
63.6; H, 7.5; N, 2.2; Cu, 10.1%. IR (cm−1): 3420 (br), 3318–3257,
2958–2865 (s), 1428 (s), 1254 (s), 990, 828, 731. Absorption spec-
trum (CH2Cl2); max (nm),  (M−1cm−1): 483, 970; 655, 900. MS (EI):
m/z = 931 [M+, 100%].
Acknowledgements
Skilful technical assistance of Mrs H. Schucht, Mr A. Göbel and
Mrs U. Westhoff is thankfully acknowledged. We are grateful to
the German Research Council (DFG) for financial support (Project:
Priority Program Ch 111/2-2).
References
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Complex [LSe2 (HLSe)Cu3(-OH)(CH3CN)]·CH3CN (5)
The ligand (0.49 g, 1 mmol) was dissolved in deaerated CH3CN
(30 cm3) and deprotonated with (iPr)2NEt (0.34 cm3, 2 mmol). To
that light yellow solution/solid [Cu(CH3CN)4]ClO4 (0.33 g, 1 mmol)
was added and the solution was refluxed under argon for 30 min.
After cooling to room temperature, the solution was opened to air
whereupon the color changed to deep brown. Upon stirring for 2 h
in air at room temperature a brown microcrystalline solid separated,
was filtered and air-dried. X-ray quality crystals were grown from a
solvent mixture of CH2Cl2 and CH3CN(1:1).
Yield: 0.33 g (56%). Anal. calcd. for C88H128Se3N2Cu3O7
(1753.42 g mol−1): C, 60.32; H, 7.36; N, 0.82; Cu, 11.13. Found: C,
60.4; H, 7.5; N, 0.8; Cu, 11.2%. IR (cm−1): 3447 (br), 2958–2867 (s),
2321, 1430 (s), 1254 (s), 1096, 832, 730. Absorption spectrum
(CH2Cl2); max (nm),  (M−1cm−1): 482, 6730; 600 (sh).
Complex [LSe2 (HLSe)Cu3(-OCH3)(CH3OH)]·CH2Cl2 (6)
The ligand (0.49 g, 1 mmol) was dissolved in dry CH3OH (30 cm3)
and deprotonated with (iPr)2NEt (0.34 cm3, 2 mmol). To that light
yellow solution, CuCl2 (0.17 g, 1 mmol) was added and the resulting
brown solution was stirred at room temperature in air for 30 min.
A brown microcrystalline solid separated, which was filtered and
air-dried. X-ray quality crystals were grown from a solvent mixture
of CH2Cl2 and CH3OH (1:1). Yield: 0.48 g (80%). Anal. calcd. for
C87H130Se3Cu3O8Cl2(1802.31 g mol−1): C, 57.98; H, 7.27; Cu, 10.58.
Found: C, 57.6; H, 7.3; Cu, 10.7%. IR (cm−1): 3472 (br), 2958–
2867 (s), 1430 (s), 1255 (s), 1011, 832, 731. Absorption spectrum
(CH2Cl2); max (nm),  (M−1cm−1): 467, 7200; 625 (sh).
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Catalytic amine oxidation reactions were performed in dry CH3OH
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General method for catalytic oxidation of primary alcohols
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bient temperature.Alcohol was taken in the solvent and treated with
base (Bu4NOCH3 20% methanolic solution) under argon. To that
solution the Cu(II) complex was added, opened to (t = 0) and stirred
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2 1 0 0
D a l t o n T r a n s . , 2 0 0 4 , 2 0 9 2 – 2 1 0 1

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D a l t o n T r a n s . , 2 0 0 4 , 2 0 9 2 – 2 1 0 1
2 1 0 1