Bis[N-(2-hydroxyethyl)-β-alaninato]-copper(II)

Article abstract of DOI:10.1107/S0108270105033780

The Cu^II ion in the title complex, [Cu(C₅H ₁₀NO₃)₂] or [Cu(He-ala)₂] [He-ala = W-(2-hydroxyethyl)-β-alaninate], resides at the inversion centre of a square bipyramid comprised of two facially arranged tridentate He-ala ligands. Each He-ala ligand binds to a Cu^II ion by forming one six-membered β-alaninate chelate ring in a twist conformation and one five-membered ethanolamine ring in an envelope conformation, with Cu-N = 2.017 (2) A, Cu-O_Coo = 1.968 (1) A and Cu-O_OH = 2.473 (2) A. The [Cu(He-ala)₂] molecules are involved in a network of O-H...O and N-H...O hydrogen bonds, forming layers parallel to the (101) plane. The layers are connected into a three-dimensional structure by van der Waals interactions, so that the molecular centres form pseudo-face-centered close packing.

Full text of DOI:10.1107/S0108270105033780

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
The molecular structure of the [Cu(He-ala) ] complex and
2
the atomic numbering scheme are shown in Fig. 1, while Table 1
lists selected bond lengths and angles. The structure of (I)
II
consists of isolated [Cu(He-ala) ] units, with the Cu ion
ISSN 0108-2701
2
Bis[N-(2-hydroxyethyl)-b-alaninato]-
copper(II)
a
b
Alexander V. Pestov, Eugenia V. Peresypkina,
b
b
Alexander V. Virovets, Nina V. Podberezskaya, Yury G.
a
c
Yatluk and Yury A. Skorik *
a
I. Ya. Postovsky Institute of Organic Synthesis, Urals Division of the Russian
Academy of Sciences, 20/22 Akademicheskaya/S. Kovalevskoy Street, 620219
b
Ekaterinburg, Russian Federation, A. V. Nikolaev Institute of Inorganic Chemistry,
Siberian Division of the Russian Academy of Sciences, 3 Acad. Lavrentyev Avenue,
c
6
30090 Novosibirsk, Russian Federation, and Department of Chemistry, University
of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA 15260, USA
Correspondence e-mail: skorik@pitt.edu
located at the inversion centre in a square-bipyramidal
geometry (4+2). The basal plane of the bipyramid is occupied
by two N atoms of secondary amino groups and by two
carboxylate O atoms, and the apices are occupied by two
hydroxyl O atoms of two symmetrically arranged He-ala
ligands. The axial CuÐO bonds are typically longer than the
other in-plane bonds. The trans OÐCuÐO or NÐCuÐN
Received 21 July 2005
Accepted 19 October 2005
Online 11 November 2005
II
The Cu ion in the title complex, [Cu(C H NO ) ] or
5
10
3 2
[
Cu(He-ala) ] [He-ala = N-(2-hydroxyethyl)-ꢀ-alaninate],
2
ꢀ
angles are 180 , as required by symmetry. The cis angles
ꢀ
resides at the inversion centre of a square bipyramid
comprised of two facially arranged tridentate He-ala ligands.
II
Each He-ala ligand binds to a Cu ion by forming one six-
involving the basal atom O2 differ only slightly from 90 , while
the largest angular distortions of the octahedron occur for the
N1ÐCu1ÐO1 angles (Table 1).
membered ꢀ-alaninate chelate ring in a twist conformation
II
Each singly deprotonated He-ala ligand binds to a Cu
0
and one ®ve-membered ethanolamine ring in an envelope
Ê
centre as an O,N,O -tridentate ligand in a fac fashion by the
conformation, with CuÐN = 2.017 (2) A, CuÐOCOO
=
formation of two chelate rings (one ꢀ-alaninate and one
ethanolamine). There are three possible fac conformations for
He-ala in a square-bipyramidal coordination, as shown in the
scheme above.
Ê Ê
.968 (1) A and CuÐOOH = 2.473 (2) A. The [Cu(He-ala) ]
2
1
molecules are involved in a network of OÐHÁ Á ÁO and NÐ
HÁ Á ÁO hydrogen bonds, forming layers parallel to the (101)
plane. The layers are connected into a three-dimensional
structure by van der Waals interactions, so that the molecular
centres form pseudo-face-centered close packing.
The isolated complex turned out to be a fac isomer (Fig. 1).
1
The selective formation of this isomer can be rationalized by
reasoning that the most thermodynamically preferable isomer
Comment
The title compound, [Cu(He-ala) ] or (I), was synthesized as
2
part of our systematic study of the coordination ability of
dipodal ligands derived from ꢀ-alanine (Skorik et al., 2002,
2
003, 2004, 2005). The acid±base and complexation equilibria
II
II
II
of N-(2-hydroxyethyl)-ꢀ-alanine with Cu , Ni and Co have
been studied by means of pH±potentiometric titration in
aqueous media. Evidence was found for the presence of the
[
1
M(He-ala)] and [M(He-ala) ] complexes (Uhlig & Linke,
2
II
964). In the case of Cu ions, the monoprotonated [CuH(He-
ala)] complex can also be formed under strong acidic condi-
tions. To the best of our knowledge, no complexes of He-ala
have previously been structurally characterized. In order to
II
determine the Cu coordination geometry and the chelating
Figure 1
The molecular structure of (I). Displacement ellipsoids are drawn at the
50% probability level and H atoms are shown as small spheres of
arbitrary radii. The axial bonds to copper are shown as dashed lines.
pattern, the present X-ray crystal structure determination has
been carried out on the title complex and the results are
presented here.
m510 # 2005 International Union of Crystallography
DOI: 10.1107/S0108270105033780
Acta Cryst. (2005). C61, m510±m512

metal-organic compounds
has the stronger ®eld ligands in equatorial positions and
the weaker ligands at the apices of an axially elongated
octahedron. Taking into account the spectrochemical series
hydrogen bonds, forming layers parallel to the (101) plane
(Fig. 2a). Six intralayer molecules are hydrogen bonded to the
reference molecule; two of them form two NÐHÁ Á ÁO contacts
each, while the other four each form one OÐHÁ Á ÁO contact
(Table 2). The whole molecular packing may be represented as
a superposition of these layers. Its topology was characterized
with coordination sequences (O'Keeffe, 1995) calculated using
the TOPOS4.0 Professional program suite for crystallo-
chemical analysis (Blatov et al., 2000). The molecular centres
of gravity form the coordination sequence 12, 42, 92; in other
words, the ®rst, second and third coordination sphere of any
molecule contains 12, 42 and 92 molecules, respectively. This
sequence corresponds topologically to three-layered face-
centred cubic (fcc) packing (O'Keeffe, 1995) which is slightly
distorted geometrically. The simpli®ed three-layered packing
motif in the structure is shown in Fig. 2(b), where the centres
of the molecules are represented as balls. Three molecules of
the upper and lower layers and six molecules of the middle
layer are shown. Thus, the hydrogen-bonded layers are joined
by van der Waals interactions to the distorted fcc packing that
is typical for molecular compounds (Kitaigorodskii, 1973;
Peresypkina & Blatov, 2000; Braun & Huttner, 2005).
�
RNH > RCOO > ROH (Bersuker, 1996), the fac confor-
2
1
mation for He-ala appears to be the most thermodynamically
stable. For the same reason, a fac isomer is favourable for the
1
glycine derivative of ethanolamine (Ananeva et al., 1975;
Ammar et al., 2001).
The six-membered ꢀ-alaninate chelate ring adopts a twist
conformation, with atoms C5 and N1 not involved in the
distortion of the initial planar hexagon. The puckering para-
meters (Cremer & Pople, 1975) generated by PLATON (Spek,
Ê
ꢀ
2
2
003) are Q = 0.7335 (19) A, ꢁ = 94.75 (15) and ' =
ꢀ
ꢀ
9.83 (15) . The sum of the internal angles [675.0 (4) ] has a
ꢀ
positive deviation from the ideal value, viz. 648 = 120 + (109.5
 4) + 90, and this exerts a stress, resulting in the ¯attening.
The ®ve-membered ethanolamine chelate ring adopts an
Ê
envelope conformation, with atom C2 tilted by 0.646 (3) A
away from the Cu1/O1/C1/N1 plane; the puckering para-
Ê
ꢀ
meters are Q = 0.475 (2) A and ꢁ = 305.4 (2) . The dihedral
angle formed by the r.m.s. planes of the two chelate rings is
7
ꢀ
0.69 (9) .
In the crystal structure of (I), the [Cu(He-ala) ] molecules
are involved in an extended two-dimensional system of
2
Experimental
N-(2-Hydroxyethyl)-ꢀ-alanine was prepared using a modi®cation of
the literature procedure of Salov et al. (1985). A mixture containing
acrylic acid (4.1 ml, 0.060 mol) and ethanolamine (10.8 ml, 0.18 mol)
in water (56 ml) was heated under re¯ux for 8 h. The solvent and the
excess ethanolamine were then evaporated on a water bath under
vacuum. The resulting solid product was recrystallized from methanol
[
yield 2.28 g, 36%; m.p. 420 K (literature value 419±420 K; Salov et al.,
985)]. Analysis found: C 44.92, H 8.62, N 10.43%; calculated for
1
1
5 3 2
C H11NO : C 45.10, H 8.33, N 10.52%. H NMR (400 MHz, D O): ꢂ
3
.84 (t, J = 5.20 Hz, 2H), 3.26 (t, J = 6.69 Hz, 2H), 3.20 (t, J = 5.20 Hz,
H), 2.58 (t, J = 6.69 Hz, 2H). For the preparation of the title complex,
2
a mixture containing N-(2-hydroxyethyl)-ꢀ-alanine (4.7 g, 0.035 mol),
CuOH) CO (9.0 g, 0.041 mol) and water (20 ml) was stirred at room
(
2
3
temperature for 48 h. After ®ltration, the resulting solution was
maintained at room temperature until evaporation resulted in the
formation of blue±violet crystals of (I) suitable for X-ray diffraction
analysis. Analysis found: C 36.53, H 6.38, N 8.55, Cu 19.14%;
2 6
calculated for C10H20CuN O : C 36.64, H 6.15, N 8.55, Cu 19.38%.
Crystal data
�
3
[
Cu(C
5
H10NO
3 2
) ]
D
x
= 1.636 Mg m
M
r
= 327.82
Mo Kꢃ radiation
Monoclinic, P2 =n
Cell parameters from 1481
re¯ections
1
Ê
a = 9.5257 (6) A
Ê
b = 5.6597 (3) A
ꢀ
ꢁ = 2.6±28.1
ꢄ = 1.67 mm
T = 295 (2) K
Ê
c = 12.4288 (7) A
� 1
ꢀ
ꢀ
= 96.779 (3)
Ê
3
V = 665.38 (7) A
Z = 2
Block, blue±violet
0.35 Â 0.33 Â 0.23 mm
Figure 2
Data collection
The crystal structure of (I), showing (a) the hexagonal layer parallel to
the (101) plane (H atoms have been omitted for clarity) and (b) a
fragment of the spatial arrangement of the centres of gravity of molecules
of (I), illustrating the three-layered fcc packing motif. Upper, medium
and lower levels are shown as dark-, medium- and light-grey balls,
respectively. Solid and dashed lines show the intra- (hydrogen bonding)
and interlayer (van der Waals) distances between the molecular centres.
Bruker X8 APEX CCD area-
detector diffractometer
! and ' scans
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
Tmin = 0.477, Tmax = 0.682
3238 measured re¯ections
1553 independent re¯ections
1204 re¯ections with I > 2ꢅ(I)
Rint = 0.019
ꢀ
ꢁmax = 28.2
h = � 12 ! 7
k = � 7 ! 6
l = � 16 ! 16
ꢁ
Acta Cryst. (2005). C61, m510±m512
Pestov et al.
[Cu(C
5
H
10NO
3
)
2
]
m511

metal-organic compounds
Re®nement
SHELXTL; molecular graphics: SHELXTL; software used to
prepare material for publication: local programs.
2
2
2
2
Re®nement on F
2
o
w = 1/[ꢅ (F ) + (0.0293P)
2
R[F > 2ꢅ(F )] = 0.027
wR(F ) = 0.069
S = 1.03
+ 0.3245P]
where P = (F
(Á/ꢅ)max < 0.001
Áꢆmax = 0.37 e A
Áꢆmin = � 0.26 e AÊ
2
2
2
c
o
+ 2F
)/3
The authors thank Professor V. A. Blatov (Samara State
University, Russia) for providing the TOPOS program set.
Ê
� 3
1
9
553 re¯ections
1 parameters
� 3
H atoms treated by a mixture of
independent and constrained
re®nement
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: BG1015). Services for accessing these data are
described at the back of the journal.
Table 1
Selected geometric parameters (A, ).
Ê
ꢀ
References
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Cu1ÐN1
Cu1ÐO1
2.0172 (17)
2.4733 (18)
Cu1ÐO2
1.9682 (14)
N1ÐCu1ÐO1
O2ÐCu1ÐN1
76.42 (7)
92.30 (7)
O2ÐCu1ÐO1
89.72 (6)
&
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Table 2
Hydrogen-bond geometry (A, ).
1
Ê
ꢀ
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
i
N1ÐH1Á Á ÁO2
0.91
0.77 (2)
2.21
1.89 (2)
3.030 (2)
2.659 (2)
150
173 (3)
ii
O1ÐH2Á Á ÁO3
1
2
1
2
1
2
Symmetry codes: (i) x; y ‡ 1; z; (ii) x ‡ ; � y � ; z ‡ .
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Romanenko, G. V. & Vshivkov, A. A. (2004). Russ. J. Inorg. Chem. 49, 386±
Atom H2 of the OH group was found in a difference electron-
density map and re®ned with the OÐH distance constrained to
Ê
0.82 (2) A and with Uiso(H) = 1.2Ueq(O). All other H atoms were
located geometrically and re®ned using a riding model, with CÐH =
Ê Ê
.97 A and NÐH = 0.91 A, and with Uiso(H) = 1.2Ueq(C,N). Inter-
0
molecular interactions and features of the crystal packing were
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ꢁ
m512 Pestov et al. [Cu(C
5 3
H10NO )
2
]
Acta Cryst. (2005). C61, m510±m512