metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
Compound (I) was complexed to copper(I) in a 2:1 ligand-
to-metal ratio via reaction of [Cu(MeCN)4]BF4 with the ligand
in MeCN±CH2Cl2, to give bis(dimethyl 2,20-bipyridine-6,60-
dicarboxylato)copper(I) tetra¯uoroborate, (II). The crystal
structure of (II) (Fig. 2) con®rms the anticipated coordination
environment in which the metal centre is coordinated solely by
the bipyridyl units, with the ester groups not participating in
metal coordination.
ISSN 0108-2701
Dimethyl 2,20-bipyridine-6,60-di-
carboxylate and bis(dimethyl
2,20-bipyridine-6,60-dicarboxylato-
j2N,N0)copper(I) tetrafluoroborate
Alexander J. Blake, Neil R. Champness,* Pamela V. Mason
and Claire Wilson
School of Chemistry, University of Nottingham, University Park, Nottingham
NG7 2RD, England
Correspondence e-mail: neil.champness@nottingham.ac.uk
Received 21 March 2007
Accepted 26 April 2007
Online 31 May 2007
In the structure of (II), there are two short CuÐN0bonds of
Ê
2.029 (3) and 2.035 (3) A for CuÐN1 and CuÐN7 , respec-
tively, and two slightly longer bonds of 2.074 (3) and
The single-crystal X-ray structures of dimethyl 2,20-bipyridine-
6,60-dicarboxylate, C14H12N2O4, and the copper(I) coordina-
tion complex bis(dimethyl 2,20-bipyridine-6,60-dicarboxylato-
ꢀ2N,N0)copper(I) tetra¯uoroborate, [Cu(C14H12N2O4)2]BF4,
are reported. The uncoordinated ligand crystallizes across an
inversion centre and adopts the anticipated anti pyridyl
arrangement with coplanar pyridyl rings. In contrast, upon
coordination of copper(I), the ligand adopts an arrangement
of pyridyl donors facilitating chelating metal coordination and
an increased inter-pyridyl twisting within each ligand. The
distortion of each ligand contrasts with comparable copper(I)
complexes of unfunctionalized 2,20-bipyridine.
0
Ê
2.077 (3) A for CuÐN7 and CuÐN1 , respectively. Three of
the ester carbonyl O atoms point towards the CuI centre but
no signi®cant interactions are present; the CuÁ Á ÁO distances
Ê
are longer than 2.9 A, the combined sum of the van der Waals
radii (Bondi, 1964).
This copper(I) complex adopts a distorted tetrahedral
geometry, with an angle of 70ꢀ between the planes de®ned by
the two bipyridyl units. This distortion is only slightly greater
than the comparable angles observed in bis(2,20-bipyridine)-
copper(I) perchlorate (76ꢀ; Munakata et al., 1987) and bis(2,20-
bipyridine)copper(I) tri¯uoromethanesulfonate (85ꢀ; Tomi-
slav, 2006). Steric interactions between the bulkier dimethyl
2,20-biypyridine-6,60-dicarboxylate ligands may account for the
slight increase in the distortion of the relatively malleable
tetrahedral CuI coordination environment.
Comment
As part of our ongoing studies of multi-modal ligands for the
construction of coordination polymers (Oxtoby et al., 2002,
By comparison with the crystal structure of the free ligand,
(I), it can be seen that the ligand in (II) adopts a different
conformation on complexation, as anticipated, allowing
chelation of the metal centre by the bipyridyl species. The
Â
2003, 2005; Thebault et al., 2006), we have prepared a diester-
substituted 2,20-bipyridyl ligand and a copper(I) complex that
serve as potentially useful building blocks for subsequent
synthetic procedures.
The diester-substituted 2,20-bipyridyl molecule, dimethyl
2,20-bipyridine-6,60-dicarboxylate, (I), was synthesized by a
HCl-catalyzed esteri®cation method in MeOH. Single-crystal
X-ray diffraction con®rmed the identity of the product and
demonstrated the lower energy conformation commonly
adopted by uncoordinated 2,20-bipyridyl systems, which has
the pyridyl N atoms adopting an anti arrangement to avoid
repulsive interactions between the nitrogen lone pairs. The
entire molecule is almost planar in the solid state. An inver-
sion centre between atoms C2 and C2i [symmetry code: (i) x,
Figure 1
1
y, 1 z] ensures coplanarity of the two pyridyl rings, with
A view of (I), showing the atom-numbering scheme. Displacement
ellipsoids are drawn at the 50% probability level and H atoms are shown
as small spheres of arbitrary radii. Unlabelled atoms are related to
labelled atoms by the symmetry operator (x, 1 y, 1 z).
the two ester groups exhibiting a slight deviation from the
plane formed by the bipyridyl unit, with an N1ÐC6ÐC7ÐO8
torsion angle of 9.84 (16)ꢀ (Fig. 1).
m280 # 2007 International Union of Crystallography
DOI: 10.1107/S0108270107020914
Acta Cryst. (2007). C63, m280±m282