The coordination chemistry of 3,3′-diamino-2,2′-bipyridine and its dication: Exploring the role of the amino groups by x-ray crystallography

Article abstract of DOI:10.1002/1099-0682(200208)2002:8<1985::AID-EJIC1985>3.0.CO;2-G

The synthesis and structural chemistry of a series of new divalent transition metal complexes of the bis-bidentate ligand 3,3′-diamino-2,2′-bipyridine (L1) and its dication L1H₂ are described. Ligand L1 reacts with salts of divalent transition metals to afford the (1:1) metal-ligand complexes (2a-2d) as well as the tris complexes (3a-3f). All complexes were fully characterised by spectroscopic methods and the following compounds [Cu(L1)Cl₂]₂ (2a), [Cu(L1)(OAc)₂] (2b), [Zn(L1)₃][OTf]₂ (3a), and [Zn(L1)₃][ZnCl₄] (3e and 3f) were structurally characterised. Results from single crystal X-ray diffraction measurements indicate that formation of an intra-molecular hydrogen bond between the two amino groups allows the ligand to coordinate divalent metal ions through their diimine binding sites. Furthermore, the structure of compound 2a reveals that it crystallises as a dimer in which each copper ion is bound to two pyridine nitrogen atoms and two chloride ions in a distorted square planar arrangement, with a long axial contact from a neighbouring amino group completing the approximately square-pyramidal geometry at Cu^II. Complexation of this ligand in acidic conditions afforded the compound [Cu(L1H₂)Cl₄] (4), as well as the two salts [L1H₂][CuCl₄] (5a) and [L1H₂][ZnCl₄] (5b). All three compounds have been structurally characterised and results indicate that the dication (L1H₂) displays a different coordination preference for the chelation of metal ions. In all three cases, both of the heterocyclic N atoms of the ligand are protonated, thus preventing chelation to the metal ion, although for compound 4 crystallographic studies reveal that the two amino functionalities coordinate the copper(II) ion. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.

Full text of DOI:10.1002/1099-0682(200208)2002:8<1985::AID-EJIC1985>3.0.CO;2-G

FULL PAPER
The Coordination Chemistry of 3,3Ј-Diamino-2,2Ј-bipyridine and Its Dication:
Exploring the Role of the Amino Groups by X-ray Crystallography
Craig R. Rice,[b] Stuart Onions,[a] Natalia Vidal,[a] John D. Wallis,*[a]
Maria-Cristina Senna,[c] Melanie Pilkington,*[c] and Helen Stoeckli-Evans[d]
Keywords: N ligands / Hydrogen bonds / Ambidentate ligands / X-ray Crystallography / Cations
The synthesis and structural chemistry of a series of new di-
valent transition metal complexes of the bis-bidentate ligand
3,3Ј-diamino-2,2Ј-bipyridine (L1) and its dication L1H2 are
described. Ligand L1 reacts with salts of divalent transition
metals to afford the (1:1) metal-ligand complexes (2a−2d) as
two chloride ions in a distorted square planar arrangement,
with a long axial contact from a neighbouring amino group
completing the approximately square-pyramidal geometry at
CuII. Complexation of this ligand in acidic conditions af-
forded the compound [Cu(L1H2)Cl4] (4), as well as the two
well as the tris complexes (3a−3f). All complexes were fully salts [L1H2][CuCl4] (5a) and [L1H2][ZnCl4] (5b). All three
characterised by spectroscopic methods and the following
compounds [Cu(L1)Cl2]2 (2a), [Cu(L1)(OAc)2] (2b),
[Zn(L1)3][OTf]2 (3a), and [Zn(L1)3][ZnCl4] (3e and 3f) were
compounds have been structurally characterised and results
indicate that the dication (L1H2) displays a different coor-
dination preference for the chelation of metal ions. In all
structurally characterised. Results from single crystal X-ray three cases, both of the heterocyclic N atoms of the ligand
diffraction measurements indicate that formation of an intra-
molecular hydrogen bond between the two amino groups al-
lows the ligand to coordinate divalent metal ions through
their diimine binding sites. Furthermore, the structure of
compound 2a reveals that it crystallises as a dimer in which
each copper ion is bound to two pyridine nitrogen atoms and
are protonated, thus preventing chelation to the metal ion,
although for compound 4 crystallographic studies reveal that
the two amino functionalities coordinate the copper(II) ion.
( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany,
2002)
Introduction
molecular inorganic architectures including helices, ladders,
grids and chains.[1] Furthermore, chemical modification of
the 2,2Ј-bipyridine ligand by the introduction of additional
functionality at the 4-, 5- and 6-positions is well-known,
and the coordination chemistry of these compounds has
been actively explored. In contrast, however, much fewer
3,3Ј-disubstituted bipyridines are available and the coor-
dination chemistry of only a small number of such com-
pounds has been studied. This is primarily due to the ex-
pectation that van der Waals repulsions between large sub-
stituents in the 3,3Ј-positions could prevent the pyridine
rings from adopting a near cis-coplanar conformation, ren-
dering them unfavourable ligands for chelation. Neverthe-
less, small substituents in the 3 and 3Ј positions such as
methyl groups,[2] carboxylic acids,[3,4] and methyl esters[5]
have all been reported not to inhibit the binding of a metal
ion to the diimine binding site, despite the fact that the
pyridine rings in these systems are indeed displaced from
co-planarity by 30Ϫ35°. Furthermore, in the early 1980’s
Rebek et al. were able to successfully exploit the 3,3Ј-substi-
tution positions for the preparation of a novel crown ether
derivative which bound transition metal ions at the diimine
site, or alkali metal ions at the crown ether.[6]
The construction of multicomponent molecular systems
represents an important first step in the development of
novel molecular and supramolecular systems for catalysis,
light-to-energy conversion, and molecule-based devices. For
systems in which the components are transition metal ions,
the emphasis lies in the design of the bridging ligands as
well as on the choice of the metal ions. Consequently, the
careful choice of bridging ligands, as suitable linkers for
transition metal ions in a wide variety of oxidation states,
is currently viewed as a critical element in successful design.
One of the simplest but most widely used organic linkers is
the bidentate ligand 2,2Ј-bipyridine. In recent years, this li-
gand has been incorporated into a huge diversity of supra-
[a]
Department of Chemistry and Physics, The Nottingham Trent
University,
Clifton Lane, Nottingham, NG11 8NS, England
E-mail: john.wallis@ntu.ac.uk
[b]
University of Huddersfield, Department of Chemical
Biological Sciences,
&
Huddersfield, HD1 3DH, W. Yorkshire, England
[c]
Department of Chemistry and Biochemistry, University of
Berne,
Freistrasse 3, 3012, Berne, Switzerland
E-mail: melanie.pilkington@iac.unibe.ch
Dinuclear complexes in which the metal fragments are
joined by an appropriate bridging organic ligand have been
of particular interest with a view to the preparation of vari-
[d]
´
ˆ
Institute de Chemie, Universite de Neuchatel,
ˆ
Avenue de Bellevaux 51, 2000, Neuchatel, Switzerland
E-mail: helen.stoeckli-evans@ich.unine.ch
Eur. J. Inorg. Chem. 2002, 1985Ϫ1997  WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 1434Ϫ1948/02/0808Ϫ1985 $ 20.00ϩ.50/0
1985

J. D. Wallis, M. Pilkington et al.
FULL PAPER
ous types of organometallic frameworks. Indeed, the dual monitoring the progress of the reaction, we found that it
coordinating ability of the oxalate ion (ox ϭ C2O42Ϫ) has was only necessary to heat the reaction mixture for 2.5 h (cf.
made it a particularly versatile bridging species for the con- 15 h in the original literature).[8] The warm reaction mixture
trolled self-assembly of one-, two- and three-dimensional could then be poured directly into water and filtered imme-
inorganic architectures.[7] Along these lines, with a view to diately, washing with concentrated ammonia solution. This
prepare novel coordination polymers, we have recently process essentially removes any insoluble impurities on the
turned our attention to study the coordination behaviour sinter, and the product which precipitates from the filtrate
of the potentially ambidentate ligand 3,3Ј-diamino-2,2Ј-bi- on cooling is easily extracted into hot dioxane, giving 3,3Ј-
pyridine (L1). This ligand has two possible modes for bind- dinitro-2,2Ј-bipyridine in good yield. This compound is
ing namely, symmetric and asymmetric (Figure 1).
then readily reduced with SnII/HCl to afford ligand L1.
Since the initial preparation of the dinitro precursor proved
to be problematic, a second route to L1 was also investig-
ated. This involves the Ullman coupling of 3-acetylamino-
2-chloropyridine following the route of Kaczmarek et al.,[10]
followed by acidic hydrolysis to afford L1 in substantially
improved yields.
Syntheses of Metal Complexes of L1
An overview of the prepared metal complexes is provided
in Scheme 1.
The complexation reactions can be divided up into three
classes: (i) binding to metal salts through the diimine nitro-
gens, (ii) tris complexation by binding to the diimine nitro-
gens, and (iii) binding of the bis-protonated ligand L1H2 to
a metal through the amino groups. The first class involves
reaction of an acetonitrile solution of the ligand L1 with
one equivalent of a salt of a divalent metal, MII ϭ Cu, Mn,
Zn. This afforded a range of complexes with 1:1 ligand-to-
metal ratios, namely compounds 2aϪ2e. From the microan-
alysis data of complex 2a, we could deduce that ligand L1
forms a 1:1 complex with copper(II) chloride, although the
crystal structure later revealed that 2a actually crystallises
as an unusual 2:2 centrosymmetric complex of ligand L1
and copper(II) chloride (Figure 2a).
Figure 1. Potential symmetric (a) and asymmetric (b) binding
modes of ligand L1
The ligand L1 binds copper through the diimine coor-
dination site, and dimers are formed by a pair of bonds
from neighbouring amino groups.
Since only one coordination compound incorporating li-
gand L1 has been previously characterised by X-ray crystal-
lography,[8] we have primarily set out to investigate the co-
ordination chemistry of this compound and determine: (i)
which pair of nitrogen atoms are preferred for coordination,
(ii) whether the second pair of nitrogen atoms can contrib-
ute to the coordination in any way, and (iii) to what degree
the substituents influence the angle between the planes of
the pyridine rings.
Copper(II) acetate forms a variety of structures with un-
substituted 2,2Ј-bipyridine. The formation of multinuclear
systems containing two or three copper ions,[11,12,13] poly-
mers[14] and a mononuclear cation[15] [Cu(bipy)2(acetate)]ϩ
are facilitated by the possibility of acetate either acting as
a bidentate ligand, or using one oxygen atom to bridge two
metal centres. To determine in our case whether or not the
amino groups of 3,3Ј-diamino-2,2Ј-bipyridine would also
contribute to the coordination of the copper ion, complex
2b was prepared and its structure determined by X-ray crys-
tallography. The molecular structure of 2b is shown in Fig-
ure 3.
Results and Discussion
Ligand Synthesis
The diimine binding site of the bipyridine together with
The synthesis of L1 has been achieved by two independ- two acetate ligands are bound to the copper ion, thus enab-
ent routes. The first method involves the preparation of ling us to conclude that the amino groups are not involved
3,3Ј-dinitro-2,2Ј-bipyridine following the Ullman coupling in coordination to the copper ion when the bidentate acet-
procedure, first described by MacBride et al.[9] This was ate ligands can each provide two donor atoms.
then followed by a reduction step to afford ligand L1. Un-
Reactions of ligand L1 with manganese(II) chloride or
fortunately, the reaction conditions described by MacBride manganese(II) bromide also gave compounds with 1:1
proved to be problematic, giving poor yields of a very insol- metal-to-ligand ratios, although crystals suitable for single
uble material that was difficult to purify. After carefully crystal X-ray diffraction could not be grown to-date. Never-
1986
Eur. J. Inorg. Chem. 2002, 1985Ϫ1997

The Coordination Chemistry of 3,3Ј-Diamino-2,2Ј-bipyridine and Its Dication
FULL PAPER
Scheme 1. An overview of the coordination chemistry of L1
˚
Figure 3. Molecular structure of 2b; selected distances [A] and
angles [°]: N(1A)ϪCu 1.969(5), N(1B)ϪCu 1.985(5), O(1)ϪCu
1.961(4), O(2)ϪCu 2.616(5), O(3)ϪCu 1.959(5), O(4)ϪCu 2.571(6);
N(1A)ϪCuϪN(1B) 82.05(19), N(1A)ϪCuϪO(1) 164.72(19),
N(1A)ϪCuϪO(2)
N(1A)ϪCuϪO(4)
110.77(17),
100.45(20),
N(1A)ϪCuϪO(3)
N(1B)ϪCuϪO(1)
93.6(2),
95.6(2),
N(1B)ϪCuϪO(2) 104.93(18), N(1B)ϪCuϪO(3) 162.85(19),
N(1B)ϪCuϪO(4)
O(1)ϪCuϪO(3)
O(2)ϪCuϪO(3)
108.32(19),
92.9(2),
92.14(18),
O(1)ϪCuϪO(2)
O(1)ϪCuϪO(4)
O(2)ϪCuϪO(4)
55.10(16),
94.64(19),
136.85(18),
O(3)ϪCuϪO(4) 55.99(18)
theless, we would expect the manganese(II) to favour an
octahedral coordination, which could be completed by
bridging halides in a similar manner to the salt formed be-
tween manganese(II) chloride and 2,2Ј-bipyridine, in which
both chlorides bridge two neighbouring MnII ions.[16] Reac-
tions of ligand L1 with one equivalent of zinc(II) chloride
in acetonitrile yielded complex 2e whose chemical analysis
suggested a 1:1 ratio of ligand to metal salt. These results
parallel the reaction of unsubstituted 2,2Ј-bipyridine with
zinc(II) chloride which forms a simple four-coordinate 1:1
complex.[17] In contrast, X-ray diffraction studies showed
˚
Figure 2. a) The dimeric structure of 2a; selected distances [A] and
angles [°]: N(1A)ϪCu 1.998(2), N(1B)ϪCu 2.105(3), N(3AЈ)ϪCu
2.625(3) (dotted line), Cl(1)ϪCu 2.2565(10), Cl(2)ϪCu 2.2880(8);
N(1A)ϪCuϪN(1B) 80.94(10), N(1A)ϪCuϪCl(1) 94.50(8),
N(1B)ϪCuϪCl(1) 156.29(8),
Cl(1)ϪCuϪCl(2) 93.20(3),
N(1A)ϪCuϪN(3AЈ) 86.04(7), N(1B)ϪCuϪN(3AЈ) 91.62(8),
Cl(1)ϪCuϪN(3AЈ) 111.36(10), Cl(2)ϪCuϪN(3AЈ) 84.27(8); b)
The molecular packing arrangement for 2a; dashed lines indicate
the intermolecular hydrogen bond between H(31B) and a neigh-
N(1A)ϪCuϪCl(2) 169.32(8),
N(1B)ϪCuϪCl(2) 94.84(7),
˚
bouring chlorine atom H(31B)···Cl ϭ 2.47 A
Eur. J. Inorg. Chem. 2002, 1985Ϫ1997
1987

J. D. Wallis, M. Pilkington et al.
FULL PAPER
that crystals grown from an acetonitrile/ethanol solution of
the 1:1 complex 2e belong to the second class of coordina-
tion compounds, i.e. that 3e is the Zn2ϩ tris complex of
L1 with a tetrachlorozincate counterion. Similarly, crystals
grown from 2e in DMF/methanol were shown by X-ray
crystallography to be a DMF solvate 3f whose asymmetric
unit contains three tris complexes each hydrogen bonded to
one DMF solvent molecule. The closely related tris complex
3a was prepared by reaction of zinc(II) triflate with three
equivalents of L1. From these observations we can conclude
that compound 2e can readily rearrange in solution to af-
ford a tris complex. Reaction of three equivalents of ligand
L1 with copper(II), nickel(II) or cobalt(II) triflates afforded
the second series of 3:1 compounds, namely the tris com-
plexes 3bϪ3d.
Under acidic conditions it is reasonable to expect the co-
ordination chemistry of ligand L1 to change significantly
as the more basic pair of nitrogens is protonated. Judging
from the pKb’s of aniline (4.6) and pyridine (5.0) the amino
nitrogen atoms would be expected to be slightly more basic;
however, the crystalline salts of 3-aminopyridine are pro-
tonated on the ring nitrogen atom.[18,19] The pKb’s of the
two nitrogen sites are probably quite similar. If the amino
groups are protonated, metal ion binding at the diimine site
may be disfavoured since there would be repulsions between
the two positively charged ammonium groups in the 3- and
3Ј positions. Protonation of the ring nitrogen atoms would
leave open the possibility of metal ion binding to the amino
groups, forming a less favourable seven-membered chelate
ring.
˚
Figure 4. Molecular structure of 4; selected distances [A] and
angles [°]: N(3A)ϪCu 2.120(4), N(3B)ϪCu 2.467(4), Cl(1)ϪCu
2.299(2), Cl(2)ϪCu 2.284(2), Cl(3)ϪCu 2.3047(15), Cl(4)ϪCu
3.079(2); N(3A)ϪCuϪN(3B) 84.3(2), N(3A)ϪCuϪCl(1) 89.62(13),
N(3A)ϪCuϪCl(2) 88.91(13), N(3A)ϪCuϪCl(3) 178.54(13),
N(3A)ϪCuϪCl(4) 79.03(12), N(3B)ϪCuϪCl(1) 86.63(11),
N(3B)ϪCuϪCl(2) 100.67(11), N(3B)ϪCuϪCl(3) 95.71(11),
N(3B)ϪCuϪCl(4)
Cl(1)ϪCuϪCl(3)
Cl(2)ϪCuϪCl(3)
161.43(11),
91.84(5),
89.67(5),
Cl(1)ϪCuϪCl(2)
Cl(1)ϪCuϪCl(4)
Cl(2)ϪCuϪCl(4)
172.37(6),
85.23(5),
87.14(5),
Cl(3)ϪCuϪCl(4) 101.21(5)
Reaction of L1 with copper(II) chloride in dilute hydro-
chloric acid yielded a third class of compound, namely
complex 4. In this case, both heterocyclic nitrogen atoms
are protonated preventing coordination to the copper and,
as a consequence, the two amino groups and four chloride
ions are bound to the CuII completing an octahedral coor-
dination sphere (Figure 4).
On one occasion, isomeric red crystals were also isolated
from the preparation of 4. X-ray crystallography showed
that this compound was the tetrachlorocopper(II) salt of
the 3,3Ј-diamino-2,2Ј-bipyridinediium dication 5a (Fig-
ure 5). The only compound isolated from the reaction of
ligand L1 with zinc(II) chloride in a hydrochloric acid/ace-
tonitrile mixture was shown by X-ray methods to be the
corresponding tetrachlorozinc(II) salt 5b (Figure 5).
Our findings clearly show that the pyridine rings are the
favoured binding sites for coordination to divalent trans-
ition metal ions. However, by controlling the pH of the re-
action mixture, it is possible to coordinate metal ions
through the diamino functionality. In theory this ligand can
adopt either an asymmetric or symmetric bridging mode
Figure 5. Compounds 4, 5a, and 5b
for coordination, although the latter mode of binding has diaminobipyridine ligands, the asymmetric mode of binding
not been observed for this ligand to-date. This is in contrast is unfavourable for dual chelation due to the fact that coor-
to the closely related ligand 3,3Ј-dihydroxy-2,2Ј-bipyridine, dination through the diimine binding site requires an essen-
which binds RuII as a mononucleating ligand through its tially planar arrangement of the two pyridine rings, whereas
diimine sites as well as in a symmetric ‘‘turned-around’’ chelation through the diamino or dihydroxy groups requires
mode presenting two N,O-donor sites to two RuII ions in it to be substantially twisted. As a consequence, the flexibil-
an ambidentate manner.[20] For both the dihydroxy and the ity of the ligand is limited by the coordination requirements
1988
Eur. J. Inorg. Chem. 2002, 1985Ϫ1997

The Coordination Chemistry of 3,3Ј-Diamino-2,2Ј-bipyridine and Its Dication
FULL PAPER
of the first binding site. In this respect the bipyridine and occur at the expense of losing the aromaticity in both of its
phenanthroline families of molecules differ quite consider- pyridine rings.
ably. The dual chelating ability of the dipyridocatecholate
(dpcat) ligand was first reported in 1975 by Balch et al.,[21]
and during recent years Ward et al. have prepared dinuclear
ruthenium(II) complexes of the ambidentate bridging li-
gand phenanthroline-5,6-diimine (pdi).[22] In this system co-
ordination through the diamino groups of the bridging li-
gand is accomplished by their oxidation to the diimine state
with the loss of two hydrogen atoms. Complexation by the
diaminobipyridine ligand in this manner is highly unlikely
since oxidation of the diamino groups would in this case
X-ray Structural Studies
The X-ray crystal structure of the free ligand L1 (Fig-
ure 6) shows that the free ligand is held in a centrosym-
metric trans conformation via a pair of intramolecular hy-
drogen bonds between an amino hydrogen atom and the
heterocyclic nitrogen atom of the opposite ring
˚
[NϪH···N ϭ 1.948(18) A, NϪH···N ϭ 132.7(14)°].
The molecules are packed so that the second amino hy-
drogen atom can participate in an intermolecular hydrogen
bond to the amino N atom of another molecule, with an
˚
N···H bond length of 2.40(2) A, and close to linear bonding
at the hydrogen [NϪH···N ϭ 168.5(15)°] (Figure 7). This
interaction leads to a slight pyramidalisation of the amino
nitrogen atom as indicated by the sum of bond angles
around nitrogen (352.5°), which enables the lone-pair elec-
tron density to participate in the intermolecular hydrogen
Table 1. Bond lengths and angles of 3,3Ј-diamino-2,2Ј-bipyridine
in compounds L1, 2a, 4, 5a and 5b
2a[a]
4[a]
5a[a]
5b[a]
˚
Bond length [A] L1
N(1)ϪC(2)
N(1)ϪC(6)
C(2)ϪC(3)
N(3)ϪC(3)
C(3)ϪC(4)
C(4)ϪC(5)
C(5)ϪC(6)
C(2)ϪC(2Ј)
Bond angle [°]
1.3502(15) 1.360(4) 1.361(6) 1.352(5) 1.374(8)
1.374(4) 1.351(6) 1.368(5) 1.360(8)
1.3320(17) 1.348(4) 1.316(7) 1.324(6) 1.323(8)
1.332(4) 1.329(7) 1.329(5) 1.330(8)
1.4241(18) 1.417(4) 1.388(7) 1.406(5) 1.396(8)
1.404(4) 1.395(7) 1.402(6) 1.400(8)
1.3728(17) 1.387(4) 1.419(6) 1.364(4) 1.350(9)
1.387(4) 1.384(6) 1.341(6) 1.369(8)
1.3984(19) 1.415(5) 1.386(7) 1.397(6) 1.392(8)
1.403(5) 1.404(7) 1.411(6) 1.414(8)
1.364(2) 1.351(5) 1.383(7) 1.378(7) 1.376(9)
1.371(5) 1.380(7) 1.373(6) 1.383(10)
1.375(2) 1.395(5) 1.393(8) 1.382(7) 1.376(9)
1.388(5) 1.391(7) 1.383(7) 1.366(10)
1.485(2) 1.481(4) 1.480(7) 1.465(5) 1.477(8)
Figure 6. The molecular structure of L1; the dotted lines indicate
˚
the pair of intramolecular H bonds (NϪH···N ϭ 1.948 A)
C(2)ϪN(1)ϪC(6) 120.77(11) 121.5(3) 123.9(5) 124.6(4) 124.1(5)
120.3(3) 123.7(5) 124.6(4) 123.6(5)
N(1)ϪC(2)ϪC(3) 119.86(11) 119.7(3) 119.5(4) 118.8(4) 118.5(5)
119.6(3) 120.1(4) 118.7(4) 118.5(5)
N(1)ϪC(2)ϪC(2Ј) 116.47(13) 113.5(2) 118.9(4) 117.7(4) 116. 1(5)
113.1(3) 118.4(4) 116.9(4) 116.8(5)
C(3)ϪC(2)ϪC(2Ј) 123.67(14) 126.7(3) 121.6(4) 123.5(4) 125.1(6)
127.3(3) 121.3(4) 124.3(4) 124.7(5)
N(3)ϪC(3)ϪC(2) 123.95(12) 124.3(3) 119.9(4) 121.3(4) 122.4(6)
123.2(3) 119.7(4) 122.7(4) 120.7(5)
N(3)ϪC(3)ϪC(4) 118.73(12) 118.5(3) 122.2(5) 121.6(4) 119.9(6)
118.8(3) 123.4(5) 120.3(4) 121.5(6)
C(2)ϪC(3)ϪC(4) 117.29(12) 116.8(3) 117.8(5) 117.1(4) 117.7(6)
118.0(3) 116.8(5) 117.0(4) 117.7(6)
C(3)ϪC(4)ϪC(5) 121.28(13) 121.5(3) 120.7(5) 121.0(4) 121.1(6)
120.8(3) 121.0(5) 121.3(4) 120.2(6)
C(4)ϪC(5)ϪC(6) 118.30(13) 119.1(3) 119.6(5) 119.8(4) 120.1(6)
118.1(3) 119.6(5) 120.1(4) 119.6(6)
N(1)ϪC(6)ϪC(5) 122.48(13) 120.6(3) 118.4(5) 118.4(4) 118.6(6)
122.4(3) 118.6(5) 118.3(4) 119.9(6)
Figure 7. Molecular packing arrangement for L1; intra- and inter-
molecular H-bonding interactions are indicated by dashed lines
[a]
2
2 2
2 2
R1 ϭ (F0 Ϫ Fc)/F0; wR2 ϭ {[w(F0 Ϫ Fc ) ]/(F0 ) ]}1/2
.
Eur. J. Inorg. Chem. 2002, 1985Ϫ1997
1989

J. D. Wallis, M. Pilkington et al.
Table 2. Selected molecular geometry of L1 and its dication in complexes 2a, 2b, 3a, 3e, 4 and in salts 5a and 5b
FULL PAPER
Compound
2a
2b
3a
3e
4
5a
5b
˚
˚
N(3A)ϪH(32A) [A]
0.78(4)
2.19(4)
136(4)
24.4(1)
0.92(8)
2.07(8)
135(7)
28.9(2)
0.93(6)
1.97(6)
149(5)
31.3(2)
35.3(2)
0.245(4)
0.152(4)
1.01(13)
2.05(14)
136(11)
37.4(4)
37.8(4)
0.234(9)
0.133(8)
Ϫ
Ϫ
Ϫ
68.4(1)
Ϫ
Ϫ
Ϫ
54.5(1)
Ϫ
Ϫ
Ϫ
53.0(3)
H(32A)···N(3B) [A]
N(3A)ϪH(32A)···N(3B) [°]
Angle between best planes of heterocyclic rings [°]
Deviation of N(3A) from best plane of ring A [°]
Deviation of N(3B) from best plane of ring B [°]
0.374(3)
0.176(3)
0.22(1)
0.26(1)
0.072(4)
0.019(4)
0.115(4)
0.072(5)
0.033(7)
0.139(6)
bond. Each pyridine ring is planar, but the amino nitrogen approaches one face of the copper ion at angles to the other
˚
atom is displaced to one side of this plane by 0.061(1) A four ligating atoms in the range of 84Ϫ111°, leaving the
and its two hydrogen atoms are displaced by Ϫ0.12 and opposite face of the copper ion exposed. The shortest con-
˚
Ϫ0.15 A to the other side. The molecular geometry of the tact from this face is intermolecular to a pyridine ring and
˚
pyridine rings is summarised in Table 1. In comparison with is 3.785(4) and 3.626(4) A for Cu···C(3A) of ring A and
the similar trans conformation also adopted by 2,2Ј-bipyr- Cu···C(4A) of ring B, respectively. An intramolecular hy-
idine in the solid state,[23] differences are observed in the drogen bond [N···H ϭ 2.19(4) A, N···HϪN ϭ 136(3)°] leads
˚
geometry of the pyridine rings.
to the best planes of the two attached pyridine rings lying
For ligand L1, the C(2)ϪC(3) bond is slightly longer at only 24.4(1)° to each other (Table 2). There is a slight
˚
1.4241(18) A [cf. 1.394(2) for bipy] and the exocyclic folding of pyridine ring A about the C(3A)···C(6A) vector,
C(3)ϪC(2)ϪC(2Ј) angle is widened from to 121.2(1)° to and a slight folding of ring B about the C(2B)···C(5B) vec-
123.67(14)°. This is accompanied by a consequent contrac- tor. This folding serves to displace the amino groups out of
tion of the endocyclic angle at C(2) by 2.7° to 119.86(11)° the best planes of their respective pyridine rings in opposite
and an increase in the endocyclic angle at N(1) by 3.5° to directions: N(3A) is displaced towards the copper ion to
˚
120.77(11)°. The amino group is displaced away from the which it binds by 0.374(3) A, while N(3B) is displaced by
˚
opposite pyridine ring by 2.6° in the plane of the molecule. only 0.174(3) A in the opposite direction. The bonding geo-
These effects enable the molecule to optimise its hydrogen metries at C(3A) and C(3B) remain planar. Small in-plane
bonding interactions.
angular displacements of the CϪN bonds at C(3A) and
The crystal structures of complexes of L1 with copper(II) C(3B) in the range of 2Ϫ3° contribute to increase the dis-
chloride (2a) and copper(II) acetate (2b), the tris complexes tance between the amino groups, as observed in the struc-
of L1 with zinc(II) (3a, 3e and 3f), the complex of the dicat- ture of the free ligand. The molecules are packed such that
ion of L1 with copper(II) chloride (4) and two salts of the there is an intermolecular hydrogen bond between H(31B)
˚
dication of L1 are described. The molecular geometry of and a neighbouring chlorine atom [H(31B)···Cl ϭ 2.47 A]
the pyridine rings for selected compounds is summarised in (Figure 2b). Two types of 1:1 complexes with copper(II)
Table 1. Intramolecular hydrogen bonding interactions as chloride have been reported for the unsubstituted 2,2Ј-bi-
well as the conformational geometry for ligand L1 are listed pyridine ligand.[24] The first complex is comprised of long
in Table 2.
chains in which the octahedrally bound copper(II) ions are
linked by bridging chloride ions. The second complex con-
tains a pentacoordinate CuII ion with only one bridging
chloride linking adjacent metal centres. The two CuϪN
[Cu(L1)Cl2]2 (2a)
Remarkably, complex 2a crystallises as a 2:2 centrosym-
metric complex of ligand L1 and copper(II) chloride (Fig-
ure 2a). The CuII metal ion adopts a near square-pyramidal
geometry with two pyridine nitrogen atoms and two chlor-
ide ions bound in a distorted square-planar arrangement
with angles between neighbouring atoms at copper in the
range 80.9(1) to 94.8(1)°. A long axial contact from an am-
ino nitrogen of a neighbouring bipyridine molecule to the
˚
bond lengths in complex 2a [1.998(2) and 2.015(3) A] are
slightly shorter than those in the 1:1 complexes of bipyrid-
˚
ine with copper(II) [2.026(5)Ϫ2.079(3) A]. In contrast, the
1:1 complex of copper(II) chloride with 5,5Ј-diamino-2,2Ј-
bipyridine adopts a tetracoordinate structure with even
[25]
˚
shorter CuϪN bond lengths of 1.981(1) A. Interestingly,
a derivative of 3-amino-2,2Ј-bipyridine-6-carboxylate is re-
ported to bind copper(II) through both a deprotonated am-
ino group, a pyridine nitrogen and a carboxylate group.[26]
˚
copper metal [Cu···NH2 ϭ 2.625(3) A] completes the five-
coordinate geometry. The CuII is displaced out of the best
˚
planes of each pyridine ring by 0.482(1) and 0.468(1) A,
respectively, and the angle between the [Cl(1), Cl(2), Cu]
[Cu(L1)(OAc)2]·3H2O (2b)
plane and the [N(1A), N(1B), Cu] plane is 25.1(1)°. As
To determine whether the amino groups of 3,3Ј-diamino-
shown in Figure 2a, these molecules are arranged in dimers 2,2Ј-bipyridine would still contribute to the coordination
as a consequence of a pair of long axial contacts between of the copper ion, the structure of the hydrated 1:1 complex
a copper ion and an amino nitrogen atom belonging to the 2b with copper(II) acetate was determined by X-ray crystal-
opposite half of the dimer. A coordinating amino group lography (Figure 3). The bipyridine binds to copper
1990
Eur. J. Inorg. Chem. 2002, 1985Ϫ1997

The Coordination Chemistry of 3,3Ј-Diamino-2,2Ј-bipyridine and Its Dication
FULL PAPER
through its pyridine nitrogen atoms [Cu(1)ϪN(3A) ϭ The second water molecule lies in a channel that runs
˚
1.969(5), Cu(1)ϪN(3B) ϭ 1.985(5) A] and two acetate li- through the crystal parallel to the c axis that contains an
gands coordinate in a bidentate manner to complete a dis- additional, disordered water molecule.
torted octahedral geometry. Both acetates form one short
bond to copper [Cu(1)ϪO(1) ϭ 1.961(4), Cu(1)ϪO(3) ϭ [Zn(L1)3][CF3SO3]2 (3a), [Zn(L1)3][ZnCl4]·CH3CN
˚
1.959(5) A]. However, in contrast to 2a, the acetate ligands (3e) and [Zn(L1y)3][ZnCl4]·DMF (3f)
make a second pair of longer contacts [Cu(1)ϪO(2) ϭ
2.616(5), Cu(1)ϪO (4) ϭ 2.571(6) A] to the copper from
The structures of the cations in all three compounds are
˚
very similar. The molecular structure of 3a is shown in Fig-
above and below the equatorial plane. The bite angles of
ure 8. (NB The structures of 3a and 3e were solved in space
each acetate at the copper metal are 55.1(2) and 56.0(2)°,
groups which require the cation to lie on twofold axes, thus
respectively. This mode of binding is very similar to that of
only one-and-a-half ligand molecules are crystallo-
the single acetate moiety in the perchlorate and tetrafluoro-
graphically unique. However, the bisected ligand does not
borate salts of the acetato-bis-bipyridinecopper(II) cation,
exactly conform to this twofold axis due to the asymmetry
which contain one short CuϪO bond [2.031(5) and 1.980(4)
expected in the arrangement of the amino groups, where
one must hydrogen bond to the other).
[14]
˚
˚
A] and a longer Cu··O contact [2.648(5) and 2.785(5) A].
The structures of the acetate ligands in 2b are asymmetric,
In all complexes three bipyridine ligands bind the zinc(II)
metal through their diimine binding sites, and the cations
are all octahedral with ZnϪN bond lengths in the range
˚
with longer CϪO bonds [1.268(8) and 1.272(7) A] to the
oxygens which bind more tightly to the copper than for the
˚
other pair of oxygens [1.238(9) and 1.236(7) A].
2ϩ
˚
2.132(3)Ϫ2.164(3) A and bond angles around the Zn in
the range 76.1(1)Ϫ97.9(1)°. The ZnϪN bond lengths fall
within the range typical for Zn2ϩtris(bipyridine) complexes
In analogy with complex 2a, the two pyridine rings are
connected by an intramolecular hydrogen bond that links
the two amino groups (Table 2). The angle between the
planes of the two pyridine rings is 28.9(2)° and each amino
nitrogen atom is displaced by similar amounts from the
[27Ϫ29]
˚
(2.133Ϫ2.166 A).
[Cu(L1H2)Cl4] (4)
˚
plane of its attached pyridine ring, namely by 0.22(1) A for
˚
N(3A) and 0.26(1) A for N(3B). This serves to orient the
Reaction of L1 with copper(II) chloride in dilute hydro-
amino groups away from each other and differs from the chloric acid yielded complex 4, which was characterised by
more asymmetric disposition of amino groups in 2a, where X-ray crystallography. The molecular structure is shown in
one amino group coordinates the copper ion. The asymmet- Figure 4. Both heterocyclic nitrogen atoms are protonated
ric unit contains two well-ordered water molecules, one of and the two amino groups, which together with four addi-
which is hydrogen bonded to an acetate oxygen O(1) and tional chloride ligands complete the charge balance, are
an amino hydrogen H(31B) from different molecules in the bound to the copper ion, giving an octahedral coordination
crystal structure as well as to the second water molecule. sphere around the CuII ion. The endocyclic bond angles at
both pyridinyl nitrogen atoms show the expected widening
by 2Ϫ3° relative to the free ligand L1 due to protonation.
The CuII metal ion shows the expected JahnϪTeller distor-
tion, namely the CϪN and CϪCl bonds along one axis are
longer than other similar bonds in the complex. The
˚
˚
˚
N(3B)ϪCu bond [2.467(4) A] is 0.35 A longer than the
N(3A)ϪCu bond [2.120(4) A], although both are shorter
than the pair of bonds from amino nitrogens to coppers in
the 2:2 complex 2a. Both amino groups show a tetrahedral
bonding geometry, indicative of the binding interactions be-
tween nitrogen and copper. The 1,6-bite angle of the diam-
ino groups at the copper metal is 84.2(1)°. The molecule
achieves this mode of coordination by increasing the angle
between the best planes of the two pyridinium rings to
68.4(1)° from the cis coplanar arrangement. The amino ni-
trogen atoms are nearly coplanar with their pyridine rings,
in contrast to the complexed neutral ligand. The two
CϪNH2 bond lengths are different; this bond is longer
˚
[1.419(6) vs. 1.384(6) A] for the amino group which binds
the copper more tightly, since the nitrogen lone pair is less
available for conjugation with the pyridine ring. Indeed, the
shorter bond is similar in length to those in the unbound
dication in 5a and 5b, suggesting that this amino group only
binds weakly to the copper. The molecules are packed in
such a way that there are intermolecular hydrogen bonds
˚
Figure 8. Molecular structure of 3a; selected distances [A] and
angles [°]: N(1A)ϪCu 2.160(3), N(1B)ϪCu 2.132(3), N(1C)ϪCu
2.164(3); N(1A)ϪCuϪN(1B) 76.1(1), N(1A)ϪCuϪN(1C) 169.2(1),
N(1A)ϪCuϪN(1AЈ), 91.2(2), N(1A)ϪCuϪN(1BЈ) 97.9(1),
N(1A)ϪCuϪN(1CЈ)
N(1B)ϪCuϪN(1BЈ)
96.5(1),
171.5(2),
N(1B)ϪCuϪN(1C)
N(1B)ϪCuϪN(1CЈ)
95.3(1),
91.3,
N(1C)ϪCuϪN(1CЈ) 76.9(2)
Eur. J. Inorg. Chem. 2002, 1985Ϫ1997
1991

J. D. Wallis, M. Pilkington et al.
FULL PAPER
˚
between all six nitrogen-bonded hydrogen atoms and neigh- 1.341(6)Ϫ1.369(8) A (Table 1), and are shorter than in 3-
[34]
˚
˚
bouring chloride ions in the range of 2.24Ϫ2.67 A.
aminopyridine (1.384 A). This is in accordance with the
Only a few structurally characterised examples of 2,2Ј- expected increase in π-overlap between each amino group’s
diaminobiaryl systems binding in this way have been re- lone pair and the positively charged heterocyclic ring. The
ported in the chemical literature. 2,2Ј-Diaminobiphenyl and corresponding bond lengths in the complexed dication 4 are
1,2-diaminocyclohexane bind platinum(II) chloride[30] and ca. 0.4 A longer than in 5a and 5b since the nitrogen atoms’
˚
two molecules of 2,2Ј-diamino-6,6Ј-dimethylbiphenyl bind lone pairs are utilised in forming dative bonds.
to rhodium(III) chloride[31] with bite angles for the diamino
groups at the metal atom in the 87Ϫ89° range. Several com-
plexes of the 3-aminopyridinium cation coordinated
NMR Spectroscopy
through the amino groups to copper(II) have been reported
All NMR spectra were measured in [D6]DMSO for con-
and provide a useful comparison.[32,33] For these complexes, sistency. The 1H NMR chemical shifts for selected com-
˚
the CuϪN distances are in the range 2.043Ϫ2.071 A, sim- pounds are shown in Table 3.
ilar to the shorter of the CuϪN bonds in 4, and the
˚
CϪNH2 bond lengths are in the range 1.400Ϫ1.432 A, sim-
ilar to the C(3A)ϪN(3A) bond length in 4.
1
Table 3. H NMR spectroscopic data for selected compounds con-
taining L1
[L1H2][CuCl4] (5a) and [L1H2][ZnCl4] (5b)
The molecular structure of the zinc salt 5b is presented
in Figure 9. The geometry and conformation of the dication
in both compounds is very similar, however the geometry
of the anion in the former is intermediate between tetrahed-
ral and square planar, whereas in the latter it is tetrahedral.
Compound
Solvent
H6, H6Ј H5, H5Ј H4, H4Ј
Free ligand (L1)
L1·2HCl
[D6]DMSO 7.76
[D6]DMSO 8.09
[D6]DMSO 8.07
7.02
7.60
7.55
7.02
7.65
7.55
(L1H2)[ZnCl4] (5b)
[Dichloro(L1)zinc(II)] (2e) [D6]DMSO 7.80 (br) 7.04 (br) 7.14 (br)
[Zn(L1)3][ZnCl4] (3e)
[Zn(L1)3][CF3SO3]2 (3a) [D6]DMSO 7.62
[D6]DMSO 7.84
7.05
7.16
7.14
7.40
In comparison with the free ligand L1, the positive
charge resulting from protonation of both rings causes a
downfield shift of the aromatic protons since they are now
more deshielded than in L1. The protons in the 4- and 5-
positions are shifted by approximately 0.6 ppm whereas the
H-6 protons are shifted to a lesser degree by 0.3 ppm. These
shifts are observed for both the HCl salt as well as com-
pound 5b. For the tris-zinc compound 3a, complexation
causes a small upfield shift of the protons in the 6-position,
Figure 9. Molecular structure of 5b
Protonation of the ring diimine nitrogens leads to since there is a small diamagnetic interaction of the ring
widening of the endocyclic ring angles at these heteroatoms current with the metal ion resulting in a shielding effect of
in the range of 123.6(5)Ϫ124.6(4)°. The best planes of the the protons α to the metal centre. The protons in the 4-
pyridinium rings lie at 54.5(1)° and 53.0(3)° from the cis and 5-positions are deshielded slightly (0.1Ϫ0.4 ppm) with
1
coplanar arrangement, which serves to separate the amino respect to the free ligand L1. Interestingly, the H NMR
˚
nitrogen atoms at van der Waals distances of 3.063(6) A spectrum for the 1:1 complex 2e is very broad, indicating
˚
and 3.023(9) A. The shortest N···H separations between the an exchange process, and has similar chemical shifts to a
˚
two amino groups are ca. 2.7 A, although the positions of solution of the tetrachlorozincate salt of the tris-zinc com-
1
the hydrogen atoms determined from these room temper- plex 3e. It is notable that the H NMR spectrum of the
ature measurements are not very accurate. In contrast to latter differs from that of 3a, the triflate salt of the tris-zinc
the complexed dication in 4, the bonding geometries at the complex, which would not be expected to be involved in
amino nitrogen atoms are in most cases nearer to planar any exchange processes. Crystalline 3e was initially grown
(the average sum of bond angles at the amino N are in the from solutions of 2e, thus it seems that the two chlorides
range 347Ϫ360°). The bonds between the amino nitrogen and ligand L1 bound to zinc in 2e are exchanging between
atoms and the pyridine rings are in the range zinc ions.
1992
Eur. J. Inorg. Chem. 2002, 1985Ϫ1997

The Coordination Chemistry of 3,3Ј-Diamino-2,2Ј-bipyridine and Its Dication
FULL PAPER
δ ϭ 8.87 (dd, J6,5 ϭ 4.7 Hz, J6,4 ϭ 1.7 Hz, 2 H, 6-,6Ј-H), 8.58 (dd,
J4,5 ϭ 8.4 Hz, J4,6 ϭ 1.5 Hz, 2 H, 4-,4Ј-H), 7.65 (m, 2 H, 5-,5Ј-H).
13C NMR (CDCl3): δ ϭ 152.9 (6-,6Ј-C), 150.7 (2-,2ЈC), 144.0 (3-,
3Ј-C), 133.1 (4-,4Ј-C), 124.6 (5-,5Ј-C). IR (KBr pellet): ν˜ ϭ 3084,
1590, 1561, 1534, 1440, 1417, 1366, 1048, 1038, 865, 855, 821, 790,
751, 621, 529 cmϪ1. The dinitro product (0.8 g, 3.25 mmol) was
added to a solution of tin(II) chloride dihydrate (5.6 g, 29.5 mmol)
in conc. HCl (32%, 14 mL).[7] The solution was refluxed for 0.5 h,
to give a yellow solution (Important: do not let the solution cool,
otherwise a green insoluble solid precipitates out of solution). After
adjustment of the pH to 12Ϫ13 with a solution of NaOH, the
solution was extracted with chloroform, and the solvents evapor-
ated to give L1 as a yellow solid. (yield 0.5 g, 86%). Single crystals
suitable for X-ray diffraction were grown from ethyl acetate by slow
evaporation of the solvent at room temperature. M.p. 133Ϫ134 °C.
1H NMR (CDCl3): δ ϭ 7.96 (dd, J6,5 ϭ 7.0 Hz, J6,4 ϭ 3.0 Hz, 2
H, 6,6Ј-H), 7.02 (m, 4 H, 5,5Ј-H and 4,4Ј-H), 6.27 (br. s, 4 H, 2 ϫ
NH2). 13C NMR (CDCl3): δ ϭ 143.8 (3,3Ј-C), 140.6 (2,2Ј-C), 135.7
(6,6Ј-C), 123.9 (4,4Ј-C), 122.9 (5,5Ј-C). IR (KBr): ν˜ ϭ 3354, 3221,
2925, 2855, 1586, 1548, 1444, 1430, 1316, 1269, 1149, 1060, 1024,
Conclusion
Substitution at the 3,3Ј-positions does not prevent coor-
dination to the pyridine rings. Compound L1 behaves as a
bidentate ligand coordinating metal ions preferentially
through the nitrogen atoms of the pyridine rings. Further-
more, this ligand displays an unusual pH-dependent coor-
dination chemistry, enabling the diamino group to particip-
ate in the coordination chemistry when both pyridine nitro-
gens are protonated. The second mode of binding, namely
the symmetrical bridging mode, has not been observed for
this ligand to-date. Attempts to prepare dinuclear com-
plexes with ligand L1 acting as an asymmetric bridge have
so far been unsuccessful. This is most probably due to the
fact that the asymmetric bridging mode is sterically difficult
for divalent metal ions since chelation through the diamino
functionality requires the ligand to be substantially more
twisted. The above findings lead us to conclude that this
ligand is not particularly well suited for linking metal ions
for the assembly of coordination polymers. Tris-bipyridine
complexes of selected paramagnetic ions do, however, dis-
play the phenomenon of spin-crossover. As a consequence,
the preparation and magnetic studies of further derivatives
of L1 are currently in progress.[35]
796, 729, 638 cmϪ1
.
Method B: Freshly distilled acetic anhydride (200 mL, 2.02 mol)
was added to 2-chloro-3-aminopyridine (20.0 g, 0.156 mol) and the
solution left to stir overnight. The excess acetic acid and acetic
anhydride were both removed by distillation under reduced pres-
sure. On cooling in ice the remaining oil produced an off-white
solid which was recrystallised from toluene to give 3-acetylamino-
2-chloropyridine (20.1 g, 74.0%) as white crystals, M.p. 89 °C. Ac-
tivated copper bronze (18 g, 0.283 mol) was added to a solution of
3-acetylamino-2-chloropyridine (20.0 g, 0.117 mol) in dry DMF
(100 mL) under nitrogen.[9] This mixture was then heated at 110
°C until TLC (SiO2,ethyl acetate) showed the absence of starting
material (3Ϫ4 h). After cooling, water (20 mL) was added and the
solution filtered. The filter cake was washed with more water (20
mL), ammonium hydroxide (40 mL, 0.88 grav) and finally more
water (20 mL). The cake was allowed to dry fully in a desiccator.
The desired solid was then extracted with dichloromethane (5 ϫ
200 mL) and the solvents evaporated to give crude 3,3Ј-diacetylam-
ino-2,2Ј-bipyridine (yield 12.2 g, 76.6%). M.p. 230°C (dec.) (ref.[9]
225Ϫ226 °C), 1H NMR (CDCl3): δ ϭ 9.13 (dd, J4,5 ϭ 8.5 Hz,
J4,6 ϭ 1.7 Hz, 2 H, 4,4Ј-H), 8.35 (dd, J6,5 ϭ 5.9 Hz, J6,4 ϭ 1.5 Hz,
2 H, 6,6Ј-H), 7.36 (dd, J5,6 ϭ 13.1 Hz, J5,4 ϭ 4.5 Hz, 2 H, 5,5Ј-H),
2.20 (s, 6 H, 2 ϫ -CH3). 13C NMR (CDCl3): δ ϭ 169.2 (CϭO),
141.7 (2,2Ј-C), 140.3 (6,6Ј-C), 136.5 (4,4Ј-C), 129.8 (3,3Ј-C), 123.9
(5,5Ј-C), 25.4 (2 ϫ -CH3). IR (KBr): ν˜ ϭ 3344 (NϪH str), 1691
(CϭO str) cmϪ1. This crude product (12.0 g, 44.4 mmol) was added
to concentrated HCl (50 mL) and the mixture refluxed for 30 min.
After cooling in ice, concentrated ammonium hydroxide was added
(80 mL, 0.88 grav) to give bright yellow crystals of pure L1 (yield
8.03 g, 95.2%).
Experimental Section
General: 3-Amino-2-chloropyridine, copper bronze (99%) and
tin(II) chloride (98%) were purchased from Aldrich. 2-Chloro-3-
nitropyridine (97%), DMF (99.8% over molecular sieves) and diox-
ane (99.5%) were purchased from Fluka. Solvents were dried before
use. NMR spectra were measured on a JEOL GX 270 spectrometer
(270 MHz for 1H and 67.8 MHz for 13C) using tetramethylsilane
(TMS) as standard, and measured in ppm downfield from TMS,
or on a Bruker AC-300 spectrometer (300 MHz for 1H and 75 MHz
for 13C) and calibrated against the deuterated solvent. Chemical
shifts δ are given in ppm and coupling constants (J) are given in
Hz. IR spectra were recorded on an ATI Mattson Genesis Series
FT-IR or a PerkinϪElmer Spectrum One FT-IR spectrophoto-
meter as liquid films, nujol mulls or KBr pellets. Mass spectra were
recorded at the EPSRC Mass Spectrometry Centre and at the Uni-
versity of Berne. Microanalyses were performed at the Analytical
Centre, University of Kent, UK, and at the University of Fribourg,
Switzerland. Flash chromatography was performed on 40Ϫ63 silica
gel (Merck).
Synthesis of 3,3Ј-Diamino-2,2Ј-bipyridine (L1)
Method A: 2-Chloro-3-nitropyridine (2.00 g, 12.62 mmol) was re-
acted with freshly activated copper bronze (2.00 g) in dry DMF (40
mL) at 150 °C under nitrogen for 2.5 h.[8] After 2 h TLC (SiO2,
CH2Cl2) indicated that the starting material had been consumed.
3,3Ј-Diamino-2,2Ј-bipyridinediium Dichloride: A 2  solution of
HCl (10 mL) was added to ligand L1 (1.0 g, 4.4 mmol) and the
solution stirred for 24 h. The desired salt was precipitated from the
The resulting mixture was poured into water (40 mL), the solid solution by the dropwise addition of acetonitrile to give a bright
filtered immediately and then washed with concentrated ammonia
(2 ϫ 20 mL). The remaining solid was then extracted into boiling
dioxane (2 ϫ 150 mL), stirring for about 20 min each time. After
evaporating the combined extracts to dryness, the solid was recrys-
tallised from ethanol to give 3,3Ј-dinitro-2,2Ј-bipyridine as a yellow
yellow, amorphous solid which was washed with water and dried
(yield 0.89 g, 63.9%). M.p. 181 °C (dec.), 1H NMR (D2O): δ ϭ 8.20
(dd, J6,5 ϭ 5.2 Hz, J6,4 ϭ 1.2 Hz, 2 H, 6,6Ј-H), 8.01 (dd, J4,5
8.9 Hz, J4,6 ϭ 5.4 Hz, 2 H, 4,4Ј-H), 7.90 (dd, J5,4 ϭ 8.9 Hz, J5,6
ϭ
ϭ
5.4 Hz, 2 H, 5,5Ј-H). 13C NMR (D2O): δ ϭ 146.7 (6,6Ј-C), 133.1
solid (yield 1.16 g, 73%). M.p. 205Ϫ206 °C. 1H NMR (CDCl3): (4,4Ј-C), 132.9 (2,2Ј-C), 129.0 (5,5Ј-C), 122.1 (3,3Ј-C) IR (KBr
Eur. J. Inorg. Chem. 2002, 1985Ϫ1997 1993

J. D. Wallis, M. Pilkington et al.
FULL PAPER
disc): ν˜ ϭ 3378Ϫ3207 (NϪH str), 2958 (CϪH, arom. str), 2631
low single crystals of 3c after recrystallisation from water (yield
0.89 g, 98%). M.p. 336 °C (dec.). C32H30F6N12NiO6S2 (915.5):
calcd. C 42.0, H 3.3, N 18.4; found C 41.9, H 3.3, N 18.6. IR
(Nujol): ν˜ ϭ 3369, 3331, 3209, 1643, 1632, 1590, 1257, 1234, 1165,
(NϩϪH str), 1546 (CϭN, arom. str) cmϪ1
.
Tetrachlorobis(3,3Ј-diamino-2,2Ј-bipyridine)dicopper(II) (2a): Equi-
molar amounts of ligand L1 (0.30 g) and copper(II) chloride dihy-
drate (0.22 g) were stirred together in acetonitrile overnight. The
resulting precipitate was filtered, dried and recrystallised from
water to give single crystals of 2a as green blocks (yield 0.49 g,
97%). M.p 266Ϫ267 °C. C10H10Cl2CuN4 (320.7): calcd. C: 37.5, H
3.1, N 17.5; found C 37.3, H 3.1, N 17.9. IR (Nujol): ν˜ ϭ 3345,
3305, 3218, 1643, 1633, 1590, 1581, 1330, 1313, 1267, 1230, 1201,
1028, 803, 641 cmϪ1
.
Tris(3,3Ј-diamino-2,2Ј-bipyridine)cobalt(II) Trifluoromethanesulfon-
ate (3d): Reaction of an acetonitrile solution of L1 (0.56 g,
3.0 mmol) with cobalt(II) trifluoromethanesulfonate tetrahydrate
(0.41 g,1.0 mmol) gave dark-red single crystals of 3d after recrys-
tallisation from water (yield 0.82 g, 97%). M.p. 330 °C (dec. starts
at 300 °C). C32H30CoF6N12O6S2 (915.7): calcd. C 42.0, H 3.3, N
18.4; found C 41.9, H 3.1, N 18.7. IR (Nujol): ν˜ ϭ 3372, 3330,
3209, 1642, 1602, 1590, 1258, 1235, 1224, 1165, 1029, 803, 724,
1149, 1076, 1064, 944, 904, 823, 798,723, 713, 686 cmϪ1
.
Diacetato(3,3Ј-diamino-2,2Ј-bipyridine)copper(II)·3H2O (2b): Fol-
lowing the above procedure for 2a, reaction of ligand L1 (0.30 g)
and copper(II) acetate hydrate (0.32 g) yielded a solid which was
collected, dried and recrystallised from aqueous ethanol to afford
single crystals of 2b as dark green prisms (yield 0.55 g, 93%). M.p.
212Ϫ214 °C. C14H16N4O4Cu·3H2O (421.9): calcd. C 39.8, H 5.2,
N 13.3; found C 40.0, H 4.8, N 13.5. IR (Nujol): ν˜ ϭ 3491, 3415,
3329, 3173, 1639, 1579, 1279, 1245, 1156, 1051, 1012, 922, 815,
641 cmϪ1
.
Dichloro(3,3Ј-diamino-2,2Ј-bipyridine)zinc(II) (2e): Ligand L1
(0.15 g, 0.81 mmol) was stirred with dry zinc(II) chloride (0.11 g,
0.81 mmol) in acetonitrile (10 mL) overnight. A fine, bright-yellow
precipitate and was separated from the solution by centrifugation,
and dried under vacuum to give 2e (yield 0.22 g, 86%). M.p. Ͼ 310
°C. C10H10Cl2N4Zn (322.5): calcd. C 37.24, H 3.13, N 17.37; found
799, 667 cmϪ1
.
1
C 37.50, H 3.13, N 17.23. H NMR ([D6]DMSO): δ ϭ 7.80 (br., 2
Catena-dichloro(3,3Ј-diamino-2,2Ј-bipyridine)manganese(II)
(2c):
H, 6,6Ј-H), 7.14 (br., 2 H, 4,4Ј-H) 7.04 (br., 2 H, 5,5Ј-H), 7.00 (br.,
4 H, 2 ϫ NH2). 13C NMR ([D6]DMSO): δ ϭ 144.4 (3,3Ј-C), 139.0
(2,2Ј-C), 134.1 (6,6Ј-C), 123.1 (4,4Ј-C), 122.9 (5,5Ј-C). IR (KBr pel-
let): ν˜ ϭ 3409, 3327, 3234, 1638, 1626, 1593, 1583, 1467, 1440,
1344, 1331, 1271, 1248, 1203, 1157, 1102, 1075, 806, 773, 726, 710,
Reaction of L1 (0.30 g) with manganese(II) chloride tetrahydrate
(0.32 g) as for 2a gave a dark crystalline solid tentatively assigned
as 2c (yield 0.41 g, 82%). M.p. Ͼ 330 °C. C10H10Cl2MnN4 (312.1):
calcd. C 38.5, H 3.3, N 18.0; found C 38.3, H 3.2, N 17.7. IR
(Nujol): ν˜ ϭ 3440, 3392, 3334, 3305, 3205, 1735, 1615, 1593, 1295,
650, 594 cmϪ1
.
1242, 1159, 1025, 952, 918, 817, 786, 770, 734 cmϪ1
.
Tris(3,3Ј-diamino-2,2Ј-bipyridine)zinc(II) Tetrachlorozincate(II) (3e)
Catena-dibromo(3,3Ј-diamino-2,2Ј-bipyridine)manganese(II) (2d):
Reaction of L1 (0.30 g) with manganese(II) bromide hexahydrate
(0.52 g) as for 2a gave a black solid tentatively assigned as 2d (yield
0.47 g, 73%). M.p. dec. 280 °C. C10H10Br2MnN4 (401.0): calcd. C
30.0, H 2.5, N 14.0; found C 29.9, H 2.5, N 13.7. IR (Nujol): ν˜ ϭ
3330, 3301, 3203, 1712, 1627, 1589, 1314, 1263, 1207, 1156, 1012,
and Its DMF Solvate (3f)
Slow evaporation of a 1:1 ethanol/acetonitrile mixture of the 1:1
complex 2e yielded single crystals which were characterised by X-
ray crystallography to be the tris complex 3e. M.p Ͼ 310 °C. 1H
NMR ([D6]DMSO): δ ϭ 7.84 (dd, J6,5 ϭ 4.2 Hz, J6,4 ϭ 1.5 Hz, 6
H, 3 ϫ 6,6Ј-H), 7.14 (dd, J4,5 ϭ 8.2 Hz, J4,6 ϭ 1.5 Hz, 6 H, 3 ϫ
4,4Ј-H), 7.05 (dd, J5,4 ϭ 8.2 Hz, J5,6 ϭ 4.2 Hz, 6 H, 3 ϫ 5,5Ј-H),
6.97 (br., 12 H, 6 ϫ NH2). IR (KBr pellet): ν˜ ϭ 3514, 3327, 3214,
2925, 1945, 1634, 1588, 1465, 1445, 1321, 1270, 1242, 1206, 1152,
1101, 1076, 1022, 875, 883, 806, 732, 707, 639, 589 cmϪ1. A second
set of crystals were grown by diffusion of methanol into a DMF
solution of 2e. The crystals were characterised as being compound
3f, a DMF solvate of 3e. M.p. 335Ϫ338 °C. 1H NMR ([D6]DMSO):
δ ϭ 7.84 (dd, J6,5 ϭ 4.2 Hz, J6,4 ϭ 1.5 Hz, 6 H 3 ϫ 6,6Ј-H), 7.14
(dd, J4,5 ϭ 8.2 Hz, J4,6 ϭ 1.5 Hz, 6 H, 3 ϫ 4,4Ј-H), 7.05 (dd, J5,4 ϭ
8.2 Hz, J5,6 ϭ 4.2 Hz, 6 H, 3 ϫ 5,5Ј-H), 6.97 (br., 12 H, 6 ϫ NH2).
13C NMR ([D6]DMSO): δ ϭ 144.39 (3,3Ј-C), 138.84 (2,2Ј-C),
134.43 (6,6Ј-C), 123.49 (4,4Ј-C), 123.04 (5,5Ј-C). IR (Nujol): ν˜ ϭ
972, 839, 801, 737 cmϪ1
.
Tris(3,3Ј-diamino-2,2Ј-bipyridine)zinc(II) Trifluoromethanesulfonate
(3a): Reaction of an acetonitrile solution of L1 (0.56 g, 3.0 mmol)
with zinc(II) trifluoromethanesulfonate tetrahydrate (0.41 g,
1.0 mmol) following the procedure as for 2a afforded yellow single
crystals of 3a after recrystallisation from water (yield 0.84 g, 91%).
M.p. 308 °C. C32H30F6N12O6S2Zn (922.2): calcd. C 41.7, H 3.3, N
18.2; found C 41.3, H 3.1, N 18.5. 1H NMR ([D6]DMSO): δ ϭ
7.84 (br. d, J ϭ 3.4 Hz, 6 H, 3 ϫ 6-,6Ј-H), 7.26 (dd, J4,5 ϭ 7.9 Hz,
J4,6 ϭ 1.3 Hz, 6 H, 3 ϫ 4-,4Ј-H), 7.16 (dd, J4,5 ϭ 8.1 Hz, J5,6
ϭ
4.6 Hz, 6 H, 3 ϫ 5-,5Ј-H). 13C NMR ([D6]DMSO): δ ϭ 144.1 (3,3Ј-
C), 138.0 (2,2Ј-C), 135.2 (6,6Ј-C), 124.5 (4,4Ј-C), 123.2 (5,5Ј-C). IR
(Nujol): ν˜ ϭ 3373, 3331, 3208, 1642, 1630, 1584, 1332, 1258, 1237,
3401, 3331, 3191, 1634, 1588, 1325, 1270, 1242, 1206, 1155, 1102,
1075, 806, 726, 707, 640 cm
1224, 1165, 1152, 1029, 804, 726, 706, 641 cmϪ1
.
Ϫ1
.
Tris(3,3Ј-diamino-2,2Ј-bipyridine)copper(II) Trifluoromethanesulfon-
ate (3b): Copper(II) trifluoromethanesulfonate (0.65 g, 1.79 mmol)
was added to solution of L1 (1.0 g, 5.38 mmol) in acetonitrile (25
mL) and stirred for 10 min. Standing overnight produced ruby red
crystals of 3b as its acetonitrile solvate (yield 0.90 g, 54%). M.p.
249 °C. C32H30CuF6N12O6S2·CH3CN (961.7): calcd. C 42.5, H 3.5,
N 18.9, Cu 6.6; found C 42.2, H 3.3, N 19.2, Cu 6.5. IR (Nujol):
3,3Ј-Diamino-2,2Ј-bipyridinium Tetrachlorocuprate(II) (4): Cop-
per(II) chloride dihydrate (0.45 g) dissolved in 1  HCl (5 mL) was
added to a solution of L1 (0.50 g) in acetonitrile (5 mL) and stirred
for 30 min. The resulting green precipitate was collected by filtra-
tion. A second batch of green solid crystallised out of the filtrate
and was collected affording compound 4 in an overall yield of
0.57 g (54%). M.p. 290Ϫ291°C. C10H12Cl4CuN4 (393.6): calcd. C
29.6, H 3.0, N 13.8, Cu 16.1; found C 29.7, H 3.0, N 14.2, Cu 15.7.
IR (Nujol): ν˜ ϭ 3346, 3295, 3215, 1634, 1586, 1582, 1330, 1314,
ν˜ ϭ 3376, 2960, 1638, 1590, 1264, 1168, 1032, 804, 724, 638 cmϪ1
.
Tris(3,3Ј-diamino-2,2Ј-bipyridine)nickel(II) Trifluoromethanesulfon-
ate (3c): Reaction of an acetonitrile solution of L1 (0.56 g,
1266, 1229, 1200, 1150, 904, 819, 799, 714, 684, 648 cmϪ1
.
3.0 mmol) with nickel(II) trifluoromethanesulfonate pentahydrate 3,3Ј-Diamino-2,2Ј-bipyridinium Tetrachlorocuprate(II) (5a): On one
(0.41 g, 1.0 mmol) following the procedure as for 2a gave pale-yel-
occasion a few red crystals were isolated on evaporation of the
1994
Eur. J. Inorg. Chem. 2002, 1985Ϫ1997

The Coordination Chemistry of 3,3Ј-Diamino-2,2Ј-bipyridine and Its Dication
FULL PAPER
above filtrate. These crystals were carefully separated from the
green crystals and characterised by X-ray crystallography as being
5a, the salt of the diprotonated ligand L1. M.p Ͼ 300°C.
C10H12Cl4CuN4 (393.6): calcd. C 29.6, H 3.0, N 13.8, Cu 16.1.%;
found C 29.6, H 3.0, N 14.2, Cu 15.9.
Structure solution was performed by Patterson or direct methods
using SHELXS-97.[36] Refinement: Full-matrix least-squares on F2
(SHELXL-97)[36] all non-hydrogen positions found and refined
with anisotropic temperature factors. Hydrogen atoms were located
from Fourier distance maps and refined isotropically. Graphics are
drawn with the WINGX package for windows.[37]
3,3Ј-Diamino-2,2Ј-bipyridinium Tetrachlorozincate(II) (5b): Aque-
ous HCl (10 mL, 4.77 ) was added to a solution of L1 (150 mg)
in acetonitrile (10 mL). Zinc(II) chloride (110 mg) was then added
and the reaction mixture was stirred overnight. The volume of the
resulting yellow solution was reduced until a solid started to precip-
itate. The product was then filtered, washed with ether and dried
under vacuum to give 5b (yield 0.23 g, 72%). M.p. Ͼ 310 °C.
C10H12Cl4N4Zn (395.4): calcd. C 30.4, H 3.1, N 14.2; found C 30.5,
H 3.1, N 13.9. 1H NMR ([D6]DMSO): δ ϭ 8.07 (dd, J6,5 ϭ 4.3 Hz,
CCDC-173203Ϫ173211 (L1, 2a, 2b, 3a, 4, 5a, 5b, 3e, 3f,
respectively) contains the supplementary crystallographic data for
this paper. These data can be 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: (internat.) ϩ44-1223/336-033; E-mail:
deposit@ccdc.cam.ac.uk].
J
6,4 ϭ 1.3 Hz, 2 H, 6,6Ј-H), 7.55 (m, 4 H, 4,4Ј-H, 5,5Ј-H), 3.76 (br.,
6 H, 2 ϫ NH2, 2 ϫ NH). 13C NMR ([D6]DMSO): δ ϭ 145.4 (3,3Ј-
C), 132.6 (6,6Ј-C), 128.8 (2,2Ј-C) 128.6 (4, 4Ј-C), 126.9 (5,5Ј-C). IR
(KBr): ν˜ ϭ 3436, 3352, 3313, 3199, 3067, 2908, 1640, 1630, 1619,
Acknowledgments
1561, 1553, 1471, 1384, 1300, 1165, 1154, 945, 806, 785 cmϪ1
.
This work was supported in part by the University of Nottingham
Trent, University of Berne and the SNF (NRP 47, Supramolecular
Functional Materials). We thank BENEFRI and EPSRC services
for single crystal X-ray crystallographic measurements and the
EPSRC and University of Berne mass spectrometry services for
data. We thank Professor Silvio Decurtins (Ph.D Supervisor of M.-
C. Senna) for his support and encouragement, and for allowing M.
X-ray Structure Determinations: All crystal data are summarised in
Table 4 and 5 unless otherwise stated. Data were collected with
˚
Mo-Kα radiation (λ ϭ 0.71073 A) using a graphite monochromator
with the exception of compounds L1 and 3e, which were collected
˚
with Cu-Kα radiation (λ ϭ 1.54178 A).
Table 4. Crystal data for ligand L1 together with complexes 2a, 2b, 4, 5a, 5b
L1
2a
2b
4
5a
5b
Empirical formula
M (g molϪ1
C10H10N4
186.2
C20H20Cl4Cu4N8 C14H22CuN4O7
641.4 421.9
C10H12Cl4CuN4
393.6
C10H12Cl4CuN4
393.6
C10H12Cl4N4Zn
395.4
)
Crystal size [mm]
Crystal description
Crystal colour
T [K]
0.38 ϫ 0.30 ϫ 0.19 0.2 ϫ 0.10 ϫ 0.10 0.49 ϫ 0.42 ϫ 0.30 0.28 ϫ 0.20 ϫ 0.18 0.08 ϫ 0.25 ϫ 0.40 0.45 ϫ 0.25 ϫ 0.05
blocks
yellow
293(2)
STOE AED2
blocks
green
150(2)
Enraf Nonius
Fast
4Ϫ51
monoclinic
P21/n
blocks
dark blue
293(2)
Blocks
green
150(2)
Enraf Nonius
Fast
5Ϫ50
monoclinic
P21/a
plates
green
plates
yellow
153(2)
STOE IPDS
293(3)
Enraf Nonius
CAD4
4Ϫ50
orthorhombic
Pna21
Diffractometer
STOE AED2
2θ range [°]
13Ϫ119
monoclinic
P21/n
4Ϫ51
monoclinic
C2/c
5.4Ϫ52
Crystal system
Space group
triclinic
¯
P1
˚
a [A]
7.7896(7)
5.3100(4)
11.0474(8)
90
100.594
90
10.110(2)
10.08122(9)
11.6522(1)
90
105.18(2)
90
18.819(4)
13.326(6)
15.950(3)
90
112.82(1)
90
10.926(3)
8.214(1)
15.890(3)
90
104.37(2)
90
17.457(9)
7.486(7)
11.213(3)
90
90
90
7.4417(11)
7.6257(10)
13.5058(18)
85.071(16)
78.467(16)
85.088(17)
746.34(18)
2
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
3
˚
V [A]
449.16(6)
2
1146.3(3)
2
3687.0(19)
8
1381.4(5)
4
1461.8(5)
4
Z
Dcalcd. [gcmϪ3
]
1.38
1.86
1.46
1.89
1.78
1.76
µ [Ϫ1
]
7.1
23.5
12.2
23.4
22.3
23.5
Absorption correction Ϫ
Min/max transmission Ϫ
Measured reflections 2618
DIFABS
0.72/0.89
4854
Ϫ
Ϫ
3647
DIFABS
0.65/0.86
5122
PSI SCANS
0.60/0.86
1685
DIFABS
0.62/0.88
5313
Unique reflect. for
Refinement (Rint
660
1766
3422
2033
1685
2702
)
Observed reflections
633
1633
2478
1223
1462
2036
[I Ͼ 2σ(I)]
Ϫ3
˚
Max/min∆ρ [e·A
]
0.13/-0.10
0.035
0.097
0.55/-0.63
0.038
0.095
0.79/-0.51
0.069
0.15
0.57/-0.50
0.034
0.093
0.64/-0.38
0.026
1.09/-1.70
0.073
0.18
R1 [I Ͼ 2σ(I)][a]
wR2 (all reflections)
GOF on F2 [b]
0.66
1.09
1.19
0.46
1.81
0.95
[a]
2
2 2
2 2
[b]
2
2 2
2
R1 ϭ (Fo Ϫ Fc)/Fo; wR2 ϭ {[w(Fo Ϫ Fc ) ]/(Fo ) ]}1/2
.
GOF ϭ {[Fo Ϫ Fc ) ]/(n Ϫ p)}1/2; w ϭ 1/[σ2(Fo ) ϩ (aP)2 ϩ bP, where P ϭ
2
2
[max(Fo or 0 ϩ 2Fc ]/3.
Eur. J. Inorg. Chem. 2002, 1985Ϫ1997
1995

J. D. Wallis, M. Pilkington et al.
FULL PAPER
Table 5. Crystal data for the 3:1 Complexes 3a, 3e, and 3f
3a
3e
3f
Empirical formula
M (g molϪ1
Crystal size [mm]
Crystal description
Crystal colour
T [K]
C32H30F6N12O6S2Zn
922.19
0.24 ϫ 0.16 ϫ 0.16
blocks
yellow
150(2)
C32H33Cl4N13Zn2
872.3
0.38 ϫ 0.30 ϫ 0.11
blocks
yellow
293(3)
C33H37Cl4N13OZn2
904.30
0.5 ϫ 0.5 ϫ 0.5
blocks
yellow
153(2)
)
Diffractometer
Scan type 2θ range [°]
Crystal system
Space group
Enraf Nonius FAST
4-50
orthorhombic
C2221
11.829(2)
14.7536(7)
21.581(5)
90
90
90
3766.3(2)
4
1.63
STOE AED2
8-120
orthorhombic
Ama2
21.721(8)
11.633(2)
15.104(5)
90
90
90
3816(2)
4
1.52
STOE IPDS
4-51
orthorhombic
Pna21
21.2015(10)
11.7334(6)
45.956(3)
90
˚
a [A]
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
90
90
3
˚
V [A]
11486.2(11)
12
1.57
Z
Dcalcd. [gcmϪ3
]
µ [Ϫ1
]
8.5
44.8
15.8
Absorption correction
Min/max transmission
Measured reflections
Unique reflect. for
DIFABS
0.98/0.82
6681
Psi scans
0.432/0.192
2974
DIFABS
0.860/0.547
30716
2884
1505
16544
Refinement (Rint
Observed reflections
)
2632
1423
12055
[I Ͼ 2σ(I)]
Ϫ3
˚
Max/min∆ρ [e·A
]
0.42/Ϫ0.33
0.036
0.085
0.47/Ϫ0.31
0.037
0.096
0.535/Ϫ0.480
0.040
0.102
R1/wR2 [I Ͼ 2σ(I)][a]
R1/wR2 (all reflections)
GOF on F2[b]
1.070
1.05
0.952
[a]
2
2 2
2 2
[b]
2
2 2
2
R1 ϭ (Fo Ϫ Fc)/Fo; wR2 ϭ {[w(Fo Ϫ Fc ) ]/(Fo ) ]}1/2
.
GOF ϭ {[Fo Ϫ Fc ) ]/(n Ϫ p)}1/2. w ϭ 1/[σ2(Fo ) ϩ (aP)2 ϩ bP where P ϭ
2
2
[max(Fo or 0 ϩ 2Fc ]/3.
2518Ϫ2524; R. V. Belzen, R. A. Klein, H. Kooijman, N. Veld-
man, A. L. Spek, C. J. Elsevier, Organometallics 1998, 17,
1812Ϫ1825; R. A. Klein, K. Vrieze, C. J. Elsevier, R. P. Thum-
mel, J. Fraanje, K. Goubitz, Coll. Czech. Chem. Commun. 1997,
62, 238Ϫ256.
J. Rebek Jr., J. E. Trend, R. V. Wattley, S. Chalravorti, J. Am.
Chem. Soc. 1979, 101, 4333Ϫ4337; J. Rebek Jr., L. R. Marshall,
J. Am. Chem. Soc. 1983, 105, 6668Ϫ6670.
M. Pilkington, S. Decurtins, in Magnetism: Molecules to Mat-
erials II (Eds.: J. S. Miller and M. Drillon), Wiley-VCH,
Weinheim, 2001, Chapter 10, 339Ϫ356.
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