[Cu(phdpa)Cl]+ (phdpa=bis(2-pyridylmethyl)aniline): A moiety of unusual stability in some 1:1 Cu(II) complexes of phdpa. Synthesis and X-ray crystal structures of [Cu(phdpa)Cl2] and [Cu2(phdpa)2Cl3]PF6 ·0.5MeOH

Article abstract of DOI:10.1016/S0020-1693(02)01063-0

1:1 copper(II) complexes of bis(dipyridylmethyl)aniline (phdpa) of various kinds, with chloride and PF₆^- as anions, were synthesized and characterized by elemental analysis, IR spectroscopy and X-ray structure crystallography. The crystal structures of [Cu(phdpa)Cl₂] (I) and [Cu₂(phdpa)₂Cl₃]PF₆ ·0.5MeOH (II) showed that the metal atoms are five-coordinated and that the structures are also stabilized by a triple intramolecular hydrogen-bond system. The resulting unusual stability of the [Cu(phdpa)Cl]⁺ moiety influences the exchange properties with PF₆^- of compound I, which gave complexes where the cationic group is maintained also under drastic reaction conditions.

Full text of DOI:10.1016/S0020-1693(02)01063-0

Inorganica Chimica Acta 340 (2002) 97ꢃ104
/
www.elsevier.com/locate/ica
[Cu(phdpa)Cl]ꢀ (phdpaꢁ
/
bis(2-pyridylmethyl)aniline):
a moiety of unusual stability in some 1:1 Cu(II) complexes of phdpa.
Synthesis and X-ray crystal structures of [Cu(phdpa)Cl2]
and [Cu2(phdpa)2Cl3]PF6×
/
0.5MeOH
Franco Ugozzoli a, Chiara Massera a, Anna Maria Manotti Lanfredi a,*,
Nazario Marsich b, Annamaria Camus b,*
a Dipartimento di Chimica Generale e Inorganica, Chimica Analitica, Chimica Fisica, Universita` degli Studi di Parma, Parco Area delle Scienze 17/A,
43100 Parma, Italy
b Dipartimento di Scienze Chimiche, Universita` degli Studi di Trieste, Via Giorgieri 1, 34127 Trieste, Italy
Received 30 January 2002; accepted 6 May 2002
Abstract
ꢂ
1:1 copper(II) complexes of bis(dipyridylmethyl)aniline (phdpa) of various kinds, with chloride and PF6 as anions, were
synthesized and characterized by elemental analysis, IR spectroscopy and X-ray structure crystallography. The crystal structures of
[Cu(phdpa)Cl2] (I) and [Cu2(phdpa)2Cl3]PF6×
/
0.5MeOH (II) showed that the metal atoms are five-coordinated and that the
structures are also stabilized by a triple intramolecular hydrogen-bond system. The resulting unusual stability of the
ꢂ
[Cu(phdpa)Cl]ꢀ moiety influences the exchange properties with PF6 of compound I, which gave complexes where the cationic
group is maintained also under drastic reaction conditions.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Cu(II) bis(2-pyridylmethyl)aniline complexes; X-ray structures
1. Introduction
ligands. It is of current interest to correlate the flexibility
of the model ligand and its sterical hindrance with the
geometry of the complex. The copper(II) ion, owing to
the well known ‘plasticity’ of the coordination sphere,
Polydentate ligands with nitrogen donor atoms are
largely employed in mimicking the proteic environment
of the copper in models of biological interest, in
particular of enzymes with a type 2 copper site, whose
coordination environment is provided by nitrogen
atoms of the protein, plus one or more exogeneous
forms complexes of co-ordination number 4ꢃ6, with a
/
variety of irregular geometries [1], both the anions and
the solvent playing often a vital role on the stoichio-
metry and stereochemistry of the complexes [2].
In mononuclear complexes, linear 3N tridentate
ligands with a central amine, can complex the metal
atom with one or two molecules and in the latter case
three potential geometric isomers are possible: meridio-
nal (a), trans-facial (b) and cis-facial (c)
* Corresponding authors. Fax: ꢀ
39-040-558-3903 (A.C.)
E-mail addresses: manotti@unipr.it (A.M. Manotti Lanfredi),
camus@dsch.univ.trieste.it (A. Camus).
/39-0521-905-557 (A.M.M.L.); fax:
ꢀ/
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 1 0 6 3 - 0

98
F. Ugozzoli et al. / Inorganica Chimica Acta 340 (2002) 97ꢃ104
/
While with the archetype dietylentriamine all the
known complexes, [Cu(dien)2](NO3)2 [3],
[Cu(dien)2]Br2×H2O [4], [Cu(dien)2]Cl2×H2O [5] and
picolylchloride with aniline in a two phases (water/
methylene chloride) system [12]. These complexes,
compared with those of the unsubstituted dipicolyla-
mine, show some interesting structural
/
/
[Cu(diene)2]Cl(ClO4) [5], form octahedral complexes
meridionally coordinated, when aromatic heterocycles
are present as substituents of the amine, fac- as well
mer-coordination have been observed. A popular li-
gand, the dipicolyl-amine (dipica), gave two [Cu(dipi-
ca)2](ClO4)2 isomers, one with a cis-fac and the other
with a mixed trans-fac and square-pyramidal structure,
the latter comprising discrete hexacoordinate and pen-
tacoordinate cations (the alifatic nitrogen of the biden-
tate dipica defining the axial position in the five-
coordination). The formation of the geometric isomers
depends on the solvent used and on the sequence of
addition of the reagents [6]. The [Cu(dipica)2](BF4)2
presents trans-fac hexacoordinated and pentacoordi-
nated cations within the same unit cell [7].
characteristics, confirming that also the introduction of
a substituent in a position not directly source of steric
hindrance can largely influence the formation of com-
plexes. Only 1:1 complexes were isolated with phdpa in
the presence of chloride anions; one of these was a new
kind of dimer, with an unusual single and nearly linear
chloride bridge.
The copper organizes a square pyramidal geometry
also in the complexes with dipica and other bidentate
ligand as picolinate [2] or L-phenylalaninate [8]. The
2. Experimental
dipica shows a mer-coordination to the copper ion in
the first compound and a fac-coordination in the second
one. On the contrary in the [Cu(dipica)(phen)](ClO4)2
complex [9] a distorted trigonal bipyramidal geometry is
observed, with the pyridine moieties of the dipica ligand
occupying two sites of the equatorial plane and the
amine nitrogen one of the axial sites. In another
complex with a copper/ligand ratio of 1:1, that is
[Cu(dipica)(NO3)2] [10], in which only inorganic anions
are present as supplementary ligands, the dipica bonds
in a tridentate planar conformation, where the pyridine
nitrogens occupy the axial positions and the alifatic
nitrogen lies on the basal plane of a trigonal bipyramidal
arrangement. The dipica ligand gives also the puzzling
2.1. Generalities
Reagents and solvents were used as received from
commercial sources. The picolyl chloride hydrochloride
was a technical Aldrich reagent (98%).
The visible spectra were registered on a Perkinꢃ
124 spectrophotometer, in the 370ꢃ800 nm range, in
methanol solutions. IR spectra (4000ꢃ
200 cmꢂ1) were
recorded on PerkinꢃElmer 983G and a P.E. System
2000 spectrometers as KBr pellets or as nujol mulls
between polythene plates for the far IR region. The
frequencies reported in Section 2 are relative to the main
absorptions in the 2000ꢃ
400 cmꢂ1 range. A Crison
/Elmer
/
/
/
/
structure [Cu(TPA)Cl] [Cu(dipica)Cl][ClO4]2 (TPAꢁ
/
micro CM 2200 apparatus, with temperature compensa-
tion, was used for the conductivity measurements, which
were performed on methanol solutions.
tris(pyridylmethyl)amine) [11], which contains two cop-
per(II) complexes with different ligands in a single
crystal: the cation with the dipica shows a square planar
structure, with three coordinated N atoms and the last
position occupied by the chloride.
2.2. Syntheses
Here we report on a series of Cu(II) complexes with a
dipica derivative, the N,N-bis(2-pyridylmethyl)aniline
(phdpa), a new ligand first prepared two years ago by
Hazell and coworkers by nucleophilic substitution of 2-
2.2.1. phdpa
The ligand was prepared following the method
described in the literature [12]. The off white needles

F. Ugozzoli et al. / Inorganica Chimica Acta 340 (2002) 97ꢃ
/104
99
obtained presented a m.p. 112ꢃ
/
113 8C. IR (cmꢂ1): shs,
Table 1
Crystal data and structure refinement parameters for I and II
1590 s, 1573 mw; 1505 s, 1464 s,br, 1435 m, 1418 w;
1377, 1353 ms; 1276, 1254 w; 1224 m, 1191 w; 1177 ms;
1091, 1060, 1047, 1026 w; 992 m, 968 w, 952 m; 893, 873
w; 809 w,br; 767, 758, 750 s,727 mw; 694, 667 mw; 615
mw; 546 w, 516 mw; 469 w; 408 mw. The NMR data
were in agreement with those previously reported.
I
II
Empirical formula
C
18H17Cl2CuN3
C36H34Cl3Cu2F6N6P×
1/2CH3OH
945.14
Formula weight
Diffractometer
409.80
CAD4
CAD4
˚
Wavelength (A)
1.54178 (Cu Ka) 1.54178 (Cu Ka)
Temperature (K)
Crystal system
Space group
293(2)
monoclinic
P21/n
293(2)
monoclinic
P21/n
2.2.2. [Cu(phdpa)Cl2] (I)
A solution of 0.100 g (0.59 mmol) of CuCl2×
/H2O in 3
a
ml of water was added dropwise to 0.138 g of phdpa
(0.50 mmol) dissolved in the minimum amount of
methanol. The needles deposited after some hours
were filtered off, washed with acetone and dried in
vacuo. The crystals obtained were directly suitable for
X-ray diffraction. Further product was recovered from
the concentration of the filtrate at about a third of the
original volume, for a total yield of 95.8%. Compound I
is recrystallizable unchanged from acetonitrile. IR
(cmꢂ1): 1605 s,sh, 1568 mw; 1495 s, 1477, 1463 ms,
1442, 1424 m; 1383 w; 1350 w; 1318 mw; 1284, 1280 m;
1250, 1231 w; 1182 m, 1150 w, 1130 m; 1099 m; 1052 m,
1029 m; 969, 946 w; 831, 817 w; 795 s,771 vs; 717 w; 692
s; 651 mw; 568, 546, 518 w; 464 w; 435 m.
Unit cell dimensions
˚
a (A)
˚
14.676(5)
14.127(5)
8.398(5)
90
11.668(5)
14.408(5)
23.851(5)
90
b (A)
˚
c (A)
a (8)
b (8)
g (8)
78.40(2)
90
101.75(2)
90
3
˚
V (A )
Z
1706(1)
4
3926(2)
4
1.599
Dcalc (g cmꢂ3
F(000)
)
1.596
836
1916
4.180
Linear absorption coeffi- 4.71
cient (mmꢂ1
)
2u Range (8)
4.39ꢃ/69.99
3.60ꢃ
/
65.02
Reflections measured
Unique data/restraints/
parameters
3437
3218/0/220
6587
6443/ 0/515
Compound I is insoluble in ether, acetone, toluene
and THF; sparingly soluble in acetonitrile and chloro-
form; fairly soluble in water and methanol.
Observed reflections
b
Final R indices
2977
2900
R1ꢁ0.0335,
wR2ꢁ0.0916
0.745
R1ꢁ0.0535,
wR2ꢁ0.1336
0.727
c
Goodness-of-fit
Highest peak, deepest
0.470 and ꢂ0.453 0.436 and ꢂ0.512
2.2.3. [Cu2(phpda)2Cl3]PF6×
/
0.5 MeOH (II)
hole in final difference
ꢂ3
˚
map (e A
A total of 0.100 g (0.613 mmol) of solid NH4PF6 was
added to a dark green solution obtained from 0.100 g
(0.363 mmol) of phdpa and 0.100 g (0.587 mmol) of
)
a
Unit cell dimensions were obtained by least-squares analysis of the
setting angles of 30 reflections found in a random search on the
reciprocal space.
CuCl2×/2H2O in 15 ml of methanol. Turquoise hexago-
b
4 1/2
R1ꢁS jjFojꢂjFcjj/S jFoj, wR2ꢁ[S w(Fo2ꢂFc2)2/S wFo
] .
Goodness-of-fitꢁ[S w(Fo2ꢂFc2)2/(nꢂp)]1/2, where n is the num-
ber of reflections and p the number of parameters.
nal platelets (II) of X-ray quality were obtained by
resting; afterwards a powder of the same colour
precipitated by fast concentration of the mother liquors.
Yield 82.9%. A slow recrystallization in the air of the
above product from methanol gave brilliant blue poly-
hedric crystals, with water as crystallization solvent.
After an evident loss of solvent during the first stage of
heating, the decomposition point is the same for the two
c
acetonitrile (5 ml) and the mixture was refluxed for 1 h
under stirring. The reagent complex solubilized, giving a
dark blueꢃgreen solution, while a white powder began
/
forms, which also show the same pattern in the 2000ꢃ
/
400 cmꢂ1 range of the IR spectra.
to form after a few minutes. At the end of the reaction
the white precipitate (NH4Cl; 12.5 mg; 0.24 mmol) was
filtered off, the filtrate evaporated to dryness and the
solid washed with water to remove the NH4PF6 excess.
The residue (yield 95.2%) recrystallized from acetone
IR (cmꢂ1): 1611 s,sh, 1574 w; 1495 m, 1482 mw, 1453,
1440 m; 1389, 1354, 1316 w; 1289 m; 1253 w,sh; 1165
mw; 1098 mw; 1053 mw, 1030 m; 973, 953 w; 899 w; 845
vs,br (nPF6), 776 s,761 w; 720 w, 696 m, 650 mw; 558 s
(dPF6), 423 w.
and ether gave blueꢃ/violet rods (III) and, from acet-
The complex is insoluble in ether, toluene, THF and
chloroform, soluble in acetone, methanol, acetonitrile
and hot water.
onitrile and ether, greenꢃ
changed to a blue colour in the air, with loss of
transparence.
/
blue needles, which rapidly
IR (cmꢂ1): 1613 ms, 1574 w; 1494 m, 1484 mw, 1453
m, 1443 mw; 1385 w; 1352 w; 1313 w, 1287 m; 1160 w;
1091 w, 1057 m, 1032 m; 978, 960 w; 842 vs (nPF6); 777
ms; 741, 721 w; 694 m; 651 w; 558 s (dPF6); 426 w.
2.2.4. [Cu(phdpa)Cl]PF6×
Solid NH4PF6 in large excess (0.100 g; 0.613 mmol)
was added to a suspension of I (0.100 g; 0.244 mmol) in
/
H2 O (III)

100
F. Ugozzoli et al. / Inorganica Chimica Acta 340 (2002) 97ꢃ104
/
Table 2
Characteristics of the Cu(II)(phdpa) complexes
a
Elemental analysis (%)
b
Complex
Colour
dec. p (8C)
Conductivity
(Sꢂ1 cm2 molꢂ1
)
C
H
Cu
N
[Cu(phdpa)Cl2]
green
186ꢃ
/
187 (red) 52.6
(52.75)
196.3 46.3
4.1
(4.18)
3.8
15.5
(15.51)
13.5
10.1 (10.25) 81.8
8.9 (8.89) 185.4
7.7 (7.82) 100.1
[Cu2(phdpa)2Cl3]PF6×0.5MeOH turquoise
196ꢃ
(red)
vio- 212.5ꢃ213
/
(46.39)
40.3
(40.23)
(3.85)
3.0
(3.56)
(13.68)
11.8
(11.83)
[Cu(phdpa)]Cl](PF6)×H2O
blueꢃ
let
/
/
a
The calculated data are given in brackets.
In methanol.
b
The complex is insoluble in ether, toluene, chloro-
form, sparingly soluble in water, soluble in THF and
methanol and very soluble in acetone and acetonitrile.
3. Results and discussion
3.1. Synthesis
The analytical data and some of the physicochemical
characteristics of the complexes are shown in Table 2.
The complex obtained most easily is the [Cu(phdpa)Cl2]
2.3. X-ray data collection and structure determination of
I and II
(I), the only isolated for Cu:L ratios in the range 2:11ꢃ
/
Intensity data and cell parameters were recorded at
room temperature using Cu Ka graphite monochro-
mated radiation. The unit cell parameters were obtained
by least-squares fit of 42 (I) and 31 (II) I(uxf)hkl
1:2. In methanol the chloride can be partially substituted
ꢂ
by PF6 with formation of a dimeric complex with the
same Cu:L ratio, [Cu2(phdpa)2Cl3]PF6 (II). In acetoni-
trile the NH4Cl, co-product of the substitution reaction
with NH4PF6, is less soluble than in methanol and its
precipitation shifts the substitution equilibrium a little
more to the right; exactly one chloride is substituted for
each copper, with formation of Cu(phdpa)ClPF6.ꢂAny-
way, the complete exchange of chloride with PF6 was
not achieved, also after heating at reflux for some hours
and in the presence of a large PF6 excess.
reflections in the range 305
/
u 5
/
448 (I) and 245
/
u 5348
/
(II).
The crystal data and the most relevant experimental
parameters used in the X-ray measurements and in the
crystal structure analysis are reported in Table 1. The
intensities were calculated from the analysis of the v/2u
diffraction profiles and were corrected for Lorentz and
polarization effects. The data were corrected for absorp-
tion using ABSORB [13]; maximum and minimum values
for the transmission coefficient were 1.000 and 0.819 (I)
and 1.000 and 0.219 (II).
Copper(II) complexes of 1:2 stoicheiometry were not
ꢂ
obtained in the presence of chloride or PF6 anions,
also by adding the copper salt to an excess of ligand. As
said, by using CuCl2×
/
2H2O and ligand in a 1:2 ratio, the
complexes isolated in methanol were I, or II after
Both the structures were solved by direct methods
using the SIR-92 program [14]. The E-maps revealed
almost all the non-hydrogen atoms of the complexes.
The remaining atoms were located by successive cycles
of Fourier DF maps and refined by full-matrix least-
ꢂ
addition of NH4PF6
(in the latter case some
ꢂ
(phdpa)PF6 was also recovered from the mother
liquors). In acetonitrile the addition of NH4PF6 caused
at first precipitation of NH4Cl, in equimolecular
amount with copper, then dilution with diethyl ether
gave white microcrystals of (phdpa)PF6. A further
addition of ether to the filtered solution furnished a
2
squares procedures (based on Fo ), using SHELX-97 [15]
with anisotropic atomic displacements for all non-
hydrogen atoms. For each complex the hydrogen atoms
were added to the corresponding C atoms in the ‘riding’
model and refined with isotropic atomic displacements.
mixture of crystals of various blueꢃgreen colours, which
/
seem to be the same complex Cu(phdpa)ClPF6, with
The weighting schemes used in the last cycle of refine-
(0.0761P)2ꢀ
2.3819P] where
ments were wꢁ
/
1/[s2Fo ꢀ
/
/
2
2
2
2
1
Pꢁ
/
(Fo ꢀ
/
2Fc )/3 for compound I and wꢁ
/
1/[s2Fo ꢀ
2Fc )/3 for compound II.
/
At first, in presence of copper excess, we thought to have also
(0.0981P)2] where Pꢁ
/
(Fo ꢀ
/
isolated an assumed Cu3(phdpa)2Cl6 complex, but we recognized then
that this product was [Cu(2-pirydylmethylaniline)Cl2], deriving from a
side-product due to an incomplete reaction of formation of the ligand.
The two formulae have practically the same percentual composition,
but the IR characteristics of the complex were incompatible with those
of a phdpa derivative. Diffraction studies confirmed the true nature of
the complex, wich is a monomer, with a square planar structure [18].
2
2
Molecular geometry calculations were carried out using
the PARST-97 program [16]. Drawings were made utiliz-
ing the ORTEP program in the WinGX suite [17]. All
calculations were carried out on DIGITAL Alpha
Station 255 computer.

F. Ugozzoli et al. / Inorganica Chimica Acta 340 (2002) 97ꢃ
/104
101
different solvation. On the contrary, a 1:2 complex
Cu(phdpa)2(ClO4)2 was prepared easily in methanol, by
adding copper(II) perchlorate to the ligand [18].
M(phdpa)2(ClO4)2, complexes are also known for nick-
el(II) and iron(II) [12].
In methanol I and III are 1:1 electrolytes. The
conductivity of II could apparently be that of a 2:1
electrolyte, but this high value is due, more probably, to
the following disproportion:
[Cu2(phdpa)2Cl3]PF6
ꢁ[Cu(phdpa)Cl2]ꢀCu(phdpa)ClPF6
which changes the dimeric structure of the solid II to
monomer moieties in solution, doubling the molar
concentration. This suggestion is supported by the
visible spectra (see later) and by the recover, in
approximately equimolecular amounts, of I and III in
tentative recrystallizations of the dimer from acetone.
Fig. 1. ORTEP view of the molecular [Cu(phdpa)Cl2] complex (I), with
the atomic numbering scheme (dotted lines indicate the hydrogen
bonds).
3.2. Spectroscopic studies
3.2.1. IR spectra
Table 3
The IR spectra of the above complexes in the 2000ꢃ
/
˚
400 cmꢂ1 region have mainly a function of fingerprints,
the absorption bands being too numerous for a reason-
ably correct assignment. Anyway, they confirm the ionic
character of the PF6 group and the presence in the
ligand of coordinated pyridyl rings (bending absorptions
Selected bond lengths (A) and bond angles (8) for [Cu(phdpa)Cl2] (I)
Bond lengths
Cuꢃ
Cuꢃ
Cuꢃ
Cuꢃ
Cuꢃ
N1ꢃ
N1ꢃ
/
Cl1
Cl2
N1
N2
N3
2.275(1)
2.366(1)
1.994(3)
2.212(3)
1.984(3)
1.345(5)
1.345(4)
C5ꢃ
C6ꢃ
N2ꢃ
N2ꢃ
C7ꢃ
N3ꢃ
N3ꢃ
/
C6
1.506(5)
1.477(4)
1.452(4)
1.475(4)
1.496(4)
1.356(4)
1.336(4)
/
/N2
/
/
C13
C7
/
/
in the phdpa complexes at about 775 cmꢂ1; 780ꢃ
cmꢂ1 in dipyam [19] and 775ꢃ772 cmꢂ1 in dipica [6]
complexes). The pyridyl vibration should overlap the
/770
/
/C8
/
/
C1
/
C8
/
C5
/
C12
CꢃH oop bending of the phenyl substituent: in I there is
/
Bond angles
a near absorption peak at 795 cmꢂ1 (masked probably
in II an III by the broad nPF6 band), but this is a value
very high for a monosubstituted benzene (usual absorp-
Cl1ꢃ
Cl1ꢃ
N2ꢃCuꢃ
N1ꢃCuꢃ
N1ꢃCuꢃ
N1ꢃCuꢃ
N3ꢃCuꢃ
N3ꢃCuꢃ
N3ꢃCuꢃ
N1ꢃCuꢃ
C8ꢃC7ꢃ
/
Cuꢃ
/
Cl2
123.95(4)
127.56(7)
108.47(7)
95.30(8)
94.31(8)
81.1(1)
Cuꢃ
Cuꢃ
C1ꢃ
Cuꢃ
Cuꢃ
Cuꢃ
Cuꢃ
Cuꢃ
C8ꢃ
C5ꢃ
C6ꢃ
/
N1ꢃ
N1ꢃ
N1ꢃ
N2ꢃ
N2ꢃ
N2ꢃ
N3ꢃ
N3ꢃ
N3ꢃ
C6ꢃN2
N2ꢃC7
/
C1
C5
C5
124.9(2)
116.0(2)
119.1(3)
103.8(2)
98.2(2)
/Cuꢃ
/
N2
/
/
/
/
Cl2
Cl1
Cl2
N2
Cl1
Cl2
N2
N3
N2
/
/
/
/
/
/C6
tion range 747ꢃ
Cꢃ
complexes (about 694 cmꢂ1; foreseen 701ꢃ
/
737 cmꢂ1 [20]), considering also that the
/
/
/
/C7
/
C oop frequency of the phenyl is regular for all the
/
/
/
/C13
112.0(2)
114.2(2)
126.1(2)
119.7(3)
112.3(3)
113.4(3)
/
694 cmꢂ1
/
/
96.37(8)
91.39(8)
80.0(1)
/
/C8
/
/
/
/C12
[20]).
400 cmꢂ1 region the spectral patterns of
[Cu2(phdpa)2Cl3]PF6 and [Cu(phdpa)Cl]PF6 complexes
/
/
/
/
C12
In the 200ꢃ
/
/
/
161.2(1)
109.0(3)
/
/
/
/
/
/
show only subtle differences, except for the relative peak
ꢂ
Relevant hydrogen bonds
C18ꢃ
H18ꢀ ꢀ ꢀN1
H18ꢀ ꢀ ꢀN1
C1ꢃ
H1ꢀ ꢀ ꢀCl1
H1ꢀ ꢀ ꢀCl1
C12ꢃ
H12ꢀ ꢀ ꢀCl1
H12ꢀ ꢀ ꢀCl1
C12ꢃ
H12ꢀ ꢀ ꢀCl1?
H7ꢀ ꢀ ꢀO3§
C11ꢃ
H11ꢀ ꢀ ꢀCl2ƒ
H11ꢀ ꢀ ꢀCl2ƒ
C7ꢃH7AꢃCl1§
H7Aꢀ ꢀ ꢀCl1§
heights of PF6 and ligand. The spectra of the two
compounds differ completely, however, in the far IR
field, where only the frequencies of the d(pyridyl ring)
/
3.377(5)
2.68(1)
3.370(4)
2.94(1)
3.370(4)
2.91(1)
3.529(3)
2.76(1)
3.662(4)
2.87(1)
3.627(4)
2.80(1)
C18ꢃ
C1ꢃH1ꢃ
C12ꢃ
C12ꢃ
C11ꢃ
C7ꢃH7Aꢃ
/
H18ꢃ
/
N1
132(1)
110(1)
112(1)
141(1)
144(1)
144(1)
/
/
/
Cl1
are similar (II, 423 cmꢂ1; III, 425 cmꢂ1). The n(Cuꢃ
/
N)
(weak) is tentatively assigned to 350 cmꢂ1 in II and to
Cl) frequencies possible
/
/
H12ꢃ
H12ꢃ
H11ꢃ
/
Cl1
336 cmꢂ1 in III; for the n(Cuꢃ
/
/
/
/
Cl1?
Cl2ƒ
attributions are 260 (terminal) and 196 (bridging) cmꢂ1
in II, but no suggestions at all can be advanced for III,
where many bands of similar absorption intensity are
present. In I the d-pyridyl absorption should be at 435
/
/
/
/
/
/
/
Cl1§
cmꢂ1, the n(Cuꢃ
/
N) at 324 cmꢂ1 and the Cuꢃ
/
Cl
stretchings, two in agreement with the different bonding
distances of the chlorine atoms, at 259 and 210 cmꢂ1
Symmetry codes: ? ꢂx, 1ꢂy, 2ꢂz; ƒ x, y, 1ꢀz; § 1/2ꢂx, ꢂ1/
2ꢀy, 3/2ꢂz.
.

102
F. Ugozzoli et al. / Inorganica Chimica Acta 340 (2002) 97ꢃ
/104
3.2.2. Electronic spectra
Table 4
˚
Selected bond lengths (A) and bond angles (8) for [Cu2(phd-
pa)2Cl3]PF6×0.5MeOH (II)
The visible absorption spectra of I, II and III in
methanol show the same pattern, with the maximum of
a broad band centered at 695 nm, so that complex
moieties of the same nature should be present in solution
for all the three complexes. In agreement with this result,
for theoretically equal molar concentrations of the
compounds, the molar absorptivity of [Cu2(phd-
Bond lengths
Cu1ꢃ
Cu1ꢃ
Cu1ꢃ
Cu1ꢃ
Cu1ꢃ
/
Cl1
Cl2
N1
N2
N3
2.235(2)
2.568(2)
1.995(6)
2.090(5)
1.973(6)
1.487(11)
1.492(8)
1.468(9)
1.467(9)
1.523(9)
Cu2ꢃ
Cu2ꢃ
Cu2ꢃ
Cu2ꢃ
Cu2ꢃ
C19ꢃ
C24ꢃ
/
Cl2
Cl3
N4
N5
N6
2.504(2)
2.244(2)
2.016(6)
2.086(5)
2.005(6)
1.483(11)
1.505(9)
1.472(10)
1.474(10)
1.516(9)
/
/
/
/
/
/
/
/
pa)2Cl3]PF6 (oꢁ
equal to the sum of those of the other complexes (I,
oꢁ200; III, oꢁ
140 Mꢂ1 cmꢂ1) and hence the dimeric
/
348 Mꢂ1 cmꢂ1), is approximately
C1ꢃ
C6ꢃ
N2ꢃ
N2ꢃ
C7ꢃ
/
C6
/C24
/N2
/N5
/
C13
N5ꢃ/C31
/
/
/
C7
N5ꢃ/C25
nature of II is destroyed in solution, as already
suggested by its conductivity.
/C8
C25ꢃC26
/
Bond angles
N1ꢃ
N2ꢃ
N1ꢃ
N3ꢃ
Cl2ꢃ
Cl2ꢃ
Cl2ꢃ
Cl2ꢃ
N1ꢃCu1ꢃ
N2ꢃCu1ꢃ
Cu1ꢃN1ꢃ
Cu1ꢃN2ꢃ
Cu1ꢃN2ꢃ
Cu1ꢃN2ꢃ
C6ꢃN2ꢃ
Cu1ꢃN3ꢃ
Cu1ꢃCl2ꢃ
/
Cu1ꢃ
Cu1ꢃ
Cu1ꢃ
Cu1ꢃ
Cu1ꢃ
Cu1ꢃ
Cu1ꢃ
Cu1ꢃ
/
N2
N3
Cl1
Cl1
82.4(2)
82.3(2)
96.8(2)
N4ꢃ
N5ꢃ
N4ꢃ
N6ꢃ
Cl2ꢃ
Cl2ꢃ
Cl2ꢃ
Cl2ꢃ
N4ꢃCu2ꢃ
N5ꢃCu2ꢃ
Cu2ꢃN4ꢃ
Cu2ꢃN5ꢃ
Cu2ꢃN5ꢃ
Cu2ꢃN5ꢃ
C24ꢃN5ꢃ
Cu2ꢃN6ꢃ
/
Cu2ꢃ
Cu2ꢃ
Cu2ꢃ
Cu2ꢃ
Cu2ꢃ
Cu2ꢃ
Cu2ꢃ
Cu2ꢃ
/
N5
N6
Cl3
Cl3
80.8(2)
81.1(2)
98.1(2)
3.3. X-ray diffraction structures of I and II
/
/
/
/
/
/
/
/
The structure of I consists of discrete copper(II)
neutral complexes (see Fig. 1) with the metal atom
five-coordinated to three nitrogens from the terdentate
phdpa and two chloride ions. Selected bond distances
and angles are given in Table 3. The Cuꢃ
˚
distance (2.275(1) A) is significantly shorter than the
/
/
97.5(2)
/
/
97.1(2)
/
/
Cl1
N1
N2
N3
110.45(8)
90.1(2)
97.1(2)
/
/
Cl3
N4
N5
N6
110.32(8)
91.5(2)
/
/
/
/
/
/
/
/
101.7(2)
92.4(2)
/
/
90.2(2)
/
/
/
Cl1 bond
/
/
N3
Cl1
C1
164.6(2)
152.4(2)
113.4(4)
104.0(4)
104.1(4)
112.5(4)
113.2(5)
114.7(5)
159.90(9)
/
/
N6
161.9(2)
148.0(2)
114.6(4)
103.1(4)
105.9(4)
111.3(4)
113.0(5)
115.5(5)
/
/
/
/
Cl3
C19
C24
C25
C31
˚
/
/
/
/
Cuꢃ
/
Cl2 one (2.336(1) A) and the average Cuꢃ
/Npyr bond
/
/C6
/
/
˚
lenght [1.989(3) A] is shorter than the Cuꢃ
/
Namine one
/
/C7
/
/
˚
[2.212(3) A]. The coordination geometry is intermediate
between that of a trigonal bipyramid with the pyridine
nitrogens occupying the axial sites and that of a
distorted square pyramid with the terdentate phdpa
ligand meridionally coordinated and the Cl2 atom
defining the apical position. The complex is also
stabilized by three intramolecular interactions. The N1
pyridine nitrogen is in fact involved in an intramolecular
/
/C13
/
/
/
/
C7
C8
Cu2
/
/
C25
C26
/
/
/
/
/
/
Relevant hydrogen bonds
C18ꢃ
H18ꢀ ꢀ ꢀN1
C5ꢃ
H5ꢀ ꢀ ꢀCl1
H5ꢀ ꢀ ꢀCl1
C12ꢃ
H12ꢀ ꢀ ꢀCl1
H12ꢀ ꢀ ꢀCl1
C32ꢃ
H32ꢀ ꢀ ꢀN4
H32ꢀ ꢀ ꢀN4
C23ꢃ
H23ꢀ ꢀ ꢀCl3
H23ꢀ ꢀ ꢀCl3
C30ꢃH30ꢃ
H30ꢀ ꢀ ꢀCl3
C3ꢃ
H3ꢀ ꢀ ꢀCl2?
H3ꢀ ꢀ ꢀCl2?
C3ꢃ
H3ꢀ ꢀ ꢀCl3?
H3ꢀ ꢀ ꢀCl3?
C10ꢃ
H10ꢀ ꢀ ꢀCl2ƒ
H10ꢀ ꢀ ꢀCl2ƒ
C27ꢃ
H27ꢀ ꢀ ꢀCl1ƒ
H27ꢀ ꢀ ꢀCl1ƒ
/
H18ꢀ ꢀ ꢀNl
3.335(10)
2.82(1)
C18ꢃ
C5ꢃH5ꢃ
C12ꢃH12ꢃ
C32ꢃH32ꢃ
C23ꢃH23ꢃ
C30ꢃH30ꢃ
C3ꢃH3ꢃ
C3ꢃH3ꢃ
C10ꢃ
C27ꢃ
/H18ꢃ
/N1
116(1)
119(1)
118(1)
114(1)
118(1)
118(1)
150(1)
122(1)
155(1)
156(1)
/
3.314(9)
2.76(1)
/
/Cl1
hydrogen bond with the adjacent C18ꢃH18 ortho group
/
/
3.325(10)
2.78(1)
/
/
Cl1
N4
Cl3
Cl3
of the aniline moiety, while the Cl1 acts as an acceptor
atom in two intramolecular hydrogen bonds with the
/
3.194(10)
2.70(1)
/
/
ortho C1ꢃ
/
H1 and C12ꢃH12 groups from the two
/
/
3.361(8)
2.82(1)
/
/
pyridine rings of phdpa. Two nearly coplanar pseudo
five-membered chelate rings and one pseudo six-mem-
bered chelate ring nearly orthogonal to the first two
/
/Cl3
3.327(9)
2.79(1)
/
/
/
3.827(11)
2.99(1)
/
/Cl2?
ones, are defined by these Cꢃ
intramolecular hydrogen bonds. Weak intermolecular
Cꢃ H
/
Hꢀ ꢀ ꢀCl and CꢃHꢀ ꢀ ꢀN
/
/
3.521(13)
2.94(1)
/
/Cl3?
/
Hꢀ ꢀ ꢀCl interactions, which do not include the Cꢃ
/
groups of the aniline moiety, determine the crystal
packing.
/
3.715(11)
2.85(1)
/H10ꢃ
/
Cl2ƒ
/
3.691(8)
2.82(1)
/H27ꢃ
/
Cl1ƒ
When I reacts with NH4PF6, in methanol or water,
only a partial substitution of the chloride with the PF-6 is
observed, which leads to the dimeric compound II, with
the same Cu:L ratio. The crystal structure of II consists
of [Cu2(phdpa)2Cl3]ꢀ dinuclear cationic complexes,
Symmetry codes: ? 1ꢂx, 1ꢂy, 1ꢂz; ƒ 1/2ꢂx, ꢂ1/2ꢀy, 1/2ꢂz.
˚
Npyr bond lengths, of 1.984(6) and 2.011(6) A around
Cu1 and Cu2, respectively, are almost similar to the
ꢂ
PF6 anions and methanol of crystallization. Selected
bond distances and angles are given in Table 4. In the
dinuclear complex (see Fig. 2) each copper(II) ion is five-
coordinated to three nitrogens from the terdentate
phdpa and two chlorides in a distorted square pyramidal
environment: the plane is defined by the nitrogens from
relative Cuꢃ
/
Namine bond distances of 2.090(5) and
˚
2.086(5) A] and by the more strongly bonded Cl1 and
˚
Cl3 chlorides [2.235(2) and 2.244(2) A]. The apical
position of both square pyramids is occupied by the
Cl2 chlorine atom which thus acts as an unusual single
the meridionally coordinated phdpa [the average Cuꢃ
/

F. Ugozzoli et al. / Inorganica Chimica Acta 340 (2002) 97ꢃ
/104
103
Also the impossibility of obtaining copper(II) com-
plexes with Cu:L ratio 1:2 in the presence of chloride
ions seems due to the stability of the [Cu(phdpa)Cl]
moiety, which could prevent the binding of a second
tridentate phdpa ligand.
An unusual aspect of II concerns the single and nearly
linear chloride bridge between two copper atoms. To
our knowledge the only other dimeric copper complexes
with a single chloride bridge are: [Cu2(tet b)2Cl]3ꢀ
(tetbꢁ
clodecane) [21], which contains a tetra-amino macro-
cyclic ligand, (py2ꢁbis(2-(2-
[Cu2(py2)2Cl3]ꢀ
pyridyl)ethylamine) [22] containing a nitrogen tridentate
ligand similar to dipica and [Cu2(bzpy)2Cl3]ꢀ (bzpyꢁ
benzyl(2-pyridylmethyl)amine) [23], with a N3 tridentate
ligating group similar to phdpa. Of these three com-
pounds only the latter shows two crystallographically
/
5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacy-
/
Fig. 2. ORTEP view of the [Cu2(phdpa)2Cl3]ꢀ cations in II, with the
atomic numbering scheme (dotted lines indicate the hydrogen bonds).
/
and nearly linear chloride bridge: the Cu1ꢃ
Cu2ꢃCl2 bond distances are 2.568(2) and 2.504(2) A,
respectively, and the Cu1ꢃCl2ꢃCu2 bond angle is
/Cl2 and
˚
/
independent copper(II) ions [Cuꢃ
/
Clꢁ
136.9(1)8], while, in the first
two, the metals are related by a twofold axis passing
/
2.639(1) and
˚
/
/
2.695(1) A, Cuꢃ
/
Clꢃ
/
Cuꢁ
/
159.9(1)8. The coordination sphere around each copper
ion in II is quite similar to that observed in I. In fact one
pyridine nitrogen (N1 and N4) is involved in an
˚
through the chloride bridge (Cuꢃ
ClꢃCuꢁ
174.2(6)8 for [Cu2(tet b)2Cl]3ꢀ and Cuꢃ
2.549 A, Cuꢃ
/
Clꢁ
/
2.501(4) A, Cuꢃ
Clꢁ
178.0(1)8 for [Cu2(py2)2Cl3]ꢀ).
/
/
/
/
/
˚
intramolecular Cꢃ
jacent ortho CꢃH group from the aniline moiety (C18ꢃ
H18 and C32ꢃH32) and each equatorial chloride atom
(Cl1 and Cl3) acts as a two hydrogen bonds acceptor
with respect to a pair of ortho CꢃH groups from
pyridine rings (C5ꢃH5, C12ꢃH12 and C23ꢃH23,
C30ꢃH30). Moreover the mutual arrangement of the
/
Hꢀ ꢀ ꢀN hydrogen bond with an ad-
/
Clꢃ
/
Cuꢁ
/
/
/
/
4. Supplementary material
/
/
/
/
Crystallographic data (excluding structure factors) for
the structural analysis have been deposited with the
Cambridge Crystallographic Data Centre, CCDC Nos.
176390 (I) and 176391 (II). Copies of this information
may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
/
coplanar pseudo five-membered and of the pseudo six-
membered chelate rings is very similar to that found in I.
Thus, complex II can be considered as formed by two
square pyramidal complexes of type I, related by a
pseudo twofold axis passing through the bridging Cl2
atom at the apical positions. In II the electrostatic
interactions between cationic complexes and anions
predominate over the weak intermolecular Cl interac-
(fax:
ac.uk or www: http://www.ccdc.cam.ac.uk).
ꢀ44-1223-336-033; e-mail: deposit@ccdc.cam.
/
tions with the adjacent CꢃH groups of the pyridine
/
Acknowledgements
rings, making the ionic bond the driving force for the
crystal packing.
The triple intramolecular hydrogen-bond system
around each metal atom in I and II, although weak,
represents the most striking feature of the structure of
these compounds. This hydrogen bonding seems to play
This work was supported by the Italian MURST. We
thank Mr. P. de Baseggio for running the IR spectra and
Dr. E. Cebulec for the elemental analyses.
a
key role in determining the stability of the
References
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