Study of the aqueous reactions of metallic ions with benzenetetracarboxylate ions: Part 1. Crystal structures of compounds of the types [M(H2O)6][C6H2(COO)2(COOH)2] (M = Mn, Co and Ni) and Ni(H2O)5(μ-C6H2(COO)4)Ni(H2O)5·6H2O

Article abstract of DOI:10.1016/S0020-1693(00)00086-4

The reactions of several divalent transition metals with 1,2,4,5-benzenetetracarboxylate ions were studied in aqueous solution. Mn(II), Co(II) and Ni(II) produced ionic products of formula [M(H₂O)₆][C₆H₂(COO)₂(COOH)₂]. The three compounds were characterized by crystallographic methods. The results have shown that the three crystals are isostructural and that they belong to the monoclinic C2/c space group. The metal atom and two O atoms (from two aqua ligands) are located on a two-fold axis, while the other four aqua ligands are located in general positions. The anions contain an inversion center. The two hydrogens on the carboxylic functions form intramolecular H bonds with the carboxylate groups. The average M-OH₂ bond distances are 2.181(1) ? for Mn(II), 2.092(1) ? for Co(II) and 2.056(1) ? for Ni(II). The ions are linked together by extensive H bonds. With the Ni salt, a dinuclear species, containing a bridging benzenetetracarboxylato ligand was synthesized and characterized by X-ray diffraction. The compound Ni(H₂O)₅(μ-C₆H₂(COO)₄)Ni(H₂O)₅·6H₂O contains an inversion center in the center of the phenyl ring. The average Ni-OH₂ distance is 2.0710(8) ? and the sixth Ni-O bond is 2.0356(7) ?. The Ni···Ni distance is 11.360(2) ?. The crystal is stabilized by a very elaborate H-bonding system forming a H-bonded three-dimensional network. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(00)00086-4

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 304 (2000) 190–198
Study of the aqueous reactions of metallic ions with
benzenetetracarboxylate ions
Part 1. Crystal structures of compounds of the types
[M(H2O)6][C6H2(COO)2(COOH)2] (M=Mn, Co and Ni) and
Ni(H2O)5(m-C6H2(COO)4)Ni(H2O)5·6H2O
Fernande D. Rochon *, Gassan Massarweh
Uni6ersite´ du Que´bec a` Montre´al, De´partement de chimie, C.P. 8888, Succ. Centre-6ille, Montre´al, Que´bec, Canada, H3P 3P8
Received 5 August 1999; accepted 7 February 2000
Abstract
The reactions of several divalent transition metals with 1,2,4,5-benzenetetracarboxylate ions were studied in aqueous solution.
Mn(II), Co(II) and Ni(II) produced ionic products of formula [M(H2O)6][C6H2(COO)2(COOH)2]. The three compounds were
characterized by crystallographic methods. The results have shown that the three crystals are isostructural and that they belong
to the monoclinic C2/c space group. The metal atom and two O atoms (from two aqua ligands) are located on a two-fold axis,
while the other four aqua ligands are located in general positions. The anions contain an inversion center. The two hydrogens on
the carboxylic functions form intramolecular H bonds with the carboxylate groups. The average MꢀOH2 bond distances are
,
,
,
2.181(1) A for Mn(II), 2.092(1) A for Co(II) and 2.056(1) A for Ni(II). The ions are linked together by extensive H bonds. With
the Ni salt, a dinuclear species, containing a bridging benzenetetracarboxylato ligand was synthesized and characterized by X-ray
diffraction. The compound Ni(H2O)5(m-C6H2(COO)4)Ni(H2O)5·6H2O contains an inversion center in the center of the phenyl ring.
,
,
,
The average NiꢀOH2 distance is 2.0710(8) A and the sixth NiꢀO bond is 2.0356(7) A. The Ni···Ni distance is 11.360(2) A. The
crystal is stabilized by a very elaborate H-bonding system forming a H-bonded three-dimensional network. © 2000 Elsevier
Science S.A. All rights reserved.
Keywords: Crystal structures; Nickel complexes; Cobalt complexes; Manganese complexes; Benzenetetracarboxylate complexes
Since the report that mixed-valent complexes of te-
tradentate ligands with delocalized electrons were good
1. Introduction
conductors [1], the coordination chemistry of aromatic
The study and design of multi-dimensional infinite
polycarboxylate transition metal complexes has re-
networks of metal complexes is of current interest in
ceived considerable attention. Besides the conducting
inorganic chemistry as well as in materials science. In
properties of such materials, the increasing interest in
recent years, the synthetic efforts have been particularly
these compounds is mainly due to: (i) the bioinorganic
directed towards the preparation of molecular-based
chemical applications of some oligonuclear carboxy-
magnetic materials, conducting compounds with ex-
lato-bridged complexes, which play an important role
tended structures and of materials with zeolite-like
in metallic active sites [2]; (ii) the study of long-range
structures.
magnetic interactions through extended bridging units
,
with separations of 5–12 A between the magnetic cen-
ters [3]; and (iii) the numerous industrial applications
[4] of such compounds in several fields, such as in metal
and leather surface coatings, as catalysts, to increase
the heat resistance of polymers, as antistatic agents for
* Corresponding author. Tel.: +1-514-987 3000 ext. 4896; fax:
+1-514-987 4054.
E-mail address: rochon.fernande@uqam.ca (F.D. Rochon)
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(00)00086-4

F.D. Rochon, G. Massarweh / Inorganica Chimica Acta 304 (2000) 190–198
191
2. Experimental
textile finishing and also in the detergent and dye
industries.
2.1. Synthesis
We have recently started a research program on the
synthesis of homo- and heteropolymetallic systems
bridged by the benzenetetracarboxylate (or pyromelli-
tato) anion, in order to study the factors that determine
the coordination mode of this ligand. Furthermore, this
type of compound is of interest for the study of long-
range magnetic interaction. This ligand has a very
versatile coordination behavior, since it can form
bridges between metallic centers, generating various
and sometimes surprising molecular architectures. Py-
romellitato complexes have been reported with several
transition metals [5–17]. In some of these compounds,
the carboxylato ligand is capable of forming one-, two-,
or three-dimensional networks, where the metal centers
are coordinated by two to four carboxylato groups. In
the latter compounds, four types of coordination were
observed: (a) the carboxylato group on the ligand is
monodentate; (b) one carboxylate group of the ligand
forms a four-membered chelate ring with the metal
center; (c) the ligand bridges two different metals; and
(d) two different carboxylate groups form a seven-mem-
bered chelate with the metal center. The most common
coordination is of type (a). The acid form of the ligand
contains four H protons, which can be deprotonated in
various degrees. The most common are the [Ph-
(COO)4]4− and the [Ph(COO)2(COOH)2]2− anions.
In an attempt to prepare heteropolynuclear com-
pounds, we have studied the reaction between the ben-
zenetetracarboxylate salt of Ba with several
transition-metal(II) sulfates. This strategy has been suc-
cessful with the oxalate ligand. We were not able to
obtain BaꢀM compounds, but one of the products with
Mn(II), Co(II) and Ni(II) gave crystals which were
characterized by crystallographic methods. These crys-
tals were not stable in air. Two types of compounds
were obtained. The first type is the simple ionic hex-
aaqua complex, which was prepared with the three
metal salts. The second type is a dinuclear species and
the crystal structure of the Ni(II) compound was deter-
mined. To our knowledge, the latter is a new type of
compound, which should help researchers to better
understand the aqueous chemistry of the reactions of
transition metals with the benzenetetracarboxylate ions.
The crystal structures of the Co(II) [4] and Ni(II) [11]
ionic hexaaqua compounds have already been reported
(prepared by a different method), but our results have
shown a different crystallographic polymorph. Re-
cently, the crystal structure of Na2[Co(H2O)6]-
[Ph(COO)2(COOH)2]2·4H2O was also reported [12]. Im-
portant differences were observed between our results
and these three published structures and they will be
discussed below.
2.1.1. [M(H2O)6][C6H2(COO)2(COOH)2] (M=Ni, Mn
and Co)
A 20 ml aqueous solution containing 0.79 mmol of
barium chloride was added to a 50 ml aqueous solution
containing 0.39 mmol of C6H2(COOH)4 and 1.6 mmol
of KOH. Almost immediately, a white powder started
to precipitate. The suspension was stirred at room
temperature (r.t.) for 2 h. An aqueous solution contain-
ing 0.39 mmol of MSO4 was then added to the mixture,
which was heated to 80°C for a few minutes. The
mixture was stirred at r.t. for 15 h and filtered. About
5 ml of DMF was added to the filtrate. Single crystals
adequate for X-ray diffraction studies were obtained by
slow concentration of the solution. The final product
was not pure, since it contained KCl. The crystals were
isolated before the solution became dry. These crystals
are not stable and must be handled immediately after
their removal from the mother liquor.
2.1.2. Barium 1,2,4,5-benzenetetracarboxylate
A 50 ml aqueous solution containing 3.9 mmol of
barium chloride was added to a 30 ml aqueous solution
containing 1.9 mmol of C6H2(COOH)4 and 7.8 mmol of
KOH. After 1 min, a white powder started to separate.
The precipitate was filtered after 1 h and washed with
water and dried. Yield: 90% (assuming a formula simi-
lar to the Ca(II) compound, Ca2(C6H2(COO)4)·6H2O
[18]).
2.1.3. Ni(H2O)5(v-C6H2(COO)4)Ni(H2O)5)·6H2O
NiSO4 (0.16 mmol) was added to a suspension of
0.16 mmol barium 1,2,4,5-benzenetetracarboxylate in
30 ml of water. The mixture was stirred at r.t. for 15 h
and then filtered. A few ml of DMF was added to the
clear red solution, which was slowly concentrated over
a period of 14 days. Green single crystals adequate for
X-ray diffractions studies were finally obtained. These
crystals are not stable and must be handled immedi-
ately after their removal from the mother liquor.
2.2. Crystallographic measurements and structure
resolution
The crystals were selected after examination under a
polarizing microscope for homogeneity. The data col-
lections were made at r.t. on a Siemens P4 diffractome-
ter with graphite-monochromatized Mo Ka radiation.
The XSCANS program [19] was used for centering the
crystal, the data collections and the reducing process.
The unit cell parameters were obtained by least-squares
refinement of the angles 2q, ꢀ and  for about 40
well-centered reflections. The coordinates of the metal

192
F.D. Rochon, G. Massarweh / Inorganica Chimica Acta 304 (2000) 190–198
atoms were determined from direct methods and the
positions of all the other atoms were found by the usual
Fourier methods. The hydrogen atoms were refined
isotropically. The refinement of the structure was car-
ried out on F2 by full-matrix least-squares analysis. The
calculations were carried out using a SHELXTL system
[20]. The crystallographic data and other pertinent in-
formation are summarized in Table 1.
zenetetracarboxylic acid with barium chloride and
KOH. The metal sulfate salt was then added and
BaSO4 precipitated almost immediately. The next day,
the precipitate was filtered out and the compound was
obtained by slow concentration of the filtrate. Crystals
adequate for X-ray diffraction studies were obtained by
recrystallization in a water–DMF solution. These crys-
tals are not very stable and must be handled rapidly
before decomposition. They were embedded in glue for
the crystallographic studies, which were carried out
quite rapidly.
3. Results and discussion
The results of the X-ray diffraction studies have
shown that the three compounds are isostructural. They
3.1. [M(H2O)6][C6H2(COO)2(COOH)2] where M=Mn
(1), Co (2) and Ni (3)
were
identified
as
the
ionic
compounds
[M(H2O)6][Ph(COO)2(COOH)2]. The crystal structure
of the cobalt (2) and the Ni (3) compounds have
already been reported (prepared by a different method)
[4,11], but the authors found a different unit cell (P2/m
space group with Z=1). We have found a C2/c cell
with Z=4. We have tried to convert one cell into the
other, without success. It seems therefore that they are
different polymorphs of the same compounds. Interest-
ingly, our structures of the Co(II) (2) and Ni(II) (3)
complexes are isomorphous with the analogous Mn(II)
(1) compound. In the published structures, the metal
atom is located on a two-fold axis and on the mirror
(2/m), with one pair of O atoms (aqua ligands) located
on the two-fold axis and the other two pairs of O atoms
With a view to synthesizing bimetallic compounds,
we have studied the reactions of barium 1,2,4,5-ben-
zenetetracarboxylate with metal(II) sulfate.
Ba2(Ph(COO)4)+MSO4“BaM(Ph(COO)4)+BaSO4¡
We have studied this reaction with several transition
metals, but we have not succeeded in preparing such
bimetallic materials. The reactions with Mn(II), Co(II)
and Ni(II) sulfates gave unstable crystals, which were
eventually studied by crystallographic methods. The
three metal ions have shown similar behaviors and gave
analogous products. A deprotonated carboxylato solu-
tion was first prepared by the reaction of 1,2,4,5-ben-
Table 1
Summary of the crystallographic data
Crystal
1
2
3
4
Empirical formula
Formula weight
Color
Crystalline system
Space group
C10H16MnO14
415.2
colorless
monoclinic
C2/c
C10H16CoO14
419.2
red
monoclinic
C2/c
C10H16NiO14
418.9
green
monoclinic
C2/c
C10H34Ni2O24
655.79
green
monoclinic
C2/c
Unit cell dimensions
,
a (A)
22.254(7)
9.819(2)
7.406(1)
105.60(1)
1558.7(7)
4
21.939(7)
9.777(3)
7.276(2)
105.36(2)
1505.0(8)
4
21.887(6)
9.736(3)
7.247(1)
105.39(1)
1488.9(6)
4
17.845(7)
7.440(2)
19.064(5)
91.94(2)
2529.6(14)
4
,
b (A)
,
c (A)
i (°)
V (A )
3
,
Z
F(000)
852
1.769
0.924
2321
860
1.850
1.220
2243
2195 (0.0461)
2052
0.0410
0.1055
864
1.869
1.384
2216
2169 (0.0294)
1733
0.0379
0.0945
1368
1.722
1.590
3793
3685 (0.0505)
3287
0.0335
0.0789
zcalc. (Mg m−3
)
v(Mo Ka) (mm−1
Number of measured reflections
Number of ind. reflections (Rint
)
)
2271 (0.0651)
Number of observed reflections I\2|(I) 2000
R1 (I\2|(I)) a
wR2 (all data) a
w−1
0.0326
0.0759
|2F2+(0.01P)2+3P
|2F2+(0.07P)2+0.9P |2F2+(0.04P)2+0.7P |2F2+(0.02P)2+6P
1.06
294(1)
a
Goodness-of-fit on F2
Temperature (K)
1.03
294(1)
1.05
294(1)
1.038
293(1)
a R1=S(ꢀFo−Fcꢀ)/SꢀFoꢀ, wR2=[S(w(Fo2−Fc2)2)/S(w(Fo2)2)]1/2, P=(Fo2+2Fc2)/3.

F.D. Rochon, G. Massarweh / Inorganica Chimica Acta 304 (2000) 190–198
Table 2 (Continued)
193
Table 2
Selected bond distances (A) and bond angles (°)
,
O(3)ꢀNiꢀO(5)
O(4)ꢀNiꢀO(5)
O(5)ꢀNiꢀO(6)
O(1)ꢀC(1)ꢀO(7)
O(1)ꢀC(1)ꢀC(2)
O(8)ꢀC(5)ꢀC(3)
C(1)ꢀC(2)ꢀC(3)
C(2)ꢀC(3)ꢀC(4)
C(3)ꢀC(2)ꢀC(4A)
C(4)ꢀC(3)ꢀC(5)
90.86(3)
178.46(3)
90.62(3)
125.85(7)
115.35(6)
119.16(7)
122.11(6)
119.21(6)
119.75(7)
118.98(6)
O(3)ꢀNiꢀO(6)
O(4)ꢀNiꢀO(6)
NiꢀO(1)ꢀC(1)
O(8)ꢀC(5)ꢀO(9)
O(7)ꢀC(1)ꢀC(2)
O(9)ꢀC(5)ꢀC(3)
C(1)ꢀC(2)ꢀC(4A) 118.08(6)
C(3)ꢀC(4)ꢀC(2A) 121.05(6)
C(2)ꢀC(3)ꢀC(5)
NiꢀOꢀH (ave.)
HꢀOwꢀH (ave.)
91.06(3)
88.57(3)
128.33(5)
124.50(7)
118.76(7)
116.33(7)
Mn (1)
Co (2)
Ni (3)
[M(H2O)6][C6H2(COO)2(COOH)2]
MꢀO(1)
MꢀO(2)
MꢀO(3)
MꢀO(4)
2.192(1)
2.134(1)
2.223(1)
2.156(1)
1.274(1)
1.237(1)
1.236(1)
1.286(1)
1.393(1)
1.522(1)
1.412(1)
1.396(1)
1.512(1)
0.82(2)
2.124(1)
2.063(1)
2.109(1)
2.072(1)
1.276(1)
1.232(1)
1.233(1)
1.285(1)
1.393(1)
1.521(1)
1.411(1)
1.394(1)
1.513(1)
0.83(2)
2.074(2)
2.028(2)
2.076(1)
2.042(1)
1.279(2)
1.232(2)
1.228(1)
1.284(2)
1.390(2)
1.520(2)
1.411(2)
1.392(2)
1.515(2)
0.82(2)
121.77(6)
112(2)
106(2)
O(5)ꢀC(4)
O(6)ꢀC(4)
O(7)ꢀC(5)
O(8)ꢀC(5)
C(1)ꢀC(2)
C(1)ꢀC(4)
C(1)ꢀC(3A)
C(2)ꢀC(3)
C(3)ꢀC(5)
OwꢀH (ave.)
O(8)ꢀH(8)
O(8)···O(5A)
HꢀOꢀH (aqua, ave.) 107(2)
in the mirror plane. In our structure, the metal atom
and one pair of O (aqua ligands) atoms are located on
a two-fold axis, while the other aqua ligands are on
general positions.
1.03(2)
2.419(1)
1.20(2)
2.408(1)
0.93(2)
2.416(2)
O(1)ꢀMꢀO(2)
O(1)ꢀMꢀO(3)
O(2)ꢀMꢀO(3)
O(1)ꢀMꢀO(4)
O(2)ꢀMꢀO(4)
O(3)ꢀMꢀO(4)
180.0
180.0
180.0
The structure of the three crystals (1, 2, 3) consists of
discrete ionic entities. A labeled diagram of the Mn
crystal (1) is shown in Fig. 1. The same nomenclature
was used for the other two compounds. The bond
distances and angles are listed in Table 2. In the
cations, the metal atom is surrounded by six aqua
ligands, exhibiting a slightly distorted octahedral stereo-
chemistry. The distortions seem to increase with the size
of the metal atom. For example, the cis angles around
the metal centers vary between 86.24(2) and 93.76(2)°
for the larger atom (Mn), while they are between
86.92(2) and 93.08(2)° for the smallest atom (Ni) and
Co is intermediate. The same is true for the trans
angles, which vary from 172.47(2) to 180.0° for Mn and
from 173.85(2) to 180.0° for Ni.
86.24(2)
93.76(2)
92.63(2)
87.37(2)
88.41(4)
172.47(4)
91.94(4)
174.74(4)
114.86(7)
117.99(7)
127.15(8)
124.09(7)
114.42(7)
117.92(7)
127.64(7)
122.91(8)
120.97(8)
128.42(8)
118.61(8)
118.83(8)
120.16(7)
120.4(11)
108(2)
86.57(2)
93.43(2)
92.58(2)
87.42(2)
89.50(4)
173.14(3)
90.81(4)
174.85(4)
114.96(7)
117.95(7)
127.09(7)
123.84(7)
114.37(7)
118.21(7)
127.38(7)
122.94(8)
121.00(7)
118.59(8)
118.39(8)
118.75(7)
120.20(7)
120.6(11)
106(2)
86.92(2)
93.08(2)
92.72(3)
87.28(3)
90.16(4)
173.85(5)
90.13(4)
174.56(5)
114.81(9)
117.57(10)
127.62(10)
123.98(10)
114.05(10)
118.45(10)
127.47(10)
122.81(11)
121.08(11)
118.07(11)
119.05(11)
119.11(10)
119.78(10)
118(2)
O(3)ꢀMꢀO(3A)
O(4)ꢀMꢀO(3A)
O(4)ꢀMꢀO(4A)
C(2)ꢀC(1)ꢀC(4)
C(2)ꢀC(1)ꢀC(3A)
C(4)ꢀC(1)ꢀC(3A)
C(1)ꢀC(2)ꢀC(3)
C(2)ꢀC(3)ꢀC(5)
C(2)ꢀC(3)ꢀC(1A)
C(5)ꢀC(3)ꢀC(1A)
O(5)ꢀC(4)ꢀO(6)
O(7)ꢀC(5)ꢀO(8)
O(5)ꢀC(4)ꢀC(1)
O(6)ꢀC(4)ꢀC(1)
O(7)ꢀC(5)ꢀC(3)
O(8)ꢀC(5)ꢀC(3)
MꢀOꢀH (ave.)
HꢀOꢀH (ave.)
O(8)ꢀH(8)···O(5A)
C(5)ꢀO(8)ꢀH(8)
C(5)ꢀO(8)···O(5A)
C(4)ꢀO(5)···O(8A)
It is interesting to compare the MꢀOH2 bond dis-
tances as the number or electrons increases. The aver-
5
,
age values are 2.181(1) A for Mn(II) (d configuration),
109(3)
168.9(2)
109.0(5)
108.2(1)
110.0(1)
170.1(2)
108.8(5)
108.3(1)
109.9(1)
167.4(3)
112.1(8)
108.6(1)
109.9(1)
Ni(H2O)5(m-C6H2(COO)4)Ni(H2O)5·6H2O (4)
NiꢀO(1)
2.0356(7)
2.0895(7)
2.0876(8)
NiꢀO(2)
NiꢀO(4)
NiꢀO(6)
2.0687(9)
2.0760(7)
2.0333(9)
1.2463(10)
1.2595(10)
1.402(1)
NiꢀO(3)
NiꢀO(5)
O(1)ꢀC(1)
O(8)ꢀC(5)
C(1)ꢀC(2)
C(2)ꢀC(4A)
C(3)ꢀC(5)
OwꢀH (ave.)
1.2719(10) O(7)ꢀC(1)
1.2437(10) O(9)ꢀC(5)
1.509(1)
1.398(1)
1.513(1)
0.86(2)
C(2)ꢀC(3)
C(3)ꢀC(4)
OꢀH (aqua, ave.) 0.78(2)
1.399(1)
O(1)ꢀNiꢀO(2)
O(1)ꢀNiꢀO(4)
O(1)ꢀNiꢀO(6)
O(2)ꢀNiꢀO(4)
O(2)ꢀNiꢀO(6)
94.16(3)
91.20(3)
85.42(3)
92.42(3)
178.93(3)
O(1)ꢀNiꢀO(3)
O(1)ꢀNiꢀO(5)
O(2)ꢀNiꢀO(3)
O(2)ꢀNiꢀO(5)
O(3)ꢀNiꢀO(4)
176.38(2)
90.05(3)
89.37(3)
88.40(3)
87.84(3)
Fig. 1. Labeled diagram of [Mn(H2O)6][C6H2(COO)2(COOH)2] (1)
(the ellipsoids correspond to 40% probability). The same labels were
used for crystals 2 and 3.

194
F.D. Rochon, G. Massarweh / Inorganica Chimica Acta 304 (2000) 190–198
7
,
,
2.092(1) A for Co(II) (d ) and 2.056(1) A for Ni(II)
(d8), corresponding to the decrease in atomic radii of
these metals. These ions have high spin configurations,
since the aqua ligand is quite low in the spectrochemical
series. All the H atoms on the aqua ligands were
located and refined. The average bond lengths are
O(5A). The H atoms on the carboxylic groups were
found on O(8). The bond distances O(8)ꢀH are 1.03(2),
,
1.20(2) and 0.93(2) A for crystals 1, 2 and 3, respec-
tively. The angles C(5)ꢀO(8)ꢀH(8) are 109.0(5)° for 1,
108.8(5)° for 2 and 112.1(8)° for 3. This bond is in-
volved in intramolecular H-bonding with O(5A) (Fig.
1) with short O(8)···O(5A) distances of 2.419(1) (1),
,
0.82(2), 0.83(2) and 0.82(2) A with average HꢀOꢀH
angles of 108(2), 106(2) and 109(2)° for crystals 1, 2 and
3, respectively.
,
2.408(1) (2) and 2.416(2) A (3). These H bonds are
almost linear with angles O(8)ꢀH(8)···O(5A) of
168.9(2)° for 1, 170.1(2)° for 2 and 167.4(3)° for 3. The
angles C(5)ꢀO(8)···O(5A) are 108.2(1)° for 1, 108.3(1)°
for 2, and 108.6(1)° for 3. In the published structure of
the Co [4] and Ni [11] compounds, this H atom was
constrained by symmetry to be equidistant from the
two O atoms. The H atom was assumed to lie in the
mirror plane. The authors could not determine from
their crystallographic results if the H atom was pre-
cisely on the mirror, or if it was disordered around the
symmetry element. They claimed that their IR spectra
indicate (absorption band at 900 cm−1 not broad) that
the H atom is on the mirror plane and that the H bond
The anions [Ph(COO)2(COOH)2]2− contain an inver-
sion center. The mean plane was calculated throughout
the six atoms of the benzene ring. The atoms C(4) and
C(5) are also in the plane with deviations of −0.007(2)
,
and 0.037(2) A, respectively, for the Mn compound (1).
The best planes were also calculated throughout each
COO− group. The dihedral angles of these groups with
the aromatic ring are 26.3(1), 24.1(1)° for 1, 26.4(1),
24.5(1)° for 2 and 26.6(1), 24.4(1)° for 3. The dihedral
angle between the two carboxylato planes is between
35.0(1) and 35.5(1)° for the three crystals. These angles
are very different from those observed in the published
Co compound, where these dihedral angles are about
92° [4]. In the latter structure, the whole ion is planar.
These published results on the Co compound (and
probably the Ni compound [11]) are very different from
those observed for the parent acid, where the dihedral
angles are 18 and 74° [21]. Our results are also different
from those reported for Na2[Co(H2O)6][Ph(COO)2-
(COOH)2]2·4H2O [12], where the COO− groups are in
the plane of the aromatic ring. Therefore, it seems that
the conformation of the benzenetetracarboxylate
anions vary with different structures. It probably de-
pends on the H-bonding system, which will be discussed
below.
The internal angles in the phenyl ring are 117.84(8)
and 118.19(8)° for the substituted C atoms and
123.97(8)° for the unsubstituted C(2) atom. The exter-
nal angles C(5)ꢀC(3)ꢀC(1A) and C(4)ꢀC(1)ꢀC(3A) are
significantly larger than 120° (average 127.50(8) and
127.29(8)°), while the other angles C(2)ꢀC(3)ꢀC(5) and
C(2)ꢀC(1)ꢀC(4) are smaller (average 114.28(8) and
114.89(8)°, respectively). This is similar to the published
structures of the Co [4] and Ni [11] compounds, but
different from the parent acid where all the external
angles are close to 120° [21]. It is of interest to note that
the bond distances and angles in Table 2 are identical
for the three isomorphous Mn(II), Co(II) and Ni(II)
compounds, except for those involving the metal atom.
The two CꢀO bonds of each carboxylato groups are
significantly different. The average (for the three crys-
tals) C(5)ꢀO(8) bond bearing the H atom is longer
,
is truly symmetric. Their O···H distance is 1.211(7) A
,
for Co and 1.206(9) A for Ni, with very short O···O%
,
distances of 2.381(2) and 2.386(5) A, respectively [4,11].
These authors have also observed that the H atom was
displaced towards the aromatic ring, from the line
joining the two O atoms involved in the H bond. Their
angle O···H···O% was 159(2)° (for Co) and 163(6)° (for
Ni). In our structures, this H atom is not in a special
position, and for the Mn and Ni compounds, it is
,
evident, from the bond distances (O(8)ꢀH=1.03(2) A
,
(1) and 0.93(2) A (3)), that the H atom is on O(8). For
the Co compound (2), the difference is much smaller,
but there might be some disorder of this H atom in 2.
Since the three structures are isomorphous and because
of the high e.s.d. values on the distances related to the
H positions, we cannot conclude at the moment that
our Co(II) structure is different from those of Mn(II)
and Ni(II). Our results seem to indicate that the H
atom in the published structures [4,11] is not on the
,
,
(1.285(1) A) than the C(5)ꢁO(7) bond (1.232(1) A).
Surprisingly, the other carboxyl groups are almost sim-
ilar, with average bond lengths C(4)ꢀO(6)=1.234(1)
and C(4)ꢀO(5)=1.276(1) A. This is caused by the
presence of intramolecular H bonds between O(8) and
,
Fig. 2. Diagram of the packing of the ions in crystal 1 showing the
extensive H-bonding system (down c axis, b axis horizontal).

F.D. Rochon, G. Massarweh / Inorganica Chimica Acta 304 (2000) 190–198
195
mirror plane, but is disordered around the symmetry
element. The IR criterion for a symmetric H bond
remains to be proven. The recent report of the crystal
structure of Na2[Co(H2O)6][Ph(COO)2(COOH)2]2·4H2O
also contains a H atom equidistant from the two O
atoms, but the authors assumed that the H atom was
disorderedly distributed into the two positions symmet-
ric with respect to the midpoint of the O···O contact,
and that the COO− and COOH groups were indistin-
guishable [12].
A view (down the c axis) of the packing of the ions in
crystal 1 is shown in Fig. 2. The diagram shows that the
ions are held together by a very extensive hydrogen
bonding system. All the hydrogen atoms of the aqua
ligands are involved in intermolecular H bonds with the
carboxylato oxygen atoms or between themselves and
play an important stabilizing role in the crystal packing
energy. The O···O distances vary between 2.706(1) and
probably involved in H bonds for crystal 1 is shown in
Table 3. Very similar values were found for crystals 2
and 3.
3.2. Ni(H2O)5(v-C6H2(COO)4)Ni(H2O)5·6H2O (crystal
4)
A different compound was prepared by a slight mod-
ification of the method used to prepare the hexaaqua
complexes described above. The main difference lies in
the separation of the intermediate product (barium
benzenetetracarboxylate), which was not done in the
preparation of the ionic products described above.
Again, the isolated crystals are not stable and must be
handled rapidly before decomposition. They were em-
bedded in epoxy for the crystallographic studies, which
were done quite rapidly. Several crystals were studied
before a suitable set of data could be obtained with the
Ni(II) salt.
,
2.811(1) A. A list of distances and angles of atoms
Table 3
,
Distances (A) and angles (°) between atoms involved in H bonds
[Mn(H2O)6][C6H2(COO)2(COOH)2] (1)
O(1)···O(3)
2.811(1)
MnꢀO(1)···O(3)
O(3)···O(1)···O(3%)
MnꢀO(2)···O(6)
O(6)···O(2)···O(6%)
MnꢀO(3)···O(6)
MnꢀO(3)···O(7)
O(6)···O(3)···O(7)
MnꢀO(4)···O(5)
MnꢀO(4)···O(7)
O(5)···O(2)···O(7)
125.3(1)
109.6(1)
124.3(1)
111.3(1)
118.1(1)
106.3(1)
116.6(1)
116.3(1)
129.3(1)
107.8(1)
O(2)···O(6)
2.765(1)
O(3)···O(6)
O(3)···O(7)
2.724(1)
2.706(1)
O(4)···O(5)
O(4)···O(7)
2.761(1)
2.789(1)
Ni(H2O)5(m-C6H2(COO)4)Ni(H2O)5·6H2O (4)
O(2)···O(8)
2.745(1)
2.750(1)
2.785(1)
NiꢀO(2)···O(8)
125.7(1)
113.8(1)
130.7(1)
95.1(1)
127.8(1)
86.6(1)
O(3)···Ow(1)
O(3)···Ow(3)
NiꢀO(3)···Ow(1)
NiꢀO(3)···Ow(3)
Ow(1)···O(3)···Ow(3)
NiꢀO(3)···O(3%)
O(3%)···O(3)···Ow(1)
O(3%)···O(3)···Ow(3)
NiꢀO(4)···O(9)
O(3)···O(3%)
2.837(1)
91.2(1)
O(4)···O(9)
O(4)···O(4%)
2.578(1)
2.791(1)
119.6(1)
119.1(1)
90.2(1)
120.8(1)
105.0(1)
96.0(1)
114.7(1)
117.4(1)
123.7(1)
111.5(1)
95.6(1)
124.1(1)
126.9(1)
112.5(1)
117.4(1)
89.4(1)
NiꢀO(4)···O(4%)
O(9)···O(4)···O(4%)
NiꢀO(4)···Ow(1)
O(4%)···O(4)···Ow(1)
O(9)···O(4)···Ow(1)
NiꢀO(5)···Ow(2)
NiꢀO(6)···O(9)
NiꢀO(6)···Ow(2)
O(9)···O(6)···Ow(2)
O(4)ꢀOw(1)···O(8)
O(4)ꢀOw(1)···O(3)
O(3)ꢀOw(1)···O(8)
NiꢀO(1)···Ow(2)
O(5)ꢀOw(2)···O(1)
O(5)ꢀOw(2)···O(6)
O(1)ꢀOw(2)···O(6)
O(7)ꢀOw(3)···Ow(1)
O(4)···Ow(1)
2.746(1)
O(5)···Ow(2)
O(6)···O(9)
O(6)···Ow(2)
2.764(1)
2.633(1)
2.754(1)
Ow(1)···O(4)
Ow(1)···O(8)
Ow(1)···O(3)
Ow(2)···O(1)
Ow(2)···O(5)
Ow(2)···O(6)
2.746(1)
2.746(1)
2.750(1)
2.846(1)
2.746(1)
2.754(1)
108.7(1)
97.1(1)
Ow(3)···O(7)
Ow(3)···Ow(1)
Ow(2)···Ow(3)
2.790(1)
2.844(1)
2.885(1)

196
F.D. Rochon, G. Massarweh / Inorganica Chimica Acta 304 (2000) 190–198
,
NiꢀOH2 bond is 2.0710(8) A, while the NiꢀOCO seems
,
slightly shorter, 2.0356(7) A. The average NiꢀO bond in
the [Niꢀ(OH2)6]2+ ion described above (crystal 3) is
,
2.056(1) A. The bond located in trans position to the
,
NiꢀOCO bond is the longest (2.0895(7) A), but it is
difficult to evaluate at the moment whether the differ-
ence is really significant (average of four cis bonds is
,
2.0664(8) A). These bonds are also probably quite
dependent on the H-bonding system, which is very
important in this structure.
The benzenetetracarboxylato ligand is centrosymmet-
rically bonded to two Ni atoms. It is coordinated in a
bis monodentate manner. Only two O atoms of the
eight carboxylato O atoms form bonds with Ni. These
Fig. 3. Labeled diagram of Ni(H2O)5(m-C6H2(COO)4)Ni(H2O)5 in
crystal 4 (the ellipsoids correspond to 40% probability).
,
C(1)ꢀO(1) bonds are longer (1.2719(10) A) than the
other CꢀO bonds (average 1.2493(10) A) as expected.
,
The mean plane was calculated throughout the six
atoms of the benzene ring. The mean deviation is
,
0.001(1) A. The other atoms C(1) and C(5) are almost
in the plane with deviations of 0.075(1) and −0.060(1)
,
A. The best plane was also calculated through each
COO− group. The dihedral angles between these
groups and the six-membered ring are 65.79(6) and
35.76(6)°. The dihedral angle between the planes of the
two carboxylate groups is 60.21(9)°. These results indi-
cate that the carboxylato groups are not in the same
plane as the aromatic ring as observed for the com-
plexes [M(H2O)6][Ph(COO)2(COOH)2] described above,
and for the parent acid [21]. The same non-planeity was
observed in the reported values for the structure of the
dimer Ni(en)(H2O)3(m-C6H2(COO)4)Ni(en)(H2O)3·4H2O
[7], where the dihedral angles of the COO− groups with
the benzene ring are 50.8(2) and 49.2(3)°, and for
the chain compound [Co(H2O)4(C6H2(COO)4)]n[Co-
(H2O)6]n·xH2O [8,10], where these angles are 53.4(1)
and 48.4(1)°. Again, these results are different from the
results on the three published structures on Co(II)
[4,12] and Ni(II) [11], where the carboxylate groups are
in the same plane as the six-membered ring. The con-
formation of these ions or ligands is very probably
influenced by the H-bonding system. The internal an-
gles in the benzene ring in crystal 4 are slightly smaller
for the substituted C atoms (average 119.48(7)°), while
it is 121.05(6)° for the unsubstituted C(4) atom. There
is also a small difference in the external angles as
observed for crystals 1, 2 and 3 described above, but
the differences are smaller (average 118.45(6) and
121.94(6)°).
Fig. 4. Packing diagram (down b axis, c axis horizontal) of the
molecules in crystal 4.
The crystallographic results have shown that this
compound (4) is the dinuclear species Ni(H2O)5(m-
C6H2(COO)4)Ni(H2O)5. The benzenetetracarboxylato
ligand forms a bridge between two Ni(H2O)5 entities,
and the molecule contains a center of inversion in the
center of the aromatic ring. To our knowledge, this
type of compound has not been previously reported in
the literature. There are two related complexes: a
dimeric compound of formula Ni(en)(H2O)3(m-
C6H2(COO)4)Ni(en)(H2O)3·4H2O [7] and a one-dimen-
sional extended-structure material of formula
[Co(H2O)4(C6H2(COO)4)]n[Co(H2O)6]n·xH2O
[8,10].
The Ni(II) dimeric molecule crystallized with six
molecules of water located in the lattice. A labeled
diagram of the molecules in crystal 4 is shown in Fig. 3.
The bond distances and angles are listed in Table 2. All
the H atoms were located and refined.
Each Ni atom is surrounded by five aqua ligands and
one O atom from the benzenetetracarboxylato ligand,
forming a slightly distorted octahedron. The cis angles
vary from 85.42(3) to 94.16(3)°, while the trans angles
are between 176.38(3) and 178.93(3)°. The average
The presence of six molecules of water in the lattice
and the ten aqua ligands in the dinuclear molecule leads
to a very extensive and complicated H-bonding system.
All the aqua ligands and the water molecules form
strong H bonds between themselves, or with the car-
boxylato O atoms. All the O atoms (O(1), O(7), O(8)

F.D. Rochon, G. Massarweh / Inorganica Chimica Acta 304 (2000) 190–198
197
and O(9)) of the carboxylato groups act as acceptors. A
list of the most probable atoms involved in H bonds
with their related angles is shown in Table 3. The O···O
This work is being continued and some preliminary
results on Co(II) and Mn(II) salts indicate that dinu-
clear species of these elements have been synthesized.
There are still difficulties related to the preparation of
crystals suitable for crystallographic studies. We have
also carried out a few experiments on mixed-metallic
centers. We have already obtained such a compound,
which should be characterized by crystallographic
methods if suitable crystals can be obtained. Since these
crystals are not stable, special handling is required.
These results will be discussed in the second part of this
paper.
,
distances vary between 2.578(1) and 2.846(1) A. A
diagram showing the packing of the molecules in the
crystal is shown in Fig. 4. The very extensive H bonds
are present in all directions, forming a H-bonded 3D
network. In the b direction, we can see some cavities,
two of these are clearly shown in Fig. 4.
4. Conclusions
Contrary to the oxalate system, barium benzenete-
tracarboxylate is not a good precursor for the prepara-
tion of bimetallic materials. In this paper we have
illustrated the importance of the experimental condi-
tions in the preparation of metal aqua species with the
benzenetetracarboxylate ions. The preparation of a
second polymorph of the compounds [M(H2O)6]-
[Ph(COO)2(COOH)2] seems to have solved the problem
of the H atoms, which were uncertain in the published
structures of the Co(II) [4] and Ni(II) [11] compounds.
Our study has shown that the H atom forming the
intramolecular H bond is located on one O atom. The
second important difference between our results and the
published ones on the first polymorph [4,11], is in the
orientation of the carboxylato groups in relation with
the benzene ring. The conformation of the [Ph-
(COO)2(COOH)2]2− ions in crystals 1, 2 and 3 is
approximately the same as the one observed for the
bridging [Ph(COO)4]4− ligand in crystal 4, although the
dihedral angles in crystal 4 are slightly larger. The
conformation of the carboxylato groups in relation to
the aromatic ring is probably an important factor in the
packing energy in the crystal, since all these groups are
involved in the H-bonding system, which is very impor-
tant in these types of crystals.
5. Supplementary material
Lists of the CIF files for the four crystals have been
deposited at the Cambridge Structural Database
(CCDC 136957–CCDC 136960). Copies of this infor-
mation may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements
The authors are grateful to the Natural Sciences and
Engineering Research Council of Canada for financial
support of the project.
References
[1] J.T. Wrobleski, D.B. Brown, Inorg. Chem. 18 (1979) 2738.
[2] R.L. Rardin, W.B. Tollman, S.J. Lippard, New J. Chem. 15
(1991) 417.
[3] O. Kahn, Molecular Magnetism, VCH, New York, 1993.
[4] D.L. Ward, D.C. Luehrs, Acta Crystallogr., Sect. C 39 (1983)
1370.
[5] B.T. Usubaliev, A.N. Shnulin, H.S. Mamadov, Koord. Khim. 8
(1982) 1532.
[6] C. Robl, Z. Anorg. Allg. Chem. 554 (1987) 79.
[7] D. Poleti, D.R. Stojakovic, B.V. Prelesnik, R.M. Herak, Acta
Crystallogr., Sect. C 44 (1988) 242.
[8] D. Poleti, Lj. Karanovic, Acta Crystallogr., Sect. C 45 (1989)
1716.
[9] J.Z. Zou, Q. Liu, Z. Xu, X.Z. You, X.Y. Huang, Polyhedron 17
(1998) 1863.
[10] C. Robl, S. Hentschel, Mater. Res. Bull. 26 (1991) 1355.
[11] S.M. Jessen, H. Ku¨ppers, D.C. Luehrs, Z. Naturforsch., Teil B
47 (1992) 1141.
[12] L. Karanovic, D. Poleti, G.A. Bogdanovic, A. Spasojevic-de
Bire´, Acta Crystallogr., Sect. C 55 (1999) 911.
[13] W. Ge-Cheng, J. Zhong, D. Zhi-Bang, Y. Kui-Yue, N. Jia-Zan,
Jiegou Huaxue (J. Struct. Chem.) 10 (1991) 106.
[14] P. Chaudhuri, K. Oder, K. Wieghardt, S. Gehring, W. Haase, B.
Nuber, J. Weiss, J. Am. Chem. Soc. 110 (1988) 3657.
Several factors, and especially the hydrogen bonding
system play an important role in the overall crystal
architecture of such compounds. These will influence
the bulk properties of the materials, especially the
magnetic ones. The magnetic measurements on crystal
4 have not been made and they might bring interesting
results. Since the two Ni atoms in the dimer are quite
far from each other (the Ni···Ni distance is 11.360(2)
,
A), the coupling between these two Ni atoms might be
,
relatively weak. But a long distance (11.3 A) strong
antiferromagnetic coupling (J=70 cm−1) has been re-
ported for a Cu(II) dimer [14] with a similar ligand. In
our structure, there are other Ni atoms which are
nearer to each other, with distances of 6.546(1),
,
7.402(1) and 7.440(1) A. Special care must be taken for
the magnetic measurements, since these crystalline com-
pounds are not stable in air.

198
F.D. Rochon, G. Massarweh / Inorganica Chimica Acta 304 (2000) 190–198
[15] F. Jaber, F. Charbonnier, R. Faure, J. Chem. Cryst. 27 (1997)
397.
[19] XSCANS
, Version 2.2, Siemens Analytical Instruments Inc.,
Madison, WI, USA.
[16] C. Robl, Mater. Res. Bull. 27 (1992) 99.
[17] W. Chen, N.H. Tioh, J.-Z. Zou, Z. Xu, X.-Z. You, Acta
Crystallogr., Sect. C (Cr. Str. Comm.) 52 (1996) 43.
[18] C. Robl, Z. Naturforsch., Teil B 43 (1988) 993.
[20] SHELXTL
,
Version 5, Siemens Analytical Instruments Inc.
Madison, WI, USA.
[21] F. Takusagawa, K. Hirotsu, A. Shimada, Bull. Chem. Soc. Jpn.
44 (1971) 1274.
.