Structure, Stability, and Redox Properties of Mn
II
, Fe
II
, Co
II
, and Co
III
Complexes with
1,3,5-Triamino-1,3,5-trideoxy-cis-inositol
1
Michele Ghisletta,
2a
Lorenza Hausherr-Primo,
2a
Krisztina Gajda-Schrantz,
2b
Ga ´ bor Machula,
2c
La ´ szlo ´ Nagy,
2b
Helmut W. Schmalle,
2d
Greti Rihs,
2e
Frank Endres,
2f
and
Kaspar Hegetschweiler*
,2f
Laboratorium fu ¨r Anorganische Chemie, ETH Zentrum, CH-8092 Zu ¨rich, Switzerland,
Anorganisch-Chemisches Institut der Universita ¨t Zu ¨rich, Winterthurerstrasse 190,
CH-8057 Zu ¨rich, Switzerland, Department of Inorganic and Analytical Chemistry, Attila Jo ´zsef
University, 6701 Szeged, P.O. Box 440, Hungary, Bioinorganic Chemistry Research Group, Hungarian
Academy of Sciences, 6701 Szeged, P.O. Box 440, Hungary, Novartis Pharma AG,
CH-4002 Basel, Switzerland, and Universita ¨t des Saarlandes, Fachrichtung Anorganische Chemie,
Postfach 15 11 50, D-66041 Saarbru ¨cken, Germany
ReceiVed September 30, 1997
The interaction of Mn
II
, Fe
II
, and Co
II
with the ligand taci ()1,3,5-triamino-1,3,5-trideoxy-cis-inositol) was studied
in the solid state and in aqueous solution. Magnetic susceptibility measurements revealed a high-spin electron
configuration for the Mn and the Fe complexes. Crystal data: [Mn(taci)
2
](NO
3
)
2
‚2H
2
O(1), C
12
H
34
MnN
8
O
14
,
monoclinic, space group P2
1
/c, a ) 7.107(5) Å, b ) 8.742(2) Å, c ) 18.527(6) Å, ) 100.20(4)°, Z ) 2;
[Fe(taci)
2
]Cl
2
‚6H
2
O(2), C
12
Cl
2
FeH
42
N
6
O
12
, monoclinic, space group C2/m, a ) 11.420(2) Å, b ) 9.300(2) Å, c
) 13.330(3) Å, ) 111.97(3)°, Z ) 2; [Co(taci)
2
](NO
3
)
2
‚1.5H
2
O(3), C
12
CoH
33
N
8
O
13.5
, monoclinic, space group
P2
1
/c, a ) 7.081(1) Å, b ) 8.743(1) Å, c ) 18.181(2) Å, ) 99.49(1)°, Z ) 2. All three structures exhibited
distorted octahedral MN
6
coordination. The stability constants for the complexes [M(taci)]
2+
(M ) Mn, Fe, Co)
and [M(taci)
2
]
2+
(M ) Fe, Co) in aqueous media have been evaluated by potentiometric titration. Comparison
with other divalent cations showed that the order of stability increases Mn
II
< Cd
II
≈ Fe
II
< Zn
II
< Co
II
< Cu
II
< Ni
II
. In alkaline aqueous media, the complexes 1-3 are readily oxidized by dioxygen. The redox properties
were analyzed by a series of polarographic and cyclic voltammetric measurements. A new isomeric form of a
bis-taci Co
III
complex was formed, where one of the taci ligands coordinates the metal cation by one nitrogen and
two oxygen atoms. The complex was isolated in crystalline form as [Co(taci)(Htaci)](NO
3
)
4
‚0.5H
2
O(4), C
12
-
CoH
32
N
10
O
18.5
, monoclinic, space group C2/c, a ) 30.541(3) Å, b ) 9.015(1) Å, c ) 17.852(2) Å, ) 95.63-
(1)°, Z ) 8. [Co(tach)(H
2
O)
x
(NO
3
)
3-x
]
x+
(tach ) all-cis-1,3,5-triaminocyclohexane, 0 e x e 3) was used as a
model to demonstrate that, for Co
III
, the substitution of the three monodentate coligands by a taci molecule resulted
generally in an asymmetric binding. An N,O,O and an N,N,O coordination mode were observed for [Co(taci)-
(tach)](NO
3
)
3
‚3H
2
O(5), and [Co(H
-1
taci)(tach)](NO
3
)
2
‚(3 - x)H
2
O‚xMeOH, 0.2 e x e 0.5 (6), respectively.
Crystal data: 5 (C
12
CoH
36
N
9
O
15
), monoclinic, P2
1
/n, a ) 8.942(5) Å, b ) 30.07(3) Å, c ) 9.354(5) Å, )
109.25(4)°, Z ) 4; 6 (x ≈ 0.2, C
12.2
CoH
35.4
N
8
O
12
), monoclinic, P2
1
/n, a ) 7.337(2) Å, b ) 19.847(4) Å, c )
15.226(3) Å, ) 93.59(3)°, Z ) 4.
Introduction
In previous contributions of this series, we described some
of the unique metal binding properties of 1,3,5-triamino-1,3,5-
trideoxy-cis-inositol (taci),
3-6
which are based on the ability of
this ligand to bind a metal center either using oxygen or nitrogen
donors (Chart 1). Ni
II
, Cu
II
, Zn
II
, and Cd
II
are all coordinated
exclusively to the nitrogen donors, whereas the alkaline earth
metal cations Mg
2+
-Ba
2+
bind to the neutral oxygen donors.
3,6
For Al
III
, coordination to deprotonated oxygen atoms (zwitter-
ionic form with protonated nitrogen donors) was found.
5
The
marked preference of the late divalent transition metal cations
for nitrogen donors is well established, and the observed
coordination mode is thus not unexpected.
7
It seems, however,
that, in the case of Mn
II
and Fe
II
, binding to a negative oxygen
donor is preferred, as exemplified by the substitution of a
coordinated amino polycarboxylate by the corresponding
polyamine (eq 1, where nta ) nitrilotriacetate and tren ) tris-
(2-aminoethyl)amine). For this system, the following log K
* To whom correspondence should be addressed.
(1) (a) Dedicated to Professor Paul Saltman on the occasion of his 70th
birthday. (b) 1,3,5-Triamino-1,3,5-trideoxy-cis-inositol, a Ligand with
a Remarkable Versatility for Metal Ions. 8. Part 7: see ref 28.
(2) (a) ETH Zu ¨rich. (b) Attila Jo ´zsef University (c) Hungarian Academy
of Sciences. (d) Universita ¨t Zu ¨rich. (e) Novartis AG. (f) Universita ¨t
des Saarlandes.
(3) Hegetschweiler, K.; Gramlich, V.; Ghisletta, M.; Samaras, H. Inorg.
Chem. 1992, 31, 2341.
(4) Ghisletta, M.; Jalett, H.-P.; Gerfin, T.; Gramlich, V.; Hegetschweiler,
K. HelV. Chim. Acta 1992, 75, 2233.
(5) Hegetschweiler, K.; Ghisletta, M.; Fa ¨ssler, T. F.; Nesper, R.; Schmalle,
H. W.; Rihs, G. Inorg. Chem. 1993, 32, 2032.
(6) Hegetschweiler, K.; Hancock, R. D.; Ghisletta, M.; Kradolfer, T.;
Gramlich, V.; Schmalle, H. W. Inorg. Chem. 1993, 32, 5273.
(7) (a) Mulla, F.; Marsicano, F.; Nakani, B. S.; Hancock, R. D. Inorg.
Chem. 1985, 24, 3076. (b) Hancock, R. D.; Martell, A. E. Chem. ReV.
1989, 89, 1875.
[M(nta)]
-
+ tren h [M(tren)]
2+
+ nta
3-
(1)
997 Inorg. Chem. 1998, 37, 997-1008
S0020-1669(97)01242-1 CCC: $15.00 © 1998 American Chemical Society
Published on Web 02/19/1998