Synthesis and crystal structure of a chloro-bridged dinuclear germanium(IV) heterocoordinate complex with 5,14-dihydro-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine

Article abstract of DOI:10.1246/cl.2001.1326

A novel chloro-bridged dinuclear germanium(IV) complex with 5,14-dihydro-6,8,15,17-tetramethyldibenzo [b,i]-[1,4,8,11]tetraazacyclotetradecine has been synthesized and its crystal structure shows an unsymmetrical heterocoordinate dinner which has a five-coordinate square pyramid and a six-coordinate octahedron.

Full text of DOI:10.1246/cl.2001.1326

1326
Chemistry Letters 2001
Synthesis and Crystal Structure of a Chloro-Bridged Dinuclear Germanium(IV) Heterocoordinate
Complex with 5,14-Dihydro-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine
Xuan Shen, Kazunori Sakata,* and Mamoru Hashimoto
Department of Applied Chemistry, Faculty of Engineering, Kyushu Institute of Technology, Tobata-ku, Kitakyushu 804-8550
(Received September 7, 2001; CL-010879)
The Ge(tmtaa)Cl2 1 was prepared as reported earlier.11 The
reaction between 1 and 3-nitrobenzyl alcohol was carried out in
chloroform containing a small amount of triethylamine under a
nitrogen atmosphere. Red powder was collected after evaporat-
ing the reaction solution. Red crystals of [{Ge(tmtaa)}(µ-
Cl){Ge(tmtaa)Cl}](Cl)[C6H4(NO2)CH2O]·CH3CN 2 were
obtained by recrystallization from acetonitrile.12 The crystals
were air- and moisture-stable. After being put in air for about
two weeks, one single crystal was selected for X-ray crystal
structure analysis.13 The crystals contain one [{Ge(tmtaa)}(µ-
Cl){Ge(tmtaa)Cl}]2+ cation, one chloro anion (near to five-coor-
dinate unit, the nearest atom-to-atom distance to the cation is
3.46 Å), one 3-nitrobenzyloxy anion (facing to five-coordinate
Ge, the nearest atom-to-atom distance to the cation is 3.35 Å) and
one acetonitrile molecule. Figure 2 shows the crystal structure of
[{Ge(tmtaa)}(µ-Cl){Ge(tmtaa)Cl}]2+ cation.
A novel chloro-bridged dinuclear germanium(IV) complex
with 5,14-dihydro-6,8,15,17-tetramethyldibenzo[b,i]-
[1,4,8,11]tetraazacyclotetradecine has been synthesized and its
crystal structure shows an unsymmetrical heterocoordinate
dimer which has a five-coordinate square pyramid and a six-
coordinate octahedron.
5,14-Dihydro-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]-
tetraazacyclotetradecine (H2tmtaa), a versatile ligand environ-
ment for transition and main group metal chemistry, has stimu-
lated continuing interest in a wide range of chemical areas for
nearly thirty years.1 Because of its non-planar and saddle-
shaped conformation, a limited number of investigations on its
macromolecular characteristics were reported. On the other
hand, not only dimers,2 but also polymers3 of other analogous
macrocyclic ligands, porphyrin and phthalocyanine, were inves-
tigated widely due to their bigger N4 coordination cavity ‘hole
size’ and planar conformations compared with H2tmtaa.
However, several types of tmtaa dimers were studied till now.
They indicate metal–metal bonded conformation (I),4 N4
plane–metal–N4 plane octacoordinate sandwich conformation
(II)5 and metal–X–metal (X=O, S, CH2, N) bridged conforma-
tion (III)6–9 (Figure 1). Although germanium(II) complexes of
H2tmtaa were investigated,10 no further structure characteristics
relating to germanium(IV) tmtaa complexes were described in
the literature. In this paper, we describe the synthesis and struc-
tural characterization of a Ge(IV)–Cl–Ge(IV)–Cl tmtaa dimer
containing five- and six-coordinate configurations (Figure 1,
IV). Its structural characteristics inspire us to attempt to do
some investigation into macromolecule of H2tmtaa in future.
3-Nitrobenzyl alcohol was selected to react with six-coor-
dinate dichloro germanium complex 1 to form a chloro-bridged
heterocoordinate dinuclear complex 2. This is very different
from those oxidative addition reactions in which two four-coor-
dinate complexes were connected by an oxidative agent to form
Copyright © 2001 The Chemical Society of Japan

Chemistry Letters 2001
1327
a dinuclear complex.6–8
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It is very interesting that the structure of [{Ge(tmtaa)}(µ-
Cl){Ge(tmtaa)Cl}]2+ cation has no symmetry, revealing one
five- and one six-coordinate macrocyclic units. This is also dif-
ferent from O, S, CH2-bridged tmtaa dimers which have two
five-coordinate configurations and C2 symmetry, with the C2
axis passing through the bridged atoms.6–8
5
6
The distance between bridged chloro and five-coordinate
germanium (1.686(3) Å) is about 0.124 Å shorter than that
between bridged chloro and six-coordinate germanium
(1.810(3) Å). Both of them are much shorter than bond length
of six-coordinate germanium atom and the mono chloro atom
(2.433(1) Å) in the cation. Two germanium atoms are all dis-
placed from the N4 planes toward the benzenoid faces of the
saddle-shaped tmtaa ligands, as commonly observed in other
six- and five-coordinate tmtaa complexes. However, because
of the steric influence, the displacements are 0.468(2) Å in the
five-coordinate unit and 0.082(2) Å in the six-coordinate unit.
The average Ge–N bond lengths in two units are all about 1.938
Å and do not depend on coordination numbers and displace-
ments of germanium atoms from the N4 planes. This suggests
that two germanium atoms are in the same oxidation states (+4)
and that Ge dπ and N pπ orbital interaction are analogous.
Parameters characterizing the Ge(IV)–Cl–Ge(IV) bridge are of
considerable interest. The angle of Ge–Cl–Ge is 171.0(2)° and
is significantly bigger than that of other analogous tmtaa bridg-
ing configurations (155.0(8)° in Ti–O–Ti,6 142.75° in
Fe–O–Fe,6 126.3(1)° in Fe–S–Fe7 and 122.5(3)° in
Sn–CH2–Sn8). This enhances the linear configuration of the
three atoms and makes two tmtaa ligands in the complex orien-
tation at an angle of 6.534(0.110)° between the two N4 planes
which are almost parallel to each other. Furthermore, two
tmtaa ligands are rotated with respect to each other by about
90° and two groups of benzenoid rings in two tmtaa ligands are
in the face-to-face configuration, which are similar to Type I
and II dinuclear complexes.4,5 It is clear that the dimer is in the
most stable state when it adopts this configuration.
7
8
9
V. L. Goedken and J. A. Ladd, Chem. Commun., 1981,
910.
10 D. A. Atwood, V. O. Atwood, A. H. Cowley, J. L. Atwood,
and E. Roman, Inorg. Chem., 31, 3871 (1992); D. A.
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11 W. J. Belcher, P. J. Brothers, M. V. Land, C. E. F. Rickard,
and D. C. Ware, J. Chem. Soc., Dalton Trans., 1993, 2101.
12 The yield of [{Ge(tmtaa)}(µ-Cl){Ge(tmtaa)Cl}](Cl)
[C6H4(NO2)CH2O]·CH3CN is 28% (Found: C, 56.57; H,
5.00; N, 12.67%. Calcd for C53H53Cl3Ge2N10O3: C, 56.35;
H, 4.73; N, 12.40%). λmax/nm (ε/dm3mol–1cm–1 )(CHCl3)
272 (28100), 380 (48200), 431 (20700). νmax (KBr)/cm–1
1581s, 1548s, 1471s and 1416s (C=N, C=C), 1548s and
1
1372s (N=O). H NMR (CDCl3, 400 MHz, 293K) δ/ppm
C6H4(NO2)CH2O: 8.23 (s, 1H, 2-H), 8.13 (d, J = 7.2 Hz,
1H, 4-H), 7.69 (d, J = 6.1 Hz, 1H, 6-H), 7.52 (dd, J = 7.2,
6.1 Hz, 1H, 5-H), 4.79 (s, 2H, CH2); [{Ge(tmtaa)}(µ-Cl)-
{Ge(tmtaa)Cl}]: 7.19, 7.15 (m, m, 8H, 8H, CH4), 5.42 (br,
s, 4H, CH), 2.53 (s, 24H, CH3); 2.00 (s, 3H, CH3CN).
Λm(CH3NO2, 298 K): 135.6 s cm2 mol–1.
We thank Mr. Daisuke Hirayama in our laboratory for X-
ray structure determination.
References and Notes
1
2
P. Mountford, Chem. Soc. Rev., 27, 105 (1998).
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Weiss, Inorg. Chem., 24, 3162 (1985); M. Moussavi, A. D.
Cian, J. Fischer, and R. Weiss, Inorg. Chem., 27, 1287
(1988).
13 Crystal data: [{Ge(tmtaa)}(µ-Cl){Ge(tmtaa)Cl}](Cl)
[C6H4(NO2)CH2O]·CH3CN, C53H53Cl3Ge2N10O3,Mr =
1129.61; red prism, 0.40 × 0.80 × 0.80 mm, monoclinic,
space group P21/n, a = 12.862(2), b = 21.089(3), c =
18.797(2) Å, β = 98.09(1)°, V = 5047(1) Å3, Z = 4, Dc =
1.486 g/cm3, µ = 1.404 mm–1. Using Mo Kα radiation (λ
= 0.71069 Å) at 293 K, a total of 12438 reflections was
collected (2θmax = 55.0°), of which 11591 were independ-
ent. Refinement converged to R1 = 0.055 [I > 2σ(I)] and R
= 0.095, Rw = 0.198 (all data).
3
4
C. W. Dirk, T. Inabe, K. F. Schoch, Jr., and T. J. Marks, J.
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