The title pendent-arm macrocyclic hexaamine ligand binds stereospecifically in a hexadentate manner, and we report here its isomorphous Ni-II and Zn-II complexes (both as perchlorate salts), namely (cis-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine-kappa(6)N)nickel(II) diperchlorate, [Ni(C12H30N6)](ClO4)(2), and (cis-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine-kappa(6)N)zinc(II) diperchlorate, [Zn(C-12 H30N6)](ClO4)(2). Distortion of the N-M-N valence angles from their ideal octahedral values becomes more pronounced with increasing metal-ion size and the present results are compared with other structures of this ligand

Bernhardt, PV

Paul V. Bernhardt

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Acta Crystallographica Section C Crystal Structure Communications

NiIIand ZnIIcomplexes of the hexadentate macrocyclic ligandcis-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine

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744 # 2000 International Union of Crystallography  Printed in Great Britain ± all rights reserved Acta Cryst. (2000). C56, 744±746
NiII and ZnII complexes of the hexa-
dentate macrocyclic ligand cis-6,13-
dimethyl-1,4,8,11-tetraazacyclotetra-
decane-6,13-diamine
Paul V. Bernhardt
Department of Chemistry, University of Queensland, Brisbane 4072, Australia
Correspondence e-mail: bernhardt@chemistry.uq.edu.au
Received 21 February 2000
Accepted 10 March 2000
The title pendent-arm macrocyclic hexaamine ligand binds
stereospeci®cally in a hexadentate manner, and we report here
its isomorphous NiII and ZnII complexes (both as perchlorate
salts), namely (cis-6,13-dimethyl-1,4,8,11-tetraazacyclotetra-
decane-6,13-diamine-6N)nickel(II) diperchlorate, [Ni-
(C12H30N6)](ClO4)2, and (cis-6,13-dimethyl-1,4,8,11-tetraaza-
cyclotetradecane-6,13-diamine-6N)zinc(II) diperchlorate,
[Zn(C12H30N6)](ClO4)2. Distortion of the NÐMÐN valence
angles from their ideal octahedral values becomes more
pronounced with increasing metal-ion size and the present
results are compared with other structures of this ligand.
Comment
The coordination chemistry of the isomeric pendent-arm
macrocycles trans- and cis-6,13-dimethyl-1,4,8,11-tetraaza-
cyclotetradecane-6,13-diamine (L1 and L2, respectively) has
revealed a number of interesting variations in the structural
and physical properties of their complexes. Complexes of the
hexadentate-coordinated trans isomer (Curtis et al., 1987;
Bernhardt et al., 1989, 1990, 1991; Borzel et al., 1998) are more
common than the corresponding cis complexes (Bernhardt et
al., 1992, 1993, 1997; Lye et al., 1994). It is an interesting
feature that L1 and L2 can only bind in one con®guration when
coordinated as hexadentates, so the structure of the organic
ligand determines the isomerism of the resulting complexes.
The hexadentate trans isomers coordinate such that the
metal is coplanar with the four secondary amines, and the
pendent amines bind in trans coordination sites. By contrast, in
the corresponding cis isomers, the macrocycle adopts a folded
conformation and the pendent amines coordinate in cis sites.
Molecular-mechanics calculations (Bernhardt & Comba,
1991) predicted that the cis isomer L2, bound as a hexadentate,
would be able to complex both small and large metal ions,
whereas the hexadentate-coordinated trans isomer could only
accommodate metals up to a certain size, until one or both
axial MÐN bonds were broken as a consequence of strain in
the complex. These computational results have been borne
out by subsequent experimental data.
The two complexes [NiL2](ClO4)2, (I), and [ZnL
2](ClO4)2,
(II), are isomorphous and the absolute con®guration was
determined in each case. The NiII and ZnII crystals studied
here, both grown from racemic solutions, were found to be
enantiomorphs. Views of the two complex cations are shown
in Figs. 1 and 2. The folded conformation of the macrocycle is
evident, with the coordinated four secondary amines having
the same absolute con®guration i.e. RRRR (SSSS). Each
complex cation has (non-crystallographic) C2 symmetry; the
principal axis bisects the N5ÐMÐN6 angle, and the MÐN
bond lengths separate into three distinct pairs (Tables 1 and
3). Both macrocyclic ®ve-membered chelate rings adopt the
same conformation ( or ), where the CÐC bond in each
ring is oblique to the C2 axis. This conformation was predicted
(Bernhardt & Comba, 1991) to be dominant for complexes
containing both small and large metal ions, and indeed no
other conformation of a hexadentate-coordinated complex of
L2 has been identi®ed. Hydrogen bonding between perchlor-
ate-O atoms and most amine-H atoms is found (Tables 2 and
4). These hydrogen bonds result in chains comprising cations
linked by perchlorate anions extending along the b axis.
The MÐN bond lengths in both structures are typical of
hexaamine complexes of NiII and ZnII, and are signi®cantly
longer than those observed in the respective trans isomers:
[NiL1](ClO4)2 2.07sec and 2.13prim AÊ (Curtis et al., 1987);
[ZnL1](ClO4)2 2.10sec and 2.21prim AÊ (Bernhardt et al., 1991),
where subscripts sec and prim indicate secondary and primary
N atoms, respectively. This is a feature that has now been
observed in the trans and cis isomers of a number of
complexes in this series (CoIII, CrIII, NiII and ZnII), where the
trans isomers invariably exhibit unusually short MÐN bond
lengths in contrast to the corresponding coordinate bond
lengths in the cis isomers, which are normal. Molecular-
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
Figure 1
View of (I) showing 30% probability ellipsoids.
mechanics calculations predicted this disparity some time ago
(Bernhardt & Comba, 1991).
The valence angles involving the metal centres (Tables 1
and 3) indicate that the larger ZnII ion exhibits a greater
distortion from octahedral geometry than its NiII analogue.
This again is a general trend across the series of known
structures of L2 complexes ranging from the smallest (CoIII;
Bernhardt et al., 1997) to the largest (PbII; Lye et al., 1994).
There are a number of structural indicators of this distortion.
It may be viewed as a pseudo-trigonal twist of the N1±N2±N5
and N4±N3±N6 octahedral faces, by analogy with tris-biden-
tate complexes. This de®nition is somewhat limited in this case
as there is no threefold axis in complexes of L2. A more
reliable indicator of the distortion present in these complexes
is the N5ÐMÐN6 valence angle, which increases with the
MÐN bond length, and this is illustrated in Fig. 3. The CdII
(Bernhardt et al., 1992) and PbII (Lye et al., 1994) structures
exhibit somewhat exaggerated bite angles caused by (or
resulting in) coordination of perchlorate anions, and their
structures approximate distorted square-antiprismatic
geometries (N6O2). It is dif®cult to say whether the presence
of these weakly bound ions (MÐO > 3.0 AÊ ) in the CdII/PbII
structures signi®cantly perturb the valence angles involving
the coordinated macrocycle or, conversely, whether these
distortions are driven by the macrocycles, which prize open
the N5ÐMÐN6 angles thus making room for incoming
ligands.
The observed distortions from octahedral geometry with
increasing MÐN bond length were predicted by molecular-
mechanics calculations. However, electronic contributions
from transition metal ions will oppose distortions away from
octahedral geometry (ligand-®eld stabilization energy), and
neglecting this effect can lead to an overestimation of the
observed distortion (Bernhardt & Comba, 1993). That is, the
geometries of the d10 ZnII and CdII complexes represent true
ligand-dictated distortions, whereas the CoIII, CrIII and NiII
structures re¯ect a balance between ligand-directed steric and
metal-based electronic effects.
Experimental
The title complexes were both synthesized readily by mixing equi-
molar amounts of the metal ion and ligand hydrochloride salt
(L26HCl) in water adjusted to pH 7 with NaOH solution. Both
compounds were precipitated by addition of excess NaClO4. Crystals
of each complex were obtained by slow evaporation of their aqueous
solutions.
Compound (I)
Crystal data
[Ni(C12H30N6)](ClO4)2
Mr = 516.03
Monoclinic, P21
a = 9.198 (4) AÊ
b = 12.771 (1) AÊ
c = 9.880 (5) AÊ
 = 113.09 (2)
V = 1067.6 (7) AÊ 3
Z = 2
Dx = 1.605 Mg m
ÿ3
Mo K radiation
Cell parameters from 25
re¯ections
 = 10±14
 = 1.210 mmÿ1
T = 295 (2) K
Prism, purple
0.50  0.50  0.50 mm
Data collection
Enraf±Nonius CAD-4 diffract-
ometer
!±2 scans
Absorption correction: scan
(North et al., 1968)
Tmin = 0.404, Tmax = 0.546
2097 measured re¯ections
1971 independent re¯ections
1892 re¯ections with I > 2(I)
Rint = 0.026
max = 24.98

h = 0! 10
k = 0! 15
l = ÿ11! 10
3 standard re¯ections
frequency: 120 min
intensity decay: <5%
Re®nement
Re®nement on F 2
R[F 2 > 2(F 2)] = 0.044
wR(F 2) = 0.117
S = 1.084
1971 re¯ections
278 parameters
H-atom parameters constrained
w = 1/[2(Fo
2) + (0.0981P)2
+ 0.2008P]
where P = (Fo
2 + 2Fc
2)/3
(/)max < 0.001
max = 0.57 e AÊ
ÿ3
min = ÿ0.83 e AÊ ÿ3
Absolute structure: Flack (1983)
Flack parameter = 0.03 (3)
Acta Cryst. (2000). C56, 744±746 Paul V. Bernhardt  [Ni(C12H30N6)](ClO4)2 and [Zn(C12H30N6)](ClO4)2 745
metal-organic compounds
Figure 2
View of (II) showing 30% probability ellipsoids (H atoms omitted).
Figure 3
Plot of observed N5ÐMÐN6 angle () as a function of average MÐN
bond length (AÊ ) for hexadentate-coordinated complexes of L2.
Table 1
Selected geometric parameters (AÊ , ) for (I).
NiÐN1 2.075 (5)
NiÐN3 2.077 (5)
NiÐN5 2.096 (5)
NiÐN6 2.124 (5)
NiÐN4 2.126 (5)
NiÐN2 2.147 (5)
N1ÐNiÐN3 171.0 (2)
N1ÐNiÐN5 78.39 (19)
N3ÐNiÐN5 107.0 (2)
N1ÐNiÐN6 106.6 (2)
N3ÐNiÐN6 79.5 (2)
N5ÐNiÐN6 102.9 (2)
N1ÐNiÐN4 83.47 (19)
N3ÐNiÐN4 91.33 (19)
N5ÐNiÐN4 161.63 (18)
N6ÐNiÐN4 79.5 (2)
N1ÐNiÐN2 91.0 (2)
N3ÐNiÐN2 82.9 (2)
N5ÐNiÐN2 81.3 (2)
N6ÐNiÐN2 162.4 (2)
N4ÐNiÐN2 101.98 (19)
metal-organic compounds
746 Paul V. Bernhardt  [Ni(C12H30N6)](ClO4)2 and [Zn(C12H30N6)](ClO4)2 Acta Cryst. (2000). C56, 744±746
Compound (II)
Crystal data
[Zn(C12H30N6)](ClO4)2
Mr = 522.69
Monoclinic, P21
a = 9.075 (1) AÊ
b = 12.891 (1) AÊ
c = 9.963 (3) AÊ
 = 112.438 (9)
V = 1077.3 (4) AÊ 3
Z = 2
Dx = 1.611 Mg m
ÿ3
Mo K radiation
Cell parameters from 25
re¯ections
 = 10±14
 = 1.439 mmÿ1
T = 295 (2) K
Prism, colourless
0.30  0.13  0.10 mm
Data collection
Enraf±Nonius CAD-4 diffract-
ometer
!±2 scans
Absorption correction: scan
(North et al., 1968)
Tmin = 0.779, Tmax = 0.866
2115 measured re¯ections
1987 independent re¯ections
916 re¯ections with I > 2(I)
Rint = 0.073
max = 24.97

h = 0! 10
k = 0! 15
l = ÿ11! 10
3 standard re¯ections
frequency: 120 min
intensity decay: <5%
Re®nement
Re®nement on F 2
R[F 2 > 2(F2)] = 0.060
wR(F 2) = 0.175
S = 0.987
1987 re¯ections
258 parameters
H-atom parameters constrained
w = 1/[2(Fo
2) + (0.0782P)2]
where P = (Fo
2 + 2Fc
2)/3
(/)max < 0.001
max = 0.72 e AÊ
ÿ3
min = ÿ0.66 e AÊ ÿ3
Absolute structure: Flack (1983)
Flack parameter = ÿ0.04 (5)
In both structures, rotational disorder in one of the perchlorate
anions (about the Cl2ÐO2A bond) was modelled by re®ning atoms
O2B/O2B0, O2C/O2C0 and O2D/O2D0 with complementary occu-
pancies and applying tetrahedral restraints to the O atoms of each
contributor.
For both compounds, data collection: CAD-4 Manual (Enraf±
Nonius, 1988); cell re®nement: SET4 in CAD-4 Manual; data
reduction: Xtal3.2 (Hall et al., 1992); program(s) used to solve
structure: SHELXS86 (Sheldrick, 1990); program(s) used to re®ne
structure: SHELXL97 (Sheldrick, 1997); molecular graphics:
PLATON (Spek, 1990); software used to prepare material for
publication: SHELXL97.
Financial support from the University of Queensland is
gratefully acknowledged.
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: FG1588). Services for accessing these data are
described at the back of the journal.
References
Bernhardt, P. V. & Comba, P. (1991). Helv. Chim. Acta, 74, 1834±1840.
Bernhardt, P. V. & Comba, P. (1993). Inorg. Chem. 30, 2798±2803.
Bernhardt, P. V., Comba, P., Curtis, N. F., Hambley, T. W., Lawrance, G. A.,
Maeder, M. & Siriwardena, A. (1990). Inorg. Chem. 29, 3208±3213.
Bernhardt, P. V., Comba, P. & Hambley, T. W. (1993). Inorg. Chem. 30, 2804±
2809.
Bernhardt, P. V., Comba, P., Hambley, T. W., Lawrance, G. A. & VaÂrnagy, K.
(1992). J. Chem. Soc. Dalton Trans. pp. 355±359.
Bernhardt, P. V., Jones, L. A. & Sharpe, P. C. (1997). Inorg. Chem. 36, 2420±
2425.
Bernhardt, P. V., Lawrance, G. A. & Hambley, T. W. (1989). J. Chem. Soc.
Dalton Trans. pp. 1059±1065.
Bernhardt, P. V., Lawrance, G. A., Maeder, M., Rossignoli, M. & Hambley,
T. W. (1991). J. Chem. Soc. Dalton Trans. pp. 1167±1170.
Borzel, H., Comba, P., Pritzkow, H. & Sickmuller, A. F. (1998). Inorg. Chem.
37, 3853±3857.
Curtis, N. F., Gainsford, G. J., Hambley, T. W., Lawrance, G. A., Morgan, K. R.
& Siriwardena, A. (1987). J. Chem. Soc. Chem. Commun. pp. 295±297.
Enraf±Nonius (1988). CAD-4 Manual. Version 5.0. Enraf±Nonius, Delft, The
Netherlands.
Flack, H. D. (1983). Acta Cryst. A39, 876±881.
Hall, S. R., Flack, H. D. & Stewart, J. M. (1992). Editors. Xtal3.2 Reference
Manual. Universities of Western Australia, Australia, Geneva, Switzerland,
and Maryland, USA.
Lye, P. G., Lawrance, G. A., Maeder, M., Skelton, B. W., Wen, H. & White,
A. H. (1994). J. Chem. Soc. Dalton Trans. pp. 793±798.
North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351±
359.
Sheldrick, G. M. (1990). Acta Cryst. A46, 467±473.
Sheldrick, G. M. (1997). SHELXL97. University of GoÈ ttingen, Germany.
Spek, A. L. (1990). Acta Cryst. A46, C-34.
Table 2
Hydrogen-bonding geometry (AÊ , ) for (I).
DÐH  A DÐH H  A D  A DÐH  A
N1ÐH1  O1Ci 0.91 2.41 3.192 (10) 144
N2ÐH2  O1D 0.91 2.49 3.283 (10) 146
N3ÐH3  O2Bii 0.91 2.14 3.039 (8) 167
N3ÐH3  O2B0 ii 0.91 2.08 2.917 (11) 152
N4ÐH4  O2A 0.91 2.38 3.213 (7) 151
N4ÐH4  O2D 0.91 2.57 3.271 (9) 135
N5ÐH5A  O2Dii 0.90 2.56 3.056 (8) 116
N5ÐH5A  O2D0 ii 0.90 2.09 2.819 (10) 137
N5ÐH5B  O1Ci 0.90 2.62 3.389 (13) 144
N6ÐH6A  O2Biii 0.90 2.31 3.120 (8) 150
N6ÐH6A  O2B0 iii 0.90 2.64 3.53 (3) 168
N6ÐH6B  O2Cii 0.90 2.50 3.341 (10) 156
N6ÐH6B  O2C0 ii 0.90 2.49 3.382 (13) 170
Symmetry codes: (i) 1ÿ x; 12 y; 1ÿ z; (ii) 1 x; y; z; (iii) ÿx; 12 y;ÿz.
Table 3
Selected geometric parameters (AÊ , ) for (II).
Zn1ÐN6 2.128 (14)
Zn1ÐN5 2.134 (12)
Zn1ÐN3 2.141 (15)
Zn1ÐN1 2.170 (13)
Zn1ÐN4 2.219 (13)
Zn1ÐN2 2.255 (12)
N6ÐZn1ÐN5 108.9 (6)
N6ÐZn1ÐN3 77.4 (5)
N5ÐZn1ÐN3 113.7 (6)
N6ÐZn1ÐN1 114.7 (6)
N5ÐZn1ÐN1 76.9 (5)
N3ÐZn1ÐN1 161.5 (5)
N6ÐZn1ÐN4 78.2 (6)
N5ÐZn1ÐN4 156.4 (5)
N3ÐZn1ÐN4 89.7 (5)
N1ÐZn1ÐN4 79.7 (5)
N6ÐZn1ÐN2 156.5 (5)
N5ÐZn1ÐN2 80.0 (6)
N3ÐZn1ÐN2 79.2 (5)
N1ÐZn1ÐN2 88.3 (5)
N4ÐZn1ÐN2 102.5 (5)
Table 4
Hydrogen-bonding geometry (AÊ , ) for (II).
DÐH  A DÐH H  A D  A DÐH  A
N1ÐH1  O1Ai 0.91 2.54 3.33 (2) 146
N2ÐH2  O1C 0.91 2.57 3.39 (2) 150
N3ÐH3  O2Bii 0.91 2.28 3.14 (2) 158
N3ÐH3  O2C0 ii 0.91 1.99 2.88 (2) 166
N4ÐH4  O2A 0.91 2.48 3.300 (16) 151
N4ÐH4  O2D 0.91 2.48 3.165 (18) 133
N5ÐH5B  O2Dii 0.90 2.61 3.12 (2) 116
N5ÐH5B  O2D0 ii 0.90 2.18 2.853 (19) 132
N6ÐH6A  O2Cii 0.90 2.37 3.22 (2) 158
N6ÐH6A  O2B0 ii 0.90 2.29 3.18 (2) 169
N6ÐH6B  O2Biii 0.90 2.41 3.201 (19) 147
N6ÐH6B  O2C0 iii 0.90 2.42 3.30 (3) 165
Symmetry codes: (i) 1ÿ x; yÿ 12; 1ÿ z; (ii) 1 x; y; z; (iii) ÿx; yÿ 12;ÿz.

Ni-II and Zn-II complexes of the hexadentate macrocyclic ligand cis-6,13-dimethyl-1,4,8,11-tetraazacyclotetra- decane-6,13-diamine

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Ni-II and Zn-II complexes of the hexadentate macrocyclic ligand cis-6,13-dimethyl-1,4,8,11-tetraazacyclotetra- decane-6,13-diamine

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