Five-co-ordinate cobalt(II) and nickel(II) complexes of 1,4,8,11-tetrakis(diphenylphosphinomethyl)-1,4,8,11-tetraazacyclotetradecane (tpta), [MCl(tpta)]X [X = ClO4, BF4, PF6 and B(C6H5)4]. Crystal structures of [CoCl(tpta)]ClO4·C6H6

Article abstract of DOI:10.1039/a701913k

A series of five-co-ordinate cobalt(II) and nickel(II) complexes with 1,4,8,11-tetrakis(diphenylphosphinomethyl)-1,4,8,11-tetraazacyclotetradecane (tpta) has been prepared and characterized. The complexes are high-spin paramagnetic substances, 1:1 electrolytes, consistent with the general formula [MCl(tpta)]X [M = Co or Ni; X = ClO₄, BF₄, PF₆ or B(C₆H₅)₄]. A binuclear cobalt(II) complex of formula [(CoCl₂)₂(tpta)]·H₂O has also been isolated. The crystal and molecular structures of [CoCl(tpta)]ClO₄·C₆H₆ and [NiCl(tpta)]ClO₄·C₆H₆ have been determined. The complexes have a distorted square-pyramidal geometry around the metal which is co-ordinated by four nitrogen atoms from the tpta ligand and an apical chlorine atom bound on the side of the four pendant chains of the macrocyclic ring. The distortions are greater in the cobalt complexes and are of the trigonal-bipyramidal type.

Full text of DOI:10.1039/a701913k

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Five-co-ordinate cobalt(II) and nickel(II) complexes of 1,4,8,11-tetrakis-
(diphenylphosphinomethyl)-1,4,8,11-tetraazacyclotetradecane (tpta),
[MCl(tpta)]X [X ؍ ClO4, BF4, PF6 and B(C6H5)4]. Crystal
structures of [CoCl(tpta)]ClO4ؒC6H6 and [NiCl(tpta)]ClO4ؒC6H6 †
,a
b
a
ˇ
Pavica Planinic´,* Dubravka Matkovic´-Calogovic´ and Henrika Meider
_
a
Department of Physical Chemistry, Ruder Bosˇkovic´ Institute, Bijenicˇka 54, 10000 Zagreb,
Croatia
b Laboratory of General and Inorganic Chemistry, Faculty of Science, University of Zagreb,
Zvonimirova 8, 10000 Zagreb, Croatia
A series of five-co-ordinate cobalt() and nickel() complexes with 1,4,8,11-tetrakis(diphenylphosphinomethyl)-
1,4,8,11-tetraazacyclotetradecane (tpta) has been prepared and characterized. The complexes are high-spin
paramagnetic substances, 1:1 electrolytes, consistent with the general formula [MCl(tpta)]X [M = Co or Ni;
X = ClO4, BF4, PF6 or B(C6H5)4]. A binuclear cobalt() complex of formula [(CoCl2)2(tpta)]ؒH2O has also been
isolated. The crystal and molecular structures of [CoCl(tpta)]ClO4ؒC6H6 and [NiCl(tpta)]ClO4ؒC6H6 have been
determined. The complexes have a distorted square-pyramidal geometry around the metal which is co-ordinated
by four nitrogen atoms from the tpta ligand and an apical chlorine atom bound on the side of the four pendant
chains of the macrocyclic ring. The distortions are greater in the cobalt complexes and are of the trigonal-
bipyramidal type.
The significance of tetraazamacrocyclic ligands and their
transition-metal complexes lies, mainly, in the resemblance of
these systems to the natural products, such as metallo-
porphyrins, vitamin B12 or chlorophylls. Related to this is the
current interest in functionalized tetraazamacrocycles the
potential for metal-ion recognition of which may be influenced
by a match between the size of the ligand hole and a particular
metal ion as well as by the nature of the substituents.1,2
1,4,8,11-Tetrakis(diphenylphosphinomethyl)-1,4,8,11-tetra-
azacyclotetradecane (tpta) with its eight donor atoms provides
a variety of modes of co-ordination. Recently, we reported
Scheme 1 Five possible configurations of the co-ordinated tetraaza
macrocycles, as introduced by Bosnich et al.,6 trans I–IV and cis V. The
signs ϩ and Ϫ indicate whether the hydrogen atoms on the nitrogens
would lie above or below the plane of the flattened macrocycle
the synthesis and structural characterization of a number of
chromium(0), molybdenum(0) and tungsten(0) complexes
with this macrocyclic ligand.3–5 In both types of species, i.e. in
the binuclear [{M(CO)4}2(tpta)] and tetranuclear [{M(CO)5}4-
(tpta)] complexes, the ligand is co-ordinated to the metal
through phosphorus donors from the pendant arms. The
metal atoms are not incorporated into the macrocyclic ring
because of a greater affinity of these soft metals for phosphorus
and the steric requirements of the ligand. By extension of our
study to the complexes of other transition metals we expected a
different way of co-ordination. Here we report the synthesis of
a series of cobalt() and nickel() complexes having the general
formula [MCl(tpta)]X, X = ClO4, BF4, PF6 or B(C6H5)4, and
also of a binuclear cobalt() complex, [(CoCl2)2(tpta)]ؒH2O. The
complexes were characterized for their magnetic, spectroscopic,
conductometric and structural properties. Crystal and molecu-
lar structures were determined for [CoCl(tpta)]ClO4ؒC6H6 and
[NiCl(tpta)]ClO4ؒC6H6, which showed the ligand to be co-
ordinated to the metal through nitrogen atoms of the macrocy-
clic ring.
It is known that the parent 14-membered tetraazamacrocycle,
i.e. 1,4,8,11-tetraazacyclotetradecane (cyclam), can adopt five
different configurations in metal complexes, trans I–IV and
cis V (Scheme 1, nomenclature given by Bosnich et al.6), the
most stable being the trans-III configuration. The first-row
transition-metal complexes having trans-III configuration are
thus square planar or trans-octahedral, with a coplanar set of
four nitrogen donor atoms. However, tetraazamacrocycles with
tertiary nitrogen atoms in the ring, 1,4,8,11-tetramethyl-
1,4,8,11-tetraazacyclotetradecane (tmc) for example, very often
assume trans-I configuration and show a marked propensity
towards five-co-ordination,
a fifth unidentate ligand co-
ordinating on the side of the four N-methyl groups of the
macrocycle. In such a way the metal atom is pulled out of the
macrocyclic plane and the complex is forced to adopt either a
square-pyramidal or trigonal-bipyramidal geometry. Different
types of intermediate structures along with the two regular
† Non-SI unit employed: µB ≈ 9.27 × 10Ϫ24 J TϪ1
.
J. Chem. Soc., Dalton Trans., 1997, Pages 3445–3451
3445

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Table 1 Microanalytical data for the new complexes
Analysis (%)*
C
Complex
Colour
H
Metal
Cl
1
[(CoCl2)2(tpta)]ؒH2O
Blue
Light lilac
Yellow
59.45 (59.45)
62.25 (62.75)
62.35 (62.75)
64.40 (64.55)
64.65 (64.55)
62.95 (63.40)
63.10 (63.45)
65.35 (65.20)
65.00 (65.20)
59.90 (60.40)
60.05 (60.45)
72.95 (73.45)
73.90 (73.44)
5.50 (5.45)
5.85 (5.75)
5.60 (5.80)
5.85 (5.90)
5.95 (5.90)
5.60 (5.85)
5.60 (5.85)
6.10 (5.95)
5.85 (5.95)
5.70 (5.55)
5.35 (5.55)
6.50 (6.30)
6.10 (6.30)
9.40 (9.40)
4.95 (4.95)
4.60 (4.95)
4.70 (4.65)
4.60 (4.65)
4.95 (5.00)
4.80 (5.00)
4.60 (4.70)
4.60 (4.70)
4.70 (4.80)
4.60 (4.75)
4.20 (4.20)
3.85 (4.15)
11.25 (11.30)
3.05 (3.00)
2.75 (3.00)
2.80 (2.80)
2.75 (2.80)
3.45 (3.00)
3.15 (3.00)
2.80 (2.85)
2.70 (2.85)
3.05 (2.90)
2.75 (2.90)
2.35 (2.50)
2.25 (2.50)
2a [CoCl(tpta)]ClO4
3a [NiCl(tpta)]ClO4
2b [CoCl(tpta)]ClO4ؒC6H6
3b [NiCl(tpta)]ClO4ؒC6H6
4a [CoCl(tpta)]BF4
5a [NiCl(tpta)]BF4
4b [CoCl(tpta)]BF4ؒC6H6
5b [NiCl(tpta)]BF4ؒC6H6
6
7
8
9
Lilac
Green-yellow
Light lilac
Yellow
Lilac
Green-yellow
Light lilac
Yellow
Lilac
Green-yellow
[CoCl(tpta)]PF6
[NiCl(tpta)]PF6
[CoCl(tpta)][B(C6H5)4]
[NiCl(tpta)][B(C6H5)4]
* Calculated values are given in parentheses.
Table 2 Magnetic moments, molar conductivitiesa and infrared spectral data for the complexes
Infrared (cmϪ1
)
Ϫ
)
Anion(ClO4Ϫ,BF4Ϫ,PF6
vibrationsc
Complex
µeff/µB
Λ/ΩϪ1 cm2 molϪ1
ν(M᎐Cl)b
1
4.80
4.93
3.11
4.90
3.01
4.85
3.62
4.87
3.26
5.12
3.35
5.18
3.41
19.14
18.94
24.83
21.32
20.17
19.15
19.73
20.75
20.08
19.81
23.46
14.96
15.95
318s, 280m
281m
275w
277m
269w
282m
273w
273m
268m
283m
275w
300m
295m
—
2a
3a
2b
3b
4a
5a
4b
5b
6
1092vs, 620s
1090vs, 618s
1102vs, 624s
1098vs, 623s
1052vs
1050vs
1063vs
1060vs
835vs, 555s
834vs, 555s
d
7
8
9
d
a
In nitrobenzene. b Polyethylene pellets. c KBr pellets. d Overlapped by the phenyl vibration bands of the ligand.
Table 3 Electronic spectral data for the complexes*
Complex
λmax/nm (ε/dm3 molϪ1 cmϪ1
)
1
515 (sh), 536 (sh, 76), 592 (444), 635 (sh, 229), 666 (428), 697 (429), 1258 (36)
518 (sh), 537, 594, 640 (sh), 665, 707, 1200
518 (61), 577 (39), 666 (sh), 809 (19), 969 (12)
512, 584, 800
reflectance
2a
reflectance
4a
6
8
517 (41), 591 (34), 661 (sh), 724 (sh), 793 (14), 965 (10)
519 (66), 583 (45), 660 (sh), 725 (sh), 822 (20), 949 (13)
522 (76), 583 (54), 666 (sh), 728 (sh), 827 (22), 967 (sh)
435 (196), 529 (sh), 603 (sh), 733 (65), 883 (sh)
360, 438, 531 (sh), 609 (sh), 731
3a
reflectance
3b reflectance
430, 520 (sh), 620 (sh), 738
5a
7
9
433 (197), 523 (sh), 600 (sh), 727 (64), 874 (sh)
438 (197), 530 (sh), 604 (sh), 740 (68), 883 (sh)
440 (306), 532 (sh), 608 (sh), 741 (102), 890 (sh)
* In benzene solutions (or solid reflectance, where stated).
geometries were found in metal complexes, depending on the
metal and on the nature of the additional ligand.7–15
summarized in Table 1 and some of their physical properties are
given in Tables 2 and 3.
The results obtained here are discussed and correlated with
the data available in the literature. This showed tpta to co-
ordinate to Co and Ni in a similar manner to that of tmc. The
present study is, however, one of the rare ones in which five-co-
ordinate complexes of functionalized tetraazamacrocycles have
been characterized both structurally and spectroscopically.
By mixing the ethanolic solutions of CoCl2ؒ6H2O and tpta
in a molar ratio of ≈2:1, at room temperature, a blue micro-
crystalline product analysing as [(CoCl2)2(tpta)]ؒH2O 1 precipi-
tated after stirring for a short time. In nitrobenzene it behaves
as a 1:1 electrolyte (Table 2). In principle, either [CoCl(tpta)]-
[CoCl3(H2O)] or [Co(tpta)][CoCl4]ؒH2O {or conceivably
[Co(H2O)(tpta)][CoCl4]} would satisfy the above requirements.
Single crystals of 1 suitable for X-ray diffraction measurements
could not be obtained. The compound was used in the prepar-
ation of cobalt complexes in the series 2–9 (below). It is to be
noted that the reaction of nickel() chloride hexahydrate and
Results and Discussion
Preparation and properties
The analytical data for complexes 1–9 prepared in this study are
3446
J. Chem. Soc., Dalton Trans., 1997, Pages 3445–3451

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tpta, performed under the same experimental conditions as for
Co, failed to give an analogous binuclear nickel() complex.
Mixing of the appropriate amounts of CoCl2ؒ6H2O (or
NiCl2ؒ6H2O), tpta and an additional metal or ammonium salt
containing the corresponding anion in absolute ethanol, with
stirring of the reaction mixture in air and at room temperature,
resulted in crystalline compounds satisfying the formula
[MCl(tpta)]X [M = Co or Ni; X = ClO4, BF4, PF6 or B(C6H5)4].
The complexes displayed conductivities, in nitrobenzene,
typical of 1:1 electrolytes (Table 2). Somewhat lower values of
molar conductivities obtained for [CoCl(tpta)][B(C6H5)4] 8 and
[NiCl(tpta)][B(C6H5)4] 9 may be due to the bulkiness of the
tetraphenylborate anion. All cobalt complexes, [CoCl(tpta)]X,
could also be obtained by a reaction of 1 and an appropriate
metal or ammonium salt.
In the solid state the complexes are fairly stable in air at room
temperature. Owing to low solubility in all common organic
solvents, recrystallization of the complexes was not possible
and prior to elemental analyses the purity was checked by
the X-ray powder diffraction and infrared spectral data. In
dimethyl sulfoxide (dmso) and dimethylformamide (dmf) they
dissolve with a change in colour as a result of decomposition.
However, the complexes of both metals dissolved in benzene
which is associated with the formation of the solvates [MCl-
(tpta)]XؒC6H6. Once these solvate species have formed they
cannot be redissolved in benzene. Single crystals of the per-
chlorate and tetrafluoroborate compounds of both metals were
obtained by crystallization from benzene in quantities sufficient
for carrying out the complete analyses (Table 1, compounds 2b,
3b, 4b and 5b). The hexafluorophosphate and tetraphenyl-
borate derivatives crystallize poorly and rather slowly and their
benzene solvates were not fully analysed.
Fig. 1 The IR spectra of (a) the tpta ligand, (b) the binuclear cobalt()
complex [(CoCl2)2(tpta)]ؒH2O 1 and (c) the mononuclear cobalt()
complex [CoCl(tpta)]PF6 6
According to the X-ray powder diffraction patterns the per-
chlorate, tetrafluoroborate and hexafluorophosphate complexes
of both metals {[MCl(tpta)]X (M = Co or Ni; X = ClO4, BF4 or
PF6)} are all isostructural but different from the correspond-
ing benzene solvate derivatives [MCl(tpta)]XؒC6H6, (M = Co or
Ni; X = ClO4, BF4 or PF6) which are mutually isostructural as
well. It is not unexpected that the tetraphenylborate com-
Ϫ
pounds (8 and 9) with the very bulky B(C6H5)4 anion are not
isostructural with the other complexes.
Spectroscopic and magnetic measurements
Infrared and electronic spectra are indicative of a five-co-
ordinate metal centre present in the [MCl(tpta)]ϩ cation.
Selected infrared spectral data of the complexes are given in
Table 2 and in Fig. 1. Co-ordination of the ligand to the metal
through nitrogen atoms caused the distinctive three-band
pattern for the :N(CH2)3 moiety16 present in the spectrum of
the tpta ligand at 2800, 2770 and 2735 cmϪ1 to disappear com-
pletely in the spectra of complexes. The characteristic bands of
the perchlorate, tetrafluoroborate and hexafluorophosphate
anions appear in all cases without splitting, indicating that
these groups act only as counter ions. All compounds exhibit a
Fig. 2 Electronic absorption spectra of (a) [CoCl(tpta)]ClO4 2a
(2 × 10Ϫ3 mol dmϪ3 in benzene) and (b) [(CoCl2)2(tpta)]ؒH2O 1 (10Ϫ3
mol dmϪ3 in benzene)
weak to medium far-infrared band in the range 270–300 cmϪ1
,
assigned as a M᎐Cl stretching vibration.17 In the far-IR spec-
trum of complex 1 two absorptions, at 318 and 280 cmϪ1, are
assigned as Co᎐Cl stretching vibrations. This spectrum displays
also weak infrared bands around 3400 and 1600 cmϪ1 assign-
able to the vibrations of the water molecule (O᎐H stretching
and H᎐O᎐H bending, respectively).
The UV/VIS absorption maxima of the new complexes,
obtained from benzene solutions and solid-reflectance spectra,
are reported in Table 3. Some characteristic spectral patterns
are shown in Figs. 2 and 3. The electronic spectrum of the
binuclear cobalt() complex 1 is predominantly that of a tetra-
hedral cobalt() species.18–21 The spectra of 2–9 can be assigned
as consistent with five-co-ordination,18,22–24 and are in accord
with the crystal structure analyses of 2b and 3b.
Fig. 3 Electronic absorption spectra of (a) [NiCl(tpta)]BF4 5a (10Ϫ3
mol dmϪ3 in benzene) and (b) [NiCl(tpta)]ClO4 3a (solid reflectance)
J. Chem. Soc., Dalton Trans., 1997, Pages 3445–3451
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Table 4 Selected bond lengths (Å), angles (Њ) and torsion angles (Њ) for complexes 2b (M = Co) and 3b (M = Ni)
2b
3b
2b
3b
M᎐Cl(1)
M᎐N(1)
M᎐N(2)
2.296(2)
2.279(4)
2.130(4)
2.306(1)
2.214(4)
2.124(3)
M᎐N(3)
M᎐N(4)
2.241(4)
2.121(4)
2.191(3)
2.109(3)
N(1)᎐M᎐N(2)
N(1)᎐M᎐N(3)
N(1)᎐M᎐N(4)
N(2)᎐M᎐N(3)
N(2)᎐M᎐N(4)
N(3)᎐M᎐N(4)
N(1)᎐M᎐Cl(1)
N(2)᎐M᎐Cl(1)
N(3)᎐M᎐Cl(1)
N(4)᎐M᎐Cl(1)
C(1)᎐N(1)᎐M
82.64(14)
168.4(2)
91.50(14)
92.46(14)
140.1(2)
85.48(14)
96.81(11)
111.76(11)
94.83(11)
108.15(12)
102.8(3)
84.44(13)
172.35(12)
92.38(13)
92.46(13)
147.79(13)
86.51(13)
94.63(9)
107.76(10)
92.98(9)
104.44(9)
103.4(2)
C(10)᎐N(1)᎐M
C(91)᎐N(1)᎐M
C(2)᎐N(2)᎐M
C(3)᎐N(2)᎐M
C(92)᎐N(2)᎐M
C(5)᎐N(3)᎐M
C(6)᎐N(3)᎐M
C(93)᎐N(3)᎐M
C(7)᎐N(4)᎐M
C(8)᎐N(4)᎐M
C(94)᎐N(4)᎐M
113.1(3)
111.8(3)
107.7(3)
117.4(3)
101.9(3)
111.6(3)
100.8(3)
117.2(3)
105.3(3)
115.8(3)
108.3(3)
111.9(2)
113.8(2)
105.2(2)
115.7(3)
106.1(2)
110.8(2)
101.4(2)
117.7(2)
103.4(2)
113.3(2)
111.7(2)
C(10)᎐N(1)᎐C(1)᎐C(2)
N(1)᎐C(1)᎐C(2)᎐N(2)
C(1)᎐C(2)᎐N(2)᎐C(3)
C(2)᎐N(2)᎐C(3)᎐C(4)
N(2)᎐C(3)᎐C(4)᎐C(5)
C(3)᎐C(4)᎐C(5)᎐N(3)
C(4)᎐C(5)᎐N(3)᎐C(6)
79.5(5)
57.2(5)
Ϫ167.0(4)
173.4(4)
Ϫ67.0(6)
73.4(6)
80.1(4)
57.7(5)
Ϫ165.9(3)
170.7(4)
Ϫ65.6(5)
72.7(5)
C(5)᎐N(3)᎐C(6)᎐C(7)
N(3)᎐C(6)᎐C(7)᎐N(4)
C(6)᎐C(7)᎐N(4)᎐C(8)
C(9)᎐C(8)᎐N(4)᎐C(7)
N(4)᎐C(8)᎐C(9)᎐C(10)
C(8)᎐C(9)᎐C(10)᎐N(1)
C(1)᎐N(1)᎐C(10)᎐C(9)
76.9(5)
76.8(4)
58.2(5)
Ϫ163.1(4)
174.4(4)
Ϫ70.2(6)
70.8(6)
60.4(4)
Ϫ162.4(3)
172.9(4)
Ϫ70.1(5)
70.3(5)
Ϫ170.6(4)
Ϫ174.8(4)
Ϫ170.2(4)
Ϫ173.2(4)
Average bond lengths and angles within the tpta ligand (m = 1–4; r = macrocyclic ring atom; Ph = phenyl ring atoms)
2b
3b
2b
3b
P᎐C(9m)
P᎐C (Ph)
1.874(2)
1.826(1)
1.868(2)
1.833(1)
N᎐C(r)
C(r)᎐C(r)
1.491(1)
1.509(1)
1.499(1)
1.509(1)
C (Ph)᎐P᎐C (Ph)
C (Ph)᎐P᎐C(9m)
N᎐C(9m)᎐P
102.7(2)
100.7(1)
116.9(2)
120.9(1)
102.6(3)
100.6(1)
116.3(3)
121.0(1)
N᎐C(r)᎐C(r)
C(r)᎐N᎐C(r)
C(r)᎐N᎐C(9m)
C(r)᎐C(r)᎐C(r)
113.7(1)
108.0(1)
110.0(1)
115.4(1)
113.2(1)
107.9(3)
110.0(1)
114.8(1)
C (Ph)᎐C (Ph)᎐P
Average bond lengths and angles within the phenyl rings (n = 1–8)
2b
3b
C(n1)᎐C(n2), C(n1)᎐C(n6)
C(n2)᎐C(n3), C(n5)᎐C(n6)
C(n3)᎐C(n4), C(n4)᎐C(n5)
1.389
1.389
1.364
1.384(1)
1.386(1)
1.363(1)
C(n2)᎐C(n1)᎐C(n6)
118.0
120.6
120.5
119.9
117.9(3)
120.8(4)
120.4(4)
119.7(2)
C(n1)᎐C(n2)᎐C(n3), C(n1)᎐C(n6)᎐C(n5)
C(n2)᎐C(n3)᎐C(n4), C(n4)᎐C(n5)᎐C(n6)
C(n3)᎐C(n4)᎐C(n5)
The cobalt() complexes exhibit room-temperature magnetic
moments between µeff = 4.8 and 5.2 µB and the nickel()
complexes between µeff = 3.0 and 3.6 µB (Table 2), indicative of
high-spin d7 and d8 electron configurations, respectively.18
Crystal structures of complexes 2b and 3b
Single crystals of [CoCl(tpta)]ClO4ؒC6H6 2b and [NiCl(tpta)]-
ClO4ؒC6H6 3b, suitable for X-ray analysis, were formed by slow
evaporation of benzene solutions of 2a and 3a, respectively.
Complexes 2b and 3b were found to be isostructural. The
crystal structures consist of [MCl(tpta)]ϩ cations (M = Co in 2b
and Ni in 3b), perchlorate anions and benzene molecules (Fig.
4). The oxygen atoms from the perchlorate anion are too far
away to form any interaction with the metal, and the benzene
solvent molecules form only van der Waals contacts.
Fig. 4 Packing diagram of complexes [CoCl(tpta)]ClO4ؒC6H6 2b and
[NiCl(tpta)]ClO4ؒC6H6 3b
The structure of the [MCl(tpta)]ϩ cation is shown in Fig. 5.
Selected bond distances, angles and torsion angles are listed in
Table 4. The metal atom is co-ordinated by four nitrogen atoms
from the tpta macrocycle and an apical chlorine atom forming a
distorted square pyramid. The distortion is greater in 2b and is
towards a trigonal-bipyramidal arrangement with the Cl(1)
atom in equatorial position and N(1) and N(3) in apical posi-
tions. The chlorine atom is bonded to the metal on the side of
the four pendant diphenylphosphinomethyl groups and inside
the cavity they form. The configuration of the macrocycle can
be characterized as trans-I using the Bosnich notation 6 or
R,S,R,S. It can be seen in the view of the [MCl(tpta)]ϩ cation
given in the packing diagram in Fig. 4 that the four diphenyl-
phosphinomethyl groups point upward at the same side of the
macrocyclic ring. This stereoisomer is kinetically stable
although it is not the most thermodynamically stable one.25
The trans M᎐N distances are either both long [M᎐N(1) and
M᎐N(3) of 2.279(4) and 2.241(4) Å in 2b; 2.214(4) and 2.191(3)
Å in 3b] or short [M᎐N(2) and M᎐N(4) of 2.130(4) and 2.121(4)
Å in 2b; 2.124(3) and 2.109(3) Å in 3b]. The difference in the
3448
J. Chem. Soc., Dalton Trans., 1997, Pages 3445–3451

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ing of the corresponding M᎐N distances and further deform-
ation of the square-pyramidal co-ordination in both 2b and
3b.
Distorted square-pyramidal co-ordination is also found in
some porphyrin complexes containing the CoN4Cl structural
unit.26 The authors suggest that the out-of-plane displacements
could not be attributed to a variation in size of the N4 core but
mainly to the presence of chlorine in the fifth co-ordination
site.26b
The zinc() complexes [ZnX(tmc)]ClO4 were found as
deformed square pyramidal when X = Cl10 or deformed tri-
gonal bipyramidal when X = O2COCH3.27 The origin of this
difference is possibly the different X ligand. All of the men-
tioned tmc complexes have the trans-I configuration of the
macrocycle. It is also found in [NiX(tmc)]ϩ, X = O2COCH3,
(CH3)2NCHO or CH3CN28 and in [Cu(H2O)(tmc)]ϩ.12
Experimental
Materials
1,4,8,11-Tetrakis(diphenylphosphinomethyl)-1,4,8,11-tetraaza-
cyclotetradecane was prepared as previously described,29
including the reaction of 1,4,8,11-tetraazacyclotetradecane
and diphenylphosphine, which were used as received. All other
chemicals, i.e. CoCl2ؒ6H2O, NiCl2ؒ6H2O, Co(ClO4)2ؒ6H2O,
Ni(ClO4)2ؒ6H2O, NaClO4ؒH2O, NaBF4, NH4PF6 and NaB-
(C6H5)4, were of reagent grade and used as supplied. The sol-
vents were purified and dried by standard methods.
Fig. 5 Structure of [NiCl(tpta)]ϩ in complex 3b. The [CoCl(tpta)]ϩ
cation in 2b is isostructural and has the same atom numbering scheme.
The thermal ellipsoids are at the 50% probability level
bond lengths of these two sets of values is much less pro-
nounced for 3b although it is still significant. The long set of
bond distances is significantly longer in 2b than in 3b and repre-
sents the greatest difference between these two complexes. The
bond angles N(1)᎐M᎐N(3) associated with the long set of
distances are 168.4(2)Њ for Co and 172.4(1)Њ for Ni, while the
bending away from Cl is much greater for the shorter set,
N(2)᎐M᎐N(4) is 140.1(2)Њ for Co and 147.8(1)Њ for Ni. The four
tpta N atoms are not planar and the distortion is of a tetra-
hedral nature, N(1) and N(3) being above and N(2) and N(4)
below the least-squares plane by approximately 0.2 Å. The Co
and Ni atoms are displaced above this plane by 0.477(2) and
0.366(2) Å, respectively.
Physical measurements
Elemental analyses for C, H, Cl, Co and Ni were obtained from
_
the Central Analytical Service of Ruder Bosˇkovic´ Institute.
Infrared spectra were recorded on a Perkin-Elmer model 580B
spectrophotometer on KBr pellets in the region 4000–200 cmϪ1
and on polyethylene pellets in the region 400–200 cmϪ1. The
electrical conductivity of 10Ϫ3 mol dmϪ3 solutions in nitro-
benzene was measured on a Tacussel conductivity bridge, type
Cd 7, at 25 ЊC. Magnetic susceptibility measurements were
performed at room temperature, by the Gouy method, using
CuSO4ؒ5H2O as calibrant. Electronic spectra were measured on
a UV-VIS-NIR Cary-5 spectrometer. Solution spectra were run
in C6H6 using 1 cm silica cells. For solid-state spectra, Nujol
mulls of the complexes were soaked into Filtrak No.391 filter-
paper with Nujol soaked filter-paper as the reference.
It is interesting to make comparison with complexes of
similar tetraazamacrocyclic ligands. The only examples of five-
co-ordination where the structures of both cobalt and nickel
Ϫ
complexes were determined are those with N3 in the apical
position, and methyl groups as substituents at N, [Co(N3)-
11
(tmc)]ClO4 and [Ni(N3)(tmc)]ClO4.8 The structure of [Co-
(N3)(tmc)]ϩ also has two short Co᎐N distances [2.106(5) and
2.130(5) Å] and two long ones [2.213(5) and 2.247(5) Å], with
the angle associated with the long distances being larger
[167.8(2)Њ] than the other one [140.8(2)Њ]. The authors describe
it as intermediate between square-pyramidal and trigonal-
bipyramidal (with the azide ion in equatorial position). The
angles and the short bond lengths are similar as in 2b, but the
long ones are significantly shorter than in 2b. In [Ni(N3)(tmc)]ϩ
the Ni᎐N bond lengths are shorter [2.102(8) and 2.105(8) Å]
and there are no significant differences among them nor among
the trans N᎐Ni᎐N angles since the crystallographic plane of
symmetry passes through atoms C(4) and C(9) (the labelling of
the macrocycle is the same as in the present structures) and the
four tmc N atoms are coplanar. The co-ordination is distorted
square pyramidal. The origin of the structural difference
between the complexes of Co and Ni was assigned to the differ-
ence in the d-electron configuration.11 We can conclude that the
difference between 2b and 3b, as well as the difference between
the tpta and tmc complexes, is influenced not only by elec-
tronic but also by steric effects. The diphenylphosphino-
methyl group represents the bulkiest nitrogen substituent in
all of the structures of 14-membered tetraazamacrocycle
complexes. The steric interactions of the phenyl rings prevent
closer approach of N(1) and N(3) atoms and cause lengthen-
Preparation of complexes
In general, the complexes were prepared by mixing appropriate
amounts of the reacting components (i.e. tpta, CoCl2ؒ6H2O or
NiCl2ؒ6H2O and a corresponding counter ion salt) in absolute
ethanol and by stirring the resulting suspension for the required
period of time, in air and at room temperature. The cobalt
complexes, [CoCl(tpta)]X, X = ClO4, BF4, PF6 or B(C6H5)4,
could also be obtained by starting from compound 1. In that
case a higher excess of the corresponding counter ion salt and a
longer stirring time were needed for completion of the reaction.
As an illustration, for tetrafluoroborate and tetraphenylborate
derivatives (4a and 8) both procedures are described below, and
only one procedure is given for the other compounds.
[(CoCl2)2(tpta)]ؒH2O 1. A mixture of tpta (0.198 g, 0.20
mmol), CoCl2ؒ6H2O (0.107 g, 0.45 mmol) and absolute ethanol
(15 cm3) was stirred in air, at room temperature, for 3 h. The
blue microcrystalline precipitate of 1 was then filtered off,
washed with a few cm3 of absolute ethanol and dried in vacuo.
The yield was 0.215 g (85%).
[CoCl(tpta)]ClO4 2a. The compound tpta (0.110 g, 0.11
mmol) and CoCl2ؒ6H2O (0.060 g, 0.25 mmol) were mixed in
absolute ethanol (13 cm3) and stirred for 3 h. Then, without
J. Chem. Soc., Dalton Trans., 1997, Pages 3445–3451
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Table 5 Crystal data, data collection and structure refinement parameters for complexes 2b and 3ba
2b
3b
Empirical formula
M
C68H74Cl2CoN4O4P4
1265.02
C68H74Cl2N4NiO4P4
1264.80
a/Å
b/Å
c/Å
α/Њ
13.468(4)
16.752(5)
17.325(6)
67.19(1)
13.459(3)
16.735(4)
17.383(5)
67.05(1)
β/Њ
69.41(1)
69.22(1)
γ/Њ
68.62(1)
3253(2)
68.48(1)
3250(1)
U/Å3
λ/Å
0.710 73
4.94
1.541 86
25.13
µ/cmϪ1
Transmission factor range
F(000)
0.74–0.95
1328
1326
Crystal size/mm
Scan type
0.06 × 0.26 × 0.28
ω
0.12 × 0.22 × 0.25
θ–2θ
θ Range for data collection/Њ
Index ranges
2.16–27.04
Ϫ15 р h р 13, Ϫ19 р k р 19,
0 р l р 21
11 340
10 284 (0.049)
3692
640
0.0684
0.0821
0.0275
2.85–60.02
Ϫ14 р h р 14, Ϫ17 р k р 18,
0 р l р 19
9740
9526 (0.057)
6150
740
0.0631
0.1569
0.1295
No. reflections collected
No. independent reflections (Rint
No. observed reflectionsb
No. parameters
R b,c
)
RЈb,d
g in we
Goodness of fit on F 2 b
1.184
0.322, Ϫ0.285
1.050
Largest difference peak and hole/e ÅϪ3
¯
0.828,f Ϫ0.525
Details in common: triclinic, space group P1; Z = 2; Dc = 1.292 g cmϪ3; maximum ∆/σ 0.001. b Criterion I > 2σ(I). c R = Σ |Fo| Ϫ |Fc| /Σ|Fo|.
a
¹
2
2
d RЈ = [Σw(Fo2 Ϫ Fc )2/Σw(Fo2)2]². e w = 1/{σ2(Fo2) ϩ [g(Fo2 ϩ 2Fc )/3]2}. f 1.02 Å from Ni.
separating the precipitate, Co(ClO4)2ؒ6H2O (0.110 g, 0.30 mmol)
was added and the reaction mixture stirred for 3 h. The result-
ing light lilac solid of 2a was filtered off, washed with a small
quantity of absolute ethanol and dried in vacuo over molecular
sieves. The yield was 0.100 g (76%).
NiCl2ؒ6H2O (0.036 g, 0.15 mmol) and Ni(ClO4)2ؒ6H2O (0.062 g,
0.17 mmol) was stirred in absolute ethanol (10 cm3) at room
temperature for 2 h. The resulting yellow precipitate, yield 0.085
g (72%), was filtered off, washed out with absolute ethanol and
dried in vacuo over molecular sieves.
The same compound in similar yield was obtained by using
NaClO4ؒH2O instead of Co(ClO4)2ؒ6H2O.
[NiCl(tpta)]BF4 5a. Absolute ethanol (10 cm3) was added to a
mixture of tpta (0.130 g, 0.13 mmol), NiCl2ؒ6H2O (0.040 g, 0.17
mmol) and NaBF4 (0.029 g, 0.26 mmol) and the suspension
stirred in air at room temperature. The yellow crystalline pre-
cipitate that resulted after stirring for 2 h was separated, washed
and dried as above. The yield was 0.090 g (59%).
[CoCl(tpta)]BF4 4a. Procedure (a). A mixture of tpta (0.149
g, 0.15 mmol), CoCl2ؒ6H2O (0.048 g, 0.20 mmol) and NaBF4
(0.044 g, 0.40 mmol) in absolute ethanol (12 cm3) was stirred at
room temperature for 4 h. The resulting light lilac precipitate
(0.135 g, 77%) was filtered off, washed with a small amount of
absolute ethanol and dried in vacuo over molecular sieves.
Procedure (b). A mixture of complex 1 (0.095 g, 0.075 mmol),
NaBF4 (0.033 g, 0.30 mmol) and absolute ethanol (10 cm3) was
stirred at room temperature overnight. The precipitate (yield
0.058 g, 66%) was filtered off, washed and dried as above.
[NiCl(tpta)]PF6 7. The compound tpta (0.099 g, 0.10 mmol),
NiCl2ؒ6H2O (0.036 g, 0.15 mmol) and NH4PF6 (0.026 g, 0.16
mmol) were mixed and stirred in absolute ethanol (10 cm3) at
room temperature for 3 h. The yellow precipitate of 7 was then
filtered off, washed and dried as usual. The yield was 0.092 g
(75%).
[CoCl(tpta)]PF6 6. A mixture of tpta (0.099 g, 0.10 mmol),
CoCl2ؒ6H2O (0.040 g, 0.17 mmol) and NH4PF6 (0.029 g, 0.18
mmol) was stirred in absolute ethanol (10 cm3) for 4 h. The
resulting light lilac precipitate was filtered off and dried as
usual. The yield was 0.095 g (77%).
[NiCl(tpta)][B(C6H5)4] 9. A mixture of tpta (0.130 g, 0.13
mmol), NiCl2ؒ6H2O (0.048 g, 0.20 mmol) and NaB(C6H5)4
(0.096 g, 0.28 mmol) was stirred in absolute ethanol (15 cm3) at
room temperature for 4 h. The green-yellow precipitate that
resulted was filtered off, washed with dry solvent and dried in
vacuo over molecular sieves. The yield was 0.144 g (78%).
[CoCl(tpta)][B(C6H5)4] 8. Procedure (a). A mixture of tpta
(0.110 g, 0.11 mmol), CoCl2ؒ6H2O (0.048 g, 0.20 mmol) and
NaB(C6H5)4 (0.075 g, 0.22 mmol) in absolute ethanol (10 cm3)
was stirred for 4 h. The lilac fine-crystalline product was filtered
off, washed with dry ethanol and dried in vacuo. The yield was
0.118 g (76%).
Procedure (b). The salt NaB(C6H5)4 (0.188 g, 0.55 mmol) was
added to a suspension of complex 1 (0.140 g, 0.11 mmol) in
absolute ethanol (15 cm3) and the reaction mixture was stirred
overnight. The lilac precipitate was filtered off, washed and
dried as above. The yield was 0.074 g (48%).
Crystallography
Crystal data and data collection parameters. X-Ray data were
collected at room temperature on the Philips PW1100 diffract-
ometer (upgraded by Stoe). The unit-cell parameters and
details of data collection are given in Table 5. Unit-cell dimen-
sions were obtained by least-squares refinement of 28 reflec-
tions, 21.3 < 2θ < 29.8Њ for complex 2b and 20.7 < 2θ < 57.6Њ
for 3b. Standard reflections monitored every 90 min indicated
no significant change of the intensities for 2b and a drop
amounting to 8% for 3b. An empirical absorption correction
was applied for 3b.
[NiCl(tpta)]ClO4 3a. A mixture of tpta (0.099 g, 0.10 mmol),
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J. Chem. Soc., Dalton Trans., 1997, Pages 3445–3451

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11 S. Reimer, M. Wicholas, B. Scott and R. D. Willett, Acta
Structure solution and refinement. The structure of complex 2b
was solved by the heavy-atom method. Subsequent full-matrix
least-squares refinement on F2 and Fourier difference maps
revealed all non-hydrogen atoms. The positions of the heavy
atom and the macrocyclic ring atoms were used as a starting
model in 3b. Owing to the small number of collected data
(small crystal) in relation to the number of parameters the
phenyl atoms were refined as rigid groups in 2b. First the atoms
were fitted by a regular hexagon, but much better results were
obtained by defining a fragment with the bond lengths and
angles in the phenyl rings obtained in our previous study of a
chromium(0) complex with tpta.5 A decrease of the endocyclic
angle α is caused by the σ-electron release from phosphorus and
a difference also occurs in the bond lengths. The values used are
given in Table 4. Hydrogen atom positions were included using
a riding model. Anisotropic Uij were used for all non-hydrogen
atoms and the hydrogen atoms were assigned values of 1.2 U of
their parent atom. The structure solution, refinement and
molecular graphics computing was performed on an IBM PC/
AT-compatible microcomputer using SHELXS 86,30 SHELXL
96,31 ORTEP 92,32 and PLUTON 33 programs.
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17 K. Nakamoto, Infrared and Raman Spectra of Inorganic and
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18 A. B. P. Lever, Inorganic Electronic Spectroscopy, Elsevier,
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19 L. W. Gosser and G. W. Parshall, Inorg. Chem., 1974, 13, 1947;
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Acknowledgements
We thank the Ministry of Science and Technology of the
Republic of Croatia for financial support.
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Received 13th March 1997; Paper 7/01913K
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