Syntheses, characterization and reactivity of iron(II), nickel(II), copper(II) and zinc(II) complexes of the ligand N,N,N′,N′- tetrakis(2-pyridylmethyl)-benzene-1,3-diamine (1,3-tpbd) and its phenol derivative 2,6-bis[bis(2-pyridylmethyl)amino]-p-cresol (

FULL PAPER

DOI: 10.1002/ejic.200600944

Syntheses, Characterization and Reactivity of Iron(II), Nickel(II), Copper(II)

and Zinc(II) Complexes of the Ligand N,N,NЈ,NЈ-Tetrakis(2-pyridylmethyl)-

benzene-1,3-diamine (1,3-tpbd) and Its Phenol Derivative

2,6-Bis[bis(2-pyridylmethyl)amino]-p-cresol (2,6-tpcd)

Simon Foxon,^[a,b]Jing-Yuan Xu,^[a,c]Sabrina Turba,^[a]Michael Leibold,^[d,e]Frank Hampel,^[f]

Frank W. Heinemann,^[g]Olaf Walter,^[d]Christian Würtele,^[a]Max Holthausen,^[h]and

Siegfried Schindler*^[a]

Keywords: Iron / Copper / Zinc / Ligand effects

N,N,NЈ,NЈ-Tetrakis(2-pyridylmethyl)benzene-1,3-diamine (1,3-

tpbd), a bis(tridentate) ligand, its protonated derivative, [1,3-

tpbdH₂]²⁺, and a series of new dinuclear complexes [Fe₂(1,3-

stoichiometrically (1:1 mixtures) under aerobic conditions.

Theoretical calculations provide evidence for the formation of

a side-on dinuclear peroxido copper complex during the oxi-

tpbd)(CH₃CN)₆](ClO₄)₄·(CH₃CN)₂·(H₂O)_0.5(1), [Fe₂(1,3-tpbd)- dation of the (1,3-tpbd)copper(I) complex. A possible reaction

(DMF)₆](ClO₄)₄(2), [Ni₂(1,3-tpbd)(DMF)₆](ClO₄)₄(3), [Zn₂(1,3- product, the dinuclear copper complex [Cu₂(2,6-tpcd)(H₂O)-

tpbd)(CH₃CN)₂(SO₃CF₃)₂(H₂O)](SO₃CF₃)₂(4), [Zn₂(1,3-tpbd)-

Cl₄]·H₂O (5), [CuZn(1,3-tpbd)Cl₄] (7) and the tetranuclear cop-

(Cl)](ClO₄)₂·2H₂O (9) of a phenolate derivative of 1,3-tpbd was

synthesized and structurally characterized independently from

per(II) complex [Cu₂(1,3-tpbd)₂(H₂O)₂](ClO₄)₄·2H₂O (8) have oxidation reactions from copper(II) perchlorate and the ligand

been prepared and structurally characterized. Complex 8, a so 2,6-bis[bis(2-pyridylmethyl)amino]-p-cresol.

called “dimetallocyclophane”, interestingly only formed in the

presence of zinc ions and not when copper(II) ions were mixed

Germany, 2007)

amino]-p-cresol (2,6-tpcd) (Figure 1) represent good struc-

tural models of the histidine-rich environments found in

many dinuclear copper proteins (such as hemocyanin and

tyrosinase).^[1,4–7]

Introduction

Previously we have demonstrated that the ligand

N,N,NЈ,NЈ-tetrakis(2-pyridylmethyl)benzene-1,3-diamine (1,3-

tpbd) shown in Figure 1 can coordinate two copper ions in

close proximity.^[1–3]In this regard copper complexes of 1,3-

tpbd or its phenol derivative 2,6-bis[bis(2-pyridylmethyl)-

[a] Institut für Anorganische und Analytische Chemie, Justus-Lie-

big-Universität Gießen,

Heinrich-Buff-Ring 58, 35392 Gießen, Germany

Fax: +49-641-9934149

E-mail: siegfried.schindler@chemie.uni-giessen.de

[b] Department of Chemistry, University of Sheffield,

Sheffield, S3 7HF, United Kingdom

[c] College of Pharmacy, Tianjiin Medical University,

300070 Tianjiin, China

[d] Institut für Technische Chemie – Chemisch-Physikalische Ver-

fahren (ITC-CPV), Forschungszentrum Karlsruhe,

Postfach 3640, 76021 Karlsruhe, Germany

[e] Fachbereich Metallorganische Chemie, Universität Kassel,

Heinrich-Plett-Strasse 40, 34132 Kassel, Germany

[f] Institut für Organische Chemie, Friedrich-Alexander-Uni-

versität Erlangen-Nürnberg,

Henkestrasse 42, 91054 Erlangen, Germany

[g] Institut für Anorganische Chemie, Friedrich-Alexander-Uni-

versität Erlangen-Nürnberg,

Egerlandstrasse 1, 91058 Erlangen, Germany

[h] Institut für Anorganische und Analytische Chemie, Johann-

Wolfgang-Goethe-Universität Frankfurt/Main,

Max-von-Laue-Strasse 7, 60438 Frankfurt, Germany

Supporting information for this article is available on the

WWW under http://ww w .eurjic.org or from the author.

Figure 1. The ligands N,N,NЈ,NЈ-tetrakis(2-pyridylmethyl)benzene-

1,3-diamine (1,3-tpbd) and 2,6-bis[bis(2-pyridylmethyl)amino]-p-

cresol (2,6-tpcd; R = CH₃).

Furthermore, the intramolecular magnetic coupling ob-

served in a series of copper(II) complexes with 1,3-tpbd

could be tuned from ferromagnetic to antiferromagnetic.^[2,3]

Similar ferromagnetic coupling has been observed for cop-

per complexes with a related m-phenylenediamine-based li-

gand system.^[8,9]Recently, a 1,3-tpbd platinum complex has

been used in mechanistic studies.^[10]However to date, only

Eur. J. Inorg. Chem. 2007, 429–443

429

S. Schindler et al.

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a small number of transition-metal complexes of related de- aliphatic amine nitrogen atoms are close to 120°. However,

rivatives of the 1,3-tpbd ligand system have been investi- as discussed above, the positions of the pyridine rings in

gated.^[11–21]

1,3-tpbd and its protonated derivative are quite different.

To gain further understanding of the ligating ability of In [1,3-tpbdH₂]²⁺adjacent pyridine nitrogen atoms on each

1,3-tpbd, we herein describe the synthesis and characteriza- ligand “arm” [N2 and N3, N5 and N6] are strongly hydro-

tion of a series of iron(II), zinc(II) and copper(II) com- gen-bonded to one another. The average distance between

plexes with 1,3-tpbd as well as a copper(II) complex of the the hydrogen-bonded pyridine nitrogen atoms is 2.741 Å.

phenol analogue of 1,3-tpbd. A similar complex with the Additionally, we obtained the protonated triflate salt of 1,3-

phenol derivative ligand shown in Figure 1 (R = tert-butyl) tpbd (see Supporting Information; for Supporting Infor-

and its interesting properties (e.g. interactions with DNA) mation see also the footnote on the first page of this paper)

was recently reported by Karlin and co-workers.^[15,16]

of which the cation is identical to [1,3-tpbdH₂](ClO₄)₂.

However, the two crystal structures differ from each other

due to the crystal-packing arrangement of the anions, and

furthermore the inclusion of additional solvent molecules.

In principle these protonated ligand salts are comparable to

the metal complexes (see below) and the protons in [1,3-

Results and Discussion

N,N,NЈ,NЈ-Tetrakis(2-pyridylmethyl)benzene-1,3-diamine tpbdH₂]²⁺can be regarded as small metal cations. The pre-

(1,3-tpbd): 1,3-tpbd was prepared in modest yields from viously reported crystal structure of [1,4-tpbdH₂]²⁺displays

commercially available m-phenylenediamine and picolyl similar bond lengths and angles to the [1,3-tpbdH₂]²⁺struc-

chloride hydrochloride as previously reported.^[1]Single ture described above.^[18]

crystals of 1,3-tpbd, suitable for structural characterization,

Iron Complexes: Ligands capable of coordinating two

were obtained by slow evaporation of a methanol solution iron ions in close proximity have been employed as struc-

of 1,3-tpbd in a glove box. Attempts to recrystallize the tural models for dinuclear iron metalloproteins (e.g. the

ligand outside of the glovebox often caused the formation oxygen carrier protein hemerythrin).^[22–24]Prior to the in-

of nearly colorless crystals in a slightly brown mother vestigations of the oxygen-sensitive iron(II) model com-

liquor. The solution turned to an intense red color during pounds, we tried to synthesize and structurally characterize

a couple of days affecting the crystals as well (most likely an iron(III) complex of 1,3-tpbd. However, all our efforts

the ligand is partially oxidized) and as a consequence nu- to date in obtaining an 1,3-tpbd iron(III) complex were un-

merous attempts to solve the crystal structure failed due to successful. Numerous attempts (employing different reac-

poor refinement. A summary of crystal structure data and tion conditions) to synthesize [Fe₂(1,3-tpbd)]⁶⁺derivatives,

refinement parameters is presented in Table 2, selected such as [Fe₂(1,3-tpbd)(DMF)₆]⁶⁺or [Fe₂(1,3-tpbd)-

bond lengths and angles in Table 1. The molecular structure (RCOO)_n]^(6–n)+, by the reaction of 1,3-tpbd with Fe(ClO₄)₃

of 1,3-tpbd is shown in Figure 2. The two pyridyl units in different solvents (coordinating or non-coordinating),

3–

bonded at each amine nitrogen atom are separated from with and without addition of anions such as AsO₄

,

each other by a large distance similar to the previously re- C₆H₅COO^–, CH₃COO^–or Cl^–, only afforded the proton-

ported molecular structure of 1,4-tpbd.^[18]1,3-tpbd crys- ated free ligand and unreacted iron salts. Over a period of

tallizes with one additional methanol solvent molecule per weeks single crystals, suitable for X-ray structural analysis,

unit, hydroxyl hydrogen atom of the methanol solvent of [1,3-tpbdH₂](SO₃CF₃)₂(see supp. inf. and Experimental

molecule were located in a difference Fourier map and iso- Section) and [1,3-tpbdH₂](ClO₄)₂described above (Fig-

tropically refined.

ure 3) were obtained. Furthermore, efforts in obtaining an

Protonation of 1,3-tpbd or coordination of 1,3-tpbd to 1,3-tpbd iron(III) complex by oxidizing the corresponding

metal ions has the consequence that the pyridyl units move iron(II) precursor complex (described below) failed. These

much closer together. In Figure 3 the molecular structure results clearly indicate that the 1,3-tpbd ligand has a low

of the cation of [1,3-tpbdH₂](ClO₄)₂is shown (crystal struc- affinity for iron(III). In the presence of water, protonation

ture data and refinement parameters, bond lengths and of the ligand occurs, however in the absence of protons no

angles are presented in Table 2 and Table 1).

complexation of the iron(III) ions was observed either.

[1,3-tpbdH₂](ClO₄)₂crystallizes with two molecules per Other pyridyl containing ligands are known to stabilize

crystallographically independent unit of the unit cell to- iron(II) relative to iron(III), however in these cases it was

gether with three molecules of acetonitrile. Two of the still possible to synthesize, isolate and characterize the ac-

–

ClO₄anions are disordered. The H atoms of the proton- cording iron(III) complexes.^[25]

ated N atoms were localized in a difference Fourier map

An iron(II) complex of 1,3-tpbd was prepared and single

and refined isotropically. The crystal structures of 1,3-tpbd crystals of [Fe₂(1,3-tpbd)(CH₃CN)₆](ClO₄)₄·2CH₃CN·

and [1,3-tpbdH₂]²⁺display similar metrical parameters. The 0.5H₂O (1) were grown. The molecular structure of the cat-

immediate geometry around the aliphatic amine nitrogen ion [Fe₂(1,3-tpbd)(CH₃CN)₆]⁴⁺of 1 is shown in Figure 4

atoms is nearly planar with C1–N1 1.388(2) Å in 1,3-tpbd (crystal structure data and refinement parameters, bond

and C13–N1 1.396(4) Å in [1,3-tpbdH₂](ClO₄)₂indicating lengths and angles are presented in Table 2 and Table 1).

delocalization of the nitrogen lone pair of electrons with the The unit cell of 1 consists of two sets of crystallographically

aromatic π systems. All the interbond angles around the independent dinuclear cations, [Fe₂(1,3-tpbd)(CH₃CN)₆]⁴⁺

,

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Eur. J. Inorg. Chem. 2007, 429–443

Complexes of N,N,NЈ,NЈ-Tetrakis(2-pyridylmethyl)benzene-1,3-diamine

FULL PAPER

Table 1. Selected bond lengths [Å] and angles [°] for 1,3-tpbd ligand and compounds 1–9.

1,3-tpbd

N(1)–C(1)

N(1)–C(7)

N(1)–C(13)

N(2)–C(8)

N(2)–C(12)

N(3)–C(18)

N(3)–C(14)

N(4)–C(3)

N(4)–C(19)

N(4)–C(25)

1.411(2)

1.451(2)

1.460(2)

1.345(2)

1.357(3)

1.342(3)

1.348(2)

1.388(2)

1.452(2)

1.454(2)

N(5)–C(24)

N(5)–C(20)

N(6)–C(30)

N(6)–C(26)

C(7)–C(8)

1.326(4)

1.336(2)

1.333(3)

1.339(2)

1.514(3)

1.382(3)

1.381(3)

1.370(3)

1.371(4)

C(1)–N(1)–C(7)

C(1)–N(1)–C(13)

C(7)–N(1)–C(13)

C(8)–N(2)–C(12)

C(18)–N(3)–C(14)

C(3)–N(4)–C(19)

C(3)–N(4)–C(25)

C(19)–N(4)–C(25)

C(24)–N(5)–C(20)

C(30)–N(6)–C(26)

120.7(2)

118.5(2)

115.1(2)

117.2(2)

121.4(2)

120.4(2)

117.9(2)

117.1(2)

C(8)–C(9)

C(9)–C(10)

C(10)–C(11)

C(11)–C(12)

[H₂1,3-tpbd](ClO₄)₂

N(2)–H(2A)

N(5)–H(5A)

N(1)–C(13)

N(1)–C(1)

N(1)–C(7)

N(2)–C(6)

N(2)–C(2)

C(1)–C(2)

C(2)–C(3)

C(3)–C(4)

C(4)–C(5)

C(5)–C(6)

0.84(4)

0.94(4)

N(3)–C(8)

N(3)–C(12)

C(7)–C(8)

1.336(4)

1.343(4)

1.517(4)

1.386(5)

1.388(6)

1.397(4)

1.447(4)

1.451(4)

1.334(4)

1.341(5)

1.337(5)

1.352(5)

C(13)–N(1)–C(1)

C(1)–N(1)–C(7)

119.8(2)

118.6(2)

119.7(2)

121.3(2)

119.6(2)

118.8(2)

120(3)

118(3)

121(2)

116(2)

1.396(4)

1.449(4)

1.453(4)

1.340(4)

1.348(4)

1.514(4)

1.378(4)

1.388(5)

1.372(6)

1.372(5)

C(13)–N(1)–C(7)

C(17)–N(4)–C(19)

C(17)–N(4)–C(25)

C(19)–N(4)–C(25)

C(6)–N(2)–H(2A)

C(2)–N(2)–H(2A)

C(24)–N(5)–H(5A)

C(20)–N(5)–H(5A)

C(8)–C(9)

C(9)–C(10)

N(4)–C(17)

N(4)–C(19)

N(4)–C(25)

N(5)–C(20)

N(5)–C(24)

N(6)–C(26)

N(6)–C(30)

[Fe₂(1,3-tpbd)(CH₃CN)₆](ClO₄)₄·2CH₃CN·0.5H₂O (1)

Fe(1)–N(3)

Fe(1)–N(9)

Fe(1)–N(7)

Fe(1)–N(8)

Fe(1)–N(2)

Fe(1)–N(1)

Fe(2)–N(10)

Fe(2)–N(5)

Fe(2)–N(12)

Fe(2)–N(11)

Fe(2)–N(6)

Fe(2)–N(4)

Fe(3)–N(19)

Fe(3)–N(20)

Fe(3)–N(21)

Fe(3)–N(15)

Fe(3)–N(14)

Fe(3)–N(13)

Fe(4)–N(22)

Fe(4)–N(24)

Fe(4)–N(18)

Fe(4)–N(17)

Fe(4)–N(23)

Fe(4)–N(16)

1.989(3)

1.997(3)

2.001(3)

2.007(3)

2.024(3)

2.131(2)

2.099(3)

2.146(3)

2.164(3)

2.183(3)

2.188(3)

2.263(3)

1.953(3)

1.955(3)

1.963(3)

1.966(3)

1.976(2)

2.095(2)

2.097(3)

2.100(3)

2.107(3)

2.124(3)

2.142(3)

2.280(3)

N(3)–Fe(1)–N(9)

N(3)–Fe(1)–N(7)

N(9)–Fe(1)–N(7)

N(3)–Fe(1)–N(8)

N(9)–Fe(1)–N(8)

N(7)–Fe(1)–N(8)

N(3)–Fe(1)–N(2)

N(9)–Fe(1)–N(2)

N(7)–Fe(1)–N(2)

N(8)–Fe(1)–N(2)

N(3)–Fe(1)–N(1)

N(9)–Fe(1)–N(1)

N(7)–Fe(1)–N(1)

N(8)–Fe(1)–N(1)

N(2)–Fe(1)–N(1)

N(10)–Fe(2)–N(5)

N(10)–Fe(2)–N(12)

N(5)–Fe(2)–N(12)

N(10)–Fe(2)–N(11)

N(5)–Fe(2)–N(11)

N(12)–Fe(2)–N(11)

N(10)–Fe(2)–N(6)

N(5)–Fe(2)–N(6)

N(12)–Fe(2)–N(6)

171.8(2)

95.0(2)

90.7(2)

84.5(2)

89.6(2)

90.4(2)

94.3(2)

91.3(2)

92.6(2)

176.8(2)

83.0(1)

92.3(1)

171.4(1)

97.7(1)

79.2(1)

95.6(2)

90.3(2)

173.6(2)

90.4(2)

93.6(1)

83.9(2)

94.3(2)

96.3(1)

85.6(1)

N(11)–Fe(2)–N(6)

N(10)–Fe(2)–N(4)

N(5)–Fe(2)–N(4)

N(12)–Fe(2)–N(4)

N(11)–Fe(2)–N(4)

N(6)–Fe(2)–N(4)

168.6(1)

165.6(2)

76.8(1)

98.0(1)

102.2(1)

74.7(1)

90.5(1)

89.5(1)

90.7(1)

93.5(1)

85.7(1)

175.4(1)

91.6(1)

177.7(1)

93.3(1)

171.7(1)

91.9(2)

93.0(1)

91.5(2)

172.4(2)

93.5(1)

172.6(2)

88.9(1)

N(19)–Fe(3)–N(20)

N(19)–Fe(3)–N(21)

N(20)–Fe(3)–N(21)

N(19)–Fe(3)–N(15)

N(20)–Fe(3)–N(15)

N(21)–Fe(3)–N(15)

N(19)–Fe(3)–N(14)

N(20)–Fe(3)–N(14)

N(15)–Fe(3)–N(14)

N(19)–Fe(3)–N(13)

N(22)–Fe(4)–N(24)

N(22)–Fe(4)–N(18)

N(24)–Fe(4)–N(18)

N(24)–Fe(4)–N(17)

N(18)–Fe(4)–N(17)

N(18)–Fe(4)–N(23)

N(17)–Fe(4)–N(23)

[Fe₂(1,3-tpbd)(DMF)₆](ClO₄)₄(2)

Fe(1)–O(1)

Fe(1)–O(2)

Fe(1)–O(3)

Fe(1)–N(1)

Fe(1)–N(2)

Fe(1)–N(3)

N(3)–Fe(1)–N(1)

2.075(2)

2.112(2)

2.110(2)

2.312(2)

2.152(2)

2.174(2)

75.51(7)

O(1)–Fe(1)–O(3)

O(1)–Fe(1)–O(2)

O(3)–Fe(1)–O(2)

O(1)–Fe(1)–N(2)

O(3)–Fe(1)–N(2)

O(2)–Fe(1)–N(2)

O(2)–Fe(1)–N(1)

89.45(8)

90.84(8)

97.45(8)

90.65(8)

95.89(8)

166.58(7)

88.79(7)

O(1)–Fe(1)–N(3)

O(3)–Fe(1)–N(3)

O(2)–Fe(1)–N(3)

N(2)–Fe(1)–N(3)

O(1)–Fe(1)–N(1)

O(3)–Fe(1)–N(1)

N(2)–Fe(1)–N(1)

177.19(8)

89.44(8)

86.74(8)

92.03(8)

105.90(7)

163.39(7)

77.98(7)

[Zn₂(1,3-tpbd)(CH₃CN)₂(SO₃CF₃)₂(H₂O)](SO₃CF₃)₂(4)

Zn(1)–N(1)

Zn(1)–N(2)

Zn(1)–N(3)

Zn(1)–N(60)

Zn(1)–O(1)

Zn(1)–O(12)

2.350(5)

2.032(5)

2.046(5)

2.078(5)

2.243(5)

2.242(4)

N(1)–Zn(1)–N(2)

N(1)–Zn(1)–N(3)

N(2)–Zn(1)–N(3)

N(1)–Zn(1)–O(12)

N(2)–Zn(1)–O(12)

N(3)–Zn(1)–O(12)

78.3(2)

78.9(2)

156.1(2)

93.1(2)

89.0(2)

99.4(2)

N(4)–Zn(2)–N(5)

N(4)–Zn(2)–N(6)

N(5)–Zn(2)–N(6)

N(4)–Zn(2)–O(11)

N(5)–Zn(2)–O(11)

N(6)–Zn(2)–O(11)

79.0(2)

79.1(2)

152.3(2)

97.6(2)

105.7(2)

93.9(2)

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Table 1. (Continued)

Zn(2)–N(4)

Zn(2)–N(5)

Zn(2)–N(6)

Zn(2)–N(70)

Zn(2)–O(11)

Zn(2)–O(21)

2.346(4)

O(1)–Zn(1)–O(12)

N(2)–Zn(1)–O(1)

O(1)–Zn(1)–N(1)

N(3)–Zn(1)–O(1)

N(60)–Zn(1)–O(1)

N(60)–Zn(1)–N(1)

N(2)–Zn(1)–N(60)

N(3)–Zn(1)–N(60)

N(60)–Zn(1)–O(12)

173.4(2)

89.2(2)

92.7(2)

84.8(2)

86.5(2)

178.9(2)

100.9(2)

101.7(2)

87.7(2)

O(11)–Zn(2)–O(21)

N(4)–Zn(2)–O(21)

N(5)–Zn(2)–O(21)

N(70)–Zn(2)–O(11)

N(5)–Zn(2)–N(70)

N(70)–Zn(2)–O(21)

N(6)–Zn(2)–O(21)

N(70)–Zn(2)–N(4)

N(6)–Zn(2)–N(70)

167.3(2)

2.024(4)

2.021(5)

2.104(5)

2.122(4)

2.578(4)

88.3(2)

86.5(2)

90.1(2)

100.2(2)

84.0(2)

76.1(2)

172.3(2)

99.3(2)

[Zn₂(1,3-tpbd)Cl₄] (5)

Zn(1)–N(11)

Zn(1)–N(21)

Zn(1)–Cl(1)

Zn(1)–Cl(2)

Zn(1)–N(1)

Zn(2)–N(31)

Zn(2)–N(41)

Zn(2)–Cl(4)

Zn(2)–Cl(3)

Zn(2)–N(2)

2.046(6)

2.055(6)

2.248(2)

2.305(2)

2.646(2)

2.066(7)

2.042(7)

2.314(3)

2.259(3)

2.594(3)

N(11)–Zn(1)–N(21)

N(11)–Zn(1)–Cl(1)

N(21)–Zn(1)–Cl(1)

N(11)–Zn(1)–Cl(2)

N(1)–Zn(1)–N(11)

N(21)–Zn(1)–Cl(2)

Cl(1)–Zn(1)–Cl(2)

Zn(1)–Cl(1)–O(1)

C(16)–N(11)–Zn(1)

N(1)–Zn(1)–Cl(1)

120.1(3)

116.6(2)

113.0(2)

98.3(2)

N(41)–Zn(2)–N(31)

N(41)–Zn(2)–Cl(3)

N(31)–Zn(2)–Cl(3)

N(41)–Zn(2)–Cl(4)

N(2)–Zn(2)–N(31)

N(31)–Zn(2)–Cl(4)

Cl(3)–Zn(2)–Cl(4)

Zn(2)–Cl(3)–O(1)

C(32)–N(31)–Zn(2)

N(2)–Zn(2)–Cl(3)

124.6(3)

105.6(2)

120.9(2)

99.1(2)

72.9(2)

98.6(2)

102.4(1)

110.2(2)

117.6(6)

97.4(2)

71.7(2)

100.8(2)

103.5(1)

89.9(2)

122.0(6)

94.8(2)

[CuZn(1,3-tpbd)Cl₄] (7)

Zn(1)–N(11)

Zn(1)–N(21)

Zn(1)–Cl(2)

Zn(1)–Cl(1)

Zn(1)–N(1)

Cu(1)–N(41)

Cu(1)–N(51)

Cu(1)–Cl(3)

Cu(1)–Cl(4)

Cu(1)–N(2)

2.03(2)

N(11)–Zn(1)–N(21)

N(11)–Zn(1)–Cl(2)

N(21)–Zn(1)–Cl(2)

N(11)–Zn(1)–Cl(1)

N(21)–Zn(1)–Cl(1)

Cl(2)–Zn(1)–Cl(1)

N(11)–Zn(1)–N(1)

N(21)–Zn(1)–N(1)

Cl(2)–Zn(1)–N(1)

Cl(1)–Zn(1)–N(1)

145.4(4)

95.1(3)

96.4(3)

99.2(3)

109.6(3)

103.3(2)

76.9(4)

77.2(4)

150.8(3)

105.6(3)

N(41)–Cu(1)–N(51) 143.4(4)

2.04(2)

2.307(4)

2.333(3)

2.37(2)

2.04(2)

2.06(2)

2.279(3)

2.284(3)

2.499(2)

N(41)–Cu(1)–Cl(3)

N(51)–Cu(1)–Cl(3)

N(41)–Cu(1)–Cl(4)

N(51)–Cu(1)–Cl(4)

Cl(3)–Cu(1)–Cl(4)

N(41)–Cu(1)–N(2)

N(51)–Cu(1)–N(2)

Cl(3)–Cu(1)–N(2)

Cl(4)–Cu(1)–N(2)

102.2(3)

104.0(3)

96.7(3)

97.9(3)

110.0(2)

74.6(3)

74.1(3)

105.2(3)

144.8(3)

[Cu₂(1,3-tpbd)₂(H₂O)₂](ClO₄)₄(8)

Cu(1)–N(1)

Cu(1)–N(2)

Cu(1)–N(3)

Cu(1)–N(5)

Cu(1)–O(1)

2.074(3)

1.986(3)

1.976(3)

2.000(3)

2.286(3)

N(3)–Cu(1)–N(2)

N(3)–Cu(1)–N(5)^[a]

N(2)–Cu(1)–N(5)^[a]

N(5)^[a]–Cu(1)–N(1)

N(5)^[a]–Cu(1)–O(1)

164.8(2)

98.4(2)

96.8(2)

157.4(2)

104.1(2)

N(2)–Cu(1)–N(1)

N(3)–Cu(1)–O(1)

N(3)–Cu(1)–N(1)

N(2)–Cu(1)–O(1)

N(1)–Cu(1)–O(1)

82.4(2)

89.4(2)

83.5(2)

87.0(2)

98.5(1)

[Cu₂(2,6-tpcd)(H₂O)(Cl)](ClO₄)₂·2H₂O (9)

Cu(1)–O(2)

Cu(1)–N(5)

Cu(1)–N(6)

Cu(1)–N(4)

Cu(1)–O(1)

Cu(2)–N(3)

Cu(2)–N(2)

Cu(2)–N(1)

Cu(2)–O(1)

Cu(2)–Cl(1)

1.993(2)

2.003(2)

2.013(2)

2.064(2)

2.153(2)

1.996(2)

2.007(2)

2.076(2)

2.106(2)

2.280(1)

O(2)–Cu(1)–N(5)

O(2)–Cu(1)–N(6)

N(5)–Cu(1)–N(6)

O(2)–Cu(1)–N(4)

N(5)–Cu(1)–N(4)

N(6)–Cu(1)–N(4)

O(2)–Cu(1)–O(1)

N(5)–Cu(1)–O(1)

N(6)–Cu(1)–O(1)

N(4)–Cu(1)–O(1)

94.3(1)

99.3(1)

163.8(1)

176.8(1)

82.9(1)

83.6(1)

94.9(1)

92.6(1)

83.7(1)

N(3)–Cu(2)–N(2)

N(3)–Cu(2)–N(1)

N(2)–Cu(2)–N(1)

N(3)–Cu(2)–O(1)

N(2)–Cu(2)–O(1)

N(1)–Cu(2)–O(1)

N(3)–Cu(2)–Cl(1)

N(2)–Cu(2)–Cl(1)

N(1)–Cu(2)–Cl(1)

O(1)–Cu(2)–Cl(1)

159.1(1)

82.9(1)

81.9(1)

96.0(1)

96.5(1)

84.0(1)

97.8(1)

96.6(1)

176.7(1)

99.1(1)

[a] –x+1, –y+1, –z+1.

and uncoordinated perchlorate anions, four acetonitrile sol-

As has been observed previously for Fe^IITPA complexes,

vent molecules and one water molecule. There are only the Fe–N_aminedistances ranging from 2.095(2) to 2.280(3) Å

minor structural differences between the two dinuclear cat- are characteristically longer than the Fe–N_pyridinebond

ions. In each cation, the intramolecular Fe···Fe separation lengths of 1.966(3) to 2.188(3) Å.^[26–28]Three fac-coordi-

is 7.488(1) and 7.697(2) Å, respectively. The 1,3-tpbd ligand nated acetonitrile molecules occupy the remaining coordi-

coordinates each iron(II) center through two pyridine nitro- nation sites to complete the slightly distorted octahedral co-

gen atoms and one aliphatic amine nitrogen atom, dis- ordination geometry around each iron(II) center, with Fe–

playing N_amine–Fe–N_pyridineangles averaging ca. 81° to ac- N–C angles ranging from 166.7(3) to 177.1(3)° and the Fe–

commodate the five-membered chelate rings.

N distances ranging from 1.953(3) to 2.183(3) Å. These

432

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Complexes of N,N,NЈ,NЈ-Tetrakis(2-pyridylmethyl)benzene-1,3-diamine

FULL PAPER

Figure 2. Molecular structure of 1,3-tpbd; hydrogen atoms are

omitted for clarity.

Figure 3. Molecular structure of the cation of [1,3-tpbdH₂]-

(ClO₄)₂; only hydrogen atoms involved in hydrogen bonding are

shown.

shorter Fe–N distances indicate that the nitrile groups of

the acetonitrile solvent molecules are strongly coordinated

to the iron(II) center. Intermolecular π···π interactions (ca.

3.675 Å) exist between C26–C27–C28–C29–C30–N6 and group. Each iron(II) center lies in a distorted N₃O₃octahe-

C56–C57–C58–C59–C60–N15 of adjacent pyridine rings dral coordination environment. The equatorial plane

from two independent dinuclear cations.

around Fe(1) comprises two pyridyl nitrogen atoms [N(2)

Furthermore, second iron(II) complex, [Fe₂(1,3- and N(3)] from the fac-coordinated 1,3-tpbd ligand and two

a

tpbd)(DMF)₆](ClO₄)₄(2), was prepared. The molecular oxygen atoms [O(1) and O(2)] from coordinated DMF sol-

structure of the cation of complex 2 is shown in Figure 5 vent molecules. Apical positions are occupied by the terti-

(crystal structure data and refinement parameters, bond ary amine nitrogen N(1) of 1,3-tpbd and oxygen atom O(3)

lengths and angles are presented in Table 2 and Table 1). from a third DMF solvent molecule. The Fe–N_pyridinebond

Compound 2 crystallizes with half a molecule per crystallo- lengths [2.152(2)–2.174(2) Å] are characteristically shorter

graphic independent unit of the unit cell, the other half is than those of Fe–N_amine[2.312(2) Å] and the cis N_pyridine

–

generated by the crystallographic twofold axis of the space Fe–N_pyridineangles [92.03°] are entirely consistent with

Table 2. Crystallographic data for 1,3-tpbd ligand and compounds 1, 2 and 4.

1,3-tpbd

[1,3-tpbdH₂](ClO₄)

2

4

Compound

1

Empirical formula

M_r

C₃₁H₃₂N₆O

504.63

C₆₆H₆₉Cl₄N₁₅O₁₆

1470.16

C₄₆H₅₃Cl₄Fe₂N₁₄O_16.5C₂₄H₃₅Cl₂FeN₆O₁₁C₄₀H₃₉F₁₂N₉O₁₃S₄Zn₂

1319.52

710.33

1340.78

Temperature [K]

193(2)

200(2)

100(2)

200(2)

293(2)

Radiation (λ [Å])

Crystal size [mm]

Crystal system

Space group

a [Å]

b [Å]

c [Å]

α [°]

β [°]

0.71073

0.8ϫ0.8ϫ0.4

monoclinic

C2/c (no. 15)

34.813(4)

11.056(2)

19.807(2)

90

0.71073

0.48ϫ0.32ϫ1.48

triclinic

0.8ϫ0.6ϫ0.6

monoclinic

P2₁/c (no. 14)

21.818(2)

19.862(2)

16.294(2)

90

102.656(2)

90

6889.1(8)

4

0.25ϫ0.21ϫ0.07

monoclinic

P2₁(no. 4)

14.532(2)

23.015(2)

17.284(2)

90

93.12(1)

90

5772(1)

0.62ϫ0.50ϫ0.42

orthorhombic

Pna2₁(no. 33)

25.712(2)

9.569(1)

21.901(2)

90

5388.5(9)

4

1.653

¯

P1 (no. 2)

8.0703(10)

13.2071(17)

14.379(2)

64.833(15)

81.997(16)

88.423(15)

1372.7(3)

2

121.515(2)

90

6499(2)

γ [°]

V [Å³]

Z

4

8

ρ_calcd.[gcm^–3

]

1.221

0.077

536

1.417

0.251

3064

1.518

0.767

2716

1.452

0.692

2952

µ [mm^–1

F(000)

]

1.154

2712

Scan range θ [°]

Index ranges

2.78 to 28.05

–9ՅhՅ9

–17ՅkՅ16

–18ՅlՅ18

12413

1.64 to 28.30

–29ՅhՅ28

–26ՅkՅ26

–21ՅlՅ21

81510

3.32 to 27.10

–18ՅhՅ18

–29ՅkՅ29

–22ՅlՅ22

140656

1.97 to 28.31

–46ՅhՅ46

–14ՅkՅ14

–26ՅlՅ26

37816

2.27 to 27.00

–32ՅhՅ32

–12ՅkՅ12

–27ՅlՅ27

12077

Reflections collected

Unique reflections

R_int

6069

0.0469

16875

0.0513

25407

0.0542

7966

0.0431

11763

0.0342

Data/restraints/parameters

Goodness-of-fit on F²

R₁, wR₂[IϾ4σ(I)]

R₁, wR₂(all data)

Flack parameter^[60]

Largest diff. peak/hole [e·Å^–3

6069/0/356

1.042

0.0511, 0.1290

0.0847, 0.1464

–

16875/42/933

1.032

0.0707, 0.1843

0.1153, 0.2218

–

25407/41/1536

1.026

0.0412, 0.0818

0.0617, 0.0883

0.009(8)

0.689, –0.707

7966/45/433

1.056

0.0460, 0.1192

0.0709, 0.1308

–

11763/3/730

0.990

0.0577, 0.0944

0.1128, 0.1130

–0.02(2)

0.373, –0.375

]

0.262, –0.205

1.107, –0.771

0.688, –0.846

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S. Schindler et al.

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Figure 4. Molecular structure of the cation of [Fe₂(1,3-tpbd)(CH₃CN)₆](ClO₄)₄·2CH₃CN·0.5H₂O (1); hydrogen atoms and solvent mole-

cules are omitted for clarity.

Figure 5. Molecular structure of the cation of [Fe₂(1,3-tpbd)(DMF)₆](ClO₄)₄(2); hydrogen atoms are omitted for clarity.

those found in 1. The Fe–O_DMFdistances [2.075(2) to aniline (phdpa), the half ligand system of 1,3-tpbd, a 2:1

2.112(2) Å] and the average cis-coordinated angles [O–Fe– ligand/metal ion ratio was observed, however, no crystal

O 92.58°] indicate that the DMF molecules are strongly co- structures were reported.^[20]

ordinated to the iron(II) center. The Fe···Fe separation of

Nickel Complexes: Reacting [Ni(DMF)₆](ClO₄)₂with

6.962 Å is shorter than in 1, probably a consequence of the 1,3-tpbd under anaerobic conditions in a glove box led to

stronger π···π interaction (ca. 3.596 Å) between the two pyr- the nickel(II) analogue of 2, [Ni₂(1,3-tpbd)(DMF)₆](ClO₄)₄

idine rings (C2–C3–C4–C5–C6–N2 and C2A–C3A–C4A– (3). Crystals suitable for X-ray crystallography were grown

C5A–C6A–N2A) each from a different tridentate end of the and isolated. Compound 3 crystallizes with nearly identical

1,3-tpbd molecule.

cell parameters as 2 (Table 2), but the structure of 3 is much

Both iron(II) complexes were found to only react slowly better described in the monoclinic space group C2 (3) than

with dioxygen, however much faster with hydrogen perox- C2/c (2). Accordingly, the systematic absences for the glide

ide. Preliminary kinetic studies of both oxidation reactions plane in C2/c for 3 are not observed, whereas for 2 these

indicated complex reaction mechanisms that could not be systematic absence conditions are fulfilled absolutely so that

elucidated. Most likely this is a consequence that 1,3-tpbd is the structure of 2 is described correctly in C2/c. However, a

not an innocent ligand and is also involved in the oxidation description of the structure of 3 in C2/c is possible but leads

reactions (see below). Furthermore, efforts to isolate reac- to a significant increase of the R₁value from 10 to 16%.

tion products from these oxidations, such as the according Therefore; even if it can be assumed from the cell param-

iron(III) complexes described above, were unsuccessful. In eters that 2 and 3 are isostructural, the crystal structure of

contrast with 1,4-tpbd as a ligand only polymeric iron(II) 3 here is presented in the lower symmetric space group C2.

complexes were obtained.^[19]With N,N-bis(2-pyridylmethyl)- A Figure of the molecular structure of the cation of 3 as

434

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Complexes of N,N,NЈ,NЈ-Tetrakis(2-pyridylmethyl)benzene-1,3-diamine

FULL PAPER

well as crystal structure data and refinement parameters, (applying different conditions), we obtained crystals of the

bond lengths and angles are presented in the Supporting zinc(II) complex [Zn₂(1,3-tpbd)(CH₃CN)₂(SO₃CF₃)₂-

Information. (H₂O)](SO₃CF₃)₂(4) with triflate as a counter anion. The

The asymmetric unit of complex 3 comprises two crystal- molecular structure of the cation of 4 in Figure 6 shows

lographically independent “half” cation units and four an unsymmetric di-zinc unit, both ions linked by the m-

–

ClO₄anions, of which three are disordered. The full con- phenylenediamine group and a triflate ion giving an intra-

tents of the unit cell is generated by applying symmetry op- molecular Zn···Zn distance of 6.007(1) Å, which is much

erations to the asymmetric unit cell. As the structure of 3 shorter than in those complexes that are only bridged by

is very similar to that of 2 and the calculations might be 1,3-tpbd. However, it is close to the Cu···Cu distance

performed as well in the centrosymmetric space group C2/c [5.873(1) Å] in the analogous complex [Cu₂(1,3-tpbd)-

the final absolute structure parameter is relatively high. The (H₂O)₂(ClO₄)₃] (ClO₄) with an additional perchlorate- in-

two crystallographically independent [Ni₂(1,3-tpbd)-

(DMF)₆]²⁺cations of 3 differ only marginally with regard

to their bond lengths and angles.

Zinc Complexes: In investigating redox-active metal com-

plexes of iron and copper it is useful to study in comparison

complexes with nonredox active centers such as zinc. Cop-

per(II) ions can be substituted by zinc(II) ions and ad-

ditionally show quite similar coordination behavior. Such

zinc(II) complexes themselves can show interesting reaction

properties, for example they can be used to hydrolyze diri-

bonucleoside monophosphate diesters.^[29]However, in con-

trast to our expectations the synthesis of a zinc(II) complex

of 1,3-tpbd turned out to be more difficult than the synthe-

sis of the according copper(II) complexes. Mixing zinc(II)

perchlorate and 1,3-tpbd in alcoholic solution, immediately

led to white gelatinous-like precipitates that could not be

(re)crystallized. Only after a large number of experiments are omitted for clarity.

Figure 6. Molecular structure of the cation of [Zn₂(1,3-

tpbd)(CH₃CN)₂(SO₃CF₃)₂(H₂O)](SO₃CF₃)₂(4). Hydrogen atoms

Table 3. Crystallographic data for compounds 5–9.

Compound

5

7

8

9

Empirical formula

M_r

C₃₀H₃₀Cl₄N₆OZn₂

763.14

173(2)

C₃₀H₂₈Cl₄CuN₆Zn

743.29

173(2)

C₆₀H₆₄Cl₄Cu₂N₁₂O₂₀

1542.11

293(2)

C₃₁H₃₅Cl₃Cu₂N₆O₁₂

917.08

200(2)

Temperature [K]

Radiation (λ [Å])

Crystal size [mm]

Crystal system

Space group

a [Å]

b [Å]

c [Å]

α [°]

β [°]

0.71073

0.20ϫ0.10ϫ0.10

monoclinic

P2₁/n (no. 14)

9.177(2)

27.304(6)

12.287(3)

90

91.79(2)

90

3077.1(2)

4

0.30ϫ0.20ϫ0.20

monoclinic

P2₁(no. 4)

8.600(2)

13.002(3)

13.690(3)

90

103.24(3)

90

1490.1(5)

2

0.65ϫ0.50ϫ0.32

monoclinic

P2₁/n (no. 14)

10.859(1)

22.660(2)

13.072(1)

90

94.54(1)

90

3206.5(5)

2

0.25ϫ0.35ϫ0.2

triclinic

¯

P1 (no. 2)

10.495(1)

12.184(2)

14.442(2)

93.880(1)

95.284(1)

94.411(1)

1828.3(3)

2

γ [°]

V [Å³]

Z

ρ_calcd.[gcm^–3]

µ [mm^–1]

F(000)

1.647

1.943

1552

1.657

1.910

754

1.597

0.916

1588

1.666

1.453

936

Scan range θ [°]

Index ranges

2.68 to 26.33

–11ՅhՅ11

–34ՅkՅ0

0ՅlՅ15

6543

6256

0.1193

2.56 to 33.67

–10ՅhՅ0

–4ՅkՅ16

–17ՅlՅ16

3407

3196

0.0611

2.08 to 27.00

–1ՅhՅ13

–28ՅkՅ1

–16ՅlՅ16

8527

7002

0.0214

1.68 to 28.31

–13ՅhՅ13

–15ՅkՅ16

–18ՅlՅ19

16512

8570

0.0363

Reflections collected

Unique reflections

R_int

Data/restraints/parameters

Goodness-of-fit on F²

R₁, wR₂[IϾ4σ(I)]

R₁, wR₂(all data)

Flack parameter^[60]

Largest diff. peak/hole [e Å^–3]

6256/0/388

1.014

0.0610, 0.1181

0.1834, 0.1670

–

3196/1/379

1.757

0.0569, 0.2133

0.0704, 0.2198

–

7002/5/507

1.016

0.0500, 0.0993

0.0932, 0.1155

–

8570/0/518

0.892

0.0388, 0.0848

0.0693, 0.0923

–

0.829, –0.790

1.361, –1.294

0.459, –0.450

0.720, –0.651

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435

S. Schindler et al.

FULL PAPER

stead of the triflate-bridge (crystal structure data and re- H_bare based on greater stabilisation of electron withdrawal

finement parameters, selected bond lengths and angles are in the para position, compared to the meta position, and

presented in Table 3 and Table 1).^[1]

previous assignments of pyridine protons in related com-

The coordination geometry around Zn1 is best described pounds.^[31]

as distorted octahedral. The equatorial plane around the

Heterodinuclear Zinc(II) and Copper(II) Complexes: Af-

zinc(II) center is occupied by three N-donor atoms of the ter achieving the synthesis of a zinc(II) complex as well as

meridional capping ligand 1,3-tpbd (N1, N2 and N3). Api- the previously reported copper(I) and copper(II) complexes

cal positions are occupied by O12 of the bridging triflate with the ligand 1,3-tpbd, it was obvious that we should try

anion and O1 of a water molecule. The nature of the ligands to prepare a heterodinuclear zinc(II) copper(II) complex as

around Zn2 differs from Zn1 in that a terminal triflate, in- a model complex for the enzyme superoxide dismutase

stead of a water molecule, occupies one of the apical coordi- (CuZnSOD).^[32–38]

However,

mixing

stoichiometric

nation sites. The N_pyridine–Zn–N_pyridinebond angles of amounts of 1,3-tpbd together with zinc(II) and copper(II)

156.1(2)° and 152.3(2)° in 4 are smaller than N_pyridine–Cu– chloride did not lead to the isolation of pure [CuZn(1,3-

N_pyridinein [Cu₂(1,3-tpbd)(H₂O)₂](ClO₄)₄·4H₂O [164.5(2)°] tpbd)Cl₄], but instead to a mixture of the three dinuclear

apparently owing to the bigger steric hindrance of the trifl- complexes: [Zn₂(1,3-tpbd)Cl₄] (5), [Cu₂(1,3-tpbd)Cl₄] (6)

ate ion. Accordingly, both distances of Zn–N_pyridinein the and [CuZn(1,3-tpbd)Cl₄] (7). Structural characterization of

range of 2.021(5)–2.046(5) Å and Zn–N_amineat 2.350(5) and all three complexes was achieved by picking individual crys-

2.346(4) Å are longer than those in [Cu₂(1,3-tpbd)- tals (that were different in color) from the reaction mixture.

(H₂O)₂](ClO₄)₄·4H₂O

[av.

Cu–N_pyridine

1.969(5) Å; The molecular structure of 5 is shown in Figure 8 and that

Cu–N_amine2.089(5) Å]. This also applies for the distance of of 7 in Figure 9 (crystal structure data and refinement pa-

the acetonitrile substituent [Zn–N_CϵNav. 2.091(5) Å] in- rameters, bond lengths and angles are presented in Table 3

stead of water [Cu–O_w1.985(5) Å] at the fourth equatorial and Table 1).

site. A triflate anion bridges the two zinc(II) centers via O11

and O12 [Zn1–O12 2.242(4) Å and Zn2–O11 2.122(4) Å].

The structure is “capped” at the apical positions by a water

molecule [Zn1–O1 2.243(5) Å] for Zn1 and by a terminal

triflate anion [Zn2–O21 2.578(4) Å]. To the best of our

knowledge there is only one further example of a crystal

structure containing a bridging triflate anion linking two

zinc(II) ions found in the Cambridge Crystallographic Dat-

abase.^[30]Efforts to obtain crystals of the (1,3-tpbd)cop-

per(II) triflate analogue failed so far. Furthermore, using

1,4-tpbd as a ligand only a mononuclear zinc complex,

[ZnCl₂(1,4-tpbd)], was obtained and its crystal structure has

been reported.^[19]

In contrast to the according copper(II) complexes, com-

1

plex 4 is diamagnetic and can be studied in solution by H

NMR spectroscopy. Four types of pyridine proton reso-

nances are found in the range 7.4–8.6 ppm (see Exp. Sect.).

These four proton resonances represent four symmetry

equivalent sets of the pyridine protons found in the com-

plex. Two triplets and two doublets are formed by the split-

ting of each pyridine proton by its adjacent proton(s). The

splitting scheme is depicted in Figure 7. H_ais split into a

doublet by H_b(J = 5 Hz), and H_dis split into a doublet by

H_c(J = 8 Hz). Proton H_ais assigned to the downfield doub-

let, and H_das the upfield doublet. H_bis split by both H_a

(J = 6 Hz) and H_c(J = 7 Hz) to form a triplet, and H_cis

split by both H_b(J = 7 Hz) and H_d(J = 8 Hz) to form a

triplet. H_cis assigned to the downfield triplet, and H_bis

assigned to the upfield triplet. The assignments of H_cand

Figure 8. Molecular structure of [Zn₂(1,3-tpbd)Cl₄] (5); hydrogen

atoms are omitted for clarity.

Figure 9. Molecular Structure of [CuZn(1,3-tpbd)Cl₄] (7); hydrogen

atoms are omitted for clarity.

Figure 7. NMR assignment in complex 1, 2 and 4.

436

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Complexes of N,N,NЈ,NЈ-Tetrakis(2-pyridylmethyl)benzene-1,3-diamine

FULL PAPER

The crystal structure of [Cu₂(1,3-tpbd)Cl₄] (6) has been parameters, bond lengths and angles are presented in

obtained previously in a different study and crystallo- Table 3 and Table 1).

graphic details will be published elsewhere.^[13]Due to the

fact that here X-ray crystallography measurements do not

allow the differentiation between zinc and copper ions, the

presence of the different metal ions was further confirmed

by photon-induced X-ray emission spectroscopy of the

crystals of 5, 6 and 7.

The metal ions are linked through the 1,3-phenylenedi-

amine group leading to an intramolecular Zn···Zn distance

of 6.925 Å for 5 and Cu···Zn separation of 6.849 Å for 7,

both of them shorter than the Cu···Cu distance of 7.434 Å

for 6. In 5, the zinc(II) ions are pentacoordinate by three

nitrogen atoms of the 1,3-tpbd ligand and two chloride

ions, with the following distances: Zn1–Cl1 2.248(2), Zn1–

Cl2 2.305(2), average Zn1–N_pyridine2.050(6) and Zn1–

N_amine2.646(2) Å. Considering such weak N_amineligation

to zinc(II) ions, the coordination geometry around Zn1 and

Zn2 can be described as distorted trigonal bipyramidal. The

axial positions of the coordination sphere around Zn1 are

occupied by N1 and Cl2 and the equatorial plane of the

ZnN₃Cl₂unit comprises N11, N22 and Cl1 with Zn1 lying

out of the basal plane by 0.2956 Å. Compared to the mono-

nuclear zinc(II) 1,4-tpbd complex with Zn–N_pyridineaverage

distance 2.14(1) Å and Zn–N_amine2.26(1) Å, where the Zn–

N_pyridinedistance is significantly longer and the Zn–N_amine

distance is significantly shorter than in 5.^[19]In 7, both co-

Figure 10. Molecular structure of the cation of [Cu₂(1,3-tpbd)₂-

(H₂O)₂](ClO₄)₄(8); water molecules and hydrogen atoms are omit-

ted for clarity.

Complex 8 is a so called “dimetallocyclophane” and it

ordination geometries around the copper(II) and zinc(II) is interesting to compare its structure with the dinuclear

centers are close to trigonal bipyramidal with N41 and N51 complex, [Cu₂LЈ₂(H₂O)₂](ClO₄)₄·2H₂O, obtained pre-

occupying the axial positions around Cu1 and N11 and viously from an impurity that was formed during the syn-

N21 occupying the axial positions of Zn1. Similar to com- thesis of 1,3-tpbd.^[1]The “impurity” LЈ is a derivative of the

plex 5, the three nitrogen atoms of one tridendate end of 1,3-tpbd ligand, missing one pyridyl “arm” (derived from

the 1,3-tpbd ligand and the metal center to which they are incomplete formation of 1,3-tpbd during synthesis). A sche-

coordinated are almost coplanar, with Cu–N_pyridineaverage matic presentation of the complex with the “impurity” as

distance 2.054(2) and Cu–N_amine2.499(2) Å, Zn–N_pyridineligand in comparison with 8 is shown in Figure 11.

average distance 2.034(2) and Zn–N_amine2.370(2) Å. The

Complex 8 likewise crystallizes with an inversion center

Cu–Cl distances are very close to each other [2.279(3) and located in the middle of the “dimetallocyclophane” core.

2.284(3) Å], likewise for the Zn–Cl bonds [2.307(4) and However, the metal coordination sphere is quite different to

2.333(3) Å]. The Zn–N_pyridineand Cu–N_pyridinedistances are that of [Cu₂LЈ₂(H₂O)₂](ClO₄)₄·2H₂O. The copper(II) ions

in accordance to those determined for related mononuclear in 8 exhibit a “4+1” square-based pyramidal geometry with

analogues, in contrast the Zn–N_amineand Cu–N_aminedis- three nitrogen atoms (N1, N2 and N3) from one tridentate

tances in the mononuclear complexes of 2.142(2) Å and end of 1,3-tpbd in the meridional form, and the pyridine

2.207(6) Å are significantly shorter.^[39,40]However, these (N5A) from the symmetry-related ligand completing the

complexes are complexes with a different ligand to metal basal plane, while a water molecule (O1) occupies the apical

cation ratio (one metal ion and two coordinated bispicolyl- site. In 8 the tertiary amine (N4A) from the symmetry-re-

amine ligands) at the amine nitrogen atom and the hydro- lated ligand is not bound to the copper(II) center with a

gen atom is not substituted by an organic group.

long distance of 4.472 Å, while the corresponding nitrogen

“Zinc-Ion-Assisted” Formation of a Dinuclear Copper (N2) as a secondary amine is coordinated to the copper(II)

Complex: During our efforts to prepare model complexes center with a bond length of 2.071(2) Å in the correspond-

for CuZnSOD described above, we observed a very sur- ing [Cu₂LЈ₂(H₂O)₂](ClO₄)₄·2H₂O complex.

prising reaction behavior when stoichiometric mixtures of

The two pyridyl “arms” from the same tertiary amine

copper(II) and zinc(II) perchlorate salts were mixed with are trans to one another [N2–Cu1–N3 164.8(2)°], [Cu1–N2

1,3-tpbd. Instead of obtaining the heterodinuclear com- 1.986(3), Cu1–N3 1.976(3) Å]. However, the corresponding

plex, we isolated a new dinuclear copper(II) complex, two pyridyl nitrogen atoms in [Cu₂LЈ₂(H₂O)₂](ClO₄)₄·2H₂O

[Cu₂(1,3-tpbd)₂(H₂O)₂](ClO₄)₄(8), in which two cop- are cis-coordinated to copper(II) with a N11–Cu1–N12 an-

per(II) ions had reacted with two 1,3-tpbd ligand units. gle of 86.2(5)°. In complex 8, all the Cu–N_pyridinelengths

The molecular structure of the cation of complex 8 is are in general slightly shorter than the trans Cu–N1_amine

shown in Figure 10 (crystal structure data and refinement [2.074(3) Å]. The steric influence of the non-coordinated

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pyridine ring results in the different coordination geometry

and an intramolecular distance of Cu···Cu [8.820(1) Å]

which is 1.3 Å longer than that of [Cu₂LЈ₂(H₂O)₂]-

(ClO₄)₄·2H₂O.

The finding that 8 forms despite the presence of zinc(II)

ions is extremely surprising due to the results described

above that zinc(II) can substitute copper(II) ions perfectly

well in complexes of the ligand 1,3-tpbd. Furthermore, 8

can also be prepared if only a small amount (e.g. 5%) of

zinc(II) ions are present. This result clearly suggests that

zinc(II) ions should not be necessarily present and that it

should be possible to synthesize 8 by mixing copper(II) per-

chlorate and 1,3-tpbd in a one to one stoichiometric ratio

(Figure 12) because the reaction in a stoichiometric ratio

of one (1,3-tpbd) to two Cu(ClO₄)₂affords the dinuclear

copper(II) complex [Cu₂(1,3-tpbd)(H₂O)₂(ClO₄)₃](ClO₄)

that has been structurally characterized previously.^[1]

However, in contrast a series of experiments showed that

8 cannot be prepared under aerobic conditions without the

presence of zinc(II) ions. For example a mixture of 1,3-tpbd

and one equivalent of copper(II) perchlorate in methanol/

H₂O, acetonitrile or DMF exposed to air caused the effect

that the green solutions rapidly started to turn to a deep-

red color within a day.

Such a phenomenon has precedence with other related

m-phenylendiamine derivatives where radical reactions were

observed during oxidation reactions.^[41–43]

mechanism (shown in Figure 13) can be postulated accord-

ing to these previous findings (most likely an oxygen atom

A possible

Figure 11. Schematic representation of the complex with the “im-

purity”LЈ as ligand (top) in comparison to 8 (bottom).

Figure 12. Scheme of reactions observed during the “zinc-assisted” formation of 8.

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Complexes of N,N,NЈ,NЈ-Tetrakis(2-pyridylmethyl)benzene-1,3-diamine

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Figure 13. Possible reaction scheme for the formation of an oxidation product of 1,3-tpbd.

reacts with the benzene ring of the 1,3-tpbd ligand).^[42]Un- more suitable solvents such as acetone we observed spectral

fortunately, all our efforts to identify this “red” material in changes that indicate the formation of a peroxido copper

order to ascertain whether 1,3-tpbd has been modified have complex (even at ambient temperature), however, so far all

been unsuccessful (only oily dark red reaction mixture efforts to isolate or to characterize this species in a pure

products could be obtained so far).

form were unsuccessful.

However, this part of the postulated mechanism of ligand

As a complimentary means to obtain insights into the

oxidation could readily explain the zinc(II) assisted structure and energetics of possible dioxygen adduct com-

crystallization of 8. If enough copper(II) ions are present plexes we performed quantum chemical calculations at the

the formation of the radical intermediate shown in Fig- B3LYP/TZVP level of density functional theory. We opti-

ure 13 will be suppressed because both coordination sites mized the structures of three isomers, i.e. the (η²:η²)-perox-

are blocked with the copper(II) ions and dinuclear cop- ido, the bis-µ-oxido, and the trans-(η¹:η¹)-peroxido species.

per(II) complexes such as [Cu₂(1,3-tpbd)(H₂O)₂(ClO₄)₃]- These calculations corroborate the interpretation of a side-

ClO₄can be easily prepared.

on-bound (η²:η²)-peroxido species as the most stable com-

If nonredox-active zinc(II) ions are present they will (as plex formed. According to the quantum chemical results,

outlined above) coordinate to 1,3-tpbd as well. Most the bis-µ-oxido species is 3.2 kcal/mol less stable, followed

likely – and not for an obvious reason – they seem to prefer by the trans-peroxido species, which is 12.1 kcal/mol less

coordination only to one of the ligand sites as observed stable than the side-on-bound peroxido isomer. Key param-

previously with the 1,4-tpbd derivative as ligand (see eters of the optimized structures are shown in Figure 14.

above), where even the crystal structure of this 1:1 complex

So far our efforts to isolate and characterize the final

was reported.^[19]Then, the other coordination site will be oxidation product(s) have been unsuccessful. A possible

filled with a copper(II) ion and in a consecutive reaction product that could arise from an intramolecular ligand hy-

the zinc(II) ion will now be substituted by a copper(II) ion droxylation similar to oxidation reactions observed pre-

already coordinated to another 1,3-tpbd ligand molecule. viously for related systems^[11]would lead to a phenol ligand

Thus the zinc(II) ion will be liberated and can again interact shown in Figure 1 (R = H). Therefore we synthesized a de-

with a different 1,3-tpbd ligand molecule [which would also rivative of this ligand (R = CH₃) from 2,6-diamino-p-cresol

explain why stoichiometric amounts of zinc(II) ions are not dihydrochloride^[44]and 2-chloromethylpyridine hydrochlo-

necessary]. Once complex 8 is formed, radical oxidations ride. The copper(II) complex was obtained easily when cop-

are again suppressed, and therefore allow the facile synthe- per(II) perchlorate was mixed with the ligand and crystals

sis and isolation of complex 8.

suitable for crystallographic characterization could be iso-

In our efforts to get a better understanding of the as- lated. The crystal structure of [Cu₂(2,6-tpcd)(H₂O)(Cl)]-

sumed ligand-oxidation processes we also reinvestigated the (ClO₄)₂·2H₂O (9) is shown in Figure 15 (crystal structure

oxidation of the dinuclear 1,3-tpbd copper(I) complex with data and refinement parameters, bond lengths and angles

dioxygen described previously.^[1]In the past this reaction are presented in Table 3 and Table 1). The coordinated chlo-

has been studied in methanol, a solvent less suitable for ride ion is a consequence of the usage of the protonated

stabilizing reactive intermediates such as copper “dioxygen ligand (isolation as the hydrochloride salt). The H atoms of

adduct” complexes.^[1]In our current experiments using water solvent molecules were derived from a difference Fou-

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Figure 14. Calculated structures of the dioxygen copper adduct complex of 1,3-tpbd.

rier map and isotropically refined. 9 crystallizes with one

coordinated and two additional water solvent molecules per

Conclusions

1,3-tpbd is a versatile ligand that can be used successfully

to coordinate two metal ions in close proximity. While the

nickel complex shows normal coordination behavior, redox

active metal centers such as iron or copper ions demon-

strate that 1,3-tpbd is a non-innocent ligand. Interestingly

1,3-tpbd does not coordinate iron(III) ions, instead proton-

ation of the ligand is preferred. Oxidations of iron(II) com-

plexes or copper(I) complexes of 1,3-tpbd led to reaction

product mixtures that could not be characterized so far.

Theoretical calculations support the formation of a dinu-

clear side-on peroxido copper complex during the reaction

of the copper(I) complex with dioxygen. Intramolecular li-

gand hydroxylation might occur during the oxidation reac-

tion, however, could not be proved experimentally. The pos-

sible reaction product, a phenolate-bridged derivative of the

1,3-tpbd complex could be synthesized in an independent

way. Most interestingly is the reaction if only one equivalent

of copper(II) salt is reacted with one equivalent of 1,3-tbpd.

Under aerobic conditions a red product was formed after

a short while, suggesting ligand oxidation. However, this

reaction could be suppressed completely in the presence of

zinc ions. Here [Cu₂(1,3-tpbd)₂(H₂O)₂](ClO₄)₄a so called

“dimetallocyclophane” formed.

unit.

Figure 15. Molecular structure of the cation of [Cu₂(2,6-

tpcd)(H₂O)(Cl)](ClO₄)₂(9).

In 9 both copper(II) ions are “4+1” coordinated forming

a distorted square-pyramidal geometry. The basal plane

consists of two pyridine nitrogen atoms (N2 and N3), the

amine nitrogen N1 and the chloride anion Cl1 while the

apical plane consists of the phenol oxygen atom O1. The

distance between both copper(II) ions is 4.027 Å. Interest-

ingly the distance Cu1–O1 with 2.153(1) Å is slightly longer

than the corresponding distance Cu2–O1 [2.106(2) Å].

Experimental Section

General Remarks: All chemicals were purchased from commercial

sources and used as received.

Parallel to our work, Karlin and co-workers investigated CAUTION! The perchlorate salts used in this study are potentially

explosive and should be handled with care.

the reactivity of a dinuclear copper(I) complex with a nearly

identical ligand (PDЈOH) (Figure 1, R = tert-butyl). Besides

selective DNA interactions of this complex^[15]they further-

more reported in that regard a very interesting hydroxyla-

tion reaction of nitriles to aldehyde and cyanide during oxi-

dation. A hydroperoxido complex has been postulated as

reactive species in these reactions.^[16]

Physical Measurements: Elemental analyses were carried out with

a Carlo Erba 1106 using a Mettler Toledo UMX-2. NMR spectra

were recorded with a 400 MHz Bruker-Aspect 2000/3000. IR spec-

tra were recorded with a Bruker Optics IFS25.

Ligand Synthesis: The ligand N,N,NЈ,NЈ-tetrakis(2-pyridylmethyl)-

benzene-1,3-diamine (1,3-tpbd) was synthesized according to litera-

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Complexes of N,N,NЈ,NЈ-Tetrakis(2-pyridylmethyl)benzene-1,3-diamine

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ture procedures.^[1]Slow evaporation of a methanol solution of 1,3-

tpbd in a glove box afforded single crystals suitable for X-ray dif-

fraction studies.

(100 mg, 0.21 mmol) in acetonitrile under an inert atmosphere. The

solution was allowed to stir at room temperature for a further 2 h.

The solvent was removed in vacuo and dichloromethane (5 mL)

was added to the residual oil. Diethyl ether (20 mL) was added

until the solution was slightly turbid. The vessel was placed in the

freezer compartment of a fridge and within 3 d, large transparent

2,6-Bis[bis(2-pyridylmethyl)amino]-p-cresol (2,6-tpcd): A solution of

sodium hydroxide (4.18 g, 0.1050 mol) in water (30 mL) was added

dropwise with stirring to

a

mixture of 2,6-diamino-p-

blocks of 4 formed. IR (Nujol mull): ν 3631 (w), 3629 (w), 3627

˜

cresole·2HCl^[44](2 g, 0.0095 mol) and 2-(chloromethyl)pyridine hy-

drochloride (7.82 g, 0.0475 mol) in 5 mL H₂O under inert condi-

tions. The crude product was recrystallized several times from ace-

tone and 0.5 g (0.001 mol) 10.5% 2,6-tpcd were obtained. ¹H NMR

(CDCl₃/TMS, 400 MHz): δ = 8.48 (m, 4 H, pyr-H_a), 7.48 (m, 4 H,

pyr-H_c), 7.45 (m, 8 H, pyr-H_b/H_d), 7.39 (s, 2 H, Ar-H), 4.75 (s, 8

H, –CH₂–), 2.15 (s, 3 H, -CH₃) ppm.

(w), 3549 (w), 3434 (w), 3245 (m), 3120 (m), 2972 (s), 2948 (s), 2885

(s), 2845 (s), 2726 (m), 2676 (m), 2416 (w), 2394 (w), 2317 (m),

2288 (m), 2211 (w), 2038 (w), 1923 (w), 1610 (m), 1582 (m), 1456

(s), 1376 (s), 1287 (s), 1246 (s), 1167 (s), 1105 (m), 1031 (s), 957

(m), 901 (m), 850 (m), 817 (m), 774 (m), 726 (m), 696 (m), 634

1

(m), 574 (m), 544 (m), 517 (m), 472 (w) cm^–1. H NMR (CD₃CN,

3

300 MHz): δ = 8.60 (d, J_HH= 4.9 Hz, 4 H, pyr-H_a), 8.10 (t, J_HH

= 7.5 Hz, 4 H, pyr-H_c), 7.63 (t, J_HH= 6.0 Hz, 4 H, pyr-Hb), 7.44

[H₄(1,3-tpbd)₂](ClO₄)₄·(CH₃CN)₃: A solution of iron(III) perchlo-

rate hydrate (141.7 mg, 0.4 mmol) in water (3 mL) was added to a

solution of 1,3-tpbd (95.2 mg, 0.2 mmol) in CH₃OH (7 mL). The

reaction mixture (a brown suspension) was stirred for 1 h at room

temperature and filtered. The precipitate was dissolved in CH₃CN

(5 mL) and allowed to stand at room temperature for 2 d affording

yellow block-shaped crystals suitable for X-ray diffraction analysis.

C₆₆H₆₉Cl₄N₁₅O₁₆(1470.16): calcd. C 53.92, H 4.73, N 14.29; found

C 53.78, H 4.94, N 14.51.

3

(d, J_HH= 7.9 Hz, 4 H, pyr-H_d), 6.90 (t, J_HH= 8.3 Hz, 1 H, Ar-

H), 6.33 (dd, J_HH= 1.9 Hz, 1 H, 8.7 Hz, Ar-H), 5.96 (s, 1 H, Ar-

3

H), 4.60 (s, 8 H, –CH₂–).

[Zn₂(1,3-tpbd)Cl₄]·H₂O (5), [Cu₂(1,3-tpbd)Cl₄] (6), [CuZn(1,3-tpbd)-

Cl₄] (7): Slow evaporation of an aqueous methanolic solution of a

stoichiometric mixture of ZnCl₂, CuCl₂and 1,3-tpbd led to a mix-

ture of yellow and two different green-colored crystals suitable for

X-ray diffraction analysis.

[H₄(1,3-tpbd)₂](SO₃CF₃)₄: The complex was obtained in a similar

way as for the perchlorate salt described above, however, for this

compound no analytical data were collected. The crystal structure

and data are reported in the Supporting Information.

[Cu₂(1,3-tpbd)₂(H₂O)₂]·(ClO₄)₄·2H₂O (8): A methanolic suspension

of 1,3-tpbd (95.2 mg, 0.2 mmol) was added to an aqueous meth-

anol solution of Cu(ClO₄)₂·6H₂O (64.1 mg, 0.2 mmol) and

Zn(ClO₄)₂·6H₂O (74.4 mg, 0.2 mmol). The mixture was stirred for

2 h, filtered and allowed to slowly evaporate at room temperature.

Large green blocks formed within 48 h. A single-crystal X-ray dif-

fraction analysis was performed and the structure of the green crys-

tals was determined to be [Cu₂(1,3-tpbd)(OH₂)₂](ClO₄)₄. That no

zinc ions were present at all was further confirmed by photon-in-

duced X-ray emission.

Synthesis of Complexes

[Fe₂(1,3-tpbd)(CH₃CN)₆](ClO₄)₄·(CH₃CN)₂·(H₂O)_0.5

(1)

and

[Fe₂(1,3-tpbd)(DMF)₆](ClO₄)₄(2): Complexes 1 and 2 were synthe-

sized by the same procedure in a glove box differing only by the

different solvents used. Fe(ClO₄)₂·H₂O (101.9 mg; 0.4 mmol) and

1,3-tpbd (95.2 mg, 0.2 mmol) were dissolved in 10 mL of CH₃CN

or DMF. The resulting clear, light-brown solution was stirred for

30 min at room temperature followed by vapor diffusion with di-

ethyl ether (20 mL) at –11 °C. Nearly colorless square crystals of 1

and light yellow plate crystals of 2 suitable for X-ray diffraction

analysis were grown after three weeks. Yield: 161 mg (0.12 mmol,

[Cu₂(2,6-tpcd)(H₂O)(Cl)](ClO₄)₂·2H₂O (9): A suspension of 2,6-

tpcd (100 mg, 0.2 mmol) in 5 mL methanol was added to a solution

of Cu(ClO₄)₂·6 H₂O (148.2 mg, 0.4 mmol) in 5 mL H₂O. The mix-

ture was stirred for 30 min at room temperature and allowed to

slowly evaporate at room temperature. Within two days small green

needles of 9 suitable for X-ray diffraction analysis were formed.

61%) for

1

and 159 mg (0.11 mmol, 56%) for 2.

C₄₆H₅₃Cl₄Fe₂N₁₄O_16.50(1319.52) (1): calcd. C 41.87, H 4.05, N

14.86; found C 41.74, H 3.99, N 14.69. C₂₄H₃₅Cl₂FeN₆O₁₁

Computational Methods: Density functional calculations have been

performed employing the B3LYP functional^[46–49]as implemented

in the Turbomole program.^[50–52]The TZVP basis set has been em-

ployed for all atoms.^[53]Solvent effects have partially been included

in these calculations employing the COSMO continuum solvent

model (dielectric constant for acetone at room temperature: ε =

36.64).^[54]

(710.33)(2): calcd. C 40.58, H 4.97, N 11.83; found C 40.65, H 4.84,

1

N 11.87. H NMR (CD₃CN, 400 MHz): for 1: δ = 9.78 (d, J_HH

=

3

1.9 Hz, 4 H, pyr-H_a), 8.97 (t, J_HH= 7.7 Hz, 4 H, pyr-H_c), 8.55 (t,

³J_HH= 5.5 Hz, 4 H, pyr-H_b), 8.49 (d, J_HH= 7.4 Hz, 4 H, pyr-H_d),

3

8.07 (t, J_HH= 14.6 Hz, 1 H, Ar-H), 7.32 (s, 1 H, Ar-H), 7.26 (dd,

J_HH= 6.99 Hz, 2 H, Ar-H), 6.00 (s, 8 H, –CH₂–) ppm; (CD₃CN,

400 MHz) for 2: δ = 8.40 (d, 4 H, pyr-Ha), 8.00 (s, 1 H, DMF-H),

7.59 (t, 4 H, pyr-Hc), 7.05–7.16 (t/d, 8 H, pyr-Hb/–Hd), 6.70 (t, 1

H, Ar-H), 5.85–5.97 (s/d, 3 H, Ar-H), 4.61 (s, 8 H, –CH₂–), 2.71–

2.87 (s, 36 H, DMF-CH₃) ppm.

X-ray Crystallographic Studies: X-ray crystallographic data for 1,3-

tpbd were collected with a STOE IPDS-diffractometer at 193 K

equipped with a low-temperature system (Karlsruher Glastechn-

isches Werk). Cell parameters were refined by using up to 5000

reflections. A sphere of data (210 frames) was collected with the φ

oscillation mode (0.9° frame width; Irradiation times/frame: 7 min.)

No absorption corrections were applied. The structures were solved

by direct methods in SHELXS97, and refined by using full-matrix

least-squares in SHELXL97.^[55]The hydrogen atoms were posi-

tioned geometrically and all non-hydrogen atoms were refined an-

isotropically, if not mentioned otherwise. All following data were

corrected for Lorentz and polarization effects. Intensity data of 1

were collected with a Bruker-Nonius KappaCCD diffractometer,

intensity data for 4 and 8 were collected with a Siemens P4 four

[Ni₂(1,3-tpbd)(DMF)₆](ClO₄)₄(3): Similar to the above procedure

for 1 and 2, this complex was synthesized by adding a solution of

[45]

[Ni(DMF)₆](ClO₄)₂in DMF to a solution of 1,3-tpbd in DMF

under the inert conditions of a glove box. Crystals suitable for X-

ray diffraction analysis were obtained by slow diffusion of diethyl

ether into the solution. C₄₈H₇₀Cl₄N₁₂Ni₂O₂₂(1426.38): calcd. C

40.42, H 4.95, N 11.78; found C 39.77, H 4.48, N 11.60. UV/Vis

(DMF): λ_max= 612, 774, 937 nm. The crystal structure and data

are reported in the Supporting Information.

[Zn₂(1,3-tpbd)(CH₃CN)₂(SO₃CF₃)₂(H₂O)](SO₃CF₃)₂(4): Zinc tri- circle diffractometer. Absorption effects were corrected either by

flate (154 mg, 0.42 mmol) was added to a solution of 1,3-tpbd

semi-empirical methods based on multiple scans (1)^[56]or on the

Eur. J. Inorg. Chem. 2007, 429–443

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441

S. Schindler et al.

FULL PAPER

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corresponding carrier atoms by a factor of 1.2 or 1.5. One of the

perchlorate anions of 1 is disordered; two preferred orientations

were refined resulting in occupancy factors of 50.1(6) and 49.9(6)

%. In 8 both of the two independent perchlorate anions are sub-

jected to disorder. Two preferred orientations refined led to occu-

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Received: October 5, 2006

Published Online: December 4, 2006

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Article Doi

Syntheses, characterization and reactivity of iron(II), nickel(II), copper(II) and zinc(II) complexes of the ligand N,N,N′,N′- tetrakis(2-pyridylmethyl)-benzene-1,3-diamine (1,3-tpbd) and its phenol derivative 2,6-bis[bis(2-pyridylmethyl)amino]-p-cresol (

DOI: 10.1002/ejic.200600944

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