Probing the dinucleating behaviour of a bis-bidentate ligand: Synthesis and characterisation of some di- and mononuclear cobalt(II), nickel(II), copper(II) and zinc(II) complexes of 3,5-di(2-pyridyl)-4-(1H-pyrrol-1-yl)-4H-1,2,4- triazole

FULL PAPER

DOI: 10.1002/ejic.200500972

Probing the Dinucleating Behaviour of a Bis-Bidentate Ligand: Synthesis and

Characterisation of Some Di- and Mononuclear Cobalt(^II), Nickel(II),

Copper(^II) and Zinc(II) Complexes of 3,5-Di(2-pyridyl)-4-(1H-pyrrol-1-yl)-4H-

1,2,4-triazole

Marco H. Klingele,^[a]Peter D. W. Boyd,^[b]Boujemaa Moubaraki,^[c]Keith S. Murray,^[c]and

Sally Brooker*^[a]

Keywords: 1,2,4-Triazoles / Bridging ligands / N ligands / Copper complexes / Cobalt complexes / Nickel complexes / Zinc

complexes / Magnetic properties

–

As a probe of the dinucleating ability of the known but little

studied bis-bidentate ligand 3,5-di(2-pyridyl)-4-(1H-pyrrol-

1-yl)-4H-1,2,4-triazole (pldpt) its reactivity towards

mode with axial DMF or ClO₄co-ligands. The near-perpen-

dicular orientation [82.4(3)–88.8(1)°] of the π-electron-rich 4-

(1H-pyrrol-1-yl) substituent with respect to the triazole ring

of pldpt, observed in all of these structures, means that no π-

interactions are expected between these rings so any elec-

tronic interaction is likely to be small. Whether a di- or mono-

nuclear complex of pldpt forms is therefore primarily deter-

–

MX₂·6H₂O (M = Co^II, Ni^IIand Zn^II; X = ClO₄and BF₄^–) as

well as Cu(ClO₄)₂·6H₂O, in a 1:1 metal-to-ligand molar ratio

in MeCN, has been investigated. In the case of Co^II, Ni^IIand

Zn^II, these reactions gave dinuclear complexes M^II₂(pldpt)₂-

X₄(MeCN)_m(H₂O)_n, whereas for Cu^IIinitially the mononu- mined by a number of other factors, including the reaction

clear complex [Cu^II(pldpt)₂(ClO₄)₂] was isolated, followed by

the dinuclear complex [Cu^II₂(pldpt)₂(MeCN)₂(H₂O)₂](ClO₄)₄.

The use of the strongly polar aprotic co-solvent DMF resulted

in the partial breakdown of the initial dinuclear entities in

stoichiometry, the nature of the counterions and the solvent,

as well as the relative solubility of the various possible prod-

ucts. Clearly the nature of the N⁴substituent can have a

major impact on the last of these factors. Magnetic studies

the case of Co^IIand Ni^IIbut not in the case of Zn^II. In all carried out on the dinuclear complexes revealed that the tri-

five of the structurally characterised dinuclear complexes the

azole bridges mediate relatively weak antiferromagnetic

(NЈ,N¹,N²,NЈЈ)₂double-bridging coordination mode is real- coupling between the two metal centres.

ised with distorted octahedral N₄Y₂-coordinated metal

centres (Y = DMF, H₂O or MeCN). The two mononuclear

complexes feature the common trans-(NЈ,N¹)₂coordination

Germany, 2006)

the dinuclear (NЈ,N¹,N²,NЈЈ)₂double bridging and the mo-

nonuclear (NЈ,N¹)₂coordination mode are the most com-

mon and most important ones (Figure 2).^[2]For octahedral

complexes featuring the latter mode, the trans type is fre-

quently encountered. Here, the pyridine–triazole moieties

of the two ligands are coordinated to the metal centre in a

common plane with axially trans-positioned co-ligands. In

contrast, there is only one example in the literature where

the isomeric cis type is realised.^[4]

Introduction

The utilisation of 1,2,4-triazole derivatives as bridging li-

gands in transition-metal complexes is currently of con-

siderable interest.^[1–3]The 4-substituted 3,5-di(2-pyridyl)-

4H-1,2,4-triazoles are bis-bidentate so they are potentially

dinucleating ligands that should be capable of bridging two

metal ions by means of the N₂unit of the central triazole

ring.^[2]Quite a large range of such ligands have been used

for the preparation of transition-metal complexes (Fig-

ure 1). In the resulting di- and mononuclear complexes a

variety of coordination modes have been observed of which

Within this ligand class the reactivity of 4-amino-3,5-

di(2-pyridyl)-4H-1,2,4-triazole (NH₂dpt, 2) (Figure 1)

towards transition-metal salts and the properties of the re-

sulting di- and mononuclear complexes have been studied

quite extensively over the last 20 years.^[5–29]From an elec-

tronic point of view the presence of the strongly electron-

donating amino group on N⁴should facilitate the formation

of dinuclear complexes of this ligand. However, of this

[a] Department of Chemistry, University of Otago,

P. O. Box 56, Dunedin, New Zealand

Fax: +64-3-479-7906

E-mail: sbrooker@alkali.otago.ac.nz

[b] Department of Chemistry, The University of Auckland,

Private Bag 92019, Auckland, New Zealand

[c] School of Chemistry, Building 23, Monash University,

Clayton, Victoria 3800, Australia

family only two dinuclear complexes, namely [Ni^II

-

2

(NH₂dpt)₂(H₂O)₂Cl₂]Cl₂·4H₂O^[5]and [Cu^II₂(NH₂dpt)-

(H₂O)₄(SO₄)₂]·H₂O,^[12]have been structurally characterised

Supporting information for this article is available on the

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

Eur. J. Inorg. Chem. 2006, 573–589

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Figure 1. Structural drawings of the 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-triazoles that have been employed to date as ligands in

coordination compounds.

(pldpt)₂(H₂O)₄]Cl₄·2MeOH·2H₂O, which was formed from

the 1:1 reaction of CoCl₂·6H₂O and pldpt (3) in MeOH/

H₂O, 4:1.^[44]

Overall it appears that the factors which combine to de-

termine the nature of the products of such a complexation

reaction, in particular whether a di- or mononuclear com-

plex is formed as the main product, include the reaction

stoichiometry, the choice of the counterions and the solvent

used, as well as the influence of the N⁴substituent on the

electronic structure and conformation of the respective li-

Figure 2. Schematic representation of the two most common coor-

gand and on the relative solubility of the various possible

dination modes of 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-tri-

product complexes. Systematic studies aimed at investiga-

azoles. In the actual complexes the metal centres can bind ad-

ting the relative importance of these factors are currently

ditional co-ligands according to the respective coordination geome-

lacking but clearly desirable so we are beginning to address

this as part of our ongoing studies which are directed

towards the synthesis and characterisation of di-

nuclear 1,2,4-triazole-bridged complexes of such li-

gands,^{[2,3,30,32,33,45–51]}with a particular interest in iron(ii)

complexes.^[52]Given that to date dinuclear 1,2,4-triazole-

bridged complexes are far less common than the corre-

sponding mononuclear complexes, here we target the con-

trolled formation of further examples of dinuclear com-

plexes of pldpt (3) by employing a metal-to-ligand molar

ratio of 1:1 in the complexation reactions and varying the

solvents and counterions.

tries.

to

date.

4-Isobutyl-3,5-di(2-pyridyl)-4H-1,2,4-triazole

(ibdpt)^[30](Figure 1), with its electron-donating alkyl sub-

stituent on N⁴, has also been found to afford both di- and

mononuclear complexes.^[31–33]In contrast, the 4-aryl-3,5-

di(2-pyridyl)-4H-1,2,4-triazoles have almost exclusively pro-

duced mononuclear complexes to date, in some cases de-

spite the reaction being carried out with a metal-to-ligand

molar ratio of 1:1.^[4,34–42]The first, and so far the only, di-

nuclear complex of a 4-aryl-3,5-di(2-pyridyl)-4H-1,2,4-tri-

azole, namely a dinuclear silver(i) complex of 4-(4-isopro-

pylphenyl)-3,5-di(2-pyridyl)-4H-1,2,4-triazole (ppdpt) (Fig-

ure 1) obtained from MeCN employing a 1:1 metal-to-li-

gand molar ratio, was reported very recently.^[43]Given that

in these complexes the aryl substituents on N⁴form angles

of about 68–84° with the triazole ring, no significant π-in-

teractions are expected between them. Therefore, any elec-

Results and Discussion

Ligand Synthesis

Following the classic two-step procedure of Geldard and

tronic effect that the aryl substituent on N⁴might exert on Lions,^[53]the condensation of 2-pyridinecarbonitrile with

the triazole ring must occur through the σ-bond framework N₂H₄·H₂O gave 3,6-di(2-pyridyl)-1,4-dihydro-1,2,4,5-tetra-

so is likely to be small. There is only one report in the litera- zine (1) in 58% yield (Scheme 1). The subsequent re-

ture dealing with 3,5-di(2-pyridyl)-4-(1H-pyrrol-1-yl)-4H- arrangement of the dihydrotetrazine 1 in 2 m HCl afforded

1,2,4-triazole (pldpt, 3) (Figure 1) and it describes the struc- NH₂dpt (2) in 84% yield.^[53]Alternatively, NH₂dpt (2)

tural characterisation of the dinuclear complex [Co^II

-

could be obtained directly from the two reactants by em-

2

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Dinucleating Behaviour of a 1,2,4-Triazole-Based Bis-Bidentate Ligand

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ploying the one-pot procedure described by Lagrenée and rial became dull which indicated the loss of some solvent.

co-workers (Scheme 1).^[54]However, it was found that the Visual examination of the resulting solid under a micro-

reaction was much slower than reported and difficult to scope showed that it contained a few tiny orange prisms,

drive to completion. The initial product thus obtained had presumably of [Co^II₂(pldpt)₂(H₂O)₄]Cl₄·2MeOH·2H₂O. The

to be recrystallised at least twice in order to obtain pure small amount of orange product was separated physically

material. This caused the final yield of NH₂dpt (2) to drop from the bulk beige material but since it could not be ob-

significantly and the two-step procedure of Geldard and tained in sufficient amounts for an elemental analysis its

Lions^[53]was therefore preferred. The reaction of NH₂dpt presumed identity could not be verified. The elemental

(2) with 2,5-dimethoxytetrahydrofuran^[55,56]in AcOH/1,4- analysis of the beige solid was in good agreement with a

dioxane (1:1) readily gave pldpt (3) in 77% yield.^[44]Com- mononuclear 1:2 complex with a composition of Co^II-

pounds 1–3 were fully characterised by spectroscopic meth- (pldpt)₂Cl₂(solvent). These findings are in marked contrast

ods. In addition, pldpt (3) was characterised by single-crys- to the results reported by Mandal and co-workers.^[44]

tal X-ray diffraction (Figures S1 and S2).

In the hope of getting a well-defined and less soluble

solid product directly from the reaction mixture the reac-

tion was subsequently carried out in neat EtOH instead of

MeOH/H₂O (4:1). Thus, the reaction of pldpt (3) with

CoCl₂·6H₂O in a 1:1 molar ratio at reflux resulted in the

initial formation of a blue solid. After 15 minutes the reac-

tion mixture was cooled and stirring the resulting suspen-

sion at room temperature for 24 hours caused the solid to

turn pink, presumably due to slow co-ligand exchange of a

kinetic product to form a thermodynamically more stable

product. The elemental analysis of this pink solid was in

good agreement with a dinuclear 2:2 complex with a com-

position of Co^II₂(pldpt)₂Cl₄(solvent). This material proved

to be insoluble in all organic solvents, including DMF,

MeNO₂and DMSO, and could only be dissolved in H₂O.

However, since all attempts to obtain a crystalline material

from H₂O were unsuccessful, further purification and char-

acterisation was not possible.

Scheme 1. Synthesis of 3,5-di(2-pyridyl)-4-(1H-pyrrol-1-yl)-4H-

1,2,4-triazole (pldpt, 3). Reagents and conditions: (a) N₂H₄·H₂O,

reflux; (b) 2 m HCl, reflux; (c) N₂H₄·H₂O, N₂H₄·H₂SO₄, 1,2-ethan-

diol, 130 °C; (d) 2,5-dimethoxytetrahydrofuran, AcOH, 1,4-diox-

ane, reflux.

As a result of these disappointing findings using

CoCl₂·6H₂O the coordination behaviour of pldpt (3)

towards Co(ClO₄)₂·6H₂O was investigated next, in the hope

of obtaining a solid product straight from the reaction mix-

ture that would exhibit better solubility in organic solvents,

thus allowing purification and proper characterisation. In

order to achieve the formation of a dinuclear 2:2 complex,

Co(ClO₄)₂·6H₂O was treated with pldpt (3) in a 1:1 molar

ratio in MeCN. The resulting orange solid, which separated

from the reaction mixture in ca. 90% yield, gave an elemen-

tal analysis in good agreement with a dinuclear 2:2 complex

There has been some confusion about the exact nature

of the dihydrotetrazine intermediates arising from the con-

densation of nitriles with hydrazine. Especially in the older

literature, including leading reviews on tetrazines and their

dihydro derivatives^[57–59]as well as one on a related topic,^[60]

these compounds are mostly considered to be the 1,2-tauto-

mers. However, at least in the case of the condensation of

2-pyridinecarbonitrile with N₂H₄·H₂O, it has now been

proven unequivocally by two independent research groups

on the basis of single-crystal X-ray diffraction that the

product of this reaction is in fact the 1,4-tautomer.^[61,62]

with

a

composition of Co^II₂(pldpt)₂(ClO₄)₄(MeCN)_m-

(H₂O)_n(4). The solvent content of this material varied

widely from batch to batch and the drying of samples at

60 °C in vacuo (CAUTION!) for several days similarly re-

sulted in the formation of materials of variable solvent con-

tent. While complex 4 was only very sparingly soluble in

Synthesis of the Cobalt(II) Complexes

According to the literature, the reaction of pldpt (3) with MeCN, the addition of a little DMF led to dissolution.

CoCl₂·6H₂O in a 1:1 molar ratio in MeOH/H₂O (4:1) gives, Vapour diffusion of Et₂O into a solution of complex 4 in

on slow evaporation of the reaction mixture, orange crystals MeCN/DMF (10:1) resulted in the formation of two dif-

of [Co^II₂(pldpt)₂(H₂O)₄]Cl₄·2MeOH·2H₂O in 60–70% ferent kinds of crystalline materials, namely orange prisms

yield.^[44]Following this procedure as closely as possible, the and yellow blocks, in variable relative amounts. Both spe-

synthesis of this material was attempted. However, instead cies were studied by single-crystal X-ray diffraction. Thus,

of orange crystals, irregular beige crystals started to sepa- the orange crystals were identified as the dinuclear complex

rate from the orange-brown solution after a few days. Over [Co^II₂(pldpt)₂(DMF)₂(H₂O)₂](ClO₄)₄·0.5Et₂O (5) (Figure 3)

the course of four weeks the solution was allowed to evapo- whereas the yellow crystals were found to be of the mono-

rate almost completely forming even more of the beige ma- nuclear complex [Co^II(pldpt)₂(DMF)₂](ClO₄)₂(6) (Fig-

terial. On filtration and drying, the beige crystalline mate- ure 4). These findings suggest that in the presence of DMF

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M. H. Klingele, P. D. W. Boyd, B. Moubaraki, K. S. Murray, S. Brooker

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the initial dinuclear complex 4 is unstable, resulting in the alone the initial dinuclear complex 7 is stable and is not

formation of a mixture of di- and mononuclear species, broken down into a mixture of di- and mononuclear spe-

complexes 5 and 6, respectively.

cies.

Synthesis of the Nickel(II) Complexes

In parallel with the attempted synthesis of [Co^II

-

2

(pldpt)₂(H₂O)₄]Cl₄·2MeOH·2H₂O^[44]the reaction of pldpt

(3) with NiCl₂·6H₂O in a 1:1 molar ratio under analogous

conditions was examined. The slow evaporation of the ol-

ive-green MeOH/H₂O (4:1) reaction mixture over the

course of six weeks produced a mixture of a greenish crys-

talline solid and blue prisms in an estimated 3:1 ratio. As

the physical separation of the two materials was practically

impossible no analytical data for either of the compounds

could be obtained. However, it is quite likely that, by anal-

ogy to the experiment employing CoCl₂·6H₂O described

above, a mixture of di- and mononuclear compounds was

formed. Carrying out the reaction of pldpt (3) with

NiCl₂·6H₂O in a 1:1 molar ratio in EtOH instead of

MeOH/H₂O (4:1) gave a pale green solid which was sub-

sequently identified, on the basis of its elemental analysis,

Figure 3. View of the molecular structure of the cation of

[Co^II₂(pldpt)₂(H₂O)₂(DMF)₂](ClO₄)₄·0.5Et₂O (5). Hydrogen atoms

have been omitted for clarity. Symmetry operation used to generate

equivalent atoms: (A) –x + 1, –y + 1, –z + 2.

as a dinuclear 2:2 complex with a composition of Ni^II

-

2

(pldpt)₂Cl₄(solvent). This material showed the same low

solubility in organic solvents as the cobalt(ii) analogue and

this prevented its purification and further characterisation.

The reaction of pldpt (3) with Ni(ClO₄)₂·6H₂O in a 1:1

molar ratio in MeCN afforded Ni^II₂(pldpt)₂(ClO₄)₄-

(MeCN)_m(H₂O)_n(9) as a pale violet powder in ca. 80%

yield. The solvent content of the initial powder was very

variable. Once again prolonged heating in vacuo (CAU-

TION!) afforded materials of variable solvent content. As

with the cobalt(ii) analogue 4 the addition of a little DMF

was necessary to dissolve the powder in MeCN. Vapour dif-

fusion of Et₂O into a solution of complex 9 in MeCN/DMF

(10:1) afforded an inseparable mixture of blue fern-like

crystals and pink buttons, none of which were suitable for

single-crystal X-ray diffraction studies. Here too, the use of

DMF as a co-solvent has resulted in the formation of two

different, presumably di- and mononuclear, species.

Figure 4. View of the molecular structure of the cation of

[Co^II(pldpt)₂(DMF)₂](ClO₄)₂(6). Hydrogen atoms have been omit-

ted for clarity. Symmetry operation used to generate equivalent

atoms: (A) –x + 1, –y, –z.

Faced with the need to use DMF as a co-solvent in order

to dissolve the ClO₄^–complex 4 and the resulting formation

of a mixture of species of different nuclearities, the synthesis

–

Employing Ni(BF₄)₂·6H₂O instead of the ClO₄salt in

the 1:1 reaction with pldpt (3) in MeCN gave Ni^II₂(pldpt)₂-

(BF₄)₄(MeCN)_m(H₂O)_n(10) as a pale violet powder in ca.

40% yield and variable degrees of solvation. It could not be

obtained in solvent-free form. As for the cobalt(ii) ana-

–

of the BF₄analogue was carried out as this material was

expected to exhibit better solubility in MeCN and therefore

might not require the use of DMF. Thus, reacting Co(BF₄)₂·

6H₂O with pldpt (3) in a 1:1 molar ratio in MeCN afforded

a pale orange powder, in ca. 80% yield, which had a com-

position of Co^II₂(pldpt)₂(BF₄)₄(MeCN)_m(H₂O)_n(7). As

–

logues, this BF₄complex exhibited good solubility in neat

–

MeCN, unlike its ClO₄analogue 9. Vapour diffusion of

Et₂O into a solution of complex 10 in MeCN or into the

MeCN mother liquor of the initial powder afforded purple-

blue prisms of [Ni^II₂(pldpt)₂(MeCN)₄](BF₄)₄·2MeCN (11)

(Figure S4). Only one crystal type was observed so once

again the initial dinuclear complex 10 is stable in MeCN.

–

found earlier for the ClO₄analogue 4, the solvent content

of the material was variable and prolonged heating in vacuo

afforded only partially desolvated materials of variable

compositions. As anticipated, this complex could be readily

redissolved in MeCN. Vapour diffusion of Et₂O into the

MeCN mother liquor, or into a solution of complex 7 in

MeCN, gave only one crystalline species which was iden-

tified as [Co^II₂(pldpt)₂(MeCN)₂(H₂O)₂](BF₄)₄(8) (Fig-

Synthesis of the Copper(II) Complexes

The reaction of Cu(ClO₄)₂·6H₂O with pldpt (3) in a 1:1

ure S3) by single-crystal X-ray diffraction. Thus, in MeCN molar ratio in MeCN gave a sea-green solution from which

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Dinucleating Behaviour of a 1,2,4-Triazole-Based Bis-Bidentate Ligand

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a blue powder separated after a few hours. This solid was precipitates consisted of dinuclear species, in the case of Cu-

identified as the mononuclear 1:2 complex [Cu^II(pldpt)₂- (ClO₄)₂·6H₂O the mononuclear complex [Cu^II(pldpt)₂-

(ClO₄)₂] (12) on the basis of its elemental analysis. Thus, (ClO₄)₂] (12) was the initial solid product despite the 1:1

the yield was subsequently calculated as 59%. Complex 12 metal-to-ligand molar ratio employed in the reaction.

could be readily dissolved in MeCN to give a blue solution.

Vapour diffusion of Et₂O into this solution afforded blue

single crystals of [Cu^II(pldpt)₂(ClO₄)₂]·2DMF (13) (Fig-

ure 5). While the origin of the DMF solvates in complex 13

could not be determined with absolute certainty it is likely

that the glassware used was contaminated with DMF.

Synthesis of the Zinc(II) Complexes

The reaction of pldpt (3) with Zn(ClO₄)₂·6H₂O in a 1:1

molar ratio in MeCN afforded Zn^II₂(pldpt)₂(ClO₄)₄-

(MeCN)_m(H₂O)_n(15) as a colourless powder in ca. 80%

yield. The solvent content of this material was variable and

it could not be obtained in a solvent-free form even by heat-

ing it in vacuo (CAUTION!) for several days. Recrystalli-

sation by vapour diffusion of Et₂O into a MeCN/DMF

(10:1) solution of complex 15 gave colourless blocks and

visually only one crystal type could be detected. Numerous

attempts to grow single crystals by this method were made

but only once could a poor X-ray data set be collected and

this indicated that the crystals were of a dinuclear product.

However, due to the very poor quality of the data, a com-

plete analysis of the structure was not possible. Consistent

with these findings, the elemental analysis of complex 15

clearly confirmed the 2:2 stoichiometry of this complex and

the symmetrical NMR spectra obtained in [D₇]DMF were

also in agreement with the presence of only one species,

specifically one with a symmetrical dinuclear architecture

(see below). It is interesting to note that this dinuclear

Figure 5. View of the molecular structure of [Cu^II(pldpt)₂(ClO₄)₂]·

2DMF (13). Hydrogen atoms have been omitted for clarity. The

DMF solvates are not shown. Symmetry operation used to generate

equivalent atoms: (A) –x, –y, –z + 1.

Interestingly, the mother liquor remaining after filtering

off the blue mononuclear complex 12, now significantly en-

riched in Cu²⁺ions relative to pldpt (3), retained its sea-

green colour, suggesting the presence of a different species

in solution. Subjecting this sea-green solution to vapour dif-

fusion of Et₂O produced a small quantity of large green

blocks. Single-crystal X-ray diffraction studies of these crys-

tals revealed their dinuclear nature and led to the formula-

tion of [Cu^II₂(pldpt)₂(MeCN)₂(H₂O)₂](ClO₄)₄(14) (Fig-

ure 6).

–

zinc(ii) ClO₄complex does not form an equilibrium with

a mononuclear species when it is dissolved in DMF as, if it

did, this should be observed in the NMR spectra. This con-

trasts with the behaviour of the dinuclear cobalt(ii) and

–

nickel(ii) ClO₄analogues, complexes 4 and 9, respectively,

which on recrystallisation from solutions containing DMF

form mixtures of di- and mononuclear solid products. The

relative amounts of these products present in solution are

unknown.

In order to access better single crystals, our attention

–

shifted from using the ClO₄salt to using the BF₄salt.

Under the same conditions as employed for the preparation

of the analogous BF₄^–complexes of cobalt(ii) and nickel(ii),

complexes 7 and 10, respectively, Zn^II₂(pldpt)₂(BF₄)₄-

(MeCN)_m(H₂O)_n(16) was obtained from pldpt (3) and

Zn(BF₄)₂·6H₂O, in ca. 60% yield, as a colourless powder.

As with all complexes of pldpt (3) synthesised in this work,

the solvent content of complex 16 varied considerably from

batch to batch and the drying of samples at 60 °C in vacuo

for several days again resulted in materials of variable sol-

vent content. Vapour diffusion of Et₂O into a solution of

complex 16 in MeCN, or into its MeCN mother liquor, gave

colourless blocks which were identified by single-crystal X-

ray diffraction as the dinuclear complex [Zn^II₂(pldpt)₂-

(MeCN)₂(H₂O)₂](BF₄)₄(17) (Figure S5).

Figure 6. View of the molecular structure of the cation of

[Cu^II₂(pldpt)₂(H₂O)₂(MeCN)₂](ClO₄)₄(14). Hydrogen atoms have

been omitted for clarity. Symmetry operation used to generate

equivalent atoms: (A) –x + 2, –y + 1, –z + 1.

Description of the Structures

–

It is noteworthy that of all the ClO₄complexes of pldpt

(3) only the copper(ii) complexes were readily soluble in

Single crystals of pldpt (3), in the form of colourless

neat MeCN. In addition, while in all other cases the initial blocks, were obtained by slow evaporation of a solution of

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M. H. Klingele, P. D. W. Boyd, B. Moubaraki, K. S. Murray, S. Brooker

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the compound in EtOH. There are two crystallographically π and other packing effects. The conformation of the N(1)-

independent molecules in the asymmetric unit (Figures S1 and N(4)-pyridine rings was established by the differences

and S2). The most noteworthy feature of this structure is in electron density for the two possible sites of the nitrogen

the dissimilar orientation of the pairs of pyridine rings in atoms within the rings. This assignment was further sup-

the two molecules. While in the first molecule the pyridine ported by the fact that a hydrogen atom could only be lo-

nitrogen atoms point in opposite directions, both pyridine cated from the difference map at one of the two possible

nitrogen atoms in the second molecule point away from the sites within the respective rings. Refinement of the structure

N₂unit of the central five-membered heterocyclic ring. For with the alternative orientations was tried but was found to

the related ligand 2,5-di(2-pyridyl)-1,3,4-thiadiazole the lat- fit less well with the data.

ter conformation was recently calculated to be energetically

In the dinuclear orange complex [Co^II₂(pldpt)₂(DMF)₂-

favoured over the other two local minima forms with one (H₂O)₂](ClO₄)₄·0.5Et₂O (5) (Figure 3) the (NЈ,N¹,N²,NЈЈ)₂

or both pyridine nitrogen atoms pointing towards the N₂double-bridging coordination mode (Figure 2) is realised.

unit.^[63]Indeed, an orientation of the pyridine rings with The two cobalt centres are 4.273(2) Å apart (Table 1) and

the nitrogen atoms pointing away from the N₂unit of the in a distorted octahedral environment with a DMF and a

central triazole ring is the only one previously observed in H₂O molecule as axial co-ligands completing the coordina-

4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-triazoles^{[30,37,64–73]}tion sphere (Table 2 and Table 3). While in this complex the

and it is also the one usually adopted by non-coordinating normal situation of longer Co–N_pyrdistances [2.235(5) and

pyridine rings in mononuclear 2:1 complexes incorporating 2.244(5) Å] than Co–N_trzdistances [2.085(5) and

such ligands.^[2]There are, in fact, only very few examples 2.098(4) Å] is again observed, the former are slightly longer

of complexes in the literature where the non-coordinated than the corresponding distances observed in dinuclear co-

pyridine ring is reported to point away from the N⁴substit- balt(ii) complexes of the related ligand 4-isobutyl-3,5-di(2-

uent.^[13,40,42]The reason for the adoption of this unusual pyridyl)-4H-1,2,4-triazole (ibdpt)^[32]and also slightly longer

conformation for one of the two crystallographically inde- than those in the mononuclear complex [Co^II(pldpt)₂-

pendent molecules of pldpt (3) is difficult to pinpoint but (DMF)₂](ClO₄)₂(6) and the dinuclear complex [Co^II

-

2

presumably arises from a complex combination of weak π– (pldpt)₂(MeCN)₂(H₂O)₂](BF₄)₄(8) described below. Within

Table 1. Metal···metal distances [Å] in dinuclear complexes of 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-triazoles.

Complex

M···M^[a]

Reference

[44]

[32]

[Co^II₂(pldpt)₂(H₂O)₄]Cl₄·2MeOH·2H₂O

[Co^II₂(ibdpt)₂(MeCN)₂(H₂O)₂](ClO₄)₄(red-orange polymorph)

[Co^II₂(ibdpt)₂(MeCN)₂(H₂O)₂](ClO₄)₄(yellow-orange polymorph)

[Co^II₂(pldpt)₂(DMF)₂(H₂O)₂](ClO₄)₄·0.5Et₂O (5)

[Co^II₂(pldpt)₂(MeCN)₂(H₂O)₂](BF₄)₄(8)

[Ni^II₂(NH₂dpt)₂(H₂O)₂Cl₂]Cl₂·4H₂O

4.226(2)

4.1481(7)

4.1722(4)

4.273(2)

4.2660(4)

4.1348(3)

4.1107(9)

4.170(1)

this work

[5]

[32]

[Ni^II₂(ibdpt)₂(MeCN)₄](ClO₄)₄

[Ni^II₂(pldpt)₂(MeCN)₄](BF₄)₄·2MeCN (11)

[Cu^II₂(NH₂dpt)(H₂O)₄(SO₄)₂]·H₂O

this work

[12]

4.415(1)

[32]

[Cu^II₂(ibdpt)₂(MeCN)₂(ClO₄)₂](ClO₄)₂·2MeCN

[Cu^II₂(pldpt)₂(MeCN)₂(H₂O)₂](ClO₄)₄(14)

[Zn^II₂(pldpt)₂(MeCN)₂(H₂O)₂](BF₄)₄(17)

[Ag^I₂(ppdpt)₂](ClO₄)₂·MeCN

4.0701(10)

4.3140(5) [4.0861(9)]

4.455(2)

this work

[43]

4.367(4)

[a] Values in square brackets refer to the second molecule within the asymmetric unit.

Table 2. Selected distances [Å] for [Co^II₂(pldpt)₂(DMF)₂(H₂O)₂](ClO₄)₄·0.5Et₂O (5), [Co^II(pldpt)₂(DMF)₂](ClO₄)₂(6), [Co^II₂(pldpt)₂-

(MeCN)₂(H₂O)₂](BF₄)₄(8), [Ni^II₂(pldpt)₂(MeCN)₄](BF₄)₄·2MeCN (11), [Cu^II(pldpt)₂(ClO₄)₂]·2DMF (13), [Cu^II₂(pldpt)₂(MeCN)₂(H₂O)₂]-

(ClO₄)₄(14) and [Zn^II₂(pldpt)₂(MeCN)₂(H₂O)₂](BF₄)₄(17).

5

6

8

13

M–N_pyrCo(1)–N(1) 2.235(5)

Co(1)–N(4A) 2.244(5)

Co(1)–N(1) 2.190(3)

Co(1)–N(1) 2.1876(12)

Co(1)–N(4A) 2.2188(12)

Co(1)–N(2) 2.0976(12)

Co(1)–N(3A) 2.0769(12)

Co(1)–N(20) 2.0876(12)

Co(1)–O(1) 2.0464(11)

Cu(1)–N(1) 2.034(2)

M–N_trz

Co(1)–N(2) 2.085(5)

Co(1)–N(3A) 2.098(4)

Co(1)–O(1) 2.052(4)

Co(1)–O(20) 2.028(4)

Co(1)–N(2) 2.210(3)

Co(1)–O(20) 1.994(3)

Cu(1)–N(2) 1.979(2)

Cu(1)–O(11) 2.470(2)

M–X

11

14

17

M–N_pyrNi(1)–N(1) 2.184(2)

Ni(1)–N(7) 2.149(2)

Ni(2)–N(4) 2.165(2)

Ni(2)–N(10) 2.171(2)

Ni(2)–N(3) 2.042(2)

Ni(2)–N(9) 2.023(2)

Ni(2)–N(60) 2.038(2)

Ni(2)–N(70) 2.034(2)

Cu(1)–N(1) 2.5170(18)

Cu(1)–N(4A) 2.0264(17)

Cu(1)–N(2) 1.9908(17)

Cu(1)–N(3A) 2.2564(17)

Cu(1)–N(20) 2.0024(19)

Cu(1)–O(1) 2.0029(16)

Zn(1)–N(1) 2.173(4)

Zn(1)–N(4A) 2.227(4)

Zn(1)–N(2) 2.164(4)

Zn(1)–N(3A) 2.119(4)

Zn(1)–N(20) 2.127(4)

Zn(1)–O(1) 2.103(4)

M–N_trz

Ni(1)–N(2) 2.026(2)

Ni(1)–N(8) 2.038(2)

Ni(1)–N(40) 2.025(2)

Ni(1)–N(50) 2.031(2)

M–X

578

www.eurjic.org

Eur. J. Inorg. Chem. 2006, 573–589

Dinucleating Behaviour of a 1,2,4-Triazole-Based Bis-Bidentate Ligand

FULL PAPER

Table 3. Selected angles [°] for [Co^II₂(pldpt)₂(DMF)₂(H₂O)₂](ClO₄)₄·0.5Et₂O (5), [Co^II(pldpt)₂(DMF)₂](ClO₄)₂(6), [Co^II₂(pldpt)₂(MeCN)₂-

(H₂O)₂](BF₄)₄(8), [Ni^II₂(pldpt)₂(MeCN)₄](BF₄)₄·2MeCN (11), [Cu^II(pldpt)₂(ClO₄)₂]·2DMF (13), [Cu^II₂(pldpt)₂(MeCN)₂(H₂O)₂](ClO₄)₄

(14) and [Zn^II₂(pldpt)₂(MeCN)₂(H₂O)₂](BF₄)₄(17).

5

6

8

N(1)–Co(1)–N(2)

N(1)–Co(1)–N(3A)

N(1)–Co(1)–N(4A)

N(1)–Co(1)–O(1)

N(1)–Co(1)–O(20)

N(2)–Co(1)–N(3A)

N(2)–Co(1)–N(4A)

N(2)–Co(1)–O(1)

N(2)–Co(1)–O(20)

N(3A)–Co(1)–N(4A)

N(3A)–Co(1)–O(1)

N(3A)–Co(1)–O(20)

N(4A)–Co(1)–O(1)

N(4A)–Co(1)–O(20)

O(1)–Co(1)–O(20)

74.21(18)

166.98(18)

119.19(18)

86.61(17)

86.62(18)

92.78(17)

166.46(16)

94.53(17)

99.46(18)

73.82(17)

94.32(16)

95.98(17)

88.53(16)

80.44(17)

162.17(18)

N(1)–Co(1)–N(2)

82.10(12)

180

97.90(12)

93.21(12)

86.79(12)

180

107.24(11)

72.76(11)

180

N(1)–Co(1)–N(2)

N(1)–Co(1)–N(3A)

N(1)–Co(1)–N(4A)

N(1)–Co(1)–N(20)

N(1)–Co(1)–O(1)

N(2)–Co(1)–N(3A)

N(2)–Co(1)–N(4A)

N(2)–Co(1)–N(20)

N(2)–Co(1)–O(1)

N(3A)–Co(1)–N(4A)

N(3A)–Co(1)–N(20)

N(3A)–Co(1)–O(1)

N(4A)–Co(1)–N(20)

N(4A)–Co(1)–O(1)

N(20)–Co(1)–O(1)

75.13(4)

166.95(5)

118.12(4)

87.89(4)

86.60(4)

91.98(4)

166.41(4)

93.56(5)

93.90(5)

74.86(4)

90.97(5)

96.46(5)

90.12(5)

84.39(5)

169.28(5)

N(1)–Co(1)–N(1A)

N(1)–Co(1)–N(2A)

N(1)–Co(1)–O(20)

N(1)–Co(1)–O(20A)

N(2)–Co(1)–N(2A)

N(2)–Co(1)–O(20)

N(2)–Co(1)–O(20A)

O(20)–Co(1)–O(20A)

11

N(1)–Ni(1)–N(2)

N(1)–Ni(1)–N(7)

N(1)–Ni(1)–N(8)

N(1)–Ni(1)–N(40)

N(1)–Ni(1)–N(50)

N(2)–Ni(1)–N(7)

N(2)–Ni(1)–N(8)

N(2)–Ni(1)–N(40)

N(2)–Ni(1)–N(50)

N(7)–Ni(1)–N(8)

N(7)–Ni(1)–N(40)

N(7)–Ni(1)–N(50)

N(8)–Ni(1)–N(40)

N(8)–Ni(1)–N(50)

N(40)–Ni(1)–N(50)

76.21(9)

115.16(9)

168.53(9)

88.80(9)

87.74(9)

168.52(9)

92.34(9)

91.94(9)

91.49(9)

76.30(9)

86.97(9)

90.53(9)

92.44(9)

91.82(9)

174.42(9)

N(3)–Ni(2)–N(4)

N(3)–Ni(2)–N(9)

N(3)–Ni(2)–N(10)

N(3)–Ni(2)–N(60)

N(3)–Ni(2)–N(70)

N(4)–Ni(2)–N(9)

N(4)–Ni(2)–N(10)

N(4)–Ni(2)–N(60)

N(4)–Ni(2)–N(70)

N(9)–Ni(2)–N(10)

N(9)–Ni(2)–N(60)

N(9)–Ni(2)–N(70)

N(10)–Ni(2)–N(60)

N(10)–Ni(2)–N(70)

N(60)–Ni(2)–N(70)

76.25(9)

92.58(9)

168.75(9)

91.21(9)

90.09(9)

168.67(9)

114.89(9)

87.54(9)

91.29(9)

76.32(9)

90.83(9)

90.64(9)

90.84(9)

88.18(9)

177.99(9)

13

14

17

N(1)–Cu(1)–N(2)

80.85(9)

180

99.15(9)

94.20(8)

85.80(8)

180

86.33(8)

93.67(8)

180

N(1)–Cu(1)–N(2)

N(1)–Cu(1)–N(3A)

N(1)–Cu(1)–N(4A)

N(1)–Cu(1)–N(20)

N(1)–Cu(1)–O(1)

N(2)–Cu(1)–N(3A)

N(2)–Cu(1)–N(4A)

N(2)–Cu(1)–N(20)

N(2)–Cu(1)–O(1)

N(3A)–Cu(1)–N(4A)

N(3A)–Cu(1)–N(20)

N(3A)–Cu(1)–O(1)

N(4A)–Cu(1)–N(20)

N(4A)–Cu(1)–O(1)

N(20)–Cu(1)–O(1)

70.77(6)

162.04(6)

120.03(7)

90.40(7)

81.71(7)

91.86(6)

169.17(7)

90.53(7)

94.59(7)

77.31(7)

94.39(7)

95.61(7)

90.21(7)

86.68(7)

168.60(7)

N(1)–Zn(1)–N(2)

N(1)–Zn(1)–N(3A)

N(1)–Zn(1)–N(4A)

N(1)–Zn(1)–N(20)

N(1)–Zn(1)–O(1)

N(2)–Zn(1)–N(3A)

N(2)–Zn(1)–N(4A)

N(2)–Zn(1)–N(20)

N(2)–Zn(1)–O(1)

N(3A)–Zn(1)–N(4A)

N(3A)–Zn(1)–N(20)

N(3A)–Zn(1)–O(1)

N(4A)–Zn(1)–N(20)

N(4A)–Zn(1)–O(1)

N(20)–Zn(1)–O(1)

75.47(14)

163.75(14)

121.33(14)

88.94(14)

86.17(15)

88.35(14)

162.70(14)

93.64(14)

93.69(14)

74.91(14)

90.66(15)

96.50(14)

90.96(14)

84.06(14)

169.89(14)

N(1)–Cu(1)–N(1A)

N(1)–Cu(1)–N(2A)

N(1)–Cu(1)–O(11)

N(1)–Cu(1)–O(11A)

N(2)–Cu(1)–N(2A)

N(2)–Cu(1)–O(11)

N(2)–Cu(1)–O(11A)

O(11)–Cu(1)–O(11A)

the pyridine–triazole–pyridine moiety of complex 5 the Table 3). In this complex the Co–N_pyrdistances are actually

N(4)-pyridine ring shows the largest twist, being inclined by shorter than the Co–N_trzdistances [2.189(3) and

10.4(3)° relative to the triazole mean plane. The pyrrole ring 2.209(3) Å, respectively], albeit only slightly, which is a geo-

intersects with the triazole mean plane at an angle of metrical feature that has not been observed previously in

82.4(3)° (Table 4). There are hydrogen bonds between the complexes of any 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-

H₂O co-ligand and the two ClO₄^–counterions [O(1)···O(11) triazole. In complexes of this ligand type the M–N_pyrdis-

2.78 and O(1)···O(21) 2.84 Å].

tances are usually longer, often significantly, than the M–

N

The mononuclear yellow complex [Co^II(pldpt)₂(DMF)₂]-

_trzdistances.^[2]In addition, both the Co–N_pyrand the Co–

(ClO₄)₂(6) (Figure 4) features the common trans-(NЈ,N¹)₂N_trzdistances are unusually long compared to those ob-

coordination mode (Figure 2). The coordination sphere served in related systems [2.102(4)–2.147(3) and 2.052(4)–

about the cobalt centre is a strongly distorted octahedron 2.124(2) Å, respectively].^[36,37,42]As is normal, the nitrogen

with two DMF molecules in the axial positions (Table 2 and atom of the non-coordinated pyridine ring points towards

Eur. J. Inorg. Chem. 2006, 573–589

www.eurjic.org

579

M. H. Klingele, P. D. W. Boyd, B. Moubaraki, K. S. Murray, S. Brooker

FULL PAPER

Table 4. Angles [°] between the mean planes of central triazole ring and the attached pyridine and pyrrole rings in 3,5-di(2-pyridyl)-4-

(1H-pyrrol-1-yl)-4H-1,2,4-triazole (pldpt, 3) and its complexes.

Compound

N(1)-pyridine^[a]

N(4)-pyridine^[a]

N(6)-pyrrole^[a]

pldpt (3)

31.1(1) [17.9(1)]

6.7(4)

6.2(2)

4.7(1)

7.7(2)

3.8(2)

4.4(1)

5.2(3)

36.8(1) [29.2(1)]

10.4(3)

24.7(2)

5.6(1)

4.1(2)

8.2(1)

82.4(1) [81.9(1)]

82.4(3)

87.4(1)

88.2(1)

88.0(1)

85.3(1)

88.8(1)

88.4(2)

[Co^II₂(pldpt)₂(DMF)₂(H₂O)₂](ClO₄)₄·0.5Et₂O (5)

[Co^II(pldpt)₂(DMF)₂](ClO₄)₂(6)

[Co^II₂(pldpt)₂(MeCN)₂(H₂O)₂](BF₄)₄(8)

[Ni^II₂(pldpt)₂(MeCN)₄](BF₄)₄·2MeCN (11)

[Cu^II(pldpt)₂(ClO₄)₂]·2DMF (13)

[Cu^II₂(pldpt)₂(MeCN)₂(H₂O)₂](ClO₄)₄(14)

[Zn^II₂(pldpt)₂(MeCN)₂(H₂O)₂](BF₄)₄(17)

4.7(1)

5.5(3)

[a] Values in square brackets refer to the N(7)-pyridine, N(10)-pyridine and N(12)-pyrrole rings of the second ligand molecule within the

asymmetric unit.

the pyrrole ring which intersects with the triazole mean architecture of complex 13 is the same as in [Cu^II(pyppt)₂-

plane at an angle of 87.4(1)°. The N(1)- and N(4)-pyridine (ClO₄)₂]·MeCN,^[49][Cu^II(ibdpt)₂(ClO₄)₂]^[32]and [Cu^II-

rings are tilted by 6.1(2)° and 24.7(2)°, respectively, relative (pmdpt)₂(ClO₄)₂]^[41]with the Cu–N_pyr, Cu–N_trzand Cu–O

to the triazole mean plane (Table 4).

distances [2.034(2), 1.979(2) and 2.470(2) Å, respectively]

The overall architecture of the dinuclear orange complex (Table 2 and Table 3) having very similar values as the cor-

[Co^II₂(pldpt)₂(MeCN)₂(H₂O)₂](BF₄)₄(8) (Figure S3) is very responding distances observed in these related complexes

–

similar to that of the corresponding ClO₄complex 5 de- [2.038(3)–2.045(2),

1.962(3)–1.989(2)

and

2.466(3)–

scribed above. Here, the (NЈ,N¹,N²,NЈЈ)₂double-bridging 2.471(3) Å, respectively]. Both the coordinated and the non-

coordination mode (Figure 2) is realised with a MeCN coordinated pyridine rings show only slight deviations from

molecule being the second axial co-ligand, instead of DMF, planarity [3.8(2) and 8.2(1)°, respectively] with respect to

in addition to the H₂O molecule which forms hydrogen the triazole mean plane. The pyrrole ring is almost perpen-

–

bonds to the two BF₄counterions [O(1)···F(11) 2.72 and dicular [85.3(1)°] to the triazole mean plane (Table 4).

O(1)···F(21) 2.73 Å]. The usual situation of longer Co–N_pyr

In all of the previous structures of dinuclear complexes

distances [2.1876(12) and 2.2188(12) Å] than Co–N_trzdis- of 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-triazoles featur-

tances [2.0769(12) and 2.0976(12) Å] is again observed ing the dinuclear (NЈ,N¹,N²,NЈЈ)₂double-bridging coordi-

(Table 2 and Table 3). The distance between the two cobalt nation mode (Figure 2), described in this paper and else-

centres of 4.2660(4) Å is almost identical to the value ob- where,^[5,32,43,44]the two ligand molecules have been found

–

served for the ClO₄complex 5 (Table 1). The pyridine–tri- to be in practically perfect alignment with each other, i.e.

azole–pyridine moiety is almost perfectly planar [4.7(1) and with the four nitrogen atoms of the bridging N₂units of the

5.6(1)°] while the pyrrole ring is practically perpendicular two triazole moieties forming a rectangle. In contrast, in

[88.2(1)°] to the triazole mean plane (Table 4).

[Cu^II₂(pldpt)₂(MeCN)₂(H₂O)₂](ClO₄)₄(14) (Figure 6) the

The dinuclear (NЈ,N¹,N²,NЈЈ)₂double-bridging coordina- two ligand molecules are offset sideways from one another,

tion mode (Figure 2) is also featured in the purple-blue i.e. with the four nitrogen atoms of the bridging N₂units

complex [Ni^II₂(pldpt)₂(MeCN)₄](BF₄)₄·2MeCN (11) (Fig- of the two triazole moieties forming a parallelogram with

ure S4). Here, each of the two nickel centres binds two acute angles of about 78°, resulting in a pronounced tetrag-

MeCN co-ligands in the axial positions resulting in dis- onal distortion of the copper(ii) centres. The consequences

torted octahedral N₆coordination environments (Table 2 with regard to the distances between the two equivalent

and Table 3). The distance of 4.170(1) Å between the two copper centres and their donor atoms are quite dramatic.

nickel centres is somewhat larger than the distances ob- The Cu–N_pyrand Cu–N_trzdistances in complex 14 are the

served in other nickel(ii) complexes of related ligands longest observed for any complex of a ligand featuring the

(Table 1).^[5,32]The Ni–N_pyrand Ni–N_trzdistances of bidentate pyridine–triazole moiety. The two Cu–N_pyrdis-

2.149(2)–2.184(2) and 2.023(2)–2.042(2) Å, respectively, in tances are markedly different from each other [2.5170(18)

complex 11 are in the same range as those observed in re- and 2.0264(17) Å] as are the two Cu–N_trzdistances

lated complexes.^[5,32]The four Ni–N_MeCNdistances are all [1.9908(17) and 2.2564(17) Å] (Table 2 and Table 3). These

very similar and within the range of 2.025(2)–2.038(2) Å. In geometrical features are a manifestation of an unsymmetri-

both ligand molecules the pyridine–triazole–pyridine moi- cal Jahn–Teller elongation of the distorted CuN₅O coordi-

ety is almost flat [7.7(2) and 4.1(2)°] while the respective nation octahedron along the N(1)–Cu(1)–N(3A) axis

pyrrole rings are virtually perpendicular [88.0(1)°] to the tri- [Cu(1)–N(1) 2.5170(18) and Cu(1)–N(3A) 2.2564(17) Å].

azole mean plane (Table 4).

The Cu(1)–N(20) and the Cu(1)–O(1) distances between the

The copper centre in [Cu^II(pldpt)₂(ClO₄)₂]·2DMF (13) metal centre and the axial MeCN and H₂O co-ligands,

(Figure 5) is octahedrally N₄O₂coordinated with two mole- respectively, are practically identical [2.0024(19) and

cules of pldpt (3) occupying the equatorial positions and 2.0029(16) Å]. In contrast, in [Cu^II(pldpt)₂(ClO₄)₂]·2DMF

two ClO₄^–ions being bound axially, giving rise to the trans- (13) (see above) as well as in analogous copper(ii) com-

(NЈ,N¹)₂coordination mode (Figure 2). Thus, the overall plexes of related ligands the Jahn–Teller elongation of the

580

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Dinucleating Behaviour of a 1,2,4-Triazole-Based Bis-Bidentate Ligand

FULL PAPER

coordination octahedron occurs along the X_axial–Cu–X_axial[M₂(pldpt)₂(ClO₄)₃]⁺at m/z = 993.3 (M = Co^II), 991.2 (M

axis and is symmetrical. The distance of 4.3140(5) Å be- = Ni^II) and 1003.1 (M = Zn^II), respectively.

tween the two copper centres in complex 14 is in between

Despite their good solubility in MeCN, and the fact that

the corresponding distances observed in [Cu^II

-

2

only one dinuclear solid state species was formed in each

–

(NH₂dpt)(H₂O)₄(SO₄)₂]·H₂O^[12]

and

[Cu^II₂(ibdpt)₂- case on crystallisation, the ESI mass spectra of the BF₄

(MeCN)₂(ClO₄)₂](ClO₄)₂·2MeCN^[32](Table 1). The axial complexes 7, 10 and 16 were not particularly informative

H₂O co-ligand is involved in hydrogen bonding to the two and showed only about half the number of assignable peaks

–

ClO₄counterions [O(1)···O(11) 2.78 and O(1)···O(21) that the analogous ClO₄complexes had. As was the case

–

2.81 Å]. Here too, the pyridine–triazole–pyridine moiety is with the ClO₄analogues, the spectra of complexes 7, 10

nearly planar [4.4(1) and 4.7(1)°], with the pyrrole ring in- and 16 all had peaks for the fragments [M(pldpt)₃]²⁺in

tersecting the triazole mean plane almost at 88.8(1)° common, while no peaks corresponding to dinuclear species

(Table 4).

were observed for these compounds.

The molecular structure of [Zn^II₂(pldpt)₂(MeCN)₂(H₂O)₂]-

The ESI mass spectrum of [Cu^II(pldpt)₂(ClO₄)₂] (12) was

(BF₄)₄(17) (Figure S5) is basically the same as that of the in full agreement with the other analytical data of this com-

cobalt(ii) analogue [Co^II₂(pldpt)₂(MeCN)₂(H₂O)₂](BF₄)₄plex, albeit that most of the peaks were assigned to cop-

(8) (Figure S3). Complex 17 is the first dinuclear zinc(ii) per(i) rather than copper(ii) species, the former arising from

complex of any 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-tri- reduction of the metal centre under the conditions of the

azole to be synthesised and structurally characterised. The experiment.

two zinc centres are separated by 4.455(2) Å (Table 1) and

the pyridine–triazole–pyridine moiety shows only a slight

deviation from planarity [5.2(3) and 5.5(3)°], while the pyr-

role ring is almost perpendicular [88.4(2)°] to the triazole

mean plane (Table 4). The complex adopts the dinuclear

NMR Spectroscopy

1

–

The H NMR spectrum of the dinuclear zinc(ii) ClO₄

(NЈ,N¹,N²,NЈЈ)₂double-bridging coordination mode (Fig- complex 15 in [D₇]DMF showed only six signals in the aro-

ure 2). Here too, the two ligand molecules are somewhat matic region, which was in agreement with only one species

shifted sideways relative to each other resulting in a slight being present (Figure S6). This confirmed that this complex

tetragonal distortion of the system which is manifested in does not exist in an equilibrium with mononuclear species

the relatively large variation of the Zn–N_pyrand Zn–N_trzin DMF solution but retains its symmetrical dinuclear

distances [2.173(4)–2.227(4) and 2.119(4)–2.164(4) Å, architecture in this solvent, in contrast to the recrystalli-

respectively] (Table 2 and Table 3). The H₂O co-ligand sation behaviour of the analogous cobalt(ii) and nickel(ii)

–

forms hydrogen bonds to the two BF₄counterions [O(1)··· complexes 4 and 9, respectively, in the presence of this sol-

F(11) 2.75 and O(1)···F(21) 2.77 Å].

vent. Five of the signals were well resolved and only the

In all of the complexes of pldpt (3) synthesised and struc- signal at δ = 7.55 ppm, which was assigned to 3-PyH, was

turally characterised in the course of this work the mean broad. While the other five signals were shifted downfield,

planes of the central triazole ring and the π-electron-rich as could be expected upon coordination, by 0.12–0.23 ppm

pyrrole ring of the ligand are not co-planar but rather inter- relative to the signals of free pldpt (3) in [D₇]DMF, the sig-

sect at almost right angles [82.4(3)–88.8(1)°] (Table 4). This nal for 3-PyH was shifted upfield by 0.40 ppm, thus swap-

precludes an electronic interaction occurring between them ping places with the signal for 5-PyH. The single-crystal X-

–

by a π-pathway. Therefore, if there is any transmission of ray structure analysis of the analogous BF₄complex 17

electron density between these two heterocyclic rings it must shows that the pyrrole ring is, as expected on steric grounds,

occur across the σ-bond between them. Consequently, it is almost perpendicular to the two pyridine rings and the tri-

likely to be small.

azole ring in the solid state. The significant upfield shift of

1

the signal for 3-PyH observed in the H NMR spectra of

–

both the ClO₄complex 15 and the BF₄complex 16 (see

below) in [D₇]DMF indicates that the same relative orienta-

tion is adopted in solution, as this proton appears to be

Mass Spectrometry

ESI mass spectra were recorded in MeCN for all of the interacting with the π-electron system of the adjacent pyr-

initial powdery complexes. In all of the spectra the parent role ring. As outlined above, the normal conformation of

peak was assigned to the species [(pldpt) + H]⁺. The spectra the pyridine rings in non-coordinated 4-substituted 3,5-

–

of the dinuclear ClO₄complexes 4, 9 and 15 showed, al- di(2-pyridyl)-4H-1,2,4-triazoles is the one where the nitro-

most exclusively, peaks that were assigned to mononuclear gen atoms of the pyridine rings point towards the face of

species, including the fragments [M(pldpt)₃]²⁺at m/z = the pyrrole ring, i.e. the pyrrole ring is almost at a right

461.7 (M = Co^II), 461.1 (M = Ni^II) and 464.3 (M = Zn^II), angle to the triazole ring in all of the structurally character-

respectively, with a metal-to-ligand molar ratio of 1:3 which ised compounds, whereas on coordination in a dinuclear

has not been observed for complexes of any 4-substituted complex the pyridine rings are held the other way round

3,5-di(2-pyridyl)-4H-1,2,4-triazole in the solid state so far. due to the binding of the metal ions, so the 3-PyH protons

As the only peaks assignable to dinuclear species, the three now point towards the face of the pyrrole ring. For complex

spectra also had in common peaks for the fragments 17 the two independent distances between the 3-PyH and

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M. H. Klingele, P. D. W. Boyd, B. Moubaraki, K. S. Murray, S. Brooker

FULL PAPER

the centroid of the pyrrole ring are 3.02 and 3.66 Å in the the molar conductivities of complexes 7, 10 and 16 in

solid state. Finally, given that in the dinuclear complex the MeCN (480, 470 and 475 Ω^–1·cm²·mol^–1, respectively) were

coordinated pyridine and triazole rings are expected to be found to be in good agreement with the expected value of

approximately co-planar, these NMR spectroscopic data in about 420–500 Ω^–1·cm²·mol^–1for 4:1 electrolytes in this sol-

[D₇]DMF are consistent with the triazole and pyrrole rings vent.^[74]The molar conductivity of the mononuclear cop-

being almost perpendicular to one another, precluding an per(ii) complex 12 was determined as 245 Ω^–1·cm²·mol^–1in

electronic interaction occurring between them by a π-path- MeCN. This value agrees well with that expected for a 2:1

way and indicating that any electronic interactions occur electrolyte in MeCN (220–300 Ω^–1·cm²·mol^–1).^[74]

via the N–N σ-bond.

–

The ¹³C NMR spectrum of the dinuclear zinc(ii) ClO₄

Magnetic Studies

complex 15 in [D₇]DMF, which was very similar to the cor-

responding spectrum of pldpt (3) with all of the signals be-

ing shifted only slightly (Figure S7), was also consistent

with the formulation of a dinuclear solution species and

with only one species being present in DMF solution.

As expected, the NMR spectra, recorded in [D₇]DMF,

Magnetic measurements were carried out on powder

samples of the two dinuclear cobalt complexes Co^II₂(pldpt)₂-

(ClO₄)₄(MeCN)_m(H₂O)_n(4) and Co^II₂(pldpt)₂(BF₄)₄-

(MeCN)_m(H₂O)_n(7) as well as of the two dinuclear nickel

complexes Ni^II₂(pldpt)₂(ClO₄)₄(MeCN)_m(H₂O)_n(9) and

Ni^II₂(pldpt)₂(BF₄)₄(MeCN)_m(H₂O)_n(10), revealing in each

case weak antiferromagnetic coupling between the metal

centres (Table 6).

The dinuclear cobalt(ii) complexes 4 and 7 exhibited al-

most identical magnetic behaviour despite the different

counterions, thus indicating that the nature of the latter has

practically no influence on the magnetism of these com-

pounds. Similarly, the magnetic behaviour of different sam-

ples of the same compound was found to be independent

within experimental error from the actual solvent content.

The magnetic moments for complexes 4 (Figure 5) and 7

–

of the dinuclear zinc(ii) BF₄complex 16, which upon

recrystallisation from MeCN/Et₂O afforded the structurally

characterised dinuclear complex 17 (see above), were practi-

–

cally identical to those observed for the analogous ClO₄

complex 15. Attempts were also made to record NMR spec-

tra of complex 16 in [D₃]MeCN for comparison but for

unknown reasons this failed and useful spectral information

could not be obtained using this solvent.

Conductivity Measurements

–

The molar conductivities of the ClO₄complexes 4, 9 (Figure S7) at room temperature were 4.50 and 4.29 μ_Bper

and 15 were determined in DMF. The values obtained (260, cobalt(ii) centre, respectively, and thus somewhat higher

300 and 255 Ω^–1·cm²·mol^–1respectively) are in agreement than for spin-only d⁷high-spin systems as a result of spin-

,

with the expected value of about 240–300 Ω^–1·cm²·mol^–1for orbit coupling and ligand field splitting effects acting on

–

4

a 4:1 electrolyte in this solvent.^[74]For the BF₄complexes the T_1gsingle ion states. For both complexes the fitted

7, 10 and 16 the corresponding values, determined in DMF, curves for the temperature dependence of the molar mag-

were found to be 280, 250 and 270 Ω^–1·cm²·mol^–1, respec- netic susceptibility showed a maximum, at T = 13 K with

tively, which are also within the expected range. Likewise, χ_m= 0.06806 cm³·mol^–1for complex 4 (Figure 7) and with

Figure 7. Temperature dependence of the effective magnetic moment μ_eff(᭺) and the molar magnetic susceptibility χ_m(ᮀ) per cobalt(ii)

centre for Co^II₂(pldpt)₂(ClO₄)₄(MeCN)_m(H₂O)_n(4) (m = 1, n = 0). The solid lines represent the best fit using the parameters given in

Table 5.

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Dinucleating Behaviour of a 1,2,4-Triazole-Based Bis-Bidentate Ligand

FULL PAPER

χ_m= 0.06166 cm³·mol^–1for complex 7 (Figure S8), a feature complex 9 was somewhat larger than in the BF₄complex

typical for antiferromagnetic exchange coupling. The mag- 10, the coupling constants being –8.8 and –7.8 cm^–1, respec-

netic data were fitted well by an S = 3/2 dimer model of tively. Here too, the magnetic behaviour of different sam-

the spin-only Heisenberg–Van Vleck type (–2JS₁·S₂)^[75]in- ples of the same compound was found to be independent

dicating that orbital degeneracy had largely been removed. within experimental error from the actual solvent content.

The best fit parameters are given in Table 5. The magnitude As with the cobalt(ii) complexes of this ligand described

of the coupling between the two cobalt(ii) centres in the above, the antiferromagnetic coupling in complexes 9 and

–

ClO₄complex 4 (J = –3.1 cm^–1) and the BF₄complex 7 10 was less than that observed in related nickel(ii) com-

(J = –3.1 cm^–1) was similar to the corresponding value plexes of other 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-tri-

observed for [Co^II₂(TsPMAT)₂](BF₄)₄·4H₂O (J

=

azoles.^[5,32]

–3.3 cm^–1)^[51]and was only slightly less than that reported

for related complexes of other 4-substituted 3,5-di(2-pyrid-

yl)-4H-1,2,4-triazoles.^[5,32]

Conclusion

Table 5. Magnetic data for Co^II₂(pldpt)₂(ClO₄)₄(MeCN)_m(H₂O)_n

(4), Co^II₂(pldpt)₂(BF₄)₄(MeCN)_m(H₂O)_n(7), Ni^II₂(pldpt)₂(ClO₄)₄-

(MeCN)_m(H₂O)_n(9) and Ni^II₂(pldpt)₂(BF₄)₄(MeCN)_m(H₂O)_n(10).

The coordination behaviour of the known ligand pldpt

(3)^[44]towards the first-row transition-metal ions Co²⁺

,

Ni²⁺, Cu²⁺and Zn²⁺in reactions with a metal-to-ligand

molar ratio of 1:1 has been investigated in detail for the

first time. From these studies it is clear that this ligand can

act as a bis-bidentate chelator and thus form dinuclear com-

plexes but it has also been revealed that its dinuclear com-

plexes can be labile in solution depending on the solvent

used. Although in most cases the initial precipitates are di-

Complex

m

n

J [cm^–1]

g

TIP

Monomer

[%]

[cm³·mol^–1]

4

1

0

2

0

4

–3.1

–8.8

–7.8

2.36 60·10^–6

0.1

0.4

0.5

7

2.25 65·10^–6

9

2.05

0

10

2.15 65·10^–6

The room temperature effective magnetic moment of nuclear, equilibria between di- and mononuclear species can

–

2.82 μ_Bper nickel(ii) centre for the ClO₄complex 9 (Fig- occur in solution, depending on the metal salt and the sol-

ure 8) was reduced from the typical uncoupled value of ca. vent employed. Thus, for example, the strongly polar apro-

3.1 μ_Bthus indicating that antiferromagnetic coupling was tic solvent DMF causes the dinuclear cobalt(ii) and

–

occurring. For the BF₄complex 10 the corresponding nickel(ii) ClO₄^–complexes 4 and 9, respectively, to break up

value was 3.00 μ_B(Figure S9) and hence the nickel(ii) to some extent giving rise to mixtures of di- and mononu-

centres are less strongly coupled than in complex 9. The clear species, while the corresponding dinuclear zinc(ii)

–

fitted curves for the temperature dependence of the molar ClO₄complex 15 appears to be perfectly stable in this sol-

–

magnetic susceptibility of complexes 9 (Figure 8) and 10 vent. In contrast, from solutions of the analogous BF₄

(Figure S9) had maxima at

T

=

26 K with χ_m

=

complexes 7, 10 and 16 in the less polar solvent MeCN only

dinuclear species are isolated.

Given that our primary interest in pldpt (3) was to use it

to prepare and study further examples of, prior to our re-

0.01639 cm³·mol^–1and

T

22 K with χ_m

0.02058 cm³·mol^–1, respectively. The antiferromagnetic

–

coupling between the two nickel(ii) centres in the ClO₄

Figure 8. Temperature dependence of the effective magnetic moment μ_eff(᭺) and the molar magnetic susceptibility χ_m(ᮀ) per nickel(ii)

centre for Ni^II₂(pldpt)₂(ClO₄)₄(MeCN)_m(H₂O)_n(9) (m = 0, n = 0). The solid lines represent the best fit using the parameters given in

Table 5.

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M. H. Klingele, P. D. W. Boyd, B. Moubaraki, K. S. Murray, S. Brooker

FULL PAPER

with a Perkin–Elmer Spectrum BX FT-IR spectrophotometer. UV/

Vis/NIR spectra were recorded with a Varian CARY 500 Scan UV/

Vis/NIR spectrophotometer in the range 200–1400 nm. Conductiv-

ity measurements were carried out at 25 °C using a Suntex SC-170

conductivity meter. ESI mass spectra of organic compounds were

run on a Shimadzu LCMS-QP8000α spectrometer while spectra of

complexes were run on a MicroMass LCT spectrometer. For all

compounds MeCN was used as the solvent. Magnetic data were

recorded in the range 300–4.2 K using a Quantum Design MPMS5

SQUID magnetometer with an applied field of 1 T.

search, rarely observed, discrete dinuclear complexes of 4-

substituted-3,5-di(2-pyridyl)-4H-1,2,4-triazoles, the deliber-

ate preparation of mononuclear complexes employing me-

tal-to-ligand molar ratios of 1:2 or 1:3 was not attempted

in the course of this particular study. However, such studies

are currently being carried out as an integral component

of our ongoing investigation into the iron(ii) coordination

chemistry of pldpt (3) and related ligands.^[52]

The enhanced dinucleating ability of pldpt (3), as com-

pared to the 4-aryl-3,5-di(2-pyridyl)-4H-1,2,4-triazoles, is

attributed largely to the effect of the 4-(1H-pyrrol-1-yl)

group on the relative solubility of the various possible prod-

ucts in the solvents employed. The X-ray crystallographic

data, and the NMR spectroscopic data for the zinc(ii) com-

plex 15, indicate that the electronic effect of this particular

substituent is probably quite small because the potentially

strong π-donation from the pyrrole ring is switched off due

to the near-perpendicular orientation of the pyrrole ring rel-

ative to the triazole ring, leaving only the effects transmitted

by the σ-pathway, which are likely to be weak. These find-

ings are consistent with the suggestion that the substituent

Caution: While no problems were encountered in the course of this

work, reactions involving N₂H₄·H₂O may form potentially explosive

mixtures so must be carried out with extreme caution. Similarly,

ClO₄^–salts are potentially explosive so should be handled with appro-

priate care.

3,6-Di(2-pyridyl)-1,4-dihydro-1,2,4,5-tetrazine (1): A heterogeneous

mixture of 2-pyridinecarbonitrile (20.8 g, 0.20 mol) and N₂H₄·H₂O

(50 mL) was refluxed for 2 hours during which time the mixture

became homogeneous, turned orange and a solid separated from

the solution with heavy foaming. After cooling, all volatiles were

evaporated under reduced pressure and the orange solid thus ob-

tained was dried in vacuo. Recrystallisation from pyridine gave

on N⁴in 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-triazoles 13.8 g (58%) of analytically pure 3,6-di(2-pyridyl)-1,4-dihydro-

1,2,4,5-tetrazine (1) as bright orange needles. M.p. 191–193 °C.

C₁₂H₁₀N₆(238.25): calcd. C 60.50, H 4.23, N 35.27; found C 60.50,

H 4.14, N 35.33. ¹H NMR (500 MHz, CDCl₃, ppm): δ = 7.34 [ddd,

influences the ability of such a ligand to form only mononu-

clear or both di- and mononuclear complexes by a complex

mixture of factors, the most important of which, in the case

of pldpt (3), appears to be its effect on the relative solubility

of the various possible products in the solvents employed

during the preparation and/or the recrystallisation of the

complexes, although in other cases subtle electronic effects

may also be at work.^[2,31,32,52]

3

4

³J_4,5= 7.7 Hz, J_5,6= 4.8 Hz, J_3,5= 1.2 Hz, 2 H, 2×5-PyH], 7.74

[dt, ³J_3,4= ³J_4,5= 7.7 Hz, ⁴J_4,6= 1.8 Hz, 2 H, 2×4-PyH], 8.05 [ddd,

³J_3,4= 7.7 Hz, ⁴J_3,5= 1.2 Hz, ⁵J_3,6= 0.9 Hz, 2 H, 2×3-PyH], 8.54–

8.59 [m,

4

H, 2×6-PyH and 2×PyCNH]. ¹³C{¹H} NMR

(125 MHz, CDCl₃, ppm): δ = 121.41 [2×3-PyC], 124.97 [2×5-

PyC], 136.83 [2×4-PyC], 146.75 [2×NCNH], 147.65 [2×2-PyC],

Magnetic studies carried out on the dinuclear cobalt(ii)

148.51 [2×6-PyC]. IR (KBr): ν = 3343, 3296, 3058, 1588, 1564,

˜

complexes 4 and 7 and the dinuclear nickel(ii) complexes 9 1470, 1446, 1387, 1288, 1251, 1155, 1117, 1089, 1077, 1041, 995,

981, 903, 885, 795, 787, 771, 745, 720, 677, 667, 655, 622, 490 cm^–1.

and 10 have shown that the two central triazole bridges pro-

vided by pldpt (3) mediate weak antiferromagnetic ex-

change coupling between the two metal centres of these

ESI-MS (pos., MeCN): m/z = 239 [M + H]⁺, 261 [M + Na]⁺, 277

[M + K]⁺.

complexes. With a view to systematically accessing families

of spin crossover systems, the exploration of the coordina-

4-Amino-3,5-di(2-pyridyl)-4H-1,2,4-triazole (NH₂dpt, 2): 3,6-Di(2-

pyridyl)-1,4-dihydro-1,2,4,5-tetrazine (1) (11.9 g, 50.0 mmol) was

tion behaviour of pldpt (3), and related ligands, towards dissolved in 2 m HCl (100 mL) and the dark brown solution was

refluxed for 30 minutes. After cooling, the resulting golden solution

was basified to pH Ϸ 9 by dropwise addition of concd. NH₃re-

sulting in the formation of a voluminous colourless precipitate. The

solid was filtered off, washed with H₂O and dried in vacuo.

Recrystallisation from H₂O/EtOH (1:1) gave 10.1 g (84%) of ana-

lytically pure NH₂dpt (2) as colourless needles. Alternatively, a mix-

ture of 2-pyridinecarbonitrile (10.4 g, 0.10 mol), N₂H₄·H₂SO₄

(13.0 g, 0.10 mol) and N₂H₄·H₂O (15.0 g, 0.30 mol) in 1,2-ethane-

diol (50 mL) was heated at 130 °C for 24 hours. An orange solid

that soon separated from the solution with heavy foaming redis-

solved almost completely over time. On cooling to room tempera-

ture, the reaction mixture solidified to give an almost colourless

solid contaminated with some orange material. H₂O (100 mL) was

added, the resulting slurry was filtered and the crude product was

washed with water and dried in vacuo. Recrystallisation from H₂O/

EtOH (1:1) gave 8.06 g (67%) of crude NH₂dpt (2) as a yellowish

solid. This material could be used in the next step without further

purification. Analytically pure material was obtained as colourless

needles only after at least one more recrystallisation from H₂O/

EtOH (1:1). M.p. 185–187 °C. C₁₂H₁₀N₆(238.25): calcd. C 60.50,

H 4.23, N 35.27; found C 60.35, H 4.10, N 35.00. ¹H NMR

iron(ii) salts in 1:1, 1:2 and 1:3 metal-to-ligand molar ratios,

in a variety of solvents, is well underway and the results of

this study will be reported in due course.^[52]

Experimental Section

General Remarks: All solvents used for reactions were laboratory

reagent grade while UV/Vis/NIR and conductivity measurements

were carried out in HPLC-grade solvents. All chemicals were pur-

chased from Aldrich and used as received. Elemental analyses were

carried out by the Campbell Microanalytical Laboratory at the

University of Otago. Melting points were determined with a Gal-

lenkamp melting point apparatus in open-glass capillaries and are

uncorrected. ¹H and ¹³C NMR spectra were recorded with a Varian

INOVA-500 spectrometer at 25 °C. Chemical shifts are given rela-

tive to TMS using the residual solvent signals as secondary refer-

ence (CDCl₃: δ_H= 7.26 ppm, δ_C= 77.16 ppm; [D₇]DMF: δ_H

=

8.02 ppm, δ_C= 163.15 ppm). Peak assignments were made on the

basis of chemical shifts, integration patterns and coupling con-

stants as well as two-dimensional correlation experiments where

necessary. IR spectra were recorded in the range 4000–400 cm^–1

3

(500 MHz, CDCl₃, ppm): δ = 7.36 [ddd, J_4,5= 7.7 Hz, J_5,6

=

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Dinucleating Behaviour of a 1,2,4-Triazole-Based Bis-Bidentate Ligand

FULL PAPER

4

3

4.8 Hz, J_3,5= 1.2 Hz, 2 H, 2×5-PyH], 7.86 [dt, J_3,4

=

³J_4,5

=

ately. The resulting suspension was refluxed for another 15 minutes

and was then stirred at room temperature for 24 hours. The solid

4

3

7.7 Hz, J_4,6= 1.8 Hz, 2 H, 2×4-PyH], 8.38 [ddd, J_3,4= 7.7 Hz,

⁴J_3,5= 1.2 Hz, J_3,6= 0.9 Hz, 2 H, 2×3-PyH], 8.49 [br. s, 2 H, was filtered off and washed with EtOH. Drying in vacuo gave

5

3

4

5

TzNH₂], 8.65 [ddd, J_5,6= 4.8 Hz, J_4,6= 1.8 Hz, J_3,6= 0.9 Hz, 2

H, 2×6-PyH]. ¹³C{¹H} NMR (125 MHz, CDCl₃, ppm): δ = 122.97

[2×3-PyC], 124.11 [2×5-PyC], 137.41 [2×4-PyC], 147.82 [3- and

388 mg (ca. 90%) of Co^II₂(pldpt)₂Cl₄(H₂O) as a pink powder.

C₃₂H₂₆Cl₄Co₂N₁₂O (854.32): calcd. C 44.99, H 3.07, N 19.67;

found C 45.38, H 3.05, N 19.51.

5-TzC], 148.10 [2×2-PyC], 148.43 [2×6-PyC]. IR (KBr): ν = 3421,

˜

Reaction of pldpt (3) with Co(ClO₄)₂·6H₂O: An orange solution of

Co(ClO₄)₂·6H₂O (366 mg, 1.00 mmol) in MeCN (5 mL) was added

to a colourless refluxing solution of pldpt (3) (288 mg, 1.00 mmol)

in MeCN (20 mL). An orange solid formed almost immediately.

The resulting suspension was cooled to room temperature and the

solid was filtered off and washed with MeCN. Drying in vacuo

gave 555 mg (ca. 90%) of Co^II₂(pldpt)₂(ClO₄)₄(MeCN)_m(H₂O)_n(4)

as a pale orange powder. The solvent content of the initial products

varied considerably from batch to batch. Heating of the powders

at 60 °C in vacuo for several days similarly afforded materials of

variable solvent content. A sample analysing as Co^II₂(pldpt)₂-

(ClO₄)₄(MeCN) was used for characterisation purposes.

C₃₄H₂₇Cl₄Co₂N₁₃O₁₆(1133.34): calcd. C 36.03, H 2.40, N 16.07;

3293, 1588, 1566, 1545, 1465, 1432, 1412, 1390, 1318, 1273, 1249,

1148, 1093, 1074, 1041, 998, 968, 912, 795, 787, 737, 693, 677, 623,

586, 489 cm^–1. ESI-MS (pos., MeCN): m/z = 239 [M + H]⁺, 261

[M + Na]⁺, 277 [M + K]⁺.

3,5-Di(2-pyridyl)-4-(1H-pyrrol-1-yl)-4H-1,2,4-triazole (pldpt, 3): A

mixture of NH₂dpt (2) (4.77 g, 20 mmol) and 2,5-dimethoxytetra-

hydrofuran (3.30 g, 25.0 mmol) in 1,4-dioxane (20 mL) and acetic

acid (20 mL) was refluxed for 24 hours. After cooling, all volatiles

were removed in vacuo to give a dark crystalline solid. This was

taken up in CH₂Cl₂(50 mL) and the mixture was filtered through

a short column of silica gel. The filtrate was evaporated under re-

duced pressure and the yellowish solid thus obtained was dried in

vacuo. Recrystallisation from EtOH gave 4.46 g (77%) of analyti-

cally pure pldpt (3) as colourless needles. M.p. 199–201 °C.

found C 36.08, H 2.54, N 16.26. IR (KBr): ν = 1611, 1544, 1517,

˜

1473, 1439, 1405, 1354, 1302, 1263, 1188, 1113, 1074, 1012, 931,

C₁₆H₁₂N₆(288.31): calcd. C 66.66, H 4.20, N 29.15; found C 66.90, 911, 794, 746, 725, 701, 654, 635, 625 cm^–1. ESI-MS (pos., MeCN):

1

H 3.96, N 29.22. H NMR (500 MHz, CDCl₃, ppm): δ = 6.22 [t,

m/z = 235.1 [Co(pldpt)(MeCN)₃]²⁺

,

289.1 [(pldpt)H]⁺, 338.1

[Co(pldpt)(ClO₄)]⁺,

461.7

3

³J = 2.4 Hz, 2 H, 3- and 4-PlH], 6.86 [t, J = 2.4 Hz, 2 H, 2- and

[Co(pldpt)₂(MeCN)]²⁺

,

446.0

3

4

5-PlH], 7.30 [ddd, J_4,5= 7.7 Hz, J_5,6= 4.8 Hz, J_3,5= 1.2 Hz, 2

[Co(pldpt)₃]²⁺, 487.0 [Co(pldpt)(MeCN)(ClO₄)]⁺, 577.4 [(pldpt)₂-

H]⁺, 734.3 [Co(pldpt)₂(ClO₄)]⁺, 993.3 [Co₂(pldpt)₂(ClO₄)₃]⁺. Molar

conductivity (DMF): Λ_m= 260 Ω^–1·cm²·mol^–1. Vapour diffusion of

Et₂O into an orange solution of complex 4 in MeCN/DMF (10:1)

afforded orange crystals of [Co^II₂(pldpt)₂(H₂O)₂(DMF)₂](ClO₄)₄·

3

4

H, 2×5-PyH], 7.75 [dt, J_3,4= J_4,5= 7.7 Hz, J_4,6= 1.8 Hz, 2 H,

2×4-PyH], 7.84 [ddd, ³J_3,4= 7.7 Hz, J_3,5= 1.2 Hz, J_3,6= 0.9 Hz,

4

5

3

4

5

2 H, 2×3-PyH], 8.52 [ddd, J_5,6= 4.8 Hz, J_4,6= 1.8 Hz, J_3,6

=

0.9 Hz, 2 H, 2×6-PyH]. ¹H NMR (500 MHz, [D₇]DMF, ppm): δ

= 6.12 [t, J = 2.4 Hz, 2 H, 3- and 4-PlH], 7.20 [t, J = 2.4 Hz, 2 0.5Et₂O (5) and yellow crystals of [Co^II(pldpt)₂(DMF)₂](ClO₄)₂(6).

3

4

H, 2- and 5-PlH], 7.51 [ddd, J_4,5= 7.7 Hz, J_5,6= 4.8 Hz, J_3,5

=

Reaction of pldpt (3) with Co(BF₄)₂·6H₂O: An orange solution of

Co(BF₄)₂·6H₂O (341 mg, 1.00 mmol) in MeCN (5 mL) was added

to a colourless refluxing solution of pldpt (3) (288 mg, 1.00 mmol)

in MeCN (20 mL). The resulting orange solution was refluxed for

10 minutes and was then stirred at room temperature for another

4 hours during which time an orange precipitate formed. The solid

was filtered off and washed with MeCN. Drying in vacuo gave

465 mg (ca. 80%) of Co^II₂(pldpt)₂(BF₄)₄(MeCN)_m(H₂O)_n(7) as a

pale orange powder. The solvent content of the initial products

varied considerably from batch to batch. Heating of the powders

at 60 °C in vacuo for several days similarly afforded materials of

variable solvent content. A sample analysing as Co^II₂(pldpt)₂(BF₄)₄-

(MeCN)(H₂O)₂was used for characterisation purposes.

C₃₄H₃₁B₄Co₂F₁₆N₁₃O₂(1118.79): calcd. C 36.50, H 2.79, N 16.28;

3

4

1.2 Hz, 2 H, 2×5-PyH], 7.95 [ddd, J_3,4= 7.7 Hz, J_3,5= 1.2 Hz,

⁵J_3,6= 0.9 Hz, 2 H, 2×3-PyH], 8.00 [dt, ³J_3,4= ³J_4,5= 7.7 Hz, ⁴J_4,6

= 1.8 Hz, 2 H, 2×4-PyH], 8.54 [ddd, ³J_5,6= 4.8 Hz, ⁴J_4,6= 1.8 Hz,

⁵J_3,6= 0.9 Hz, 2 H, 2×6-PyH]. ¹³C{¹H} NMR (125 MHz, CDCl₃,

ppm): δ = 108.44 [3- and 4-PlC], 122.34 [2- and 5-PlC], 123.54

[2×3-PyC], 124.90 [2×5-PyC], 136.84 [2×4-PyC], 145.33 [2×2-

PyC], 149.93 [2×6-PyC], 153.16 [3- and 5-TzC]. ¹³C{¹H} NMR

(125 MHz, [D₇]DMF, ppm): δ = 108.51 [3- and 4-PlC], 124.02 [2-

and 5-PlC], 124.74 [2×3-PyC], 126.16 [2×5-PyC], 138.21 [2×4-

PyC], 146.69 [2×2-PyC], 150.79 [2×6-PyC], 154.15 [3- and 5-TzC].

IR (KBr): ν = 3118, 1587, 1569, 1533, 1465, 1443, 1435, 1423, 1332,

˜

1281, 1246, 1181, 1150, 1088, 1069, 1044, 1010, 992, 963, 912, 790,

736, 729, 710, 703, 633, 619, 608, 524, 489 cm^–1. ESI-MS (pos.,

MeCN): m/z = 289 [M + H]⁺, 311 [M + Na]⁺, 327 [M + K]⁺.

UV/Vis/NIR (MeCN): λ_max(ε/L·mol^–1·cm^–1) = 251 (14600), 281 nm

(18500).

found C 36.37, H 2.75, N 16.17. IR (KBr): ν = 1610, 1577, 1545,

˜

1518, 1474, 1440, 1402, 1356, 1297, 1263, 1189, 1073, 911, 862,

796, 765, 749, 727, 705, 655, 636, 563, 533, 521, 436, 414 cm^–1.

Reaction of pldpt (3) with CoCl₂·6H₂O (Method A): A pinkish-red ESI-MS (pos., MeCN): m/z = 289.1 [(pldpt)H]⁺, 317.6 [Co-

solution of CoCl₂·6H₂O (238 mg, 1.00 mmol) in H₂O (5 mL) was

added to a colourless solution of pldpt (3) (288 mg, 1.00 mmol) in

MeOH (20 mL) dropwise at room temperature and the resulting

orange-brown solution was stirred for 30 minutes. Slow evapora-

tion over the course of 4 weeks led to the formation of a large

quantity of a beige solid and a few tiny orange prisms. The solid

products were filtered off and washed with MeOH. Drying in

vacuo gave Co^II(pldpt)₂Cl₂(H₂O)_1.5. C₃₂H₂₇Cl₂CoN₁₂O_1.5(733.49):

calcd. C 52.40, H 3.71, N 22.92, Cl 9.67; found C 52.36, H 3.49,

N 23.17, Cl 9.66.

(pldpt)₂]²⁺

722.3

,

338.1 [Co(pldpt)₂(MeCN)]²⁺

,

461.7 [Co(pldpt)₃]²⁺

(MeCN): λ_max

,

[Co(pldpt)₂(BF₄)]⁺.

UV/Vis/NIR

(ε/L·mol^–1·cm^–1) = 252 (25200), 291 (37000), 481 (46), 1022 nm

(12). Molar conductivity (MeCN): Λ_m= 480 Ω^–1·cm²·mol^–1. Molar

conductivity (DMF): Λ_m= 280 Ω^–1·cm²·mol^–1. Vapour diffusion of

Et₂O into the orange MeCN mother liquor or an orange solution

of complex 7 in MeCN afforded orange crystals of [Co^II₂(pldpt)₂-

(MeCN)₂(H₂O)₂](BF₄)₄(8).

Reaction of pldpt (3) with NiCl₂·6H₂O (Method A): A grass green

solution of NiCl₂·6H₂O (238 mg, 1.00 mmol) in H₂O (5 mL) was

Reaction of pldpt (3) with CoCl₂·6H₂O (Method B): A deep blue added to a colourless solution of pldpt (3) (288 mg, 1.00 mmol) in

solution of CoCl₂·6H₂O (238 mg, 1.00 mmol) in EtOH (5 mL) was MeOH (20 mL) dropwise at room temperature and the resulting

added to a colourless refluxing solution of pldpt (3) (288 mg,

1.00 mmol) in EtOH (20 mL). A blue solid formed almost immedi-

olive-green solution was stirred for 30 minutes. Slow evaporation

over the course of 6 weeks led to the formation of an inseparable

Eur. J. Inorg. Chem. 2006, 573–589

www.eurjic.org

585

M. H. Klingele, P. D. W. Boyd, B. Moubaraki, K. S. Murray, S. Brooker

FULL PAPER

mixture of a greenish crystalline solid and blue prisms in an esti-

mated 3:1 ratio. These were not easily separable so no analytical

data were obtained for either of the products.

afforded purple crystals of [Ni^II₂(pldpt)₂(MeCN)₄](BF₄)₄·2MeCN

(11).

Reaction of pldpt (3) with Cu(ClO₄)₂·6H₂O: A blue solution of Cu-

(ClO₄)₂·6H₂O (371 mg, 1.00 mmol) in MeCN (5 mL) was added to

Reaction of pldpt (3) with NiCl₂·6H₂O (Method B): A grass green

solution of NiCl₂·6H₂O (238 mg, 1.00 mmol) in EtOH (5 mL) was a colourless refluxing solution of pldpt (3) (288 mg, 1.00 mmol)

added to a colourless solution of pldpt (3) (288 mg, 1.00 mmol) in

EtOH (20 mL) dropwise at room temperature. The resulting green

solution was stirred at room temperature for 4 hours during which

time a green precipitate formed. The solid was filtered off and

washed with EtOH. Drying in vacuo gave 275 mg (ca. 60%) of

in MeCN (20 mL). The resulting green solution was refluxed for

10 minutes and was then stirred at room temperature for another

4 hours during which time a blue precipitate formed. The solid was

filtered off and washed with a minimum amount of MeCN. Drying

in vacuo gave 249 mg (59%) of [Cu^II(pldpt)₂(ClO₄)₂] (12) as a blue

powder. C₃₂H₂₄Cl₂CuN₁₂O₈(839.07): calcd. C 45.81, H 2.88, N

Ni^II₂(pldpt)₂Cl₄(H₂O)₃as

a

very pale green powder.

C₃₂H₃₀Cl₄Ni₂N₁₂O₃(889.86): calcd. C 43.19, H 3.40, N 18.89;

found C 43.62, H 3.28, N 18.74.

20.03; found C 45.52, H 2.78, N 20.05. IR (KBr): ν = 1614, 1588,

˜

1571, 1554, 1533, 1513, 1485, 1456, 1434, 1340, 1311, 1272, 1193,

1105, 1023, 991, 929, 913, 793, 750, 742, 722, 698, 645, 622, 568,

495 cm^–1. ESI-MS (pos., MeCN): m/z = 289.1 [(pldpt)H]⁺, 319.6

[Cu(pldpt)₂]²⁺, 340.1 [Cu(pldpt)₂(MeCN)]²⁺, 351.0 [Cu(pldpt)]⁺,

369.1 [Cu(pldpt)(H₂O)]⁺, 392.1 [Cu(pldpt)(MeCN)]⁺, 639.2

[Cu(pldpt)₂]⁺, 738.2 [Cu(pldpt)₂(ClO₄)]⁺. UV/Vis/NIR (MeCN):

λ_max(ε/L·mol^–1·cm^–1) = 242 (35000), 295 (33500), 659 nm (90). Mo-

lar conductivity (MeCN): Λ_m= 245 Ω^–1·cm²·mol^–1. Vapour dif-

fusion of Et₂O into a blue solution of complex 12 in MeCN gave

blue crystals of [Cu^II(pldpt)₂(ClO₄)₂]·2DMF (13) while vapour dif-

fusion of Et₂O into the green MeCN mother liquor afforded green

crystals of [Cu^II₂(pldpt)₂(H₂O)₂(MeCN)₂](ClO₄)₄(14). The occur-

rence of the DMF solvates in complex 13 was probably due to the

use of contaminated glassware.

Reaction of pldpt (3) with Ni(ClO₄)₂·6H₂O: A blue solution of

Ni(ClO₄)₂·6H₂O (366 mg, 1.00 mmol) in MeCN (5 mL) was added

to a colourless refluxing solution of pldpt (3) (288 mg, 1.00 mmol)

in MeCN (20 mL). A purple solid formed almost immediately. The

resulting suspension was cooled to room temperature and the solid

was filtered off and washed with MeCN. Drying in vacuo gave

475 mg (ca. 80%) of Ni^II₂(pldpt)₂(ClO₄)₄(MeCN)_m(H₂O)_n(9) as a

pale violet powder. The solvent content of the initial products var-

ied considerably from batch to batch. Heating of the powders at

60 °C in vacuo for several days similarly afforded materials of vari-

able solvent content. A sample analysing as Ni^II₂(pldpt)₂(ClO₄)₄

was used for characterisation purposes. C₃₂H₂₄Cl₄Ni₂N₁₂O₁₆

(1091.81): calcd. C 35.20, H 2.22, N 15.39; found C 35.18, H 2.53,

N 15.59. IR (KBr): ν = 1612, 1548, 1526, 1517, 1474, 1440, 1410,

Reaction of pldpt (3) with Zn(ClO₄)₂·6H₂O: A colourless solution

˜

1355, 1304, 1265, 1195, 1114, 1074, 1025, 1012, 931, 911, 793, 747, of Zn(ClO₄)₂·6H₂O (372 mg, 1.00 mmol) in MeCN (5 mL) was

725, 700, 659, 636, 625 cm^–1. ESI-MS (pos., MeCN): m/z = 214.1

added to a colourless refluxing solution of pldpt (3) (288 mg,

1.00 mmol) in MeCN (20 mL). A colourless solid formed almost

immediately. The resulting suspension was cooled to room tem-

[Ni(pldpt)(MeCN)₂]²⁺

[Ni(pldpt)(MeCN)₄]²⁺

,

234.6

[Ni(pldpt)(MeCN)₃]²⁺

,

255.1

289.1 [(pldpt)H]⁺, 317.1 [Ni(pldpt)₂]²⁺

,

337.7 [Ni(pldpt)₂(MeCN)]²⁺, 358.2 [Ni(pldpt)₂(MeCN)₂]²⁺, 445.0 perature and the solid was filtered off and washed with MeCN.

[Ni(pldpt)(ClO₄)]⁺, 461.1 [Ni(pldpt)₃]²⁺

,

486.0 [Ni(pldpt)-

Drying in vacuo gave 470 mg (ca. 80%) of Zn^II₂(pldpt)₂(ClO₄)₄-

(MeCN)_m(H₂O)_n(15) as a colourless powder. The solvent content

of the initial products varied considerably from batch to batch.

Heating of the powders at 60 °C in vacuo for several days similarly

afforded materials of variable solvent content. A sample analysing

as Zn^II₂(pldpt)₂(ClO₄)₄(H₂O)₄was used for characterisation pur-

poses. C₃₂H₃₂Cl₄N₁₂O₂₀Zn₂(1177.25): calcd. C 32.65, H 2.74, N

(MeCN)(ClO₄)]⁺, 527.1 [Ni(pldpt)(MeCN)₂(ClO₄)]⁺, 568.2

[Ni(pldpt)(MeCN)₃(ClO₄)]⁺, 577.4 [(pldpt)₂H]⁺, 733.2 [Ni(pldpt)₂-

(ClO₄)]⁺, 991.2 [Ni₂(pldpt)₂(ClO₄)₃]⁺. Molar conductivity (DMF):

Λ_m= 300 Ω^–1·cm²·mol^–1.

Reaction of pldpt (3) with Ni(BF₄)₂·6H₂O: A blue solution of

Ni(BF₄)₂·6H₂O (340 mg, 1.00 mmol) in MeCN (5 mL) was added

to a colourless refluxing solution of pldpt (3) (288 mg, 1.00 mmol)

in MeCN (20 mL). The resulting purple solution was refluxed for

10 minutes and was then stirred at room temperature for another

4 hours during which time a purple precipitate formed. The solid

was filtered off and washed with MeCN. Drying in vacuo gave

215 mg (ca. 40%) of Ni^II₂(pldpt)₂(BF₄)₄(MeCN)_m(H₂O)_n(10) as a

pale violet powder. The solvent content of the initial products var-

ied considerably from batch to batch. Heating of the powders at

60 °C in vacuo for several days similarly afforded materials of vari-

1

14.28; found C 32.28, H 2.59, N 14.30. H NMR (500 MHz, [D₇]-

3

DMF, ppm): δ = 6.35 [t, J = 2.4 Hz, 4 H, 2×3- and 4-PlH], 7.37

3

[t, J = 2.4 Hz, 4 H, 2×2- and 5-PlH], 7.55 [br. s, 4 H, 4×3-PyH],

3

4

7.69 [ddd, J_4,5= 7.7 Hz, J_5,6= 4.8 Hz, J_3,5= 1.2 Hz, 4 H, 4×5-

3

4

PyH], 8.12 [dt, J_3,4

=

³J_4,5= 7.7 Hz, J_4,6= 1.8 Hz, 4 H, 4×4-

PyH], 8.68 [ddd, ³J_5,6= 4.8 Hz, J_4,6= 1.8 Hz, J_3,6= 0.9 Hz, 4 H,

4×6-PyH]. ¹³C{¹H} NMR (125 MHz, [D₇]DMF, ppm): δ = 109.91

[2×3- and 4-PlC], 123.38 [2×2- and 5-PlC], 124.08 [4×3-PyC],

127.49 [4×5-PyC], 139.61 [4×4-PyC], 144.25 [4×2-PyC], 150.95

4

5

[4×6-PyC], 154.01 [2×3- and 5-TzC]. IR (KBr): ν = 1611, 1546,

˜

able solvent content.

A

sample analysing as Ni^II₂(pldpt)₂-

1525, 1517, 1476, 1441, 1354, 1306, 1297, 1264, 1192, 1117, 1089,

(BF₄)₄(H₂O)₄was used for characterisation purposes.

C₃₂H₃₂B₄F₁₆N₁₂Ni₂O₄(1113.28): calcd. C 34.52, H 2.90, N 15.10;

1014, 930, 911, 795, 748, 724, 703, 653, 636, 625 cm^–1. ESI-MS

(pos., MeCN): m/z = 217.1 [Zn(pldpt)(MeCN)₂]²⁺

,

237.6

found C 34.55, H 2.70, N 15.09. IR (KBr): ν = 1612, 1578, 1549,

˜

[Zn(pldpt)(MeCN)₃]²⁺, 289.1 [(pldpt)H]⁺, 320.1 [Zn(pldpt)₂]²⁺

,

1521, 1475, 1441, 1410, 1356, 1300, 1265, 1190, 1073, 911, 796,

750, 727, 705, 694, 659, 637, 564, 533, 522, 439, 415 cm^–1. ESI-MS

(pos., MeCN): m/z = 289.1 [(pldpt)H]⁺, 317.1 [Ni(pldpt)₂]²⁺, 337.6

340.7 [Zn(pldpt)₂(MeCN)]²⁺

[Zn(pldpt)₃]²⁺

492.2

,

451.1 [Zn(pldpt)(ClO₄)]⁺, 464.3

,

[Zn(pldpt)(MeCN)(ClO₄)]⁺,

577.4

[(pldpt)₂H]⁺, 739.3 [Zn(pldpt)₂(ClO₄)]⁺, 1003.1 [Zn₂(pldpt)₂-

[Ni(pldpt)₂(MeCN)]²⁺

,

358.1 [Ni(pldpt)₂(MeCN)₂]²⁺

,

461.1

(ClO₄)₃]⁺. Molar conductivity (DMF): Λ_m= 255 Ω^–1·cm²·mol^–1

.

[Ni(pldpt)₃]²⁺, 721.3 [Ni(pldpt)₂(BF₄)]⁺. UV/Vis/NIR (MeCN):

λ_max(ε/L·mol^–1·cm^–1) = 238 (24400), 295 (36400), ca. 530 sh (ca.

Reaction of pldpt (3) with Zn(BF₄)₂·6H₂O: A colourless solution of

Zn(BF₄)₂·6H₂O (347 mg, 1.00 mmol) in MeCN (5 mL) was added

to a colourless refluxing solution of pldpt (3) (288 mg, 1.00 mmol)

in MeCN (20 mL). The resulting colourless solution was refluxed

for 10 minutes and was then stirred at room temperature for an-

70), 866 nm (40). Molar conductivity (MeCN): Λ_m

=

470 Ω^–1·cm²·mol^–1. Molar conductivity (DMF): Λ_m

250 Ω^–1·cm²·mol^–1. Vapour diffusion of Et₂O into the purple

MeCN mother liquor or a purple solution of complex 10 in MeCN

586

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Eur. J. Inorg. Chem. 2006, 573–589

Dinucleating Behaviour of a 1,2,4-Triazole-Based Bis-Bidentate Ligand

FULL PAPER

Table 6. Crystallographic data for 3,5-di(2-pyridyl)-4-(1H-pyrrol-1-yl)-4H-1,2,4-triazole (pldpt, 3), [Co^II₂(pldpt)₂(DMF)₂(H₂O)₂](ClO₄)₄·

0.5Et₂O (5), [Co^II(pldpt)₂(DMF)₂](ClO₄)₂(6), [Co^II₂(pldpt)₂(MeCN)₂(H₂O)₂](BF₄)₄(8), [Ni^II₂(pldpt)₂(MeCN)₄](BF₄)₄·2MeCN (11),

[Cu^II(pldpt)₂(ClO₄)₂]·2DMF (13), [Cu^II₂(pldpt)₂(MeCN)₂(H₂O)₂](ClO₄)₄(14) and [Zn^II₂(pldpt)₂(MeCN)₂(H₂O)₂](BF₄)₄(17).

3

5

6

8

Empirical formula

C₁₆H₁₂N₆

288.32

monoclinic

P2₁

C₄₀H₄₇Cl₄Co₂N₁₄O_20.5C₃₈H₃₈Cl₂CoN₁₄O₁₀

C₃₆H₃₄B₄Co₂F₁₆N₁₄O₂

1159.87

Formula weight [gmol^–1]

1311.58

triclinic

980.65

monoclinic

P2₁/c

Crystal system

Space group

triclinic

¯

P1

¯

P1

a [Å]

b [Å]

c [Å]

α [°]

10.0461(2)

7.3951(2)

19.1277(5)

90

103.000(1)

90

1384.61(6)

4

1.383

10.349(2)

12.680(3)

13.065(3)

76.62(3)

88.30(3)

72.46(3)

1588.9(5)

1

8.8443(1)

13.3043(2)

18.2462(2)

90

82.518(1)

90

2128.70(5)

2

1.530

9.9087(3)

10.3844(4)

11.8599(4)

76.834(1)

74.254(1)

85.140(1)

1143.33(7)

1

β [°]

γ [°]

V [Å³]

Z

ρ_calcd.[g cm^–3]

1.371

0.765

1.685

0.844

μ [mm^–1]

0.089

0.604

Temperature [K]

F(000)

Crystal colour and shape

Crystal size [mm³]

Θ_min./Θ_max.[°]

h

83(2)

600

200(2)

671

200(2)

1010

83(2)

582

colourless block

0.50×0.50×0.36

2.08/25.63

–12 Ǟ 12

–7 Ǟ 9

–21 Ǟ 23

7900

4140 [R(int) = 0.0109]

99.6

4140/1/397

1.055

orange prism

0.34×0.32×0.30

1.60/26.45

–12 Ǟ 12

–15 Ǟ 15

–16 Ǟ 16

11447

6364 [R(int) = 0.0741] 4677 [R(int) = 0.0632]

97.3

6364/10/421

1.023

yellow block

0.36×0.12×0.10

1.90/31.07

–11 Ǟ 11

–17 Ǟ 17

–23 Ǟ 23

20754

orange prism

0.40×0.22×0.18

1.83/27.13

–12 Ǟ 12

–12 Ǟ 13

0 Ǟ 15

11760

4996 [R(int) = 0.0156]

98.6

k

l

Reflections collected

Independent reflections

Completeness to Θ_max.[%]

Data/restraints/parameter

GOF

68.5

4677/0/295

1.067

4996/0/343

1.026

R₁/wR₂[I Ͼ 2σ(I)]

R₁/wR₂(all data)

Absolute structure factor

Max. peak/hole [e·Å^–3]

0.0242/0.0610

0.0249/0.0613

–0.2(11)

0.156/–0.189

0.0902/0.2579

0.1204/0.2926

0.0677/0.1622

0.1035/0.1818

0.0245/0.0597

0.0286/0.0618

1.316/–1.049

0.511/–0.712

0.349/–0.357

11

13

14

17

Empirical formula

C₄₄H₄₂B₄F₁₆N₁₈Ni₂

1287.62

C₃₈H₃₈Cl₂CuN₁₄O₁₀

985.26

C₃₆H₃₄Cl₄Cu₂N₁₄O₁₈

1219.65

C₃₆H₃₄B₄F₁₆N₁₄O₂Zn₂

1172.76

Formula weight [gmol^–1]

Crystal system

Space group

triclinic

P1

monoclinic

P2₁/n

triclinic

P1

triclinic

P1

¯

a [Å]

b [Å]

c [Å]

α [°]

12.621(5)

13.122(5)

18.940(5)

76.283(5)

76.145(5)

62.922(5)

2681.7(16)

2

8.584(5)

18.854(5)

13.105(5)

90

98.793(5)

90

2096.0(16)

2

1.561

9.8490(1)

10.4408(1)

12.1340(2)

76.178(1)

74.267(1)

84.505(1)

1165.62(3)

1

9.981(5)

10.458(5)

11.968(5)

76.824(5)

74.183(5)

85.209(5)

1170.0(9)

1

β [°]

γ [°]

V [Å³]

Z

ρ_calcd.[g cm^–3]

1.595

0.811

1.738

1.233

1.664

1.141

μ [mm^–1]

0.725

Temperature [K]

F(000)

Crystal colour and shape

Crystal size [mm³]

Θ_min./Θ_max.[°]

h

83(2)

1304

83(2)

1014

83(2)

618

83(2)

588

purple-blue prism

0.32×0.18×0.18

1.12/27.25

–15 Ǟ 16

–16 Ǟ 16

–24 Ǟ 24

27141

11701 [R(int) = 0.0445]

97.4

11701/0/763

1.077

blue needle

0.21×0.16×0.12

1.91/25.72

–10 Ǟ 10

–23 Ǟ 22

–15 Ǟ 15

18555

3987 [R(int) = 0.0475] 5077 [R(int) = 0.0225]

99.8

3987/0/297

1.132

green block

0.48×0.34×0.28

1.79/27.15

–12 Ǟ 12

–12 Ǟ 13

0 Ǟ 15

colourless plate

0.30×0.25×0.12

1.81/25.63

–12 Ǟ 12

–14 Ǟ 14

10501

4334 [R(int) = 0.0771]

98.2

4334/0/343

0.975

k

l

Reflections collected

Independent reflections

Completeness to Θ_max.[%]

Data/restraints/parameters

GOF

11913

98.0

5077/0/343

1.047

R₁/wR₂[I Ͼ 2σ(I)]

R₁/wR₂(all data)

Absolute structure factor

Max. peak/hole [e·Å^–3]

0.0485/0.1070

0.0716/0.1200

0.0405/0.0815

0.0537/0.0884

0.0333/0.0875

0.0379/0.0911

0.0622/0.1561

0.0826/0.1663

0.906/–0.662

0.352/–0.401

0.820/–0.868

1.647/–1.462

Eur. J. Inorg. Chem. 2006, 573–589

www.eurjic.org

587

M. H. Klingele, P. D. W. Boyd, B. Moubaraki, K. S. Murray, S. Brooker

FULL PAPER

other 4 hours during which time a colourless precipitate formed.

The solid was filtered off and washed with MeCN. Drying in vacuo

gave 345 mg (ca. 60%) of Zn^II₂(pldpt)₂(BF₄)₄(MeCN)_m(H₂O)_n(16)

as a colourless powder. The solvent content of the initial products

varied considerably from batch to batch. Heating of the powders

MHK and a Bridging Grant) and the Australian Research Council

(Discovery Grant). The authors are grateful to Ms. T. Groutso and

Prof. G. R. Clark (University of Auckland) for collecting some of

the X-ray data, to Mr. B. M. Clark (University of Canterbury) for

recording the ESI mass spectra of the complexes reported in this

at 60 °C in vacuo for several days similarly afforded materials of paper and to Mr. R. M. Hellyer (University of Otago) for his help.

variable solvent content. A sample analysing as Zn^II₂(pldpt)₂-

(BF₄)₄(H₂O)₂was used for characterisation purposes.

C₃₂H₂₈B₄F₁₆N₁₂O₂Zn₂(1090.63): calcd. C 35.24, H 2.59, N 15.41;

Prof. G. B. Jameson (Massey University), Prof. W. T. Robinson

(University of Canterbury) as well as Dr. D. S. Larsen, Dr. J. Kling-

ele (née Hausmann) and Dr. C. D. Brandt (University of Otago)

found C 35.13, H 2.58, N 15.33. IR (KBr): ν = 1609, 1576, 1546, are thanked for helpful discussions.

˜

1526, 1518, 1477, 1442, 1400, 1355, 1298, 1264, 1192, 1073, 911,

862, 797, 766, 750, 727, 706, 653, 640, 563, 533, 522, 436, 412 cm^–1).

ESI-MS (pos., MeCN): m/z = 289.1 [(pldpt)H]⁺, 320.1 [Zn-

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340.6 [Zn(pldpt)₂(MeCN)]²⁺

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464.2 [Zn(pldpt)₃]²⁺

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(H₂O)₂](BF₄)₄(17).

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X-ray Crystallography: X-ray data (Table 6) were collected with a

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mated Mo-K_αradiation (λ = 0.71073 Å). The structures were

solved by direct methods with SIR-92^[76]or SHELXS-97^[77,78]and

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niques with SHELXL-97.^[79]All non-hydrogen atoms were refined

anistropically. All hydrogen atoms, except H(101) and H(102) of

the axial H₂O co-ligands in complexes 5, 8, 14 and 17, were placed

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(for 3), -277058 (for 5), -277059 (for 6), -277060 (for 8), -277061

(for 11), -277062 (for 13), -277063 (for 14) and -277064 (for 17)

contain the supplementary crystallographic data for this paper.

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Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_requ-

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Supporting Information (see also the footnote on the first page of

this article): A PDF file (six pages) with supporting information for

this article is available on the WWW under http://ww w .eurjic.org or

from the authors. It contains a view of the asymmetric unit of li-

gand 3 (Figure S1), an overlay of the two crystallographically inde-

pendent molecules within the asymmetric unit of ligand 3 (Fig-

ure S2), views of the molecular structures of the cations of com-

plexes 8, 11 and 17 (Figure S3, S4 and S5, respectively), compari-

1

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This work was supported by grants from the University of Otago

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588

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Eur. J. Inorg. Chem. 2006, 573–589

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Published Online: December 21, 2005

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589

Article Doi

Probing the dinucleating behaviour of a bis-bidentate ligand: Synthesis and characterisation of some di- and mononuclear cobalt(II), nickel(II), copper(II) and zinc(II) complexes of 3,5-di(2-pyridyl)-4-(1H-pyrrol-1-yl)-4H-1,2,4- triazole

DOI: 10.1002/ejic.200500972

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