Synthesis and some first-row transition-metal complexes of the 1,2,4-triazole-based bis(terdentate) ligands TsPMAT and PMAT

Article abstract of DOI:10.1002/chem.200500387

The employment of a strategy based on nucleophilic substitution, rather than Schiff base condensation, for the preparation of 1,2,4-triazole-based ligands has been investigated and has led to the synthesis of two new ligands, 4-amino-3,5-bis{[N-(2-pyridyl

Full text of DOI:10.1002/chem.200500387

DOI: 10.1002/chem.200500387
Synthesis and Some First-Row Transition-Metal Complexes of the 1,2,4-
Triazole-Based Bis(terdentate) Ligands TsPMAT and PMAT
Marco H. Klingele,[a] Boujemaa Moubaraki,[b] Keith S. Murray,[b] and Sally Brooker*[a]
Abstract: The employment of a strat-
egy based on nucleophilic substitution,
rather than Schiff base condensation,
for the preparation of 1,2,4-triazole-
based ligands has been investigated
and has led to the synthesis of two new
ligands, 4-amino-3,5-bis{[N-(2-pyridyl-
methyl)-N-(4-toluenesulfonyl)amino]-
ed in a metal-to-ligand molar ratio of
2:1. Similarly, the reaction of PMAT
(15) with Mn(ClO4)2·6H2O or M-
(BF4)2·6H2O (M=Fe, Co, Ni, Zn) in a
ligand-to-metal molar ratio of 1:1 has
afforded a series of complexes with the
and doubly bridged by the N2 units of
the 1,2,4-triazole moieties, which gives
rise to N6 coordination spheres that are
strongly distorted from octahedral, as
evidenced by the X-ray crystal struc-
ture analyses of [CoII (TsPMAT)2]-
2
general formula [MII (PMAT)2]X4. The
(BF4)4·6MeCN (24·6MeCN) and [FeII -
2
2
metal centres in these complexes of
TsPMAT (14) and PMAT (15) are en-
capsulated by two ligand molecules
(PMAT)2](BF4)4·DMF (27·DMF). Stud-
methyl}-4H-1,2,4-triazole
(TsPMAT,
ies of the magnetic properties of [CoII -
2
14) and 4-amino-3,5-bis{[(2-pyridyl-
methyl)amino]methyl}-4H-1,2,4-triazole
(PMAT, 15). These are the first exam-
ples of bis(terdentate) ligands incorpo-
rating the 1,2,4-triazole unit. TsPMAT
(14) forms a dinuclear 2:2 complex
with Co(BF4)2·6H2O even when react-
(TsPMAT)2](BF4)4·4H2O (24·4H2O),
[MnII (PMAT)2](ClO4)4
(26),
and
2
[CoII (PMAT)2](BF4)4 (28) have re-
2
Keywords: bridging ligands · dinu-
clear complexes · magnetic proper-
vealed weak antiferromagnetic cou-
pling (J=À3.3, À0.16, and À2.4 cmÀ1,
respectively) between the two metal
centres in these complexes.
ties
· nucleophilic substitution ·
X-ray diffraction
Introduction
porating the 1,2,4-triazole moiety into novel acyclic and
macrocyclic ligand systems capable of binding and bridging
two metal ions.[26–31] Owing to its versatility and relative sim-
plicity the Schiff base approach[32–36] was initially considered
for the construction of the target 1,2,4-triazole-based li-
gands. This approach requires that the 1,2,4-triazole moiety
forms a part of either the dicarbonyl head unit or the di-
amine lateral component. We focused our attention on the
former option as a literature search revealed that five such
3,5-diacyl-1,2,4-triazole head units, compounds 2–6, were
known.[37–40] However, two of these head units, namely 1-(4-
methoxybenzyl)-1H-1,2,4-triazole-3,5-dicarbaldehyde
The incorporation of 3,6-pyridazinedicarbaldehyde (1) into
Schiff base ligands has facilitated the isolation of a wide
range of transition-metal complexes with intriguing electro-
chemical and magnetic properties,[1–19] including the first ex-
ample of a cobalt complex to exhibit both magnetic ex-
change coupling and the spin-crossover phenomenon.[5,9] In
light of this and with regard to the considerable recent inter-
est in transition-metal complexes derived from 1,2,4-tri-
azole-based ligands[15,20,21] that are known to be particularly
suited to produce spin-crossover systems with iron(ii)
salts,[22–25] we decided to investigate the possibility of incor-
(5)[38,39] and 1-dodecyl-1H-1,2,4-triazole-3,5-dicarbaldehyde
(6),[39] are unsuitable for our purposes as in both compounds
one of the nitrogen atoms of the potentially metal ion bridg-
ing N2 unit is blocked by the alkyl group. This left three po-
tentially suitable head units, compounds 2–4, of which di-
aldehyde 3 and diketone 4 are ionisable, due to the presence
of an acidic proton on the 1,2,4-triazole ring, whereas dike-
tone 2 is not. Metal-ion-templated condensation reactions of
3,5-dibenzoyl-4-phenyl-4H-1,2,4-triazole (2),[37] a sterically
encumbered but very soluble diketone head unit, with a va-
riety of amines were not found to be very promising.
[a] Dr. M. H. Klingele, Assoc. Prof. S. Brooker
Department of Chemistry, University of Otago
PO Box 56, Dunedin (New Zealand)
Fax : (+64)3-479-7906
E-mail: sbrooker@alkali.otago.ac.nz
[b] Dr. B. Moubaraki, Prof. K. S. Murray
School of Chemistry, Building 23, Monash University
Clayton, Victoria 3800 (Australia)
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
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extend the approach used for the synthesis of TsPMAT (14)
and PMAT (15) to the preparation of other acyclic and mac-
rocyclic ligands are also described. Employing PMAT (15),
we were recently able to identify, for the first time by means
of single-crystal X-ray diffraction, that the half-spin-cross-
over species of the doubly 1,2,4-triazole-bridged complex
[FeII (PMAT)2](BF4)4·DMF (27·DMF) is composed of dis-
2
crete dinuclear high-spin/low-spin units.[31] Thus, we were
able to confirm the conclusions drawn by Real, Gütlich, and
co-workers[48,49] on the basis of magnetic and applied-field
Mçssbauer data on the pathway of the transition in their
two-step spin-crossover systems. These results are in con-
trast to the recent results of Kaizaki and co-workers[50] who
found a 1:1 mixture of high-spin/high-spin and low-spin/low-
spin dinuclear units present at the half-spin-crossover pla-
teau of the two-step transition in their pyrazolate-bridged
system. Here, we detail the synthesis of complex 27·DMF
and some analogous first-row transition-metal complexes of
PMAT (15), as well as reporting the results of our initial in-
vestigation of the coordination chemistry of TsPMAT (14).
Torres and co-workers reported the synthesis of 1H-1,2,4-
triazole-3,5-dicarbaldehyde (3) and 3,5-diacetyl-1H-1,2,4-tri-
azole (4) in 1992[40] and the incorporation of these head
units into Schiff base ligands was subsequently stud-
ied.[39,41–43] As they found that dialdehyde 3 was unsuitable
for the preparation of such ligands due to its instability and
its insolubility in all solvents other than water,[39] we initially
concentrated our efforts on diketone 4. Thus, we were re-
cently able to prepare and structurally characterise the first
dinuclear [2+2] macrocyclic complexes of any 1,2,4-triazole-
derived ligand.[26–28] However, we found it difficult to isolate
and purify these doubly 1,2,4-triazolate-bridged macrocyclic
complexes and we concluded that diketone 4 was not an
ideal head unit. Owing to the lack of any other more suita-
ble 3,5-diacyl-1,2,4-triazoles, we decided to also investigate a
strategy other than Schiff base chemistry for the construc-
tion of the desired metal-ion-bridging 1,2,4-triazole-based li-
gands, namely an approach based on nucleophilic substitu-
tion of a 1,2,4-triazole precursor that has suitable leaving
groups within the substituents in the 3- and 5-positions. The
known compound 4-amino-3,5-bis(chloromethyl)-4H-1,2,4-
triazole (9)[44] was chosen for this purpose. In this paper we
report the stepwise synthesis of two new ligands, 4-amino-
3,5-bis{[N-(2-pyridylmethyl)-N-(4-toluenesulfonyl)amino]-
methyl}-4H-1,2,4-triazole (TsPMAT, 14) and 4-amino-3,5-
bis{[(2-pyridylmethyl)amino]methyl}-4H-1,2,4-triazole (PMAT,
15). To the best of our knowledge, these are the first exam-
Results and Discussion
Organic syntheses: The only method described in the litera-
ture for the preparation of the required 1,2,4-triazole precur-
sor, 4-amino-4H-1,2,4-triazole-3,5-dimethanol (7), is the con-
densation of glycolic acid with hydrazine monohydrate
(Scheme 1).[51–53] The original protocol by Adµmek[51] starts
Scheme 1. Synthesis of 4-amino-3,5-bis(chloromethyl)-4H-1,2,4-triazole
(9).
with anhydrous glycolic acid and involves a rather compli-
cated temperature programme. In a more recent modifica-
tion of this synthesis by Haasnoot and co-workers,[52,53] the
two reactants are simply heated together at 1808C until
water formation ceases. Both protocols were reviewed. We
did not find it advantageous to follow Adµmekꢁs tempera-
ture programme, and our attempt using the procedure by
Haasnoot and co-workers yielded an unidentified red glassy
solid. It seemed to be crucial to maintain the reaction tem-
perature below approximately 1658C at all times and to use
an excess (1.5 equivalents) of hydrazine monohydrate, as the
same discoloured glassy solid was obtained when equimolar
ples of bis(terdentate) ligands incorporating a metal-ion-
bridging 1,2,4-triazole unit. Kaden and co-workers[45] recent-
ly reported the synthesis of a related bis(quadridentate)
ligand bearing two 1,3,7-triazacyclononane moieties as later-
al units. A bis(terdentate)[46] and a mixed quadridentate–
quinquedentate ligand[47] based on 2,5-disubstituted 1,3,4-ox-
adiazoles have also recently been reported. Attempts to
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S. Brooker et al.
amounts of the reactants were used. Moreover, it was found
that glycolic acid could be used in the form of the commer-
cially available 70% aqueous solution instead of the much
more expensive anhydrous material.
alkylated amines and ammonium salts. To couple the 1,2,4-
triazole head unit with the lateral units in a controlled
manner we decided to use sulfonamide derivatives of the
amines rather than the free amines themselves. Thus, to pre-
pare acyclic ligands, we treated commercially available 2-
(aminomethyl)pyridine and 2-(2-aminoethyl)pyridine with 4-
toluenesulfonyl chloride in water/tetrahydrofuran in the
presence of sodium hydroxide (Scheme 2), a slight modifica-
The synthesis of dialcohol 7 was carried out several times
in exactly the same way. Interestingly, the crude products
from these experiments varied considerably in composition.
While in one case the crude product consisted of almost
pure dialcohol 7, other experiments gave only about 70%
conversion, the major impurity being the intermediate gly-
colohydrazide. In the latter case prolonged heating did not
result in further conversion unless a new portion of hydra-
zine monohydrate was added first. Regardless of the actual
composition of the crude product, recrystallisation from
water consistently gave yields of approximately 60% of ana-
lytically pure material. The use of water[51] for the recrystal-
lisation proved to be preferable, as a very large volume of
solvent was required when ethanol[52] was used. In addition,
due to the high solubility of glycolohydrazide in water, the
water-recrystallised product was of higher purity than the
ethanol-recrystallised material. Therefore the yield of 60–
65% obtained by Haasnoot and co-workers[52,53] seems more
realistic than the 94% yield that Adµmek[51] reported. Con-
sistent with this, Kaden and co-workers[45] recently reported
that they obtained a 68% yield of dialcohol 7 following
Adµmekꢁs procedure.
The conversion of dialcohol 7 into 4-amino-3,5-bis(chloro-
methyl)-4H-1,2,4-triazole monohydrochloride (8) was
straightforward and proceeded smoothly in an excess of
thionyl chloride at room temperature (Scheme 1).[54] The
crude product was obtained in virtually quantitative yield as
a yellowish solid after removal of the excess thionyl chloride
in vacuo. Recrystallisation from ethanol afforded analytical-
ly pure material as colourless prisms in 76% yield. In an at-
tempt to obtain dichloride 9 directly, without prior isolation
and purification of hydrochloride 8, the crude material was
taken up in an excess of saturated aqueous sodium hydrogen
carbonate.[44] However, only a low yield of dichloride 9 was
obtained after exhaustive extraction with ethyl acetate. This
was attributed to partial hydrolysis of dichloride 9 under the
basic conditions. Careful neutralisation of hydrochloride 8
under heterogeneous conditions with one equivalent of
sodium hydrogen carbonate in water/ethyl acetate gave pure
dichloride 9 in 87% yield (Scheme 1). Attempts to recrystal-
lise dichloride 9 from hot mixtures of ethyl acetate and cy-
clohexane led to decomposition and the formation of a col-
ourless insoluble material, which is thought to be a polymer
formed by the intermolecular nucleophilic displacement of
the chlorides by 4-amino groups. Dichloride 9 degraded
within a few days when stored at room temperature and ex-
posed to light, again appearing to form a polymeric materi-
al. However, it should be pointed out that others have suc-
cessfully carried out nucleophilic substitutions on dichloride
9, even at high temperatures, and have made no comments
on its instability.[44,55,56]
Scheme 2. Synthesis of N-(2-pyridylmethyl)-4-toluenesulfonamide (10)
and N-[2-(2-pyridyl)ethyl]-4-toluenesulfonamide (11).
tion of the procedure reported by Newkome and co-work-
ers.[57] This method afforded good yields of the desired prod-
ucts. Interestingly, we found that N-(2-pyridylmethyl)-4-tol-
uenesulfonamide (10), unlike its homologue N-[2-(2-pyrid-
yl)ethyl]-4-toluenesulfonamide (11), crystallises with half a
molecule of water in the lattice. This fact had not been re-
ported when this project was launched, even though sulfon-
amide 10 had been prepared and used by a number of au-
thors over the years. However, recently the single-crystal X-
ray structure analysis of sulfonamide 10·0.5H2O was pub-
lished by Sousa and co-workers,[58] thus confirming our ob-
servation.
For the preparation of macro-
cyclic ligands,
a sulfonamide
bearing second functional
a
group to allow the controlled
stepwise construction of the
target macrocycle was required.
We chose N-{3-[(4-toluenesulfo-
nyl)amino]propyl}acetamide
(13)[59,60] (Scheme 3) for this
purpose as, after coupling with
the 1,2,4-triazole head unit, hy-
drolysis of its acetamide group
could provide the required func-
tionality for ring-closure. Initial-
ly we followed the procedure
for the preparation of sulfon-
amide 13 reported by Hesse and
co-workers,[59,60] but found it
Scheme 3. Synthesis of N-{3-
[(4-toluenesulfonyl)amino]pro-
pyl}acetamide (13).
necessary to modify the reported workup procedure. The
product obtained by the resulting extractive workup of the
reaction mixture was contaminated with considerable
amounts of byproducts and proved to be difficult to purify.
Therefore we used a different approach to prepare sulfon-
amide 13 (Scheme 3).
While the selective monoacylation of symmetrical di-
amines is not trivial,[61,62] N-(3-aminopropyl)acetamide (12)
can be readily obtained by using ethyl acetate as the acetyla-
The reaction of free amines with alkyl halides is usually
difficult to control and often leads to a mixture of multiply
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Triazole Complexes
FULL PAPER
tion agent as described by Aspinall.[63,64] Thus, we treated a
threefold excess of 1,3-diaminopropane with ethyl acetate at
room temperature for five days to give acetamide 12 in
87% yield and good purity.[65] Subsequent reaction with 4-
toluenesulfonyl chloride gave NMR- and TLC-clean sulfo-
namide 13 in 92% yield (Scheme 3). This new approach
simplified the synthesis and increased the yield of sulfona-
mide 13 significantly. The crude material was pure enough
for subsequent reactions. Recrystallisation from ethyl ace-
tate[60] was impractical due to the low solubility of the mate-
rial in this solvent. A number of other solvents were tested
of which 1,4-dioxane proved to be the best. However, only
about 30–45% of sulfonamide 13 was recovered and the
crystallisation process was very slow.
With the required 1,2,4-triazole (8 or 9) and sulfonamide
components (10, 11 or 13) in hand, we investigated their
coupling reactions. Owing to the instability of dichloride 9,
the usefulness of hydrochloride 8 was explored. Initially the
acyclic ligands TsPMAT (14) and PMAT (15) were targeted
(Scheme 4). After 24 h under reflux, we could not detect
any product when the reaction of hydrochloride 8 with sul-
1,2,4-triazole (TsPEAT, 16), which could then be converted
into 4-amino-3,5-bis({[2-(2-pyridyl)ethyl]amino}methyl)-4H-
1,2,4-triazole (PEAT, 17). However, TsPEAT (16) could not
be isolated from these experiments and only unchanged sul-
fonamide 11 was recovered, almost quantitatively, when the
reaction was carried out under identical conditions as for
TsPMAT (14). In fact, no 1,2,4-triazole compound of any
kind was present in the filtered reaction mixture, as evi-
denced by 13C NMR analysis of the residue after evapora-
tion. Under the basic reaction conditions employed, the
actual reactive species is dichloride 9, formed in situ by the
neutralisation of hydrochloride 8. Considering the establish-
ed instability of dichloride 9, it presumably decomposed
faster than it could react with sulfonamide 11. This suggests
a significant difference in reactivity between the two sul-
fonamides 10 and 11. The polymeric material resulting from
the decomposition of dichloride 9 was presumably filtered
off along with the inorganic salts during workup. In summa-
ry, we could prepare the acyclic ligands TsPMAT (14) and
PMAT (15) by this route, but their homologues TsPEAT
(16) and PEAT (17) could not be prepared this way.
Aiming at macrocyclic ligand
preparation, we initially at-
tempted to couple hydrochlo-
ride
8 with sulfonamide 13,
again in N,N-dimethylform-
amide in the presence of potas-
sium carbonate at 608C for
24 h. NMR and TLC analysis of
the residue obtained after filtra-
tion of the reaction mixture and
evaporation of the filtrate in
vacuo showed that a mixture of
several different compounds
was present, including unreact-
ed sulfonamide 13, and indicat-
ed that some coupling had
indeed occurred. However, pro-
longed reaction times did not
result in the formation of a
single species or the consump-
tion of the remaining sulfona-
mide 13, and isolation and iden-
Scheme 4. Synthesis of 4-amino-3,5-bis{[N-(2-pyridylmethyl)-N-(4-toluenesulfonyl)amino]methyl}-4H-1,2,4-tri-
azole (TsPMAT, 14) and 4-amino-3,5-bis{[(2-pyridylmethyl)amino]methyl}-4H-1,2,4-triazole (PMAT, 15) and
attempted synthesis of 4-amino-3,5-bis({N-[2-(2-pyridyl)ethyl]-N-(4-toluenesulfonyl)amino}methyl)-4H-1,2,4-
triazole (TsPEAT, 16) and 4-amino-3,5-bis({[2-(2-pyridyl)ethyl]amino}methyl)-4H-1,2,4-triazole (PEAT, 17).
fonamide 10·0.5H2O in the presence of potassium carbonate
was carried out in acetonitrile. This was attributed to the in-
solubility of hydrochloride 8 in this solvent. Carrying out
the reaction at 608C in N,N-dimethylformamide, in which
hydrochloride 8 is readily soluble, we obtained TsPMAT
(14) as a colourless powder in 60% yield after workup. Re-
moval of the 4-toluenesulfonyl group was achieved by heat-
ing a solution of TsPMAT (14) in concentrated sulfuric acid
at 1008C for 8 h. Thus, PMAT (15) was isolated as a yellow-
ish oil in virtually quantitative yield (Scheme 4).
tification of the reaction products proved to be very diffi-
cult. Given the problems faced earlier in the attempted syn-
thesis of TsPEAT (16), further experiments to optimise the
coupling of hydrochloride 8 with sulfonamide 13 were not
carried out. Rather, the reactivity of the latter compound to-
wards other, potentially more suitable, 1,2,4-triazole deriva-
tives is currently being investigated.[19]
To overcome the problems caused by the presence of
both the nucleophilic 4-amino group and the chloride leav-
ing groups in hydrochloride 8 and dichloride 9, a way was
sought to eliminate the 4-amino group by derivatisation.
Therefore, we prepared the two hitherto unknown com-
pounds 4-(diacetylamino)-3,5-bis(chloromethyl)-4H-1,2,4-tri-
azole (18) and 3,5-bis(chloromethyl)-4-(1H-pyrrol-1-yl)-4H-
Encouraged by these results we examined the coupling of
hydrochloride 8 and sulfonamide 11 (Scheme 4). This was
expected to lead to the formation of 4-amino-3,5-bis({N-[2-
(2-pyridyl)ethyl]-N-(4-toluenesulfonyl)amino}methyl)-4H-
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S. Brooker et al.
1,2,4-triazole (19) as colourless crystalline solids in good
yields, by the reaction of hydrochloride 8 with acetic anhy-
dride or 2,5-dimethoxytetrahydrofuran,[66,67] respectively
(Scheme 5). Dichlorides 18 and 19 were found to exhibit
good thermal stability and to be readily soluble in organic
Scheme 5. Synthesis of 4-(diacetylamino)-3,5-bis(chloromethyl)-4H-1,2,4-
triazole (18) and 3,5-bis(chloromethyl)-4-(1H-pyrrol-1-yl)-4H-1,2,4-tri-
azole (19).
Scheme 6. Synthesis of 4-(diacetylamino)-4H-1,2,4-triazole-3,5-dimethyl
diacetate (20) and 4-(1H-pyrrol-1-yl)-4H-1,2,4-triazole-3,5-dimethanol
(21) and hydrolysis of the latter.
solvents. Initial attempts to couple dichlorides 18 and 19
with two simple nucleophiles, the sodium salts of 2-amino-
phenol and 4-toluenesulfonamide, indicate that dichloride
19 is the more promising candidate.[68] Coupling reactions of
dichloride 19 with sulfonamides 10, 11 and 13 are now being
investigated and the results of these studies will be reported
in due course.[19]
It should be noted that throughout these synthetic devel-
opments the possibility of developing access to new dicar-
bonyl head units that are more suitable than compounds 2–6
for the generation of Schiff base ligands has been borne in
mind. Hence a brief, unsuccessful attempt was made to oxi-
dise the highly polar dialcohol 7, which is only soluble in
water, dimethyl sulfoxide and N,N-dimethylformamide, to
the corresponding dialdehyde. Given the increase in solubili-
ty noted when the 4-amino group in dichloride 8 was con-
verted into either a 4-(diacetylamino) (18) or a 4-(1H-
pyrrol-1-yl) (19) group, a similar approach was tried with di-
alcohol 7, rather than pursuing its oxidation further. Specifi-
cally, derivatisation of dialcohol 7 generated 4-(diacetyl-
amino)-4H-1,2,4-triazole-3,5-dimethyl diacetate (20) and 4-
ings of Adµmek,[51] who had reported obtaining 4-amino-3,5-
dimethyl-4H-1,2,4-triazole diacetate, that is, the diacetylated
compound with the 4-amino group unchanged. It also con-
[69]
ˇ ˇ
tradicted the report of Vorísek, who observed the forma-
tion of a triacetate, that is, monoacetylation of the 4-amino
group, on acetylation of a related dialcohol. However, it was
consistent with the observed diacetylation of 4-amino
groups in related 1,2,4-triazoles reported by other research
groups.[70,71] To obtain pure tetraacetate 20 in good yield it
was crucial to reflux the reaction mixture vigorously and to
immerse the reaction vessel in a preheated oil bath (1608C)
rather than increasing the temperature gradually. Insepara-
ble mixtures of differently acetylated compounds were ob-
tained when these directions were not followed. NMR data
obtained on the crude products of preliminary experiments
clearly indicate that stirring tetraacetate 20 with concentrat-
ed aqueous ammonia in methanol at room temperature for
one hour facilitates the selective hydrolysis of this com-
pound to triacetate 23, which is readily soluble in chloro-
form and other organic solvents, whereas the use of concen-
trated hydrochloric acid in methanol appears to result in the
formation of dialcohol 22, the latter compound being insolu-
ble in chloroform but readily soluble in dimethyl sulfoxide
(Scheme 6).[68] Dialcohol 22 did not exhibit improved solu-
bility in organic solvents over that of the original dialco-
hol(7), so to date its preparation has not been optimised.
We turned our attention to the reaction of dialcohol 7
with 2,5-dimethoxytetrahydrofuran in acetic acid[66,67] which
gave pure dialcohol 21 as a greyish powder in 24% yield
(Scheme 6). The synthesis of dialcohol 21 is currently being
optimised, as it is proving to be a good starting material for
further reactions.[19] To summarise, the preparation of more
(1H-pyrrol-1-yl)-4H-1,2,4-triazole-3,5-dimethanol
(21)
(Scheme 6).
The acetylation of dialcohol 7 was carried out in essential-
ly the same way as described by Adµmek (Scheme 6).[51]
Thus, a suspension of dialcohol 7 in an excess of acetic anhy-
dride was refluxed for 30 min. Evaporation of all volatiles
afforded a yellow oil that crystallised on drying in vacuo
1
and was identified by H and 13C NMR spectroscopy as the
tetraacetylated compound 20. Recrystallisation of the crude
product from ethanol gave pure tetraacetate 20 as colourless
flakes in 62% yield. It is interesting to note that diacetyla-
tion of the 4-amino group of dialcohol 7 occurred, resulting
in the formation tetraacetate 20. This contradicted the find-
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Triazole Complexes
FULL PAPER
convenient dialdehyde head
units from such dialcohols (for
example, 7, 21 or 22) is looking
promising and is an active line
of enquiry in this research
group.[19] We are concurrently
working on alternative strategies
to access new 1,2,4-triazole-
based
head
and
lateral
units.[19,68]
Complexes of TsPMAT: We ex-
pected TsPMAT (14) to be ca-
pable of acting as a dinucleating
ligand offering two terdentate
binding sites. While there are
numerous examples in the liter-
ature of secondary sulfonamides
coordinating to metal ions in
their deprotonated form, there
are, to the best of our knowl-
edge, only two examples in
which tertiary sulfonamides, no-
toriously weak donor groups,
Figure 1. View of the molecular structure of the cation of [CoII2(TsPMAT)2](BF4)4·6MeCN (24·6MeCN). Hy-
À
À
drogen atoms have been omitted for clarity. Selected distances [Š]: Co(1) N(1) 2.048(5), Co(1) N(2)
À
À
À
À
2.626(5), Co(1) N(3) 2.062(5), Co(1) N(4A) 2.028(5), Co(1) N(5A) 2.551(5), Co(1) N(6A) 2.044(5),
Co(1)···Co(1A) 4.056(2). Selected angles [8]: N(1)-Co(1)-N(2) 73.3(2), N(1)-Co(1)-N(3) 91.6(2), N(1)-Co(1)-
N(4A) 103.8(2), N(1)-Co(1)-N(5A) 94.2(2), N(1)-Co(1)-N(6A) 152.0(2), N(2)-Co(1)-N(3) 73.7(2), N(2)-Co(1)-
N(4A) 171.6(2), N(2)-Co(1)-N(5A) 113.8(2), N(2)-Co(1)-N(6A) 88.9(2), N(3)-Co(1)-N(4A) 98.8(2), N(3)-
Co(1)-N(5A) 171.6(2), N(3)-Co(1)-N(6A) 104.2(2), N(4A)-Co(1)-N(5A) 74.0(2), N(4A)-Co(1)-N(6A) 96.6(2),
N(5A)-Co(1)-N(6A) 73.0(2), Co(1)-N(3)-N(4) 130.0(4), Co(1)-N(4A)-N(3A) 131.2(4). Symmetry operation
used to generate equivalent atoms: (A) Àx+2, Ày+2, Àz+2.
are bound to metal ions.[72,73] In the case of TsPMAT (14)
the likelihood of the tertiary sulfonamides coordinating to
the metal centres is improved due to the fact that these
donors are well positioned within the two chelating N3 bind-
ing pockets of the ligand.
N(6A) angle between the axial pyridine nitrogen atoms
showing the largest deviation from linearity (152.0(2)8). The
mean planes of the two independent pyridine rings intersect
with the CoN4 mean plane, made up of the metal centre and
the four equatorial nitrogen donors, at angles of 82.0(2) and
89.9(2)8, respectively. The Co···Co separation (4.056(2) Š) in
this dinuclear cobalt(ii) complex of the bis(terdentate)
ligand TsPMAT (14) is significantly less than the corre-
sponding distances (4.1481(7)–4.273(2) Š) observed in the
handful of known dinuclear cobalt(ii) complexes of bis(bi-
The reaction of TsPMAT (14) with Co(BF4)2·6H2O in
both a 1:1 and a 1:2 ratio in refluxing ethanol gave a purple
powder that was formulated as [CoII (TsPMAT)2]-
2
(BF4)4·4H2O (24·4H2O) on the basis of its elemental analy-
sis. The same compound was obtained when the reaction
was carried out in either dry acetonitrile or laboratory re-
agent-grade acetonitrile to which a little water had been de-
liberately added, followed in both cases by precipitation
with diethyl ether. The molar conductivity of complex
24·4H2O in acetonitrile was 441 WÀ1 cm2 molÀ1, in good
dentate)
4-substituted
3,5-di(2-pyridyl)-4H-1,2,4-tri-
azoles.[30,68,75,76] It is also significantly less than the Fe···Fe
separations (4.2124(14) Š at 123 K and 4.297(2) Š at 298 K)
observed in the dinuclear iron(ii) complex of the very close-
ly related bis(terdentate) ligand PMAT (15), [FeII -
2
agreement with the expected value of 420–500 WÀ1 cm2 molÀ1
(PMAT)2](BF4)4·DMF (27·DMF) (see below), both at
123 K, when it contains one high-spin and one low-spin
iron(ii) centre, and at 298 K, when both iron(ii) centres are
high-spin.[31]
[74]
for
a
4:1electrolyte.
Recrystallisation of complex
24·4H2O from acetonitrile by vapour diffusion of diethyl
ether produced single crystals of [CoII (TsPMAT)2]-
2
(BF4)4·6MeCN (24·6MeCN) suitable for an X-ray crystal
structure analysis (Figure 1). This confirmed that TsPMAT
(14) is indeed able to bind and bridge two metal ions. All
twelve of the donor atoms to the two cobalt(ii) centres are
provided by the two ligand molecules, which fully encapsu-
late them, giving rise to a sandwich-like structure. The asym-
metric unit comprises one half of the complex with the
other half generated by a centre of inversion. The N6 coordi-
nation sphere about the cobalt(ii) centres is strongly distort-
Measurements of magnetic properties carried out on a
powder sample of complex 24·4H2O revealed that the two
1,2,4-triazole bridges mediate weak antiferromagnetic cou-
pling between the two cobalt(ii) centres, which are d7 high-
spin (Figure 2). The curve for the temperature dependence
of the molar magnetic susceptibility showed a maximum at
1 9 K (cm =0.05305 cm3 molÀ1), a feature characteristic of an-
tiferromagnetic exchange coupling. The corresponding effec-
tive magnetic moment per cobalt(ii) centre was found to be
4.30 mB at room temperature and gradually decreasing until
a sharp drop occurred below approximately 50 K. The data
were best fitted to an S=3/2 dimer model using the parame-
ters J=À3.3 cmÀ1 and g=2.26. While cobalt(ii) centres for-
À
ed from octahedral with very much longer Co Nsulfonamide
À
bonds (2.551(5) and 2.626(5) Š) than Co Npyridine (2.044(5)
À
and 2.048(5) Š) and Co Ntriazole bonds (2.028(5) and
2.062(5) Š). The angles between trans-positioned donor
atoms are considerably less than 1808 with the N(1)-Co(1)-
4
mally have T1g orbitally degenerate states, the low symme-
Chem. Eur. J. 2005, 11, 6962 – 6973
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6967

S. Brooker et al.
ed first-row transition-metal
tetrafluoroborates or perchlo-
rates and dinuclear 2:2 com-
plexes were obtained instead.
All subsequent reactions were
therefore carried out by using a
metal-to-ligand molar ratio of
1:1. Thus, the reaction of
PMAT
(ClO4)2·6H2O
(15)
with
or
Mn-
M-
(BF4)2·6H2O (M=Fe, Co, Ni,
Zn) in acetonitrile readily gave
the five corresponding com-
plexes with the general formula
[MII (PMAT)2]X4 as powdery
2
solids. All members of this
series, except [NiII (PMAT)2]-
2
*
( ) and the molar magnetic suscepti-
Figure 2. Temperature dependence of the effective magnetic moment meff
bility cm (&) for [CoII2(TsPMAT)2](BF4)4·4H2O (24·4H2O). The solid lines represent the best fit to an S=3/2
(BF4)4 (29), which was obtained
in only 28% yield, were practi-
cally insoluble in acetonitrile
and precipitated straight from
dimer model (see text).
try observed in the structure leads to orbital singlet behav-
iour, thus making a simple Heisenberg spin coupling model
(À2JS1·S2) a good approximation. The g value allows for
spin-orbit coupling effects. The small value of J is similar in
magnitude and sign to those of other 1,2,4-triazole-bridged
dinuclear cobalt(ii) systems[15,26,30,77] and a little lower, on
average, than in related pyridazine-bridged species.[9,14,16]
The reactivity of TsPMAT (14) was also tested towards a
few other d-block ions, but with very limited success. By
using Ni(BF4)2·6H2O a green crystalline but heterogeneous
material was obtained, the identity of which could not be
readily established. In the case of Cu(BF4)2·4H2O a dark-
green oily material was formed. A more defined product
could only be isolated from the reaction of Fe(BF4)2·6H2O
with TsPMAT (14), by using the same reaction conditions as
for the preparation of the cobalt(ii) complex 24·4H2O. This
the reaction mixture in yields greater than 70%. The yield
of the more soluble nickel(ii) complex, 29, was improved by
the addition of diethyl ether to the initial filtrate as crystals
were grown from the filtrate this way (see below). The
molar conductivities (230–265 WÀ1 cm2 molÀ1) of all five com-
plexes, 26–30, were at the low-end of the expected range for
4:1electrolytes
in
N,N-dimethylformamide
(240–
300 WÀ1 cm2 molÀ1).[74] The iron(ii) complex 27 and the co-
balt(ii) complex 28 did not seem to be sensitive towards
oxygen in the solid state. However, solutions of the cobalt(ii)
complex 28 in N,N-dimethylformamide turned dark-brown
within a few hours when left to stand in air, presumably due
to oxidation of the metal centres. The solubility of the
zinc(ii) complex 30 was too low, even in deuterated N,N-di-
methylformamide, to obtain a 13C NMR spectrum showing
all expected peaks, even when the experiment was run for
1
was tentatively formulated as [FeII (TsPMAT)2](BF4)4 (25)
an extended period of time. The H NMR spectrum of this
2
on the basis of its elemental analysis. Complex 25 was ob-
tained as an almost colourless solid that quickly turned
yellow-brown when taken out of the mother liquor or han-
dled in air. Even when it was prepared under a protective
nitrogen atmosphere, it could only be isolated in impure
form which prevented its proper characterisation. It is inter-
esting to note that, in contrast, the cobalt(ii) analogue
24·4H2O did not exhibit such pronounced air-sensitivity.
Even in acetonitrile the latter complex was oxidised only
very slowly when exposed to air and was reasonably stable
for a few days, as evidenced by the fact that it could be re-
crystallised successfully in air. Given the very interesting
complex in deuterated N,N-dimethylformamide was incon-
clusive and broad split peaks were observed that could not
be assigned.
The X-ray crystal structures of the half-spin-crossover
form LS–HS (at 123 K) and of the complete high-spin form
HS–HS (at 298 K) of [FeII (PMAT)2](BF4)4·DMF (27·DMF)
2
have been described in a preliminary communication.[31] The
two bis(terdentate) molecules of PMAT (15) sandwich the
two iron(ii) centres resulting in an overall architecture anal-
ogous to that of the dinuclear cobalt(ii) complex of
TsPMAT
(14),
[CoII (TsPMAT)2](BF4)4·6MeCN
2
(24·6MeCN) (Figure 1). Crystals of complex 27·DMF were
obtained by slow evaporation of a solution of complex 27 in
acetonitrile/N,N-dimethylformamide. We attempted various
methods to crystallise the nickel(ii) complex 29, the most
soluble member of this series. Vapour diffusion of diethyl
ether into a solution of the initially obtained powder in ace-
tonitrile failed to produce single crystals, whereas applica-
tion of the same technique to the acetonitrile mother liquor
magnetic
properties
of
[FeII (PMAT)2](BF4)4·DMF
2
(27·DMF) (see below), complex 25, while air-sensitive, is the
topic of further work.[19]
Complexes of PMAT: Similarly to TsPMAT (14), the amine
congener PMAT (15) did not give complexes with a metal-
to-ligand molar ratio of 2:1when it was treated with hydrat-
6968
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ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2005, 11, 6962 – 6973

Triazole Complexes
FULL PAPER
occasionally afforded a crystalline material. Unfortunately,
the X-ray data collected on this material were of insufficient
quality. Attempts to recrystallise the other complexes, 26, 28
and 30, using these and other methods failed. It is expected
that all of these complexes have the same overall sandwich-
like architecture as that observed in complexes 24·6MeCN
and 27·DMF, although it should be noted that, in principle,
each of the two molecules of PMAT (15) may bind with the
two pyridine rings coordinating to the two metal centres
from the same side (as seen in Figure 1) or from opposite
sides, that is, one from above and the other from under-
neath.
the instability of the 1,2,4-triazole component used in these
experiments, the usefulness of this approach has clearly
been demonstrated. We anticipate that the use of the hither-
to unknown dichlorides 18 and 19, which do not have a free
4-amino group on the 1,2,4-triazole ring, will facilitate the
synthesis of analogous ligand systems, the complexes of
which might well exhibit better crystallisation behaviour.
Work in this direction is in progress and the results will be
reported in due course.[19]
Experimental Section
In addition to the magnetic studies carried out to date on
the iron(ii) complex 27·DMF,[31] we examined the magnetic
properties of [MnII (PMAT)2](ClO4)4 (26) and [CoII -
General remarks: Melting points were determined with a Gallenkamp
melting point apparatus in open-glass capillary tubes and are uncorrect-
ed. Elemental analyses were carried out by the Campbell Microanalytical
2
2
(PMAT)2](BF4)4 (28). Weak antiferromagnetic coupling be-
tween the two metal centres was observed in both com-
plexes. The room-temperature effective magnetic moment
per manganese centre for the manganese(ii) complex 26 was
5.98 mB (Figure S1in the Supporting Information) and thus
in very good agreement with the expected value of 5.92 mB
for a spin-only d5 high-spin system. The corresponding value
for complex 28 was 4.42 mB (Figure S2 in the Supporting In-
formation), revealing that the cobalt(ii) centres were d7
high-spin by analogy to the related cobalt(ii) complex
24·4H2O of TsPMAT (14). The curve for the molar magnet-
ic susceptibility of the cobalt(ii) complex 28 reached a maxi-
mum at T=11 K with cm =0.0825 cm3 molÀ1, while for the
manganese(ii) complex 26 no maximum was observed in the
accessible temperature range of 300–4.2 K. The data were
best fitted to an S=5/2 dimer model for the manganese(ii)
complex 26 and an S=3/2 dimer model for the cobalt(ii)
complex 28 using the parameters J=À0.16 cmÀ1, g=2.02
and 1% monomer, and J=À2.4 cmÀ1, g=2.31and TIP=
90”10À6 cm3 molÀ1, respectively.
1
Laboratory at the University of Otago. H and 13C NMR spectra were re-
corded on a Varian INOVA-300 (or INOVA-500) spectrometer at 258C.
For spectra recorded in deuterated chloroform (dH =7.26 ppm; dC =
77.16 ppm) or deuterated dimethyl sulfoxide (dH =2.50 ppm; dC =
39.52 ppm) chemical shifts are quoted relative to tetramethylsilane
(TMS) with the residual solvent signal as secondary reference.[78] IR spec-
tra were obtained on a Perkin–Elmer SpectrumBX FTIR spectropho-
tometer. ESI mass spectra were run on a Shimadzu LCMS-QP8000a
spectrometer in acetonitrile. Molar conductivities were measured with a
Suntex SC-170 conductivity meter at 258C. Magnetic data were recorded
over the range 300–4.2 K using a Quantum Design MPMS5 SQUID mag-
netometer with an applied field of 1T. Commercially available materials
were used as received. N-(3-Aminopropyl)acetamide (12) was prepared
as previously described.[65]
Caution: While no problems were encountered in the course of this
work, reactions involving hydrazine hydrate may form potentially explo-
sive mixtures so must be carried out with extreme caution. Similarly,
À
ClO4 salts are potentially explosive so should be handled with appropri-
ate care.
4-Amino-4H-1,2,4-triazole-3,5-dimethanol (7): Hydrazine monohydrate
(37.5 g, 0.75 mol) was added dropwise at 08C to 70% aqueous glycolic
acid (54.3 g, 0.50 mol). The resulting solution was heated at 1208C for
6 h. Then the reflux condenser was replaced with a downward condenser
and the reaction mixture was heated at 1608C for a further 18 h allowing
excess hydrazine and water to distil off. After cooling, the resulting yel-
lowish crystalline solid was recrystallised from water to give analytically
pure 7 (21.1 g, 58%) as colourless flakes. M.p. 206–2088C; elemental
analysis calcd (%) for C4H8N4O2 (144.13): C 33.33, H 5.59, N 38.87;
found: C 33.29, H 5.41, N 39.05; 1H NMR (300 MHz, [D6]DMSO): d=
4.54 (d, 3J=6.0 Hz, 4H; 2”TzCH2OH), 5.37 (t, 3J=6.0 Hz, 2H; 2”
TzCH2OH), 5.81ppm (s, 2H; TzN H2); 13C{1H} NMR (75 MHz,
[D6]DMSO): d=52.7 (2”TzCH2OH), 154.4 ppm (3-, 5-TzC); IR (KBr):
n˜ =3344, 3220, 2877, 2687, 1639, 1518, 1479, 1461, 1440, 1379, 1351, 1305,
Conclusion
We have been able to synthesise the two novel ligands
TsPMAT (14) and PMAT (15) which are hydrolytically
stable and isolable as the metal-free compounds by using an
approach based on nucleophilic substitution rather than
Schiff base condensation. To the best of our knowledge, to
date these ligands are the only examples of bis(terdentate)
ligands capable of bridging two metal ions by means of a
central 1,2,4-triazole moiety. It was expected that these bis-
(terdentate) ligands would facilitate the formation of dinu-
1280, 1204, 1068, 1029, 976, 953, 875, 819, 774, 720, 498 cmÀ1
4-Amino-3,5-bis(chloromethyl)-4H-1,2,4-triazole monohydrochloride (8):
suspension of compound (28.8 g, 0.20 mol) in thionyl chloride
.
A
7
(80 mL) was stirred at room temperature for 8 h, during which time a vig-
orous exothermic reaction took place. Excess thionyl chloride was re-
moved under reduced pressure and the resulting yellowish solid was
dried in vacuo. Recrystallisation from ethanol gave analytically pure 8
(33.4 g; 76%) as colourless needles. M.p. 139–1418C; elemental analysis
calcd (%) for C4H7Cl3N4 (217.48): C 22.09, H 3.24, N 25.76; found: C
clear doubly 1,2,4-triazole-bridged complexes, [M2L2]2n+
,
over mononuclear complexes, [ML2]n+, to a much greater
extent than is observed with related bis(bidentate) 1,2,4-tri-
azole-based ligands.[21,30,76] This has been borne out by ex-
periment with the formation of a series of [M2L2]2n+ com-
plexes, 24–30. While the methodology employed for the syn-
thesis of these two bis(terdentate) ligands, TsPMAT (14)
and PMAT (15), could not be extended to the analogous
systems TsPEAT (16) and PEAT (17), presumably due to
1
22.24, H 3.24, N 25.83; H NMR (300 MHz, [D6]DMSO): d=4.92 ppm (s,
4H; 2”TzCH2Cl); 13C{1H} NMR (75 MHz, [D6]DMSO): d=32.9 (2”
TzCH2Cl), 152.5 ppm (3-, 5-TzC); IR (KBr): n˜ =3414, 3253, 3145, 2970,
2642, 1637, 1617, 1576, 1417, 1328, 1264, 1165, 1105, 1034, 975, 937, 919,
888, 807, 759, 668, 646, 605, 568, 513 cmÀ1
.
4-Amino-3,5-bis(chloromethyl)-4H-1,2,4-triazole (9): Sodium hydrogen
carbonate (3.36 g, 40.0 mmol) was added in portions to a vigorously stir-
Chem. Eur. J. 2005, 11, 6962 – 6973
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6969

S. Brooker et al.
red heterogeneous mixture of compound 8 (8.70 g, 40.0 mmol), water
(50 mL) and ethyl acetate (50 mL). After complete addition, the layers
were separated and the aqueous layer was extracted with ethyl acetate
(3”25 mL). The combined organic layers were dried over anhydrous
sodium sulfate. Evaporation of the solvent under reduced pressure gave
analytically pure 9 (6.34 g, 87%) as a colourless crystalline solid. M.p.
97–998C; elemental analysis calcd (%) for C4H6Cl2N4 (181.02): C 26.54,
H 3.34, N 30.95; found: C 26.88, H 3.33, N 30.98; 1H NMR (300 MHz,
[D6]DMSO): d=4.87 (s, 4H; 2”TzCH2Cl), 6.12 ppm (s, 2H; TzNH2);
13C{1H} NMR (75 MHz, [D6]DMSO): d=33.0 (2”TzCH2Cl), 152.2 ppm
(3-, 5-TzC); IR (KBr): n˜ =3414, 3233, 3115, 1659, 1637, 1616, 1514, 1482,
1423, 1370, 1286, 1261, 1246, 1162, 1144, 1079, 984, 921, 800, 758, 730,
pressure and the residue was taken up in chloroform (100 mL). The in-
soluble materials were filtered off and washed with chloroform. The fil-
trate was evaporated under reduced pressure to give a thick, yellowish
oil. Trituration with ethyl acetate (100 mL) gave a colourless solid which
was filtered off and washed with ethyl acetate. Drying in vacuo gave 13
(32.5 g, 92%) as a colourless fluffy powder. This material was used in
subsequent reactions without further purification. An analytically pure
sample was obtained as colourless blocks by recrystallisation from 1,4-di-
oxane. M.p. 100–1028C; elemental analysis calcd (%) for C12H18N2O3S
(270.35): C 53.31, H 6.71, N 10.36, S 11.86; found: C 53.42, H 6.40, N
10.26, S 12.01; 1H NMR (300 MHz, CDCl3): d=1.64 (quint, 3J=6.3 Hz,
2H; CH2CH2NHSO2), 1.93 (s, 3H; CH3CONHCH2), 2.41(s, 3H;
PhCH3), 2.91(q, 3J=6.3 Hz, 2H; CH2CH2NHSO2), 3.30 (q, 3J=6.3 Hz,
2H; CH3CONHCH2), 5.74 (t, 3J=6.3 Hz, 1H; CH2CH2NHSO2), 6.08 (t,
3J=6.3 Hz, 1H; CH3CONHCH2), 7.29 (d, 3J=8.2 Hz, 2H; 3-, 5-PhH),
7.73 ppm (d, 3J=8.2 Hz, 2H; 2-, 6-PhH); 13C{1H} NMR (75 MHz,
683, 607, 490 cmÀ1
.
N-(2-Pyridylmethyl)-4-toluenesulfonamide hemihydrate (10·0.5H2O): A
solution of 4-toluenesulfonyl chloride (7.63 g, 40.0 mmol) in tetrahydro-
furan (40 mL) was added dropwise at room temperature to a solution of
2-(aminomethyl)pyridine (4.33 g, 40.0 mmol) and sodium hydroxide
(1.60 g, 40.0 mmol) in water (40 mL). The resulting heterogeneous mix-
ture was stirred vigorously at room temperature for 2 h. Then the tetra-
hydrofuran was evaporated under reduced pressure to crystallise the
product from the remaining aqueous phase. It was filtered off, washed
with water, and dried in air. Recrystallisation from ethanol gave analyti-
cally pure 10·0.5H2O (8.38 g, 77%) as colourless rods. M.p. 95–978C; ele-
mental analysis calcd (%) for C13H15N2O2.5S (271.34): C 57.54, H 5.57, N
10.32, S 11.82; found: C 57.47, H 5.71, N 10.39, S 11.83; 1H NMR
CDCl3):
d=21.8
(PhCH3),
23.4
(CH3CONH2CH2),
29.9
(CH2CH2NHSO2), 36.4 (CH3CONHCH2), 40.3 (CH2CH2NHSO2), 127.3
(2-, 6-PhC), 130.0 (3-, 5-PhC), 137.4 (4-PhC), 143.6 (1-PhC), 171.5 ppm
(CH3CONHCH2); IR (KBr): n˜ =3372, 3143, 2934, 2861, 1656, 1596, 1550,
1497, 1458, 1430, 1370, 1323, 1310, 1213, 1162, 1092, 1065, 967, 923, 868,
811, 777, 734, 661, 578, 551, 512, 475 cmÀ1
.
4-Amino-3,5-bis{[N-(2-pyridylmethyl)-N-(4-toluenesulfonyl)amino]meth-
yl}-4H-1,2,4-triazole (TsPMAT, 14): A mixture of compound 8 (2.17 g,
10.0 mmol), 10·0.5H2O (5.43 g, 20.0 mmol), and potassium carbonate
(8.29 g, 60.0 mmol) in N,N-dimethylformamide (100 mL) was heated at
608C for 24 h. After cooling, the suspension was filtered and the clear
orange filtrate was evaporated under reduced pressure. The remaining oil
was thoroughly dried in vacuo to give a brown paste which was redis-
solved in dichloromethane (50 mL). The cloudy solution was filtered
through a short pad of celite. Evaporation of the solvent and drying in
vacuo gave a brownish foam which was taken up in ethanol (50 mL). On
standing at room temperature, the product separated from the solution.
It was filtered off and washed with a minimum amount of ethanol.
Drying in vacuo gave analytically pure 14 (3.81g, 60%) as a colourless
powder. Elemental analysis calcd (%) for C30H32N8O4S2 (632.76): C
56.95, H 5.10, N 17.71, S 10.13; found: C 56.57, H 4.96, N 17.65, S 10.02;
(300 MHz, CDCl3): d=2.39 (s, 3H; PhCH3), 4.24 (d, 3J=5.4 Hz, 2H;
3
SO2NHCH2), 6.10 (t, 3J=5.4 Hz, 1H; SO2NHCH2), 7.15 (ddd, J4,5
=
7.7 Hz, 3J5,6 =4.8 Hz, 4J3,5 =1.2 Hz, 1H; 5-PyH), 7.18 (ddd, 3J3,4 =7.7 Hz,
4J3,5 =1.2 Hz, 5J3,6 =0.9 Hz, 1H; 3-PyH), 7.24 (d, 3J=8.4 Hz, 2H; 3-, 5-
3
4
3
PhH), 7.60 (dt, J3,4 =3J4,5 =7.7 Hz, J4,6 =1.8 Hz, 1H; 4-PyH), 7.73 (d, J=
8.4 Hz, 2H; 2-, 6-PhH), 8.44 ppm (ddd, 3J5,6 =4.8 Hz, 4J4,6 =1.8 Hz, J3,6
=
5
0.9 Hz, 1H; 6-PyH); 13C{1H} NMR (75 MHz, CDCl3): d=21.5 (PhCH3),
47.5 (SO2NHCH2), 122.0 (3-PyC), 122.6 (5-PyC), 127.2 (2-, 6-PhC), 129.6
(3-, 5-PhC), 136.7 (1-PhC), 136.8 (4-PyC), 143.3 (4-PhC), 149.0 (6-PyC),
155.0 ppm (2-PyC); IR (KBr): n˜ =3414, 3093, 2879, 1928, 1667, 1638,
1616, 1599, 1574, 1492, 1466, 1442, 1430, 1385, 1329, 1308, 1287, 1240,
1165, 1111, 1090, 1053, 1007, 852, 819, 763, 662, 605, 553, 544 cmÀ1
.
1H NMR (500 MHz, CDCl3): d=2.45 (s, 6H; 2”PhCH3), 4.44 (s, 4H; 2”
Drying of compound 10·0.5H2O in vacuo at 608C for three days gave an-
alytically pure 10 as dull colourless crystals. Elemental analysis calcd (%)
for C13H14N2O2S (262.33): C 59.52, H 5.38, N 10.68, S 12.22; found: C
59.44, H 5.39, N 10.55, S 12.27.
3
PyCH2), 4.51(s, 4H; 2”TzC H2), 5.57 (s, 2H; TzNH2), 7.11 (ddd, J4,5
=
3
7.7 Hz, 3J5,6 =4.8 Hz, 4J3,5 =1.2 Hz, 2H; 2”5-PyH), 7.24 (ddd, J3,4
=
7.7 Hz, 4J3,5 =1.2 Hz, 5J3,6 =0.9 Hz, 2H; 2”3-PyH), 7.31(d, 3J2,3 =8.4 Hz,
4H; 2”3-, 5-PhH), 7.57 (dt, 3J3,4 =3J4,5 =7.7 Hz, 4J4,6 =1.8 Hz, 2H; 2”4-
3
PyH), 7.73 (d, 3J2,3 =8.4 Hz, 4H; 2”2-, 6-PhH), 8.41ppm (ddd, J5,6
=
N-[2-(2-Pyridyl)ethyl]-4-toluenesulfonamide (11): The procedure de-
scribed above for the preparation of compound 10 was followed using 2-
(2-aminoethyl)pyridine (4.89 g, 40.0 mmol), 4-toluenesulfonyl chloride
(7.63 g, 40.0 mmol) and sodium hydroxide (1.60 g, 40.0 mmol) in water
(40 mL) and tetrahydrofuran (40 mL) to obtain analytically pure 11
(9.11 g, 82%) as colourless blocks after recrystallisation from ethanol.
M.p. 118–1208C; elemental analysis calcd (%) for C14H16N2O2S (276.36):
C 60.85, H 5.84, N 10.14, S 11.60; found: C 60.70, H 5.91, N 10.16, S
11.64; 1H NMR (300 MHz, CDCl3): d=2.40 (s, 3H; PhCH3), 2.93 (t, 3J=
4.8 Hz, 4J4,6 =1.8 Hz, 5J3,6 =0.9 Hz, 2H; 2”6-PyH); 13C{1H} NMR
(125 MHz, CDCl3): d=21.8 (2”PhCH3), 42.6 (2”TzCH2), 53.2 (2”
PyCH2) 122.7 (2”3-PyC), 122.8 (2”5-PyC), 127.7 (2”2-, 6-PhC), 130.0
(2”3-, 5-PhC), 135.5 (2”1-PhC), 137.0 (2”4-PyC), 144.1 (2”4-PhC),
149.3 (2”6-PyC), 150.5 (3-, 5-TzC), 156.2 ppm (2”2-PyC); IR (KBr): n˜ =
3424, 1636, 1617, 1591, 1569, 1520, 1493, 1476, 1436, 1342, 1305, 1162,
1101, 931, 908, 892, 814, 765, 660, 605, 556, 541 cmÀ1; ESI-MS (positive
mode, MeCN): m/z: 633 [M+H]+.
6.0 Hz, 2H; PyCH2), 3.34 (q, 3J=6.0 Hz, 2H; SO2NHCH2), 6.25 (t, 3J=
4-Amino-3,5-bis{[(2-pyridylmethyl)amino]methyl}-4H-1,2,4-triazole
(PMAT, 15): Compound 14 (1.27 g, 2.00 mmol) was dissolved in concen-
trated sulfuric acid (20 mL) and the reaction mixture was heated at
1008C for 8 h. After cooling, the almost colourless solution was basified
by slow and careful addition of aqueous sodium hydroxide (60 mL, 15m)
at 08C. Chloroform (50 mL) was added to the suspension and the solids
were allowed to settle. The supernatant layers were decanted off and
then separated. The aqueous layer was further extracted with chloroform
(3”50 mL). The combined organic layers were dried over anhydrous
sodium sulfate. Evaporation of the solvent gave 15 (0.64 g, 98%) as a col-
ourless oil. This material was used in subsequent reactions without fur-
ther purification. 1H NMR (500 MHz, CDCl3): d=2.57 (s, 2H; 2”
TzCH2NH), 3.86 (s, 4H; 2”PyCH2), 3.98 (s, 4H; 2”TzCH2), 5.66 (s, 2H;
TzNH2), 7.13 (ddd, 3J4,5 =7.7 Hz, 3J5,6 =4.8 Hz, 4J3,5 =1.2 Hz, 2H; 2”5-
5
6.0 Hz, 1H; SO2NHCH2), 7.07 (ddd, 3J3,4 =7.7 Hz, 4J3,5 =1.2 Hz, J3,6
=
0.9 Hz, 1H; 3-PyH), 7.12 (ddd, 3J4,5 =7.7 Hz, 3J5,6 =4.8 Hz, 4J3,5 =1.2 Hz,
1H; 5-PyH), 7.26 (d, 3J2,3 =8.4 Hz, 2H; 3-, 5-PhH), 7.57 (dt, 3J3,4 =3J4,5
=
7.7 Hz, 4J4,6 =1.8 Hz, 1H; 4-PyH), 7.72 (d, 3J2,3 =8.4 Hz, 2H; 2-, 6-PhH),
8.45 ppm (ddd, 3J5,6 =4.8 Hz, 4J4,6 =1.8 Hz, 5J3,6 =0.9 Hz, 1H; 6-PyH);
13C{1H} NMR (75 MHz, CDCl3): d=21.5 (PhCH3), 36.3 (PyCH2), 42.3
(SO2NHCH2), 121.7 (5-PyC), 123.5 (3-PyC), 127.0 (2-, 6-PhC), 129.6 (3-,
5-PhC), 136.7 (4-PyC), 137.2 (1-PhC), 143.1 (4-PhC), 149.0 (6-PyC)
158.9 ppm (2-PyC); IR (KBr): n˜ =3474, 3055, 2856, 1636, 1616, 1595,
1569, 1493, 1476, 1439, 1324, 1303, 1287, 1155, 1092, 916, 820, 763, 660,
631, 593, 561, 546, 502 cmÀ1
.
N-{3-[(4-Toluenesulfonyl)amino]propyl}acetamide (13): A solution of 4-
toluenesulfonyl chloride (24.8 g, 0.13 mol) in tetrahydrofuran (100 mL)
was added within 30 min to a solution of 12[65] (15.1 g, 0.13 mol) and
sodium hydrogen carbonate (10.9 g, 0.13 mol) in water (100 mL). The re-
sulting heterogeneous mixture was then stirred vigorously at room tem-
perature for 18 h. The resulting solution was evaporated under reduced
4
5
PyH), 7.21(ddd, 3J3,4 =7.7 Hz, J3,5 =1.2 Hz, J3,6 =0.9 Hz, 2H; 2”3-PyH),
7.60 (dt, 3J3,4 =3J4,5 =7.7 Hz, 4J4,6 =1.8 Hz, 2H; 2”4-PyH), 8.49 ppm (ddd,
3J5,6 =4.8 Hz, 4J4,6 =1.8 Hz, 5J3,6 =0.9 Hz, 2H; 2”6-PyH); 13C{1H} NMR
(125 MHz, CDCl3): d=42.9 (2”TzCH2), 54.0 (2”PyCH2), 122.3 (2”5-
6970
www.chemeurj.org
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2005, 11, 6962 – 6973

Triazole Complexes
FULL PAPER
PyC), 122.7 (2”3-PyC), 136.7 (2”4-PyC), 149.3 (2”6-PyC) 152.8 (3-, 5-
TzC) 158.8 ppm (2”2-PyC); ESI-MS (positive mode MeCN): m/z=325
[M+H]+.
1615, 1596, 1573, 1560, 1491, 1446, 1358, 1261, 1170, 1085, 1032, 910, 844,
816, 762, 730, 705, 662, 618, 555, 522 cmÀ1; molar conductivity (MeCN):
Lm =441 WÀ1 cm2 molÀ1. Vapour diffusion of diethyl ether into a solution
of complex 24·4H2O in acetonitrile gave single crystals of [CoII
(TsPMAT)2](BF4)4·6MeCN (24·6MeCN).
-
2
4-(Diacetylamino)-3,5-bis(chloromethyl)-4H-1,2,4-triazole (18):
A sus-
pension of compound 8 (10.9 g, 50.0 mmol) in acetic anhydride (75 mL)
was quickly heated to 1408C and the resulting yellowish solution was
kept at this temperature for another 10 min, during which time an orange
solution was obtained. After cooling, all volatiles were removed in vacuo
to give an orange crystalline solid which was recrystallised from ethanol
to give analytically pure 18 (8.33 g, 62%) as fine colourless needles. M.p.
150–1528C; elemental analysis calcd (%) for C8H10Cl2N4O2 (265.10): C
36.25, H 3.80, N 21.13; found: C 36.50, H 3.55, N 20.97; 1H NMR
(300 MHz, CDCl3): d=2.48 (s, 6H; 2”CH3CON), 4.60 ppm (s, 4H; 2”
TzCH2Cl); 13C{1H} NMR (75 MHz, CDCl3): d=25.1(2” CH3CON), 32.8
(2”TzCH2Cl), 151.2 (3-, 5-TzC), 169.4 ppm (2”CH3CON); IR (KBr):
n˜ =3455, 3044, 3005, 2360, 2343, 1750, 1736, 1637, 1541, 1517, 1455, 1435,
1413, 1370, 1310, 1282, 1258, 1233, 1193, 1174, 1147, 1053, 1033, 1019,
[FeII2(TsPMAT)2](BF4)4 (25): A colourless solution of Fe(BF4)2·6H2O
(68 mg, 0.20 mmol) in ethanol (10 mL) was added dropwise to a refluxing
colourless solution of compound 14 (127 mg, 0.20 mmol) in ethanol
(20 mL), and the resulting yellowish solution was refluxed for a further
30 min before it was allowed to cool to room temperature. The solvent
volume was reduced to about one third of the original volume and the re-
sulting solid was filtered off and washed with a little ethanol and diethyl
ether. Drying in vacuo gave an air-sensitive cream-coloured powder
(124 mg, 71%) that quickly turned yellow-brown when exposed to air.
On the basis of its elemental analysis this material was tentatively formu-
lated as [FeII2(TsPMAT)2](BF4)4 (25). Elemental analysis calcd (%) for
C60H64B4F16Fe2N16O8S4 (1724.42): C 41.79, H 3.74, N 13.00, S 7.44; found:
C 42.58, H 4.20, N 13.51, S 6.96.
General procedure for [MII2(PMAT)2]X4 (26–30): A solution of Mn-
(ClO4)2·6H2O or M(BF4)2·6H2O (M=Fe, Co, Ni, Zn) (0.25 mmol) in ace-
tonitrile (5 mL) was added dropwise to a colourless solution of com-
pound 15 (81mg, 0.25 mmol) in acetonitrile (10 mL). The mixture was
stirred at room temperature for 1h, during which time the product pre-
cipitated. The solid was filtered off and washed with acetonitrile and di-
ethyl ether. Drying in vacuo gave the complexes as colourless (Mn, Zn)
or pale-coloured (Fe, Co, Ni) powders.
941, 797, 751, 706, 665, 626, 592, 493 cmÀ1
3,5-Bis(chloromethyl)-4-(1H-pyrrol-1-yl)-4H-1,2,4-triazole (19):
.
A
mix-
ture of compound 8 (21.8 g, 0.10 mol) and 2,5-dimethoxytetrahydrofuran
(13.2 g, 0.10 mol) in ethanol (100 mL) was refluxed for 2 h, during which
time a purplish-black solution was obtained. On cooling, the product
crystallised out. It was filtered off, washed with ethanol and dried in
vacuo to give analytically pure 19 (16.2 g, 70%) as fine colourless nee-
dles. M.p. 142–1448C; elemental analysis calcd (%) for C8H8Cl2N4
(231.09): C 41.58, H 3.49, N 24.25; found: C 41.87, H 3.56, N 24.21.
1H NMR (300 MHz, CDCl3): d=4.50 (s, 4H; 2”TzCH2Cl), 6.41(t, 3J=
2.4 Hz, 2H; 3-, 4-PlH), 6.89 ppm (t, 3J=2.4 Hz, 2H; 2-, 5-PlH);
13C{1H} NMR (75 MHz, CDCl3): d=31.8 (2”TzCH2Cl), 110.5 (3-, 4-PlC),
121.9 (2-, 5-PlC), 152.0 ppm (3-, 5-TzC). IR (KBr): n˜ =3413, 3131, 3118,
3028, 2973, 1512, 1454, 1423, 1344, 1335, 1267, 1168, 1148, 1122, 1064,
[MnII2(PMAT)2](ClO4)4 (26): Mn(ClO4)2·6H2O (90 mg) were used to
obtain complex 26 (122 mg, 84%) as a colourless powder. Elemental
analysis calcd (%) for C32H40Cl4Mn2N16O16 (1156.46): C 33.24, H 3.49, N
19.38; found: C 33.54, H 3.28, N 19.40; IR (KBr): n˜ =3152, 2920, 1605,
1570, 1555, 1490, 1438, 1377, 1312, 1237, 1146, 1117, 1086, 1018, 908, 812,
1027, 1005, 919, 842, 799, 751, 734, 705, 651, 584, 475, 454 cmÀ1
.
765, 735, 627 cmÀ1; molar conductivity (DMF): Lm =247 WÀ1 cm2 molÀ1
.
4-(Diacetylamino)-4H-1,2,4-triazole-3,5-dimethyl diacetate (20): A sus-
pension of compound 7 (2.88 g, 20.0 mmol) in acetic anhydride (20 mL)
was refluxed vigorously for 30 min, during which time a yellow solution
was obtained. After cooling, all volatiles were removed in vacuo to give
a yellow oil, which crystallised on standing. Recrystallisation from etha-
nol gave analytically pure 20 (3.90 g, 62%) as colourless flakes. M.p. 109–
1118C; elemental analysis calcd (%) for C12H16N4O6 (312.28): C 46.15, H
5.16, N 17.94; found: C 46.21, H 5.22, N 18.23; 1H NMR (300 MHz,
CDCl3): d=2.06 (s, 6H; 2”CH3CON), 2.38 (s, 6H; 2”CH3COO),
5.16 ppm (s, 4H; 2”TzCH2); 13C{1H} NMR (75 MHz, CDCl3): d=20.3
(2”CH3CON), 24.5 (2”CH3COO), 54.7 (2”TzCH2), 150.4 (3-, 5-TzC),
169.3 (2”CH3COO), 169.5 ppm (2”CH3CON); IR (KBr): n˜ =3477, 1751,
1729, 1636, 1618, 1531, 1451, 1430, 1373, 1295, 1271, 1230, 1201, 1074,
[FeII2(PMAT)2](BF4)4 (27):[31] Fe(BF4)2·6H2O (84 mg) was used to obtain
complex 27 (105 mg, 76%) as a pale yellow powder. Elemental analysis
calcd (%) for C32H40B4F16Fe2N16 (1107.69): C 34.70, H 3.64, N 20.23;
found: C 34.68, H 3.50, N 19.89; IR (KBr): n˜ =3125, 2916, 1607, 1570,
1558, 1489, 1438, 1375, 1306, 1239, 1083, 1036, 891, 816, 766, 730, 668,
645, 538, 521, 467 cmÀ1
;
molar conductivity (DMF): Lm =
224 WÀ1 cm2 molÀ1
. Slow evaporation of an acetonitrile/N,N-dimethyl-
formamide mixture containing the powder gave single crystals of [FeII
-
2
(PMAT)2](BF4)4·DMF (27·DMF).[31]
[CoII2(PMAT)2](BF4)4 (28): Co(BF4)2·6H2O (85 mg) was used to obtain
complex 28 (113 mg, 81%) as a pale purple powder. Elemental analysis
calcd (%) for C32H40B4Co2F16N16 (1113.86): C 34.51, H 3.62, N 20.12;
found: C 34.35, H 3.43, N 19.72; IR (KBr): n˜ =3177, 2919, 1608, 1569,
1562, 1490, 1439, 1374, 1308, 1241, 1083, 1034, 898, 814, 765, 731, 638,
1049, 1019, 944, 896, 836, 797, 756, 601 cmÀ1
4-(1H-Pyrrol-1-yl)-4H-1,2,4-triazole-3,5-dimethanol (21):
compound (2.88 g, 20.0 mmol) and 2,5-dimethoxytetrahydrofuran
.
A
mixture of
533, 521, 470, 423, 413 cmÀ1
; molar conductivity (DMF): Lm =
7
264 WÀ1 cm2 molÀ1
.
(2.64 g, 20.0 mmol) in acetic acid (50 mL) was refluxed for 30 min to give
an almost black solution. After cooling, all volatiles were removed in
vacuo. The solid residue was suspended in ethanol (50 mL) and the mix-
ture was refluxed for 30 min. After cooling, the remaining solid was fil-
tered off and washed with ethanol. Drying in vacuo gave analytically
pure 21 (0.94 g, 24%) as a greyish powder. M.p. 202–2048C; elemental
analysis calcd (%) for C8H10N4O2 (194.19): C 49.48, H 5.19, N 28.85;
found: C 49.39, H 5.31, N 28.80; IR (KBr): n˜ =3210, 3143, 2854, 1524,
1456, 1436, 1395, 1355, 1333, 1218, 1124, 1065, 1026, 978, 949, 913, 812,
[NiII2(PMAT)2](BF4)4 (29): Ni(BF4)2·6H2O (85 mg) was used to obtain
complex 29 (39 mg, 28%) as a pale lilac powder. Elemental analysis
calcd (%) for C32H40B4F16N16Ni2 (1113.37): C 34.52, H 3.62, N 20.13;
found: C 34.53, H 3.57, N 19.73; IR (KBr): n˜ =3175, 2918, 1608, 1571,
1490, 1441, 1374, 1306, 1242, 1083, 1035, 898, 817, 771, 730, 667, 642, 533,
521, 476, 429, 418 cmÀ1
241 WÀ1 cm2 molÀ1
;
molar conductivity (DMF): Lm =
.
[ZnII2(PMAT)2](BF4)4 (30): Zn(BF4)2·6H2O (87 mg) was used to obtain
complex 30 (105 mg, 74%) as a colourless powder. Elemental analysis
calcd (%) for C32H40B4F16N16Zn2 (1126.75): C 34.11, H 3.58, N 19.89;
found: C 33.79, H 3.33, N 19.89; IR (KBr): n˜ =3171, 2920, 1607, 1563,
1491, 1440, 1376, 1311, 1240, 1083, 1035, 909, 812, 767, 732, 636, 533, 522,
724, 680, 580, 499, 466, 420 cmÀ1
[CoII2(TsPMAT)2](BF4)4·4H2O (24·4H2O):
.
A
pink solution of Co-
(BF4)2·6H2O (68 mg, 0.20 mmol) in ethanol (10 mL) was added dropwise
to a refluxing colourless solution of compound 14 (127 mg, 0.20 mmol) in
ethanol (20 mL). The resulting clear purple solution was refluxed for a
further 30 min, during which time the product precipitated from the reac-
tion mixture. After cooling, the solid was filtered off and washed with
ethanol and diethyl ether. Drying in vacuo gave 24·4H2O (139 mg, 77%)
472 cmÀ1; molar conductivity (DMF): Lm =231 WÀ1 cm2 molÀ1
.
Crystal data for [CoII2(TsPMAT)2](BF4)4·6MeCN (24·6MeCN):
C72H82B4Co2F16N22O8S4, Mr =1976.94 gmolÀ1, triclinic, space group P1,
¯
a=12.9415(1), b=13.0630(2), c=14.1653(3) Š, a=71.882(1)8, b=
as
a
pale purple powder. Elemental analysis calcd (%) for
83.338(1)8, g=70.329(1)8, V=2142.98(6) Š3, 1calcd =1.532 gcmÀ3
, T=
C60H72B4Co2F16N16O12S4 (1802.68): C 39.98, H 4.03, N 12.43, S 7.12;
found: C 40.36, H 3.89, N 12.75, S 6.84; IR (KBr): n˜ =3417, 2972, 2364,
150(2) K, Z=1, F(000)=1014, m=0.587 mmÀ1. Brown prism, 0.22”0.16”
0.08 mm3; 17032 reflections collected in the range 1.518<q<24.008
Chem. Eur. J. 2005, 11, 6962 – 6973
ꢀ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6971

S. Brooker et al.
(À14ꢀhꢀ14, À14ꢀkꢀ14, À16ꢀlꢀ16), 6694 independent reflections.
Final indices: R1=0.0738, wR2=0.1830 [I>2s(I)]; R1=0.1243, wR2=
0.2122 (all data); GOF=1.037; max/min residual electron density 1.287/
À0.608 eŠÀ3. Data were collected on a Bruker SMART CCD area detec-
tor using graphite-monochromated MoKa radiation (l=0.71073 Š). The
structure was solved by direct methods with SHELXS-97[79,80] and refined
against F2 using all data by full-matrix least-squares techniques using
SHELXL-97.[81] CCDC-265770 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of charge
from the Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif.
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Acknowledgements
This work was supported by a number of grants from the University of
Otago (including a University of Otago Postgraduate Scholarship to
M.H.K. and a Bridging Grant), the Marsden Fund (Royal Society of
New Zealand), and the Australian Research Council (Discovery Grant).
Financial support from the Inorganic and Organometallic Specialist
Group of the New Zealand Institute of Chemistry as well as from the
Department of Chemistry of the University of Otago towards the cost of
attendance (M.H.K.) at the Conference of the Inorganic Division of the
Royal Australian Institute of Chemistry (IC-03) in Melbourne, where this
research was first presented, is also gratefully acknowledged. The authors
thank Assoc. Prof. C. E. F. Rickard (University of Auckland) as well as
Prof. W. T. Robinson and Dr. J. Wikaira (University of Canterbury) for
the collection of the X-ray data. Dr. J. Klingele (nØe Hausmann) (Univer-
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