Storr et al.
1131
isopropanol (13) and synthesized several other cobalt(II)
C-substituted pyrazolate analogues by reacting cobalt(II)
salts with the appropriate pyrazole in basic solutions.
Trofimenko reported, as unpublished results, the preparation
of nickel(II) and copper(II) pyrazolates by pyrolysis of the
appropriate M(pzH) (OAc) (OAc = acetate) complexes or
chains of metal ions doubly bridged by pyrazolate ligands.
The polymeric copper(II) and cobalt(II) pyrazolates, previ-
ously studied, have been shown to exhibit this structural mo-
tif, with the structures of three of the copper compounds
having been determined by single crystal X-ray diffraction
studies (8a, 8d).
4
2
by reacting pyrazole with metal salts in basic solutions (1).
The preparation of [Co(dmpz) ] , and [Ni(dmpz) ·2H O] by
2
x
2
2
x,
the reaction of the appropriate bis-acetylacetonato metal(II)
complex with hydrazine, was described by Singh et al. (14).
A series of reports by Vos and Groeneveld described the
synthesis and characterization of metal pyrazolate complexes
of Mn, Co, Ni, Cu, Zn, and Cd with 4-Xpz and 4-Xdmpz (X
Syntheses
Nickelocene and manganocene were prepared using the
method of R.B. King (23). Ni(Cp)2 was prepared from
nickel powder, bromine, and cyclopentadiene while Mn(Cp)2
was prepared from manganese powder, bromine, and sodium
cyclopentadienide. Pyrazoles were used as supplied
=
H, CH , Cl, Br, I, NO ) (15, 16). The materials were pre-
3 2
pared by reacting aqueous solutions of metal salts with basic
aqueous solutions of pyrazoles. It should be noted that in
many cases the reported purity of the materials described in
this latter work was based on metal analysis alone, and at-
tempts in this laboratory to reproduce much of this work led,
at best, to the formation of impure products. The synthesis
of [Fe(pz) ] from FeCl and lithium pyrazolate in toluene
(
Aldrich) or prepared as described previously (8d, 24). Sol-
vents used were reagent grade and were dried and distilled
under an atmosphere of dry dinitrogen before use.
[
Ni(4-Hpz)2]x
Ni(4-Hpz) ] was prepared using two different synthetic
2
x
2
[
2
x
has been described by Strahle et al. (17) and recently
Vecchio-Sadus described an electrochemical synthesis route
to a series of transition metal pyrazolates (18).
A novel synthetic approach, detailed in our previous re-
ports, involving the reaction between metal shot (Cu or Co)
and molten pyrazoles under a dioxygen atmosphere led not
only to transition metal pyrazolates of high purity but also,
in some cases, afforded crystalline materials (8a, 8d). In ad-
approaches. The complex was first produced by heating
110°C) nickel powder (0.24 g, 4.1 mmol) with an excess of
(
molten pyrazole (1.25 g, 18 mmol) under normal atmosphere
conditions for 48 h. The mixture was allowed to cool and
the excess pyrazole was removed by washing with dichloro-
methane. The pure product was isolated as an insoluble or-
ange powder by physical separation, using a magnet to
remove the unreacted nickel powder. Anal. calcd. for
NiC H N : C 37.4, H 3.1, N 29.1; found: C 37.4, H 3.4, N
dition, three [Cu(4-Xdmpz) ] complexes (X = Cl, Br, CH )
2
x
3
6
6
4
were prepared by reacting the corresponding trimetallic
2
8.9.
copper(I) complex, [Cu(4-Xdmpz)] , again with the appropriate
3
[Ni(4-Hpz) ] was also prepared by reacting a mixture of
2 x
molten pyrazole under an atmosphere of dioxygen (9a).
freshly sublimed nickelocene (0.5 g, 2.6 mmol) with an ex-
cess of molten pyrazole (4.5 g, 65 mmol) at 100°C under a
dry nitrogen atmosphere for 24 h. After cooling, the excess
pyrazole was dissolved in dichloromethane and the insoluble
orange powder was isolated by vacuum filtration. TGA:
61% weight loss between 400°C and 515°C. Anal. calcd. for
NiC H N : C 37.4, H 3.1, N 29.1; found: C 37.2, H 3.2, N
*
Another method of producing binary metal pyrazolates, [M(pz ) ]
2
x
*
(
M = Zn, Pt, Pd and pz = substituted pyrazolates), involves
*
removing thermally the neutral coordinated pz H from com-
plexes of formulation [M(pz ) (pz H)] (8c, 19–21).
*
*
2
2
Our attempts to prepare pyrazolate complexes of
nickel(II) by the metal – molten azole method yielded pure
samples only for [Ni(pz) ] . In an earlier report we described
6
6
4
2
x
29.2.
an alternative synthetic approach involving nickelocene that
led to the preparation of diamagnetic oligometallic nickel(II)
pyrazolate complexes (6). The present report details the use
of metallocenes to obtain several paramagnetic linear chain
polymers containing either nickel(II) or manganese(II). The
idea to synthesize pyrazolates via this pathway came from a
[Ni(4-CIpz)2]x
This compound was prepared in a manner analogous to
the latter method described above for the preparation of
[Ni(4-Hpz) ] . TGA: 70% weight loss between 360°C and
2
x
545°C. Anal. calcd. for NiC H N Cl : C 27.5, H 1.5, N
21.4; found: C 27.8, H 1.4, N 21.2.
6
4
4
2
1
977 article by Blake et al. in which two diamagnetic
nickel(II) pyrazolate polymers, prepared by reacting
nickelocene with the appropriate azole in benzene solvent,
were reported (22). In the current work, eight paramagnetic
complexes of composition [M(4-Xdmpz)2]x (where M =
[Ni(4-Hdmpz)2]x
The synthesis of [Ni(4-Hdmpz) ] was attempted, without
2
x
success, using the nickel metal in molten pyrazole reaction
that was employed in the [Ni(4-Hpz)2]x preparation de-
scribed above. The target compound was successfully pre-
pared, however, using nickelocene and 3,5-dimethylpyrazole
under inert atmosphere conditions. Freshly sublimed
Ni(II), Mn(II) and X = H, Cl, Br, CH ), two paramagnetic
3
complexes of composition [Mn(4-Xpz) (4-XpzH)] (where
2
x
X = Br, Cl), and two diamagnetic complexes of composition
Ni(4-Xpz) ] (where X = H, Cl) were obtained. We report
[
2
x
here variable temperature (2–300 K) magnetic susceptibili-
ties and other studies on these systems. The materials pre-
pared in the present work were not obtained in a form
suitable for single crystal X-ray diffraction studies; however,
on the basis of indirect spectroscopic and other evidence
they are proposed to have structures involving extended
Ni(Cp) (0.25 g, 1.3 mmol) was mixed intimately with an
2
excess of 3,5-dimethylpyrazole (1.34 g, 19 mmol) and
placed in a dry and oxygen-free glass Carius tube. The tube
was flame-sealed under vacuum and placed in an oven
(140°C) for 48 h. Following the initial melting of the 3,5-
dimethylpyrazole
a
green solution, presumably of
©
1998 NRC Canada