Cs2NiO2 Revisited. Crystal Structure and Magnetic Properties
Katarina Durisˇ and Martin Jansen
Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
Reprint requests to Prof. Dr. Dr. h. c. Martin Jansen. Fax: +49 (0)711/689 1502.
E-mail: m.jansen@fkf.mpg.de
Z. Naturforsch. 2012, 67b, 57 – 60; received December 9, 2011
Single crystals as well as microcrystalline powders of Cs2NiO2 were obtained via the azide/nitrate
route from appropriate mixtures of CsN3, CsNO3 and NiO. The single-crystal structure analysis
confirmed that Cs2NiO2 crystallizes in the tetragonal space group I4/mmm (Z = 2, a = 4.4090(3),
˚
c = 13.576(3) A, R1 = 0.036, wR2 = 0.093). Above 45 K, Cs2NiO2 is paramagnetic, and an analysis
based on the Curie-Weiss law has resulted in µ = 2.89 µB paramagnetic units, θ = −30.8 K and
TN ∼ 20 K.
Key words: High-spin Nickel(II) Compounds, Linear Coordination, Antiferromagnetic Ordering,
Azide/Nitrate Route
Introduction
Single crystals of the title compound were obtained when
an excess of azide and nitrate as compared to Eq. 1 was
used (30 mol-% excess for CsN3 and 150 mol-% excess for
CsNO3) and the mixture heated with the following temper-
ature program: 298 → 533 K (100 K h−1), 533 → 653 K
(5 K h−1), 653 → 723 K (20 K h−1), with a subsequent an-
nealing for 100 h at 723 K. Green microcrystalline sam-
ples of Cs2NiO2 were obtained from stochiometric mixtures
Linear coordination geometries constitute a charac-
teristic structural feature in the chemistry of species
with nd10(n + 1)s0(n + 1)p0 electron configuration.
Surprisingly, linear [X–M–X]nm− anions are also quite
common for Fe, Co and Ni in low oxidation states, ob-
viously independent of the respective valence electron
counts. Among them is the family of nickelates(II), of the reactants according to Eq. 1, and applying the fol-
lowing temperature treatment: 298 → 533 K (100 K h−1),
K2NiO2, Rb2NiO2 and Cs2NiO2, as discovered by
H. Rieck and R. Hoppe [1, 2]. While the potassium and
rubidium representatives have been well characterized
and reinvestigated with respect to their magnetic and
optical properties [3, 4], knowledge about Cs2NiO2 has
remained rudimentary. Here we report on the growth
of single-crystals and a structure determination from
single-crystal data, as well as on the magnetic proper-
533 → 653 K (5 K h−1), 653 → 773 K (20 K h−1) and sub-
sequent annealing for 30 h at 773 K.
Hazards: In order to carry out the reaction in a controlled
manner, specially designed containers have to be used (with
no welded seals), and a slow heating regime in the 533 →
653 K temperature range must be applied.
The obtained powders as well as the single crystals are
very sensitive towards air and moisture. Therefore they were
sealed in glass ampoules under argon atmosphere, and all
ties of a single-phase sample.
further manipulations were made in an inert atmosphere of
purified argon.
Experimental Section
Starting materials for the preparation of dicaesium nicke-
Powder X-ray patterns were collected with a linear
late(II) were caesium azide, caesium nitrate (Riedel-De Hae¨n
position-sensitive detector on a STADIP diffractometer in
AG Seelze Hannover 99.5 %) and NiO, prepared by decom-
Debye-Scherrer geometry (Stoe & Cie GmbH, Germany,
position of Ni(C2O4) · 0.5H2O (Alfa Aesar, 98 %) in a flow
˚
Ge(111)-monochromatized MoKα1 radiation, λ = 0.7093 A,
of oxygen at 623 K for 20 h. The caesium azide was syn-
thesised from aqueous HN3 and CsCO3 (Sigma Aldrich,
99 %). The starting compounds were dried under vacuum
(10−3 mbar) at 393 K over night, mixed and thoroughly
ground in an agate mortar in a glove box, and placed un-
der argon in a tightly closed steel container, provided with a
silver inlay [5].
4 < 2θ < 40◦, in steps of 0.01◦), with the samples sealed
in glass capillaries of 0.3 mm diameter. The data were cali-
brated with respect to an external Si standard. Structure pa-
rameters were calculated and refined from the powder X-ray
patterns using TOPAS-ACADEMIC software [6].
The single-crystal measurements were carried out on
a Stoe IPDS-II diffractometer with graphite-monochrom-
˚
5 CsN3 +CsNO3 +3 NiO → 3 Cs2NiO2 +8 N2 (1) atized MoKα radiation at r. t. (λ = 0.71073 A). Intensities
c
Brought to you by | University of Texas at Austin
Authenticated
Download Date | 6/4/15 8:37 PM