Artikel
Solid State Structures of AsCl
5
and SbCl
5
Silvia Haupt and Konrad Seppelt*
Berlin, Institut für Chemie der Freien Universität
Received September 25
th
, 2001.
Abstract. Arsenic pentachloride has a trigonal bipyramidal struc-
ture in the solid state with As-Cl
eq
5 210.6,211.9 pm, As-Cl
ax
5
220.7 pm, space group Pmmn, a 5 706.2 (1); b 5 760.3 (2), c 5
623.3 (1) pm. Antimony pentachloride exists in two modifications:
above 2 54.1°C it is also trigonal bipyramidal with Sb-Cl
eq
5 227.0
and Sb-Cl
ax
5 233.3 pm, space group P6
3
/mmc, a 5 741.4 (1),
c 5 799.0(2)pm. Below 254.1°C it changes reversibly into a double
chlorine bridged dimer resulting in an edge shared double octa-
hedral structure, space group P2
1
/c, a 5 952.4 (1), b 5 1189.9 (1),
c 5 1219.7 (1) pm, β 5108,27 (1): In presence of water the forma-
tion of AsCl
5
is hindered, two salts containing the octahedral anion
Die Festkörperstrukturen von AsCl
5
und von SbCl
5
Inhaltsübersicht. Arsenpentachlorid ist im festen Zustand trigonal-
bipyramidal aufgebaut, As-Cl
eq
5 210.6, 211.9 pm und As-Cl
ax
5
220.7 pm, Raumgruppe Pmmn, a 5 706.2 (1), b 5 760.3 (2), c 5
623.3 (1) pm. Antimonpentachlorid kommt in zwei Modifikationen
vor: oberhalb 254.1°C ist es ebenfalls trigonal-bipyramidal aufge-
baut, Sb-Cl
äq
5 227.0 und Sb-Cl
ax
233.3 pm, Raumgruppe
P6
3
/mmc, a 5 741.4 (1), c 5 794.0 (2) pm. Unterhalb 2 54.1°C
lagert es sich reversibel um in ein doppelt chlorverbrücktes Dimer
mit einer kantenverknüpften doppeloktahedrischen Struktur,
Raumgruppe P2
1
/c, a5 952.4 (1), b 5 1189.9 (1), c 5 1219.7 (1)
Introduction
AsCl
5
was prepared approximately 160 years after the prep-
aration of PCl
5
and SbCl
5
[1]. It is unstable with respect to
AsCl
3
and Cl
2
. It is now textbook knowledge that the rela-
tive instability of the highest oxidation state of the third
period of main group elements is due to incomplete shield-
ing of the nucleus by the first filled shell of d-electrons. The
relative instability of BrO
4
2
and its late preparation is the
other historic example [2]. AsCl
5
has originally been pre-
pared from AsCl
3
and Cl
2
under uv irradiation. The proof
for its existence stems mainly from the characteristic raman
spectrum, which could easily be assigned assuming a trig-
onal bipyramidal (D
3h
) structure [1].
The Raman spectra of dissolved and solid AsCl
5
are
quite similar, and the conclusion was drawn that solid AsCl
5
*Prof. Dr. K. Seppelt
Institut für Anorg. und Analyt. Chemie der Freien Universität Berlin
Fabeckstraße 34-36
D-14195 Berlin
FAX: Int. code 1 (30)83854289
e-mail: seppelt@chemie.fu-berlin.de
Z. Anorg. Allg. Chem. 2002, 628,7292734 WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 004422313/02/628/7292734 $ 20.001.50/0
729
AsCl
6
2
have been isolated, [(H
5
O
2
1
)
5
AsCl
6
2
(Cl
2
)
4
], space group
C2/c, a5 1416.9 (2), b 5 1316.6 (3), c 5 1215.3 (2) pm, β 5 94.96
(1)°, and [(H
5
O
2
1
)(AsCl
6
2
)·AsOCl
3
], space group P2
1
/n, a 5 771.6
(3), b 5 904.5 (3), c 5 2140.7(2)pm, β 5 100.21(1). The AsOCl
3
moiety in this compound appears as a monomer, in contrast to
pure AsOCl
3
, which is a doubly oxygen bridged dimer in the
solid state.
Keywords: Arsenic; Antimony; Arsenic pentachloride; Antimony
pentachloride; Crystal structure
pm, β 5 108.27 (1)°. In Gegenwart von Wasser bildet sich kein
AsCl
5
, dagegen können zwei Salze isoliert werden, die das oktahe-
drische AsCl
6
2
enthalten: [(H
5
O
2
1
)
5
AsCl
6
2
(Cl
2
)
4
], Raumgruppe
C2/c, a 5 1416.9 (2), b 5 1316.6 (3), c 5 1215.3 (2) pm,
β 5 94.96 (1)°, und [(H
5
O
2
1
)(AsCl
6
2
)·AsOCl
3
], Raumgruppe P2
1
/n,
a 5 771,6 (3), b 5 904.5 (3), c 5 2140.7 (7) pm, β 5 100.21(1)°.
Die AsOCl
3
Einheit in dieser Verbindung ist monomer, im Gegen-
satz zum doppelt sauerstoffüberbrückten Dimer des reinen AsOCl
3
im festen Zustand.
will retain the trigonal bipyramidal structure which is
clearly the expected structure for the isolated molecule. The
similarity of the molecular and solid state structure came
as a surprise, since PCl
5
as a molecule has a trigonal bipyr-
amidal structure [3], but in the solid state it crystallizes as
[(PCl
4
1
)(PCl
6
2
)] [4]. SbCl
5
, also trigonal bipyramidal as a
molecule [5], has the same structure in the solid state, ac-
cording to an early x-ray analysis [6]. But changes in the
vibrational, n.q.r, and Sb-Mößbauer spectra at low tem-
peratures have already previously been interpreted as a di-
merisation into [Cl
4
SbCl
2
SbCl
4
], namely a double chlorine
bridged (two edge sharing octahedral) structure like in
Nb
2
Cl
10
[7, 12]. The aim of the present work has been to
establish the solid state structures of AsCl
5
and SbCl
5
with certainty.
Results
AsCl
5
The original preparation of AsCl
5
by uv irradiation of
AsCl
3
/Cl
2
solutions is easily reproducible, if water and with
this HCl is strictly avoided. This has been outlined before [1].