Two ne
w transi
tion-me
tal
tellurium oxy-chlorides of
the general formula Ni
5(TeO
3)
4X
2 (X= Cl, Br) have been isola
ted during
the inves
tiga
tion of
the
ternary phase diagram NiO-NiCl
2-TeO
2. They crys
tallize in
the monoclinic sys
tem, space group
C2/
c, and for
the caseof Ni
5(TeO
3)
4Cl
2 the uni
t cell is
a = 19.5674(2) Å,
b = 5.2457(1) Å, and
c = 16.3084(1) Å,
wi
th
ta2.gif" BORDER=0 ALIGN="middle"> = 125.289(1)
ti
ties/deg.gif">. The s
truc
ture is layered and buil
t up of corner-connec
ted [Ni
5O
17X
2]en
ti
ties, made of five nickel(II) oc
tahedra associa
ted by edge and face sharing. The
tellurium(IV) a
toms are fixed upon
the nickel layers. Their lone pairs
E and
the halogen a
toms arepacked in a double layer perpendicular
to
the [010] direc
tion. From
the magne
tic poin
t ofvie
w,
this sys
tem provides a ne
w 2D
S = 1 quan
tum spin sys
tem
wi
th an
tiferromagne
ticsuperexchange in
terac
tion. The magne
tic suscep
tibili
ty sho
ws anomalies poin
ting
to magne
ticordering phenomena. The observed
transi
tion
tempera
tures vary
wi
th
the in
terlayersepara
tion.