The conjugate acids of benzo-2,1,3-selena- and
benzo-2,1,3-telluradiazole are the simplest members of the family of
N-substituted chalcogenadiazolium cations. Four crystalline phases that in
principle contain such molecular ions were isolated and structurally
characterized:
C
$_{6}$
H
$_{4}$
(NH)
$_{2}$
TeCl
$_{2}$
,
[C
$_{6}$
H
$_{5}$
(NH)]
$_{3}$
[C
$_{6}$
H
$_{4}$
(NH)
$_{2}$
TeCl
$_{4}$
]Cl,
C
$_{6}$
H
$_{4}$
N(NH)SeCl and
C
$_{6}$
H
$_{4}$
N(NH)SeCl · 1/2
[H
$_{5}$
O
$_{2}$
]Cl. The stepwise protonation
of benzo-2,1,3-teluradiazole in DMSO solution was monitored by
$^{1}$
H NMR, providing an estimate of the basicity of this
molecule relative to pyridine. While most of the structures are consistent with
the chalcogen in oxidation state II, the molecular geometry of
C
$_{6}$
H
$_{4}$
(NH)
$_{2}$
TeCl
$_{4}$
is suggestive of oxidation state IV. The relationship between the two
structural types was examined with DFT calculations.
