Abstract
We report the preparations and electron spin resonance (ESR) studies of a series of Cs
+
and Rb
+
crown ether (15-crown-5 and 18-crown-6) salts of [TcNCl
4
]
-
and [MoOCl
4
]
-
, and a new refinement of the X-ray structure of [Cs(18-crown-6)] [TcNCl
4
] involving a twinned
P4/n
scattering model. This refinement addresses some unsatisfactory aspects of the original disordered model. The structure consists of an ‘infinite sandwich’ Cs
+
cation/crown ether configuration and polymeric [TcNCL
4
]
-
anions, with Tc≡N distances of 1.561(36) Å, and anti-parallel chains of –––Tc≡N–––Tc≡N –––with Tc···Tc separations of 4.275(4) Å. The structure determination of [Rb(15-crown-5)
2
][TcNCl
4
(OH
2
)] is also described and shows a lattice containing 2:1 ‘sandwich’-type crown ether/alkali-metal cations and isolated anions in the disordered lattice. The presence of Tc≡N infrared stretching frequencies at
ca
. 1074 cm
-1
indicates the absence of strong electron donors coordinated to Tc in the sixth position (i. e. isolated anions), whereas the polymeric chain structure of [Cs(18-crown-6)] [TcNCL
4
] is characterized by a Tc≡N stretching frequency of 1041 cm
-1
. Three product compounds, the ‘infinite sandwich’ [Cs(18-crown6)][TcNCl
4
], [Cs(18-crown-6)] [TcNCL
4
(OH
2
)] with two Tc≡N stretching frequencies at 1055 and 1046.5 cm
-1
, and [Cs(18-crown-6)
2
][TcNCl
4
containing 2:1 crown ether/Cs
+
‘sandwich’ cations and isolated [TcNCl
4
]
-
anions, could be obtained from reaction of Cs
+
/18-crown-6 and [TcNCL
4
]
-
depending on reaction conditions and solvent. The ESR spectra of [Cs(18-crown-6)] [TcNCl
4
] over the temperature range 130-290 K indicate the presence of exchange interactions along the linear ––– Tc≡N––– Tc≡N––– chains. Spectra for other crown ether salts are consistent with isolated [TcNCL
4
]
-
or [TcNCL
4
(OH
2
)]
-
anions, with dipolar broadening effects apparent.
Cited by
10 articles.
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