Cameron J. Kepert, Mohamedally Kurmoo, Mary R. Truter and Peter Day
Two new charge-transfer salts of BEDT-TTF
[bis(ethylenedithio)tetrathiafulvalene] with paramagnetic anionic
complexes of Group 6 elements have been prepared. The crystal structure
of the salt [BEDT-TTF][MoOCl4(H2O)] is unusual in
containing no segregated layers of cations and anions but chains of
hydrogen-bonded [MoOCl4(H2O)]-
sandwiched between ribbons of BEDT-TTF+ edge linked by
S·
·
·
S contacts. The
structure of
[BEDT-TTF]2[Cr(NCS)4(NH3)2]
consists of alternating layers of [(BEDT-TTF)2]+
and [Cr(NCS)4(NH3)2]-.
The molecular packing in the cation layer is unique in comprising double
stacks which alternate in orientation with close
S
·
·
·
S contacts not
only between cations but between cations and NCS. Both compounds are
semiconductors and their magnetic behaviour is dominated by the anions,
though there is evidence that the cation ribbons in the molybdenum salt
behave as antiferromagnetic chains (J ≈ 110
K).