Crystal architecture of the cocrystaline salt [Ru(#eta#~5-C_5H_5)(#eta#~6-trans-PhCH=CHPh)][PF_6] centre dot 0.5trans-PhCH=CHPh and the reversible order-disorder phase transition in [Ru(#eta#~5-C_5H_5)(#eta#~6-C_6H_6)][PF_6]

摘要

the crystal architecture, stability and behaviour with temperature of the hexafluorophosphate salts [Ru(#eta#~5-C_5H_5)(#eta#~6-arene)]~+ (arene=benzene 1 or trans-stilbene 2) have been investigated by variable temperature X-ray diffraction and differential scanning calorimetry. Compound 1 shows a reversible high temperature phase transition to a semi-disordered phase at 332 K. It is pseudo-isomorphous with [Cr(#eta#~6-C_6H_6)_2][PF_6] and with the room temperature form of [M(#eta#~5-C_5H_5)_2][PF_6] (M=Co or Fe), the latter species also undergoing reversible phase transitions. Crystalline 2 has been characterised in its cocrystallised form [Ru(#eta#~5-C_5H_5)(#eta#~6-trans-PhCH=CHPh)][PF_6] centre dot 0.5 trans-PhCH=CHPh. The trans-stilbene molecules fill in the voids formed in the packing when the small [PF_6]~- anions assemble with the large and asymmetric [Ru(#eta#~5-C_5H_5)(#eta#~6-trans-PhCH=CHPh)]~+ cations. The role of charge assisted C-H~(#delta#+)...F~(#delta#-) interactions is discussed.