C2-isomer of [Pd(tfd)]6[tfd is S2C2(CF3)2] as its benzene solvate: a new member of the small but growing class of homoleptic palladium(II) monodithiolenes in the form of hexameric cubes

Abstract

The title compound, hexakis[μ3-1,2-bis(trifluoromethyl)ethene-1,2-dithiolato]-octahedro-hexapalladium(II), [Pd(C4F6S2)]6, crystallizes as its benzene solvate, [Pd(tfd)]6·2.5C6H6, where tfd is the dithiolene S2C2(CF3)2. The molecular structure of [Pd(tfd)]6is of the hexametallic cube type seen previously in three examples of hexameric homoleptic palladium monodithiolene structures. All structures have in common: (a) the cluster closely approximates a cube containing six PdIIatoms, one at the centre of each cube face; (b) 12 S atoms occupy the mid-points of all 12 cube edges, providing for each PdIIatom an approximately square-planarS4environment; (c) each S atom is part of a dithiolene molecule, where the size of the dithiolene ligand necessitates that only sulfur atoms on adjacent cube edges can be part of the same dithiolene. This general cube-type framework has so far given rise to two isomeric types: anS6-symmetric isomer and aC2-chiral type (two isomers that are enantiomers of each other). The structure of [Pd(tfd)]6is of theC2-type. Out of the 12 CF3groups, three are rotationally disordered over two positions. Further, we answer the question of whether additional, previously undiscovered, isomers could follow from the cube rules (a) through (c) above. An exhaustive analysis shows that no additional isomers are possible and that the list of isomers (oneS6isomer, twoC2enantiomers) is complete. Each isomer type could give rise to an unlimited number of compounds if the specific dithiolene used is varied.