Abstract
The title compound, hexa-kis-[μ3-1,2-bis-(tri-fluoro-meth-yl)ethene-1,2-di-thiol-ato]-octa-hedro-hexa-palladium(II), [Pd(C4F6S2)]6, crystallizes as its benzene solvate, [Pd(tfd)]6·2.5C6H6, where tfd is the di-thiol-ene S2C2(CF3)2. The mol-ecular structure of [Pd(tfd)]6 is of the hexa-metallic cube type seen previously in three examples of hexa-meric homoleptic palladium monodi-thiol-ene structures. All structures have in common: (a) the cluster closely approximates a cube containing six PdII atoms, one at the centre of each cube face; (b) 12 S atoms occupy the mid-points of all 12 cube edges, providing for each PdII atom an approximately square-planar S4 environment; (c) each S atom is part of a di-thiol-ene mol-ecule, where the size of the di-thiol-ene ligand necessitates that only sulfur atoms on adjacent cube edges can be part of the same di-thiol-ene. This general cube-type framework has so far given rise to two isomeric types: an S6-symmetric isomer and a C2-chiral type (two isomers that are enanti-omers of each other). The structure of [Pd(tfd)]6 is of the C2-type. Out of the 12 CF3 groups, 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 (one S6 isomer, two C2 enanti-omers) is complete. Each isomer type could give rise to an unlimited number of compounds if the specific di-thiol-ene used is varied.
Highlights
The title compound, hexakis[3-1,2-bis(trifluoromethyl)ethene-1,2-dithiolato]octahedro-hexapalladium(II), [Pd(C4F6S2)]6, crystallizes as its benzene solvate, [Pd(tfd)]6Á2.5C6H6, where tfd is the dithiolene S2C2(CF3)2
All structures have in common: (a) the cluster closely approximates a cube containing six PdII atoms, one at the centre of each cube face; (b) 12 S atoms occupy the mid-points of all 12 cube edges, providing for each PdII atom an approximately square-planar S4 environment; (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
The structure is of the hexametallic cube type seen previously in the hexameric homoleptic palladium monodithiolenes characterized by Stiefel and co-workers (Beswick et al, 2002), Stibrany (Stibrany, 2012), and Rawson and co-workers (Wrixon et al 2015)
Summary
Metal–dithiolene complexes (dithiolene = S2C2R2) are relevant for a host of new materials and several metalloenzymes (Stiefel, 2004; Harrison et al, 2006). Homoleptic complexes normally contain two or three dithiolenes per metal, for bisdithiolenes M(dithiolene) or trisdithiolenes M(dithiolene). The class of hexameric homoleptic palladium monodithiolenes [Pd(dithiolene)]6, where dithiolene = R2C2S2 with any substituent R was suggested by Stiefel and coworkers (Beswick et al, 2002), and a charge-neutral hexanuclear complex was crystallographically characterized (as its toluene solvate) using the dithiolene S2C2(COOMe). The partially reduced complex, with a tetraphenylphosphonium counter-ion, was later structurally characterized by Stibrany (2012). A crystal was obtained, and the structure was determined by X-ray crystallography
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