Dimorphs of (Ph<sub>4</sub>P)<sub>2</sub>[Cd<sub>2</sub>(SPh)<sub>6</sub>]: Crystal Packing Analyses and the Interplay of Intermolecular and Intramolecular Energies
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The crystallization and structure of a triclinic dimorph (1T) of (Ph4P)2[(PhS)2Cd(μ-SPh)2Cd(SPh)2] are reported and its crystallization conditions compared with those of the monoclinic dimorph 1M. The variations in molecular structure and crystal packing of both crystals are analyzed and compared, in the context of the issue of the relative influences and energies of intramolecular and intermolecular interactions. Both crystals contain parallel chains of Ph4P+ ions and stacks of [Cd2(SPh)6]2- ions. In 1T the cation chain is the classic zigzag infinite chain of 6-fold phenyl embraces (ZZI6PE), while in 1M the cation chain contains alternating 6PE and P4PE (parallel 4-fold phenyl embrace) motifs, with a longer repeat distance. The canting of [Cd2(SPh)6]2- ions relative to their stack axis is correlated with the repeat length of the cation chain, and there are EF (edge-to-face) and OFF (offset-face-to-face) phenyl···phenyl interactions between Ph4P+ and [Cd2(SPh)6]2-. The conformations of the SPh ligands differ in the two [Cd2(SPh)6]2- ions, and in 1T there is a differentiation of bridging Cd−S distances that is not present in 1M. Density functional methods have been used to assess the energy surface associated with the variable geometry of the anion. The conclusion is that intermolecular energies are larger than the energies associated with the variation of molecular geometry for this complex.
