The supramolecular architecture of arene complexes of bis(polyfluorophenyl) -mercurials

The 1:1 (arene)mercury complexes [HgR₂(arene)] [R = C ₆F₄-o-NO₂, C₆F₄-m-NO ₂, C₆F₄-o-H, C₆F₅; arene = TMB (1,2,4,5-tetramethylbenzene), PMB (1,2,3,4,5-pentamethylbenzene)] are readily formed when mixtures of the mercurial and arene are crystallised from CH₂Cl₂ or CH₂Cl₂/hexane. Analogous 1:1 complexes are also formed from Hg(C₆F₅)₂ and PhMe, whereas novel 1:2 complexes [HgR₂(arene)₂] result from Hg(C₆F₄-o-NO₂)₂ and PhMe or TMO (1,2,4-trimethoxybenzene) and from Hg(C₆F₅) ₂ and TMO. In the crystalline state, the 1:1 [HgR₂(arene)] complexes exist as canted columns of alternating planar HgR₂ and arene layers linked by weak (Hg···C 3.2-3.5 Å) η¹ or η² π-arene-mercury interactions. For the TMB (R = C₆F₄-o-NO₂, C₆F ₄-o-H, C₆F₅) and PhMe (R = C₆F ₅) complexes, the packing of neighbouring columns shows aligned, alternating fluoroarene and arene ring planes resulting in a 2D brick-wall motif with potential supramolecular components (fluoroarene-fluoroarene and fluoroarenearene stacking). For the TMB complex with R = C₆F ₄-m-NO₂ the 2D array is distorted into a herringbone motif by weak C-H···O interactions. The 1:2 complex [Hg(C ₆F₄-o-NO₂)₂-(PhMe)₂] has an analogous mercury environment to the 1:1 complexes, and the packing shows a distinct layer structure of alternating rows of PhMe and HgR₂ with two PhMe units per HgR₂ unit but with no inter-stack interactions. The TMO complexes have long Hg···O contacts (3.2 Å) rather than Hg···C and similarly show a layered structure, but in this case, with a single column of alternating HgR₂ and pairs of TMO. Theoretical calculations for the 1:2 [HgR₂(TMB)₂] complexes (R = C₆F₄-o-NO₂, C₆F ₄-m-NO₂) are consistent with the findings from the observed crystal structures.