Crystal supramolecularity: elaborate six-, eight- and twelve-fold concerted phenyl embraces in compounds [M(PPh3)3]z and [M(PPh3)4]z

Abstract

Multiple phenyl embraces are concerted supramolecular motifs based on intermolecular phenyl–phenyl attractions, mainly in the edge-to-face (ef) geometry. Variations of the six-fold phenyl embrace (6PE) and higher order multiple phenyl embraces involving eight or twelve phenyl groups are described. They occur in crystals of metal complexes with three or four Ph₃ ligands. The enlarged 6PE (E6PE) involves phenyl groups from three Ph₃X ligands in each of two molecules, and is formulated generally as (XPh)₃···(PhX)₃: the H6PE, or (XPh)₃···(Ph₃X), is a hybrid of the E6PE and the 6PE [which is (XPh₃)···(Ph₃X)]. The 8PE uses {M(XPh₂)₂}···{(Ph₂X)₂M} and occurs in two variants according to whether the XMX planes on the two molecules are approximately parallel (P8PE) or orthogonal (O8PE). Molecules [M(PPh₃)₃]^z can form a 12PE, which uses {M(XPh₂)₃}···{(Ph₂X)₃M} and includes ten intermolecular ef interactions. The crystal packing in various compounds containing [M(PPh₃)₃]^z or [M(PPh₃)₄]^z is described, and involves either multiple instances of one embrace type in high symmetry crystal lattices or combinations of various multiple phenyl embraces in lower symmetry crystal lattices. The current hierarchy of multiple phenyl embraces is summarised.