Multiple phenyl interactions. Part 1: relative frequencies of six-fold phenyl embraces (6PE) in crystalline compounds containing the fragment XPh3 (X=any tetrahedral atom)

Abstract

Using the Cambridge Structural Database, the frequencies of occurrence are determined for 6-fold phenyl embraces (6PEs) between all fragments –XPh₃, where X can be any tetrahedral atom. The relative frequencies are high for the family of cations Ph₄X⁺, highest of all for Ph₄P⁺ where 1121 6PEs are found for 1647 cations. For R–XPh₃ units (R≠Ph) with group IV and V central atoms, the relative frequencies are much lower, ranging between 13 and 28% depending on R–X. It is very low, about 2%, for the Ph₄B⁻ anion and R–XPh₃ groups with X=B, Al and Ga. The formation of the hetero-pairs R₁–XPh₃···Ph₃Y–R₂ (X≠Y) is neither strongly favoured nor disfavoured over the formation of homo-pairs.