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

Using the Cambridge Structural Database, the frequencies of occurrence are determined for 6-fold phenyl embraces (6PEs) between all fragments -XPh3, w here X can be any tetrahedral atom. The relative frequencies are high for t he family of cations Ph4X+, highest of all for Ph4P+ where 1121 6PEs are fo und for 1647 cations. For R-XPh3 units (R not equal 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 an d R-XPh3 groups with X = B, Al and Ga. The formation of the hetero-pairs R- 1-XPh3... Ph3Y-R-2 (X not equal Y) is neither strongly favoured nor disfavo ured over the formation of home-pairs.