The effect of trifluoromethyl groups in the para positions of a perfluoroaryl phosphine: A comparison of the structures of [{η5,κP-C5Me4CH2C6F3X-5-P(C6F4X-4)-2-CH2P(C6F4X-4)2}RhCl2], X = F and CF3

The complex [{η5,κP-C5Me4CH2C6F3CF3-5-P(C6F4CF3-4)-2-CH2P(C6F4CF3-4)2}RhCl2] (2) was formed by dehydrofluorinative carbon–carbon coupling in the reaction between bis{bis(4-trifluoromethyltetrafluorophenyl)phosphino}methane and [(η5-C5Me5)RhCl(μ-Cl)]2. The structure of 2 has been determined by single crystal X-ray diffraction and compared to that of the pentafluorophenyl analogue [{η5,κP-C5Me4CH2C6F4P(C6F5)-2-CH2P(C6F5)2}RhCl2] (3). The presence of the trifluoromethyl groups, although not affecting the local structure about rhodium, disrupts the packing and consequently the structure of the two complexes is very different. The structure of 2 contains channels about 3-fold axes comprising fluoroaryl cavities separated by aliphatic constrictions arising from hexagonal rings of alternating enantiomers.

Replacement of the para fluorine atoms of {(C6F5)2P}2CH2 has a minimal steric or electronic effect on the title complex, but dramatically affects the packing in the crystal structure generating channels of large fluoroaryl cavities separated by aliphatic constrictions.Figure optionsDownload as PowerPoint slide