Synthetic and Structural Study of peri-Substituted Phosphine-Arsines

A series of phosphorus-arsenic peri-substituted acenaphthene species have been isolated and fully characterised, including single crystal X-ray diffraction. Reactions of EBr3 (E = P, As) with iPr(2)PAcenapLi (Acenap = acenaphthene-5,6-diyl) afforded the thermally stable peri-substitution supported donor-acceptor complexes, iPr(2)PAcenapEBr(2) 3 and 4. Both complexes show a strong P -> E dative interaction, as observed by X-ray crystallography and P-31 NMR spectroscopy. DFT calculations indicated the unusual As center dot center dot center dot As contact (3.50 angstrom) observed in the solid state structure of 4 results from dispersion forces rather than metallic interactions. Incorporation of the excess AsBr3 in the crystal structure of 3 promotes the formation of the ion separated species [iPr(2)PAcenapAsBr]Br-+(-) 5. A decomposition product 6 containing the rare [As6Br8](2-) heterocubane dianion was isolated and characterised crystallographically. The reaction between iPr(2)PAcenapLi and EtAsI2 afforded tertiary arsine (BrAcenap)(2)AsEt 7, which was subsequently lithiated and reacted with PhPCl2 and Ph2PCl to afford cyclic PhP(Acenap)(2)AsEt 8 and acyclic EtAs(AcenapPPh(2))(2) 9.