Sterically Crowded peri ‐Substituted Naphthalene Phosphines and their P V Derivatives

Three sterically crowded peri ‐substituted naphthalene phosphines, Nap[PPh 2 ][ER] (Nap=naphthalene‐1,8‐diyl; ER=SEt, SPh, SePh) 1–3 , which contain phosphorus and chalcogen functional groups at the peri positions have been prepared. Each phosphine reacts to form a complete series of P V chalcogenides Nap[P(E′)(Ph 2 )(ER)] (E′=O, S, Se). The novel compounds were fully characterised by using X‐ray crystallography and multinuclear NMR spectroscopy, IR spectroscopy and MS. X‐ray data for 1 , 2 , n   O , n   S , n   Se ( n =1–3) are compared. Eleven molecular structures have been analysed by naphthalene ring torsions, peri ‐atom displacement, splay angle magnitude, X⋅⋅⋅E interactions, aromatic ring orientations and quasi‐linear arrangements. An increase in the congestion of the peri region following the introduction of heavy chalcogen atoms is accompanied by a general increase in naphthalene distortion. P⋅⋅⋅E distances increase for molecules that contain bulkier atoms at the peri positions and also when larger chalcogen atoms are bound to phosphorus. The chalcogenides adopt similar conformations that contain a quasi‐linear E⋅⋅⋅PC fragment, except for 3 O , which displays a twist‐axial‐twist conformation resulting in the formation of a linear O⋅⋅⋅SeC alignment. Ab initio MO calculations performed on 2 O , 3 O , 3 S and 3 Se reveal Wiberg bond index values of 0.02 to 0.04, which indicates only minor non‐bonded interactions; however, calculations on radical cations of 3 O , 3 S and 3 Se reveal increased values (0.14–0.19).