Peri-Interactions in Naphthalenes, 9 [1]. On Hypercoordination in Non-Quaternary Phosphonium Salts and a Secondary Phosphine with the (8-Dimethylamino-Naphth-1-Yl) Substituent

The 31P NMR data of non-quaternary (8-dimethylamino-naphth-1-yl)phosphonium salts, with emphasis on the 1J(31P, 1H) coupling constants, where scrutinized for their potential to yield information about N→P dative interactions. As for δ (29Si) and 1J(29Si, 1H) in the isosteric silanes, the data do not permit conclusions in favour of such interactions. 1J(31P, 1H) of bis(8-dimethylaminonaphth- 1-yl)phosphine in conjunction with the distances d(N···P) invalidates the basic assumption on which the claim of dative N→P/Si bonding in such phosphorus and silicon compounds rests, viz. that N···P/Si distances of ca. 270 pm are evidence for P/Si-hypercoordination. No evidence for hydrogen bonds N···H-P was found.