Hydrides and organic derivatives

The hydrides stibine SbH₃ ,phosphine PH₃, arsine AsH₃ can be prepared through hydrolysis of metal phosphides, or through reduction of molecular compounds like PCl₃. The molecules comprise a pyramidal (C_3v) structure but with bond angles less than within NH₃. They are extremely toxic gases, with reducing thermal stability P>As>Sb. Different from ammonia they are not essential in water. The hydrazine analog diphosphane P₂H₄ and some other catenated compounds with P-P bonds can be made, even though their stability is low.

Organic derivatives involve alkyl and aryl phosphines like triphenyl phosphine (C₆H₅)₃P. Like  with the hydrides these compounds are very much less essential than the subsequent nitrogen compounds in the direction of acceptors like H⁺, but are good ligands for transition metals in low oxidation states, like they comprise π-acceptor properties. Cyclic polyarsanes like (AsPh)₆ (in which Ph is a phenyl group, C₂H₅) with As-As bonds are readily complete, and with extremely bulky organic groups it is feasible to prepare compounds with E=E double bonds, for instance,

(compare C, Si and Ge; Topic F4). Different with nitrogen, the five-coordinate compounds Ph₅E are well-known. The P and As compounds comprise the normal trigonal bipyramidal geometry but Ph₅Sb is unpredictably square pyramidal (2).

Phosphorus creates the binary compounds P₂X₄ (through a P-P bond), PX₃ and PX₅ with all halogens. With As and Sb a comprehensive set of EX₃ compounds is identified, but the only E^V halides stable below the normal circumstances are AsF₅, SbF₅ and SbCl₅. AsCl₅ has been recognized by the UV irradiation of PCl₃ in liquid Cl₂ but decomposes above -50°C. Several known halides can be obtained through direct reaction of the elements in suitable proportions, but P and F together form just PF₅ and the trihalide can be prepared through reacting PCl₃ with ZnF₂ or HgF₂. The molecular substances have the supposed structures, pyramidal (C_3v) for EX₃ and trigonal bipyramidal (D₃h) for EX₅. Though, some have a marked tendency to go through halide transfer and within the solid state PCl₅ and PBr₅ form the ionic structures [PCl₄] ⁺[PCl₆]^- and [PBr₄]⁺Br^-, correspondingly. Presumably it is the lattice energy related with an ionic solid that stabilizes these forms. Several halide complexes are known. AsF₅ and SbF₅ are Lewis acids with a extremely strong affinity for F-, giving [AsF6]- or fluoride bridged species like [Sb₂Fn]^- (3).

Oxohalides EOX₃ create tetrahedral molecules with E=P, but polymeric structures with As and Sb. POCl₃ is an significant intermediate in the manufacture of organophosphorus compounds, used, for instance, like insecticides.