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The first step of hydrolysis of compounds 1 , 2 and 4 involves the protonation of the PN nitrogen atom. 3 does not react with water in the absence of a catalyst. Protonation of compounds 1 – 3 by a strong acid such as CF3SO3H is studied by 15N and 31P nmr spectroscopy. In all cases the PN nitrogen appears to be the strongest basic site.

Addition of diazadienes 5 to dicoordinated phosphorus derivatives such as triazaphospholes 1 or diazaphospholes 3 leads to new tetracoordinated phosphorus spirocompounds 2 or 4. The tricoordinated phosphorus species 7 and 9 exist in a monomer tetramer PIII equilibrium but only the monomeric PII form reacts with diazadienes 5 leading to the spirocompounds 8 and 10. The monomers of 7 and 9 stabilized by complexation react with 5 to afford spirocompounds analogous to 2 and 4. In all these reactions the dicoordinated phosphorus atom is a good electrophile.

Triazaphospholes react with 1,2-diketones to give spirocyclic phosphorus compounds by a 1.1 addition at phosphorus atom; with o-quinones one obtains spirobicyclic hexacoordinated phosphorus compounds. The reaction of 1,2-diketones with λ 3 -phosphazene oligomers appears different, to some extent, and can be used as a test for the existence of a monomer-oligomer equilibrium.