Iminophosphoranes, deboronation

In the presence of air at 20°C, the reaction of the iminophosphorane 5 with ortho carborane 1 resulted in deboronation to yield the H2NP(NMe2)3+ salt 6 of the nido anion 7,8-C2B9Hi2 and boric acid.7... 

Crystals formed from the reaction mixture were identified by X-ray crystallography as a 1 1 polymeric adduct of [H2NP(NMe2)3+]2C032"-B(0H)3. Unlike HMPA 4, the iminophosphorane 5 absorbs carbon dioxide and water in the presence of air. Base 5 converts or/Ao-carborane into the nido-anion just as effectively in the absence of air indicating that water and C02 are not vital ingredients in the deboronation process. 

Tlie steps by which deboronation of orz/io-carborane occurs have been established by the isolation and characterization of key intermediates in systems in which the deboronating nucleophile was the iminophosphorane HNP(NMe2)3 [Eq. (3.6), or pyridine [Eq. (3.6), Nir. rhc structure... 

Davidson, M. G. Fox, M. A. Hibbert, T.G. Howard, J.A.K. Mackinnon, A. Neretin, I.S. Wade, K. Deboronation of ortho-carborane by an iminophosphorane crystal structures of the novel carborane adduct <7o-C2BioHi2 HNP(NMe2)3 and the borenium salt [(Me2N)3PNHBNP(NMe2)3]20 +(C2B9H )2, Chem. Commun., 1999, 1649. 

---