Synthesis of Bis(Phospha-λ⁵-Azenes) by a Redox-Condensation Reaction. Formation of an Anomalous N-Cyanophospha-λ⁵-Azene from Urea

The reaction of diphosphines [Ph₂P(CH₂)_nPPh₂; n = 1, 2] with sulfonamides, a phosphinamide, and cyanamide as well as of a dicarboxamide, a disulfonamide, urea, thiourea, and sulfamide with triphenylphosphine in the presence of diethyl azodicarboxylate has been shown to produce bis(phospha-λ⁵-azenes). In the case of cyanamide with bis(diphenylphosphino)methane a mono-(10) as well as a bis(phospha-λ⁵-azene) (9) could be prepared. Further, the monophospha-λ⁵-azene monooxide 11 was also isolated. In the case of thiourea, the monophospha-λ⁶-azene intermediate was also isolated. The reaction of urea with bis(diphenylphosphino)methane gave the mono-N-cyanophospha-λ⁵-azene monooxide (11) along with bis(diphenylphosphino)methane dioxide. This is the first observation of a nitrile produced in the reaction of an amide, a phosphine, and diethyl azodicarboxylate at room temperature.