Synthesis of Unique Phosphazane Macrocycles via Steric Activation of C-N Bonds.

Herein we describe that oxidation reactions of the dimeric cyclophosphazanes, [{P(μ-NR)}(μ-NR)], R = Bu (1), to produce a series of diagonally dioxidized products P(μ-N Bu)E [E = O (2), S (3), and Se (4)] and tetraoxidized frameworks. The latter display an unexpected C-N bond activation and cleavage to produce a series of novel phosphazane macrocyclic arrangements containing newly formed N-H bonds. Macromolecules P(μ-N Bu)(μ-NH)O (5) and P(μ-N Bu)(μ-NH)E, E = S (6) and Se (7), dicleaved and tricleaved products, respectively, are rare examples of dimeric macrocycles containing NH bridging groups.

Steric C-N bond activation on the dimeric macrocycle [{P(μ-NR)}2(μ-NR)]2.

Dimeric cyclophosphazanes [{P(μ-NR)}2(μ-NR)]2 [R = (t)Bu ( 1) and iPr ( 3)] were oxidized with elemental selenium. During these reactions an unexpected C–N bond cleavage and N–H bond formation occurred. Compound 1 produced P4(μ-N(t)Bu)3(μ-NH)3Se4 ( 2) where three tBu groups were lost in the form of isobutylene.