A Modular Approach to Inorganic Phosphazane Macrocycles.

Inorganic macrocycles, based on non-carbon backbones, present exciting synthetic challenges in the systematic assembly of inorganic molecules, as well as new avenues in host-guest and supramolecular chemistry. Here we demonstrate a new high-yielding modular approach to a broad range of trimeric and hexameric S- and Se-bridged inorganic macrocycles based on cyclophosphazane frameworks, using the building blocks [S=(H)P(μ-NR)]2 . The method involves the in situ generation of the key intermediate [E....._ (S....._ )P(μ-NR)]2(2-) (E=S, Se) dianion, which can be reacted with electrophilic [ClP(μ-NR)]2 to give P(III) /P(V) hexameric rings or reacted with I2 to give trimeric P(V) variants. Important issues which are highlighted in this work are the competitive bridging ability of S versus Se in these systems and the synthesis of the first air-stable and chiral inorganic macrocycles.