Titanium complexes of bis(1°-amido)cyclodiphosph(III)azanes and bis(1°-amido)cyclodiphosph(V)azanes: facial versus lateral coordination

Abstract

Bis(1°-amino)cyclodiphosph(III)azanes and bis(1°-amino)cyclodiphosph(V)azanes show different coordination preferences with titanium(IV). The bis(tert-butylamino)cyclodiphosph(III)azane cis-[Bu^t(H)N(Bu^tNP)₂N(H)Bu^t] (1) reacts with TiCl₄ to afford {[(Bu^tNP)₂(NBu^t)₂]TiCl₂} (2), in which the ligand chelates the metal as a diamide, above the heterocycle. Oxidations of 1 with phenyl- or p-tolyl azide yield the cyclodiphosph(V)azanes cis-[Bu^t(H)N(ArNPNBu^t)₂N(H)Bu^t] (Ar = phenyl (3), p-tolyl (4)). Single-crystal X-ray studies of 3 and 4 reveal structures similar to those of their parent cyclodiphosph(III)azanes, but with pendent arylimino groups attached to the phosphorus(V) atoms. When 3 and 4 are allowed to react with TiCl₄ the complexes {[Bu^t(H)N(ArNPNBu^t)₂NBu^t]TiCl₃} (Ar = phenyl (5), p-tolyl (6)) are isolated. In these compounds the cyclodiphosph(V)azanes coordinate the metal laterally as monoanionic N–P–N ligands, similar to phosphoranates. An analogous side-on coordination is also found for the dichalcogeno complexes {[Bu^t(H)N(EPNBu^t)₂NBu^t]TiCl₃} (E = S (9), Se (10)).