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-[But(H)N(ButNP)2N(H)But] (1) reacts with TiCl4 to afford {[(ButNP)2(NBut)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-[But(H)N(ArNPNBut)2N(H)But] (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 {[But(H)N(ArNPNBut)2NBut]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 {[But(H)N(EPNBut)2NBut]TiCl3} (E = S (9), Se (10)).

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