Zircona-phosphazine complexes: synthesis and X-ray determination

Abstract

Addition of diazoalkane derivatives RCH(N₂) [R = CO₂Et (a), SiMe₃ (b)] on α-phosphino zirconocene complexes 1, 4 and 6 affords stable N-metal phosphazine compounds 3a,b, 5a,b and 7a,b, respectively. The single crystal X-ray structure of 3a is reported and shows an s-transoid (E) geometry for the phosphazine substructure P1–N1–N2–C9 with a zirconium-to-nitrogen distance in the range of that of Cp₂Zr–N σ-bonds in zirconate complexes, which reveals a zwitterionic canonical form for 3a.