Synthesis, structure and reactivity of mononuclear paramagnetic complexes of zirconium and hafnium

Article abstract of DOI:10.1016/0277-5387(95)00287-3

The reduction of the zirconium(IV) precursor Zr(n⁵-C⁵H⁵)Cl₂[N(SiMe₂ CH₂PPr¹₂)₂] with sodium-amalgam under argon or vacuum generates the mononuclear Zr^III complex Zr(n⁵-C₅H₅)Cl[N(SiMe₂CH ₂PPr¹₂)₂] as a thermally stable, crystalline material. Further functionalization of the remaining chloride is possible by the addition of a variety of organometallic reagents, as well as heteroatom nucleophiles. Thus, the hydrocarbyl complexes Zr(n⁵-C₅H₅)R[N(SiMe₂CH ₂PPr¹₂)₂] (R = Ph, Me, Et, CH₂Ph and CH₂SiMe₃) were prepared as well as the heteroatom derivatives Zr(n⁵-C₅H₅)X[N(SiMe₂CH ₂PPr¹₂)₂] (X = OPh, NPh₂ and PPh₂); all of the hydrocarbyl and heteroatom substituted Zr^III derivatives are mononuclear and were characterized by ESR spectroscopy. In addition, the hafnium(III) complex Hf(n⁵-C₅H₅)Cl[N(SiMe₂CH ₂PPr¹₂)₂] could be isolated via the same procedure but in this case, one could observe the analogous Zr^III complex as an impurity. Oxidation of the Zr^III and Hf^III complexes could be effected by the addition of TiCl₃, PbCl₂ or PhSSPh. Two crystal structures are also included : Zr(n⁵-C₅H₅)Ph[N(SiMe₂CH ₂PPr¹₂)₂] and Zr(n⁵-C₅H₅)CH₂SiMe ₂[N(SiMe₂CH₂PPr¹₂) ₂].