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

The reduction of the zirconium(IV) precursor Zr(mu(5)-C5H5)Cl-2[N(SiMe(2) CH2PPr2i)(2)] with sodium-amalgam under argon or vacuum generates the mononuclear Zr-III complex Zr(eta(5)-C5H5)Cl[N(SiMe(2)CH(2)PPr(2)(i))(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(eta(5)-C5H5)R[N(SiMe(2)CH(2)PPT(2)(i))(2)] (R = Ph, Me, Et, CH(2)Ph and CH(2)SiMe(3)) were prepared as well as the heteroatom derivatives Zr(eta(5)-C5H5)X[N(SiMe(2)CH(2)PPr(2)(i))(2)] (X = OPh, NPh(2) and PPh(2)); 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(eta(5)-C5H5)Cl[N(SiMe(2)CH(2)PPr(2)(i))(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(eta(5)-C5H5)Ph[N(SiMe(2)CH(2)PPr(2)(i))(2)] and Zr(eta(5)-C5H5)CH(2)SiMe(3)[N(SiMe(2)CH(2)PPr(2)(i))(2)].