LIGAND REDISTRIBUTION REACTIONS AS A ROUTE TO CYCLOPENTADIENYLZIRCONIUM(IV) OR 1-AZA-ALLYLZIRCONIUM(IV) TRICHLORIDES AND THE X-RAY STRUCTURES OF [(ZR(LL')CL(2)(MU-CL))(2)] AND [ZR(LL')(2)CL(2)] [LL'=N(R)C(BU(T))CHR, R=SIME(3)]

Mixing equimolar portions of ZrCl4 and [Zr(Cp(x))(2)Cl-2] in toluene at ambient temperature rapidly gave, in a very high yield, a precipitate of ZrCp(x)Cl(3) [Cp(x) = C5H5 (1), C(5)H(4)Bu(t) (2) or C(5)H(3)Bu(2)(t)-1,3 (3)]. Addition of tetrahydrofuran (THF) to each of 2 or 3 at ca 20 degrees C caused the bright yellow colour to be discharged and the solid to dissolve, due to the formation of [Zr(Cp(x))(2)Cl-2] and [ZrCl4(THF)(2)]; this was established by preparative scale experiments and also by Zr-91 NMR spectroscopic studies. The 1-aza-allylzirconium(IV) chloride [{(Zr(LL')Cl-2(mu-Cl)}(2)] (4) was obtained by a similar redistribution reaction as 1-3, from rac-[Zr(LL')(2)Cl-2] (5) and ZrCl4 [LL' = N(R)C(Bu(t))CHR, R = SiMe(3)]. The X-ray structures of 4 and 5 have been determined.