Synthesis and Structure of Zirconium(IV) Complexes Stabilized by the Bis(amido−phosphine) Macrocycle [P₂N₂] {[P₂N₂] = PhP(CH₂SiMe₂NSiMe₂CH₂)₂PPh}

The preparation and characterization of a series of zirconium(IV) complexes that incorporate the macrocyclic bis(amido−phosphine) ligand PhP(CH 2 SiMe 2 NSiMe 2 CH 2 ) 2 PPh, [P 2 N 2 ], are described. The starting material, ZrCl 2 [P 2 N 2 ], is prepared by reaction of syn -Li 2 (S)[P 2 N 2 ] (S = dioxane or THF) with ZrCl 4 L 2 (L = THT, tetrahydrothiophene; L = THF, tetrahydrofuran). Subsequent replacement of the chloride ligands can be achieved to generate the dialkyl complexes ZrR 2 [P 2 N 2 ] (R = Me, CH 2 Ph). Reaction with “magnesium butadiene”, Mg(C 4 H 6 )·2THF, results in the formation of π-η 4 -butadiene complex Zr(η 4 -C 4 H 6 )[P 2 N 2 ]. In addition, the tert -butylimido complex Zr(NBu t )[P 2 N 2 ] can be prepared by addition of LiNHBu t to ZrCl 2 [P 2 N 2 ]. A number of the above complexes have been characterized by X-ray crystallography, and all show that the Zr center sits above the plane defined by the donor atoms of the macrocyclic ligand. The distortions of the macrocyclic ring observed in the solid state are not evident in solution and suggest that these ligand backbones are considerably flexible.