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(CH2SiMe2NSiMe2CH2)(2)PPh, [P2N2], are described. The starting material, ZrCl2[P2N2], is prepared by reaction of syn-Li-2(S)[P2N2] (S = dioxane or THF) with ZrCl4L2 (L = THT, tetrahydrothiophene; L = THF, tetrahydrofuran). Subsequent replacement of the chloride ligands can be achieved to generate the dialkyl complexes ZrR2[P2N2] (R = Me, CH2Ph). Reaction with "magnesium butadiene", Mg(C4H6). 2THF, results in the formation of pi-eta(4)-butadiene complex Zr(eta(4)-C4H6)[P2N2]. In addition, the tert-butylimido complex Zr(NBut)[P2N2] can be prepared by addition of LiNHBut to ZrCl2[P2N2]. 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.