Bulky chelating diamide complexes of zirconium: Synthesis, structure, and reactivity of d(0) alkyl derivatives

The reaction of 2 equiv of LiNHAr (Ar = 2,6-(Pr2C6H3)-Pr-i) with 1,3-dibromopropane yields the diamine ArHN(CH2)(3)NHAr ((BAIP)H-2, 1). The reaction of (BAIP)H-2 with Zr(NMe2)(4) yields the complex (BAIP)Zr(NMe2)(2) (2) and 2 equiv of NHMe2. Compound 2 reacts with 2 equiv of [Me2NH2]Cl to yield (BAIP)ZrCl2(NHMe2)(2) (3) and in the presence of excess pyridine affords the complex (BAIP)ZrCl(2)py(2) (4). The base-free dichloride complex (BAIP)ZrCl2 (5) can be prepared from 2 and excess ClSiMe3. The alkylation of 4 or 5 with 2 equiv of MeMgBr, 2 equiv of PhCH2MgCl, and 1 equiv of NaCp(DME) yields the alkyl derivatives (BAIP)ZrR2 (6a, R = Me; 6b, R = CH2Ph) and (BAIP)Zr(eta(5)-C5H5)Cl (8), respectively. The reaction of 2 equiv of PhMe2CCH2MgCl with complex 4 yields the eta(2)-pyridyl complex (BAIP)Zr(eta(2)-N,C-NC5H4)(CH2CMe2Ph) (7). An X-ray study of 7 revealed a capped tetrahedron geometry with the pyridyl nitrogen occupying the capping position. Complex 7 is likely formed via proton abstraction from coordinated pyridine. The catalyst system 6a/MAO polymerizes 1-hexene to a mixture of high polymer and oligomers. Activation with {Ph3C}[B(C6F5)(4)] yields only oligomers (n = 2-7). Rapid beta-hydride elimination precludes polymer formation in these systems.