Bulky Chelating Diamide Complexes of Zirconium: Synthesis, Structure, and Reactivity of d0 Alkyl Derivatives

The reaction of 2 equiv of LiNHAr (Ar = 2,6- i Pr 2 C 6 H 3 ) with 1,3-dibromopropane yields the diamine ArHN(CH 2 ) 3 NHAr ((BAIP)H 2, 1 ). The reaction of (BAIP)H 2 with Zr(NMe 2 ) 4 yields the complex (BAIP)Zr(NMe 2 ) 2 ( 2 ) and 2 equiv of NHMe 2 . Compound 2 reacts with 2 equiv of [Me 2 NH 2 ]Cl to yield (BAIP)ZrCl 2 (NHMe 2 ) 2 ( 3 ) and in the presence of excess pyridine affords the complex (BAIP)ZrCl 2 py 2 ( 4 ). The base-free dichloride complex (BAIP)ZrCl 2 ( 5 ) can be prepared from 2 and excess ClSiMe 3 . The alkylation of 4 or 5 with 2 equiv of MeMgBr, 2 equiv of PhCH 2 MgCl, and 1 equiv of NaCp(DME) yields the alkyl derivatives (BAIP)ZrR 2 ( 6a, R = Me; 6b, R = CH 2 Ph) and (BAIP)Zr(η 5 -C 5 H 5 )Cl ( 8 ), respectively. The reaction of 2 equiv of PhMe 2 CCH 2 MgCl with complex 4 yields the η 2 -pyridyl complex (BAIP)Zr(η 2 -N,C−NC 5 H 4 )(CH 2 CMe 2 Ph) ( 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 {Ph 3 C}[B(C 6 F 5 ) 4 ] yields only oligomers ( n = 2−7). Rapid β-hydride elimination precludes polymer formation in these systems.