The rate of reductive elimination for a family of zirconocene isobutyl hydride complexes, Cp*(CpR_n)Zr(CH₂CHMe₂)H (Cp* = η⁵-C₅Me₅, CpR_n = substituted cyclopentadienyl), has been measured as a function of cyclopentadienyl substituent. In general, the rate of reductive elimination increases modestly with the incorporation of sterically demanding substituents such as [CMe₃] or [SiMe₃]. A series of isotopic labeling experiments was used to elucidate the mechanism and rate-determining step for the reductive elimination process. From these studies, a new zirconocene isobutyl hydride complex, Cp‘ ‘₂Zr(CH₂CHMe₂)(H) (Cp‘ ‘ = η⁵-C₅H₃-1,3-(SiMe₃)₂), was designed and synthesized such that facile reductive elimination of isobutane and activation of dinitrogen was observed. The resulting dinitrogen complex, [Cp‘ ‘₂Zr]₂(μ₂, η²,η²-N₂), has been characterized by X-ray diffraction and displays a bond length of 1.47 Å for the N₂ ligand, the longest observed in any metallocene dinitrogen complex. Solution magnetic susceptibility demonstrates that [Cp‘ ‘₂Zr]₂(μ₂, η², η²-N₂) is a ground-state triplet, consistent with two Zr(III), d¹ centers. Mechanistic studies reveal that the dinitrogen complex is derived from the reaction of N₂ with the resulting cyclometalated zirconocene hydride rather than directly from reductive elimination of alkane.

Publications with shared reference:

0 publications found