Insertion of alkynes into zirconium-nitrogen bonds leading to 2,3-diazametallacyclopentenes. Generation and reactivity of Cp 2Zr(N 2Ph 2)

Abstract

Methyl η 2-1,2-diphenylhydrazido(1 −)zirconocene ( 1) has been synthesized from the monopotassium salt of 1,2-diphenylhydrazine and Cp 2Zr(Me)(Cl). Heating 1 in THF causes extrusion of methane, generating the transient hydrazido complex Cp 2Zr(N 2Ph 2) ( 2) which is trapped by solvent to yield the THF adduct Cp 2Zr(N 2Ph 2)(THF) ( 3). The THF ligand of compound 3 was replaced with a variety of σ-donor ligands to form the ligated hydrazido complexes Cp 2Zr(N 2Ph 2)(L) (L  pyridine) ( 4), PMe 3 ( 5), NCPh ( 6) and CNCMe 3 ( 7)). Compound 4 was characterized by X-ray diffraction. The THF adduct 3 also undergoes a reaction involving insertion of alkynes into one of its metal-nitrogen bonds. Thus, reaction of 3 with 2-butyne and 3-hexyne leads to zirconocene 2,3-diazametallacyclopentenes 8 and 9 respectively. The structure of these metallacycles was supported by an X-ray diffraction study of 8. Compound 3 also reacted with phenylacetylene and acetophenone via deprotonation to furnish the η 2-hydrazido(1 −)acetylide ( 10) and enolate ( 11), respectively.