INSERTION OF ALKYNES INTO ZIRCONIUM NITROGEN BONDS LEADING TO 2,3-DIAZAMETALLACYCLOPENTENES - GENERATION AND REACTIVITY OF CP2ZR(N2PH2)

Methyl eta-2-1,2-diphenylhydrazido(1-)zirconocene (1) has been synthesized from the monopotassium salt of 1,2-diphenylhydrazine and Cp2Zr(Me)(CI). Heating 1 in THF causes extrusion of methane, generating the transient hydrazido complex Cp2Zr(N2Ph2) (2) which is trapped by solvent to yield the THF adduct Cp2Zr(N2Ph2)(THF) (3). The THF ligand of compound 3 was replaced with a variety of sigma-donor ligands to form the ligated hydrazido complexes Cp2Zr(N2Ph2)(L) (L = pyridine) (4), PMe3 (5), NCPh (6) and CNCMe3 (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 eta-2-hydrazido(1-)acetylide (10) and enolate (11), respectively.