Zirconium and Hafnium Hydrazinediido Half-Sandwich Complexes: Synthesis and Reactivity

The hydrazinediido complexes [Cp*M­(NxylN)­(NNPh2)­(dmap)] (M = Zr, 3a; M = Hf, 3b; NxylN = 2-(N-xylylamino)­pyrrolinate) have been synthesized, and their reactivity has been investigated. Both complexes were prepared from [Cp*M­(NxylN)­Cl2] (1a,b) and [Cp*M­(NxylN)­(NHNPh2)­Cl] (2a,b), respectively, as precursors. While 3a was obtained by dehydrohalogenation of 2a using LiHMDS in the presence of dmap, reaction of 2b with LiHMDS initially afforded a mixture of [Cp*Hf­(NxylN)­(NHNPh2)2] (6) and [Cp*Hf­(NxylN)­(NNPh2)­LiHMDS] (4), which was thermolyzed subsequently in the presence of dmap to yield 3b. [Cp*Zr­(NxylN)­(NNPh2)­(dmap)] (3a) reacted with diisopropylcarbodiimide, giving the rearranged [2 + 2] cycloaddition product [Cp*Zr­(NXylN)­{κ2-NiPrC­(NNPh2)­NiPr}] (7) and the six-membered zirconacycle [Cp*Zr­(NXylN)­{κ2-N­(NPh2)­C­(NiPr)­NiPrC­(NiPr)­NiPr}] (8a). With N-phenylbenzimine the cycloaddition product [Cp*Zr­(NXylN)­{κ2-N­(NPh2)­CHPhNPh}] (9) was isolated, and upon reaction with diphenylacetylene the seven-membered zirconacycle [Cp*Zr­(NXylN)­{κ2-N­(Ph)-o-phenylene-C­(Ph)C­(Ph)­NH}] (10) was obtained. Reaction of the previously synthesized compound [Zr­(N2TBSNpy)­(NNPh2)­py] (11) with iPrNCNiPr and with PhCHNPh gave the four-membered zirconacycles [Zr­(N2TBSNpy)­{κ2-N­(NPh2)­C­(NiPr)­NiPr}] (12) and [Zr­(N2TBSNpy)­{κ2-N­(NPh2)­CHPhNPh}] (13), respectively.