Jellyfish-type Dinuclear Hafnium Azido Complexes Synthesis and Reactivity.

Di- and multinuclear hafnium complexes bridged by ligands have been rarely reported. In this article, a novel 3,5-disubstituted pyrazolate-bridged ligand LH5 with two [N2N]2--type chelating side arms was designed and synthesized, which supported a series of dinuclear hafnium complexes. Dinuclear hafnium azides [LHf2(μ-1,1-N3)2(N3)2][Na(THF)4] 3 and [LHf2(μ-1,1-N3)2(N3)2][Na(2,2,2-Kryptofix)] 4 were further synthesized and structurally characterized, featuring two sets of terminal and bridging azido ligands like jellyfishes. The reactivity of 3 under reduction conditions was conducted, leading to a formation of a tetranuclear hafnium imido complex [L1Hf2(μ1-NH)(N3){μ2-K}]25. DFT calculations revealed that the mixed imido azide 5 was generated via an intramolecular C-H insertion from a putative dinuclear HfIV-nitridyl intermediate.