Bis-Guanidinate Scaffold for the Construction of Unique Zr(IV)-Li(I) Heterobimetallic Complexes

Herein, we report bis-guanidinate (BG)-bridged heterobimetallic lithium-zirconium organometallic compounds, revealing new dimensions of ligand-induced structural versatility. Reactions of lithiated salts of bis-guanidinates bearing 2,6-dimethylphenyl (^XylLLi) or 2,6-diethylphenyl (^DepLLi) aryl-substituents (where L = {(ArHN)(ArN)-C═N-C═(NAr)(NHAr)}; Ar = Xyl = 2,6-Me₂C₆H₃ or Dep = 2,6-Et₂C₆H₃) with Cp₂ZrHCl (Schwartz's reagent) in benzene proceed via elimination of H₂ and HCl to afford well-defined Li/Zr heterobimetallic complexes. The formation of these heterobimetallic compounds was confirmed by multinuclear NMR spectroscopy (¹H, ^{1 3}C{¹H}, and ⁷Li and DOSY NMR) and single-crystal X-ray diffraction studies. Structural analysis shows that the LX-type bis-guanidinate framework in LLi undergoes conversion to an unprecedented L₂X₃ coordination mode, wherein the ligand acts as trianionic (tritopic) toward zirconium and neutral (ditopic) toward lithium, generating two four-membered and one six-membered metallacycles. Solid-state analysis reveals pronounced structural diversity, with one complex adopting a dimeric arrangement and the other forming a zig-zag coordination polymer composed of CpZr-bis-guanidinate-LiCp units. Notably, the polymeric complex exhibits catalytic activity, showing efficient dihydroboration of nitriles under neat conditions and effective hydroboration of α,β-unsaturated ketones, carbodiimide, alkyne, and isocyanates, highlighting the catalytic relevance of polymeric BG-supported Li/Zr architecture.