Lithium and Chromium Complexes of a Bulky Guanidinate – Synthesis and Structure

Insertion of a bulky carbodiimide, ArN=C=NAr (Ar = C₆H₃iPr₂-2,6) into the Li–N bond of LiN[CH(CH₃)₂]₂ in THF and subsequent extraction with hexane leads to lithium guanidinate complex, [Li{ArNC(NiPr₂)NAr}(THF)] (1). Salt metathesis reaction between equimolar ratios of 1 and CrCl₂ in THF and extraction with hexane resulted in a mono(guanidinate) chloride-bridged dimeric chromium complex, [Cr{ArNC(NiPr₂)NAr}(µ-Cl)]₂ (2). X-ray analysis confirms 1 to be monomeric in which guanidinate ligand shows η¹ and η³ coordination through one of the N atoms and an arene moiety. In complex 2 guanidinate ligand adopts η² coordination mode, thus Cr atom is four-coordinated with distorted square planar geometry. Extraction of chromium with ether instead leads to an “ate” complex, [Cr{ArNC(NiPr₂)NAr}(µ-Cl)₂Li(THF)₂] (3). Hirshfeld surface analysis indicated that H⋯H interactions and H⋯C/C⋯H H-bonding were the two main contributors to the intermolecular interactions in the solid state.