Lithium complexes of N-donor-functionalized cyclopentadienyl -: A pyrazolate-based bimetallic version

The two new pyrazole-based dinucleating ligands 3,5-bis(fluoren-9-ylmethyl)-1H-pyrazole (H3La) and 3,5-bis(inden-3-ylmethyl)-1H-pyrazole (H3Lb) have been prepared and structurally characterized in the case of H3La, and their lithium complexes Li3La and Li3Lb are reported. These systems can be viewed as coupled dinucleating versions of two widely used Cp fragments bearing pendant amino or amido side chains, which is confirmed by the crystal structure of the solvent-separated ion pair [Li2La(thf)(4)][Li(thf)(4)]. In solution, Li-7 NMR spectroscopy indicates the predominant presence of contact ion pairs. The crystal structure of the partially lithiated compound [Li2HLa(thf)(5)] is also presented.