Group‐13 Metal‐Induced Coordination Variation of the Bis(2‐pyridyl)amide Ligand in Solution and in the Solid State

Ligands containing aromatic nitrogen heterocycles play a leading role in the molecular self assembling processes that lead to macromolecular architectures. The inductive effect of various metal fragments on those building blocks has not yet been studied systematically. To evaluate this effect we synthesized the homologous series of Group‐13 metal complexes [Me 2 AlPy 2 N] ( 1 ), [Me 2 GaPy 2 N] ( 2 ), [Me 2 InNPy 2 ] 2 ( 3 ), and [Me 2 TlNPy 2 ] ∞ ( 4 ) (Py = 2‐NC 5 H 4 ), and characterized them by low‐temperature X‐ray structure analysis and 15 N‐NMR spectroscopy in solution. The electronic equivalence of the central and the ring nitrogen atoms leaves the energetic hyperface of the anion quite flat, and the electron density is polarized according to the requirements of the metal. In the aluminum and the gallium complexes 1 and 2 the metal center is coordinated exclusively through the nitrogen atoms within the pyridyl rings. The complexes with these hard metals are close‐contact ion pairs. In the indium complex 3 the cis ‐ cis orientation gives rise to a dimeric structure, while the unprecedented cis ‐ trans arrangement in the thallium compound 4 leads to a polymeric structure. The complexes 3 and 4 have to be regarded as separated ion pairs of Me 2 M + cations and Py 2 N − anions without any covalent bonds between the anionic moiety and the dimethylmetal cations, even in the solid state. The series of complexes proves the bis(2‐pyridyl)amide to be an excellent self‐adapting ligand. These findings are substantiated by NMR‐spectroscopic studies in solution. Not only do the steric requirements of N heteroaromatic ligands have to be considered in molecular self‐assembling processes but also the inductive effect of the different metal fragments.