Interaction of In(I) and Tl(I) Cations with 2,6-Diaryl Pyridine Ligands: Cation Encapsulation within a Very Weakly Interacting N/Arene Host Environment

The interaction of 2,6-dimesitylpyridine with Tl­(I) and In­(I) cations has been investigated with a view to developing tractable molecular M­(I) compounds which are soluble in organic media. In stark contrast to isosteric and isoelectronic terphenyl systems, complexes featuring the [(2,6-Mes2py)­M]+ fragment feature very weak metal–ligand interactions in the solid state, as revealed by M-N distances of the order of 2.45 Å (M = In) and 2.64 Å (M = Tl). While additional weak π interactions are observed with arene solvate molecules in these systems, the related 2:1 complex [(2,6-Mes2py)2In]­[BArf4] features an In­(I) center wholly encapsulated by the bulky Mes2py donors, and even longer In–N distances [2.586(6) and 2.662(5) Å]. These contacts are about 0.5 Å greater than the sum of the respective covalent radii (2.13 Å) and provide evidence for an effectively “naked” In­(I) cation stabilized to a minor extent by orbital interactions.