Metal⋅⋅⋅F−C Bonding in Low‐Coordinate Alkaline Earth Fluoroarylamides

A set of calcium and barium complexes containing the fluoroarylamide N(C6F5)2− is presented. These compounds illustrate the key role of stabilising M⋅⋅⋅F−C secondary interactions in the construction of low‐coordinate alkaline earth complexes. The nature of Ca⋅⋅⋅F−C bonding in calcium complexes is examined in the light of structural data, bond valence sum (BVS) analysis and DFT computations. The molecular structures of [Ca{N(C6F5)2}2(Et2O)2] (4′), [Ca{μ‐N(SiMe3)2}{N(C6F5)2}]2 (52), [Ba{μ‐N(C6F5)2}{N(C6F5)2}⋅toluene]2 (62), [{BDIDiPP}CaN(C6F5)2]2 (72), [{N^NDiPP}CaN(C6F5)2]2 (82), and [Ca{μ‐OB(CH(SiMe3)2)2}{N(C6F5)2}]2 (92), where {BDIDiPP}− and {N^NDiPP}− are the bidentate ligands CH[C(CH3)NDipp]2− and DippNC6H4CNDipp− (Dipp=2,6‐iPr2‐C6H3), are detailed. Complex 62 displays strong Ba⋅⋅⋅F−C contacts at around 2.85 Å. The calcium complexes feature also very short intramolecular Ca−F interatomic distances at around 2.50 Å. In addition, the three‐coordinate complexes 72 and 82 form dinuclear structures due to intermolecular Ca⋅⋅⋅F−C contacts. BVS analysis shows that Ca⋅⋅⋅F−C interactions contribute to 15–20 % of the bonding pattern around calcium. Computations demonstrate that Ca⋅⋅⋅F−C bonding is mostly electrostatic, but also contains a non‐negligible covalent contribution. They also suggest that Ca⋅⋅⋅F−C are the strongest amongst the range of weak Ca⋅⋅⋅X (X=F, H, Cπ) secondary interactions, due to the high positive charge of Ca2+ which favours electrostatic interactions. Beneficial interations: A set of alkaline earth complexes bearing the fluoroarylamide N(C6F5)2− is reported. As illustrated in this study, stabilising M⋅⋅⋅F−C secondary interactions play a crutial role in the construction of this class of low‐coordinate compounds. Moreover, the nature of Ca⋅⋅⋅F−C bonding in calcium complexes is examined by solid‐state crystallography, bond valence sum (BVS) analysis and DFT calculations.