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

A set of calcium and barium complexes containing the fluoroarylamide N(C 6 F 5 ) 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(C 6 F 5 ) 2 } 2 (Et 2 O) 2 ] ( 4 ′), [Ca{μ‐N(SiMe 3 ) 2 }{N(C 6 F 5 ) 2 }] 2 ( 5 2 ), [Ba{μ‐N(C 6 F 5 ) 2 }{N(C 6 F 5 ) 2 }⋅toluene] 2 ( 6 2 ), [{BDI DiPP }CaN(C 6 F 5 ) 2 ] 2 ( 7 2 ), [{N^N DiPP }CaN(C 6 F 5 ) 2 ] 2 ( 8 2 ), and [Ca{μ‐OB(CH(SiMe 3 ) 2 ) 2 }{N(C 6 F 5 ) 2 }] 2 ( 9 2 ), where {BDI DiPP } − and {N^N DiPP } − are the bidentate ligands CH[C(CH 3 )NDipp] 2 − and DippNC 6 H 4 CNDipp − (Dipp=2,6‐ i Pr 2 ‐C 6 H 3 ), are detailed. Complex 6 2 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 7 2 and 8 2 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, C π ) secondary interactions, due to the high positive charge of Ca 2+ which favours electrostatic interactions.