Two barium-amide complexes bearing crown-ether-functionalised amidinate and iminoanilide ligands that act as competent precatalysts for the intermolecular hydrophosphination of vinylarenes are presented.
As et of calcium and barium complexes containing the fluoroarylamide N(C 6 F 5 ) 2 À is presented.T hese compounds illustrate the key role of stabilising M···FÀCs econdary interactions in the construction of low-coordinate alkaline earth complexes. The nature of Ca···FÀCb onding in calcium complexes is examined in the light of structural data, bond valence sum (BVS) analysisa nd DFT computations. The 8 2 ), and [Ca{m-OB(CH(SiMe 3 ) 2 ) 2 }{N(C 6 F 5 ) 2 }] 2 (9 2 ), where {BDI DiPP } À and {N^N DiPP } À are the bidentate ligands CH[C(CH 3 )NDipp] 2 À and DippNC 6 H 4 CNDipp À (Dipp = 2,6-iPr 2 -C 6 H 3 ), are detailed. Com-plex 6 2 displays strongB a···FÀCc ontacts at around2 .85 . The calcium complexes feature also very short intramolecular CaÀFi nteratomic distances at around2 .50 .I na ddition, the three-coordinate complexes 7 2 and 8 2 form dinuclear structures due to intermolecular Ca···FÀCc ontacts. BVS analysis shows that Ca···FÀCi nteractions contribute to 15-20 % of the bonding pattern aroundc alcium. Computations demonstrate that Ca···FÀCb onding is mostly electrostatic, but also contains an on-negligible covalentc ontribution. They also suggest that Ca···FÀCa re the strongest amongstt he range of weak Ca···X (X = F, H, C p )s econdary interactions, due to the high positive charge of Ca 2 + which favourse lectrostatic interactions.
Secondary interactions stabilize coordinatively demanding complexes of s-block metals. The structures of potassium fluoroalkoxides that, in addition to intra-and intermolecular K + ···F contacts, also exhibit K + ···C π interactions with tethered π ligands, are reported. A potassium-arene, a rare potassium-alkyne, and a potassium-olefin complex have been prepared by deprotonation of functionalized α,α-bis(trifluoromethyl)alcohols with KN(SiMe 2 R) 2 . They all feature a cuboid K 4 O 4 core with µ 3 -bridging O atoms, and multiple stabilizing K + ···F contacts in the range 2.71-3.33 Å.The potassium-arene complex shows η 2 , η 3 , and η 6 K + ···C π (arene) interactions in the range 3.35-3.47 Å. The potassium-alkyne and potassium-olefin compounds are stabilized by η 2 interactions with the unsaturated carbon-carbon bond, in the range 3.17-3.49 Å and 3.15-3.19 Å, respectively. Comparison with the parent complex devoid of a flanking π ligand illustrates the role of K + ···C π interactions.
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