Lewis Acidic Cationic Strontium and Barium Complexes

Lewis acidic (BDI)Ae+ cations of the heavier metals Sr and Ba, which are not stabilized by polar solvents, have been obtained double deprotonation (BDI)H2+ with either SrN’’2 or BaN’’2; BDI = HC[C(Me)N(DIPP)]2, DIPP 2,6-diisopropylphenyl, Ae alkaline earth, N’’ N(SiMe3)2. Due to clathrate formation [(BDI)Ae+][B(C6F5)4−] could be crystallized, but pyrene addition gave crystalline [(BDI)Ae+ ⋅ pyrene][B(C6F5)4−] was structurally characterized for Mg, Ca, Sr, Ba. (R2N)Ae+ Ba were reaction Ae(NR2)2 [Ph3C+][B(C6F5)4−] [PhNMe2H+][B(C6F5)4−]. Following complexes characterized: [N’’Ba+ (tol)2][B(C6F5)4−], [N*Sr+ PhNMe2][B(C6F5)4−], [N*Ba+ tol][B(C6F5)4−] C6H6][B(C6F5)4−]; tol toluene N* N(SiiPr3)2. DFT calculations show that Sr⋅⋅⋅PhNMe2 coordination is preferred over Sr⋅⋅⋅toluene bonding. The can used as Brønsted bases (reaction (BDI)H (BDI)Ae+) may useful precursors a variety base-free RAe+ cations. calculations, limited monomeric model systems including B(C6F5)4− (ωB97XD/def2tzvpp//ωB97XD/def2svp), there negligible electron transfer from ligands Ae2+ cation. Electrostatic attraction originates charge-induced polarization -electron density in ligands.