Lipophilic strontium and calcium alkyls, amides and phenoxides; X-ray structures of the crystalline square-planar [{trans-Sr(NR′2)2(µ-1,4-dioxane)}∞] and tetrahedral [CaR2(1,4-dioxane)2]; R′= SiMe3, R = CH(SiMe3)2]

Abstract

Treatment of pyrophoric strontium powder in tetrahydrofuran with ArOH (Ar = C₆H₂Bu^t₃-2,4,6) or HNR′₂ at ambient temperature affords crystalline [Sr(OAr)₂(THF)₄] or [Sr(NR′₂)₂(THF)₂]3, respectively, and 3 with 1,4-dioxane yields crystalline [{trans-Sr(NR′₂)₂(µ-1,4-dioxane)}∞]4; co-condensation of calcium vapour and RBr in THF at 77 K affords [CaR₂(THF)₃]5, which with 1,4-dioxane gives [CaR₂(1,4-dioxane)₂]6; X-ray structures reveal the alkaline earth metal environment to be square-planar for 4[Sr-N 2.449(7), Sr-O 2.533(9)Å] but tetrahedral for 6[Ca-C 2.483(5), Ca-O 2.373(4)Å] with dioxane as a bridging bidentate 4 or monodentate 6 ligand.