LIPOPHILIC STRONTIUM AND CALCIUM ALKYLS, AMIDES AND PHENOXIDES - X-RAY STRUCTURES OF THE CRYSTALLINE SQUARE-PLANAR [(TRANS-SR(NR'2)2(MU-1,4-DIOXANE)) INFINITY] AND TETRAHEDRAL [CAR2(1,4-DIOXANE)2], R' = SIME3, R = CH(SIME3)2]

Treatment of pyrophoric strontium powder in tetrahydrofuran with ArOH (Ar = C6H2Bu(t)3-2,4,6) 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(mu-1,4-dioxane)}infinity] 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) angstrom] but tetrahedral for 6 [Ca-C 2.483(5), Ca-O 2.373(4) angstrom] with dioxane as a bridging bidentate 4 or monodentate 6 ligand.