A Novel Group of Alkaline Earth Metal Amides:  Syntheses and Characterization of M[N(2,6-ⁱPr₂C₆H₃)(SiMe₃)]₂(THF)₂ (M = Mg, Ca, Sr, Ba) and the Linear, Two-Coordinate Mg[N(2,6-ⁱPr₂C₆H₃)(SiMe₃)]₂

Novel alkaline earth metal aryl-substituted silylamides were prepared using alkane (Mg) and salt elimination reactions (Mg, Ca, Sr, and Ba). The salt elimination regime involved the treatment of the alkaline earth metal iodides with 2 equiv of the respective potassium amide KNDiip(SiMe₃), (Diip = 2,6-i-Pr₂C₆H₃). The organomagnesium source for the alkane elimination was (ⁿBu/^sBu)₂Mg. All compounds were characterized using ¹H, ¹³C NMR, and IR spectroscopy, in addition to X-ray crystallography (except Mg[NDiip(SiMe₃)]₂THF₂). Crystal data with Mo Kα (λ = 0.710 73 Å) are as follows:  Mg[NDiip(SiMe₃)]₂, 1, a = 9.4687(6) Å, b = 9.6818(6) Å, c = 17.9296(1) Å, α = 96.487(1)°, β = 94.537(1)°, γ = 89.222(1)°, V = 1608.8(2) ų, Z = 2 (two independent molecules), triclinic, space group P1̄, R1 (all data) = 0.0508; ⁿBuMg[NDiip(SiMe₃)]THF₂, 2, a = 9.5413(1) Å, b = 16.493(2) Å, c = 9.8218(1) Å, β = 108.149(2)°, V = 1468.7(4) ų, Z = 2, monoclinic, space group P2₁, R1(all data) = 0.1232; Ca[NDiip(SiMe₃)]₂THF₂, 4, a = 9.7074(1) Å, b = 20.9466(4) Å, c = 21.6242(3) Å, α = 73.573(1)°, β = 78.632(1)°, γ = 89.621(1)°, V = 4129.1(1) ų, Z = 4 (two independent molecules), triclinic, space group P1̄, R1 (all data) = 0.0902; Sr[NDiip(SiMe₃)]₂THF₂, 5, a = 20.5874(5) Å, b = 9.8785(2) Å, c = 20.8522(5) Å, β = 102.035(2)°, V = 4147.6(2) ų, Z = 4 (two independent molecules), monoclinic, space group P2/n, R1 (all data) = 0.0756; Ba[NDiip(SiMe₃)]₂THF₂, 6, a = 20.5476(2) Å, b = 10.0353(2) Å, c = 20.9020(4) Å, β = 101.657(1)°, V = 4221.0(1) ų, Z = 4 (two independent molecules), monoclinic, space group P2/n, R1 (all data) = 0.0573.