Synthesis and structural characterization of barium complexes containing the bulky amino-siloxide hybrid ligand −OSi(tBu)2((CH2)3NMe2)

The bulky amino-siloxide hybrid ligand −OSi(tBu)2((CH2)3NMe2) allows isolation of dinuclear, hydrocarbon-soluble barium complexes. The structures of two mono(ligand) complexes, {Ba[OSi(tBu)2((CH2)3NMe2)][N(SiMe3)2]}2 (1) and {Ba[OSi(tBu)2((CH2)3NMe2)][N(SiMe3)2][THF]}2 (3), have been determined by X-ray diffraction (crystal data: 1, monoclinic, C2/c, a = 20.451(4) Å, b = 14.277(3) Å, c = 22.258(5) Å, β = 101.14(2)°, V = 6376.1(2) Å3, Z = 4 (dimers), R = 0.069,Rw = 0.100; 3, monoclinic, P21/c, a = 11.025(4) Å, b = 22.414(3) Å, c = 13.925(2) Å, β = 104.05(2)°, V = 3338.0(1) Å3, Z = 2 (dimers), R = 0.090, Rw = 0.117). Complex 1 is stable towards ligand redistribution in d6-benzene or d8-toluene, but in d8-THF both 1 and 3 exist in equilibrium with the ligand redistribution products Ba[N(SiMe3)2]2[THF]2 and Ba[OSi(tBu)2((CH2)3NMe2)]2 (2). Complex 2 was prepared independently and appears to exist as a monomer–dimer equilibrium in d6-benzene solution. Complexes 1–3 do not sublime when heated under high vacuum (200 °C, 10−4Torr). Keywords: siloxide, barium, synthesis, structure, bis(trimethylsilyl)amide.