Monomeric Three- and Four-Coordinate Magnesium Amides

Treatment of
bis(bis(trimethylsilyl)amido)bis(tetrahydrofuran)magnesium
with 2 equiv of 2,3,5-collidine, 2-picoline,
4-picoline, or 3,5-lutidine in benzene at room temperature for 18 h
afforded
bis(bis(trimethylsilyl)amido)bis(2,3,5-collidine)magnesium (80%),
bis(bis(trimethylsilyl)amido)bis(2-picoline)magnesium
(70%), bis(bis(trimethylsilyl)amido)bis(4-picoline)magnesium (48%),
or
bis(bis(trimethylsilyl)amido)bis(3,5-lutidine)magnesium
(58%), respectively. Sublimation of
bis(bis(trimethylsilyl)amido)bis(2,3,5-collidine)magnesium
(90 °C, 0.1 mmHg)
and
bis(bis(trimethylsilyl)amido)bis(2-picoline)magnesium
(115 °C, 0.1 mmHg) afforded colorless crystals of
bis(bis(trimethylsilyl)amido)(2,3,5-collidine)magnesium
(53%) and
bis(bis(trimethylsilyl)amido)(2-picoline)magnesium (46%), respectively. Treatment of
bis(bis(trimethylsilyl)amido)bis(tetrahydrofuran)magnesium
with
1 equiv of 2,6-lutidine in benzene at room temperature for 18 h
afforded
bis(bis(trimethylsilyl)amido)(2,6-lutidine)magnesium (56%). The X-ray crystal structures of
bis(bis(trimethylsilyl)amido)bis(2,3,5-collidine)magnesium,
bis(bis(trimethylsilyl)amido)bis(4-picoline)magnesium,
bis(bis(trimethylsilyl)amido)(2-picoline)magnesium,
and
bis(bis(trimethylsilyl)amido)(2,6-lutidine)magnesium
were determined.
Bis(bis(trimethylsilyl)amido)bis(2,3,5-collidine)magnesium crystallizes in the monoclinic space group
C2/c with a = 11.8410(7) Å,
b = 20.5413(13)
Å, c = 15.5746(10) Å, β = 93.072(2)°,
V = 3782.8(4) Å3, and Z =
4.
Bis(bis(trimethylsilyl)amido)bis(4-picoline)magnesium crystallizes in the triclinic space group P1̄
with a = 10.4914(6) Å, b =
11.8504(6) Å, c = 15.4546(9)
Å, α = 99.3180(10)°, β = 98.4180(10)°, γ =
111.5320(10)°, V = 1718.8(2) Å3,
and Z = 2.
Bis(bis(trimethylsilyl)amido)(2-picoline)magnesium crystallizes in the orthorhombic
space group Pbca with a = 18.4536(14) Å,
b =
15.2326(9) Å, c = 20.614(2) Å, V
= 5794.6(7) Å3, and Z = 8.
Bis(bis(trimethylsilyl)amido)(2,6-lutidine)magnesium crystallizes in the orthorombic space group Pbca
with a = 18.6221(13) Å, b =
15.3236(9) Å, c =
20.9085(14) Å, V = 5966.4(7) Å3,
and Z = 8. Application of the these complexes as
source compounds in
chemical vapor deposition processes is discussed.