Lithium butyl (2.50 M in hexanes, Aldrich)
tris(2-aminoethyl)amine (TREN) (Aldrich, distilled)
THF (distilled from K)
tert-butylchlorodimethylsilane (TBSCl, sublimed)
pentane (distilled from Na/K)

Lithium butyl (98.5 cm³, 2.50 M in hexanes, 3 equivalents) was added dropwise at -50^oC to a solution of distilled tris(2-aminoethyl)amine (TREN) (12 g, 0.082 mol) in dry tetrahydrofuran (200 cm³). The mixture was stirred for 30 min. during which time it was allowed to warm to 0^oC. The solution was then cooled to -50^oC and a solution of sublimed tert-butylchlorodimethylsilane (37.1 g, 0.246 mol, 3 equivalents) in tetrahydrofuran (40 cm³) was added over a period of 5 min. The mixture was stirred for 30 min. with slow warming to 0^oC. After evaporation of volatiles under reduced pressure at ambient temperature, a liquid nitrogen cooled probe was inserted into the flask in order to facilitate removal of the last traces of solvent in vacuo. The oily residue was extracted into pentane (3 x 50 cm³) and filtered. If required, this solution may be evaporated to give virtually pure H₃(NN'₃). Lithium butyl (98 cm³, 2.5 M in hexanes) was added dropwise to the combined extracts at -80^oC. The mixture was allowed to warm slowly to -30^oC and was stirred for a further 15 minutes. The solution was then cooled to -50^oC and tetrahydrofuran (18 cm³, 3 equivalents) was added. The white microcrystalline solid which precipitated was isolated by cannula filtration and dried in vacuo (46 g, 78%).

Using pure TBSCl is important. The material from Aldrich is frequently a liquid. The Fluka material is a solid and usually good enough as supplied. If you need to sublime/distil it be careful not to pump the stuff away into a cold trap. It is a pretty volatile solid. We do the sublimation in a closed systen, making sure the chamber is frequently re-evacuated. The amount of THF present in the sample is frequently less than 3 equivalents. The exact figure is determined by NMR. The solid is stable for months at room temperature in the absence of air.

¹H NMR (293 K d₈-toluene) 3.52 (m, 12H, THF), 3.15 (t, 6H, CH₂), 2.35 (t, 6H, CH₂), 1.37 (m, 12H, THF), 1.01 (s, 27H, Bu^t), 0.05 (s, 18H, SiMe₂).

P. Roussel, N. W. Alcock, and P. Scott, Inorganic Chemistry, 1998, 37, 3435

Cummins, C. C.; Lee, J.; Schrock, R. R.; Davis, W. M. Angew. Chem., Int. Ed. Eng., 1992, 31, 1501. Duan, Z.; Verkade, J. G. Inorg. Chem., 1995, 34, 1576.