Synthesis and crystal structure of trimeric sodium 2,2,6,6- tetramethylpiperidide (NaTMP)

The title compound has been synthesised in powder form by two distinct methods: namely by sodiation of the parent amine 2,2,6,6-tetramethylpiperidine with n-butylsodium in a hydrocarbon solvent or by transmetallation from lithium 2,2,6,6-tetramethylpiperidide through the action of sodium t-butoxide in hexane solution. An alternative crystalline specimen suitable for X-ray crystallographic study was grown from a solution which additionally contained n,s-dibutylmagnesium. This study reveals a trimeric molecule of C3h symmetry, its salient feature being a strictly planar (NaN)3 ring. The sterically encumbered amide anions are separated by large N---Na---N bond angles of 143.76(6)°, the bonding in which is slightly asymmetrical (Na---N bond lengths: 2.307(2) and 2.362(2) î..). Discussion focuses on the contrast between the tetrameric ring arrangement of the lithium congener, which was reported several years ago.