Synthesis and crystal structures of the 15-crown-5 solvates of potassium- and rubidium-2-trimethylsilylamidopyridine

Abstract

Metathesis of “[Li(PyNSiMe 3)(15C5)]” (15C5=15-crown-5 ether) with potassium tert-butoxide or rubidium 2-ethylhexoxide yields the two new amide complexes [{K(PyNSiMe 3)(μ-15C5)} 2] ( 3) and [{Rb(μ-PyNSiMe 3)(15C5)} 2] ( 4). X-ray crystallography reveals 3 to be a ‘slipped’ centrosymmetric dimer, in which the crown ethers exhibit a bridging coordination mode via one crown oxygen from each crown to form a (KO) 2 four-membered ring; the amide adopts a terminal chelating mode. In contrast, 4 is a centrosymmetric amido-bridged dimer with a transoid (RbN) 2 core having additional bonding via bridging pyridyl groups; the crown ethers cap both ends of the dimer.