Alkali metal derivatives of sulfinimidamides. Preparation and crystal structures

A series of compounds has been prepared in which the NH proton of the sulfiniminamines Me3SiN=S(R)---NHR′ (R = Ph (mainly) or tBu, R′ = tBu or SiMe3) is replaced by Li, Na, K, Rb, or Cs. The compounds form a series of reagents of increasing reactivity which could be used, for example, to introduce chelating ligands into transition metal complexes. The structures of the compounds have been determined by X-ray diffraction. When there is a phenyl substituent on the sulfur atom, the metal derivatives are isomorphic dimers, involving three fused four-membered rings in a step-shaped structure. The higher the atomic number of the metal, the stronger is the η-coordination of the phenyl group to the metal. With a t-butyl group on the sulfur atom the structures of the lithium derivatives [(Me3SiN=S(tBu)---NR′)Li]2 are different for R′ = SiMe3 and tBu. For the former the step-shaped structure is still present, but the latter forms an eight-membered ring. Although these tBu derivatives are synthesized in diethyl ether, their lithium atoms are not coordinated by donor molecules, in contrast to those in the phenyl-substituted species.