N-silylated benzamidines: versatile building blocks in main group and coordination chemistry

Abstract

The main group and coordination chemistry of N-silylated benzamidines, RC 6H 4C(NSiMe 3)[N(SiMe 3) 2], and the corresponding anions, [RC 6H 4C(NSiMe 3) 2] −, is reviewed. Lithium and sodium salts of the type M[RC 6H 4C(NSiMe 3) 2] (MLi, Na) are easily accessible via addition of LiN(SiMe 3) 2 or NaN(SiMe 3) 2 to various substituted benzonitriles. Subsequent reactions with Me 3SiCl lead to the fully silylated benzamidine derivatives. Both the neutral species and the anions are highly useful precursors in main group chemistry, for example, for the preparation of various inorganic heterocycles. They also react with transition metal halides to give in most cases benzamidinato chelate complexes containing planar, four-membered MNCN rings. Other reaction pathways include the formation of transition metal amido, imido, nitrido, and hydrazido complexes. In some cases hydrolytic cleavage of one or more SiN bonds is observed. The silylated benzamidinate anions [RC 6H 4C(NSiMe 3) 2] − are especially useful as novel observer ligands for f-elements. They form low-coordinate, hydrocarbon-soluble complexes with lanthanide and actinide elements.