Scandium SALEN complexes bearing chloro, aryloxo, and hydroxo ligands.

Heteroleptic amide complexes (SALEN)Sc[N(SiHMe(2))(2)] (SALEN = Salen(tBu,tBu), Salcyc(tBu,tBu), or Salpren(tBu,tBu) if not stated differently) were examined as synthesis precursors according to silylamine elimination reactions. Treatment of (SALEN)Sc[N(SiHMe(2))(2)] with H(2)O or phenols (HOAr(R,R); R = tBu, iPr) afforded complexes (SALEN)Sc(mu-OH) and (SALEN)Sc(OAr(R,R)), while chloro exchange products were formed from the respective reactions with NH(4)Cl or AlMe(2)Cl. Such complexes (SALEN)Sc(mu-Cl) and (SALEN)ScCl(thf) were also obtained by utilizing alternative synthesis protocols, allowing for controlled donor absence and presence. Heteroleptic amide precursors Sc(NiPr(2))(2)(mu-Cl)(thf) and ScN(SiHMe(2))(2)(mu-Cl)(thf) readily undergo amine elimination reactions with H(2)SALEN derivatives to form the corresponding chloride complexes. Spectroscopic and X-ray structural data of the heteroleptic scandium complexes revealed an exclusive intramolecular tetradentate coordination mode of the SALEN ligands independent of the SALEN ligand bite angle and the nature of the "second" ligand (chloro, amido, aryloxo, hydroxo). The coordination of the SALEN ligands is rationalized on the basis of (a) the displacement d of the metal center from the [N(2)O(2)] least-squares plane, (b) the dihedral angle alpha between the phenyl rings of the salicylidene moieties, and (c) the angle beta = Ct-Ln-Ct (Ct = centroid of the phenyl rings) in the case of strongly twisted ligands.