Small Steric Variations in Ligands with Large Synthetic and Structural Consequences

Abstract

AbstractThe reaction of ytterbium metal with the aminopyridines2,6‐(diisopropylphenyl)‐[6‐(2,6‐dimethylphenyl)pyridin‐2‐yl]amine (1, Ap′H) and (2,4,6‐trimethylphenyl)‐[6‐(2,4,6‐trimethylphenyl)pyridin‐2‐yl]amine (2, ApMeH) at elevated temperature under vacuum in the presence of mercury gave rise to divalent [Yb(Ap′)2] (3) and trivalent [Yb(ApMe)3] (4), respectively. The single‐crystal X‐ray structure analysis of 3 revealed a four‐coordinate ytterbium atom with two chelating (N,N′) Ap′ ligands inclined to each other at an angle of 126.93(7)° (Cl–Yb–C26). Additionally the complex forms intermolecular CAryl–H agostic interactions [Yb1···C17 2.981(2) Å and Yb1···H17 2.56(3) Å] (all H atoms refined). Complex 4 contains a six‐coordinate ytterbium atom having three chelating (N,N′) ApMe ligands and has distorted octahedral stereochemistry. The reaction of the potassium salts of Ap′H (5) and ApMeH (6) with [YbI2 (thf)4] in thf gave rise to the divalent lanthanoid complexes [Yb(Ap′)2(thf)] (7), and [Yb(ApMe)2(thf)2] (8), respectively, and 7 was also obtained by redox transmetallation/ligand exchange from Yb metal, HgPh2 and Ap′H. X‐ray crystal structures show that 7 and 8 have five‐ and six‐coordinate ytterbium atoms and distorted trigonal‐bipyramidal and distorted octahedral stereochemistry, respectively, the difference in coordination number reflecting the difference in steric demand of the Ap′ and ApMe ligands.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)