Coordination behavior of the (diphenylphosphanyl)[α-(2-pyridyl) benzyl]amide anion toward lithium and zinc cations

Article abstract of DOI:10.1002/ejic.201000039

A two-step synthesis allows the preparation of [α-(2-pyridyl)benzyl] amine (1) in good yield. Phosphanylation in the presence of triethylamine gives (diphenylphosphanyl)[α-(2-pyridyl)benzyljamine (2), which crystallizes as a racemate in the centrosymmetric triclinic space group P1. The P-N bond lengths exhibit an average value of 168.3 pm. Lithiation of 2 with n-butyllithium yields dimeric semi(tetrahydrofuran)lithium (diphenylphosphanyl)[α-(2- pyridyl)benzyl]amide (3) with the lithium atoms in different environments. One Li atom, is in a distorted, tetrahedral environment and the other in a trigonal-planar coordination sphere with bridging amide moieties (av. Li-N 201.8, Li-O 192.4 pm). Zincation of 2 with dimethylzinc leads to the formation of dimeric methylzinc (diphenylphosphanyl)[α-(2-pyridyl)benzyr]amide (4) with a central six-membered (ZnNP)₂ ring in a boat conformation (av. Zn-N 201.8, Zn-P 245.9 pm). The endocyclic P-N bonds are rather short (av. value 162.7 pm).