title: Unsymmetrical bidentate ligands of alpha-aminoaldimines leading to sterically controlled selectivity of geometrical isomerism in square planar coordination.
abstract: New alpha-aminoaldimines with the formula of Et(2)NCMe(2)CH[double bond, length as m-dash]NR (R = (i)Pr, (t)Bu, Ph) and their dichloro or diacetato complexes of Ni, Pd, Pt are prepared and structurally characterized. A nickel complex is in a distorted tetrahedral configuration, and the Pd and Pt complexes () are of square planar form. The alpha-aminoaldimines can chelate to the metal in a C(2)-unsymmetric bidentate motif through the hetero functionalities of amine and imine, which show comparable trans influence. Square planar organometallic palladium derivatives bearing alpha-aminoaldimines, including Pd-methyl, Pd-acetyl, and Pd-(eta(2)-acetylnorboryl) (), are also synthesized. The latter two species are a result of CO-insertion into Pd-methyl complexes and ensuing norbornene-insertion, respectively. The geometrical isomerism is found in the trans configuration in most studied cases. Such a stereoselectivity results from the thermodynamic stability governed predominantly by steric control. The stereoselectivity is also supported by DFT calculations.
authors.affiliation: Department of Chemistry, National Taiwan University, No 1, Section 4, Roosevelt Road, Taipei 106, Taiwan.
authors.forename: Jen-Jeh
authors.initials: JJ
authors.lastname: Lee
authors.forename: Feng-Zhao
authors.initials: FZ
authors.lastname: Yang
authors.forename: Ya-Fan
authors.initials: YF
authors.lastname: Lin
authors.forename: Ya-Chun
authors.initials: YC
authors.lastname: Chang
authors.forename: Kuo-Hsuan
authors.initials: KH
authors.lastname: Yu
authors.forename: Mu-Chieh
authors.initials: MC
authors.lastname: Chang
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.forename: Yi-Hung
authors.initials: YH
authors.lastname: Liu
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Shiuh-Tzung
authors.initials: ST
authors.lastname: Liu
authors.forename: Jwu-Ting
authors.initials: JT
authors.lastname: Chen