A readily accessible chiral nnn pincer ligand with a pyrrole backbone and its Ni(II) chemistry

• Verfasst von: Wenz, Jan [VerfasserIn]
• Verfasst von: Wadepohl, Hubert [VerfasserIn]
• Verfasst von: Gade, Lutz H. [VerfasserIn]
• Titel: A readily accessible chiral nnn pincer ligand with a pyrrole backbone and its Ni(II) chemistry
• Titelzusatz: syntheses, structural chemistry, and bond activations
• Verf.angabe: Jan Wenz, Alexander Kochan, Hubert Wadepohl, and Lutz H. Gade
• E-Jahr: 2017
• Jahr: 20 March 2017
• Umfang: 13 S.
• Fussnoten: Gesehen am 26.11.2018
• Titel Quelle: Enthalten in: Inorganic chemistry
• Ort Quelle: Washington, DC : American Chemical Society, 1962
• Jahr Quelle: 2017
• Band/Heft Quelle: 56(2017), 6, Seite 3631-3643
• ISSN Quelle: 1520-510X
• DOI: doi:10.1021/acs.inorgchem.7b00077
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1584441526

Abstract

A new class of chiral C2-symmetric N-donor pincer ligands, 2,5-bis(2-oxazolinyldimethylmethyl)pyrroles (PdmBox)H, was synthesized starting from the readily available ethyl 2,2-dimethyl-3-oxobutanoate (1). The synthesis of the ligand backbone was achieved by oxidative enole coupling with CuC12 followed by Paal-Knorr-type pyrrole synthesis. The corresponding protioligands (RPdmBox)H (R = iPr: 5a; Ph: 5b) were obtained by condensation with amino alcohols and subsequent zinc-catalyzed cyclization. Reaction of the lithiated ligands with [NiCl2(dme)] yielded the corresponding square-planar nickel(II) complexes [(RPdmBox)NiCl] (6a/b). Salt metathesis of 6a with the corresponding alkali or cesium salts in acetone led to the formation of air- and moisture-stable [(iPrPdmBox)NiX] (X = F (7), X = Br (8), X = I (9), X = N3 (10), X = OAc (11). Furthermore, the conversion of [(iPrPdmBox)NiF] (7) with hydride transfer reagents such as PhSiH3 led to the stable hydrido species [(iPrPdmBox)NiH] (27), the stoichiometric transformations of which were studied. Treatment of 6a with organometallic reagents such as ZnEt2, PhLi, PhC≡CLi, NsLi, or (4FBn)2Mg(THF)2 gave the corresponding alkyl, alkynyl, or aryl complexes. The availability of the new nonisomerizable PdmBox pincer ligands allowed the comparative study of their ligation to square-planar complexes as helically twisted spectator ligands as opposed to the enforced planar rigidity of their iso-PmBox analogues and the way this influences the reactivity of the Ni complexes.