Issue 6, 2019

PNN′ & P2NN′ ligands via reductive amination with phosphine aldehydes: synthesis and base-metal coordination chemistry

Abstract

Novel PNN′ & P2NN′ ligands based on 2-aminopyridine (APyPNN-R) R = Ph (1a), Cy (1b), iBu (1c), 8-aminoquinoline (AQPNN-R) R = Ph (2a), Cy (2b), iBu (2c), iPr (2d), and 2-picolylamine (P2NN-R) R = Ph (3a), Cy (3b), iBu (3c), have been synthesized via a versatile, one-pot, single-step, reductive amination of tertiary phosphine acetaldehydes with the amine by reaction with STAB (where STAB is sodium(triacetoxy)borohydride). Ligands 1b and 1c bridge between paramagnetic Co(II) and form dimeric complexes Co2Cl4(APyPNN-R)2 (4 and 5) when reacted with cobalt dichloride. Ligands 2a–c coordinate in a tridentate fashion forming chelate complexes MCl2(AQPNN-R) M = Co(II) (6–8), and, for 2d, the Fe(II) complex FeCl2(AQPNN-iPr) (9). A solution magnetic susceptibility value for 9 of 3.9μB is consistent with a monomer–dimer equilibrium. The synthesis of the dimeric complex [FeCl2(AQPNN-Ph)]2 (10) using 2a as well as solid state magnetic susceptibility measurements on 9 and 10 confirm this phenomenon. Ligand 3a coordinates to Fe(II) in an interesting tetradentate fashion despite bearing a tertiary amine moiety giving octahedral FeCl2(P2NN′) (11). All of the metal complexes have been characterized by elemental analysis, paramagnetic 1H NMR spectroscopy, solution magnetic susceptibility, and single crystal X-ray diffraction (XRD).

Graphical abstract: PNN′ & P2NN′ ligands via reductive amination with phosphine aldehydes: synthesis and base-metal coordination chemistry

Supplementary files

Article information

Article type
Paper
Submitted
09 Oct 2018
Accepted
16 Jan 2019
First published
16 Jan 2019

Dalton Trans., 2019,48, 2150-2159

PNN′ & P2NN′ ligands via reductive amination with phosphine aldehydes: synthesis and base-metal coordination chemistry

M. V. Gradiski, B. T. H. Tsui, A. J. Lough and R. H. Morris, Dalton Trans., 2019, 48, 2150 DOI: 10.1039/C8DT04058C

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