Synthesis, structure and electrochemical behavior of new (PONOP)-P-R (R = Bu-t, Pr-i) pincer complexes of Fe2+,Co2+, Ni2+, and Zn2+ ions

摘要

The coordination chemistry of the M2+ ions of the first-row elements iron, cobalt, nickel and zinc was explored with the ligands (PONOP)-P-R (2,6-(R2PO)(C5H3N), R = Pr-i and Bu-t). Syntheses and characterization of the complexes Fe((PONOP)-P-R)Br-2, Co((PONOP)-P-tBu)Cl-2, Ni((PONOP)-P-R)I-2 and Zn((PONOP)-P-R)I-2 (R= Bu-t, Pr-i) are reported together with the crystal structures of Fe((PONOP)-P-R)Br-2 (R = Pr-i and Bu-t), Co((PONOP)-P-tBu)Cl-2, Co((PONOP)-P-iPr)Cl(mu-Cl)CoCl2(THF), Ni((PONOP)-P-iPr)I-2, Zn((PONOP)-P-iPr)I-2 and of the oxidation product Zn[P-tBu(=O)ONOP(=O)]I-2 resulting from the reaction with oxygen. The electrochemical behavior of the M((PONOP)-P-tBu) X-2 complexes has been investigated in acetonitrile. While the nickel compound is stable, all the complexes are sensitive to dissociation of the (PONOP)-P-R ligand or ligand scrambling in strongly coordinating media. Catalytic activity in formic acid dehydrogenation with TONs up to 1143 has been found for Ni((PONOP)-P-tBu)I-2. (C) 2015 Academie des sciences. Published by Elsevier Masson SAS.