579504-99-7Relevant academic research and scientific papers
Aminoalkyl-substituted indenyl-nickel compounds: Tuning reactivities as a function of the pendant, hemilabile moiety
Groux, Laurent F.,Zargarian, Davit
, p. 3124 - 3133 (2008/10/08)
Indenyl ligands bearing three different aminoalkyl substituents have been used to prepare the complexes (IndNR2)Ni(PPh3)Cl (IndNR2 = 2-(1-indenylmethyl)pyridine (1), N-(1-indenylethyl)pyrrolidine (2), and N-(1-indenylethyl)diisopropylamine (3)). The solution NMR spectra of complexes 1 and 2 point to the existence of a dynamic process involving the reversible coordination of the pendant amine moieties to the Ni center, but no N-Ni interaction is evident in complex 3. Abstraction of Cl- from the neutral precursors 1-3 yields the corresponding cationic derivatives [(η3:η1-IndNR2)Ni(PPh3)] + (4-6) wherein the amino tether is chelated to the nickel center. Complexes 1-5 have been isolated and fully characterized by multinuclear NMR spectroscopy and, in the case of 1 and 4, by single-crystal X-ray diffraction studies. The isolation of complex 6 is complicated by its partial conversion to the bis(phosphine) derivative [{η3:η0-IndCH2CH2N(i-Pr) 2}Ni(PPh3)2]+ (7). Studies on the displacement of the chelating amine moiety in 4 and 5 by dppe, PPh3, and pyridine showed the pyridine moiety to be the least labile. Cyclic voltammetry studies have shown that the reduction potentials of the complexes vary as a function of the Ni-N interaction, the complexes bearing the NMe2 moieties showing the strongest resistance to reduction. Olefin polymerization reactions also showed that the nature of the N-moiety has a considerable influence on the catalytic reactivity of the cationic complexes.
