1233486-90-2Relevant academic research and scientific papers
Monomeric and dimeric nickel complexes derived from a pincer ligand featuring a secondary amine donor moiety
Spasyuk, Denis M.,Zargarian, Davit
, p. 6203 - 6213 (2010/08/21)
Reaction of NiBr2(CH3CN)x with the unsymmetrical pincer ligand m-(i-Pr2PO)(CH2NHBn)C 6H4 (Bn = CH2Ph) gives the complex (R,S)-κP,κC,κN-{2-(i-Pr 2PO),6-(CH2NHBn)-C6H3}Ni IIBr, 1, featuring an asymmetric secondary amine donor moiety. Deprotonation of the latter with methyl lithium gave a dark brown compound that could not be characterized directly, but fully characterized derivatives prepared from this compound indicate that it is the LiBr adduct of the 14-electron amido species [κP,κC, κN-{2-(i-Pr2PO),6-(CH2NBn)-C 6H3}Ni], 2. Thus, 2·LiBr reacts with water to regenerate 1, while reaction with excess benzyl or allyl bromide gave the POCN-type pincer complexes 3 and 4, respectively, featuring tertiary amine donor moieties. On the other hand, heating 2·LiBr at 60 °C led to loss of LiBr and dimerization to generate the orange crystalline compound [μN;κP,κC,κN- {2-(i-Pr2PO),6-(CH2NBn)-C6H3}Ni] 2, 5. Solid state structural studies show that 1, 3, and 4 are monomeric, square planar complexes involving one Ni?N interaction, whereas complex 5 is a C2-symmetric dimer involving four Ni?N interactions and a Ni2N2 core featuring a short Ni?Ni distance (2.51 A). Preliminary reactivity tests have shown that 5 is stable toward weak nucleophiles such as acetonitrile but reacts with strong nucleophiles such as CO or 2,6-Me2(C6H3)NC. Reactions with protic reagents showed that phthalimide appears to break the dimer to generate a monomeric species, whereas alcohols appear to leave the dimer intact, giving rise instead to adducts through N...H...O interactions. These ROH adducts of 5 were found to be active precatalysts for the alchoholysis of acrylonitrile with up to 2000 catalytic turnover numbers.
