587848-54-2Relevant articles and documents
Neutral β-diketiminato nickel(II) monoalkyl complexes
Wiencko, Heather L.,Kogut, Elzbieta,Warren, Timothy H.
, p. 199 - 208 (2008/10/08)
Reaction of NiCl2(2,4-lutidine)2 (1) with Tl[Me2NN] (3) in THF results in the transmetallation of the β-diketiminate ligand from which the tetrahedral {[Me2NN]NiCl}2 (4) was isolated in poor yield. After filtration of the TlCl formed in the reaction between 1 and 3 in THF, addition of Grignard reagents RMgBr results in the isolation of monoalkyl complexes [Me2NN]Ni(R)(2,4-lutidine) (R=Me (5), Et (6), Pr (7)) in 40-70% yield. X-ray structures 5-7 of show these monoalkyls to be somewhat crowded, square planar species. NMR studies of the diamagnetic monoalkyl complexes show that lutidine dissociation/reassociation occurs on the NMR timescale at room temperature. In ethyl and propyl complexes 6 and 7, an equilibrium between the four coordinate [Me2NN]Ni(R)(2,4-lutidine) and a lutidine-free species [Me2NN]Ni(R) (R=Et, Pr) is observed. Broad, high-field 1H resonances consistent with the presence of β-H agostic alkyl groups are observed for the base-free species. The observation of two broad upfield 1H NMR signals at δ -2.7 and -7.3 ppm for the base-free Ni-propyl complex suggests a mixture of primary and secondary β-agostic isomers that reversibly interconvert by β-H elimination/reinsertion. Ethylene slowly inserts into monoalkyls 5-7 demonstrate to give highly branched ethylene oligomers.
