Redoxstabilität in der σ‐Organoübergangsmetallchemie

Abstract

Starting from usual principles of redox stability in coordination chemistry and from the donor‐acceptor characteristic of organyl ligands the review covers the redox behaviour of transition metals in the coordination with simple carbanions. The main topics are the stabilization of high oxidation states and the electron variability in s̀‐organyl transition metal complexes as well as the stabilization of low oxidation states, especially in electron rich phenyl complexes by coordination of lithium ions to the transition metal.

Unmasking the constitution and bonding of the proposed lithium nickelate “Li3NiPh3(solv)3”: revealing the hidden C6H4ligand

“…[7][8][9][10][11] In parallel, s-organyl complexes of rst row transition metals (Ni, Fe and Co) were synthesised by Taube and others and transformed into intriguing complexes again bearing organolithium ligands. [12][13][14][15][16][17][18][19] Finally, there is also the nding that organolithium reagents may behave as oxidants in certain cases. 20 Amongst these complexes, our attention was drawn to "Li 3 -NiPh 3 (solv) 3 ", which was proposed to adopt a planar geometry based exclusively on 13 C NMR spectroscopy (Scheme 1).…”

“…20 Amongst these complexes, our attention was drawn to "Li 3 -NiPh 3 (solv) 3 ", which was proposed to adopt a planar geometry based exclusively on 13 C NMR spectroscopy (Scheme 1). 13,16,19,21 Although it seems to have been almost completely overlooked since its publication in 1979, the implications of this purported homoleptic phenyllithium complex are numerous. First, without crystallographic studies it is not clear whether the "Li 3 NiPh 3 (solv) 3 " complex contains the extremely rare hexagonal planar coordination geometry recently reported by the Crimmin group for a Pd complex.…”

“…7–11 In parallel, σ-organyl complexes of first row transition metals (Ni, Fe and Co) were synthesised by Taube and others and transformed into intriguing complexes again bearing organolithium ligands. 12–19 Finally, there is also the finding that organolithium reagents may behave as oxidants in certain cases. 20…”

Low-Valent Transition Metalate Anions in Synthesis, Small Molecule Activation, and Catalysis

“…In further investigations, Campos and Hevia revisited the structure of the homoleptic lithium nickelate “Li 3 NiPh 3 (solv) 3 ”, reported by Taube and co-workers over four decades ago. − Based exclusively on its 13 C NMR spectroscopic characterization, this species was thought to adopt an extremely rare hexagonal planar coordination environment around the Ni atom which would be composed of three Li + cations and three phenyl ligands. The two initial synthetic routes proposed by Taube were reexamined.…”

“…None of these experiments suggested the presence of a planar complex. While treatment of the Ni(0) precursor with donor-free PhLi (5 equiv) led to the formation of a deep red solution, as previously described by Taube, NMR spectroscopic characterization of this solution did not match the previous reports. − The choice of solvent influences the type of product obtained. If the reaction is carried out in THF, the major product will correspond to the nickelate 627 .…”