New Perspectives for Aminotroponiminates: Coordination Chemistry, Redox Behavior, Cooperativity, and Catalysis

Abstract

Aminotroponiminates (ATIs) are monoanionic ligands with an N,N‐binding pocket and a rigid, planar, unsaturated, C7‐ring as a ligand backbone. Recent findings show that this ligand backbone can play an active role in coordination chemistry, redox reactions, and ligand‐centered reactivity of ATI complexes. Based on these results, ATIs have been recognized as redox‐active and cooperative ligands, which has implications for existing and potential future applications of ATI compounds in synthesis, catalysis, and materials science. The catalytic applications of ATI complexes are summarized in this Microreview, including results from the fields of hydroamination, epoxidation, cyanosilylation, ε‐caprolactone‐, olefin‐, epoxide‐, and epoxide/CO2 (co‐)polymerization as well as electron transfer catalysis. Furthermore, recent advances in the use of ATI ligands for stabilizing heavy analogs of carbon oxo compounds are showcased.

Alkali‐Metal Aminotroponiminates: Selectivities and Equilibria in Reversible Radical Coupling of Delocalized π‐Electron Systems

“…In these calculations, the coordination spheres of the metal centers were saturated by THF ligands. Although bonding between the π‐electron cloud of the C 7 ligand backbone and the metal center plays an important role in diamagnetic alkali‐metal ATIs, DFT calculations suggest that this is not the case for the radical intermediates discussed in this work (for details see the Supporting Information). In agreement with the results from EPR spectroscopy, the spin density in the calculated radical intermediates 1‐Li‐int and 3‐Li‐int is delocalized through the π‐electron system of the ATI ligands (Figure , Table ).…”

Ligands with Two Monoanionic N,N‐Binding Sites: Synthesis and Coordination Chemistry

“…Aminotroponimines belong to an interesting class of ligands, which exhibit a1 0-electron p-systemd elocalizedo ver seven carbon and two nitrogen atoms, and recently experienced a renaissance in coordination chemistry. [107] Their macrocyclic (tropocoronands) or N-bridged relatives have been introduced by the groupso fL ippard [108] and Roesky, [109] respectively,b ut after ap eriod of intense research, [110] interest in this compound class faded almostc ompletely.T he synthesis of bis(aminotroponimine)s resembles to ac ertain extent the synthesis of bis(b-diimine)s( see above). Activation of aminotropones (route i)o rb is(aminotropone)s (route ii) [108] by Meerwein'ss alt and subsequent treatment with ap rimary diamine gives rise to the relatedN -bridgedo rm acrocyclic bis(aminotroponimine)s, respectively (Scheme 12).…”

Dimerization of 2-[(2-((2-aminophenyl)thio)phenyl)amino]-cyclohepta-2,4,6-trien-1-one through hydrogen bonding, C19H16N2OS

“…The C-S bond lengths are identical within limits of error and virtually identical to those in the free 2,2′-thiodianiline substituent [1.772(2) Å][7][8][9][10][11][12]29] In the solid state, the title compound is linked via two N-H• • • O hydrogen bonds, forming dimers with C i symmetry (see the…”

“…Table 1 contains crystallographic data and Table 2 contains the list of the atoms including atomic coordinates and displacement parameters. Bruker [1,2], SHELX [3,4], Mercury [5], Olex2 [6] Comment Aminotroponiminates (ATIs) are monoanionic ligands with applications in fields such as hydroamination and polymerization catalysis and the stabilization of low-valent main group species [7][8][9][10][11][12]. Their potential to act as redox-active ligands has recently been demonstrated [13][14][15].…”