Syntheses, spectroscopy, X-ray and DFT/TDDFT investigations of Rh(η4-cod)-enantiopure aminocarboxylate complexes

Synthesis, X-ray, and Spectroscopic Study of Dissymmetric Tetrahedral Zinc(II) Complexes from Chiral Schiff Base Naphthaldiminate Ligands with Apparent Exception to the ECD Exciton Chirality

“…Transition metal- N , O -chelate complexes exhibit thermally induced structural phase transformation from low temperature crystalline phase (distorted tetrahedral/square planar) to high temperature isotropic liquid phase (regular tetrahedral/square planar). − ,− ,, Differential scanning calorimetry (DSC) has been used to analyze the phenomenon. Thus, DSC heating and cooling curves (first cycle) show both exothermic and endothermic peaks at 173–178 and 125–127 °C, respectively, for Zn-1 R or Zn-1 S (Figure and Table ).…”

“…For more quantitative analysis of the coordination geometry, also in comparison with DFT results discussed in the following, the deviation from tetrahedral to square-planar can be calculated by the dihedral angle θ between the two planes N1–M–O1 and N2–M–O2 (Table ). ,− The value of θ varies from 0 to 90° for square-planar to tetrahedral geometry (not considering the inherent distortion induced by the chelate ring formation) . In addition, θ can be normalized to give the geometric index τ tet‑sq (Scheme ), whose values vary from 1.0 (regular tetrahedral) to 0 (regular square-planar). ,− Also, another geometry index τ 4 (Scheme ) for four-coordinate complexes has been proposed that is similar to Addison and Reedijk’s τ 5 index for five-coordinate complexes .…”

“… ,− The value of θ varies from 0 to 90° for square-planar to tetrahedral geometry (not considering the inherent distortion induced by the chelate ring formation) . In addition, θ can be normalized to give the geometric index τ tet‑sq (Scheme ), whose values vary from 1.0 (regular tetrahedral) to 0 (regular square-planar). ,− Also, another geometry index τ 4 (Scheme ) for four-coordinate complexes has been proposed that is similar to Addison and Reedijk’s τ 5 index for five-coordinate complexes . The values of τ 4 are 1.0 and 0 for perfect tetrahedral and square-planar geometry, respectively.…”

“…Transition metal complexes with chiral N^O-chelate Schiff base ligands are of continued interest − and have been used efficiently as chiral catalysts. , We have recently paid attention to the syntheses, characterization, diastereoselectivity, and molecular structures of four-coordinated nonplanar chiral M­( R - or S -N^O) 2 complexes (N^O = chiral deprotonated Schiff base ligands, M = Rh/Cu/Ni/Zn). − In the formation of tetrahedral or distorted tetrahedral/square-planar complexes containing two chiral N^O-chelate units, diastereoselectivity plays a major role because the resulting C 2 -symmetrical molecules may show preferential chirality at metal center (Λ- or Δ-configuration) induced by the ligand chirality. Thus, use of the enantiopure R - or S -N^O chelates can lead to the formation of diastereomeric pairs of Λ-M- R -N^O and Δ-M- R -N^O (or Δ-M- S -N^O and Λ-M- S -N^O) in a selective way, while the racemic R / S -N^O ligands give all four isomers.…”

Schiff Base in Ketoamine Form and Rh(η4-cod)-Schiff Base Complex with Z′ = 2 Structure from Pairwise C-H···Metallochelate-π Contacts

“…Extended studies on Rh(η 4 -cod)-complexes using chiral-amino acids/-amino alcohols instead of Schiff bases showed the interesting features of coordination and supramolecular chemistry [20,22,23]. In this connection, we have reported the mononuclear neutral [Rh(η 4 -cod)(AA)] (AA = chiral/achiral-amino carboxylato) and the cationic [Rh(η 4 cod)(AOH)](O 2 CMe) (AOH = chiral-amino alcohol) [20][21][22].…”