Ligand dynamics in pentacoordinate copper(I) and zinc(II) complexes

Comparative Activities of Nickel(II) and Zinc(II) Complexes of Asymmetric [NN′O] Ligands as 26S Proteasome Inhibitors

“…The metal centers also dictate the preferential cis or trans orientation of equivalent phenolates and other donor sets in vicinal ligands, with 3d 5 high spin ions40 displaying a cis-arrangement and 3d 6 low spin and 3d 7 high spin ions36,37 supporting a trans -orientation. Species 1 reinforces38 the notion of an all-trans mode for 3d 8 configurations, whereas 2 seems to fall within other 3d 10 configurations26,41,42,43 lacking a clear preference. Another remark is that while most of the O phenolate bond lengths for 1 and 2 are comparable at 2.02-2.05 Å, one of the Zn-O phenolate bonds for 2 is elongated reaching ca .…”

“…The nickel species yielded broad and ill-defined 1 H-NMR results in agreement with the paramagnetic nature of a 3d 8 high spin species. A detailed investigation of the ligand dynamics38 of 1 and its gallium-containing counterpart26 using VT-NMR properties is under development.…”

“…The energy difference between the two structures is 3.7 kcal/mol, clearly favoring 1 as the lowest energy state. Interestingly, we recently compared similar isomers with unsubstituted phenolate rings38 and the energy difference was a mere 1.1 kcal/mol. It can be suggested that the iodine substituents play a significant role in favoring 1 instead of 1' .…”

Highly Efficient Copper‐Mediated Atom‐Transfer Radical Addition (ATRA) in the Presence of Reducing Agent

“…The resonances for H 2 The broadened resonances in the solution 1 H NMR spectra of Cu I (TPMA)Br (260-298 K) in (CD 3 ) 2 CO could be induced by the occurrence of the fluxional processes such as the ligand dissociation, which are well known in copper(I) complexes with nitrogen-containing ligands. [57][58][59] In the case of the tetradentate TPMA ligand, the dissociation and association of the pyridine nitrogen atoms has been proposed in the previous studies, as well as the possibility for the formation of dimers in which each copper(I) ion is ligated with two pyridine nitrogen atoms and one tertiary amine nitrogen atom of a single TPMA and one pyridine nitrogen atom of the second adjacent TPMA ligand. [60,61] The 1 H NMR spectra of Cu I (TPMA)Br in Figure 2 are not consistent with the dimer formation because such coordination environment would result in two chemically inequivalent methylene groups.…”

Configurational landscape of chiral iron(ii) bis(phosphane) complexes

“…These descriptors are used to define the absolute configuration of dissymmetric pentacoordinated complexes: ∆ is used when the rings describe the right-handed helix as the complex is viewed along the C2 axis, and Λ is used when they describe a lefthanded helix. 68,69 Since the (R,R)-and (S,S)-Me-DuPhos ligands are chiral, in principle, both ∆ and Λ diastereomers of each ironbis(phosphane) complex could be formed. The structure of each bis(phosphane) could facilitate the preferential formation of one diastereomer, and even though the stereocenters of the phosphane lie far from the iron atom, the formation of only one diastereomer seems be favoured.…”