Diastereopure Fe(II) and Zn(II) Complexes Derived from a Tridentate N,N‘,N-Bis(methyl-l-prolinate)-Substituted Pyridine Ligand

Abstract

A series of mononuclear iron(II) and zinc(II) complexes of the new chiral Py(ProMe) 2 (5) are reported. They all show a meridional NN′N coordination of the Py(ProMe) 2 ligand. The bis-chloride derivatives 1 and 2 represent neutral isostructural five-coordinated complexes with a distorted geometry around the metal center. Unusual sevencoordinate iron(II) complexes 3 and 4 having a pentagonal bipyramidal geometry were obtained using weakly coordinating triflate anions. The reaction of Zn(OTf) 2 with the Py(ProMe) 2 ligand afforded complex 5 with a distorted octahedral geometry around the zinc center. All complexes were formed as single diastereoisomers. In the case of complexes 3−5, the oxygen atoms of both carbonyl groups of the ligand are also coordinated to the metal. The stereochemistry of the coordinated tertiary amine donors in complexes 3−5 is of opposite configuration as in complexes 1 and 2 as a result of the planar penta-coordination of the ligand Py(ProMe) 2 . Complexes 1, 2, and 5 have an overall Λ-configuration at their metal center, while the Fe(II) ion in complexes 3 and 4 has the opposite ∆-configuration (crystal structures and CD measurements). The magnetic moments of iron complexes 1, 3, and 4 correspond to that of high-spin d 6 Fe(II) complexes. The solution structures of complexes 1−5 were characterized by means of UV−vis, IR, conductivity, and CD measurements and their electrochemical behavior. These studies showed that the coordination environment of 1 and 2 observed in the solid state is maintained in solution. In coordinating solvents, the triflate anion (3, 5) or water (4) co-ligands of complexes 3−5 are replaced by solvent molecules with retention of the original pentagonal bipyramidal and octahedral geometry, respectively.

A Chemical Device That Exhibits Dual Mode Motions: Dynamic Coupling of Amide Coordination Isomerism and Metal‐Centered Helicity Inversion in a Chiral Cobalt(II) Complex

“…[21] [14] The paramagnetic 1 H NMR spectrum of [CoA C H T U N G T R E N N U N G (H 2 L1)A C H T U N G T R E N N U N G (CF 3 SO 3 )A C H T U N G T R E N N U N G (H 2 O)]-A C H T U N G T R E N N U N G (CF 3 SO 3 )·A C H T U N G T R E N N U N G (CHCl 3 ) in CD 3 CN/CDCl 3 (1/9) revealed the presence of three different species, two of which have independent C 2 -symmetrical patterns (see Figure S5 in the Supporting Information). One of these species has an NMR spectrum similar to that observed in CD 3 CN, in which none of the CF 3 SO 3 À ion coordinates directly to the Co II center.…”

Mononuclear diastereopure non-heme Fe(II) complexes of pentadentate ligands with pyrrolidinyl moieties: Structural studies, and alkene and sulfide oxidation

“…1) built from pyridyl and prolinate ester building blocks. In these complexes, a g 3 -meridional NN 0 N coordination of the Py(ProMe) 2 ligand was observed, which in combination with strongly coordinating anions yielded penta-coordinate iron(II) complexes [14]. In the presence of weakly coordinating anions, 1 acts as a pentadentate ligand with additional coordination of the carbonyl oxygen atoms of both ester moieties, forming iron(II) complexes with a sevencoordinate geometry.…”

“…alkanes and alkenes, and eventually sulfide substrates. Initial oxidation tests in acetonitrile under ambient conditions using 6 In the case where octahedral metal complexes of penta-coordinate ligands with an R C configuration of the C atom of pyrrolidinyl moieties [33b] or when metal complexes with pentagonal bipyramidal geometries with all five donor atoms of the ligand forming a pentagonal plane around the metal center would have formed [14], a D-configuration would have resulted at the metal. 7 The 1 H and…”

“…The highest selectivity and the lowest amount of sulfone was obtained when p-anisic acid was used as an additive in excess to the amount of iron catalyst (catalyst:additive = 1:10). Better yields ($90%) with shorter reaction times and improved enantioselectivities (up to 26% ee) were found with p-anisic acid as an additive for o-and p-substituted aryl methyl sulfides (entries [11][12][13][14].…”

Oxidative Double Dehalogenation of Tetrachlorocatechol by a Bio‐Inspired CuII Complex: Formation of Chloranilic Acid

“…[19] Furthermore, the four sharp bands observed at 1259, 1224, 1148 and 1028 cm À1 are indicative of the presence of uncoordinated triflate anions. [20][21][22] Further insight into the structure of [1] …”