Structure and electrochemical properties of bis(pyridine)cobalt(III) complexes of N,N′-ethylenebis(salicylideneimine) homologues with an aryl substituent on the ethylene backbone. Crystal structures of [Co(salpen)(py)₂]PF₆·0.5 Et₂O and [Co(salcppn)(py)₂]PF₆·2py (py = pyridine)

Abstract

ChemInform Abstract The title complexes (Ia) are prepared by known methods. (Ib)-(Id) are obtained in the reaction of the Schiff base in MeOH with Co acetate in the presence of NaOH and Py under reflux, followed by addition of KPF6 in water. (Ib) crystallizes in the space group P1 with Z=2, (Ic) in P21/n with Z=4. The ethylene conformation is gauche for both complexes. The Co(III)/Co(II) reduction potentials of the complexes are not affected by mono-substitution on the ethylene carbon but change on disubstitution. The conformations and electrochemical properties of the complexes are discussed in terms of the steric interaction between the substituents R1 and R2 and the Py molecule coordinated at the apical site (no yields given).

Electrochemistry of Oxygenation Catalysts, Part 6 Electrosynthesis, Structure, Analytical and Electrochemical Properties of Monomeric [CoIII(salen)(DMF)2]+ X- Salts (X = PF6, ClO4)

“…Due to the increased strain in a planar structure, however, we consider such a conform ation as unlikely. This assum ption is in accordance w ith structural results at com plexes o f ethylene-bridge substituted hom ologues o f salen [23]. The voltam m ogram s were analyzed quantita tively according to such an Eqr m echanism .…”

“…Structures o f bis-pyridine cobalt(III) Schiff-base com plexes [23], oxygen adducts to Co(salen) [42], substrate adducts [43], or dim ers [27,28] Table I, bond lengths and angles in Table II The ethylene diam ine bridge in the salen ligand form s together with the central Co atom a fivem em bered ring. One o f the C atoms (here, C8) is placed above, and the other one (C9) below the plane through N2, Co and N l. Thus, in the crys tal, the N -C H 2-C H 2-N bridge attains a non-planar conform ation, forcing the two arom atic units o f the ligand from coplanarity.…”

Different Ground Spin States in Iron(III) Complexes with Quadridentate Schiff Bases: Synthesis, Crystal Structures, and Magnetic Properties

“…Previous studies on hexacoordinated iron(III) complexes with a N 4 O 2 donor set have revealed that the bond distances and angles of the iron atom are sensitive to its spin state. − The HS-to-LS spin state change involves depopulation of the e g orbitals, which have an antibonding character. This change is concomitant with the shortening of the iron-to-ligand bond distances.…”

Synthesis, structure, and electrochemistry of trans-[CoIII{(BA)2pn}(L)2]ClO4 complexes

“…The structural diversity of transition metal complexes of these ligands and the structure-function relationships of the resulting complexes have been the focus of extensive research in recent years [1][2][3][4][5][6][7][8][9][10][11][12]. Their facile synthesis and easily tunable steric, electronic, and catalytic properties have led to the wide application of transition metal Schiff base complexes [13][14][15][16][17].…”