Effect of Partial Hydrolysis in Switching the Mode of Inter-molecular Bonding between Metal Complexes

Abstract

The assembly of [Cd(L 1 )] Ϫ {[L 1 ] 3Ϫ ϭ N[CH 2 CH 2 Nϭ C(CH 3 )COO Ϫ ] 3 } into the tetranuclear cluster {[Cd(L 1 )]Na-(H 2 O) 2 } 2 in the presence of Na ϩ is mediated by Na ϩ -carboxylate interactions; in contrast In 3ϩ and Fe 3ϩ induce the partial hydrolysis of [L 1 ] 3Ϫ to afford the complexes [In(L 2 )Cl] and {[Fe(L 2 )] 2 O} Der Effekt partieller Hydrolyse beim Wechsel der Art der intermolekularen Bindung zwischen Metall-Komplexen Inhaltsübersicht. Die Umwandlung von [Cd(L 1 )] Ϫ ([L 1 ] 3Ϫ ϭ N[CH 2 CH 2 NϭC(CH 3 )COOϪ] 3 ) in den vierkernigen Cluster {[Cd(L 1 )]Na(H 2 O) 2 } 2 in Anwesenheit von Na ϩ wird durch Na ϩ -Carboxylat-Wechselwirkungen vermittelt. Im Gegensatz hierzu Polymers and oligomers formed from metal complexes are currently the subject of much interest due to the possibility that such compounds may exhibit catalytic, magnetic, optical and conductivity properties [1]. Several strategies have been developed towards the assembly of such aggregates [2Ϫ5]. One such strategy has involved the incorporation of groups onto the ligand periphery that are capable of forming intermolecular hydrogen-bonds with other substrate molecules [3]. Another approach has been to chelate metal ions with polychelate ligands that contain carboxylate ligands, facilitating the formation of aggregates via induzieren In 3ϩ und Fe 3ϩ die partielle Hydrolyse von [L 1 ] 3Ϫ unter Bildung der Komplexe [In(L 2 )Cl] und {[Fe(L 2 )] 2 O} ([L 2 ] 2Ϫ ϭ N[CH 2 CH 2 NH 2 ][CH 2 CH 2 NϭC(CH 3 )COOϪ] 2 ), die über intermolekulare Wasserstoffbrücken-Bindungen aggregieren.interaction with hard metal cations [4,5]. We have become interested in the possibility of being able to 'switch' the mode of complex aggregation to that of hydrogen-bonding through the partial hydrolysis of one arm of [L 1 ] 3Ϫ to give the hexadentate ligand [L 2 ] 2Ϫ . There have been reports of the partial hydrolysis of Schiff-base ligands upon complexation with a metal centre [6Ϫ8] either to alleviate unfavourable steric interactions within the complex [7] or to form a ligand of improved donor ability [8]. Therefore, our approach to the synthesis of complexes of [L 2 ] 2Ϫ has been to investigate the reaction of [L 1 ] 3Ϫ with a range of metal ions of differing size and co-ordination requirements. The preliminary studies reported herein have utilised the metal ions In 3ϩ , Cd 2ϩ and Fe 3ϩ .Reaction of [L 1 ]Na 3 · 3H 2 O 1) with one molar equivalent of InCl 3 in MeOH results in the precipitation of irregular block shaped crystals. Single crystal X-ray diffraction re-1) [L 1 ]Na 3 · 3H 2 O is prepared via the Schiff-base condensation of tris(2-aminoethylamine) with three molar equivalents of sodium pyruvate in MeOH. Satisfactory elemental analytical data, mass spectra and infrared spectra were obtained for all compounds reported. Satisfactory 1 H and 13 C NMR spectra were obtained for [L 1 ]Na 3 · 3H 2 O, 1 and 2.

Strategic Synthesis of Heptacoordinated FeIII Bifunctional Complexes for Efficient Water Electrolysis

“…An exhaustive search of iron coordination complexes revealed that 0.7 % of all iron compounds exhibit the coordination number seven. Of all the hepta ‐coordinate complexes 23 are dinuclear, among these 13 correspond to Fe III systems having pentagonal bipyramidal (PBP) coordination geometry around the central metal and only a few heptacoordinated diiron (III) complexes containing alkoxide and μ‐sulphate bridge are reported in the literature to date [29–42] . Herein two new diiron complexes with a preorganised ligand (L, S1.1.)…”

“…Of all the hepta-coordinate complexes 23 are dinuclear, among these 13 correspond to Fe III systems having pentagonal bipyramidal (PBP) coordination geometry around the central metal and only a few heptacoordinated diiron (III) complexes containing alkoxide and μ-sulphate bridge are reported in the literature to date. [29][30][31][32][33][34][35][36][37][38][39][40][41][42] Herein two new diiron complexes with a preorganised ligand (L, S1.1.) are reported, both of which have been characterized by single crystal structural studies.…”