Novel vic-dioxime ligands and their poly-metal complexes bearing 1,8-diamino-3,6-dioxaoctane: synthesis, characterization, spectroscopy and electrochemistry

Three novel vic-dioxime ligands containing the 1,8-diamino-3,6-dioxaoctane group, N,N′-(1,8-diamino-3,6-dioxaoctane)-p-tolylglyoxime (L¹SL¹H₄), N,N′-(1,8-diamino-3,6-dioxaoctane)-phenylglyoxime (L²SL²H₄), and N,N′-(1,8-diamino-3,6-dioxaoctane)-glyoxime (L³SL³H₄) have been prepared from 1,8-diamino-3,6-dioxaoctane with anti-p-tolylchloroglyoxime, anti-phenylchloroglyoxime or anti-monochloroglyoxime. Polynuclear complexes [M(L ^x SL ^x )] _n or [M(L ^x SL ^x )(H₂O)] _n (x = 1, 2 and 3), where M = Cu^II, Co^II, and Ni^II, have been obtained with 1:1 metal/ligand ratio. The Cu^II and Ni^II poly-metal complexes of these ligands are proposed to be square planar, while also the prepared Co^II complexes are proposed to be octahedral with two water molecules as axial ligands. The detection of H-bonding in the [Ni(L¹SL¹)] _n , [Ni(L²SL²)] _n and [M(L³SL³)(H₂O)] _n metal complexes by FT i.r. spectra revealed the square planar or octahedral [MN₄·H₂O)] _n coordination of poly-nuclear metal complexes. [MN₄] _n coordination of the [Ni(L¹SL¹)] _n and [Ni(L²SL²)] _n complexes were also determined by ¹H-n.m.r. spectroscopy. The ligands and poly-metal complexes were characterized by elemental analyses, FT-i.r., u.v.-vis., ¹H and ¹³C-n.m.r. spectra, magnetic susceptibility measurements, molar conductivity, cyclic voltammetry, and differential pulse voltammetric (DPV) techniques.     

Coordination chemistry of 5,6,7-trimethyl-[1,2,4]triazolo[1,5-a]pyrimidine with first-row transition-metal salts: Synthesis, spectroscopy and single-crystal structures, with counter-anion dependence of the structures

A variety of new coordination compounds with transition-metal salts and the ligand trimethyl[1,2,4]triazolo[1,5-a]pyrimidine (abbreviated as tmtp) is described, together with several of their 3D crystal structures and spectroscopic and magnetic properties. The compounds were selected based on the coordination ability of the counterion, halide, nitrate, sulfate, thiocyanate and perchlorate. The formed coordination compounds and their coordination numbers were found to be strongly dependent on both the cation and the used counter-anion. The several compounds studied have the following structural formulae: [CuCl₂(tmtp)₂], [CuBr₂(tmtp)₂], [ZnBr₂(tmtp)₂], [Cu(NO₃)₂(tmtp)₂], [CuSO₄(tmtp)₂]₂(H₂O)(MeOH), [Cu(H₂O)(NCS)₂(tmtp)₂], [Zn(NCS)₂(tmtp)₂], [Cd(NCS)₂(tmtp)₂] and [M(H₂O)₂(tmtp)₄](BF₄)₂, in which M = Co, Ni, Zn.The new coordination compounds have been further characterized by NMR, (far-)IR and LF spectra, as well as by C, H, N element analyses, and EPR spectra for the Cu(II) compounds. The coordination around the metal varies from 4 (Zn, Cu), via 5 (Cu) to 6 (for Co, Cu and Cd). The anions usually complete the coordination sphere; only the Co and Zn compounds with the tetrafluoridoborate anions have no coordinated anions, but water ligands complete the octahedral coordination sphere. In the 5-coordinated [Cu(H₂O)(NCS)₂(tmtp)₂] water completes the square pyramid geometry.     

Synthesis of new boron complexes: application to transfer hydrogenation of acetophenone derivatives

Two new boron complexes were synthesized from N‐[3‐(methylmercapto)aniline]‐3,5‐di‐tert‐butylsalicylaldimine ( LH ) with boron reagent BPh₃ or BF₃.Et₂O. These boron complexes are stable and easily soluble in protic solvents such as ethanol (C₂H₅OH) but hardly soluble in nonprotic solvents such as chloroform (CHCl₃), dichloromethane (CH₂Cl₂) and tetrahydrofuran (THF). All new boron complexes have been fully characterized by both analytical and spectroscopic methods. The catalytic activities of complexes [LBPh₂], 2 , and [LBF₂], 3 , in the transfer hydrogenation of acetophenone derivatives were tested. Stable boron complexes were found to be efficient catalysts in the transfer hydrogenation of aromatic ketones in good conversions up to 99% in the presence of iso‐PrOH/KOH. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis,electrochemical and in situ spectroelectrochemical studies of new transition metal complexes with two new Schiff-bases containing N2O2/N2O4 donor groups

New Schiff-base copper and cobalt complexes, [Cu(L¹)], [Cu(L²)] and [Co(L¹)], [Co(L²)] (where L¹ = N-N′-bis(3,5-di-tert-butylsalicylaldimine)-1,4-cyclohexane bis(methylamine) and L² = N-N′-bis(3,5-di-tert-butylsalicylaldimine)-1,8-diamino-3,6-dioxaoctane), were synthesized and characterized using elemental analysis, IR spectra, UV–Vis spectra, magnetic susceptibility measurements, ¹H and ¹³C NMR spectroscopy, thermal analysis and molar conductance (Λ_M). Their electro-spectrochemical properties were investigated using cyclic voltammetric (CV) and thin-layer spectroelectrochemical techniques in a dichloromethane solution (CH₂Cl₂). The CV of [Cu(L²)] showed a lower oxidation potential than that of [Cu(L¹)] under the same experimental conditions. The oxidation wave (II) of [Cu(L²)] was accompanied by an EC process (II′), which was not observed for [Cu(L¹)]. Also, [Cu(L²)] exhibited a reduction process, but [Cu(L¹)] did not. These results indicate that the Cu(II) ion in [Cu(L²)] is coordinated by N₂O₄ donor sites while [Cu(L¹)] presents a square-planar structure with N₂O₂ donor sites. Both oxidation processes for [Co(L¹)] and [Co(L²)] are based on the cobalt center, and they are assigned to Co(II)/Co(III) couples. The spectroelectrochemical results indicate that the oxidized species of [Cu(L²)] is similar to that of [Cu(L¹)], the only difference being that the absorption bands of the oxidized species for [Cu(L²)] shift to lower energy compared with those of [Cu(L¹)] because of their different coordination environment. The geometry of [Cu(L²)] changed into square-planar after the complex was totally oxidized and the neutral complex was only recovered following the EC process, as observed from the CV of [Cu(L²)]. For the two cobalt complexes, the bands corresponding to the π → π^∗transitions disappeared and new bands with small red shifts and of lower intensity were observed during the oxidation process. These new bands are attributed to the LMCT transition as observed in the case of the oxidation processes of the cobalt complexes.     

Synthesis,spectral characterization,electrochemical studies and catalytic properties in Suzuki–Miyaura coupling reactions of the mononuclear PdII,trinuclear PdII(BPh2)2 and RuII?PdII?RuII type complexes containing 4‐amino‐1‐benzyl piperidine and phenyl groups

The ligand containing the 4‐amino‐1‐benzyl piperidine group, N, N′‐(4‐amino‐1‐benzyl piperidine)‐glyoxime, (LH₂) (1) was prepared from 4‐amino‐1‐benzyl piperidine with anti‐dichloroglyoxime at ? 15 °C in absolute Tetrahydrofuran (THF). In the trinuclear [Pd(L)₂Ru₂(phen)₄](ClO₄)₂ (4) and [Pd(L)₂Ru₂(bpy)₄](ClO₄)₂ (5) metal complexes, the Pd^II ion centered into the main oxime core by the coordination of the imino groups while the two Ru^II ions coordinated dianionic oxygen donors of the oxime groups and linked to the ligands of 1,10‐phenanthroline and 2,2′‐bipyridine. The mono and trinuclear metal complexes were characterized by elemental analyses, FT‐IR, UV–vis, ¹H and ¹³C‐NMR spectra, magnetic susceptibility measurements, molar conductivity, cyclic voltammetry, mass spectra, X‐ray powder techniques and their morphology by SEM measurements. The cyclic voltammetric results show that the cathodic peak (E_pc) potential of (3) shifts towards more positive values compared with that of (2) as a result of the BPh₂⁺‐bridged complex formation. The Suzuki–Miyaura reaction was used to investigate their activity as catalyst either prepared in‐situ or from well‐defined complexes. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis,characterization and redox properties of a new vic-dioxime and its transition metal complexes

A novel vic-dioxime, 1,2 dihydroxyimino-1-p-tolyl-3-aza-6-morpholine heptane (LH₂) was prepared by reacting anti-p-tolylchloroglyoxime with 4-(3-aminopropyl)morpholine in absolute THF. Mononuclear complexes with a metal–ligand ratio of 1:2 were prepared using Co^II, Cu^II and Ni^II salts. The ligand and its complexes were characterized by elemental analyses, FT-IR, u.v.–vis., ¹H- and ¹³C-n.m.r. spectra, magnetic susceptibility measurements, thermogravimetric analyses (t.g.a.), and by cyclic voltammetry.     

Synthesis, Spectroscopic and Electrochemical Investigations of Two vic-Dioximes and Their Mononuclear Ni（Ⅱ）, Cu（Ⅱ） and Co（Ⅱ） Metal Complexes Containing Morpholine Group

Two vic-dioxime ligands （LxH2） containing morpholine group have been synthesized from 4-[2-（dimethylaminoethyl）] morpholine with anti-phenylchloroglyoxime or anti-monochloroglyoxime in absolute THF at -15 ℃. Reaction of two vic-dioxime ligands with MCl2·nH2O （M： Ni, Cu or Co and n=2 or 6） salts in 1 ： 2 molar ratio afforded metal complexes of type [M（LxH）2] or [M（LxH）2·2H2O]. All of metal complexes are non-electrolytes as shown by their molar conductivities （Am） in DMF （dimethyl formamide） at 10^-3 mol·L^-1. Structures of the ligands and metal complexes have been solved by elemental analyses, FT-IR, UV-Vis, ^1H NMR and ^13C NMR, magnetic susceptibility measurements, molar conductivity measurements. Furthermore, redox properties of the metal complexes were investigated by cyclic voltammetry.     

Red and Blue Compounds Formed from Copper(II) Bromide and the Ligand 7-Isobutyl-5-methyl-[1,2,4]triazolo[1,5-a]pyrimidine: Synthesis, Spectroscopy and Single-Crystal Structures

Abstract  

Two newly synthesized coordination compounds copper(II) bromide with the ligand 7-isobutyl-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine (abbreviated as ibmtp) are presented, together with their 3D crystal structure and spectroscopic and magnetic properties. The compounds are CuBr₂(ibmtp)₂ (1) (red crystals) and [CuBr(ibmtp)₄]Br(H₂O)₃ (2) (blue crystals). In (1) the Cu(ii) ion is present in a distorted tetrahedral environment, while in (2) the Cu(ii) ion has a square pyramidal geometry. These crystal structures are also the first ones reported with the ligand ibmtp.     

Synthesis, Spectral Characterization and Electrochemical Properties of New vic-dioxime Complexes Bearing Carboxylate

Three new vic-dioxime ligands, [N-(ethyl-4-amino-1-piperidine carboxylate)-phenylglyoxime (L¹H₂), N-(ethyl-4-amino-1-piperidine carboxylate)-glyoxime (L²H₂), and N,N′-bis(ethyl-4-amino-1-piperidine carboxylate)-glyoxime (L³H₂)], and their Co(II) with Cu(II) metal complexes, were synthesized for the first time. Mononuclear complexes of these ligands with a 1:2 metal-ligand ratio were prepared with Co(II) and Cu(II) salts. The BF₂⁺-capped Co(II) and mononuclear complexes of the vic-dioxime were prepared for [Co(L¹·BF₂)₂] and [Co(L²·BF₂)₂]. The ligands act in a polydentate fashion bonding through nitrogen atoms in the presence of a base, as do most vic-dioximes. The cobalt(II) and copper(II) complexes are non-electrolytes as shown by their molar conductivities (Λ_M) in DMF. The structures of the ligands and complexes were determined by elemental analyses, FT-i.r., u.v.–vis., ¹H- and ¹³C-n.m.r. spectra, magnetic susceptibility measurements, and molar conductivity. The comparative electrochemical studies show that the stabilities of the reduced or oxidized species and the electrode potentials of the complexes are affected by the substituents attached on the oxime moieties of the complexes.     

Synthesis,Characterization and Redox Properties of Three New <Emphasis Type="Italic">vic</Emphasis>-dioximes and their Nickel(II) Metal Complexes

Three novel vic-dioximes: cyclohexylamine-p-tolylglyoxime (L₁H₂), t-butylamine-p-tolylglyoxime (L₂H₂) and sec-butylamine-p-tolylglyoxime (L₃H₂) were prepared by the reaction of anti-p-tolylchloroglyoxime with cyclohexylamine, t-butylamine and sec-butylamine in absolute THF. The detection of H-bonding in all of the Ni(II) complexes by i.r. revealed the square-planar MN₄ coordination of mononuclear complexes. MN₄ coordination of the [(L₁H)₂Ni] complex was also determined by ¹H and ¹³C-n.m.r spectroscopy. Mononuclear complexes with a 1:2 metal-ligand ratio were prepared using Ni(II) salts. All Ni(II) complexes are insoluble in common solvents. The ligands and complexes were characterized by elemental analyses, FT-i.r., u.v.–vis., ¹H and ¹³C-n.m.r. spectra, magnetic susceptibility measurements, thermogravimetric analyses (t.g.a.) and cyclic voltammetry.