Racemic and chiral expanded salen-type complexes derived from biphenol and binaphthol: Salbip and salbin

The reaction of 2-fluoronitrobenzene with 2,2′-biphenol or (R)-binaphthol, followed by reduction and subsequent reaction of the resulting diamine with two equivalents of a salicylaldehyde, affords expanded salen-type ligands having backbones based on biphenol or binaphthol: salbipH₂, (R)-salbinH₂ and (R)-salbin(t-Bu)₄H₂. Deprotonation of these ligands with sodium methoxide or potassium hydride, followed by metallation with M(OAc)₂ (M = Mn, Co, Ni, or Cu), affords the corresponding metal complexes in good yield (61-85%). The species containing Mn, Co, and Ni all have distorted octahedral geometry, as determined by X-ray crystallography. The ethereal oxygen atoms occupy two coordination sites with metal-oxygen distances ranging from 2.19 to 2.36 Å. The imine nitrogen atoms are trans to each other in the solid state, an impossible geometry in traditional salen-type complexes. The species containing Cu are distorted square planar and show much longer metal-ethereal oxygen distances ranging from 2.79 to 3.22 Å. The manganese complexes are competent catalysts for the epoxidation of olefins.     

New boronates prepared from 2,4-pentanedione derived ligands of the NO2 and N2O2 type - comparison to the complexes obtained from the corresponding salicylaldehyde derivatives

2,4-Pentanedione (=acetylacetone) has been reacted with 2-aminoethanol, 1,2-diaminoethane and 1,3-diaminopropane to give the NO₂ and N₂O₂ type ligands named acacaminolH₂, acacenH₂ and acpenH₂, which are structurally and electronically related to the corresponding ligands derived from salicylaldehyde (salaminolH₂ and salenH₂). On reaction of acacaminolH₂ with phenylboronic acid a dinuclear monomeric complex has been obtained containing one three- and one four-coordinate boron atoms as well as one six-membered and one seven-membered heterocyclic ring. Since with salaminolH₂ a dimeric complex with a central 10-membered heterocycle had been reported, it becomes apparent that there may be differences in reactivity when comparing 2,4-pentanedione and salicylaldehyde derived ligands. The molecular compositions of the boron complexes prepared from acacenH₂ and acacpenH₂ are analogous to the corresponding salen and salpen derivatives, however, the presence of two methyl groups in the six-membered chelate rings generates some structural changes, the most important being the distortion of the boat conformation of the central heterocyclic ring. This was predicted by computational methods and confirmed experimentally for one of the complexes. A further important observation was that the products described in here are much more soluble than the salicylaldehyde derivatives. As lateral product the adduct of acacenH₂ with 1,3,5-triphenylboroxine was crystallized. Elemental analysis, IR and NMR (¹H, ¹³C, ¹¹B) spectroscopy, mass spectrometry, ab intio theoretical calculations and X-ray crystallography have been applied to carry out this study.     

水溶性salen-Co(Ⅲ)配合物催化的端炔水合反应

报道了一种用于端炔水合反应的水溶性salen-Co(III)配合物催化剂,在使用硫酸作为共催化剂的条件下能高效得到产物甲基酮.该催化剂用量少,反应结束后可利用简单的萃取实现产物与催化剂分离,简化了后处理过程.此外,催化剂还可回收重复使用,但催化剂活性会略有下降.     

Metallic macrocycle with a 1,3-alternate calix[4]arene salicylideneamine ligand

The calix[4]arene-based podand which incorporates two salicylideneamine units in 1,3-alternate positions of the lower rim has been prepared and subjected to complexation studies with transition metal ions. The nickel and copper complexes form a 2 : 2 stoichiometric metallic macrocyclic framework.     

Synthesis and photophysical properties of water-soluble sulfonato-Salen-type Schiff bases and their applications of fluorescence sensors for Cu in water and living cells

A series of water-soluble sulfonato-Salen-type ligands derived from different diamines including 1,2-ethylenediamine (Et-1–Et-4), 1,2-cyclohexanediamine (Cy-1 and Cy-2), 1,2-phenylenediamine (Ph-1–Ph-3 and PhMe-1–PhMe-4), and dicyano-1,2-ethenediamine (CN-1) has been designed and prepared. Sulfonate groups of ligands ensure good stability and solubility in water without affecting their excited state properties. These ligands exhibit strong UV/Vis-absorption and blue, green, or orange fluorescence. Time-dependent-density functional theory calculations have been undertaken to reveal the influence of ligand nature, especially sulfonate groups, on the frontier molecular orbitals. Since their fluorescence is selectively quenched by Cu²⁺, the sulfonato-Salen-type ligands can be used as highly selective and sensitive turn-off fluorescence sensors for the detection of Cu²⁺ in water and fluorescence imaging in living cells.     

Structure and conformational motion of seven-coordinate diorganotin(IV) complexes derived from salen and salan type ligands

Reaction of R₂SnCl₂ (R = Me, nBu, Ph) and the potassium salts of salenN₃H₃ (N,N′-bis(salicylidene)diethylenetriamine) and saleanN₃H₅ (N,N′-bis(o-hydroxybenzyl)diethylenetriamine) provided diorganotin(IV) complexes of the composition [Me₂Sn(salenN₃H)]·solvate (solvate = 2.5H₂O, MeOH or DMSO), [nBu₂Sn(salenN₃H)]·H₂O, [Ph₂Sn(salenN₃H)]·2EtOH and [Me₂Sn(saleanN₃H₃)]·2.5H₂O. In all compounds the tin atoms are seven-coordinate and have pentagonal-bipyramidal coordination environments, in which the organic substituents attached to the tin atoms occupy the axial positions. This occurs both in solution and the solid state; however, in solution the molecules are involved in conformational equilibria that require the presence of intermediates, in which the N → Sn bonds are dissociated. Although the [saleanN₃H₃]²⁻ ligand is more flexible and basic, a very similar complexing behavior to that of [salenN₃H]²⁻ has been found, and there is evidence that it is even a weaker ligand. Both ligands show the tendency to adopt a curved conformation within the complex, thus indicating that the dynamic process resembles the flapping of butterfly wings. However, the folding is reduced with increasing steric bulk of the organic substitutents attached to the tin atoms. The six-membered heterocyclic rings in the [R₂Sn(salenN₃H)] derivatives have envelope conformation, while those in [Me₂Sn(saleanN₃H₃)] have distorted boat-conformation. Thus, small changes in the hybridization and basicity of the nitrogen atoms cause significant differences of the stability and the dynamic behavior of the resulting molecules.     

Effect of Cu(II)/H2 Salen complex on the non-conventional initiated emulsion polymerization of acrylonitrile

Radical polymerization of acrylonitrile was carried out in an emulsifier-free condition initiated by KHSO₅ catalyzed with Cu(II)/bis-salicylidene ethylene diamine (H₂ Salen) complex. The Cu(II) salt alone, Cu(II)/salicylaldehyde and Cu(II)/ethylene diamine have a retarding effect on the polymerization reaction, while the chelate of Cu(II) with the tetradentate Schiff base ligand, H₂ Salen has a catalytic effect. Prior to this, the catalytic effect of various bivalent transition metal salts and their couple with the Schiff base, H₂ Salen on the polymerization reaction has been examined to be not significant. The in situ developed complex produces the stable emulsion leading to high conversion. In the polymerization, the variables studied were the concentration of monomer, initiator, Cu(II), H₂ Salen and temperature. The overall activation energy was computed to be 13.1 kcal/mol. From the kinetic and spectral analyses, the mechanism of the initiator decomposition and initiation of polymerization by Cu(II)/H₂ Salen complex were suggested. The rate of polymerization (R_p) was found to be dependent on the monomer, initiator, Cu(II) ion, H₂ Salen concentrations to the 1.4, 0.3, 1.6, 1.5 power respectively. The polymers are characterized by IR and molecular weight by viscosity and GPC methods.     

Oxidation of Alkenes and Sulfides with Transition Metal Catalysts

Alkenes and sulfides were oxidized with transition-metal catalysts. The oxidant sources include molecular dioxygen, air and iodosylbenzene. The metal ions Mn(III), Fe(III), Co(II) and Ni(II) were used. The Catalysts 1-18 of 1,3-dioxo-, β-ketoimine- or salen-types were prepared and their efficacy was examined. 1,2-Dihydronaphthalene is most efficiently epoxidized with O₂/Me₂CHCHO or PhIO in the presence of Mn(III)-salen catalysts. The Ni(II)-, Co(II)- and Fe(III)-catalysts of either β-ketoimine- or salen-types are useful for epoxidation of styrene, (E)-stilbene and (E)-benzalacetone in the O₂/Me₂HCHO system; these epoxidations are stereospecific without formation of corresponding diastereomeric epoxides. Oxidation of methyl p-tolyl sulfide with O₂/Me₂CHCHO is facilitated by the 1,3-dioxo-catalyst Co(II)-1. Monooxidation is achieved with Me₂CHCHO in equimolar proportions to give the corresponding sulfoxide, whereas overoxidation is realized with excess Me₂CHCHO to give the sulfone. These epoxidation and sulfide oxidations all occur at 25 °C and are complete in less than a day.     

Room Temperature Ionic Liquid： a Powerful Additive of Mn（Salen） Catalyzed Oxidation of sec-Alcohols

A simple, mild, efficient Mn(salen)-catalyzed oxidation system of secondary alcohols, in which the ionic liquid [bmim]PF6 acts as a powerful additive, has been described. The reaction proceeded with higher efficiency. The catalyst was more easier to recycle in ionic liquid [bmim]PF6 with a well-proportioned CH2Cl2 than in the single CH2Cl2 or ionic liquid.