Polynuclear Heteroligand Yb(III)–Er(III) Complexes as Potential Upconversion Materials

Russian Journal of Coordination Chemistry - The synthesis of complexes LnI(C6F5O)2 and LnCp(L)2 (Ln = Er, Yb; L = C6F5O, SONF), which are convenient precursors for the preparation of heteroligand...     

Triphenylantimony(V) Catecholates Based on o-Quinones,Derivatives of Benzo[b][1,4]-Dioxines and Benzo[b][1,4]-Dioxepines

Russian Journal of Coordination Chemistry - New catecholate complexes of triphenylantimony(V), (Etgly-3,6-DBCat)SbPh3 (I), (Propgly-3,6-DBCat)SbPh3 (II), and (Cat-3,6-DBCat)SbPh3 (III), based on...     

Template Assembling of the Pentadentate Redox-Active Ligand in the Coordination Sphere of Tin(IV)

Heptacoordinated tin complexes with pentadentate redox-active ligands containing the diiminopyridine fragment combined with two sterically hindered phenolate coordination centers, LSn-Cl₂ and L'SnCl₂ (L and L' are dianions of deprotonated 2,6-bis[2,4-di-tert-butyl-6-(methylidenylamino) phenol]pyridine and 2,6-bis[2,4-di-tert-butyl-6-(ethylidenylamino)phenol]pyridine, respectively), are synthesized. The molecular and electronic structures of the synthesized compounds were studied by X-ray diffraction analysis (for complex I, CIF file CCDC no. 1557838), a set of spectral methods, and quantum-chemical calculations. The redox properties of the obtained complexes are characterized by cyclic voltammetry.     

Lanthanide chloride complexes of amine-bis(phenolate) ligands and their reactivity in the ring-opening polymerization of epsilon-caprolactone

Reaction of two equivalents of n-BuLi with sterically demanding amine-bis(phenol) compounds, H(2)O(2)NN'(R) (Me(2)NCH(2)CH(2)N{CH(2)-3,5-R(2)-C(6)H(2)OH}(2); R = t-Bu or t-Pe (tert-pentyl)) yields isolable lithium complexes, Li(2)(O(2)NN'(R)), in good yields. Upon reaction with one equivalent of LnCl(3)(THF)(x), the lithium salts afford rare earth amine-phenolate chloride complexes in good yields, Ln(O(2)NN'(R))Cl(THF); Ln = Y, Yb, Ho, Gd, Sm, Pr. Crystals of Y(O(2)NN'(t-Bu))Cl(THF), 1, and Sm(O(2)NN'(t-Bu))Cl(DME), 2, suitable for single crystal X-ray crystallographic analysis were obtained. In contrast to previously reported [{Gd(O(2)NN'(t-Pe))(THF)(micro-Cl)}(2)] and related La and Sm complexes, these species are monomeric. 1 contains Y in a distorted octahedral environment bonded to two amine, two phenolate, one THF and one chloride donor. 2 contains Sm in a distorted capped trigonal prismatic environment bonded to two amine, two phenolate, two DME oxygens and one chloride donor. The Ln(O(2)NN'(t-Pe))Cl(THF) complexes were active initators for the controlled ring-opening polymerization of epsilon-caprolactone with a tendency to form low molecular weight cyclic polyesters (M(n) 3000-5000). The conversion rates, although slower than related amido and alkyl species, were different for monomeric and dimeric initiators. The size of the metal centre also affected the conversions and the molecular weights achieved.     

New organobimetallic compounds containing catecholate and o-semiquinolate ligands

New organobimetallic compounds CatSn[CpM(CO)_n]₂ (2-4) were obtained by the insertion of CatSn(II) (1) into the metal-metal bond of [CpM(CO)_n]₂ (Cat - 3,6-di-tert-butylcatecholate dianion; M = Fe (2), n = 2; M = Mo (3), W (4), n = 3). The structure of CatSn[CpMo(CO)₃]₂ was determined by X-ray analysis. The oxidation of compounds 2-4 with silver(I) triflate was found to produce stable paramagnetic o-semiquinolate derivatives which keep both Sn-M bonds. New paramagnetic tin(IV) complexes were investigated by EPR spectroscopy.     

Oxidation of aromatic compounds: XVI. Radical cations derived from acetylenic compounds with electron-withdrawing groups: Reactions and ESR parameters

One-electron oxidation of aryl-substituted acetylenes ArC≡CX where X is an electron-withdrawing group gives different products, depending on the X substituent. Acetylenic substrates with medium-strength electron-withdrawing substituents, X = CO₂R, COAr, COR, PO(OEt)₂, give rise to tetrasubstituted ethenes X(ArCO)C=C(COAr)X. Compounds with strong electron-withdrawing groups (X = COCF₃, COCO₂R, CN) are converted into furan derivatives. Probable mechanisms of transformations of ArC≡CX radical cations into the final products are discussed. Radical cations derived from disubstituted acetylenes were characterized by ESR spectroscopy.     

Specific features of the photolytic transformations of the polynuclear quinone-aliphatic hydrocarbon systems

Dependence of the quantum yield of decomposition of quinone on the intensity of the absorbed irradiation in the compositions of 1,2-naphthoquinone, 9,10-phenanthrenequinone, and 4-nitro-9,10-phenathrenequinone with nonane has the extremal character.     

Oxidation by oxygen and sulfur of Tin(IV) derivatives containing a redox-active o-amidophenolate ligand

Oxidation of tin(IV) o-amidophenolate complexes [Sn(ap)Ph(2)] (1) and [Sn(ap)Et(2)(thf)] (2) (ap=dianion of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone (ImQ)) with molecular oxygen and sulfur in toluene solutions was investigated. The reaction of oxygen with 1 at room temperature forms a paramagnetic derivative [Sn(isq)(2)Ph(2)] (3) (isq=radical anion of ImQ) and diphenyltin(IV) oxide [{Ph(2)SnO}(n)]. Interaction of 1 with sulfur gives another monophenyl-substituted paramagnetic tin(IV) complex, [Sn(ap)(isq)Ph] (4), and the sulfide, [Ph(3)Sn](2)S. The oxidation of 2 with oxygen and with sulfur proceeds through the derivative [Sn(isq)(2)Et(2)] (7), which undergoes alkyl elimination to give two new tin(IV) compounds, [Sn(ap)(isq)Et] (5) and [Sn(ap)(EtImQ)Et] (6) (EtImQ=2,4-di-tert-butyl-6-(2,6-diisopropylphenylimino)-3-ethylcyclohexa-1,4-dienolate ligand), respectively, along with the corresponding alkyltin(IV) oxide and sulfide. Complexes 3-5 and 7 were studied by EPR spectroscopy. The structures of 3, 4 and 6 were investigated by X-ray analysis.     

Oxidation of aromatic compounds: XV. Oxidation of arylacetylenes in a system HF-PbO<Subscript>2</Subscript>

The oxidation of symmetrically substituted diarylacetylenes ArC≡CAr (Ar=C₆H₄R) containing strong electron-withdrawing groups R = 4-COMe, 4-CO₂Me, 3-CO₂Et, and 4-NO₂ in a system HF-PbO₂ at ?10÷?20°C led within 0.5–3 h to the formation of Z,Z-1,2,3,4-tetrakis(aryl)-1,4-difluorobuta-1,3-dienes ArFC=C(Ar)?(Ar)C=CFAr. The butadiene structures obtained exist in solutions as s-cis-and s-trans-conformers and in the crystalline state are present in the stable s-cis-form.