Triphenylantimony(V) Catecholates of the Type (3-RS-4,6-DBCat)SbPh3-Catechol Thioether Derivatives: Structure, Electrochemical Properties, and Antiradical Activity

A new series of triphenylantimony(V) 3-alkylthio/arylthio-substituted 4,6-di-tert-butylcatecholates of the type (3-RS-4,6-DBCat)SbPh3, where R = n-butyl (1), n-hexyl (2), n-octyl (3), cyclopentyl (4), cyclohexyl (5), benzyl (6), phenyl (7), and naphthyl-2 (8), were synthesized from the corresponding catechol thioethers and Ph3SbBr2 in the presence of a base. The crystal structures of 1, 2, 3, and 5 were determined by single-crystal X-ray analysis. The coordination polyhedron of 1–3 is better described as a tetragonal pyramid with a different degree of distortion, while that for 5- was a distorted trigonal bipyramid (τ = 0.014, 0.177, 0.26, 0.56, respectively). Complexes demonstrated different crystal packing of molecules. The electrochemical oxidation of the complexes involved the catecholate group as well as the thioether linker. The introduction of a thioether fragment into the aromatic ring of catechol ligand led to a shift in the potential of the “catechol/o-semiquinone” redox transition to the anodic region, which indicated the electron-withdrawing nature of the RS group. The radical scavenging activity of the complexes was determined in the reaction with DPPH radical

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

Reaction of two equivalents of n-BuLi with sterically demanding amine-bis(phenol) compounds, H2O2NN′R (Me2NCH2CH2N{CH2-3,5-R2-C6H2OH}2; R = t-Bu or t-Pe (tert-pentyl)) yields isolable lithium complexes, Li2(O2NN′R), in good yields. Upon reaction with one equivalent of LnCl3(THF)x, the lithium salts afford rare earth amine-phenolate chloride complexes in good yields, Ln(O2NN′R)Cl(THF); Ln = Y, Yb, Ho, Gd, Sm, Pr. Crystals of Y(O2NN′t-Bu)Cl(THF), 1, and Sm(O2NN′t-Bu)Cl(DME), 2, suitable for single crystal X-ray crystallographic analysis were obtained. In contrast to previously reported [{Gd(O2NN′t-Pe)(THF)(μ-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(O2NN′t-Pe)Cl(THF) complexes were active initators for the controlled ring-opening polymerization of ε-caprolactone with a tendency to form low molecular weight cyclic polyesters (Mn 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

Amido Analogues of Nonbent Lanthanide (II) and Calcium Metallocenes. Heterolytic Cleavage of π-Bond Ln–Carbazolyl Ligand Promoted by Lewis Base Coordination

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Rare-Earth Complexes with Multidentate Tethered Phenoxy-Amidinate Ligands: Synthesis, Structure, and Activity in Ring-Opening Polymerization of Lactide

International audienceNew multidentate tethered amidine-phenol proligands {4,6-tBu2C6H2O-(2-C(N-R)dN-R}H2 ({LONR}H2, R = iPr, cyclohexyl (Cy), 2,6-iPr2C6H3 (Ar)) were synthesized from the corresponding carbodiimines and 2-bromo-2,4-(ditert-butyl)phenol. Pro-ligands {LONiPr}H2 and {LONAr}H2 were metalated by 2 equiv of nBuLi to provide the corresponding dilithiumsalts {LONiPr}Li2 (1) and {LONAr}Li2 (2), which were authenticated by elemental analysis, X-ray crystallography, and NMR spectroscopy. Three different approaches were explored to coordinate these (pro)ligands onto rare earths: salt metathesis, and amine and methane elimination reactions. The salt metathesis reaction between 1 and YCl3 afforded the chloro complex [{LONiPr}YCl]n (3), which was, in turn, converted into the corresponding amide {LONiPr}YN(SiMe3)2 (6) by reaction withMN(SiMe3)2 (M = Li, Na). Similar reactions between 2 and YCl3, followed by recrystallization from DME, led systematically to the isolation of the monoprotonated product, that is, phenoxy-amidino complex {LOHNAr}YCl2(DME) (5). Amine elimination reactions between {LONiPr}H2 or {LONCy}H2 and Ln[N(SiMe3)2]3 afforded the corresponding phenoxy-amidinate amides {LONR}LnN(SiMe3)2 (Ln = Y, R = iPr, 6; R = Cy, 8; Ln = Nd, R = Cy, 9), whereas the same reaction between{LONAr}H2 and Y[N(SiMe3)2]3, under various conditions, always yielded the homoleptic tris(phenoxy-amidinate) complex {LOHNAr}3Y (11). Bimetallic "ate"-complexes {LONR}2Ln2Me4Li2(TMEDA)2 of yttrium (12 and 13), neodymium (14), samarium (15), and {LONiPr}2Yb2Me2(OH)2Li2(TMEDA)2 (16) were prepared by alkane elimination of the corresponding pro-ligand and [Li(TMEDA)][LnMe4] complex. Both amido and methyl "ate"- complexes were shown by X-ray diffraction studies to be dimeric in the solid state. The multidentate nature of the ligands in these dimeric species generates a cis/trans isomerism related to the nitrogen atoms in the nonsymmetrically coordinated amidinate fragments. Amido complexes 6, 8, and 9 are effective initiators for the ring-opening polymerization (ROP) of racemic lactide (rac-LA), giving atactic or heterotactic-enriched (Pr up to 76%) polymers with high molecular weights (Mn up to 158 800 g 3 mol#1), but broad molecular weight distributions (Mw/Mn = 1.5#2.8). An effective immortal ROP of rac-LA was feasible by combining complex 6 with 5#50 equiv of isopropanol or benzyl alcohol, affording PLAs with well-controlled molecular weights and narrow polydispersities (Mw/Mn = 1.11#1.38)

Binuclear Triphenylantimony(V) Catecholates through N-Donor Linkers: Structural Features and Redox Properties

A series of binuclear triphenylantimony(V) bis-catecholato complexes 1–11 of the type (Cat)Ph3Sb-linker-SbPh3(Cat) was prepared by a reaction of the corresponding mononuclear catecholates (Cat)SbPh3 with a neutral bidentate donor linker ligands pyrazine (Pyr), 4,4′-dipyridyl (Bipy), bis-(pyridine-4-yl)-disulfide (PySSPy), and diazobicyclo[2,2,2]octane (DABCO) in a dry toluene: Cat = 3,6-di-tert-butyl-catecholate (3,6-DBCat), linker = Pyr (1); PySSPy (2); Bipy (3); DABCO (4); Cat = 3,5-di-tert-butyl-catecholate (3,5-DBCat), linker = Bipy (5); DABCO (9); Cat = 4,5-(piperazine-1,4-diyl)-3,6-di-tert-butylcatecholate (pip-3,6-DBCat), linker = Bipy (6); DABCO (10); Cat = 4,5-dichloro-3,6-di-tert-butylcatecholate (4,5-Cl2-3,6-DBCat), linker = Bipy (7); DABCO (11); and Cat = 4,5-dimethoxy-3,6-di-tert-butylcatecholate (4,5-(MeO)2-3,6-DBCat), linker = Bipy (8). The same reaction of (4,5-Cl2-3,6-DBCat)SbPh3 with DABCO in an open atmosphere results in a formation of 1D coordination polymer {[(4,5-Cl2-3,6-DBCat)SbPh3·H2O]·DABCO}n (12). Bis-catecholate complex Ph3Sb(Cat-Spiro-Cat)SbPh3 reacts with Bipy as 1:1 yielding a rare macrocyclic tetranuclear compound {Ph3Sb(Cat-Spiro-Cat)SbPh3∙(Bipy)}2 (13). The molecular structures of 1, 3, 4, 5, 8, 10, 12, and 13 in crystal state were established by single-crystal X-ray analysis. Complexes demonstrate different types of relative spatial positions of mononuclear moieties. The nature of chemical bonds, charges distribution, and the energy of Sb...N interaction were investigated in the example of complex 5. The electrochemical behavior of the complexes depends on the coordinated N-donor ligand. The coordination of pyrazine, Bipy, and PySSPy at the antimony atom changes their mechanism of electrooxidation: instead of two successive redox stages Cat/SQ and SQ/Cat, one multielectron stage was observed. The coordination of the DABCO ligand is accompanied by a significant shift in the oxidation potentials of the catecholate ligand to the cathodic region (by 0.4 V), compared to the initial complex

Highly Active, Chemo- and Regioselective Yb II and Sm II Catalysts for the Hydrophosphination of Styrene with Phenylphosphine

International audienceStable heteroleptic amido YbII and SmII complexes bearing aminoether–phenolate ligands and devoid of coordinated solvent have been structurally characterized. They afford highly active, chemoselective and, in the case of monoadditions, 100% anti-Markovnikov regiospecific catalysts (down to 0.04 mol% loading) for the hydrophosphination of styrene with PhPH2 under mild conditions

Synthesis, structure and magnetic properties of tris(pyrazolyl)methane lanthanide complexes: effect of the anion on the slow relaxation of magnetization

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