Arylamide Ligands Research Articles

Syndio-specific polymerization of styrene promoted by rare-earth metal bis(aminobenzyl) complexes bearing pyrrolyl-modified arylamide ligands

Acid-base reaction of the rare-earth metal tris(o-dimethylaminobenzyl) complexes Ln (CH2C6H4NMe2-o)3 with 1 equiv. of the pyrrolyl-modified arylamide ligands 2,5-Me2C4H2NSiMe2NHC6H4R (R = H, Cl-p, OMe-p) in toluene gave (2,5-Me2C4H2NSiMe2NC6H5)Ln (CH2C6H4NMe2-o)2 (Ln = Sc (1), Y (2), Lu (3)), (2,5-Me2C4H2NSiMe2NC6H4Cl-p)Y(CH2C6H4NMe2-o)2 (4), and (2,5-Me2C4H2NSiMe2NC6H4OMe-p)Y(CH2C6H4NMe2-o)2 (5) in good isolated yields. These complexes were well-characterized by elemental analysis and NMR spectroscopy. 1, 2 and 4 were structurally determined by single crystal X-ray diffraction. The catalyst systems of 1–5/AliBu3/[Ph3C][B(C6F5)4] were able to promote styrene polymerization to afford pure and highly syndio-tactic polystyrene (rrrr > 99%). Among these rare-earth metal complexes, the complexes with the central metal being the cheapest yttrium showed much higher activity than the expensive scandium analogues. The styrene polymerization catalyzed by 4/AliBu3/[Ph3C][B(C6F5)4] proceeded in a controlled fashion.

Rare-earth metal bis(aminobenzyl) complexes supported by pyrrolyl-functionalized arylamide ligands: synthesis, characterization and styrene polymerization performance.

An acid-base reaction between the rare-earth tris(o-dimethylaminobenzyl) complexes Ln(CH2C6H4NMe2-o)3 and the pyrrolyl-functionalized arylamide ligands 2,5-Me2C4H2NCH2SiMe2NHC6H4R (R = H, (HL1); R = Cl-p, (HL2)) was investigated. Treatment of HL1 and HL2 with 1 equiv. of Ln(CH2C6H4NMe2-o)3 in toluene at room temperature gave (2,5-Me2C4H2CH2NSiMe2NC6H5)Ln(CH2C6H4NMe2-o)2 (Ln = Sc (1), La (2), Lu (3)) and (2,5-Me2C4H2NCH2SiMe2NC6H4Cl-p)Ln(CH2C6H4NMe2-o)2 (Ln = Sc (4), La (5), Lu (6)) in good isolated yields. These complexes were characterized by elemental analysis and NMR spectroscopy. 2, 4 and 5 were structurally authenticated by single crystal X-ray diffraction. NMR and X-ray diffraction show that there are no interactions between the central metal and the pyrrolyl moiety in small sized metal complexes, while in large lanthanum complexes, besides the coordination of the arylamide moiety to La3+ in η1-bonding mode through a N atom, the pyrrolyl ring also has close contact with La3+ in 2 and 5. The binary systems of 1-6/[Ph3C][B(C6F5)4] were employed as catalysts for syndio-specific polymerization of styrene, and the pyrrolyl-ligated lanthanum complexes showed much higher activity than the complexes in which the pyrrolyl moiety had no coordination with the central metal.

Ruthenium porphyrins with axial π-conjugated arylamide and arylimide ligands.

A series of ruthenium porphyrins [Ru(IV)(por)(NHY)2] and [Ru(VI)(por)(NY)2] bearing axially coordinated π-conjugated arylamide and arylimide ligands, respectively, have been synthesized. The crystal structures of [Ru(IV)(tmp)(NHY)2] (tmp = 5,10,15,20-tetramesitylporphyrinato(2-)) with Y = 4'-methoxy-biphenyl-4-yl (Ar-Ar-p-OMe), 4'-chloro-biphenyl-4-yl (Ar-Ar-p-Cl), and 9,9-dibutyl-fluoren-2-yl (Ar^Ar) show axial Ru-N(arylamide) distances of 1.978(4), 1.971(6), and 1.985(13) Å, respectively. [Ru(IV)(tmp)(NH{Ar^Ar})2] is an example of metalloporphyrins that bind an arylamide ligand featuring a co-planar biphenyl unit. The [Ru(IV)(por)(NHY)2] complexes show a quasi-reversible reduction couple or irreversible reduction wave attributed to Ru(IV)→Ru(III) with Epc from -1.06 to -1.40 V versus Cp2Fe(+/0) and an irreversible oxidation wave with Epa from -0.04 to 0.19 V versus Cp2Fe(+/0). Reaction of the [Ru(IV)(por)(NHY)2] with bromine afforded [Ru(IV)(por)(NHY)Br]. PhI(OAc)2 oxidation of the [Ru(IV)(por)(NHY)2] gave [Ru(VI)(por)(NY)2]; the latter can be prepared from reaction of [Ru(II)(por)(CO)] with aryl azides N3Y. The crystal structure of [Ru(VI)(tmp)(N{Ar-Ar-p-OMe})2] features Ru-N(arylimide) distances of 1.824(5) and 1.829(5) Å. Alkene aziridination and C-H amination catalyzed by "[Ru(II)(tmp)(CO)]+π-conjugated aryl azides", or mediated by [Ru(VI)(por)(NY)2] with Y = biphenyl-4-yl (Ar-Ar) and Ar-Ar-p-Cl, gave aziridines and amines in moderate yields. The electronic structure of [Ru(VI)(por)(NY)2] was examined by DFT calculations.

Synthesis, characterization, luminescence properties and antioxidant activity of Ln(III) complexes with a new aryl amide bridging ligand

A novel Aryl amide ligand H2L and its eight complexes, [LnH2L(NO3)2·H2O]NO3 [Ln=Sm(III), Er(III), Tb(III), Dy(III), La(III), Gd(III), Nd(III), and Pr(III)], are presented. The ligand and complexes were synthesized and characterized based on elemental analyses, molar conductance, IR, 1H and 13C-NMR, UV–VIS., and TGA studies. The conductivity data show a 1:1 electrolytic nature with a general formula [LnH2L(NO3)2·2H2O]NO3 The IR spectra reveal coordination of the ligand through the azomethine nitrogen and the phenolic hydroxyl of the ligand to the lanthanide ion. The coordinated nitrate ions behave in a bidentate fashion. The thermal decomposition studies indicate the presence of two water molecules in the inner coordination sphere. Under the excitation at 319nm, the luminescence emission properties for Sm, Tb, and Dy complexes are observed. These observations show that the ligand favors energy transfers to the emitting energy level of these lanthanide ions. Furthermore, the antioxidant activity of the ligand and its Ln(III) complexes was determined by DPPH radical scavenging method, which indicates that the Ln(III) complexes exhibit more effective antioxidant activity than the ligand alone.

Synthesis and Fluorescent Properties of Eu and Tb Complexes of a New Aryl Amide Ligand

A new ligand, 1,2-bis[(2-benzyloxy)benzoylamino]ethane, and its complexes of europium and terbium have been synthesised and characterised. Under UV light, the europium and terbium complexes exhibited characteristic emissions and measurement of the lowest triplet state energy level of the ligand indicates that it matches better to the lowest resonance energy level of the Tb(III) ion than to that of the Eu(III) ion.

Intermolecular, Catalytic Asymmetric Hydroamination of Bicyclic Alkenes and Dienes in High Yield and Enantioselectivity

A set of catalytic, intermolecular hydroaminations of strained bicyclic olefins and dienes are reported that occur in both high yield and high enantioselectivity. These reactions occur with a catalyst generated from [Ir(cyclooctene)Cl]2, sterically hindered and electron-rich derivatives of the Segphos and BIPHEP family of ligands, and a soluble base. This system catalyzes the addition of various anilines to norbornene, norbornadiene, and other bicyclic olefins. The products from addition of p-anisidine can be transformed to BOC-protected norbornylamine and to substituted cyclopentanes in nearly enantiopure form. Mechanistic studies show that addition of aniline-d2 occurs in a syn fashion and suggest that the catalytic cycle comprises oxidative addition of aniline to form a bis-anilide hydride complex, followed by migratory insertion of olefin and reductive elimination of product in a series of steps involving iridium complexes containing ancillary bisphosphine and arylamide ligands.

Synthesis, characterization and fluorescent properties of lanthanide complexes with two aryl amide ligands

Two aryl amide ligands, N-(p-tolyl)-2-(quinolin-8-yloxy)acetamide (L1 ) and N-(4-chlorophenyl)-2-(quinolin-8-yloxy)acetamide (L2 ), were synthesized. With these ligands, two series of lanthanide(III) complexes were prepared, Ln(L n )2(NO3)3 (n = 1, 2; Ln = La, Sm, Eu, Gd, Dy), and characterized by the elemental analyses, molar conductivity, 1H NMR spectra, IR spectra and TG-DTA. The fluorescence properties of the complexes and the triplet state energies of the ligands were studied in detail. In addition, the quantum yields of both Eu(III) complexes and Eu(L0)2(NO3)3 [where L0 is N-(phenyl)-2-(quinolin-8-yloxy)acetamide] 1 were calculated. The results indicate that among the lowest triplet energies (T) of the three ligands, that of L2 is most suitable to the resonance level (5D1) of Eu(III) ion. Furthermore, Eu(L2)2(NO3)3 has the highest fluorescence intensity and quantum yield of the three Eu(III) complexes.

Synthesis, structure and spectroscopic properties of rare earth complexes with a new aryl amide 2,2′-bipydine derivative

Solid complexes of rare earth nitrates and picrates with a new aryl amide ligand 3.3′-bis(benzylamido)-2,2′-bipyridine ( L) were synthesized and characterized by elemental analysis, IR and molar conductivity measurements. The molecular structures of the complex [TbL 2(NO 3) 3H 2O]·2H 2O have been determined by single-crystal X-ray diffraction. The fluorescent properties of the Eu(III) and Tb(III) nitrates and picrates complexes in solid state were also investigated in detail. Under the excitation, these complexes exhibited characteristic emissions of europium and terbium ions. It is worth noting that the nature of the anion has a great effect upon the composition of the complexes as well as emission properties of them.

A comparative study of pi-arene-bridged lanthanum arylamide and aryloxide dimers. Solution behavior, exchange mechanisms, and X-ray crystal structures of La2(NH-2,6-iPr2C6H3)6, La(NH-2,6-iPr2C6H3)3(THF)3, and La(NH-2,6-iPr2C6H3)3(py)2.

Reaction of 3 equiv of 2,6-diisopropylaniline with La[N(SiMe(3))(2)](3) produces the dimeric species La(2)(NHAr)(6) (1). X-ray crystallography reveals a centrosymmetric structure, where the dimeric unit is bridged by intermolecular eta(6)-arene interactions of a unique arylamide ligand attached to an adjacent metal center. Exposure of 1 to THF results in formation of the monomeric tris-THF adduct La(NHAr)(3)(THF)(3) (2), which was shown by X-ray crystallography to maintain a fac-octahedral structure in the solid state. (1)H NMR spectroscopy illustrates that the binding of THF to 1 to form 2 is reversible and removal of THF under vacuum regenerates dimeric 1. Addition of pyridine to 1 yields the monomeric bis-pyridine adduct La(NHAr)(3)(py)(2) (3), which exhibits a distorted trigonal-bipyramidal La metal center. Solution (1)H NMR, IR, and Raman spectroscopy indicate that the pi-arene-bridged dimeric structure of 1 is maintained in solution. Variable-temperature (1)H NMR spectroscopic investigations of 1 are consistent with a monomer-dimer equilibrium at elevated temperature. In contrast, variable-temperature (1)H NMR spectroscopic investigations of the aryloxide analogue La(2)(OAr)(6) (4) show that the bridging and terminal aryloxide groups exchange by a mechanism in which the dimeric nature of the compound is retained. Density functional theory (DFT) calculations were carried out on model compounds La(2)(OC(6)H(5))(6), La(2)(NHC(6)H(5))(6), and (C(6)H(5)R)La(XC(6)H(5))(3), where X = O or NH and R = H, OH, or NH(2). The formation of eta(6)-arene interactions is energetically favored over monomeric LaX(3) (X = OPh or NHPh) with the aryloxide pi-arene interaction being stronger than the arylamide pi-arene interaction. Calculation of vibrational frequencies reveals the origin of the observed IR spectral behavior of both La(2)(OC(6)H(5))(6) and La(2)(NHC(6)H(5))(6), with the higher energy nu(C=C) stretch due to terminal ligands and the lower energy stretch associated with the bridging ligands.

Bowl-shaped molybdenum complexes containing tris(3- p-methoxyphenylpyrazol-1-yl)borate (Tp An). Crystal structures of [Mo(Tp An)(NO)(Cl)(NHC 6H 4-p-CH 3)] and [Mo(Tp An)(NO)(Cl){NHC 6H 4-p-N(CH 3) 2}

New arylamide complexes of the type [Mo(Tp An)(NO)(Cl)(NHC 6H 4 -p-R)] (Tp An=hydrotris(3- p-methoxyphenylpyrazol-1-yl)borate; R=CH 3O ( 1), N(CH 3) 2 ( 2), Cl ( 3), CH 3 ( 4)) have been prepared in order to deduce the influence different arylamide para-substituents have on their molecular structure and properties. The single-crystal X-ray structures of [Mo(Tp An)(NO)(Cl){NHC 6H 4 -p-N(CH 3) 2}] ( 2) and [Mo(Tp An)(NO)(Cl)(NHC 6H 4 -p-CH 3)] ( 4) have been solved, both of them having a characteristic bowl-like molecular shape. The influence of electronic and steric factors on the shape of the bowl cavity is discussed. Both compounds have a columnar packing arrangement with molecular interpenetrating between neighbouring columns. Given that columnar stacking could be appropriate for liquid crystal materials, new related complexes bearing long-chain substituted arylamide ligands [Mo(Tp An)(NO)(Cl)(NHC 6H 4 -p-C n H 2 n+1 )] ( n=6, 10, 12, 14, 16; 5– 9) have been prepared.

P- versus P,O- coordination in complexes of N-(diphenylphosphino)arylamide ligands ArC(O)NHPPh 2 (Ar=3-pyridyl, phenyl). X-ray crystal structures of [RhCl 2(η 5-C 5Me 5)L 2] and [NiCl(EtOH)L 2 2]·Cl·[NiCl 2L 2 2] (L 2=C 6H 5CONHPPh 2)

The N-(diphenylphosphino)arylamide ligands 3-NC 5H 4CONHPPh 2 (L 1) and C 6H 5CONHPPh 2 (L 2) function as monodentate p-donors in the complexes [RhCl 2(η 5-C 5Me 5)L], [RuCl 2(η 6- p-cymene)L] and cis-[PtCl 2L 2], as exemplified by the X-ray crystallographically determined structure of [RhCl 2(η 5-C 5Me 5)L 2]. For nickel(II), P,O - chelation by L 1,2 is exhibited in the bis(bidentate) complexes [NiCl 2L 2], as demonstrated by the crystal structure of [NiCl(EtOH)L 2 2]·Cl·[NiCl 2L 2 2]; the five-membered NiOCNP chelate rings are approximately planar with the phosphorus atoms in the dichloro complex being trans whereas their arrangement is cis in the cation. Comparison of this structure with [RhCl 2(η 5-C 5Me 5)L 2] reveals slight elongation of the CO and PN lengths upon P,O -chelation of L 2. Solvatochromism for the Ni(II)-L 2 complex (green in ethanol or acetone, brown in chlorinated solvents) arises from solvent-dependent hemilability of the amide oxygen atom, although the L 1 complex of Ni(II) is exempt from this behaviour.

Tripodal trisamides based on nicotinic and picolinic acid derivatives

A number of polydentate arylamide ligands have been prepared by coupling various acyclic tripodal or linear polyamines with derivatives of nicotinic and picolinic acids. Two synthetic procedures were utilized; tris{[(2-hydroxynicotinyl)carbonyl]-2-aminoethyl}amine (H3NICTREN) was prepared by Method A, the HOSu/DCC method, and the other arylamides in this study were prepared by Method B, the CDI method. Method A involved the reaction of N-hydroxysuccinimide with 2-hydroxynicotinic acid (in the presence of dicyclohexylcarbodiimide (DCC) as a dehydrative coupling reagent) to form the succinimide ester, followed by reaction with TREN to yield H3NICTREN. Method B involved reaction of a carboxylic acid (2-hydroxynicotinic, 3-hydroxypicolinic, nicotinic, or picolinic acids) with carbonyldiimidazole (CDI) to form the N-acylimidazolide, followed by reaction with the amine (TREN, TAME, spermidine, or TRPN) to yield the desired arylamide. The X-ray structure of 1,1,1-tris{[(3-hydroxypicolinyl)carbonyl]-2-aminomethyl}ethane (H3PICTAME) was determined; crystals of H3PICTAME are monoclinic, a = 10.257(2), b = 15.572(3), c = 15.208(2) Å, β = 96.124(15)°, Z = 4, space group P21/a. The structure was solved by direct methods and refined by full-matrix least-squares procedures to R = 0.041 and Rw = 0.038 for 2506 reflections with I >= 3 sigma (I). In the solid state, H3PICTAME contains an extensive hydrogen-bonding network, with eight intra- and one intermolecular H-bonds per molecule; the ligand is partially preorganized for metal ion chelation. The acid dissociation constants of H3NICTREN and those of 1,1,1-tris{[(2-hydroxynicotinyl)carbonyl]-2- aminomethyl}ethane (H3NICTAME) have been determined; pKa1 = 11.2 (10.68), pKa2 = 10.7 (10.58), pKa3 = 10.0 (9.71), and pKa4 = 6.25 for H3NICTREN (H3NICTAME); the high phenolic pKa's are consistent with the hydrogen bonding observed in the solid state.Key words: arylamide, hydrogen bonding, preorganization.