Phenoxide Oxygen Atoms Research Articles

Polymeric Copper(II) Complexes with a Newly Synthesized Biphenyldicarboxylic Acid Schiff Base Ligand—Synthesis, Structural and Thermal Characterization

The newly synthesized biphenyldicarboxylic acid Schiff base and its complexes with Cu(II) were synthesized, and their spectroscopic and structural analysis was performed. The reaction of the ligand and copper(II) acetate in different solvents resulted in the formation of two solvatomorphic complexes, one with MeOH, and the other with DMF molecules, in the crystal lattice. The differences in the results of the thermal analysis could be explained by the different polarities of the solvents present. SC-XRD analysis revealed that the ligand is coordinated as a dianion, in a pentadentate manner, through two phenoxide oxygen atoms, two azomethine nitrogen atoms, and with the oxygen atom of one carboxylate functioning as a bridge that connects the monomeric units. The coordination polyhedron was described with several parameters obtained from different methods of calculation. The presence of different solvents in the crystal structure results in differences in the H-bond networks, and an overall different crystal packing of the structural units in the obtained complexes.

Structures and magnetic properties of two dinuclear lanthanide complexes based on 8-hydroxyquinoline Schiff base derivatives

Based on 8-hydroxyquinoline Schiff base derivative and auxiliary ligand β-diketonate, two new dinuclear lanthanide complexes [Gd2(L1)2(bfac)4] (1) and [Dy2(L2)2(acac)2(CH3OH)2]•CH3OH (2) (HL1 = 2-[((4-phenethyl)-imino)methyl]-8-hydroxyquinoline, H2L2 = 2-[((4-methyl)-2-(arboxyl)-imino)]methyl]-8-hydroxyquinoline, Hbfac = hexafluoroacetylacetonate, Hacac = acetylacetonate,) were successfully isolated and characterized. Structural analysis reveal that complexes 1 and 2 both contain a binuclear Ln2 cluster, in which two eight-coordinated Ln(III) ions are located in distorted dodecahedral geometry and bridged by phenoxide oxygen atom. In addition, their magnetic properties are investigated in detail. The results suggest that ferromagnetic interactions between adjacent Gd3+ ions can be observed in 1, which exhibits remarkable magnetic refrigeration properties with -ΔSmax = 17.74 J kg−1 K−1 (T = 2.0 K and ΔH = 7.0 T). Complex 2 displays slow magnetic relaxation behaviors with ΔE/kB ≈ 2.16 K and τ0 ≈ 1.38 × 10−5 s.

Reformatsky Reaction of 1-Aryl-3-(2-hydroxyphenyl)prop-2-en-1-ones with Methyl 1-Bromocyclohexanecarboxylate

1-Aryl-3-(2-hydroxy-5-R-phenyl)prop-2-en-1-ones reacted with the Reformatsky reagent derived from methyl 1-bromocyclohexanecarboxylate to give 4-(2-aryl-2-oxoethyl)-6-R-2H,4H-spiro[[1]benzopyran-3,1′-cyclohexan]-2-ones. The products are formed as a result of intramolecular cyclization of the adduct of the organozinc reagent and substituted chalcone via nucleophilic attack of the phenoxide oxygen atom on the ester carbonyl carbon atom. No cyclization products resulting from attack of the enolate oxygen atom on the ester carbonyl carbon atom were detected.

Synthesis, characterization, crystal structures and anti-diabetic activity of organotin (IV) complexes with 2-(4-hydroxynaphthylazo)-benzoic acid

Three new organotin(IV) complexes 1–3 were synthesized by the reaction of 2-(4-hydroxynaphthylazo)-benzoic acid with bis-tributyltin(IV) oxide (1), dibutyltin(IV) oxide (3) or trimethyltin(IV) chloride (2), respectively. The complete characterization of the complexes was accomplished by elemental analysis, IR and multinuclear [1H- and 13C- and 119Sn-] NMR spectroscopy. The crystal structures of all the complexes were elucidated with the help of X-ray single crystal diffraction analysis. The geometry around tin atoms in 1 and 2 was trigonal bipyramidal geometry where the equatorial plane was occupied by the three alkyl groups (Bu or Me) and the axial positions in 1 were being occupied by carboxylate and phenoxide oxygen atoms giving rise to a polymeric structure. In 2, a hydroxy oxygen atom bridges two tin atoms occupying axial position while the other axial positions in each tin atom were being occupied by a carboxylate oxygen atom or oxygen atom of a water molecule respectively thereby completing trigonal bipyramidal geometry. The structure of 3 was a di-nuclear complex with six-coordinate distorted skew trapezoidal and seven-coordinate pentagonal bipyramidal geometry around the tin atoms, respectively. In the dinuclear structure, one of the tin atoms is coordinated by a terminal azo-ligand while the other tin atom is coordinated by two terminal azo-ligands. In addition to this, another azo-carboxylate ligand bridges the two atoms in the dinuclear structure. The NMR study showed that in the solution the complexes 1 and 2 adopted four-coordinate geometry, while in 3 there is five-coordinate structure. Complexes 1 and 3 were screened for their antidiabetic activities against α-glucosidase enzyme and results of the assay found that compound 3 exhibited significant inhibition activity.

Polypyridines, Picrates, Lanthanides: A Plethora of Stacks?

Reactions of the lanthanide(iii) picrates (picrate=2,4,6-trinitrophenoxide=pic) with 1,10-phenanthroline (phen) and 2,2′:6′,2′′-terpyridine (terpy) in a 1:2 molar ratio have provided crystals suitable for X-ray structure determinations in instances predominantly involving the lighter lanthanides. In all, the aza-aromatic ligands chelate the lanthanide ion, none being found as ‘free’ ligands within the lattice. The complexes of 1,10-phenanthroline have been characterised in two forms, one unsolvated (Ln=La, Sm, Eu; monoclinic, C2/c, Z 8), one an acetonitrile monosolvate (Ln=Gd; monoclinic, P21/a, Z 4), the latter being the only previously known form (with Ln=La). In both forms, the LnIII is nine-coordinate, in an approximately tricapped trigonal-prismatic environment, with two picrate ligands chelating through phenoxide and 2-nitro group oxygen atoms, the third being bound through phenoxide-O only. The 2,2′:6′,2′′-terpyridine complexes, all acetonitrile monosolvates defined for Ln=La, Gd, Er, and Y (monoclinic, C2/c, Z 4), are ionic, one picrate having been displaced from the primary coordination sphere. For Ln=La, the two bound picrates are again chelating, making the LaIII 10-coordinate in a distorted bicapped square-antiprismatic environment but in the other species they are bound through phenoxide-O only, making the LnIII ions eight-coordinate in a distorted square-antiprismatic environment. Stacked arrays of the ligands can be found in both series of complexes, with intramolecular picrate–picrate and picrate–aza-aromatic stacks being prominent features.

Synthesis, structural characterization and antimicrobial activities of triorganotin(IV)azo-carboxylates derived from ortho/para-amino benzoic acids and β-naphthol

Triorganotin (IV) complexes 1–3 were synthesized by the reaction of azo-carboxylic acid viz. 2/4-(2-hydroxynaphthylazo)benzoic acids with appropriate triorganotin(IV) chlorides [R = Me (compounds 1 and 2) and Bu (compound 3)] in presence of triethyl amine base. The complexes were characterized by elemental analysis, IR and multinuclear (1H and 13C- and 119Sn)-NMR spectroscopy. The structures and mode of coordination around tin ions in the complexes were determined by single crystal X-ray crystallography. The complexes exhibit trigonal bipyramidal geometry around tin atoms where the base of the equatorial plane is being occupied by the three alkyl groups [Me or Bu] while the axial positions are occupied by carboxylate oxygen atoms in 2 and in case of 1 and 3, by carboxylate and phenoxide oxygen atoms, respectively. It has been found that, the crystal structure of 1 or 3 is a cyclic dimeric, whereas 2 exhibits a polymeric structure. The 119Sn NMR studies show that all complexes have four-coordinate structures indicating dissociation of these complexes in solution state. The complexes were also screened for their antimicrobial activity and the compound 3 was found to exhibit effective antimicrobial activity.

Butterfly shaped tetranuclear dysprosium compound displaying slow magnetic relaxation features

One new tetranuclear dysprosium compound, namely [Dy4(μ3-OH)2(L)6(tmhd)4]·CH3CN (1) (HL=5-(4-methylbenzylidene)-8-hydroxylquinoline; tmhd=2,2,6,6-tetramethyl-3,5-heptanedione) was successfully synthesized and characterized. The structure of 1 was established by the single crystal X-ray diffraction technique, and the center Dy(III) ions was bridged by μ3-OH molecules and phenoxide oxygen atoms, displaying a ‘butterfly’ arrangement. Magnetic studies reveal that weak ferromagnetic interaction between adjacent Dy(III) exists in 1. Additionally, it also exhibits slow magnetic relaxation behaviors with the energy barrier of 46.4K.

Synthesis, characterisation and anti-diabetic activities of triorganotin(IV) azo-carboxylates derived from amino benzoic acids and resorcinol: Crystal structure and topological study of a 48 membered macrocyclic-tetrameric trimethyltin(IV) complex

Triorganotin(IV) complexes of azo-carboxylic acids derived from amino benzoic acids and resorcinol were synthesized by the reaction of 2/4-(2,4-dihydroxy-phenylazo)-benzoic acids with appropriate triorganotin(IV) chlorides [R=Me (1 and 3), Ph (2 and 4) and Bu (5)] in presence of triethylamine. The characterisation of the complexes was accomplished by elemental analyses, UV, IR and multinuclear (1H, 13C and 119Sn) NMR spectroscopy. Structure of compound 3 was established by X-ray crystal structure analysis. X-ray crystal structure of 3 revealed that the compound exhibits a 48 membered macrocyclic-tetrameric structure with trigonal bipyramidal geometry around the tin atoms in which the three methyl groups occupy the equatorial positions while the apical positions are being occupied by the oxygen atom of carboxylate group of one ligand and the phenoxide oxygen atom of another ligand. The coordination network in 3 has also been analysed from the topological viewpoint. All the complexes display a sharp singlet 119Sn resonance in the range specified for the four coordinate structures suggesting that complexes have tetrahedral structures in solution. The five coordinate structure of the complexes in solid state dissociated into monomeric species with four coordinate structures in solution. Anti-diabetic activities of the complexes were studied and the results showed that the compounds 2, 3 and 4 exhibited effective activity even higher than the standard compound.

A tetranuclear holmium compound exhibiting single molecule magnet behavior

The synthesis, structure, and magnetic properties of a new tetranuclear holmium cluster [HoIII4(μ3-OH)2(L)4(piv)2(DMF)2]·2DMF (1) is reported, where the Schiff base H2L ligand is 2-hydroxy-3-methoxy-phenylsalicylaldimine and piv is pivalate. The cluster has a planar “butterfly” Ho4 core, which is bridged by two μ3-hydroxide and six phenoxide oxygen atoms. Magnetically, compound 1 displays field-induced slow relaxation of magnetization. Fitting the dynamic magnetic data to the Arrhenius law gives energy barrier ΔE/kB=21.49K and τ0=6.97×10−7s.

Diorganotin(IV) complexes of 3,5-dichloro-2-hydroxybenzaldehyde-N(4)-ethylthiosemicarbazone: Synthesis, spectral characterization and crystal structure

Three new diorganotin(IV) complexes of the formulae [Me2Sn(cdet)] (2), [Bu2Sn(cdet)] (3) and [Ph2Sn(cdet)] (4) have been synthesized by the reaction of 3,5-dichloro-2-hydroxybenzaldehyde-N(4)-ethylthiosemicarbazone [H2cdet, (1)] and appropriate diorganotin(IV) chloride in the presence of KOH in absolute methanol. These compounds have been characterized by CHN analyses, UV–Vis, FT-IR, 1H, 13C and 119Sn NMR spectroscopic techniques. The molecular structures of the ligand (1) and its diphenyltin(IV) complex (4) have been determined by X-ray diffraction analysis. The ligand H2cdet (1) remains as the thione form in the solid state. The crystal structure of [Ph2Sn(cdet)] (4) revealed that the ligand is coordinated to central tin(IV) atom as a dinegatively tridentate chelating agent via the phenoxide oxygen atom, the azomethine nitrogen atom and the thiolate sulfur atom. The 119Sn NMR chemical shift for the complexes (2–4) are found to be −177.08 to −169.22ppm, confirming five coordinated tin(IV) centre. X-ray crystal structure showed that the coordination geometry of central tin(IV) atom is distorted trigonal bipyramid. The oxygen and sulfur atoms are in axial positions while two phenyl groups and the azomethine nitrogen atom of the ligand occupy the equatorial positions.

Synthesis, spectroscopic characterization, biological screening, and theoretical studies of organotin(IV) complexes of semicarbazone and thiosemicarbazones derived from (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone

New organotin(IV) complexes of (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone thiosemicarbazone [L1H2], (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone phenylthiosemicarbazone [L2H2], and (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone semicarbazone [L3H2] with formula [R2SnL] (where R = Bu and Me) have been synthesized. The ligands and their organotin(IV) complexes were characterized by elemental analyses, molar conductivity, molecular weight determination, electronic, Fourier-transform infrared, and 1H, 13C, and 119Sn nuclear magnetic resonance spectral studies. The ligands act as tridentate and coordinate with organotin(IV) atom through the thiolate sulfur, azomethine nitrogen, and phenoxide oxygen atoms. The low molar conductance values in dimethylformamide indicate that the metal complexes are nonelectrolytes. Theoretical calculation is provided in support of the structures. The in vitro antimicrobial activities have been evaluated against Klebsiella sp., Bacillus cereus, Staphylococcus sp., Escherichia coli, Rhizopus, Aspergillus, Alternaria, and Penicillium. The screening results show that the organotin(IV) complexes have better antibacterial activities and have potential as drugs. Furthermore, it has been shown that dibutyltin(IV) derivative exhibits significantly better activity than the other organotin(IV) derivatives.

Switching on Single‐Molecule‐Magnet Behavior in Mn III –Schiff Base Out‐of‐Plane Dimers by the Phosphonate Terminal Ligand

This paper reports two metal phosphonate clusters containing MnIII–Schiff base units, namely, [Mn2(5-Brsalen)2(C10H7PO3H)2]·2CH3OH (1) and [Mn6(5-Brsalen)6(C10H7PO3)2(H2O)2](ClO4)2·7.6H2O (2) [5-Brsalen = N,N′-ethylenebis(5-bromosalicylideneiminate) dianion]. Compound 1 shows a discrete dinuclear structure in which dimers of Mn2(5-Brsalen)2 are terminated by the naphthylphosphonate ligand. In 2, each naphthylphosphonate ligand connects three Mn atoms, forming triangular units of {Mn3PO3}, which are further cross-linked through phenoxide oxygen atoms into a hexanuclear cluster. Magnetic studies reveal that the exchange couplings mediated through the phenoxide bridges within the dimer are ferromagnetic in compounds 1 and 2. Further, slow magnetization relaxation, characteristic of single-molecule magnets (SMMs), is observed in both 1 and 2, in contrast to the non-SMM behavior in the precursor of [Mn(5-Brsalen)(H2O)]2(ClO4)2.

A new linear double phenoxide-bridged trinuclear Cu(II) Schiff base complex: Synthesis, crystallographic elucidation, magneto-structural correlation and DFT Study

The tetradentate (ONNO) donor Schiff base ligand LH2, derived from the condensation of salicylaldehyde and 1,3-diaminopropane, has been synthesized and reacted with CuBr2 to yield a trinuclear complex with the molecular formula [Cu3L2Br2]. Single crystal X-ray diffraction study reveals that the two terminal copper atoms adopt a square pyramidal geometry, whereas the central copper atom, situated at the inversion centre, is surrounded by four phenoxide oxygen atoms in a square planar fashion. Variable temperature magnetic susceptibility measurement study shows strong antiferromagnetic intra-trimer interactions between the copper centers with a J value of −302cm−1. EPR study of the complex depicts that, due to the exchange coupling between the copper ions, the EPR spectra were unresolved, having very broad resonances with g=2.133. A theoretical DFT calculation was also carried out to supplement the experimental results.

Crystal structure and magnetic properties of the binuclear copper(II) complex with 2,6-diformyl-4-tert-butylphenol bis(imidazolinylhydrazone)

The binuclear copper(II) complex with 2,6-diformyl-4-tert-butylphenol bis(imidazolinylhydrazone) (H3L), [Cu2(H2L)Br2]ClO4 (I), was synthesized. The structure of complex I was determined by X-ray diffraction analysis. The antiferromagnetic exchange interaction (2J = −108 cm−1) translated through the phenoxide oxygen atom is observed between the copper(II) ions. The exchange parameter was calculated by the quantum-chemical “broken symmetry” method.

Dioxidovanadium(V) complexes with pyridoxalaminoguanidine: Synthesis, spectral and structural characterization

Three square-pyramidal complexes of dioxidovanadium(V) with pyridoxalaminoguanidine (PLAG), of the formulas NH4[VO2(PLAG?2H)]?H2O (1), VO2(PLAG?H) (2) and K[VO2(PLAG?2H)]?H2O (3) have been synthesized and characterized by IR and UV-Vis spectral analysis and in case of 1 and 3 by X-ray crystallography as well. The reaction of aqueous ammoniacal solution of NH4VO3 and PLAG resulted in formation of 1, which in MeOH undergoes spontaneous transformation into 2, which, in turn, in the reaction with KOH transforms into 3. In these complexes PLAG is coordinated in a common tridentate ONN mode, via phenoxide oxygen atom and nitrogen atoms of azomethine and imino groups of the aminoguanidine fragment. In all previously characterized complexes PLAG was coordinated in neutral form. However, here we have proven that this ligand can be coordinated in both mono- (2) and doubly deprotonated form (1 and 3) as well. [Projekat Ministarstva nauke Republike Srbije, br. 172014].

Syntheses, Structures, and Catalytic Activity of Copper(II)‐Aroylhydrazone Complexes

AbstractTwo CuII complexes of tridentate Schiff base ligands, [Cu(L1)(CH3OH)2]NO3·CH3OH (1) and [Cu2(L2)2(CH3OH)2](NO3)2 (2), were prepared and characterized by elemental analyses and spectroscopic methods [H2L1 = (E)‐N‐(4‐hydroxy benzoic acid (2‐hydroxy‐3‐methoxybenzylidene)benzohydrazide, and H2L2 = (E)‐N‐4‐hydroxy benzoic acid (5‐bromo‐2‐hydroxybenzylidene)benzohydrazide]. The crystal structures of 1 and 2 were established by X‐ray crystallography. The complex cation in 1 is based on a square pyramid with the uninegative Schiff base coordinating in a tridentate mode via O, N, O′‐donor atoms with the remaining sites being occupied by two methanol oxygen atoms with one of these in the axial position. By contrast, the Schiff base coordinates in a tridentate ligand fashion in dinuclear compound 2 as the phenoxide oxygen atom bridges two central copper atoms. The NO4 coordination donor set is completed by a methanol oxygen atom, which occupies an axial position in the distorted square pyramidal arrangement. Complexes 1 and 2 are very active catalysts in clean epoxidation reactions using aqueous hydrogen peroxide and acetonitrile. The effects of reaction parameters such as solvent and oxidant in the epoxidation of cis‐cyclooctene were investigated and showed that cyclooctene and cyclohexene were oxidized efficiently to their corresponding epoxide with 100 and 31 % selectivity, respectively, in the presence of catalyst 2. This catalytic system showed also excellent selectivity in the oxidation of benzyl alcohol.

Synthesis, structural characterization and electrochemical studies of nickel(II), copper(II) and cobalt(III) complexes of some ONS donor ligands derived from thiosemicarbazide and S-alkyl/aryl dithiocarbazates

Four tridentate ONS ligands, namely 2-hydroxyacetophenonethiosemicarbazone (H2L1), the 2-hydroxyacetophenone Schiff base of S-methyldithiocarbazate (H2L2), the 2-hydroxy-5-nitrobenzaldehyde Schiff base of S-methyldithiocarbazate (H2L3), and the 2-hydroxy-5-nitrobenzaldehyde Schiff base of S-benzyldithiocarbazate (H2L4), and their complexes of general formula [Ni(HL1)2], [ML] (M = NiII or CuII; L = L1, L2, L3 and L4), [Co(HL)(L); L = L1, L2, L3 and L4] and [ML(B)] (M = NiII or CuII; L = L2 and L4; B = py, PPh3) have been prepared and characterized by physico-chemical techniques. Spectroscopic evidence indicates that the Schiff bases behave as ONS tridentate chelating agents. X-ray crystallographic structure determination of [NiL2(PPh3)] and [CuL4(py)] indicates that these complexes have an approximately square-planar structure with the Schiff bases acting as dinegatively charged ONS tridentate ligands coordinating via the phenoxide oxygen, azomethine nitrogen and thiolate sulfur atoms. The electrochemical properties of the complexes have been studied by cyclic voltammetry.

Elongation of Phenoxide C–O Bonds Due to Formation of Multifold Hydrogen Bonds: Statistical, Experimental, and Theoretical Studies

Statistical studies using the Cambridge Structural Database have revealed that there are several elongated phenoxide C-O bonds. They are characterized by the formation of 3-fold (or occasionally 2-fold) hydrogen bonds to the phenoxide oxygen atoms, and their mean bond length extends up to 1.320 Å, which is quite different from the theoretically predicted carbon-oxygen bond length of C(6)H(5)O(-) (1.26 Å). Elongated phenoxide C-O bonds associated with the formation of 3-fold hydrogen bonds were also observed in the X-ray structures of proton-transfer complexes (2X-O(-))(TEAH(+))s derived from 5'-X-substituted 5,5''-dimethyl-1,1':3',1''-terphenyl-2,2',2''-triols (2X-OHs, where X = NO(2), CN, COOCH(3), Cl, F, H, and CH(3)) and triethylamine (TEA). By comparing the X-ray structures, C-O bond elongation was found to be only slightly affected by an electron-withdrawing substituent at the para position (X). This along with strong bathochromic shifts of N-H(···O(-)) and O-H(···O(-)) stretching vibrations in the IR spectra indicates that the elongated C-O bonds in (2X-O(-))(TEAH(+))s essentially have single-bond character. This is further confirmed by molecular orbital calculations on a model complex, showing that the negatively charged phenoxide oxygen atom is no longer conjugated to the central benzene ring, and the NICS values of the three benzene rings are virtually identical. However, C-O bond elongation in (2X-O(-))(TEAH(+))s was considerably influenced by a change in the hydrogen-bond geometry. This also suggests that hydrogen bonds significantly affect phenoxide C-O bond elongation.

Thiacalix[4]arene–potassium assemblies: a supramolecular architecture based on coordination polymers and a dimeric structure based on triangular pyramidal arrangements

The crystal structures of two potassium metal complexes {[K4(1·2H)2]·(MeOH)2·(H2O)1.5}2 (2) and {[K8(1)2]·(μ2-n-BuOH)2·(n-BuOH)4} (3) of partially- or fully-deprotonated p-H-thiacalix[4]arenes were determined by single-crystal X-ray diffraction studies. In the crystal structure of complex 2, a coordination polymer was formed by continuing of complementary metal coordination and π-stacking interactions between the base dimer and a ca. 90° turned neighboring dimer. In addition, coordinated methanol molecules in the polymer play a significant role in the construction of a supramolecular architecture. In the case of the complex 3, eight potassium cations exhibited two triangular pyramidal arrangements, which are bridged at planar phenoxide oxygen atoms and linking sulfur atoms belonging to the thiacalixarene ligands further support via alkali-metal cation–π interactions in the thiacalixarene cavities.

Insight into the Steric and Electronic Effects of Ancillary Ligands: Synthesis and Structure−Reactivity Relationship of Well-Defined, Air- and Moisture-Stable (NHC)Pd(sal)Cl Complexes (sal = Salicylaldimine)

Synthesis of a series of (NHC)Pd(sal)Cl complexes, 1−5, bearing a salicylaldimine (sal) unit was described. The structure−reactivity relationship, especially the steric and electronic effects of the salicylaldimine ligands on their catalytic activities, was investigated intensively in the Buchwald−Hartwig coupling reaction. Our study demonstrated that the sterically encumbered N-aryl groups in the salicylaldimine unit give rise to an obviously negative effect in the aryl amination reaction. Additionally, incorporating a steric substituent into the ortho-position of the phenoxide oxygen atom does not appear to be beneficial to their catalytic activity. Notably, the electronic nature of N-substituted aryl groups in the salicylaldimine ligands plays a significant role in their catalytic activities. An electron-rich N-aryl group causes an obviously decreasing yield, while an electron-deficient one, such as complex 5b, leads to enhanced reactivity. The aryl amination reaction with complex 5b was also found to ...