The X‐ray Single Crystal Structures of an Acid‐functionalized Bis(2‐picolyl)amine (bpa) Ligand with Palladium(II) and Zinc(II) Display Different Intermoleclar Interactions around the Common (H2O)2(anion)2 Motif

This work reports structural investigations on two metal complexes of the functionalized (p‐carboxylatobenzyl)‐bis(2‐picolyl)amine ligand 1 (HL). The complex {[HLPdCl]Cl × H₂O}₂ ( 2_Pd ) has a square‐planar coordination around the Pd ion. It forms discrete dimers by intermolecular hydrogen bonding involving the protonated ligand HL. The coordination around the Zn²⁺ ion in {[(H₂O)LZn]CF₃SO₃ × 2 H₂O}_∞ ( 3_Zn ) is best described as distorted trigonal‐bipyramidal. The N₃O₂ ligand sphere is composed of three nitrogen atoms from the bpa ligand, one water molecule, and a carboxylate oxygen atom from a neighbouring molecule, thus forming infinite chains along the crystallographic a axis. Further intermolecular interactions are based on the same (H₂O)₂(anion)₂ motif as for 2_Pd , but whereas the former forms discrete dimers, 3_Zn forms a more complicated two‐dimensional coordination polymer with additional intermolecular hydrogen bonds.     

Copper(II)‐Mediated Transformation of a Tridentate Non‐Innocent Ligand into a Tetradentate Salen‐Type Innocent Ligand

A non‐innocent ligand, H₄L, was synthesized by introducing a ? CH₂NH₂ group at the ortho carbon atom to the aniline moiety of 2‐anilino‐4,6‐di‐tert‐butylphenol. The new ligand was characterized by IR and NMR spectroscopy and mass spectrometry techniques. Upon treatment with CuCl₂ ? 2 H₂O, this non‐innocent ligand provided a mononuclear four‐coordinate salen‐type Cu^II complex by complete modification of the ligand backbone. The complex was characterized by IR spectroscopy, mass spectrometry, X‐ray single‐crystal diffraction, electron paramagnetic resonance (EPR) spectroscopy, and UV/Vis/near‐IR spectroscopy techniques. X‐ray crystallographic analysis showed an asymmetric environment around the Cu^II center with a small (≈12°) twist between the two biting planes. Analysis of the X‐band EPR spectrum also supported the asymmetric environment and also indicated the presence of an unpaired electron on the d orbital. The UV/Vis/near‐IR spectrum showed strong absorption bands for metal‐to‐ligand charge transfer and ligand‐to‐metal charge transfer along with a Cu^II‐centered d–d transition. Mechanistic investigation of the formation of complex 1 indicated that modification of the ligand backbone proceeded through ligand‐centered amine to imine oxidation as well as through C? N bond‐breaking processes. During these processes, 3,5‐di‐tert‐butyl‐1,2‐benzoquinone and 2‐aminobenzylidene were produced. Ammonia, generated in situ through hydrolysis of the imine to the aldehyde, reacted with 3,5‐di‐tert‐butyl‐1,2‐benzoquinone to form the corresponding 3,5‐di‐tert‐butyl‐1,2‐iminobenzoquinone moiety, which upon two‐electron reduction in the reaction medium formed 3,5‐di‐tert‐butyl‐1,2‐aminophenol. This aminophenol underwent condensation with the H₂L5 ligand that was formed by self‐condensation of two molecules of 2‐aminobenzaldehyde and provided the modified ligand backbone.     

Stabilization of the Triphosphallyl Ligand η3‐P3{P(O)H} at Iridium via Alkaline Activation of P4

The selective functionalization of the polyphosphorus moiety Ph₂PCH₂PPh₂PPPP present as a tetrahapto‐ligand in complex [Ir(dppm)(Ph₂PCH₂PPh₂PPPP)]⁺ ( 1 , dppm=Ph₂PCH₂PPh₂) was obtained by reaction of 1 with water under basic conditions at room temperature. The formation of the new triphosphaallyl moiety η³‐P₃{P(O)H} was determined in solution by NMR spectroscopy, and confirmed in the solid state by a single‐crystal X‐ray structure of the stable product [Ir(κ²‐dppm)(κ¹‐dppm)(η³‐P₃{P(O)H})] ( 2 ). In solution, 2 has a fluxional behavior attributable to the four P atoms belonging to the tetraphosphorus moiety in 1 and exhibits a chemical exchange process involving the two PPh₂ moieties of the same bidentate ligand, as determined by 1D and 2D NMR spectroscopy experiments carried out at variable temperature. The mechanism of the reaction was investigated at the DFT level, which suggested a selective attack of an in‐situ generated OH^? anion on one of the non‐coordinated phosphorus atoms of the P₄ moiety. The reaction then evolves through an acid‐assisted tautomerization, which leads to the final compound 2 . Bonding analysis pointed out that the new unsubstituted P₃‐unit in the η³‐P₃{P(O)H} moiety behaves as a triphosphallyl ligand.     

Solid‐State Thermolysis of a fac‐Rhenium(I) Carbonyl Complex with a Redox Non‐Innocent Pincer Ligand

The development of rhenium(I) chemistry has been restricted by the limited structural and electronic variability of the common pseudo‐octahedral products fac‐[ReX(CO)₃L₂] (L₂=α‐diimine). We address this constraint by first preparing the bidentate bis(imino)pyridine complexes [(2,6‐{2,6‐Me₂C₆H₃N?CPh}₂C₅H₃N)Re(CO)₃X] (X=Cl 2 , Br 3 ), which were characterized by spectroscopic and X‐ray crystallographic means, and then converting these species into tridentate pincer ligand compounds, [(2,6‐{2,6‐Me₂C₆H₃N?CPh}₂C₅H₃N)Re(CO)₂X] (X=Cl 4 , Br 5 ). This transformation was performed in the solid‐state by controlled heating of 2 or 3 above 200 °C in a tube furnace under a flow of nitrogen gas, giving excellent yields (≥95 %). Compounds 4 and 5 define a new coordination environment for rhenium(I) carbonyl chemistry where the metal center is supported by a planar, tridentate pincer‐coordinated bis(imino)pyridine ligand. The basic photophysical features of these compounds show significant elaboration in both number and intensity of the d–π* transitions observed in the UV/Vis spec tra relative to the bidentate starting materials, and these spectra were analyzed using time‐dependent DFT computations. The redox nature of the bis(imino)pyridine ligand in compounds 2 and 4 was examined by electrochemical analysis, which showed two ligand reduction events and demonstrated that the ligand reduction shifts to a more positive potential when going from bidentate 2 to tridentate 4 (+160 mV for the first reduction step and +90 mV for the second). These observations indicate an increase in electrostatic stabilization of the reduced ligand in the tridentate conformation. Elaboration on this synthetic methodology documented its generality through the preparation of the pseudo‐octahedral rhenium(I) triflate complex [(2,6‐{2,6‐Me₂C₆H₃N?CPh}₂C₅H₃N)Re(CO)₂OTf] ( 7 , 93 % yield).     

Experimental and DFT Evidence for the Fractional Non‐Innocence of a β‐Diketonate Ligand

New compounds [Ru(pap)₂(L)](ClO₄), [Ru(pap)(L)₂], and [Ru(acac)₂(L)] (pap=2‐phenylazopyridine, L^?=9‐oxidophenalenone, acac^?=2,4‐pentanedionate) have been prepared and studied regarding their electron‐transfer behavior, both experimentally and by using DFT calculations. [Ru(pap)₂(L)](ClO₄) and [Ru(acac)₂(L)] were characterized by crystal‐structure analysis. Spectroelectrochemistry (EPR, UV/Vis/NIR), in conjunction with cyclic voltammetry, showed a wide range of about 2 V for the potential of the Ru^III/II couple, which was in agreement with the very different characteristics of the strongly π‐accepting pap ligand and the σ‐donating acac^? ligand. At the rather high potential of +1.35 V versus SCE, the oxidation of L^? into L^. could be deduced from the near‐IR absorption of [Ru^III(pap)(L^.)(L^?)]²⁺. Other intense long‐wavelength transitions, including LMCT (L^?→Ru^III) and LL/CT (pap^.?→L^?) processes, were confirmed by TD‐DFT results. DFT calculations and EPR data for the paramagnetic intermediates allowed us to assess the spin densities, which revealed two cases with considerable contributions from L‐radical‐involving forms, that is, [Ru^III(pap⁰)₂(L^?)]²⁺?[Ru^II(pap⁰)₂(L^.)]²⁺ and [Ru^III(pap⁰)(L^?)₂]⁺?[Ru^II(pap⁰)(L^?)(L^?)]⁺. Calculations of electrogenerated complex [Ru^II(pap^.?)(pap⁰)(L^?)] displayed considerable negative spin density (?0.188) at the bridging metal.     

Two New Zinc(II) Coordination Polymers Based on 1, 6‐Bis(2‐methyl‐imidazole‐1‐yl)‐hexane Ligand: Synthesis,Structures, and Properties

Two coordination polymers based on 1, 6‐bis(2‐methyl‐imidazole‐1‐yl)‐hexane (bimh), namely {[Zn₃(BTC)₂(bimh)] · (bimh)}_n ( 1 ) and {[Zn(IPA)(bimh)] · (CH₃CH₂OH)_0.5}_n ( 2 ) (H₃BTC = trimesic acid, H₂IPA = isophthalic acid), were synthesized through hydrothermal reactions. In compound 1 , the zinc(II) ions are bridged by BTC^3– ligands to form an undulating infinite two‐dimensional (2D) polymeric network. The 3D networks of 1 show a twofold interpenetrating net. In compound 2 , zinc(II) ions are bridged by IPA^2– ligands to form one‐dimensional (1D) helical structures. The 2D structures of 2 are further assembled into 3D networks through aromatic π–π stacking interactions. Both compounds exhibit strong photoluminescence at room temperature and may be good candidates for potential luminescence materials.     

Synthesis,Crystal Structure,and Electrochemistry of Iron and Cobalt Complexes Supported by a Pentadentate Amine‐bis(phenolate) Ligand

The pentadentate amine‐bis(phenolate) ligand 6,6′‐(dipyridin‐2‐ylmethylazanediyl)bis(methylene)bis(2,4‐dimethylphenol) (H₂L) was prepared and characterized. This ligand readily coordinates with Fe^III or Co^III ions, and the resulting complexes [Fe^IIILCl] ( 1 ) and [Co^IIIL(H₂O)]Cl ( 2 ) were characterized by elemental analysis. X‐ray structural studies show that the ligand in complexes 1 and 2 acts as a pentadentate ligand, leaving one coordination side of the transition metal available for exogenous ligands such as chloride ion ( 1 ) or water ( 2 ) ligand, and the central metal atoms are hexacoordinate in a similar distorted octahedral arrangement. Electrochemical studies reveal that each of the complexes exhibits multiple redox processes in the potential window investigated. Complex 1 shows one reversible oxidative event at 0.32 V and one quasi‐reversible reduction event at –1.03 V, while the complex 2 displays one reversible oxidative event at 0.18 V and one quasi‐reversible reduction at –0.64 V.     

Not Guilty on Every Count: The “Non‐Innocent” Nitrosyl Ligand in the Framework of IUPAC′s Oxidation‐State Formalism

Nitrosyl–metal bonding relies on the two interactions between the pair of N–O‐π* and two of the metal's d orbitals. These (back)bonds are largely covalent, which makes their allocation in the course of an oxidation‐state determination ambiguous. However, apart from M‐N‐O‐angle or net‐charge considerations, IUPAC′s “ionic approximation” is a useful tool to reliably classify nitrosyl metal complexes in an orbital‐centered approach.     

An Efficient Palladium and Bis(2‐pyridylmethyl)amine‐based System for Suzuki‐Miyaura Cross‐Coupling under Aqueous and Aerobic Condition

A novel PdCl₂/bis(2‐pyridylmethyl)amine‐based ligand ( 1 ) catalytic system, which is water‐soluble and air‐stable, has been successfully synthesized and applied for Suzuki‐Miyaura cross‐coupling reaction. In the presence of catalytic amount of PdCl₂/ 1 system, arylboronic acids can couple with a wide range of aryl halides, including aryl bromides and aryl chlorides. The reactions proceed under mild conditions to give excellent yields, and a wide range of functionalities is tolerated.     

Titanium complexes bearing amine bis(phenolate) ligands: Synthesis,structure and catalysis in ring‐opening polymerization of lactide

Monomeric bis(isopropoxy) titanium complexes LTi(Oⁱ Pr)₂ (L =  ─ OC₆H₂–4‐R¹–6‐R²–2‐CH₂N[(CH₂)₂N(R³)₂]CH₂–4‐R⁴–6‐R⁵‐C₆H₂O ─ , R¹ = R² = ^t Bu, R³ = Et, R⁴ = R⁵ = Cl, (L¹)Ti(Oⁱ Pr)₂; R¹ = R² = Me, R³ = Et, R⁴ = R⁵ = Me, (L²)Ti(Oⁱ Pr)₂; R¹ = R² = ^t Bu, R³ = Et, R⁴ = OMe, R⁵ = ^t Bu, (L³)Ti(Oⁱ Pr)₂; R¹ = R⁴ = OMe, R³ = Et, R² = R⁵ = ^t Bu, (L⁴)Ti(Oⁱ Pr)₂; R¹ = R² = ^t Bu, R³ = Me, R⁴ = OMe, R⁵ = ^t Bu, (L⁵)Ti(Oⁱ Pr)₂) supported by amine bis(phenolate) ligands were synthesized and characterized using NMR spectroscopy and elemental analysis. The solid‐state structure of (L³)Ti(Oⁱ Pr)₂ was determined using single‐crystal X‐ray diffraction. (L^1–5)Ti(Oⁱ Pr)₂ were all found to initiate the ring‐opening polymerization of l ‐lactide and rac ‐lactide in a controlled manner at 110–160°C. As shown by kinetic studies, (L¹)Ti(Oⁱ Pr)₂ polymerized l ‐lactide faster than did (L^2–5)Ti(Oⁱ Pr)₂. In addition, good number‐average molecular weight and narrow polydispersity index (1.00–1.71) of polymers were also obtained. The microstructure of the polymers and a possible mechanism of coordination–insertion of polymerization were evidenced by MALDI‐TOF and ¹H NMR spectra of the polylactides.     

Redox Non‐Innocent Behavior of a Terminal Iridium Hydrazido(2−) Triple Bond

The synthesis of the first terminal Group 9 hydrazido(2‐) complex, Cp*IrN(TMP) ( 6 ) (TMP=2,2,6,6‐tetramethylpiperidine) is reported. Electronic structure and X‐ray diffraction analysis indicate that this complex contains an Ir?N triple bond, similar to Bergman's seminal Cp*Ir(N^tBu) imido complex. However, in sharp contrast to Bergman's imido, 6 displays remarkable redox non‐innocent reactivity owing to the presence of the N_β lone pair. Treatment of 6 with MeI results in electron transfer from N_β to Ir prior to oxidative addition of MeI to the iridium center. This behavior opens the possibility of carrying out facile oxidative reactions at a formally Ir^III metal center through a hydrazido(2?)/isodiazene valence tautomerization.     

Synthesis, Structure and Biological Activity of Zn（Ⅱ） Complex with Tris（benzimidazol-2-yl-methyl）amine Ligand

A new Zn(II) mononuclear complex with tris(benzimidazol‐2‐yl‐methyl)amine (NTB) was synthesized with stoichiometry of [Zn(NTB)NO₃]NO₃ · DIPY · DMF (DIPY : 4,4′‐dipyridyl). The complex was characterized by elemental analysis, UV and IR spectra. The crystal structure was determined by using X‐ray diffraction analysis. The crystal structure indicates that four N atoms and one O atom coordinate to zinc ion to construct a distorted trigonal‐dipyramid configuration. Three nonprotonated N atoms from imidazole groups are in the equatorial plane, one alkylamino N atom and one O atom from NO₃^?_‐ in the axial directions. The biological activity assay shows that this complex presents certain biological activity by means of pyrogallol autoxidation and it can be called a model compound of superoxide dismutase (SOD).     

Synthesis and Crystal Structure of a Tetranuclear Silver Complex with Bis（diphenylphosphino） amine-dioxide as a Tridentate Ligand

1 INTRODUCTION The coordination chemistry of the nitrogen-contai- ning diphosphine ligand bis(diphenylphosphino)ami- ne (Ph2PNHPPh2) has recently received much atten- tion because the P atoms can bridge metal centers in μ-bonding mode to form bi- or polynuclear complex- es[1~10]. It has been shown that the acidity of N–H proton would promote functionalization on the ligand backbone[4, 5, 11]. Although a few complexes contain- ing deprotonated tridentate Ph2PNPPh2 have been synthesi…     

Heterograft copolymers of poly(ε‐caprolactone) prepared by combination of ATRA “grafting onto” and ATRP “grafting from” processes

This paper aims at reporting on the synthesis of a heterograft copolymer by combining the “grafting onto” process based on atom transfer radical addition (ATRA) and the “grafting from” process by atom transfer radical polymerization (ATRP). The statistical copolymerization of ε‐caprolactone (εCL) and α‐chloro‐ε‐caprolactone (αClεCL) was initiated by 2,2‐dibutyl‐2‐stanna‐1,3‐dioxepane (DSDOP), followed by ATRA of parts of the chlorinated units of poly(αClεCL‐co‐εCL) on the terminal double bond of α‐MeO,ω‐CH₂?CH? CH₂? CO₂‐poly(ethylene oxide) (PEO). The amphiphilic poly(εCL‐g‐EO) graft copolymer collected at this stage forms micelles as supported by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The unreacted pendant chloro groups of poly(εCL‐g‐EO) were used to initiate the ATRP of styrene with formation of copolymer with two populations of randomly distributed grafts, that is PEO and polystyrene. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6015–6024, 2006     

Catalysis by Aluminum(III) Complexes of Non‐Innocent Ligands

Non‐Innocent ligand complexes of aluminum are described in this Concept article, beginning with a discussion of their synthesis, and then structural and electronic characterization. The main focus concerns the ability of the ligands in these complexes to mediate proton transfer reactions. As examples, aluminum–ligand cooperation in the activation of polar bonds is described, as is the importance of hydrogen bonding to stabilization of a transition state for β‐hydride abstraction. Taken together these reactions enable catalytic processes such as the dehydrogenation of formic acid.     

“Smart” poly(2‐(dimethylamino)ethyl methacrylate‐ran‐9‐(4‐vinylbenzyl)‐9H‐carbazole) copolymers synthesized by nitroxide mediated radical polymerization

A series of poly(2‐(dimethylamino)ethyl methacrylate‐ran‐9‐(4‐vinylbenzyl)‐9H‐carbazole) (poly(DMAEMA‐ran‐VBK)) random copolymers, with VBK molar feed compositions f_VBK,0 = 0.02–0.09, were synthesized using 10 mol % [tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino] nitroxide (SG1) relative to 2‐([tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino]oxy)‐2‐methylpropionic acid (BlocBuilder) at 80 °C and 90 °C. Controlled polymerizations were observed, even with f_VBK,0 = 0.02, as reflected by a linear increase in number average molecular weight (M_n) versus conversion X ≤ 0.6 with final copolymers characterized by relatively narrow, monomodal molecular weight distributions (M_w/M_n ≈ 1.5). Poly(DMAEMA‐ran‐VBK) copolymers were deemed sufficiently pseudo‐“living” to reinitiate a second batch of N,N‐dimethylacrylamide (DMAA), with very few apparent dead chains, as indicated by the monomodal shift in the gel permeation chromatography chromatograms. Poly(DMAEMA‐ran‐VBK) random copolymers exhibited tuneable lower critical solution temperature (LCST), in aqueous solution, by modifying copolymer composition, solution pH and by the addition of the water‐soluble poly(DMAA) segment. ¹H NMR analysis determined that, in water, the VBK units of the poly(DMAEMA‐ran‐VBK) random copolymer were segregated to the interior of the copolymer aggregate regardless of solution temperature and that poly(DMAEMA‐ran‐VBK)‐b‐poly(DMAA) block copolymers formed micelles above the LCST. In addition, the final random copolymer and block copolymer exhibited temperature dependent fluorescence due to the VBK units. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011