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1.
Experimental and Theoretical Studies on Arene‐Bridged Metal–Metal‐Bonded Dimolybdenum Complexes 下载免费PDF全文
Dr. Mario Carrasco Natalia Curado Dr. Eleuterio Álvarez Dr. Celia Maya Dr. Riccardo Peloso Prof. Dr. Manuel L. Poveda Dr. Amor Rodríguez Prof. Dr. Eliseo Ruiz Prof. Dr. Santiago Álvarez Prof. Dr. Ernesto Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(20):6092-6102
The bis(hydride) dimolybdenum complex, [Mo2(H)2{HC(N‐2,6‐iPr2C6H3)2}2(thf)2], 2 , which possesses a quadruply bonded Mo2II core, undergoes light‐induced (365 nm) reductive elimination of H2 and arene coordination in benzene and toluene solutions, with formation of the MoI2 complexes [Mo2{HC(N‐2,6‐iPr2C6H3)2}2(arene)], 3?C6H6 and 3?C6H5Me , respectively. The analogous C6H5OMe, p‐C6H4Me2, C6H5F, and p‐C6H4F2 derivatives have also been prepared by thermal or photochemical methods, which nevertheless employ different Mo2 complex precursors. X‐ray crystallography and solution NMR studies demonstrate that the molecule of the arene bridges the molybdenum atoms of the MoI2 core, coordinating to each in an η2 fashion. In solution, the arene rotates fast on the NMR timescale around the Mo2‐arene axis. For the substituted aromatic hydrocarbons, the NMR data are consistent with the existence of a major rotamer in which the metal atoms are coordinated to the more electron‐rich C?C bonds. 相似文献
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Marina Pérez-Jiménez Dr. Natalia Curado Dr. Celia Maya Dr. Jesús Campos Prof. Dr. Eliseo Ruiz Prof. Dr. Santiago Álvarez Prof. Ernesto Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(21):6569-6578
This contribution focuses on complex [Mo2(H)2(μ-AdDipp2)2] ( 1 ) and tetrahydrofuran and pyridine adducts [Mo2(H)2(μ-AdDipp2)2(L)2] ( 1⋅thf and 1⋅py ), which contain a trans-(H)Mo≣Mo(H) core (AdDipp2=HC(NDipp2)2; Dipp=2,6-iPr2C6H3). Computational studies provide insights into the coordination and electronic characteristics of the central trans-Mo2H2 unit of 1 , with four-coordinate, fourteen-electron Mo atoms and ϵ-agostic interactions with Dipp methyl groups. Small size C- and N-donors give rise to related complexes 1⋅L but only one molecule of P-donors, for example, PMe3, can bind to 1 , causing one of the hydrides to form a three-centered, two-electron (3c-2e) Mo-H→Mo bond ( 2⋅PMe3 ). A DFT analysis of the terminal and bridging hydride coordination to the Mo≣Mo bond is also reported, along with reactivity studies of the Mo−H bonds of these complexes. Reactions investigated include oxidation of 1⋅thf by silver triflimidate, AgNTf2, to afford a monohydride [Mo2(μ-H)(μ-NTf2)(μ-AdDipp2)2] ( 4 ), with an O,O’-bridging triflimidate ligand. 相似文献
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Benjamin M. Gridley Dr. Graeme J. Moxey Dr. William Lewis Prof. Alexander J. Blake Dr. Deborah L. Kays 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(34):11446-11453
The synthesis and characterization of the first series of low‐coordinate bis(terphenyl) complexes of the Group 12 metals, [Zn(2,6‐Naph2C6H3)2] ( 1 ), [Cd(OEt2)(2,6‐Naph2C6H3)2] ( 2 ) and [Hg(OEt2)(2,6‐Naph2C6H3)2] ( 3 ) (Naph=1‐C10H7) are described. The naphthyl substituents of the terphenyl ligands confer considerable steric bulk, and as a result of limited flexibility introduce multiple conformations to these unusual systems. In the solid state, complex 1 features a two‐coordinate Zn centre with the ligands oriented in a syn/anti conformation, whereas the three‐coordinate distorted T‐shaped complexes 2 and 3 feature the ligands in the syn/syn configurations. The results of DFT calculations are in good agreement with the solid‐state configurations for these complexes and support the spectroscopic measurements, which indicate several conformers in solution. 相似文献
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Dipl.‐Chem. Jürgen Bauer Prof. Dr. Holger Braunschweig Dipl.‐Chem. Peter Brenner Dipl.‐Chem. Katharina Kraft Dr. Krzysztof Radacki Dipl.‐Chem. Katrin Schwab 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(39):11985-11992
Syntheses of the first heteroleptic N‐heterocyclic carbene (NHC)–phosphane platinum(0) complexes and formation of the corresponding Lewis acid–base adducts with aluminum chloride is reported. The influence of N‐heterocyclic carbenes on tuning the Lewis basic properties of the metal complexes was judged from spectroscopic, structural, and computational data. Conclusive experimental evidence for the enhanced Lewis basicity of NHC‐containing complexes was provided by a transfer reaction. 相似文献
6.
Malcolm H. Chisholm Jason S. D’Acchioli Christopher M. Hadad 《Journal of Cluster Science》2007,18(1):27-49
The electronic structures and the physical properties (vertical excitation energies, vibrational stretching frequencies, and
bond lengths) of a variety of M–M quadruply bonded (M = Mo, W) complexes are investigated using density functional theory
(DFT). By utilizing a variety of pure and hybrid exchange-correlation (XC) functionals and a number basis sets, we are able
to recommend a theoretical methodology for most efficiently probing the electronic structures of homoleptic M2(O2CR)4 and bridged M2(O2C-X-CO2)M2 (R = organic group, typically H; X = conjugated organic group) complexes.
相似文献
Jason S. D’AcchioliEmail: |
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Aya Eizawa Kazuya Arashiba Akihito Egi Hiromasa Tanaka Kazunari Nakajima Kazunari Yoshizawa Yoshiaki Nishibayashi 《化学:亚洲杂志》2019,14(12):2091-2096
Molybdenum–iodide complexes bearing a PCP[1] ligand have been found to work as excellent catalysts toward ammonia formation under ambient reaction conditions among dinitrogen‐bridged dimolybdenum complexes and other molybdenum complexes bearing PNP and PCP[2] ligands. 相似文献
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New RuII(arene) Complexes with Halogen‐Substituted Bis‐ and Tris(pyrazol‐1‐yl)borate Ligands 下载免费PDF全文
Dr. Serena Orbisaglia Dr. Corrado Di Nicola Prof. Fabio Marchetti Prof. Claudio Pettinari Dr. Riccardo Pettinari Prof. Luísa M. D. R. S. Martins Prof. Elisabete C. B. A. Alegria Prof. M. Fátima C. Guedes da Silva Bruno G. M. Rocha Dr. Maxim L. Kuznetsov Prof. Armando J. L. Pombeiro Prof. Brian W. Skelton Dr. Alexandre N. Sobolev Prof. Allan H. White 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(13):3689-3704
[RuCl(arene)(μ‐Cl)]2 dimers were treated in a 1:2 molar ratio with sodium or thallium salts of bis‐ and tris(pyrazolyl)borate ligands [Na(Bp)], [Tl(Tp)], and [Tl(TpiPr, 4Br)]. Mononuclear neutral complexes [RuCl(arene)(κ2‐Bp)] ( 1 : arene=p‐cymene (cym); 2 : arene=hexamethylbenzene (hmb); 3 : arene=benzene (bz)), [RuCl(arene)(κ2‐Tp)] ( 4 : arene=cym; 6 : arene=bz), and [RuCl(arene)(κ2‐TpiPr, 4Br)] ( 7 : arene=cym, 8 : arene=hmb, 9 : arene=bz) have been always obtained with the exception of the ionic [Ru2(hmb)2(μ‐Cl)3][Tp] ( 5′ ), which formed independently of the ratio of reactants and reaction conditions employed. The ionic [Ru(CH3OH)(cym)(κ2‐Bp)][X] ( 10 : X=PF6, 12 : X=O3SCF3) and the neutral [Ru(O2CCF3)(cym)(κ2‐Bp)] ( 11 ) have been obtained by a metathesis reaction with corresponding silver salts. All complexes 1 – 12 have been characterized by analytical and spectroscopic data (IR, ESI‐MS, 1H and 13C NMR spectroscopy). The structures of the thallium and calcium derivatives of ligand Tp, [Tl(Tp)] and [Ca(dmso)6][Tp]2 ? 2 DMSO, of the complexes 1 , 4 , 5′ , 6 , 11 , and of the decomposition product [RuCl(cym)(HpziPr, 4Br)2][Cl] ( 7′ ) have been confirmed by using single‐crystal X‐ray diffraction. Electrochemical studies showed that 1 – 9 and 11 undergo a single‐electron RuII→RuIII oxidation at a potential, measured by cyclic voltammetry, which allows comparison of the electron‐donor characters of the bis‐ and tris(pyrazol‐1‐yl)borate and arene ligands, and to estimate, for the first time, the values of the Lever EL ligand parameter for Bp, Tp, and TpiPr, 4Br. Theoretical calculations at the DFT level indicated that both oxidation and reduction of the Ru complexes under study are mostly metal‐centered with some involvement of the chloride ligand in the former case, and also demonstrated that the experimental isolation of the μ3‐binuclear complex 5′ (instead of the mononuclear 5 ) is accounted for by the low thermodynamic stability of the latter species due to steric reasons. 相似文献
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Daniel Lupp Dr. Niels Johan Christensen Dr. Johannes R. Dethlefsen Dr. Peter Fristrup 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(8):3435-3442
The mechanism of the molybdenum‐catalyzed deoxydehydration (DODH) of vicinal diols has been investigated using density functional theory. The proposed catalytic cycle involves condensation of the diol with an MoVI oxo complex, oxidative cleavage of the diol resulting in an MoIV complex, and extrusion of the alkene. We have compared the proposed pathway with several alternatives, and the results have been corroborated by comparison with the molybdenum‐catalyzed sulfoxide reduction recently published by Sanz et al. and with experimental observations for the DODH itself. Improved understanding of the mechanism should expedite future optimization of molybdenum‐catalyzed biomass transformations. 相似文献
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Univalent Gallium Complexes of Simple and ansa‐Arene Ligands: Effects on the Polymerization of Isobutylene 下载免费PDF全文
Martin R. Lichtenthaler Steffen Maurer Robert J. Mangan Florian Stahl Florian Mönkemeyer Julian Hamann Prof. Dr. Ingo Krossing 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):157-165
Using [Ga(C6H5F)2]+[Al(ORF)4]?( 1 ) (RF=C(CF3)3) as starting material, we isolated bis‐ and tris‐η6‐coordinated gallium(I) arene complex salts of p‐xylene (1,4‐Me2C6H4), hexamethylbenzene (C6Me6), diphenylethane (PhC2H4Ph), and m‐terphenyl (1,3‐Ph2C6H4): [Ga(1,4‐Me2C6H4)2.5]+ ( 2+ ), [Ga(C6Me6)2]+ ( 3+ ), [Ga(PhC2H4Ph)]+ ( 4+ ) and [(C6H5F)Ga(μ‐1,3‐Ph2C6H4)2Ga(C6H5F)]2+ ( 52+ ). 4+ is the first structurally characterized ansa‐like bent sandwich chelate of univalent gallium and 52+ the first binuclear gallium(I) complex without a Ga?Ga bond. Beyond confirming the structural findings by multinuclear NMR spectroscopic investigations and density functional calculations (RI‐BP86/SV(P) level), [Ga(PhC2H4Ph)]+[Al(ORF)4]?( 4 ) and [(C6H5F)Ga(μ‐1,3‐Ph2C6H4)2Ga(C6H5F)]2+{[Al(ORF)4] ?}2 ( 5 ), featuring ansa‐arene ligands, were tested as catalysts for the synthesis of highly reactive polyisobutylene (HR‐PIB). In comparison to the recently published 1 and the [Ga(1,3,5‐Me3C6H3)2]+[Al(ORF)4]? salt ( 6 ) (1,3,5‐Me3C6H3=mesitylene), 4 and 5 gave slightly reduced reactivities. This allowed for favorably increased polymerization temperatures of up to +15 °C, while yielding HR‐PIB with high contents of terminal olefinic double bonds (α‐contents=84–93 %), low molecular weights (Mn=1000–3000 g mol?1) and good monomer conversions (up to 83 % in two hours). While the chelate complexes delivered more favorable results than 1 and 6 , the reaction kinetics resembled and thus concurred with the recently proposed coordinative polymerization mechanism. 相似文献
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Sammual Yu‐Lut Leung Elizabeth Suk‐Hang Lam Dr. Wai Han Lam Dr. Keith Man‐Chung Wong Prof. Dr. Wing‐Tak Wong Prof. Dr. Vivian Wing‐Wah Yam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(31):10360-10369
A new class of luminescent alkynylplatinum(II) complexes with a tridentate pyridine‐based N‐heterocyclic carbene (2,6‐bis(1‐butylimidazol‐2‐ylidenyl)pyridine) ligand, [PtII(C^N^C)(C?CR)][PF6], and their chloroplatinum(II) precursor complex, [PtII(C^N^C)Cl][PF6], have been synthesized and characterized. One of the alkynylplatinum(II) complexes has also been structurally characterized by X‐ray crystallography. The electrochemistry, electronic absorption and luminescence properties of the complexes have been studied. Nanosecond transient absorption (TA) spectroscopy has also been performed to probe the nature of the excited state. The origin of the absorption and emission properties has been supported by computational studies. 相似文献
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Combined Experimental and Computational Studies on the Physical and Chemical Properties of the Renewable Amide, 3‐Acetamido‐5‐acetylfuran 下载免费PDF全文
The pKa of 3‐acetamido‐5‐acetylfuran (3A5AF) was predicted to be in the range 18.5–21.5 by using the B3LYP/6‐311+G(2d,p) method and several amides as references. The experimental pKa value, 20.7, was determined through UV/Vis titrations. Its solubility was measured in methanol‐modified supercritical CO2 (mole fraction, 3.23×10?4, cloud points 40–80 °C) and it was shown to be less soluble than 5‐hydroxymethylfurfural (5‐HMF). Dimerization energies were calculated for 3A5AF and 5‐HMF to compare hydrogen bonding, as such interactions will affect their solubility. Infrared and 1H nuclear magnetic resonance spectra of 3A5AF samples support the existence of intermolecular hydrogen bonding. The highest occupied molecular orbital, lowest unoccupied molecular orbital, and electrostatic potential of 3A5AF were determined through molecular orbital calculations using B3LYP/6‐311+G(2d,p). The π–π* transition energy (time‐dependent density functional theory study) was compared with UV/Vis data. Calculated atomic charges were used in an attempt to predict the reactivity of 3A5AF. A reaction between 3A5AF and CH3MgBr was conducted. As 3A5AF is a recently developed renewable compound that has previously not been studied extensively, these studies will be helpful in designing future reactions and processes involving this molecule. 相似文献
14.
Aleix Comas‐Vives Dr. Agustí Lledós Prof. Rinaldo Poli Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(7):2147-2158
A DFT analysis of the epoxidation of C2H4 by H2O2 and MeOOH (as models of tert‐butylhydroperoxide, TBHP) catalyzed by [Cp*MoO2Cl] ( 1 ) in CHCl3 and by [Cp*MoO2(H2O)]+ in water is presented (Cp*=pentamethylcyclopentadienyl). The calculations were performed both in the gas phase and in solution with the use of the conductor‐like polarizable continuum model (CPCM). A low‐energy pathway has been identified, which starts with the activation of ROOH (R=H or Me) to form a hydro/alkylperoxido derivative, [Cp*MoO(OH)(OOR)Cl] or [Cp*MoO(OH)(OOR)]+ with barriers of 24.9 (26.5) and 28.7 (29.2) kcal mol?1 for H2O2 (MeOOH), respectively, in solution. The latter barrier, however, is reduced to only 1.0 (1.6) kcal mol?1 when one additional water molecule is explicitly included in the calculations. The hydro/alkylperoxido ligand in these intermediates is η2‐coordinated, with a significant interaction between the Mo center and the Oβ atom. The subsequent step is a nucleophilic attack of the ethylene molecule on the activated Oα atom, requiring 13.9 (17.8) and 16.1 (17.7) kcal mol?1 in solution, respectively. The corresponding transformation, catalyzed by the peroxido complex [Cp*MoO(O2)Cl] in CHCl3, requires higher barriers for both steps (ROOH activation: 34.3 (35.2) kcal mol?1; O atom transfer: 28.5 (30.3) kcal mol?1), which is attributed to both greater steric crowding and to the greater electron density on the metal atom. 相似文献
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Exploring Excited‐State Tunability in Luminescent Tris‐cyclometalated Platinum(IV) Complexes: Synthesis of Heteroleptic Derivatives and Computational Calculations 下载免费PDF全文
Fabio Juliá Dr. Gabriel Aullón Dr. Delia Bautista Dr. Pablo González‐Herrero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(52):17346-17359
The synthesis, structure, electrochemistry, and photophysical properties of a series of heteroleptic tris‐ cyclometalated PtIV complexes are reported. The complexes mer‐[Pt(C^N)2(C′^N′)]OTf, with C^N=C‐deprotonated 2‐(2,4‐difluorophenyl)pyridine (dfppy) or 2‐phenylpyridine (ppy), and C′^N′=C‐deprotonated 2‐(2‐thienyl)pyridine (thpy) or 1‐phenylisoquinoline (piq), were obtained by reacting bis‐ cyclometalated precursors [Pt(C^N)2Cl2] with AgOTf (2 equiv) and an excess of the N′^C′H pro‐ligand. The complex mer‐[Pt(dfppy)2(ppy)]OTf was obtained analogously and photoisomerized to its fac counterpart. The new complexes display long‐lived luminescence at room temperature in the blue to orange color range. The emitting states involve electronic transitions almost exclusively localized on the ligand with the lowest π–π* energy gap and have very little metal character. DFT and time‐dependent DFT (TD‐DFT) calculations on mer‐[Pt(ppy)2(C′^N′)]+ (C′^N′=thpy, piq) and mer/fac‐[Pt(ppy)3]+ support this assignment and provide a basis for the understanding of the luminescence of tris‐cyclometalated PtIV complexes. Excited states of LMCT character may become thermally accessible from the emitting state in the mer isomers containing dfppy or ppy as chromophoric ligands, leading to strong nonradiative deactivation. This effect does not operate in the fac isomers or the mer complexes containing thpy or piq, for which nonradiative deactivation originates mainly from vibrational coupling to the ground state. 相似文献
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Luminescent Di‐ and Trinuclear Boron Complexes Based on Aromatic Iminopyrrolyl Spacer Ligands: Synthesis,Characterization, and Application in OLEDs 下载免费PDF全文
Dr. D. Suresh Dr. Clara S. B. Gomes Patrícia S. Lopes Dr. Cláudia A. Figueira Bruno Ferreira Prof. Pedro T. Gomes Dr. Roberto E. Di Paolo Prof. António L. Maçanita Prof. M. Teresa Duarte Dr. Ana Charas Prof. Jorge Morgado Diogo Vila‐Viçosa Prof. Maria José Calhorda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(25):9133-9149
New bis‐ and tris(iminopyrrole)‐functionalized linear (1,2‐(HNC4H3‐C(H)?N)2‐C6H4 ( 2 ), 1,3‐(HNC4H3‐C(H)?N)2‐C6H4 ( 3 ), 1,4‐(HNC4H3‐C(H)?N)2‐C6H4 ( 4 ), 4,4′‐(HNC4H3‐C(H)?N)2‐(C6H4‐C6H4) ( 5 ), 1,5‐(HNC4H3C‐(H)?N)2‐C10H6 ( 6 ), 2,6‐(HNC4H3C‐(H)?N)2‐C10H6 ( 7 ), 2,6‐(HNC4H3C‐(H)?N)2‐C14H8 ( 8 )) and star‐shaped (1,3,5‐(HNC4H3‐C(H)?N‐1,4‐C6H4)3‐C6H3 ( 9 )) π‐conjugated molecules were synthesized by the condensation reactions of 2‐formylpyrrole ( 1 ) with several aromatic di‐ and triamines. The corresponding linear diboron chelate complexes (Ph2B[1,3‐bis(iminopyrrolyl)‐phenyl]BPh2 ( 10 ), Ph2B[1,4‐bis(iminopyrrolyl)‐phenyl]BPh2 ( 11 ), Ph2B[4,4′‐bis(iminopyrrolyl)‐biphenyl]BPh2 ( 12 ), Ph2B[1,5‐bis(iminopyrrolyl)‐naphthyl]BPh2 ( 13 ), Ph2B[2,6‐bis(iminopyrrolyl)‐naphthyl]BPh2 ( 14 ), Ph2B[2,6‐bis(iminopyrrolyl)‐anthracenyl]BPh2 ( 15 )) and the star‐shaped triboron complex ([4′,4′′,4′′′‐tris(iminopyrrolyl)‐1,3,5‐triphenylbenzene](BPh2)3 ( 16 )) were obtained in moderate to good yields, by the treatment of 3 – 9 with B(C6H5)3. The ligand precursors are non‐emissive, whereas most of their boron complexes are highly fluorescent; their emission color depends on the π‐conjugation length. The photophysical properties of the luminescent polyboron compounds were measured, showing good solution fluorescence quantum yields ranging from 0.15 to 0.69. DFT and time‐dependent DFT calculations confirmed that molecules 10 and 16 are blue emitters, because only one of the iminopyrrolyl groups becomes planar in the singlet excited state, whereas the second (and third) keeps the same geometry. Compound 13 , in which planarity is not achieved in any of the groups, is poorly emissive. In the other examples ( 11 , 12 , 14 , and 15 ), the LUMO is stabilized, narrowing the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO–LUMO), and the two iminopyrrolyl groups become planar, extending the size of the π‐system, to afford green to yellow emissions. Organic light‐emitting diodes (OLEDs) were fabricated by using the new polyboron complexes and their luminance was found to be in the order of 2400 cd m?2, for single layer devices, increasing to 4400 cd m?2 when a hole‐transporting layer is used. 相似文献
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Janna Börner M. Sc. Ulrich Flörke Dr. Klaus Huber Prof. Dr. Artjom Döring Dipl.‐Chem. Dirk Kuckling Prof. Dr. Sonja Herres‐Pawlis Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(10):2362-2376
New class of air‐stable catalysts for lactide polymerisation: Guanidine–pyridine hybrid ligands (picture, left) were used to prepare a series of zinc complexes (e.g., depicted cation [ZnL2(CF3SO3)]+, where L is the quinoline‐containing ligand with R1=R2=R3=R4=Me), in which the ligand binds through two different N‐donor atoms. The zinc complexes show high activity in ring‐opening polymerisation of d,l ‐lactide (right), giving polylactide with molecular masses up to 176 000 g mol?1 and in high yield.
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Nickel(II) Complexes of Pentadentate N5 Ligands as Catalysts for Alkane Hydroxylation by Using m‐CPBA as Oxidant: A Combined Experimental and Computational Study 下载免费PDF全文
Dr. Muniyandi Sankaralingam Dr. Mani Balamurugan Prof. Dr. Mallayan Palaniandavar Dr. Prabha Vadivelu Dr. Cherumuttathu H. Suresh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(36):11346-11361
A new family of nickel(II) complexes of the type [Ni(L)(CH3CN)](BPh4)2, where L=N‐methyl‐N,N′,N′‐tris(pyrid‐2‐ylmethyl)‐ethylenediamine (L1, 1 ), N‐benzyl‐N,N′,N′‐tris(pyrid‐2‐yl‐methyl)‐ethylenediamine (L2, 2 ), N‐methyl‐N,N′‐bis(pyrid‐2‐ylmethyl)‐N′‐(6‐methyl‐pyrid‐2‐yl‐methyl)‐ethylenediamine (L3, 3 ), N‐methyl‐N,N′‐bis(pyrid‐2‐ylmethyl)‐N′‐(quinolin‐2‐ylmethyl)‐ethylenediamine (L4, 4 ), and N‐methyl‐N,N′‐bis(pyrid‐2‐ylmethyl)‐N′‐imidazole‐2‐ylmethyl)‐ethylenediamine (L5, 5 ), has been isolated and characterized by means of elemental analysis, mass spectrometry, UV/Vis spectroscopy, and electrochemistry. The single‐crystal X‐ray structure of [Ni(L3)(CH3CN)](BPh4)2 reveals that the nickel(II) center is located in a distorted octahedral coordination geometry constituted by all the five nitrogen atoms of the pentadentate ligand and an acetonitrile molecule. In a dichloromethane/acetonitrile solvent mixture, all the complexes show ligand field bands in the visible region characteristic of an octahedral coordination geometry. They exhibit a one‐electron oxidation corresponding to the NiII/NiIII redox couple the potential of which depends upon the ligand donor functionalities. The new complexes catalyze the oxidation of cyclohexane in the presence of m‐CPBA as oxidant up to a turnover number of 530 with good alcohol selectivity (A/K, 7.1–10.6, A=alcohol, K=ketone). Upon replacing the pyridylmethyl arm in [Ni(L1)(CH3CN)](BPh4)2 by the strongly σ‐bonding but weakly π‐bonding imidazolylmethyl arm as in [Ni(L5)(CH3CN)](BPh4)2 or the sterically demanding 6‐methylpyridylmethyl ([Ni(L3)(CH3CN)](BPh4)2 and the quinolylmethyl arms ([Ni(L4)(CH3CN)](BPh4)2, both the catalytic activity and the selectivity decrease. DFT studies performed on cyclohexane oxidation by complexes 1 and 5 demonstrate the two spin‐state reactivity for the high‐spin [(N5)NiII?O.] intermediate (ts1hs, ts2doublet), which has a low‐spin state located closely in energy to the high‐spin state. The lower catalytic activity of complex 5 is mainly due to the formation of thermodynamically less accessible m‐CPBA‐coordinated precursor of [NiII(L5)(OOCOC6H4Cl)]+ ( 5 a ). Adamantane is oxidized to 1‐adamantanol, 2‐adamantanol, and 2‐adamantanone (3°/2°, 10.6–11.5), and cumene is selectively oxidized to 2‐phenyl‐2‐propanol. The incorporation of sterically hindering pyridylmethyl and quinolylmethyl donor ligands around the NiII leads to a high 3°/2° bond selectivity for adamantane oxidation, which is in contrast to the lower cyclohexane oxidation activities of the complexes. 相似文献