- The Co-ordination Chemistry of Mixed Pyridine-Phenol Ligands; Synthesis of 6-(2-Hydroxyphenyl)-2,2'-bipyridine (HL) and the Crystal Structures of *1.5CH2Cl2 and *MeCN
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The new N,N,O-tridentate ligand 6-(2-hydroxyphenyl)-2,2'-bipyridine (HL) has been prepared in 41percent yield overall by reaction of 2-lithioanisole with 2,2'-bipyridine, followed by rearomatisation with KMnO4 and subsequent conversion of the anisole grou
- Jeffery, John C.,Schatz, Erik,Ward, Michael D.
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Read Online
- Role of the X Coligands in Cyclometalated [Ni(Phbpy)X] Complexes (HPhbpy = 6-Phenyl-2,2′-bipyridine)
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The coligand X was varied in the organonickel complexes [Ni(Phbpy)X] (X = F, Cl, Br, I, C6F5) carrying the anionic tridentate CNN ligand 6-(phen-2-ide)-2,2′-bipyridine (Phbpy-) to study its effect on electronic structures of these complexes and their activity in Negishi-like C-C cross-coupling catalysis. The complexes were synthesized from the precursor [Ni(COD)2] (COD = 1,5-cyclooctadiene) by chelate-assisted oxidative addition into the phenyl C-X bond of the protoligand 6-(2-halidophenyl)-2,2′-bipyridine) and were obtained as red powders. Protoligands X-Phbpy carrying the halide surrogates X = OMe, OTf (triflate) failed in this reaction. Single-crystal XRD allowed us to add the structures of [Ni(Phbpy)Cl] and [Ni(Phbpy)I] to the previously reported Br derivative. Cyclic voltammetry showed reversible reductions for X = C6F5, F, Cl, while for Br and I the reversibility is reduced through rapid splitting of X- after reduction (EC mechanism). UV-vis spectroelectrochemistry confirmed the decreasing degree of reversibility along the series C6F5 > F > Cl ? Br > I, which parallels the "leaving group character"of the X coligands. This method also revealed mainly bpy centered reduction and essentially Ni(II)/Ni(III) oxidations, as corroborated by DFT calculations. The rather X-invariant long-wavelength UV-vis absorptions and excited states were analyzed in detail using TD-DFT and were consistent with predominant metal to ligand charge transfer (MLCT) character. Initial catalytic tests under Negishi-like conditions showed the complexes to be active as catalysts in C-C cross-coupling reactions but did not display marked differences along the series from Ni-F to Ni-I.
- Chin, Mason T.,H?rner, Gerald,Klein, Axel,Kletsch, Lukas,Sandleben, Aaron,Sch?fer, Sascha,Vicic, David A.,Vogt, Nicolas
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p. 1776 - 1785
(2021/06/28)
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- Evidence for Oxidative Decay of a Ru-Bound Ligand during Catalyzed Water Oxidation
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In the evaluation of systems designed for catalytic water oxidation, ceric ammonium nitrate (CAN) is often used as a sacrificial electron acceptor. One of the sources of failure for such systems is oxidative decay of the catalyst in the presence of the st
- Kagalwala, Husain N.,Tong, Lianpeng,Zong, Ruifa,Kohler, Lars,Ahlquist, M?rten S. G.,Fan, Ting,Gagnon, Kevin J.,Thummel, Randolph P.
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p. 2607 - 2615
(2017/06/01)
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- Deprotonative metalation of substituted benzenes and heteroaromatics using amino/alkyl mixed lithium-zinc combinations
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Different homoleptic and heteroleptic lithium-zinc combinations were prepared, and structural elements obtained on the basis of NMR spectroscopic experiments and DFT calculations. In light of their ability to metalate anisole, pathways were proposed to justify the synergy observed for some mixtures. The best basic mixtures were obtained either by combining ZnCl 2·TMEDA (TMEDA = N,N,N',N'tetramethylethylenediamine) with [Li(tmp)] (tmp = 2,2,6,6-tetramethylpiperidino; 3 equiv) or by replacing one of the tmp in the precedent mixture with an alkyl group. The reactivity of the aromatic lithium zincates supposedly formed was next studied, and proved to be substrate-, base-, and electrophile-dependent. The aromatic lithium zincates were finally involved in palladium-catalyzed cross-coupling reactions with aromatic chlorides and bromides.
- Snegaroff, Katia,Komagawa, Shinsuke,Chevallier, Floris,Gros, Philippe C.,Golhen, Stephane,Roisnel, Thierry,Uchiyama, Masanobu,Mongin, Florence
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experimental part
p. 8191 - 8201
(2010/09/11)
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- PLATINUM COMPLEX
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A platinum complex represented by the following formula (1) or (2): wherein, ring A, ring B, ring C, ring D and ring G each independently represent an aromatic ring optionally having substituent(s) or an aromatic heterocyclic ring optionally having substi
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Page/Page column 20
(2010/11/08)
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