アニオン性支持配位子を有するイミド配位二塩化バナジウム(V)錯体の溶液XAS分析 —エチレンとノルボルネンとの共重合におけるアルミニウム助触媒の効果— Solution XAS Analysis of Various (Imido)vanadium(V) Dichloride Complexes Containing Monodentate Anionic Ancillary Donor Ligands: Effect of Aluminium Cocatalyst in Ethylene/Norbornene (Co)polymerization

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Abstract

<p>単座アニオン性支持配位子を有する4配位型のイミド配位バナジウムジクロリド錯体,V(NAr)Cl<sub>2</sub>(L) [Ar=2,6-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>; L=OAr, O-2,6-Ph<sub>2</sub>C<sub>6</sub>H<sub>3</sub>, N=C<i><sup>t</sup></i>Bu<sub>2</sub>, 1,3-<i><sup>t</sup></i>Bu<sub>2</sub>(CHN)<sub>2</sub>C=N, WCA-NHC (<i>N</i>-heterocyclic carbenes with a weakly coordinating borate moiety)およびV(NAd)Cl<sub>2</sub>(OAr) (Ad=1-adamantyl),のトルエン溶液のXANESスペクトルにより,バナジウム原子周辺の局所構造に対する配位子および配位子上の置換基効果を検討した。バナジウム原子周辺のゆがんだ4配位テトラヘドラル構造を有するいずれの錯体においてもプレエッジピークの位置に大きな違いは見られず,バナジウム_塩素結合に帰属されるshoulder-edgeピークが観察された。また,(エチレン/ノルボルネン共重合に活性を有する)フェノキシ配位錯体にMAOやノルボルネンを添加してもスペクトルに大きな変化は見られないことから,この触媒による重合は価数変化を伴わずに活性種が生成することが示唆された。一方,V(N-2,6-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)Cl<sub>2</sub>(WCA-NHC) 錯体にAl<i><sup>i</sup></i>Bu<sub>3</sub>助触媒を添加すると顕著な変化(プレエッジピーク強度の減少とエッジ領域の低エネルギーシフト)が観察され,3価種の生成が示唆された。このスペクトルは,Al<i><sup>i</sup></i>Bu<sub>3</sub>の添加量の増加でわずかにプレエッジピークの強度に変化が観察されるもののノルボルネンの添加による変化は見られないことから,いったん生成した還元種(3価バナジウム種)が直接触媒反応に寄与する可能性が強く示唆された。</p>

<p>Effects of ligand and ligand substituents in a series of (imido)vanadium(V) complexes containing monodentate anionic ancillary donor ligands of the type, V(NAr)Cl<sub>2</sub>(L) [Ar = 2,6-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>; L = OAr, O-2,6-Ph<sub>2</sub>C<sub>6</sub>H<sub>3</sub>, N = C<i><sup>t</sup></i>Bu<sub>2</sub>, 1,3-<i><sup>t</sup></i>Bu<sub>2</sub>(CHN)<sub>2</sub>C = N, WCA-NHC (anionic <i>N</i>-heterocyclic carbenes with a weakly coordinating borate moiety)] and V(NAd)Cl<sub>2</sub>(OAr) (Ad = 1-adamantyl), were explored by the solution V K-edge XANES (pre-edge and edge region) spectra. No significant differences in the pre-edge (and the edge) peaks were observed between these complexes which fold a distorted 4 coordinate tetrahedral geometry around vanadium; the shoulder-edge peaks ascribed to the presence of V_Cl bonds were also observed in all cases. No significant spectral changes were observed when the phenoxy analogues (exhibiting catalytic activities for ethylene/norbornene copolymerization) were treated with MAO, and even addition of norbornene, suggesting preservation of the oxidation state. Remarkable changes in the XANES spectrum (decrease in the intensity of the pre-edge peak and low-energy shift of the edge region) were observed after addition of Al<i><sup>i</sup></i>Bu<sub>3</sub> toward V(NAr)Cl<sub>2</sub>(WCA-NHC), and no notable changes were observed upon further addition of Al<i><sup>i</sup></i>Bu<sub>3</sub> and norbornene; these results suggest that the formed species, presumably vanadium(III), act directly as the active species in this catalysis.</p>

Journal

  • Journal of the Japan Petroleum Institute

    Journal of the Japan Petroleum Institute 61(5), 282-287, 2018

    The Japan Petroleum Institute

Codes

  • NII Article ID (NAID)
    130007480051
  • NII NACSIS-CAT ID (NCID)
    AA11590615
  • Text Lang
    ENG
  • ISSN
    1346-8804
  • NDL Article ID
    029253420
  • NDL Call No.
    Z17-177
  • Data Source
    NDL  J-STAGE 
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