Werner Daniel, Deacon Glen B, Junk Peter C, Anwander Reiner
Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen (EKUT), Auf der Morgenstelle 18, 72076, Germany.
Dalton Trans. 2017 May 16;46(19):6265-6277. doi: 10.1039/c7dt00635g.
Two stable cerium(iv) 3,5-dialkylpyrazolate complexes are presented, namely dimeric [Ce(Mepz)] (Mepz = 3,5-dimethylpyrazolate) and monomeric Ce(tBupz) (tBupz = 3,5-di-tert-butylpyrazolate) along with their trivalent counterparts [Ce(Mepz)] and [Ce(tBupz)]. All complexes were obtained from protonolysis reactions employing the silylamide precursors Ce[N(SiHMe)] and Ce[N(SiMe)]. Treatment of homoleptic Ce and Ce Mepz complexes with 1,4-hydroquinone (Hhq) or 1,4-benzoquinone (bq), respectively, ultimately gave the same trimetallic Ce species via a cerium redox equilibrium. The Ce complex Ce(Mepz)(pchd)(L) (pchd = 1,4-bis(3,5-dimethylpyrazol-1-yl)cyclohex-2,5-diene-1,4-diolato; L = MepzH or (thf)) results from a di-1,4-pyrazolyl attack on pre-coordinated bq. The reduction of bq by [Ce(Mepz)(thf)], and re-oxidation by the resulting Ce species was supported by UV-vis spectroscopic investigations. Comparisons with the redox-innocent complexes [Ln(Mepz)(thf)] (Ln = La and Pr) revealed far less selective reactions with bq, giving hexametallic and octametallic rare-earth metal side products containing 2-Mepz substituted hq ligands.
本文报道了两种稳定的铈（IV）3,5-二烷基吡唑配合物，即二聚体[Ce(Mepz)]（Mepz = 3,5-二甲基吡唑）和单体Ce(tBupz)（tBupz = 3,5-二叔丁基吡唑）及其三价对应物[Ce(Mepz)]和[Ce(tBupz)]。所有配合物均通过使用硅烷基酰胺前体Ce[N(SiHMe)]和Ce[N(SiMe)]的质子解反应获得。分别用1,4-对苯二酚（Hhq）或1,4-苯醌（bq）处理均配体Ce和Ce Mepz配合物，最终通过铈氧化还原平衡得到相同的三金属Ce物种。Ce配合物Ce(Mepz)(pchd)(L)（pchd = 1,4-双（3,5-二甲基吡唑-1-基）环己-2,5-二烯-1,4-二醇盐；L = MepzH或（thf））是由对预配位的bq进行双-1,4-吡唑基进攻而产生的。紫外可见光谱研究支持了[Ce(Mepz)(thf)]对bq的还原以及所得Ce物种的再氧化。与氧化还原惰性配合物[Ln(Mepz)(thf)]（Ln = La和Pr）的比较表明，与bq的反应选择性要低得多，会生成含有2-Mepz取代hq配体的六金属和八金属稀土金属副产物。
