Pyrazolates advance cerium chemistry: a CeIII/CeIV redox equilibrium with benzoquinone. Issue 19 (26th April 2017)

• Record Type: Journal Article
• Authors: Werner, Daniel; Deacon, Glen B.; Junk, Peter C.; Anwander, Reiner
• Is Part Of: Dalton transactions. Volume 46:Issue 19(2017)
• Page Start: 6265
• Page End: 6277
• Publication Date: 2017-04-26
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c7dt00635g
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Homoleptic Ce IV and Ce III 3, 5-dimethylpyrazolate (L) complexes react with 1, 4-hydroquinone (H2 hq) and 1, 4-benzoquinone (bq), respectively, to form a new O2 N2 diolato ligand (phcd) by means of a Ce III /Ce IV redox equilibrium. Abstract : Two stable cerium(iv ) 3, 5-dialkylpyrazolate complexes are presented, namely dimeric [Ce(Me2 pz)4 ]2 (Me2 pz = 3, 5-dimethylpyrazolate) and monomeric Ce( t Bu2 pz)4 ( t Bu2 pz = 3, 5-di- tert -butylpyrazolate) along with their trivalent counterparts [Ce(Me2 pz)3 ] and [Ce( t Bu2 pz)3 ]2 . All complexes were obtained from protonolysis reactions employing the silylamide precursors Ce[N(SiHMe2 )2 ]4 and Ce[N(SiMe3 )2 ]3 . Treatment of homoleptic Ce IV and Ce III Me2 pz complexes with 1, 4-hydroquinone (H2 hq) or 1, 4-benzoquinone (bq), respectively, ultimately gave the same trimetallic Ce III species via a cerium redox equilibrium. The Ce III complex Ce3 (Me2 pz)5 (pchd)2 (L) (pchd = 1, 4-bis(3, 5-dimethylpyrazol-1-yl) c yclohex-2, 5-diene-1, 4- d iolato; L = Me2 pzH or (thf)2 ) results from a di-1, 4-pyrazolyl attack on pre-coordinated bq. The reduction of bq by [Ce(Me2 pz)3 (thf)]2, and re-oxidation by the resulting Ce IV species was supported by UV-vis spectroscopic investigations. Comparisons with the redox-innocent complexes [Ln(Me2 pz)3 (thf)]2 (Ln = La and Pr) revealed far less selective reactions with bq, giving hexametallic and octametallic rare-earth metal side products containing 2-Me2 pz substituted hq ligands.