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Cerium(III/IV) Formamidinate Chemistry, and a Stable Cerium(IV) Diolate
Author(s) -
Werner Daniel,
Deacon Glen B.,
Junk Peter C.,
Anwander Reiner
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201304582
Subject(s) - cerium , protonolysis , chemistry , homoleptic , medicinal chemistry , lanthanide , nuclear chemistry , inorganic chemistry , catalysis , organic chemistry , ion , metal
Abstract Four new cerium(III) formamidinate complexes comprising [Ce( p ‐TolForm) 3 ], [Ce(DFForm) 3 (thf) 2 ], [Ce(DFForm) 3 ], and [Ce(EtForm) 3 ] were synthesized by protonolysis reactions using [Ce{N(SiMe 3 ) 2 } 3 ] and formamidines of varying functionality, namely N , N ′‐bis(4‐methylphenyl)formamidine ( p ‐TolFormH), N , N ′‐bis(2,6‐difluorophenyl)formamidine (DFFormH), and the sterically more demanding N , N ′‐bis(2,6‐diethylphenyl)formamidine (EtFormH). The bimetallic cerium lithium complex [LiCe(DFForm) 4 ] was synthesized by treating a mixture of [Ce{N(SiHMe 2 ) 2 } 3 (thf) 2 ] and [Li{N(SiHMe 2 ) 2 }] with four equivalents of DFFormH in toluene. Oxidation of the trivalent cerium(III) formamidinate complexes by trityl chloride (Ph 3 CCl) caused dramatic color changes, although the cerium(IV) species appeared transient and reformed cerium(III) complexes and N′ ‐trityl‐ N,N′ ‐diarylformamidines shortly after oxidation. The first structurally characterized homoleptic cerium(IV) formamidinate complex [Ce( p ‐TolForm) 4 ] was obtained through a protonolysis reaction between [Ce{N(SiHMe 2 ) 2 } 4 ] and four equivalents of p ‐TolFormH. [Ce{N(SiHMe 2 ) 2 } 4 ] was also treated with DFFormH and EtFormH, but the resulting cerium(IV) complexes decomposed before isolation was possible. The new cerium(IV) silylamide complex [Ce{N(SiMe 3 ) 2 } 3 (bda) 0.5 ] 2 (bda=1,4‐benzenediolato) was synthesized by treatment of [Ce{N(SiMe 3 ) 2 } 3 ] with half an equivalent of 1,4‐benzoquinone, and showed remarkable resistance towards protonolysis or reduction.