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Metal Complexes of a Redox‐Active [1]Phosphaferrocenophane: Structures, Electrochemistry and Redox‐Induced Catalysis
Author(s) -
Feyrer Alexander,
Armbruster Markus K.,
Fink Karin,
Breher Frank
Publication year - 2017
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.201700868
Subject(s) - chemistry , redox , bimetallic strip , reductive elimination , catalysis , selectivity , cyclic voltammetry , hydrosilylation , rhodium , metal , electrochemistry , reactivity (psychology) , transition metal , reaction mechanism , photochemistry , combinatorial chemistry , inorganic chemistry , organic chemistry , electrode , medicine , alternative medicine , pathology
The synthesis and characterisation of several metal complexes of a redox‐active, mesityl(Mes)‐substituted [1]phosphaferrocenophane, FcPMes ( 1 ), are reported. Cyclic voltammetry studies on the bimetallic complexes [M(κ 1 P ‐ 1 )(cod)Cl] (M=Rh: 2 ; M=Ir: 4 ), [Rh(κ 1 P ‐ 1 ) 2 (CO)Cl] ( 3 ) and [AuCl(κ 1 P ‐ 1 )] ( 5 ), in conjunction with DFT calculations, provided indications for a good electronic communication between the metal atoms. To confirm that the ferrocenophane unit might be able to electrochemically influence the reactivity of the coordinated transition metal, the rhodium complex 2 was employed as stimuli‐responsive catalyst in the hydrosilylation of terminal alkynes. All reactions were greatly accelerated with in situ generated 2 + as a catalyst as compared to 2 . Even more importantly, a markedly different selectivity was observed. Both factors were attributed to different mechanisms operating for 2 and 2 + (alternative Chalk–Harrod and Chalk–Harrod mechanism, respectively). DFT calculations revealed relatively large differences for the activation barriers for 2 and 2 + in the reductive elimination step of the classical Chalk–Harrod mechanism. Thus, the key to the understanding is a cooperative “oxidatively induced reductive elimination” step, which facilitates both a higher activity and a markedly different selectivity.