Cobalt-Catalyzed Hydrogenations via Olefin Cobaltate and Hydride Intermediates

Abstract

Redox noninnocent ligands are a promising tool to moderate electron transfer processes within base-metal catalysts. This report introduces bis(imino)acenaphthene (BIAN) cobaltate complexes as hydrogenation catalysts. Sterically hindered trisubstituted alkenes, imines, and quinolines underwent clean hydrogenation under mild conditions (2−10 bar, 20−80°C) by use of the stable catalyst precursor [(Dipp BIAN)CoBr 2 ] and the cocatalyst LiEt 3 BH. Mechanistic studies support a homogeneous catalysis pathway involving alkene and hydrido cobaltates as active catalyst species. Furthermore, considerable reaction acceleration by alkali cations and Lewis acids was observed. The dinuclear hydridocobaltate anion with bridging hydride ligands was isolated and fully characterized.

The Role of Organoferrates in Iron‐Catalyzed Cross‐Couplings

“…These organometallic studies of metalate‐catalyzed reactions have also demonstrated the opportunities for catalyst tuning through the nature of the counterion. Co‐catalytic assistance of counterions can involve diverse modes of substrate or catalyst activation . Upon implementation of metal‐based cations, bimetallic catalysis mechanisms can be engineered.…”

Zur Rolle von Organoferraten in eisenkatalysierten Kreuzkupplungen

“…Diese Untersuchungen metallkatalysierter Reaktionen haben auch die Möglichkeit der Feinabstimmung von Katalysatoren über die Art des Gegenions aufgezeigt. Die cokatalytische Unterstützung durch Gegenionen kann verschiedene Arten der Substrat‐ oder Katalysatoraktivierung beinhalten . Durch Einführung metallbasierter Kationen können bimetallische Katalysemechanismen entwickelt werden.…”

“…Die cokatalytische Unterstützung durch Gegenionen kann verschiedene Arten der Substrat-oder Katalysatoraktivierung beinhalten. [20][21][22][23] Durch Einführung metallbasierter Kationen kçnnen bimetallische Katalysemechanismen entwickelt werden. Die ausgeprägte Reaktivitätvon Magnesium gegenüber Lithiumorganoferraten in diesen Studien spiegelt die Dominanz von Grignard-Reagenzien als nukleophile Komponenten in eisenkatalysierten Kreuzkupplungen wider.…”

Rich redox-activity and solvatochromism in a family of heteroleptic cobalt complexes

“…[43][44][45] The redox lability of the Co-BIAN moiety, in particular, has led to its use in numerous catalytic applications. [46][47][48][49][50] While VT has not been observed experimentally in Co-BIAN systems, 24,51 its occurrence in three complexes with the general formula [Co(L NO ) 2 (BIAN)] (L NO = a Schiff base ligand, Chart S1 †) has been computationally predicted, involving an interconversion between low-spin (LS) Co III -BIAN •− and high-spin (HS) Co II -BIAN 0 forms. 52 However, the calculated [Co(L NO ) 2 (BIAN)] complexes are difficult to access experimentally as they each contain either an ancillary ligand that cannot be isolated because it self-reacts and/or a BIAN ligand that has never been reported.…”