Bond Activation and Catalysis by Ruthenium Pincer Complexes

Gunanathan, Chidambaram; Milstein, David

doi:10.1021/cr5002782

Cited by 837 publications

(506 citation statements)

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“…[9][10][11][12] For example, Milstein and coworkers demonstrated the role of PCP and PNP pincer ligands in catalysis and small molecule activation and proposed mechanisms in which metal-ligand cooperation plays a major role (Chart 1c). [13][14][15][16][17][18][19][20][21] In addition, Chirik and coworkers exploited the potential of base metals in catalytic transformations by using flexible and redox non-innocent ligands to overcome the limitation of first row transition metals that usually undergo single electron processes (Chart 1d). [22][23][24][25] Besides traditional phosphine and nitrogen donors, an arene is suitable for metal-ligand cooperation as well: first, the coordination mode of the arene can vary from  6 to  2 according to the degree of delocalization.…”

Section: Introductionmentioning

confidence: 99%

Reactivity and Properties of Metal Complexes Enabled by Flexible and Redox-Active Ligands with a Ferrocene Backbone

Huang

Diaconescu

2016

Inorg. Chem.

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Our group has focused on the organometallic chemistry of rare-earth metals and actinides for a decade. By installing ferrocene diamide ligands at electropositive metal centers, we have been able to disclose unprecedented reactivity toward aromatic N-heterocycles, arenes, and other small molecules such as P 4 . Systematic studies employing X-ray crystallography, spectroscopy, cyclic voltammetry, and DFT calculations revealed that the ferrocene backbone could stabilize the electron-deficient metal through a donor-acceptor type interaction. Most noteworthy is that this interaction can be readily turned on or off by the addition or removal of a Lewis base. In addition to its flexible coordination, the redox active nature of the ferrocene backbone enabled us to explore redox-switchable transformations. The introduction of ferrocene-based ligands into organolanthanide chemistry not only helped to study intriguing fundamental problems but also led to fruitful chemistry including small molecule activation and controlled co-polymerization reactions.3

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Section: Introductionmentioning

confidence: 99%

Reactivity and Properties of Metal Complexes Enabled by Flexible and Redox-Active Ligands with a Ferrocene Backbone

Huang

Diaconescu

2016

Inorg. Chem.

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“…In continuation of our research on design of novel catalysts for selective organic transformations, we have synthesized more flexible, expanded PNN-type pincer ruthenium complexes (18)(19)(20). However, only modest catalytic activity and selectivity was observed with these bridged-bipyridine-based PNN-Ru(II) complexes in amide hydrogenation (25-65% yields) and other reactions [70].…”

Section: Selective Hydrogenation Of Amides To Alcohols and Aminesmentioning

confidence: 99%

“…These complexes show a new mode of metal-ligand cooperation (MLC) [18] based on ligand aromatization-dearomatization, which has led to a number of bond activation processes [19][20][21][22]. Deprotonation of a methylenic side-arm proton of pyridyl-and bypridyl-based pincer complexes leads to the corresponding dearomatized, coordinatively unsaturated 16 electron complexes.…”

Section: Introductionmentioning

confidence: 99%

Hydrogenation of Polar Bonds Catalysed by Ruthenium-Pincer Complexes

Balaraman

Milstein

2014

Ruthenium in Catalysis

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Catalytic hydrogenation of polar bonds using molecular hydrogen is an important, atom-economical synthetic reaction. Classical reduction methods of polar bond often require reactive metal-hydride reagents in stoichiometric amount and produce copious waste. Hydrogenation of carbonyl compounds in particular provides 'green' approaches to synthetically important building blocks, such as alcohols and amines. We have designed and synthesized several ruthenium-based pincer catalysts for unprecedented hydrogenation reactions including: (1) amides to alcohols and amines, (2) biomass-derived di-esters to 1,2-diols and (3) CO 2 and CO derivatives to methanol. These atom-economical reactions operate under neutral, homogeneous conditions, at mild temperatures, mild hydrogen pressures, and can operate in absence of solvent with no generation of waste. The postulated mechanisms involve metal-ligand cooperation (MLC) by aromatization-dearomatization of the heteroaromatic pincer core.

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“…Analogous Fe catalysts were studied by Casey and Guan with the Knölker complex which offered excellent tolerance to functional groups such as halides, nitro groups, benzyl ethers, and cyclopropyl rings [38,39]. One unique type of metal-ligand cooperation via aromatization-dearomatization of the central pyridine on pyridine-based pincer complexes via deprotonation-reprotonation of one of the pyridylic CH 2 arms was recently demonstrated by Milstein and co-workers [40][41][42]. Pincertype metal complexes have been studied extensively in recent years as they offer several advantages to catalyst design [43][44][45][46][47][48][49][50][51][52][53][54].…”

Section: Introductionmentioning

confidence: 99%