Homogeneous Functionalization of Methane

Homogeneous Functionalization of Methane

Gunsalus, N. J.; Koppaka, A.; Park, S. H.; Bischof, S. M.; Hashiguchi, B. G.; Periana, R. A.*
The Scripps Research Institute

Chem. Rev. ASAP
http://pubs.acs.org/doi/pdf/10.1021/acs.chemrev.6b00739

Abstract:

One of the remaining “grand challenges” in chemistry is the development of a next generation, less expensive, cleaner process that can allow the vast reserves of methane from natural gas to augment or replace oil as the source of fuels and chemicals. Homogeneous (gas/liquid) systems that convert methane to functionalized products with emphasis on reports after 1995 are reviewed. Gas/solid, bioinorganic, biological, and reaction systems that do not specifically involve methane functionalization are excluded. The various reports are grouped under the main element involved in the direct reactions with methane. Central to the review is classification of the various reports into 12 categories based on both practical considerations and the mechanisms of the elementary reactions with methane. Practical considerations are based on whether or not the system reported can directly or indirectly utilize O2 as the only net coreactant based only on thermodynamic potentials. Mechanistic classifications are based on whether the elementary reactions with methane proceed by chain or nonchain reactions and with stoichiometric reagents or catalytic species. The nonchain reactions are further classified as CH activation (CHA) or CH oxidation (CHO). The bases for these various classifications are defined. In particular, CHA reactions are defined as elementary reactions with methane that result in a discrete methyl intermediate where the formal oxidation state (FOS) on the carbon remains unchanged at −IV relative to that in methane. In contrast, CHO reactions are defined as elementary reactions with methane where the carbon atom of the product is oxidized and has a FOS less negative than −IV. This review reveals that the bulk of the work in the field is relatively evenly distributed across most of the various areas classified. However, a few areas are only marginally examined, or not examined at all. This review also shows that, while significant scientific progress has been made, greater advances, particularly in developing systems that can utilize O2, will be required to develop a practical process that can replace the current energy and capital intensive natural gas conversion process. We believe that this classification scheme will provide the reader with a rapid way to identify systems of interest while providing a deeper appreciation and understanding, both practical and fundamental, of the extensive literature on methane functionalization. The hope is that this could accelerate progress toward meeting this “grand challenge.”

TOC:

Over a million turnovers for a molecular WOC

http://onlinelibrary.wiley.com/doi/10.1002/anie.201609167/abstract

A Million Turnover Molecular Anode for Catalytic Water Oxidation

• 
  

• First published: 7 November 2016Full publication history
• DOI: 10.1002/anie.201609167View/save citation
• Cited by: 0 articles

• 
  
• 

Abstract

Molecular ruthenium-based water oxidation catalyst precursors of general formula [Ru(tda)(Lⁱ)₂] (tda²⁻ is [2,2′:6′,2′′-terpyridine]-6,6′′-dicarboxylato; L¹=4-(pyren-1-yl)-N-(pyridin-4-ylmethyl)butanamide, 1 b; L²=4-(pyren-1-yl)pyridine), 1 c), have been prepared and thoroughly characterized. Both complexes contain a pyrene group allowing ready and efficiently anchoring via π interactions on multi-walled carbon nanotubes (MWCNT). These hybrid solid state materials are exceptionally stable molecular water-oxidation anodes capable of carrying out more than a million turnover numbers (TNs) at pH 7 with an E_app=1.45 V vs. NHE without any sign of degradation. XAS spectroscopy analysis before, during, and after catalysis together with electrochemical techniques allow their unprecedented oxidative ruggedness to be monitored and verified.

Research Progress on the Indirect Hydrogenation of Carbon Dioxide to Methanol

Xian-Long Du, Zheng Jiang, Dang Shen Su, Jian-Qiang Wang

First published: 21 December 2015   DOI: 10.1002/cssc.201501013

Abstract

Methanol is a sustainable source of liquid fuels and one of the most useful organic chemicals. To date, most of the work in this area has focused on the direct hydrogenation of CO₂ to methanol. However, this process requires high operating temperatures (200–250 °C), which limits the theoretical yield of methanol. Thus, it is desirable to find a new strategy for the efficient conversion of CO₂ to methanol at relatively low reaction temperatures. This Minireview seeks to outline the recent advances on the indirect hydrogenation of CO₂ to methanol. Much emphasis is placed on discussing specific systems, including hydrogenation of CO₂ derivatives (organic carbonates, carbamates, formates, cyclic carbonates, etc.) and cascade reactions, with the aim of critically highlighting both the achievements and remaining challenges associated with this field.

http://onlinelibrary.wiley.com/doi/10.1002/cssc.201501013/full

Conversion of alkanes to linear alkylsilanes using an iridium–iron-catalysed tandem dehydrogenation–isomerization–hydrosilylation

Xiangqing Jia & Zheng Huang

Nature Chemistry Volume: 8, Pages: 157–161  Year published: (2016) doi:10.1038/nchem.2417 Received 04 August 2015    Accepted  11 November 2015  Published online 21 December 2015      

Abstract
The conversion of inexpensive, saturated hydrocarbon feedstocks into value-added speciality chemicals using regiospecific, catalytic functionalization of alkanes is a major goal of organometallic chemistry. Linear alkylsilanes represent one such speciality chemical—they have a wide range of applications, including release coatings, silicone rubbers and moulding products. Direct, selective, functionalization of alkanes at primary C–H bonds is difficult and, to date, methods for catalytically converting alkanes into linear alkylsilanes are unknown. Here, we report a well-defined, dual-catalyst system for one-pot, two-step alkane silylations. The system comprises a pincer-ligated Ir catalyst for alkane dehydrogenation and an Fe catalyst that effects a subsequent tandem olefin isomerization–hydrosilylation. This method exhibits exclusive regioselectivity for the production of terminally functionalized alkylsilanes. This dual-catalyst strategy has also been applied to regioselective alkane borylations to form linear alkylboronate esters.

http://www.nature.com/nchem/journal/v8/n2/full/nchem.2417.html

Conversion of CO2 from Air into Methanol Using a Polyamine and a Homogeneous Ruthenium Catalyst

http://pubs.acs.org/doi/abs/10.1021/jacs.5b12354
 
Conversion of CO2 from Air into Methanol Using a Polyamine and a Homogeneous Ruthenium Catalyst
Jotheeswari Kothandaraman, Alain Goeppert, Miklos Czaun, G. K. Surya Prakash, and George A Olah
J. Am. Chem. Soc., Just Accepted Manuscript
DOI: 10.1021/jacs.5b12354
Publication Date (Web): December 29, 2015
Copyright © 2015 American Chemical Society

Abstract: A highly efficient homogeneous catalyst system for the continuous production of CH3OH from CO2 using PEHA and Ru-Macho-BH (1) at 125-165 °C in an ethereal solvent has been developed (initial TOF = 70 h-1 at 145 °C). Ease of separation of CH3OH is demonstrated by simple distillation from the reaction mixture. The robustness of the catalytic system was shown by recycling the catalyst over 5 runs without significant loss of activity (TON>2000 h-1). Various sources of CO2 can be used for this reaction including the air, despite its low CO2 concentration (400 ppm). For the first time, we have demonstrated that CO2 captured from air can be directly converted to CH3OH in 79% yield using the homogeneous catalytic system.

Fighting Fenton Chemistry: A Highly Active Iron(III) Tetracarbene Complex in Epoxidation Catalysis

Jens W. Kück, Markus R. Anneser, Benjamin Hofmann, Dr. Alexander Pöthig, Dr. Mirza Cokoja, Prof. Dr. Fritz E. Kühn

Abstract

Organometallic Fe complexes with exceptionally high activities in homogeneous epoxidation catalysis are reported. The compounds display Fe^II and Fe^III oxidation states and bear a tetracarbene ligand. The more active catalyst exhibits activities up to 183 000 turnovers per hour at room temperature and turnover numbers of up to 4300 at −30 °C. For the Fe^III complex, a decreased Fenton-type reactivity is observed compared with Fe^II catalysts reported previously as indicated by a substantially lower H₂O₂ decomposition and higher (initial) turnover frequencies. The dependence of the catalyst performance on the catalyst loading, substrate, water addition, and the oxidant is investigated. Under all applied conditions, the advantageous nature of the use of the Fe^III complex is evident.

http://onlinelibrary.wiley.com/doi/10.1002/cssc.201500930/full

A manganese catalyst for highly reactive yet chemoselective intramolecular C(sp3)–H amination

 Shauna M. Paradine, Jennifer R. Griffin, Jinpeng Zhao, Aaron L. Petronico, Shannon M. Miller, & M. Christina White

 

Nature Chemistry 7,  987–994  (2015)  doi:10.1038/nchem.2366  Received 01 July 2015             Accepted 01 September 2015    Published online 05 October 2015      

 

Abstract

C–H bond oxidation reactions underscore the existing paradigm wherein high reactivity and high selectivity are inversely correlated. The development of catalysts capable of oxidizing strong aliphatic C(sp³)–H bonds while displaying chemoselectivity (that is, tolerance of more oxidizable functionality) remains an unsolved problem. Here, we describe a catalyst, manganese tert-butylphthalocyanine [Mn(^tBuPc)], that is an outlier to the reactivity–selectivity paradigm. It is unique in its capacity to functionalize all types of C(sp³)–H bond intramolecularly, while displaying excellent chemoselectivity in the presence of π functionality. Mechanistic studies indicate that [Mn(^tBuPc)] transfers bound nitrenes to C(sp³)–H bonds via a pathway that lies between concerted C–H insertion, observed with reactive noble metals such as rhodium, and stepwise radical C–H abstraction/rebound, as observed with chemoselective base metals such as iron. Rather than achieving a blending of effects, [Mn(^tBuPc)] aminates even 1° aliphatic and propargylic C–H bonds, demonstrating reactivity and selectivity unusual for previously known catalysts.

 

http://www.nature.com/nchem/journal/v7/n12/full/nchem.2366.html

Removing Homogeneous Catalysts from Reaction Mixtures for Product Isolation

Metathesis Catalyst Removal Techniques

 http://allthingsmetathesis.com/metathesis-catalyst-removal-techniques/

While this is directed towards removal of Metathesis Catalysts. The techniques and tips, I believe, could have application with a variety of homogeneous catalysts.

Abstract:

Purification of a metathesis mixture can give you all sorts of problems (especially when using high catalyst loadings). Sometimes you need multiple columns to get a colorless product. Sometimes residual ruthenium can cause the product to isomerize during distillation or decompose over time. Numerous methods have been reported for the removal of metathesis catalysts after a reaction. In general, you need a ligand or adsorbent that binds ruthenium better than your product, or a reagent that will react with the residual ruthenium preferentially. Unfortunately the optimal process tends to vary on a case by case basis.

Synthesis and Characterization of New (η5-Cyclopentadienyl)dicarbonylruthenium(II) Amine Complexes: Their Application as Homogeneous Catalysts in Styrene Oxidation

http://pubs.acs.org/doi/10.1021/acs.organomet.5b00564



Synthesis and Characterization of New (η5-Cyclopentadienyl)dicarbonylruthenium(II) Amine Complexes: Their Application as Homogeneous Catalysts in Styrene Oxidation
Eunice A. Nyawade, Holger B. Friedrich*, Bernard Omondi, and Philani Mpungose

School of Chemistry and Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa
Organometallics, 2015, 34 (20), pp 4922–4931
DOI: 10.1021/acs.organomet.5b00564
Publication Date (Web): October 14, 2015







The water-soluble ruthenium(II) mononuclear complexes [CpRu(CO)2NH2R]BF4 (Cp = η5-C5H5; R = C6H11 (1), C6H5 (2), CH2C6H5 (3), CH(CH3)C6H5 (4), CH2(C6H4O)CH3 (5), CH2(C6H4)CN (6), C6H2(CH3)3 (7), CH2CHCH2 (8), CH(CH3)2 (9)) were synthesized from the reaction of the organometallic Lewis acid [CpRu(CO)2]BF4 with amine ligands at room temperature. These complexes are reported for the first time and have been fully characterized by IR, high-resolution mass spectrometry, 1H and 13C NMR spectroscopy, and elemental analysis. Spectral data show that the amines are σ-bonded to the metal center via the nitrogen atom. The crystal structures of complexes 3 and 8 were determined by single-crystal X-ray crystallography. The 4-methoxybenzylamine, 4-aminomethylbenzonitrile and allylamine groups preferentially bind to the metal center via the amine nitrogen. The ruthenium complexes 1, 3–6, 9, and [CpRu(CO)2NH2CH3]BF4 (10) and the dinuclear complex [CpRu(CO)2NH2(CH2)6NH2(CO)2-RuCp][BF4]2 (11) demonstrated excellent catalytic activity in the oxidation of styrene using NaIO4 as the co-oxidant with over 95% conversion and benzaldehyde yields, respectively, in some cases.

Substituent Effect on the Catalytic Activity of Ruthenium(II) Complexes Bearing a Pyridyl-Supported Pyrazolyl-Imidazolyl Ligand for Transfer Hydrogenation of Ketones

http://pubs.acs.org/doi/10.1021/acs.organomet.5b00727



Substituent Effect on the Catalytic Activity of Ruthenium(II) Complexes Bearing a Pyridyl-Supported Pyrazolyl-Imidazolyl Ligand for Transfer Hydrogenation of Ketones
Huining Chai†, Tingting Liu†, Qingfu Wang†, and Zhengkun Yu*†‡

† Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, Liaoning 116023, People’s Republic of China
‡ State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, People’s Republic of China
Organometallics, Article ASAP
DOI: 10.1021/acs.organomet.5b00727
Publication Date (Web): October 20, 2015





Air- and moisture-stable ruthenium(II) complexes bearing a multisubstituted pyrazolyl-imidazolyl-pyridine ligand were synthesized and structurally characterized by NMR and X-ray single-crystal crystallographic analyses. The substituents on the imidazolyl moiety of the NNN ligand exhibited a remarkable impact on the catalytic activity of the corresponding Ru(II) complexes for transfer hydrogenation of ketones in refluxing 2-propanol, following the order NHTs > Me > H > NO2, to tune the catalytic activity. The highest final TOF value of 345 600 h–1was reached by means of 0.05 mol % of the Ru(II)-NHTs-substituted NNN complex as the catalyst. The corresponding structurally confirmed RuH complexes are proposed as the catalytically active species.

Nickel-catalyzed arylation of heteroaryl-containing diarylmethanes: exceptional reactivity of the Ni(NIXANTPHOS)-based catalyst

http://pubs.rsc.org/en/Content/ArticleLanding/2016/SC/C5SC03704B?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FSC+%28RSC+-+Chem.+Sci.+latest+articles%29#!divAbstract


Nickel-catalyzed arylation of heteroaryl-containing diarylmethanes: exceptional reactivity of the Ni(NIXANTPHOS)-based catalyst
Xinyu Cao,ab Sheng-Chun Sha,b Minyan Li,b Byeong-Seon Kim,b Catherine Morgan,b Rudan Huang,a Xiaodong Yangc and Patrick J. Walsh*b

Show Affiliations
Chem. Sci., 2016, Advance Article
DOI: 10.1039/C5SC03704B
Received 30 Sep 2015, Accepted 07 Oct 2015
First published online 26 Oct 2015





Nickel(0)-catalyzed cross-coupling of heteroaryl-containing diarylmethanes with both aryl bromides and chlorides has been achieved. The success of this reaction relies on the introduction of a unique nickel/NIXANTPHOS-based catalyst system, which provides a direct route to triarylmethanes from heteroaryl-containing diarylmethanes. Reactivity studies indicate the Ni(NIXANTPHOS)-based catalyst exhibits enhanced reactivity over XANTPHOS derivatives and other Ni(phosphine)-based catalysts in the reactions examined.

Chemoselective Palladium-Catalyzed Deprotonative Arylation/[1,2]-Wittig Rearrangement of Pyridylmethyl Ethers

http://pubs.rsc.org/en/Content/ArticleLanding/2015/SC/C5SC02739J?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FSC+%28RSC+-+Chem.+Sci.+latest+articles%29#!divAbstract


Chemoselective Palladium-Catalyzed Deprotonative Arylation/[1,2]-Wittig Rearrangement of Pyridylmethyl Ethers
Feng Gao, Byeong-Seon Kim and Patrick Walsh

Chem. Sci., 2015, Accepted Manuscript
DOI: 10.1039/C5SC02739J
Received 27 Jul 2015, Accepted 26 Oct 2015
First published online 27 Oct 2015


Control of chemoselectivity is one of the most challenging problems facing chemists and is particularly important in the synthesis of bioactive compounds and medications. Herein, the first highly chemoselective tandem C(sp3)–H arylation/[1,2]-Wittig rearrangement of pyridylmethyl ethers is presented. The efficient and operationally simple protocols enable generation of either arylation products or tandem arylation/[1,2]-Wittig rearrangement products with remarkable selectivity and good to excellent yields (60−99%). Choice of base, solvent, and reaction temperature play a pivotal role in tuning the reactivity of intermediates and controlling the relative rates of competing processes. The novel arylation step is catalyzed by a Pd(OAc)2/NIXANTPHOS-based system via a deprotonative cross-coupling process. The method provides rapid access to skeletally diverse aryl(pyridyl)methanol core structures, which are central components of several medications.

http://pubs.acs.org/doi/10.1021/jacs.5b09824

Complete Switch of Selectivity in the C–H Alkenylation and Hydroarylation Catalyzed by Iridium: The Role of Directing Groups

Jiyu Kim†‡, Sung-Woo Park*‡†, Mu-Hyun Baik‡†, and Sukbok Chang*‡†

† Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea
‡ Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 305-701, Korea

J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/jacs.5b09824
Publication Date (Web): October 8, 2015

A complete switch in the Cp*Ir(III)-catalyzed paths between C–H olefination and hydroarylation was found to be crucially dependent on the type of directing groups. This dichotomy in product distribution was correlated to the efficiency in attaining syn-coplanarity of olefin-inserted 7-membered iridacycles. Theoretical studies support our hypothesis that the degree of flexibility of this key intermediate modulates the β-H elimination, which ultimately affords the observed chemoselectivity.

Homogeneous Pd catalysts on polymer supports for easy recovery and recycling

 http://www.sciencedirect.com/science/article/pii/S156673671530011X

An easily recoverable and recyclable homogeneous polyester-based Pd catalytic system for the hydrogenation of α,β-unsaturated carbonyl compounds

• Mattia Bartoli^a,
• Luca Rosi^{a, b},
• Giorgio Petrucci^a,
• Lidia Armelao^c,
• Werner Oberhauser^d,
• Marco Frediani^a, ,
• Oreste Piccolo^{e, f},
• Vikas Damu Rathod^e,
• Stefano Paganelli^{e, ,}

---

Highlights

•

trans-[Pd(OAc)₂(L)₂] was synthesized from Pd(OAc)₂ and the poly(l-lactide) (L).

•

trans-[Pd(OAc)₂(L)₂] was used as catalytic precursor in hydrogenations.

•

trans-[Pd(OAc)₂(L)₂] is a homogeneous catalytic precursor.

•

The homogeneous catalyst can be easily recovered from the reaction mixture.

•

The catalytic system maintained its activity in recycle experiments.

---

Abstract

Homogeneous catalysis is an efficient tool to carry out hydrogenation processes but the major drawback is represented by the separation of the expensive catalyst from the product mixture. In this view we prepared a polyester-based Pd catalytic system that offers the advantages of both homogenous and heterogeneous catalyses: efficacy, selectivity and recyclability. Here its application in the hydrogenation of selected α,β-unsaturated carbonyl compounds is described.

---

Graphical abstract

Homogeneous Cobalt Catalyst for Hydrogenation of Carboxylic Acids

http://www.sciencemag.org/content/350/6258/298.abstract

 

Science 16 October 2015:
Vol. 350 no. 6258 pp. 298-302
DOI: 10.1126/science.aaa8938

Hydrogenation of carboxylic acids with a homogeneous cobalt catalyst

1. Ties J. Korstanje,
2. Jarl Ivar van der Vlugt,
3. Cornelis J. Elsevier*,
4. Bas de Bruin*

The reduction of esters and carboxylic acids to alcohols is a highly relevant conversion for the pharmaceutical and fine-chemical industries and for biomass conversion. It is commonly performed using stoichiometric reagents, and the catalytic hydrogenation of the acids previously required precious metals. Here we report the homogeneously catalyzed hydrogenation of carboxylic acids to alcohols using earth-abundant cobalt. This system, which pairs Co(BF₄)₂·6H₂O with a tridentate phosphine ligand, can reduce a wide range of esters and carboxylic acids under relatively mild conditions (100°C, 80 bar H₂) and reaches turnover numbers of up to 8000.