Potential of Ru(III/II) Couple Increases with Increased Sterics of Scorpionate Ligands

http://www.sciencedirect.com/science/article/pii/S0020169313000674.

Volume 405, 24 August 2013, Pages 470–476

Synthesis and electrochemical characterization of [Ru(NCCH₃)₆]²⁺, tris(acetonitrile) tris(pyrazolyl)borate, and tris(acetonitrile) tris(pyrazolyl)methane ruthenium(II) complexes

• Christopher C. Underwood,
• Bradley S. Stadelman,
• Mark L. Sleeper,
• Julia L. Brumaghim^,

http://dx.doi.org/10.1016/j.ica.2013.02.027

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Abstract

Tris(acetonitrile) tris(pyrazolyl)borato- and tris(pyrazolyl)methano ruthenium(II) complexes would make good synthons in ruthenium chemistry for synthesis of catalysts and DNA binding drugs. However, these complexes are not widely used as starting materials due to the long reaction times and multiple synthetic steps required or the lack of their successful synthesis. We have developed a new synthesis for the ruthenium(II) acetonitrile complex [Ru(NCCH₃)₆]²⁺ with noncoordinating BF₄⁻ or OTf (OTf = trifluoromethanesulfonate) counterions. Using this [Ru(NCCH₃)₆]²⁺ complex, the previously reported tris(acetonitrile) tris(pyrazolyl)borato ruthenium(II) complexes [Tp^RRu(NCCH₃)₃]⁺ (Tp^R = tris(pyrazolyl)borate; R = H, Me) and the unreported tris(acetonitrile) tris(pyrazolyl)borato ruthenium(II) complex (R = Ph) have been synthesized using an improved synthetic pathway that reduces the number of required steps by up to six and the average synthesis times by up to 45 h. Novel tris(acetonitrile) tris(pyrazolyl)methano ruthenium(II) complexes of the formula [Tpm^RRu(NCCH₃)₃]²⁺ (Tpm^R = tris(pyrazolyl)methane; R = Me, Ph) have also been synthesized in one step in 12 h using this method. Cyclic voltammetry studies of the synthesized complexes show that Ru^2+/3+ redox potentials generally increase with increasing steric bulk of the Tp^R or Tpm^R ligand. The ability to sterically tune Ru^2+/3+ redox potentials may be used to promote catalysis development and in the development of ruthenium-based drugs.

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Graphical abstract

We report improved syntheses for [Ru(NCCH₃)₆]²⁺ and complexes of the formula [Tp^RRu(NCCH₃)₃]⁺ (Tp^R = tris(pyrazolyl)borate; R = H, Me, Ph), as well as syntheses for unreported [Tpm^RRu(NCCH₃)₃]²⁺ (Tpm^R = tris(pyrazolyl)methane; R = Me, Ph) complexes. Electrochemical studies indicate that the Ru^2+/3+ redox potentials of these complexes vary by up to 427 mV, a trait that may be useful for ruthenium-based drug and catalysis development.

Synthesis of Pincer Hydrido Ruthenium Olefin Complexes for Catalytic Alkane Dehydrogenation

Synthesis of Pincer Hydrido Ruthenium Olefin Complexes for Catalytic Alkane Dehydrogenation

Yuxuan Zhang, Huaquan Fang, Wubing Yao, Xuebing Leng, and Zheng Huang*
The State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, 345 Lingling Road, Shanghai 200032, People’s Republic of China
Organometallics, 2016, 35 (2), pp 181–188
DOI: 10.1021/acs.organomet.5b00912
Publication Date (Web): January 13, 2016








A series of new hydrido Ru(II) olefin complexes supported by isopropyl-substituted pincer ligands have been synthesized and characterized. These complexes are thermally robust and active for catalytic transfer and acceptorless alkane dehydrogenation. Notably, the alkane dehydrogenation catalysts are tolerant of a number of polar functional species.

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.

Oxidative Coupling between Two Hydrocarbons: An Update of Recent C–H Functionalizations

Oxidative Coupling between Two Hydrocarbons: An Update of Recent C-H Functionalizations

Chao Liu,† Jiwen Yuan,† Meng Gao,‡ Shan Tang,† Wu Li,† Renyi Shi,† and Aiwen Lei*,†,‡

† College of Chemistry and Molecular Sciences, Institute for Advanced Studies (IAS), Wuhan University, Wuhan 430072, People’s Republic of China ‡ National Research Center for Carbohydrate Synthesis, Jiangxi Normal University, Nanchang, Jiangxi 330022, People’s Republic of China

Chemical Reviews; http://pubs.acs.org/doi/pdf/10.1021/cr500431s
DOI: 10.1021/cr500431s

Abstract: Somewhat comprehensive review of recent C-H functionalizations. Note this was received August 7, 2014.

Bulky N‑Phosphino-Functionalized N‑Heterocyclic Carbene Ligands: Synthesis, Ruthenium Coordination Chemistry, and Ruthenium Alkylidene Complexes for Olefin Metathesis

Bulky N‑Phosphino-Functionalized N‑Heterocyclic Carbene Ligands: Synthesis, Ruthenium Coordination Chemistry, and Ruthenium Alkylidene Complexes for Olefin Metathesis

Bing Wu, Kathryn M. Gramigna, Mark W. Bezpalko, Bruce M. Foxman, and Christine M. Thomas*

Department of Chemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02454, United States

Inorganic Chemistry; http://pubs.acs.org/doi/pdf/10.1021/acs.inorgchem.5b00513

Abstract:
Ruthenium chemistry and applications in catalytic olefin metathesis based on N-phosphino-functionalized N-heterocyclic carbene ligands (NHCPs) are presented. Alkyl NHCP Ru coordination chemistry is described, and access to several potential synthetic precursors for ruthenium alkylidene complexes is outlined, incorporating both trimethylsilyl and phenyl alkylidenes. The Ru alkylidene complexes are evaluated as potential olefin metathesis catalysts and were shown to behave in a latent fashion. They displayed catalytic activity at elevated temperatures for both ring closing metathesis and ring opening metathesis polymerization.

TOC:

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.