Gateway for:

Member Countries

Catalytic Olefin Hydroamination

#G-1802


Metallocene-Based Bis(Phosphine) and Bis(N-Heterocyclic Carbene) Pincer Complexes as Catalysts for Olefin Hydroamination

Tech Area / Field

  • CHE-SYN/Basic and Synthetic Chemistry/Chemistry

Status
3 Approved without Funding

Registration date
13.11.2009

Leading Institute
Tbilisi State University, Georgia, Tbilisi

Collaborators

  • The University of Montana, Chemistry Department, USA, MT, Missoula\nWilfrid Laurier University, Canada, ON, Waterloo\nUniversita` degli studi del Piemonte Orientale “A. Avogadro” / Dipartimento di Scienze dell'Ambiente e della Vita, Italy, Alessandria

Project summary

Amines are valuable and commercially important bulk chemicals, fine chemicals, and pharmaceuticals. Among various synthetic routes, hydroamination, the direct formation of a new C-N bond by addition of an ammonia or an amine to an unsaturated CC bond is of particular importance (T.E. Müller, K.C. Hultzsch, M. Yus, F. Foubelo, M. Tada, Chem. Rev. 2008, 108, 3795-3892). The catalytic hydroamination of alkenes has attracted tremendous attention because it provides efficient and direct entry to synthetically and biologically significant organonitrogen compounds. Accordingly, much effort has been focused on the development of new catalytic methods for the hydroamination of alkenes (J.F. Hartwig, Pure Appl. Chem. 2004, 76, 507-516. R. Severin, S. Doye, Chem. Soc. Rev. 2007, 36, 1407-1420). Much progress in this area has been accomplished, especially in the intramolecular and intermolecular hydroamination of activated alkenes or/and activated amines. However, the catalytic intermolecular hydroamination of nonactivated alkenes is still a challenging task. A few exceptions include the intermolecular hydroamination of 1-pentene with propylamine reported by Marks and co-workers (S. Hong, T.J. Marks, Acc. Chem. Res. 2004, 37, 673-686) and hydroamination of nonactivated olefins with aniline reported by Bergman (L.L. Anderson, J. Arnold, R.G. Bergman, J. Am. Chem. Soc. 2005, 127, 14542-14543). Although these are so far the most efficient systems for the intermolecular hydroamination of nonactivated alkenes, their performance are still largely insufficient for application to industrial-scale production. It should be also noted, that while the rare-earth metal catalysts introductd by Marks are efficient systems for hydroamination, their sensitivity to oxygen and moisture have limited their use in many applications.

A particular challenge is the reversal of the regiochemistry to obtain the anti-Markovnikov product of hydroamination. The catalytic anti-Markovnikov addition of H-NR2 to alkenes was listed as one of the so-called “Ten Challenges for Catalysis”(J. Haggin, Chem. Eng. News. 1993, 71 (¹ 22), 21). The preference of this process for ecology is evident.

Clearly, despite some important advances, general catalysts that operate for unactivated alkenes and basic amines, such as aniline and ammonia, have to be discovered.

Research Objectives. The present project embraces the design and creation of a new family of pincer complexes, metallocene-based bis(phosphine) and bis(N-heterocyclic carbene) pincer complexes, which are supposed to possess the high efficiency and selectivity in catalytic hydroamination of alkenes. The advantage of the metallocene-based pincer complexes recently discovered by Prof. A.A. Koridze group as compared to the known benzene-based pincer systems is that stereochemistry and electron density at the catalytic center can be altered in a wider range, thus allowing fine tuning of pincer complexes for the desired application in a broad spectrum of catalytic reactions. Thus, Koridze and co-workers have recently demonstrated (Organometallics, 2006, 25, 5460-5476) that iridium bis(phospine) pincer complexes with ferrocene and ruthenocene backbone are the most active among all known homogeneous catalysts for alkane dehydrogenation.

The project target is creation of general catalysts for alkene hydroamination superior to current catalytic systems. This objective can be broken down into sub-objectives as detailed below:

  1. The elaboration of a new generation bis(phosphine) pincer complexes based on ferrocene and ruthenocene with chelated rhodium and iridium atoms, MH2[{2,5-(R2PCH2)2C5H2}M'(C5R'5)] (M=Rh, Ir; M'= Fe, Ru; R= iPr, tBu, Cy; R'= H, Me, Cy, Ph).
  2. The elaboration of novel complexes with bis(N-heterocyclic carbene) pincer ligands based on ferrocene and ruthenocene, MH2[{2,5-(LCH2)2C5H2}M'(C5R'5)] (M=Rh, Ir; M'= Fe, Ru; L=3-R-imidazolin-2-yliden-1-yl, where R= iPr, tBu, Cy; R'= H, Me, Cy, Ph). Electronic properties of the metallocene-based bis(phosphine) and bis(NHC) ligands will be investigated, and ability of the complexes with the two types of pincer ligands to activate a N–H bond of ammonia and amines with formation of the corresponding amido-hydrido complexes will be studied and compared.
  3. The study of reactions of the synthesized amido-hydrido complexes MH(NHY)[P,C,P] and MH(NHY)[C,C,C] (Y=H, Ar) with olefins and styrenes. The influence of steric availability of the catalytic center for a substrate and electronic factors will be studied by the variation of organyl groups at the P and N atoms in bis(phosphine) and bis(NHC) pincer ligands, correspondingly, substituents R' in cyclopentadienyl ring, and the nature of metallocene central atom and its redox state.
  4. Testing of synthesized metallocene-based pincer complexes as catalysts for alkene hydroamination. A comparative study of the related benzene-based pincer complexes of rhodium and iridium will be conducted. The most promising catalysts will be selected for the preparation of anchoring pincer systems for practical application.

As a result of the endeavour, novel approaches to the design and synthesis of efficient and selective catalysts for alkene hydroamination will be elaborated.

Participants of the Project. The project authors discovered a new generation pincer complexes, binuclear pincer complexes based on ferrocene (A.A. Koridze, A.M. Sheloumov, S.A. Kuklin, V.Yu. Lagunova, I.I. Petukhova, F.M. Dolgushin, M.G. Ezernitskaya,P.V. Petrovskii, A.A. Macharashvili, R.V.Chedia. PCP pincer ligands based on metallocenes. Crystal structure of the rhodium complex cis-RhCl2(CO)[{2,5-(iPr2PCH2)2C5H2}Fe(C5H5)]. Russ.Chem.Bull.,Int.Ed. 2002, 51,1077-1078). At present, they have occupied the leading position in the field of metallocene-based pincer complexes of platinum group metals: ferrocene- and ruthenocene- based P,C,P complexes of rhodium, iridium, ruthenium, and palladium have been synthesized and these results were published in the Russian, European, and US journals (see, for example: A.A. Koridze, et al. Ferrocene-based pincer complexes of palladium: synthesis, structures, and spectroscopic and electrochemical properties. Organometallics, 2004, 23, 4585-4593. A.M. Sheloumov, F.M. Dolgushin, M.V. Kondrashov, P.V. Petrovskii, Kh.A. Barbakadze, O.I. Lekashvili, A.A. Koridze. Ruthenium complexes with ferrocene-based P,C,P pincer ligand. Russ. Chem. Bull., Int. Ed. 2007, 56, 1757-1764). Recently (S.A. Kuklin, A.M. Sheloumov, F.M. Dolgushin, M.G. Ezernitskaya, A.S. Peregudov, P.V. Petrovskii, A.A. Koridze. Highly active iridium catalysts for alkane dehydrogenation. Synthesis and properties of iridium pincer complexes based on ferrocene and ruthenocene. Organometallics 2006, 25, 5466-5476) it has been demonstrated that hydrido iridium bis(phosphine) pincer complexes based on ferrocene and ruthenocene are the most active among all known homogeneous catalysts for alkane transfer dehydrogenation.

The participants of the project are researchers of I. Javakhishvili Tbilisi State University, which have long term experimental and theoretical experience in the given field and their scientific works are published in the international prestigious journals. Each member of the group has a work experience with organometallic compounds. They participated in several international and local projects such as ISTC, CRDF, GRDF, INTAS, NATO, and etc.

Expected Results and Their Application. New generation bis(phosphine) and bis(N-heterocyclic carbene) pincer complexes with metallocene backbone will synthesized. Steric and electronic factors that may affect the rate of activation of amine N-H bond at a catalytic center, and catalytic hydroamination of alkenes will be elucidated. Studies of these reactions by experimental and computational methods will shed light on the mechanisms of intimate steps of the catalytic cycle. The most efficient metallocene-based pincer complexes will be used as base units for the development of applied catalysts for alkene hydroamination. The creation of efficient catalysts for alkene hydroamination could have tremendous environmental and economic impact.

Meeting ISTC Goals and Objectives. The project will fulfill the objectives of ISTC in the following way: Providing weapons scientists and engineers opportunities to redirect their talents to peaceful activities; Promoting integration of scientists into the international scientific community; Supporting basic and applied research and technology development for peaceful purposes; Reinforcing the transition to market-based economies responsive to civil needs.

Scope of Activities

  • The elaboration of a new generation bis(phosphine) pincer complexes based on ferrocene and ruthenocene with chelated rhodium and iridium atoms, MH2[{2,5-(R2PCH2)2C5H2}M'(C5R'5)] (M=Rh, Ir; M'= Fe, Ru; R= iPr, tBu, Cy; R'= H, Me, Cy, Ph).
  • The elaboration of novel pincer complexes with bis(N-heterocyclic carbene) ligands based on ferrocene and ruthenocene, MH2[{2,5-(LCH2)2C5H2}M'(C5R'5)] (M=Rh, Ir; M'= Fe, Ru; L=3-R-imidazolin-2-yliden-1-yl, where R= iPr, tBu, Cy; R'= H, Me, Cy, Ph). Evaluation of electronic properties of the metallocene-based bis(phosphine) and bis(NHC) ligands, and ability of the complexes with the two types of pincer ligands to activate a N-H bond of ammonia and amines with formation of corresponding amido-hydrido complexes.
  • The study of reactions of the synthesized amido-hydrido complexes MH(NHY)[P,C,P] and MH(NHY)[C,C,C] (Y=H, Ar) with olefins and styrenes: investigation of influence of steric availability of the catalytic center for a substrate and electronic effects of bis(phosphine) and bis(NHC) ligands.
  • Testing of synthesized metallocene-based pincer complexes of rhodium and iridium as catalysts for alkene hydroamination. Comparative study of the related benzene-based pincer complexes. The development of applied catalysts for alkene hydroamination by anchoring of the most efficient metallocene-based pincer complexes.

Role of Foreign Collaborators. Information exchange during the execution of the Project; Carrying out of joint experiments and investigation of synthesized complexes; Discussion of obtained experimental results; Joint publications; Offering of conclusions on Technical Reports (quarterly, annual, and final) submitted to ISTC by Project executors;Conducting some experiments at the laboratories of Western collaborators.

Technical Approach and Methodology. Applying group discovered a new generation bis(phosphine) pincer complexes based on metallocenes. The peculiarity of this approach and methodology is that alkenes, the feedstocks for catalytic hydroamination, can be obtained by alkane dehydrogenation with the related metallocene-based pincer complexes, efficient catalysts also developed by the applicants. The suggested approach to the design of bis(N-heterocyclic carbene) pincer complexes with metallocenes backbone is novel and no previous data on this class complexes are available. Approach to the design of transition metal catalysts for olefin hydroamination is based on the use of metallocene-derived complexes with unique sandwich pincer ligands.

Metallocene-based pincer complexes allow the variation of steric availability of catalytic center, as well as electronic density at this center in a wide range and more efficient than current metal complexes. Catalytic activity of synthesized complexes will be studied in hydroamination of simple olefins and styrenes.

All experiments will be accompanied by X-ray studies of the complexes generated. Multinuclear NMR, IR, and electrochemical studies will be performed to give better understanding of electronic structure of compounds of interest.


Back

The International Science and Technology Center (ISTC) is an intergovernmental organization connecting scientists from Kazakhstan, Armenia, Tajikistan, Kyrgyzstan, and Georgia with their peers and research organizations in the EU, Japan, Republic of Korea, Norway and the United States.

 

ISTC facilitates international science projects and assists the global scientific and business community to source and engage with CIS and Georgian institutes that develop or possess an excellence of scientific know-how.

Promotional Material

Значимы проект

See ISTC's new Promotional video view