Messerle Research Group

Organometallics and Catalysis

Research in our group involves organometallic synthesis, catalysis, computational molecular modelling and advanced NMR Spectroscopy. Our overall goal is to create highly active catalysts that promote atom-efficient organic transformations. We target key organic transformations that can simultaneously expedite the preparation of high value fine chemicals and at the same time reduce energy consumption and waste We are particularly interested in the synthesis of heterocycles and the development of tandem reactions that facilitate multiple chemical transformations in the same flask.

Novel Highly Active Transition Metal Catalysts (in collaboration with Prof. Les Field, UNSW, Australia)

In order to develop robust and effective late transition metal catalysts it is essential to finely tune the ligands occupying the primary coordination sphere around the active metal ion. To address this goal we have developed new ligand systems for iridium, rhodium ruthenium and iron ions that facilitate a high reaction rate whilst maintaining the structural integrity of the catalyst. Our ligand systems are primarily based on nitrogen donors, including mixed ligand systems containing sp2-nitrogen donors,[1] N-heterocyclic carbenes[2] and phosphines.[3],[4],[5] These ligands provide a wide range of metal binding strengths for catalyst optimization. (e.g. a bidentate phosphine-pyrazole ligand bound to Ir(I) to form catalyst 1).

Multimetallic Catalysts for Enhanced Reactivity

Bimetallic complexes are important homogeneous catalysts as the immobilization of two metal centres in close proximity can lead to cooperative effects between the metal centres, so that the resulting catalysts have exceptional efficiency and selectivity. We have shown a direct correlation between bimetallic catalyst structure and catalyst efficiency.[6] We develop new scaffolds and catalysts for promoting the synthesis of heterocycles and are also interested in understanding how these cooperative effects work.[7],[8]

Catalysing Multistep Reactions

The synthesis of pharmaceuticals relies on the stepwise formation of multiple bonds. Promoting multistep reactions in a single reaction vessel is highly desirable as it reduces the energy required and number of by-products formed. We are developing mono-metallic as well as multimetallic catalysts that mediate two or more sequential reaction steps.[10],[11] These reactions provide efficient routes to the synthesis of oxygen and nitrogen containing heterocycles.

C-X bond formation: The metal catalysed addition of X-H bonds, X = N (hydroamination),[12],[13] O (hydroalkoxylation) [14] and S (hydrothiolation), [15],[16] to alkynes and alkenes is a direct method for the synthesis of C-N, C-O and C-S bonds, and is important in the synthesis of pharmaceuticals as well as new materials and fine chemicals (e.g. Scheme 1).

Reduction of imines and alcoholysis of silanes: Silyl ethers are among the most widely used protecting groups for the hydroxyl functionality in organic synthesis, and also play an important role in inorganic synthesis as precursors in the preparation of sol-gels and other condensed siloxane materials. Our iridium complexes with N donor ligands catalyze the alcoholysis of hydrosilanes under mild conditions with extremely high levels of efficiency. The catalysts are effective for the alcoholysis of a range of alcohols and hydrosilanes,[17] including secondary and tertiary hydrosilanes.

Pincer ligands (in collaboration with Prof. Tony Hill, ANU, Canberra, Australia)

Pincer ligands have been extensively investigated as chelating agents for TM ions as the co-planar geometry of the resultant complex serves to inhibit deleterious cyclometallation in various catalytic cyclesWe are currently working on the development of novel complexes with pincer ligands[9] containing N-heterocyclic carbene donors in collaboration with Professor Anthony Hill (ANU, Canberra, Australia). Together we also seek to develop new classes of catalysts containing ligands based on the unconventional elements boron and silicon.

NMR Spectroscopy and Organometallic Reaction Mechanisms

Understanding the mechanism of any transition metal catalysed reaction pathway is a critical part of the design process when developing of new more efficient catalysts. In the Messerle group we use several different tools to gain insight into the mechanism by which our catalysts operate.

(i)            Computational Studies (in collaboration with Prof. Stuart Macgregor, Heriot Watt University, Edinburgh, UK and Prof. Odile Eisenstein (Institut Charles Gerhardt Montpellier, France)).

We use density functional theory (DFT) calculations to model catalysts and reaction intermediates. This allows us to assess the relationship between the geometry of the TM-catalyst/substrate species and the likely reaction pathway.

(ii)           Reaction Kinetics: To learn more about the efficacy of our catalysts we routinely use NMR spectroscopy and GC-MS to determine substrate conversion and calculate turn over numbers. This allows us to quantitatively ‘rank’ catalyst performance and, in combination with computational studies, we are then able to further tune our ligand design.

(iii)          Para-Hydrogen Enhanced NMR Spectroscopy (in collaboration with Prof. S. B. Duckett, The University of York, UK):

A good understanding of the spatial structure of a catalyst and the mechanism by which it drives a given reaction is essential in order to optimise its performance in a catalytic process. We use NMR spectroscopy to probe the geometry of metal complexes and investigate the mechanism of catalysed reactions. However, catalytically active species are normally present at such low concentrations in a reaction mixture that they are not normally observable by NMR.

The para-hydrogen effect represents one efficient way of achieving signal enhancement. We are collaborating with Professor S. B. Duckett (The University of York, UK) to use the significantly enhanced signals from para-hydrogen to observe low concentration organometallic species in solution and further understand their behavior.

Catalysts on Surfaces (in collaboration with Prof Justin Gooding, UNSW)

The separation of homogeneous catalysts from products or substrates continues to be a challenge. To overcome this, we are attaching catalysts already developed by our group onto a variety of robust structures and surfaces.[18] The new anchored catalyst systems can be readily separated from reaction mixtures. This will not only allow easy catalyst/product separation, but will also provide a greater control over the nature of catalyst reactivity. The supports themselves can use the electrochemical properties of the catalysts to promote reactivity, or induce high enantioselectivity in asymmetric transformations.


[1] S. Burling; L. D Field, B. A. Messerle and Sarah L. Rumble, Late Transition Metal Catalyzed Intramolecular Hydroamination – The effect of Ligand and Substrate Structure, Organometallics, 2007, 26, 4335-4343.

[2] S. Burling, L.D. Field, H.L. Li, B.A. Messerle and P.Turner, “Mononuclear Rhodium(I) Complexes with Chelating N-Heterocyclic Carbene Ligands – Catalytic Activity for Intramolecular Hydroamination”, Eur. J. Inorg. Chem., 2003, 3179-3184.

[3] L.D. Field, B.A. Messerle, K.Q. Vuong and P. Turner, “Rhodium(I) and iridium(I) complexes containing bidentate phosphine-imidazolyl donor ligands as catalysts for the hydroamination and hydrothiolation of alkynes”, Dalton Trans, 2009, 3599-3614.

[4] S. Burling, L.D. Field, B.A. Messerle, K.Q. Vuong, and P. Turner, “Rhodium(I) and Iridium(I) Complexes with Bidentate N,N and P,N Ligands as Catalysts for the Hydrothiolation of Alkynes”, Dalton Trans, 2003, 21, 4181-4191.

[5] L.D. Field, B.A. Messerle,K.Q. Vuong, and P. Turner, “Intramolecular Hydroamination with Rhodium(I), Iridium(I) Complexes containing a Phosphine, N-Heterocyclic Carbene Ligand”, Organometallics, 2005, 24, 4241-4250.

[6] J. H. H. Ho, S. Choy, S. A. Macgregor, B. A. Messerle, Cooperativity in Bimetallic Dihydroalkoxylation Catalysts Built on Aromatic Scaffolds: Significant Rate Enhancements with a Rigid Anthracene Scaffold, Organometallics, 2011, 30, 5978-5984.

[7] Timerbulatova, M. G.; Gatus, M. R. D.; Vuong, K. Q.; Bhadbhade, M.; Algarra, A. G.; MacGregor, S. A.; Messerle, B. A., Bimetallic Complexes for Enhancing Catalyst Efficiency: Probing the Relationship between Activity and Intermetallic Distance. Organometallics 2013, 32 (18), 5071-5081.

[8] Choy, S. W. S.; Page, M. J.; Bhadbhade, M.; Messerle, B. A., Cooperative Catalysis: Large Rate Enhancements with Bimetallic Rhodium Complexes. Organometallics 2013, 32 (17), 4726-4729.

[9] Page, M. J.; Wagler, J.; Messerle, B. A., Pyridine-2,6-bis(thioether) (SNS) Complexes of Ruthenium as Catalysts for Transfer Hydrogenation. Organometallics 2010, 29 (17), 3790-3798.

[10] Kennedy, D. F.; Nova, A.; Willis, A. C.; Eisenstein, O.; Messerle, B. A., The mechanism of N-vinylindole formation via tandem imine formation and cycloisomerisation of o-ethynylanilines. Dalton Trans. 2009,  (46), 10296-10304.

[11] Wong, C. M.; Vuong, K. Q.; Gatus, M. R. D.; Hua, C.; Bhadbhade, M.; Messerle, B. A., Catalyzed tandem C-N/C-C bond formation for the synthesis of tricyclic indoles using Ir(III) pyrazolyl-1,2,3-triazolyl complexes. Organometallics 2012, 31 (21), 7500-7510.

[12] L.D. Field, B.A. Messerle, K.Q. Vuong and P. Turner, “Rhodium(I) and iridium(I) complexes containing bidentate phosphine-imidazolyl donor ligands as catalysts for the hydroamination and hydrothiolation of alkynes”, Dalton Trans, 2009, 3599-3614.

[13] S. Burling, L.D. Field, H.L. Li, B.A. Messerle and P.Turner, “ Mononuclear Rhodium(I) Complexes with Chelating N-Heterocyclic Carbene Ligands – Catalytic Activity for Intramolecular Hydroamination”, Eur. J. Inorg. Chem., 2003, 3179-3184.

[14] S. Elgafi, L. D. Field and B. A. Messerle “Cyclisation of Acetylenic Carboxylic Acids and Acetylenic Alcohols to Oxygen-containing Heterocycles using Cationic Rhodium(I) Complexes”, J. Organomet. Chem., 2000, 607, 97-104.

[15] L.D. Field, B.A. Messerle, K.Q. Vuong, and P. Turner, “Intramolecular Hydroamination with Rhodium(I), Iridium(I) Complexes containing a Phosphine, N-Heterocyclic Carbene Ligand”, Organometallics, 2005, 24, 4241-4250.

[16] S. Burling, L.D. Field, B.A. Messerle, K.Q. Vuong, and P. Turner, “Rhodium(I) and Iridium(I) Complexes with Bidentate N,N and P,N Ligands as Catalysts for the Hydrothiolation of Alkynes”, Dalton Trans, 2003, 21, 4181-4191.

[17] L.D. Field, B.A. Messerle, L.P. Soler, M. Rehr, and T.W. Hambley, “Cationic Ir(I) Complexes  as Catalysts in the Alcoholysis of Silanes”, Organometallics, 2003, 22, 2387-2395.

[18] A. A. Tregubov, K. Q. Vuong, E. Luais, J. J. Gooding, and B. A. Messerle* Rh(I) Complexes Bearing N,N and N,P Ligands Anchored on Glassy Carbon Electrodes: towards Recyclable Hydroamination Catalysts, Journal of the American Chemical Society, 2013 published online Oct. 2nd.