Eike Bauer

Research Interests

Dr. Bauer’s research interests are in the area of Organic and Organometallic Chemistry. Organometallic chemistry is the study of compounds having metal-carbon bonds. Organometallic compounds often have unique geometries and exhibit reactivities as a result of the electronic properties of the metal. Organometallic compounds are important in catalysis, medicine, and the construction of molecular scale devices (nanoscience).

Phopshoramidite and phosphinooxazoline ligands have recently attracted considerable interest as ligands for a variety of transition metal catalyzed organic transformations. These ligands are easy to synthesize and can be sterically and electronically modified at several positions in their molecular framework.

Dr. Bauer designed and synthesized several novel, electronically and sterically fine-tuned phosphoramidite and phosphinooxazoline ligands. As a new class of ligands, thio derivatives of phosphoramidites were synthesized. These ligands were subsequently converted to a variety of ruthenium, rhodium, iridium and iron complexes. The impact of the ligand structure on the physical and chemical properties of its respective metal complexes was investigated.

The Bauer group has shown that phosphoramidite containing half sandwich complexes of ruthenium are catalytically active in the formation of b-oxo esters from propargylic alcohols and carboxylic acids (see graphics). The ligand structure has a profound impact on the catalytic activity of the corresponding metal complex. Structurally related chiral at metal ruthenium complexes have exhibited catalytic activity in the Mukaiyama aldol reaction.

Iron is a cheap and non-toxic alternative to well-established, catalytically active transition metals. The Bauer group has demonstrated for the first time that phosphinooxazoline complexes of iron are catalytically active in the oxidation of benzylic methylene groups to ketones utilizing t-BuOOH as the oxidant. 

Allenylidene complexes are cumulene-type compounds, which are readily accessible from propargylic alcohols and appropriate precursor metal complexes. The allenylidene complexes are of interest as possible intermediate in catalytic propargylic substitution reactions. Dr. Bauer has also demonstrated a route to chiral at metal allenylidene complexes, which were obtained from corresponding precursors with chirality transfer. Catalytic investigations are currently underway.

Selected Publications

"New Chiral Phosphoramidite Allenylidene Complexes of Ruthenium Obtained with Chirality Transfer" S. Costin, N. P. Rath and E. B. Bauer, Tetrahedron Lett. 2009, 5485.

"Oxidation of activated methylene groups to ketones catalyzed by new iron phosphinooxazoline complexes and by iron(II) triflate" M. Lenze and E. B. Bauer, J. Mol. Catal. A: Chem. 2009, 309, 117.

"The coordination chemistry and reactivity of amino-dithiaphospholanes with rhodium, iridium, and ruthenium" S. Costin, S. Sedinkin and E. B. Bauer, Tetrahedron Lett.  2009, 50, 922.

"Synthesis and structural characterization of new chiral mixed phosphine phosphoramidite complexes of ruthenium" S. Costin, N. P. Rath and E. B. Bauer, Inorg. Chimica Acta 2009, 362, 1935

"Conversion of propargylic alcohols to b -oxo esters catalyzed by novel ruthenium-phosphoramidite complexes" S. Costin, N. P. Rath and E. B. Bauer,  Adv. Synth. & Catal. 2008, 350, 2414

"Synthesis and structural characterization of new phosphinooxazoline complexes of iron". S. L. Sedinkin, N. P. Rath and E. B. Bauer, J. Organomet. Chem. 2008, 693, 3081

"Ligands for catalytic reactions in aqueous systems". C. Prasang, and E. B. Bauer, Phosphorus Ligands in Phosphorus Ligands in Asymmetric Catalysis, Börner, A. Ed.; Wiley/VCH, Weinheim, 2008, pp 917-954

"Isomerization in bent phosphametallocenes: Combining rotational barriers and the intramolecular slip-inversion-slip mechanism to control stereo-conformation". W. P. Freeman, Y. J. Ahn, K. T. Hollis, A. J. Whitaker, V. C. Vargas, R. J. Rubio, K. D. Alingog, E. B. Bauer and F. S. Tham, J. Organomet. Chem. 2008, 693, 2415

"Air- and Water-Stable Catalysts for Hydroamination/Cyclization. Synthesis and Application of CCC-NHC Pincer Complexes of Rh and Ir" E. B. Bauer, G. T. S. Andavan, T. K. Hollis,R. R. Rubio, J. Cho, G. R. Kuchenbeiser, T. R.   Helgert,C. S. Letko and F. S. Tham, Org. Lett. 2008, 1175.

"sp Carbon Chains Surrounded by sp3 Carbon Double Helices: Directed Syntheses of Wirelike Pt(CºC)nPt Moieties That Are Spanned by Two P(CH₂)mP Linkages via Alkene Metathesis". L. de Quadras, E. B. Bauer, W. Mohr, J. C. Bohling, T. B. Peters, J-M. Martin-Alvarez, F. Hampel and J. A. Gladysz, J. Am. Chem. Soc. 2007, 129, 8296.

"sp Carbon chains surrounded by sp³ carbon double helices: wire-like Pt(CºC)_nPt moieties that are spanned by two a,w-diphosphines that bear heteroatoms or alkyl substituents", L. de Quadras, E. B. Bauer, J. Stahl, F. Zhuravlev, F. Hampel, and J. A. Gladysz, New J. Chem. 2007, 31, 1594.

"Synthesis and Charaterization of a Free Phenylene Bis(N-Heterocylcic Carbene) and its di-Rh complex. Catalytic Activity of the di-Rh and CCC-NHC Rh Pincer complexes in Intermolecular Hydrosilylation of Alkynes." G. T. S. Andavan, E. B. Bauer, C. S. Letko, T. K. Hollis and F. S. Tham, J. Organomet. Chem. 2005, 5938.

"Toward a General Method for CCC N-Heterocyclic Carbene Pincer Synthesis: Metallation and Transmetallation Strategies for Activation of Three C-H bonds Concurrently." R. R. Rubio, G. T. S. Andavan, E. B. Bauer, T. K. Hollis, J. Cho, F. S. Tham and B. J. Donnadieu, Organomet. Chem. 2005, 5353.

"Alkene metatheses in transition metal coordination spheres: dimacrocyclizations that join trans positions of square-planar platinum complexes to give topologically novel diphosphine ligands." T. Shima, E. B. Bauer, F. Hampeland J. A. Gladysz, Dalton Transactions 2004, 7, 1012. 

"Alkyne Metatheses in Transition Metal Coordination Spheres: Convenient tungsten- and molybdenum-catalyzed syntheses of novel metallamacrocycles." E. B. Bauer, F. Hampel and J. A. Gladysz, Advanced Synthesis & Catalysis 2004, 346, 812.