Dr. Robert Beer
Research Interests
Studies in our laboratory concentrate on the design, synthesis and characterization of new metal complexes. These molecules often exhibit interesting reactivity and spectroscopic properties related to a broad range of chemical disciplines. Using Nature as a guide and some creative synthetic chemistry, our research explores new aspects of catalysis, bioinorganic chemistry, molecular recognition, electron transfer and solid-state materials.
Specific research objectives include: (1) the derivatization of soluble polynuclear metal oxides for binding to other metal compounds to produce novel catalysts or materials as well as for modifying surfaces and biological macromolecules and (2) active site and reaction intermediate models of metalloprotein catalyzed reactions, particularly those involved in dioxygen activation.
Our studies rely on upon inert atmosphere synthetic methods that include the use of a glove box and vacuum-inert gas manifolds. Physical methods are used extensively for both characterizing and understanding the reactivity of a particular compound. These methods include multinuclear nmr, vibrational, and electronic spectroscopy, X-ray crystallography, mass spectrometry, and electrochemistry.
Any level of research ability is welcome to join our laboratory!
Current Research
Metal Salicylaldimine Complexes
The salicylaldimine ligand, salHNR (R = alkyl, aryl), forms the basis of an extensive class of chelating ligands that has enjoyed popular use in the coordination chemistry of transition and post-transition elements. The reaction of salicylaldimine with a suitable metal starting material, often in the presence of base, is a simple and direct means of preparing complexes M(salNR) in which the deprotonated salicylaldiminato ligand, salNR-, acts as a bidentate anionic N/O donor. Despite the frequent use of this preparative method, little is known of the intermediates involved in this reaction.
Recent synthetic, spectroscopic and crystallographic studies in our laboratory have established that the reaction of ZnCl2 with salNHR forms the adduct Zn(salNHR)2Cl2. In these complexes, the ligand is coordinated atypically in its enolate-iminium zwitterionic form in which the phenolate oxygen donor is coordinated solely to the metal as shown below. Upon the addition of base, these adducts form the known complexes Zn(salNR)2. This unusual salicylaldimine coordination mode is likely, therefore, to be important in the formation of metal salicylaldiminato complexes.
We are interested in exploring the scope of this coordination mode with other ligands and metals. Attempts to determine whether or not this precursor is an intermediate and especially whether this coordination mode might be related to how metals are incorporated into metalloprotein sites with similar donors are among other objectives.
Manganese Trifluoroacetate Complexes: Synthetic Models of Photosystem II
The water oxidizing complex (WOC) involved in photosynthesis is believed currently to contain four manganese atoms bridged by oxo and carboxylato bridges derived from amino acid residues in the WOC supporting protein. Water oxidation to dioxygen is thought to occur when four oxidizing equivalents are transferred to the WOC, oxidizing the manganese atoms. The oxidation of two terminally coordinated water molecules in close proximity to one another followed by O-O bond formation is one possible mechanism for dioxgen formation by the WOC.
Efforts to model this chemistry in our laboratory have been initiated. The tetranuclea manganese complex {Mn4O2(O2CCF3)8(bpy)2}+ with two adjacent monodentate trifluoroacetate ligands, shown below (F atoms not shown) has been isolated. Since trifluoroacetate is a relatively weak coordinating anion, we are hoping to displace it with aquo, peroxo and other ligands that may help explain how the WOC works.
Polyoxometalate Supported Metallocenes
Past studies in our laboratory have succeeded in the preparation and established the extensive reaction chemistry of the niobium substituted polyoxometalate supported zirconocene [Cp2Zr(PNbW11O40)2]6-, the structure of which is shown below. We are developing this chemistry, particularly with a focus on preparing cationic Group 4 metallocenes with a non-coordinating polyoxometalate anion. Considering the marked affect counterions are purported to have on the reactivity of the metallocene cations, which are catalyst precursors for the production of polyethylene and other plastics, the preparation of a Group 4 metallocene cation with a phosphotungstate counterion should yield a very reactive species.
Publications (1995-current)
"A Comprehensive Series of Group 14 Derivatives of the Plenary Mixed-Metal Polyoxometalate [PNbW11O40]4-", E. Radkov and R. H. Beer, Inorg. Chim. Acta, 2000, 297 (1-2), 191.
"A Polyoxometalate Transfer Reagent: Synthesis, Structure and Reactivity of [(PW11O39NbO)2ZrCp2]6-", E. Radkov, V. G. Young and R. H. Beer, J. Am. Chem. Soc. 1999, 121, 8953-8954.
"Lineshape Fitting of Deuterium Magic Angle Spinning Spectra of Paramagnetic Compounds in Slow and Fast Limit Regimes", H. Lee, T. Polenova, R. H. Beer, A. E. McDermott, J. Am. Chem. Soc., 1999, 121, 6884.
"The Reaction of Polynuclear Tungstates with Thionyl Chloride: Formation of (n-Bu4N)W(O)Cl5", Y.-J. Lu and R. H. Beer, Polyhedron, 1996, 15, 1667.
"A Hydrolysis Resistant Terminal ME Bond (M = Nb, Ta; E = S, Se) in a Chalcogenido Substituted Mixed-Metal Polyoxoanion" E. Radkov, Y.-J. Lu and R. H. Beer, Inorg. Chem. 1996, 35, 551.
"Deoxygenation of Polynuclear Metal Oxo Anions: Synthesis, Structure and Reactivity of the Condensed Polyoxoanion [(C4H9)4(NbW5O18)2O]", Y.-J. Lu and R. H. Beer, Inorg. Chem. 1996, 35, 2524.
"High Yield Synthesis of Mixed-Metal Keggin Polyoxoanions in Nonaqueous Solvents: "Preparation of (n-Bu4N)4[PMW11O40] (M = V, Nb, Ta)", E. Radkov and R. H. Beer, Polyhedron 1995, 14, 2139.
"Guidelines for the Supervision of Undergraduate Research" R. H. Beer, J. Chem. Educ. 1995, 72, 721.
SCHEDULE, Fall2000
| Monday |
Tuesday |
Wednesday |
Thursday |
Friday |
|
|
General Chem. Lab I
8:30-9:20
JMH 108
|
General Chem. Lab I
8:30-9:20
JMH 108
|
|
|
|
General Chem. Lab I
9:30-12:20
JMH 120
|
General Chem. Lab I
9:30-12:20
JMH 120
|
|
|
|
Office Hours
JMH 512
12:20-1:30
|
Office Hours
JMH 512
12:20-1:30
|
|
|
|
|
Gen. Chem. Rec. I
JMH 132
4:30-5:20 pm
|
|
| Office Hours
JMH 512
4:00-5:00
|
Office Hours
JMH 512
4:00-5:00
|
Seminar
JMH 4th Fl.
4:30-5:30
|
|
|
Contact info
E-mail
Phone (718) 817 4451
Fax (718) 817 4432
