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Associate Professor of Chemistry
Office: 461 CBIowa City, IA 52242
Email: email@example.comWeb: More About Dr. Messerle - Related Websites and Resources
BS, Chemistry, Brown UniversityPhD, Inorganic Chemistry, Massachusetts Institute of Technology
Post Doctorate, Organometallic Chemistry, University of Michigan-Ann Arbor
Biosciences Graduate Program
The synthesis, structure, and reactivity of novel coordinatively and electronically unsaturated organotransition metal complexes and of metal cluster compounds of the early transition metals are the major interests of my research group. Mid-valent organometallic chemistry and cluster chemistry with þ-donor ligands of the early transition metals are underdeveloped areas. In organometallic chemistry, we are studying the reactivity of catalysis-relevant functional groups, e.g., metal-metal double and triple bonds, h 2-acyls, alkyls, and µ-hydrides, particularly in mono(permethylcyclo-pentadienyl) (C5Me5, Cp*)M environments. Reactions of interest include reductive dimerization, CO insertion, hydrocarbon C-H bond activation, and reduction leading to altered functional group reactivity.
Projects of current interest include synthesis and reactivity studies on (1) organoditantalum complexes with metal-metal double bonds, (2) metal cluster compounds of tungsten, tantalum, and hafnium relevant to new classes of diagnostic medical imaging contrast agents, (3) organoditantalum complexes with bridging alkylidyne, alkyne, vinylidene, and allenediyl ligands, and (4) organometallic clusters of vanadium and tantalum with metal-metal bonding.
We have synthesized a new class of Ta==Ta complexes, Cp*2Ta2(µ-Cl)4 which insert into vinylic C-H bonds (the first example of C-H activation by a M-M multiple bond), add H2, and couple BH4- to H2 and diborane(2-) ligands. Allene coordination results in an unusual µ, h 1, h 3-allene moiety which yields the novel bridging allenediyl ligand upon reduction, as shown below. Cp*2Ta2(µ-Cl)4 undergoes rearrangement in solution to the cluster Cp*3Ta3(µ-Cl)6 + and coordinates and reduces dinitrogen to the hydrazido(4-) ligand, both shown below. We are exploring the reactivity of these and related multiply-bonded early metal derivatives with small ring carbocycles/heterocycles, nitrogen oxides, and unsaturated organic species.
We have extended our organoditan-talum methodology to vanadium and developed high yield routes to Cp*VX3 and the novel Cp*2V2Br4 and Cp*3V3Cl6, new synthons in organo-vanadium chemistry that can be methylated to give Cp*2V2(µ-CH3) 4, a complex with four methyl bridges and an unusually short V-V distance.
Experimental methods include inert atmosphere techniques (glove box, Schlenk line), IR, high-field multinuclear, flow, and stopped-flow NMR spectroscopies, mass spectrometry, X-ray diffractometry, and MO calculations.
Date Last Modified: 08/04/2015 -
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