Carl D. Hoff

Ph.D., University of Missouri-Kansas City, 1977
Research Associate, University of Georgia, 1977-79

E-mail: c.hoff@miami.edu

Research in a Nugget

Brief description of research

Publications 2004-Present


Research in a Nugget


Brief description of research

Catalysis
Thermochemistry
Metal Complexes
Sulfur Chemistry
Kinetic Studies
Spectroscopy

 

The goal of our research is to understand what controls reactions important to catalysis of reactions like nitrogen fixation.  Binding and activation of dinitrogen, nitriles, hydrogen, carbenes, and sulfur to metal complexes are all studied in our laboratory. Our principle focus is on molybdenum chemistry.  Molybdenum is one of the most versatile of all transition metals, and also important in several enzymatic reactions--most notably a Mo/S protein complex is at the center of the active site of the nitrogenase enzyme. It is also the active metal in hydrodesulfurization to remove sulfur containing compounds from gasoline. Both nitrogen fixation, and hydrodesulfurization are of major economic and environmental importance, and there is need for improvement for both. The actual reactions are deceptively simple, but the interactions of the reactants, products, and intermediates with the metal complex catalyst is challenging and not well understood.

Nitrogen Fixation:      
                                  "catalyst"
            2 N2 + 3 H2   ------------->  2 NH3

 

Hydrodesulfurization:           

                                  "catalyst"
            RSR + 2 H2   ------------->  2 RH + H2S

Research in our group focuses on understanding catalytic interactions as well as synthesis of metal complexes of potential use in catalytic processes, both thermal and photochemical. The fundamental steps of individual steps in catalytic processes are investigated to try to understand what controls the reaction process-what barriers are involved, and how these can be lowered. A full range of techniques is used to attack these problems, including synthesis, calorimetry, high pressure infrared studies, ESR,  NMR , kinetic, isotopic labeling, and collaboration with theoretical chemists. Students are trained in skills and techniques of real use in future academic, government, and industrial research. 


Publications 2004-Present

2010

George C. Fortman, Manuel Temprado, Tamas Kegl, Carl D. Hoff, "Organometallic Radicals", in "Physical Inorganic Chemistry: Applications", Adreja Bakac Editor, John Wiley, New York, in press, 2010.

2009

Germain, M.; Temprado, M., Kryatova, O. P.; Rybak-Akimova, E. V.; Mendriatta, A.; Tsai, Y. C.; Cummins, C. C.; McDonough, J. E.; Hoff, C. D.; "Ligand Binding and Reactivity Studies of [η2-N=C=NMe2]Mo([NtBu]Ar)3 Compared to [η1-N=C=NMe2]Mo([NtBu]Ar)3 --Metal Versus Ligand Based Radical Systems Depending on Organonitrile Hapticity".  J. Am. Chem. Soc.2009131, 15412.

George C. Fortman, Burjor Captain, Carl D. Hoff, "Thermodynamic Investigations of the Staudinger Reaction of Trialkylphosphines with 1-Adamantyl Azide and the Isolation of an Unusual s-cis Phosphazide", Inorg. Chem. 2009, 48, 1808.

George C. Fortman, Burjor Captain, Carl D. Hoff, "Stoichiometric and  Catalytic Conversion of 1-Adamantyl Azideto 1-Adamantyl Isoyanate by [Cr(CO)3Cp]2 and Reaction with Mo(CO)3(PiPR3)2 to form Mo(k­-iPr3P=N-N=N-Ad)(PiPR3)(CO)3. f the Staudinger Reaction of Trialkylphosphines with 1-Adamantyl Azide and the Isolation of an Unusual s-cis Phosphazide", Organometallics, 200928, 3587.

Patrick Achord, Manuel Temrado, George C. Fortman, Derek Isrow, John Weir, Eric McDonough, Carl D. Hoff, James T. Muckerman, Etsuko Fujita.   "The Role of p-Backbonding in the Strengths of N-donor to Molybdenum Bonds. Experimental and Computational Studies of Enthalpies of Binding of Dintrogen, Diazoalkanes, Azides, Nitriles, and Pyridines to Mo(PiPr3)2(CO)­3 "Inorg. Chem.200948, 7891.

2008

"Determination of N-Heterocyclic [NHC] Stereoelectronic Parameters using the (NHC)Ir(CO)2Cl System", Organometallics200827, 208. Kelly, R. A. III, Clavier, H., Guidice, S., Scott, N, M.; Stevens, E. D.; Bordner, J.; Samardjiev, I.; Hoff, C. D.; Cavallo, L.; Nolan, S. P.;

"Thermodynamic, Kinetic, and Computational Study of  Bonding to Heavier Chalcogenides in the Complexes E=Mo(NtBuAr)3 and E=NHC; E = S, Se, Te, NHC = N-Heterocyclic Carbene".  Inorg. Chem. 200847, 2133. James E. McDonough, Arjun Mendriatta, George C. Fortman, Derek M. Isrow, Christopher C. Cummins, Elena V. Rybak-Akimova, Steven P. Nolan, and Carl D. Hoff.

"Kinetic, Thermodynamic, and Mechanistic Aspects of Oxidative Addition Reactions of RE-ER (E = S, Se, Te) and Transition Metal Complexes." Topics in Current Organic Chemistry2008, 12, 1279. George C. Fortman, Tamás Kégl, Carl D. Hoff,

"Thermodynamic and Kinetic Studies of H atom Transfer from H-Mo(CO)3C5H5 to  Mo(N[tBu]Ar)3 and Mo(N[tBu]Ar)3(·NCPh)--Direct Insertion of Benzonitrile into the Mo-H Bond of H- Mo(N[tBu]Ar)3 forming Mo(N[tBu]Ar)3(N=C(H)Ph)"  Inorg. Chem.2008, 47, 9380.  Manuel TempradoΦ, James Eric McDonough, Arjun Mendiratta, Yi-Chou Tsai, George C. Fortman, Christopher C. Cummins, Elena V. Rybak-Akimova, Carl D. Hoff. 

"Kinetic and Thermodynamic Studies of Reactivity of Trimethylsilyldiazomethane and HMo(CO)3C5R5.(R = H, Me). Estimation of the Mo-N2CH2SiMe3 Bond Strength and Experimental Determination of the Enthalpy of Formation of Trimethylsilyldiazomethane." Organometallics,  2008, 47, 4873. George Fortman, Derek Isrow, Eric McDonough, John Weir, Paul von Rague Schleyer, Brian Scott, Gregory J. Kubas, Ferenc Ungvary, Carl D. Hoff.

2007

"Synthesis, Structure, and Thermochemistry of Formation of the Metal-Metal Bonded Dimers {Mo(m-TeAr)(CO)­3(PiPr3)2]2 ( Ar = Ph, Napth) by Phosphine Elimination from ·Mo(TeAr)(CO)3(PiPr3)2. Inorg. Chem.200746, 652. Weir, J. J.; McDonough, J. E.; Fortman, G. C.; Isrow, D.; Hoff, C. D.; Scott, B.; Kubas, G. J.

"Theoretical Investigation of the Binding of Small Molecules and the Intramolecular Agostic Interaction at Tungsten Centers with Carbonyl and Phosphine Ligands.", J. Chem. Phys. B2007111, 6815.  James T. Muckerman, Etsuko Fujita, Carl D. Hoff, and Gregory J. Kubas.

"Spectroscopic Detection and Theoretical Confirmation of the Role of Cr2(CO)5(C5R5)2 and ·Cr(ketene)(CO)2(C5R5) as Intermediates in Carbonylation of N=N=CHSiMe3 to O=C=CHSiMe3 Catalyzed by ·Cr(CO)3(C5R5) (R = H, CH3). J. Am. Chem. Soc..2007129, 14389. Fortman, G. C., Kegl, T., Li, Q. S.; Zhang, X.;  Schaefer, H. F., Xie, Y.; R.;  King, R. B.;  Telser, J.;  and Hoff, C. D.

2006

"Comparison of Themodynamic and Kinetic Aspects of Dichalcogenide and Ligand Binding Reactions of Mo(CO)3(PR3)2 , W(CO)3(PR3)2, and Mo(NArR)­3 Complexes. The Role of Oxidation States and Ancillary Ligands in Metal Complex Induced Chalcogenyl Radical Generation." J. Am. Chem. Soc.; 2006128, 10295. McDonough, J. E.; Weir, J. J.; Sukcharoenphon, K.; Hoff, C. D.; Kryatov, O. P.; Rybak-Akimova, E. V.; Scott, B.; Kubas, G. J.; Stephens, F. H.; Mendriatta, A.; Cummins, C. C.

"Benzonitrile Extrusion from Molybdenum (IV) Ketimide Complexes Obtained via Radical C-E ( E = O, S, Se) Bond Formation: Toward a New Nitrogen Atom Transfer Reaction"; J. Am. Chem. Soc.; 2006, 128, 4881. Mendriatta, A.; Cummins, C. C.; Kryatova, O. P.; Rybak-Akimova, E. V.; McDonough, J. E.; Hoff, C. D.

 2005

"Cluster Compounds: Dinuclear Organometallic Complexes", Encyclopedia of Inorganic Chemistry2nd  Edition  2005, John Wiley, New York. Kiss, G., McDonough, J. E.; Weir, J. J.; Hoff, C. D.

"Steric and Electronic Properties of N-Heterocyclic Carbenes (NHC): A Detailed Study of their Interaction with Ni(CO)4." Dorta, R.; Stevens, E. D.; Scott, N. M.; Costabilie, C.; Carvallo, L.; Hoff, C. D.; Nolan, S. P.; J. Am. Chem. Soc2005127, 2485-2495.

"Solution Calorimetric and Stopped Flow Kinetic Studies of Reaction of Cr(CO)3C5Me5 with PhSe-SePh and PhTe-TePh.  Experimental and Theoretical Estimates of the Se-Se and Te-Te Bond Strength."; Inorg. Chem.2005, 44, 3127.  McDonough, J. E.; Carlson, M. J.; Weir, J. J.; Hoff C. D.; Kryatov, O. P.;  Rybak-Akimova E. V.; Cummins C. C.             

"Activaiton of White Phosphorus by a Molybdaziridine-Hydride", J. Am.. Chem. Soc.2005127, 15191.  Stephens, F. H.; Johnson, M. J. A.; Diasconescu, P. L.; Cummins C. C., Kryatov, O. P.;  Rybak-Akimova E. V, .McDonough, J. E.; Hoff C. D.

2004

"Small Molecule Activation by Metallaziridine Hydride Complexes: Mechanistic Sequence of the Small Molecule-Binding and Metallaziridine Ring-Opening Steps"Organometallics,  2004, 23, 3126-3138. Stephens, F. H.; Figueroa, J. S.; Cummins, C. C.; Kryatova, O.; Kryatov, S. V.; Rybak-Akimova, E. V.; McDonough, J. E.; Hoff, C. D.