Protasiewicz Research Group

Research Overview

Inorganic and Organometallic Chemistry

Our work is aimed at understanding the fundamental details of transition-metal catalyzed atom and group transfer reactions and to use this knowledge for the development of new catalytic reactions and for the construction of novel materials. Our approach involves the rational design of new reagents and ligands for achieving these goals. Our research cuts through the traditional boundaries of Organic, Inorganic, Organometallic and Main Group Chemistry.

1) Novel Materials for Molecular Electronics and Nanotechnology:

Transition Metal- and Main Group-Phosphinidene Complexes for Precursors to Hybrid Polymeric Materials

We are interested in the construction of novel conjugated materials that incorporate multiply bonded low coordinate phosphorus centers. For example, many fascinating conducting polymers having backbones comprised of C=C units in a conjugated fashion are being intensely studied for new electronic and optical properties. Using the well-known diagonal relationship between carbon and phosphorus, our goal is to prepare new materials having having P=C and P=P double bonds along the conjugation pathway. One recent successful polymer (left) is compared to a model oligomer (right) below .

As the pi-bonds involving phosphorus are weaker than for carbon, these redox active sites have smaller HOMO-LUMO gaps and should add new mechanisms for modulating electronic and optical properties of the materials. An added challenge to this work is the need to design new multifunctional ligands for phosphorus that also are sterically encumbered. In addition, we are exploring new modes of synthesis of such materials. recently we discovered a new type of "phospha-Wittig" reaction (equation 1). The "phospha-Wittig" reaction allows for rapid construction of P=C bonds in a selective manner.

During the course of our work we have devloped new protective groups for phosphorus based on m-terphenyl and tertra-arylphenyl ligands. A structurally characterized conjugated bis-diphosphene, DmpP=P(C6Ar4)P=PDmp (below) has been prepared, and discovered to undergo novel structural changes upon 1 and 2 electron reductions. Such behavior is akin to a "molecular switch"..

Some Recent Papers:

"Solution and Film Photoluminescence of Mesityl-Substituted PPVs and Low Molecular Weight Models" Smith, R. C.; Gleason, L. B.; Protasiewicz, J. D. J. Materials Chemistry 2006, 16, 2445-2452.
"Photochemical E-Z Isomerization of meta-Terphenyl-Protected Phosphaalkenes and Structural Characterizations" Gudimetla, V. B.; Rheingold, A. L.; Payton, J. L.; Peng, H.-L.; Simpson, M. C.; Protasiewicz, J. D. Inorganic Chemistry 2006, 45, 4895-4901.
"Conjugated Polymers Featuring Heavier Main Group Element Multiple Bonds: A Diphosphene-PPV" Smith, R. C.; Protasiewicz, J. D. J. Am. Chem. Soc. 2004, 126, 2268-22691.
"A cyclic diphosphinite by a formal [4+4] cycloaddition reaction of beta-phosphaenone" Chen, X; Chen, W.; Ren, T.; Protasiewicz, J. D. Tet. Lett. 2005, 46, 5941-5944.
"Systematic Investigation of PPV Analogue Oligomers Incorporating Low-Coordinate Phosphorus Centers" Smith, R. C.; Shah, S.; Urnezius, E.; Protasiewicz, J. D. Eur. J. Inorg. Chem. 2004, 998-1006.
"Arsa-Wittig Complexes (ArAs=PMe3) as Intermediates to Diarsenes" Smith, R. C.; Gantzel, P.; Rheingold, A. L.; Protasiewicz, J. D. Organometallics 2004, 23, 5124-5126.
"Metal-Ion Adsorption on Carboxyl-Bearing Self-Assembled Monolayers Covalently Bound to Magnetic Nanoparticles" Hai, B.; Wu, J.; Chen, X.; Protasiewicz, J. D.; Scherson, D. A. Langmuir 2005, 21, 3104-3105.
"An Unusual Equilibrium Chlorine Atom Transfer Process and its Potential for Assessment of Steric Pressure by Bulky Aryls" Smith, R. C.; Shah, S.; Urnezius, E.; Protasiewicz, J. D. J. Am. Chem. Soc. 2003, 40-41.
"Synthesis and luminescence properties of a series of tris(4-styrylphenyl)phosphorus-(III) and -(V) compounds and of a [Cu(PR3)4]BF4 complex" Smith, R. C.; Protasiewicz, J. D. Dalton Trans. 2003, 24, 4738-4741.
"Cycloaddition of phosphanylidene-sigma-4-phosphoranes ArPPMe3 and quinones to yield 1,3,2-dioxophospholanes " Chen, X.; Smith, R. C.; Protasiewicz, J. D. J. C. S. Chem. Comm. 2004, 146-147.
"Synthesis and Solid State Structures of Increasingly Sterically Crowded 1,4-Diiodo-2,3,5,6-tetraarylbenzenes: A New Series of Bulky Benzenes and Aryls" Shah, S.; Eichler, B. E.; Smith, R. C.; Power, P. P.; Protasiewicz, J. D. New J. Chem. 2003, 27, 442-445.
"Sterically Encumbered Diphosphaalkenes and a Bis-diphosphene as Potential Multi-Redox Active Molecular Switches: EPR and DFT investigations" Dutan, C.; Shah, S.; Smith, R. C.; Choua, S.; Berclaz, T.; Protasiewicz, J. D.; Geoffroy, M. Inorg. Chem. 2003, 42, 6241.
"Robust, reactive, and remarkably simple to prepare sterically encumbered meta-terphenyl ligand" Smith, R. C.; Ren, T.; Protasiewicz, J. D. Europ. J. Inorg. Chem. 2002, 2779-2783.
"A role for free phosphinidenes in the reaction of magnesium and sterically encumbered ArPCl2 in solution at room temperature" Smith, R. C.; Shah, S.; Protasiewicz, J. D. J. Organomet. Chem. 2002, 646, 255-261.
"Three Different Fates for Phosphinidenes Generated by Photocleavage of Phospha-Wittig Reagents ArP=PMe3" Shah, S.; Simpson, M. C.; Smith, R. C.; Protasiewicz, J. D., J. Am. Chem. Soc., 2001, 123, 6925-6926.
"Triphosphane formation from the terminal zirconium phosphinidene complex [Cp2Zr=PDmp(PMe3)] (Dmp = 2,6-Mes2C6H3) and crystal structure of DmpP(PPh2)2" Urnezius, E.; Lam, K.-C.; Rheingold, A. L.; Protasiewicz, J. D., J. Organomet. Chem., 2001, 630, 193-197.
"Sterically Encumbered Systems for Two Low Coordinate Phosphorus Centers" Shah, S.; Concolino, T.; Rheingold A. L.; Protasiewicz, J. D. Inorganic Chemistry, 2000, 39, 3860-3867.
"Crystal Structure of the Phosphanylidene-s⁴-phosphorane DmpP=PMe₃ (Dmp = 2,6-Mes₂C₆H₃) and Reactions with Electrophiles" ShahS.; YapG. P. A.; Protasiewicz, J. D. J. Organomet. Chem. 2000, 608, 12-20.
""Phospha-variations" On The Themes Of Staudinger and Wittig: Phosphorus analogs of Wittig Reagents" Shah, S.; Protasiewicz, J. D. Coord. Chem. Rev. 2000, 210/1, 181-201 (invited review).

2) Mechanistic & Catalytic Reactions:

New Ligands for Catalysis based on meta-Terphenyls

Meta-Terphenyls that are being used in our labd also make great platforms upon which we can build many new exciting ligands. Shown above is one of our new ligands and its palladium complex. The trans spanning mode of this ligand is unusual. These materials also act as catalysts for many important Suzuki and Heck coupling reactions that we are currently studying.

Some Recent Papers:

"A New Twist on Pincer Ligands and Complexes" Ma, L.; Woloszynek, R. A.; Chen, W.; Ren, T.; Protasiewicz, J. D. Organometallics 2006, 25, 3301-3304.
"Synthesis and Reactivity of Cationic Palladium Phosphine Carboxylate Complexes" Thirupathi, N.; Amoroso, D.; Bell, A.; Protasiewicz, J. D., Organometallics 2005, 24, 4099-4102.
"A Trans-Spanning Diphosphine Ligand Based on a m-Terphenyl Scaffold and Its Palladium and Nickel Complexes " Smith, R. C.; Protasiewicz, J. D. Organometallics 2004, 23, 4215-4522.
"Metal-Ion Adsorption on Carboxyl-Bearing Self-Assembled Monolayers Covalently Bound to Magnetic Nanoparticles" Hai, B.; Wu, J.; Chen, X.; Protasiewicz, J. D.; Scherson, D. A., Langmuir 2005, 21, 3104-3105.
"Self-Assembly of Cationic Palladium Complexes by Redistribution of Pyridine Ligands " Ma, L.; Smith, R. C.; Protasiewicz, J. D. Inorg. Chim. Acta 2005, 358, 3478-3482.
"Suzuki and Heck coupling reactions mediated by palladium complexes bearing trans-spanning diphosphines" Rhett C. Smith, Christina R. Bodner, Meredith J. Earl, Nathaniel C. Sears, Nicholas E. Hill, Lee M. Bishop, Nicholas Sizemore, Dave T. Hehemann, Justin J. Bohn, John D. Protasiewicz J. Organomet. Chem. 2005, 690, 477-481
"Suzuki reactions catalyzed by palladium complexes bearing the bulky (2,6-dimesitylphenyl)dimethylphosphine " Smith, R. C.; Woloszynek, R. A.; Chen, W; Ren, T.; Protasiewicz, J. D. Tetrahedron Letters 2004, 45, 8327-8330

Oxo- and Nitrene-Transfer Reactions of Organoiodine(III) Complexes

Iodosylbenzene, (PhI=O)n, and (Tosyliminoiodo)benzene, (PhI=NTs)n, are two of the most important sources of oxygen atoms and tosylimino groups for transition metal catalyzed processes such as epoxidation and aziridination (left, S = olefin). A full understanding of these powerful oxidants containing a hypervalent iodine(III) center is currently lacking due to their limited solubility and polymeric essence. Any sort of mechanistic studies of the catalytic reactions are therefore impeded by the heterogeneous nature of the reaction medium.We have recently gained important insights to the nature of the insolubility of these reagents by the characterization of the solid state details of ArI=NTs by single crystal X-ray studies. An analysis of this data has led to the successful design of new reagents that incorporate intramolecular secondary bonds (analogues of hydrogen bonds that involve heavy atoms) between iodine and oxygen atoms (below). These newly developed species display unprecedented solubility in conventional organic solvents and allow for standard spectroscopic measurements. Work is currently in progress to determine how the solid state structures of these new materials pertain to their solution behavior and to their atom and nitrene transfer proficiency. These new organoiodine(III) reagents will thus allow us to fully maximize the potential of transition metal catalyzed atom and group transfer reactions. New applications are also anticipated.

Some Recent Papers:

"ortho-Phosphoryl stabilized hypervalent iodosyl- and iodyl-benzene reagents " Meprathu, B. V.; Justik, M. W.; Protasiewicz, J. D.,Tet. Lett. 2005, 46, 5187-5190.
"Synthesis and characterization of novel polyvalent organoiodine compounds" Meprathu, B. V.; Protasiewicz, J. D. Arkivoc (65th birthday of Professor Anastasios Varvoglis issue) 2003, 83-90.
"Redirecting Secondary Bonds to Control Molecular and Crystal Properties of an Iodosylbenzene and an Iodoxybenzene" Macikenas, D.; Skrzypczak-Jankun, E.; and John D. Protasiewicz, J. D., Angew. Chem. 200011, 2007-2010.
"A New Class of Iodonium Ylides Engineered as Soluble Primary Oxo and Nitrene Sources" Macikenas, D.; Skrzypczak-Jankun, E.; Protasiewicz, J. D. Journal of the American Chemical Society 1999, 121, 7164-7165.
"Hypervalent Iodine Nitrene Precursors Bearing N-Heterocyclic Rings" Meprathu, B. V.; Diltz, S.; Walsh, P. J.; Protasiewicz, J. D. Tetrahedron Letters 1999, 40, 5459-5460.
"Solubilization of the Primary Nitrene Sources (Tosyliminoiodo)arenes (ArINTs)" Macikenas, D.; Meprathu, B. V.; Protasiewicz, J. D. Tetrahedron Lett. 1998, 39, 191-194.
"Secondary Bonding as a Force Dictating Structure and Solid-State Aggregation of the Primary Nitrene Sources (Arylsulfonylimino)iodoarenes (ArINSO2Ar')" Boucher, M.; Macikenas, D.; Ren, T.; Protasiewicz, J. D. J. Am. Chem. Soc. 1997, 119, 9366-9376.
"Polymorphism of (Tosylimino)iodo-o-toluene: Two New Modes of Polymeric Association for ArINTs" Cicero, R. L.; Zhao, D.; Protasiewicz, J. D. Inorg. Chem. 1996, 35, 275-276.
"(Tosyliminoiodo)benzene at 298 K" Protasiewicz, J. D. Acta. Cryst. C 1996, 1570-1572.
"Reduction of Intermolecular Association in the Sterically Encumbered (Dichloroiodo)arene ArICl2 [Ar = 2,6-bis(3,5-dichloro-2,4,6-trimethylphenyl)benzene]" Protasiewicz, J. D. J. Chem. Soc. Chem. Comm. 1995, 1115-1116.