A5024174359- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Crystallography and molecular interactions
- Organometallic Complex Synthesis and Catalysis
- Metal complexes synthesis and properties
- Synthesis and characterization of novel inorganic/organometallic compounds
- Asymmetric Hydrogenation and Catalysis
- Ferrocene Chemistry and Applications
- Magnetism in coordination complexes
- Metal-Catalyzed Oxygenation Mechanisms
- Lanthanide and Transition Metal Complexes
- Electrocatalysts for Energy Conversion
- Inorganic and Organometallic Chemistry
- Metalloenzymes and iron-sulfur proteins
- Coordination Chemistry and Organometallics
- Carbohydrate Chemistry and Synthesis
- Synthetic Organic Chemistry Methods
- Ammonia Synthesis and Nitrogen Reduction
- Organophosphorus compounds synthesis
- Catalytic Cross-Coupling Reactions
- Electrochemical Analysis and Applications
- Crystal structures of chemical compounds
- Vanadium and Halogenation Chemistry
- Electron Spin Resonance Studies
- Metal-Organic Frameworks: Synthesis and Applications
Albright College
2017-2023
Villanova University
2013-2018
University of Pennsylvania
2013
University of California, Berkeley
2011-2013
Lawrence Berkeley National Laboratory
2011-2013
Howard Hughes Medical Institute
2011
Massachusetts Institute of Technology
2005-2010
IIT@MIT
2010
California Institute of Technology
2004
A set of robust molecular cobalt catalysts for the generation hydrogen from water is reported. The complex supported by parent pentadentate polypyridyl ligand PY5Me2 features high stability and activity 100% Faradaic efficiency electrocatalytic production neutral water, with a turnover number reaching 5.5 × 104 mol H2 per mole catalyst no loss in over 60 h. Control experiments establish that simple Co(II) salts, free ligand, an isostructural containing redox-inactive Zn(II) are all...
A pseudotetrahedral cobalt(II) complex with a positive axial zero-field splitting parameter of D = 12.7 cm(-1), as determined by high-field EPR spectroscopy, is shown to exhibit slow magnetic relaxation under an applied dc field.
We report a mild method for generating the diphosphorus molecule or its synthetic equivalent in homogeneous solution; P2 allotrope of element phosphorus is normally obtained only under extreme conditions (for example, from P4 at 1100 kelvin). Diphosphorus extruded niobium complex designed this purpose and can be trapped efficiently by two equivalents an organic diene to produce organodiphosphorus compound. stabilized coordination tungsten pentacarbonyl generated similarly 25 degrees C, form...
The pentapyridine cobalt complex [Co(PY5Me2)]2+ and its congeners have been shown to catalyze proton reduction hydrogen in aqueous solution over a wide pH range using electrical or solar energy input. Here, we employ electrochemical spectroscopic studies examine the mechanisms of by this parent under soluble, diffusion-limited conditions acetonitrile with acetic acid as donor. Two pathways for are identified via cyclic voltammetry: one pathway occurring from an acetonitrile-bound CoII/I...
The transformation of acid chlorides (RC(O)Cl) to organic nitriles (RC[triple bond]N) by the terminal niobium nitride anion [N[triple bond]Nb(N[Np]Ar)3]- ([1a-N]-, where Np = neopentyl and Ar 3,5-Me2C6H3) via isovalent N for O(Cl) metathetical exchange is presented. Nitrido [1a-N]- obtained in a heterodinuclear N2 scission reaction employing molybdenum trisamide system, Mo(N[R]Ar)3 (R t-Bu, 2a; R Np, 2b), as partner. Reductive bridging complexes, (Ar[R]N)3Mo-(mu-N2)Nb(N[Np]Ar)3 3b; 3c) with...
Electrochemical experiments performed on the complex CeIV[2-(tBuNO)py]4, where [2-(tBuNO)py]− = N-tert-butyl-N-2-pyridylnitroxide, indicate a 2.51 V stabilization of 4+ oxidation state Ce compared to [nBu4N]2[Ce(NO3)6] in acetonitrile and 2.95 standard potential for ion under aqueous conditions. Density functional theory calculations suggest that this preference higher is result tetrakis(nitroxide) ligand framework at cation, which allows effective electron donation into, partial covalent...
The geometric constraints imposed by a tetradentate P4N2 ligand play an essential role in stabilizing square planar Fe complexes with changes metal oxidation state. pyramidal Fe0(N2)(P4N2) complex catalyzes the conversion of N2 to N(SiR3)3 (R = Me, Et) at room temperature, representing highest turnover number any Fe-based silylation catalyst date (up 65 equiv N(SiMe3)3 per center). Elevated pressures (>1 atm) have dramatic effect on catalysis, increasing solubility and thermodynamic binding...
We report ammonia oxidation by homolytic cleavage of all three H atoms from a [Mo-NH3]+ complex using the 2,4,6-tri-tert-butylphenoxyl radical to yield Mo-alkylimido ([Mo═NR]+) (R = 2,4,6-tri-tert-butylcyclohexa-2,5-dien-1-one). Chemical reduction [Mo═NR]+ generates terminal Mo≡N nitride upon N-C bond cleavage, and [Mo═NH]+ is formed protonation nitride. Computational analysis describes energetic profile for stepwise removal formation [Mo═NR]+.
Aiding and abetting a wanted radical: The neutral phosphorus radical [.P{NV[N(Np)Ar]3}2] (Np=neopentyl, Ar=3,5-Me2C6H3) exists as monomer in the solid state is resonance-stabilized by two nitridovanadium trisanilide metalloligands through VIV/VV redox couple (see EPR trace calculated SOMO of [.P{NV[N(Me)Ph]3}2]). compound undergoes reactions at its center to form diamagnetic compounds. Supporting information for this article available on WWW under...
Nitrous oxide (N2O), a widespread greenhouse gas, is thermodynamically potent and environmentally green oxidant that an attractive target for activation by metal centers. However, N2O remains underutilized owing to its high kinetic stability, the poor ligand properties of this molecule have made well-characterized metal−N2O complexes rarity. We now report vanadium−pyrrolide system reversibly binds at room temperature provide first single-crystal X-ray structure such complex. Further...
While P4 is the stable molecular form of phosphorus, a recent study illustrated possibility P2 generation for reactions in organic media under mild conditions. The heavier group 15 element arsenic can exist as As4 molecules, but cannot be stored pure substance because it both light-sensitive and reverts thermally to its stable, metallic gray form. Herein we report activation giving rise μ-As2 diniobium complex, serving turn precursor terminal arsenide anion complex niobium. Functionalization...
Metallo prodrugs that take advantage of the inherent acidity surrounding cancer cells have yet to be developed. We report a new class pH-activated metallo (pHAMPs) are activated by light- and pH-triggered ligand dissociation. These ruthenium complexes key characteristic hypoxic solid tumors (acidity) can exploited lessen side effects chemotherapy. Five type [(N,N)2Ru(PL)]2+ were synthesized, fully characterized, tested for cytotoxicity in cell culture (1A: N,N = 2,2′-bipyridine (bipy) PL,...
The diphosphaazide complex (Mes*NPP)Nb(N[Np]Ar)3 (Mes* = 2,4,6-tri-tert-butylphenyl, Np neopentyl, Ar 3,5-Me2C6H3), 1, has previously been reported to lose the P2 unit upon gentle heating, form (Mes*N)Nb(N[Np]Ar)3, 2. first-order activation parameters for this process have estimated here using an Eyring analysis values ΔH⧧ 19.6(2) kcal/mol and ΔS⧧ −14.2(5) eu. eliminated can be transferred terminal phosphide complexes P≡M(N[iPr]Ar)3, 3-M (M Mo, W), [P≡Nb(N[Np]Ar)3]−, 3-Nb, give cyclo-P3...
A series of cerium complexes containing a 2,2'-methylenebis(6-tert-butyl-4-methylphenolate) (MBP(2-)) ligand framework is described. Electrochemical studies the compound [Li(THF)2Ce(MBP)2(THF)2] (1) reveal that metal based oxidation wave occurs at -0.93 V vs Fc/Fc(+). This potential demonstrates significant stabilization cerium(IV) ion in MBP(2-) with shift ∼2.25 from typically reported value for cerium(III/IV) couple E°' = +1.30 Fc/Fc(+) Ce(ClO4)3 HClO4 solutions. Compound 1 undergoes to...
The reaction of [Pd(dtbpf)Cl2] (dtbpf = 1,1′-bis(di-tert-butylphosphino)ferrocene) with a chemical oxidant led unexpectedly to the formation [Pd(dtbpf)Cl]+. Further study found that variety reagents could be used abstract chloride ligand from yield solid-state structure suggests an Fe–Pd interaction. presence bulky tert-butyl groups is essential, as similar reactions [Pd(PP)Cl2] (PP other 1,1′-bis(phosphino)ferrocene ligands) results in [Pd(PP)(μ-Cl)]22+. analogous platinum compounds have...
The aluminum complexes (LMes(2-))AlCl(THF) (3) and (LDipp(-))AlCl2 (4) (LMes = N,N'-bis[2,4,6-trimethylphenyl]-2,3-dimethyl-1,4-diazabutadiene, LDipp N,N'-bis[2,6-diisopropylphenyl]-2,3-dimethyl-1,4-diazabutadiene) were prepared by direct reduction of the ligands with sodium metal followed salt metathesis AlCl3. (LMes(-))AlCl2 (5) complex was through one-electron oxidative functionalization 3 either AgCl or CuCl. Complex characterized using (1)H (13)C NMR spectoscopies. Single-crystal X-ray...
Ligands lost, ligands gained: A terminal tungsten nitride is converted into the corresponding phosphide by a one-pot sequence of atom-transfer reactions (see scheme). The complex subsequently functionalized treatment with phosphorus-based electrophile. resulting phosphorus-rich displays PP multiple-bonding character.
A terminal molybdenum arsenide complex is synthesized in one step from the reactive As(4) molecule. The properties of this with its arsenic atom ligand are discussed relation to analogous nitride and phosphide complexes.
Complexes of group 13 metal (Al, Ga, In) ions with neutral α-diimine ligands have been prepared and characterized. The Al(III) Ga(III) [M(α-diimine)2Cl2][MCl4] complexes catalyze the epoxidation alkenes by peracetic acid under ambient conditions. two display nearly identical reactivity, demonstrating that inexpensive highly abundant aluminum is a viable catalytic for these reactions.
The first complete structurally and spectroscopically characterized series of isostructural Group 6 N2 complexes is reported. Protonolysis experiments on cis-[M(N2)2(P(Et)N(R)P(Et))2] (M = Cr, Mo, W; R 2,6-difluorobenzyl) reveal that only Cr affords N2H5(+) NH4(+) from the reduction ligands.
The terminal phosphorus monoxide complex (OP)Mo(N[tBu]Ar)3, 1 (Ar = 3,5-Me2C6H3), undergoes an O-for-PSiR3 metathesis reaction with the niobium phosphinidene iPr3SiPNb(N[CH2tBu]Ar)3, 2, to generate oxoniobium ONb(N[CH2tBu]Ar)3, 3, and diphosphenido iPr3SiPPMo(N[tBu]Ar)3, 4. structure of 4, as determined by X-ray crystallography, contains a "singly bent" moiety, suggesting that ligand serves 3e− donor formally d2 metal center. This bonding characterization was supported DFT calculations is...
The syntheses of several new zinc compounds with 1,1′‐bis(phosphino)ferrocene ligands and their phosphine chalcogenide derivatives are reported. X‐ray crystal structures [Zn(dppdtbpf)Cl 2 ] [dppdtbpf = 1‐diphenylphosphino‐1′‐(di‐ tert ‐butylphosphino)ferrocene], [Zn(dippfO )Cl [dippf 1,1′‐bis(diisopropylphosphino)ferrocene], [Zn(dtbpfO [dtbpf 1,1′‐bis(di‐ [Zn( 4 S)Cl ( dppdtbpf) were determined. oxidative electrochemistry the was examined typically produced irreversible oxidations. reactions...