Calvin J Curtis

Publications (30)57.61 Total impact

• Article: Inkjet printed metallizations for Cu(In1−xGax)Se2 photovoltaic cells

  Peter A. Hersh, Calvin J. Curtis, Maikel F.A.M. van Hest, John J. Kreuder, Robert Pasquarelli, Alex Miedaner, David S. Ginley
  Progress in Photovoltaics Research and Applications 03/2011; 19(8):973 - 976. · 5.79 Impact Factor
• Article: Enhanced Efficiency in Plastic Solar Cells via Energy Matched Solution Processed NiOx Interlayers

  K. Xerxes Steirer, Paul F. Ndione, N. Edwin Widjonarko, Matthew T. Lloyd, Jens Meyer, Erin L. Ratcliff, Antoine Kahn, Neal R. Armstrong, Calvin J. Curtis, David S. Ginley, Joseph J. Berry, Dana C. Olson
  Adv. Energy. Mater. 01/2011; 1(5):813–820.
• Article: Stoichiometric analysis of compositionally graded combinatorial amorphous thin film oxides using laser-induced breakdown spectroscopy.

  N Edwin Widjonarko, John D Perkins, Jennifer E Leisch, Philip A Parilla, Calvin J Curtis, David S Ginley, Joseph J Berry
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  ABSTRACT: Laser-induced breakdown spectroscopy (LIBS) is a recently developed locally destructive elemental analysis technique that can be used to analyze solid, liquid, and gaseous samples. In the system explored here, a neodymium-doped yttrium aluminum garnet laser ablates a small amount of the sample and spectral emission from the plume is analyzed using a set of synchronized spectrometers. We explore the use of LIBS to map the stoichiometry of compositionally graded amorphous indium zinc oxide thin-film libraries. After optimization of the experimental parameters (distance between lens and samples, spot size on the samples, etc.), the LIBS system was calibrated against inductively coupled plasma atomic emission spectroscopy which resulted in a very consistent LIBS-based elemental analysis. Various parameters that need to be watched closely in order to produce consistent results are discussed. We also compare LIBS and x-ray fluorescence as techniques for the compositional mapping of libraries.
  The Review of scientific instruments 07/2010; 81(7):073103. · 1.52 Impact Factor
• Source

  Available from: Robert M Pasquarelli

  Article: Solution synthesis and characterization of indium-zinc formate precursors for transparent conducting oxides.

  Robert M Pasquarelli, Calvin J Curtis, Alexander Miedaner, Maikel F A M van Hest, Ryan P O'Hayre, David S Ginley
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  ABSTRACT: A series of In-Zn formate mixtures were investigated as potential precursors to amorphous In-Zn-oxide (IZO) for transparent conducting oxide (TCO) applications. These mixtures were prepared by neutralization from formic acid and characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction, and thermogravimetry-differential scanning calorimetry (TG-DSC) measurements. Thermal analysis revealed that a mixture of In and Zn formates reduced the overall decomposition temperature compared to the individual constituents and that OH-substitution enhanced the effect. In terms of precursor feasibility, it was demonstrated that the decomposition products of In-Zn formate could be directed toward oxidation or reduction by controlling the decomposition atmosphere or with solution acid additives. For TCO applications, amorphous IZO films were prepared by ultrasonic spray deposition from In-Zn formate solutions with annealing at 300-400 degrees C.
  Inorganic Chemistry 06/2010; 49(12):5424-31. · 4.60 Impact Factor
• Article: Solution Synthesis and Characterization of Indium−Zinc Formate Precursors for Transparent Conducting Oxides

  Robert M. Pasquarelli, Calvin J. Curtis, Alexander Miedaner, Maikel F.A.M. van Hest, Ryan P. O’Hayre, David S. Ginley
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  ABSTRACT: A series of In−Zn formate mixtures were investigated as potential precursors to amorphous In−Zn-oxide (IZO) for transparent conducting oxide (TCO) applications. These mixtures were prepared by neutralization from formic acid and characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction, and thermogravimetry-differential scanning calorimetry (TG-DSC) measurements. Thermal analysis revealed that a mixture of In and Zn formates reduced the overall decomposition temperature compared to the individual constituents and that OH-substitution enhanced the effect. In terms of precursor feasibility, it was demonstrated that the decomposition products of In−Zn formate could be directed toward oxidation or reduction by controlling the decomposition atmosphere or with solution acid additives. For TCO applications, amorphous IZO films were prepared by ultrasonic spray deposition from In−Zn formate solutions with annealing at 300−400 °C.
  05/2010;
• Source

  Available from: Michael Kaufman

  Article: Atmospheric pressure synthesis of In2Se3, Cu2Se, and CuInSe2 without external selenization from solution precursors

  Jennifer A. Nekuda Malik, Maikel F.A.M. van Hest, Alexander Miedaner, Calvin J. Curtis, Jennifer E. Leisch, Philip A. Parilla, Michael Kaufman, Matthew Taylor, B.J. Stanbery, Ryan P. O’Hayre, David S. Ginley
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  ABSTRACT: In2Se3, Cu2Se, and CuInSe2 thin films have been successfully fabricated using novel metal organic decomposition (MOD) precursors and atmospheric pressure-based deposition and processing. The phase evolution of the binary (In-Se and Cu-Se) and ternary (Cu-In-Se) MOD precursor films was examined during processing to evaluate the nature of the phase and composition changes. The In-Se binary precursor exhibits two specific phase regimes: (i) a cubic-InxSey phase at processing temperatures between 300 and 400 °C and (ii) the γ-In2Se3 phase for films annealed above 450 °C. Both phases exhibit a composition of 40 at.% indium and 60 at.% selenium. The binary Cu-Se precursor films show more diverse phase behavior, and within a narrow temperature processing range a number of Cu-Se phases, including CuSe2, CuSe, and Cu2Se, can be produced and stabilized. The ternary Cu-In-Se precursor can be used to produce relatively dense CuInSe2 films at temperatures between 300 and 500 °C. Layering the binary precursors together has provided an approach to producing CuInSe2 thin films; however, the morphology of the layered binary structure exhibits a significant degree of porosity. An alternative method of layering was explored where the Cu-Se binary was layered on top of an existing indium-gallium-selenide layer and processed. This method produced highly dense and large-grained (>3 µm) CuInSe2 thin films. This has significant potential as a manufacturable route to CIGS-based solar cells.
  Journal of Materials Research. 03/2009; 24(04):1375 - 1387.
• Source

  Available from: Jennifer Leisch

  Conference Proceeding: Spray deposition of high quality CuInSe2 and CdTe films

  Calvin J. Curtis, Maikel van Hest, Alex Miedaner, Jennifer Nekuda, Peter Hersh, Jennifer Leisch, David S. Ginley
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  ABSTRACT: A number of different ink and deposition approaches have been used for the deposition of CuInSe 2 (CIS), Cu(In,Ga)Se 2 (CIGS), and CdTe films. For CIS and CIGS, soluble precursors containing Cu, In, and Ga have been developed and used in two ways to produce CIS films. In the first, In-containing precursor films were sprayed on Mo-coated glass substrates and converted by rapid thermal processing (RTP) to In 2 Se 3 . Then a Cu-containing film was sprayed down on top of the In 2 Se 3 and the stacked films were again thermally processed to give CIS. In the second approach, the Cu-, In-, and Ga-containing inks were combined in the proper ratio to produce a mixed Cu-In-Ga ink that was sprayed on substrates and thermally processed to give CIGS films directly. For CdTe deposition, ink consisting of CdTe nanoparticles dispersed in methanol was prepared and used to spray precursor films. Annealing these precursor films in the presence of CdCl 2 produced large-grained CdTe films. The films were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM). Optimized spray and processing conditions are crucial to obtain dense, crystalline films.
  Photovoltaic Specialists Conference, 2008. PVSC '08. 33rd IEEE; 06/2008
• Article: Calculated Hydride Donor Abilities of Five-Coordinate Transition Metal Hydrides [HM(diphosphine)2]+ (M = Ni, Pd, Pt) as a Function of the Bite Angle and Twist Angle of Diphosphine Ligands

  Mark R. Nimlos, Christopher H. Chang, Calvin J. Curtis, Alex Miedaner, Heidi M. Pilath, Daniel L. DuBois
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  ABSTRACT: Density functional theory (BLYP and B3LYP) and the polarized continuum model (PCM-UA0) for solvation have been used to investigate the effect of bite angle (P−M−P) of diphosphine ligands and the dihedral or twist angle between diphosphine ligands on the hydride donor abilities of Ni, Pd, and Pt [HM(diphosphine)2]+ complexes. It is found that an increased bite angle for a given transition metal atom results in poorer hydride donor abilities. However, hydride donor abilities for these complexes also decrease as the size of the alkyl side groups on the phosphorus atom increase (Et > Me > H) and with the length of the metal phosphorus bond (Ni > Pd Pt). These trends correlate with an increase in the twist angle between the two diphosphine ligands, which increases from 0° for a square-planar configuration to 90° for a tetrahedral geometry. Shorter M−P bonds, larger substituents on the diphosphine ligands, and larger bite angles all result in increased steric interactions between diphosphine ligands and larger dihedral or twist angles between the diphosphine ligands. The twist angle correlates much more strongly with hydride donor abilities than do bite angles alone. As the twist angle increases, the hydride donor ability decreases in a linear fashion. A frontier orbital analysis has been carried out, and it is shown that the hydride donor ability of [HM(diphosphine)2]+ complexes is largely determined by the energy of the lowest unoccupied molecular orbital of the corresponding [M(diphosphine)2]2+ complex.
  05/2008;
• Article: Direct-write contacts: Metallization and contact formation

  Maikel F. A. M. van Hest, Calvin J. Curtis, Alex Miedaner, Robert M. Pasquarelli, Tanya Kaydanova, Peter Hersh, David S. Ginley
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  ABSTRACT: Using direct-write approaches in photovoltaics for metallization and contact formation can significantly reduce the cost per watt of producing photovoltaic devices. Inks have been developed for various materials, such as Ag, Cu, Ni and Al, which can be used to inkjet print metallizations for various kinds of photovoltaic devices. Use of these inks results in metallization with resistivities close to those of bulk materials. By means of inkjet printing a metallization grid can be printed with better resolution, i.e. smaller lines, than screen-printing. Also inks have been developed to deposit transparent conductive oxide films by means of ultrasonic spraying.
  01/2008;
• Article: Fabrication of nanoporous titania on glass and transparent conducting oxide substrates by anodization of titanium films

  Andrew J. Leenheer, Alexander Miedaner, Calvin J. Curtis, Maikel F.A.M. van Hest, David S. Ginley
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  ABSTRACT: Nanoporous titania (TiO2) or titania nanotubes could provide a continuous nanostructured electron-conducting anode for organic photovoltaics. In this work, nanoporous titania was formed by anodizing thin films of titanium on both glass and transparent conducting oxide (TCO) substrates. Titanium thin films (500–700 nm) were deposited by radio frequency (RF) magnetron sputtering. Films were anodized in acidic electrolytes containing small amounts of hydrofluoric acid (HF) at constant voltages ranging from 7 to 15 V. Scanning electron microscope (SEM) analysis revealed a nanoporous structure. Nanoporous titania structures were grown on glass in an electrolyte containing sulfuric acid, trisodium citrate, and potassium fluoride, with pore diameters around 50 nm. Analyzing the films at different anodization times, the stages of nanopore formation were elucidated. Additionally, nanoporous titania was formed on a TCO substrate by anodizing in an electrolyte containing acetic acid and hydrofluoric acid. While not completely transparent, the nanoporous titania is promising for use in organic photovoltaics.
  Journal of Materials Research. 02/2007; 22(03):681 - 687.
• Article: Hydride Transfer from Rhodium Complexes to Triethylborane

  Daniel L. DuBois, Daniel M. Blake, Alex Miedaner, Calvin J. Curtis, M. R. DuBois, James A. Franz, John C. Linehan
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  ABSTRACT: The hydrides HRh(depe)2 and HRh(dmpe)2 (depe = Et2PCH2CH2PEt2, dmpe = Me2PCH2CH2PMe2) have thermodynamic hydride donor abilities comparable to LiHBEt3, as indicated by their ability to transfer a hydride ligand to Et3B to sequentially form [Et3BHBEt3]- and [HBEt3]-. HRh(depe)2 and HRh(dmpe)2 can be generated from [Rh(dmpe)2](CF3SO3) and [Rh(depe)2](CF3SO3) and hydrogen gas in the presence of a strong base such as potassium tert-butoxide or lithium diisopropylamide. This reaction proceeds through the oxidative addition of hydrogen to form the [H2Rh(diphosphine)2](CF3SO3) complexes, followed by deprotonation. The oxidative addition of H2 is favored by diphosphine ligands with electron-donating substituents and large chelate bites. In the present study, the driving force for oxidative addition of H2 follows the order [Rh(dmpe)2](CF3SO3) > [Rh(depe)2](CF3SO3) > [Rh(dppe)2](CF3SO3) with [Rh(dmpe)2](CF3SO3) binding H2 more strongly than [Rh(dppe)2](CF3SO3) (dppe = Ph2PCH2CH2PPh2) by at least 2.7 kcal/mol. The effect of the chelate bite size is larger. [H2Rh(depx)2](CF3SO3) (depx = 1,2-(Et2PCH2)2C6H4) binds H2 more strongly than [Rh(depe)2](CF3SO3) by 12 kcal/mol. An understanding of both hydrogen activation and hydride donor abilities is important for developing powerful hydride donors from H2.
  08/2006;
• Article: Electrochemical Reduction of CO2 to CO Catalyzed by a Bimetallic Palladium Complex

  James W. Raebiger, Jeffrey W. Turner, Bruce C. Noll, Calvin J. Curtis, Alex Miedaner, Brian Cox, Daniel L. DuBois
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  ABSTRACT: The bis(triphosphine) ligand C6H4{P[CH2CH2P(C6H11)2]2}2, m-(triphos)2 (1), is synthesized by the reaction of m-bis(phosphino)benzene with 4 equiv of vinyldicyclohexylphosphine. Reaction of 1 with 2 equiv of [Pd(CH3CN)4](BF4)2 results in the formation of the bimetallic complex {m-(triphos)2[Pd(CH3CN)]2}(BF4)4 (2). A structural study of 2 confirms the presence of two [Pd(triphosphine)(CH3CN)]2+ substituents at the meta positions of a benzene ring. Complex 2 catalyzes the electrochemical reduction of CO2 to CO in acidic dimethylformamide solutions. The kinetics of this reaction have been studied, and the reaction is 0.5 order in catalyst and first order in CO2. This catalyst exhibits catalytic rates comparable to that of its monometallic analogues. Significantly higher turnover numbers are observed for 2 than observed previously for monometallic, bimetallic, and dendritic complexes of this class of catalysts.
  06/2006;
• Article: Using ligand bite angles to control the hydricity of palladium diphosphine complexes.

  James W Raebiger, Alex Miedaner, Calvin J Curtis, Susie M Miller, Oren P Anderson, Daniel L DuBois
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  ABSTRACT: A series of [Pd(diphosphine)(2)](BF(4))(2) and Pd(diphosphine)(2) complexes have been prepared for which the natural bite angle of the diphosphine ligand varies from 78 degrees to 111 degrees. Structural studies have been completed for 7 of the 10 new complexes described. These structural studies indicate that the dihedral angle between the two planes formed by the two phosphorus atoms of the diphosphine ligands and palladium increases by over 50 degrees as the natural bite angle increases for the [Pd(diphosphine)(2)](BF(4))(2) complexes. The dihedral angle for the Pd(diphosphine)(2) complexes varies less than 10 degrees for the same range of natural bite angles. Equilibrium reactions of the Pd(diphosphine)(2) complexes with protonated bases to form the corresponding [HPd(diphosphine)(2)](+) complexes were used to determine the pK(a) values of the corresponding hydrides. Cyclic voltammetry studies of the [Pd(diphosphine)(2)](BF(4))(2) complexes were used to determine the half-wave potentials of the Pd(II/I) and Pd(I/0) couples. Thermochemical cycles, half-wave potentials, and measured pK(a) values were used to determine both the homolytic ([HPd(diphosphine)(2)](+) --> [Pd(diphosphine)(2)](+) + H*) and the heterolytic ([HPd(diphosphine)(2)](+) --> [Pd(diphosphine)(2)](2+) + H(-)) bond-dissociation free energies, Delta G(H*)* and Delta G(H-)*, respectively. Linear free-energy relationships are observed between pK(a) and the Pd(I/0) couple and between Delta G(H-)* and the Pd(II/I) couple. The measured values for Delta G(H*)* were all 57 kcal/mol, whereas the values of Delta G(H-)* ranged from 43 kcal/mol for [HPd(depe)(2)](+) (where depe is bis(diethylphosphino)ethane) to 70 kcal/mol for [HPd(EtXantphos)(2)](+) (where EtXantphos is 9,9-dimethyl-4,5-bis(diethylphosphino)xanthene). It is estimated that the natural bite angle of the ligand contributes approximately 20 kcal/mol to the observed difference of 27 kcal/mol for Delta G(H-)*.
  Journal of the American Chemical Society 05/2004; 126(17):5502-14. · 9.91 Impact Factor
• Article: Thermodynamic Studies of [HPt(EtXantphos)2]+ and [(H)2Pt(EtXantphos)2]2+

  Alex Miedaner, James W. Raebiger, Calvin J. Curtis, Susie M. Miller, Daniel L. DuBois
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  ABSTRACT: [HPt(EtXantphos)2](PF6) (where EtXantphos is 9,9-dimethyl-4,5-bis(diethylphosphino)xanthene) can be prepared by the reduction of Pt(COD)Cl2 (where COD is 1,4-cyclooctadiene) with hydrazine in the presence of 2 equiv of the diphosphine ligand followed by exchange of Cl- with PF6-. Deprotonation of [HPt(EtXantphos)2](PF6) (pKa = 27.3 in acetonitrile) leads to the formation of Pt(EtXantphos)2, which has been characterized by an X-ray diffraction study. Pt(EtXantphos)2 has a distorted tetrahedral geometry. The average chelate bite angle is 108.2°, and the dihedral angle between the two planes formed by the phophorus atoms of each diphophine ligand and platinum is 80.4°. Protonation of [HPt(EtXantphos)2]+ results in the formation of [(H)2Pt(EtXantphos)2]2+, which has a pKa of 6.8 in acetonitrile. Oxidation of Pt(EtXantphos)2 with ferrocenium tetrafluoroborate produces [Pt(EtXantphos)2]2+. [Pt(EtXantphos)2]2+ undergoes two reversible one-electron reductions (E1/2(II/I) = −0.81 V versus ferrocene and E1/2(I/0) = −0.97 V), and [HPt(EtXantphos)2]+ undergoes a reversible one-electron oxidation (E1/2(II/III) = +0.23 V). These half-wave potentials and the pKa values of [HPt(EtXantphos)2]+ and [(H)2Pt(EtXantphos)2]2+ have been used to calculate five additional homolytic and heterolytic bond-dissociation free energies for these two hydride species and for [HPt(EtXantphos)2]2+. The extensive thermodynamic characterization of this hydride system provides useful insights into the factors controlling the reactivity of these complexes.
  04/2004;
• Article: Hydricities of BzNADH, CH5Mo(PMe3)(CO)2H, and C5Me5Mo(PMe3)(CO)2H in acetonitrile.

  William W Ellis, James W Raebiger, Calvin J Curtis, Joseph W Bruno, Daniel L DuBois
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  ABSTRACT: The thermodynamic hydride donor abilities of 1-benzyl-1,4-dihydronicotinamide (BzNADH, 59 +/- 2 kcal/mol), C(5)H(5)Mo(PMe(3))(CO)(2)H (55 +/- 3 kcal/mol), and C(5)Me(5)Mo(PMe(3))(CO)(2)H (58 +/- 2 kcal/mol) have been measured in acetonitrile by calorimetric and/or equilibrium methods. The hydride donor abilities of BzNADH and C(5)H(5)Mo(PMe(3))(CO)(2)H differ by 13 and 24 kcal/mol, respectively, from those reported previously for these compounds in acetonitrile. These results require significant revisions of the hydricities reported for related NADH analogues and metal hydrides. These compounds are moderate hydride donors as compared to previously determined compounds.
  Journal of the American Chemical Society 04/2004; 126(9):2738-43. · 9.91 Impact Factor
• Article: Hydricities of BzNADH, C5H5Mo(PMe3)(CO)2H, and C5Me5Mo(PMe3)(CO)2H in Acetonitrile

  William W. Ellis, James W. Raebiger, Calvin J. Curtis, Joseph W. Bruno, Daniel L. DuBois
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  ABSTRACT: The thermodynamic hydride donor abilities of 1-benzyl-1,4-dihydronicotinamide (BzNADH, 59 ± 2 kcal/mol), C5H5Mo(PMe3)(CO)2H (55 ± 3 kcal/mol), and C5Me5Mo(PMe3)(CO)2H (58 ± 2 kcal/mol) have been measured in acetonitrile by calorimetric and/or equilibrium methods. The hydride donor abilities of BzNADH and C5H5Mo(PMe3)(CO)2H differ by 13 and 24 kcal/mol, respectively, from those reported previously for these compounds in acetonitrile. These results require significant revisions of the hydricities reported for related NADH analogues and metal hydrides. These compounds are moderate hydride donors as compared to previously determined compounds.
  02/2004;
• Article: [Ni(Et2PCH2NMeCH2PEt2)2]2+ as a functional model for hydrogenases.

  Calvin J Curtis, Alex Miedaner, Rebecca Ciancanelli, William W Ellis, Bruce C Noll, M Rakowski DuBois, Daniel L DuBois
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  ABSTRACT: The reaction of Et(2)PCH(2)N(Me)CH(2)PEt(2) (PNP) with [Ni(CH(3)CN)(6)](BF(4))(2) results in the formation of [Ni(PNP)(2)](BF(4))(2), which possesses both hydride- and proton-acceptor sites. This complex is an electrocatalyst for the oxidation of hydrogen to protons, and stoichiometric reaction with hydrogen forms [HNi(PNP)(PNHP)](BF(4))(2), in which a hydride ligand is bound to Ni and a proton is bound to a pendant N atom of one PNP ligand. The free energy associated with this reaction has been calculated to be -5 kcal/mol using a thermodynamic cycle. The hydride ligand and the NH proton undergo rapid intramolecular exchange with each other and intermolecular exchange with protons in solution. [HNi(PNP)(PNHP)](BF(4))(2) undergoes reversible deprotonation to form [HNi(PNP)(2)](BF(4)) in acetonitrile solutions (pK(a) = 10.6). A convenient synthetic route to the PF(6)(-) salt of this hydride involves the reaction of PNP with Ni(COD)(2) to form Ni(PNP)(2), followed by protonation with NH(4)PF(6). A pK(a) of value of 22.2 was measured for this hydride. This value, together with the half-wave potentials of [Ni(PNP)(2)](BF(4))(2), was used to calculate homolytic and heterolytic Ni-H bond dissociation free energies of 55 and 66 kcal/mol, respectively, for [HNi(PNP)(2)](PF(6)). Oxidation of [HNi(PNP)(2)](PF(6)) has been studied by cyclic voltammetry, and the results are consistent with a rapid migration of the proton from the Ni atom of the resulting [HNi(PNP)(2)](2+) cation to the N atom to form [Ni(PNP)(PNHP)](2+). Estimates of the pK(a) values of the NiH and NH protons of these two isomers indicate that proton migration from Ni to N should be favorable by 1-2 pK(a) units. Cyclic voltammetry and proton exchange studies of [HNi(depp)(2)](PF(6)) (where depp is Et(2)PCH(2)CH(2)CH(2)PEt(2)) are also presented as control experiments that support the important role of the bridging N atom of the PNP ligand in the proton exchange reactions observed for the various Ni complexes containing the PNP ligand. Similarly, structural studies of [Ni(PNBuP)(2)](BF(4))(2) and [Ni(PNP)(dmpm)](BF(4))(2) (where PNBuP is Et(2)PCH(2)N(Bu)CH(2)PEt(2) and dmpm is Me(2)PCH(2)PMe(2)) illustrate the importance of tetrahedral distortions about Ni in determining the hydride acceptor ability of Ni(II) complexes.
  Inorganic Chemistry 02/2003; 42(1):216-27. · 4.60 Impact Factor
• Article: HRh(dppb)2, a Powerful Hydride Donor

  Andrew J. Price, Rebecca Ciancanelli, Bruce C. Noll, Calvin J. Curtis, Daniel L. DuBois, M. Rakowski DuBois
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  ABSTRACT: The Rh(I) and Rh(III) hydrides HRh(dppb)2 and [HRh(dppb)2(NCCH3)](BF4)2 (where dppb is 1,2-(bis(diphenylphosphino)benzene) have been prepared, and a structural study of [HRh(dppb)2(NCCH3)](BF4)2 has been completed. The latter complex is an octahedral complex with a trans arrangement of the hydride and acetonitrile ligands. A pKa value of 9.4 was measured for this complex by equilibration of [Rh(dppb)2](BF4) with 4-bromoanilinium tetrafluoroborate in acetonitrile. [Rh(dppb)2](BF4) reacts with H2 in the presence of Pt(dmpp)2, which acts as a base, to form HRh(dppb)2 and [HPt(dmpp)2](BF4) (where dmpp = 1,2-bis(dimethylphosphino)propane). An equilibrium constant of 0.42 ± 0.2 was measured for this reaction. Using this equilibrium measurement and a thermodynamic cycle, the hydride donor ability (ΔG°H-) of HRh(dppb)2 was determined to be 34 kcal/mol. This value indicates that HRh(diphosphine)2 complexes are powerful hydride donors. Similarly the pKa value of HRh(dppb)2 was calculated to be 35 from a thermodynamic cycle that included the potential of the Rh(I/−I) couple (E1/2 = −2.02 V vs ferrocene). These results combined with results from the literature suggest the following order of hydricity for five-coordinate, 18-electron hydrides:  second row > third row > first row. Similarly an acidity order of second row ≥ first row > third row is deduced.
  09/2002;
• Article: Electrochemical Reduction of CO2 Catalyzed by a Dinuclear Palladium Complex Containing a Bridging Hexaphosphine Ligand: Evidence for Cooperativity

  Bryan D. Steffey, Calvin J. Curtis, Daniel L. DuBois
  04/2002;
• Article: Generation of metal formyl complexes using nickel and platinum hydrides as reducing agents

  Alex Miedaner, Daniel L. DuBois, Calvin J. Curtis, R. Curtis Haltiwanger
  04/2002;