Safety and Outcome of Transsphenoidal Pituitary Adenoma Resection in Elderly Patients.

Objective: Pituitary adenomas account for 10%-20% of intracranial brain tumors but have greater incidence in elderly patients. We assessed microsurgical treatment for pituitary adenomas in this population.

Methods: A retrospective cohort of patients ≥60 years of age was identified.

Anxious anticipation prolongs emotional interference for rapid visual detection.

When we view emotionally arousing images, our perception of stimuli that follow soon afterward is transiently impaired-a phenomenon known as emotion-induced blindness. Previous studies have demonstrated that the magnitude and time course of this visual processing impairment is exaggerated by the presence of psychopathology and anxiety-related traits. Here, we tested whether emotional interference on a primary task can be modulated on a more dynamic basis, by the anticipation of unpredictable electric shock.

Crystal structure of di-methyl-formamidium bis-(tri-fluoro-methane-sulfon-yl)amide: an ionic liquid.

At 100 K, the title mol-ecular salt, CHNO·CFNOS, has ortho-rhom-bic (222) symmetry; the amino H atom of bis-(tri-fluoro-methane-sulfon-yl)amine (HNTf) was transferred to the basic O atom of di-methyl-formamide (DMF) when the ionic liquid components were mixed. The structure displays an O-H⋯N hydrogen bond, which links the cation to the anion, which is reinforced by a non-conventional C-H⋯O inter-action, generating an (7) loop. A further very weak C-H⋯O inter-action generates an [001] chain.

Controlling Proton Delivery through Catalyst Structural Dynamics.

The fastest synthetic molecular catalysts for H production and oxidation emulate components of the active site of hydrogenases. The critical role of controlled structural dynamics is recognized for many enzymes, including hydrogenases, but is largely neglected in designing synthetic catalysts. Our results demonstrate the impact of controlling structural dynamics on H production rates for [Ni(P N ) ] catalysts (R=n-hexyl, n-decyl, n-tetradecyl, n-octadecyl, phenyl, or cyclohexyl).

Putting chromium on the map for N2 reduction: production of hydrazine and ammonia. A study of cis-M(N2)2 (M = Cr, Mo, W) bis(diphosphine) complexes.

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(+) and NH4(+) from the reduction of the N2 ligands.

Combined Spectroscopic and Electrochemical Detection of a Ni(I) ⋅⋅⋅H-N Bonding Interaction with Relevance to Electrocatalytic H2 Production.

The [Ni(P(R) 2 N(R') 2 )2 ](2+) family of complexes are exceptionally active catalysts for proton reduction to H2 . In this manuscript, we explore the first protonation step of the proposed catalytic cycle by using a catalytically inactive Ni(I) complex possessing a sterically demanding variation of the ligand. Due to the paramagnetic nature of the Ni(I) oxidation state, the protonated Ni(I) intermediate has been characterized through a combination of cyclic voltammetry, electron nuclear double resonance (ENDOR) spectroscopy, and hyperfine sublevel correlation (HYSCORE) spectroscopy.

Water-assisted proton delivery and removal in bio-inspired hydrogen production catalysts.

Electrocatalysts for H2 production are envisioned to play an important role in renewable energy utilization systems. Nickel-based catalysts featuring pendant amines functioning as proton relays in the second coordination sphere of the metal center have led to catalysts achieving turnover frequencies as high as 10(7) s(-1) for H2 production. The fastest rates are observed when water is present in solution, with rates up to 10(3) times faster than those found in dry solvent.

Protonation studies of a mono-dinitrogen complex of chromium supported by a 12-membered phosphorus macrocycle containing pendant amines.

The reduction of fac-[CrCl3(P(Ph)3N(Bn)3)], (1(Cl3)), (P(Ph)3N(Bn)3 = 1,5,9-tribenzyl-3,7,11-triphenyl-1,5,9-triaza-3,7,11-triphosphacyclododecane) with Mg in the presence of dmpe (dmpe = 1,2-bis(dimethylphosphino)ethane) affords the first example of a monodinitrogen Cr(0) complex, Cr(N2)(dmpe)(P(Ph)3N(Bn)3), (2(N2)), containing a pentaphosphine coordination environment. 2(N2) is supported by a unique facially coordinating 12-membered phosphorus macrocycle containing pendant amine groups in the second coordination sphere. Treatment of 2(N2) at -78 °C with 1 equiv of [H(OEt2)2][B(C6F5)4] results in protonation of the metal center, generating the seven-coordinate Cr(II)-N2 hydride complex, [Cr(H)(N2)(dmpe)(P(Ph)3N(Bn)3)][B(C6F5)4], [2(H)(N2)](+).

Controlling proton movement: electrocatalytic oxidation of hydrogen by a nickel(II) complex containing proton relays in the second and outer coordination spheres.

A nickel bis(diphosphine) complex containing proton relays in the second and outer coordination spheres, Ni(P(Cy)2N((CH2)2OMe))2, (P(Cy)2N((CH2)2OMe) = 1,5-di(methoxyethyl)-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane), is an electrocatalyst for hydrogen oxidation. The addition of hydrogen to the Ni(II) complex results in rapid formation of three isomers of the doubly protonated Ni(0) complex, [Ni(P(Cy)2N((CH2)2OMe)2H)2](2+). The three isomers show fast interconversion at 40 °C, unique to this complex in this class of catalysts.

Dinitrogen reduction by a chromium(0) complex supported by a 16-membered phosphorus macrocycle.

We report a rare example of a Cr-N2 complex supported by a 16-membered phosphorus macrocycle containing pendant amine bases. Reactivity with acid afforded hydrazinium and ammonium, representing the first example of N2 reduction by a Cr-N2 complex. Computational analysis examined the thermodynamically favored protonation steps of N2 reduction with Cr leading to the formation of hydrazine.

Proton delivery and removal in [Ni(P(R)2N(R')2)2]2+ hydrogen production and oxidation catalysts.

To examine the role of proton delivery and removal in the electrocatalytic oxidation and production of hydrogen by [Ni(P(R)(2)N(R')(2))(2)](2+) (where P(R)(2)N(R')(2) is 1,5-R'-3,7-R-1,5-diaza-3,7-diphosphacyclooctane), we report experimental and theoretical studies of the intermolecular proton exchange reactions underlying the isomerization of [Ni(P(Cy)(2)N(Bn)(2)H)(2)](2+) (Cy = cyclohexyl, Bn = benzyl) species formed during the oxidation of H(2) by [Ni(II)(P(Cy)(2)N(Bn)(2))(2)](2+) or the protonation of [Ni(0)(P(Cy)(2)N(Bn)(2))(2)]. Three protonated isomers are formed (endo/endo, endo/exo, or exo/exo), which differ in the position of the N-H bond's with respect to nickel. The endo/endo isomer is the most productive isomer due to the two protons being sufficiently close to the nickel to proceed readily to the transition state to form/cleave H(2).

Acidic ionic liquid/water solution as both medium and proton source for electrocatalytic H2 evolution by [Ni(P2N2)2]2+ complexes.

The electrocatalytic reduction of protons to H(2) by [Ni((P(Ph)(2)N(C6H4-hex))(2)(2)]((BF(4))(2) (where P(Ph)(2)N(C6H4-hex)(2) = 1,5-di(4-n-hexylphenyl)-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) in the highly acidic ionic liquid dibutylformamidium bis(trifluoromethanesulfonyl)amide shows a strong dependence on added water. A turnover frequency of 43,000-53,000 s(-1) has been measured for hydrogen production at 25 °C when the mole fraction of water (χ(H(2)O)) is 0.72.

Synthesis, characterization, and reactivity of Fe complexes containing cyclic diazadiphosphine ligands: the role of the pendant base in heterolytic cleavage of H2.

The iron complexes CpFe(P(Ph)(2)N(Bn)(2))Cl (1-Cl), CpFe(P(Ph)(2)N(Ph)(2))Cl (2-Cl), and CpFe(P(Ph)(2)C(5))Cl (3-Cl)(where P(Ph)(2)N(Bn)(2) is 1,5-dibenzyl-1,5-diaza-3,7-diphenyl-3,7-diphosphacyclooctane, P(Ph)(2)N(Ph)(2) is 1,3,5,7-tetraphenyl-1,5-diaza-3,7-diphosphacyclooctane, and P(Ph)(2)C(5) is 1,4-diphenyl-1,4-diphosphacycloheptane) have been synthesized and characterized by NMR spectroscopy, electrochemical studies, and X-ray diffraction. These chloride derivatives are readily converted to the corresponding hydride complexes [CpFe(P(Ph)(2)N(Bn)(2))H (1-H), CpFe(P(Ph)(2)N(Ph)(2))H (2-H), CpFe(P(Ph)(2)C(5))H (3-H)] and H(2) complexes [CpFe(P(Ph)(2)N(Bn)(2))(H(2))]BAr(F)(4), [1-H(2)]BAr(F)(4), (where BAr(F)(4) is B[(3,5-(CF(3))(2)C(6)H(3))(4)](-)), [CpFe(P(Ph)(2)N(Ph)(2))(H(2))]BAr(F)(4), [2-H(2)]BAr(F)(4), and [CpFe(P(Ph)(2)C(5))(H(2))]BAr(F)(4), [3-H(2)]BAr(F)(4), as well as [CpFe(P(Ph)(2)N(Bn)(2))(CO)]BAr(F)(4), [1-CO]Cl. Structural studies are reported for [1-H(2)]BAr(F)(4), 1-H, 2-H, and [1-CO]Cl.

Synthesis and hydride transfer reactions of cobalt and nickel hydride complexes to BX3 compounds.

Hydrides of numerous transition metal complexes can be generated by the heterolytic cleavage of H(2) gas such that they offer alternatives to using main group hydrides in the regeneration of ammonia borane, a compound that has been intensely studied for hydrogen storage applications. Previously, we reported that HRh(dmpe)(2) (dmpe = 1,2-bis(dimethylphosphinoethane)) was capable of reducing a variety of BX(3) compounds having a hydride affinity (HA) greater than or equal to the HA of BEt(3). This study examines the reactivity of less expensive cobalt and nickel hydride complexes, HCo(dmpe)(2) and [HNi(dmpe)(2)](+), to form B-H bonds.

A rare terminal dinitrogen complex of chromium.

Cis and trans-Cr-N(2) complexes supported by the diphosphine ligand P(Ph)(2)N(Bn)(2) have been prepared. Positioned pendant amines in the second coordination sphere influence the thermodynamically preferred geometric isomer. Electronic structure calculations indicate negligible Cr-N(2) back-bonding; rather, electronic polarization of N(2) ligand is thought to stabilize Cr-N(2) binding.

Moving protons with pendant amines: proton mobility in a nickel catalyst for oxidation of hydrogen.

Proton transport is ubiquitous in chemical and biological processes, including the reduction of dioxygen to water, the reduction of CO(2) to formate, and the production/oxidation of hydrogen. In this work we describe intramolecular proton transfer between Ni and positioned pendant amines for the hydrogen oxidation electrocatalyst [Ni(P(Cy)(2)N(Bn)(2)H)(2)](2+) (P(Cy)(2)N(Bn)(2) = 1,5-dibenzyl-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane). Rate constants are determined by variable-temperature one-dimensional NMR techniques and two-dimensional EXSY experiments.

Binuclear complexes containing a methylnickel moiety: relevance to organonickel intermediates in acetyl coenzyme A synthase catalysis.

A series of binuclear NiNi complexes supported by a single thiolate bridge and containing a methylnickel moiety have been prepared and fully characterized. The complexes represent structural analogues for the proposed organonickel intermediate in the acetyl coenzyme A synthase catalytic cycle. Variable temperature 31P NMR spectroscopy was used to examine dynamic behavior of the thiolate bridging interaction in two of the derivatives.

Identification of Mn2+-binding aspartates from alpha, beta, and gamma subunits of human NAD-dependent isocitrate dehydrogenase.

The human NAD-dependent isocitrate dehydrogenase (IDH), with three types of subunits present in the ratio of 2alpha:1beta:1gamma, requires a divalent metal ion to catalyze the oxidative decarboxylation of isocitrate. With the aim of identifying ligands of the enzyme-bound Mn(2+), we mutated aspartates on the alpha, beta, or gamma subunits. Mutagenesis target sites were based on crystal structures of metal-isocitrate complexes of Escherichia coli and pig mitochondrial NADP-IDH and sequence alignments.