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Jennifer V Obligacion, Hongyu Zhong, Paul J Chirik
The activation of readily prepared, air-stable cobalt (II) bis(carboxylate) pre-catalysts for the functionalization of C( sp 2 )-H bonds has been systematically studied. With the pyridine bis(phosphine) chelate,iPr PNP, treatment of 1-(O2 Ct Bu)2 with either B2 Pin2 or HBPin generated cobalt boryl products. With the former, reduction to (iPr PNP)CoI BPin was observed while with the latter, oxidation to the cobalt(III) dihydride boryl, trans -(iPr PNP)Co(H)2 BPin occurred. The catalytically inactive cobalt complex, Co[PinB(O2 Ct Bu)2 ]2, accompanied formation of the cobalt-boryl products in both cases...
November 2017: Israel Journal of Chemistry
Hsiu-Jung Lin, Sean Lutz, Catherine O'Kane, Matthias Zeller, Chun-Hsing Chen, Talal Al Assil, Wei-Tsung Lee
A low-coordinate iron(ii) complex (Cz tBu (Pz tBu ) 2 )Fe[N(SiMe 3 ) 2 ], 1 bearing an NNN-pincer ligand was prepared and fully characterized. Intramolecular C-H activation on the 5-position of a pyrazole at elevated temperatures was observed. Complex 1 was found to be an efficient and chemoselective pre-catalyst for the hydrosilylation of organo carbonyl substrates.
February 15, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Brian J Cook, Chun-Hsing G Chen, Kenneth G Caulton
The divalent cobalt complex of the diprotic pincer ligand bis-pyrazolylpyridine, (H2L)CoCl2, is dehydrohalogenated twice by LiN(SiMe3)2 in the presence of PEt3 to give monomeric S = 1/2 LCo(PEt3)2, fully characterized in solid and solution as a square pyramidal monomer with a long axial Co-P bond. This 17 electron species reacts in time of mixing with N2O to form L2Co2(OPEt3) + 3 OPEt3, the former the first example of phosphine oxide bridging two transition metals. The same products are formed from O2, and divalent cobalt persists even in the presence of excess oxidant...
February 13, 2018: Chemistry: a European Journal
Eduardo Peris, Robert H Crabtree
Pincers, tridentate ligands that prefer a meridional geometry, are a rising class because of their distinctive combination of properties. They permit a good level of control on the nature of the coordination sphere by holding the donor groups in a predictable arrangement. Some groups, such as an aryl or a pyridine, that would normally be easily lost as monodentate ligands, become reliably coordinated, especially if they form the central donor unit of the three. Many pincer complexes show exceptional thermal stability, a property that is particularly prized in homogeneous catalysis where they can permit high temperature operation...
February 12, 2018: Chemical Society Reviews
Patrick Finton Carton, David Filan
Arthroscopic labral 'takedown' and refixation is utilized to permit adequate visualization and resection of the acetabular rim deformity, in patients with pincer or mixed femoroacetabular impingement. Deficiencies exist in present techniques, which include disruption of vital anatomical support and vascular structures to the labrum and chondrolabral junction, drill or anchor articular penetration risk, bunching, elevation and instability of the labrum. A new operative technique is described which preserves the important chondrolabral interface, accurately restoring the 'flap seal' of the acetabular labrum while minimizing vascular disruption and reducing the risk of drill and anchor penetration...
January 2018: Journal of Hip Preservation Surgery
Jennifer Tangtiphaiboontana, Alan L Zhang, Nirav K Pandya
Intra-articular injection of corticosteroid and anesthetic (CSI) is a useful diagnostic tool for hip pain secondary to labral tears or femoroacetabular impingement (FAI). However, the effectiveness of CSI as a stand-alone treatment for hip pain in adolescents is unknown. The purpose of this study is to evaluate the use of CSI for the treatment of hip pain and determine factors that may affect outcomes after injection. Retrospective analysis of 18 patients and 19 hips that underwent fluoroscopic guided hip injection for the treatment of pain at a single institution from 2012 to 2015 was carried out in this study...
January 2018: Journal of Hip Preservation Surgery
Quinton J Bruch, Brian M Lindley, Bjorn Askevold, Sven Schneider, Alexander J M Miller
A series of ruthenium(II) hydrido dinitrogen complexes supported by pincer ligands in different formal oxidation states have been prepared and characterized. Treating a ruthenium dichloride complex supported by the pincer ligand bis(di-tert-butylphosphinoethyl)amine (H-PNP) with reductant or base generates new five-coordinate cis-hydridodinitrogen ruthenium complexes each containing different forms of the pincer ligand. Further ligand transformations provide access to the first isostructural set of complexes featuring all six different forms of the pincer ligand...
February 8, 2018: Inorganic Chemistry
G Kalaiarasi, S Rex Jeya Rajkumar, S Dharani, Nigam P Rath, R Prabhakaran
New Schiff base ligands are prepared by the condensation of 7-hydroxy-3-formylchromone with semicarbazone and phenyl semicarbazone. The complexation of these ligands with Cu(II) ion is proposed in the light of spectral studies (IR, UV-Vis, 1H NMR, 13C NMR, Mass and ESR). In the complexes 1 and 2, the ligands coordinate to the Cu(II) ion in a neutral fashion via ONO donor atoms. The single crystal XRD studies reveal a slightly distorted square-pyramidal geometry for cationic complex (1) and an octahedral geometry for neutral complex (2)...
January 31, 2018: Journal of Photochemistry and Photobiology. B, Biology
H-L Qin, J Leng, W Zhang, E A B Kantchev
DFT calculations confirmed that the rearrangement of a PCP-Rh-H pincer to a CCP-Rh-phosphane pincer occured by C-P oxidative addition (ΔG‡ = 29.5 kcal mol-1, rate-determining step), followed by P-H reductive elimination (ΔG‡ = 4.8 kcal mol-1). The oxidative addition proceeded via a 3-centered transition state and is accelerated by electron-withdrawing substituents p- to the reacting C-P bond, resulting in a reaction constant (ρ) of 2.12 for ΔG‡ and 2.76 for ΔH‡ in a Hammett-type linear free energy relationship...
February 7, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Takahiro Ishikawa, Aya Nishizawa, Takahiro Satoh
No abstract text is available yet for this article.
February 1, 2018: European Journal of Dermatology: EJD
Alexander R Vap, Justin J Mitchell, Karen K Briggs, Shannen C McNamara, Marc J Philippon
PURPOSE: To determine the prevalence of chronic trochanteric bursitis (TB) in patient being treated for femoroacetabular impingement (FAI) and determine the effectiveness of arthroscopic bursectomy and iliotibial band lengthening (AB-ITB-L) at the time of hip arthroscopy for FAI. METHODS: Patients diagnosed with primary FAI and chronic TB were included in the study. Patients were included if they underwent hip arthroscopy with labral repair, femoral and/or acetabular osteoplasty, and AB-ITB-L...
January 27, 2018: Arthroscopy: the Journal of Arthroscopic & related Surgery
Kseniya K Borisova, Eugeniya V Nikitina, Roman A Novikov, Victor N Khrustalev, Pavel V Dorovatovskii, Yan V Zubavichus, Maxim L Kuznetsov, Vladimir P Zaytsev, Alexey V Varlamov, Fedor I Zubkov
The tandem [4+2] cycloaddition between hexafluoro-2-butyne and bis-furyl dienes, like difurfuryl ester, at room temperature leads to the kinetically controlled "pincer"-adducts - annulated 4a,8a-bis(trifluoromethyl)hexahydro-1,4:5,8-diepoxynaphthalenes. On the other hand, if these reactions proceed at 140 °C, only the thermodynamically controlled "domino"-adducts - annulated 2,3-bis(trifluoromethyl)hexahydro-1,4:5,8-diepoxynaphthalenes - are formed. Therefore, a very rare and unexpected example of full kinetic and thermodynamic control in the Diels-Alder reaction is reported in this paper...
February 2, 2018: Chemical Communications: Chem Comm
Robert Langer, Lisa Vondung, Lukas Alig, Monika Ballmann
Easy to prepare η²-coordinated phosphine-borane ligands are demonstrated to liberate hydrogen upon treatment with different σ-donor/π-acceptor ligands (CO, tBuNC, CN-). Depending on the utilized ancillary ligand different reaction pathways are observed, ranging from simple hydride protonation to iron-boron-bond formation and subsequent rearrangement to pincer-type ligands, which are based on a tri-coordinate boron centre. The latter reactivity is in line with a formal Umpolung at boron centre from a Lewis-acidic borane to a Lewis-basic boron-based donor ligand...
February 1, 2018: Chemistry: a European Journal
Anitha S Gowda, Jeffrey L Petersen, Carsten Milsmann
The three- and four-membered redox series [Cr(MePDP)2]z (z = 1-, 2-, 3-) and [Mo(MePDP)2]z (z = 0, 1-, 2-, 3-) were synthesized to study the redox properties of the pincer ligand MePDP2- (H2MePDP = 2,6-bis(5-methyl-3-phenyl-1H-pyrrol-2-yl)pyridine). The monoanionic complexes were characterized by X-ray crystallography, UV/vis/NIR spectroscopy, and magnetic susceptibility measurements. Experimental and density functional theory (DFT) studies are consistent with closed-shell MePDP2- ligands and +III oxidation states (d3, S = 3/2) for the central metal ions...
January 27, 2018: Inorganic Chemistry
Brian J Cook, Chun-Hsing Chen, Maren Pink, Kenneth G Caulton
The behavior of the complex (H2L)CoCl2, where H2L is a bis-(pyrazol-3-yl)pyridine, towards Brønsted bases is studied, to evaluate peripheral NH deprotonation as a route to a dianionic pincer ligand on a d7 center. Deprotonation is found to also remove chloride from cobalt, and the decreased metal coordination number is then satisfied by bimolecular reaction of the newly formed peripheral deprotonated pyrazolate nitrogen, leading to Co2 units bridged by some of the pyrazolates, in the analogous species [Co2(L)(LH)]2(L) and [Co2(L)(HL)]2[Co(L)2], but also occasionally by chloride retention, in LiCo2L2Cl...
January 22, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Sandra Y de Boer, Ties J Korstanje, Stefan R La Rooij, Rogier Kox, Joost N H Reek, Jarl Ivar van der Vlugt
The novel tridentate PNNOH pincer ligand LH features a reactive 2-hydroxypyridine functionality as well as a bipyridyl-methylphosphine skeleton for meridional coordination. This proton-responsive ligand coordinates in a straightforward manner to RuCl(CO)(H)(PPh3)3 to generate complex 1. The methoxy-protected analogue LMe was also coordinated to Ru(II) for comparison. Both species have been crystallographically characterized. Site-selective deprotonation of the 2-hydroxypyridine functionality to give 1' was achieved using both mild (DBU) and strong bases (KOtBu and KHMDS), with no sign of involvement of the phosphinomethyl side arm that was previously established as the reactive fragment...
April 24, 2017: Organometallics
Laura E Diamond, Kim L Bennell, Tim V Wrigley, Rana S Hinman, Michelle Hall, John O'Donnell, Paul W Hodges
BACKGROUND: Femoroacetabular impingment (FAI) syndrome is common among young active adults and a proposed risk factor for the future development of hip osteoarthritis. Pain is dominant and drives clinical decision-making. Evidence for altered hip joint function in this patient population is inconsistent, making the identification of treatment targets challenging. A broader assessment, considering adjacent body segments (i.e. pelvis, trunk) and individual movement strategies, may better inform treatment programs...
January 11, 2018: Gait & Posture
Matthew R Mills, Charles L Barnes, Wesley H Bernskoetter
Pincer ligated coordination complexes bearing bifunctional sites have been at the center of recent developments in reversible hydrogenation catalysis, especially in cases utilizing base metals. The influence of bifunctional ligands on low valent cobalt complexes is detailed here using comparisons between the PNP-pincer ligands MeN[CH2CH2(PR2)]2 and HN[CH2CH2(PR2)]2 (R = iPr, Cy). Comparative catalytic studies of CO2 hydrogenation show that cobalt(I) precatalysts bearing the tertiary amine ligand dramatically outperform those bearing the secondary amine pincer ligand...
January 19, 2018: Inorganic Chemistry
Dipankar Sahoo, Changho Yoo, Yunho Lee
Addition of CO2 to a low-valent nickel species has been explored with a newly designed acriPNP pincer ligand (acriPNP- = 4,5-bis(diisopropylphosphino)-2,7,9,9-tetramethyl-9H-acridin-10-ide). This is a crucial step in understanding biological CO2 conver-sion to CO found in carbon monoxide dehydrogenase (CODH). A four-coordinate nickel(0) state was reliably accessed in the pres-ence of a CO ligand, which can be prepared from a stepwise reduction of a cationic {(acriPNP)Ni(II)-CO}+ species. All three Ni(II), Ni(I) and Ni(0) monocarbonyl species were cleanly isolated and spectroscopically characterized...
January 17, 2018: Journal of the American Chemical Society
Bertrand Benoît, Maria A O'Connell, Zöe A E Waller, Manfred Bochmann
Cyclometalated (C^N^C)Au(III) complexes bearing functionalized N-heterocyclic carbene (NHC) ligands provide a high-yielding, modular route to bioconjugated and binuclear complexes. That methodology has been applied to the synthesis of bioconjugated complexes presenting biotin and 17α-ethynylestradiol vectors, as well as to the synthesis of bimetallic Au(III)/Au(I) complexes. The in vitro antiproliferative activities of these compounds against various cancer cells lines depend on the linker length, with the longer linker being the most potent...
January 15, 2018: Chemistry: a European Journal
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