bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ligand‐ Substrate Communication in Group 4 Aminopyridinato Complexes
Authors: Oberthür Markus , Hillebrand Gerhard , Arndt Perdita , Kempe Rhett 
Published: July 2007

AbstractTris(aminopyridinato) zirconium and ansa‐aminopyridinato titanium complexes have been sythesized. The reaction of (TMS‐APy)3‐Zr‐Cl (4‐methyl‐2‐trimethylsilyl‐aminopyridine=TMS‐APy‐H) with trimethylsilylbutadiynyl lithium generated in situ affords (TMS‐APy)3ZrCCCCTMS (1). (TMS‐apy)3‐Zr‐Me2 (2). Compound 2 shows an agostic interaction of the dimethylamido moiety. The reaction of Ti(NMe,2),4 with silox(Apy‐H)21,3‐di(4′‐picolin‐2′‐yl‐amino)‐1,1,3,3‐tetraisopropyldisiloxane=silox (APy‐H)2] gives rise to silox(Apy)2‐Ti‐(NMe2)2‐Ti‐[NMe,2)2 (3). Complex 3 reacts with ε‐caprolactam to form a caprolactamato complex (4). X‐ray crystal structure analyses of 1, 2, 3 and 4 are reported. The complexes 1, 2, 3 and 4 may be considered to be strained donor‐functionalized amido(metal) complexes due to the η2 binding mode of the ligand cores,
TMS‐APy and silox(APy)2, to meet the requirements of the ancillary coordinated substrates is observed. Thus, aminopyridinato complexes seem to be valuable model compounds for investigations of ligand‐substrate communications in early transition metal chemistry.
N‐Alkylation of Ammine—Undecahydro‐Closo‐dodecaborate(1−)
Authors: Peymann Toralf , Lork Enno , Schmidt Martin , Nöth Heinrich , Gabel Detlef 
Published: July 2007

AbstractThe reactions of the ammine‐undecahydro‐closo‐dodecaborate(1−) anion with alkyl halides have been studied in detail. The degree of alkylation of the nitrogen was found to be dependent upon the steric demands of the alkyl groups. The derivatives were characterized by NMR and infrared spectroscopy. Four compounds were crystallized for single crystal X‐ray diffraction studies. The tetrahedral coordination of the nitrogen atom of the bis‐alkylated derivatives was found to deviate towards planarity with increasing steric hindrance of the substitutents. ‐ The syntheses, crystal structures, and spectral properties of four N‐alkyl derivatives of [H3NB12H11]‐, ammine—undecahydro‐closo‐dodecaborate(1−) (3), are reported. Alkylation of 3 with ethyl iodide was achieved in dimethyl sulfoxide using potassium hydroxide as base. This led to orthorhombic crystals of [N(nC4H94][(CH3CH2)3NB12H11] (4). The reaction of 3 with benzyl chloride resulted in the bisbenzylated product, isolated as triclinic crystals of [PPN][(C6H5CH2)2 NHB12H11] (5). The alkylation of 3 with 2‐bromopropane gave a mixture of the mono‐ and bisalkylated products. The monoalkylated derivative [PPN][(CH3)2CH)NH2–12H11] (6, crystallized in the triclinic space group p1) and the bisalkylated product [PPN]{[(CH3)2NHB12H11) (7, monoclinic, P21./c) were separated on the basis of their different water solubilities. The solid‐state structures of the compounds 4–7 revealed a slight distortion of the B12 icosahedron. The length of the B(1)–N(1) bond was found to be dependent on the steric requirements of the attached amine, e.g. primary amine < secondary amine < tertiary amine. This is demonstrated by the variation in the BN bond length; from 157.8(2) pm for 6, 158.5(5) pjm for 5, 160.0(3) pm for 7, to 163.7(6) pm for 4.
Mono‐ and Bicyclic Organometallic Ring Systems with Exocyclic CC and CS Bonds
Authors: Werner Helmut , Xiaolan Liu , Peters Karl , von Schnering Hans Georg 
Published: July 2007

AbstractThe cobaltaheterocycles [C5H5Co{κ2(C,S)‐C(=CH2)‐N(R)C(=S)S](PMe2Ph)] (5‐7), which contain both an exocyclic CC and CS bond, were prepared from the iminoacylcobalt compounds [C5H5Co(C(CH3)=NCH} (PMe2Ph)]I (2‐4) on treatment with either CS2/NaOCH3 or K[S2CNMe2], respectively. While protonation of 5 (R = CH3) and 7 (R = CH2Ph) with HBF4 occurs at the exocyclic CCH2 bond to give cations containing a CoC(CH3)N(R)C(=S)S ring, the methylation of 5 and 7 with [OMe3]BF4 takes place at the exocyclic CS bond and generates five‐membered heterocycles heterocycles with an SCH4 substituent. The reaction of 5‐7 with S8 leads to the elimination of the phosphane ligand and affords the bicyclic dithiolenecobalt complexes 14 ‐ 16 in moderate to good yields. On treatment of 5‐7 with C2(CO2R′)2 (R′ = Me,Et), an insertion of the alkyne into the CCH2 bond occurs and five‐membered ring systems 19‐22 with an unsaturated exocyclic =C(CO2R′)‐C(CO2R′)=CH2 group are formed. As in the case of 5 and 7, protonation and methylation reactions of 19 also take place at different sites leading to cations with either a delocalized CoCN or NCS unit.
Chemistry in Environmentally Benign Media, 8 Hydroxymethyl Functionalized Phosphanes as Building Blocks to new Water‐Soluble Gold(I) Complexes ‐ synthesis, Characterization, and X‐ray crystal Structures of Novel Tetrahedral [Au{P(CH2OH)3}4]+ and Trigonal Planar [Au(Ph2PCH2OH)3]+ Gold (I) Complexes
Authors: Berning Douglas E. , Katti Kattesh V. , Barnes Charles L. , Volkert Wynn A. 
Published: July 2007

AbstractThe reactions of water‐soluble phosphanes P(CH2OH)3 (1) and Ph2PCH2OH (2) with NaAuCl4 in aqueous or alcoholic media, produced the water/alcoholic‐soluble AuI complexes [Au(Ph(CH2OH)3)4]+ (3) and [Au(Ph2PCH2OH)3+ (4) in near quantitative yields. The X‐ray structures of 3 and 4, reported in this paper, confirm the structures of these new generation of water‐soluble transition metal complexes. All compounds were characterized by 1H‐, 13C‐, 31P‐NMR spectroscopy and mass spectrometry. The structures of 3 and 4 were determined by X‐ray crystallography.
Complex Catalysis, XLIX On the Coordination of Olefins and Secondary Amines at the Cationic [2,6‐Bis(diphenylphosphanylmethyl)pyridine]rhodium(I) Fragment [Rh(PNP)]+ ‐ Synthesis and Characterization of [Rh(PNP)(L)]X (L = Ethylene, Styrene, HNR2; X = BF4, PF6, CF3SO3)
Authors: Hahn Christine , Sieler Joachim , Taube Rudolf 
Published: July 2007

AbstractThe cationic rhodium(1) complexes [Rh(PNP)(C2H4)]X; X = BF4 (1a), PF6 (1b), CF3SO3 (1c ) were prepared by addition of the tridentate ligand 2,6‐bis(diphenylphosphanylmethyl)pyridine (PNP) to a solution of [Rh(C2H4)2(solv)2]X (solv = acetone or THF) under ethylene. The complexes were characterized by IR and 1H‐, 13C‐, and 31P‐NMR spectroscopy. The coordination of two ethylene molecules at the [Rh(PNP)]+ fragment could be detected by dynamic proton resonance of a solution of 1a under free ethylene. The styrene complex [Rh(PNP)(styrene)]BF4 (4) was obtained by substitution of the ethylene from 1a with an excess of styrene. The π coordination of C2H4 and styrene in 1a and 4 respectively was confirmed by X‐ray crystal structure analysis. The olefin complexes react with an excess of the secondary amine to give the corresponding amine complexes [Rh(PNP)(HNR2)]X; HNR2 = piperidine (5), HNMe2 (6 ), HNEt2 (7). Conversly, the amine could be released from the amine complexes with an excess of ethylene at low temperature by the formation of the ethylene complex 1.
Synthesis and Iron‐Binding Properties of Protochelin, the Tris (catecholamide) Siderophore of Azotobacter vinelandii
Authors: Dubme Anne‐Kathrin , Hider Robert Charles , Khodr Hicham Hussein 
Published: July 2007

AbstractProtochelin, the tris(catecholamide) siderophore recently identified in the culture medium of A. vinelandii, can be synthesised by coupling of suitably protected azotochelin and aminochelin derivatives in preparative yields, Based on the ligand protonation constants of pK1 = 6.67, pK2 = 8.09 and pK3 = 9.68, the proton‐independent stability constant for ferric protochelin could be estimated to be 1044.6. The solubilisation of FeIII hydroxide by protochelin has been investigated spectrophotometrically in aqueous solution at pH = 7. Since the production of protochelin by A. vinelandii depends on high molybdate levels in the growth medium, the studies have been carried out in the presence as well as in the absence of an equimolar amount of molybdate. Although the protochelin promoted dissolution of FeIII hydroxide is delayed significantly in presence of molybdate, the effect is far less pronounced than the one observed for azotochelin, the bis(catecholamide) siderophore of A. vinelandii.
Zinc Pyrazolylborate Complexes with Phenoxide and Alkoxide Ligands
Authors: Walz Rainer , Weis Karl , Ruf Michael , Vahrenkamp Heinrich 
Published: July 2007

AbstractThe zinc hydroxide complexes Tp*Zn‐OH of highly substituted pyrazolylborate ligands react with phenols, and alcohols, of sufficient acidity, in a condensation reaction with release of H2O. Starting with phenols the following were attached:phenolate, p‐nitropehnolate, o‐vanillinate, o‐hydroxymethylphenolate, o,o‐bis(hydroxymethyl) ‐p‐methylphenolate. Whilst aliphatic alcohols and benzyl alcohol did not react, their derivatives, with highly electronegative substituents could be incorporated. Thus, the arylmethoxides OCH2C6F5 and OCH2C6H4NO2‐p, as well as the alkoxides OCH2CF3 and OCH2CCl3, were attached. 2‐Mercaptoethanol was bound via its thiolate function. The crystal structures of TpCum,Me ZN‐OC6H4NO2‐p,TpCum,Me ZN‐OCH2‐C6F5, TpCum,Me ZN‐OCH2CF3, TpCum,Me ZN‐OCH2CCl3 and TpCum,MeZn‐SCH2CH2OH were determined.
New Coupling Reactions and Phosphorylations Using Organozinc Reagents
Authors: Knochel Paul , Langer Falk , Longeau Alexia , Rottländer Mario , Stüdemann Thomas 
Published: July 2007

AbstractThis Microreview on the chemistry of organozinc reagents starts by briefly showing the methods of preparation of organozinc compounds and then discusses the considerable synthetic utility of zinc organometallics for the formation of new carbon‐carbon bonds in the presence of transition‐metal catalysts. Finally, the use of organozinc chemistry for the preparation of polyfunctional and chiral phosphanes is described.
Synthesis and Structure of Allenyl‐Substituted η6‐Benzene(tricarbonyl)‐chromium Complexes
Authors: Müller Thomas J. J. , Ansorge Markus 
Published: July 2007

AbstractThe Cr(CO)3‐complexed η6‐phenylpropargylic alcohols 3 react in a displacement rearrangement with thionyl chloride or chlorodiphenylphosphane to give the chloro‐ or phosphoryl allenyl substituted η6‐phenyl complexes 4 and 6, respectively. In the X‐ray crystal structure of the novel organometallic allenic derivatives 4b and 6b the vicinal chloro or phosphoryl substituent and the benzene(tricarbonyl)chromium fragment are arranged coplanarily. Palladium/copper‐catalyzed couplings of the chloroallene 4b with terminal alkynes disclose a facile access to ynallene derivatives 8, novel carbon‐rich organometallic π‐systems.
Tripod Ligands Containing a Mixed P/N/S Doner Set: Synthesis and Coordination Chemistry
Authors: Jacobi Albrecht , Huttner Gottfried , Winterhalter Ute 
Published: July 2007

AbstractThe preparation of neopentane‐based tripod ligands CH3C(CH2X)(CH2Y)(CH2Z( 3 (X = NR2, NHR; Y = PR2; Z = PR2, SR, S−) in a convergent manner is described. The procedure is based on the aminolytic cleavage of functionalized oxetanes CH3C(CH2OCH2)CH2R 1 by primary or secondary amines, leading to functionalized amino alcohols CH3C(CH2NHR)(CH2OH)(CH2R) or CH3C(CH2NR2)‐(CH2OH)(CH2R) 2. The appropriate activation of the R (e.g. OR) and OH groups present in 2 allows for substitution vs. SR or PR2 donor functions. Depending on the nature of the groups present in each reaction step, various protection and groups present in each reaction step, various protection and deprotection steps have to be taken in the course of this type of preparation of the tripod ligands 3. By reaction with (CH3CN)3Mo(CO)3, ligands 3 form Mo(CO)4 derivatives 4 or Mo(CO)3 derivatives 5, depending on the reaction conditions. In compounds 4, the ligands are coordinated in a bidentate mode with the soft donor atoms (P, S) coordinated and the hard donor function playing the role of the dangling arm. In the trihapto bonding mode present in 5, all three donor functions, two soft (P, S) and one hard (NHR′, NR′2), are coordinated. The two types of coordination compounds may be interconverted: 4e (X = NMe2′ Y = PPh2, Z = SiPr) with a non‐coordinating CH2NMe2 group is transformed into 5c upon photolytic decarbonylation. Under 1 bar CO at 20°C, 5c reverts to 4e. X‐ray structure analysis of a series of compounds of types 4 and 5 reveals characteristics of the relevant conformational patterns. All compounds have been fully characterized by the standard analytical techniques (NMR, MS), as well as elemental analysis.
Coronary artery ectasia–Is it time for a reappraisal?
Authors: Ramappa P. , Kottam A. , Kuivanemi H. , Thatai D. 
Published: July 2007

AbstractCoronary artery ectasia (CAE) is a well recognized clinical entity encountered during diagnostic cardiac catheterization. The etiopathogenesis of this condition is poorly understood. Due to the frequent presence of associated obstructive coronary artery disease it is considered to be a maladaptive process of atherosclerosis. Based on its association with aortic aneurysm, coronary ectasia is considered to be caused by genetic abnormalities. It is usually not a benign condition, as normal smooth laminar flow is disrupted with a potential of thrombus formation. The role of long‐term anticoagulation in this condition has not been well established. It is speculated that with increasing use of newer, noninvasive modalities the incidence of ectasia may rise, therefore necessitating this review. Copyright © 2007 Wiley Periodicals, Inc.
Portable enhanced external counterpulsation for Acute Coronary Syndrome and cardiogenic shock: A pilot study
Authors: Cohen, Joshua , Grossman, William , Michaels, Andrew D. 
Published: July 2007

AbstractBackgroundEnhanced external counterpulsation (EECP) currently is used as an outpatient therapy for patients with refractory chronic angina.HypothesisWe sought to determine the safety and feasibility of a portable EECP unit to treat patients with acute coronary syndrome and/or cardiogenic shock in the coronary care unit (CCU).MethodsTen patients with acute coronary syndrome and/or cardiogenic shock who were not considered candidates for invasive intra‐aortic balloon counterpulsation (IABP) by the treating cardiologist were prospectively enrolled in this single‐center study. Each patient received 2–4 one‐hour EECP treatments performed at the bedside in the CCU. Anticoagulation or recent femoral access was not an exclusion criterion.ResultsThe mean age was 58 ± 19 years (range 28–81), and half were women. Patients had either acute coronary syndrome alone (n = 4), cardiogenic shock alone (n = 3), or both (n = 3). The cardiac indications for study enrollment included: acute inferior wall ST‐segment elevation myocardial infarction with cardiogenic shock (n = 2), non‐ST‐segment elevation myocardial infarction with postinfarction angina (n = 2) or heart failure (n = 1), unstable angina with refractory rest angina (n = 2), cardiogenic shock from ischemic cardiomyopathy with severe mitral regurgitation (n = 1), and cardiogenic shock from nonischemic cardiomyopathy (n = 2). No adverse events were recorded during or as a consequence of EECP therapy, including no bleeding complications, no heart failure exacerbations, and no skin breakdown. The portable EECP unit did not interfere with ongoing critical care nursing.ConclusionsEECP is safe and feasible for acute bedside therapy of critically ill patients with acute coronary syndrome and/or cardiogenic shock who are not candidates for IABP. Copyright © 2007 Wiley Periodicals, Inc.
Amphiphilic Poly[(propylene glycol)‐block‐(2‐methyl‐2‐oxazoline)] Copolymers for Gene Transfer in Skeletal Muscle
Authors: Brissault Blandine , Kichler Antoine , Leborgne Christian , Jarroux Nathalie , Cheradame Hervé , Guis Christine 
Published: July 2007

AbstractAmphiphilic triblock copolymers such as poly(ethylene glycol‐b‐propylene glycol‐b‐ethylene glycol) PE6400 (PEG13‐PPG30‐PEG13) have been recently shown to promote gene transfer in muscle. Herein we investigated the effect of a chemical change of the PEG moiety on the transfection activity of these compounds. We synthesized new amphiphilic copolymers in which the PEG end blocks are replaced by more hydrophilic poly(2‐methyl‐2‐oxazoline) (PMeOxz) chains of various lengths. The resulting triblock PMeOxz‐PPG‐PMeOxz compounds were characterized by NMR, SEC, TGA, and DSC techniques and assayed for in vivo muscle gene transfer. The results confirm both the block structure and the monomer unit composition (DPPG/DPMeOxz) of the new PPG34‐PMeOxz41 and PPG34‐PMeOxz21 triblock copolymers. Furthermore, in vivo experiments show that these copolymers are able to significantly increase DNA transfection efficiency, despite the fact that their chemical nature and hydrophilic character are different from the poloxamers. Overall, these results show that the capacity to enhance DNA transfection in skeletal muscle is not restricted to PEG‐PPG‐PEG arrangements.
Generation of a conditional Ppap2b/Lpp3 null allele
Authors: Escalante‐Alcalde Diana , Sánchez‐Sánchez Roberto , Stewart Colin L. 
Published: July 2007

AbstractLpp3, formerly known as Pap2b, is a lipid phosphohydrolase enzyme. Some of its substrates and products are lipids with potent biological and signaling activities such as phosphatidic acid, lysophosphatidic acid, sphingosine‐1‐phosphate, diacylglycerol, sphingosine, and ceramide. Lpp3 is dynamically expressed during development and is widely distributed in adult tissues. Targeted inactivation of Lpp3 gene (Ppap2b) in the mouse results in embryonic lethality because of defects in extraembryonic vascular development and gastrulation. To study the participation of Lpp3 later in development and in specific cell lineages we generated a conditional allele of Ppap2b. This was accomplished by flanking critical exons, responsible for its catalytic activity with loxP sites. A generalized Cre‐mediated recombination of this allele yielded a phenotype fundamentally identical to our previously reported Ppap2b null allele. genesis 45:465–469, 2007. Published 2007 Wiley‐Liss, Inc.
A fate map of Tbx1 expressing cells reveals heterogeneity in the second cardiac field
Authors: Huynh Tuong , Chen Li , Terrell Phillip , Baldini Antonio 
Published: July 2007

AbstractTbx1 is required for the expansion of second heart field (SHF) cardiac progenitors destined to the outflow tract of the heart. Loss of Tbx1 causes heart defects in humans and mice. We report a novel Tbx1Cre knock‐in allele that we use to fate map Tbx1‐expressing cells during development in conjunction with a reporter and 3D image reconstruction. Tbx1 descendants constitute a mesodermal cell population that surrounds the primitive pharynx and approaches the arterial pole of the heart from lateral and posterior, but not anterior directions. These cells populate most of the outflow tract with the exception of the anterior portion, thus identifying a population of the SHF of distinct origin. Both myocardial and underlying endocardial layers were labeled, suggesting a common origin of these cell types. Finally, we show that Tbx1Cre‐positive and Tbx1Cre‐negative cell descendants occupy discrete domains in the outflow tract throughout development. genesis 45:470–475, 2007. Published 2007 Wiley‐Liss, Inc.
Organic Photochemical Rearrangements of Triplets and Zwitterions; Mechanistic and Exploratory Organic Photochemistry
Authors: Zimmerman Howard E. , Suryanarayan Vijay 
Published: July 2007

AbstractThere has been some controversy about the mechanisms of reactions of enones and dienones. The question has been whether a zwitterion or diradical is involved as the intermediate. In the case of ground state species it has not been recognized that zwitterions may have diradical character. In triplet reactions there is the question of whether the rearrangements take place at the initial T1 stage or subsequently as S0 ground state zwitterions or diradicals. We now have some new rearrangements bearing on these questions. In some cases it is the triplet which rearranges, while in others it is the S0 zwitterion. The zwitterion vs. diradical nature of the S0 species has been assessed by both experimental as well as theoretical means. Similarly, both experiment and computational theory have been used to determine at what stage the triplet rearrangements occur and to determine the characteristics of the rearranging species. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Geomorphic and riparian forest influences on characteristics of large wood and large‐wood jams in old‐growth and second‐growth forests in Northern Michigan, USA
Authors: Morris Arthur E. L. , Goebel P. Charles , Palik Brian J. 
Published: July 2007

AbstractLarge wood (LW; pieces with diameter greater than 10 cm and length greater than 1 m) and large‐wood jams (LWJs; two or more pieces of LW in contact with each other) are important components of stream ecosystems that are often distributed along stream channels in response to geomorphic and riparian forest factors that interact hierarchically. As a result, information on these relationships is valuable for predicting patterns of wood accumulation and characteristics of individual pieces of wood. We studied relationships between geomorphic and riparian factors and LW and LWJ structure in different geomorphic settings associated with old‐growth and second‐growth settings in Upper Michigan. We used redundancy analysis (RDA) and regression tree analysis to evaluate changes in LW and LWJ structural characteristics among geomorphic and riparian forest settings. Geomorphic factors explained 38·5% of the variability in LW and LWJ characteristics, riparian forest factors uniquely explained 18·4% of the variance and the intersection of the two categories of environmental factors (i.e. the redundant portion) was 29·8%. At the landscape scale, our multivariate analyses suggest that the presence of rock‐plane bedding was an important predictor of the number of LWJs and the percent of channel spanned by LWJs. Our analyses suggest differences in relationships between geomorphic factors and LW and LWJ structure. Channel width, distance from headwaters, gradient and sinuosity were identified by regression tree analyses as the most important variables for predicting LW characteristics, while channel width and confinement were the most important variables for predicting LWJ characteristics. Old‐growth settings generally contained a higher proportion of conifer and LW (both in and out of LWJs) with greater diameter and volume than in second‐growth settings. Our study supports the view that restoration of wood to streams will benefit from considering the associations of wood structure with landscape and reach‐scale geomorphology. Copyright © 2007 John Wiley & Sons, Ltd.