bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of Mono‐, Di‐, and Tri‐arylgold(III) Complexes Using Organomercury Compounds – Synthesis of the First Aurated Schiff Bases
Authors: Vicente Jose , Berm údez María‐Dolores , Carri ón Francisco‐José , Jones Peter G.
Published: July 2007

The formylarylmercury(II) complex [Hg{C6H(CHO)‐6‐(OMe)3‐2,3,4}2] reacts with 4‐butylaniline (1:2) to give [Hg{C6H(CH=NC6H4C4H9‐4′)‐6‐(OMe) 3‐2,3,4}2] (1) by a condensation reaction. This complex reacts with Me4‐N[AuCl4] (1:1) to give [Hg{C6H(CH=NC6H4C4H9‐4′)‐6‐(OMe) 3‐2,3,4}Cl] (2) and the monoarylgold(III) compound cis‐C6H4‐nBu‐4′)‐6‐(OMe)3‐2,3,4}Cl2] (3). This complex reacts with PPh3 (1:1) to give the adduct cis‐[Au{C6H(CH=NC6H4‐n, Bu‐4′)‐6‐(OMe)3‐2,3,4}Cl2(PPh3)] (4) and with AgClO4 (1:1) in acetone to give the ketonyl complex cis‐[C6H4‐nBu‐4′)‐6‐ (OMe)3‐2,3,4}‐{CH2C(O)Me}Cl] (5). cis‐Me4N[Au(C6H4NO2‐2)2Cl 2] react with [Hg{C6H3(N=NC6H4OMe‐4′)‐2‐(OMe)‐5}Cl] and Me4NCl (1:1:1) to give cis‐[C6H4OMe‐4′)‐2‐ (OMe)‐5}(C6H4NO2‐2)2] (6): Similarly, cis‐Me4N‐[Au(C6H4CF3‐2)2 Cl2] (7), obtained by treating [Hg(C6H4CF3‐2)2] with Me4N[AuCl4] and Me4NCl (1:1:1), reacts with [Hg(C6H4CH2NMe2‐2)Cl] and Me4NCl (1:1:1) to give the triarylgold(III) complex cis‐[Me2‐2)(C6H4CF3‐2)2] (8). This complex can also be obtained by treating cis‐[Me2‐2)Cl2] with [Hg(C6H4CF3‐2)2] and Me4NCl (1:1:1). The crystal structure of 3 reveals the presence of two independent molecules, in one of which the butylphenyl group is disordered. The geometry at the gold atom is square planar; distortions may be attributed to the narrow bite angle and steric repulsion between a chloride ligand and the ortho‐methoxy group. The greater trans influence of the aryl ligand causes a great difference in Au–Cl bond lengths.
Molecular Gymnastics of Alkynes Orchestrated by Ruthenium Complexes
Authors: Trost Barry M.
Published: July 2007

Ruthenium complexes catalyze a variety of addition or isomerization reactions that are highly atom economical. Terminal alkynes react with allyl alcohols to form β,γ‐unsaturated ketones that can be readily isomerized to α,β‐unsaturated ketones via transient vinylidene complexes. A cyclization via a transient allenylidene complex concomitant with this addition represents a novel way to build heterocycles. Ancillary studies with these catalysts revealed an internal oxidation reduction whereby allyl alcohols are isomerized to saturated ketones and propargyl alcohols are isomerized to α,β‐unsaturated carbonyl compounds. Consideration of the reaction mechanism led to a general Alder ene type reaction wherein alkynes serve as the enophile and alkenes serve as the ene component. These discoveries have led to a number of efficient total syntheses of biologically interesting targets. Mechanistic investigations into the activation of a ruthenium complex led to the discovery of a novel bis‐homo‐Diels‐Alder reaction of 1,4‐cyclooctadiene.
Direct Synthesis of Organometallics, IV. The Mechanism of the Activation of Aromatic Hydrocarbons with Lithium Atoms: Spectroscopic Results and Their Ab initio Interpretation
Authors: Tacke Matthias
Published: July 2007

In the presence of THF, lithium atoms are known to be able to activate benzene derivatives under cryogenic reaction conditions. This synthesis affords solid lithium hydride and ring‐metalated products selectively. For the determination of the reaction mechanism, the cocondensation reaction was repeated on a reduced scale in a 77‐K cryostate, which allowed the measurement of UV/Vis and IR spectra. The spectroscopic results exclude any generation of free electrons; their interpretation suggests that small solvated lithium clusters activate the hydrocarbon bonds. A model reaction was developed by using the spectroscopic results and ab initio calculations. Thus, benzene was added to a Li2 cluster, which reduces the carbon‐hydrogen bond to the phenyl anion and hydride on the surface without the formation of free radicals. In the last step the intermediate mixed organolithium species dismutate to solid lithium hydride and phenyllithium.

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The reduction process on the cluster surface is facilitated by coordinating THF to the lithium, which results in a higher redox potential. The complete mechanism is discussed in the terms of geometries of the intermediates and reaction enthalpies in connection with the experimental values. Thus, a distinct new reaction pathway for a substitution on the benzene ring is established.
(Allyl)zirconium(IV) Complexes with the N,N′ ‐bis(trimethylsilyl)benzamidinato (“siam”) Ligand — Molecular Structures and η1–η3 Interconversions of the Allyl Groups
Authors: Walther Dirk , Fischer Reinald , Friedrich Manfred , Gebhardt Peter , Görls Helmar
Published: July 2007

Complexes of the type (siam)2Zr(allyl)2 (1a) and (siam)Zr(allyl)nClm are described (2a: n = 1, m = 2; 2b: n = 2, m = 1; 2c: n = 3, m = 0; siam: N,N′ ‐bis(trimethylsilyl)benzamidinato group). The molecular structure of 1a shows that both allyl groups are differently bonded. One allyl ligand is η3‐, the other η1‐coordinated. The X‐ray crystal structure of the tris‐(allyl) complex 2c shows a chiral molecule with two η3‐allyl ligands. The third allyl ligand is coordinated in a mode intermediate between η3 and η1, thus serving as a model for an intermediate in the η3‐η1 intramolecular rearrangement of the allyl ligands observed in solution. Temperature‐dependent 1H‐ and 13C‐NMR spectra of 1a, 2b and 2c indicate a rapid η1‐η3 rearrangement of the allyl groups at 60°C. At −50°C two different coordination modes of the allyl groups can be observed in the case of 2b and 2c.
Reactions of Tetrakis[bis(trimethylsilyl)methyl]digallane(4) with Carboxylic Acids — Substituent Exchange and Bridging of the GaGa bond by two Carboxylato Groups
Authors: Uhl Werner , Hahn Ingo , Reuter Hans
Published: July 2007

Yellow tetrakis[bis(trimethylsilyl)methyl]digallane(4) 1 reacts with two equivalents of the carboxylic acids RCOOH (R = −C6H5, −p−BrC6H4, −3,5‐Me2C6H3, −CMe3) to yield almost quantitatively colorless products in which two bis(trimethylsilyl)methyl groups are replaced by two carboxylato ligands. As shown by a crystal structure determination with the 4‐bromo‐phenyl derivative (3), the GaGa bond is bridged by both carboxylato groups in a chelating manner. The GaGa distance is shortened to 238.5(2) pm (1: 254.1(1) pm) and the coordination number of the Ga atoms increased to four.
The Coordination and Transformations of a Dicarboxylate Substituted Allene on a Dimanganese Carbonyl Grouping
Authors: Adams Richard D. , Huang Mingsheng
Published: July 2007

Two products, Mn2(CO)7(PMe2Ph)[μ‐η2‐η2‐MeO2C(H)CCC‐(H)CO2Me] (1) in 9% yield and Mn2(CO)6(PMe2Ph)[μ‐η3‐η1‐MeO2CC(H)CC(H)CO2Me] (2) in 34% yield, were obtained from the reaction of Mn2(CO)8(PMe2Ph)(MeCN) with MeO2C(H)C=C=C(H)CO2Me. Compound 1 contains a bridging η2‐η2‐MeO2C(H)CCC(H)CO2Me allene ligand and compound 2 contains a bridging η3‐η1‐MeO2C(H)CCC(H)‐CO2Me allene ligand in which the oxygen atom of one of the carbonyl groups is also coordinated. Compound 1 slowly converts to 2, which establishes that it is a precursor to 2. Compound 2 reacts with NEtH2 to give the mononuclear manganese complex fac‐Mn(CO)3(PMe2Ph)[MeO2CCH2‐C=C(H)CO2Me] (3) in 96% yield. Compound 3 contains a chelating 1,3‐di(methoxycarbonyl)propenyl grouping formed by addition of a hydrogen atom to the allene and the loss of a manganese grouping. Compounds 1–3 were characterized by single crystal x‐ray diffraction methods.
Mass Spectrometric Study of [Fe,C3,H6,O]+ Isomers Relevant in the Gas‐phase Oxidation of Hydrocarbons by “Bare” FeO+
Authors: Schwarz Joseph , Wesendrup Ralf , Schröder Detlef , Schwarz Helmut
Published: July 2007

The structures and energetics of [Fe,C3,H6,O]+ isomers are probed by mass spectrometric means. The complexes Fe‐(CH3COCH3)+, Fe(CH3CH2CHO)+, Fe(CH3OCH=CH2)+, Fe(CH2O)(C2H4)+, c‐(FeOCH2CH2CH2)+, Fe(CH2=CH‐CH2OH)+, and Fe(OH)(C3H5)+ can be distinguished by comparing their reactivity toward benzene and their collision‐induced dissociation mass spectra, respectively. These findings are used to interpret the formation of [Fe,C3,H6,O]+ in oxidation reactions of hydrocarbons by the highly reactive FeO+ cation. For example, in the reactions of FeO+ with norbornane and pentanol Fe(OH)(C3H5)+ is produced, while the reaction of FeO+ with norbornane to yield [Fe,C3,H6,O]+ is one of the rare cases of initial CC bond activation by a “bare” transition‐metal oxide. The reaction of FeO+ with propene involves formation of metalla oxetanes as primary products. In general, “bare” FeO+ is not selective and allylic CH bond activation of propene competes efficiently, thus pointing to a potentially rich chemistry.
1,3‐Heterobinuclear Cyclobutenylidene Complexes with an Exocyclic CC bond — Synthesis, Structure, and Spectroscopic Properties
Authors: Fischer Helmut , Leroux Frédéric , Stumpf Rüdiger , Roth Gerhard
Published: July 2007

Pentacarbonyl(allenylidene)chromium and ‐tungsten, [(CO)5MCCCR2] (M=Cr, R=C6H4CH3‐p(1a), C6H4OCH3 (1b); M=W, R=C6H4CH3‐p (1c), react with the alkynyl complexes [Cp(CO)2FeCCR′] (R′ = nBu (2), Ph (4)), [Cp*(CO)2FeCCnBu] (6), [Cp(CO){P(OMe)3}‐FeCCnBu] (8) and [Cp(PPh3)NiCCnBu] (10) by cycloaddition of the CC bond of the alkynyl complexes to the Cα=Cβ bond of the allenylidene ligand to give 3a–c), (5), (7), and respectively. The cycloaddition is highly selective. The spectroscopic data of these 1,3‐heterobinuclear complexes indicate a delocalized π‐system (M=Cr, W; Y=[Fe(CO)2Cp], [Fe(CO)(P{OMe}3)Cp], [Fe(CO)2Cp*], [Ni(PPh3)‐Cp]). X‐ray structural analyses of the compounds 3a, 9a, and 11c reveal a “butterfly” conformation of the four‐membered ring. Its puckering angle is 142° (3a), 152° (9a), and 151° (11c). All Complexes exhibit a moderate to strong negative solvatochromic behavior. The extent of the solvatochromic effect depends on [(CO)5M] and Y and considerably decreases when C=CR2 is replaced by e.g. CMe2.
Preparation and Crystal Structure of the New Quaternary Europium‐polysulfide KCuEu2s6
Authors: Bensch Wolfgang , Dürichen Peter
Published: July 2007

The new quaternary europium polysulfide KCuEu2S6 was obtained using the reactive flux method at an intermediate temperature of 380°C by reacting K2S3 with elemental Cu, EuS and an excess of sulfur. The Eu3+ ions exhibit a bicapped trigonal prismatic coordination and the Cu+ ions are in a tetrahedral environment. The crystal structure is characterized by anionic layers of interconnected Eu and Cu polyhedra with K+ ions residing between the anionic sheets [Cu‐Eu2S6]nn—. The Cu+ ions occupy one half of the tetrahedral sites in an ordered fashion.
Mixed Bent Sandwich Titanium Complexes with the [2‐(Diisopropylamino)ethyl]cyclopentadienyl Ligand — Catalysts for the Polymerization of Ethylene and the Dehydrocoupling of Phenylsilane
Authors: Jutzi Peter , Redeker Thomas , Neumann Beate , Stammler Hans‐Georg
Published: July 2007

Mixed bent sandwich titanium (IV) complexes containing the donor‐substituted [2‐(diisopropylamino)ethyl]cyclopentadienyl (C5H4CH2CH2NiPr2  CpN) ligand are described. The highly moisture‐sensitive metallocene dichloride (C5H4CH2CH2NNiPr2)(C5H4SiMe3)TiCl2 (1) was synthesized by reaction of CpNLi with CpSTiCl3 (CpS  C5H4SiMe3). Complex 1 reacts with one equivalent of HCl with protonation of the amino group to give the air‐ and water‐stable metallocene dichloride‐hydrochloride [(C5H4CH2CH2‐N(H)iPr2)(C5H4SiMe3)TiCl2]+Cl− (2). The structure of 2 was determined by a single‐crystal X‐ray diffraction study. Compounds 1 and 2 are precursors for ethylene polymerization catalysts. The reaction of 2 with one equivalent of Na+B[3,5‐(CF3)2C6H3]4− afforded the borate [(C5H4CH2CH2N(H)iPr2)‐(C5H4SiMe3)TiCl2]+B[3,5‐(CF3)2C6H3]4− (3). The dimethyl compounds (C5H4CH2CH2NiPr2)(C5H4SiMe3)Time2 (4) was obtained by reaction of 1 with two equivalents of methyllithium. The diphenoxy complex (C5H4CH2CH2‐NiPr2)(C5H4SiMe3)Ti(OPh)2 (5) was prepared analogously with a stoichiometric amount of lithium phenoxide. Compounds 4 and 5 show remarkable activity in the catalytic dehydrocoupling of phenylsilane.
Derivate des Imidazols, XIX. Koordination oder Reduktion? Zur Reaktion von 1,3‐Diisopropyl‐4,5‐dimethylimidazol‐2‐yliden mit Schwefelhalogeniden und Schwefeloxidhalogeniden
Authors: Kuhn Norbert , Bohnen Hans , Fahl Joanna , Bläser Dieter , Boese Roland
Published: July 2007

Imidazole Derivatives, XIX

Part XVIII: Ref.[1]

.
— Coordination or reduction? On the Reaction of 1,3‐Diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene with Sulfur Halides and Sulfur Oxygen Halides

Herrn Professor Max Herberhold zum 60. Geburtstag gewidmet.

The reaction of 1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene (4, Im) with sulfur halides and sulfur oxygen halides may be described as a coordination (1) or reduction (2) process in respect to the sulfur centre. With SCl2 and SOCl2 the hypervalent sulfur compounds Im · SCl2 (5) and Im · S(O)Cl2 (13) are obtained. The SF2 adduct Im · SF2 (11) is formed on treatment of 5 with AgF. 13 is alkylated by methyl iodide to give the Im · S(Me)OCl2 cation (15). Surprisingly, reduction of the sulfur centre (2) occurs on treatment of 4 with SF4 to form the ImF+SF3− salt 18 containing the new SF3 anion. As expected, the same type of reaction occurs with the sulfuryl halides SO2ClF and SO2F2 to give the fluorosulfites ImCl+‐SO2F− (21) and ImF+SO2F− (23). The X‐ray structures of 5, 13 and 23 are reported.
Tripodliganden mit Neopentangrundgerüst und zwei verschiedenen Donorfunktionen CH3C(CH2PPh2)2(CH2SR): Synthese, Struktur, Redoxchemie und Spektroskopie von Komplexen des Typs tripodM{ortho‐(X)(Y)C6H4}
Authors: Körner Volkmar , Huttner Gottfried , Zsolnai Laszlo , Büchner Michael , Jacobi Albrecht , Günauer Diethelm
Published: July 2007

Tripod Ligands with Neopentane Frame and two Different Donor Groups CH3C(CH2PPh2)2(CH2SR): Synthesis, Structure, Redox Chemistry, and Spectroscopy of the Complexes tripodM{ortho‐(X)(Y)C6H4}

Prof. Dr. Jörn Müller zum 60. Geburtstag gewidmet.

Neopentane‐based tripod ligands CH3C(CH2PPh2)2(CH2Z) (Z = SBn, SH, S−) form pentacoordinate compounds [tripodM{ortho(X)(Y)C6H4}]m 1–4 with ortho‐phenylene‐bridged coligands (X)(Y)C6H4 (X, Y = O−, S−, NH−) and Co(II), Co(III), Fe(II), or Fe(III) as the metal centers. The structures of these complexes are very similar to those observed for CH3C(CH2PPh2)3 as the tripod ligand. The redox potentials, however, for the corresponding one‐electron oxidation and reduction processes are highly affected by the change in the tripod donor groups. Both potentials are shifted by a maximum of 700 mV upon replacement of a PPh2 donor group by a sulfur‐centered donor with the difference between the potential of the oxidation step and the potential of the reduction step staying almost constant for the whole series of compounds. This difference of around 1.7 eV nicely corresponds to the energy of the HOMO‐LUMO chargetransfer bands observed around 2 eV for all of the compounds. It may be inferred therefore that both observations (electron spectroscopy and cyclic voltammetry) refer in a similar way to the HOMO‐LUMO gap of the compounds. It is shown that the formation of [tripodCo(III){ortho‐(NH)2C6H4}]+(BF) from ortho‐phenylenediamine as the source of the coligand involves precoordination of the amine ligand followed by deprotonation of the coordinated ligand. The capability of the tripodCo(II) template to form five‐coordinate compounds with diamines is further corroborated by the characterization of [tripodCo(en)]2+ (52+). In addition to the standard analytical data, EPR, UV/Vis, cyclovoltammetric data and X‐ray structure analyses are presented where appropriate.
Photochemical reactions of transition metal organyl complexes with olefins, 17. Light‐Induced [6+2] Cycloadditions of Dienes to Tricarbonyl(η6‐1,3,5,7‐cyclooctatetraene)chromium(0)
Authors: Kreiter Cornelius G. , Eckert Ralf
Published: July 2007

Tricarbonyl(η6‐1,3,5,7‐cyclooctatetraene)chromium (1) yields upon UV irradiation in ether at 233 K with 2,3‐dimethyl‐1,3‐butadiene (2) or 2‐methyl‐1,3‐butadiene (3) by [6+2] cycloadditions the correspondingly substituted tricarbonyl(η6‐bicyclo[4.2.2]deca‐2,4,7‐triene)chromium complexes 4, 5a and 5b. With ammonium cerium(IV) nitrate the organic ligand of complex 4, 9‐isopropenyl‐9‐methyl‐bicyclo[4.2.2]‐deca‐2,4,7‐triene (6) is liberated. The complexes 4, 5a and 5b were characterised by IR and NMR spectroscopy, the ligand 6 by NMR spectroscopy.
Synthesis of the Hexakis[(triphenylphosphane)gold(I)]methanium(2+) Cation from Trimethylsilyldiazomethane; Crystal Structure Determination of the Tetrafluoroborate Salt
Authors: Gabbaï FraņOis P. , Schier Annette , Riede Jürgen , Schmidbaur Hubert
Published: July 2007

A new synthetic route to the bis(tetrafluoroborate) salt of the hexakis[(triphenylphosphane)gold(I)]methanium dication has been opened up through the reaction of trimethylsilyldiazomethane and tris[(triphenylphosphane)gold(I)]oxonium tetrafluoroborate in dichloromethane. Yields are close to 65% if the reaction is carried out in the presence of triethylamine as a base. The process is a sequence of desilylation, deprotonation and deazotation reactions at the carbon function of the diazomethane, as shown by the detection of intermediates. The crystal structure of the title compound (with three equivalents of crystal dichloromethane) has been determined in a single‐crystal X‐ray study. The dication has no crystallographically imposed symmetry, but the core is a distorted, carbon‐centered octahedron of gold atoms. This result confirms the data from previous structural studies of salts with other anions and interstitial solvents.
The Gas‐Phase Structure of Trifluoromethyl Vinyl Sulfide, CF3SC(H)CH2
Authors: Lieb Max , Oberhammer Heinz
Published: July 2007

The geometric structure of trifluoromethyl vinyl sulfide, CF3SC(H)CH2, was determined by gas electron diffraction and ab initio calculations (HF/3‐21G* and MP2/6‐31G*). A single conformer with a dihedral angle ϕ(CC–S–C) = 129(4)° is present. The conformational properties are compared to those of the parent compound, CH3SC(H)CH2, and of the perfluorinated species CF3SC(F)CF2.
Synthesis and Electrochemistry of Diels‐Alder Adducts of [60] Fullerene with a Phthalocyanine and a Hemiporphyrazine
Authors: Dürr Kai , Fiedler Stefan , Linßen Torsten , Hirsch Andreas , Hanack Michael
Published: July 2007

The synthesis of a new Diels‐Alder adduct 7 of [60]fullerene and a phthalocyaninenickel compound containing a longer spacer than the originally reported Diels‐Alder adduct 1 is described. The bisenophilic hemiporphyrazinenickel compound 11 reacts with [60]fullerene to form a Diels‐Alder adduct 12 containing two fullerene units. Spectroelectrochemical investigations of 7 and 12 reveal multiple reductions, which are attributed to the corresponding subunits of the molecules. In contrast to 1, the election acceptor properties of the [60]fullerene unit in both molecules have no influence on the electronic properties of the phthalocyanine and hemiporphyrazine, respectively.
Tetramethylguanidine and Benzophenoneimine as Ligands in Gold Chemistry
Authors: Schneider Wolfgang , Bauer Andreas , Schier Annette , Schmidbaur Hubert
Published: July 2007

(Tetramethylguanidine)gold(I) chloride (1) and bromide (2) are readily prepared in high yield from (Me2N)2CNH and [AuCl(Me2S)] or [AuBr(tht) (tht = tetrahydrothiophene), repectively. NMR spectra of chloroform solutions of the two products indicate equilibria of the type 2 LAuX = L2Au+AuX2−. The cationic complex [Au(NHC(NMe2)2)(PPh3)]+ is obtained as the triflate salt 3 from tetramethylguanidine and [Au(PPh3)]+O3SCF3−. In solution at low temperature (−60°C), this compound adopts a rigid structure whereby the NMe2 groups are rendered non‐equivalent, but at ambient temperature there is coalescence of the NMe2 signals in the 1H‐ and 13C‐NMR spectra. The related benzophenoneimine complex [Au{NHCPh2}(PPh3)]+BF4− (4), which was synthesized as a reference3 compound, exhibits similar behaviour. In solution at low temperature (‐60°C) the two phenyl rings of the ligand are diastereotopic. In contrast, the triisopropylphosphane derivative [Au[NHCPh2](PiPr3)]+BF4− (5) is rigid on the NMR time scale, even at 25°C. Thbe solid‐state structures of 2, 3, 4, and 5 have been determined by single‐crystal X‐ray diffraction. Compound 2 crystallizes in the ionic form with discrete Au … Au bonded ion pairs [Au[NHC(NMe2)2]2]+ [AuBr2]− [Au … Au 3.1413(8) Å]. The cations of 3, 4, and 5 show the [Au(PPh3)]+ units N‐coordinated to the imino groups, with the nitrogen atoms in a trigonal‐planar configuration.
Reactivity of the Heavier Group‐13 Monochlorides [{CH(SiMe3)2}2AlCl], InCl, TlCl, and of the Elements Ga and Hg Towards the Unsupported Ni‐Ni Bond of [{(η5‐Cp)Ni(PEt3)}2] — A Straightforward Synthetic Approach to the Synthesis of Mixed Main‐Group/Transition‐Metal Clusters Containing Unsupported Metal‐Metal Bonds
Authors: Schneider Jörg J. , Denninger Uwe , Hagen Jörg , Krüger Carl , Bläser Dieter , Boese Roland
Published: July 2007

The dinuclear compound [{(η5—Cp)Ni(PEt3)}2] (1) containing an unbridged Ni‐Ni bond reacts with the heavier group 13 monochlorides [{CH(SiMe3)2)2}AlIIICl], InCl, and TlCl by scission of the metal‐metal bond. In the case of InCl and TlCl the chloro‐bridged dimmers [{(η5‐Cp)Ni(PEt3)2ECl2Ecl}2] (E = In 2, Tl 5) were formed. The Tl compound 5 is unstable and decomposes via disproportionation a and formation of the halogen‐free Tl [III] compound [{(η5‐Cp)Ni(PEt3)}3Tl] (6). 2 can be dehalogenated with activated magnesium to yield the halogen‐free In [III] compund [{(η5‐Cp}Ni(PEt3)}3In] (4). The Ga analogue of 4 and 6 [{(η5‐Cp)Ni(PEt3)}3Ga] (7) is accessible by a conproportionation of 1 with Ga metal in refluxing THF. In contrast to InCl and TlCl the aluminium (III) monochloride [{CH(SiMe3)2}2AlCl] reacts with 1 by a ligand redistribution reaction and formation of the salt [{(η5‐Cp)Ni(PEt3)2]+‐[{CH(SiMe3)2]2AlCl]2−. (8). Elemental Hg or Mg amalgam show the same activity as elemental Ga towards 1 and insert into the NiNi bond by forming the linear Hg‐bridged complex [(n3‐Cp)Ni(PEt3)]2Hg] (9). The molecular structures of 2, 4, 8, and 9 were determined by X‐ray crystallography. The In atom in 4 has a distorted trigonal‐planar configuration with the central In atom being surrounded by three [(n5‐Cp)Ni(PEt3)] fragments. 4 represents the first Ni‐In cluster containing exclusively unsupported In—Ni bonds, as well as the first carbonyl‐free Ni—In cluster. On the basis of spectroscopic data the same structure is assigned to the Ga and Tl analogues of 4. The NiHgNi arrangement in 9 is exactly linear, as determined by X‐ray crystallography.
Hydrocarbon‐Bridged Metal Complexes, XLI. Addition of Aniline Tricarbonyl Chromium Complexes to the Cyclohexadienyl Ligand of (μ5‐C6H7)M(CO)3+ (M = Fe, Ru)
Authors: Bentele Hans‐Jörg , Sünkel Karheinz , Beck Wolfgang
Published: July 2007

The addition of aniline tricarbonyl chromium complexes (η6‐C6H4(R)NHR1)Cr(CO)3 (RH, CH3; R1H, CH3) to [(n5‐C6H7)M(CO)3]+ (MFe, Ru) gives the heterobimetallic ligand‐bridged complexes (OC)3Cr(n6‐C6H4(R)N(R1)C6H7‐n4)M(CO)3. The structure of (OC)3Cr(n6‐C6H4(CH3)N(H)‐C6H7‐n4)Ru(CO)3 has been determined by X‐ray diffraction.
1,8‐Bis(phosphanyl)naphthalenes: 1,8‐Bis[(diethylamino)phosphanyl]‐naphthalene, 1,8‐Bis(dichlorophosphany)naphthalene, and 1, 3‐Dichloro‐2,‐3‐dihydro‐1,3‐dioxo‐2‐oxa‐1,3‐diphosphaphenalene
Authors: Karaçar Atilla , Thönnessen Holger , Jones Peter G. , Bartsch Rainer , Schmutzler Reinhard
Published: July 2007

1.8‐dilithionaphthalene 1 reacted with bis(dimethylamino)‐chlorophosphane to form 1,8‐bis[(diethylamino)phosphanyl]‐naphthalene 2, whose structure was confirmed by X‐ray crystal structure analysis; there are two independent molecules, in which the P(NEt2)2 groups adopt an eclipsed conformation. Reaction of 2 with gaseous HCl gave in low yield 1,8‐bis‐(dichlorophosphanyl)naphthalene 3, which was characterized by 1H‐ and 31P‐NMR spectroscopy, mass spectrometry and elemental analysis. Attempted recrystallization of 3 led to oxidative hydrolysis which furnished 4, an anhydride of a bis(chlorophosphonic acid), whose structure was elucidated by X‐ray crystal structure analysis. The geometry of 4 reveals a relief of strain from the bis (aminophosphane) 2; the naphthalene groups are less distorted and the P atoms are displaced less far from the naphthalene best plane.
Enantioselective Catalysis. New Chiral Expanded Phosphanes Derived from Substituted Deltacyclenes
Authors: Brunner Henri , Reimer Alfred
Published: July 2007

The suitability of enantiomerically pure deltacyclenes as building blocks in the synthesis of expanded phosphanes was examined. Different substituted deltacyclenes were irradiated with diphenylphosphane and three bisphosphanyl derivatives. With these PH addition reactions, new chiral deltacyclane‐derived phosphorus ligands were synthesized. They were tested in the Rh‐catalyzed asymmetric hydrogenation of (Z)‐(ã)‐N‐acetamidocinnamic acid and in the Pd‐catalyzed asymmetric allylation of 1,5‐dimethylbarbituric acid.
Coordination Compounds of Coinage Metals with Vinylidenebis(diphenyl‐phosphane) and Its Disulfide and Their Reactivity towards Nucleophiles
Authors: Fernández Eduardo J. , Gimeno M. Concepción , Jones Peter G. , Laguna Antonio , López‐de‐Luzuriaga José M. , Olmos Elena
Published: July 2007

Vinylidenebis(diphenylphosphane) reacts with gold(I) or gold(III) compounds to give dinuclear {[{Au(C6F5)]2[(PPh2)2CCH2{] or [Au{PPh2C(CH2)Ph2P)]2(ClO4)2] or mononuclear complexes ([Au(C6F5)3(PPh2C(CH2)Ph2P)]}, respectively. The latter reacts with gold(I) or silver(I) compounds to afford dinuclear [[Au(C6F5)3[PPh2C(CH2)Ph2P}AuX], XCl or C6F5) or trinuclear species {[{Au(C6F5)3{PPh2C(CH2)Ph2P{]2M]ClO4, MAu or Ag}. No addition of nucleophiles to the CC double bond is observed in these complexes, which contain the diphosphane acting as bridging or monodentate ligand. (SPPh2)2CCH2 reacts with AgClO4 to give [Ag{SPPh2C(CH2)Ph2PS}]2‐(ClO4)2or[Ag[PPh2C(CH2)Ph2P]2]ClO4. The crystal structure of [Au(C6F5)3{PPh2C(CH2)Ph2P}Au(C6F5)] has been established by X‐ray crystallography, and confirms the expected square planar and linear geometry for the Au111 and Au1 centres, respectively.
Unusual Dinuclear Hydridorhodium(III) Complexes Containing Bulky Phosphanyl(stibanyl)methanes as Chelating Ligands
Authors: Manger Matthias , Gevert Olaf , Werner Helmut
Published: July 2007

The mononuclear starting materials [Rh(η4‐C8H12)(k2‐P,Sb‐iPr2PCH2SbR2)]PF6 (la, b) react with CF3CO2H in the presence of H2 to give the dinuclear hydridorhodium(II1) complexes [{RhH(k2‐P,Sb‐iPr2PCH2SbR2)]PF6 (2a, b) in almost quantitative yield. The X‐ray crystal structural analysis of 2b (R = tBu) reveals a distorted octahedral geometry around the two metal centers with the two phosphanyl(stibanyl)methanes in a chelating and the two trifluoracetate ligands in a bridging coordination mode.
X‐ray and Solution Structure of Inosine 5' ‐Monophosphate Coordinated to (Ethylenediamine)palladium(II). —the Importance of Intramolecular Hydrogen Bonding
Authors: Rau Tobias , Van Eldik Rudi
Published: July 2007

The compound [Pd(en)(5′‐IMP‐N7)2].11 H2O, where 5′‐IMP = inosine 5′‐monophosphate, crystallizes in the tetragonal space group P4322 with the unit cell parameters: a = b = 12.060(5) and c = 28.510(5) Å, V = 4147(3) Å3, Z = 4. A head‐to‐tail orientation with A configuration is observed for the nucleotides which are coordinated through the N(7) positions such that d[Pd‐N(7)] = 2.053(8) Å. The sugar moieties exhibitantiorientations toward the purine bases while their pukkers adopt C(3)′‐endoconformation. The overall conformation about the phosphate backbone is gauche+. Intramolecular hydrogen bonding is observed between the phosphates and the NH groups of the en ligand with a donor‐acceptor distance of 2.88 Å. The coordination mode of the solid‐state structure is shown to be identical to that observed by1H‐NMR spectroscopy in solution under slightly acidic conditions, where the N (l) positions of the nucleotides are protonated. The results are discussed in reference to closely related systems reported in the literature with emphasis on the importance of hydrogen bonding in such complexes.
A Series of Carbonyl‐, Olefin‐, Alkyne‐, Hydrido‐, and Vinyliridium Complexes Containing Bulky Bifunctional Phosphanes iPr2PCH2X as Ligands
Authors: Steinert Paul , Werner Helmut
Published: July 2007

Etheneiridium(I) complexes of the general composition trans‐[IrCl(C2H4)L2] [L = iPr2PCH2CO2Me (2a), iPr2PCH2CO2Et (2b), iPr2P(CH2)3NMe2 (2c)] have been prepared either from [IrClL2] (3) or [IrCl(C2H4)2]2 (7) as starting materials. The corresponding carbonyl derivatives trans‐[IrCl(CO)L2] (6, 10, 11) are obtained along similar routes. Photolysis of trans‐[IrCl(C2H4)L2] (L = 2a, 2b) leads, by intramolecular C–H activation, to the formation of the octahedral hydrido(vinyl)iridium(III) compounds [IrHCl(CHCH2)(k‐L)(k2‐L)] (16, 17), which are highly fluctional in solution. Carbonyl(hydrido)(vinyl) complexes are accessible either from 16 or 17 and CO, or from trans‐[IrCl(C2H4)L2] (L = 2a) and the propargylic alcohol HCCCH(Ph)OH, respectively. Treatment of 3 or the corresponding dihydrido compound [IrH2ClL2] (4) with methyl vinyl ketone or methyl acrylate also yields hydrido(vinyl)iridium(III) complexes [IrHCl(CHCHX)L2] [X = C(=O)Me (18), C(=O)OMe (19)], in which instead of the CO function of the phosphanyl ester the carbonyl group of the vinylic moiety is coordinated to the metal. The reaction of 16 (L = 2a) with terminal alkynes HCCR (R = Ph, CO2Me) affords the structurally related alkynyl(hydrido)iridium(III) compounds [IrHCl(CCR)(k‐L)(k2‐L)] (28, 29), while from 16 and internal alkynes RCCR) the iridium(I) complexes trans‐[IrCl1(RCCR)L2] (30, 31) are obtained, Stepwise treatment of trans‐[IrCl(RCCR)L2] (6: L = 2a) with NaN(SiMe3)2, (ii) H2O, and (iii) HCl leads, in the coordination sphere of the metal center, to a conversion of iPr2PCH2CO2Me to iPr2PCH2CO2H via the isolated phosphanylenolate and phosphanylacetate complexes 32 and 33 as intermediates.
Reversible Rearrangements of Chlorophosphane‐Dichlorogermylene Ylides to Trichlorogermylphosphanes — Structure Determination of a Tetranuclear Bis(chlorophosphane)bis(trichlorogermylphosphane) Silver Bromide Complex
Authors: Mont Wolf‐Walther Du , Karnop Michael , Mahnke Jens , Martens Reiner , Druckenbrodt Christian , Jeske Jörg , Jones Peter G.
Published: July 2007

Chlorophosphanes RR'PCl (1a: R,R' = 1b: R = tBu, R' = iPr, 1c: R = iPr, R' = Et2N, 1d: R = Et2N react with the dichlorogermylene dioxane complex 2 furnishing trichlorogermylphosphanes RR'PGeCl3 4a–d. In the cases of 1c/4c and 1d/4d the insertion reaction remain incomplete; similarly, 4a always contains, shortly after isolation in pure state, small amounts of 1a that can be detected by NMR. A provided by the reaction of trichlorosilylphosphane tBu(Et2N)PSiCl3 (5d) with GeCl4. The alkyl(dialkylamino) trichlorogermylphosphane 4d exists only in an equilibrium with chlorophosphane 1d, which coordinates GeCl2 leading to the dichlorogermylene complex 3d. A 1:1 mixture of 4a with 1a is formed by the novel cleavage (“chlorogermylation”) of the P–P bond of tetraisopropyldiphosphane with germanium tetrachloride. Di‐tert‐butyl(trichlorogermyl)phosphane 4e (R, R' = tBu) reacts with silver bromide providing a crystalline silver complex 7. A structure determination by X‐ray diffraction reveals that 7 is [Ag4Br4(tBu2PCl)2(tBu2PGeCl3)2]. 2C7H8. Two of the Ag atoms of the cubane‐like (AgBr)4 core of 7 are coordinated by chlorophosphane 1e, the other two by trichlorogermylphosphane 4e.
Investigation of Host‐Guest Interactions between Rubidium Salts and N‐(Arylazoalkenoyl)azacoronands by Solid‐State NMR Spectroscopy
Authors: Costisella Burkhard , Müller Dirk , Baumann Hendrik
Published: July 2007

Rubidium salts with N‐(Arylazoalkenoyl)azacoronands (2a–c), were investigated using 87Rb and 13C solid‐state NMR spectroscopy. From the NMR results it is concluded that there is a host‐gust interaction. This suggests that the rubidium and ammonium ions, respectively, are incorporated into the cavity between the coronand and the chromophore.
Chlorides and Acetylacetonates of Transition Metals as Catalysts for the Oxidation of 1‐Indanol by Sodium Percarbonate
Authors: Aït‐Mohand Samia , Muzart Jacques , Lunak Stanislav
Published: July 2007

The screening of metal chlorides and metal acetylacetonates as catalysts for the oxidation of 1‐indanol by sodium percarbonate (at reflux in 1,2‐dichloroethane in the presence of small amounts of Adogen 464) has been carried out. The efficiency of the process depended on the nature of the transition metal and its oxidation state but, except for iron, was not greatly influenced by the nature of the ligands. Good conversions and yields have been obtained using PdCl2, RhCl3, RuCl3 and, particularly, MoO2(acac)2 as catalysts.
A New Route to Sila‐ and Phosphaheterocycles: Nucleophilic Aminomethylation
Authors: Karsch Hans H. , Schreiber Kai A. , Herker Martin
Published: July 2007

The aminals tetramethylmethylenediamine (TMMDA) la, dicyclohexyldimethylmethylenediamine (CMMDA) lb, and di‐isopropyldimethylmethylenediamine (IMMDA) lc are doubly metalated by LitBu to give LiCH2N(R)CH2N(R)CH2Li [2a: R = Me, 2b: R = Cy (Cy = cyclohexyl), 2c: R = iPr], which precipitate out of pentane as highly pyrophoric substances. Deuteration confirms N‐methyl metalation exclusively. A series of aminomethylation reactions were performed by means of the doubly lithiated aminals 2a‐c. The reactions of 2a‐c with monochlorosilanes yield the silylated species R′3SiCH2MN(R)CH2N(R)CH2SiR′3 (3a: R′= Me, R == Me; 3b: R′ == Me, R == Cy; 3c: R′= Me, R = iPr 4: R′= Ph, R = Me, see Scheme 2). The use of dichlorosilanes lead to six‐membered heterocycles 6a‐6d. 6a is transferred into a mono quarternary ammonium salt 7 by methylation with MeI. The spirocycle 8 is obtained from SiCl4 and two equivalents of 2a. Similarly, several substituted 1,3‐diaza‐5‐phosphacyclohexanes 9a‐e (R1 = Me, Ph, NPh2, NCy2, see Scheme 3) are synthesized by the reaction of dichlorophosphanes R1PC2, with 2a and 2b, respectively. Oxidation of 9d with sulfur yields 12a, which is characterized by X‐ray structure determination.
Kinetics and Mechanism of Substitution Reactions of cis‐[PtMe2(dmso)2] with Pyridine
Authors: Schmüling Michael , van Eldik Rudi
Published: July 2007

The substitution reactions of cis‐[PtMe,(dmso),] with pyridine (py) to produce cis‐[PtMe2py2] in toluene proceeds in two steps. In the absence of added dimethylsulfoxide (dmso), these steps can not be separated due to the rate constants being very similar. In the presence of added dmso, the rate of the first step, the formation of the monopyridine complex is retarded, which is indicative of a dissociative mechanism. A parallel associative reaction path with pyridine could also be observed. This pathway is independent of the concentration of added dmso. Above a 40‐fold excess of dmso, the dissociative pathway is suppressed and only the associative reaction occurs. A plot of Kobs vs the pyridine concentration for this pathway is linear at low [py], but shows a saturation at high [py]. This suggests that the reaction occurs via the formation of a precursor‐complex, for which the formation constant was found to be 0.32 · 0.03 M−1. The volume of activation at a high pyridine concentration is −11.4 · 0.8 cm3 mol−1, which indicates that the ligand interchange process is of the associative type. The second step, the formation of the bispyridine complex, can clearly be separated from the first reaction step. This step occurs via a dissociative mechanism, as demonstrated by the decrease in kobs with increasing pyridine concentration. The dissociation of dmso was characterized by a rate constant of (8.1 · 0.9).10−45−1 at 25°C, ·H = 116 ·9 kJ mol−1 and AS. = 86 · 29 JK−1 mol−1. At higher pyridine concentrations evidence for a parallel associative reaction was found, for which the rate constant is (1.3 · 0.2).10−3 M−1S−1 25°C. The results are discussed in reference to available literature data.
An Ylide‐Substituted Tetraphosphene, Cyclotetraphosphane, and Bicyclotetraphosphane
Authors: Schrödel Haus‐Peter , Nöth Heinrich , Schmidt‐Amelunxen Martin , Schoeller Wolfgang W. , Schmidpeter Alfred
Published: July 2007

The reaction of two specific ylidyl dichlorophosphanes, Ph3P=CR‐PCl2, with P(SiMe3)3 yields the ylidyl trimethylsilyl diphosphenes Ph3P=CR.P=P‐SiMe3 as primary products which form two different types of dimers: the cyclotetraphosphane 9 (R = SiMe3), and the tetraphosphene 10 (R = 2,6‐Cl, 2,/C6H3). The latter compound is readily converted to the bis(ylidyl)biocyclotetraphosphane 11. The molecular structures of 9 and 11 allow a strong transanular interaction between teh ylide‐substituted phosphorus atoms, which results in very large two‐bond coupling constants (2Jpp = 184 and 332 Hz respectively). The central P bond in 11 is relatively long (220.7 pm); quantum chemical calculations show the lengthening to be a consequence of the perpendicular orientation of the ylidic donor p‐orbital.
Preparation, Properties, and Reactions of Metal‐Containing Heterocycles, XCVII – Differently Substituted Benzomolybdacrown Ethers and Their Capability of Including Alkali Metal Cations
Authors: Lindner Ekkehard , Günther Matthias F. , Mayer Hermann A. , Fawzi Raid , Steimann Manfred
Published: July 2007

The reaction of the diphosphanes 2a‐i with (OC)4Mo(nbd) under high dilution conditions affords the mononuclear benzomolybdacrown ethers cis‐(OC)4Mo{1,2‐, 1,3‐, 1,4‐[PH2PCH2(CH2OCH2)πCH2]2C6H4‐P, P′] (3a‐i) (n = 1, 2). On the basis of the 31P nucleus the inclusion behavior of the molydacycles 3a‐i toward the alkali metal salts LiBF4 and NaBPh4 was investigated with the aid of a NMR titration technique by using the program EQNMR. Only 3dshows an interaction with the alkali metal cation Na+ forming a 1:1 and 2:1 complex (3d/cation) while no interaction with Li+ could be detected. The molecular structures of 3a and 3d were elucidated by X‐ray structural analyses. Complexes 3a and 3d crystallize in the monoclinic space groups P21/c and P21/n with Z = 8 and 4, respectively.
Quantitative structure–activity relationship of hydroxyl‐substituent Schiff bases in radical‐induced hemolysis of human erythrocytes
Authors: Tang You‐Zhi , Liu Zai‐Qun
Published: July 2007

The major objective of this work was to explore the quantitative structure–activity relationship (QSAR) of hydroxyl‐substituent Schiff bases in protecting human erythrocytes against 2,2′‐azobis(2‐amidinopropane hydrochloride) (AAPH)‐ induced hemolysis, in which 10 Schiff bases including 4‐phenyliminomethylphenol (PIH); 4‐((4‐hydroxybenzylidene) amino)phenol (PAH); 2‐methoxy‐4‐((4‐hydroxyphenylimino)methyl)phenol (PMH); 4‐((furan‐2‐ylmethylene)amino) phenol (FAH); 4‐((4‐N,N‐dimethylaminobenzylidene)amino)phenol (PDH); 2‐((4‐N,N‐dimethylaminobenzylidene)amino) phenol (ODH); 2‐(naphthalene‐1‐yliminomethyl)phenol (NAH); 2‐(benzyliminomethyl)phenol (BPH); 1,4‐di((2‐hydroxyphenylimino) methyl)benzene (DOH); 1,4‐di((4‐hydroxyphenylimino)methyl)benzene DPH, were available for this in vitro experimental system. The results revealed that the radical‐scavenging activity of the OH attached to the para position of methylene in Schiff base was much lower than that attached to the ortho position of the N atom. The large conjugate system and low steric hindrance in the framework of Schiff base benefit the Schiff base to trap radicals. Meanwhile, since a Schiff base, even without any substituent, can also play an antioxidative role in this experimental system, the QSAR results suggest that hydroxyl‐substituent Schiff bases are potential drugs in the treatment of radical‐related diseases, and provide more information for designing novel drugs. Copyright © 2007 John Wiley & Sons, Ltd.
The Use of Non‐natural Nucleotides to Probe Template‐Independent DNA Synthesis
Authors: Berdis Anthony J. , McCutcheon David
Published: July 2007

The vast majority of DNA polymerases use the complementary templating strand of DNA to guide each nucleotide incorporation. There are instances, however, in which polymerases can efficiently incorporate nucleotides in the absence of templating information. This process, known as translesion DNA synthesis, can alter the proper genetic code of an organism. To further elucidate the mechanism of template‐independent DNA synthesis, we monitored the incorporation of various nucleotides at the “blunt‐end” of duplex DNA by the high‐fidelity bacteriophage T4 DNA polymerase. Although natural nucleotides are not incorporated at the blunt‐end, a limited subset of non‐natural indolyl analogues containing extensive π‐electron surface areas are efficiently utilized by the T4 DNA polymerase. These analogues possess high binding affinities that are remarkably similar to those measured during incorporation opposite an abasic site. In contrast, the kpol values are significantly lower during blunt‐end extension when compared to incorporation opposite an abasic site. These kinetic differences suggest that the single‐stranded region of the DNA template plays an important role during polymerization through stacking interactions with downstream bases, interactions with key amino acid residues, or both. In addition, we demonstrate that terminal deoxynucleotide transferase, a template‐independent enzyme, can efficiently incorporate many of these non‐natural nucleotides. However, that this unique polymerase cannot extend large, bulky non‐natural nucleotides suggests that elongation is limited by steric constraints imposed by structural features present within the polymerase. Regardless, the kinetic data obtained from using either DNA polymerase indicate that template‐independent synthesis can occur without the contributions of hydrogen‐bonding interactions and suggest that π‐electron interactions play an important role in polymerization efficiency when templating information is not present.
LaMnO3 Perovskite Supported Noble Metal Catalysts for the Total Oxidation of Methane
Authors: Giebeler L. , Kießling D. , Wendt G.
Published: July 2007

Two series of LaMnO3 supported noble metal (Pt, Pd, Rh) catalysts prepared by the citrate method and calcined in air at 600 and 800 °C, respectively, were investigated. The catalysts resulting from method A were prepared by simultaneous incorporation of the noble metals during perovskite preparation and those following method B were generated by impregnation of the calcined perovskites with the noble metal compounds. The noble metals form solid solutions with the perovskite lattice. Reduction of the catalysts with hydrogen prior to the catalytic reaction led to a significant enhancement of the catalytic activity. During the catalytic reaction, the noble metal clusters are partially transformed to highly dispersed noble metal oxides or nonstoichiometric noble metal oxide phases, which are the catalytically active phases for the total oxidation of methane. The best results were obtained with the Pd containing catalysts prepared by method B.
Predicting the Displacement of Yoghurt by Water in a Pipe Using CFD
Authors: Regner M. , Henningsson M. , Wiklund J. , Östergren K. , Trägårdh C.
Published: July 2007

A numerical scheme based on the volume of fluid (VOF) method for predicting the displacement of one liquid by another has been verified versus electrical resistance tomography (ERT) and ultrasonic velocity profile (UVP) measurements for the displacement of yoghurt by water. The scheme using the VOF method predicts the skewed phase distribution as measured using ERT and the global structure of the velocity profile as measured using UVP. The phase distribution using the VOF method was compared with the results using the species transport model which allows for mixing between the phases. The species transport model was found to be less suitable for predicting the displacement of yoghurt by water since the turbulence model was unable to accurately predict the turbulent viscosity in the mixing zone between yoghurt and water, which resulted in a too high rate of mixing.
Vapor Condensation Heat Transfer in a Thermoplate Heat Exchanger
Authors: Mitrovic J. , Peterson R.
Published: July 2007

The heat transfer and pressure drop in a thermoplate heat exchanger operating as a condenser have been investigated experimentally. In order to separate the heat transfer resistances in the condensation process, the single phase forced convection has been studied using distilled water and Marlotherm oil in the thermoplate and correlations developed for the Nusselt number and the friction factor. For the condensation experiments, an apparatus has been constructed comprising two identical condensers composed of the same thermoplate type as employed in the single phase experiments. Isopropanol is used as a test fluid at pressures below atmospheric pressure. The heat transfer resistances in the condensation experiments are separated and expressions for the condensation heat transfer and pressure drop are developed with the aid of the results obtained in the single phase studies.
The Concept of Protobranching and Its Many Paradigm Shifting Implications for Energy Evaluations
Authors: Wodrich Matthew D. , Wannere Chaitanya S. , Mo Yirong , Jarowski Peter D. , Houk Kendall N. , Schleyer Paul von Ragué
Published: July 2007

Branched alkanes like isobutane and neopentane are more stable than their straight chain isomers, n‐butane and n‐pentane (by 2 and 5 kcal mol−1, respectively). Electron correlation is largely responsible. Branched alkanes have a greater number of net attractive 1,3‐alkyl–alkyl group interactions, there are three such stabilizing 1,3 “protobranching” dispositions in isobutane, but only two in n‐butane. Neopentane has six protobranches but n‐pentane only three. Propane has one protobranch and is stabilized appreciably, by 2.8 kcal mol−1, relative to methane and ethane. This value per protobranch also applies to the n‐alkanes and cyclohexane. Consequently, energy evaluations employing alkane reference standards, for example, of small ring strain and stabilizations due to conjugation, hyperconjugation, and aromaticity, should be corrected for protobranching, for example, by employing Pople's isodesmic bond separation reaction method. This reduces the ring strain of cyclopropane to 19.2 from the conventional 27.7 kcal mol−1, while the stabilization energies of alkenes and alkynes due to hyperconjugation (5.5 and 7.7 kcal mol−1 for propene and propyne) and conjugation (14.8 and 27.1 kcal mol−1 for butadiene and butadiyne) are considerably larger than the traditional estimates. Widely diverging literature evaluations of benzene resonance energy all give ≈65 kcal mol−1 after adjusting for conjugation, hyperconjugation, and protobranching “contaminations.” The BLW (block localized wavefunction) method, which localizes π bonds and precludes their interactions, largely confirms these stabilization estimates for hyperconjugation, conjugation, and aromaticity. Protobranching is seriously underestimated by theoretical computations at the HF and most DFT levels, which do not account for electron correlation satisfactorily. Such levels give bond separation energies, which can differ greatly from experimental values.