bluuebunny/crossref_metadata_2025_split huggingface dataset:
{Bis[bis(trimethylsilyl)methyl]stannio(II)}bis(η2‐ethen)nickel(0) und verwandte Verbindungen, Teil II
Authors: Pluta Christian , Pörschke Klaus‐R. , Gabor Barbara , Mynott Richard 
Published: July 2007

{Bis[bis(trimethylsilyl)methyl]stannio(II)}bis(η2‐ethene)nickel(0) and Related Compounds, Part IIThe coordinatively unsaturated (16e) (ethene)nickel(0) stannylene complex (C2H4)2Ni=Sn{CH(SiMe3)2}2 (1) reacts with 1,6‐heptadiene with preservation of the Ni=Sn bond to yield quantitatively the 1,6‐diene derivative (η2,η2‐C7H12)Ni=Sn‐{CH(SiMe3)2}2 (2). The alkene ligands of both 1 and 2 are readily displaceable. Compounds 1 and 2 react with butadiene at −50°C by a 4‐e oxidation of the metal‐metal pair Ni(0)/Sn(II) to Ni(II)/Sn(IV) and concomitant reduction of two butadiene molecules to butenediyl moieties to afford stereo‐selectively the 16‐e complex Ni‐cis‐{η3(Ni),η1(Sn)‐anti‐C3H4CH2}2Sn{CH(SiMe3)2}2 (3). Similarly, the reaction of 1 or 2 with isoprene yields regio‐ and stereoselectively the derivative Ni‐cis‐{η3(Ni,η1(Sn)‐anti‐C3(3‐Me)H3CH2}2Sn{CH‐(SiMe3)2}2 (4). These reactions imply the cleavage of one formal NiSn bond and the formation of two new SnC bonds. Upon reaction of 3 with PMe3 the configuration of the allyl system changes and, again fully stereoselectively, the 18‐e addition compound (Me3P)Ni‐cis‐{η3(Ni),η1(Sn)‐syn‐C3H4‐CH2}2Sn{CH(SiMe3)2}2 (5) is formed. When 5 is treated with BPh3, the phosphane ligand is trapped and, kinetically controlled, Ni‐cis‐{η3(Ni),η1(Sn)‐syn‐C3H4CH2}2Sn{CH(SiMe3)2}2 (6) is obtained as a stereoisomer of 3. At 40°C 6 slowly rearranges into the thermodynamically stable stereoisomer Ni‐trans‐{η3(Ni),η1(Sn)‐syn‐C3H4CH2}2Sn{CH(SiMe3)2}2 (7). Mild protolysis of 3 with pyridine hydrochloride or hydrobromide affords region and stereoselectively (Me3Si)2CH}2(X)SnNi‐(η3‐1‐MeC3H4)(NC5H5) (X = C1, 8a; Br, 8b). In the course of this protonation reaction one butadiene molecule is eliminated, accompanied by a 2‐e reduction of the metal‐metal pair Ni(II)/Sn(IV) to Ni(II)/Sn(II) and, at the expense of two SnC bonds, reformation of a NiSn bond. All compounds are isolated in high yield and fully characterized by 1H‐, 13C‐, and 31P‐NMR spectroscopy.
Synthese, Deprotonierung und Ringerweiterung eines 2,3‐Diboratetralins
Authors: Weinmann Wolfgang , Pritzkow Hans , Siebert Walter 
Published: July 2007

Synthesis, Deprotonation, and Ring Expansion of a 2,3‐DiboratetralinHerrn Prof. Dr. Helmut Werner zum 60. Geburtstag gewidmet.
Reaction of K2[1,2‐C6H4(CH2)2] with [Cl(Me2N)B]2 leads to 2,3‐bis(dimethylamino)‐2,3‐diboratetralin (4a) in 58% yield. Deprotonation of 4a with lithium 2,2,6,6‐tetramethylpiperi‐dide yields the crystalline dilithium salt 6a. Insertion of 3‐hexyne into the BB bond of 4a results in the formation of 2,5‐bis(dimethylamino)‐3,4‐diethyl‐1,2,5,6‐tetrahydro‐2,5‐benzodiborocine (7a) in 38% yield. The constitutions of 4a, 6a, and 7a were derived from 1H‐, 11B‐, 13C‐NMR, and MS data and proven for 6a and 7a by X‐ray,structure analyses.
Hohervalente Derivate der d‐Metall‐Sauren, 13. Homoscorpionate als tripodale Ankerliganden chlorfunktioneller Oxo‐ und Imidokomplexe von Elementen der 5.‐7. Gruppe
Authors: Sundermeyer Jörg , Putterlik Jürgen , Foth Margarete , Field John S. , Ramesar Niyum 
Published: July 2007

Higher‐Valent Derivatives of the d‐Metal Acids, 13. — Homoscorpionates as Tripodal Anchoring Ligands of Chloro Functionalized Oxo and Imido Complexes of Elements of Group 5–7Hydridotris(pyrazolyl)borate complexes of elements of group 5–7 have been prepared by reaction of d0‐metalloyl chlorides [M(Y)nClm]x (Y = O, NR) with KTp* (Tp* = κ3‐HB(3,5‐Me2pz)3). Thus [NbOCl3]x and [TaOCl3]x are converted into monomeric and well‐characterized oxo complexes [Tp* Nb(O)Cl2] (1) and [Tp*Ta(O)Cl2] (2). In a similar way [Tp* Mo(O)2Cl] (3) and [Tp*W(O)2Cl] (4) have been obtained from the oxo chlorides [MoO2Cl2]x and [WO2Cl2]x, respectively. tert‐Butylamine reacts with NbCl5 and TaCl5 in the presence of pyridine to give the imido pyridine complexes [Nb(NtBu)Cl3(py)2] (5) and [Ta(NtBu)Cl3(py)2] (6) in excellent yield. Imido complexes [Tp*V(NtBu)Cl2] (7), [Tp* Nb(NtBu)Cl2] (8), and [Tp*Ta(NtBu)Cl2] (9) are formed by the reaction of KTp* with the precursers [V(NtBu)Cl3]x or 5 and 6, respectively. The corresponding imido complexes of group 6, namely [Tp*Cr(NtBu)2Cl] (10), [Tp*Mo(NtBu)2Cl] (11), and [Tp*W(NR)2Cl] (R = tBu 12a, 2,4,6‐Mesityl 12b, SO2Ph 12c) are obtained directly from the imidoyl chlorides or their complexes with Lewis bases. 11 and 12 are prone to protonation at the imido ligand to yield cationic amido species [Tp*M(NtBu)(NHtBu)Cl]BF4 (M = Mo 13, W 14). Finally the preparation of cationic imido rhenium complex [Tp*Re(NtBu)2Cl]PF6 (15), isoelectronic with 10–12, is described. The molecular structure of 11 has been determined by X‐ray diffraction. Despite of a maximum electron count of 20 valence electrons, all three pyrazolyl groups of the tripodal ligand are facially coordinated. In a way similar to the well‐known ring slippage of analogous cyclopentadienyl complexes, the weakest bound pyrazolyl ligand is asymmetrically attached to molybdenum deviating from the positions expected for local C3v symmetry.
New Organophosphorus Ligands: Cyclopropanation and Other Reactions of Cumulenes Bearing Diphenylphosphanyl Substituents
Authors: Manhart Stefan , Schier Annette , Paul Martin , Riede Jürgen , Schmidbaur Hubert 
Published: July 2007

AbstractHydrophosphorylation of 1,4‐bis(diphenylphosphanyl)butadiyne with diphenylphosphane leads to the butadiene (Ph2P)2CCHCHC(PPh2)2 (1). Treatment of 1 with dimethylsulfonium methylide gives the vinylcyclopropane (Ph2P)2CCHCH(CH2)C(PPh2)2 (2). Compound 2 reacts with aqueous hydrogen peroxide, elemental sulfur, or selenium to afford the tetrachalcogenides (Ph2XP)2CCHCH(CH2)C(PXPh2)2 with X = O (3), X = S (4), X = Se (5), respectively. While the tetraphosphane 1 and the vinyl‐cyclopropane compound 2 cannot be converted into a bis‐(cyclopropyl) compound with an excess of Me2SCH2, the tetrasulfide 4 readily affords a mixture of (1R,1′R)‐/(1S,1′S)‐and meso‐2,2,2′,2′‐tetrakis(diphenylthiophosphinyl)‐1,1′‐bicyclopropyl (6, 7) in good yield. Treatment of 1,1,4,4‐tetrakis‐(diphenylphosphanyl)butatriene with dimethylsulfonium methylide leads to the vinylidenecyclopropane (Ph2P)2CCC(CH2)C(PPh2)2 (8). Compound 8 is converted into its tetrasulfide (Ph2SP)2CCC(CH2)C(PSPh2)2 (9) by treatment with elemental sulfur. The crystal structures of 1, 2, 4, 7, and 8 have been determined by single‐crystal X‐ray diffraction.
Palladium‐Copper‐Catalyzed Coupling of Tricarbonylchromium‐Complexed Phenylacetylene with Iodoarenes – A Facile Access to Alkynyl‐Bridged Cr(CO)3‐Complexed Benzenes
Authors: Müller Thomas J. J. , Lindner Hans Jörg 
Published: July 2007

AbstractThe palladium‐copper‐catalyzed coupling of the tricarbonyl‐chromium‐complexed chlorobenzene 1 with (trimethylsilyl)‐acetylene gives tricarbonyl{η6‐[(trimethylsilyl)ethynyl]‐benzene}chromium(0) (2) in high yield. After desilylation of 2 tricarbonyl[η6‐(ethynylbenzene)]chromium(0) (3) is obtained quantitatively. Using the palladium‐copper‐catalyzed methodology, we can readily introduce Cr(CO)3‐complexed phenylethynyl units by a multifold coupling of 3 with iodobenzene, 1,2‐, 1,3‐, 1,4‐di‐ and 1,3,5‐tiiodobenzene (4a–e) or 1 to give polynuclear Cr(CO)3‐complexed (phenylethynyl)benzenes 5a–e and doubly Cr(CO)3‐complexed tolane 6 in good to moderate yield. The crystal structure analyses of μ3‐{η6:η6:η6[1,3,5‐benzenetriyltris(2,1‐ethynediyl)]tris(benzene)}tris[tricarbonylchromium(0)] (5e) and μ‐{η6:η6‐[1,2‐ethynediylbis(benzene)]}bis[tricarbonylchromium(0)] (6) reveal that the tricarbonylchromium tripods in the same molecule are arranged in antiparallel syn‐eclipsed conformations. The Eglington coupling of 3 affords a doubly Cr(CO)3‐complexed diphenylbutadiyne 7 in excellent yield.
Enantioselective Catalysis, XII. Synthesis of Bis(phosphane) Palladium and Rhodium Complexes on a Polyethylene Oxide Grafted Polystyrene Matrix (TentaGel) and the Catalytic Behavior of the Rhodium Complexes
Authors: Nagel Ulrich , Leipold Joachim 
Published: July 2007

AbstractA new polymer‐attached rhodium catalyst on a polyethylene oxide‐grafted styrene matrix (TentaGel) is described. The corresponding anchor molecules were prepared by starting from different Boc‐protected chiral pyrrolidinebis(phosphane)Pd complexes. The crystal structure of [3R,4R)‐N‐(4‐carboxybutanoyl)‐3,4‐bis(diphenylphosphanyl)pyrrolidine‐P,P′]‐diiodopalladium (1c) was determined. The formation of an amide bond between TentaGel and anchor molecules resulted in polymer‐bound Pd bisphosphane complexes. De‐complexation of the Pd with cyanide and reaction of the free polymeric ligand with [Rh(COD)2]BF4 led to the active hydrogenation catalyst. The influence of different solvents on the swelling volume and the catalytic behavior was tested. The polymer‐bound rhodium complex [(3R,4R)‐N‐(1,5‐dioxo‐5‐TentaGel‐amino‐pentyl)‐3,4‐bis (diphenylphosphanyl)pyrrolidineP,P′] (1,5‐cyclooctadiene)rhodium tetrafluoroborate (7) has about the same catalytic activity and enantioselectivity as the homogeneous complex [(3R,4R)‐N‐(tert‐butoxycarbonyl)‐3,4‐bis(diphenylphosphanyl)pyrrolidine‐P,P′] (1,5‐cyclooctadiene)rhodium tetrafluoroborate (9) in the same solvent mixture. It is possible to reuse 7 once, then it abruptly loses activity. This behavior remains to be clarified.
Euler characteristics of algebraic varieties
Authors: Cappell Sylvain E. , Maxim Laurentiu G. , Shaneson Julius L. 
Published: July 2007

AbstractThis note studies the behavior of Euler characteristics and of intersection homology Euler characteristics under proper morphisms of algebraic (respectively, analytic) varieties. The methods also yield, for algebraic (respectively, analytic) varieties, formulae comparing these two kinds of Euler characteristics. The main results are direct consequences of the calculus of constructible functions and Grothendieck groups of constructible sheaves. Similar formulae for Hodge‐theoretic invariants of algebraic varieties under morphisms were announced by the first and third authors in [5, 14]. © 2007 Wiley Periodicals, Inc.
Synthesis of a useful class of transmission line networks
Authors: Valtonen Martti 
Published: June 2007

AbstractA general class of networks consisting of cascaded commensurate transmission lines and shunt imaginary conductances is considered. This kind of network performs an excellent approximation to transmission line networks with shunt stubs or lumped elements. The realizability conditions for the driving‐point admittance and transfer function have been given in a previous paper. The imaginary conductances were generated by introducing an extra phase angle into the scattering function. In the present paper two alternative methods are given
by identifying in different ways the roots of the numerator polynomial in the input scattering function.
by using non‐symmetric gain functions.
The influence of different factorizations and non‐symmetric gain functions upon the element values variation is examined.
Network analysis of strongly coupled transverse apertures in waveguide
Authors: Rozzi T. E. 
Published: June 2007

AbstractMethods of field and network theory are jointly applied to the problem of transverse aperture‐type discontinuities in cascade under the conditions of multimodal excitation and interaction. A space Fourier transformation (modal analysis) translates the field problem into a network problem, whereby discontinuities take the significance of Hilbert‐ports à la Zemanian. When a discontinuity is considered as enclosed by an ideal cavity, representing energy storage in the ‘localized’ modes, Foster's form of the reactance matrix of the discontinuity is recovered. The relationship with the variational method in computing the resonance matrix of the ‘accessible’ modes is illustrated. Green's function of cascaded apertures is obtained by finite network analysis. A few examples of thick interacting inductive irises in cascade are numerically investigated. Results show very good agreement with experiment.
Application of an extended maximum modulus principle to minimum‐energy‐storage multiresistor realizations of an impedance
Authors: Smith William E. 
Published: June 2007

AbstractIt is shown by direct appeal to the analytic properties of current transfer functions, that minimum energy storage by a passive linear network implies that the current transfer to each resistor of the realization is a constant fraction of the corresponding single minimum‐phase‐shift transfer function of Darlington synthesis. The demonstration makes use of an extended version of the maximum modulus principle.
Efficient computation of large change multiparameter sensitivity
Authors: Singhal K. , Vlach J. , Bryant P. R. 
Published: June 2007

AbstractIn many applications, a network has to be solved repeatedly while certain element values are changed. The computation is reduced significantly if the network functions are generated in terms of these variable parameters explicitly. This paper presents a method of doing this which requires the solution of the network with at most m+1 excitations when there are m variable parameters.
On the solvability of DC equations and the implicit integration formula
Authors: Roska Tamás , Klimó János 
Published: June 2007

AbstractThe paper contains the following new results concerning the solvability of the DC equations and the implicit integration formula of a broad class of nonlinear networks.
A new method of proof is given.
Conditions are given for checking the unique solvability of the DC equation F(x)+Ax = b in case of monotone (not strictly monotone) and ‘steep’ characteristics and in the case when the characteristics have negative slope. Furthermore existence theorems are given under very weak conditions.
In the case of a broad class of nonlinear networks sufficient conditions are presented for the unique solvability of the implicit integration formula when the characteristics are monotone or have negative slope.
Some practical consequences of the theorems are also discussed.
Two active rc configurations for realizing nonminimum phase transfer functions
Authors: Soliman Ahmed M. 
Published: June 2007

AbstractTwo different realizations are given for synthesizing a second order nonminimum phase transfer function. The first circuit uses a single operational amplifier and a passive RC bandpass building block and has the advantage of being always stable. The second configuration uses two operational amplifiers to activate a symmetrical twin T, and has the advantage of providing a unity gain factor. Sensitivities to all circuit components and the frequency limitation equations for both networks are given.
Gain‐phase analysis of digital filters with applications
Authors: Haykin Simon S. 
Published: June 2007

AbstractThe article includes two fundamental sets of relations for minimum phase digital filters; the one set defines the relations between the gain and phase components, and the other set defines the relations between the group delay and gain slope components of the pulse transfer function of the filter. Two applications of these relations are considered: (i) Graphical computation of the phase characteristic of a digital filter with a prescribed gain characteristic. (ii) Computation of the gain characteristic of a linear phase digital filter.
An active rc filter for pcm systems
Authors: Gensel Joachim , Meissner Rolf , Seidel Volkmar 
Published: June 2007

AbstractAn active RC low‐pass filter using two high‐gain amplifiers with bridge feedback is described which serves as terminating unit of a PCM system channel. Some conditions derived from telecommunication applications and effecting the choice of the filter structure are discussed in detail, and the principles guaranteeing imaginary zeros under the condition of absolute stability of the filter sections are explained. The measurement results confirm that, using the method described, the fairly severe requirements, particularly the high pass‐band constancy demanded for units of telecommunication equipments, can be met at an economical cost.
Reciprocity, inter‐reciprocity, and transposition in wave digital filters
Authors: Fettweis Alfred 
Published: June 2007

AbstractFor wave digital filters, basic theorems which, although being more general, have a similarity to the difference form of Tellegen's theorem for classical networks, are derived, and the properties of reciprocity and inter‐reciprocity are defined. To each wave digital filter, there corresponds an entire family of transposed wave digital filters; each of these is inter‐reciprocal with the original one.Two types of transposition, called intrinsic and elementary transposition, are of particular importance. For these, the number of multipliers is the same after transposition as before, which is of interest for obtaining equivalent realizations. Intrinsic and elementary transposition are related to transposition (in the classical sense) and duality in the reference filter from which the wave digital filter is derived.
New general approach to commensurate tem transmission line networks using state space techniques
Authors: Kittel Ludwig 
Published: June 2007

AbstractThe paper begins with an investigation of the scattering properties of commensurate TEM transmission line networks, and emphasis is placed upon the distinction between normal networks and general (including non‐normal) networks.It is then shown that the state space concept of linear discrete systems is applicable to these networks. This provides a general and powerful systemtheoretical method for determining the network behaviour in the time and frequency domains. The waves on the transmission line elements are chosen as state variables; and for the important technical case of normal networks it is shown that each transmission line element contributes one state variable only. The entries in the state space matrices are formed by the scattering parameters of the connections and endings of the line elements; and the general method of obtaining these matrices is explained by detailed examples.An automatic network analysis program based on the state space approach needs only matrix multiplications. The program works primarily in the time domain, and the frequency behaviour is then computed by Fast Fourier Transform. The advantages of the program are demonstrated by a typical example.Finally an application to digital filters imitating TEM transmission line networks is presented.
Single‐tuned solid‐state microwave oscillators
Authors: Kenyon N. D. 
Published: June 2007

AbstractThe incorporation of a lossy stabilizing element into a microwave oscillator circuit is described. Such an element facilitates the application of dc bias to the circuit, and makes it unlikely that oscillations occur at undesired frequencies. There follows a description of configurations that have been used for solid‐state oscillators at frequencies from 8 GHz to over 110 GHz. These circuits have two outstanding features which facilitate characterization both of the circuits themselves and of diodes mounted therein.
Analysis of nonlinear model for operational amplifiers in active RC networks
Authors: Forsén Anders , Kristiansson Lars 
Published: June 2007

AbstractIn active RC networks certain nonlinear phenomena may occur due to the nonlinear properties of the amplifiers. It is shown that one of these, the slew rate limitation, may give rise to the jump phenomenon. The class of networks to be studied are described by a third order nonlinear differential equation. The theoretical and experimental results are found to correspond well.
Reciprocity in lumped linear‐time‐varying circuits
Authors: Howson D. P. 
Published: June 2007

AbstractReciprocity conditions applicable to LLTV circuits are considered. The sensitivity of some of these to time‐zero changes, and to LLTI network embedding is shown. Generalization from element to network is discussed and demonstrated to be sometimes possible. An equivalent circuit for a LLTV element is devised to show the essential non‐reciprocity of the general case.
Computer‐aided design of broad band reflection type amplifiers
Authors: Hammershaimb Edgar , Jeppesen Palle , Schjaer‐Jacobsen Hans 
Published: June 2007

AbstractMicrowave negative resistance reflection type amplifiers using stable transferred electron devices (TED's) are optimized by numerical optimization techniques programmed for an interactive graphic datascreen.The small signal impedance of packaged TED's is measured on an automatic network analyzer. At the same time the impedance of unpackaged devices are obtained by on‐line correction for the package parasitics. The microwave circuit chosen is a multiple slug coaxial cavity, that is modelled by sections of lossy transmission lines including step susceptances. The measured small signal impedance of the packaged TED's and the cavity model are used in a direct optimization procedure, in which the calculated minimum gain in the prescribed frequency range is progressively maximized by adjusting the lengths, characteristic impedances and positions of the slugs. The computed results are displayed on a datascreen, which allows for interactive programming.Comparisons of predicted amplifier performance for packaged and unpackaged devices form a basis for evaluating the possible degrading effect of package parasitics. The predictions of the computer‐aided design are in good agreement with experimental results. The design procedure imposes no restraint on the frequency variation of the active device impedance and is therefore useful for any stable broad‐banded negative resistance device.
Representation of noise in a particular type of linear n‐port network
Authors: Trofimenkoff F. N. , Treleaven D. H. , Bruton L. T. 
Published: June 2007

AbstractA noisy linear N‐port network that can be represented by a noise‐free linear N‐port network with voltage and current noise sources at the ports is considered. If the linear N‐port network has a particular type of admittance matrix, it is possible to show that as many as N/2 when N is even and (N – 1)/2 when N is odd of the ports may be cleared of noise sources. The total number of unique representations of such a network is given for both the general case and for the case when a particular port or ports must be free of noise sources.
A gyrator‐rc double‐tuned band‐pass amplifier a step towards the integrated I.F. amplifier of a broadcast receiver
Authors: Atiya Fuad S. , Ibrahim I. Hanna 
Published: June 2007

AbstractA gyrator‐RC twoport has the response of a conventional double‐tuned transformer‐coupled intermediate frequency amplifier stage. It uses two grounded gyrators and a π of capacitors to replace the transformer, and is designed for low sensitivity. Stages can be stagger‐tuned for a prescribed response. Suitable novel gyrator circuits are developed and measured. Measurements of the gyrator‐RC double‐tuned circuits give the known double‐tuned response with critical, over‐ and under‐critical coupling. A receiver circuit is suggested from the mixer to the detector in view of the gain, selectivity, A.G.C., swing and stability requirements. This circuit has to be reconsidered and possibly modified in later work for the purpose of integration.
Wave digital filters with reduced number of delays
Authors: Fettweis Alfred 
Published: June 2007

AbstractA method is described which allows one to design wave digital filters with a reduced number of excess delays. It consists in first multiplying all impedances of the original LC‐filter either by ϕ = tanh (pT/2) or by 1/ϕ, similar to what has been proposed by Bruton, although for different reasons, for active filter design. The restrictions inherent in this latter case do not apply, but some structures are preferable over others. The excellent sensitivity properties of wave digital filters still hold; they can again be proved directly by a modification of the earlier concepts of pseudopower, pseudopassivity, and pseudo‐losslessness.