Reactivity of Sodium Pentaphospholide Na[cyclo-P5] towards C≡E (E=C,N, P) Triple Bonds

A diglyme solution of Na[cyclo-P₅] ( 1 ) reacts with alkynes and isolobal nitriles and phosphaalkynes to afford the otherwise elusive (aza)phospholide anions 2 a – c , 4 a,b , and 6 . The reaction of Na[cyclo-P₅] with alkynes and nitriles was studied by means of DFT methods, which suggested a concerted mechanism for the formation of 2 a and 4 b . The anions 2 a – c , 4 a,b , and 6 coordinate in an η⁵-fashion towards Fe^II to give the sandwich (aza)phosphametallocenes 3 a – c , 5 a,b and 7 in moderate to good yields. The new compounds were characterized by means of multinuclear NMR spectroscopy, single-crystal X-ray diffraction and cyclic voltammetry.     

Ein ungewöhnlicher trimerer Bimetallkomplex mit dem Gerüst [Zr3(μ2-OH)3(μ3-O)Li5] durch Reaktion von Zirconiumorgano- und -hydrido-Komplexen mit Wasser

An Unusual Trimeric Bimetallic Li? Zr Complex with the Backbone [Zr₃(μ₂-OH)₃(μ₃-O)Li₅] by Reaction of Zirconiumorgano and Hydrido Complexes with Water The reaction of compounds of the type [(LZr)(LiH)(L′)]_n and [(LZr)(LiH)(L′)(alkyne)]_n (L: 2,2′-Biphenolato-dianion, L′: thf, Bu₃P, alkyne: Ph? C?C? SiMe₃, CH?CH) with water at 0°C in a thf solution results in the formation of th trimeric bimetallic complex 8 [(L₂Zr)₃(μ₂-OH)₃(μ₃-O)Li₅(thf)₈(H₂O)₅] in 50% yield. The X-ray analysis of 8 shows that a planar six-membered ring Zr₃(μ₂-OH)₃ is formed. In the middle of this ring is a dianionic oxygen atom placed, coordinating to the three L₂Zr centres in a planar μ₃-coordination (bond angles 120,05μ). Five lithium ions stabilize the anionic backbone by bridging the biphenolato chelate ligands, which form seven-membered chelate rings with the atoms. ¹H-, ¹³C-, and ⁷Li-NMR spectra exhibit that the solid state structure remains unchanged in solution (thf).     

Zur Reaktivität von Titanocenkomplexen [Ti(Cp′)2(η2‐Me3SiC≡CSiMe3)] (Cp′ = Cp,Cp*) gegenüber Benzoldicarbonsäuren

On the Reactivity of Titanocene Complexes [Ti(Cp′)₂(η²‐Me₃SiC≡CSiMe₃)] (Cp′ = Cp, Cp*) towards Benzenedicarboxylic Acids Titanocene complexes [Ti(Cp′)₂(BTMSA)] ( 1a , Cp′ = Cp = η⁵‐C₅H₅; 1b , Cp′ = Cp* = η⁵‐C₅Me₅; BTMSA = Me₃SiC≡CSiMe₃) were found to react with iodine and methyl iodide yielding [Ti(Cp′)₂(μ‐I)₂] ( 2a / b ; a refers to Cp′ = Cp and b to Cp′ = Cp*), [Ti(Cp′)₂I₂] ( 3a / b ) and [Ti(Cp′)₂(Me)I] ( 4a / b ), respectively. In contrast to 2a , complex 2b proved to be highly moisture sensitive yielding with cleavage of HCp* [{Ti(Cp*)I}₂(μ‐O)] ( 7 ). The corresponding reactions of 1a / b with p‐cresol and thiophenol resulted in the formation of [Ti(Cp′)₂{O(p‐Tol)}₂] ( 5a / b ) and [Ti(Cp′)₂(SPh)₂] ( 6a / b ), respectively. Reactions of 1a and 1b with 1,n‐benzenedicarboxylic acids (n = 2–4) resulted in the formation of dinuclear titanium(III) complexes of the type [{Ti(Cp′)₂}₂{μ‐1,n‐(O₂C)₂C₆H₄}] (n = 2, 8a / b ; n = 3, 9a / b ; n = 4, 10a / b ). All complexes were fully characterized analytically and spectroscopically. Furthermore, complexes 7 , 8b , 9a ·THF, 10a / b were also be characterized by single‐crystal X‐ray diffraction analyses.     

Electron Transfer in a Supramolecular Associate of a Fullerene Fragment

Herein, we investigate the association of a fullerene fragment, hemifullerene C₃₀H₁₂, with an electron‐donating bowl‐shaped tetrathiafulvalene derivative (truxTTF). UV/Vis titrations and DFT calculations support formation of the supramolecular complex, for which an association constant of log K_a=3.6±0.3 in CHCl₃ at room temperature is calculated. Remarkably, electron transfer from truxTTF to C₃₀H₁₂ to form the fully charge‐separated species takes place upon irradiation of the associate with light, constituting the first example in which a fullerene fragment mimics the electron‐accepting behavior of fullerenes within a supramolecular complex.     

The total ponderomotive force and inhomogeneity indicators

Droplets on outdoor high‐voltage equipment suffer a total ponderomotive force which is non‐vanishing in general. We show that this force can be given as a series of inhomogeneity indicators of the undisturbed electric field in the absence of the droplet. We use 2d and 3d Fourier techniques to prove the series expansion as a relation between the solutions of two Poisson's equations on different domains. The order of magnitude of the terms in the series expansion is discussed. It is found that the expansion converges fast in applicatory cases. The results are applied for droplets on a realistically shaped insulator. Copyright © 2006 John Wiley & Sons, Ltd.     

Local order in polycarbonate glasses by 13C{19F} rotational‐echo double‐resonance NMR

Nearest‐neighbor chain packing in a homogeneous blend of carbonate ¹³C‐labeled bisphenol A polycarbonate and CF₃‐labeled bisphenol A polycarbonate has been characterized using a shifted‐pulse version of magic‐angle spinning ¹³C{¹⁹F} rotational‐echo double‐resonance (REDOR) NMR. Complementary NMR experiments have also been performed on a polycarbonate homopolymer containing the same ¹³C and ¹⁹F labels. In the blend, the ¹³C observed spin was at high concentration, and the ¹⁹F dephasing or probe spin was at low concentration. In this situation, an analysis in terms of a distribution of isolated heteronuclear pairs of spins is valid. A comparison of the results for the blend and homopolymer defines the NMR conditions under which higher concentrations of probe labels can be used and a simple analysis of the REDOR results is still valid. The nearest neighbors of a CF₃ on one chain generally include a carbonate group on an adjacent chain. A direct interpretation of the REDOR total dephasing for the polycarbonate blend indicates that at least 75% of carbonate‐carbon ¹³C ··· F₃ nearest neighbors are separated by a narrow distribution of distances 4.7 ± 0.3 Å. In addition, analysis of the variations in REDOR spinning‐sideband dephasing shows that most of the ¹³C ··· F₃ dipolar vectors have a preferred orientation relative to the polycarbonate mainchain axis. This combination of distance and orientational constraints is interpreted in terms of local order in the packing of the carbonate group of one polycarbonate chain relative to the isopropylidene moiety in a neighboring chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2760–2775, 2006     

The random planar graph process

We consider the following variant of the classical random graph process introduced by Erd?s and Rényi. Starting with an empty graph on n vertices, choose the next edge uniformly at random among all edges not yet considered, but only insert it if the graph remains planar. We show that for all ε > 0, with high probability, θ(n²) edges have to be tested before the number of edges in the graph reaches (1 + ε)n. At this point, the graph is connected with high probability and contains a linear number of induced copies of any fixed connected planar graph, the first property being in contrast and the second one in accordance with the uniform random planar graph model. © 2007 Wiley Periodicals, Inc. Random Struct. Alg., 2008