Koordinativ ungesättigte Dirutheniumkomplexe: Synthese und Kristallstrukturen von [Ru2(CO)n(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] (n = 4; 5) und [Ru2(CO)4(μ‐CH2)(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)]

Coordinatively Unsaturated Diruthenium Complexes: Synthesis and X‐ray Crystal Structures of [Ru₂(CO)_n(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] (n = 4; 5) and [Ru₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] The reaction of [Ru₂(μ‐CO)(CO)₅(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] ( 2 ) with dppm yields the dinuclear species [Ru₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 3 ) (dppm = Ph₂PCH₂PPh₂). Under thermal or photolytic conditions 3 loses very easily one carbonyl ligand and affords the corresponding electronically and coordinatively unsaturated complex [Ru₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 4 ). 4 is also obtainable by an one‐pot synthesis from [Ru₃(CO)₁₂], an excess of ^tBu₂PH and stoichiometric amounts of dppm via the formation of [Ru₂(CO)₄(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)₂] ( 1 ). 4 exhibits a Ru–Ru double bond which could be confirmed by addition of methylene to the dimetallacyclopropane [Ru₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 5 ). The molecular structures of 3 , 4 and 5 were determined by X‐ray crystal structure analyses.     

Diacetonalkohol als Komplexligand. Die Kristallstrukturen von [MnBr2{O=C(Me)CH2–C(Me)2OH}2] und [M{O=C(Me)CH2–C(Me)2OH}2][MCl4] mit M = Fe,Co und Zn

Diacetone Alcohol as Complex Ligand. Crystal Structures of [MnBr₂{O=C(Me)CH₂–C(Me)₂OH}₂] and [M{O=C(Me)CH₂–C(Me)₂OH}₂][MCl₄] with M = Fe, Co, and Zn The metal halides MnBr₂ and MCl₂ (M = Fe, Co, Zn) react with diacetone alcohol (4-hydroxy-4-methyl-2-pentanon) forming the title compounds, which are characterized by IR spectroscopy and crystal structure analyses. [MnBr₂{O=C(Me)CH₂–C(Me₂)OH}₂] ( 1 ): Space group C2/c, Z = 4, lattice dimensions at 293 K: a = 1189.2(4), b = 1317.2(3), c = 1200.0(3) pm, β = 102.25(3)°, R₁ = 0.0256. In 1 the manganese atom is coordinated in a distorted octahedral fashion by the two cis bromine atoms and by the four oxygen atoms of the two diacetone alcohol chelating molecules. The distances Mn–[OH] (223.8 pm) and Mn–[O=C] (222.1 pm) are only slightly different. [M{O=C(Me)CH₂–C(Me)₂OH}₂][MCl₄] [M = Fe ( 2 ), Co ( 3 ), Zn ( 4 )]: 2 and 3 crystallize isotypically with each other in the space group Pc, Z = 4. Lattice dimensions for 2 at 293 K: a = 865.8(3), b = 926.3(2), c = 1401.5(1) pm, β = 104.19(2)°, R₁ = 0.0421. Lattice dimensions for 3 at 293 K: a = 872.3(1), b = 925.7(1), c = 1394.2(3) pm, β = 104.79(2)°, R₁ = 0.0481. As in 1 , the metal atoms of the [M{O=C(Me)CH₂–C(Me)₂OH}₂]²⁺ ions in 2 and 3 are chelated in a distorted octahedral fashion by two diacetone alcohol molecules and associated cis via two μ-Cl atoms of the [MCl₄]^2– anions to form strands. [Zn{O=C(Me)CH₂–C(Me)₂OH}₂][ZnCl₄] ( 4 ): Space group C2/c, Z = 4. Lattice dimensions at 213 K: a = 1582.27(13), b = 1356.15(13), c = 941.93(7) pm, β = 107.283(10)°, R₁ = 0.0328. The zinc atom of the dication in 4 is associated in a distorted octahedral fashion by the two diacetone alcohol chelating molecules in the equatorial positions and trans by two μ-Cl atoms of the [ZnCl₄]^2– ions to form strands.     

Koordinativ ungesättigte Dieisenkomplexe: Synthese und Kristallstrukturen von [Fe2(CO)4(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] und [Fe2(CO)4(μ‐CH2)(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)]

Coordinatively Unsaturated Diiron Complexes: Synthesis and Crystal Structures of [Fe₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] and [Fe₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] [Fe₂(μ‐CO)(CO)₆(μ‐H)(μ‐P^tBu₂)] ( 1 ) reacts spontaneously with dppm (dppm = Ph₂PCH₂PPh₂) to give [Fe₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 2 c ). By thermolysis or photolysis, 2 c loses very easily one carbonyl ligand and yields the corresponding electronically and coordinatively unsaturated complex [Fe₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 3 ). 3 exhibits a Fe–Fe double bond which could be confirmed by the addition of methylene to the corresponding dimetallacyclopropane [Fe₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 4 ). The reaction of 1 with dppe (Ph₂PC₂H₄PPh₂) affords [Fe₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppe)] ( 5 ). In contrast to the thermolysis of 2 c , yielding 3 , the heating of 5 in toluene leads rapidly to complete decomposition. The reaction of 1 with PPh₃ yields [Fe₂(CO)₆(H)(μ‐P^tBu₂)(PPh₃)] ( 6 a ), while with ^tBu₂PH the compound [Fe₂(μ‐CO)(CO)₅(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] ( 6 b ) is formed. The thermolysis of 6 b affords [Fe₂(CO)₅(μ‐P^tBu₂)₂] and the degradation products [Fe(CO)₃(^tBu₂PH)₂] and [Fe(CO)₄(^tBu₂PH)]. The molecular structures of 3 , 4 and 6 b were determined by X‐ray crystal structure analyses.     

Hydrogendiazid Synthese und Kristallstruktur von PPh4[N3HN3]

Hydrogen Diazide – Synthesis and Crystal Structure of PPh₄[N₃HN₃] PPh₄[N₃HN₃] has been prepared from PPh₄N₃ and Me₃SiN₃ by the reaction with water or ethanol forming colourless nonexplosive crystal needles, which were characterized by IR spectroscopy and by a crystal structure determination. Space group C2/c, Z = 12, lattice dimensions at –70 °C: a = 3782.4(3), b = 727.8(2), c = 2512.4(2) pm, β = 110.13(1)°, R = 0.0841. The [N₃HN₃]^– ion is characterized by an asymmetric N–H…N hydrogen bridge with a NN distance of 272(1) pm.     

Interfacial properties of glassy polymer melts: A Monte Carlo study

The properties of the interface between a polymer melt and a solid wall are studied over a wide range of temperatures by dynamic Monte Carlo simulations. It is shown that in the supercooled state near the glass transition of the melt an “interphase” forms, the structure of which is influenced by the wall. The thickness of this interphase is determined from the monomer density profile near the surface and is strongly temperature dependent. At low glass-like temperatures it is larger than the bulk radius of gyration of the chains.     

Singlet Sigma: The "Other" Singlet Oxygen in Solution

The lowest excited electronic state of molecular oxygen, O₂(a^1-DL_g), is often called simply singlet oxygen. This singlet delta state is an acknowledged and well-studied intermediate in many solution-phase photosystems. However, the second excited electronic state of oxygen, O₂(b¹δ_g+), is also a singlet. It has recently become possible to monitor this singlet sigma state in solution, which, in combination with studies of the singlet delta state, contributes to a better understanding of a variety of general problems in chemistry.     

Artificial Light-Harvesting Antennae: Singlet Excitation Energy Transfer from Zinc Chlorin Aggregate to Bacteriochlorin in Homogeneous Hexane Solution

Abstract— Zinc chlorins possessing 3¹-hydroxyl and 13¹-carbonyl groups self-assemble in nonpolar solvents, such as hexane, in a manner similar to bacteriochlorophyll c in the chlorosomes of green photosynthetic bacteria. Visible absorption and steady-state fluorescence measurements of zinc chlorin aggregates containing a small amount of the bacteriochlorin-zinc chlorin dyad molecules showed that singlet excitation energy transfer from the zinc chlorin aggregate to the bacteriochlorin moiety of the coaggre-gated dyad occurs in the homogeneous solution. In the coaggregated dyad, the bacteriochlorin moiety plays the role of an efficient energy trap and the chlorin moiety the role of an anchor to the donor aggregate. The artificial assembly thus mimics the structure and function of natural chlorosomes and can be considered as the first in vitro supramolecular light-harvesting antenna.     

A Tracking Controller for a Certain Class of Nonlinear Systems

Controller design methods based on flatness and passivity are well established. These methods are applied to PCHD systems such that flatness is used to achieve a high tracking performance and passivity ensures disturbance rejection and robustness. Since the error system, written in displacement coordinates, is not a PCHD system in general, we present conditions, which ensures this property. Therefore, one can apply methods from passivity control to stabilize the error dynamics. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)