PdS2C2(COOMe)2](6n) (n = 0, -1, -2, -3, -4): hexanuclear homoleptic palladium dithiolene complexes

Reaction of a stoichiometric equivalent of the zinc-dithiolene complex, (tmeda)ZnS2C2(COOMe)2 (tmeda = tetramethylethylenediamine), with (MeCN)2PdCl2 results in a 1:1 homoleptic dithiolene that forms the hexanuclear cluster [PdS2C2(COOMe)2]6 (1). X-ray structure analysis of 1 indicates a Pd6S12 core comprised of six face-centered palladium atoms and 12 edge-centered sulfur atoms situated on an imaginary approximate cube. Complex 1 undergoes four distinct and reversible one-electron redox steps in dichloromethane at -186, -484, -1174, and -1524 mV versus a standard calomel electrode (ferrocenium+/ferrocene redox couple 409 mV). The two-electron reduction product of 1, [Bu4N]2[(PdS2C2(COOMe)2)6] (2), has been chemically isolated and characterized.     

Neuere numerische methoden in der himmelsmechanik

The main problem of celestial mechanics is to compute the movement of a point mass in space. The force entering the relevant differential equations can often be split into two parts, one of which can be considered as a small perturbation. This paper reviews some methods useful for the solution of such equations. Gröbner's non-linear method is briefly mentioned. Further, a regularization technique, appropriate for the perturbed Kepler problem, is discussed and compared with other methods. Finally, the treatment in the case of forced perturbations which are of interest for satellites, is briefly outlined.

---

---

This paper was presented at the NordSAM conference in Stockholm, Aug. 1964.     

Rechenautomat 704 IBM

Ohne Zusammenfassung     

Buchbesprechungen

Ohne Zusammenfassung

---

Book revies

---

Notices bibliographiques

     

Ermittlung von allgemeinen Störungen einer Planetenbewegung mit Hilfe der Ergebnisse einer speziellen Störungsrechnung

Ohne ZusammenfassungHerrnAlexander Ostrowski zum 60. Geburtstag gewidmet     

Resolving the CO/CN ligand arrangement in CO-inactivated [FeFe] hydrogenase by first principles density functional theory calculations

The currently presumed assignment of CO/CN ligands in the structure of the active cluster in CO-inactivated [FeFe] hydrogenase is shown to be inconsistent with the available IR data in the enzyme from Clostridium pasteurianum I. A different arrangement has the correct qualitative and quantitative features, reproducing the observed line spacing and intensities and the observed line shift consequent to inactivation with labeled 13CO instead of 12CO. The new assignment is also consistent with the observed change from rhombic to axial symmetry of the electron paramagnetic resonance g tensor upon inactivation.     

Theoretical studies of [FeFe]-hydrogenase: structure and infrared spectra of synthetic models

First-principles density functional theory calculations of synthetic models of [FeFe]-hydrogenase are used to show that the theoretical methods reproduce observed structures and infrared spectra to high accuracy. The accuracy is demonstrated for synthetic Fe(I)Fe(I) models ([(mu-PDT)Fe2(CO)6] and [(CN)(CO)2(mu-PDT)Fe2(CO)2(CN)]2-), for which we show that their infrared spectra are sensitive to the geometric arrangement of their CO/CN ligands and can be used in conjunction with quantum-mechanical total energies to predict the correct ligand geometry. We then analyze and predict the structure of mixed-valence Fe(II)Fe(I) models ([(mu-MeSCH2C(Me)(CH2S)2)Fe2(CO)4(CN)2]x-). These capabilities promise to distinguish among the various structural isomers of the enzyme's active site which are consistent with the limited accuracy of the X-ray observations.