Synthesis of Low-Valent Dinuclear Group 14 Compounds with Element–Element Bonds by Transylidation

Dinuclear low-valent compounds of the heavy main group elements are rare species owing to their intrinsic reactivity. However, they represent desirable target molecules due to their unusual bonding situations as well as applications in bond activations and materials synthesis. The isolation of such compounds usually requires the use of substituents that provide sufficient stability and synthetic access. Herein, we report on the use of strongly donating ylide-substituents to access low-valent dinuclear group 14 compounds. The ylides not only impart steric and electronic stabilization, but also allow facile synthesis via transfer of an ylide from tetrylene precursors of type ^RY₂E to ECl₂ (E=Ge, Sn; ^RY=TolSO₂(PR₃)C with R=Ph, Cy). This method allowed the isolation of dinuclear complexes amongst a germanium analogue of a vinyl cation, [(^PhY)₂GeGe(^PhY)]⁺ with an electronic structure best described as a germylene-stabilized Ge^II cation and a ylide(chloro)digermene [^CyY(Cl)GeGe(Cl)^CyY] with an unusually unsymmetrical structure.     

Nilpotent completely positive maps

We study the structure of nilpotent completely positive maps in terms of Choi-Kraus coefficients. We prove several inequalities, including certain majorization type inequalities for dimensions of kernels of powers of nilpotent completely positive maps.     

Survival of Classical and Quantum Particles in the Presence of Traps

We present a detailed comparison of the motion of a classical and of a quantum particle in the presence of trapping sites, within the framework of continuous-time classical and quantum random walk. The main emphasis is on the qualitative differences in the temporal behavior of the survival probabilities of both kinds of particles. As a general rule, static traps are far less efficient to absorb quantum particles than classical ones. Several lattice geometries are successively considered: an infinite chain with a single trap, a finite ring with a single trap, a finite ring with several traps, and an infinite chain and a higher-dimensional lattice with a random distribution of traps with a given density. For the latter disordered systems, the classical and the quantum survival probabilities obey a stretched exponential asymptotic decay, albeit with different exponents. These results confirm earlier predictions, and the corresponding amplitudes are evaluated. In the one-dimensional geometry of the infinite chain, we obtain a full analytical prediction for the amplitude of the quantum problem, including its dependence on the trap density and strength.     

Synthesis of sugar-derived spiroaminals via lactamization and metathesis reactions

A series of sugar-derived spiroaminals has been synthesized by utilizing cross metathesis, ring closing metathesis and lactamization reactions as key steps from 1-C-alkylated glycosyl azides and important correlations in the spectral data between spiroaminals and their respective anomers are reported.     

Utility of a Ferrocene Unit in a Cyclometallated Cp*Ir(III) Catalyst during Water Oxidation: Exploring Bimetallic Cooperativity

Ferrocene functionalized 2-phenylpyridine iridium(III) pentamethylcyclopentadienyl complex is synthesized and probed for oxygen evolution from water. The excellent activity of this system has been rationalized by proposing a Fe(III)/Ir(IV) transient intermediate where bimetallic redox synergism between the Fe and Ir centres possibly provide an alternative pathway rather than a conventional Ir(V) based cycle.