Publications by Paul Varava | EPFL Graph Search

Ambiphilic Reactivity of Iridium Complexes with N-Heterocyclic Vinylidene Ligands

Kay Severin, Rosario Scopelliti, Farzaneh Fadaei Tirani, Paul Varava, Tak Hin Wong

Room-temperature stable diazoolefins provide access to a unique class of carbon-donor ligands: N-heterocyclic vinylidenes. Herein, we describe iridium complexes with terminal N-heterocyclic vinylidene ligands. Cationic complexes of type [Cp*IrClL]X (X = Sb ...

American Chemical Society (ACS)2025

Head‐to‐Tail Dimerization of N‐Heterocyclic Diazoolefins

Andrzej Sienkiewicz, Kay Severin, Rosario Scopelliti, Farzaneh Fadaei Tirani, Paul Varava, Zhaowen Dong, Anastasia Gitlina, Wolfram Feuerstein, Tak Hin Wong

The head-to-tail dimerization of N-heterocyclic diazoolefins is described. The products of these formal (3+3) cycloaddition reactions are strongly reducing quinoidal tetrazines. Oxidation of the tetrazines occurs in a stepwise fashion, and we were able to ...

Wiley-VCH Verlag GmbH2023

Copper Complexes with Diazoolefin Ligands and their Photochemical Conversion into Alkenylidene Complexes

Kay Severin, Rosario Scopelliti, Farzaneh Fadaei Tirani, Paul Varava, Bastiaan Kooij

Homometallic copper complexes with alkenylidene ligands are discussed as intermediates in catalysis but the isolation of such complexes has remained elusive. Herein, we report the structural characterization of copper complexes with bridging and terminal a ...

Wiley-VCH Verlag GmbH2023

Vanadium complexes with N-heterocyclic vinylidene ligands

Kay Severin, Rosario Scopelliti, Farzaneh Fadaei Tirani, Paul Varava, Zhaowen Dong, Bastiaan Kooij, Laura Piveteau

The preparation and the structural characterization of vanadium complexes with terminal and bridging N-heterocyclic vinylidene ligands is reported. The synthesis of the complexes was enabled by utilization of diazoolefins as ligand precursors. Structural d ...

Royal Society of Chemistry2022

Isolation, Characterisation and Reactivity of N-Heterocyclic Diazoolefins

Paul Varava

Examples for applications of nitrous oxide in organic synthesis remain rare up until today. First mayor contributions of our group were published in 2012, when nitrous oxide was successfully captured by N-heterocyclic carbenes. Subsequent studies investiga ...

EPFL2022

Isolation and characterization of diazoolefins

Kay Severin, Rosario Scopelliti, Farzaneh Fadaei Tirani, Paul Varava, Zhaowen Dong

Diazoolefins tend to be highly reactive compounds that rapidly lose dinitrogen. So far, most experimental evidence for diazoolefins is indirect, via trapping experiments. Here we show that diazoolefins are observed to form in reactions of N-heterocyclic ol ...

2021

Synthesis, structural characterization, and coordination chemistry of imidazole-based alkylidene ketenes

Kay Severin, Rosario Scopelliti, Farzaneh Fadaei Tirani, Paul Varava, Wolfram Feuerstein

Alkylidene ketenes typically display high intrinsic reactivity, impeding isolation on a preparative scale. Herein, we report the synthesis of alkylidene ketenes by reaction of imidazole-based diazoolefins with carbon monoxide. The good thermal stability of ...

Royal Society of Chemistry2021

Synthesis of aminyl biradicals by base-induced Csp3–Csp3 coupling of cationic azo dyes

Andrzej Sienkiewicz, Kay Severin, Rosario Scopelliti, Euro Solari, Léonard Yannick Maurice Eymann, Alexander Tskhovrebov, Alberto Fabrizio, Farzaneh Fadaei Tirani, Yizhu Liu, Ophélie Marie Planes, Paul Varava

2019

Synthesis of Organic Super-Electron-Donors by Reaction of Nitrous Oxide with N-Heterocyclic Olefins

Andrzej Sienkiewicz, Kay Severin, Rosario Scopelliti, Basile Curchod, Léonard Yannick Maurice Eymann, Farzaneh Fadaei Tirani, Yizhu Liu, Ophélie Marie Planes, Paul Varava, Andrei Shved

The reaction of nitrous oxide (N2O) with N-heterocyclic olefins (NHOs) results in cleavage of the N–O bond and formation of azo-bridged NHO dimers. The latter represent very electron-rich compounds with a low ionization energy. Cyclic voltammetry studies s ...

2019