Cobaltocenylidene: A Mesoionic Metalloceno Carbene, Stabilized in a Gold(III) Complex.

Stefan Vanicek,Michael Pittracher,Maren Podewitz,Klaus Wurst,Rainer F Winter,Holger Kopacka,Klaus R Liedl,Thomas Müller,Benno Bildstein,Christopher Hassenrück

doi:10.1002/chem.201800147

Stefan Vanicek, Michael Pittracher + Show 8 more

Open Access

https://doi.org/10.1002/chem.201800147

Copy DOI

Journal: Chemistry	Publication Date: Feb 5, 2018
Citations: 16	License type: CC BY 4.0

Affiliation: Universität Innsbruck, University of Konstanz

Abstract

Oxidative addition of cobaltoceniumdiazonium bis(hexafluoridophosphate) with (pseudo)halide aurates gave gold(III) complexes containing zwitterionic cobaltoceniumide as a ligand. Its selenium derivative, cobaltoceniumselenolate, was obtained by an electrophilic aromatic substitution reaction of iodocobaltocenium iodide with Na2Se. Spectroscopic and structural data in combination with DFT calculations showed that this cobaltocenylidene species is a mesoionic carbene quite different from common N‐heterocyclic carbenes. Its ligand properties (TEP, singlet‐triplet gap, nucleophilicity, π‐acidity, Brønsted basicity) are in part comparable to those of cyclic (amino)(alkyl/aryl)carbenes. Electrochemistry data showed that the mesoionic cobaltoceniumides are more electron‐rich than their parent ferrocenes. The reversible reduction of the tricyanido gold complex appears 50 mV negative of the cobaltocenium/cobaltocene couple, whereas that of the selenide derivative is shifted cathodically by 550 mV.

Highlights

Oxidative addition of cobaltoceniumdiazonium bis(hexafluoridophosphate) withhalide aurates gave gold(III) complexes containing zwitterionic cobaltoceniumide as a ligand
The reaction of a mixture of cobaltoceniumdiazonium bis(hexafluoridophosphate) (1),[3] potassium dicyanidoaurate, and potassium cyanide in nitromethane solution resulted in an oxidative addition at gold(I) with concomitant N2 evolution, affording the cobaltocenylidene complex (CcC)Au(CN)3 (2) as an air-stable, yellow solid (Scheme 2 and the Supporting Information)
Applying a correlation of 77Se chemical shifts and 1J(13CÀ77Se) coupling constants with Tolman electronic parameter (TEP) values proposed by Ganter et al.,[19] TEP = ad(77Se) + b1J(13CÀ77Se) + c with a = 0.0191, b = 0.0424, c = 2040.8, gave for the mesoionic CcC ligand a rather high value of 2054 cmÀ1 not supported by our experimental data, most likely due to limitations of this unique; rather rough correlation (R2 = 0.833) to N-heterocyclic carbenes (NHCs) ligands.[19]

Summary

Introduction

Oxidative addition of cobaltoceniumdiazonium bis(hexafluoridophosphate) with (pseudo)halide aurates gave gold(III) complexes containing zwitterionic cobaltoceniumide as a ligand.

Results

Conclusion