Anion exchange in [Ni(η5-C5H4R)(Cl)(NHC)]. Counterion effect on the structure and catalytic activity

Włodzimierz Buchowicz,Piotr Buchalski,Joanna Conder,Piotr A Guńka,Dominik Kubicki,Łukasz Banach

doi:10.1039/c3dt53352b

Włodzimierz Buchowicz, Piotr Buchalski + Show 4 more

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https://doi.org/10.1039/c3dt53352b

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Journal: Dalton Transactions	Publication Date: Jan 1, 2014
Citations: 24	License type: cc-by

Affiliation: Warsaw University of Technology

Abstract

A series of novel complexes [Ni(η(5)-C5H4R)(L)(NHC)](+)A(-)2a-2j and [Ni(η(5)-C5H5)(A)(NHC)] 3a-3c has been obtained by anion metathesis from the corresponding chlorides 1a-1d, depending on the anion binding properties and reaction conditions. Solid-state structures of two cationic complexes (2c, 2j) and two complexes with a coordinated anion (3a, 3c) have been determined by X-ray diffraction revealing a trigonal planar geometry in all cases. Unexpectedly, 3c displayed unprecedented for this type of compounds temperature-dependent NMR spectra that were interpreted in terms of spin equilibrium. The cationic complexes 2 were less efficient in styrene polymerization than the parent chlorides 1. However, the activity of 2 and 3 in Suzuki cross-coupling did not depend considerably on the counterion.

Highlights

Transition metal N-heterocyclic carbene (NHC) complexes are a growing field of interest in organometallic chemistry, homogeneous catalysis, and other areas of chemistry.[1]
We explore the scope of halogen substitution in complexes [Ni(η5-C5H4R)(Cl)(NHC)] with various metal salts, including non-coordinating and weakly-coordinating anions, and catalytic properties of the resulting complexes
Nolan and co-workers reported that nickelocene did not react with NHC tetrafluoroborates or hexafluorophosphates in refluxing THF.4a when we attempted to synthesize [Ni(η5-C5H5)(CH3CN)(NHC)]+(BF4)− directly from nickelocene and an imidazolium tetrafluoroborate in refluxing acetonitrile, a gradual decomposition of nickelocene was observed (Scheme 1, path b)

Summary

Introduction

Transition metal N-heterocyclic carbene (NHC) complexes are a growing field of interest in organometallic chemistry, homogeneous catalysis, and other areas of chemistry.[1]. The expected cationic complexes 2 were obtained as yellow-brown solids in high yields for KPF6, AgClO4, and AgCF3SO3 (Scheme 2).

Results

Conclusion