Piperidinium and Pyrrolidinium Ionic Liquids as Precursors in the Synthesis of New Platinum Catalysts for Hydrosilylation

Magdalena Jankowska-Wajda,Hieronim Maciejewski,Przemysław Pietras,Olga Bartlewicz

doi:10.3390/catal10080919

Magdalena Jankowska-Wajda, Hieronim Maciejewski + Show 2 more

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https://doi.org/10.3390/catal10080919

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Journal: Catalysts	Publication Date: Aug 10, 2020
Citations: 10	License type: CC BY 4.0

Affiliation: Adam Mickiewicz University in Poznań

Abstract

Six new air-stable anionic platinum complexes were synthesized in simple reactions of piperidinium [BMPip]Cl or pyrrolidinium [BMPyrr]Cl ionic liquids with platinum compounds ([Pt(cod)Cl2] or K2[PtCl6]). All these compounds were subjected to isolation and spectrometric characterization using NMR and ESI-MS techniques. Furthermore, the determination of melting points and thermal stability of the above derivatives was performed with the use of thermogravimetric analysis. The catalytic performance of the synthesized complexes was tested in hydrosilylation of 1-octene and allyl glycidyl ether with 1,1,1,3,5,5,5-heptamethyltrisiloxane. The study has shown that they have high catalytic activity and are insoluble in the reaction medium which enabled them to isolate and reuse them in consecutive catalytic cycles. The most active complex [BMPip]2[PtCl6] makes it possible to conduct at least 10 catalytic runs without losing activity which makes it an attractive alternative not only to commonly used homogeneous catalysts, but also to heterogeneous catalysts for hydrosilylation processes. The activity of the studied catalysts is also affected by the kind of anion and, to some extent, the kind of cation.

Highlights

Environmental, economic and technological reasons prompt researchers to pay more and more attention to planning new paths of synthesis of chemical compounds and continuing work on already known reactions and processes successfully employed in the industry, which can be optimized in the aspects of the improvement in yield, reduction in produced waste and possibility of reusing catalysts
In the case of the synthesis of tetrachloroplatinates, depending on the amount of the precursor and ionic liquid, complexes were formed with a different form of the anion
Six new air-stable anionic platinum complexes were synthesized with high yields in the reaction of a suitable ionic liquid and platinum compound and the complexes were fully characterized

Summary

Introduction

Environmental, economic and technological reasons prompt researchers to pay more and more attention to planning new paths of synthesis of chemical compounds and continuing work on already known reactions and processes successfully employed in the industry, which can be optimized in the aspects of the improvement in yield, reduction in produced waste and possibility of reusing catalysts. Attempts are made at reaching the equilibrium between the costs of conducting a process, its yield, and the environmental impact. All these aspects are in line with the premises of “green chemistry” [1]. One of the processes commonly used on the industrial scale and being the main way of synthesis of organosilicon compounds is hydrosilylation [2,3,4] Catalysts for this process are most often transition-metal-based systems of which the most important are platinum complexes, Karstedt ([Pt2 {H2 C=CHSiMe2 ) O}3 ] and Speier (H2 PtCl6 /i-PrOH) catalysts [5]. Taking into consideration high price of platinum and the necessity to separate the catalyst from the postreaction mixture (because the presence of heavy metals, even in trace amounts, is impermissible in many applications of the reaction product), efforts are made to employ catalytic systems based on other metals or to heterogenize the most active platinum complexes [5,6]

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