Tailored activation of new platinum hydrosilylation catalysts

Bruske, Ericka

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https://hdl.handle.net/2142/122209 Copy

Description

Title

Tailored activation of new platinum hydrosilylation catalysts

Author(s)

Bruske, Ericka

Issue Date

2023-11-30

Director of Research (if dissertation) or Advisor (if thesis)

Fout, Alison R

Doctoral Committee Chair(s)

Fout, Alison R

Committee Member(s)

• Guironnet, Damien S
• Girolami, Gregory S
• Vura-Weis, Josh

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Catalysis
• Hydrosilylation
• Organometallic
• Activation

Language

eng

Abstract

Hydrosilylation (HS) is one of the largest fields in industrial chemistry due to the value of the many silicon-based products such as adhesives and resins. The goal of the work is to develop platinum catalysts featuring a triggering mechanism to initiate HS activity. Ideally, this catalyst would be inactive for up to 6 months and then, upon activation, would quickly catalyze the reaction. We propose that ligated Pt acetate complexes would serve well as dormant catalysts for this project. It has been shown that cobalt biscarboxylate complexes and analogous palladium acetate precatalysts can be reduced to their active form upon addition of silane; however, L2Pt(OAc)2 complexes have not previously been used as HS catalysts or as precursors to Pt0 species. A survey of L-type ligands was explored to promote RT stability and rapid HS activity upon activation. Starting from the diiodide precursors, altering the equivalences of AgOAc led to two different products, later characterized as the cis and trans isomers of (Py)2Pt(OAc)2. Structural modifications were explored to incorporate a 19F NMR handle which showed non-overlapping 19F NMR shifts that are chemically distinct for the isomers. Reacting the (Py)2Pt(OAc)2 complexes with 2 eq of MD’M resulted in the silyl acetate product expected along with Pt black and free pyridine. The loss of pyridine and rapid HS reaction rate does indicate the produced active species is comparable to Karstedt’s active catalyst, an industrially-relevant HS catalyst. Modified catalysts have shown greater room temperature stability. Additionally, we are exploring the design of Pt HS catalysts with a tailored latency period based on latency seen with a derivative of Markό’s catalyst. A variety of Pt0 complexes bearing an alkenesubstituted NHC of varying alkene chain length, C#ImPt(dvtms) (# = alkene chain length), have been synthesized. The alkene arms are proposed to coordinate to the Pt0 center and we expect HS of the alkene arms to cause a latency period as evidenced by observation of the C5 hydrosilylated catalyst. At -35 oC, the bound species, C4ImPt, was isolated from a pentane solution and later crystallized from diffusion of pentane into toluene. This species will be further investigated for HS activity. The analogous species, C5ImPt, has not been isolated or observed. Additionally, the hydrosilylated catalyst for the C4 complex is not cleanly observed, indicating the C4 bound species is more stable than the C5 species. In the HS of 1-octene at 0.05 mol%, C5satImPt(dvtms) showed no latency period followed by C4ImPt(dvtms) and C5ImPt(dvtms) with 4 and 20 min latency periods, respectively. Preliminary data utilizing styrene as the substrate shows drastic reactivity differences that are still being investigated in a substrate scope. In collaboration with Dow, Inc, we investigated the incorporation of the catalyst into a polymer to prevent leaching and post-cure crosslinking. At 20 ppm catalyst loading, the C5ImPt(dvtms) complex showed lower viscosity drift over 10 days than C5satImPt(dvtms), CyImPt(dvtms) [Markό’s catalyst], and Karstedt’s catalyst, indicating the active Pt species was successfully immobilized in the polymer.

Graduation Semester

2023-12

Type of Resource

Text

Handle URL

https://hdl.handle.net/2142/122209

Copyright and License Information

Copyright 2023 Ericka Bruske

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