The synthesis and characterization of platinum(II) oxalate complexes and investigations into their potential as UV-triggerable hydrosilylation catalysts

Weaver, Jenelle N

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https://hdl.handle.net/2142/120535 Copy

Description

Title

The synthesis and characterization of platinum(II) oxalate complexes and investigations into their potential as UV-triggerable hydrosilylation catalysts

Author(s)

Weaver, Jenelle N

Issue Date

2023-05-02

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

Girolami, Gregory S

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• synthesis
• catalysis
• hydrosilylation
• UV

Abstract

The hydrosilylation (HS) reaction, the addition of silicon hydride to a vinyl group, is one of the most important reactions in the silicone industry, affording high value elastomers used as sealant materials, adhesives, and coatings. Currently, the conventional catalyst used for this transformation is Karstedt’s catalyst, a homogenous platinum(0) compound that exhibits a very fast rate of reaction. Contemporary technology trends demand long shelf lives and storage stability combined with fast reactions upon activation at temperatures as close to ambient as possible. In collaboration with Dow Chemical Company, we were challenged to provide ideas for “UV-triggerable” HS catalysts. Upon activation of the complex by light, an active HS catalyst will be created that will catalytically activate the dormant species causing a rapid increase in catalyst concentration resulting in very fast curing. It has been known that ultraviolet irradiation of transition-metal oxalate complexes results in the irreversible fragmentation of the oxalate dianion to two molecules of carbon dioxide and reduction of the metal center. This aforementioned art suggests that platinum oxalate complexes show promise as UV-triggerable HS catalysts. In chapter 1, we describe the synthesis and characterization of the new compounds, Pt(C2O4)(dcpd) (1) and Pt(C2O4)(COD) (2), where dcpd = dicyclopentadiene and COD = 1,5-cyclooctadiene. We found that treatment of PtCl2(dcpd) or PtX2(COD), where X is Cl or I, with an excess (1.2-2 equiv.) of silver (I) oxalate in a 1:2 ratio of refluxing acetonitrile: dichloromethane for 5 to 7 days affords the new compounds 1 and 2. Compound 2 can also be synthesized via other synthetic routes. The isolated yields for compound 1 are moderate (40%) and modest for compound 2 (10%). We have also fully characterized the known platinum(dialkyl sulfide) oxalate complexes Pt(C2O4)(SMe2)2 (6) and Pt(C2O4)(SEt2)2 (7) by 1H NMR and 13C{1H} NMR spectroscopy, IR spectroscopy, and crystallographic X-ray diffraction. Chapter 2 describes investigations into the catalytic HS activity of platinum(II) oxalate compounds and their related starting materials, including catalytic control HS studies using 1-octene and 1,1,1,3,5,5,5-heptamethyltrisiloxane (HTMS), and qualitative catalytic HS studies using oligomeric substrates. Complexes 1 and 2 demonstrate promise as UV-triggerable HS catalysts based on quantitative catalytic 1H NMR rate studies and IR decomposition data and behave as heat-triggerable catalysts in certain solvents. We also report the UV-Vis absorption spectra of compounds 1, 2, 6, and 7 and have demonstrated that complexes 1 and 2 decompose photochemically via UV irradiation with approximate photolysis rates of 1.6 × 10-6 and 6.9 × 10-7 moles/min for compounds 1 and 2, respectively.

Graduation Semester

2023-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Jenelle N. Weaver

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