Short-Chained Platinum Complex Catalyzed Hydrosilylation under Thermomorphic Conditions: Heterogeneous Phase Separation at Ice Temperature

Chiao-Fan Chiu; Jinn-Hsuan Ho; Eskedar Tessema; Yijing Lu; Chia-Rui Shen; Chang-Wei Lin; Norman Lu

doi:10.3390/molecules26020378

Short-Chained Platinum Complex Catalyzed Hydrosilylation under Thermomorphic Conditions: Heterogeneous Phase Separation at Ice Temperature

Molecules. 2021 Jan 13;26(2):378. doi: 10.3390/molecules26020378.

Authors

Chiao-Fan Chiu^{1

2}, Jinn-Hsuan Ho³, Eskedar Tessema⁴, Yijing Lu⁴, Chia-Rui Shen^{5

6}, Chang-Wei Lin⁷, Norman Lu^{4

8}

Affiliations

¹ Department of Pediatrics, Linkou Medical Center, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan.
² Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan.
³ Department of Chemical Engineering, National Taiwan University of Technology, Taipei 106, Taiwan.
⁴ Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei 106, Taiwan.
⁵ Department of Medical Biotechnology and Laboratory Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan.
⁶ Department of Ophthalmology, Linkou Medical Center, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan.
⁷ Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital & Chang Gung University, Taoyuan 333, Taiwan.
⁸ Development Center for Smart Textile, National Taipei University of Technology, Taipei 106, Taiwan.

Abstract

Homogeneous catalysts PtCl₂[5,5'-bis-(n-ClCF₂(CF₂)₃CH₂OCH₂)-2,2'-bpy] (2A) and PtCl₂[5,5'-bis-(n-HCF₂(CF₂)₃CH₂OCH₂)-2,2'-bpy] (2B), which contained short fluorous chains, were synthesized and used in catalysis of hydrosilylation of alkynes. In these reactions the thermomorphic mode was effectively used to recover these catalysts from the reaction mixture up to eight cycles by taking advantage of heterogeneous phase separation at ice temperature. This kind of catalysis had previously been observed in fluorous catalysts of platinum containing about 50% F-content, but in this work the percentage of F-content is decreased to only about 30%, by which we termed them as "very light fluorous". Our new type of catalyst with limited number of F-content is considered as the important discovery in the fluorous technology field as the reduced number of fluorine atoms will help to be able to comply the EPA 8-carbon rule. The metal leaching after the reaction has been examined by ICP-MS, and the testing results show the leaching of residual metal to be minimal. Additionally, comparing these results to our previous work, fluorous chain assisted selectivity has been observed when different fluorous chain lengths of the catalysts are used. It has been found that there exists fluorous chain assisted better selectivity towards β-(E) form in the Pt-catalyzed hydrosilylation of non-symmetric terminal alkyne when the Pt catalyst contains short fluorous chain (i.e., 4 Cs). Phenyl acetylenes showed the opposite regioselectivity due to pi-pi interaction while using the same catalyst via Markovnikov's addition to form terminal vinyl silane, which is then a major product for Pt-catalyzed hydrosilylation of terminal aryl acetylene with triethylsilane. Finally, the kinetic studies indicate that the insertion of alkyne into the Pt-H bond is the rate-determining step.

Keywords: catalyst; fluorous; heterogeneous separation; hydrosilylation; platinum; recovery; selectivity; thermomorphic.

MeSH terms

Catalysis
Ice*
Molecular Structure
Organoplatinum Compounds / chemistry*
Silanes / chemical synthesis*
Silanes / chemistry
Temperature*

Substances

Ice
Organoplatinum Compounds
Silanes

Grants and funding

MOST 106-2113-M-027-001/Ministry of Science and Technology in Taiwan