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Although silane diamine copolymers have captured the attention of the catalysis community, the optimization of their synthesis and end uses have yet to be explored. In this study, a well-defined Earth-abundant metal catalyst, [(2,6-iPr2PhBDI)Mn(µ-H)]2, has been found to couple organosilanes to diamines to prepare networks that feature varied silane substitution and diamine chain lengths. By performing dehydrocoupling in the absence of solvent with 0.01 mol% catalyst loading, substrate utilisation turnover frequencies of up to 300 s-1 have been achieved at early reaction times, the highest Si–N dehydrocoupling activity ever observed. These networks have been employed as absorbents for common organic solvents, a property that had not been studied for this class of materials. By incorporating a long-chain hydrophobic linker, one network has been found to absorb 7.7× its orginal mass in THF and recycling has been demonstrated upon solvent removal. Controlling the degree of dehydrocoupling also offered an opportunity to deposit coatings from freshly-prepared silane diamine polymer solutions and monitor their integrity upon curing in air. While uniform and persistent coatings have been obtained from 1,6-hexanediamine derived polymers, the need to prepare dilute solutions that have a short shelf-life and the tackiness associated with extended dry times have been identified as potential limitations.
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Manganese catalysed dehydrocoupling of silanes and siloxanes with ammonia to prepare oligosilazanes and polysiloxazanes
The halogen-free synthesis of oligosilazanes has been observed upon dehydrocoupling silanes with ammonia at 25 °C using [(2,6-iPr2PhBDI)Mn(µ-H)]2. Extending this methodology to polymethyl-hydrosiloxanes afforded thermally robust polysiloxazane solids, and the dehydrocoupling of 1,3,5,7-tetramethylcyclotetrasiloxane with ammonia afforded a polysiloxazane having a weight-average molecular weight of 4300 g/mol. A representative oligosilazane has been applied to a copper surface and found to afford a 20 μm thick coating that resists corrosion after 24 h under water. Addition of ammonia to [(2,6-iPr2PhBDI)Mn(µ-H)]2 allowed for characterization of the catalyst resting state, [(2,6-iPr2PhBDI)Mn(µ-NH2)]2, which has been found to mediate Si‒N dehydrocoupling.
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- Award ID(s):
- 2154359
- PAR ID:
- 10590704
- Publisher / Repository:
- RSC
- Date Published:
- Journal Name:
- Dalton Transactions
- Volume:
- 53
- Issue:
- 34
- ISSN:
- 1477-9226
- Page Range / eLocation ID:
- 14272 to 14277
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d4dt01982b
