Advances in the Synthesis of Preceramic Polymers for the Formation of Silicon-Based and Ultrahigh-Temperature Non-Oxide Ceramics.

Preceramic polymers (PCPs) are a group of specialty macromolecules that serve as precursors for generating inorganics, including ceramic carbides, nitrides, and borides. PCPs represent interesting synthetic challenges for chemists due to the elements incorporated into their structure. This group of polymers is also of interest to engineers as PCPs enable the processing of polymer-derived ceramic products including high-performance ceramic fibers and composites. These finished ceramic materials are of growing significance for applications that experience extreme operating environments (e.g., aerospace propulsion and high-speed atmospheric flight). This Review provides an overview of advances in the synthesis and postpolymerization modification of macromolecules forming nonoxide ceramics. These PCPs include polycarbosilanes, polysilanes, polysilazanes, and precursors for ultrahigh-temperature ceramics. Following our review of PCP synthetic chemistry, we provide examples of the application and processing of these polymers, including their use in fiber spinning, composite fabrication, and additive manufacturing. The principal objective of this Review is to provide a resource that bridges the disciplines of synthetic chemistry and ceramic engineering while providing both insights and inspiration for future collaborative work that will ultimately drive the PCP field forward.

Evidence for Iron-Catalyzed α-Phosphinidene Elimination with Phenylphosphine.

The ubiquitous half-sandwich iron complex [CpFe(CO)2 Me] (Cp=η5 -C5 H5 ) appears to be a catalyst for α-phosphinidene elimination from primary phosphines. Dehydrocoupling reactions provided initial insight into this unusual reaction mechanism, and trapping reactions with organic substrates gave products consistent with an α elimination mechanism, including a rare example of a three-component reaction. The substrate scope of this reaction is consistent with generation of a triplet phosphinidene. In all, this study presents catalytic phosphinidene transfer to unsaturated organic substrates.

Visible-light and thermal driven double hydrophosphination of terminal alkynes using a commercially available iron compound.

A commercially available iron compound, [CpFe(CO)2]2 (1) (Cp = η5-C5H5), is an efficient catalyst for the double hydrophosphination of terminal aryl alkynes with diphenylphosphine under visible light irradiation or thermal conditions with a reduction of reaction times of up to two orders of magnitude for some substrates over literature reports. The 1,2-bis(diphenylphosphino)ethane products generated in these reactions are readily isolated in high yields.