Hydrosilylation

<h2 id="scope-and-mechanism">Scope and mechanism</h2>
 
Hydrosilylation of alkenes represents a commercially important method for preparing <a href="/facts/Organosilicon/JvUwzDQ4">organosilicon compounds</a>. The process is mechanistically similar to the <a href="/facts/Hydrogenation/l7EzNSA7">hydrogenation</a> of alkenes. In fact, similar catalysts are sometimes employed for the two catalytic processes.
The prevalent mechanism, called the Chalk-Harrod mechanism, assumes an intermediate metal complex that contains a <a href="/facts/Hydride/v2rlBGMg">hydride</a>, a silyl ligand (R3Si), and the alkene substrate. Oxidative addition proceeds by the intermediacy of a <a href="/facts/Transition_metal_silane_complexes/7jV5pWnB">sigma-complex</a>, wherein the Si-H bond is not fully broken. Variations of the Chalk-Harrod mechanism exist. Some cases involve insertion of alkene into M-Si bond followed by reductive elimination, the opposite of the sequence in the Chalk-Harrod mechanism. In certain cases, hydrosilylation results in vinyl or allylic silanes resulting from <a href="/facts/Beta-hydride_elimination/x0BBXj9K">beta-hydride elimination</a>.<a class="footnote-ref" id="fnref:3" href="#fn:3">3</a>
Hydrosilylation of alkenes usually proceeds via <a href="/facts/Anti-Markovnikov_addition/WJokRx6l">anti-Markovnikov addition</a>, i.e., silicon is placed at the terminal carbon when hydrosilylating a <a href="/facts/Terminal_alkene/lzbLgU7Q">terminal alkene</a>;<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a> however, in the recent years, <a href="/facts/Markovnikov_addition/WJokRx6l">Markovnikov addition</a> has become a growing field of research.<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a>
Alkynes also undergo hydrosilylation, e.g., the addition of <a href="/facts/Triethylsilane/QTL8MaQ3">triethylsilane</a> to <a href="/facts/Diphenylacetylene/d6APXh1A">diphenylacetylene</a>:<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a>

Et3SiH + PhC≡CPh → Et3Si(Ph)C=CH(Ph)
<h2 id="asymmetric-hydrosilylation">Asymmetric hydrosilylation</h2>
Using <a href="/facts/Chirality_(chemistry)/p5a9pftB">chiral</a> phosphines as spectator <a href="/facts/Ligand/6etB3qeW">ligands</a>, catalysts have been developed for catalytic asymmetric hydrosilation. A well studied reaction is the addition of <a href="/facts/Trichlorosilane/nEYfkAeP">trichlorosilane</a> to <a href="/facts/Styrene/B8uXm78L">styrene</a> to give 1-phenyl-1-(trichlorosilyl)ethane:

Cl3SiH + PhCH=CH2 → (Ph)(CH3)CHSiCl3
Nearly perfect <a href="/facts/Enantiomer/wjPv5J3y">enantioselectivities</a> (ee's) can be achieved using <a href="/facts/Palladium-catalyzed_coupling_reactions/cF8RBvCx">palladium catalysts</a> supported by binaphthyl-substituted monophosphine ligands.<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a>

<h2 id="surface-hydrosilylation">Surface hydrosilylation</h2>
<a href="/facts/Silicon_wafer/lCBJAoUL">Silicon wafers</a> can be etched in <a href="/facts/Hydrofluoric_acid/wdXqu4bE">hydrofluoric acid</a> (HF) to remove the native oxide and form a <a href="/facts/Hydrogen-terminated_silicon_surface/nFBNdFCc">hydrogen-terminated silicon surface</a>. The hydrogen-terminated surfaces undergo hydrosilation with unsaturated compounds (such as terminal alkenes and alkynes), to form a stable monolayer on the surface. For example:

Si-H + H2C=CH(CH2)7CH3 → Si-CH2CHH-(CH2)7CH3
The hydrosilylation reaction can be initiated with UV light at room temperature or with heat (typical reaction temperature 120-200 °C), under moisture- and oxygen-free conditions.<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a> The resulting monolayer, which is stable and inert, inhibits oxidation of the base silicon layer, relevant to various device applications.<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a>

<h2 id="catalysts">Catalysts</h2>

Before introduction of platinum catalysts by Speier, hydrosilylation was not practiced widely. A peroxide-catalyzed process was reported in academic literature in 1947,<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a> but the introduction of Speier's catalyst (<a href="/facts/Chloroplatinic_acid/3F3cuA1b">H2PtCl6</a>) was a big breakthrough.
<a href="/facts/Karstedt%27s_catalyst/C5Rmtflg">Karstedt's catalyst</a> was later introduced. It is a lipophilic complex that is soluble in the organic substrates of industrial interest.<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a> Complexes and compounds that catalyze hydrogenation are often effective catalysts for hydrosilylation, e.g. <a href="/facts/Wilkinson%27s_catalyst/c7lrFXfo">Wilkinson's catalyst</a>.

<h2 id="further-reading">Further reading</h2>
Books

<ul><li>Applied homogeneous catalysis with organometallic compounds : a comprehensive handbook : applications, developments. Boy Cornils; W A Herrmann. Publisher: Weinheim; New York : Wiley-VCH, 2000.</li>
<li>Comprehensive handbook on hydrosilylation. Bogdan Marciniec. Publisher: Oxford [u.a.] : Pergamon Press, 1992.</li>
<li>Rhodium complexes as hydrosilylation catalysts. N.K. Skvortsov. // Rhodium Express. 1994. No 4 (May). P. 3 - 36 (Eng). <a href="https://sites.google.com/site/rhodiumexpress/">[1]</a> <a href="https://web.archive.org/web/20220623191029/https://sites.google.com/site/rhodiumexpress/">Archived</a> 2022-06-23 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a> <a href="/facts/ISSN_(identifier)/DPAflDvU">ISSN</a> <a href="https://www.worldcat.org/search?fq=x0:jrnl&q=n2:0869-7876">0869-7876</a></li></ul>
Articles

<ul><li>"Alkyl Monolayers on Silicon Prepared from 1-Alkenes and Hydrogen-Terminated Silicon," M. R. Linford, P. Fenter, P. M. Eisenberger and C. E. D. Chidsey, J. Am. Chem. Soc. 117, 3145-3155 (1995).</li>
<li>"Synthesis and characterization of DNA-modified Si(111) Surfaces," T. Strother, W. CAi, X. Zhao, R.J. Hamers, and L.M. Smith, J. Am. Chem. Soc. 122, 1205-1209 (2000).</li>
<li>"T. Strother, R.J. Hamers, and L.M. Smith, "Surface Chemistry of DNA Covalent Attachment to the Silicon(100) Surface". Langmuir, 2002, 18, 788-796.</li>
<li>"Covalently Modified Silicon and Diamond Surfaces: Resistance to Non-Specific Protein Adsorption and Optimization for Biosensing," T.L. Lasseter, B.H. Clare, N.L. Abbott, and R.J. Hamers. J. Am. Chem. Soc. 2004, 126, 10220-10221.</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">"Hydrosilylation A Comprehensive Review on Recent Advances" B. Marciniec (ed.), Advances in Silicon Science, Springer Science, 2009. doi:10.1007/978-1-4020-8172-9 <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Renner, H.; Schlamp, G.; Kleinwächter, I.; Drost, E.; Lüschow, H. M.; Tews, P.; Panster, P.; Diehl, M.; Lang, J.; Kreuzer, T.; Knödler, A.; Starz, K. A.; Dermann, K.; Rothaut, J.; Drieselman, R. (2002). "Platinum group metals and compounds". Ullmann's Encyclopedia of Industrial Chemistry. Wiley. doi:10.1002/14356007.a21_075. ISBN 3527306730. <a href="3527306730" target="_blank">3527306730</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Troegel, D.; Stohrer, J. (2011). "Recent Advances and Actual Challenges in Late Transition Metal Catalyzed Hydrosilylation of Olefins from an Industrial Point of View". Coord. Chem. Rev. 255 (13–14): 1440–1459. doi:10.1016/j.ccr.2010.12.025. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">"Hydrosilylation A Comprehensive Review on Recent Advances" B. Marciniec (ed.), Advances in Silicon Science, Springer Science, 2009. doi:10.1007/978-1-4020-8172-9 <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">Zaranek, Maciej; Pawluc, Piotr (2018-10-05). "Markovnikov Hydrosilylation of Alkenes: How an Oddity Becomes the Goal". ACS Catalysis. 8 (10): 9865–9876. doi:10.1021/acscatal.8b03104. ISSN 2155-5435. <a href="https://pubs.acs.org/doi/10.1021/acscatal.8b03104" target="_blank">https://pubs.acs.org/doi/10.1021/acscatal.8b03104</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">James L. Fry, Ronald J. Rahaim Jr., Robert E. Maleczka, Jr. "Triethylsilane", Encyclopedia of Reagents for Organic Synthesis, John Wiley & Sons, 2007. doi:10.1002/047084289X.rt226.pub2 <a href="/wiki/John_Wiley_%26_Sons" target="_blank">/wiki/John_Wiley_%26_Sons</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">Hayashi, T.; Yamasaki, K. (2007). "C–E Bond Formation through Asymmetric Hydrosilylation of Alkenes". In Crabtree, Robert H.; D. Michael P. Mingos (eds.). Comprehensive Organometallic Chemistry III. Amsterdam: Elsevier. doi:10.1016/B0-08-045047-4/00140-0. ISBN 978-0-08-045047-6. <a href="978-0-08-045047-6" target="_blank">978-0-08-045047-6</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">"Photoreactivity of Unsaturated Compounds with Hydrogen-Terminated Silicon (111)," R. L. Cicero, M. R. Linford, C. E. D. Chidsey, Langmuir 16, 5688-5695 (2000) <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Direct electrical detection of DNA Hybridization at DNA-modified silicon surfaces, W.Cai, J. Peck, D. van der Weide, and R.J. Hamers, Biosensors and Bioelectronics 19, 1013-1019 (2004) <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">Sommer, L.; Pietrusza, E.; Whitmore, F. (1947). "Peroxide-catalyzed addition of trichlorosilane to 1-octene". J. Am. Chem. Soc. 69 (1): 188. doi:10.1021/ja01193a508. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">C. Elschenbroich, Organometallics (2006) Wiley and Sons-VCH: Weinheim. ISBN 978-3-527-29390-2 <a href="/wiki/ISBN_(identifier)" target="_blank">/wiki/ISBN_(identifier)</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
</ol>

Hydrosilylation open-in-new

Hydrosilylation