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id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Pi backbonding</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. 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href="https://de.wikipedia.org/wiki/R%C3%BCckbindung" title="Rückbindung – German" lang="de" hreflang="de" data-title="Rückbindung" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Retrodonaci%C3%B3n_%CF%80" title="Retrodonación π – Spanish" lang="es" hreflang="es" data-title="Retrodonación π" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/R%C3%A9trocoordination_%CF%80" title="Rétrocoordination π – French" lang="fr" hreflang="fr" data-title="Rétrocoordination π" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%ED%8C%8C%EC%9D%B4_%EC%97%AD%EA%B2%B0%ED%95%A9" title="파이 역결합 – Korean" lang="ko" hreflang="ko" data-title="파이 역결합" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Pengikatan_balik_%CF%80" title="Pengikatan balik π – Indonesian" lang="id" hreflang="id" data-title="Pengikatan balik π" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Retrodonazione_%CF%80" title="Retrodonazione π – Italian" lang="it" hreflang="it" data-title="Retrodonazione π" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Pi-backbonding" title="Pi-backbonding – Dutch" lang="nl" hreflang="nl" data-title="Pi-backbonding" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E9%80%86%E4%BE%9B%E4%B8%8E" title="逆供与 – Japanese" lang="ja" hreflang="ja" data-title="逆供与" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/Pi_retrodonacija" title="Pi retrodonacija – Serbian" lang="sr" hreflang="sr" data-title="Pi retrodonacija" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Pi_retrodonacija" title="Pi retrodonacija – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Pi retrodonacija" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E5%8F%8D%E9%A6%88%CF%80%E9%94%AE" title="反馈π键 – Chinese" lang="zh" hreflang="zh" data-title="反馈π键" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q901238#sitelinks-wikipedia" title="Edit interlanguage 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class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Form of interaction between two atoms</div> <p>In <a href="/wiki/Chemistry" title="Chemistry">chemistry</a>, <b>pi backbonding</b> or <b>π backbonding</b> is a <a href="/wiki/Pi_bond" title="Pi bond">π-bonding</a> interaction between a filled (or half filled) <a href="/wiki/Atomic_orbital" title="Atomic orbital">orbital</a> of a transition metal atom and a vacant <a href="/wiki/Atomic_orbital" title="Atomic orbital">orbital</a> on an adjacent ion or molecule.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> In this type of interaction, electrons from the metal are used to bond to the <a href="/wiki/Ligand" title="Ligand">ligand</a>, which dissipates excess negative <a href="/wiki/Electric_charge" title="Electric charge">charge</a> and stabilizes the metal. It is common in <a href="/wiki/Transition_metal" title="Transition metal">transition metals</a> with low oxidation states that have ligands such as <a href="/wiki/Metal_carbonyl" title="Metal carbonyl">carbon monoxide</a>, <a href="/wiki/Olefins" class="mw-redirect" title="Olefins">olefins</a>, or <a href="/wiki/Phosphine" title="Phosphine">phosphines</a>. The <a href="/wiki/Ligand" title="Ligand">ligands</a> involved in π backbonding can be broken into three groups: <a href="/wiki/Metal_carbonyl" title="Metal carbonyl">carbonyls</a> and nitrogen analogs, <a href="/wiki/Alkene" title="Alkene">alkenes</a> and <a href="/wiki/Alkyne" title="Alkyne">alkynes</a>, and <a href="/wiki/Phosphines" class="mw-redirect" title="Phosphines">phosphines</a>. Compounds where π backbonding is prominent include <a href="/wiki/Nickel_carbonyl" class="mw-redirect" title="Nickel carbonyl">Ni(CO)<sub>4</sub></a>, <a href="/wiki/Zeise%27s_salt" title="Zeise's salt">Zeise's salt</a>, and <a href="/wiki/Abiological_nitrogen_fixation_using_homogeneous_catalysts" title="Abiological nitrogen fixation using homogeneous catalysts">molybdenum and iron dinitrogen complexes</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Metal_carbonyls,_nitrosyls,_and_isocyanides"><span id="Metal_carbonyls.2C_nitrosyls.2C_and_isocyanides"></span>Metal carbonyls, nitrosyls, and isocyanides</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Pi_backbonding&action=edit&section=1" title="Edit section: Metal carbonyls, nitrosyls, and isocyanides"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:CO-M_%CF%83_bonding.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/CO-M_%CF%83_bonding.png/220px-CO-M_%CF%83_bonding.png" decoding="async" width="220" height="88" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/CO-M_%CF%83_bonding.png/330px-CO-M_%CF%83_bonding.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/aa/CO-M_%CF%83_bonding.png/440px-CO-M_%CF%83_bonding.png 2x" data-file-width="571" data-file-height="228" /></a><figcaption>σ bonding from electrons in CO's HOMO to metal center d-orbital.</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:CO-M_Pi_Backbond.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/2f/CO-M_Pi_Backbond.png/220px-CO-M_Pi_Backbond.png" decoding="async" width="220" height="102" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/2f/CO-M_Pi_Backbond.png/330px-CO-M_Pi_Backbond.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/2f/CO-M_Pi_Backbond.png/440px-CO-M_Pi_Backbond.png 2x" data-file-width="530" data-file-height="245" /></a><figcaption>π backbonding from electrons in metal center d-orbital to CO's LUMO.</figcaption></figure> <p>The electrons are partially transferred from a d-orbital of the metal to anti-bonding molecular orbitals of CO (and its analogs). This electron-transfer strengthens the metal–C bond and weakens the C–O bond. The strengthening of the M–CO bond is reflected in increases of the vibrational frequencies for the M–C bond (often outside of the range for the usual IR spectrophotometers). Furthermore, the M–CO bond length is shortened. The weakening of the C–O bond is indicated by a decrease in the wavenumber of the <i>ν</i><sub>CO</sub> band(s) from that for free CO (2143 cm<sup>−1</sup>), for example to 2060 cm<sup>−1</sup> in Ni(CO)<sub>4</sub> and 1981 cm<sup>−1</sup> in Cr(CO)<sub>6</sub>, and 1790 cm<sup>−1</sup> in the anion [Fe(CO)<sub>4</sub>]<sup>2−</sup>.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> For this reason, <a href="/wiki/IR_spectroscopy" class="mw-redirect" title="IR spectroscopy">IR spectroscopy</a> is an important diagnostic technique in <a href="/wiki/Metal_carbonyl" title="Metal carbonyl">metal–carbonyl chemistry</a>. The article <a href="/wiki/Infrared_spectroscopy_of_metal_carbonyls" class="mw-redirect" title="Infrared spectroscopy of metal carbonyls">infrared spectroscopy of metal carbonyls</a> discusses this in detail. </p><p>Many ligands other than CO are strong "backbonders". Nitric oxide is an even stronger π-acceptor than CO and ν<sub>NO</sub> is a diagnostic tool in <a href="/wiki/Metal_nitrosyl_complex" title="Metal nitrosyl complex">metal–nitrosyl chemistry</a>. <a href="/wiki/Isocyanide" title="Isocyanide">Isocyanides</a>, RNC, are another class of ligands that are capable of π-backbonding. In contrast with CO, the σ-donor lone pair on the C atom of isocyanides is antibonding in nature and upon complexation the CN bond is strengthened and the ν<sub>CN</sub> increased. At the same time, π-backbonding lowers the <i>ν</i><sub>CN</sub>. Depending on the balance of σ-bonding versus π-backbonding, the ν<sub>CN</sub> can either be raised (for example, upon complexation with weak π-donor metals, such as Pt(II)) or lowered (for example, upon complexation with strong π-donor metals, such as Ni(0)).<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> For the isocyanides, an additional parameter is the MC=N–C angle, which deviates from 180° in highly electron-rich systems. Other ligands have weak π-backbonding abilities, which creates a labilization effect of CO, which is described by the <a href="/wiki/Cis_effect" title="Cis effect"><i>cis</i> effect</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Metal–alkene_and_metal–alkyne_complexes"><span id="Metal.E2.80.93alkene_and_metal.E2.80.93alkyne_complexes"></span>Metal–alkene and metal–alkyne complexes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Pi_backbonding&action=edit&section=2" title="Edit section: Metal–alkene and metal–alkyne complexes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Alkene-M_Sigma_Bond.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/84/Alkene-M_Sigma_Bond.png/220px-Alkene-M_Sigma_Bond.png" decoding="async" width="220" height="142" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/84/Alkene-M_Sigma_Bond.png/330px-Alkene-M_Sigma_Bond.png 1.5x, //upload.wikimedia.org/wikipedia/commons/8/84/Alkene-M_Sigma_Bond.png 2x" data-file-width="426" data-file-height="275" /></a><figcaption>σ bonding from electrons in alkene's HOMO to metal center d-orbital.</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Alkene-M_Pi_Backbond.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Alkene-M_Pi_Backbond.png/220px-Alkene-M_Pi_Backbond.png" decoding="async" width="220" height="144" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Alkene-M_Pi_Backbond.png/330px-Alkene-M_Pi_Backbond.png 1.5x, //upload.wikimedia.org/wikipedia/commons/d/df/Alkene-M_Pi_Backbond.png 2x" data-file-width="407" data-file-height="267" /></a><figcaption>π backbonding from electrons in metal center d-orbital to alkene's LUMO.</figcaption></figure> <p>As in metal–carbonyls, electrons are partially transferred from a d-orbital of the metal to antibonding molecular orbitals of the alkenes and alkynes.<sup id="cite_ref-:02_5-0" class="reference"><a href="#cite_note-:02-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-:12_6-0" class="reference"><a href="#cite_note-:12-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> This electron transfer strengthens the metal–ligand bond and weakens the C–C bonds within the ligand.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> In the case of metal-alkenes and alkynes, the strengthening of the M–C<sub>2</sub>R<sub>4</sub> and M–C<sub>2</sub>R<sub>2</sub> bond is reflected in bending of the C–C–R angles which assume greater sp<sup>3</sup> and sp<sup>2</sup> character, respectively.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-:12_6-1" class="reference"><a href="#cite_note-:12-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Thus strong π backbonding causes a metal-alkene <a href="/wiki/Coordination_complex" title="Coordination complex">complex</a> to assume the character of a metallacyclopropane.<sup id="cite_ref-:02_5-1" class="reference"><a href="#cite_note-:02-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> Alkenes and alkynes with electronegative substituents exhibit greater π backbonding.<sup id="cite_ref-:12_6-2" class="reference"><a href="#cite_note-:12-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Some strong π backbonding ligands are <a href="/wiki/Tetrafluoroethylene" title="Tetrafluoroethylene">tetrafluoroethylene</a>, <a href="/wiki/Tetracyanoethylene" title="Tetracyanoethylene">tetracyanoethylene</a>, and <a href="/wiki/Hexafluoro-2-butyne" title="Hexafluoro-2-butyne">hexafluoro-2-butyne</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Metal-phosphine_complexes">Metal-phosphine complexes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Pi_backbonding&action=edit&section=3" title="Edit section: Metal-phosphine complexes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Connelly-Orpen-R3P-M-sigma-bonding.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Connelly-Orpen-R3P-M-sigma-bonding.png/150px-Connelly-Orpen-R3P-M-sigma-bonding.png" decoding="async" width="150" height="118" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Connelly-Orpen-R3P-M-sigma-bonding.png/225px-Connelly-Orpen-R3P-M-sigma-bonding.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Connelly-Orpen-R3P-M-sigma-bonding.png/300px-Connelly-Orpen-R3P-M-sigma-bonding.png 2x" data-file-width="2000" data-file-height="1570" /></a><figcaption>R<sub>3</sub>P–M σ bonding</figcaption></figure> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Connelly-Orpen-R3P-M-pi-backbonding.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/24/Connelly-Orpen-R3P-M-pi-backbonding.png/150px-Connelly-Orpen-R3P-M-pi-backbonding.png" decoding="async" width="150" height="123" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/24/Connelly-Orpen-R3P-M-pi-backbonding.png/225px-Connelly-Orpen-R3P-M-pi-backbonding.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/24/Connelly-Orpen-R3P-M-pi-backbonding.png/300px-Connelly-Orpen-R3P-M-pi-backbonding.png 2x" data-file-width="2000" data-file-height="1646" /></a><figcaption>R<sub>3</sub>P–M π backbonding</figcaption></figure> <p>Phosphines accept electron density from metal p or d orbitals into combinations of P–C σ* antibonding orbitals that have π symmetry.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> When phosphines bond to electron-rich metal atoms, backbonding would be expected to lengthen P–C bonds as P–C σ* orbitals become populated by electrons. The expected lengthening of the P–C distance is often hidden by an opposing effect: as the phosphorus lone pair is donated to the metal, P(lone pair)–R(bonding pair) repulsions decrease, which acts to shorten the P–C bond. The two effects have been deconvoluted by comparing the structures of pairs of metal-phosphine complexes that differ only by one electron.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> Oxidation of R<sub>3</sub>P–M complexes results in longer M–P bonds and shorter P–C bonds, consistent with π-backbonding.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> In early work, phosphine ligands were thought to utilize 3d orbitals to form M–P pi-bonding, but it is now accepted that d-orbitals on phosphorus are not involved in bonding as they are too high in energy.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="IUPAC_definition_of_Back_Donation">IUPAC definition of Back Donation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Pi_backbonding&action=edit&section=4" title="Edit section: IUPAC definition of Back Donation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The full <a href="/wiki/IUPAC" class="mw-redirect" title="IUPAC">IUPAC</a> definition of back donation is as follows: </p> <blockquote><p>A description of the bonding of π-conjugated ligands to a transition metal which involves a <a href="/wiki/Synergy" title="Synergy">synergic</a> process with donation of electrons from the filled π-orbital or lone electron pair orbital of the ligand into an empty orbital of the metal (donor–acceptor bond), together with release (back donation) of electrons from an <i>n</i>d orbital of the metal (which is of π-symmetry with respect to the metal–ligand axis) into the empty π*-<a href="/wiki/Antibonding" class="mw-redirect" title="Antibonding">antibonding</a> orbital of the ligand.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup></p></blockquote> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Pi_backbonding&action=edit&section=5" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Bridging_carbonyl" class="mw-redirect" title="Bridging carbonyl">Bridging carbonyl</a></li> <li><a href="/wiki/Dewar%E2%80%93Chatt%E2%80%93Duncanson_model" title="Dewar–Chatt–Duncanson model">Dewar–Chatt–Duncanson model</a></li> <li><a href="/wiki/18-electron_rule" title="18-electron rule">18-electron rule</a></li> <li><a href="/wiki/Ligand_field_theory" title="Ligand field theory">Ligand field theory</a></li> <li><a href="/wiki/Metal%E2%80%93ligand_multiple_bond#Pi-donor_ligands" title="Metal–ligand multiple bond">Pi-donor ligands</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Pi_backbonding&action=edit&section=6" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFMiesslerTarr1999" class="citation book cs1">Miessler, Gary L.; Tarr, Donald A. (1999). <i>Inorganic chemistry</i> (2nd ed.). Upper Saddle River, N.J: Prentice Hall. p. 338. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-13-841891-5" title="Special:BookSources/978-0-13-841891-5"><bdi>978-0-13-841891-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Inorganic+chemistry&rft.place=Upper+Saddle+River%2C+N.J&rft.pages=338&rft.edition=2nd&rft.pub=Prentice+Hall&rft.date=1999&rft.isbn=978-0-13-841891-5&rft.aulast=Miessler&rft.aufirst=Gary+L.&rft.au=Tarr%2C+Donald+A.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APi+backbonding" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFCottonWilkinsonMurillo1999" class="citation book cs1">Cotton, Frank Albert; Wilkinson, Geoffrey; Murillo, Carlos A., eds. 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Pearson Prentice-Hall. p. 702. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-130-39913-7" title="Special:BookSources/978-0-130-39913-7"><bdi>978-0-130-39913-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Inorganic+Chemistry&rft.pages=702&rft.edition=2nd&rft.pub=Pearson+Prentice-Hall&rft.date=2005&rft.isbn=978-0-130-39913-7&rft.aulast=Housecroft&rft.aufirst=C.+E.&rft.au=Sharpe%2C+A.+G.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APi+backbonding" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFCrabtree2014" class="citation book cs1">Crabtree, Robert H. 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Wiley. pp. <span class="nowrap">105–</span>106. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-11813807-6" title="Special:BookSources/978-1-11813807-6"><bdi>978-1-11813807-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Organometallic+Chemistry+of+the+Transition+Metals&rft.pages=%3Cspan+class%3D%22nowrap%22%3E105-%3C%2Fspan%3E106&rft.edition=6th&rft.pub=Wiley&rft.date=2014&rft.isbn=978-1-11813807-6&rft.aulast=Crabtree&rft.aufirst=Robert+H.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APi+backbonding" class="Z3988"></span></span> </li> <li id="cite_note-:02-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-:02_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:02_5-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFEliasGupta2013" class="citation book cs1">Elias, Anil J.; Gupta, B D (January 1, 2013). <i>Basic Organometallic Chemistry: Concepts, Syntheses and Applications</i> (2nd ed.). 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Rev.</a></i> <b>94</b> (5): <span class="nowrap">1339–</span>1374. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fcr00029a008">10.1021/cr00029a008</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/27704785">27704785</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Chem.+Rev.&rft.atitle=No+d+Orbitals+but+Walsh+Diagrams+and+Maybe+Banana+Bonds%3A+Chemical+Bonding+in+Phosphines%2C+Phosphine+Oxides%2C+and+Phosphonium+Ylides&rft.volume=94&rft.issue=5&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1339-%3C%2Fspan%3E1374&rft.date=1994&rft_id=info%3Adoi%2F10.1021%2Fcr00029a008&rft_id=info%3Apmid%2F27704785&rft.aulast=Gilheany&rft.aufirst=D.+G.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APi+backbonding" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFFeyOrpenHarvey2009" class="citation journal cs1">Fey, N.; Orpen, A. G.; Harvey, J. N. (2009). "Building ligand knowledge bases for organometallic chemistry: Computational description of phosphorus(III)-donor ligands and the metal–phosphorus bonds". <i><a href="/wiki/Coordination_Chemistry_Reviews" title="Coordination Chemistry Reviews">Coord. Chem. Rev.</a></i> <b>253</b> (<span class="nowrap">5–</span>6): <span class="nowrap">704–</span>722. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.ccr.2008.04.017">10.1016/j.ccr.2008.04.017</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Coord.+Chem.+Rev.&rft.atitle=Building+ligand+knowledge+bases+for+organometallic+chemistry%3A+Computational+description+of+phosphorus%28III%29-donor+ligands+and+the+metal%E2%80%93phosphorus+bonds&rft.volume=253&rft.issue=%3Cspan+class%3D%22nowrap%22%3E5%E2%80%93%3C%2Fspan%3E6&rft.pages=%3Cspan+class%3D%22nowrap%22%3E704-%3C%2Fspan%3E722&rft.date=2009&rft_id=info%3Adoi%2F10.1016%2Fj.ccr.2008.04.017&rft.aulast=Fey&rft.aufirst=N.&rft.au=Orpen%2C+A.+G.&rft.au=Harvey%2C+J.+N.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APi+backbonding" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMcNaughtWilkinson2006" class="citation book cs1">McNaught, A. D.; Wilkinson, A. (2006). <i>IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book")</i>. Oxford: Blackwell Scientific Publications. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1351%2Fgoldbook">10.1351/goldbook</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-9678550-9-7" title="Special:BookSources/978-0-9678550-9-7"><bdi>978-0-9678550-9-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=IUPAC.+Compendium+of+Chemical+Terminology%2C+2nd+ed.+%28the+%22Gold+Book%22%29&rft.place=Oxford&rft.pub=Blackwell+Scientific+Publications&rft.date=2006&rft_id=info%3Adoi%2F10.1351%2Fgoldbook&rft.isbn=978-0-9678550-9-7&rft.aulast=McNaught&rft.aufirst=A.+D.&rft.au=Wilkinson%2C+A.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APi+backbonding" class="Z3988"></span></span> </li> </ol></div></div> <div class="navbox-styles"><style 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href="/wiki/Hypervalent_molecule" title="Hypervalent molecule">Hypervalence</a> <ul><li><a href="/wiki/Three-center_four-electron_bond" title="Three-center four-electron bond">3c–4e</a></li></ul></li> <li><a href="/wiki/Agostic_interaction" title="Agostic interaction">Agostic</a></li> <li><a href="/wiki/Bent_bond" title="Bent bond">Bent</a></li> <li><a href="/wiki/Coordinate_covalent_bond" title="Coordinate covalent bond">Coordinate (dipolar)</a></li> <li><a class="mw-selflink selflink">Pi backbond</a></li> <li><a href="/wiki/Metal%E2%80%93ligand_multiple_bond" title="Metal–ligand multiple bond">Metal–ligand multiple bond</a></li> <li><a href="/wiki/Charge-shift_bond" title="Charge-shift bond">Charge-shift</a></li> <li><a href="/wiki/Hapticity" title="Hapticity">Hapticity</a></li> <li><a href="/wiki/Conjugated_system" title="Conjugated system">Conjugation</a></li> <li><a href="/wiki/Hyperconjugation" title="Hyperconjugation">Hyperconjugation</a></li> <li><a href="/wiki/Aromaticity" title="Aromaticity">Aromaticity</a> <ul><li><a href="/wiki/Homoaromaticity" title="Homoaromaticity">homo</a></li> <li><a href="/wiki/Bicycloaromaticity" title="Bicycloaromaticity">bicyclo</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Metallic_bonding" title="Metallic bonding">Metallic</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Metal_aromaticity" title="Metal aromaticity">Metal aromaticity</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Ionic_bonding" title="Ionic bonding">Ionic</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li class="mw-empty-elt"></li></ul> </div></td></tr></tbody></table><div></div></td><td class="noviewer navbox-image" rowspan="4" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"><a href="/wiki/File:Ligatio-covalens.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/21/Ligatio-covalens.svg/200px-Ligatio-covalens.svg.png" decoding="async" width="200" height="89" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/21/Ligatio-covalens.svg/300px-Ligatio-covalens.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/21/Ligatio-covalens.svg/400px-Ligatio-covalens.svg.png 2x" data-file-width="597" data-file-height="265" /></a></span><br /><span typeof="mw:File"><a href="/wiki/File:Chemfm_carbon_monoxide_3_1.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/77/Chemfm_carbon_monoxide_3_1.svg/200px-Chemfm_carbon_monoxide_3_1.svg.png" decoding="async" width="200" height="113" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/77/Chemfm_carbon_monoxide_3_1.svg/300px-Chemfm_carbon_monoxide_3_1.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/77/Chemfm_carbon_monoxide_3_1.svg/400px-Chemfm_carbon_monoxide_3_1.svg.png 2x" data-file-width="99" data-file-height="56" /></a></span><br /><span typeof="mw:File"><a href="/wiki/File:Pi-Bond.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/Pi-Bond.svg/200px-Pi-Bond.svg.png" decoding="async" width="200" height="113" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/Pi-Bond.svg/300px-Pi-Bond.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/70/Pi-Bond.svg/400px-Pi-Bond.svg.png 2x" data-file-width="1920" data-file-height="1080" /></a></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Intermolecular_force" title="Intermolecular force">Intermolecular</a><br />(weak)</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Van_der_Waals_force" title="Van der Waals force">Van der Waals<br />forces</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/London_dispersion_force" title="London dispersion force">London dispersion</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Hydrogen_bond" title="Hydrogen bond">Hydrogen</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Low-barrier_hydrogen_bond" title="Low-barrier hydrogen bond">Low-barrier</a></li> <li><a href="/wiki/Resonance-assisted_hydrogen_bond" class="mw-redirect" title="Resonance-assisted hydrogen bond">Resonance-assisted</a></li> <li><a href="/wiki/Symmetric_hydrogen_bond" title="Symmetric hydrogen bond">Symmetric</a></li> <li><a href="/wiki/Dihydrogen_bond" title="Dihydrogen bond">Dihydrogen bonds</a></li> <li><a href="/wiki/C%E2%80%93H%C2%B7%C2%B7%C2%B7O_interaction" title="C–H···O interaction">C–H···O interaction</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Non-covalent_interactions" class="mw-redirect" title="Non-covalent interactions">Noncovalent</a><br />other</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Mechanically_interlocked_molecular_architectures" title="Mechanically interlocked molecular architectures">Mechanical</a></li> <li><a href="/wiki/Halogen_bond" title="Halogen bond">Halogen</a></li> <li><a href="/wiki/Chalcogen_bond" title="Chalcogen bond">Chalcogen</a></li> <li><a href="/wiki/Metallophilic_interaction" title="Metallophilic interaction">Metallophilic</a> (<a href="/wiki/Aurophilicity" title="Aurophilicity">aurophilic</a>)</li> <li><a href="/wiki/Intercalation_(chemistry)" title="Intercalation (chemistry)">Intercalation</a></li> <li><a href="/wiki/Stacking_(chemistry)" title="Stacking (chemistry)">Stacking</a></li> <li><a href="/wiki/Cation%E2%80%93pi_interaction" class="mw-redirect" title="Cation–pi interaction">Cation–pi</a></li> <li><a href="/wiki/Cation%E2%80%93pi_interaction#Anion–π_interaction" class="mw-redirect" title="Cation–pi interaction">Anion–pi</a></li> <li><a href="/wiki/Salt_bridge_(protein_and_supramolecular)" title="Salt bridge (protein and supramolecular)">Salt bridge</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Bond_cleavage" title="Bond cleavage">Bond cleavage</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Heterolysis_(chemistry)" title="Heterolysis (chemistry)">Heterolysis</a></li> <li><a href="/wiki/Homolysis_(chemistry)" title="Homolysis (chemistry)">Homolysis</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Electron_counting" title="Electron counting">Electron counting</a> rules</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Aromaticity" title="Aromaticity">Aromaticity</a> <ul><li><a href="/wiki/H%C3%BCckel%27s_rule" title="Hückel's rule">Hückel's rule</a></li> <li><a href="/wiki/Baird%27s_rule" title="Baird's rule">Baird's rule</a></li> <li><a href="/wiki/M%C3%B6bius_aromaticity" title="Möbius aromaticity">Möbius</a></li> <li><a href="/wiki/Spherical_aromaticity" title="Spherical aromaticity">spherical</a></li></ul></li> <li><a href="/wiki/Polyhedral_skeletal_electron_pair_theory" title="Polyhedral skeletal electron pair theory">Polyhedral skeletal electron pair theory</a></li> <li><a href="/wiki/Jemmis_mno_rules" title="Jemmis mno rules">Jemmis mno rules</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235" /></div><div role="navigation" class="navbox" aria-labelledby="Organometallic_chemistry378" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231" /><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Organometallics" title="Template:Organometallics"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Organometallics" title="Template talk:Organometallics"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Organometallics" title="Special:EditPage/Template:Organometallics"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Organometallic_chemistry378" style="font-size:114%;margin:0 4em"><a href="/wiki/Organometallic_chemistry" title="Organometallic chemistry">Organometallic chemistry</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Principles</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Crystal_field_theory" title="Crystal field theory">Crystal field theory</a></li> <li><a href="/wiki/Ligand_field_theory" title="Ligand field theory">Ligand field theory</a></li> <li><a href="/wiki/18-electron_rule" title="18-electron rule">18-electron rule</a></li> <li><a href="/wiki/D_electron_count" title="D electron count">d electron count</a></li> <li><a href="/wiki/Polyhedral_skeletal_electron_pair_theory" title="Polyhedral skeletal electron pair theory">Polyhedral skeletal electron pair theory</a></li> <li><a href="/wiki/Isolobal_principle" title="Isolobal principle">Isolobal principle</a></li> <li><a class="mw-selflink selflink">π backbonding</a></li> <li><a href="/wiki/Dewar%E2%80%93Chatt%E2%80%93Duncanson_model" title="Dewar–Chatt–Duncanson model">Dewar–Chatt–Duncanson model</a></li> <li><a href="/wiki/Hapticity" title="Hapticity">Hapticity</a></li> <li><a href="/wiki/Spin_states_(d_electrons)" title="Spin states (d electrons)">spin states</a></li> <li><a href="/wiki/Agostic_interaction" title="Agostic interaction">Agostic interaction</a></li> <li><a href="/wiki/Metal%E2%80%93ligand_multiple_bond" title="Metal–ligand multiple bond">Metal–ligand multiple bond</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Reactions</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Oxidative_addition" title="Oxidative addition">Oxidative addition</a> / <a href="/wiki/Reductive_elimination" title="Reductive elimination">reductive elimination</a></li> <li><a href="/wiki/Migratory_insertion" title="Migratory insertion">Migratory insertion</a></li> <li><a href="/wiki/Beta-Hydride_elimination" class="mw-redirect" title="Beta-Hydride elimination">β-hydride elimination</a></li> <li><a href="/wiki/Transmetalation" title="Transmetalation">Transmetalation</a></li> <li><a href="/wiki/Carbometalation" title="Carbometalation">Carbometalation</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Types of compounds</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Gilman_reagent" title="Gilman reagent">Gilman reagents</a></li> <li><a href="/wiki/Grignard_reagent" title="Grignard reagent">Grignard reagents</a></li> <li><a href="/wiki/Cyclopentadienyl_complex" title="Cyclopentadienyl complex">Cyclopentadienyl complexes</a></li> <li><a href="/wiki/Transition_metal_indenyl_complex" title="Transition metal indenyl complex">Transition metal indenyl complexes</a></li> <li><a href="/wiki/Transition_metal_fullerene_complex" title="Transition metal fullerene complex">Transition metal fullerene complexes</a></li> <li><a href="/wiki/Metallocene" title="Metallocene">Metallocenes</a></li> <li><a href="/wiki/Metal_tetranorbornyl" title="Metal tetranorbornyl">Metal tetranorbornyls</a></li> <li><a href="/wiki/Sandwich_compound" title="Sandwich compound">Sandwich compounds</a></li> <li><a href="/wiki/Half_sandwich_compound" title="Half sandwich compound">Half sandwich compounds</a></li> <li><a href="/wiki/Transition_metal_acyl_complexes" title="Transition metal acyl complexes">Transition metal acyl complexes</a></li> <li><a href="/wiki/Transition_metal_carbene_complex" title="Transition metal carbene complex">Transition metal carbene complexes</a></li> <li><a href="/wiki/Transition_metal_carbyne_complex" title="Transition metal carbyne complex">Transition metal carbyne complexes</a></li> <li><a href="/wiki/Transition_metal_alkene_complex" title="Transition metal alkene complex">Transition metal alkene complexes</a></li> <li><a href="/wiki/Transition_metal_alkyne_complex" title="Transition metal alkyne complex">Transition metal alkyne complexes</a></li> <li><a href="/wiki/Transition-metal_allyl_complex" title="Transition-metal allyl complex">Transition-metal allyl complexes</a></li> <li><a href="/wiki/Metal_carbido_complex" title="Metal carbido complex">Transition metal carbides</a></li> <li><a href="/wiki/Arene_complexes_of_univalent_gallium,_indium,_and_thallium" title="Arene complexes of univalent gallium, indium, and thallium">Arene complexes of univalent gallium, indium, and thallium</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Applications</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Carbonylation" title="Carbonylation">Carbonylation</a></li> <li><a href="/wiki/Cativa_process" title="Cativa process">Cativa process</a></li> <li><a href="/wiki/Grignard_reaction" title="Grignard reaction">Grignard reaction</a></li> <li><a href="/wiki/Monsanto_process" title="Monsanto process">Monsanto process</a></li> <li><a href="/wiki/Olefin_metathesis" title="Olefin metathesis">Olefin metathesis</a></li> <li><a href="/wiki/Shell_higher_olefin_process" title="Shell higher olefin process">Shell higher olefin process</a></li> <li><a href="/wiki/Ziegler%E2%80%93Natta_catalyst" title="Ziegler–Natta catalyst">Ziegler–Natta process</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related branches of <a href="/wiki/Chemistry" title="Chemistry">chemistry</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Organic_chemistry" title="Organic chemistry">Organic chemistry</a></li> <li><a href="/wiki/Inorganic_chemistry" title="Inorganic chemistry">Inorganic chemistry</a></li> <li><a href="/wiki/Bioinorganic_chemistry" title="Bioinorganic chemistry">Bioinorganic chemistry</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="Category"><img 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