{"id":124,"date":"2024-11-16T16:54:10","date_gmt":"2024-11-16T15:54:10","guid":{"rendered":"https:\/\/pandora.anorg.chemie.uni-frankfurt.de\/?page_id=124"},"modified":"2025-09-22T14:16:00","modified_gmt":"2025-09-22T13:16:00","slug":"small-molecules-activation","status":"publish","type":"page","link":"https:\/\/holthausen.anorg.chemie.uni-frankfurt.de\/index.php\/small-molecules-activation\/","title":{"rendered":"Small Molecules Activation"},"content":{"rendered":"\n
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An iridium(III\/IV\/V) redox series featuring a terminal imido complex with triplet ground state<\/h5>\n\n\n\n

The iridium(III\/IV\/V)<\/strong> imido redox series [Ir(NtBu){N(CHCHPtBu2)2}]0\/+\/2+ was synthesized and examined spectroscopically, magnetically, crystallographically and computationally. The monocationic iridium(IV) imide exhibits an electronic doublet ground state with considerable \u2018imidyl\u2019 character as a result of covalent Ir\u2013NtBu bonding. Reduction gives the neutral imide [Ir(NtBu){N(CHCHPtBu2)2}] as the first example of an iridium complex with a triplet ground state. Its reactivity with respect to nitrene transfer to selected electrophiles (CO2) and nucleophiles (PMe3), respectively, is reported.<\/p>\n\n\n\n

Figure: <\/strong>Computed state-energy diagram of [Ir(NtBu)(PNP)] . Relative energies of the lowest non-relativistic (left) and spin\u2013orbit states (right) in red (cm\u22121<\/sup>) and corresponding |S, MS\u3009 labels in blue.<\/em><\/p>\n\n\n\n

Chem. Sci.<\/em>\u00a09, 4325\u20134332 (2018<\/strong>)<\/a><\/p>\n\n\n\n

in cooperation with Prof. Schneider (G\u00f6ttingen), Prof. de Bruin (Amsterdam) and Prof. van Slageren (Stuttgart)<\/em><\/p>\n<\/div>

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A square-planar osmium(II) complex<\/h5>\n\n\n\n

Reduction of the pincer complex <\/strong>[OsIII<\/sup>Cl2<\/sub>(PNP)] (PNP = N(CHCHPtBu2<\/sub>)2<\/sub>) affords the isolation and full characterization of an osmium(II) complex with square-planar coordination geometry, i.e. [OsII<\/sup>Cl(PNP)]. Spectroscopic, structural and magnetic data in combination with multireference computations indicate strong temperature independent paramagnetism, which arises from an energetically well separated ground state that mixes with excited states through spin\u2013orbit coupling.<\/p>\n\n\n\n

Figure: <\/strong>State-energy diagram for [Os[OsII<\/sup>Cl(PNP)] based on NEVPT2\/SA-CASSCF(16,10) computations. Non-relativistic energies of the lowest four states are shown with their corresponding |S,MS\u3009 label (left). The lowest nine spin\u2013orbit states (right) are complemented with selected contributions (weights >10%) of the corresponding spin-free states (dashed red lines).<\/em><\/p>\n\n\n\n

Chem. Commun.<\/em> 53, 5511\u20135514 (2017<\/strong>)<\/a><\/p>\n\n\n\n

in cooperation with Prof. Schneider (G\u00f6ttingen)<\/em><\/p>\n<\/div>

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Dinitrogen Splitting Coupled to Protonation<\/h5>\n\n\n\n

Acid splits: <\/strong>Protonation of an N2<\/sub>\u2010bridged dimolybdenum complex in the pincer periphery results in splitting into MoV nitrides. This proton\u2010coupled metal\u2010to\u2010ligand charge transfer reaction provides a mechanism to control the thermochemistry and kinetics of N\u2212N bond cleavage with proton\u2010responsive ligands.<\/p>\n\n\n\n

Angew. Chem. Int. Ed.<\/em> 56, 5872\u20135876 (2017<\/strong>)<\/a><\/p>\n\n\n\n

in cooperation with Prof. Schneider (G\u00f6ttingen)<\/em><\/p>\n<\/div>

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Fe-PNP Mediated Dehydrogenation Catalysis<\/h5>\n\n\n\n

Chemical hydrogen storage materials<\/strong>: The pincer-supported iron catalyst [Fe] was successfully employed in highly-efficient dehydrogenation reactions of different substrates. The development of iron-based homogeneous catalysts for these applications (i.e. dehydrogenation of potential chemical hydrogen storage materials) is a major advancement in this field, since conventional approaches used precious or heavy metals exclusively.<\/p>\n\n\n\n

ACS Catal.<\/em> 5, 7214 \u20137217 (2015<\/strong>)<\/a>
ACS Catal.<\/em>\u00a05, 2404 \u20132415 (2015<\/strong>)<\/a>;\u00a0Highlighted in<\/mark>\u00a0ACS Catal.<\/em> 5, 5584 \u20135585 (2015<\/strong>)<\/a>
ACS Catal.<\/em>\u00a04, 3994 \u20134003 (2014<\/strong>)<\/a><\/p>\n\n\n\n

in cooperation with Prof. Schneider (G\u00f6ttingen), Prof. Schmedt a. d. G\u00fcnne (Siegen), Prof. Bernskoetter (Brown University), Prof. Hazari (Yale University), and Prof. Jones (Rochester)<\/em><\/p>\n<\/div>

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Oxygen Reduction with a Bifunctional Iridium Dihydride Complex<\/h5>\n\n\n\n

A mononuclear mechanism<\/strong>: The oxygen-reduction reaction (ORR) with an iridium dihydride results in formation of an unusual square-planar iridium(III) hydroxide and water. The dihydride is regenerated with H2<\/em> in a quasi-catalytic synthetic cycle. Experimental and computational studies are in agreement with a four-electron ORR mechanism at a single metal site.<\/p>\n\n\n\n

Angew. Chem. Int. Ed.<\/em> 54, 15271\u201315275 (2015<\/strong>)<\/a>
Angew. Chem.<\/em> 127, 15486\u201315490 (2015<\/strong>)<\/a><\/p>\n\n\n\n

in cooperation with Prof. Schneider (G\u00f6ttingen)<\/em><\/p>\n<\/div>

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Ammonia formation by metal\u2013ligand cooperative hydrogenolysis of a nitrido ligand<\/h5>\n\n\n\n

Bioinspired hydrogenation of N2<\/sub> to ammonia<\/strong> at ambient conditions by stepwise nitrogen protonation\/reduction with metal complexes in solution has experienced remarkable progress. In contrast, the highly desirable direct hydrogenation with H2<\/sub> remains difficult. In analogy to the heterogeneously catalysed Haber\u2013Bosch process, such a reaction is conceivable via metal-centred N2<\/sub> splitting and unprecedented hydrogenolysis of the nitrido ligands to ammonia. We report the synthesis of a ruthenium(IV) nitrido complex. The high nucleophilicity of the nitrido ligand is demonstrated by unusual N\u2013C coupling with \u03c0-acidic CO. Furthermore, the terminal nitrido ligand undergoes facile hydrogenolysis with H2<\/sub> at ambient conditions to produce ammonia in high yield. Kinetic and quantum chemical examinations of this reaction suggest cooperative behaviour of a phosphorus\u2013nitrogen\u2013phosphorus pincer ligand in rate-determining heterolytic hydrogen splitting.<\/p>\n\n\n\n

Nature Chem.<\/em> 3, 532\u2013537 (2011<\/strong>)<\/a>
Highlighted in<\/mark>\u00a0Nature Chem.<\/em> 3, 502\u2013504 (2011<\/strong>)<\/a>,\u00a0Chemistry World<\/em>, May 25, 2011<\/strong><\/a><\/p>\n\n\n\n

in cooperation with Prof. Schneider (G\u00f6ttingen), and Dr. Herdtweck (M\u00fcnchen)<\/em><\/p>\n<\/div>

\"\"<\/figure><\/div>\n","protected":false},"excerpt":{"rendered":"

An iridium(III\/IV\/V) redox series featuring a terminal imido complex with triplet ground state The iridium(III\/IV\/V) imido redox series [Ir(NtBu){N(CHCHPtBu2)2}]0\/+\/2+ was synthesized and examined spectroscopically, magnetically, crystallographically and computationally. The monocationic iridium(IV) imide exhibits an electronic doublet ground state with considerable \u2018imidyl\u2019 character as a result of covalent Ir\u2013NtBu bonding. Reduction gives…<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-124","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/holthausen.anorg.chemie.uni-frankfurt.de\/index.php\/wp-json\/wp\/v2\/pages\/124","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/holthausen.anorg.chemie.uni-frankfurt.de\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/holthausen.anorg.chemie.uni-frankfurt.de\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/holthausen.anorg.chemie.uni-frankfurt.de\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/holthausen.anorg.chemie.uni-frankfurt.de\/index.php\/wp-json\/wp\/v2\/comments?post=124"}],"version-history":[{"count":22,"href":"https:\/\/holthausen.anorg.chemie.uni-frankfurt.de\/index.php\/wp-json\/wp\/v2\/pages\/124\/revisions"}],"predecessor-version":[{"id":656,"href":"https:\/\/holthausen.anorg.chemie.uni-frankfurt.de\/index.php\/wp-json\/wp\/v2\/pages\/124\/revisions\/656"}],"wp:attachment":[{"href":"https:\/\/holthausen.anorg.chemie.uni-frankfurt.de\/index.php\/wp-json\/wp\/v2\/media?parent=124"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}