<p> Detailed herein are the synthesis, characterization, and reactivity of three isolable four-coordinate iridium(I) monohydride complexes. Iridium(I) monohydrides containing the simple formula HIrL<sub>3</sub> have been postulated as reactive intermediates for over four decades escaping definitive evidence. The judicious use of the C–H activation resistant methyleneadamantyl phosphine P(CH<sub>2</sub><sup>1</sup>Ad)(<i>i</i>-Pr)<sub> 2</sub> (abbreviated L<sup>mAd</sup>) and phosphinite P(O<sup>1</sup>Ad)(i-Pr)<sub> 2</sub> (abbreviated L<sup>oAd</sup>) ligands allowed for the successful isolation and characterization of several four-coordinate iridium(I) monohydride complexes.</p><p> These electron-rich monohydride complexes rapidly deprotonate protic reagents, such as H<sub>2</sub>N(2,6-(<i>i</i>-Pr)<sub>2</sub>C<sub> 6</sub>H<sub>3</sub>) and C<sub>6</sub>F<sub>5</sub>OH, and activate N–H, O–H, and H–H bonds. The sequential addition of 12-crown-4 with 1.0 equ. of a strong lewis base, i.e. Li(CH<sub>3</sub>)<sub>3</sub>CLi to cyclometallated complexes H<sub>2</sub>Ir(κ<sup>2</sup>-<i> P,C</i>-L<sup>oAd</sup>)(L<sup>oAd</sup>) and H<sub>2</sub>Ir(κ<sup> 2</sup>-<i>P,C</i>-L<sup>mAd</sup>)(L<sup>mAd</sup>) produces four-coordinate anionic complexes [Li(12-c-4)][HIr(κ<sup> 2</sup>-<i>P,C</i>-L<sup>mAd</sup>)(L<sup>mAd</sup>)] and Li[12-c-4)2][H<sub>3</sub>Ir(κ<sup>2</sup>-P,<i>C</i>-L<sup> oAd</sup>)(L<sup>oAd</sup>)], respectively.</p><p> Herein we also report the X-ray characterization of coordinated alkanes, <i> n</i>-hexane and <i>n</i>-heptane, forming two cobalt metal complexes. A continued effort to isolate and characterize alkane σ-complexes stems from the desire to control alkane C–H bond transformations, a significant synthetic challenge with high economic benefit.</p><p> Support for a distinct &eegr;<sup>2</sup>-H,C σ-type interaction with <i>n</i>-hexane or <i>n</i>-heptane was provided by DFT and AIM analysis computations as well as <i>r</i><sub>bp </sub> parameter calculations. The diamagnetic complex, Co(SiMe<sub>3</sub>)(CNAr<sup> Mes2</sup>)<sub>3</sub> forms from the addition of (CH<sub>3</sub>)<sub> 3</sub>SiCl to the zwitterionic complex (κ<sup>2</sup>-PPN)(Co(CNAr<sup> Mes2</sup>)<sub>3</sub> (PPN = (C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>P=N=P(C<sub> 6</sub>H<sub>5</sub>)<sub>3</sub>). Crystallization of Co(SiMe<sub>3</sub>)(CNAr<sup> Mes2</sup>)<sub>3</sub> with 5% v/v of C<sub>6</sub>H<sub>6</sub> in <i> n</i>-hexane or <i>n</i>-heptane at -35 °C under an argon atmosphere produces single crystals of the respective alkane σ-complexes. When <i>n</i>-nonane (C<sub>9</sub>H<sub>20</sub>) is employed as the crystallization solvent, the unsaturated Co(SiMe<sub>3 </sub>)(CNAr<sup>Mes2</sup>)<sub>3</sub> forms single crystals of Ar<sub> 1/7</sub>Co((SiCH<sub>3</sub>)<sub>3</sub>)(CNAr<sup>Mes2</sup>)<sub> 3</sub> which were manipulated in single crystal to single crystal (SC-SC) dinitrogen intercalation experiments, resulting in full occupancy and binding of dinitrogen to the cobalt metal center. Persistent in the solid-state are weak Van der Waals interactions from the CNAr<sup>Mes2</sup> ligands to the bound alkanes, <i>n</i>-hexane and <i>n</i>-heptane, possibly mimicking a clathrate-type entrapment mechanism. Distinct from clathrate networks is the strategic placement of a highly Lewis acidic cobalt center of proper electronic structure to engage in bonding.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:3594595 |
| Date | 26 October 2013 |
| Creators | Millard, Matthew David |
| Publisher | University of California, San Diego |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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