A Nonheme, High-Spin {FeNO}⁸ Complex that Spontaneously Generates N₂O

One-electron reduction of [Fe­(NO)-(N3PyS)]­BF₄ (<b>1</b>) leads to the production of the metastable nonheme {FeNO}⁸ complex, [Fe­(NO)­(N3PyS)] (<b>3</b>). Complex <b>3</b> is a rare example of a high-spin (<i>S</i> = 1) {FeNO}⁸ and is the first example, to our knowledge, of a mononuclear nonheme {FeNO}⁸ species that generates N₂O. A second, novel route to <b>3</b> involves addition of Piloty’s acid, an HNO donor, to an Fe^II precursor. This work provides possible new insights regarding the mechanism of nitric oxide reductases

Unsaturated Vicinal Frustrated Lewis Pair Formation by Electrocyclic Ring Closure and Their Reaction with Nitric Oxide

The Lewis acidic β-styryl-B­(C₆F₅)₂ reagent <b>6a</b> undergoes a clean 1,1-carboboration reaction with 1-(PMes₂)-2-cyclohexenyl acetylene <b>9</b> at 60 °C to give the vicinal P/B-substituted conjugated triene product <b>10a</b>. At 80 °C this undergoes a stereoselective thermally induced disrotatory electrocyclic ring closure to give the cyclohexadiene-derived P/B system <b>11</b>. Subsequent TEMPO oxidation gave the substituted phenylene-bridged P/B product <b>12</b>. Both <b>11</b> and <b>12</b> are active phosphane/borane frustrated Lewis pairs (FLPs). The FLP <b>11</b> reacts in a typical way with phenylacetylene to give the phosphonium/alkynylborate product <b>13</b>. Compound <b>12</b> cleaves dihydrogen at near ambient conditions to give the respective phosphonium/hydridoborate zwitterion <b>14</b>. Both the FLPs <b>11</b> and <b>12</b> cooperatively add P/B to the nitrogen atom of nitric oxide (NO) within minutes at room temperature to give the persistent P/B FLPNO^• radicals <b>19</b> and <b>21</b>, respectively (both characterized by X-ray diffraction and by EPR spectroscopy). The FLPs <b>11</b> and <b>12</b> are thermally robust. At elevated temperatures (<b>11</b>: 75 °C, <b>12</b>: 100 °C) they undergo a coupling reaction with dimethyl acetylenedicarboxylate with carbon–carbon bond activation at a P-mesityl substituent