School census autumn 2017 : 16 to 19 reports : user guide

The synthesis of a series of cobalt NHC complexes of the types [Co­(NHC)₂(CO)­(NO)] (NHC = <i>i</i>Pr₂Im (<b>2</b>), <i>n</i>Pr₂Im (<b>3</b>), Cy₂Im (<b>4</b>), Me₂Im (<b>5</b>), <i>i</i>Pr₂ImMe (<b>6</b>), Me₂ImMe (<b>7</b>), Me<i>i</i>PrIm (<b>8</b>), Me<i>t</i>BuIm (<b>9</b>); R₂Im = 1,3-dialkylimidazolin-2-ylidene) and [Co­(NHC)­(CO)₂(NO)] (NHC = <i>i</i>Pr₂Im (<b>13</b>), <i>n</i>Pr₂Im (<b>14</b>), Me₂Im (<b>15</b>), <i>i</i>Pr₂ImMe (<b>16</b>), Me₂ImMe (<b>17</b>), Me<i>i</i>PrIm (<b>18</b>), Me<i>t</i>BuIm (<b>19</b>)) from the reaction of the NHC with [Co­(CO)₃(NO)] (<b>1</b>) is reported. These complexes have been characterized using elemental analysis, IR spectroscopy, multinuclear NMR spectroscopy, and in many cases by X-ray crystallography. Bulky NHCs tend to form the mono-NHC-substituted complexes [Co­(NHC)­(CO)₂(NO)], even from the reaction with an stoichiometric excess of the NHC, as demonstrated by the synthesis of [Co­(Dipp₂Im)­(CO)₂(NO)] (<b>11</b>), [Co­(Mes₂Im)­(CO)₂(NO)] (<b>12</b>), and [Co­(^MecAAC)­(CO)₂(NO)] (<b>20</b>). For <i>t</i>Bu₂Im a preferred coordination via the NHC backbone (“abnormal” coordination at the 4-position) was observed and the complex [Co­(<i>t</i>Bu₂^aIm)­(CO)₂(NO)] (<b>10</b>) was isolated. All of these complexes are volatile, are stable upon sublimation and prolonged storage in the gas phase, and readily decompose at higher temperatures. Furthermore, DTA/TG analyses revealed that the complexes [Co­(NHC)₂(CO)­(NO)] are seemingly more stable toward thermal decomposition in comparison to the complexes [Co­(NHC)­(CO)₂(NO)]. We thus conclude that the cobalt complexes of the type [Co­(NHC)­(CO)₂(NO)] and [Co­(NHC)₂(CO)­(NO)] have potential for application as precursors in the vapor deposition of thin cobalt films

NHC Nickel-Catalyzed Suzuki–Miyaura Cross-Coupling Reactions of Aryl Boronate Esters with Perfluorobenzenes

An efficient Suzuki–Miyaura cross-coupling reaction of perfluorinated arenes with aryl boronate esters using NHC nickel complexes as catalysts is described. The efficiencies of different boronate esters (<i>p</i>-tolyl-Beg, <i>p</i>-tolyl-Bneop, <i>p</i>-tolyl-Bpin, <i>p</i>-tolyl-Bcat) and the corresponding boronic acid (<i>p</i>-tolyl-B­(OH)₂) in this type of cross-coupling reaction were evaluated (eg, ethyleneglycolato; neop, neopentylglycolato; pin, pinacolato; cat, catecholato). Aryl-Beg was shown to be the most reactive boronate ester among those studied. The use of CsF as an additive is essential for an efficient reaction of hexafluorobenzene with aryl neopentylglycolboronates

Asymmetrically Substituted Tetrahedral Cobalt NHC Complexes and Their Use as ALD as well as Low-Temperature CVD Precursors

The synthesis of novel asymmetrically substituted cobalt complexes of the type [Co­(CO)­(NO)­(NHC)­(PR₃)] (NHC = ^<i>i</i>Pr₂Im, PR₃ = PMe₃ (<b>1</b>), PEt₃(<b>2</b>), PH^<i>i</i>Pr₂ (<b>3</b>); PR₃ = PMe₃;, NHC = Me₂Im^Me (<b>4</b>), Me^<i>i</i>PrIm (<b>5</b>), Me^<i>t</i>BuIm (<b>6</b>), ^<i>i</i>Pr₂Im^Me (<b>7</b>); R₂Im = 1,3-dialkylimidazolin-2-ylidene) is reported. These complexes are stabilized by N-heterocyclic carbene (NHC), phosphine, carbonyl, and nitrosyl ligands and have been synthesized from the reaction of a NHC-substituted precursor of the type [Co­(CO)₂(NO)­(NHC)] and the corresponding phosphine. The synthesis of [Co­(CO)­(NO)­(Me^<i>t</i>BuIm)­(PMe₃)] (<b>6</b>) and [Co­(CO)­(NO)­(^<i>i</i>Pr₂Im^Me)­(PMe₃)] (<b>7</b>) proceeds in a thermal reaction even at room temperature by quantitative replacement of one carbonyl with a phosphine ligand. All of the other complexes were synthesized using photochemical conditions. Complexes <b>1</b>–<b>6</b> have been characterized by elemental analysis, IR spectroscopy, and multinuclear NMR spectroscopy and in some cases by X-ray crystallography. All complexes are volatile, are stable upon sublimation, and decompose readily in a stepwise manner at elevated temperature. The complex [Co­(CO)­(NO)­(^<i>i</i>Pr₂Im)­(PMe₃)] (<b>1</b>) as well as cobalt complexes that were reported earlier, i.e. [Co­(CO)­(NO)­(^<i>i</i>Pr₂Im)₂], [Co­(CO)­(NO)­(Me^<i>t</i>BuIm)₂], and [Co­(CO)₂(NO)­(^<i>i</i>Pr₂Im)], are evaluated and have been successfully applied in the deposition of cobalt-based thin films