Reactivity and Derivatization of Five-Coordinate, Chelated Aluminum

The convenient five-coordinate starting materials, Salen(<i>^t</i>Bu)AlCl (Salen(<i>^t</i>Bu) = <i>N</i>,<i>N</i>‘-alkylene (or arylene) bis (3,5-di-<i>tert</i>-butyl-2-hydroxybenzylideneamine) (<b>1</b>−<b>4</b>) can be used in a wide range of reactions to form five-coordinate aluminum compounds. Herein, these reagents were used to produce new five-coordinate azides, LAlN₃ (L = Salen(<i>^t</i>Bu) (<b>5</b>), Salpen(<i>^t</i>Bu) (<b>6</b>), and Salomphen(<i>^t</i>Bu) (<b>7</b>)) through trimethylsilylhalide elimination. The decomposition of the azides produce first hydroxide (LAlOH (L = Salen(<i>^t</i>Bu) (<b>8</b>)) and, subsequently in the presence of chlorotrimethylsilane, the siloxide compounds, LAlOSiMe₃ (L = Salen(<i>^t</i>Bu) (<b>9</b>), Salpen(<i>^t</i>Bu) (<b>10</b>), and Salomphen(<i>^t</i>Bu) (<b>11</b>)). Alkane elimination reactions may also be used to access this type of compound as evidenced by the formation of Salomphen(^<i>t</i>Bu)AlOSiPh₃ (<b>12</b>). Additionally, the first structurally characterized five-coordinate monomeric amide, Salcen(<i>^t</i>Bu)AlN(SiMe₃)₂ (<b>13</b>), can prepared by a salt elimination utilizing Salcen(<i>^t</i>Bu)AlCl (<b>4</b>). The compounds were characterized by spectroscopic methods (¹H and ²⁷Al NMR, MS, and IR) and, in the case of <b>2 </b>(Salpen(<i>^t</i>Bu)AlCl),<b> 3 </b>(Salomphen(<i>^t</i>Bu)AlCl)<b> 9</b>, <b>11</b>,<b> 12</b>, and <b>13, </b>by X-ray analysis. Several of the compounds were explored as potential catalysts for the living polymerization of propylene oxide.