Base Effects on the Formation of Four- and Five-Coordinate Cationic Aluminum Complexes
1997-05-07T00:00:00Z (GMT) by
This work was conducted as part of our continuing effort to determine the factors that affect cation formation for organometallic aluminum complexes. In this study, the interactions of R<sub>2</sub>AlX (where R = Me, <sup>i</sup>Bu, <sup>t</sup>Bu; X = Cl, Br, I) with the monodentate bases thf, pyridine, NEt<sub>3</sub>, HN<sup>i</sup>Pr<sub>2</sub>, H<sub>2</sub>N<sup>i</sup>Bu, H<sub>2</sub>N<sup>t</sup>Bu, and OPPh<sub>3</sub> are examined to determine the role of the base in cation formation. These reactions resulted in the neutral adducts of the general form R<sub>2</sub>AlX·base (<b>1</b>−<b>6</b>, <b>8</b>, <b>10</b>, and <b>12</b>) as well as the cationic complexes [R<sub>2</sub>Al(base)<sub>2</sub>]X (<b>7</b>, <b>9</b>, and <b>11</b>). The reactions of Me<sub>2</sub>AlX (where X = Cl, Br) with PMDETA (<i>N</i>,<i>N</i>‘,<i>N</i>‘‘,<i>N</i>‘‘‘-pentamethyldiethylenetriamine) and the catalytic activity of the resulting cationic complexes (<b>13</b> and <b>14</b>) are also discussed. All of the compounds were characterized by mp, IR, <sup>1</sup>H-NMR, and elemental analyses, and in one an X-ray crystallographic study was carried out. X-ray data for <b>13</b>: triclinic, <i>P</i>1̄, <i>a</i> = 6.9542(6) Å, <i>b</i> = 12.2058(10) Å, <i>c</i> = 13.2417(11) Å, α = 106.236(2)°, β = 98.885(2)°, γ = 93.807(2)°, <i>V</i> = 1059.06(15) Å<sup>3</sup>, and <i>Z</i> = 2 for 181 parameters refined on 4358 reflections having <i>F</i> > 6.0σ(<i>F</i>), <i>R</i> = 0.0697, and <i>R</i><sub>w</sub> = 0.0697.