Synthesis and Reactivity of Four-Membered Azapalladacycles Derived from <i>N</i>,<i>N</i>-Dialkyl-2-iodoanilines:  Insertion Reactions of Carbenes into the Carbon−Palladium Bond

Three new four-membered azapalladacycles derived from <i>N</i>,<i>N</i>-dialkyl-2-iodoanilines have been synthesized:  [Pd(<i>κ</i><sup>2</sup>-C<sub>6</sub>H<sub>4</sub>NMe<sub>2</sub>-2)I(PPh<sub>3</sub>)] (<b>4a</b>), [Pd{<i>κ</i><sup>2</sup>-C<sub>6</sub>H<sub>4</sub>N(Me)CH<sub>2</sub>Ph-2}I(PPh<sub>3</sub>)] (<b>4b</b>), and [Pd{<i>κ</i><sup>2</sup>-C<sub>6</sub>H<sub>4</sub>N(Me)Pr-2}I(PPh<sub>3</sub>)] (<b>4c</b>). On heating in solution azapalladacycles <b>4a</b> and <b>4c</b> undergo aryl−aryl interchange between the palladium atom and the phosphine ligand to give the phosphanyl-amine palladium complexes [PdPhI(PNMe<sub>2</sub>)] (<b>7a</b>) and [PdPhI{PN(Me)Pr}] (<b>7c</b>), respectively. Azapalladacycles <b>4a</b>−<b>c</b> react with dichlorocarbene to give acyl palladium complexes [Pd{<i>κ</i><sup>2</sup>-C(O)C<sub>6</sub>H<sub>4</sub>NMe<sub>2</sub>-2}I(PPh<sub>3</sub>)] (<b>8a</b>), [Pd{<i>κ</i><sup>2</sup>-C(O)C<sub>6</sub>H<sub>4</sub>N(Me)CH<sub>2</sub>Ph-2}I(PPh<sub>3</sub>)] (<b>8b</b>), and [Pd{<i>κ</i><sup>2</sup>-C(O)C<sub>6</sub>H<sub>4</sub>N(Me)Pr-2}I(PPh<sub>3</sub>)] (<b>8c</b>), respectively. Smooth insertion of N<sub>2</sub>CHCO<sub>2</sub>Et into the carbon−palladium bond of azapalladacycles <b>4a</b>−<b>c</b> results in the formation of the single-insertion products [Pd{<i>κ</i><sup>2</sup>-CH(CO<sub>2</sub>Et)C<sub>6</sub>H<sub>4</sub>NMe<sub>2</sub>-2}I(PPh<sub>3</sub>)] (<b>9a</b>), [Pd{<i>κ</i><sup>2</sup>-CH(CO<sub>2</sub>Et)C<sub>6</sub>H<sub>4</sub>N(Me)CH<sub>2</sub>Ph-2}I(PPh<sub>3</sub>)] (<b>9b</b>), and [Pd{<i>κ</i><sup>2</sup>-CH(CO<sub>2</sub>Et)C<sub>6</sub>H<sub>4</sub>N(Me)Pr-2}I(PPh<sub>3</sub>)] (<b>9c</b>), respectively. On the other hand, complexes <b>4a</b> and <b>4c</b> react with N<sub>2</sub>CHTMS to give mainly the single-insertion products [Pd{<i>κ</i><sup>2</sup>-CH(SiMe<sub>3</sub>)C<sub>6</sub>H<sub>4</sub>NMe<sub>2</sub>-2}I(PPh<sub>3</sub>)] (<b>10a</b>) and [Pd{<i>κ</i><sup>2</sup>-CH(SiMe<sub>3</sub>)C<sub>6</sub>H<sub>4</sub>N(Me)Pr-2}I(PPh<sub>3</sub>)] (<b>10c</b>), respectively, while under similar reaction conditions <b>4b</b> affords <i>N</i>-benzyl-<i>N</i>-methyl-2-[(<i>Z</i>)-2-(trimethylsilyl)vinyl]aniline (<b>11b</b>) as a consequence of a double-insertion process. Solid state structures of palladium complexes <b>4b</b>, <b>8b</b>·EtOAc, <b>9a</b>, <b>9b</b>, and <b>9c</b>·Et<sub>2</sub>O have been determined by X-ray analysis.