Synthesis, X-ray structural and DFT studies of <i>n</i>-membered ring P, C-chelated complexes of Pd(II) and Pt(II) derived from unsymmetrical phosphorus ylides and application of Pd(II) complexes as catalyst in Suzuki reaction

<p>The phosphonium salts [Ph<sub>2</sub>P(CH<sub>2</sub>)<sub>n</sub>PPh<sub>2</sub>CH<sub>2</sub>C(O)C<sub>6</sub>H<sub>4</sub>-<i>m</i>-OMe]Br (<i>n</i> = 1 (<b>S</b><sub><b>1</b></sub>) and <i>n</i> = 2 (<b>S</b><sub><b>2</b></sub>)) were synthesized in the reaction of bis(diphenylphosphino)methane (dppm) and bis(diphenylphosphino)ethane (dppe) with 2-bromo-3ʹ-methoxy acetophenone, respectively. Further treatment with NEt<sub>3</sub> gave the phosphorus ylides Ph<sub>2</sub>P(CH<sub>2</sub>)<sub>n</sub>PPh<sub>2</sub>C(H)C(O)C<sub>6</sub>H<sub>4</sub>-<i>m</i>-OMe (<i>n</i> = 1 (<b>Y</b><sub><b>1</b></sub>) and <i>n</i> = 2 (<b>Y</b><sub><b>2</b></sub>)). These ligands were treated with [MCl<sub>2</sub>(cod)] (M = Pd or Pt; cod = 1,5-cyclooctadiene) to give the P, C-chelated complexes, [MCl<sub>2</sub>(Ph<sub>2</sub>P(CH<sub>2</sub>)<sub>n</sub>PPh<sub>2</sub>C(H)C(O)C<sub>6</sub>H<sub>4</sub>-<i>m</i>-OMe)] (<i>n</i> = 1, M = Pd (<b>3</b>), Pt (<b>4</b>), and <i>n</i> = 2, M = Pd (<b>5</b>), Pt (<b>6</b>)). These compounds were characterized by elemental analysis, spectroscopic methods, UV–visible, and fluorescence emission spectra. Further, the structures of complexes <b>3</b> and <b>6</b> were characterized crystallographically. The palladium complexes <b>3</b> and <b>5</b> proved to be excellent catalysts for the Suzuki reactions of various aryl chlorides. Also, a theoretical study on the structure of complexes <b>3–6</b> has been investigated at the BP86/def2-SVP level of theory. The strength and nature of donor−acceptor bonds between the phosphorus ylides (L) and MCl<sub>2</sub> fragment in the [LMCl<sub>2</sub>] (M = Pd, Pt, L = <b>Y</b><sub><b>1</b></sub>, <b>Y</b><sub><b>2</b></sub>) were studied by NBO and energy decomposition analysis (EDA), as well as their natural orbitals for chemical valence variation (EDA-NOCV).</p>