Synthesis, structure, reactivity, and catalytic activity of C,N- and C,N,N-orthopalladated iminophosphoranes

The orthopalladated complexes [Pd(mu-Cl)(C6H4-2-PPh2=NPh-kappa-C,N)](2) (1) and [Pd(C6H4-2-PPh2=N-C(O)-2-NC5H4- kappa-C,N,N)Cl] (11) have been obtained by reaction of Pd(OAc)(2) (OAc = acetate) with the iminophosphoranes Ph3P=NPh and Ph3P=N-C(O)-2-NC5H4, respectively, in the presence of excess LiCl. Complex 11 has been characterised by X-ray diffraction methods. The orthoplatinated derivative [Pt(C6H4-2-PPh2=N-C(O)-2-NC5H4-kappa-C,C,N,N)Cl] (12) can be obtained by reaction of [PtCl2(NCPh)(2)] with Ph3P =N-C(O)-2-NC5H4 in refluxing 2-methoxyethanol. Complex 1 shows the typical reactivity of C,N-orthopalladated complexes, while complex 11 shows that the C,N,N-orthometallated ligand is strongly bonded to the Pd atom and cannot be easily displaced. The catalytic activity of the complexes [Pd(mu-Cl)(C6H4-2-PPh2=NPh-kappa-C,N)12 (1), [Pd(C6H4-2-PPh2=NPh-kappa-C,N)(Cl)(py)] (4), [Pd(C6H4-2-PPh2=N-C(O)-2-NC5H4- kappa-C,N,N)Cl] (11) and [Pd(C6H4-2-PPh2=N-C(O)-2-NC5H4-kappa-C,N,N)(NCMe)]ClO4 (13) in the Mizoroki-Heck (MH) reaction between methyl acrylate and different haloarenes has been examined. All complexes behave as moderate to good catalysts, yielding turnover numbers (TON) up to 526000. Their role as catalysts or precatalysts and the formation of nanoparticles is also discussed. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim Germany, 2005).