Selenated Schiff bases of 2-hydroxyacetophenone and their palladium(II) and platinum(II) complexes: Syntheses, crystal structures and applications in the Heck reaction

Selenated Schiff bases 2-HO-C6H4C(CH3)=N(CH2)(n)SePh (n = 2, L-1; n = 3, L-2) and their complexes with Pd(II) and Pt(II), viz [Pd(L-1-H)Cl] (1), [Pt(L-1-H)Cl] (2), [Pd(L-2-H)Cl] (3) and [(PtLCl2)-Cl-2] (4), have been synthesized and characterized with proton, carbon-13 and 77 Se{H-1} NMR spectra. In the Se-77{H-1} NMR spectrum of 2 the signal at delta 387.4 ppm appears as a triplet due to (1)J(Pt-195-Se) coupling (2043 Hz). The single-crystal structures of L-1, L-2, 1 and 2 were solved. The C-Se-C bond angles in L-1 and L 2 have been found to be around 99 degrees. The geometry around Pd and Pt is square planar. The Pd-Se and Pt-Se bond distances are 2.3669(11) and 2.3543(16) angstrom, respectively. Complexes I and 2 are the first examples of crystal structures of Pd and Pt complexes of a (Se, N, O-) ligand. Complex 1 has been explored as a homogeneous catalyst for a Heck type C-C coupling reaction between methyl acrylate and p-iodo-nitrobenzene (yield similar to 80%; reaction time 14 h). (c) 2007 Elsevier Ltd. All rights reserved.