trans-Dichloro{P,P′-[3,3′-oxybis(m-phenylenemethylene)]bis(diphenylphosphine)}palladium(II)

Abstract

The square-planar title complex, [PdCl 2 (C 38 H 32 OP 2)], shows the P atoms to be trans coordinated, with a P-Pd-P angle of 176.50 (4). The phenyl rings in the phosphorus ligand are inclined at an angle of 61.2 (1) to each other. Comment Square-planar complexes of palladium(II) have long been recognized to play a central role in catalytic reactions (Cornils & Herrmann, 1996). Recently, we studied the catalytic activity of trans-palladium complexes in Suzuki cross-coupling reactions. For comparison, we have synthesized the title compound, (I). Although it has been known for almost 20 years (Marty et al., 1987), its structure has never been solved by X-ray structure analysis. The single-crystal X-ray structure analysis of (I) shows the Pd atom to be in a square-planar geometry, surrounded by two Cl and two P atoms (Fig. 1). The chelating diphosphine ligand adopts a trans coordination geometry. Despite the formation of a 12-membered chelate ring, the distortion imposed around the Pd atom is negligible. The P-Pd-P angle [176.50 (4) ] is almost 180 , as expected for trans coordination. Atoms Pd1, P1, P2, Cl1 and Cl2 are essentially coplanar, with an average deviation from planarity of 0.0345 Å. Selected bond lengths and angles for (I) are listed in Table 1, and are very similar to that of the PtBr 2 analogous complex [PtBr 2 (C 38 H 32 OP 2)] (Stoeckli-Evans et al., 1987). The two C 6 H 4 planes of the 3,3 0oxydibenzyl ligand are inclined at an angle of 61.2 (1) to each other. The CO -C angle is 120.3 (3). In the crystal structure, the molecules exist as dimers due to the presence of weak intermolecular interactions between a CH 2 proton and the Cl atom of a neighbouring molecule. (Table 2). Experimental Compound (I) was prepared according to the published method of Marty et al. (1987). Crystals were obtained by slow evaporation of a chloroform solution.

Trans-chelating diphosphines, the elusive ligands!

“…Many trans-complexes of ligand 14 have been synthesized as Ni14X 2 (X = Cl, I, NCS, CN), Pd14X 2 (X = Cl, Br, I, ONO, N 3 ), Pt14X 2 (X = Br, I, Cl), Pt14HCl, Pt14HBr, Ag14Cl or Rh14(CO)Cl and fully characterized by spectroscopic techniques [110][111][112][113]. The data analysis suggested that ligand 14 forms exclusively monomeric species in high yields with Ni(II) and Pd(II).…”