bidentate chelate binding mode with two donors functions coordinating and the third one serving as a dangling arm; M = NiII, PdII, PtII). With nickel(II) as the d8 species, tetrahedral or square-planar coordination geometries ensue, depending on the kind of donor functions and on the kind of co-ligands R. With palladium(II) and platinum(II) as the d8 centres, square-planar coordination is observed throughout
π-allyl complexes [Rh(η3-C3H5)(PR3)2] [PR3 = PiPr2Ph (4), PiPrPh2 (5)], prepared from [RhCl(C8H14)2]2, PR3 and the Grignard reagent C3H5MgBr, react with carboxylic acids and p-toluenesulfonic acid to give the chelate compounds [Rh(κ2-O2CR′)(PR3)2] (8−10) and [Rhκ2-O2S(O)-p-Tol}(PR3)2] (11, 12), respectively. While the reactions of 8, 10 and 12 with CO afford the square-planar rhodium(I) complexes 13−15