Olefin ligands. Syntheses and structures of 2,6-diallylpyridine (DAP) complexes of rhodium(I); crystal structures of [Rh(COD)(DAP)][RhCl 2(COD)] and [Rh(COD)(DAP)][CuCl 2

Abstract

The olefinic ligand 2,6-diallylpyridine (DAP) has been shown to react with various rhodium(I) compounds to give complexes of the type [RhCl(DAP)] n , RhCl(L)(DAP) (L = CO, PPh 3), [Rh(diene)(DAP)]Y (diene = cycloocta-1,5-diene (COD), bicyclo[2.2.1]hepta-2,5-diene (NBD); Y = [RhCl 2(diene)], [CuCl 2], ClO 4). These complexes have been characterised by chemical and spectroscopic means. In addition, the crystal structures of [Rh(COD)(DAP)][RhCl 2(COD)] ( 1) and [Rh(COD)(DAP)][CuCl 2] ( 2) have been determined by X-ray methods. Crystal of 1 are triclinic, space group P 1 , with Z = 2 in a unit cell of dimensions a 10.481(4), b 13.041(4), c 10.456(4) Å, α 106.77(2), β 112.10(2), γ 79.57(1)°. Crystals of 2 are monoclinic, space group P2 1/ c, with Z = 4 in a unit cell of dimension a 14.303(8), b 10.453(5), c 13.412(6) Å, β 110.95(4)°. Both structures were solved from diffractometer data by direct and Fourier methods and refined by blocked full-matrix least-squares to R = 0.0316 (2204 observed reflections) for 1 and by full matrix least-squares to R = 0.0545 (1897 observed reflections) for 2. The crystals consist of cationic [Rh(COD)(DAP)] + and anionic [Rh(COD)Cl 2] − ( 1) and [CuCl 2] − ( 2) complexes. The cations are similar in the two compounds, and the coordination around the Rh I atoms can be described as trigonal bipyramidal, with a “short” RhN axial bond and four η 2-CC olefinic interactions. The DAP acts as a tridentate ligand.