Palladium(II) complexes with hemilabile amphiphilic phosphines

A series of trans-PdCl2L2 complexes were prepared and characterized with the following hemilabile amphiphilic phosphines: R-(C6H4)-(OCH2CH2) n-PPh2 {1 (R=tert-octyl, n=1), 2 (R=tert-octyl, n̄=5), 3 (R=tert-octyl, n̄=13), 4 (R=n-nonyl, n̄=1.4), 5 (R=n-nonyl, n̄=5), 6 (R=n-nonyl, n̄=11)}, CH3(OCH2CH2)3PPh2 (7), CH3(OCH2CH2)3PPhR (8, R=isopentyl) and HOCH2CH2(OCH2CH2)2PPhR (9, R=n-octyl). The molecular structure of trans-PdCl2(1)2 was determined by X-ray crystallography. The reaction between the trans-PdCl2L2 complexes and Ag+ was studied by 31P-NMR spectroscopy. The formation of chelated P∩O species in tetrahydrofuran solution was observed in complexes with ligands 2, 3, 5, 6, 7, 8 and 9. However, with ligand 1 the formation of chelated species was only observed in the less coordinating solvent dichloromethane. This different behavior can be attributed to the electronic and steric effects of the aryl group bonded to the oxygen atom. Ligand 4 is a mixture of a molecule similar to 1 and molecules with more than one oxygen atom and thus displays both characteristics. © 2001 Elsevier Science B.V.