Synthesis of new heterotridentate ligands comprising mixed hard–soft donor sets, and their complexation with Group 10 metals

Abstract

The new phosphorus-containing heterotridentate ligands 2-(2-Ph₂P)C₆H₄CHNCH(Me)CH(OH)Ph-1S,2R (HL¹) and 2-(2-Ph₂P)C₆H₄NCHC₆H₄OH (HL²) were prepared by the condensation of 2-(diphenylphosphino)benzaldehyde with 1S,2R-norephedrine (HL¹) and 2-(diphenylphosphino)aniline with salicylaldehyde (HL²). The co-ordination chemistry of HL¹ and HL² with Group 10 metals was explored, together with that of the previously reported ligand 2-(2-Ph₂P)C₆H₄CHNC₆H₄OH (HL³) which is isomeric with (HL²). Compound HL¹ affords cationic complexes of general formula [M(HL¹)Cl]Cl, where M = Ni (1), Pd (2) or Pt (3). Spectroscopic, microanalytical and crystallographic data for 1–3 confirm that deprotonation of the hydroxyl group does not occur on complexation. In contrast, both HL² and HL³ deprotonate on complexation to form neutral species of general formula [MLCl] where L = L², M = Ni (4), Pd (5) or Pt (6); L = L³, M = Ni (7), Pd (8) or Pt (9). The crystal structures of 4, 5, 7 and 9 confirm tridentate PNO co-ordination of the deprotonated ligands to the metal centres, forming 5- and 6-membered rings.