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.