Palladium(ii) and platinum(ii) complexes with tridentate iminophosphineligands; synthesis and structural studies

Abstract

The previously synthesised Schiff-base ligands 2-(2-Ph₂PC₆H₄NCH)–R′–C₆H₃OH (R′ = 3-OCH₃, HL¹; 5-OCH₃, HL²; 5-Br, HL³; 5-Cl, HL⁴) were prepared by a faster, more efficient route involving a microwave assisted co-condensation of 2-(diphenylphosphino)aniline with the appropriate substituted salicylaldehyde. HL^1–4 react directly with M^IICl₂ (M = Pd, Pt) or Pt^III₂(cod) affording neutral square-planar complexes of general formula [M^IICl(η³-L^1–4)] (M = Pd, Pt, 1–8) and [Pt^III(η³-L^1–4)] (M = Pd, Pt, 9–12). Reaction of complexes 1–4 with the triarylphosphines PR₃ (R = Ph, p-tolyl) gave the novel ionic complexes [Pd^II(PR₃)(η³-L^1–4)]ClO₄ (13–20). Substituted platinum complexes of the type [Pt^II(PR₃)(η³-L^1–4)]ClO₄ (R = P(CH₂CH₂CN)₃21–24) and [Pt^II(P(p-tolyl)₃)(η³-L^3,4)]ClO₄ (25 and 26) were synthesised from the appropriate [Pt^IICl(η³-L^1–4)] complex (5–8) and PR₃. The complexes are characterised by microanalytical and spectroscopic techniques. The crystal structures of 3, 6, 10, 15, 20 and 26 were determined and revealed the metal to be in a square-planar four-coordinate environment containing a planar tridentate ligand with an O,N,P donor set together with one further atom which is trans to the central nitrogen atom.