Palladium(II) and platinum(II) complexes with tridentate iminophosphine ligands; synthesis and structural studies

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. HL1–4 react directly with MIICl2 (M = Pd, Pt) or PtIII2(cod) affording neutral square-planar complexes of general formula [MIICl(η3-L1–4)] (M = Pd, Pt, 1–8) and [PtIII(η3-L1–4)] (M = Pd, Pt, 9–12). Reaction of complexes 1–4 with the triarylphosphines PR3 (R = Ph, p-tolyl) gave the novel ionic complexes [PdII(PR3)(η3-L1–4)]ClO4 (13–20). Substituted platinum complexes of the type [PtII(PR3)(η3-L1–4)]ClO4 (R = P(CH2CH2CN)321–24) and [PtII(P(p-tolyl)3)(η3-L3,4)]ClO4 (25 and 26) were synthesised from the appropriate [PtIICl(η3-L1–4)] 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.