Synthesis and characterisation of E,O-mixed donor (E=P, S or Se) ligand complexes of palladium(II) and platinum(II)

New palladium(II) and platinum(II) complexes with the hybrid ligands Ph2PNHP(O)Ph2, [Ph2PNP(O)Ph2]− or [Ph2P(E)NP(O)Ph2]− (E=S or Se) have been prepared and characterised. Hence reaction of the cyclometallated dimers [{Pd(μ-Cl)(C∼N)}2] [C∼N=C12H9N2 or C13H8N] with Ph2PNHP(O)Ph2 gave the mononuclear compounds [PdCl(C∼N){Ph2PNHP(O)Ph2-P}]. Chloride abstraction, or amine deprotonation, afforded [Pd(C∼N){Ph2PNHP(O)Ph2-P,O}][BF4] or [Pd(C∼N){Ph2PNP(O)Ph2-P,O}] bearing a neutral or anionic P,O-chelating ligand, respectively. Reaction of [{Pd(μ-Cl)(C9H12N)}2] with Ph2PNHP(O)Ph2 in CDCl3 solution gave the known, rather unstable compound, [PdCl(C9H12N){Ph2PNHP(O)Ph2-P}]. Spectroscopic and analytical evidence presented here suggest that [PdCl(C9H12N){Ph2PNHP(O)Ph2-P}] undergoes amine deprotonation/PdC bond rupture to give an isomeric compound, tentatively assigned as [PdCl{Ph2PNP(O)Ph2-P,O}(NMe2CH2Ph)]. Bridge cleavage of [{Pd(μ-Cl)(C12H9N2)}2] with the unsymmetrical anions [Ph2P(E)NP(O)Ph2]− (E=S or Se) gave the square–planar complexes [Pd(C12H9N2){Ph2P(E)NP(O)Ph2-E,O}] exclusively as one isomer (E trans to N). In a similar manner the new metal(II) compounds [PtCl{Ph2P(E)NP(O)Ph2-E,O}(PMe2Ph)] (E trans to Cl) and [Pd(C9H15O){Ph2P(E)NP(O)Ph2-E,O}] (E trans to olefin double bond) were synthesised. All compounds were characterised by a combination of multinuclear NMR [1H, 31P{1H}, 195Pt{1H}], IR spectroscopy and elemental analyses. Furthermore, the X-ray structures of [Pd(C12H12N){Ph2PNHP(O)Ph2-P,O}][BF4] and [Pd(C12H12N){Ph2PNP(O)Ph2-P,O}] are reported and reveal, upon amine deprotonation, π-delocalisation within the PNPO backbone of the anionic P,O-chelating ligand.