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

Abstract

New palladium(II) and platinum(II) complexes with the hybrid ligands Ph 2PNHP(O)Ph 2, [Ph 2PNP(O)Ph 2] − or [Ph 2P(E)NP(O)Ph 2] − (E=S or Se) have been prepared and characterised. Hence reaction of the cyclometallated dimers [{Pd(μ-Cl)(C∼N)} 2] [C∼N=C 12H 9N 2 or C 13H 8N] with Ph 2PNHP(O)Ph 2 gave the mononuclear compounds [PdCl(C∼N){Ph 2PNHP(O)Ph 2- P}]. Chloride abstraction, or amine deprotonation, afforded [Pd(C∼N){Ph 2PNHP(O)Ph 2- P, O}][BF 4] or [Pd(C∼N){Ph 2PNP(O)Ph 2- P, O}] bearing a neutral or anionic P,O-chelating ligand, respectively. Reaction of [{Pd(μ-Cl)(C 9H 12N)} 2] with Ph 2PNHP(O)Ph 2 in CDCl 3 solution gave the known, rather unstable compound, [PdCl(C 9H 12N){Ph 2PNHP(O)Ph 2- P}]. Spectroscopic and analytical evidence presented here suggest that [PdCl(C 9H 12N){Ph 2PNHP(O)Ph 2- P}] undergoes amine deprotonation/PdC bond rupture to give an isomeric compound, tentatively assigned as [PdCl{Ph 2PNP(O)Ph 2- P, O}(NMe 2CH 2Ph)]. Bridge cleavage of [{Pd(μ-Cl)(C 12H 9N 2)} 2] with the unsymmetrical anions [Ph 2P(E)NP(O)Ph 2] − (E=S or Se) gave the square–planar complexes [Pd(C 12H 9N 2){Ph 2P(E)NP(O)Ph 2- E, O}] exclusively as one isomer (E trans to N). In a similar manner the new metal(II) compounds [PtCl{Ph 2P(E)NP(O)Ph 2- E, O}(PMe 2Ph)] (E trans to Cl) and [Pd(C 9H 15O){Ph 2P(E)NP(O)Ph 2- 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(C 12H 12N){Ph 2PNHP(O)Ph 2- P, O}][BF 4] and [Pd(C 12H 12N){Ph 2PNP(O)Ph 2- 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.