Synthesis and conformational studies of palladium(II) complexes containing [Ph₂P(O)NP(E)Ph₂]- (E = S or Se)

The ligands [Ph2P(O)NP(E)Ph-2](-) (E = S I: E = Se II) can readily be complexed to a range of palladium(II) starting materials affording new six-membered Pd-O-P-N-P-E palladacycles. Hence ligand substitution reaction of the chloride complexes [PdCl2(bipy)] (bipy - 2,2'-bipyridine), [{Pd(mu-Cl)(L-L)}(2)] (HL-L = C9H13N or C12H13N), [{Pd(mu Cl)Cl(PMe2Ph)}(2)] or [PdCl2(PR3)(2)] [PR3 = PPh3; 2PR(3) = Ph2PCH2CH2PPh2 or cis-Ph2PCH = CHPPh2] with either I (or II) in thf or CH3OH gave [Pd{Ph2P(O)NP(E)Ph-2-O,E}(bipy)]PF6, [Pd{Ph2P(O)NP(E)Ph-2-O,E} (L-L)], [Pd{Ph2P(O)NP(E)Ph-2-O,E}Cl(PMe2Ph)] or [Pd{Ph2P(O)NP(E)Ph-2-O,E} (PR3)(2)]PF6 in good yields. All compounds described have been characterised by a combination of multinuclear NMR [P-31{H-1} and H-1] and IR spectroscopy and microanalysis. The molecular structures of five complexes containing the selenium ligand II have been determined by single-crystal X-ray crystallography. Three different ring conformations were observed, a pseudo-butterfly, hinge and in the case of: all three PR, complexes, pseudo-boat conformations. Within the Pd-O-P-N-P-Se rings there is evidence for x-electron delocalisation. (C) 1998 Elsevier Science Ltd. All rights reserved.