Here are described several new nickel(II), palladium(II), and platinum(II) complexes of bis(chelate)-type with didentate phosphine ligands having an amino or thioether donor group: Me2PCH2CH2NH2 (edmp), Ph2PCH2CH2NH2 (edpp), Me2PCH2CH2NMe2 (dmedmp), or Me2PCH2CH2SMe (mtdmp). Bis(tetrafluoroborate) salts of [M(P-N or S)2]2+ (M=Ni, Pd, and Pt; (P-N or S)=the ligands above) have been prepared and the geometrical structures determined by NMR spectroscopy. All the palladium(II) complexes prepared in this study are cis-isomers, in contrast to the analogous Me2PCH2CH2S- (dmsp) complex (trans-[Pd(dmsp)2]), which indicates that the anionic phosphine-thiolate ligand prefers the trans geometry more than the neutral phosphine-amine or -thioether ligand does. The dichloride salts of the bis(edmp) complexes, cis-[M(edmp)2]Cl2 (M=Ni (4a), Pd(5a), and Pt(6a)), and those of the bis(edpp) complexes have been obtained as crystals, while the corresponding salts of dmedmp, mtdmp, and 8-(dimethylphosphino)quinoline complexes can not be isolated due to their oily properties. Further, addition of LiBF4 to a methanolic solution of 4a, 5a, or 6a gives exclusively a precipitate of the chloride tetrafluoroborate salt, cis-[M(edmp)2]Cl(BF4) (M=Ni (4c), Pd(5c), or Pt(6c)). The crystal structures of 4a, 5c, and 6a determined by X-ray analyses indicate a weak (not strong enough to form a five-coordinated complex) interaction between cis-[M(edmp)2]2+ and Cl- anion. The average M-N bond lengths in 4a, 5c, and 6a are considerably longer than those in the corresponding 1,2-ethanediamine complexes, owing to the strong trans influence of the -PMe2 group in edmp. The order of strength of the trans influence among NiII, PdII, and PtII triad metal series is nonperiodical: NiII < PtII < PdII. This order is similar to the order among CoIII, RhIII, and IrIII triad metal series found in our previous study on fac-[M′(edmp)3]3+ (M′ =CoIII, RhIII, and IrIII) complexes.
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