Tri(allyl)- and tri(methylallyl)arsine complexes of palladium(II) and platinum(II): synthesis, spectroscopy, photochemistry and structures

Tri(allyl)- and tri(methylallyl) arsine complexes of palladium(II) and platinum(II) with the formulae [MX2L2] (M = Pd, Pt and X = Cl, Br, I): [Pd2Cl2(mu-Cl)(2)L-2], [PdCl(S2CNEt2) L] and [Pd2Cl2(mu-dmpz)(2)L-2] [L = As(CH2CH= CH2)(3) (L'), As(CH2CMe= CH2)(3) (L"), dmpz = 3,5-dimethylpyrazolate] have been prepared. All the complexes have been characterized by elemental analyses and by IR and NMR (H-1, C-13, Pt-195) spectroscopy. The stereochemistry of the complexes has been deduced from the spectroscopic data. The molecular structures of complexes [MX2{As(CH2CH= CH2)(3)}(2)] (M = Pd, X = Cl or Br), [MX2{As(CH2CMe = CH2)(3)}(2)] (M = Pd, X = Cl or Br; M = Pt, X = Cl) and [Pd2Cl2(mu-Cl)(2){As(CH2CMe= CH2)(3)}(2)] have been established by single crystal X-ray diffraction analyses. The mononuclear complexes exclusively adopt the trans configuration with the exception of [PdCl2L"(2)], which could be isolated as cis and trans isomers. In the binuclear derivative the arsine ligands are attached to an envelope-shaped Pd-(mu-Cl)(2) - Pd rectangle with a trans ( anti) orientation towards each other. The mononuclear complexes are slightly photoreactive upon irradiation in their long-wavelength absorption band.