摘要：

A series of five-coordinate complexes of the type [M(tetars)X]+, where tetars is a linear quadridentate tetra(tertiary arsine) ligand, where M = Ni(II), Pd(II), or Pt(II) and where X is a halide ligand, have been prepared and characterized. The absorption and circular dichroism spectra of these square-pyramidal complexes show consistent patterns and suggest that the d-orbital functions have the ordering dxy < dxz, dyz < dz2 dx2-y2. The halogeno ligands, although very stable in nonpolar solvents, are at the same time very labile at 30°. A variable-temperature NMR study indicates that both axial-site interchange and intermolecular exchange can occur by three different bimolecular mechanisms which involve halogen attack of the metal, as well as attack by either a four- or a five-coordinate complex resulting in the formation of dimers.

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