Four- and five-co-ordination in complexes of palladium(II) and platinum(II) with NN′-disubstituted thio- and seleno-ureas
- 1 January 1968
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc. A
- p. 1717-1724
- https://doi.org/10.1039/j19680001717
Abstract
Complexes of NN′-disubstituted thio- or seleno-ureas (L) with bivalent palladium or platinum (Pd, Pt = M) belong mostly to the following types: (i) MIIL4X2(X = halogen), behaving typically as 1 : 1 electrolytes containing the five-co-ordinated cation [MIIL4X]+; (ii)[MIIL4X]ClO4, resulting from replacement of the outer halide ion of MIIL4X2 through ClO4 –; (iii) MIIL4(ClO4)2, where one perchlorate tends to be co-ordinated to M, thus again achieving five-co-ordination. True four-co-ordinate species [MIIL2X2] are formed in solution equilibria from [MIIL4X]+ in the presence of an excess of X–, but are not stable in the solid state, except in a few instances with platinum(II). The spectrochemical parameters of the involved chromophores are discussed on the assumption of a distorted square-pyramidal structure of the five-co-ordinated forms; S-bonded thioureas have a position quite close to water in the spectrochemical series of quadratic chromophores, and their optical electronegativity (xopt) is about 2·65, while seleno-ureas have slightly lower values of both the ligand-field strength and xopt.Keywords
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