Some complexes of cobalt(II), nickel(II), and palladium(II), with multidentate ligands and the ligand field strength of co-ordinated ethers and sulphides

The multidentate ligands (o-X·C6H4·Y·CH2)2(X = NH2, Y = O:ON; X = NH2, Y = S:SN; X = NH2, Y = NH:NN; X = Ph2As, Y = O:OAS; X = Ph2As, Y = S:SAS) and (Y = O:ONO; Y = S:NNO; Y = NH:NNO) have been prepared. Comparison of the complexes of cobalt(III), of the types [CoCl2(chelate)]+(chelate = ON, SN, and NN) and [Co(chelate)]+(chelate = ONO, SNO, and NNO) shows that the ligand field strength of the ether-oxygen in cobalt(III) is similar to that of the sulphide-sulphur and lower than that of the imino-nitrogen. The nickel(II) complexes [NiX2(SN)](X = Cl, Br, I, and NCS) have S= 1 and are octahedral while the corresponding nitrato- and perchlorato-derivatives (X = NO3 and ClO4) may have lower co-ordination numbers. The palladium(II) complexes, of the type [PdX2(chelate)](chelate = ON, SN, OAS, and SAS; X = Cl, Br, I, and SCN) are tetracoordinate, the organic ligands acting as bidentate. The ON and OAS ligands appear to be bonded through the nitrogen and arsenic atoms, respectively, spanning trans positions in the complex.