Coordination behavior of thiocyanate in the complexes [CH 3P(C 6H 5) 2] 2M(CNS) 2 (M = Ni, Pd, Pt)

Abstract

The complexes [CH 3P(C 6H 5) 2] 2M(CNS) 2 (M = Ni, Pd, Pt) have been prepared and characterized. The structures of these complexes are markedly metal ion and physical state dependent. All of the complexes are square planar. In the solid state the nickel complex is trans-L 2M(NCS) 2 (by crystal structure analysis), the palladium complex is trans-L 2Pd(SCN) 2 and the platinum complex it cis-L 2(NCS) 2 (both determined by infrared spectroscopy, including integrated intensity measurements). Fourier transform phosphorus nmr spectra on chloroform solutions at ambient temperature indicate that for the platinum complex, all six possible isomers are present in solution in the relative ratios: trans-L 2Pt(NCS) 2: trans-L 2Pt(SCN)(NCS): trans-L 2Pt(SCN) 2: cis-L 2Pt(NCS) 2: cis-L 2Pt(SCN) 2: cis-L 2Pt(SCN)(NCS): 0.38:0.57:0.38: 0.34:0.28:1, respectively. For the palladium complex, under similar conditions, all of the isomers but cis-L 2Pd(SCN)(NCS) are present, with trans-L 2Pd(NCS) 2 and cis-L 2Pd(NCS) 2 predominant in a ratio of O.15:1, respectively. The relative population of cis isomers decreases in the sequence Pd > Pt > Ni, and the relative population of mixed linkage isomers decreases in the sequence Pt > Pd > Ni. The differences in the structures are discussed in light of current theories.