Platinum(II), palladium(II), and nickel(II) complexes of bisthiourea ligands

A series of alkyl-bridged bisthiourea ligands and their group 10 complexes, of the types [Pt-2{(SC(NPh)NHC6H4)(2)CH2}(PPh3)(4)]center dot 2BPh(4), [M-2{(SC(NPh)NHC6H4)(2)CH2}(dppe)(2)]center dot 2BPh(4) (M = Pd, Ni), [Pt-2{SC(NPh)NH}(2)(CH2)n(PPh3)(4)]center dot 2BPh(4) (n = 4, 6, 8, 12), and [M-2{SC(NPh)NH}(2)(CH2)(4)(dppe)(2)]center dot 2BPh(4) (M = Pd, Ni) have been synthesised, where dppe = Ph2PCH2CH2PPh2. The ESI mass spectral analysis of the complexes showed the presence of monochelated and dichelated species, with respectively one or two metal centres coordinated to the bisthiourea. Increasing the molar ratio of the metal precursor and reaction time (from 2 to 8 h) resulted in the disappearance of the monochelated species from the ESI mass spectra of the platinum complexes. P-31{H-1} NMR characterisation of the diarylmethane-bridged bisthiourea complexes [M-2{(SC(NPh)NHC6H5)(2)CH2}L-4]center dot 2BPh(4) (M = Pt, Pd, Ni; L = PPh3 or L-2 = dppe) showed complex multiplets indicative of the formation of several isomers of the products. In contrast, the complexes with bridging alkylene chains showed only a single isomer in solution, and X-ray crystallographic studies on several derivatives confirmed the formation of a four-membered M-S-C-N ring involving the chelating thiourea monoanions, with a coordinated NPh group in each case. The cytotoxicities of the ligands and metal complexes towards HepG2 and DLD-1 cell lines are also reported.

Automated summary

A series of alkyl-bridged bisthiourea ligands and their group 10 metal complexes have been synthesized, showing different coordination states and isomeric structures. The ESI mass spectral analysis and NMR characterization revealed complex multiplets and the formation of various isomers in the products. X-ray crystallographic studies confirmed the coordination of NPh group and the formation of M-S-C-N rings involving chelating thiourea monoanions in some derivatives.