Cobalt(II) and nickel(II) trithiocarbonate complexes as nucleophilic reagents. Reactivity and X-ray structure of the trithiocarbonate complex [Co(tppme)(S2CSCH3)][BPh4]·1.5thf

Abstract

The trithiocarbonate complexes [Co(tppme)(S₂CS)][tppme = 1,1,1 -tris(diphenylphosphinomethyl)ethane] and [Ni(dppe)(S₂CS)][dppe = 1,2-bis(diphenylphosphino)ethane] are highly activated toward electrophilic reagents. The unco-ordinated sulphur atom is found to displace the halide ion from alkyl halides or weakly bound ligands from other organometallic derivatives to give sulphur alkylated cations or CS₃- bridged binuclear complexes respectively. The crystal and molecular structure of the trithiocarbonate complex [Co(tppme)(S₂CSCH₃)][BPh₄]·1.5 thf has been determined by standard X-ray methods. The compound is monoclinic, space group C_2/c′z= 8, a= 42.420(7), b= 10.221(4), c= 35.449(7)Åβ= 124.93(8)°. The complex cation is five-co-ordinated by the three phosphorus of the tppme ligand and two sulphur atoms of the trithiocarbonate anion. The latter group can be considered planar, the methyl carbon atom almost lying in the CS₃ plane. The bonding between the Co(tppme) and S₂CS fragments is analysed in terms of qualitative molecular orbital arguments. This trithiocarbonate complex undergoes ligand nucleophilic substitution with diethylamine to form the dithiocarbamate complex [Co(tppme)-(S₂CNEt₂)][BPh₄]·0.5CH₂Cl₂.