Thionation of 3-methylbutylmagnesium bromide with Lawesson's Reagent (LR) gave 4-methoxyphenyl (3-methylbutyl)dithiophosphinic acid (DTPA), and the latter was converted to the ammonium salt (NH4L = Ammonium 4-methoxyphenyl (3-methylbutyl) dithiophosphinate). The complex, trans-bis[4-methoxyphenyl(3-methylbutyl) dithiophosphinato] nickel(II) [NiL2], was prepared by the reaction of NH4L with NiCl2.6H(2)O in EtOH. Bis [4-methoxyphenyl (3-methylbutyl) dithiophosphinato]cobalt(II) [(CoL2)(2)] was also prepared in the same way. The structures of the complexes have been characterized by elemental analysis, FTIR, H-1, C-13, P-31 NMR and X-ray diffraction. The single crystal X-ray structures of [NiL2] and [(CoL2)(2)] show that the nickel complex is square planar while the cobalt counterpart has tetrahedral coordination with a dimeric structure. Bond lengths, angles, torsion angles and dihedral angles are correlated to the structures and also compared with the literature data on similar compounds.