The compounds (Ph 4 P) 2 [Ni(RSO 2 NCS 2 ) 2 ] [Ph 4 P + =tetraphenylphosphonium cation; R=CH 3 (1b), CH 3 CH 2 (2b), CH 3 (CH 2 ) 3 (3b) and CH 3 (CH 2 ) 7 (4b)] were synthesized by the reaction of RSO 2 NCS 2 K 2 ·2H 2 O (1a-4a) with NiCl 2 ·6H 2 O and Ph 4 PBr. The elemental analyses of C, H, N and Ni were consistent with the proposed formula for 1b–4b. The IR data were consistent with the formation of bis(dithiocarbimato)-nickel(II)-complexes. The NMR spectra showed the expected signals for the cation and the dithiocarbimate anionic complex in a 2:1 proportion. The compounds 2b and 3b were also characterized by X-ray diffraction techniques. Compounds 2b and 3b crystallize in the P2 1 /c and P1¯ space groups, respectively. The nickel(II) ions are positioned in special positions being coordinated by four sulfur atoms of the dithiocarbimate moieties in a square planar environment. The Ph 4 P + counter-ions enter the structure interstice performing weak C–H···O and C–H···S intermolecular interactions. The activity of compounds 1b–4b in the vulcanization of the natural rubber was evaluated. These studies confirm that the bis(dithiocarbimato)-nickel(II)-complexes are new vulcanization accelerators worth of further investigation.