New complexes of CoII, NiII and CuII with siliconisothiocyanates of the type Rx,Si(NCS)4-x, (where x = 0, 1, 2, 3) have been synthesized and characterized using elemental analyses, magnetic susceptibility measurements and spectral (electronic and infrared) data. The CoII and NiII complexes have a polymeric tetrahedral structure, whereas a tetragonal structure has been assigned to the CuII complexes