The effects of metal insertion (iron, cobalt and nickel) into 1T-CdI-type TiS layered crystals, expressed as M TiS , have 2 2 x 2 been studied by X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM) and band structure calculations (FLAPW method). The stoichiometry x51 / 4 was chosen because of specific crystallographic features of the compounds studied. We focused our interest on the role played by chalcogen atoms. S 2p core spectra are found to depend strongly on their chemical surroundings (Ti or Ti and M) and on the guest metal. We imaged the top sulfur plane (001) for Fe TiS , Co TiS and Ni TiS and note that the results also depend on the compound considered. Theoretical 1 / 4 2 1 / 4 2 1 / 4 2 calculations have been carried out in order to improve our knowledge of the electronic structure of M TiS compounds and 1 / 4 2 attempts are made to rationalize the experimental data.