Molecular Precursors to Group IV Dichalcogenides MS2 (M=Ti, Zr, Hf)

New chemical routes to synthesize layered 2D transition metal dichalcogenides (TMDCs) are highly desired. We report here a new class of molecular precursors of general formula [M-IV(SC2H4N(Me)C2H4S)(2)] (M-IV=Ti, Zr, Hf) that offers a reliable synthetic access to 2D TMDC materials as demonstrated in the representative case of TiS2 synthesis. The complexation of the TM centers by the chelating tridentate ligand (HSC2H4)(2)NMe produced stable monomeric complexes, [Ti(SC2H4N(Me)C2H4S)(2)], [Zr(SC2H4N(Me)C2H4S)(2)] and [Hf(SC2H4N(Me)C2H4S)(2)], displaying a distorted octahedral environment around metal centers formed by four S and two N donor atoms of the ligand moiety. The characterization of molecular precursors by NMR, single-crystal diffraction analysis, IR spectroscopy and elemental analysis confirmed the presence of metal-sulfur bonds that are crucial in facilitating the formation of MS2 phases. Thermal decomposition behaviour of the three molecular compounds was investigated by TG-DCS measurements that confirmed their decomposition into solid phases. Interestingly, the preorganized M-S bonds in the precursor molecules also influenced the formation of titanium disulfide thin films by chemical vapor phase deposition. The solid thin films of TiS2 were characterized by X-ray spectroscopy analysis and atomic scale imaging. The complexes presented in this work represent a promising chemistry driven approach towards reproducible and scalable synthesis of van der Waals 2D heterostructures.