Synthesis and Volatility Characterization of Mo(II) and W(II) Compounds for Thin Films

Mo(II) and W(II) compounds, Mo(η³-allyl)(CO)₂(Tri-MEDA)Br (1), Mo(η³-allyl)(CO)₂(TMEDA)Br (2), W(η³-allyl)(CO)₂(Tri-MEDA)Br (3), and W(η³-allyl)(CO)₂(TMEDA)Br (4) (Tri-MEDA = N,N,N'-trimethylethylenediamine), were synthesized and characterized. The molecular structures of 1 and 3 were nearly identical with a pseudo-octahedral geometry except for the different Mo and W metal centers. The thermogravimetric analysis of 1 and 3 showed approximately 53 and 64% residues at 550 °C, respectively, which were significantly higher than the values for the expected materials. However, 1 and 3 sublimed at 100 °C under 0.40 Torr and 120 °C under 0.50 Torr, respectively, confirming that they were volatile. For 1 and 3, the temperatures at a vapor pressure of 1 Torr and enthalpies of vaporization (ΔH_vap) were 168.78 °C and 143.8 kJ mol^-1, and 167.48 °C and 148.5 kJ mol^-1, respectively. The tungsten compound (3) exhibited good durability for 5 weeks under a thermal stability test at a sublimation temperature of 120 °C.