Volatility and High Thermal Stability in Mid- to Late-First-Row Transition-Metal Diazadienyl Complexes
摘要:
Treatment of MCl2 (M = Cr, Mn, Fe, Co, Ni) with 2 equiv of lithium metal and 1,4-di-tert-butyl-1,3-diazadiene ((tBu2)DAD) in tetrahydrofuran at ambient temperature afforded Cr((tBu2)DAD)(2) (38%), Mn((tBu2)DAD)(2) (81%), Fe((tBu2)DAD)(2) (47%), Co((tBu2)DAD)(2) (36%), and Ni((tBu2)DAD)(2) (41%). Crystal structure determinations revealed monomeric complexes that adopt tetrahedral coordination environments and were consistent with (tBu2)DAD radical anion ligands. To evaluate the viability of M((tBu2)DAD)(2) (M = Cr, Mn, Fe, Co, Ni) as potential film growth precursors, thermogravimetric analyses, preparative sublimations, and solid-state decomposition studies were performed. Mn((tBu2)DAD)(2) is the most thermally robust among the series, with a solid-state decomposition temperature of 325 degrees C, a sublimation temperature of 120 degrees C/0.05 Torr, and a nonvolatile residue of 4.3% in a preparative sublimation. Thermogravimetric traces of all complexes show weight loss regimes from 150 to 225 degrees C with final percent residues at 500 degrees C ranging from 1.5 to 3.6%. Thermolysis studies reveal that all complexes except Mn((tBu2)DAD)(2) decompose into their respective crystalline metal powders under an inert atmosphere. Mn((tBu2)DAD)(2) may afford amorphous manganese metal upon thermolysis.