Molecular Routes to Metal Carbides, Nitrides, and Oxides. 2. Studies of the Ammonolysis of Metal Dialkylamides and Hexamethyldisilylamides

Abstract

Ammonolysis of metal amides M(NR2)n, where M = a group 4, 5, or 6 transition metal, M2(NMe2)6, where M = Mo, W, and metal hexamethyldisilylamides M(N(SiMe3)2)n, where M = Ti, V, Cr, Mn, Co, Cu, La, Y, and Sn have been carried out in hydrocarbon solvents. The initially formed products are hydrocarbon-insoluble powders wherein the metal retains its original oxidation state. Elemental analysis of these powders reveals a dramatic loss of NR2 ligands as evidenced by relatively low C and H content. Thermogravimetric analysis coupled with mass spectroscopy indicates that these powders readily eliminate amine (HNR2) and ammonia to form metal nitrides upon heating, typically in the temperature range 200−400 °C. Upon further heating, redox reactions may occur with the evolution of N2 gas leading to more thermodynamically stable nitrides or the metal, i.e., where M = Fe, Co, Cu. The nitrogen content of the nitrides has been shown to be derived from ammonia and not from the parent amide. Ammonolyses of mixtures of me...