| Three different classes of nitrogen-donor ligand systems, namely, β-diketiminato, pyrazolato, and amidinato have been used to prepare source compounds of Group 2 metals for GaN doping and for use in thin film fabrication of related materials. The work described mostly entailed the use of diketiminato ligands in an effort aimed at controlling molecular oligomerization which generally retards volatility. Accordingly, a series of momomeric Group 2 metal complexes containing β-diketiminato ligands LtBu and LiPr has been prepared and fully characterized by spectral and analytical methods and by X-ray crystallography. Surprisingly, the β-diketiminato ligands adopt diverse bonding modes, including η2, η5, μ-η 1:η1, and μ-η5:η 5. Also all of these complexes are volatile and should serve well in thin film deposition processes. In addition, several monomeric pyrazolato complexes of strontium and barium have been prepared by protonolysis routes in the presence of multidentate oxygen or nitrogen donor ligands. In another route, the combination of pyrazolato and β-diketiminato ligands afforded dimeric complexes featuring terminal η5-β-diketiminato ligands. Neither the monomeric nor the dimeric species were volatile, and, instead, they decompose upon losing their capping ligands under sublimation conditions.;The β-diketiminato chemistry was extended to the first row transition metals. A series of β-diketiminato complexes of the first row transition metals has been prepared in an effort aimed at the preparation of volatile and oxygen-free metal source compounds for doping GaN with chromium and manganese, as well as to provide reactive precursors for pure metal and metal oxide deposition by ALD. All of these complexes are volatile and thermally stable under sublimation conditions. The alkyl substituted β-diketiminato ligands exhibit the η 5-bonding mode with chromium and the η2-bonding mode with manganese, iron, and cobalt. |
