What should be impossible: resolution of the mononuclear gallium coordination complex, Tris(benzohydroxamato)gallium(III).
Complexes of Ga3+, a d10 metal ion which lacks ligand-field-stabilization energy, are considered labile. In fact, hexaaquagallium(III) has a ligand exchange rate of 403 s-1, 2.5 times that of the analagous Fe3+ complex (Hugi-Cleary, D.; Helm, L.; Merbach, A. E. J. Am. Chem. Soc. 1987, 109, 4444-4450). Given this lability, resolution of Ga3+ complexes should be impossible. Despite this, we report the resolution of the Lambda and Delta isomers of tris(benzohydroxamate)gallium (III) (1), the first resolution of a mononuclear gallium complex. Not only is resolution possible, but these resolved complexes show remarkable resistance to racemization in aprotic solvents. The unprecedented stability of Lambda- and Delta-1 is a surprise, and as such, alters our understanding of classical coordination chemistry.
D002942:Circular Dichroism; D005290:Ferric Compounds / Q000737:chemistry / Q000302:isolation & purification; D005708:Gallium / Q000737:chemistry*; D006877:Hydroxamic Acids / Q000737:chemistry / Q000302:isolation & purification*; D009942:Organometallic Compounds / Q000737:chemistry / Q000302:isolation & purification*; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
D005290:Ferric Compounds; D006877:Hydroxamic Acids; D009942:Organometallic Compounds; D005708:Gallium