59368-50-2Relevant academic research and scientific papers
An NMR study of mixed, tartrate-containing TiIV complexes
Potvin, Pierre G.,Fieldhouse, Benjamin G.
, p. 401 - 413 (2007/10/03)
The reactions of amines and amino alcohols with diisopropyl or diethyl R,R- or S,S-tartrate and Ti(OiPR)4 were examined by 1H and 13C NMR to obtain and characterize nonfluxional complexes with the tartrate units in novel binding modes.The mildly acidic 8-hydroxyquinoline and N-phenyl-N-benzoylhydroxylamine selectively formed the products of a double OiPr substitution, Ti2(tartrate)2(ligand)2(OiPr)2, and the products of double tartrate substitution, Ti(ligand)2(OiPr)2, while 2,4-pentanedione formed only the latter.Basic amino alkanols formed diastereomerically pure Ti2(tartrate)2(aminoalkoxide)(OiPr)3 species.N,N-Dimethyl-2-aminoethanol (Hdmae) also and uniquely formed monomeric Ti(tartrate)2(Hdmae)2 species that could be described as doubly zwitterionic.Secondary or tertiary amines formed triply C2-symmetric Ti3(tartrate)4(amine)2(OiPr)4 assemblies.Some minor components were belived to be μ-OiPr species.All mixed complexes except Ti(tartrate)2(Hdmae)2 contained chelating and bridging tartrate units, without coordination by ester carbonyls.A nonchelating, nonbridging tartrate unit was also present in the amino alcohol cases.Primary amines, aromatic amines, and hydrazines all failed to provide identifiable complexes.As well, N,N-dibenzylhydroxylamine failed to generate in solution the complex that had previously been characterized by X-ray crystallography.Amidst the rich chemistry of TiIV-tartrate systems, the evident selectivities in product formation were described to macro-ring closures that are specifically directed by the electronic nature of the addend.Transient OiPr-bridged intermediates were also implicated.Key words: mixed TiIV alkoxides, chiral TiIV alkoxides, enantiospecific complexation.
