AN NMR-STUDY OF MIXED, TARTRATE-CONTAINING TI-IV COMPLEXES

The reactions of amines and amino alcohols with diisopropyl or diethyl R,R- or S,S-tartrate and Ti((OPr)-Pr-i)(4) were examined by H-1 and C -13 NMR to obtain and characterize nonfluxional complexes with the tar trate units in novel. binding modes. The mildly acidic 8-hydroxyquinol ine and N-phenyl-N-benzoylhydroxylamine selectively formed the product s of a double (OPr)-Pr-i substitution, Ti-2(tartrate)(2)(ligand)(2)((O Pr)-Pr-i)(2), and the products of double tartrate substitution, Ti(lig and)(2)((OPr)-Pr-i)(2), while 2,4-pentanedione formed only the latter. Basic amino alkanols formed diastereomerically pure Ti-2(tartrate)(2) (aminoalkoxide)((OPr)-Pr-i)(3) species. N,N-Dimethyl-2-aminoethanol (H dmae) also and uniquely formed monomeric Ti(tartrate)(2)(Hdmae)(2) spe cies that could be described as doubly zwitterionic. Secondary or tert iary amines formed triply C-2-symmetric Ti-3(tartrate)(4)-(amine)(2)(( OPr)-Pr-i)(4) assemblies. Some minor components were believed to be mu -(OPr)-Pr-i species. All mixed complexes except Ti-2(tartrate)(2)(Hdma e), contained chelating and bridging tartrate units, without coordinat ion by ester carbonyls. A nonchelating, nonbridging tartrate unit was also present in the amino alcohol cases. Primary amines, aromatic amin es, and hydrazines all failed to provide identifiable complexes. As we ll, N,N-dibenzyl hydroxylamine failed to generate in solution the comp lex that had previously been characterized by X-ray crystallography. A midst the rich chemistry of T1(IV)-tartrate systems, the evident selec tivities in product formation were ascribed to macro-ring closures tha t are specifically directed by the electronic nature of the addend. Tr ansient (OPr)-Pr-i-bridged intermediates were also implicated.