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.