Synthesis and Reactivity of Binaphtholate Complexes of a d3-d3 Ditungsten Template

Steven D. Dietz, Nancy W. Eilerts, Joseph A. Heppert, David Vander Velde

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

W2(O-t-Bu)6 reacts with binaphthol derivatives (H2BINO, R = H (1); H2Me2BINO, R = CH3 (2)) to produce monosubstituted products of the formula (R2BINO) W2(O-t-Bu)4. The presence of a single product in the 1H NMR spectra of these compounds supports the hypothesis that the binaphtholate ligand adopts a preferential mode of binding. Disubstituted products can be formed when 2 equiv of binaphthol is reacted with W2(O-t-Bu)6: racemic binaphthol generates anti-(R,S)-(BINO)2W2(O-t-Bu)2 (3) with small quantities of anfi-(R*,R*)-(BINO)2W2(O-t-Bu)2 (5), while optically pure (R)-binaphthol yields gauche-(R,R)-(BINO)2W2(O-t-Bu)2 (6). The enantiomers of 6 appear to undergo intermolecular exchange reactions in the presence of tert-butyl alcohol, forming 3 as the main product along with small quantities of (R*,R*,R*)-(BINO)3W2 (4). A reaction between 2 and 2 equiv of acetylene generates a flyover complex, (μ2-C4H4)(Me2BINO)W2(O-t-Bu)4 (7), as identified by 1H and 13C NMR spectroscopy. When greater than 6 equiv of acetylene is employed, (η2-C2H2)(μ2-C4H4)(Me2BINO)2W2(O-t-Bu)2 (8), a complex containing a flyover fragment with an additional terminal acetylene ligand, is produced. Complex 3 is also reactive toward acetylene, generating diastereomeric tris(acetylene) derivatives of the formula (μ2-C4H4)-(η2-C2H2)(BINO)2W2(O-t-Bu)2 (9) in a nonstatistical ratio. This result suggests that the presence of chiral chelating ligands in the coordination sphere can influence the stereochemistry of complex formation at the W2 template.

Original languageEnglish
Pages (from-to)1689-1697
Number of pages9
JournalInorganic Chemistry
Volume32
Issue number9
DOIs
StatePublished - 1993

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