SYNTHESIS AND REACTIVITY OF BINAPHTHOLATE COMPLEXES OF A D(3)-D(3) DITUNGSTEN TEMPLATE

W2(O-t-Bu)6 reacts with binaphthol derivatives (H2BINO, R = H (1); H2M e2BINO, R = CH3 (2)) to produce monosubstituted products of the formul a (R2BINO)W2(O-t-Bu)4. The presence of a single product in the H-1 NMR spectra of these compounds supports the hypothesis that the binaphtho late ligand adopts a preferential mode of binding. Disubstituted produ cts 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) wit h small quantities of anti-(R,R*)-(BINO)2W2(O-t-Bu)2 (5), while optic ally pure (R)-binaphthol yields gauche-(R,R)-(BINO)2W2(O-t-Bu)2 (6). T he enantiomers of 6 appear to undergo intermolecular exchange reaction s 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 b etween 2 and 2 equiv of acetylene generates a flyover complex, (mu2-C4 H4)(Me2BINO)W2(O-t-Bu)4 (7), as identified by H-1 and C-13 NMR spectro scopy. When greater than 6 equiv of acetylene is employed, (eta2-C2H2) (mu2-C4H4)(Me2BINO)2W2(O-t-Bu)2 (8), a complex containing a flyover fr agment with an additional terminal acetylene ligand, is produced. Comp lex 3 is also reactive toward acetylene, generating diastereomeric tri s(acetylene) derivatives of the formula (mu2-C4H4)-(eta2-C2H2)(BINO)2W 2(O-t-Bu)2(9) in a nonstatistical ratio. This result suggests that the presence of chiral chelating ligands in the coordination sphere can i nfluence the stereochemistry of complex formation at the W2 template.