Reductive cleavage of aldehydes to oxo-alkylidene and oxo-Alkylidyne complexes in their reactions with W-2((OCH2Bu)-Bu-t)(6)(py)(2)

Aldehydes react with W-2((OCH2Bu)-Bu-t)(6)(py)(2) to give W-2(mu-CHR)(O)((O CH2Bu)-Bu-t)(6)(py) compounds, where R = alkyl or aryl, which, in the prese nce of excess pyridine, yield W2(mu-CR)(mu-O)((OCH2Bu)-Bu-t)(5)(py)(2) comp ounds and neopentanol. A relative order of rates of reductive cleavage of t he C=O bond is found to be aryl > alkyl, and for p-X-C6H4CHO, the rates fol low the order X = CF3 > H > F > Me > OMe. Four complexes have been structur ally characterized by single-crystal X-ray crystallography: W-2(mu-(CHC3H5) -C-c)(O)((OCH2Bu)-Bu-t)(6)(py), 1; W-2(mu-CH(tolyl))(O)((OCH2Bu)-Bu-t)(6)(p y), 2; W-2(mu-(CC3H5)-C-c)(mu-O)((OCH2Bu)-Bu-t)(5)(py)(2), 3, and W-2(mu-C( p-MeOC6H4))((OCH2Bu)-Bu-t)(5)(py)(2), 4. Factors influencing the reductive cleavage of the C=O bond are discussed in light of earlier studies of relat ed reactions, and most notably comparisons are made with the development of a molecular alternative to the McMurry reagent.