DIHYDROPYRIDINE-INDUCED REDUCTIONS OF METHYL(ETHOXY)CARBENE COMPLEXES OF CHROMIUM AND TUNGSTEN - FORMATION AND X-RAY CRYSTAL-STRUCTURE OF THE ADDUCT BETWEEN PYRIDINE AND THE CORRESPONDING ETHYLIDENE CARBENE COMPLEXES

The reactions of [(CO)5MC(OEt)Me] (1) (M = W or Cr) with 1,4-dihydropyridines (R')C5H5N(R) (2) (R = H or Me; R' = H or Me) give either the ylides [(CO)5MCH(Me)(R)NC5H5(R')] (R = H, R' = H or Me) (5) or the pyridinium tungstates and chromates [(CO)5MCH(Me)(OEt)]-[(R)NC5H5-(R')]+ (R = Me, R' = H or 4-Me) (7) via hydride transfer to the carbene carbon atom. Sa (R = H, R' = 4-Me) was characterized spectrally and by single crystal X-ray diffraction.