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

Abstract

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