Site of ring opening of an asymmetric cyclopropene with iron carbonyls: the X-ray crystal structure of a vinylketen–iron tricarbonyl complex

Metallacyclobutane Complexes of the Group Eight Transition Metals: Synthesis, Characterizations, and Chemistry

“…Another example of a proposed ferra(II)cyclobutene intermediate is shown in Scheme 26 for the formation of 80 from diphenylacetylene and pentakisfrer£-butyl isocyanide)iron(0).212 An oxidative cyclization reaction is believed to occur from the ?/2-bonded acetylene 78 to form the metallacyclic intermediate 79. In the formation of 81, a ferra(II)cyclobutene intermediate is believed to form by insertion of Fe(0) into the most highly substituted bond of 1,3,3trimethylcyclopropene (eq 95). 213 Although having greater steric hindrance, this site may be favorable due to the increased electron density created by the methyl substituents. This conclusion appears tenuous and clearly needs additional support.…”

Structure of tricarbonyl(dimethyl 4-methyl-1-oxo-1,3-pentadiene-2,3-dicarboxylate)iron

“…In recent years, a number of crystal structures concerning complexes between FeL a [L = CO or P(C6Hs) a] and the vinylketene ligand (r/a : r/l-allylcarbonyl) with various substituents have been published: [(1,2-diphenylvinyl)phenylketene]Fe(CO)3 (2) (Dettlaf, Behrens & Weiss, 1978), [(2,2-dimethylvinyl)ketene]Fe(CO) a (3) (Binger, Cetinkaya & Kriiger, 1978), [(2,2-dimethylvinyl)methylketene]-Fe(CO) a (4) (Newton, Pantaleo, King & Chu, 1979), and (methyl 3-methoxy-4-oxo-1,3-butadiene-2-carboxylate)Fe(CO)2[P(C6Hs) 3] (5) (Mitsudo, Sasaki, Watanabe & Takegami, 1978). We report here the crystal structure of (dimethyl 4-methyl-l-oxo-l,3-pentadiene-2,3-dicarboxylate)Fe(CO) 3 (1) and compare it to the other known structures in order to discover the influence of the substituents.…”