The reaction of TpRu(CO)(NCMe)(Me) (1) and pyrrole forms TpRu(CO){κ2-N,N-(H)NC(Me)(NC4H3)} (2). The formation of complex 2 involves the cleavage of the N−H bond and
2-position C−H bonds of pyrrole as well as a C−C bond forming step between pyrrole and
the acetonitrile ligand of 1. Mechanistic studies indicate that the most likely reaction pathway
involves initial metal-mediated N−H activation of pyrrole to produce TpRu(CO)(N-pyrrolyl)(NCMe) (3) followed by C−C bond formation and proton transfer. Complex 3 has been
independently prepared and demonstrated to convert to 2. Computational studies support
the suggested selectivity for initial N−H bond cleavage in preference to C−H bond activation.
Cyclopentadienylmolybdenumdicarbonyl anion reacts with a variety of allenic electrophiles to produce η 3 -2-alkylidene cyclobutanoyl complexes. Three of these complexes have been characterized by X-ray crystallography, and the 2-alkylidene cyclobutanone has been removed and recovered from one complex via oxidative demetalation.
Reduced cobaloxime (cobaloxime ) [(pyridine)(dimethylglyoxime) 2 cobalt]) compounds react with a variety of oxygen-substituted allenic and propargyl electrophiles to produce cobaloxime-substituted R,β-or β,γ-unsaturated ketones and aldehydes. Two of the new unsaturated acyl complexes prepared have been characterized by X-ray crystallography. Several of the R,β-unsaturated acyl complexes were subsequently converted into 1-cobaloxime-1,3-dienyl complexes using Peterson or Petasis olefinations. One of these new dienyl complexes has also been characterized by X-ray crystallography.
The syntheses of two optically active Co-(salen)-1,3-butadien-2-yl complexes are reported. One of the dienyl complexes was characterized by X-ray crystallography. The dienyl complexes underwent Diels-Alder reactions with high enantioselectivity with dimethyl fumarate. A highlight of this chemistry is that Diels-Alder cycloadduct cobalt complexes were cleanly cleaved at the cobalt-carbon bond with concomitant optically active cobalt complex starting material and optically active cyclohexene cycloadduct recovery.
Cyclopentadienylmolybdenumtricarbonyl anion reacts with a variety of allenic electrophiles to produce η 3 -2-alkylidene cyclobutanonyl and/or η 3 -butadienyl complexes. The 2-alkylidene cyclobutanone can be synthetically modified, while still complexed to molybdenum, by nucleophilic addition to the carbonyl or via enolate chemistry. The cyclobutanone can then be removed from the metal via oxidative demetalation. Several of the new complexes reported here have been characterized by X-ray crystallography.
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