Hydridotris(3,5-dimethylpyrazolyl)boratorhenium(V) diolates cyclorevert to Tp‘ReO3 and alkene at elevated temperatures in nonpolar solvents. Comparison of activation parameters to those of the analogous pentamethylcyclopentadienyl complexes show the former have similar ΔS ⧧'s, but higher ΔH ⧧'s by 2−4 kcal/mol. Computation of the frontier orbitals for this ligand system show that the appropriate acceptor orbital on the metal is pushed to higher energy compared to the case where the ligand is pentamethylcyclopentadienyl, consistent with predictions for the proposed stepwise mechanism of this reaction.

rf-(2Z,4E)-5-phenylpentadienoyl)Mn(CO)5 (2) was prepared by the reaction ofLi(CO)¡Mn and (2Z,4E)-5-phenylpentadienoyl chloride. Introduction of 2 to N-methylmorpholine N-oxide in the presence of selected amines gives the amine-substituted if-oxapentadienyl complexes 3a-d, which may also be described as (rfallyl-amide)Mn(CO)3 complexes. Reaction of 2 with trimethylamine N-oxide in the absence of nucleophiles gives the dimethylamine-rf-oxapentadienyl complex 3e. X-ray crystallographic analysis of this complex corroborates that the oxapentadienyl ligand is bonded in an 4 fashion. Addition of CH3OH and N-methylmorpholine N-oxide to 2 forms the carbomethoxy ester substituted 3-allyl complex 6.We here report (1) the synthesis of amine-substituted (?74-oxapentadienyl)Mn(CO)3 complexes from the reaction of an (?71-pentadienoyl)Mn(CO)5 complex with selected amines and N-methylmorpholine N-oxide, (2) the reaction of an (?;1 3-pentadienoyl)Mn(CO)5 complex with trimethylamine N-oxide to give a dimethylaminesubstituted (^4-oxapentadienyl)Mn(CO)3 species, and (3) the reaction of an (?/1-pentadienoyl)Mn(CO)5 complex with N-methylmorpholine N-oxide and methanol to give a carbomethoxy ester substituted (v3-allyl)Mn(CO)3 complex. To our knowledge, these reported oxapentadienyl complexes contain the first examples of 4coordinated pentadienyl ligands.Recently we reported the characterization of ( 5-CsHslFeCpentadienoyl) complexes where a terminal

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