Exploring the peri-, chemo-, and regioselectivity of addition oftechnetium metal oxides of the type TcO3L(L=Cl–,O–, OCH3,CH3) to substituted ketenes: a DFT computational study

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NRC Research Press
The addition of TcO3L(L=Cl,O–, OCH3,CH3) to substituted ketenes along various addition pathways was studied withdensity functional theory calculations to explore the peri-, chemo-, and regioselectivity of the reactions. In the reactions of TcO3L withdimethyl ketene, the results show that forL=O–and CH3, [1 + 1] addition to form a triplet zwitterionic intermediate is the preferredfirst step; for L = Cl, the [3 + 2]C=Caddition across the O–Tc–Cl bond is the preferred first step and forL=OCH3the [3 + 2]C=Cadditionacross the O–Tc–OCH3 bond is the preferred first step. In the reactions of TcO3Cl with substituted ketenes, [1 + 1] addition to form atriplet zwitterionic intermediate is the preferred first step for X = Ph, CN, and Cl; the [3 + 2]C=Caddition across the O–Tc–O bond of thecomplex is the preferred first step forX=H,while the [3 + 2]C=Caddition across the O–Tc–CH3 bond is the preferred first step. Reactionsinvolving a change in the oxidation state of metal have high activation barriers, while reactions that do not involve a change inoxidation state have low activation barriers. Reactions of ketenes with TcO3L complexes have lower activation barriers for thepreferred addition pathways than those of the ReO3L complexes reported in the literature. Thus, the TcO3L complexes may be bettercatalysts for the activation of the C=C bonds of substituted ketenes than the reported ReO3L complexes.
An article published by NRC Research Press and also available at dx.doi.org/10.1139/cjc-2015-0295
ketene, technetium, oxidation, computational