CHEMICAL AND IR SPECTRAL DETAILS OF REACTIONS INVOLVING STEREOSPECIFIC INCORPORATION OF O-18 INTO SUBSTITUTED MANGANESE AND RHENIUM CARBONYL DERIVATIVES VIA EXCHANGE-REACTIONS WITH H2O-18
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The reactions of substituted group 7B metal carbonyl cationic derivatives, [M(CO)5L]+ (M = Mn, Re and L = phosphine, C5H5N, CH3CN) and [Mn(CO)4(diphos)]+, with labeled water are described. The carbonyl ligands in these derivatives are found to undergo facile oxygen-exchange reactions with H218O, presumably through hydroxycarbonyl intermedi-ates, to afford C18O enriched species. In all cases investigated, the carbonyl sites with the higher CO stretching force constant (implying more positive character at carbon as well as a more stable LUMO) were found to be more susceptible to oxygen exchange, thus leading to stereospecifically labeled species. In addition, the reactivity of the substrate toward oxygen exchange with water was found to decrease in the order [M(CO)6]+ > [M(CO)sL]+[M(CO)4(L-L)]+. The preparation of cis-[Mn(CO)4(l3CO)L]+ (L = PMe2Ph, PPh3, and AsPha) species is reported along with oxygen-18 exchange reactions of these derivatives to yield mixed labeled (l3C18O) metal carbonyls. The incorporation of oxygen-18 into metal carbonyl cations was found to be greatly accelerated by the addition of small quantities of triethylamine. 1977, American Chemical Society. All rights reserved.