A parallel right-handed duplex of the hexamer d(TpTpTpTpTpT) with phosphate triester linkages.

In this paper it is proposed that the ion-molecule reaction between Cr(CO)5- and O2 to produce Cr(C0)302- and Cr(CO),Ooccurs by a competitive reaction mechanism. The two mechanisms involve (i) simple ligand exchange to produce the Cr(CO),O,anion and (ii) addition of O2 to Cr(CO),- followed by intramolecular nucleophilic addition of 0- to a CO ligand to form Cr(CO),O- and CO plus C02. A surprisingly large temperature dependence for the rate of reaction of Cr(CO)< with O2 is observed. The strong temperature dependence of the reaction rate is attributed to formation of a high-energy [Cr(CO),-] * species. The high-energy Cr(CO),anion may be formed by thermal decomposition of Cr(C0)6 to give a high spin state of Cr(CO)5, which is subsequently ionized by electron attachment to give [Cr(CO),-I*. A particularly important result of this study is the proton and electron affinity data obtained for Cr(CO),O- and Cr(C0),02-.