Formation of the chelate bonds in the cluster Ominus;2(CO2)n, COminus;3(CO2)n, and NOminus;2(CO2)n

摘要

The equilibria of gashyphen;phase clustering reactions of Ominus;2, COminus;3, and NOminus;2with CO2were studied with a pulsed electron beam highhyphen;pressure mass spectrometer. Thermochemical stabilities of the clusters Ominus;2(CO2)n, COminus;3(CO2)n, and NOminus;2(CO2)nwithn=1ndash;8 were determined. For Ominus;2(CO2)n, irregular decreases in the values of minus;Dgr;H0nminus;1,nwere observed betweenn=1 and 2, andn=3 and 4. These gaps indicate that the bond with covalent character is formed through the charge transfer (CT) Ominus;2rarr;CO2and the CT complex of O2COOminus;accommodates two CO2molecules preferably lsqb;i.e., O2COOminus;(CO2)2rsqb;. The minus;Dgr;H0nminus;1,nvalues of both COminus;3(CO2)nand NOminus;2(CO2)nclusters show an irregular decrease betweenn=4 and 5. This suggests the formation of shells, OCOminus;2(CO2)4and NOminus;2(CO2)4.Abinitiooptimized geometries of these clusters are found to be composed of bridge (i.e., chelate) intermolecular bonds.