Theoretical Investigations of Structural Properties and Isomerization Mechanism of Weakly Bound Silicon Monocation Binary Carbonyl and Isocarbonyl Complexes

Abstract

The structures, properties, and bonding character for the Si binary carbonyl and isocarbonyl monovalent cations, Si(CO)2+ (2B1), COSiCO+ (2A‘ ‘), and Si(OC)2+ (2B1), in their doublet states have been investigated using four density functional theory (DFT) methods and the MP2 method with the 6-311+G* and aug-cc-pvtz basis sets. Results indicate that, for the binary carbonyl and isocarbonyl Si cations, there exist three stable isomers; all of them exhibit V-type structures in the doublet state, and no linear geometry has been found. The most stable isomer is Si(CO)2+ (2B1), the dicarbonyl Si cation, and can be assigned to the global energy minimum. The other two isomers are COSiCO+ (2A‘ ‘), the carbonyl and isocarbonyl Si cation, and Si(OC)2+ (2B1), the di-isocarbonyl Si cation. They lie 22.8 and 40.9 kcal/mol above Si(CO)2+ (2B1) at the CCSD(T)/aug-cc-pvtz level. The calculated results and bonding analysis have indicated that the binding strength of CO with Si+ by the C-terminal is stronger than that by th...