The isomeric structures and stability of pentacoordinate silylenoid PhCH2(OH)CH3SiLiF

The structures and stability of pentacoordinate silylenoid PhCH2(OH)CH3SiLiF were studied by density functional theory. Two equilibrium structures, the three-membered ring and the p-complex structures, were located. The three-membered ring structure has the lowest energy both in vacuum and in solvents (ether, THF and acetone). The Si-O coordination energy is 13.5 kJ/mol in the three-membered ring structure of pentacoordinate PhCH2(OH)CH3SiLiF at the B3LYP/6-311+G(d, p) level. The substitution barrier of the three-membered ring structure with CH3F is only 1.7 kJ/mol lower than that of PhCH3CH3SiLiF at the B3LYP/6-31G(d) level, showing that the pentacoordinate silylenoid PhCH2(OH)CH3SiLiF has almost the same stability as the corresponding tetracoordinate silylenoid PhCH3CH3SiLiF.