Theoretical Study on Inverse Sandwich Complexes E-C_5-nH_5-nN_n-E⁺ and E-C_5-nH_5-nP_n-E⁺ (n=1, 2, 3; E=Al, Ga, In, Tl)

The inverse sandwiches E-C_5-nH_5-nN_n-E⁺ and E-C_5-nH_5-nP_n-E⁺ (n=1, 2, 3; E=Al, Ga, In, Tl) with low-valent boron group elements are studied. The (η5,η5) coordinated inverse sandwich E-C_5-nH_5-nN_n-E⁺ is unstable in energy or nonexistent. However, the (η5,η5) coordinated E-C_5-nH_5-nP_n-E⁺ is not only stable in energy, but also stable against dissociation. The dissoction stability E-C_5-nH_5-nP_n-E⁺ with the same E element decreases as the number n increases, while for the certain n number, the dissociation energies with different E elements are close to each other. E-C₄H₄P-E⁺ has similar dissocition stability to the well-known E-C₅H₅-E⁺. The inteaction between C_5-nH_5-nP_n and lowvalent E element is mainly ionic. Since lone pairs of electrons locate on both E and P atoms, the (η5, η5) coordinated inverse sandwich E-C_5-nH_5-nP_n-E⁺ would act as multi electron-donors.