Gallium Ligand Coordinated Group 15 Compounds (LGa-ECp', L=(CHNMe)(2)CH, E=N - Bi, Cp'=eta(1)-C5H5): Changeover from Electron-Sharing to Donor-Acceptor sigma-Interaction

摘要

We have analyzed the electronic structure and bonding situation in monomeric compounds of gallium with group 15 elements (LGa-ECp', L=(CHNMe)(2)CH, E=N (1), P (2), As (3), Sb (4) and Bi (5)) at the M06/def2-TZVPP//BP86/def2-SVP level of theory. The compounds 1-5 have a singlet ground state with a polarized Ga-E double bond. The molecular orbital analysis indicates that the Ga-E pi-MO and the lone pair on E are susceptible to nucleophilic reactivity. The nucleophilic reactivity of Ga-E pi-MO increases, and that of lone pair on E reduces when the compound changes from 1 to 5. The EDA-NOCV analysis indicates that the nitrogen and phosphorous form charge-separated electron-sharing sigma-bond with Ga. The apparent switchover between the electron-sharing sigma-interaction and donor-acceptor sigma-interaction occurs when the group 15 element is arsenic. On the other hand, antimony and bismuth exhibit donor-acceptor interaction with the LGa fragment in compounds 4 and 5. The pi-bond in 1-5 is similar and is formed by the donation of the p-type lone pair on E-atom (p(z)) to the empty p(z)-orbital of Ga. The bonding analysis also shows that the strength of pi-bonding is reduced on moving towards the heavier elements. A very high first and second proton affinity indicates that group 15 elements in compounds 1-5 act as double Lewis bases.