Ab initio molecular orbital configuration interaction study of Ni(PH sub 3 ) sub 2 (N sub 2 ). Differences in electron correlation effects between. eta. sup 1 -end-on and. eta. sup 2 -side-on N sub 2 coordination modes
- Kumamoto Univ. (Japan)
Structure and bonding nature of Ni(PH{sub 3}){sub 2}({eta}{sup 1}-N{sub 2}), Ni(PH{sub 3}){sub 2}({eta}{sup 2}-N{sub 2}) ({eta}{sup 1}-N{sub 2} = {eta}-end-on N{sub 2}, {eta}{sup 2}-N{sub 2} = {eta}{sup 2}-N{sub 2} = {eta}{sup 2}-side-on N{sub 2}), and Ni(PH{sub 3}){sub 2}(C{sub 2}h{sub 4}) are studied with ab initio MO Moeller-Plesset (MP) perturbation and single-double configuration interaction (SD-CI) methods. Introduction of electron correlation effects is indispensable for investigating the relative stability of two coordination modes, {eta}{sup 1}-end-on and {eta}{sup 2}-side-on coordinations, of the N{sub 2} complex. Although the binding energies of both coordination modes are almost the same on the Hartree-Fock level, introducing electron correlation effects with MP2, MP4(DQ), MP4(SDQ), and SD-CI methods yield much larger binding energy of the {eta}{sup 1}-end-on N{sub 2} coordination than that of the {eta}{sup 2}-side-on N{sub 2} coordination. Electron correlation effects on the Ni-N{sub 2} distance are also noticeable; in the {eta}{sup 1}-end-on mode, the Ni-N{sub 2} distance shortens by about 0.1 {angstrom} upon introducing electron correlation effects with MP2, MP4, and SD-CI methods, and the resultant Ni-N{sub 2} distance agrees well with the experimental value. However, introducing electron correlation effects with the SD-CI method only slightly changes the Ni-N{sub 2} distance of Ni(PH{sub 3}){sub 2}({eta}{sup 2}-N{sub 2}) and slightly lengthens the Ni-C distance of Ni(PH{sub 3}){sub 2}(C{sub 2}H{sub 4}), whereas both Ni-N and Ni-C bonds significantly lengthen by about 0.2-0.3 {angstrom} upon MP2 and MP4 calculations. A comparison of the optimized Ni-C distance and the calculated binding energy of the {eta}{sup 1}-end-on N{sub 2} coordination with the experimental values suggests that the SD-CI method is more reliable than the MP method in these complexes.
- OSTI ID:
- 7171242
- Journal Information:
- Journal of Physical Chemistry; (USA), Vol. 93:15; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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