Fenske-Hall

The Fenske-Hall method is a modification of crystal held theory. This is done by using a population analysis scheme, then replacing orbital interactions with point charge interactions. This has been designed for the description of inorganic metal-ligand systems. There are both parameterized and unparameterized forms of this method. 

Fenske Hall is essentially a quantification of ligand field theory. The interactions are primarily electrostatic in nature. It does a reasonable job of re-... 

The conformational properties of various 1,1 -diheteroferrocenes (7-10) have been the subject of three computational studies using extended Huckel methods.19,46 471,1 -Diphosphaferrocene has also been studied using the Fenske-Hall approach.48 and an MS Xa method.46 Where they overlap, the four treatments are in reasonable qualitative agreement. 

CpNi(H3C3B2H2)NiCp Tetradecker sandwiches Fenske-Hall 43... 

Comparisons between the electronic structures (using a ZINDO analysis) of [Ru(bpy)3] " and [Ru(bpy)(NH3)4], and between related pairs of compounds where bpy is replaced by 2,2 -bipyrazine or 1,2-benzoquinonediimine, show that bpy is unable to accept extra electron density from the metal center whereas the opposite is true for 1,2-benzoquinonediimine. The acceptor properties of the 2,2 -bipyrazine ligand fall between those of bpy and 1,2-benzoquinonediimine. Using the Fenske-Hall method, the electronic structures of [Ru(bpy)3 (ppy) ] "A (Hppy = 2-phenylpyridine) have been investigated. The coordinated ppy is a C,A-donor. The electronic structures of the heteroleptic complexes exhibit a separation of the Ru—C and Ru—N f7-bonding character. It is proposed that the observed preference for cis- over trans- and for fac- over nrer-isomers may arise from the enhanced cr-donating ability of the C atom when it is trans to an N rather than C-donor. ... 

The hemicapped cluster is an eight electron system and a Fenske-Hall type molecular orbital calculation238 shows that in addition to the six M—M bonding electrons comparable to those in the bicapped species, an additional electron pair occupies an orbital which is weakly M—M bonding, in agreement with the observed shortening of the W—W bond length. 

The four-coordinate complexes [Mo(SBu,)4] and [Mo(NR2)4] are also diamagnetic. The UV-PE spectrum of [Mo(SBu )4] exhibits a low ionization potential at 6.8 eV which has been assigned to the ionization of electrons with predominant molybdenum Adz2 character, on the basis of discrete variational-Xa MO calculations on the model compounds [Mo(SH)4] and [Mo(SMe)4].210 For [Mo(NR2)4] (R = Me, Et), the UV-PE spectrum contains a low energy ionization at 5.3 eV which has been attributed to ionization from the molybdenum Adx2-y orbital. This assignment was based on Fenske-Hall calculations on [Mo(NMe2)4].2U... 

The UPS of the bent bis(cyclopentadienyl) metal chlorides (CSH5)2MC12 and (CsH4Me)2MCl2, M = Ti, V have also been measured and interpreted with the aid of Fenske-Hall MO calculations (235). In the Ti complexes the 3a, metal-localized MO is vacant, while in the V complexes this orbital is singly occupied, leading to the additional spectral complexities that are expected for the ionization of an open-shell system comparable studies have been made of analogous Zr and Hf compounds (64a). 

FIGURE 1. Molecular orbital diagram for (CO)3Co(j/3-C3H3) based on Fenske-Hall calculations310... 

Figure 8-18. Charge densities in the pyridine molecule, calculated using the Fenske-Hall method. The total charge density indicates that pyridine might be expected to react with electrophiles at C(2) and C(4). Also shown are the residual charges associated with the gain or loss of electrons as a result of o- and 7t-bonding at each carbon and nitrogen atom within the molecule.

Its absorption spectrum shows one band at 320 nm (e = 2900 M 1cm 1), assigned to the cti - ct2 transition localized in the Au-Tl moiety. The emission spectrum in the solid state at 77 K shows a band at 602 nm, which is attributable to a transition between orbitals that appear as a result of the metal-metal interaction. In this sense, Fenske-Hall molecular orbital calculations indicate that the ground state is the result of the mixing of the empty 6s and 6pz orbitals of gold(I) with the filled 6,v and the empty 6pz orbitals of thallium(I). In frozen solution, this derivative shows a shift of the emission to 536 nm, which has been explained by a higher aggregation of [AuT1(MTP)2] units in the solid state if compared to the situation in solution. 

The absorption spectrum of the gold-lead complex shows two bands at 290 nm (e = 28598 M-1cm-1) and 385 nm (e = 7626 M-1cm-1), while the emission spectrum in the solid state shows only one band at 752 nm at room temperature. It was assigned to a transition between orbitals that appear as a result of the gold-lead interaction. Thus Fenske-Hall molecular orbital calculations indicated that the HOMO is constituted from the 6pz orbital of gold and 6s orbital of lead and the LUMO is entirely constituted from the 6pz orbitals of these atoms. 

We thank the National Science Foundation, the donors of the Petroleum Research Fund administered by the American Chemical Society, and the Wrubel Computing Center for financial support. We are also indebted to Drs. John Huffman, Kirsten Folting, and William Streib at the Molecular Structure Center for single-crystal X-ray studies, to Mr. David L. Clark for assistance with the Fenske-Hall calculations, and to Drs. Dennis Lichtenberger and Edward Kober for obtaining photoelectron spectra. 

Further enlarging the set of Coulomb integrals has been done in the Fenske-Hall method practiced more or less widely in the 1970s and 1980s. It takes into account all possible two-electron integrals, but calculates them using the Mulliken approximation eq. (2.29). Nevertheless no decisive success has been achieved in this direction. 

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