Structural and Bonding Properties

The previous chapters are exclusively devoted to the measurements and interpretation of Fe spectra of various iron-containing systems. Iron is, by far, the most extensively explored element in the field of chemistry compared with all other Mdssbauer-active elements because the Mossbauer effect of Fe is very easy to observe and the spectra are, in general, well resolved and they reflect important information about bonding and structural properties. Besides iron, there are a good number of other transition metals suitable for Mossbauer spectroscopy which is, however, less extensively studied because of technical and/or spectral resolution problems. In recent years, many of these difficulties have been overcome, and we shall see in the following sections a good deal of successful Mossbauer spectroscopy that has been performed on compounds of... 

They tested the approach on various systems for which the A -> B transition led to a number of different changes in bonding and structural properties. Moreover, they used different approaches for the QM part, but as Table 17 shows, the method is reliable and leads to accurate results. 

Vibrational spectroscopy is an important probe used to determine the bonding and structural properties of molecules. Powerful techniques such as electron energy loss spectroscopy (EELS) have been developed, which allow one to obtain the vibrational properties of molecules chemisorbed upon surfaces. Due to low concentration, the highly reactive nature of the clusters, and the large number of possible species which are typically present in the cluster beams used to date, unconventional techniques are required in order to obtain spectroscopic information. One unconventional but powerful technique, infrared multiple photon dissociation (IRMPD), has recently been applied to the study of the vibrational properties of gas-phase metal clusters upon which one or more molecules have been chemisorbed. This same technique, IRMPD, has previously been used to obtain the vibrational spectra of ions, species for which it is difficult to apply conventional absorption techniques. 

Molecular SiS2 (125) was generated in a solid argon matrix by a reaction of SiS with S atoms. The antisymmetric stretching vibration Vas(SiS) is observed at 918 cm . Bonding and structure properties (force constants from experimentally observed frequencies and results from ab initio SCF calculations) of SiS2 were compared with those of similar molecules CO, CS, CO2, COS, CS2, SiO, SiS, Si02 and SiOS. ... 

Electronic spectra and structural properties of complex tetracyanides of Pt, Pd and Ni, M. L. Moreau-Colin, Struct. Bonding (Berlin), 1972,10,167-190 (33). 

The role of vibronic coupling in the interpretation of spectroscopic and structural properties of biomolecules. M. Bacci, Struct. Bonding (Berlin), 1983,55, 67-99 (169). 

Bacci M (1984) The Role of Vibronic Coupling in the Interpretation of Spectroscopic and Structural Properties of Biomolecules. 55 67-99 Baekelandt BG, Mortier WJ, Schoonheydt RA (1993) The EEM Approach to Chemical Hardness in Molecules and Solids Fundamentals and Applications. 80 187-228 Baker EC, Halstead GW, Raymond KN (1976) The Structure and Bonding of 4/and 5/Series Organometallic Compounds. 25 21-66 Baibas LC, see Alonso JA (1987) 66 41-78 Baibas LC, see Alonso JA (1993) 80 229-258... 

Guilard R, Lecomte C, Kadish KM (1987) Synthesis, Electrochemistry, and Structural Properties of Porphyrins with Metal-Carbon Single Bonds and Metal-Metal Bonds. 64 205-268... 

Oxide- and Zeolite-supported "Molecular" Metal Clusters Synthesis, Structure, Bonding, and Catalytic Properties... 

Gates BC (2005) Oxide- and Zeolite-supported Molecular Metal Clusters Synthesis, Structure, Bonding, and Catalytic Properties. 16 211-231 Gibson SE (nee Thomas), Keen SP (1998) Cross-Metathesis. 1 155-181 Gisdakis P, see Rosch N (1999) 4 109-163 Gdrling A, see Rosch N (1999) 4 109-163... 

Metal clusters in metal oxide systems have not been well-characterized or abundantly investigated up to the present time. Only isolated examples of metal-metal bonded units in oxide lattices have appeared from time to time. It will be the thesis of this presentation to show that highly unusual structures determined by strong metal-metal bonding will be found in ternary and quaternary metal oxide systems, and that opportunities abound for creative work on the synthesis, theory and structure-property relationships of such compounds. Because of the well-known correlation of d-electron population and d-orbital radial extension with metal-metal bond formation,... 

This article reviews recent results on the chemical, spectral and structural properties of bis(pentamethylcyclopentadienyl) thorium and uranium dihaptoacyl complexes produced by migratory insertion of carbon monoxide into actinide-carbon sigma bonds. 

It must be emphasized that the duodectet rule (4.6) initially has no structural connotation, but is based on composition only. Indeed, the compositional regularity expressed by (4.6) encompasses both molecular species (such as the metal alkyls) and extended lattices (such as the oxides and halides) and therefore appears to transcend important structural classifications. Nevertheless, we expect (following Lewis) that such a rule of 12 may be associated with specific electronic configurations, bond connectivities, and geometrical propensities (perhaps quite different from those of octet-rule-conforming main-group atoms) that provide a useful qualitative model of the chemical and structural properties of transition metals. 

Further evidence of the importance of intermolecular donor-acceptor interactions can be obtained by deleting these interactions from the variational calculation, and recalculating the optimized geometries with charge transfer (CT) omitted. The structures resulting from such CT-deleted species are shown in Fig. 5.2. Energetic and structural properties of CT-deleted species are summarized in Table 5.4 for direct comparison with the actual H-bonded species in Table 5.1. 

Figure 5.9 displays the equilibrium structures assumed by these cation-assisted H-bond complexes, and Table 5.12 summarizes energetic and structural properties... 

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