Theoretical calculations congeners

Studies on borohydride complexes of post-transition metals are as follows. Theoretical calculations on M(BH4) (M = Cu, Ag, Au) at the ab initio level indicate that Cu(i) and Ag(i) congeners have tetrahydridoborate structures, while the gold complex adopts a hydridoborane structure HAu(BH3).37 MeZn 2 /-BH4) 30 is prepared by addition of B2H6 to ZnMe2 or MeZnCl and Li[BH4]. The X-ray structure shows a polymeric helical arrangement of ZnMe + and [BH4]- fragments—similar to Be(BH4) or H2Ga(BH4) 50.38... 

Theoretical analyses of the reaction path of photocyclization point to the same conclusion. Thus the qualitative state correlation procedure clearly indicates that photocyclization takes place by a conrotatory process in the Orbital Symmetry Conservation sense requiring a C2 molecular symmetry in 7 and in its symmetric congeners. The same conclusion were reached in the subsequent numerical analysis of the photocyclization of 7 and of 44 The detailed molecular structures of these two molecules and of 61 have been calculated by semi-empirical energy minimization procedures (cf also Ref. ). 

Extensive DFT and PP calculations have permitted the establishment of important trends in chemical bonding, stabilities of oxidation states, crystal-field and SO effects, complexing ability and other properties of the heaviest elements, as well as the role and magnitude of relativistic effects. It was shown that relativistic effects play a dominant role in the electronic structures of the elements of the 7 row and heavier, so that relativistic calculations in the region of the heaviest elements are indispensable. Straight-forward extrapolations of properties from lighter congeners may result in erroneous predictions. The molecular DFT calculations in combination with some physico-chemical models were successful in the application to systems and processes studied experimentally such as adsorption and extraction. For theoretical studies of adsorption processes on the quantum-mechanical level, embedded cluster calculations are under way. RECP were mostly applied to open-shell compounds at the end of the 6d series and the 7p series. Very accurate fully relativistic DFB ab initio methods were used for calculations of the electronic structures of model systems to study relativistic and correlation effects. These methods still need further development, as well as powerful supercomputers to be applied to heavy element systems in a routine manner. Presently, the RECP and DFT methods and their combination are the best way to study the theoretical chemistry of the heaviest elements. 

In 1993, the number of theoretically possible polychlorinated bornanes was calculated as 32,768 congeners (16,128 pairs of enantiomers and 512 achiral structures) [71]. This surprisingly high number is obtained by the product of the possibility to chlorinate nine positions on secondary or tertiary carbons (29) and three primary carbon positions (C8, C9, and CIO) with a variety of 4 giving... 

Theoretical investigations (density functional investigations studying the influence of relativistic effects on the reactivity of the metal center) have been performed to account for the differences in chemical behavior of MTO and its Tc congener, which should be isostructural with their different behavior therefore originating solely or at least overwhelmingly from electronic reasons [45]. In order to quantify the Lewis acidity of the central metal atom, adduct formation with NH3 as a probe molecule has been examined. MTO was calculated to form stable base adducts, which is in accordance with experimental results. The calculation for the... 

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