Superstoichiometric compounds

The superstoichiometric compounds TijAlC, x > 1 ([TiAl3C6Ti9 + C] clusters) and Ti-enriched compounds in the perovskite-like structure were studied. The latter are a complete phase (TijAlC) and a C-defect phase (TisAlCi-J described by the clusters [TiAl4C2Tig], [TiA CoTig]. 

Indeed, in this case the formation of neutral surface compound (Me Of-) is accompanied by binding of neutral superstoichiometric Me and, therefore, decrease in concentration of donors responsible for dope electric conductivity of adsorbent. In the case when the formed surface state possesses sufficient electron affinity one can-... 

CH3 -Zn with superstoichiometric (defect) zinc atoms (Zn -impurity centres of conductivity). The larger is the electric positivity of the metal in these complexes, the larger is the ionicity of the carbon-metal bond, carbon being at the negative end of the dipole. Thus, in the case of C - K bond, ionicity amounts to 51%, whereas for C - Mg and C - Zn bonds ionicity amounts to 35% and 18%, respectively [55]. Consequently, metalloorganic compounds are characterized by only partially covalent metal-carbon bonds (except for mercury compounds). 

The asymmetric reduction of prochiral ketones to their corresponding enantiomerically enriched alcohols is one of the most important molecular transformations in synthetic chemistry (20,21). The products are versatile intermediates for the synthesis of pharmaceuticals, biologically active compounds and fine chemicals (22,23). The racemic reversible reduction of carbonyls to carbinols with superstoichiometric amounts of aluminium alkoxides in alcohols was independently discovered by Meerwein, Ponndorf and Verley (MPV) in 1925 (21—26). Only in the early 1990s, first successful versions of catalytic... 

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