Т 52 (9) ИЗВЕСТИЯ ВЫСШИХ УЧЕБНЫХ ЗАВЕДЕНИЙ ХИМИЯ И ХИМИЧЕСКАЯ ТЕХНОЛОГИЯ Marwan Dakkouri Марван Даккури HOW EASY ARE THE BONDING PROPERTIES OF Si TO ELUCIDATE?* КАК ЛЕГЧЕ ИСТОЛКОВАТЬ СВОЙСТВА СВЯЗИ Si?* (Department of Electrochemistry, University of Ulm, D-89069 Ulm, Germany) Various theoretical approaches for the determination of bond lengths in silicon compounds and their structures have been critically considered. <...> Рассмотрены различные теоретические подходы к определению длин связей для соединений кремния и их строения. <...> Key words: bond length, H, C, F, Cl, Si, quantum chemical calculation, molecule structure Ключевые слова: длина связи, H, C, F, Cl, Si, квантовохимические расчеты, строение молекул Marwan Dakkouri – PhD, professor for physical chemistry at the university of Ulm. <...> Despite the vast number of papers that have been published about silicon and its compounds and their chemical properties the nature of its bonding is still the focal point of controversial discussions. <...> The particular interest that has been devoted to this element is based on four major pillars: (I) Its tendency to form hypervalent compounds with five and six coordinations, (II) The inversion of the electro-negativity order between Ge and Si (there is clear evidence showing that germanium is more electronegative than silicon), and (III) The probable participation of its dorbital on a dative (p-d)π bond, (IV) The accentuated biological activity of its organic compounds in comparison to analogous carbon counterparts. <...> First, I would like to focus on some structural features of silicon compounds and to investigate how easy is to describe and understand the Si-X bond _____________________________ * Review article * Обзорная статья ХИМИЯ И ХИМИЧЕСКАЯ ТЕХНОЛОГИЯ 2009 том 52 вып. 9 (whereas X represents any element within the periodic table) in particular. <...> Now, if we like to predict the Si-X bond length in the hypothetical compound shown in scheme 1, we may - more or less naively - would first think of using the concept of the covalent radii to come up with the answer. <...> That means, we simply add the covalent radii of Si and X to obtain the Si-X bond length [1-4]. <...> Table 1 <...>