Computational Quantum Mechanical Studies on Quadruple Bonded Transition Metal Beryllium Complexes and Beryllacycles with Fluxional Electronic Properties

Abstract

The chemistry of beryllium is unique as compared to other alkaline earth metals. Among newlines-block elements, beryllium has the highest tendency to form covalent bonds due to its newlineunique quantum primogenic effect. However, the chemistry of beryllium is less explored newlinedue to its high toxicity. Hence the theoretical studies would help the experimentalist to newlineunderstand the chemistry of beryllium compounds before the experimental realization. newlineHere, we have shown by computational quantum mechanical calculations that beryllium newlinecan form many rule-breaking compounds with exotic electronic properties. In this thesis, newlinewe studied the structure, bonding, and reactivity of complexes of transition metal newlinefragment with a naked beryllium atom as ligand and three and five-membered aromatic newlineberyllacycles. The quantum mechanical calculations were carried out using Gaussian 09 newlineand Amsterdam Density Functional (ADF) programme packages. The equilibrium newlinegeometries of these complexes were optimized at the BP86/def2-TZVPP level of theory. newlineThe energy decomposition analysis combined with the natural orbital of the chemical newlinevalance (EDA-NOCV) has been employed to understand the nature of the binding of newlineberyllium with other atoms in the studied compounds. The molecular properties were newlinestudied at the M06/def2-TZVPP//BP86/def2-TZVPP level of theory. newlineThe chemical bonding in 18 valence electrons (VE) complex [BeM(CO)4; M = Fe - newlineOs], and 16 VE complexes BeM(PMe3)2 and BeM(CO)2 (M = Ni, Pd, and Pt) were newlinestudied in detail. The studies indicate that the bonding between the beryllium and newlinetransition metal can be best described by dative quadruple bonds between transition metal newlineand beryllium viz., one Beand#8594;M and#963;-bond, one Beand#8592;M and#963;-bond, and two Beand#8592;M and#960;-bonds. It newlineis noteworthy that the quadruple bonds consist of two and#963;- and two and#960;- interactions. The newlinebonding interactions in 18 VE complexes are much stronger as compared to 16 VE newlinecomplexes.