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Browsing Student Corner by Author "Perera K. Sarath D"

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    Agostic interaction and metallacycles
    (Institute of Chemistry Ceylon, 2023-06) Perera K. Sarath D
    An interaction that occurs between an unsaturated metal center and a C-H bond of a group attached to that metal center is called an agostic interaction. These interactions are denoted by a half-headed arrow ( ) as given in following examples.
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    Bonding in Organometallic Complexes
    (Institute of Chemistry, 2024-05) Perera K. Sarath D
    Neutral ligands (:L) and monoanionic ligands (X–) donate a pair of electrons or a lone-pair to a vacant orbital in a transition metal centre (M) to form a covalent σ-bond between them. Ligands such as :C≡O, :C≡NR (isonitrile or isocyanide) and :PR3 (tertiary phosphine or phosphite) can donate a pair of electrons to a metal centre to form a σ-bond. These ligands are considered as σ-donors.
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    Diels-Alder Reaction
    (Institute of Chemistry Ceylon, 2023-06) Perera K. Sarath D
    Diels-Alder (D-A) reaction is a (4π+2π) cycloaddition reaction. It is used to generate six-membered rings by combining two π-systems. The key components of this reaction are a conjugated diene (an alkene with two π-bonds) and a dienophile (simple alkene or alkyne). During this concerted reaction, two new sigma bonds are formed and change of two π-bonds into sigma bonds takes place.
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    Dihydrogen Complexes
    (Institute of Chemistry Ceylon, 2024-05) Perera K. Sarath D
    Neutral ligands such as H2 O, NMe3 and PPh3 donate a pair of electrons on the heteroatom to a metal center when coordinate bond is formed. Transition metal hydrides contain at least one M-H bond where a pair of electrons is shared between hydrogen and the metal center. In this article, syntheses and properties of complexes with molecular hydrogen (H2 ) are presented.
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    Elements in Biology
    (Institute of Chemistry Ceylon, 2023-09) Perera K. Sarath D
    Research findings suggest that eleven elements are predominantly present in all biological systems. However, hydrogen, carbon, oxygen and nitrogen correspond to 99% of the total. Hydrogen constitutes 62.8% of the atoms in a human body. The percentage of oxygen, carbon and nitrogen are 25.4, 9.4 and 1.4%, respectively. Other essential elements make up the remaining 1% {sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), phosphorus (P), sulphur (S) and chlorine (Cl)}. Very large percentages of hydrogen and oxygen arise from the high-water content present in living systems. Regarding our health and well-being, it is important to know about the elements found in biological systems, their functions and the level of toxicity.
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    Nucleophilic Attack on Coordinated Ligands
    (Institute of Chemistry Ceylon, 2024-05) Perera K. Sarath D
    Reactions of nucleophiles with transition metal complexes are useful in the preparation of new metal complexes. Unsaturated ligands such as C≡O, isonitriles, olefins, dienes, and arenes are not normally reactive towards nucleophiles. When these ligands or molecules are coordinated to an electron-deficient metal they become activated towards nucleophilic attack. The factors which facilitate nucleophilic attack on a coordinated ligands are (i) formal positive charge on the metal, (ii) coordination of π acceptor ligands, (iii) the metal should be coordinatively saturated. and (iv) high reactivity of the nucleophile
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    Styx Numbers and Rules of Boron Hydrides
    (Institute of Chemistry Ceylon, 2023-06) Perera K. Sarath D
    Boron hydrides are a class of electron deficient compounds that have unusual bonding behavior and form cages and clusters. The electron deficient BH3 is the simplest boron hydride which exists as a dimer B2 H6 (diborane). The structure of B2 H6 contains bridging B-H-B (or BHB) bonds; quite different to those of carbon hydrides.