For example, name as diamminetetrachloroplatinum(IV). The four common exceptions are aqua (H 2O), ammine (NH 3), carbonyl (CO), and nitrosyl (NO). For most neutral ligands, the name of the molecule is used. Negative ligands (anions) have names formed by adding - o to the stem name of the group. Name the ligands first, followed by the central metal.If a coordination compound is ionic, name the cation first and the anion second, in accordance with the usual nomenclature.The following five rules are used for naming complexes: The nomenclature of the complexes is patterned after a system suggested by Alfred Werner, a Swiss chemist and Nobel laureate, whose outstanding work more than 100 years ago laid the foundation for a clearer understanding of these compounds. It contains a polydentate ligand with four donor atoms that coordinate to iron.įigure 19.17 Each of the anionic ligands shown attaches in a bidentate fashion to platinum(II), with both a nitrogen and oxygen atom coordinating to the metal.
The heme complex in hemoglobin is another important example ( Figure 19.16). Figure 19.15 showed one example of a chelate. A chelating ligand holds the metal ion rather like a crab’s claw would hold a marble. A chelating ligand is also known as a chelating agent. Many polydentate ligands are chelating ligands, and a complex consisting of one or more of these ligands and a central metal is a chelate. The term chelate (pronounced “KEY-late”) from the Greek for “claw” is also used to describe this type of interaction. (b) The cobalt(III) complex 3+ 3+ contains three of these ligands, each forming two bonds to the cobalt ion.Īny ligand that bonds to a central metal ion by more than one donor atom is a polydentate ligand (or “many teeth”) because it can bite into the metal center with more than one bond. In this case, the number of ligands and the coordination number are equal.įigure 19.15 (a) The ethylenediamine (en) ligand contains two atoms with lone pairs that can coordinate to the metal center. Each of these ligands is monodentate, from the Greek for “one toothed,” meaning that they connect with the central metal through only one atom. For the copper(II) ion in 2−, the coordination number is four, whereas for the cobalt(II) ion in 2+ the coordination number is six. The coordination number for the silver ion in + is two ( Figure 19.14). The coordination number of the central metal ion or atom is the number of donor atoms bonded to it. Brackets in a formula enclose the coordination sphere species outside the brackets are not part of the coordination sphere.
#Where does metal ion bonding occur in cells plus
The coordination sphere consists of the central metal ion or atom plus its attached ligands. The lone pairs from six water molecules form bonds to the scandium ion to form an octahedral complex. (b) However, coordinate covalent bonds involve electrons from a Lewis base being donated to a metal center.
Most often, this involves a donor atom with a lone pair of electrons that can form a coordinate bond to the metal.įigure 19.13 (a) Covalent bonds involve the sharing of electrons, and ionic bonds involve the transferring of electrons associated with each bonding atom, as indicated by the colored electrons. The only requirement is that they have one or more electron pairs, which can be donated to the central metal. The Lewis base donors, called ligands, can be a wide variety of chemicals-atoms, molecules, or ions. The Lewis acid in coordination complexes, often called a central metal ion (or atom), is often a transition metal or inner transition metal, although main group elements can also form coordination compounds. They primarily form coordinate covalent bonds, a form of the Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). Transition metals do not normally bond in this fashion. The one valence electron leaves sodium and adds to the seven valence electrons of chlorine to form the ionic formula unit NaCl ( Figure 19.13). For instance, the four valence electrons of carbon overlap with electrons from four hydrogen atoms to form CH 4. Remember that in most main group element compounds, the valence electrons of the isolated atoms combine to form chemical bonds that satisfy the octet rule. This figure shows, from left to right, solutions containing n+ ions with M = Sc 3+( d 0), Cr 3+( d 3), Co 2+( d 7), Ni 2+( d 8), Cu 2+( d 9), and Zn 2+( d 10). Figure 19.12 Metal ions that contain partially filled d subshell usually form colored complex ions ions with empty d subshell ( d 0) or with filled d subshells ( d 10) usually form colorless complexes.
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