Chap 5 notes

Chap 5 notes - What Is A Coordination Compound? A...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: What Is A Coordination Compound? A coordination complex is the product of a Lewis acid-base reaction in which neutral molecules or anions (called ligands ) bond to a central metal atom (or ion) by coordinate covalent bonds . Ligands are Lewis bases - they contain at least one pair of electrons to donate to a metal atom/ion. Ligands are also called complexing agents . Metal atoms/ions are Lewis acids - they can accept pairs of electrons from Lewis bases. Within a ligand, the atom that is directly bonded to the metal atom/ion is called the donor atom . A coordinate covalent bond is a covalent bond in which one atom (i.e., the donor atom) supplies both electrons. This type of bonding is different from a normal covalent bond in which each atom supplies one electron. If the coordination complex carries a net charge, the complex is called a complex ion . Compounds that contain a coordination complex are called coordination compounds . Coordination compounds and complexes are distinct chemical species - their properties and behavior are different from the metal atom/ion and ligands from which they are composed. The coordination sphere of a coordination compound or complex consists of the central metal atom/ion plus its attached ligands. The coordination sphere is usually enclosed in brackets when written in a formula. The coordination number is the number of donor atoms bonded to the central metal atom/ion. Some Coordination Complexes example molecular formula Lewis base/ligand Lewis acid donor atom coordination number [Ag(NH 3 ) 2 ] + NH 3 Ag + N 2 [Zn(CN) 4 ] 2- CN- Zn 2+ C 4 [Ni(CN) 4 ] 2- CN- Ni 2+ C 4 [PtCl 6 ] 2- Cl- Pt 4+ Cl 6 [Ni(NH 3 ) 6 ] 2+ NH 3 Ni 2+ N 6 Common Structures Why do we want to know the structure for a coordination compound? The compound's structure (i.e., how the ligands are arranged around the metal atom) determines its physical and chemical properties. For example, a tetrahedral compound will behave differently than a square planar compound that contains the same metal atom and the same ligands. Consider the complex ion, [CoCl 4 ] 2- . The coordination number of [CoCl 4 ] 2- is equal to 4; thus, the structure of [CoCl 4 ] 2- might be: 1. tetrahedral- ligands attached at the corners of a tetrahedron 2. square planar- ligands attached at the corners of a square 3. something else? Coordination compounds with a coordination number (CN) of 4 are generally either tetrahedral or square planar . The [CoCl 4 ] 2- complex ion is experimentally known to have a tetrahedral structure. A Comparison of Tetrahedral and Square Planar Structures example sketch model [CoCl 4 ] 2- tetrahedral CN = 4 ligands attached at the corners of a tetrahedron [Ni(CN) 4 ] 2- square planar CN = 4 ligands attached at the corners of a square Coordination numbers range from 1 to 12, with 2, 4 and 6 being the most common. Linear and octahedral are the most common structures for coordination numbers 2 and 6, respectively....
View Full Document

Page1 / 22

Chap 5 notes - What Is A Coordination Compound? A...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online