types of ligands
unidentate- only contains one donor atom ( coordination site
polydentate- ligand has 2 or more donor atoms (coordination sites)
tridentate- 3 donor atoms
tetradentate, etc
bidentate
symmetrical
unsymmetrical
ambidentate ligands- have 2 or more donor sites but only one is attached to a single metal atom at a time
bridging ligand- ligand that can simultaneously bind itself to more tan one atom
chelating- multidentate ligand which coordinates with metal atom to form a ring compound
terminology
polynuclear complexes- more than one metal atom is present
central ions and ligands-neutral metal atom or cation to which one or some neutral molecules or anions are attached with the help of coordinate bonds
coordination polyhedron- ligand atoms directly attached to central atom
coordination entity- electrically charged ion or a neutral molecule formed by the combination of a central atom (metal) with one or more other simple ions
types of complexes
coordination sphere- the central ions and ligands which are directly attached to it are enclosed in square brackets and are collectively termed as coordination sphere
coordination number-- the total number of coordinate bonds made by all the ligands with the metal
homonuclear complexes- only one metal atom is present
homoleptic complex- central atom/ ion is only bond to one type of ligand
heteroleptic complex- central atom/ ion is bound to more than one type of ligand
isomerism
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stuctural
stereo
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solvate isomerism- solvent molecules appear inside and outside coordination sphere to give solvate isomers
coordination isomerism- show by compounds which contain both cationic and anionic species
ionization isomerism- counter ion itself is a ligand and can displace a ligand which can then become a counter ion
linkage isomerism-shown by complexes which contain a monodentate ligand having more than one donor atom
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geometrical- ligands occupy different positions around central metal ion
optical-exhibits 2 non superimposable structures
cis isomers- 2 identical ligands occupy positions next to each other
trans isomers
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square planar
octahedral
M(AA)2X2
MA4X2
M(AB)3
MA3B3
MABCDEF
M2A2X2
MA2XY
MA2X2
MABCD
M (AB)2
MAAB2C2
in square planar compexes
tetrahedral
Werner's theory
types of valency ( werner's theory)
primary- satisfied by negative ions,corresponds to the oxidation state of the atoms and is represented by dotted lines
utility of werner's theory
helps explain the behavior of corrdination compounds
helps provide an explanation for isomerism in compounds
drawbacks of werner's theory
couldn't explain magnetic and optical properties
couldn't explain why only certain elements yield coordination compounds
couldn't explain why coordination bonds are directional in nature
secondary- satisfied by negative or positive ions -corresponds to the corrdination number
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