Coordination Chem Flashcards
Complex
An electron acceptor surrounded in a symmetrical manner by a shell of ions or molecules called ligands, held together by dative bonds
Chelate ligands
Subset of polydentate ligands, involving simultaneous binding of multiple donor atoms by forming rings around the central atom
Bridging ligands
Attached to multiple metallic central ions
Ambidentate ligands
Molecules that can vary which atom bonds to the central electron acceptor
Coordination number
Number of ligand atoms directly bonded to central electron acceptor
Isomerism
Same formula, different structure
Geometric isomers
Different arrangement round central electron acceptor (e.g. cis and trans)
Optical
Enantiomers: Non-superimposable mirror images, interact differently in chiral environments
Coordination isomerism
Variation of ions in compounds made up of both ionic and cationic complex ions, no neutral species
Hydrate isomerism
Possible when water is present
Ionisation isomerism
Possible in compounds with complex ions and a counter ion, different distribution of ions between directly coordinated and counter ions
Linkage isomerism
Possible when ambidentate ligands are present
Ligand isomerism
Only organic ligands (e.g. 2-,3-,4-aminotoluene)
Ligand Formulae order
Square brackets
Metal ion
Anionic ligands (alphabetical)
Neutral ligands (alphabetical)
Ligand nomenclature order
Ligands listed alphabetically before metal, ignoring prefixes
Anionic complex ending
“-ate”
Prefixes
Mono Di Tri Tetra Penta Hexa Hepta Octa
Multiplicative prefixes
bis tris tetrakis pentakis hekakis
Bridging ligands
Indicated by μ
Overall stability constant β
Eqm constant for overall reaction, taking each water displacement step into consideration.
Large β means that ligand substitution reaction is favoured
Statistical factor for β
Constants decrease if there is no change in geometry
Steric factor for β
Bulky substituents can hinder the approach of subsequent ligands
Electrostatic factor for β
Each successive replacement of water reduces +ve charge, causing repulsion
Chelate effect for β
Chelate complexes more stable than similar monodentate complexes
Macrocyclic effect
3 or more potential donors in a ring of at least 9. Stability constants for complexes of macrocyclic ligands are greater than acyclic equivalents
Hard acid
Non-polarisable cations, small-radius, high effective nuclear charge, high energy LUMO
Hard base
Small
Electronegative
Non-polarisable
Low energy HOMO
