Inorganic Chemistry: Coordination Chemistry

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Crystal Field Theory
Designed for coordination compounds: Ligands+ Metal ion (+charge)
Orbital Energy
Determined by ligand number, compound structure, and electric field strength of ligands
Nucleophilicity order of ligands
1. Across a row: C⁻>N⁻>O⁻>F⁻ since increasing electronegativity decreases the lone pair availability. 2. Comparing same atom: higher electron density increases nucleophilicity (HO⁻>H₂O) 3. Within a period: increasing polarization of nucleophiles, I⁻>Br⁻>Cl⁻>F⁻
Extreme conditions of ligands affecting color
CF strength: CN⁻>H₂O>F⁻ [Fe(H₂O)₆]³⁺: Red [FeF₆]³⁻: Colorless [Fe(CN)₆]³⁻: Colorless
Stereoisomerism
cis/trans
Ionization Isomer
the ligands coordinate to the metal or present as counterions [CrSO₄(NH₃)₅]Cl
Coordination Isomer
in compounds where both the cation and the anion are complex, the distribution of ligands can vary, giving rise to isomers [Co(NH₃)₆][CrCN₆]
Linkage Isomer
-Some ligands can bind in a more than one way
-Ambidentate ligand-a ligand that can bond in two ways
-Isomeric complexes with different modes of binding can be isolate
Stability of coordination compounds
Slowly descending progressives in the values of K’s in any particular system because of decreasing space for more ligands to be added
Mechanism of ligand exchange reactions in octahedral complexes
ML_ⁿX+Y→ML_ⁿY+X
Solvent Intervention
Rxn observed as first order because of high and constant concentration of entering ligand, H₂O
Ion-Pair Formation
Reacting complex +Entering Ligand=ions, when ion pairs are featured as intermediates in the reaction path, the observed rate law will be second order
Water exchange reactions
(Aqua ion) [M(H₂O)_ⁿ]+^m, displaced by other ligands, a ligand can be added into an aqua complex
Aquation (hydrolysis)
-governed by both charge effects and steric effects: large ligands are substituted quickly, when the charge is higher, rate of substitution is slower
Chelate Effect
Complexes with 1 or more chelate rings are more stable than those without chelate rings because effect is from the entropy effect since it leads to a net decrease of molecule freedom
Rule 1
-Neutralcoordination
-Ionic: cation comes before anion
-No spaces used within name of ion
Example:
Diamminesilver(I)chloride
Rule 2
ligands then metals (no space)
Rule 3
-if 2 or more of same ligand bound–>use regular prefixes
or 2(bis), 3(tris), 4(tetrakis), 5(pentakis) etc.
Rule 4
(NH₂)₂CO: Urea, terpy: terpyridine, Bpy: 2,2′-bipyridine
Molecules with special names: amine, aqua, nitrosyl
Rule 5
-anionic ligands given names ending in “o” “ate–>ato”: acetate–>acetato
“ide–>ito”: nitride–>nitrito
(Cyano, fluoro, chloro, methyl, ethyl)
Rule 6
Ligands named in groups according to charge:
-anionic ligands, then neutral, then cationic
-alphabetical within charge group
Rule 7
Entity is an anion, metal name turns to “-ate” “ium”–>”ate”
or Cobalt–>cobaltate
or the latin name
Rule 8
optical isomers are designated by ∆, geometrical isomers are designated by cis/trans and mer/fac
Rule 9
Bridging ligands are designated with a prefix (mu)
Rule 10
Ligands w/linkage isomer are given specific names for each mode of attachment (Ex: -NCS⁻ isothiocyanato)
Rule 11
Hydrated compounds are designated as the last step (Ex: Monohydrate or sesquihydrate)
Categories: Inorganic Chemistry