Advanced Inorganic · PDF fileMetal atomic orbitals (AOs) and ligand group orbitals (LGOs)...
Transcript of Advanced Inorganic · PDF fileMetal atomic orbitals (AOs) and ligand group orbitals (LGOs)...
Advanced Inorganic Chemistry
CHMI 3317 EL
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Classes of coordination compounds
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The d orbitals
d orbital splitting(octahedral environment)
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Metal atomic orbitals(AOs) and ligand grouporbitals (LGOs) involvedin forming the MOs ofan octahedral complex
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Metal atomic orbitals (AOs) and ligand group orbitals (LGOs) involved informing the MOs of an octahedral complex
Molecular orbital diagram (Oh)σ bonding only
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Another simplified depiction of an MO diagram for an octahedral complex
Here: The antibonding orbitals are identified by an asterisk.
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π-Bonding
π-Acceptor π-Donor
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Metal carbonyls
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Structures of binary metal carbonyls
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Structures of binary metal carbonyls
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Preparation ofcarbonyl compounds
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Why are most carbonyls in the centre of this table?
Electron counting with tetranuclear osmium carbonyls
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CO as a ligand
MO diagram Contour lines
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Dependence of bond order and stretching frequencies on orbital interactions
Carbonyl stretching frequencies
d(C-O)/pm ν CO (cm-1)
CO (free) 113 2143 CO bond order = 3
CO* (singlet excited state) 124 1489 2p strongly antibonding
M-CO(e.g. Cr(CO)6)
~ 115 1850-2120(2000)
CO bond order = 2-3
M2-µ2-CO 1750-1850
M3-µ3-CO 1620-1730
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CO stretching frequencies
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The number of IR bands depends on molecular symmetry
L ν CO (cm-1)PF3 2055, 2090PCl3 1991, 2040P(OMe)3 1888, 1977PPh3 1835, 1934pyridine 1746, 1888
Carbonyl stretching frequenciesfor fac-L3Mo(CO)3
NO > CO > RNC > PF3 > PCl3 > PCl2R > P(OR)3 > PR3 > RCN > NH3
Order of π-acceptor strength
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Complex ν CO (cm-1)[Ti(CO)6]2- 1748[V(CO)6]- 1859[Cr(CO)6] 2000[Mn(CO)6]+ 2100[Fe(CO)6]2+ 2204free CO 2143
Dependence of stretching frequencieson complex charge
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Terminal and bridging NO in complexes
(a) [Ir(PPh3)2(CO)(NO)Cl]+
(b) [Ru(PPh3)2(NO)2Cl]+
Structures of some NO complexes
Complexes containing bent NO ligands
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Stereochemical control of valence: [Co(diars)2(NO)]2+
diars