Quimica dos Complexos

Chapter 19

d-Block Chemistry: General Consideration

19.2 d-Block vs. Transition

Elements

• d-block refers to elements filling the d- orbitals

• transition elements refers to elements with incomplete d-orbitals, thus Group IIB (12, zinc group) are not transition metals

• triad of elements (ignores Z=104 and higher)

• heavier d-block elements • platinum-group metals

19.2 Electronic Configurations

• progressive filling of the d atomic orbitals, with minor deviations

• more deviations seen in the filling of 4d and 5d than in the 3d

19.3 Physical Properties

• hard, ductile, and malleable

19.3 Ionization Energies

19.4 Reactivity of the Metals

• moderately reactive

• form binary compounds with oxygen, sulfur, or halogens

Os + O₂ OsO₄

Fe + S FeS

heat heat

19.5 Color

• observed for all species with electronic configurations d1 through d9

• color originates through electronic d-d transitions giving a low intensity

19.5 Oxidation States

• varied among the d-block elements

Sc Ti V Cr Mn Fe Co Ni Cu Zn 3 0,2,3, 0,1,2 0,1,2, 0,1,2, 0,1,2 0,1,2, 0,1,2, [0],1,2, 2 4 3,4,5 3,4,5, 3,4,5, 3,4,6 3,4 3,4 3,[4] 6 6,7 Y Zr Nb Mo Tc Ru Rh Pd Ag Cd 3 2,3,4 2,3,4, 0,2,3, 0,1,[2], 0,2,3, 0,1,2, 0,2,4 1,2,3 2 5 4,5,6 [3],4,5, 4,5,6, 3,4,5, 6,7 7,8 6 La Hf Ta W Re Os Ir Pt Au Hg 3 2,3,4 2,3,4, 0,2,3, 0,1,2, 0,2,3, 0,1,2, 0,2,4, [0],1,[2], 1,2 5 4,5,6 3,4,5, 4,5,6, 3,4,5, 5,6 3,5 6,7 7,8 6

19.6 Electroneutrality Principle

• approximate method for estimating charge distribution proposed by Linus Pauling

• states the distribution of charge in a

molecules or ion is such that on any atom the charge is anywhere from +1 to -1

19.6 Electroneutrality Principle

19.7 The Kepert Bonding Model

• ignores non-bonding electrons on ligands • metal lies at the center of a sphere and the

ligands move over the surface of the sphere • ligands adopt a geometry to minimize

19.7 The Kepert Bonding Model

19.7 Coordination Number: 2

• linear

• uncommon

• Cu(I), Ag(I), Au(I), and Hg(II) and other d10

19.7 Coordination Number: 3

[AgTe₇]3- [Fe{N(SiMe

3)2}3]

• trigonal planar or trigonal pyramidal • uncommon

• Cu(I), Ag(I), Au(I), Hg(II), Pt(0) and other

19.7 Coordination Number: 4

• tetrahedral

– very common

– not seen in d3 ions and uncommon in d4 ions

• square planar

– not as common

– normally seen in d8 ions

19.7 Coordination Number: 5

• square pyramidal and trigonal bipyramidal

– many distorted structures can lie between these two

[Zn{N(CH₂CH₂NH₂)₃}Cl]+ _{[Cu(bpy){NH(CH}

19.7 Coordination Number: 6

• Octahedral

– found in all configurations from d0 to d10

– d4 and d9 ions tend to undergo

Jahn-Teller distortions

• be tetragonally distorted (elongated or squashed)

• Trigonal Prismatic

– rare

19.7 Coordination Number: 7

19.7 Coordination Numbers:

Others

Coordination 9

– most often observed with yttrium, lanthanum, and f-block elements

– arranged in a tricapped trigonal prism

Coordination 10 and above

– generally only for f-block elements

19.8 Isomerism in d-block Metal

Complexes

 cis/trans  d and l

19.8 Ionizational Isomerism

• Interchange of a coordinated, anionic ligand with an uncoordinated anion

• Can usually be distinguished by qualitative means or IR spectroscopy

CoBr₂ NH4Br,NH3,O2 [Co(NH₃)₅(H₂O)]Br₃ heat [Co(NH₃)₅Br]Br₂ Ag2SO4 [Co(NH₃)₅Br][SO₄]

[Co(NH₃)₅Br]Br₂ conc. H2SO4 [Co(NH₃)₅(SO₄)][HSO₄] BaBr2 [Co(NH₃)₅(SO₄)]Br

violet

red

three _SO

19.8 Hydration Isomerism

• Interchange between water and another ligand inside and outside the coordination sphere

CrO₃ conc. HCl [Cr(H₂O)₄Cl₂]Cl 2H₂O

[Cr(H₂O)₄Cl₂]Cl 2H₂O H2O [Cr(H₂O)₅Cl]Cl₂ H₂O H2O [Cr(H₂O)₆]Cl₃

19.8 Coordination Isomerism

• possible only for compounds in which both cation and anion are complex ions

• isomers arise from ligand interchange between metal centers

[Co(NH₃)₆][Cr(CN)₆] and [Cr(NH₃)₆][Co(CN)₆] [PtII(NH₃)₄][PtIVCl₆] and [PtIV(NH₃)₄Cl₂][PtIICl₄]

19.8 Linkage Isomerism

• are formed when a ligand can coordinate in more than one way (ex. [SCN]-)

[Co(NH₃)₅Cl]Cl₂ [Co(NH₃)₅(H₂O)]Cl₃

[Co(NH₃)₅(NO₂-O)]Cl₂ [Co(NH₃)₅(NO₂-N)]Cl₂

NaNO₂

dil. NH₃

NaNO₂, conc. HCl

heat UV

19.8 Polymerization Isomerism

• complexes which have the same empirical formulae but different molecular masses

[PtCl₂(NH₃)₂] and [Pt(NH₃)₄] [PtCl₄]

19.8 Geometric Isomerism

• most commonly denoted by cis/trans isomers

19.8 Geometric Isomerism

• distinguish between the two forms by x-ray diffraction, IR, and NMR

[NiBr₂(PPh₃)₂]

– exhibits both cis/trans in square planar configuration

19.8 Optical Isomerism

19.8 Optical Isomerism

• in a neutral complex can have two complexes,  or .

• in a complex with a chiral cation and chiral anion, can have four complexes:

Problem 19.6

• Suggest why:

– high coordination numbers are not usual for first row d-block elements

Problem 19.6

• Suggest why:

– high coordination numbers are not usual for first row d-block elements

• High coordination numbers are usually not feasible on steric grounds because cations of the first row metals are too small to accommodate large numbers of donor atoms. Coordination number of 6 is the highest common, normally in hydrated ions.

Problem 19.6

• Suggest why:

– in early d-block metal complexes the

combination of a high oxidation state and high coordination number is common

Problem 19.6

• Suggest why:

– in early d-block metal complexes the

combination of a high oxidation state and high coordination number is common

• A high oxidation state places a high formal charge on the metal center; by the electroneutrality

principle, the distribution of charge in the metal-containing species is such that the actual charge on the metal atom is no greater than ~ +1. The greater the number of ligands, the greater the distribution of the charge

Problem 19.6

• Suggest why:

– in first row d-block metal complexes, high

oxidation states are stabilized by fluoro or oxo ligands

Problem 19.6

• Suggest why:

– in first row d-block metal complexes, high

oxidation states are stabilized by fluoro or oxo ligands

• Ligands which are formally F- or O2- are highly

electronegative and can remove charge from metal centers in high oxidation states. They are also

strongly oxidizing and are often associated with higher oxidation states.

Problem 19.7

• Give the oxidation state of the metal and its

dn configuration.

4-Problem 19.7

• Give the oxidation state of the metal and its

dn configuration.

– [Mn(CN)₆]

4-• Oxidation state of Mn = +2

• Ground state electronic configuaration is [Ar]4s23d5

Problem 19.7

• Give the oxidation state of the metal and its

dn configuration.

2-Problem 19.7

• Give the oxidation state of the metal and its

dn configuration.

– [FeCl₄]

2-• Oxidation state of Fe = +2

• Ground state electronic configuaration is [Ar]4s23d6

Problem 19.7

• Give the oxidation state of the metal and its

dn configuration.

Problem 19.7

• Give the oxidation state of the metal and its

dn configuration.

– [CoCl₃(py)₃]

• Oxidation state of Co = +3

• Ground state electronic configuaration is [Ar]4s23d7

Problem 19.7

• Give the oxidation state of the metal and its

dn configuration.

-Problem 19.7

• Give the oxidation state of the metal and its

dn configuration.

– [ReO₄]

-• Oxidation state of Re = +7

• Ground state electronic configuaration is [Xe]4f146s25d5

Problem 19.10

• In the solid state, Fe(CO)₅ possesses a

trigonal bipyramidal structure. How many carbon environments are there?

Problem 19.10

• In the solid state, Fe(CO)₅ possesses a

trigonal bipyramidal structure. How many carbon environments are there?

– Structure of Fe(CO)5 contains 2 axial and 3 equatorial CO ligands. Therefore, there are 2 axial and 3 equatorial C environments

Problem 19.10

• In the solid state, Fe(CO)₅ possesses a trigonal bipyramidal structure. Why is there only one signal observed in the 13C

Problem 19.10

• In the solid state, Fe(CO)₅ possesses a trigonal bipyramidal structure. Why is there only one signal observed in the 13C

NMR spectrum?

– The molecule undergoes rapid conversion

between axial and equatorial carbons. Faster than the 13C timescale is able to pick up.

Assignment

• End of Chapter 19 Problems:

– 19.1, 19.5, 19.9, 19.11,

– Plus, assignment #2 on the website – Due Wednesday, September 24, 2003