Transition Metals: Valence Orbitals, Coordination Geometry, and Coordination Number, Schemes and Mind Maps of Geometry

Download Transition Metals: Valence Orbitals, Coordination Geometry, and Coordination Number and more Schemes and Mind Maps Geometry in PDF only on Docsity!

The Transition Metals

-^ d electrons in group 3 are readily removed

via ionization

-^ d electrons in group 11 are stable and generally form part of the core electronconfiguration.

Transition Metal Valence Orbitals

-^ nd orbitals •^ (n^ + 1)s and (

n^ + 1)p orbitals (^22) • dx-dyand dz 2 (e) lobes located on the axesg

-^ dxy, dxz, dyz lobes (t

) located between axes2g

-^ for free (gas phase) transition metals: (n+1)s is below (n)d in energy(recall: n = principal quantum #). •^ for complexed transition metals: the (n)d levels are below the (n+1)s and thus getfilled first. (note that group # = d electron count) •^ for oxidized metals, subtract the oxidation state from the group #.

Geometry of Transition Metals Coordination Geometry

• arrangement of ligands around metal centre
  ^ Valence Shell Electron Pair Repulsion (VSEPR) theory is generally not applicable totransition metals complexes (ligands still repel each other as in VSEPR theory)
  ^ For example, a different geometry would be expected for metals of different d electroncount[V(OH

3+^2 )]d 26 3+^4 [Mn(OH)]d 26

all octahedral geometry! 3 +^ [Co(OH ) ]d 6 3 +^ [Co(OH)]d 26 6 Coordination geometry is

, in most cases

, independent of ground state electronicconfiguration

^ Steric:^ M-L bonds are arranged to have the maximum possible separation around the M.
^ Electronic:

d electron count combined with the complex electron count must beconsidered when predicting geometries for TM complexes with non-bonding d electrons^8 −−−− e.g. CN = 4, d(16 e))^ prefers square planar geometry))^10 −−−−d(18e) prefers tetrahedral geometry

-^ Coordination Number

(CN) – the number of bonding groups at metal centre
^ Low CN favored by:^ 1. Low oxidation state (e

−^ rich) metals.

2. Large, bulky ligands.

Although Pd(P(

tBu)Ph)is^ coordinatively^22 unsaturated electronically

, the steric bulk unsaturated electronically

, the steric bulk t of both P(Bu) Ph ligands prevents 2 additional ligands from coordinating tothe metal. What is the d electron count for Pd?

-^ Coordination Number

(CN) – the number of bonding groups at metal centre
^ High CN favored by:^ 1. High oxidation state (e

−^ poor) metals.

2. Small ligands. Muckerman & Thummel Water oxidation by mononuclear Ru complex involving a 7 coordinate Ru(IV) species.^ Inorg. Chem.^2008

-^ CN # 1^
^ Very rare In(CH-2,6-(C^63

iH-2,4,6-Pr)) 62 Haubrich S. T.; Power P. P. J. Am. Chem. Soc.

1998, 120, 2202-

-^ CN # 2^
^ Relatively rare (^5) (ηηηη-Cp)(CO)MnIn(C^2

H-2,6-(CH 6362

i-2,4,6-Pr))

Haubrich S. T.; Power P. P. J. Am. Chem. Soc.

1998, 120, 2202-

-^ CN # 3^
^ CN of three is extremely rare^
^ [HgI]^3 -^ , K[Cu(CN)] in the solid state.^2
ions are arranged at the corner of a distorted triangle.

-^ CN # 3 contd.^
^ The use of the very

bulky bis(trimethylsilylamido) ligand

has allowed the

characterization of Ce(III) in the coordination number 3.

-^ CN # 4 contd.^
^ tetrahedral geometry is preferred for d

0 10 or d Oxidation state of Ti?

-^ CN # 4 contd.^8
^ delectron configuration usually leads to square planar geometries(as only one d-orbital required for forming the 4 metal ligand s-bonds)

-^ CN # 5 contd. Iron pentacarbonyl^ very toxic !!!

(DABCO)Fe(CO)

4

[DABCO = 1,4-diazabicyclo[2.2.2]octane]

-^ CN # 5 contd.^
^ {FeCl[

tBuN(SiMe)]^2

O} 22