Symmetry of Polyoxometalate-Based Late-Transition-Metal-Oxo Complexes And The “Oxo Wall”

Mixtli Campos-PinedaGroup Theory. December 4th, 2013

OutlineIntroduction

◦The Oxo Wall◦The Vanadyl Ion (C4v)

Late transition metal M=O symmetries◦AuO (C2v)

◦Pt-oxo and Pd-oxo (C4v)

Revisiting the late transition metal M=O complexes. ◦The square planar Pd unit (D4h)

Conclusions

IntroductionTerminally bound oxo species are

proposed as intermediates of important catalyzed reactions.

The Oxo Wall:◦“M=O groups are stabilized at metal

centers with an oxidation state of no less than 4+ and no more than four d electrons”

Groups 3-6 are stableGroups 7-8 are more reactiveGroups 9-11 are rare (electrons

begin to populate antibonding orbitals)

The Vanadyl IonC4v symmetry of VO(H2O)5

s-orbitals transform as A1

p-orbitals transform as A1+Ed-orbitals transform as A1+B1+B2+E

a.s.=5 1 1 3 1 = 2A1+B1+E

B2 is a non bonding orbital

Transitions (B2 initial state)◦B2(A1+E)=B2 + E

◦Only 2B2E is symmetry allowed

◦2B22B1 and 2B2 2A1 are vibronically allowed

Late transition metal M=O symmetriesAuO

C2v symmetry of AuO

s-orbital transforms as A1

p-orbitals transform as A1+B1+B2

d-orbitals transform as A1+A2+B1+B2

Transitions (A2 initial)◦A2(A1+B1+B2)= A2+B1+B2

◦A2A1 transition is a vibronic one

Pt-oxo and Pd-oxo

s-orbitals transform as A1

p-orbitals transform as A1+Ed-orbitals transform as A1+B1+B2+E

a.s.=5 1 1 3 1 = 2A1+B1+E

Transitions (E initial state)◦E(A1+E)=E + A1+A2+B1+B2

◦All allowed transitions

Transitions (B2 initial state)◦B2(A1+E)=E +B2

◦Only pure electronic transitions to states with E or B2 symmetry are allowed.

Electronic transitions:

Revisiting the late transition metal M=O complexes. The square planar Pd unit (D4h)

D4h symmetry of Pd unit

s-orbital transforms as A1g

p-orbitals transform as Eu+A2u

d-orbitals transform as Eg+B1g+B2g+A1g

a.s.=4 0 0 2 0 0 0 4 2 0= A1g+B1g+Eu

Transitions (tentatively)◦EB1 becomes EgB1g

◦EA1becomes EgA1g

◦B2B1 becomes B2gB1g

ConclusionsGroup Theory can help us assign

and describe the symmetry of MOs.

We can assess the symmetry of transitions even if we don’t know their energy.

Group Theory can’t help us in structure determinations, since it requires us to postulate a structure with a point group

ReferencesC J Ballhausen et al, Inorg. Chem.

1962, 1(1), 111.K P Halloran et al, Inorg. Chem.,

2012, 51 (13), 7025–7031.T M Anderson et al, Science, 2012,

306, 2074 .T M Anderson et al, J. Am. Chem.

Soc., 2005, 127, 11948.R Cao et al, J. Am. Chem. Soc.,

2007, 129, 11118.