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- 1. Symmetry of PolyoxometalateBased Late-Transition-MetalOxo Complexes And The “Oxo Wall” Mixtli Campos-Pineda Group Theory. December 4th, 2013
- 2. Outline Introduction ◦ 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
- 3. Introduction Terminally 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”
- 4. Groups 3-6 are stable Groups 7-8 are more reactive Groups 9-11 are rare (electrons begin to populate antibonding orbitals)
- 5. The Vanadyl Ion C4v symmetry of VO(H2O)5
- 6. s-orbitals transform as A1 p-orbitals transform as A1+E d-orbitals transform as A1+B1+B2+E a.s.=5 1 1 3 1 = 2A1+B1+E
- 7. B2 is a non bonding orbital
- 8. Transitions (B2 initial state) ◦ B2 (A1+E)=B2 + E ◦ Only 2B2E is symmetry allowed ◦ 2B22B1 and 2B2 2A1 are vibronically allowed
- 9. Late transition metal M=O symmetries AuO
- 10. C2v symmetry of AuO s-orbital transforms as A1 p-orbitals transform as A1+B1+B2 d-orbitals transform as A1+A2+B1+B2
- 11. Transitions (A2 initial) ◦ A2 (A1+B1+B2)= A2+B1+B2 ◦ A2A1 transition is a vibronic one
- 12. Pt-oxo and Pd-oxo
- 13. s-orbitals transform as A1 p-orbitals transform as A1+E d-orbitals transform as A1+B1+B2+E a.s.=5 1 1 3 1 = 2A1+B1+E
- 14. 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.
- 15. Electronic transitions:
- 16. Revisiting the late transition metal M=O complexes. The square planar Pd unit (D4h)
- 17. D4h symmetry of Pd unit
- 18. 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
- 19. Conclusions Group 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
- 20. References C 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.

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