Metal-Metal Multiple bond

1. Metal-Metal Multiple bond 201405112 이지홍

2. Contents Covalent bond (basic) (1)Covalent bond (2)Type of Covalent bond (3)molecular orbital of main group - example 2. Metal-Metal bond (1)Isolobal analogy (2)metal-metal bond 3. Metal-Metal multiple bond (1)multiple bond (2)experimental data

3. 1. Covalent bond (basic)(1)Covalent bond Covalent bondis made by sharing electron of two atoms. In the view of Atomic Orbital, orbitals of two atom has overlapped andformed molecular orbital.

4. 1. Covalent bond (basic)(2)Type of Covalent bond The multiple covalent bond can be formed depending on the number of sharing electron. and type of covalent bond include sigma bond and pi bond depending on the method of orbital overlapping. Sigma bond : it is formed by head-on overlapping between atomic orbitals. pi bond : it is formed by overlapping sidewise between two lobes of atomic orbitals

5. 1. Covalent bond (basic)(2)Type of Covalent bond The multiple covalent bond can be formed depending on the number of sharing electron. One covalent bond is single bond. two covalent bond is double bond. three covalent bond is triple bond.

6. 1. Covalent bond (basic) (2)Type of Covalent bond Single bond : by sharing two electron between two atoms, a sigma bond is formed. Double bond : by sharing four electron between two atoms, one sigma bond and one pi bond is formed. Triple bond : by sharing six electron between two atoms, one sigma bond and two pi bond is formed.

7. 1. Covalent bond (basic) (3) main group 에서의 molecular orbital - example Molecular orbital of N2 bond length = 109.76 pm.

8. 1. Covalent bond (basic) (3) molecular orbital of main group - example Molecular orbital of O2 bond length = 120.741 pm.

9. 1. Covalent bond (basic) (3) molecular orbital of main group - example Molecular orbital of F2 bond length = 141.8 pm.

10. 2. Metal-Metal bond(1)Isolobalanalogy Isobal analogy is theory that related between similar organic and inorganic molecular fregments to predict properties of organometallic compound . On 1982, Roald Hoffmann described molecular fragments as isolobal "if the number, symmetry properties, approximate energy and shape of the frontier orbitals and the number of electrons in them are similar – not identical, but similar."

11. 2. Metal-Metal bond(1) Isolobal analogy example)

12. 2. Metal-Metal bond(1) Isolobal analogy View of Molecular orbital ….

13. 2. Metal-Metal bond(1) Isolobal analogy Isolobal molecular Fragments can be combined into molecule. Furthermore, these organic and organometallic fragments can be combined

14. 2. Metal-Metal bond(2)metal-metal bond As application of Isolobal analogy, It can describe how metal-metal bond is formed. metal-metal bond can be formed by only using d-orbitals. So M-M bond can makesingle, double Triple bond and quadruple bond.

15. 2. Metal-Metal bond(2)metal-metal bond The modern development of the chemistry of metal-metal-bonded species was spurred by the crystal structures of [Re3cl12]3- and [Re2cl8]2- . specially[Re2cl8]2-had a remarkably short metal-metal distance (224 pm) and was the first complex found to have a quadruple bond.(general bond length of Re-Re is known as 248pm.)

16. 3. Metal-Metal multiple bond(1)Metal-Metal multiple bond Metal-Metal bond of Transition Metal is formed by only using d-orbital. because Molecular orbital(MO) is formed when symmetry properties and energy of orbitals is Similar, So, By interaction of same d-orbitals,MO can appear

17. 3. Metal-Metal multiple bond(1)Metal-Metal multiple bond Dz2 orbitals of two metal atoms Overlap each other. And sigma(σ) Bond is made. Dyz, Dxz orbital of two metal Atoms overlap with same Dyz, Dxz Orbital. And these orbitals can Make two Pi(π) bonds. Dx2-y2, DXYorbital two metal Atoms overlap with same Dyz, Dxz Orbital. And these orbitals can Make two delta(δ) bonds.

18. 3. Metal-Metal multiple bond(1)Metal-Metal multiple bond delta bonds (δ bonds) are covalent chemical bonds, where four lobes of one involved atomic orbital overlap four lobes of the other involved atomic orbital This overlap leads to the formation of a bonding molecular orbital with Two nodal planes which contain The internuclearaxis and go through Both atoms.

19. 3. Metal-Metal multiple bond(1)Metal-Metal multiple bond First picture describe the energy levels of d-orbitals when Metal-Metal bond is formed. Second picture show the energy levels of d-orbitals when 8 monodentate ligand has bonded to M-M bond and formed [M2L8] in this picture. In this picture, dx2-y2 orbital of metal, which is the strongest overlap with ligand is formed MO by interacting with 8 ligands Therefore, quadruple bond is formed Because one of five M-Mbond subtract by overlapping with ligands

20. 3. Metal-Metal multiple bond(2) experimental explanation The difference of energy between Delta bond andanti-delta bond correspond to the energy of visible light. So most compound contained Quadruple bond are vividly colored For instance,[Re2cl8]2- is royal blue and[Mo2cl8]2- bright red. But if additionald-electron occupy δ* orbital, reduce the bond order. in case of[Os2cl8]2-,M-M bond is triple bond. Because, delta bond order iszeroin this compound.

21. 3. Metal-Metal multiple bond(2) experimental explanation

22. 3. Metal-Metal multiple bond(2) experimental explanation Metal-metal multiple bonding can have dramatic effects on bond distances, as measured by X-ray crystallography. One way of describing the shortening of interatomic distances by multiple bonds is by comparing the bond distances in multiple bonds to the distances for single bonds. The ratios of these distances is sometimes called the formal shortness ratio.

23. 3. Metal-Metal multiple bond(2) experimental explanation As electron of delta* orbital removed, bond length is slightly decresed. A possible explanation for small change in bond distanse is that as increasing oxidation state of d-orbital, d-orbital is contracted. So overlap of pi-bonding become ineffective.

24. Reference Inorganic Chemistry (3rd Edition) Gary L. Miessler Wikipedia the free encyclopedia Webelements