1. Five slides about…

2. Consider…

3. The ‘ionic’ method says  2 Cp - 6e - each(-1 each)  2 Me - 2e - each(-1 each)  Ligand total16e - -4  So Ti +4 (d 0 ) since it is neutral  16e - exception?  Problem…is this really a +4 metal interacting with four anions?

4. The ‘covalent’ method says  2 Cp5e - each  2 Me1e - each  Ligand total12e -  So Ti 0 (d 4 ) since it is neutral  16e - exception?  Problem…assuming the d-electrons are non- bonding how is this diamagnetic?

5. CBC ligand classification LL Ligand donates two electrons CO, phosphines, alkenes XX Ligand donates one electron H, halides, alkyl ZZ Ligand donates zero electrons boranes

6. How to count? [ML l X x Z z ]  Total electron count From ligands: 2l + x From metal: m m + 2l + x  Valence number (VN) for the metal = x + 2z  Ligand bond number (LBN) for the metal = l + x + z  d n count for metal = m - VN

7. Current example H3CH3C X L L2XL2X X

8. Counting  Metal is classified as ML 4 X 4  Electron count: 4 + 10 + 2 = 16  VN: 4  LBN: 8  d n : 0

9. What have we learned? Ti Electron Count 89101112131415161718 Valence 0ML 2 ML 3 ML 4 ML 5 ML 6 2% ML 7 1% 1ML 2 XML 3 XML 4 XML 5 XML 6 X <1% 2MLX 2 ML 2 X 2 ML 3 X 2 ML 4 X 2 1% ML 5 X 2 1% ML 6 X 2 4% 3MLX 3 ML 2 X 3 <1% ML 3 X 3 <1% ML 4 X 3 5% ML 5 X 3 9% 4MX 4 6% MLX 4 1% ML 2 X 4 7% ML 3 X 4 6% ML 4 X 4 49% ML 5 X 4 4%  Electrons: 16  VN: 4  Classification: ML 4 X 4 http://www.columbia.edu/cu/chemistry/groups/parkin/mlxz.htm

10. A different view http://www.columbia.edu/cu/chemistry/groups/parkin/mlxz.htm Ti

11. What about valence?  VN: 4 is not saying it is +4  Gives the d 0 count http://www.columbia.edu/cu/chemistry/groups/parkin/mlxz.htm Ti

12. What is LBN?  Not coordination number  Number of sites on the metal  LBN: 8 while CN: 12 http://www.columbia.edu/cu/chemistry/groups/parkin/mlxz.htm Ti

13. Further readings  M.L.H. Green J. Organomet. Chem. 1995, 500, 127-148.  G. Parkin, in Comprehensive Organometallic Chemistry III, Volume 1, Chapter 1; R.H. Crabtree and D.M.P. Mingos (Eds), Elsevier, Oxford, 2006.  http://www.columbia.edu/cu/chemistry/grou ps/parkin/cbc.htm