CORSO DI DOTTORATO DI RICERCA IN SCIENZE CHIMICHE CICLO XXIII TESI DI DOTTORATO DI RICERCA ORGANOMETALLIC CHEMISTRY FROM THE INTERACTING QUANTUM ATOMS APPROACH sigla del settore scientifico disciplinare CHIM03 NOME DEL TUTOR NOME DEL DOTTORANDO Prof: Angelo Sironi Davide Tiana NOME DEL COORDINATORE DEL DOTTORATO Prof. Silvia Ardizzone ANNO ACCADEMICO 2009/2010 1 2 Index Introduction ............................................................................................................................................................................ 5 The ligand field theory (LFT) .................................................................................................................................... 5 The chemistry from a real space point of view ................................................................................................. 9 Chapter 1: The quantum theory of atoms in molecules (QTAM) ............................................................... 12 Topological analysis of electron charge density ........................................................................................... 12 Analysis of the electronic charge density Laplacian ................................................................................... 16 Other properties ........................................................................................................................................................... 18 Chapter 2: The interacting quantum atoms theory (IQA) ............................................................................. 20 Introduction .................................................................................................................................................................... 20 The total energy from the first and second order density matrix partition .................................... 21 The electron-electron repulsion term ................................................................................................................ 23 The IQA approach ........................................................................................................................................................ 26 The correlation inside the IQA ............................................................................................................................... 28 Chapter 3: The domain averaged Fermi hole (DAFH) .................................................................................... 31 Chapter 4: Using pseudopotentials within the IQA approach ..................................................................... 34 Introduction .................................................................................................................................................................... 34 The topology of from pseudopotential calculations ............................................................................... 35 IQA partitioning from ECP pseudo-wavefunctions ..................................................................................... 38 How to perform an IQA-ECP analysis ................................................................................................................. 41 Chapter 5: The metal carbonyl bond ....................................................................................................................... 45 IQA results ....................................................................................................................................................................... 47 Bonding in Td M(CO)4 systems ......................................................................................................................... 47 Bonding in D3h M(CO)5 systems ....................................................................................................................... 50 Bonding in Oh M(CO)6 systems ......................................................................................................................... 51 2+ Bonding in D4h [M(CO)4] systems................................................................................................................ 53 Energetic orbital contributions ............................................................................................................................. 54 The Td complex ......................................................................................................................................................... 54 The D4h complex ....................................................................................................................................................... 59 Chapter 6: The metal-metal interaction ................................................................................................................. 62 Bridged systems ........................................................................................................................................................... 63 The bridged M(μ2-CO)M bond in Co2(CO)8 ................................................................................................. 63 3 - The semi-bridged M(μ-CO)M bond [FeCo(CO)8] .................................................................................... 65 Unbridged systems ...................................................................................................................................................... 68 The metal-metal multiple bond ............................................................................................................................. 69 Chapter 7: The metal hydrogen bond...................................................................................................................... 73 Metal hydride bond ..................................................................................................................................................... 74 Non classic metal hydrogen interaction............................................................................................................ 76 Metals bridge hydrogen interaction ................................................................................................................... 79 - [Cr2(μ2-H)(CO)10] .................................................................................................................................................. 81 Metals hydride bridge interaction in Mo and W cases .......................................................................... 82 2 Breaking the H2 bond. A study of the complex (PH3)3FeH2(η -H2) ..................................................... 83 Conclusions and perspectives ..................................................................................................................................... 89 Appendix A: Computational details .......................................................................................................................... 91 Appendix B: Code manuals ........................................................................................................................................... 93 Promolden ....................................................................................................................................................................... 93 Input keywords ........................................................................................................................................................ 94 Output ........................................................................................................................................................................... 97 Appendix C: Publications ............................................................................................................................................. 100 4 Introduction Organometallic chemistry is very important for industrial processes, organic synthesis and “green chemistry”. It consists of the study of chemical compounds containing bonds between carbon and metal (M). Situations where metal is bounded to an organic ligand (L) but not directly to C should be instead referred to metal-organic area but, nowadays, these two terms result almost interchangeable. As usual, the presence of electrons in the d shell makes differences in organometallic chemistry of the transition metals (TM) and of the main group (1, 2, 12-18) elements. The TM organometallic chemistry will be treated in this thesis. This can be considered as a subfield of the more general coordination chemistry in which the complexes contain M-C and M-H bond1. Nowadays coordination chemistry is treated by the ligand field theory which will be briefly summarized. The ligand field theory (LFT) This theory is an improvement of the crystal field theory (CFT) and represents an application of molecular orbital (MO) theory to transition metal complexes. Developed in 1930s, CFT explains compound colors, magnetism and other properties not taking into account the description of TM-L bond. Based on the energy changes of the five d metal orbitals, this theory considers interactions between metal and ligand as purely electrostatic. Depending on the geometry, when ligand approaches TM, L electrons will be closer to some -electrons than to others. Thus, because of charges repulsion between electrons, -orbitals divide themselves removing their degeneracy. For instance, in octahedral complexes there are six L around metal: and point to the ligand resulting higher in energy than , ,, ,. Thus