MOLECULAR ORBITALS OF TRANSITION METAL COMPLEXES
CHAPTER SETTING THE SCENE 1 1 ELECTRON COUNT IN A COMPLEX: THE COVALENT MODEL 1 1 1 LIGAND CLASSI?CATION (L OR X) 1 1 2 ELECTRON COUNT AND THE 18-ELECTRON RULE 1 2 AN ALTERNATIVE MODEL: THE IONIC MODEL 1 2 1 LEWIS BASES AS LIGANDS 1 2 2 EQUIVALENCE OF THE COVALENT AND IONIC MODELS: EXAMPLES 1 3 PRINCIPLES OF ORBITAL INTERACTIONS 1 3 1 INTERACTION BETWEEN TWO ORBITALS WITH THE SAME ENERGY 1 3 2 INTERACTION BETWEEN TWO ORBITALS WITH DIFFERENT ENERGIES 1 3 3 THE ROLE OF SYMMETRY 1 3 4 ? AND ? INTERACTIONS 1 4 METAL ORBITALS 1 4 1 DESCRIPTION OF THE VALENCE ORBITALS 1 4 2 ORBITAL ENERGIES 1 5 LIGAND ORBITALS 1 5 1 A SINGLE LIGAND ORBITAL: ? INTERACTIONS 1 5 2 SEVERAL ORBITALS: ? AND ? INTERACTIONS 1 6 INITIAL ORBITAL APPROACH TO ML?COMPLEXES 1 6 1 SIMPLI?ED INTERACTION DIAGRAM 1 6 2 STRONG-?ELD AND WEAK-?ELD COMPLEXES 1 6 3 ELECTRONIC CON?GURATION AND THE 18-ELECTRON RULE 1 6 4 ANALOGY WITH THE OCTET RULE EXERCISES CHAPTER PRINCIPAL LIGAND ?ELDS: ? INTERACTIONS 2 1 OCTAHEDRAL ML6 COMPLEXES 2 1 1 INITIAL ANALYSIS OF THE METAL–LIGAND ORBITAL INTERACTIONS 2 1 2 COMPLETE INTERACTION DIAGRAM 2 1 3 ELECTRONIC STRUCTURE 2 2 SQUARE-PLANAR ML4 COMPLEXES 2 2 1 CHARACTERIZATION OF THE D BLOCK COMPLEXES 2 3 SQUARE-BASED PYRAMIDAL ML5 COMPLEXES 2 3 1 CHARACTERIZATION OF THE D BLOCK (METAL IN THE BASAL PLANE) 2 3 2 CHARACTERIZATION OF THE D BLOCK (METAL OUT OF THE BASAL PLANE) 2 3 3 ELECTRONIC STRUCTURE AND GEOMETRY 2 4 TETRAHEDRAL ML4 COMPLEXES 2 4 1 CHARACTERIZATION OF THE D BLOCK 2 4 2 ELECTRONIC STRUCTURE 2 4 3 ML4 COMPLEXES: SQUARE-PLANAR OR TETRAHEDRAL? 2 5 TRIGONAL-BIPYRAMIDAL ML5 COMPLEXES 2 5 1 CHARACTERIZATION OF THE D BLOCK 2 5 2 ELECTRONIC STRUCTURE 2 6 TRIGONAL-PLANAR ML3 COMPLEXES 2 6 1 CHARACTERIZATION OF THE D BLOCK 2 6 2 16-ELECTRON D10 COMPLEXES 2 7 LINEAR ML2 COMPLEXES 2 7 1 CHARACTERIZATION OF THE D BLOCK 2 7 2 ELECTRONIC STRUCTURE 2 8 OTHER COMPLEXES OR MLN FRAGMENTS 2 8 1 PYRAMIDAL ML3 COMPLEXES 2 8 2 ‘T-SHAPED’ ML3 COMPLEXES 2 8 3 ‘BUTTER?Y’ ML4 COMPLEXES 2 8 4 BENT ML2 COMPLEXES 2 8 5 ML COMPLEXES APPENDIX A: POLARIZATION OF THE D ORBITALS APPENDIX B: ORBITAL ENERGIES ?-TYPE INTERACTIONS 3 1 ?-DONOR LIGANDS: GENERAL PROPERTIES 3 1 1 THE NATURE OF THE ? ORBITAL ON THE LIGAND 3 1 2 ‘SINGLE-FACE’ AND ‘DOUBLE-FACE’ ?-DONORS 3 1 3 PERTURBATION OF THE D ORBITALS: THE GENERAL INTERACTION DIAGRAM 3 1 4 A ?RST EXAMPLE: THE OCTAHEDRAL COMPLEX [ML5CL] 3 2 ?-ACCEPTOR LIGANDS: GENERAL PROPERTIES 3 2 1 THE NATURE OF THE ? ORBITAL ON THE LIGAND 3 2 2 ‘SINGLE-FACE’ AND ‘DOUBLE-FACE’ ?-ACCEPTORS 3 2 3 PERTURBATION OF THE D ORBITALS: THE GENERAL INTERACTION DIAGRAM 3 2 4 A ?RST EXAMPLE: THE OCTAHEDRAL COMPLEX [ML5CO] 3 3 COMPLEXES WITH SEVERAL ?-DONOR OR ?-ACCEPTOR LIGANDS 3 3 1 THE TRANS-[ML4CL2] OCTAHEDRAL COMPLEX 3 3 2 THE TRANS-[ML4(CO)2] OCTAHEDRAL COMPLEX 3 3 3 CONSTRUCTION OF THE D-BLOCK ORBITALS ‘BY HAND’ 3 3 4 [MCL6] AND [M(CO)6] OCTAHEDRAL COMPLEXES 3 4 ? COMPLEXES: THE EXAMPLE OF ETHYLENE 3 4 1 ORBITAL INTERACTIONS: THE DEWAR–CHATT–DUNCANSON MODEL 3 4 2 ELECTRONIC STRUCTURE OF A D6 COMPLEX [ML5(?2-C2H4)] 3 4 3 METALLOCENES CP2M 3 4 4 CP2MLN COMPLEXES 3 5 ? INTERACTIONS AND ELECTRON COUNTING APPENDIX C: THE CARBONYL LIGAND, A DOUBLE-FACE ?-ACCEPTOR APPLICATIONS 4 1 CONFORMATIONAL PROBLEMS 4 1 1 D8-[ML4(?2-C2H4)] COMPLEXES 4 1 2 D6-[ML5(?2-C2H4)] COMPLEXES: STAGGERED OR ECLIPSED CONFORMATION? 4 1 3 D6-[ML4(?2-C2H4)2] COMPLEXES: COUPLING OF TWO ?-ACCEPTOR LIGANDS 4 1 4 ORIENTATION OF H2 IN THE ‘KUBAS COMPLEX’ [W(CO)3(PR3)2(?2-H2)] 4 2 ‘ABNORMAL’ BOND ANGLES 4 2 1 AGOSTIC INTERACTIONS 4 2 2 D6 ML5 COMPLEXES: A ‘T-SHAPED’ OR ‘Y-SHAPED’ GEOMETRY? 4 3 CARBENE COMPLEXES 4 3 1 AMBIGUITY IN THE ELECTRON COUNT FOR CARBENE COMPLEXES 4 3 2 TWO LIMITING CASES: FISCHER CARBENES AND SCHROCK CARBENES 4 4 BIMETALLIC COMPLEXES: FROM A SINGLE TO A QUADRUPLE BOND 4 4 1 ?, ?, AND ? INTERACTIONS 4 4 2 M2L10 COMPLEXES 4 4 3 THE [RE2(CL)8]2?COMPLEX: A STAGGERED OR AN ECLIPSED CONFORMATION? 4 5 THE REDUCTIVE ELIMINATION REACTION 4 5 1 DE?NITION 4 5 2 SIMPLI?ED MODEL FOR THE REACTION [LNMR2] ?[LNM] + R??R 4 5 3 AN EXAMPLE: D8-[L2MR2] ?D10-[L2M] + R??R 4 6 PRINCIPAL REFERENCES USED THE ISOLOBAL ANALOGY 5 1 1 FRAGMENT ORBITALS BY THE VALENCE-BOND METHOD 5 1 2 FRAGMENT MOLECULAR ORBITALS 5 2 OTHER ANALOGOUS FRAGMENTS 5 3 APPLICATIONS 5 3 1 METAL–METAL BONDS 5 3 2 CONFORMATIONAL PROBLEMS 5 4 LIMITATIONS ELEMENTS OF GROUP THEORY AND APPLICATIONS 6 1 SYMMETRY ELEMENTS AND SYMMETRY OPERATIONS 6 1 1 RE?ECTION PLANES 6 1 2 INVERSION CENTRE 6 1 3 ROTATION AXES 6 1 4 IMPROPER ROTATION AXES 6 2 SYMMETRY GROUPS 6 2 1 DE?NITIONS 6 2 2 DETERMINATION OF THE SYMMETRY POINT GROUP 6 2 3 BASIS OF AN IRREDUCIBLE REPRESENTATION 6 2 4 CHARACTERS 6 2 5 CHARACTER TABLES 6 3 THE REDUCTION FORMULA 6 3 1 THE REDUCTION FORMULA 6 3 2 CHARACTERS OF A REDUCIBLE REPRESENTATION 6 3 3 APPLICATIONS 6 3 4 DIRECT PRODUCTS 6 4 SYMMETRY-ADAPTED ORBITALS 6 4 1 PROJECTION OPERATOR 6 4 2 APPLICATION 6 5 CONSTRUCTION OF MO: H2O AS AN EXAMPLE 6 5 1 SYMMETRY AND OVERLAP 6 5 2 MOLECULAR ORBITALS FOR H2O 6 6 SYMMETRY-ADAPTED ORBITALS IN SEVERAL MLN COMPLEXES 6 6 1 SQUARE-PLANAR ML4 COMPLEXES 6 6 2 TETRAHEDRAL ML4 COMPLEXES 6 6 3 TRIGONAL-PLANAR ML3 COMPLEXES 6 6 4 TRIGONAL-BIPYRAMIDAL ML5 COMPLEXES 6 6 5 OCTAHEDRAL ML6 COMPLEXES 6 6 6 TRIGONAL-PLANAR ML3 COMPLEXES WITH A ‘? SYSTEM’ ON THE LIGANDS ANSWERS TO EXERCISES