Ligand field theory donor ligands

Note In this table all metal ions are in high-spin states and liganding atoms are small O, N donors. S-donors favour lower co-ordination numbers. Ligand-field theory, that is polarisation of and binding by the core electrons and orbitals of the metal ion compounds, can explain the above observations see inorganic chemistry textbooks in Further Reading . 

Fielder SS, Osborne MC, Lever ABP, Ketro WJ (1995) First-principles interpretation of ligand electrochemical E (L) parameters. Factorization of the a and K donor and K acceptor capabilities of ligands. J Am Chem Soc 117 6990-6993 Figgis BN, Hitchman M (2000) Ligand field theory and its applications. WUey, New York... 

If we return to ligand field theory, recall that the d electrons for an octahedral complex lie in the 2g and eg levels, also designated as tt and a respectively to equate with the character of bonding in which they participate in a complex exhibiting both donor/acceptor bonding character. For electron transfer, a metal d electron needs to move from a location in a -it or a orbital on one metal ion to a it or a orbital on the other metal ion. Generally, it will be more favourable for an electron to move between orbitals of the same symmetry (or from like to like orbitals) that is tt->tt or ct ct transitions are energetically favoured. Further, the character of tt and a orbitals differ, and so the electron transfer process will be affected by the nature of the donor and acceptor orbitals. Models predict that the d-ir orbitals are more exposed than da orbitals, thus more able to interact with orbitals on a different metal complex, and as a result it is anticipated that tt tt electron transfer should occur faster than a a electron transfer. Let s examine this for a Ru(III)/Ru(II) and a Co(III)/Co(II) couple. 

Carbonyl does not appear in the nephelauxetic series. Indeed, or-ganometallic compounds fall outside the scope of ligand field theory, due to the fact that these systems are usually characterized by stronger covalent bonds than those of the Werner complexes. Yet CO is closely related to CN . As CN it is a o- donor and a tt acceptor, although the... 

In most donor solvents, the nickel ion forms solvate complexes with octahedral symmetry. According to the ligand-field theory, the energy levels of the d orbitals of the nickel are split into and t2g orbitals. The magnitude of this splitting depends... 

The solvents are classified from the point of view of coordination chemistry, as either acceptors or donors and reactions occurring in the solutions are related to the coordinating properties of the solvents. For this reason, the various physicochemical methods in use in the authors own laboratories, and the semi-quantitative data thereby available, have been utilized to establish the coordination forms of transition metals in various non-aqueous solutions and to correlate the results with the various solvent properties. The reader will, however, not find in the text discussion of ligand field theory, analytical applications of some of the reactions mentioned, or the electrochemistry (including polarography) of the solutions, because these aspects of non-aqueous chemistry, although of extense interest, are outside the scope of this volume. 

Thus, the ligand-stabilized d-orbital splitting pattern is qualitatively consistent with the expectation of crystal-field theory, but the physical origin of this splitting should be attributed to attractive donor-acceptor interactions such as (4.86b) rather than to any inherent electrostatic repulsions toward the incoming ligands. More accurate treatment of the spectroscopic 10Dq value should, of course, be based on separate consideration of the two spectroscopic states. 

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