Coordination and redox properties in solution

Abstract

A primitive description of the functional electron cloud is given and is used to account for the mutual influence between coordinating and redox properties. Rules are given for the change in redox properties by coordination and vice versa. It is further shown that the redox potential in a donor solvent is determined by its donor number and an empirical approach is suggested to obtain the electromotive series for any solvent of given donor number. The donor number is also considered important for the ionization of a covalent substrate. Finally a new classification is suggested for charge-transfer complexes. THE PRIMITIVE DESCRIPTION OF THE FUNCTIONAL ELECTRON CLOUD In a primitive way, a characteristic 'electron cloud' may be ascribed to each atom, ion or molecule. Even in the state of highest stability of the entity, the ground state, the electronic arrangement is usually far from 'ideal' as is evidenced by the tendency to undergo chemical reactions. In the primitive description of the 'functional electron cloud', the 'non-ideality' of the cloud is considered responsible for its tendency to change; the actual function will depend also on the properties of the reactant. The functional cloud may deviate from the ideal by being either too 'dilute' or too 'dense' compared with that of the reacting molecule. An entity with a 'dilute' electron cloud will tend to gain electrons or to achieve an appropriate share of them and will thus function as an acceptor of electrons. A system with 'dense' electron cloud will function as a donor of electrons, as it will try to make electrons available. Thus the description emphasizes the actual function of a molecule or ion towards a given reactant and so takes into account amphoteric properties. It has been said that a dense cloud system will function as a donor and a dilute cloud system will function as an acceptor of electrons. Each of these functions may involve either the interaction of an electron pair or the complete exchange of an electron between the reacting species. The interactions of an electron pair donor (EPD or Lewis base) with an electron pair acceptor (EPA or Lewis acid) lead to the formation of a coordinate bond. If an electron is given up completely, the system is regarded as a reducing agent or an electron donor, ED. The oxidizing agent is characterized by accepting the electron and is thus considered the electron acceptor,