Theory and importance of oxygen bridge-bonding

Abstract

An oxygen atom as a donor bridge causes the bonding of two atoms at lower electronegativity. In a case of paramagnetic centres such as transition metal ions the magnetic criterion occurs, i.e. spin queuehing follows. The MO model for the Single oxygen bridge bonding in of d 4 , d\ d 2 , d 1 and d 5 electronic structure were calculated using the SCCC method. This model gives a good explanation of magnetic properties of all the known complexes with one linear or angular bridge. The influence of other ligands on the ground term and on the complex properties has been explained. The structures most convenient to linear bridge formation are those ofthe d 0-d 4 electronic ones. At d 5 the angular bridge is more enocgetic-ally convenient. Double oxygen-bridge bondingwas studied on the large group of Mo-V dimers. The probable MO system explaining their magnetic properties is given. The spectroscopic characteristic in the infra-red of single and double oxygen bonding confirmed the bonding of the oxygen bridge. The nature of the bonding of oxygen to other atoms, and the role of the oxygen atoms as a bonding bridge have been two of the main problems with which investigators of the structure of chemical compounds and condensed phases have had to deal in recent years. Mutual interaction of atoms through oxygen in solid lattices has been known since the discovery of antiferromagnetism in metal oxide lattices. This effect has been qualitatively explained in the theory of superexchange proposed by Anderson 1 , Kramers 2 and Goodenough 3-5. The turning point in the development of views on the role of oxygen was the discovery of molecular antiferromagnetism, that is, spin-spin quenching within one molecule. Melor 6 , Dunitz and OrgeF found in 1953 that the diamagnetic ruthenium(Iv) compound, the oxychlororuthenate(Iv) built of paramagnetic ions, isadimer containing a linear Ru-0-Ru core. Later in 1954, the second case of spin-quenching in metal ions by the oxygen bridge in a binuclear complex of rhenium p-oxobis(pentachlororhenate) (rv) was discovered by B. Jezowska-Trzebiatowska and S. Wajda 8 • In 1962 Morrow 9 demonstrated by x-ray diffraction that the core is in fact, linear 177°, forming the oxo-bridged Re-0-Re dimer. In the early 1950s, Pauling's model based upon the valence bond theory was commonly employed to explain the magnetic properties and the electronic structure of complex compounds. This model explained the magnetic properties of the ruthenium complex of a d 4-d 4 electron structure if the 89