Sulfur atoms, electronic states with oxygen

The S02 molecule has unshared pairs of electrons on both the sulfur and oxygen atoms. As a result, it forms numerous complexes with transitions metals in which it is known to attach in several ways. These include bonding through the sulfur atom, through an oxygen atom, by both oxygen atoms, and various bridging schemes. In most cases, the complexes involve soft metals in low oxidation states. Another important reaction of sulfur dioxide is known as the insertion reaction, in which it is placed... 

The Benson mechanism can in principle be extended without major modifications to insertion reactions of other divalent species, such as oxygen and sulfur atoms. With oxygen, Yamaaaki and Cvetanovid have shown recently that 0( Z>) atoms preferentially insert, while 0( P) atoms abstract. This despite the fact that the singlet state hes some 48 kcal./ mole above the ground triplet state. On the other hand, sulfur atom reactions seem compatible with the proposed mechanism. Thus, if one attempts to apply it for the insertion of S( D) atoms, one finds that its predictions are consistent with the experimentally observed trend in the reaction rates. Here the transition state, due to the ionization potential and electron affinity of S( Z)) atoms being higher than those of alkyl radicals (9.2 and 2.2 e.v., respectively) could be formulated as... 

The two special features of this problem are that both the ion and sulfur in FeS2 undergo a change in oxidation state and that the reduction product of oxygen gas occurs in combination with both iron and sulfur. The electron balance diagram for oxidation must contain Fe and S atoms in the ratio of 1 to 2, since this is the ratio in which they are oxidized. The two diagrams, with their multiplying factors, are... 

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