Bond orders, significance electron systems

This feature of the electronic structure of these inorganic rings is especially dramatic for the six-atom system [SsNs], which is able to accommodate ten r-electrons, cf. six r-electrons for CeHg. The electron-richness of [SsNs] results in a significantly lower r-bond order of 0.17... 

Recently, clusters (18) with one capping oxygen atom and one capping ethylidyne moiety have also been prepared.237 The +1 cluster is prepared by refluxing W(CO)6 with a mixture of acetic add and its anhydride in MeCN. A one electron oxidation of the +1 ion leads to the +2 ion, whose crystal structure analysis reveals a W—W distance of 2.81 A. This distance is significantly longer than the one observed for (15), in agreement with the fact that the +2 ion is a five electron system and therefore the W—W bond order is less than unity. 

Bergson has also calculated the electronic structure of the trithione molecule using the above approximations. A very close agreement was found between the calculated bond lengths and those found experimentally by X-ray analysis of 4-methyltrithione. 124 Even in this case, however, there is some controversy regarding the significance of the calculated S—S bond order (0.243) as a measure of the participation of the S—S bond in the mesomeric system. The measured deviation (0.04 A) of the S—S bond length from the... 

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